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Sample records for model combustion chamber

  1. Comprehensive modeling of a liquid rocket combustion chamber

    NASA Technical Reports Server (NTRS)

    Liang, P.-Y.; Fisher, S.; Chang, Y. M.

    1985-01-01

    An analytical model for the simulation of detailed three-phase combustion flows inside a liquid rocket combustion chamber is presented. The three phases involved are: a multispecies gaseous phase, an incompressible liquid phase, and a particulate droplet phase. The gas and liquid phases are continuum described in an Eulerian fashion. A two-phase solution capability for these continuum media is obtained through a marriage of the Implicit Continuous Eulerian (ICE) technique and the fractional Volume of Fluid (VOF) free surface description method. On the other hand, the particulate phase is given a discrete treatment and described in a Lagrangian fashion. All three phases are hence treated rigorously. Semi-empirical physical models are used to describe all interphase coupling terms as well as the chemistry among gaseous components. Sample calculations using the model are given. The results show promising application to truly comprehensive modeling of complex liquid-fueled engine systems.

  2. IDENTIFICATION OF AN IDEAL REACTOR MODEL IN A SECONDARY COMBUSTION CHAMBER

    EPA Science Inventory

    Tracer analysis was applied to a secondary combustion chamber of a rotary kiln incinerator simulator to develop a computationally inexpensive networked ideal reactor model and allow for the later incorporation of detailed reaction mechanisms. Tracer data from sulfur dioxide trace...

  3. Numerical modeling of boundary-layer cooling of rocket engine combustion chambers

    NASA Astrophysics Data System (ADS)

    Pitalo, Gerald Alexander

    2000-10-01

    This study investigates boundary-layer cooling of rocket engine combustion chambers by means of numerical modeling. Using computational fluid dynamic methods to model the reacting viscous flow field in rocket combustion chambers, various propellant combinations and chamber geometries are analyzed. Specific propellants are hydrogen-oxygen and methane-oxygen mixtures. Chamber geometries used are the Space Shuttle Main Engine, 5.7 diameter research chamber, and the Apollo/Saturn F-1. Several modifications to existing codes are required to accommodate proposed boundary-layer cooling using fuel as the boundary fluid. This work discusses the mathematical basis for the numerical scheme used and the chemistry models needed to solve the reacting flow field, including specifically the field's boundary layer. Variables considered in the flow field are temperature, pressure, Mach number, species concentration, velocity, density, acoustic velocity, and heat transfer. Using results obtained in the study, a high pressure (Pc > 3000 psi) methane fueled rocket engine is proposed. Included is an analytical estimate of how thrust can be increased, with no loss of performance due to the active fuelfed boundary layer. The author concludes that numerical methods can effectively model the flow processes in boundary-layer cooled combustion chambers, giving designers the requisite information for analyzing rocket engines.

  4. Iridium-Coated Rhenium Combustion Chamber

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Tuffias, Robert H.; Rosenberg, Sanders D.

    1994-01-01

    Iridium-coated rhenium combustion chamber withstands operating temperatures up to 2,200 degrees C. Chamber designed to replace older silicide-coated combustion chamber in small rocket engine. Modified versions of newer chamber could be designed for use on Earth in gas turbines, ramjets, and scramjets.

  5. Combustion chamber analysis code

    NASA Technical Reports Server (NTRS)

    Przekwas, A. J.; Lai, Y. G.; Krishnan, A.; Avva, R. K.; Giridharan, M. G.

    1993-01-01

    A three-dimensional, time dependent, Favre averaged, finite volume Navier-Stokes code has been developed to model compressible and incompressible flows (with and without chemical reactions) in liquid rocket engines. The code has a non-staggered formulation with generalized body-fitted-coordinates (BFC) capability. Higher order differencing methodologies such as MUSCL and Osher-Chakravarthy schemes are available. Turbulent flows can be modeled using any of the five turbulent models present in the code. A two-phase, two-liquid, Lagrangian spray model has been incorporated into the code. Chemical equilibrium and finite rate reaction models are available to model chemically reacting flows. The discrete ordinate method is used to model effects of thermal radiation. The code has been validated extensively against benchmark experimental data and has been applied to model flows in several propulsion system components of the SSME and the STME.

  6. Formation mechanisms of combustion chamber deposits

    E-print Network

    O'Brien, Christopher J. (Christopher John)

    2001-01-01

    Combustion chamber deposits are found in virtually all internal combustion engines after a few hundred hours of operation. Deposits form on cylinder, piston, and head surfaces that are in contact with fuel-air mixture ...

  7. Non-grey radiation in a liquid rocket combustion chamber

    NASA Technical Reports Server (NTRS)

    Kehtarnavaz, H.; Dang, A. L.; Chiu, H. H.; Gross, K. W.

    1990-01-01

    The effects of radiation on droplets gasification in liquid rocket combustion chambers has been studied. The modeling includes a Legendre pseudo-spectral collocation approximation to solve the Radiative Transfer Equation (RTE). The band model has been utilized to account for non-grey emitting and absorbing gases present in the comustion chamber. The GEMCHIP II code has been utilized to study the fuel and oxidizer droplets combustion and interaction. The submodels within this code are capable of accounting for group combustion and conjugate effects between many droplets. The radiative model has been coupled with the GEMCHIP II code accounting for radial effects only, to provide the tool for studying the combustion-radiation coupling effects in a bipropellant system. The results indicate that the gasification/combustion process will be enhanced upstream of the chamber causing thicker flame sheet and associated higher combustion efficiency.

  8. Ribbed Coolant Liners for Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Wagner, W. R.

    1984-01-01

    Coolant-carrying liner for combustion chambers runs cooler and tolerates high-temperature excursions without burning out. Hot gases flowing through core prevented by liner from damaging shell. Concept applicable to such high-temperature chambers as rocket pre-burners, turbojet cans, stationary-turbine combustors, oil burners, and high-pressure chemical reactors.

  9. Computation of azimuthal combustion instabilities in an helicopter combustion chamber

    E-print Network

    Nicoud, Franck

    chambers possible,22 but these computations still remain too expensive to be used in an industrial context with the fuel. The swirling effects create a low pressure recirculation zone which stabilizes the flame the primary holes. Burnt gases are exhausted through the outlet of the combustion chamber and enter the stator

  10. Investigation of Ignition and Combustion Processes of Diesel Engines Operating with Turbulence and Air-storage Chambers

    NASA Technical Reports Server (NTRS)

    Petersen, Hans

    1938-01-01

    The flame photographs obtained with combustion-chamber models of engines operating respectively, with turbulence chamber and air-storage chambers or cells, provide an insight into the air and fuel movements that take place before and during combustion in the combustion chamber. The relation between air velocity, start of injection, and time of combustion was determined for the combustion process employing a turbulence chamber.

  11. Mathematical modelling of physical and chemical processes of coal combustion in chamber furnaces of boiler aggregates based on the package of applied programs FIRE 3D

    NASA Astrophysics Data System (ADS)

    Gil, A. V.; Starchenko, A. V.

    2012-09-01

    The furnace processes of the combustion of poly-fraction high-ashes Ekibastuz coal in the furnace chamber of the boiler aggregate PK-39 and of the combustion of highly humid brown Berezov's coal in the furnace of the BKZ-210-140 boiler are investigated by mathematical modeling using the package of applied programs FIRE 3D [1-3]. Results of the numerical modeling of the processes of aerodynamics, heat exchange, and combustion in the furnace volume and their comparison with the results of nature tests are presented.

  12. High-pressure promoted combustion chamber

    NASA Technical Reports Server (NTRS)

    Rucker, Michelle A. (inventor); Stoltzfus, Joel M. (inventor)

    1991-01-01

    In the preferred embodiment of the promoted combusiton chamber disclosed herein, a thick-walled tubular body that is capable of withstanding extreme pressures is arranged with removable upper and lower end closures to provide access to the chamber for dependently supporting a test sample of a material being evaluated in the chamber. To facilitate the real-time analysis of a test sample, several pressure-tight viewing ports capable of withstanding the simulated environmental conditions are arranged in the walls of the tubular body for observing the test sample during the course of the test. A replaceable heat-resistant tubular member and replaceable flame-resistant internal liners are arranged to be fitted inside of the chamber for protecting the interior wall surfaces of the combustion chamber during the evaluation tests. Inlet and outlet ports are provided for admitting high-pressure gases into the chamber as needed for performing dynamic analyses of the test sample during the course of an evaluation test.

  13. Stability analysis of a liquid fuel annular combustion chamber. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Mcdonald, G. H.

    1979-01-01

    The problems of combustion instability in an annular combustion chamber are investigated. A modified Galerkin method was used to produce a set of modal amplitude equations from the general nonlinear partial differential acoustic wave equation. From these modal amplitude equations, the two variable perturbation method was used to develop a set of approximate equations of a given order of magnitude. These equations were modeled to show the effects of velocity sensitive combustion instabilities by evaluating the effects of certain parameters in the given set of equations. By evaluating these effects, parameters which cause instabilities to occur in the combustion chamber can be ascertained. It is assumed that in the annular combustion chamber, the liquid propellants are injected uniformly across the injector face, the combustion processes are distributed throughout the combustion chamber, and that no time delay occurs in the combustion processes.

  14. Study of vortex core precession in combustion chambers

    NASA Astrophysics Data System (ADS)

    Alekseenko, S. V.; Markovich, D. M.; Dulin, V. M.; Chikishev, L. M.

    2013-12-01

    The article presents the results of experimental investigation of swirling flow of lean propane/air flame in a model combustion chamber at atmospheric pressure. To study the unsteady turbulent flow, the particle image velocimetry technique was used. It was concluded that dynamics of high swirl flows with and without combustion was determined by a global helical mode, complying with a precessing double-spiral coherent vortex structure. The studied low swirl flame had similar size and stability characteristics, but amplitude of the coherent helical structure substantially oscillated in time. The oscillations were associated with intermittently appearing central recirculation zone that was absent in the nonreacting flow. It is expected that the low swirl flow without the permanent central recirculation zone should be more sensitive to an external active control. In particular, this result may be useful for suppression of thermoacoustic resonance in combustion chambers.

  15. Study of vortex core precession in combustion chambers

    NASA Astrophysics Data System (ADS)

    Alekseenko, S. V.; Markovich, D. M.; Dulin, V. M.; Chikishev, L. M.

    2014-12-01

    The article presents the results of experimental investigation of swirling flow of lean propane/air flame in a model combustion chamber at atmospheric pressure. To study the unsteady turbulent flow, the particle image velocimetry technique was used. It was concluded that dynamics of high swirl flows with and without combustion was determined by a global helical mode, complying with a precessing double-spiral coherent vortex structure. The studied low swirl flame had similar size and stability characteristics, but amplitude of the coherent helical structure substantially oscillated in time. The oscillations were associated with intermittently appearing central recirculation zone that was absent in the nonreacting flow. It is expected that the low swirl flow without the permanent central recirculation zone should be more sensitive to an external active control. In particular, this result may be useful for suppression of thermoacoustic resonance in combustion chambers.

  16. Design handbook for gaseous fuel engine injectors and combustion chambers

    NASA Technical Reports Server (NTRS)

    Calhoon, D. F.; Ito, I.; Kors, D. L.

    1973-01-01

    Results of investigation of injection, mixing, and combustion processes using gaseous fuels and oxidizers have been summarized in handbook presenting succinct design procedures for injectors and methods for estimating combustion efficiency, chamber heat flux and stability characteristics. Handbook presents two approaches to injector and combustion chamber design: empirical and analytical.

  17. Nonlinear acoustics instabilities in combustion chambers

    SciTech Connect

    Awad, E.A.

    1983-01-01

    Analytical expressions for the amplitude, and the conditions for existence and stability of limit cycles for pressure oscillations in combustion chambers are given. Two techniques are used an asymptotic-perturbation technique where the asymptotic oscillatory behavior is sought by expanding the asymptotic solution in a measure of the amplitude of the wave, mainly the amplitude of the fundamental and perturbation-averaging technique where an approximate solution is sought by applying a perturbation method followed by an expansion of the solution in the normal modes of the acoustic field in the chamber. It is shown, to third order in the amplitude of the wave, that both techniques yield the same results regarding the amplitude and the conditions for existence and stability of the limit cycle. A stable limit cycle seems to be unique. The conditions for existence and stability are found to be dependent only on the linear parameters. The nonlinear parameter affects only the wave amplitude. In very special cases, the initial conditions can change the stability of the limit cycle. The imaginary parts of the linear responses, to pressure oscillations, of the different processes in the chamber play an important role in the stability of the limit cycle. They also affect the direction of flow of energy among modes. The triggering of pressure oscillations in solid propellant rockets is discussed. In order to explain the triggering of the oscillations to a non-trivial stable limit cycle, the treatment of two modes and the inclusion in the combustion response of either a second order nonlinear velocity coupling or a third order nonlinear pressure couplng seem to be sufficient.

  18. Method and apparatus for active control of combustion rate through modulation of heat transfer from the combustion chamber wall

    DOEpatents

    Roberts, Jr., Charles E.; Chadwell, Christopher J.

    2004-09-21

    The flame propagation rate resulting from a combustion event in the combustion chamber of an internal combustion engine is controlled by modulation of the heat transfer from the combustion flame to the combustion chamber walls. In one embodiment, heat transfer from the combustion flame to the combustion chamber walls is mechanically modulated by a movable member that is inserted into, or withdrawn from, the combustion chamber thereby changing the shape of the combustion chamber and the combustion chamber wall surface area. In another embodiment, heat transfer from the combustion flame to the combustion chamber walls is modulated by cooling the surface of a portion of the combustion chamber wall that is in close proximity to the area of the combustion chamber where flame speed control is desired.

  19. Combustion chamber struts can be effectively transpiration cooled

    NASA Technical Reports Server (NTRS)

    Palmer, G. H.

    1966-01-01

    Vapor-deposited sintering technique increases the feasible temperature range of transpiration-cooled structural members in combustion chambers. This technique produces a porous mass of refractory metal wires around a combustion chamber structural member. This mass acts as a transpiration-cooled surface for a thick-walled tube.

  20. NASA Teams With Army in Vortex Combustion Chamber Engine Test

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This photograph depicts one of over thirty tests conducted on the Vortex Combustion Chamber Engine at Marshall Space Flight Center's (MSFC) test stand 115, a joint effort between NASA's MSFC and the U.S. Army AMCOM of Redstone Arsenal. The engine tests were conducted to evaluate an irnovative, 'self-cooled', vortex combustion chamber, which relies on tangentially injected propellants from the chamber wall producing centrifugal forces that keep the relatively cold liquid propellants near the wall.

  1. Ducted combustion chamber for direct injection engines and method

    DOEpatents

    Mueller, Charles

    2015-03-03

    An internal combustion engine includes an engine block having a cylinder bore and a cylinder head having a flame deck surface disposed at one end of the cylinder bore. A piston connected to a rotatable crankshaft and configured to reciprocate within the cylinder bore has a piston crown portion facing the flame deck surface such that a combustion chamber is defined within the cylinder bore and between the piston crown and the flame deck surface. A fuel injector having a nozzle tip disposed in fluid communication with the combustion chamber has at least one nozzle opening configured to inject a fuel jet into the combustion chamber along a fuel jet centerline. At least one duct defined in the combustion chamber between the piston crown and the flame deck surface has a generally rectangular cross section and extends in a radial direction relative to the cylinder bore substantially along the fuel jet centerline.

  2. Fabrication of Composite Combustion Chamber/Nozzle for Fastrac Engine

    NASA Technical Reports Server (NTRS)

    Lawrence, T.; Beshears, R.; Burlingame, S.; Peters, W.; Prince, M.; Suits, M.; Tillery, S.; Burns, L.; Kovach, M.; Roberts, K.

    2001-01-01

    The Fastrac Engine developed by the Marshall Space Flight Center for the X-34 vehicle began as a low cost engine development program for a small booster system. One of the key components to reducing the engine cost was the development of an inexpensive combustion chamber/nozzle. Fabrication of a regeneratively cooled thrust chamber and nozzle was considered too expensive and time consuming. In looking for an alternate design concept, the Space Shuttle's Reusable Solid Rocket Motor Project provided an extensive background with ablative composite materials in a combustion environment. An integral combustion chamber/nozzle was designed and fabricated with a silica/phenolic ablative liner and a carbon/epoxy structural overwrap. This paper describes the fabrication process and developmental hurdles overcome for the Fastrac engine one-piece composite combustion chamber/nozzle.

  3. Fabrication of Composite Combustion Chamber/Nozzle for Fastrac Engine

    NASA Technical Reports Server (NTRS)

    Lawerence, T.; Beshears, R.; Burlingame, S.; Peters, W.; Prince, M.; Suits, M.; Tillery, S.; Burns, L.; Kovach, M.; Roberts, K.; Clinton, R. G., Jr. (Technical Monitor)

    2000-01-01

    The Fastrac Engine developed by the Marshall Space Flight Center for the X-34 vehicle began as a low cost engine development program for a small booster system. One of the key components to reducing the engine cost was the development of an inexpensive combustion chamber/nozzle. Fabrication of a regeneratively cooled thrust chamber and nozzle was considered too expensive and time consuming. In looking for an alternate design concept, the Space Shuttle's Reusable Solid Rocket Motor Project provided an extensive background with ablative composite materials in a combustion environment. An integral combustion chamber/nozzle was designed and fabricated with a silica/phenolic ablative liner and a carbon/epoxy structural overwrap. This paper describes the fabrication process and developmental hurdles overcome for the Fastrac engine one-piece composite combustion chamber/nozzle.

  4. Performance of Several Combustion Chambers Designed for Aircraft Oil Engines

    NASA Technical Reports Server (NTRS)

    Joachim, William F; Kemper, Carlton

    1928-01-01

    Several investigations have been made on single-cylinder test engines to determine the performance characteristics of four types of combustion chambers designed for aircraft oil engines. Two of the combustion chambers studied were bulb-type precombustion chambers, the connecting orifice of one having been designed to produce high turbulence by tangential air flow in both the precombustion chamber and the cylinder. The other two were integral combustion chambers, one being dome-shaped and the other pent-roof shaped. The injection systems used included cam and eccentric driven fuel pumps, and diaphragm and spring-loaded fuel-injection valves. A diaphragm type maximum cylinder pressure indicator was used in part of these investigations with which the cylinder pressures were controlled to definite valves. The performance of the engines when equipped with each of the combustion chambers is discussed. The best performance for the tests reported was obtained with a bulb-type combustion chamber designed to give a high degree of turbulence within the bulb and cylinder. (author)

  5. Liquid rocket engine fluid-cooled combustion chambers

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A monograph on the design and development of fluid cooled combustion chambers for liquid propellant rocket engines is presented. The subjects discussed are (1) regenerative cooling, (2) transpiration cooling, (3) film cooling, (4) structural analysis, (5) chamber reinforcement, and (6) operational problems.

  6. Pyrolysis reactor and fluidized bed combustion chamber

    DOEpatents

    Green, Norman W. (Upland, CA)

    1981-01-06

    A solid carbonaceous material is pyrolyzed in a descending flow pyrolysis reactor in the presence of a particulate source of heat to yield a particulate carbon containing solid residue. The particulate source of heat is obtained by educting with a gaseous source of oxygen the particulate carbon containing solid residue from a fluidized bed into a first combustion zone coupled to a second combustion zone. A source of oxygen is introduced into the second combustion zone to oxidize carbon monoxide formed in the first combustion zone to heat the solid residue to the temperature of the particulate source of heat.

  7. Rocket combustion chamber life-enhancing design concepts

    NASA Technical Reports Server (NTRS)

    Quentmeyer, Richard J.

    1990-01-01

    NASA continues to pursue technologies which can lead to an increase in life and reduce the costs of fabrication of the Space Shuttle Main Engine. The joint NASA/Air Force Advanced Launch System Program has set its prime objectives to be high reliability and low cost for their new advanced booster engine. In order to meet these objectives, NASA will utilize the results of several ongoing programs to provide the required technologies. An overview is presented of those programs which address life enhancing design concepts for the combustion chamber. Seven different design concepts, which reduce the thermal strain and/or increase the material strength of the combustion chamber liner wall are discussed. Subscale rocket test results are presented, where available, for life enhancing design concepts. Two techniques for reducing chamber fabrication costs are discussed, as well as issues relating to hydrocarbon fuels/combustion chamber liner materials compatibility.

  8. Fabrication process for combustion chamber/nozzle assembly

    NASA Technical Reports Server (NTRS)

    Myers, W. Neill (Inventor); Cornelius, Charles S. (Inventor)

    2001-01-01

    An integral, lightweight combustion chamber/nozzle assembly for a rocket engine has a refractory metal shell defining a chamber of generally frusto-conical contour. The shell communicates at its smaller end with a rocket body, and terminates at its larger end in a generally contact contour, which is open at its terminus and which serves as a nozzle for the rocket engine. The entire inner surface of the refractory metal shell has a thermal and oxidation barrier layer applied thereto. An ablative silica phenolic insert is bonded to the exposed surface of the thermal and oxidation barrier layer. The ablative phenolic insert provides a chosen inner contour for the combustion chamber and has a taper toward the open terminus of the nozzle. A process for fabricating the integral, lightweight combustion chamber/nozzle assembly is simple and efficient, and results in economy in respect of both resources and time.

  9. Liquid rocket engine self-cooled combustion chambers

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Self-cooled combustion chambers are chambers in which the chamber wall temperature is controlled by methods other than fluid flow within the chamber wall supplied from an external source. In such chambers, adiabatic wall temperature may be controlled by use of upstream fluid components such as the injector or a film-coolant ring, or by internal flow of self-contained materials; e.g. pyrolysis gas flow in charring ablators, and the flow of infiltrated liquid metals in porous matrices. Five types of self-cooled chambers are considered in this monograph. The name identifying the chamber is indicative of the method (mechanism) by which the chamber is cooled, as follows: ablative; radiation cooled; internally regenerative (Interegen); heat sink; adiabatic wall. Except for the Interegen and heat sink concepts, each chamber type is discussed separately. A separate and final section of the monograph deals with heat transfer to the chamber wall and treats Stanton number evaluation, film cooling, and film-coolant injection techniques, since these subjects are common to all chamber types. Techniques for analysis of gas film cooling and liquid film cooling are presented.

  10. Experimental biomass burning emission assessment by combustion chamber

    NASA Astrophysics Data System (ADS)

    Lusini, Ilaria; Pallozzi, Emanuele; Corona, Piermaria; Ciccioli, Paolo; Calfapietra, Carlo

    2014-05-01

    Biomass burning is a significant source of several atmospheric gases and particles and it represents an important ecological factor in the Mediterranean ecosystem. In this work we describe the performances of a recently developed combustion chamber to show the potential of this facility in estimating the emission from wildland fire showing a case study with leaves, small branches and litter of two representative species of Mediterranean vegetation, Quercus pubescens and Pinus halepensis. The combustion chamber is equipped with a thermocouple, a high resolution balance, an epiradiometer, two different sampling lines to collect organic volatile compounds (VOCs) and particles, a sampling line connected to a Proton Transfer Reaction Mass-Spectrometer (PTR-MS) and a portable analyzer to measure CO and CO2 emission. VOCs emission were both analyzed with GC-MS and monitored on-line with PTR-MS. The preliminary qualitative analysis of emission showed that CO and CO2 are the main gaseous species emitted during the smoldering and flaming phase, respectively. Many aromatics VOCs as benzene and toluene, and many oxygenated VOC as acetaldehyde and methanol were also released. This combustion chamber represents an important tool to determine the emission factor of each plant species within an ecosystem, but also the contribution to the emissions of the different plant tissues and the kinetics of different compound emissions during the various combustion phases. Another important feature of the chamber is the monitoring of the carbon balance during the biomass combustion.

  11. SSME main combustion chamber and nozzle flowfield analysis

    NASA Technical Reports Server (NTRS)

    Farmer, R. C.; Wang, T. S.; Smith, S. D.; Prozan, R. J.

    1986-01-01

    An investigation is presented of the computational fluid dynamics (CFD) tools which would accurately analyze main combustion chamber and nozzle flow. The importance of combustion phenomena and local variations in mixture ratio are fully appreciated; however, the computational aspects of the gas dynamics involved were the sole issues addressed. The CFD analyses made are first compared with conventional nozzle analyses to determine the accuracy for steady flows, and then transient analyses are discussed.

  12. Numerical simulation of the 3D unsteady turbulent flow in a combustion chamber

    NASA Astrophysics Data System (ADS)

    Stuparu, Adrian; Holotescu, Sorin

    2011-06-01

    The influence of turbulence models on the 3D unsteady flow in a combustion chamber with a central bluff body is analyzed. Three different turbulence models are used (realizable k-?, Reynolds Stress Model and Large Eddy Simulation) and a comparison is made on the evolution of the velocity field over time. The numerical simulation of the gas flow in the combustion chamber was performed using FLUENT 6.3 software and the computational geometry, consisting of a structured mesh with 810,000 cells, was built using the pre-processor GAMBIT 2.4. The extent of the recirculation region behind the bluff body was determined for each turbulence model.

  13. Numerical simulation of the 3D unsteady turbulent flow in a combustion chamber

    NASA Astrophysics Data System (ADS)

    Stuparu, Adrian; Holotescu, Sorin

    2011-06-01

    The influence of turbulence models on the 3D unsteady flow in a combustion chamber with a central bluff body is analyzed. Three different turbulence models are used ( realizable k-?, Reynolds Stress Model and Large Eddy Simulation) and a comparison is made on the evolution of the velocity field over time. The numerical simulation of the gas flow in the combustion chamber was performed using FLUENT 6.3 software and the computational geometry, consisting of a structured mesh with 810,000 cells, was built using the pre-processor GAMBIT 2.4. The extent of the recirculation region behind the bluff body was determined for each turbulence model.

  14. Analysis of 5 KHz combustion instabilities in 40K methane/LOX combustion chambers

    NASA Technical Reports Server (NTRS)

    Breisacher, Kevin J.; Priem, Richard J.

    1988-01-01

    In 40K methane/LOX 5 KHz engine tests, (first transverse mode) combustion instabilities observed by Rocketdyne are analyzed using Heidmann and Wieber's vaporization model to include LOX flow oscillations. The LOX flow oscillations are determined by including acoustic waves in the feed system analysis. The major parameter controlling stability is the distance (or time delay) associated with atomizing the LOX stream in the coaxial injection system. Results of the analysis that show the influence of mixture ratio, oxidizer and fuel injection velocities, burning time and combustion chamber/injector dimensions on stability are used to explain the existing data. Calculated results to predict the influence of design changes being made for the next set of experiments are also presented.

  15. EMISSIONS OF TRACE PRODUCTS OF INCOMPLETE COMBUSTION FROM A PILOT-SCALE INCINERATOR SECONDARY COMBUSTION CHAMBER

    EPA Science Inventory

    Experiments were performed on a 73 kW rotary kiln incinerator simulator equipped with a 73 kW secondary combustion chamber (SCC) to examine emissions of products of incomplete combustion (PICs) resulting from incineration of carbon tetrachloride (CCl4) and dichlorometh...

  16. Hot fire test results of subscale tubular combustion chambers

    NASA Technical Reports Server (NTRS)

    Kazaroff, John M.; Jankovsky, Robert S.; Pavli, Albert J.

    1992-01-01

    Advanced, subscale, tubular combustion chambers were built and test fired with hydrogen-oxygen propellants to assess the increase in fatigue life that can be obtained with this type of construction. Two chambers were tested: one ran for 637 cycles without failing, compared to a predicted life of 200 cycles for a comparable smooth-wall milled-channel liner configuration. The other chamber failed at 256 cycles, compared to a predicted life of 118 cycles for a comparable smooth-wall milled-channel liner configuration. Posttest metallographic analysis determined that the strain-relieving design (structural compliance) of the tubular configuration was the cause of this increase in life.

  17. Optical Power Source Derived from Engine Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J. (Inventor)

    1999-01-01

    An optical power source is disclosed that collects the spectra of the light emissions created in a combustion chamber to provide its optical output signals that serve the needs of optical networks. The light spectra is collected by a collection ring serving as an optical waveguide.

  18. Development of technologies for a CMC-based combustion chamber

    NASA Astrophysics Data System (ADS)

    Haidn, O. J.; Riccius, J.; Suslov, D.; Beyer, S.; Knab, O.

    2009-09-01

    Within the 'Propulsion 2010' Memorandum of Understanding (MoU) which was signed in 2006, Astrium and DLR agreed to work jointly on Ceramic Matrix Composite (CMC) materials and related technologies with the aim to have finally within the next three years all components and subsystems available for an entirely CMC-based thrust chamber assembly. Hence, propellant injection, combustion chamber liner, and appropriate cooling technologies as well as CMC nozzle parts will be developed and tested within the years to come. The paper reports the current status and focuses on propellant injection applying a porous face plate, heat and mass transfer within and along an effusion-cooled porous combustion chamber liner and design and heat transfer issues of a cooled thrust nozzle.

  19. Numerical simulations of industrial-scale combustion chamber - LES versus RANS

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, Kamil; Jasi?ski, Daniel; Bajer, Konrad

    2011-12-01

    In this work we focus on the simulation of the process of biomass syngas combustion in the industrial combustion chamber directly linked with gasification chamber, where this gas is continuously producing from the biomass. Conflicting demands from the engineers to have rapid results and hints how to ensure the best conditions for combustion of this particular fuel and to lower the emission of pollutants, with simultaneously deep view inside the process and its stability motivates us to use both the RANS and LES techniques of turbulence modelling, compare it and take their advantages. We designed and performed series of 3D numerical simulations of both cold flow and combustion in complex geometry of industrial burner. It seems to us that the proper approach for modelling of biomass syngas combustion is steady flamelets model. Simulations performed with RANS closure are used as the initialisation of LES models, but their main goal is to predict the long-time oscillation of pressure and temperature observed in the working combustion chamber. On the other hand the main goal of the simulations with LES closure is to predict the proper level of short-time behaviour of the flame and local phenomena.

  20. Promoted-Combustion Chamber with Induction Heating Coil

    NASA Technical Reports Server (NTRS)

    Richardson, Erin; Hagood, Richard; Lowery, Freida; Herald, Stephen

    2006-01-01

    An improved promoted-combustion system has been developed for studying the effects of elevated temperatures on the flammability of metals in pure oxygen. In prior promoted-combustion chambers, initial temperatures of metal specimens in experiments have been limited to the temperatures of gas supplies, usually near room temperature. Although limited elevated temperature promoted-combustion chambers have been developed using water-cooled induction coils for preheating specimens, these designs have been limited to low-pressure operation due to the hollow induction coil. In contrast, the improved promoted-combustion chamber can sustain a pressure up to 10 kpsi (69 MPa) and, through utilization of a solid induction coil, is capable of preheating a metal specimen up to its melting point [potentially in excess of 2,000 F (approximately equal to 1,100 C)]. Hence, the improved promoted combustion chamber makes a greater range of physical conditions and material properties accessible for experimentation. The chamber consists of a vertical cylindrical housing with an inner diameter of 8 in. (20.32 cm) and an inner height of 20.4 in. (51.81 cm). A threaded, sealing cover at one end of the housing can be unscrewed to gain access for installing a specimen. Inlet and outlet ports for gases are provided. Six openings arranged in a helical pattern in the chamber wall contain sealed sapphire windows for viewing an experiment in progress. The base of the chamber contains pressure-sealed electrical connectors for supplying power to the induction coil. The connectors feature a unique design that prevents induction heating of the housing and the pressure sealing surfaces; this is important because if such spurious induction heating were allowed to occur, chamber pressure could be lost. The induction coil is 10 in. (25.4 cm) long and is fitted with a specimen holder at its upper end. At its lower end, the induction coil is mounted on a ceramic base, which affords thermal insulation to prevent heating of the base of the chamber during use. A sapphire cylinder protects the coil against slag generated during an experiment. The induction coil is energized by a 6-kW water-cooled power supply operating at a frequency of 400 kHz. The induction coil is part of a parallel-tuned circuit, the tuning of which is used to adjust the coupling of power to the specimen. The chamber is mounted on a test stand along with pumps, valves, and plumbing for transferring pressurized gas into and out of the chamber. In addition to multiple video cameras aimed through the windows encircling the chamber, the chamber is instrumented with gauges for monitoring the progress of an experiment. One of the gauges is a dual-frequency infrared temperature transducer aimed at the specimen through one window. Chamber operation is achieved via a console that contains a computer running apparatus-specific software, a video recorder, and real-time video monitors. For safety, a blast wall separates the console from the test stand.

  1. Analysis of liquid rocket combustion chamber turbulence levels from diffusion data

    NASA Technical Reports Server (NTRS)

    Smith, L. O., Jr.; Partus, F. P.; Ohara, J. C.

    1975-01-01

    The intensity of turbulence and the Lagrangian correlation coefficient in a liquid-rocket combustion chamber have been analytically determined from an analysis of experimental diffusion data obtained in a small rocket engine which operated at 300-psia chamber pressure and produced approximately 250 pounds thrust. Results of gas-sample measurements obtained by Orsat and gas-chromatograph techniques to determine helium-concentration profiles were analyzed on the basis of Taylor's (1921) turbulent diffusion theory to obtain turbulence flow-field parameters. The results of the analysis indicate that turbulent diffusion in a combustion chamber can be adequately modeled by the one-dimensional Taylor theory, which assumes that the intensity of turbulence is a function only of axial distance in the chamber and that the Lagrangian correlation coefficient is expressed by a power law. The results indicate a higher intensity of turbulence and lower correlation than previously expected.

  2. Effects of high combustion chamber pressure on rocket noise environment

    NASA Technical Reports Server (NTRS)

    Pao, S. P.

    1972-01-01

    The acoustical environment for a high combustion chamber pressure engine was examined in detail, using both conventional and advanced theoretical analysis. The influence of elevated chamber pressure on the rocket noise environment was established, based on increase in exit velocity and flame temperature, and changes in basic engine dimensions. Compared to large rocket engines, the overall sound power level is found to be 1.5 dB higher, if the thrust is the same. The peak Strouhal number shifted about one octave lower to a value near 0.01. Data on apparent sound source location and directivity patterns are also presented.

  3. Advanced Main Combustion Chamber structural jacket strength analysis

    NASA Astrophysics Data System (ADS)

    Johnston, L. M.; Perkins, L. A.; Denniston, C. L.; Price, J. M.

    1993-04-01

    The structural analysis of the Advanced Main Combustion Chamber (AMCC) is presented. The AMCC is an advanced fabrication concept of the Space Shuttle Main Engine main combustion chamber (MCC). Reduced cost and fabrication time of up to 75 percent were the goals of the AMCC with cast jacket with vacuum plasma sprayed or platelet liner. Since the cast material for the AMCC is much weaker than the wrought material for the MCC, the AMCC is heavier and strength margins much lower in some areas. Proven hand solutions were used to size the manifolds cutout tee areas for combined pressure and applied loads. Detailed finite element strength analyses were used to size the manifolds, longitudinal ribs, and jacket for combined pressure and applied local loads. The design of the gimbal actuator strut attachment lugs were determined by finite element analyses and hand solutions.

  4. Advanced Main Combustion Chamber structural jacket strength analysis

    NASA Technical Reports Server (NTRS)

    Johnston, L. M.; Perkins, L. A.; Denniston, C. L.; Price, J. M.

    1993-01-01

    The structural analysis of the Advanced Main Combustion Chamber (AMCC) is presented. The AMCC is an advanced fabrication concept of the Space Shuttle Main Engine main combustion chamber (MCC). Reduced cost and fabrication time of up to 75 percent were the goals of the AMCC with cast jacket with vacuum plasma sprayed or platelet liner. Since the cast material for the AMCC is much weaker than the wrought material for the MCC, the AMCC is heavier and strength margins much lower in some areas. Proven hand solutions were used to size the manifolds cutout tee areas for combined pressure and applied loads. Detailed finite element strength analyses were used to size the manifolds, longitudinal ribs, and jacket for combined pressure and applied local loads. The design of the gimbal actuator strut attachment lugs were determined by finite element analyses and hand solutions.

  5. Method of fabricating a rocket engine combustion chamber

    NASA Technical Reports Server (NTRS)

    Holmes, Richard R. (inventor); Mckechnie, Timothy N. (inventor); Power, Christopher A. (inventor); Daniel, Ronald L., Jr. (inventor); Saxelby, Robert M. (inventor)

    1993-01-01

    A process for making a combustion chamber for a rocket engine wherein a copper alloy in particle form is injected into a stream of heated carrier gas in plasma form which is then projected onto the inner surface of a hollow metal jacket having the configuration of a rocket engine combustion chamber is described. The particles are in the plasma stream for a sufficient length of time to heat the particles to a temperature such that the particles will flatten and adhere to previously deposited particles but will not spatter or vaporize. After a layer is formed, cooling channels are cut in the layer, then the channels are filled with a temporary filler and another layer of particles is deposited.

  6. Hydrocarbon-fuel/combustion-chamber-liner materials compatibility

    NASA Technical Reports Server (NTRS)

    Gage, Mark L.

    1990-01-01

    Results of material compatibility experiments using hydrocarbon fuels in contact with copper-based combustion chamber liner materials are presented. Mil-Spec RP-1, n- dodecane, propane, and methane fuels were tested in contact with OFHC, NASA-Z, and ZrCu coppers. Two distinct test methods were employed. Static tests, in which copper coupons were exposed to fuel for long durations at constant temperature and pressure, provided compatibility data in a precisely controlled environment. Dynamic tests, using the Aerojet Carbothermal Test Facility, provided fuel and copper compatibility data under realistic booster engine service conditions. Tests were conducted using very pure grades of each fuel and fuels to which a contaminant, e.g., ethylene or methyl mercaptan, was added to define the role played by fuel impurities. Conclusions are reached as to degradation mechanisms and effects, methods for the elimination of these mechanisms, selection of copper alloy combustion chamber liners, and hydrocarbon fuel purchase specifications.

  7. Stability analysis of a liquid fuel annular combustion chamber. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Mcdonald, G. H.

    1978-01-01

    High frequency combustion instability problems in a liquid fuel annular combustion chamber are examined. A modified Galerkin method was used to produce a set of modal amplitude equations from the general nonlinear partial differential acoustic wave equation in order to analyze the problem of instability. From these modal amplitude equations, the two variable perturbation method was used to develop a set of approximate equations of a given order of magnitude. These equations were modeled to show the effects of velocity sensitive combustion instabilities by evaluating the effects of certain parameters in the given set of equations.

  8. SSME main combustion chamber life prediction

    NASA Technical Reports Server (NTRS)

    Cook, R. T.; Fryk, E. E.; Newell, J. F.

    1983-01-01

    Typically, low cycle fatigue life is a function of the cyclic strain range, the material properties, and the operating temperature. The reusable life is normally defined by the number of strain cycles that can be accrued before severe material degradation occurs. Reusable life is normally signified by the initiation or propagation of surface cracks. Hot-fire testing of channel wall combustors has shown significant mid-channel wall thinning or deformation during accrued cyclic testing. This phenomenon is termed cyclic-creep and appears to be significantly accelerated at elevated surface temperatures. This failure mode was analytically modelled. The cyclic life of the baseline SSME-MCC based on measured calorimeter heat transfer data, and the life sensitivity of local hot spots caused by injector effects were determined. Four life enhanced designs were assessed.

  9. Liquid fuel vaporizer and combustion chamber having an adjustable thermal conductor

    SciTech Connect

    Powell, Michael R; Whyatt, Greg A; Howe, Daniel T; Fountain, Matthew S

    2014-03-04

    The efficiency and effectiveness of apparatuses for vaporizing and combusting liquid fuel can be improved using thermal conductors. For example, an apparatus having a liquid fuel vaporizer and a combustion chamber can be characterized by a thermal conductor that conducts heat from the combustion chamber to the vaporizer. The thermal conductor can be a movable member positioned at an insertion depth within the combustion chamber that corresponds to a rate of heat conduction from the combustion chamber to the vaporizer. The rate of heat conduction can, therefore, be adjusted by positioning the movable member at a different insertion depth.

  10. Nonlinear behavior of acoustic waves in combustion chambers

    NASA Technical Reports Server (NTRS)

    Culick, F. E. C.

    1975-01-01

    The nonlinear growth and limiting amplitude of acoustic waves in a combustion chamber are considered. A formal framework is provided within which practical problems can be treated with a minimum of effort and expense. The general conservation equations were expanded in two small parameters, one characterizing the mean flow field and one measuring the amplitude of oscillations, and then combined to yield a nonlinear inhomogeneous wave equation. The unsteady pressure and velocity fields were expressed as syntheses of the normal modes of the chamber, but with unknown time-varying amplitudes. This procedure yielded a representation of a general unsteady field as a system of coupled nonlinear oscillators. The system of nonlinear equations was treated by the method of averaging to produce a set of coupled nonlinear first order differential equations for the amplitudes and phases of the modes. The analysis is applicable to any combustion chamber. The most interesting applications are probably to solid rockets, liquid rockets, or thrust augmentors on jet engines.

  11. Heat transfer in rocket engine combustion chambers and regeneratively cooled nozzles

    NASA Technical Reports Server (NTRS)

    1993-01-01

    A conjugate heat transfer computational fluid dynamics (CFD) model to describe regenerative cooling in the main combustion chamber and nozzle and in the injector faceplate region for a launch vehicle class liquid rocket engine was developed. An injector model for sprays which treats the fluid as a variable density, single-phase media was formulated, incorporated into a version of the FDNS code, and used to simulate the injector flow typical of that in the Space Shuttle Main Engine (SSME). Various chamber related heat transfer analyses were made to verify the predictive capability of the conjugate heat transfer analysis provided by the FDNS code. The density based version of the FDNS code with the real fluid property models developed was successful in predicting the streamtube combustion of individual injector elements.

  12. Slag monitoring system for combustion chambers of steam boilers

    SciTech Connect

    Taler, J.; Taler, D.

    2009-07-01

    The computer-based boiler performance system presented in this article has been developed to provide a direct and quantitative assessment of furnace and convective surface cleanliness. Temperature, pressure, and flow measurements and gas analysis data are used to perform heat transfer analysis in the boiler furnace and evaporator. Power boiler efficiency is calculated using an indirect method. The on-line calculation of the exit flue gas temperature in a combustion chamber allows for an on-line heat flow rate determination, which is transferred to the boiler evaporator. Based on the energy balance for the boiler evaporator, the superheated steam mass flow rate is calculated taking into the account water flow rate in attemperators. Comparing the calculated and the measured superheated steam mass flow rate, the effectiveness of the combustion chamber water walls is determined in an on-line mode. Soot-blower sequencing can be optimized based on actual cleaning requirements rather than on fixed time cycles contributing to lowering of the medium usage in soot blowers and increasing of the water-wall lifetime.

  13. Combustion modeling in internal combustion engines

    NASA Technical Reports Server (NTRS)

    Zeleznik, F. J.

    1976-01-01

    The fundamental assumptions of the Blizard and Keck combustion model for internal combustion engines are examined and a generalization of that model is derived. The most significant feature of the model is that it permits the occurrence of unburned hydrocarbons in the thermodynamic-kinetic modeling of exhaust gases. The general formulas are evaluated in two specific cases that are likely to be significant in the applications of the model.

  14. Robust Low Cost Liquid Rocket Combustion Chamber by Advanced Vacuum Plasma Process

    NASA Technical Reports Server (NTRS)

    Holmes, Richard; Elam, Sandra; McKechnie, Timothy; Hickman, Robert; Stinson, Thomas N. (Technical Monitor)

    2002-01-01

    Next-generation, regeneratively cooled rocket engines require materials that can meet high temperatures while resisting the corrosive oxidation-reduction reaction of combustion known as blanching, the main cause of engine failure. A project was initiated at NASA-Marshal Space Flight Center (MSFC) to combine three existing technologies to build and demonstrate an advanced liquid rocket engine combustion chamber that would provide a 100 mission life. Technology developed in microgravity research to build cartridges for space furnaces was utilized to vacuum plasma spray (VPS) a functional gradient coating on the hot wall of the combustion liner as one continuous operation, eliminating any bondline between the coating and the liner. The coating was NiCrAlY, developed previously as durable protective coatings on space shuttle high pressure fuel turbopump (HPFTP) turbine blades. A thermal model showed that 0.03 in. NiCrAlY applied to the hot wall of the combustion liner would reduce the hot wall temperature 200 F, a 20% reduction, for longer life. Cu-8Cr-4Nb alloy, which was developed by NASA-Glenn Research Center (GRC), and which possesses excellent high temperature strength, creep resistance, and low cycle fatigue behavior combined with exceptional thermal stability, was utilized as the liner material in place of NARloy-Z. The Cu-8Cr-4Nb material exhibits better mechanical properties at 650 C (1200 F) than NARloy-Z does at 538 C (1000 F). VPS formed Cu-8Cr-4Nb combustion chamber liners with a protective NiCrAlY functional gradient coating have been hot fire tested, successfully demonstrating a durable coating for the first time. Hot fire tests along with tensile and low cycle fatigue properties of the VPS formed combustion chamber liners and witness panel specimens are discussed.

  15. 72. VISITOR'S CENTER, MODEL OF BOILER CHAMBER, AUXILIARY CHAMBER, REACTOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    72. VISITOR'S CENTER, MODEL OF BOILER CHAMBER, AUXILIARY CHAMBER, REACTOR AND CANAL (LOCATION T) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  16. Design, analysis, and fabrication of oxide-coated iridium/rhenium combustion chambers

    NASA Technical Reports Server (NTRS)

    Jang, Q.; Tuffias, R. H.; Laferla, R.; Ghoniem, N. M.

    1993-01-01

    Iridium-coated rhenium (Ir/Re) combustion chambers provide high temperature, oxidation-resistant operation for radiation-cooled liquid-fueled rocket engines. A 22-N (5-lb(sub f)) chamber has been operated for 15 hours at 2200 C (4000 F) using nitrogen tetroxide/monomethyl hydrazine (NTO/MMH) propellant, with negligible internal erosion. The oxidation resistance of these chambers could be further increased by the addition of refractory oxide coatings, providing longer life and/or operation in more oxidizing and higher temperature environments. The oxide coatings would serve as a thermal and diffusion barrier for the iridium coating, lowering the temperature of the iridium layer while also preventing the ingress of oxygen and egress of iridium oxides. This would serve to slow the failure mechanisms of Ir/Re chambers, namely the diffusion of rhenium to the inner surface and the oxidation of iridium. Such protection could extend chamber lifetimes by tens or perhaps hundreds of hours, and allow chamber operation on stoichiometric or higher mixture ratio oxygen/hydrogen (O2/H2) propellant. Extensive thermomechanical, thermochemical, and mass transport modeling was performed as a key material/structure design tool. Based on the results of these analyses, several 22-N oxide-coated Ir/Re chambers were fabricated and delivered to NASA Lewis Research Center for hot-fire testing.

  17. On the dynamic nature of azimuthal thermoacoustic modes in annular gas turbine combustion chambers

    E-print Network

    Daraio, Chiara

    On the dynamic nature of azimuthal thermoacoustic modes in annular gas turbine combustion chambers turbine combustion chamber. A detailed statistical analysis of the spatial Fourier amplitudes extracted is proposed and supported by real gas turbine data. The stochastic differential equations that govern

  18. Development and test of combustion chamber for Stirling engine heated by natural gas

    NASA Astrophysics Data System (ADS)

    Li, Tie; Song, Xiange; Gui, Xiaohong; Tang, Dawei; Li, Zhigang; Cao, Wenyu

    2014-04-01

    The combustion chamber is an important component for the Stirling engine heated by natural gas. In the paper, we develop a combustion chamber for the Stirling engine which aims to generate 3˜5 kWe electric power. The combustion chamber includes three main components: combustion module, heat exchange cavity and thermal head. Its feature is that the structure can divide "combustion" process and "heat transfer" process into two apparent individual steps and make them happen one by one. Since natural gas can mix with air fully before burning, the combustion process can be easily completed without the second wind. The flame can avoid contacting the thermal head of Stirling engine, and the temperature fields can be easily controlled. The designed combustion chamber is manufactured and its performance is tested by an experiment which includes two steps. The experimental result of the first step proves that the mixture of air and natural gas can be easily ignited and the flame burns stably. In the second step of experiment, the combustion heat flux can reach 20 kW, and the energy utilization efficiency of thermal head has exceeded 0.5. These test results show that the thermal performance of combustion chamber has reached the design goal. The designed combustion chamber can be applied to a real Stirling engine heated by natural gas which is to generate 3˜5 kWe electric power.

  19. Modifications of a Composite-Material Combustion Chamber

    NASA Technical Reports Server (NTRS)

    Williams, Brian E.; McNeal, Shawn R.

    2005-01-01

    Two short reports discuss modifications of a small, lightweight combustion chamber that comprises a carbon/carbon composite outer shell and an iridium/ rhenium inner liner. The first report discusses chamber design modifications made as results of hot-fire tests and post-test characterization. The Books & Reports 32 NASA Tech Briefs, June 2005 modifications were intended to serve a variety of purposes, including improving fabrication, reducing thermal-expansion mismatch stresses, increasing strength-to-weight ratios of some components, and improving cooling of some components. The second report discusses (1) the origin of stress in the mismatch between the thermal expansions of the Ir/Re liner and a niobium sleeve and flange attached to the carbon/ carbon shell and (2) a modification intended to relieve the stress. The modification involves the redesign of an inlet connection to incorporate a compressible seal between the Ir/Re liner and the Nb flange. A nickel alloy was selected as the seal material on the basis of its thermal-expansion properties and its ability to withstand the anticipated stresses, including the greatest stresses caused by the high temperatures to be used in brazing during fabrication.

  20. Prevention of Over-Pressurization During Combustion in a Sealed Chamber

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Niehaus, Justin E.; Olson, Sandra L.; Dietrich, Daniel L.; Ruff, Gary A.; Johnston, Michael C.

    2012-01-01

    The combustion of flammable material in a sealed chamber invariably leads to an initial pressure rise in the volume. The pressure rise is due to the increase in the total number of gaseous moles (condensed fuel plus chamber oxygen combining to form gaseous carbon dioxide and water vapor) and, most importantly, the temperature rise of the gas in the chamber. Though the rise in temperature and pressure would reduce with time after flame extinguishment due to the absorption of heat by the walls and contents of the sealed spacecraft, the initial pressure rise from a fire, if large enough, could lead to a vehicle over-pressure and the release of gas through the pressure relief valve. This paper presents a simple lumped-parameter model of the pressure rise in a sealed chamber resulting from the heat release during combustion. The transient model considers the increase in gaseous moles due to combustion, and heat transfer to the chamber walls by convection and radiation and to the fuel-sample holder by conduction, as a function of the burning rate of the material. The results of the model are compared to the pressure rise in an experimental chamber during flame spread tests as well as to the pressure falloff after flame extinguishment. The experiments involve flame spread over thin solid fuel samples. Estimates of the heat release rate profiles for input to the model come from the assumed stoichiometric burning of the fuel along with the observed flame spread behavior. The sensitivity of the model to predict maximum chamber pressure is determined with respect to the uncertainties in input parameters. Model predictions are also presented for the pressure profile anticipated in the Fire Safety-1 experiment, a material flammability and fire safety experiment proposed for the European Space Agency (ESA) Automated Transfer Vehicle (ATV). Computations are done for a range of scenarios including various initial pressures and sample sizes. Based on these results, various mitigation approaches are suggested to prevent vehicle over-pressurization and help guide the definition of the space experiment.

  1. CFD Analysis of Spray Combustion and Radiation in OMV Thrust Chamber

    NASA Technical Reports Server (NTRS)

    Giridharan, M. G.; Krishnan, A.; Przekwas, A. J.; Gross, K.

    1993-01-01

    The Variable Thrust Engine (VTE), developed by TRW, for the Orbit Maneuvering Vehicle (OMV) uses a hypergolic propellant combination of Monomethyl Hydrazine (MMH) and Nitrogen Tetroxide (NTO) as fuel and oxidizer, respectively. The propellants are pressure fed into the combustion chamber through a single pintle injection element. The performance of this engine is dependent on the pintle geometry and a number of complex physical phenomena and their mutual interactions. The most important among these are (1) atomization of the liquid jets into fine droplets; (2) the motion of these droplets in the gas field; (3) vaporization of the droplets (4) turbulent mixing of the fuel and oxidizer; and (5) hypergolic reaction between MMH and NTO. Each of the above phenomena by itself poses a considerable challenge to the technical community. In a reactive flow field of the kind occurring inside the VTE, the mutual interactions between these physical processes tend to further complicate the analysis. The objective of this work is to develop a comprehensive mathematical modeling methodology to analyze the flow field within the VTE. Using this model, the effect of flow parameters on various physical processes such as atomization, spray dynamics, combustion, and radiation is studied. This information can then be used to optimize design parameters and thus improve the performance of the engine. The REFLEQS CFD Code is used for solving the fluid dynamic equations. The spray dynamics is modeled using the Eulerian-Lagrangian approach. The discrete ordinate method with 12 ordinate directions is used to predict the radiative heat transfer in the OMV combustion chamber, nozzle, and the heat shield. The hypergolic reaction between MMH and NTO is predicted using an equilibrium chemistry model with 13 species. The results indicate that mixing and combustion is very sensitive to the droplet size. Smaller droplets evaporate faster than bigger droplets, leading to a well mixed zone in the combustion chamber. The radiative heat flux at combustion chamber and nozzle walls are an order of negligible less than the conductive heat flux. Simulations performed with the heat shield show that a negligible amount of fluid is entrained into the heat shield region. However, the heat shield is shown to be effective in protecting the OMV structure surrounding the engine from the radiated heat.

  2. Effects of inlet distortion on gas turbine combustion chamber exit temperature profiles

    NASA Astrophysics Data System (ADS)

    Maqsood, Omar Shahzada

    Damage to a nozzle guide vane or blade, caused by non-uniform temperature distributions at the combustion chamber exit, is deleterious to turbine performance and can lead to expensive and time consuming overhaul and repair. A test rig was designed and constructed for the Allison 250-C20B combustion chamber to investigate the effects of inlet air distortion on the combustion chamber's exit temperature fields. The rig made use of the engine's diffuser tubes, combustion case, combustion liner, and first stage nozzle guide vane shield. Rig operating conditions simulated engine cruise conditions, matching the quasi-non-dimensional Mach number, equivalence ratio and Sauter mean diameter. The combustion chamber was tested with an even distribution of inlet air and a 4% difference in airflow at either side. An even distribution of inlet air to the combustion chamber did not create a uniform temperature profile and varying the inlet distribution of air exacerbated the profile's non-uniformity. The design of the combustion liner promoted the formation of an oval-shaped toroidal vortex inside the chamber, creating localized hot and cool sections separated by 90° that appeared in the exhaust. Uneven inlet air distributions skewed the oval vortex, increasing the temperature of the hot section nearest the side with the most mass flow rate and decreasing the temperature of the hot section on the opposite side. Keywords: Allison 250, Combustion, Dual-Entry, Exit Temperature Profile, Gas Turbine, Pattern Factor, Reverse Flow.

  3. Thermodynamics and combustion modeling

    NASA Technical Reports Server (NTRS)

    Zeleznik, Frank J.

    1986-01-01

    Modeling fluid phase phenomena blends the conservation equations of continuum mechanics with the property equations of thermodynamics. The thermodynamic contribution becomes especially important when the phenomena involve chemical reactions as they do in combustion systems. The successful study of combustion processes requires (1) the availability of accurate thermodynamic properties for both the reactants and the products of reaction and (2) the computational capabilities to use the properties. A discussion is given of some aspects of the problem of estimating accurate thermodynamic properties both for reactants and products of reaction. Also, some examples of the use of thermodynamic properties for modeling chemically reacting systems are presented. These examples include one-dimensional flow systems and the internal combustion engine.

  4. SSME Main Combustion Chamber (MCC) hot oil dewaxing

    NASA Technical Reports Server (NTRS)

    Akpati, Anthony U.

    1995-01-01

    In an attempt to comply with the changing environmental regulations, a process was developed for the replacement of perchloroethylene in the dewaxing of the Space Shuttle Main Engine (SSME) Main Combustion Chamber (MCC) and other associated hardware filled with the Rigidax (R) casting compound. Rigidax (R) is a hard blue-dyed, calcium carbonate filled thermoplastic casting compound (melting point 77 C) that is melted and poured into hardware cavities to prevent contamination during material removal processes, i.e. machining, grinding, drilling, and deburring. Additionally, it serves as a maskant for designated areas during electroforming processes. Laboratory testing was conducted to evaluate seven alternate fluids for the replacement of perchloroethylene in the dewaxing process. Based upon successful laboratory results, a mineral oil was selected for testing on actual hardware. The final process developed involves simultaneous immersion and flushing of the MCC channels using a distinct eight stage process. A nonvolatile hydrocarbon analysis of a solvent flush sample is performed to determine the hardware cleanliness for comparison to the previous perchloroethylene dewaxing process.

  5. SSME Main Combustion Chamber (MCC) 'Hot Oil' Dewaxing

    NASA Technical Reports Server (NTRS)

    Akpati, Anthony U.

    1994-01-01

    In an attempt to comply with the changing environmental regulations, a process was developed for the replacement of perchloroethylene in the dewaxing of the Space Shuttle Main Engine (SSME) Main Combustion Chamber (MCC) and other associated hardware filled with the Rigidax(registered mark) casting compound. Rigidax(registered mark) is a hard blue-dyed, calcium carbonate filled thermoplastic casting compound (melting point 77 C) that is melted and poured into hardware cavities to prevent contamination during material removal processes, i.e. machining, grinding, drilling, and deburring. Additionally, it serves as a maskant for designated areas during electroforming processes. Laboratory testing was conducted to evaluate seven alternate fluids for the replacement of perchloroethylene in the dewaxing process. Based upon successful laboratory results, a mineral oil was selected for testing on actual hardware. The final process developed involves simultaneous immersion and flushing of the MCC channels using a distinct eight stage process. A nonvolatile hydrocarbon analysis of a solvent flush sample is performed to determine the hardware cleanliness for comparison to the previous perchloroethylene dewaxing process.

  6. Combustion-chamber Performance Characteristics of a Python Turbine-propeller Engine Investigated in Altitude Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Campbell, Carl E

    1951-01-01

    Combustion-chamber performance characteristics of a Python turbine-propeller engine were determined from investigation of a complete engine over a range of engine speeds and shaft horsepowers at simulated altitudes. Results indicated the effect of engine operating conditions and altitude on combustion efficiency and combustion-chamber total pressure losses. Performance of this vaporizing type combustion chamber was also compared with several atomizing type combustion chambers. Over the range of test conditions investigated, combustion efficiency varied from approximately 0.95 to 0.99.

  7. Fluids and Combustion Facility: Combustion Integrated Rack Modal Model Correlation

    NASA Technical Reports Server (NTRS)

    McNelis, Mark E.; Suarez, Vicente J.; Sullivan, Timothy L.; Otten, Kim D.; Akers, James C.

    2005-01-01

    The Fluids and Combustion Facility (FCF) is a modular, multi-user, two-rack facility dedicated to combustion and fluids science in the US Laboratory Destiny on the International Space Station. FCF is a permanent facility that is capable of accommodating up to ten combustion and fluid science investigations per year. FCF research in combustion and fluid science supports NASA's Exploration of Space Initiative for on-orbit fire suppression, fire safety, and space system fluids management. The Combustion Integrated Rack (CIR) is one of two racks in the FCF. The CIR major structural elements include the International Standard Payload Rack (ISPR), Experiment Assembly (optics bench and combustion chamber), Air Thermal Control Unit (ATCU), Rack Door, and Lower Structure Assembly (Input/Output Processor and Electrical Power Control Unit). The load path through the rack structure is outlined. The CIR modal survey was conducted to validate the load path predicted by the CIR finite element model (FEM). The modal survey is done by experimentally measuring the CIR frequencies and mode shapes. The CIR model was test correlated by updating the model to represent the test mode shapes. The correlated CIR model delivery is required by NASA JSC at Launch-10.5 months. The test correlated CIR flight FEM is analytically integrated into the Shuttle for a coupled loads analysis of the launch configuration. The analysis frequency range of interest is 0-50 Hz. A coupled loads analysis is the analytical integration of the Shuttle with its cargo element, the Mini Payload Logistics Module (MPLM), in the Shuttle cargo bay. For each Shuttle launch configuration, a verification coupled loads analysis is performed to determine the loads in the cargo bay as part of the structural certification process.

  8. Numerical investigation of a helicopter combustion chamber using LES and tabulated chemistry

    NASA Astrophysics Data System (ADS)

    Auzillon, Pierre; Riber, Eléonore; Gicquel, Laurent Y. M.; Gicquel, Olivier; Darabiha, Nasser; Veynante, Denis; Fiorina, Benoît

    2013-01-01

    This article presents Large Eddy Simulations (LES) of a realistic aeronautical combustor device: the chamber CTA1 designed by TURBOMECA. Under nominal operating conditions, experiments show hot spots observed on the combustor walls, in the vicinity of the injectors. These high temperature regions disappear when modifying the fuel stream equivalence ratio. In order to account for detailed chemistry effects within LES, the numerical simulation uses the recently developed turbulent combustion model F-TACLES (Filtered TAbulated Chemistry for LES). The principle of this model is first to generate a lookup table where thermochemical variables are computed from a set of filtered laminar unstrained premixed flamelets. To model the interactions between the flame and the turbulence at the subgrid scale, a flame wrinkling analytical model is introduced and the Filtered Density Function (FDF) of the mixture fraction is modeled by a ? function. Filtered thermochemical quantities are stored as a function of three coordinates: the filtered progress variable, the filtered mixture fraction and the mixture fraction subgrid scale variance. The chemical lookup table is then coupled with the LES using a mathematical formalism that ensures an accurate prediction of the flame dynamics. The numerical simulation of the CTA1 chamber with the F-TACLES turbulent combustion model reproduces fairly the temperature fields observed in experiments. In particular the influence of the fuel stream equivalence ratio on the flame position is well captured.

  9. Vacuum Plasma Spray Forming of Copper Alloy Liners for Regeneratively Cooled Liquid Rocket Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2003-01-01

    Vacuum plasma spray (VPS) has been demonstrated as a method to form combustion chambers from copper alloys NARloy-Z and GRCop-84. Vacuum plasma spray forming is of particular interest in the forming of CuCrNb alloys such as GRCop-84, developed by NASA s Glenn Research Center, because the alloy cannot be formed using conventional casting and forging methods. This limitation is related to the levels of chromium and niobium in the alloy, which exceed the solubility limit in copper. Until recently, the only forming process that maintained the required microstructure of CrNb intermetallics was powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. This paper discusses the techniques used to form combustion chambers from CuCrNb and NARloy-Z, which will be used in regeneratively cooled liquid rocket combustion chambers.

  10. Trapped Vortex Combustion Chamber: Design and Experimental Investigations Using Hydrogen as Fuel

    NASA Astrophysics Data System (ADS)

    Kulshreshtha, D. B.; Channiwala, S. A.

    2014-01-01

    The design of trapped vortex combustion chamber was undertaken as a part of ongoing research on micro combustion chamber using hydrogen as fuel. The reacting experimental studies were then carried out on the designed chamber. The fuel was injected directly into the cavity. The combustion was first initiated in the cavity with 3 % of the main flow air supplied in reverse direction to the fuel flow. The combustion in cavity was of rich type. Temperature levels in the range of 900 K were encountered in the cavity. Thereafter, diffusion combustion was initiated using the flame generated in the cavity. The temperature levels in this stage were in the range of 1,800 K. The overall pressure drop for a trapped vortex combustor was less than 5 % at all operating parameters.

  11. Redesign and Test of an SSME Turbopump for the Large Throat Main Combustion Chamber

    NASA Technical Reports Server (NTRS)

    Lunde, K. J.; Lee, G. A.; Eastland, A. H.; Rojas, L.

    1994-01-01

    The preburner oxidizer turbopump for the Space Shuttle Main Engine (SSME) was successfully redesigned for use with the Large Throat Main Combustion Chamber (LTMCC) and tested in air utilizing rapid prototyping. The redesign increases the SSME's operating range with the current Main Combustion Chamber (MCC) while achieving full operational range with the LTMCC. The use of rapid prototyping and air testing to validate the redesign demonstrated the ability to design, fabricate and test designs rapidly and at a very low cost.

  12. An Extended Combustion Model for the Aircraft Turbojet Engine

    NASA Astrophysics Data System (ADS)

    Rotaru, Constantin; Andres-Mih?il?, Mihai; Matei, Pericle Gabriel

    2014-08-01

    The paper consists in modelling and simulation of the combustion in a turbojet engine in order to find optimal characteristics of the burning process and the optimal shape of combustion chambers. The main focus of this paper is to find a new configuration of the aircraft engine combustion chambers, namely an engine with two main combustion chambers, one on the same position like in classical configuration, between compressor and turbine and the other, placed behind the turbine but not performing the role of the afterburning. This constructive solution could allow a lower engine rotational speed, a lower temperature in front of the first stage of the turbine and the possibility to increase the turbine pressure ratio by extracting the flow stream after turbine in the inner nozzle. Also, a higher thermodynamic cycle efficiency and thrust in comparison to traditional constant-pressure combustion gas turbine engines could be obtained.

  13. Development and application of noninvasive technology for study of combustion in a combustion chamber of gas turbine engine

    NASA Astrophysics Data System (ADS)

    Inozemtsev, A. A.; Sazhenkov, A. N.; Tsatiashvili, V. V.; Abramchuk, T. V.; Shipigusev, V. A.; Andreeva, T. P.; Gumerov, A. R.; Ilyin, A. N.; Gubaidullin, I. T.

    2015-05-01

    The paper formulates the issue of development of experimental base with noninvasive optical-electronic tools for control of combustion in a combustion chamber of gas turbine engine. The design and specifications of a pilot sample of optronic system are explained; this noninvasive system was created in the framework of project of development of main critical technologies for designing of aviation gas turbine engine PD-14. The testbench run data are presented.

  14. A review of internal combustion engine combustion chamber process studies at NASA Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Schock, H. J.

    1984-01-01

    The performance of internal combustion stratified-charge engines is highly dependent on the in-cylinder fuel-air mixing processes occurring in these engines. Current research concerning the in-cylinder airflow characteristics of rotary and piston engines is presented. Results showing the output of multidimensional models, laser velocimetry measurements and the application of a holographic optical element are described. Models which simulate the four-stroke cycle and seal dynamics of rotary engines are also discussed.

  15. Chamber Clearing First Principles Modeling

    SciTech Connect

    Loosmore, G

    2009-06-09

    LIFE fusion is designed to generate 37.5 MJ of energy per shot, at 13.3 Hz, for a total average fusion power of 500 MW. The energy from each shot is partitioned among neutrons ({approx}78%), x-rays ({approx}12%), and ions ({approx}10%). First wall heating is dominated by x-rays and debris because the neutron mean free path is much longer than the wall thickness. Ion implantation in the first wall also causes damage such as blistering if not prevented. To moderate the peak-pulse heating, the LIFE fusion chamber is filled with a gas (such as xenon) to reduce the peak-pulse heat load. The debris ions and majority of the x-rays stop in the gas, which re-radiates this energy over a longer timescale (allowing time for heat conduction to cool the first wall sufficiently to avoid damage). After a shot, because of the x-ray and ion deposition, the chamber fill gas is hot and turbulent and contains debris ions. The debris needs to be removed. The ions increase the gas density, may cluster or form aerosols, and can interfere with the propagation of the laser beams to the target for the next shot. Moreover, the tritium and high-Z hohlraum debris needs to be recovered for reuse. Additionally, the cryogenic target needs to survive transport through the gas mixture to the chamber center. Hence, it will be necessary to clear the chamber of the hot contaminated gas mixture and refill it with a cool, clean gas between shots. The refilling process may create density gradients that could interfere with beam propagation, so the fluid dynamics must be studied carefully. This paper describes an analytic modeling effort to study the clearing and refilling process for the LIFE fusion chamber. The models used here are derived from first principles and balances of mass and energy, with the intent of providing a first estimate of clearing rates, clearing times, fractional removal of ions, equilibrated chamber temperatures, and equilibrated ion concentrations for the chamber. These can be used to scope the overall problem and provide input to further studies using fluid dynamics and other more sophisticated tools.

  16. Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

    The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners while maintaining the superior CuCrNb properties are also presented.

  17. The next step in chemical propulsion: Oxide-iridium/rhenium combustion chambers

    SciTech Connect

    Fortini, Arthur J.; Tuffias, Robert H.

    1999-01-22

    Chemical propulsion systems are currently limited by materials issues. Until recently, the state-of-the-art material for liquid propellant combustion chambers was silicide-coated niobium. However, combustion chamber performance demands have exceeded the capabilities of this material system, requiring development of better materials. The iridium/rhenium combustion chamber, comprising a rhenium structural shell with an iridium inner liner for oxidation protection, represents the current state of the art in high-performance, high temperature, long-life propulsion systems using nitrogen tetroxide/monomethyl hydrazine propellant. However, oxygen/hydrogen (O{sub 2}/H{sub 2}) and new 'green' monopropellants under development to replace hydrazine will be significantly more oxidizing at operating temperature. For these more highly aggressive combustion environments, Ultramet has shown that substantial additional life can be obtained by lining the interior of the combustion chamber with a refractory metal oxide, which functions as a thermal and gas diffusion barrier and provides dramatically increased oxidation resistance. Ultramet has fabricated numerous 22-N (5-lb{sub f}) thrust chambers with this oxide-iridium/rhenium architecture that have been hot-fire tested at NASA Lewis Research Center in O{sub 2}/H{sub 2} propellant at mixture ratios of 6 and 16, with steady-state exterior wall temperatures ranging from 2433 to 2899 K, comprising the most severe temperature and oxidizing conditions ever utilized. Of the seven chambers tested to date, three failed due to facility problems, and two never failed. The best-performing chamber was hot-fired for 13,595 seconds (227 minutes; 3.8 hours) and showed no visible signs of degradation. Additional chambers are being fabricated for future testing.

  18. A review of internal combustion engine combustion chamber process studies at NASA Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Schock, H. J.

    1984-01-01

    The performance of internal combustion stratified-charge engines is highly dependent on the in-cylinder fuel-air mixing processes occurring in these engines. Current research concerning the in-cylinder airflow characteristics of rotary and piston engines is presented. Results showing the output of multidimensional models, laser velocimetry measurements and the application of a holographic optical element are described. Models which simulate the four-stroke cycle and seal dynamics of rotary engines are also discussed. Previously announced in STAR as N84-24999

  19. Two-phase flow predictions of the turbulent flow in a combustion chamber including particle-particle interactions

    NASA Astrophysics Data System (ADS)

    Breuer, Michael; Alletto, Michael

    2011-12-01

    Relying on large-eddy simulation (LES) and an efficient algorithm to track a huge number of Lagrangian particles through turbulent flow fields in general complex 3D domains, the flow in a pipe and a model combustion chamber is tackled. The influence of particle-fluid (two-way coupling) as well as particle-particle interactions (four-way coupling) is investigated. The latter is modeled based on deterministic collision detection. First, the LES results of a particle-laden vertical pipe flow with a specular wall and a mass loading of 110% are evaluated based on DNS data from the literature. Second, the predicted LES data of a ring combustion chamber at two different mass loadings (22% and 110%) are analyzed and compared with experimental measurements.

  20. The effect of insulated combustion chamber surfaces on direct-injected diesel engine performance, emissions, and combustion

    NASA Technical Reports Server (NTRS)

    Dickey, Daniel W.; Vinyard, Shannon; Keribar, Rifat

    1988-01-01

    The combustion chamber of a single-cylinder, direct-injected diesel engine was insulated with ceramic coatings to determine the effect of low heat rejection (LHR) operation on engine performance, emissions, and combustion. In comparison to the baseline cooled engine, the LHR engine had lower thermal efficiency, with higher smoke, particulate, and full load carbon monoxide emissions. The unburned hydrocarbon emissions were reduced across the load range. The nitrous oxide emissions increased at some part-load conditions and were reduced slightly at full loads. The poor LHR engine performance was attributed to degraded combustion characterized by less premixed burning, lower heat release rates, and longer combustion duration compared to the baseline cooled engine.

  1. Numerical analysis of bipropellant combustion in liquid thrust chambers by an Eulerian-Eulerian approach

    NASA Technical Reports Server (NTRS)

    Dang, A. L.; Navaz, H. K.; Rangel, R. H.

    1992-01-01

    The liquid thrust chambers performance (LTCP) code is used for parametric studies of flow and combustion in liquid rocket engines. Multiphase flow equations are solved in an Eulerian-Eulerian framework, and multistep finite rate chemistry is incorporated. The discretization scheme is fully implicit and is based on the total variation diminishing (TVD) scheme, which is accurate, robust, very efficient and capable of handling steep gradients and stiff chemistry. Effects of injection velocity and chamber size have been considered, and the effect of group combustion on the evaporation rate has been studied for a dense spray.

  2. Hydrocarbon-fuel/copper combustion chamber liner compatibility, corrosion prevention, and refurbishment

    NASA Technical Reports Server (NTRS)

    Rosenberg, S. D.; Gage, M. L.; Homer, G. D.; Franklin, J. E.

    1991-01-01

    An evaluation is made of combustion product/combustion chamber compatibility in the case of a LOX/liquid hydrocarbon booster engine based on copper-alloy thrust chamber which is regeneratively cooled by the fuel. It is found that sulfur impurities in the fuel are the primary causes of copper corrosion, through formation of Cu2S; sulfur levels as low as 1 ppm can result in sufficiently severe copper corrosion to degrade cooling channel performance. This corrosion can be completely eliminated, however, through the incorporation of an electrodeposited gold coating on the copper cooling-channel walls.

  3. Novel application of a combustion chamber for experimental assessment of biomass burning emission

    NASA Astrophysics Data System (ADS)

    Lusini, Ilaria; Pallozzi, E.; Corona, P.; Ciccioli, P.; Calfapietra, C.

    2014-09-01

    Biomass burning is an important ecological factor in the Mediterranean ecosystem and a significant source of several atmospheric gases and particles. This paper demonstrates the performance of a recently developed combustion chamber, showing its capability in estimating the emission from wildland fire through a case study with dried leaf litter of Quercus robur. The combustion chamber was equipped with a thermocouple, a high resolution balance, an epiradiometer, two different sampling lines to collect volatile organic compounds (VOCs) and particles, and a portable analyzer to measure carbon monoxide (CO) and carbon dioxide (CO2) emission. VOCs were determined by gas chromatography-mass spectrometry (GC-MS) after enrichment on adsorption traps, but also monitored on-line with a proton-transfer-reaction mass spectrometer (PTR-MS). Preliminary qualitative analyses of emissions from burning dried leaf litter of Q. robur found CO and CO2 as the main gaseous species emitted during the flaming and smoldering stages. Aromatic VOCs, such as benzene and toluene, were detected together with several oxygenated VOCs, like acetaldehyde and methanol. Moreover, a clear picture of the carbon balance during the biomass combustion was obtained with the chamber used. The combustion chamber will allow to distinguish the contribution of different plant tissues to the emissions occurring during different combustion phases.

  4. Influence of the Structure of a Solid-Fuel Mixture on the Thermal Efficiency of the Combustion Chamber of an Engine System

    NASA Astrophysics Data System (ADS)

    Futko, S. I.; Koznacheev, I. A.; Ermolaeva, E. M.

    2014-11-01

    On the basis of thermodynamic calculations, the features of the combustion of a solid-fuel mixture based on the glycidyl azide polymer were investigated, the thermal cycle of the combustion chamber of a model engine system was analyzed, and the efficiency of this chamber was determined for a wide range of pressures in it and different ratios between the components of the combustible mixture. It was established that, when the pressure in the combustion chamber of an engine system increases, two maxima arise successively on the dependence of the thermal efficiency of the chamber on the weight fractions of the components of the combustible mixture and that the first maximum shifts to the side of smaller concentrations of the glycidyl azide polymer with increase in the pressure in the chamber; the position of the second maximum is independent of this pressure, coincides with the minimum on the dependence of the rate of combustion of the mixture, and corresponds to the point of its structural phase transition at which the mole fractions of the carbon and oxygen atoms in the mixture are equal. The results obtained were interpreted on the basis of the Le-Chatelier principle.

  5. Low-cycle fatigue analysis of a cooled copper combustion chamber

    NASA Technical Reports Server (NTRS)

    Miller, R. W.

    1974-01-01

    A three-dimensional finite element elastoplastic strain analysis was performed for the throat section of regeneratively cooled rocket engine combustion chamber. The analysis included thermal and pressure loads, and the effects of temperature dependent material properties, to determine the strain range corresponding to the engine operating cycle. The strain range was used in conjunction with OFHC copper isothermal fatigue test data to predict engine low-cycle fatigue life. The analysis was performed for chamber configuration and operating conditions corresponding to a hydrogen-oxygen chamber which was fatigue tested to failure at the NASA Lewis Research Center.

  6. Numerical analysis of bipropellant combustion in orbit maneuvering vehicle thrust chamber

    NASA Technical Reports Server (NTRS)

    Chiu, H. H.; Jiang, T. L.; Krebsback, A. N.; Gross, K. W.

    1990-01-01

    The combustion and aerodynamic processes of liquid-liquid bipropellant; monomethylhydrazine and nitrogen tetroxide in the combustion chamber of a variable thrust engine (VTE) have been examined to assess the flow structure, combustion characteristics, and wall heat transfer under the simulated engine operations at two power levels. The Generalized Elliptic Multi-phase flow with Chemical reaction, Heat transfer and Interfacial Processes (GEM-CHIP) code and the Bipropellant Combustion (BICOMB) code, which is the GEMCHIP algorithm reformulated in the frame work of a body fitted coordinate system, have been used for the numerical study. Combustion flow structure with non-premixed type injection that simulates the impingement type injector is predicted and the results are compared with that of the premixed injector.

  7. Fundamental criteria for the better design of secondary combustion chambers

    SciTech Connect

    Sacchi, G.F.; Lee, Tai-Gyu; Longwell, J.P.

    1995-10-01

    The major concern regarding organic emissions from hazardous waste incineration systems is the formation of products of incomplete combustion (PICs). The toxic and, possibly, mutagenic character of these compounds represents one of the major problems to public acceptance of incineration as a safe waste disposal technology. Ongoing studies at MIT, sponsored by the US EPA Northeast Hazardous Substance Research Center (NHSRC), have shed light on the mechanisms of formation and emission of PICs, showing that the formation of PICs is highly dependent upon the local ratio of fuel and oxidant, and their amount and composition are sensitive to both turbulent mixing and chemical kinetic constraints. A recent critical review on incineration science and technology, presented as a plenary lecture at the XXV International Symposium on Combustion by J.O.L. Wendt of University of Arizona, has clearly encouraged the scientific community to focus on turbulent mixing, rather than kinetics alone, in order to reach the goal of controlling and minimizing PIC emission from incinerators. Also, it has shown that PIC emissions are closely related to transient phenomena (as rogue droplets formation caused by poor atornization, formation of puffs in kilns, fluctuations in feed rate and composition, etc.) which lead to failure modes tied to incomplete mixing. The current approach followed at MIT during the NHSRC-sponsored project thus seems to be very promising in giving a correct interpretation of the complex mechanisms involved in PIC formation, and in providing useful application of combustion science to incineration technology.

  8. 46 CFR 59.15-5 - Stayed furnaces and combustion chambers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...the four staybolts. (b) Where it is desired to rivet a patch to the wall of a stayed furnace or combustion chamber, the...plate shall be cut away until solid material is reached, the patch shall be riveted on the waterside, and the staybolts...

  9. 46 CFR 59.15-5 - Stayed furnaces and combustion chambers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...the four staybolts. (b) Where it is desired to rivet a patch to the wall of a stayed furnace or combustion chamber, the...plate shall be cut away until solid material is reached, the patch shall be riveted on the waterside, and the staybolts...

  10. 46 CFR 59.15-5 - Stayed furnaces and combustion chambers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...the four staybolts. (b) Where it is desired to rivet a patch to the wall of a stayed furnace or combustion chamber, the...plate shall be cut away until solid material is reached, the patch shall be riveted on the waterside, and the staybolts...

  11. 46 CFR 59.15-5 - Stayed furnaces and combustion chambers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...the four staybolts. (b) Where it is desired to rivet a patch to the wall of a stayed furnace or combustion chamber, the...plate shall be cut away until solid material is reached, the patch shall be riveted on the waterside, and the staybolts...

  12. 46 CFR 59.15-5 - Stayed furnaces and combustion chambers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...the four staybolts. (b) Where it is desired to rivet a patch to the wall of a stayed furnace or combustion chamber, the...plate shall be cut away until solid material is reached, the patch shall be riveted on the waterside, and the staybolts...

  13. Development of eddy current testing system for inspection of combustion chambers of liquid rocket engines.

    PubMed

    He, D F; Zhang, Y Z; Shiwa, M; Moriya, S

    2013-01-01

    An eddy current testing (ECT) system using a high sensitive anisotropic magnetoresistive (AMR) sensor was developed. In this system, a 20 turn circular coil with a diameter of 3 mm was used to produce the excitation field. A high sensitivity AMR sensor was used to measure the magnetic field produced by the induced eddy currents. A specimen made of copper alloy was prepared to simulate the combustion chamber of liquid rocket. Scanning was realized by rotating the chamber with a motor. To reduce the influence of liftoff variance during scanning, a dual frequency excitation method was used. The experimental results proved that ECT system with an AMR sensor could be used to check liquid rocket combustion chamber. PMID:23387673

  14. Coal-feeding mechanism for a fluidized bed combustion chamber

    DOEpatents

    Gall, Robert L. (Morgantown, WV)

    1981-01-01

    The present invention is directed to a fuel-feeding mechanism for a fluidized bed combustor. In accordance with the present invention a perforated conveyor belt is utilized in place of the fixed grid normally disposed at the lower end of the fluidized bed combustion zone. The conveyor belt is fed with fuel, e.g. coal, at one end thereof so that the air passing through the perforations dislodges the coal from the belt and feeds the coal into the fluidized zone in a substantially uniform manner.

  15. Hypergolic bipropellant spray combustion and flow modelling in rocket engines

    NASA Technical Reports Server (NTRS)

    Larosiliere, Louis M.; Litchford, Ron J.; Jeng, San-Mou

    1990-01-01

    A predictive tool for hypergolic bipropellant spray combustion and flow evolution in small rocket combustion chambers is described. It encompasses a computational technique for the gas-phase governing equations, a discrete particle method for liquid bipropellant sprays, and constitutive models for combustion chemistry, interphase exchanges, and unlike impinging hypergolic spray interactions. Emphasis is placed on the phenomenological modeling of the hypergolic liquid bipropellant gasification processes. Sample computations with the N2H4-N2O4 propellant system are given in order to show some of the capabilities and inadequacies of this tool.

  16. Experimental and Numerical Research of a Novel Combustion Chamber for Small Gas Turbine Engines

    NASA Astrophysics Data System (ADS)

    Tuma, J.; Kubata, J.; Betak, V.; Hybl, R.

    2013-04-01

    New combustion chamber concept (based on burner JETIS-JET Induced Swirl) for small gas turbine engine (up to 200kW) is presented in this article. The combustion chamber concept is based on the flame stabilization by the generated swirl swirl generated by two opposite tangentially arranged jet tubes in the intermediate zone, this arrangement replaces air swirler, which is very complicated and expensive part in the scope of small gas turbines with annular combustion chamber. The mixing primary jets are oriented partially opposite to the main exhaust gasses flow, this enhances hot product recirculation and fuel-air mixing necessary for low NOx production and flame stability. To evaluate the designed concept a JETIS burner demonstrator (methane fuel) was manufactured and atmospheric experimental measurements of CO, NOx for various fuel nozzles and jet tubes the configuration were done. Results of these experiments and comparison with CFD simulation are presented here. Practical application of the new chamber concept in small gas turbine liquid fuel combustor was evaluated (verified) on 3 nozzles planar combustor sector test rig at atmospheric conditions results of the experiment and numerical simulation are also presented.

  17. High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner For Advanced Rocket Engines

    NASA Technical Reports Server (NTRS)

    Bhat, Biliyar N.; Ellis, David; Singh, Jogender

    2014-01-01

    Advanced high thermal conductivity materials research conducted at NASA Marshall Space Flight Center (MSFC) with state of the art combustion chamber liner material NARloy-Z showed that its thermal conductivity can be increased significantly by adding diamond particles and sintering it at high temperatures. For instance, NARloy-Z containing 40 vol. percent diamond particles, sintered at 975C to full density by using the Field assisted Sintering Technology (FAST) showed 69 percent higher thermal conductivity than baseline NARloy-Z. Furthermore, NARloy-Z-40vol. percent D is 30 percent lighter than NARloy-Z and hence the density normalized thermal conductivity is 140 percent better. These attributes will improve the performance and life of the advanced rocket engines significantly. By one estimate, increased thermal conductivity will directly translate into increased turbopump power up to 2X and increased chamber pressure for improved thrust and ISP, resulting in an expected 20 percent improvement in engine performance. Follow on research is now being conducted to demonstrate the benefits of this high thermal conductivity NARloy-Z-D composite for combustion chamber liner applications in advanced rocket engines. The work consists of a) Optimizing the chemistry and heat treatment for NARloy-Z-D composite, b) Developing design properties (thermal and mechanical) for the optimized NARloy-Z-D, c) Fabrication of net shape subscale combustion chamber liner, and d) Hot fire testing of the liner for performance. FAST is used for consolidating and sintering NARlo-Z-D. The subscale cylindrical liner with built in channels for coolant flow is also fabricated near net shape using the FAST process. The liner will be assembled into a test rig and hot fire tested in the MSFC test facility to determine performance. This paper describes the development of this novel high thermal conductivity NARloy-Z-D composite material, and the advanced net shape technology to fabricate the combustion chamber liner. Properties of optimized NARloy-Z-D composite material will also be presented.

  18. Robust Low Cost Aerospike/RLV Combustion Chamber by Advanced Vacuum Plasma Process

    NASA Technical Reports Server (NTRS)

    Holmes, Richard; Ellis, David; McKechnie

    1999-01-01

    Next-generation, regeneratively cooled rocket engines will require materials that can withstand high temperatures while retaining high thermal conductivity. At the same time, fabrication techniques must be cost efficient so that engine components can be manufactured within the constraints of a shrinking NASA budget. In recent years, combustion chambers of equivalent size to the Aerospike chamber have been fabricated at NASA-Marshall Space Flight Center (MSFC) using innovative, relatively low-cost, vacuum-plasma-spray (VPS) techniques. Typically, such combustion chambers are made of the copper alloy NARloy-Z. However, current research and development conducted by NASA-Lewis Research Center (LeRC) has identified a Cu-8Cr-4Nb alloy which possesses excellent high-temperature strength, creep resistance, and low cycle fatigue behavior combined with exceptional thermal stability. In fact, researchers at NASA-LeRC have demonstrated that powder metallurgy (P/M) Cu-8Cr-4Nb exhibits better mechanical properties at 1,200 F than NARloy-Z does at 1,000 F. The objective of this program was to develop and demonstrate the technology to fabricate high-performance, robust, inexpensive combustion chambers for advanced propulsion systems (such as Lockheed-Martin's VentureStar and NASA's Reusable Launch Vehicle, RLV) using the low-cost, VPS process to deposit Cu-8Cr-4Nb with mechanical properties that match or exceed those of P/M Cu-8Cr-4Nb. In addition, oxidation resistant and thermal barrier coatings can be incorporated as an integral part of the hot wall of the liner during the VPS process. Tensile properties of Cu-8Cr-4Nb material produced by VPS are reviewed and compared to material produced previously by extrusion. VPS formed combustion chamber liners have also been prepared and will be reported on following scheduled hot firing tests at NASA-Lewis.

  19. Combustion modeling in waste tanks

    SciTech Connect

    Mueller, C.; Unal, C.; Travis, J.R. |

    1997-08-01

    This paper has two objectives. The first one is to repeat previous simulations of release and combustion of flammable gases in tank SY-101 at the Hanford reservation with the recently developed code GASFLOW-II. The GASFLOW-II results are compared with the results obtained with the HMS/TRAC code and show good agreement, especially for non-combustion cases. For combustion GASFLOW-II predicts a steeper pressure rise than HMS/TRAC. The second objective is to describe a so-called induction parameter model which was developed and implemented into GASFLOW-II and reassess previous calculations of Bureau of Mines experiments for hydrogen-air combustion. The pressure time history improves compared with the one-step model, and the time rate of pressure change is much closer to the experimental data.

  20. Lean stability augmentation study. [on gas turbine combustion chambers

    NASA Technical Reports Server (NTRS)

    Mcvey, J. B.; Kennedy, J. B.

    1979-01-01

    An analytical conceptual design study and an experimental test program were conducted to investigate techniques and develop technology for improving the lean combustion limits of premixing, prevaporizing combustors applicable to gas turbine engine main burners. The use of hot gas pilots, catalyzed flameholder elements, and heat recirculation to augment lean stability limits was considered in the conceptual design study. Tests of flameholders embodying selected concepts were conducted at a pressure of 10 arm and over a range of entrance temperatures simulating conditions to be encountered during stratospheric cruise. The tests were performed using an axisymmetric flametube test rig having a nominal diameter of 10.2 cm. A total of sixteen test configurations were examined in which lean blowout limits, pollutant emission characteristics, and combustor performance were evaluated. The use of a piloted perforated plate flameholder employing a pilot fuel flow rate equivalent to 4 percent of the total fuel flow at a simulated cruise condition resulted in a lean blowout equivalence ratio of less than 0.25 with a design point (T sub zero = 600k, Phi = 0.6) NOx emission index of less than 1.0 g/kg.

  1. The N.A.C.A. Combustion Chamber Gas-sampling Valve and Some Preliminary Test Results

    NASA Technical Reports Server (NTRS)

    Spanogle, J A; Buckley, E C

    1933-01-01

    A gas sampling valve of the inertia-operated type was designed for procuring samples of the gases in the combustion chamber of internal combustion engines at identical points in successive cycles so that the analysis of the gas samples thus procured may aid in the study of the process of combustion. The operation of the valve is described. The valve was used to investigate the CO2 content of gases taken from the quiescent combustion chamber of a high speed compression-ignition engine when operating with two different multiple-orifice fuel injection nozzles. An analysis of the gas samples thus obtained shows that the state of quiescence in the combustion chamber is maintained during the combustion of the fuel.

  2. Hydrocarbon-fuel/combustion-chamber-liner materials compatibility

    NASA Technical Reports Server (NTRS)

    Homer, G. David

    1991-01-01

    The results of dynamic tests using methane and NASA-Z copper test specimen under conditions that simulate those expected in the cooling channels of a regeneratively cooled LOX/hydrocarbon booster engine operating at chamber pressures up to 3000 psi are presented. Methane with less than 0.5 ppm sulfur contamination has little or no effect on cooling channel performance. At higher sulfur concentrations, severe corrosion of the NASA-Z copper alloy occurs and the cuprous sulfide Cu2S, thus formed impedes mass flow rate and heat transfer efficiency. Therefore, it is recommended that the methane specification for this end use set the allowable sulfur content at 0.5 ppm (max). Bulk high purity liquid methane that meets this low sulfur requirement is currently available from only one producer. Pricing, availability, and quality assurance are discussed in detail. Additionally, it was found that dilute sodium cyanide solutions effectively refurbish sulfur corroded cooling channels in only 2 to 5 minutes by completely dissolving all the Cu2S. Sulfur corroded/sodium cyanide refurbished channels are highly roughened and the increased surface roughness leads to significant improvements in heat transfer efficiency with an attendant loss in mass flow rate. Both the sulfur corrosion and refurbishment effects are discussed in detail.

  3. Modeling of microgravity combustion experiments

    NASA Technical Reports Server (NTRS)

    Buckmaster, John

    1995-01-01

    This program started in February 1991, and is designed to improve our understanding of basic combustion phenomena by the modeling of various configurations undergoing experimental study by others. Results through 1992 were reported in the second workshop. Work since that time has examined the following topics: Flame-balls; Intrinsic and acoustic instabilities in multiphase mixtures; Radiation effects in premixed combustion; Smouldering, both forward and reverse, as well as two dimensional smoulder.

  4. Design of a prototype Advanced Main Combustion Chamber for the Space Shuttle Main Engine

    NASA Technical Reports Server (NTRS)

    Lackey, J. D.; Myers, W. N.

    1992-01-01

    Development of a prototype advanced main combustion chamber is underway at NASA Marshall Space Flight Center. The Advanced Main Combustion Chamber (AMCC) project is being approached utilizing a 'concurrent engineering' concept where groups from materials, manufacturing, stress, quality, and design are involved from the initiation of the project. The AMCC design has been tailored to be compatible with the investment casting process. Jacket, inlet/outlet manifolds, inlet/outlet neck coolant flow splitters, support ribs, actuator lugs, and engine controller mounting bracket will all be a part of the one-piece AMCC casting. Casting of the AMCC in a one-piece configuration necessitated a method of forming a liner in its structural jacket. A method of vacuum plasma spraying the liner is being developed. In 1994, the AMCC will be hot-fired on the Technology Test Bed Space Shuttle Main Engine.

  5. Friction Stir Welding of GR-Cop 84 for Combustion Chamber Liners

    NASA Technical Reports Server (NTRS)

    Russell, Carolyn K.; Carter, Robert; Ellis, David L.; Goudy, Richard

    2004-01-01

    GRCop-84 is a copper-chromium-niobium alloy developed by the Glenn Research Center for liquid rocket engine combustion chamber liners. GRCop-84 exhibits superior properties over conventional copper-base alloys in a liquid hydrogen-oxygen operating environment. The Next Generation Launch Technology program has funded a program to demonstrate scale-up production capabilities of GR-Cop 84 to levels suitable for main combustion chamber production for the prototype rocket engine. This paper describes a novel method of manufacturing the main combustion chamber liner. The process consists of several steps: extrude the GR-Cop 84 powder into billets, roll the billets into plates, bump form the plates into cylinder halves and friction stir weld the halves into a cylinder. The cylinder is then metal spun formed to near net liner dimensions followed by finish machining to the final configuration. This paper describes the friction stir weld process development including tooling and non-destructive inspection techniques, culminating in the successful production of a liner preform completed through spin forming.

  6. Chemical kinetics and combustion modeling

    SciTech Connect

    Miller, J.A.

    1993-12-01

    The goal of this program is to gain qualitative insight into how pollutants are formed in combustion systems and to develop quantitative mathematical models to predict their formation rates. The approach is an integrated one, combining low-pressure flame experiments, chemical kinetics modeling, theory, and kinetics experiments to gain as clear a picture as possible of the process in question. These efforts are focused on problems involved with the nitrogen chemistry of combustion systems and on the formation of soot and PAH in flames.

  7. Combustion instability modeling and analysis

    SciTech Connect

    Santoro, R.J.; Yang, V.; Santavicca, D.A.; Sheppard, E.J.

    1995-12-31

    It is well known that the two key elements for achieving low emissions and high performance in a gas turbine combustor are to simultaneously establish (1) a lean combustion zone for maintaining low NO{sub x} emissions and (2) rapid mixing for good ignition and flame stability. However, these requirements, when coupled with the short combustor lengths used to limit the residence time for NO formation typical of advanced gas turbine combustors, can lead to problems regarding unburned hydrocarbons (UHC) and carbon monoxide (CO) emissions, as well as the occurrence of combustion instabilities. The concurrent development of suitable analytical and numerical models that are validated with experimental studies is important for achieving this objective. A major benefit of the present research will be to provide for the first time an experimentally verified model of emissions and performance of gas turbine combustors. The present study represents a coordinated effort between industry, government and academia to investigate gas turbine combustion dynamics. Specific study areas include development of advanced diagnostics, definition of controlling phenomena, advancement of analytical and numerical modeling capabilities, and assessment of the current status of our ability to apply these tools to practical gas turbine combustors. The present work involves four tasks which address, respectively, (1) the development of a fiber-optic probe for fuel-air ratio measurements, (2) the study of combustion instability using laser-based diagnostics in a high pressure, high temperature flow reactor, (3) the development of analytical and numerical modeling capabilities for describing combustion instability which will be validated against experimental data, and (4) the preparation of a literature survey and establishment of a data base on practical experience with combustion instability.

  8. Robust Low Cost Liquid Rocket Combustion Chamber by Advanced Vacuum Plasma Process

    NASA Technical Reports Server (NTRS)

    Holmes, Richard; Elam, Sandra; Ellis, David L.; McKechnie, Timothy; Hickman, Robert; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Next-generation, regeneratively cooled rocket engines will require materials that can withstand high temperatures while retaining high thermal conductivity. Fabrication techniques must be cost efficient so that engine components can be manufactured within the constraints of shrinking budgets. Three technologies have been combined to produce an advanced liquid rocket engine combustion chamber at NASA-Marshall Space Flight Center (MSFC) using relatively low-cost, vacuum-plasma-spray (VPS) techniques. Copper alloy NARloy-Z was replaced with a new high performance Cu-8Cr-4Nb alloy developed by NASA-Glenn Research Center (GRC), which possesses excellent high-temperature strength, creep resistance, and low cycle fatigue behavior combined with exceptional thermal stability. Functional gradient technology, developed building composite cartridges for space furnaces was incorporated to add oxidation resistant and thermal barrier coatings as an integral part of the hot wall of the liner during the VPS process. NiCrAlY, utilized to produce durable protective coating for the space shuttle high pressure fuel turbopump (BPFTP) turbine blades, was used as the functional gradient material coating (FGM). The FGM not only serves as a protection from oxidation or blanching, the main cause of engine failure, but also serves as a thermal barrier because of its lower thermal conductivity, reducing the temperature of the combustion liner 200 F, from 1000 F to 800 F producing longer life. The objective of this program was to develop and demonstrate the technology to fabricate high-performance, robust, inexpensive combustion chambers for advanced propulsion systems (such as Lockheed-Martin's VentureStar and NASA's Reusable Launch Vehicle, RLV) using the low-cost VPS process. VPS formed combustion chamber test articles have been formed with the FGM hot wall built in and hot fire tested, demonstrating for the first time a coating that will remain intact through the hot firing test, and with no apparent wear. Material physical properties and the hot firing tests are reviewed.

  9. Structural Analysis of Combustion Models

    E-print Network

    Tóth, J; Zsély, I

    2013-01-01

    Using ReactionKinetics, a Mathematica based package a few dozen detailed models for combustion of hydrogen, carbon monoxide and methanol are investigated. Essential structural characteristics are pulled out, and similarities and differences of the mechanisms are highlighted. These investigations can be used before or parallel with usual numerical investigations, such as pathway analysis, sensitivity analysis, parameter estimation, or simulation.

  10. Investigation of gaseous propellant combustion and associated injector/chamber design guidelines

    NASA Technical Reports Server (NTRS)

    Calhoon, D. F.; Ito, J. I.; Kors, D. L.

    1973-01-01

    Injector design criteria are provided for gaseous hydrogen-gaseous oxygen propellants. Design equations and procedures are presented which will allow an injector-chamber designer to a priori estimate of the performance, compatibility and stability characteristics of prototype injectors. The effects of chamber length, element geometry, thrust per element, mixture ratio, impingement angle, and element spacing were evaluated for four element concepts and their derivatives. The data from this series of tests were reduced to a single valued mixing function that describes the mixing potential of the various elements. Performance, heat transfer and stability data were generated for various mixture ratios, propellant temperatures, chamber pressures, contraction ratios, and chamber lengths. Applications of the models resulted in the design of procedures, whereby the performance and chamber heat flux can be calculated directly, and the injector stability estimated in conjunction with existing models.

  11. Modeling the internal combustion engine

    NASA Technical Reports Server (NTRS)

    Zeleznik, F. J.; Mcbride, B. J.

    1985-01-01

    A flexible and computationally economical model of the internal combustion engine was developed for use on large digital computer systems. It is based on a system of ordinary differential equations for cylinder-averaged properties. The computer program is capable of multicycle calculations, with some parameters varying from cycle to cycle, and has restart capabilities. It can accommodate a broad spectrum of reactants, permits changes in physical properties, and offers a wide selection of alternative modeling functions without any reprogramming. It readily adapts to the amount of information available in a particular case because the model is in fact a hierarchy of five models. The models range from a simple model requiring only thermodynamic properties to a complex model demanding full combustion kinetics, transport properties, and poppet valve flow characteristics. Among its many features the model includes heat transfer, valve timing, supercharging, motoring, finite burning rates, cycle-to-cycle variations in air-fuel ratio, humid air, residual and recirculated exhaust gas, and full combustion kinetics.

  12. Comparison of High Aspect Ratio Cooling Channel Designs for a Rocket Combustion Chamber

    NASA Technical Reports Server (NTRS)

    Wadel, Mary F.

    1997-01-01

    An analytical investigation on the effect of high aspect ratio (height/width) cooling channels, considering different coolant channel designs, on hot-gas-side wall temperature and coolant pressure drop for a liquid hydrogen cooled rocket combustion chamber, was performed. Coolant channel design elements considered were: length of combustion chamber in which high aspect ratio cooling was applied, number of coolant channels, and coolant channel shape. Seven coolant channel designs were investigated using a coupling of the Rocket Thermal Evaluation code and the Two-Dimensional Kinetics code. Initially, each coolant channel design was developed, without consideration for fabrication, to reduce the hot-gas-side wall temperature from a given conventional cooling channel baseline. These designs produced hot-gas-side wall temperature reductions up to 22 percent, with coolant pressure drop increases as low as 7.5 percent from the baseline. Fabrication constraints for milled channels were applied to the seven designs. These produced hot-gas-side wall temperature reductions of up to 20 percent, with coolant pressure drop increases as low as 2 percent. Using high aspect ratio cooling channels for the entire length of the combustion chamber had no additional benefit on hot-gas-side wall temperature over using high aspect ratio cooling channels only in the throat region, but increased coolant pressure drop 33 percent. Independent of coolant channel shape, high aspect ratio cooling was able to reduce the hot-gas-side wall temperature by at least 8 percent, with as low as a 2 percent increase in coolant pressure drop. The design with the highest overall benefit to hot-gas-side wall temperature and minimal coolant pressure drop cooling can now be done in relatively short periods of time with multiple iterations.

  13. Steady state HNG combustion modeling

    SciTech Connect

    Louwers, J.; Gadiot, G.M.H.J.L.; Brewster, M.Q.; Son, S.F.; Parr, T.; Hanson-Parr, D.

    1998-04-01

    Two simplified modeling approaches are used to model the combustion of Hydrazinium Nitroformate (HNF, N{sub 2}H{sub 5}-C(NO{sub 2}){sub 3}). The condensed phase is treated by high activation energy asymptotics. The gas phase is treated by two limit cases: the classical high activation energy, and the recently introduced low activation energy approach. This results in simplification of the gas phase energy equation, making an (approximate) analytical solution possible. The results of both models are compared with experimental results of HNF combustion. It is shown that the low activation energy approach yields better agreement with experimental observations (e.g. regression rate and temperature sensitivity), than the high activation energy approach.

  14. Preliminary Investigation of a Ceramic Lining for a Combustion Chamber for Gas-turbine Use

    NASA Technical Reports Server (NTRS)

    Woodward, William H; Bobrowsky, A R

    1948-01-01

    Combustion chamber liners for gas turbines and experimental set-ups were tested for failure. A ceramic-lined test chamber was operated at fuel/air ratios up to 0.050. Thermal-shock evaluation indicated that a ceramic lining, which expands after firing, would crack but would not fall apart during operation. Refractoriness of the lining and the resistance to mechanical shock were adequate. In general, shell temperature reductions of approximately 400 deg F were effected by the use of this lining at fuel/air ratios of 0.016 and 0.050. The mechanism of failure of the ceramic lining was induced by sudden heating and cooling during operation.

  15. Experimental performance of a high-area-ratio rocket nozzle at high combustion chamber pressure

    NASA Technical Reports Server (NTRS)

    Jankovsky, Robert S.; Kazaroff, John M.; Pavli, Albert J.

    1996-01-01

    An experimental investigation was conducted to determine the thrust coefficient of a high-area-ratio rocket nozzle at combustion chamber pressures of 12.4 to 16.5 MPa (1800 to 2400 psia). A nozzle with a modified Rao contour and an expansion area ratio of 1025:1 was tested with hydrogen and oxygen at altitude conditions. The same nozzle, truncated to an area ratio of 440:1, was also tested. Values of thrust coefficient are presented along with characteristic exhaust velocity efficiencies, nozzle wall temperatures, and overall thruster specific impulse.

  16. Corrosion prevention in copper combustion chamber liners of liquid oxygen/methane booster engines

    NASA Technical Reports Server (NTRS)

    Rosenberg, S. D.; Gage, M. L.

    1990-01-01

    The use of a protective gold coating for preventing the corrosion of copper combustion chamber liners in liquid oxygen/methane booster engines is discussed with reference to experimental results. Gold-plated and unplated copper alloy specimens were tested in a carbothermal test facility providing realistic simulations of booster engine cooling channel conditions, such as temperature, pressure, flow velocity, and heat flux. Metallographic examinations of the unplated specimens showed severe corrosion as a result of the reaction with the sulfur-containing contaminant in the fuel. In contrast, gold-plated specimens showed no corrosion under similar operating conditions.

  17. Advanced Materials and Manufacturing for Low-Cost, High-Performance Liquid Rocket Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Williams, Brian E.; Arrieta, Victor M.

    2013-01-01

    A document describes the low-cost manufacturing of C103 niobium alloy combustion chambers, and the use of a high-temperature, oxidation-resistant coating that is superior to the standard silicide coating. The manufacturing process involved low-temperature spray deposition of C103 on removable plastic mandrels produced by rapid prototyping. Thin, vapor-deposited platinum-indium coatings were shown to substantially improve oxidation resistance relative to the standard silicide coating. Development of different low-cost plastic thrust chamber mandrel materials and prototyping processes (selective laser sintering and stereolithography) yielded mandrels with good dimensional accuracy (within a couple of mils) for this stage of development. The feasibility of using the kinetic metallization cold-spray process for fabrication of free-standing C1O3 thrusters on removable plastic mandrels was also demonstrated. The ambient and elevated temperature mechanical properties of the material were shown to be reasonably good relative to conventionally processed C103, but the greatest potential benefit is that coldsprayed chambers require minimal post-process machining, resulting in substantially lower machining and material costs. The platinum-iridium coating was shown to provide greatly increased oxidation resistance over the silicide when evaluated through oxyacetylene torch testing to as high as 300 F (= 150 C). The iridium component minimizes reaction with the niobium alloy chamber at high temperatures, and provides the high-temperature oxidation resistance needed at the throat.

  18. Numerical modeling of pulverized coal combustion at thermal power plant boilers

    NASA Astrophysics Data System (ADS)

    Askarova, Aliya; Bolegenova, Saltanat; Maximov, Valeryi; Beketayeva, Meruyert; Safarik, Pavel

    2015-06-01

    The paper deals with development and application the numerical model for solution of processes at combustion chamber of the thermal power plant boiler. Mathematical simulation is based on solution of physical and chemical processes occuring at burning pulverized coal in the furnace model. Three-dimensional flows, heat and mass transfer, chemical kinetics of the processes, effects of thermal radiation are considered. Obtained results give quantitative information on velocity distributions, temperature and concentration profiles of the components, the amount of combustion products including harmful substances. The numerical model becomes a tool for investigation and design of combustion chambers with high-efficiency and reliable operation of boiler at thermal power plants.

  19. Development and integration of a scalable low NOx combustion chamber for a hydrogen-fueled aerogas turbine

    NASA Astrophysics Data System (ADS)

    Boerner, S.; Funke, H. H.-W.; Hendrick, P.; Recker, E.; Elsing, R.

    2013-03-01

    The usage of alternative fuels in aircraft industry plays an important role of current aero engine research and development processes. The micromix burning principle allows a secure and low NOx combustion of gaseous hydrogen. The combustion principle is based on the fluid phenomenon of jet in cross flow and achieves a significant lowering in NOx formation by using multiple miniaturized flames. The paper highlights the development and the integration of a combustion chamber, based on the micromix combustion principle, into an Auxiliary Power Unit (APU) GTCP 36-300 with regard to the necessary modifications on the gas turbine and on the engine controller.

  20. Modeling of microgravity combustion experiments

    NASA Technical Reports Server (NTRS)

    Buckmaster, John

    1993-01-01

    Modeling plays a vital role in providing physical insights into behavior revealed by experiment. The program at the University of Illinois is designed to improve our understanding of basic combustion phenomena through the analytical and numerical modeling of a variety of configurations undergoing experimental study in NASA's microgravity combustion program. Significant progress has been made in two areas: (1) flame-balls, studied experimentally by Ronney and his co-workers; (2) particle-cloud flames studied by Berlad and his collaborators. Additional work is mentioned below. NASA funding for the U. of Illinois program commenced in February 1991 but work was initiated prior to that date and the program can only be understood with this foundation exposed. Accordingly, we start with a brief description of some key results obtained in the pre - 2/91 work.

  1. Multi-injector modeling of transverse combustion instability experiments

    NASA Astrophysics Data System (ADS)

    Shipley, Kevin J.

    Concurrent simulations and experiments are used to study combustion instabilities in a multiple injector element combustion chamber. The experiments employ a linear array of seven coaxial injector elements positioned atop a rectangular chamber. Different levels of instability are driven in the combustor by varying the operating and geometry parameters of the outer driving injector elements located near the chamber end-walls. The objectives of the study are to apply a reduced three-injector model to generate a computational test bed for the evaluation of injector response to transverse instability, to apply a full seven-injector model to investigate the inter-element coupling between injectors in response to transverse instability, and to further develop this integrated approach as a key element in a predictive methodology that relies heavily on subscale test and simulation. To measure the effects of the transverse wave on a central study injector element two opposing windows are placed in the chamber to allow optical access. The chamber is extensively instrumented with high-frequency pressure transducers. High-fidelity computational fluid dynamics simulations are used to model the experiment. Specifically three-dimensional, detached eddy simulations (DES) are used. Two computational approaches are investigated. The first approach models the combustor with three center injectors and forces transverse waves in the chamber with a wall velocity function at the chamber side walls. Different levels of pressure oscillation amplitudes are possible by varying the amplitude of the forcing function. The purpose of this method is to focus on the combustion response of the study element. In the second approach, all seven injectors are modeled and self-excited combustion instability is achieved. This realistic model of the chamber allows the study of inter-element flow dynamics, e.g., how the resonant motions in the injector tubes are coupled through the transverse pressure waves in the chamber. The computational results are analyzed and compared with experiment results in the time, frequency and modal domains. Results from the three injector model show how applying different velocity forcing amplitudes change the amplitude and spatial location of heat release from the center injector. The instability amplitudes in the simulation are able to be tuned to experiments and produce similar modal combustion responses of the center injector. The reaction model applied was found to play an important role in the spatial and temporal heat release response. Only when the model was calibrated to ignition delay measurements did the heat release response reflect measurements in the experiment. While insightful the simulations are not truly predictive because the driving frequency and forcing function amplitude are input into the simulation. However, the use of this approach as a tool to investigate combustion response is demonstrated. Results from the seven injector simulations provide an insightful look at the mechanisms driving the instability in the combustor. The instability was studied over a range of pressure fluctuations, up to 70% of mean chamber pressure produced in the self-exited simulation. At low amplitudes the transverse instability was found to be supported by both flame impingement with the side wall as well as vortex shedding at the primary acoustic frequency. As instability level grew the primary supporting mechanism shifted to just vortex impingement on the side walls and the greatest growth was seen as additional vortices began impinging between injector elements at the primary acoustic frequency. This research reveals the advantages and limitations of applying these two modeling techniques to simulate multiple injector experiments. The advantage of the three injector model is a simplified geometry which results in faster model development and the ability to more rapidly study the injector response under varying velocity amplitudes. The possibly faster run time is offset though by the need to run multiple cases to calibrate the

  2. Calculating the parameters of self-oscillations in the vertical combustion chamber of the blast-furnace air heater during unstable combustion

    NASA Astrophysics Data System (ADS)

    Basok, B. I.; Gotsulenko, V. V.

    2015-01-01

    A procedure for simplified calculation of the parameters of self-oscillations excited during unstable (vibrating) combustion in the vertical combustion chambers of blast-furnace air heaters is developed. The proposed procedure is based on an independent nonlinear dynamic system similar to the equations from the theory of a blade supercharger stalling and surging mode. The head characteristic considered in the blade supercharger stalling and surging theory determines the part of the supercharger drive rotation energy that is converted into the head developed by the supercharger. In the considered system, the supercharger head characteristic is replaced by the combustion chamber head characteristic. Being a function of flow rate, this characteristic describes the part of heat supplied to flow that is converted to the flow head. Unlike the supercharger head characteristic, which is determined by experiment, the combustion chamber head characteristic is determined by calculation, due to which it becomes much easier to calculate the parameters of self-oscillations according to the proposed procedure. In particular, an analysis of the periodic solutions of the obtained dynamic system made it possible to determine the pattern in which the amplitude of considered self-oscillations depends on the surge impedance of the vertical combustion chamber.

  3. Particle-Bound PAH Emission from the Exhaust of Combustion Chamber

    NASA Astrophysics Data System (ADS)

    Asgari Lamjiri, M.; Medrano, Y. S.; Guillaume, D. W.; Khachikian, C. S.

    2013-12-01

    Polycyclic Aromatic Hydrocarbons (PAHs) are harmful, semi-volatile organic compounds which are generated due to the incomplete combustion of organic substances. PAHs are of concern as a pollutant because some of these compounds are carcinogenic and mutagenic even at low levels. Most of the PAHs are recalcitrant and persistent in the environment. The PAHs carcinogenic potential can be increased by the adsorption onto small size particles (< 1?m) which can easily get into the bronchioles and alveoli of the lungs. PAHs associated with sub-micron particles are mostly generated from high temperature sources like combustion chambers. In this current study, the presence of 16 priority PAHs (listed by United States Environmental Protection Agency) which are attached to the particulates emitted from the exhaust of the jet engine are evaluated. The engine was operated at different swirl numbers (S; the ratio of tangential air flow to axial air flow) to investigate the effect of this parameter on the effluent of combustion chamber. The samples were collected using two instruments simultaneously: a particle analyzer and a Micro-Orifice Uniform Deposited Impactor (MOUDI). Particle analyzer was used to count the number of particles in different sizes and MOUDI was used to collect particles with respect to their size as they were emitted from the exhaust. The MOUDI's aluminum substrates were weighed before and after the experiment in order to measure the mass of particles that were collected during the sampling period. The concentration of PAHs associated with the particles was measured by extracting the particles with dichloromethane followed by analysis via gas chromatography/mass spectrometry (GC/MS). In general, lower molecular weight PAHs emitted from the exhaust of combustion chamber are mostly in gas phase while PAHs of higher molecular weight are adsorbed onto particles. Preliminary results from GC/MS confirm the presence of higher molecular weight PAHs like Benzo[a]pyrene in most of the samples. Better recirculation between air and fuel in higher swirl numbers results in better combustion. In higher swirl numbers, the temperature of the combustion process increases which leads to a more complete combustion. Another result of higher swirl number is a longer residence time which allows the organic substances in the fuel to remain in the reaction longer and also leads to a more complete combustion. The preliminary results from particle analyzer show that the abundance ratio of smaller particles to larger particles increases at higher swirl numbers. For example, at swirl 86, the abundance ratio of 0.3 micron particles to 0.7 micron particles was 400 while at swirl 0, this ratio was 35. Smaller particles have higher specific surface area which allows for more PAH adsorption. The preliminary results show that operating the jet engine at higher swirl numbers can have positive or negative effects on particle-bound PAH emissions. Higher temperature and residence time as well as better mixture of fuel and air can reduce PAH emission while generating more small size particles can increase surface available for PAH adsorption and, as a result, increases PAH emission. In future experiments, particle-bound PAHs of different swirl numbers will be compared in order to find a swirl number range which generates fewer Particle-bound PAHs.

  4. Correlation of knocking characteristics of fuels in an engine having a hemispherical combustion chamber

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Biermann, Arnold E

    1940-01-01

    Data are presented to show the effects of inlet-air pressure, inlet-air temperature, and compression ratio on the maximum permissible performance obtained with having a hemispherical-dome combustion chamber. The five aircraft-engine fuels used have octane numbers varying from 90 to 100 plus 2 ml of tetraethyl lead per gallon. The data were obtained on a 5 1/4-inch by 4 3/4-inch liquid-cooled engine operating at 2,500 r.p.m. The compression ratio was varied from 6.0 to 8.9. The inlet-air temperature was varied from 110 to 310 F. For each set of conditions, the inlet-air pressure was increased until audible knock occurred and then reduced 2 inches of mercury before data were recorded. The results for each fuel can be correlated by plotting the calculated end-gas density factor against the calculated end-gas temperature. Measurements of spark-plugs, cutting off the switch to one spark plug lowered the electrode temperature of that plug from a value of 1,365 F to a value of 957 F. The results indicate that the surface temperatures of combustion-chamber areas which become new sources of ignition markedly increase after ignition.

  5. The effects of intake valve detergent structure on combustion chamber deposits (CCD)

    SciTech Connect

    Kelemen, S.R.; Maxey, C.T.

    1995-12-31

    Combustion chamber deposits (CCD) have been heavily researched in the past with regard to Octane Requirement Increase (ORI). New concerns about their role in combustion chamber deposit interference (CCDI) and their potential contribution to exhaust emissions have reinforced interest in defining the underlying factors that contribute to CCD. In this study, intake valve detergents were evaluated in the absence of any fluidizer in L-6 1987 BMW 325e engines using 10,000 mile tests run with a BMW IVD driving cycle. The chemical structure of detergents used to reduce Intake Valve Deposits (IVD) has been systematically varied to determine its effect on the quantity and the composition of CCD. In general, chemical changes in the intake valve detergent had little effect on the amount and chemical composition of CCD. The composition of CCD was determined by X-ray Photoelectron Spectroscopy (XPS). All CCDs produced with fuels containing intake valve detergents showed the same types and similar levels of organic oxygen, sulfur and aromatic carbon. The CCDs did not contain intact additive backbone fragments or detergent head groups. The only distinguishing feature of these CCDs was the varying nitrogen content that appeared to depend on the type and number of amine groups in the detergent. However, the types of nitrogen present in the CCDs were chemically different from those present in the initial detergent suggesting that, although some of the nitrogen in the detergent head group remains in the CCD, it is chemically transformed.

  6. Modeling of Laser-Induced Metal Combustion

    SciTech Connect

    Boley, C D; Rubenchik, A M

    2008-02-20

    Experiments involving the interaction of a high-power laser beam with metal targets demonstrate that combustion plays an important role. This process depends on reactions within an oxide layer, together with oxygenation and removal of this layer by the wind. We present an analytical model of laser-induced combustion. The model predicts the threshold for initiation of combustion, the growth of the combustion layer with time, and the threshold for self-supported combustion. Solutions are compared with detailed numerical modeling as benchmarked by laboratory experiments.

  7. Use, Assessment, and Improvement of the Loci-CHEM CFD Code for Simulation of Combustion in a Single Element GO2/GH2 Injector and Chamber

    NASA Technical Reports Server (NTRS)

    Westra, Douglas G.; Lin, Jeff; West, Jeff; Tucker, Kevin

    2006-01-01

    This document is a viewgraph presentation of a paper that documents a continuing effort at Marshall Space Flight Center (MSFC) to use, assess, and continually improve CFD codes to the point of material utility in the design of rocket engine combustion devices. This paper describes how the code is presently being used to simulate combustion in a single element combustion chamber with shear coaxial injectors using gaseous oxygen and gaseous hydrogen propellants. The ultimate purpose of the efforts documented is to assess and further improve the Loci-CHEM code and the implementation of it. Single element shear coaxial injectors were tested as part of the Staged Combustion Injector Technology (SCIT) program, where detailed chamber wall heat fluxes were measured. Data was taken over a range of chamber pressures for propellants injected at both ambient and elevated temperatures. Several test cases are simulated as part of the effort to demonstrate use of the Loci-CHEM CFD code and to enable us to make improvements in the code as needed. The simulations presented also include a grid independence study on hybrid grids. Several two-equation eddy viscosity low Reynolds number turbulence models are also evaluated as part of the study. All calculations are presented with a comparison to the experimental data. Weaknesses of the code relative to test data are discussed and continuing efforts to improve the code are presented.

  8. Altitude-Wind-Tunnel investigation of Westinghouse 19B-2, 19B-8, and 19XB-1 jet-propulsion engines V : combustion chamber performance

    NASA Technical Reports Server (NTRS)

    Boyd, Bemrose

    1948-01-01

    Pressure losses through the combustion chamber and the combustion efficiency of the 19B-2 and 19B-8 jet-propulsion engines and the combustion efficiency of the 19XB-1 jet-propulsion engine are presented.Data were obtained from an investigation of the complete engine in the NACA Cleveland altitude wind tunnel over a range of simulated altitudes from 5000 to 30,000 feet and tunnel Mach numbers from less than 0.100 to 0.455. The combustion-chamber pressure loss due to friction was higher for the 19B-2 combustion chamber than for the 19B-8. The 19B-2 combustion chamber had a screen of 40-percent open area interposed between the compressor outlet and the combustion-chamber inlet. The screen for the 19B-8 combustion chamber had a 60-percent open area, which except for a small difference in tail-pipe-nozzle outlet area represents the only point of difference between the standard 19B-2 and 19B-8 combustion chambers. The pressure loss due to heat addition to the flowing gases in the combustion chamber was approximately the same for the 19B-2 and 19B-8 configurations. Altitude and tunnel Mach number had no significant effect on the over-all total-pressure loss through the combustion chamber. A decrease in tail-pipe-nozzle outlet area (tail cone out) resulted in a decrease in combustion-chamber total-pressure loss at high engine speeds.

  9. Modeling Combustion in Supersonic Flows

    NASA Technical Reports Server (NTRS)

    Drummond, J. Philip; Danehy, Paul M.; Bivolaru, Daniel; Gaffney, Richard L.; Tedder, Sarah A.; Cutler, Andrew D.

    2007-01-01

    This paper discusses the progress of work to model high-speed supersonic reacting flow. The purpose of the work is to improve the state of the art of CFD capabilities for predicting the flow in high-speed propulsion systems, particularly combustor flow-paths. The program has several components including the development of advanced algorithms and models for simulating engine flowpaths as well as a fundamental experimental and diagnostic development effort to support the formulation and validation of the mathematical models. The paper will provide details of current work on experiments that will provide data for the modeling efforts along with with the associated nonintrusive diagnostics used to collect the data from the experimental flowfield. Simulation of a recent experiment to partially validate the accuracy of a combustion code is also described.

  10. PREMIXED FLAME PROPAGATION AND MORPHOLOGY IN A CONSTANT VOLUME COMBUSTION CHAMBER

    SciTech Connect

    Hariharan, A; Wichman, IS

    2014-06-04

    This work presents an experimental and numerical investigation of premixed flame propagation in a constant volume rectangular channel with an aspect ratio of six (6) that serves as a combustion chamber. Ignition is followed by an accelerating cusped finger-shaped flame-front. A deceleration of the flame is followed by the formation of a "tulip"-shaped flame-front. Eventually, the flame is extinguished when it collides with the cold wall on the opposite channel end. Numerical computations are performed to understand the influence of pressure waves, instabilities, and flow field effects causing changes to the flame structure and morphology. The transient 2D numerical simulation results are compared with transient 3D experimental results. Issues discussed are the appearance of oscillatory motions along the flame front and the influences of gravity on flame structure. An explanation is provided for the formation of the "tulip" shape of the premixed flame front.

  11. Advanced radiation techniques for inspection of diesel engine combustion chamber materials components. Final report

    SciTech Connect

    1995-10-09

    Heavy duty truck engines must meet stringent life cycle cost and regulatory requirements. Meeting these requirements has resulted in convergence on 4-stroke 6-in-line, turbocharged, and after-cooled engines with direct-injection combustion systems. These engines provide much higher efficiencies (42%, fuel consumption 200 g/kW-hr) than automotive engines (31%, fuel consumption 270 g/kW-hr), but at higher initial cost. Significant near-term diesel engine improvements are necessary and are spurred by continuing competitive, Middle - East oil problems and Congressional legislation. As a result of these trends and pressures, Caterpillar has been actively pursuing a low-fuel consumption engine research program with emphasis on product quality through process control and product inspection. The goal of this project is to combine the nondestructive evaluation and computational resources and expertise available at LLNL with the diesel engine and manufacturing expertise of the Caterpillar Corporation to develop in-process monitoring and inspection techniques for diesel engine combustion chamber components and materials. Early development of these techniques will assure the optimization of the manufacturing process by design/inspection interface. The transition from the development stage to the manufacturing stage requires a both a thorough understanding of the processes and a way of verifying conformance to process standards. NDE is one of the essential tools in accomplishing both elements and in this project will be integrated with Caterpillar`s technological and manufacturing expertise to accomplish the project goals.

  12. Subgrid Combustion Modeling for the Next Generation National Combustion Code

    NASA Technical Reports Server (NTRS)

    Menon, Suresh; Sankaran, Vaidyanathan; Stone, Christopher

    2003-01-01

    In the first year of this research, a subgrid turbulent mixing and combustion methodology developed earlier at Georgia Tech has been provided to researchers at NASA/GRC for incorporation into the next generation National Combustion Code (called NCCLES hereafter). A key feature of this approach is that scalar mixing and combustion processes are simulated within the LES grid using a stochastic 1D model. The subgrid simulation approach recovers locally molecular diffusion and reaction kinetics exactly without requiring closure and thus, provides an attractive feature to simulate complex, highly turbulent reacting flows of interest. Data acquisition algorithms and statistical analysis strategies and routines to analyze NCCLES results have also been provided to NASA/GRC. The overall goal of this research is to systematically develop and implement LES capability into the current NCC. For this purpose, issues regarding initialization and running LES are also addressed in the collaborative effort. In parallel to this technology transfer effort (that is continuously on going), research has also been underway at Georgia Tech to enhance the LES capability to tackle more complex flows. In particular, subgrid scalar mixing and combustion method has been evaluated in three distinctly different flow field in order to demonstrate its generality: (a) Flame-Turbulence Interactions using premixed combustion, (b) Spatially evolving supersonic mixing layers, and (c) Temporal single and two-phase mixing layers. The configurations chosen are such that they can be implemented in NCCLES and used to evaluate the ability of the new code. Future development and validation will be in spray combustion in gas turbine engine and supersonic scalar mixing.

  13. Combustion Stability Verification for the Thrust Chamber Assembly of J-2X Developmental Engines 10001, 10002, and 10003

    NASA Technical Reports Server (NTRS)

    Morgan, C. J.; Hulka, J. R.; Casiano, M. J.; Kenny, R. J.; Hinerman, T. D.; Scholten, N.

    2015-01-01

    The J-2X engine, a liquid oxygen/liquid hydrogen propellant rocket engine available for future use on the upper stage of the Space Launch System vehicle, has completed testing of three developmental engines at NASA Stennis Space Center. Twenty-one tests of engine E10001 were conducted from June 2011 through September 2012, thirteen tests of the engine E10002 were conducted from February 2013 through September 2013, and twelve tests of engine E10003 were conducted from November 2013 to April 2014. Verification of combustion stability of the thrust chamber assembly was conducted by perturbing each of the three developmental engines. The primary mechanism for combustion stability verification was examining the response caused by an artificial perturbation (bomb) in the main combustion chamber, i.e., dynamic combustion stability rating. No dynamic instabilities were observed in the TCA, although a few conditions were not bombed. Additional requirements, included to guard against spontaneous instability or rough combustion, were also investigated. Under certain conditions, discrete responses were observed in the dynamic pressure data. The discrete responses were of low amplitude and posed minimal risk to safe engine operability. Rough combustion analyses showed that all three engines met requirements for broad-banded frequency oscillations. Start and shutdown transient chug oscillations were also examined to assess the overall stability characteristics, with no major issues observed.

  14. Predictive modeling of combustion processes

    E-print Network

    Sharma, Sandeep, Ph. D. Massachusetts Institute of Technology

    2009-01-01

    Recently, there has been an increasing interest in improving the efficiency and lowering the emissions from operating combustors, e.g. internal combustion (IC) engines and gas turbines. Different fuels, additives etc. are ...

  15. Gasdynamic Model of Turbulent Combustion in TNT Explosions

    SciTech Connect

    Kuhl, A L; Bell, J B; Beckner, V E

    2010-01-08

    A model is proposed to simulate turbulent combustion in confined TNT explosions. It is based on: (i) the multi-component gasdynamic conservation laws, (ii) a fast-chemistry model for TNT-air combustion, (iii) a thermodynamic model for frozen reactants and equilibrium products, (iv) a high-order Godunov scheme providing a non-diffusive solution of the governing equations, and (v) an ILES approach whereby adaptive mesh refinement is used to capture the energy bearing scales of the turbulence on the grid. Three-dimensional numerical simulations of explosion fields from 1.5-g PETN/TNT charges were performed. Explosions in six different chambers were studied: three calorimeters (volumes of 6.6-l, 21.2-l and 40.5-l with L/D = 1), and three tunnels (L/D = 3.8, 4.65 and 12.5 with volumes of 6.3-l) - to investigate the influence of chamber volume and geometry on the combustion process. Predicted pressures histories were quite similar to measured pressure histories for all cases studied. Experimentally, mass fraction of products, Y{sub p}{sup exp}, reached a peak value of 88% at an excess air ratio of twice stoichiometric, and then decayed with increasing air dilution; mass fractions Y{sub p}{sup calc} computed from the numerical simulations followed similar trends. Based on this agreement, we conclude that the dominant effect that controls the rate of TNT combustion with air is the turbulent mixing rate; the ILES approach along with the fast-chemistry model used here adequately captures this effect.

  16. Aerothermal environment induced by mismatch at the SSME main combustion chamber-nozzle joint

    NASA Technical Reports Server (NTRS)

    Mcconnaughey, H. V.; O'Farrell, J. M.; Olive, T. A.; Brown, G. B.; Holt, J. B.

    1990-01-01

    The computational study reported here is motivated by a Space Shuttle main engine hardware problem detected in post-flight and post-test inspections. Of interest are the potential for hot gas ingestion into the joint (G15) at the main combustion chamber-to-nozzle interface and the effect of particular goemetric nonuniformities on that gas ingestion. The flowfield in the G15 region involves supersonic flow past a rounded forward facing step preceded by a deep narrow cavity. This paper describes the physical problem associated with joint G15 and computational investigations of the G15 aerothermal environment. The associated flowfield was simulated in two and three space dimensions using the United Solutions Algorithm (USA) computational fluid dynamics code series. A benchmark calculation of experimentally measured supersonic flow over of a square cavity was performed to demonstrate the accuracy of the USA code in analyzing flows similar to the G15 computational flowfield. The G15 results demonstrate the mechanism for hot gas ingestion into the joint and reveal the sensitivity to salient geometric nonuniformities.

  17. Investigating combustion as a method of processing inedible biomass produced in NASA's biomass production chamber

    NASA Technical Reports Server (NTRS)

    Dreschel, T. W.; Wheeler, R. M.; Hinkle, C. R.; Sager, J. C.; Knott, W. M.

    1991-01-01

    The Controlled Ecological Life Support System (CELSS) Breadboard Project at the John F. Kennedy Space Center is a research program to integrate and evaluate biological processes to provide air, water, and food for humans in closed environments for space habitation. This project focuses on the use of conventional crop plants as grown in the Biomass Production Chamber (BPC) for the production and recycling of oxygen, food, and water. The inedible portion of these crops has the potential to be converted to edible biomass or directly to the elemental constituents for direct recycling. Converting inedible biomass directly, by combustion, to carbon dioxide, water, and minerals could provide a baseline for estimating partitioning of the mass balance during recycling in a CELSS. Converting the inedible biomass to carbon dioxide and water requires the same amount of oxygen that was produced by photosynthesis. The oxygen produced during crop growth is just equal to the oxygen required to oxidize all the biomass produced during growth. Thus, the amount of oxygen produced that is available for human consumption is in proportion to the amount of biomass actually utilized by humans. The remaining oxygen must be available to oxidize the rest of the biomass back to carbon dioxide and water or the system will not be a regenerative one.

  18. The Effect of Pulsed Injection on Shear Layer Dynamics in a Scramjet Combustion Chamber

    NASA Astrophysics Data System (ADS)

    Smith, Leslie

    One of the greatest problems that scramjet research faces is fuel air mixing. The residence time for a scramjet engine, or the time it takes for a volume of air to completely pass through the engine, is on the order of 0.1 ms. In that extremely short period of time fuel must be injected and fully mirco-mixed at stoichiometric ratios with the combustion chamber airflow. The fuel-air mixture must then be combusted and expanded through the nozzle to produce thrust. The goal of this research is to develop a new more efficient method of fuel air mixing within a scramjet combustion chamber. A possible way to speed up the mixing process of parallel injection without incurring the total pressure losses that would occur in normal injection is to inject the fuel from the rear side of a backward facing step. Backward facing steps in supersonic flow produce a Prandtl-Meyer expansion fan followed by a shear layer. The instabilities in this shear layer have dominant resonant frequencies. It is believed that if fuel is injected in pulses that impinge on the shear layer at these dominant resonant frequencies that the shear layer will resonate. When the shear layer resonates the vortices that form in the shear layer will grow in magnitude, thus mixing the injected fuel with the air. To test this hypothesis a new test section was designed and built that features a one inch step under which an injector can be housed. This new test section was installed in the supersonic facility at the University of Kansas. Two injectors were also designed that each feature a face plate, one with eight injection ports arranged in a ring and one with 5 injection ports. Between the face plate and a back plate there is a cavity that houses a rotating valve that is powered by a pneumatic motor. Five valves were built: one with 8 teeth, one with 16 teeth, one with 5 teeth that are the same size as the gaps between the teeth, one with 5 teeth where the teeth are 50% larger than the gaps, and one with 5 teeth where the teeth are 50% smaller than the gaps. The 8 tooth valve and 16 tooth valve where used with the 8 port injector face plate. The 5 tooth valves were used with the 5 port injector face plate. As the valve rotates the teeth block and unblock the injection ports injecting carbon dioxide gas into the test section. The 8 port injector was tested over a range of frequencies from 1.6 kHz to 10.0 kHz. The 5 port injector was tested for each valve over a range of frequencies from 1.0 kHz to 4.0 kHz. Static pressure data was taken along the upper and lower walls of the test section by means of an array of pressure sensors. The pressure data from the test section was compared to results generated using a three dimensional CFD simulation of the test section. Overall the pressure data on the lower wall agreed reasonably well with the CFD simulation. The vorticity and turbulence contours generated by the STAR-CCM+ simulation suggest that as a pulse is injected into the test section from the step it causes the shear layer to curve outward near the point of injection. After the pulse the shear layer returns to the state it was in before injection. The shear layer showed no resonance behavior as a result of pulsed injection. A spectral analysis was performed on the wall static pressure data. The results of this analysis showed no indication of resonance behavior of the shear layer in the wind tunnel tests.

  19. Utilizing Chamber Data for Developing and Validating Climate Change Models

    NASA Technical Reports Server (NTRS)

    Monje, Oscar

    2012-01-01

    Controlled environment chambers (e.g. growth chambers, SPAR chambers, or open-top chambers) are useful for measuring plant ecosystem responses to climatic variables and CO2 that affect plant water relations. However, data from chambers was found to overestimate responses of C fluxes to CO2 enrichment. Chamber data may be confounded by numerous artifacts (e.g. sidelighting, edge effects, increased temperature and VPD, etc) and this limits what can be measured accurately. Chambers can be used to measure canopy level energy balance under controlled conditions and plant transpiration responses to CO2 concentration can be elucidated. However, these measurements cannot be used directly in model development or validation. The response of stomatal conductance to CO2 will be the same as in the field, but the measured response must be recalculated in such a manner to account for differences in aerodynamic conductance, temperature and VPD between the chamber and the field.

  20. Spray combustion model improvement study, 1

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Kim, Y. M.; Shang, H. M.

    1993-01-01

    This study involves the development of numerical and physical modeling in spray combustion. These modeling efforts are mainly motivated to improve the physical submodels of turbulence, combustion, atomization, dense spray effects, and group vaporization. The present mathematical formulation can be easily implemented in any time-marching multiple pressure correction methodologies such as MAST code. A sequence of validation cases includes the nonevaporating, evaporating and_burnin dense_sprays.

  1. A two-dimensional numerical study of the flow inside the combustion chambers of a motored rotary engine

    NASA Technical Reports Server (NTRS)

    Shih, T. I. P.; Yang, S. L.; Schock, H. J.

    1986-01-01

    A numerical study was performed to investigate the unsteady, multidimensional flow inside the combustion chambers of an idealized, two-dimensional, rotary engine under motored conditions. The numerical study was based on the time-dependent, two-dimensional, density-weighted, ensemble-averaged conservation equations of mass, species, momentum, and total energy valid for two-component ideal gas mixtures. The ensemble-averaged conservation equations were closed by a K-epsilon model of turbulence. This K-epsilon model of turbulence was modified to account for some of the effects of compressibility, streamline curvature, low-Reynolds number, and preferential stress dissipation. Numerical solutions to the conservation equations were obtained by the highly efficient implicit-factored method of Beam and Warming. The grid system needed to obtain solutions were generated by an algebraic grid generation technique based on transfinite interpolation. Results of the numerical study are presented in graphical form illustrating the flow patterns during intake, compression, gaseous fuel injection, expansion, and exhaust.

  2. Modeling Secondary Organic Aerosol Formation From Emissions of Combustion Sources

    NASA Astrophysics Data System (ADS)

    Jathar, Shantanu Hemant

    Atmospheric aerosols exert a large influence on the Earth's climate and cause adverse public health effects, reduced visibility and material degradation. Secondary organic aerosol (SOA), defined as the aerosol mass arising from the oxidation products of gas-phase organic species, accounts for a significant fraction of the submicron atmospheric aerosol mass. Yet, there are large uncertainties surrounding the sources, atmospheric evolution and properties of SOA. This thesis combines laboratory experiments, extensive data analysis and global modeling to investigate the contribution of semi-volatile and intermediate volatility organic compounds (SVOC and IVOC) from combustion sources to SOA formation. The goals are to quantify the contribution of these emissions to ambient PM and to evaluate and improve models to simulate its formation. To create a database for model development and evaluation, a series of smog chamber experiments were conducted on evaporated fuel, which served as surrogates for real-world combustion emissions. Diesel formed the most SOA followed by conventional jet fuel / jet fuel derived from natural gas, gasoline and jet fuel derived from coal. The variability in SOA formation from actual combustion emissions can be partially explained by the composition of the fuel. Several models were developed and tested along with existing models using SOA data from smog chamber experiments conducted using evaporated fuel (this work, gasoline, fischertropschs, jet fuel, diesels) and published data on dilute combustion emissions (aircraft, on- and off-road gasoline, on- and off-road diesel, wood burning, biomass burning). For all of the SOA data, existing models under-predicted SOA formation if SVOC/IVOC were not included. For the evaporated fuel experiments, when SVOC/IVOC were included predictions using the existing SOA model were brought to within a factor of two of measurements with minor adjustments to model parameterizations. Further, a volatility-only model suggested that differences in the volatility of the precursors were able to explain most of the variability observed in the SOA formation. For aircraft exhaust, the previous methods to simulate SOA formation from SVOC and IVOC performed poorly. A more physically-realistic modeling framework was developed, which was then used to show that SOA formation from aircraft exhaust was (a) higher for petroleum-based than synthetically derived jet fuel and (b) higher at lower engine loads and vice versa. All of the SOA data from combustion emissions experiments were used to determine source-specific parameterizations to model SOA formation from SVOC, IVOC and other unspeciated emissions. The new parameterizations were used to investigate their influence on the OA budget in the United States. Combustion sources were estimated to emit about 2.61 Tg yr-1 of SVOC, 1VOC and other unspeciated emissions (sixth of the total anthropogenic organic emissions), which are predicted to double SOA production from combustion sources in the United States. The contribution of SVOC and IVOC emissions to global SOA formation was assessed using a global climate model. Simulations were performed using a modified version of GISS GCM 11'. The modified model predicted that SVOC and IVOC contributed to half of the OA mass in the atmosphere. Their inclusion improved OA model-measurement comparisons for absolute concentrations, POA-SOA split and volatility (gas-particle partitioning) globally suggesting that atmospheric models need to incorporate SOA formation from SVOC and IVOC if they are to reasonably predict the abundance and properties of aerosols. This thesis demonstrates that SVOC/IVOC and possibly other unspeciated organics emitted by combustion sources are very important precursors of SOA and potentially large contributors to the atmospheric aerosol mass. Models used for research and policy applications need to represent them to improve model-predictions of aerosols on climate and health outcomes. The improved modeling frameworks developed in this dissertation are suitable for implementa

  3. Evaluation and Improvement of Liquid Propellant Rocket Chugging Analysis Techniques. Part 2: a Study of Low Frequency Combustion Instability in Rocket Engine Preburners Using a Heterogeneous Stirred Tank Reactor Model. Final Report M.S. Thesis - Aug. 1987

    NASA Technical Reports Server (NTRS)

    Bartrand, Timothy A.

    1988-01-01

    During the shutdown of the space shuttle main engine, oxygen flow is shut off from the fuel preburner and helium is used to push the residual oxygen into the combustion chamber. During this process a low frequency combustion instability, or chug, occurs. This chug has resulted in damage to the engine's augmented spark igniter due to backflow of the contents of the preburner combustion chamber into the oxidizer feed system. To determine possible causes and fixes for the chug, the fuel preburner was modeled as a heterogeneous stirred tank combustion chamber, a variable mass flow rate oxidizer feed system, a constant mass flow rate fuel feed system and an exit turbine. Within the combustion chamber gases were assumed perfectly mixed. To account for liquid in the combustion chamber, a uniform droplet distribution was assumed to exist in the chamber, with mean droplet diameter determined from an empirical relation. A computer program was written to integrate the resulting differential equations. Because chamber contents were assumed perfectly mixed, the fuel preburner model erroneously predicted that combustion would not take place during shutdown. The combustion rate model was modified to assume that all liquid oxygen that vaporized instantaneously combusted with fuel. Using this combustion model, the effect of engine parameters on chamber pressure oscillations during the SSME shutdown was calculated.

  4. Combustion modeling and performance evaluation in a full-scale rotary kiln incinerator.

    PubMed

    Chen, K S; Hsu, W T; Lin, Y C; Ho, Y T; Wu, C H

    2001-06-01

    This work summarizes the results of numerical investigations and in situ measurements for turbulent combustion in a full-scale rotary kiln incinerator (RKI). The three-dimensional (3D) governing equations for mass, momentum, energy, and species, together with the kappa - epsilon turbulence model, are formulated and solved using a finite volume method. Volatile gases from solid waste were simulated by gaseous CH4 distributed nonuniformly along the kiln bed. The combustion process was considered to be a two-step stoichiometric reaction for primary air mixed with CH4 gas in the combustion chamber. The mixing-controlled eddy-dissipation model (EDM) was employed to predict the conversion rates of CH4, O2, CO2, and CO. The results of the prediction show that reverse flows occur near the entrance of the first combustion chamber (FCC) and the turning point at the entrance to the second combustion chamber (SCC). Temperature and species are nonuniform and are vertically stratified. Meanwhile, additional mixing in the SCC enhances postflame oxidation. A combustion efficiency of up to 99.96% can be achieved at approximately 150% excess air and 20-30% secondary air. Reasonable agreement is achieved between numerical predictions and in situ measurements. PMID:11417680

  5. Validation of High Aspect Ratio Cooling in a 89 kN (20,000 lb(sub f)) Thrust Combustion Chamber

    NASA Technical Reports Server (NTRS)

    Wadel, Mary F.; Meyer, Michael L.

    1996-01-01

    In order to validate the benefits of high aspect ratio cooling channels in a large scale rocket combustion chamber, a high pressure, 89 kN (20,000 lbf) thrust, contoured combustion chamber was tested in the NASA Lewis Research Center Rocket Engine Test Facility. The combustion chamber was tested at chamber pressures from 5.5 to 11.0 MPa (800-1600 psia). The propellants were gaseous hydrogen and liquid oxygen at a nominal mixture ratio of six, and liquid hydrogen was used as the coolant. The combustion chamber was extensively instrumented with 30 backside skin thermocouples, 9 coolant channel rib thermocouples, and 10 coolant channel pressure taps. A total of 29 thermal cycles, each with one second of steady state combustion, were completed on the chamber. For 25 thermal cycles, the coolant mass flow rate was equal to the fuel mass flow rate. During the remaining four thermal cycles, the coolant mass flow rate was progressively reduced by 5, 6, 11, and 20 percent. Computer analysis agreed with coolant channel rib thermocouples within an average of 9 percent and with coolant channel pressure drops within an average of 20 percent. Hot-gas-side wall temperatures of the chamber showed up to 25 percent reduction, in the throat region, over that of a conventionally cooled combustion chamber. Reducing coolant mass flow yielded a reduction of up to 27 percent of the coolant pressure drop from that of a full flow case, while still maintaining up to a 13 percent reduction in a hot-gas-side wall temperature from that of a conventionally cooled combustion chamber.

  6. The Evaluation of High Temperature Adhesive Bonding Processes for Rocket Engine Combustion Chamber Applications

    NASA Technical Reports Server (NTRS)

    McCray, Daniel; Smith, Jeffrey; Rice, Brian; Blohowiak, Kay; Anderson, Robert; Shin, E. Eugene; McCorkle, Linda; Sutter, James

    2003-01-01

    NASA Glenn Research Center is currently evaluating the possibility of using high- temperature polymer matrix composites to reinforce the combustion chamber of a rocket engine. One potential design utilizes a honeycomb structure composed of a PMR-II- 50/M40J 4HS composite facesheet and titanium honeycomb core to reinforce a stainless steel shell. In order to properly fabricate this structure, adhesive bond PMR-II-50 composite. Proper prebond surface preparation is critical in order to obtain an acceptable adhesive bond. Improperly treated surfaces will exhibit decreased bond strength and durability, especially in metallic bonds where interface are susceptible to degradation due to heat and moisture. Most treatments for titanium and stainless steel alloys require the use of strong chemicals to etch and clean the surface. This processes are difficult to perform due to limited processing facilities as well as safety and environmental risks and they do not consistently yield optimum bond durability. Boeing Phantom Works previously developed sol-gel surface preparations for titanium alloys using a PETI-5 based polyimide adhesive. In support of part of NASA Glenn Research Center, UDRI and Boeing Phantom Works evaluated variations of this high temperature sol-gel surface preparation, primer type, and primer cure conditions on the adhesion performance of titanium and stainless steel using Cytec FM 680-1 polyimide adhesive. It was also found that a modified cure cycle of the FM 680-1 adhesive, i.e., 4 hrs at 370 F in vacuum + post cure, significantly increased the adhesion strength compared to the manufacturer's suggested cure cycle. In addition, the surface preparation of the PMR-II-50 composite was evaluated in terms of surface cleanness and roughness. This presentation will discuss the results of strength and durability testing conducted on titanium, stainless steel, and PMR-II-50 composite adherends to evaluate possible bonding processes.

  7. Design Analysis and Thermo-mechanical Fatigue of a Polyimide Composite for Combustion Chamber Support

    NASA Technical Reports Server (NTRS)

    Thesken, J. C.; Melis, M.; Shin, E.; Sutter, J.; Burke, Chris

    2004-01-01

    Polyimide composites are being evaluated for use in lightweight support structures designed to preserve the ideal flow geometry within thin shell combustion chambers of future space launch propulsion systems. Principles of lightweight design and innovative manufacturing techniques have yielded a sandwich structure with an outer face sheet of carbon fiber polyimide matrix composite. While the continuous carbon fiber enables laminated skin of high specific stiffness; the polyimide matrix materials ensure that the rigidity and durability is maintained at operation temperatures of 316 C. Significant weight savings over all metal support structures are expected. The protypical structure is the result of ongoing collaboration, between Boeing and NASA-GRC seeking to introduce polyimide composites to the harsh environmental and loads familiar to space launch propulsion systems. Design trade analyses were carried out using relevant closed form solutions, approximations for sandwich beams/panels and finite element analysis. Analyses confirm the significant thermal stresses exist when combining materials whose coefficients of thermal expansion (CTEs) differ by a factor of about 10 for materials such as a polymer composite and metallic structures. The ramifications on design and manufacturing alternatives are reviewed and discussed. Due to stringent durability and safety requirements, serious consideration is being given to the synergistic effects of temperature and mechanical loads. The candidate structure operates at 316 C, about 80% of the glass transition temperature T(sub g). Earlier thermomechanical fatigue (TMF) investigations of chopped fiber polyimide composites made this near to T(sub g), showed that cyclic temperature and stress promoted excessive creep damage and strain accumulation. Here it is important to verify that such response is limited in continuous fiber laminates.

  8. An acoustic energy framework for predicting combustion- driven acoustic instabilities in premixed gas-turbines

    E-print Network

    Ibrahim, Zuhair M. A.

    2007-01-01

    to Gas-Turbine Combustion Instability Analysis," Combustionanalysis of the chamber, once the portion of the chamber in which combustionanalysis. Unsteady Computational Fluid Dynamics Simulation (CFD) Direct modeling of combustion

  9. Transport Properties for Combustion Modeling

    SciTech Connect

    Brown, N.J.; Bastein, L.; Price, P.N.

    2010-02-19

    This review examines current approximations and approaches that underlie the evaluation of transport properties for combustion modeling applications. Discussed in the review are: the intermolecular potential and its descriptive molecular parameters; various approaches to evaluating collision integrals; supporting data required for the evaluation of transport properties; commonly used computer programs for predicting transport properties; the quality of experimental measurements and their importance for validating or rejecting approximations to property estimation; the interpretation of corresponding states; combination rules that yield pair molecular potential parameters for unlike species from like species parameters; and mixture approximations. The insensitivity of transport properties to intermolecular forces is noted, especially the non-uniqueness of the supporting potential parameters. Viscosity experiments of pure substances and binary mixtures measured post 1970 are used to evaluate a number of approximations; the intermediate temperature range 1 < T* < 10, where T* is kT/{var_epsilon}, is emphasized since this is where rich data sets are available. When suitable potential parameters are used, errors in transport property predictions for pure substances and binary mixtures are less than 5 %, when they are calculated using the approaches of Kee et al.; Mason, Kestin, and Uribe; Paul and Warnatz; or Ern and Giovangigli. Recommendations stemming from the review include (1) revisiting the supporting data required by the various computational approaches, and updating the data sets with accurate potential parameters, dipole moments, and polarizabilities; (2) characterizing the range of parameter space over which the fit to experimental data is good, rather than the current practice of reporting only the parameter set that best fits the data; (3) looking for improved combining rules, since existing rules were found to under-predict the viscosity in most cases; (4) performing more transport property measurements for mixtures that include radical species, an important but neglected area; (5) using the TRANLIB approach for treating polar molecules and (6) performing more accurate measurements of the molecular parameters used to evaluate the molecular heat capacity, since it affects thermal conductivity, which is important in predicting flame development.

  10. Spray combustion modeling. Final report

    SciTech Connect

    Bellan, J.

    1997-03-01

    Concern over the future availability of high quality liquid fuels or use in furnaces and boilers prompted the U. S. Department of Energy (DOE) to consider alternate fuels as replacements for the high grade liquid fuels used in the 1970`s and 1980`s. Alternate fuels were defined to be combinations of a large percentage of viscous, low volatility fuels resulting from the low end of distillation mixed with a small percentage of relatively low viscosity, high volatility fuels yielded by the high end of distillation. The addition of high volatility fuels was meant to promote desirable characteristics to a fuel that would otherwise be difficult to atomize and burn and whose combustion would yield a high amount of pollutants. Several questions thus needed to be answered before alternate fuels became commercially viable. These questions were related to fuel atomization, evaporation, ignition, combustion and pollutant formation. This final report describes the results of the most significant studies on ignition and combustion of alternative fuels.

  11. Challenges of oxyfuel combustion modeling for carbon capture

    NASA Astrophysics Data System (ADS)

    Kangwanpongpan, T.; Klatt, M.; Krautz, H. J.

    2012-04-01

    From the policies scenario from Internal Energy Agency (IEA) in 2010, global energy demand for coal climbs from 26% in 2006 to 29% in 2030 and most of demands for coal comes from the power-generation sector [1]. According to the new Copenhagen protocol [3], Global CO2 emission is rising from power generation due to an increasing world demand of electricity. For Energy-related CO2 emission in 2009, 43% of CO2 emissions from fuel combustion were produced from coal, 37% from oil and 20% from gas [4]. Therefore, CO2 capture from coal is the key factor to reduce greenhouse gas emission. Oxyfuel combustion is one of the promising technologies for capturing CO2 from power plants and subsequent CO2 transportation and storage in a depleted oil or gas field or saline-aquifer. The concept of Oxyfuel combustion is to remove N2 from the combustion process and burn the fuel with a mixture composed of O2 and CO2 together with recycled flue gas back into combustion chamber in order to produce a flue gas consisting mainly of CO2. This flue gas can be easily purified, compressed and transported to storage sites. However, Oxyfuel plants are still in the phase of pilot-scaled projects [5] and combustion in Oxyfuel conditions must be further investigated for a scale-up plant. Computational fluid dynamics (CFD) serves as an efficient tool for many years in Oxyfuel combustion researches [6-12] to provide predictions of temperature, heat transfer, and product species from combustion process inside furnace. However, an insight into mathematical models for Oxyfuel combustion is still restricted due to many unknown parameters such as devolatilization rate, reaction mechanisms of volatile reactions, turbulent gaseous combustion of volatile products, char heterogeneous reactions, radiation properties of gaseous mixtures and heat transfer inside and through furnace's wall. Heat transfer drastically changes due to an increasing proportion of H2O and CO2 in these Oxyfuel conditions and the degree of changes depends on the amount of both mentioned gases because both gases have higher thermal heat capacity than N2 in air-fired combustion processes and also are a good emitter and absorber of radiation [13-14]. The mentioned mathematical models are investigated using numerical CFD software (ANSYS FLUENT 12.0) [15] to provide predictions of aerodynamics, thermo-chemical and heat transfer quantities. The numerical models of lignite combustion under oxy-fuel conditions are first investigated in laboratory scaled furnace applying correlations for weighted sum of gray gases (WSGG) model for the predictions of radiation properties of oxy-fuel gas mixture [16]. The developed numerical models are further used for the predictions of temperature, hemi-spherical incident intensity and species concentrations (O2, CO2, H2O) for a 0.4 MWth oxy-fuel furnace at BTU Cottbus.

  12. A two-phase restricted equilibrium model for combustion of metalized solid propellants

    NASA Technical Reports Server (NTRS)

    Sabnis, J. S.; Dejong, F. J.; Gibeling, H. J.

    1992-01-01

    An Eulerian-Lagrangian two-phase approach was adopted to model the multi-phase reacting internal flow in a solid rocket with a metalized propellant. An Eulerian description was used to analyze the motion of the continuous phase which includes the gas as well as the small (micron-sized) particulates, while a Lagrangian description is used for the analysis of the discrete phase which consists of the larger particulates in the motor chamber. The particulates consist of Al and Al2O3 such that the particulate composition is 100 percent Al at injection from the propellant surface with Al2O3 fraction increasing due to combustion along the particle trajectory. An empirical model is used to compute the combustion rate for agglomerates while the continuous phase chemistry is treated using chemical equilibrium. The computer code was used to simulate the reacting flow in a solid rocket motor with an AP/HTPB/Al propellant. The computed results show the existence of an extended combustion zone in the chamber rather than a thin reaction region. The presence of the extended combustion zone results in the chamber flow field and chemical being far from isothermal (as would be predicted by a surface combustion assumption). The temperature in the chamber increases from about 2600 K at the propellant surface to about 3350 K in the core. Similarly the chemical composition and the density of the propellant gas also show spatially non-uniform distribution in the chamber. The analysis developed under the present effort provides a more sophisticated tool for solid rocket internal flow predictions than is presently available, and can be useful in studying apparent anomalies and improving the simple correlations currently in use. The code can be used in the analysis of combustion efficiency, thermal load in the internal insulation, plume radiation, etc.

  13. Discharge Chamber Primary Electron Modeling Activities in Three-Dimensions

    NASA Technical Reports Server (NTRS)

    Steuber, Thomas J.

    2004-01-01

    Designing discharge chambers for ion thrusters involves many geometric configuration decisions. Various decisions will impact discharge chamber performance with respect to propellant utilization efficiency, ion production costs, and grid lifetime. These hardware design decisions can benefit from the assistance of computational modeling. Computational modeling for discharge chambers has been limited to two-dimensional codes that leveraged symmetry for interpretation into three-dimensional analysis. This paper presents model development activities towards a three-dimensional discharge chamber simulation to aid discharge chamber design decisions. Specifically, of the many geometric configuration decisions toward attainment of a worthy discharge chamber, this paper focuses on addressing magnetic circuit considerations with a three-dimensional discharge chamber simulation as a tool. With this tool, candidate discharge chamber magnetic circuit designs can be analyzed computationally to gain insight into factors that may influence discharge chamber performance such as: primary electron loss width in magnetic cusps, cathode tip position with respect to the low magnetic field volume, definition of a low magnetic field region, and maintenance of a low magnetic field region across the grid span. Corroborating experimental data will be obtained from mockup hardware tests. Initially, simulated candidate magnetic circuit designs will resemble previous successful thruster designs. To provide opportunity to improve beyond previous performance benchmarks, off-design modifications will be simulated and experimentally tested.

  14. Experimental and numerical study of premixed hydrogen/air flame propagating in a combustion chamber.

    PubMed

    Xiao, Huahua; Sun, Jinhua; Chen, Peng

    2014-03-15

    An experimental and numerical study of dynamics of premixed hydrogen/air flame in a closed explosion vessel is described. High-speed shlieren cinematography and pressure recording are used to elucidate the dynamics of the combustion process in the experiment. A dynamically thickened flame model associated with a detailed reaction mechanism is employed in the numerical simulation to examine the flame-flow interaction and effect of wall friction on the flame dynamics. The shlieren photographs show that the flame develops into a distorted tulip shape after a well-pronounced classical tulip front has been formed. The experimental results reveal that the distorted tulip flame disappears with the primary tulip cusp and the distortions merging into each other, and then a classical tulip is repeated. The combustion dynamics is reasonably reproduced in the numerical simulations, including the variations in flame shape and position, pressure build-up and periodically oscillating behavior. It is found that both the tulip and distorted tulip flames can be created in the simulation with free-slip boundary condition at the walls of the vessel and behave in a manner quite close to that in the experiments. This means that the wall friction could be unimportant for the tulip and distorted tulip formation although the boundary layer formed along the sidewalls has an influence to a certain extent on the flame behavior near the sidewalls. The distorted tulip flame is also observed to be produced in the absence of vortex flow in the numerical simulations. The TF model with a detailed chemical scheme is reliable for investigating the dynamics of distorted tulip flame propagation and its underlying mechanism. PMID:24486615

  15. Low Pressure Plasma Sprayed Overlay Coatings for GRCop-84 Combustion Chamber Liners for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Barrett, C.; Ghosn, L. J.; Lerch, B.; Robinson,; Thorn, G.

    2005-01-01

    An advanced Cu-8(at.%)Cr-4%Nb alloy developed at NASA's Glenn Research Center, and designated as GRCop-84, is currently being considered for use as combustor chamber liners and nozzle ramps in NASA s future generations of reusable launch vehicles (RLVs). However, past experience has shown that unprotected copper alloys undergo an environmental attack called "blanching" in rocket engines using liquid hydrogen as fuel and liquid oxygen as the oxidizer. Potential for sulfidation attack of the liners in hydrocarbon-fueled engines is also of concern. Protective overlay coatings alloys are being developed for GRCop-84. The development of this coatings technology has involved a combination of modeling, coatings development and characterization, and process optimization. Coatings have been low pressure plasma sprayed on GRCop-84 substrates of various geometries and shapes. Microstructural, mechanical property data and thermophysical results on the coated substrates are presented and discussed.

  16. High-Area-Ratio Rocket Nozzle at High Combustion Chamber Pressure: Experimental and Analytical Validation

    NASA Technical Reports Server (NTRS)

    Jankovsky, Robert S.; Smith, Timothy D.; Pavli, Albert J.

    1999-01-01

    Experimental data were obtained on an optimally contoured nozzle with an area ratio of 1025:1 and on a truncated version of this nozzle with an area ratio of 440:1. The nozzles were tested with gaseous hydrogen and liquid oxygen propellants at combustion chamber pressures of 1800 to 2400 psia and mixture ratios of 3.89 to 6.15. This report compares the experimental performance, heat transfer, and boundary layer total pressure measurements with theoretical predictions of the current Joint Army, Navy, NASA, Air Force (JANNAF) developed methodology. This methodology makes use of the Two-Dimensional Kinetics (TDK) nozzle performance code. Comparisons of the TDK-predicted performance to experimentally attained thrust performance indicated that both the vacuum thrust coefficient and the vacuum specific impulse values were approximately 2.0-percent higher than the turbulent prediction for the 1025:1 configurations, and approximately 0.25-percent higher than the turbulent prediction for the 440:1 configuration. Nozzle wall temperatures were measured on the outside of a thin-walled heat sink nozzle during the test fittings. Nozzle heat fluxes were calculated front the time histories of these temperatures and compared with predictions made with the TDK code. The heat flux values were overpredicted for all cases. The results range from nearly 100 percent at an area ratio of 50 to only approximately 3 percent at an area ratio of 975. Values of the integral of the heat flux as a function of nozzle surface area were also calculated. Comparisons of the experiment with analyses of the heat flux and the heat rate per axial length also show that the experimental values were lower than the predicted value. Three boundary layer rakes mounted on the nozzle exit were used for boundary layer measurements. This arrangement allowed total pressure measurements to be obtained at 14 different distances from the nozzle wall. A comparison of boundary layer total pressure profiles and analytical predictions show good agreement for the first 0.5 in. from the nozzle wall; but the further into the core flow that measurements were taken, the more that TDK overpredicted the boundary layer thickness.

  17. Improving the performance and emission characteristics of a single cylinder diesel engine having reentrant combustion chamber using diesel and Jatropha methyl esters.

    PubMed

    Premnath, S; Devaradjane, G

    2015-11-01

    The emissions from the Compression ignition (CI) engines introduce toxicity to the atmosphere. The undesirable carbon deposits from these engines are realized in the nearby static or dynamic systems such as vehicles, inhabitants, etc. The objective of this research work is to improve the performance and emission characteristics of a diesel engine in the modified re-entrant combustion chamber using a diesel and Jatropha methyl ester blend (J20) at three different injection pressures. From the literature, it is revealed that the shape of the combustion chamber and the fuel injection pressure have an impact on the performance and emission parameters of the CI engine. In this work, a re-entrant combustion chamber with three different fuel injection pressures (200, 220 and 240bars) has been used in the place of the conventional hemispherical combustion chamber for diesel and J20. From the experimental results, it is found that the re-entrant chamber improves the brake thermal efficiency of diesel and J20 in all the tested conditions. It is also found that the 20% blend of Jatropha methyl ester showed 4% improvement in the brake thermal efficiency in the re-entrant chamber at the maximum injection pressure. Environmental safety directly relates to the reduction in the undesirable effects on both living and non-living things. Currently environmental pollution is of major concern. Even with the stringent emission norms new methods are required to reduce the harmful effects from automobiles. The toxicity of carbon monoxide (CO) is well known. In the re-entrant combustion chamber, the amount of CO emission is reduced by 26% when compared with the conventional fuel operation of the engine. Moreover, the amount of smoke is reduced by 24% and hydrocarbons (HC) emission by 24%. Thus, the modified re-entrant combustion chamber reduces harmful pollutants such as unburned HC and CO as well as toxic smoke emissions. PMID:26256249

  18. Analysis and flamelet modelling for spray combustion

    NASA Astrophysics Data System (ADS)

    Baba, Yuya; Kurose, Ryoichi

    The validity of a steady-flamelet model and a flamelet/progress-variable approach for gaseous and spray combustion is investigated by a two-dimensional direct numerical simulation (DNS) of gaseous and spray jet flames, and the combustion characteristics are analysed. A modified flamelet/progress-variable approach, in which total enthalpy rather than product mass fraction is chosen as a progress variable, is also examined. DNS with an Arrhenius formation, in which the chemical reaction is directly solved in the physical flow field, is performed as a reference to validate the combustion models. The results show that the diffusion flame is dominant in the gaseous diffusion jet flame, whereas diffusion and premixed flames coexist in the spray jet flame. The characteristics of the spray flame change from premixed-diffusion coexistent to diffusion-dominant downstream. Comparisons among the results from DNS with various combustion models show the modified flamelet/progress-variable approach to be superior to the other combustion models, particularly for the spray flame. Where the behaviour of the gaseous total enthalpy is strongly affected by the energy transfer (i.e. heat transfer and mass transfer) from the dispersed droplet, and this effect can be accounted for only by solving the conservation equation of the total enthalpy. However, even the DNS with the modified flamelet/progress-variable approach tends to underestimate the gaseous temperature in the central region of the spray jet flame. To increase the prediction accuracy, a combustion model for the partially premixed flame for the spray flame is necessary.

  19. Nonlinear behavior of acoustic waves in combustion chambers. I, II. [stability in solid propellant rocket engine and T burner

    NASA Technical Reports Server (NTRS)

    Culick, F. E. C.

    1976-01-01

    The general problem of the nonlinear growth and limiting amplitude of acoustic waves in a combustion chamber is treated in three parts: (1) the general conservation equations are expanded in two small parameters, and then combined to yield a nonlinear inhomogeneous wave equation, (2) the unsteady pressure and velocity fields are expressed as a synthesis of the normal modes of the chamber, but with unknown time-varying amplitudes, and (3) the system of nonlinear equations is treated by the method of averaging to produce a set of coupled nonlinear first order differential equations for the amplitudes and phases of the modes. This approximate analysis is applied to the investigation of the unstable motions in a solid propellant rocket engine and in a T burner.

  20. A statistical model for combustion resonance from a DI diesel engine with applications

    NASA Astrophysics Data System (ADS)

    Bodisco, Timothy; Low Choy, Samantha; Masri, Assaad; Brown, Richard J.

    2015-08-01

    Introduced in this paper is a Bayesian model for isolating the resonant frequency from combustion chamber resonance. The model shown in this paper focused on characterising the initial rise in the resonant frequency to investigate the rise of in-cylinder bulk temperature associated with combustion. By resolving the model parameters, it is possible to determine: the start of pre-mixed combustion, the start of diffusion combustion, the initial resonant frequency, the resonant frequency as a function of crank angle, the in-cylinder bulk temperature as a function of crank angle and the trapped mass as a function of crank angle. The Bayesian method allows for individual cycles to be examined without cycle-averaging-allowing inter-cycle variability studies. Results are shown for a turbo-charged, common-rail compression ignition engine run at 2000 rpm and full load.

  1. Combustion modeling in advanced gas turbine systems

    SciTech Connect

    Smoot, L.D.; Hedman, P.O.; Fletcher, T.H.; Brewster, B.S.; Kramer, S.K.

    1995-12-31

    Goal of DOE`s Advanced Turbine Systems program is to develop and commercialize ultra-high efficiency, environmentally superior, cost competitive gas turbine systems for base-load applications in utility, independent power producer, and industrial markets. Primary objective of the program here is to develop a comprehensive combustion model for advanced gas turbine combustion systems using natural gas (coal gasification or biomass fuels). The efforts included code evaluation (PCGC-3), coherent anti-Stokes Raman spectroscopy, laser Doppler anemometry, and laser-induced fluorescence.

  2. Preliminary Results of an Altitude-Wind-Tunnel Investigation of a TG-100A Gas Turbine-Propeller Engine. V; Combustion-Chamber Characteristics

    NASA Technical Reports Server (NTRS)

    Gensenheyner, Robert M.; Berdysz, Joseph J.

    1947-01-01

    An investigation to determine the performance and operational characteristics of the TG-1OOA gas turbine-propeller engine was conducted in the Cleveland altitude wind tunnel. As part of this investigation, the combustion-chamber performance was determined at pressure altitudes from 5000 to 35,000 feet, compressor-inlet rm-pressure ratios of 1.00 and 1.09, and engine speeds from 8000 to 13,000 rpm. Combustion-chamber performance is presented as a function of corrected engine speed and.correcte& horsepower. For the range of corrected engine speeds investigated, over-all total-pressure-loss ratio, cycle efficiency, ana the frac%ional loss in cycle efficiency resulting from pressure losses in the combustion chambers were unaffected by a change in altitude or compressor-inlet ram-pressure ratio. The scatter of combustion- efficiency data tended to obscure any effect of altitude or ram-pressure ratio. For the range of corrected horse-powers investigated, the total-pressure-loss ratio an& the fractional loss in cycle efficiency resulting from pressure losses in the combustion chambers decreased with an increase in corrected horsepower at a constant corrected engine speed. The combustion efficiency remained constant for the range of corrected horse-powers investigated at all corrected engine speeds.

  3. Chemical Kinetic Modeling of Biofuel Combustion

    NASA Astrophysics Data System (ADS)

    Sarathy, Subram Maniam

    Bioalcohols, such as bioethanol and biobutanol, are suitable replacements for gasoline, while biodiesel can replace petroleum diesel. Improving biofuel engine performance requires understanding its fundamental combustion properties and the pathways of combustion. This study's contribution is experimentally validated chemical kinetic combustion mechanisms for biobutanol and biodiesel. Fundamental combustion data and chemical kinetic mechanisms are presented and discussed to improve our understanding of biofuel combustion. The net environmental impact of biobutanol (i.e., n-butanol) has not been studied extensively, so this study first assesses the sustainability of n-butanol derived from corn. The results indicate that technical advances in fuel production are required before commercializing biobutanol. The primary contribution of this research is new experimental data and a novel chemical kinetic mechanism for n-butanol combustion. The results indicate that under the given experimental conditions, n-butanol is consumed primarily via abstraction of hydrogen atoms to produce fuel radical molecules, which subsequently decompose to smaller hydrocarbon and oxygenated species. The hydroxyl moiety in n-butanol results in the direct production of the oxygenated species such as butanal, acetaldehyde, and formaldehyde. The formation of these compounds sequesters carbon from forming soot precursors, but they may introduce other adverse environmental and health effects. Biodiesel is a mixture of long chain fatty acid methyl esters derived from fats and oils. This research study presents high quality experimental data for one large fatty acid methyl ester, methyl decanoate, and models its combustion using an improved skeletal mechanism. The results indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which ultimately lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular weight oxygenated compounds such as carbon monoxide, formaldehyde, and ketene. The study concludes that the oxygenated molecules in biofuels follow similar combustion pathways to the hydrocarbons in petroleum fuels. The oxygenated moiety's ability to sequester carbon from forming soot precursors is highlighted. However, the direct formation of oxygenated hydrocarbons warrants further investigation into the environmental and health impacts of practical biofuel combustion systems.

  4. Modelling of fission chambers in current mode—Analytical approach

    NASA Astrophysics Data System (ADS)

    Chabod, Sébastien; Fioni, Gabriele; Letourneau, Alain; Marie, Frédéric

    2006-10-01

    A comprehensive theoretical model is proposed to explain the functioning of fission chambers operated in current mode, even in very high neutron fluxes. The calibration curves are calculated as a function of basic physical parameters as fission rate, gas pressure and geometry of the chambers. The output current at saturation is precisely calculated, as well as the maximum voltage to be applied in order to avoid avalanche phenomena. The electric field distortion due to the space charge phenomena is also estimated. Within this model, the characteristic responses of fission chambers are correctly reproduced, in agreement with the experience feedback obtained at the ILL/Grenoble High-Flux Reactor.

  5. Combustion response modeling for composite solid propellants

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A computerized mathematical model of the combustion response function of composite solid propellants was developed with particular attention to the contributions of the solid phase heterogeneity. The one-dimensional model treats the solid phase as alternating layers of ammonium perchlorate and binder, with an exothermic melt layer at the surface. Solution of the Fourier heat equation in the solid provides temperature and heat flux distributions with space and time. The problem is solved by conserving the heat flux at the surface from that produced by a suitable model of the gas phase. An approximation of the BDP flame model is utilized to represent the gas phase. By the use of several reasonable assumptions, it is found that a significant portion of the problem can be solved in closed form. A method is presented by which the model can be applied to tetramodal particle size distributions. A computerized steady-state version of the model was completed, which served to validate the various approximations and lay a foundation for the combustion response modeling. The combustion response modeling was completed in a form which does not require an iterative solution, and some preliminary results were acquired.

  6. Modelling ionization chamber response to nonstandard beam configurations

    NASA Astrophysics Data System (ADS)

    Tantot, L.; Seuntjens, J.

    2008-02-01

    Novel technologies aiming at improving target dose coverage while minimising dose to organs at risk use delivery of radiation fields that significantly deviate from reference conditions defined in protocols such as TG-51 and TRS-398. The use of ionization chambers for patient-specific quality assurance of these new delivery procedures calibrated in reference conditions increases the uncertainties on dose delivery. The conversion of the dose to the chamber cavity to the dose to water becomes uncertain; and the geometrical details of the chamber, as well as the details of the delivery, are expected to be significant. In this study, a realistic model of the Exradin® A12 Farmer chamber is simulated. A framework is applied for the calculation of ionization chamber response to arbitrarily modulated fields as a summation of responses to pencil beams. This approach is used with the chamber model and tested against measurements in static open fields and dynamic MLC IMRT fields. As a benchmark test of the model, quality conversion factors values calculated by Monte-Carlo simulation with the chamber model are in agreement within 0.1 % and 0.4 % with those in the AAPM TG-51, for 6 MV and 18 MV photon beams, respectively. Pencil-beam kernels show a strong dependence on the geometrical details of the chamber. Kernel summations with open fields show a relative agreement within 4.0 % with experimental data; the agreement is within 2.0 % for dynamic MLC IMRT beams. Simulations show a strong sensitivity of chamber response on positioning uncertainties, sometimes leading to dose uncertainties of 15 %.

  7. Combustion

    NASA Technical Reports Server (NTRS)

    Bulzan, Dan

    2007-01-01

    An overview of the emissions related research being conducted as part of the Fundamental Aeronautics Subsonics Fixed Wing Project is presented. The overview includes project metrics, milestones, and descriptions of major research areas. The overview also includes information on some of the emissions research being conducted under NASA Research Announcements. Objective: Development of comprehensive detailed and reduced kinetic mechanisms of jet fuels for chemically-reacting flow modeling. Scientific Challenges: 1) Developing experimental facilities capable of handling higher hydrocarbons and providing benchmark combustion data. 2) Determining and understanding ignition and combustion characteristics, such as laminar flame speeds, extinction stretch rates, and autoignition delays, of jet fuels and hydrocarbons relevant to jet surrogates. 3) Developing comprehensive kinetic models for jet fuels.

  8. A Study of Combustion Process of LOX/Hydrogen Rocket Engine at Supercritical Pressure by Macroscopic Model (Part 1)

    NASA Astrophysics Data System (ADS)

    Yatsuyanagi, Nobuyuki

    This paper describes a study of combustion process of LOX/hydrogen rocket engine at supercritical pressure by macroscopic model. The model consists of rate controlling one by mixing process of supercritical temperature oxygen with hydrogen. Here, local mixing efficiency of the propellants is evaluated by Rupe's mixing index. And if we assumed that the local combustion rate was related to the Rupe's index as the exponential function, then the pressure distribution of combustion along chamber length calculated by the presented model could duplicate the pressure distribution observed by the experiments.

  9. Preliminary Results of an Altitude-Wind-Tunnel Investigation of an Axial-Flow Gas Turbine-Propeller Engine. 5; Combustion-Chamber Characterisitcs

    NASA Technical Reports Server (NTRS)

    Geisenheyner, Robert M.; Berdysz, Joseph J.

    1948-01-01

    An investigation to determine the performance and operational characteristics of an axial-flow gas turbine-propeller engine was conducted in the Cleveland altitude wind tunnel. As part of this investigation, the combustion-chamber performance was determined at pressure altitudes from 5000 to 35,000 feet, compressor-inlet ram-pressure ratios of 1.00 and 1.09, and engine speeds from 8000 to 13,000 rpm. Combustion-chamber performance is presented as a function of corrected engine speed and corrected horsepower. For the range of corrected engine speeds investigated, overall total-pressure-loss ratio, cycle efficiency, and the fractional loss in cycle efficiency resulting from pressure losses in the combustion chambers were unaffected by a change in altitude or compressor-inlet ram-pressure ratio. For the range of corrected horsepowers investigated, the total-pressure-loss ratio and the fractional loss in cycle efficiency resulting from pressure losses in the combustion chambers decreased with an increase in corrected horsepower at a constant corrected engine speed. The combustion efficiency remained constant for the range of corrected horsepowers investigated at all corrected engine speeds.

  10. Modeling the lubrication of the piston ring pack in internal combustion engines using the deterministic method

    E-print Network

    Chen, Haijie

    2011-01-01

    Piston ring packs are used in internal combustion engines to seal both the high pressure gas in the combustion chamber and the lubricant oil in the crank case. The interaction between the piston ring pack and the cylinder ...

  11. Engine Hydraulic Stability. [injector model for analyzing combustion instability

    NASA Technical Reports Server (NTRS)

    Kesselring, R. C.; Sprouse, K. M.

    1977-01-01

    An analytical injector model was developed specifically to analyze combustion instability coupling between the injector hydraulics and the combustion process. This digital computer dynamic injector model will, for any imposed chamber of inlet pressure profile with a frequency ranging from 100 to 3000 Hz (minimum) accurately predict/calculate the instantaneous injector flowrates. The injector system is described in terms of which flow segments enter and leave each pressure node. For each flow segment, a resistance, line lengths, and areas are required as inputs (the line lengths and areas are used in determining inertance). For each pressure node, volume and acoustic velocity are required as inputs (volume and acoustic velocity determine capacitance). The geometric criteria for determining inertances of flow segments and capacitance of pressure nodes was set. Also, a technique was developed for analytically determining time averaged steady-state pressure drops and flowrates for every flow segment in an injector when such data is not known. These pressure drops and flowrates are then used in determining the linearized flow resistance for each line segment of flow.

  12. Comparison of High Aspect Ratio Cooling Channel Designs for a Rocket Combustion Chamber with Development of an Optimized Design

    NASA Technical Reports Server (NTRS)

    Wadel, Mary F.

    1998-01-01

    An analytical investigation on the effect of high aspect ratio (height/width) cooling channels, considering different coolant channel designs, on hot-gas-side wall temperature and coolant pressure drop for a liquid hydrogen cooled rocket combustion chamber, was performed. Coolant channel design elements considered were: length of combustion chamber in which high aspect ratio cooling was applied, number of coolant channels, and coolant channel shape. Seven coolant channel designs were investigated using a coupling of the Rocket Thermal Evaluation code and the Two-Dimensional Kinetics code. Initially, each coolant channel design was developed, without consideration for fabrication, to reduce the hot-gas-side wall temperature from a given conventional cooling channel baseline. These designs produced hot-gas-side wall temperature reductions up to 22 percent, with coolant pressure drop increases as low as 7.5 percent from the baseline. Fabrication constraints for milled channels were applied to the seven designs. These produced hot-gas-side wall temperature reductions of up to 20 percent, with coolant pressure drop increases as low as 2 percent. Using high aspect ratio cooling channels for the entire length of the combustion chamber had no additional benefit on hot-gas-side wall temperature over using high aspect ratio cooling channels only in the throat region, but increased coolant pressure drop 33 percent. Independent of coolant channel shape, high aspect ratio cooling was able to reduce the hot-gas-side wall temperature by at least 8 percent, with as low as a 2 percent increase in coolant pressure drop. ne design with the highest overall benefit to hot-gas-side wall temperature and minimal coolant pressure drop increase was the design which used bifurcated cooling channels and high aspect ratio cooling in the throat region. An optimized bifurcated high aspect ratio cooling channel design was developed which reduced the hot-gas-side wall temperature by 18 percent and reduced the coolant pressure drop by 4 percent. Reductions of coolant mass flow rate of up to 50 percent were possible before the hot-gas-side wall temperature reached that of the baseline. These mass flow rate reductions produced coolant pressure drops of up to 57 percent.

  13. Simulation and modelling of the waves transmission and generation in a stator blade row in a combustion-noise framework

    NASA Astrophysics Data System (ADS)

    Leyko, Matthieu; Duran, Ignacio; Moreau, Stéphane; Nicoud, Franck; Poinsot, Thierry

    2014-11-01

    The combustion noise in aero-engines is known to have two different origins. First, the direct combustion noise is directly generated by the flame itself. Second, the indirect combustion noise is caused by the acceleration in the turbine stages of entropy spots generated by the combustion. In both cases, the turbo-machinery is involved in the combustion-noise transmission and generation. Numerical simulations are performed in the present study to assess the global noise for a real aeronautical configuration. On the one hand, the acoustic and entropy transfer functions of an isolated blade row are obtained using two-dimensional unsteady simulations. The transfer functions of the blade row are compared with the model of Cumpsty and Marble that assumes an axially compact configuration. On the other hand, the acoustic and entropy sources coming from a combustion chamber are calculated from a three-dimensional Large Eddy Simulation (LES). This allows an evaluation of the error introduced by the model for the present combustion chamber using the previous numerical simulations. A significant error is found for the indirect combustion noise, whereas it stays reasonable for the direct one.

  14. Dynamic Modelling and Control Design of Pre-combustion Power

    E-print Network

    Foss, Bjarne A.

    Lei Zhao Dynamic Modelling and Control Design of Pre-combustion Power Cycles Thesis for the degree-8181 ITK Report 2012-5-W Doctoral theses at NTNU, 2012:227 Printed by NTNU-trykk #12;Summary Pre-combustion capture is an important CCS technology. Pre-combustion capture of CO2 incurs less of an energy penalty

  15. Modeling gas exchange in a closed plant growth chamber

    NASA Technical Reports Server (NTRS)

    Cornett, J. D.; Hendrix, J. E.; Wheeler, R. M.; Ross, C. W.; Sadeh, W. Z.

    1994-01-01

    Fluid transport models for fluxes of water vapor and CO2 have been developed for one crop of wheat and three crops of soybean grown in a closed plant growth chamber. Correspondence among these fluxes is discussed. Maximum fluxes of gases are provided for engineering design requirements of fluid recycling equipment in growth chambers. Furthermore, to investigate the feasibility of generalized crop models, dimensionless representations of water vapor fluxes are presented. The feasibility of such generalized models and the need for additional data are discussed.

  16. Modeling Gas Exchange in a Closed Plant Growth Chamber

    NASA Technical Reports Server (NTRS)

    Cornett, J. D.; Hendrix, J. E.; Wheeler, R. M.; Ross, C. W.; Sadeh, W. Z.

    1994-01-01

    Fluid transport models for fluxes of water vapor and CO2 have been developed for one crop of wheat and three crops of soybean grown in a closed plant a growth chamber. Correspondence among these fluxes is discussed. Maximum fluxes of gases are provided for engineering design requirements of fluid recycling equipment in growth chambers. Furthermore, to investigate the feasibility of generalized crop models, dimensionless representations of water vapor fluxes are presented. The feasibility of such generalized models and the need for additional data are discussed.

  17. A review of acoustic dampers applied to combustion chambers in aerospace industry

    NASA Astrophysics Data System (ADS)

    Zhao, Dan; Li, X. Y.

    2015-04-01

    In engine combustion systems such as rockets, aero-engines and gas turbines, pressure fluctuations are always present, even during normal operation. One of design prerequisites for the engine combustors is stable operation, since large-amplitude self-sustained pressure fluctuations (also known as combustion instability) have the potential to cause serious structural damage and catastrophic engine failure. To dampen pressure fluctuations and to reduce noise, acoustic dampers are widely applied as a passive control means to stabilize combustion/engine systems. However, they cannot respond to the dynamic changes of operating conditions and tend to be effective over certain narrow range of frequencies. To maintain their optimum damping performance over a broad frequency range, extensive researches have been conducted during the past four decades. The present work is to summarize the status, challenges and progress of implementing such acoustic dampers on engine systems. The damping effect and mechanism of various acoustic dampers, such as Helmholtz resonators, perforated liners, baffles, half- and quarter-wave tube are introduced first. A summary of numerical, experimental and theoretical studies are then presented to review the progress made so far. Finally, as an alternative means, ';tunable acoustic dampers' are discussed. Potential, challenges and issues associated with the dampers practical implementation are highlighted.

  18. Effect of Combustion-chamber Shape on the Performance of a Prechamber Compression-ignition Engine

    NASA Technical Reports Server (NTRS)

    Moore, C S; Collins, J H , Jr

    1934-01-01

    The effect on engine performance of variations in the shape of the prechamber, the shape and direction of the connecting passage, the chamber volume using a tangential passage, the injection system, and the direction od the fuel spray in the chamber was investigated using a 5 by 7 inch single-cylinder compression-ignition engine. The results show that the performance of this engine can be considerably improved by selecting the best combination of variables and incorporating them in a single design. The best combination as determined from these tests consisted of a disk-shaped chamber connected to the cylinder by means of a flared tangential passage. The fuel was injected through a single-orifice nozzle directed normal to the air swirl and in the same plane. At an engine speed of 1,500 r.p.m. and with the theoretical fuel quantity for no excess air, the engine developed a brake mean effective pressure of 115 pounds per square inch with a fuel consumption of 0.49 pound per brake horsepower-hour and an explosion pressure of 820 pounds per square inch. A brake mean effective pressure of 100 pounds per square inch with a brake-fuel consumption of 0.44 pound per horsepower-hour at 1,500 r.p.m. was obtained.

  19. Dry low NOx combustion system with pre-mixed direct-injection secondary fuel nozzle

    DOEpatents

    Zuo, Baifang; Johnson, Thomas; Ziminsky, Willy; Khan, Abdul

    2013-12-17

    A combustion system includes a first combustion chamber and a second combustion chamber. The second combustion chamber is positioned downstream of the first combustion chamber. The combustion system also includes a pre-mixed, direct-injection secondary fuel nozzle. The pre-mixed, direct-injection secondary fuel nozzle extends through the first combustion chamber into the second combustion chamber.

  20. RSRM Chamber Pressure Oscillations: Transit Time Models and Unsteady CFD

    NASA Technical Reports Server (NTRS)

    Nesman, Tom; Stewart, Eric

    1996-01-01

    Space Shuttle solid rocket motor low frequency internal pressure oscillations have been observed since early testing. The same type of oscillations also are present in the redesigned solid rocket motor (RSRM). The oscillations, which occur during RSRM burn, are predominantly at the first three motor cavity longitudinal acoustic mode frequencies. Broadband flow and combustion noise provide the energy to excite these modes at low levels throughout motor burn, however, at certain times during burn the fluctuating pressure amplitude increases significantly. The increased fluctuations at these times suggests an additional excitation mechanism. The RSRM has inhibitors on the propellant forward facing surface of each motor segment. The inhibitors are in a slot at the segment field joints to prevent burning at that surface. The aft facing segment surface at a field joint slot burns and forms a cavity of time varying size. Initially the inhibitor is recessed in the field joint cavity. As propellant burns away the inhibitor begins to protrude into the bore flow. Two mechanisms (transit time models) that are considered potential pressure oscillation excitations are cavity-edge tones, and inhibitor hole-tones. Estimates of frequency variation with time of longitudinal acoustic modes, cavity edge-tones, and hole-tones compare favorably with frequencies measured during motor hot firing. It is believed that the highest oscillation amplitudes occur when vortex shedding frequencies coincide with motor longitudinal acoustic modes. A time accurate computational fluid dynamic (CFD) analysis was made to replicate the observations from motor firings and to observe the transit time mechanisms in detail. FDNS is the flow solver used to detail the time varying aspects of the flow. The fluid is approximated as a single-phase ideal gas. The CFD model was an axisymmetric representation of the RSRM at 80 seconds into burn.Deformation of the inhibitors by the internal flow was determined through an iterative structural and CFD analysis. The analysis domain ended just upstream of the nozzle throat. This is an acoustic boundary condition that caused the motor to behave as a closed-open organ pipe. This differs from the RSRM which behaves like a closed-closed organ pipe. The unsteady CFD solution shows RSRM chamber pressure oscillations predominately at the longitudinal acoustic mode frequencies of a closed-open organ pipe. Vortex shedding in the joint cavities and at the inhibitors contribute disturbances to the flow at the second longitudinal acoustic mode frequency. Further studies are planned using an analysis domain that extends downstream of the nozzle throat.

  1. Altitude Test Chamber Investigation of Performance of a 28-inch Ram-jet Engine II : Effects of Gutter Width and Blocked Area on Operating Range and Combustion Efficiency

    NASA Technical Reports Server (NTRS)

    Shillito, T B; Jones, W L; Kahn, R W

    1950-01-01

    Altitude-test-chamber investigation of effects of flame-holder blocked area and gutter width on performance of 28-inch diameter ram jet at simulated flight Mach number of 2.0 for altitudes from 40,000 to 55,000 feet was conducted at NACA Lewis laboratory. Ten flame holders investigated covered gutter widths from 1.00 to 2.50 inches and blocked areas from 40.5 to 62.0 percent of combustion-chamber area. Gutter width did not appreciably affect combustion efficiency. Increase in blocked area from 40 to 62 percent resulted in 5- to 10-percent increase in combustion efficiency. Increasing gutter width resulted in improvement in fuel-air-ratio operating range.

  2. Combustion Model for a CFB Boiler with Consideration of Post-Combustion in the Cyclone

    NASA Astrophysics Data System (ADS)

    Li, S. H.; Yang, H. R.; Zhang, H.; Wu, Y. X.; Lu, J. F.; Yue, G. X.

    Severe post combustion in the cyclone of CFB boilers could destroy heat absorbing balance among the heating surfaces and cause overheating problem for reheaters and superheaters. However, post combustion in the cyclone is rarely considered in the design phase of a CFB boiler. Based on our previous experiment results, group combustion model is used in this study to estimate the combustion of particles in the cyclone. It is found that the combustion of particles in the cyclone did not contribute as much as we anticipated to the temperature augment in the cyclone because of great oxygen diffusion resistance in near-wall particle layer. Post combustion model in the cyclone is then added into a one-dimensional combustion model of CFB boiler, in which the gas-solid flow, reaction, and heat absorption at different vertical locations in a CFB boiler can be well predicted with the knowledge of operation parameters. The new model was used to estimate the influence of some operation parameters on the post combustion in the cyclone and heat releasing fraction in the cyclone. The prediction results are very good.

  3. Carbon Deposition Model for Oxygen-Hydrocarbon Combustion, Volume 2

    NASA Technical Reports Server (NTRS)

    Hernandez, R.; Ito, J. I.; Niiya, K. Y.

    1987-01-01

    Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at chamber pressures of 1000 to 1500 psia. No carbon deposition on chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational concequences of carbon deposition on preburner/gas generator performance. This is Volume 2 of the report, which contains data plots of all the test programs.

  4. Numerical Modeling of Spray Combustion with an Unstructured-Grid Method

    NASA Technical Reports Server (NTRS)

    Shang, H. M.; Chen, Y. S.; Liaw, P.; Shih, M. H.; Wang, T. S.

    1996-01-01

    The present unstructured-grid method follows strictly the basic finite volume forms of the conservation laws of the governing equations for the entire flow domain. High-order spatially accurate formulation has been employed for the numerical solutions of the Navier-Stokes equations. A two-equation k-epsilon turbulence model is also incorporated in the unstructured-grid solver. The convergence of the resulted linear algebraic equation is accelerated with preconditioned Conjugate Gradient method. A statistical spray combustion model has been incorporated into the present unstructured-grid solver. In this model, spray is represented by discrete particles, rather than by continuous distributions. A finite number of computational particles are used to predict a sample of total population of particles. Particle trajectories are integrated using their momentum and motion equations and particles exchange mass, momentum and energy with the gas within the computational cell in which they are located. The interaction calculations are performed simultaneously and eliminate global iteration for the two-phase momentum exchange. A transient spray flame in a high pressure combustion chamber is predicted and then the solution of liquid-fuel combusting flow with a rotating cup atomizer is presented and compared with the experimental data. The major conclusion of this investigation is that the unstructured-grid method can be employed to study very complicated flow fields of turbulent spray combustion. Grid adaptation can be easily achieved in any flow domain such as droplet evaporation and combustion zone. Future applications of the present model can be found in the full three-dimensional study of flow fields of gas turbine and liquid propulsion engine combustion chambers with multi-injectors.

  5. Design and testing of a model CELSS chamber robot

    NASA Technical Reports Server (NTRS)

    Davis, Mark; Dezego, Shawn; Jones, Kinzy; Kewley, Christopher; Langlais, Mike; Mccarthy, John; Penny, Damon; Bonner, Tom; Funderburke, C. Ashley; Hailey, Ruth

    1994-01-01

    A robot system for use in an enclosed environment was designed and tested. The conceptual design will be used to assist in research performed by the Controlled Ecological Life Support System (CELSS) project. Design specifications include maximum load capacity, operation at specified environmental conditions, low maintenance, and safety. The robot system must not be hazardous to the sealed environment, and be capable of stowing and deploying within a minimum area of the CELSS chamber facility. This design consists of a telescoping robot arm that slides vertically on a shaft positioned in the center of the CELSS chamber. The telescoping robot arm consists of a series of links which can be fully extended to a length equal to the radius of the working envelope of the CELSS chamber. The vertical motion of the robot arm is achieved through the use of a combination ball screw/ball spline actuator system. The robot arm rotates cylindrically about the vertical axis through use of a turntable bearing attached to a central mounting structure fitted to the actuator shaft. The shaft is installed in an overhead rail system allowing the entire structure to be stowed and deployed within the CELSS chamber. The overhead rail system is located above the chamber's upper lamps and extends to the center of the CELSS chamber. The mounting interface of the actuator shaft and rail system allows the entire actuator shaft to be detached and removed from the CELSS chamber. When the actuator shaft is deployed, it is held fixed at the bottom of the chamber by placing a square knob on the bottom of the shaft into a recessed square fitting in the bottom of the chamber floor. A support boot ensures the rigidity of the shaft. Three student teams combined into one group designed a model of the CELSS chamber robot that they could build. They investigated materials, availability, and strength in their design. After the model arm and stand were built, the class performed pre-tests on the entire system. A stability pre-test was used to determine whether the model robot arm would tip over on the stand when it was fully extended. Results showed the stand tipped when 50 Newtons were applied horizontally to the top of the vertical shaft while the arm was fully extended. This proved that it was stable. Another pre-test was the actuator slip test used to determine if there is an adequate coefficient of friction between the actuator drive wheels and drive cable to enable the actuator to fully extend and retract the arm. This pre-test revealed that the coefficient of friction was not large enough to prevent slippage. Sandpaper was glued to the drive wheel and this eliminated the slippage problem. The class preformed a fit test in the CELSS chamber to ensure that the completed robot arm is capable of reaching the entire working envelope. The robot was centered in the chamber and the arm was fully extended to the sides of the chamber. The arm was also able to retract to clear the drain pipes separating the upper and lower plant trays.

  6. Design and testing of a model CELSS chamber robot

    NASA Astrophysics Data System (ADS)

    Davis, Mark; Dezego, Shawn; Jones, Kinzy; Kewley, Christopher; Langlais, Mike; McCarthy, John; Penny, Damon; Bonner, Tom; Funderburke, C. Ashley; Hailey, Ruth

    1994-08-01

    A robot system for use in an enclosed environment was designed and tested. The conceptual design will be used to assist in research performed by the Controlled Ecological Life Support System (CELSS) project. Design specifications include maximum load capacity, operation at specified environmental conditions, low maintenance, and safety. The robot system must not be hazardous to the sealed environment, and be capable of stowing and deploying within a minimum area of the CELSS chamber facility. This design consists of a telescoping robot arm that slides vertically on a shaft positioned in the center of the CELSS chamber. The telescoping robot arm consists of a series of links which can be fully extended to a length equal to the radius of the working envelope of the CELSS chamber. The vertical motion of the robot arm is achieved through the use of a combination ball screw/ball spline actuator system. The robot arm rotates cylindrically about the vertical axis through use of a turntable bearing attached to a central mounting structure fitted to the actuator shaft. The shaft is installed in an overhead rail system allowing the entire structure to be stowed and deployed within the CELSS chamber. The overhead rail system is located above the chamber's upper lamps and extends to the center of the CELSS chamber. The mounting interface of the actuator shaft and rail system allows the entire actuator shaft to be detached and removed from the CELSS chamber. When the actuator shaft is deployed, it is held fixed at the bottom of the chamber by placing a square knob on the bottom of the shaft into a recessed square fitting in the bottom of the chamber floor. A support boot ensures the rigidity of the shaft. Three student teams combined into one group designed a model of the CELSS chamber robot that they could build. They investigated materials, availability, and strength in their design. After the model arm and stand were built, the class performed pre-tests on the entire system. A stability pre-test was used to determine whether the model robot arm would tip over on the stand when it was fully extended. Results showed the stand tipped when 50 Newtons were applied horizontally to the top of the vertical shaft while the arm was fully extended. chamber to ensure that the completed robot arm is capable of reaching the entire working envelope. -The robot was centered in the chamber and the arm was fully extended to the sides of the chamber. The arm was also able to retract to clear the drain pipes separating the upper and lower plant trays.

  7. ZMOTTO- MODELING THE INTERNAL COMBUSTION ENGINE

    NASA Technical Reports Server (NTRS)

    Zeleznik, F. J.

    1994-01-01

    The ZMOTTO program was developed to model mathematically a spark-ignited internal combustion engine. ZMOTTO is a large, general purpose program whose calculations can be established at five levels of sophistication. These five models range from an ideal cycle requiring only thermodynamic properties, to a very complex representation demanding full combustion kinetics, transport properties, and poppet valve flow characteristics. ZMOTTO is a flexible and computationally economical program based on a system of ordinary differential equations for cylinder-averaged properties. The calculations assume that heat transfer is expressed in terms of a heat transfer coefficient and that the cylinder average of kinetic plus potential energies remains constant. During combustion, the pressures of burned and unburned gases are assumed equal and their heat transfer areas are assumed proportional to their respective mass fractions. Even the simplest ZMOTTO model provides for residual gas effects, spark advance, exhaust gas recirculation, supercharging, and throttling. In the more complex models, 1) finite rate chemistry replaces equilibrium chemistry in descriptions of both the flame and the burned gases, 2) poppet valve formulas represent fluid flow instead of a zero pressure drop flow, and 3) flame propagation is modeled by mass burning equations instead of as an instantaneous process. Input to ZMOTTO is determined by the model chosen. Thermodynamic data is required for all models. Transport properties and chemical kinetics data are required only as the model complexity grows. Other input includes engine geometry, working fluid composition, operating characteristics, and intake/exhaust data. ZMOTTO accommodates a broad spectrum of reactants. The program will calculate many Otto cycle performance parameters for a number of consecutive cycles (a cycle being an interval of 720 crankangle degrees). A typical case will have a number of initial ideal cycles and progress through levels of nonideal cycles. ZMOTTO has restart capabilities and permits multicycle calculations with parameters varying from cycle to cycle. ZMOTTO is written in FORTRAN IV (IBM Level H) but has also been compiled with IBM VSFORTRAN (1977 standard). It was developed on an IBM 3033 under the TSS operating system and has also been implemented under MVS. Approximately 412K of 8 bit bytes of central memory are required in a nonpaging environment. ZMOTTO was developed in 1985.

  8. Analysis of the Effect of Geometry Generated Turbulence on HCCI Combustion by Multi-Zone Modeling

    SciTech Connect

    Aceves, S M; Flowers, D L; Martinez-Frias, J; Espinosa-Loza, F; Christensen, M; Johansson, B; Hessel, R P

    2004-12-13

    This paper illustrates the applicability of a sequential fluid mechanics, multi-zone chemical kinetics model to analyze HCCI experimental data for two combustion chamber geometries with different levels of turbulence: a low turbulence disc geometry (flat top piston), and a high turbulence square geometry (piston with a square bowl). The model uses a fluid mechanics code to determine temperature histories in the engine as a function of crank angle. These temperature histories are then fed into a chemical kinetic solver, which determines combustion characteristics for a relatively small number of zones (40). The model makes the assumption that there is no direct linking between turbulence and combustion. The results show that the multi-zone model yields good results for both the disc and the square geometries. The model makes good predictions of pressure traces and heat release rates. The experimental results indicate that the high turbulence square geometry has longer burn duration than the low turbulence disc geometry. This difference can be explained by the sequential multi-zone model, which indicates that the cylinder with the square bowl has a thicker boundary layer that results in a broader temperature distribution. This broader temperature distribution tends to lengthen the combustion, as cold mass within the cylinder takes longer to reach ignition temperature when compressed by the expansion of the first burned gases. The multi-zone model, which makes the basic assumption that HCCI combustion is controlled by chemical kinetics, is therefore capable of explaining the experimental results obtained for different levels of turbulence, without considering a direct interaction between turbulence and combustion. A direct connection between turbulence and HCCI combustion may still exists, but it seems to play a relatively minor role in determining burn duration at the conditions analyzed in this paper.

  9. Subgrid scale modelling for MILD combustion

    E-print Network

    Minamoto, Y.; Swaminathan, N.

    2014-07-27

    these requirements it is highly susceptible to thermo-acoustic instability. Moderate or Intense Low-oxygen Dilution (MILD) combus- tion is another technology employing diluted and preheated reactants which can overcome the shortcoming of lean premixed combustion... . The (EGR or FRG) or staged fuel injection methods. Direct photographs of MILD combustion from previous experimental studies [1–3] suggest spatially uniform and steady combustion. A possible theo- retical explanation for this uniform combustion has been...

  10. On the TFNS Subgrid Models for Liquid-Fueled Turbulent Combustion

    NASA Technical Reports Server (NTRS)

    Liu, Nan-Suey; Wey, Thomas

    2014-01-01

    This paper describes the time-filtered Navier-Stokes (TFNS) approach capable of capturing unsteady flow structures important for turbulent mixing in the combustion chamber and two different subgrid models used to emulate the major processes occurring in the turbulence-chemistry interaction. These two subgrid models are termed as LEM-like model and EUPDF-like model (Eulerian probability density function), respectively. Two-phase turbulent combustion in a single-element lean-direct-injection (LDI) combustor is calculated by employing the TFNS/LEM-like approach as well as the TFNS/EUPDF-like approach. Results obtained from the TFNS approach employing these two different subgrid models are compared with each other, along with the experimental data, followed by more detailed comparison between the results of an updated calculation using the TFNS/LEM-like model and the experimental data.

  11. Performance of thin-ceramic-coated combustion chamber with gasoline and methanol as fuels in a two-stroke SI engine

    SciTech Connect

    Poola, R.B.; Nagalingam, B.; Gopalakrishnan, K.V.

    1994-10-01

    The performance of a conventional, carburated, two-stroke, spark-ignition (SI) engine can be improved by providing moderate thermal insulation in the combustion chamber. In the present investigation the combustion chamber surface was coated with a 0.5-mm thickness of partially stabilized zirconia, and experiments were carried out in a single cylinder, two-stroke SI engine with gasoline and methanol as fuels. The results indicate that with gasoline as fuel, the thin ceramic-coated combustion chamber improves the part load to medium load operation considerably, but it affects the performance at higher speeds and at higher loads to the extent of knock and loss of brake power by about 18%. However with methanol as a fuel the performance is better under most of the operating range and free from knock. Emissions are significantly reduced by about 3 to 4% volume, for both gasoline and methanol fuels due to relatively lean operation and more complete combustion. 35 refs., 13 figs., 3 tabs.

  12. Carbon deposition model for oxygen-hydrocarbon combustion, volume 1

    NASA Technical Reports Server (NTRS)

    Hernandez, R.; Ito, J. I.; Niiya, K. Y.

    1987-01-01

    Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at pressures of 1000 to 1500 psia. No carbon deposition on the chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational consequences of carbon deposition on preburner/gas generator performance. The report is in two volumes, of which this is Volume 1 covering the main body of the report plus Appendixes A through D.

  13. Control-oriented modeling of combustion and flow processes in liquid propellant rocket engines

    NASA Technical Reports Server (NTRS)

    Bentsman, Joseph; Pearlstein, Arne J.; Wilcutts, Mark A.

    1990-01-01

    This paper presents a control-oriented model of the flow, reaction, and transport processes in liquid propellant rocket combustion chambers, based on the multicomponent conservation laws of gas dynamics. This model provides a framework for the inclusion of detailed chemical kinetic relations, viscous and other dissipative effects, a variety of actuators and sensors, as well as process and measurement disturbances. In addition to its potential usefulness to the designer in understanding the dynamical complexity of the system and the sources of model uncertainty, the model provides a rigorous basis for control system design. An appraisal of current and feasible actuators and sensors, and their mathematical representation are included.

  14. Chemical Kinetic Models for HCCI and Diesel Combustion

    SciTech Connect

    Pitz, W J; Westbook, C K; Mehl, M

    2008-10-30

    Hydrocarbon fuels for advanced combustion engines consist of complex mixtures of hundreds or even thousands of different components. These components can be grouped into a number of chemically distinct classes, consisting of n-paraffins, branched paraffins, cyclic paraffins, olefins, oxygenates, and aromatics. Biodiesel contains its own unique chemical class called methyl esters. The fractional amounts of these chemical classes are quite different in gasoline, diesel fuel, oil-sand derived fuels and bio-derived fuels, which contributes to the very different combustion characteristics of each of these types of combustion systems. The objectives of this project are: (1) Develop detailed chemical kinetic models for fuel components used in surrogate fuels for diesel and HCCI engines; (2) Develop surrogate fuel models to represent real fuels and model low temperature combustion strategies in HCCI and diesel engines that lead to low emissions and high efficiency; and (3) Characterize the role of fuel composition on low temperature combustion modes of advanced combustion engines.

  15. Insights into Conventional and Low Temperature Diesel Combustion Using Combustion Trajectory Prediction Model 

    E-print Network

    Bittle, Joshua A

    2014-04-18

    Attempting to bridge the gap between typical off-line engine simulations and online real-time control strategies a computationally efficient model has been created that predicts the combustion trajectory (path through the ?-T plane). To give...

  16. Finite difference seismic modeling of axial magma chambers

    SciTech Connect

    Swift, S.A.; Dougherty, M.E.; Stephen, R.A. )

    1990-11-01

    The authors tested the feasibility of using finite difference methods to model seismic propagation at {approximately}10 Hx through a two-dimensional representation of an axial magma chamber with a thin, liquid lid. This technique produces time series of displacement or pressure at seafloor receivers to mimic a seismic refraction experiment and snapshots of P and S energy propagation. The results indicate that the implementation is stable for models with sharp velocity contrasts and complex geometries. The authors observe a high-energy, downward-traveling shear phase, observable only with borehole receivers, that would be useful in studying the nature and shape of magma chambers. The ability of finite difference methods to model high-order wave phenomena makes this method ideal for testing velocity models of spreading axes and for planning near-axis drilling of the East Pacific Rise in order to optimize the benefits from shear wave imaging of sub-axis structure.

  17. Modeling complex chemical effects in turbulent nonpremixed combustion

    NASA Technical Reports Server (NTRS)

    Smith, Nigel S. A.

    1995-01-01

    Virtually all of the energy derived from the consumption of combustibles occurs in systems which utilize turbulent fluid motion. Since combustion is largely related to the mixing of fluids and mixing processes are orders of magnitude more rapid when enhanced by turbulent motion, efficiency criteria dictate that chemically powered devices necessarily involve fluid turbulence. Where combustion occurs concurrently with mixing at an interface between two reactive fluid bodies, this mode of combustion is called nonpremixed combustion. This is distinct from premixed combustion where flame-fronts propagate into a homogeneous mixture of reactants. These two modes are limiting cases in the range of temporal lag between mixing of reactants and the onset of reaction. Nonpremixed combustion occurs where this lag tends to zero, while premixed combustion occurs where this lag tends to infinity. Many combustion processes are hybrids of these two extremes with finite non-zero lag times. Turbulent nonpremixed combustion is important from a practical standpoint because it occurs in gas fired boilers, furnaces, waste incinerators, diesel engines, gas turbine combustors, and afterburners etc. To a large extent, past development of these practical systems involved an empirical methodology. Presently, efficiency standards and emission regulations are being further tightened (Correa 1993), and empiricism has had to give way to more fundamental research in order to understand and effectively model practical combustion processes (Pope 1991). A key element in effective modeling of turbulent combustion is making use of a sufficiently detailed chemical kinetic mechanism. The prediction of pollutant emission such as oxides of nitrogen (NO(x)) and sulphur (SO(x)) unburned hydrocarbons, and particulates demands the use of detailed chemical mechanisms. It is essential that practical models for turbulent nonpremixed combustion are capable of handling large numbers of 'stiff' chemical species equations.

  18. Development of a CuNiCrAl Bond Coat for Thermal Barrier Coatings in Rocket Combustion Chambers

    NASA Astrophysics Data System (ADS)

    Fiedler, Torben; Rösler, Joachim; Bäker, Martin

    2015-10-01

    The lifetime of rocket combustion chambers can be increased by applying thermal barrier coatings. The standard coating systems usually used in gas turbines or aero engines will fail at the bond coat/substrate interface due to the chemical difference as well as the different thermal expansion between the copper liner and the applied NiCrAlY bond coat. A new bond coat alloy for rocket engine applications was designed previously with a chemical composition and coefficient of thermal expansion more similar to the copper substrate. Since a comparable material has not been applied by thermal spraying before, coating tests have to be carried out. In this work, the new Ni-30%Cu-6%Al-5%Cr bond coat alloy is applied via high velocity oxygen fuel spraying. In a first step, the influence of different coating parameters on, e.g., porosity, amount of unmolten particles, and coating roughness is investigated and a suitable parameter set for further studies is chosen. In a second step, copper substrates are coated with the chosen parameters to test the feasibility of the process. The high-temperature behavior and adhesion is tested with laser cycling experiments. The new coatings showed good adhesion even at temperatures beyond the maximum test temperatures of the NiCrAlY bond coat in previous studies.

  19. Thermal radiation of heterogeneous combustion products in the model rocket engine plume

    NASA Astrophysics Data System (ADS)

    Kuzmin, V. A.; Maratkanova, E. I.; Zagray, I. A.; Rukavishnikova, R. V.

    2015-05-01

    The work presents a method of complex investigation of thermal radiation emitted by heterogeneous combustion products in the model rocket engine plume. Realization of the method has allowed us to obtain full information on the results in all stages of calculations. Dependence of the optical properties (complex refractive index), the radiation characteristics (coefficients and cross sections) and emission characteristics (flux densities, emissivity factors) of the main determining factors and parameters was analyzed. It was found by the method of computational experiment that the presence of the gaseous phase in the combustion products causes a strongly marked selectivity of emission, due to which the use of gray approximation in the calculation of thermal radiation is unnecessary. The influence of the optical properties, mass fraction, the function of particle size distribution, and the temperature of combustion products on thermal radiation in the model rocket engine plume was investigated. The role of "spotlight" effect-increasing the amount of energy of emission exhaust combustion products due to scattering by condensate particles radiation from the combustion chamber-was established quantitatively.

  20. A combustion model for IC engine combustion simulations with multi-component fuels

    SciTech Connect

    Ra, Youngchul; Reitz, Rolf D.

    2011-01-15

    Reduced chemical kinetic mechanisms for the oxidation of representative surrogate components of a typical multi-component automotive fuel have been developed and applied to model internal combustion engines. Starting from an existing reduced mechanism for primary reference fuel (PRF) oxidation, further improvement was made by including additional reactions and by optimizing reaction rate constants of selected reactions. Using a similar approach to that used to develop the reduced PRF mechanism, reduced mechanisms for the oxidation of n-tetradecane, toluene, cyclohexane, dimethyl ether (DME), ethanol, and methyl butanoate (MB) were built and combined with the PRF mechanism to form a multi-surrogate fuel chemistry (MultiChem) mechanism. The final version of the MultiChem mechanism consists of 113 species and 487 reactions. Validation of the present MultiChem mechanism was performed with ignition delay time measurements from shock tube tests and predictions by comprehensive mechanisms available in the literature. A combustion model was developed to simulate engine combustion with multi-component fuels using the present MultiChem mechanism, and the model was applied to simulate HCCI and DI engine combustion. The results show that the present multi-component combustion model gives reliable performance for combustion predictions, as well as computational efficiency improvements through the use of reduced mechanism for multi-dimensional CFD simulations. (author)

  1. A filter-independent model identification technique for turbulent combustion modeling

    E-print Network

    Data analysis Dimensionality reduction Principal Component Analysis (PCA) Turbulent combustion modelingA filter-independent model identification technique for turbulent combustion modeling Amir Biglari be solved via application of Principal Component Analysis (PCA). This technique provides a robust

  2. Influence of air-staging on the concentration profiles of NH{sub 3} and HCN in the combustion chamber of a CFB boiler burning coal

    SciTech Connect

    Kassman, H.; Karlsson, M.; Aamand, L.E.

    1999-07-01

    The characterization of the concentration profiles of NH{sub 3} and HCN are of great importance for increasing the knowledge of the formation and destruction pathways of NO and N{sub 2}O in a fluidized bed boiler. Further improvements of the sampling methods for the determination of both NH{sub 3} and HCN in the combustion chamber in full-scale CFB boilers are also needed. A gas-sampling probe connected to a Fourier Transform Infrared (FTIR) instrument and a gas-quenching (GQ) probe in which the sample is quenched directly in the probe tip by a circulating trapper solution were used. The FTIR technique is based on analysis of hot combustion gases, whereas the trapper solutions from the GQ probe were analyzed by means of wet chemistry. The tests were performed during coal combustion in a 12 MW CFB boiler, which was operated at three air-staging cases with the addition of limestone for sulfur capture. The concentration profiles of NH{sub 3} and HCN in the combustion chamber showed a different pattern concerning the influence of air-staging. The highest levels of NH{sub 3} were observed during reducing condition (severe air-staging), and the lowest were found under oxidizing conditions (no air-staging). The levels of HCN were much lower than those measured for NH{sub 3}. The highest levels of HCN were observed for reversed air-staging and severe air-staging showed almost no HCN. The potential reactors involving NH{sub 3} and HCN in the combustion chamber as well as the potential measurement errors in each sampling technique are discussed for the three air-staging cases.

  3. A practical approach to estimate emission rates of indoor air pollutants due to the use of personal combustible products based on small-chamber studies.

    PubMed

    Szulejko, Jan E; Kim, Ki-Hyun

    2016-02-01

    As emission rates of airborne pollutants are commonly measured from combusting substances placed inside small chambers, those values need to be re-evaluated for the possible significance under practical conditions. Here, a simple numerical procedure is investigated to extrapolate the chamber-based emission rates of formaldehyde that can be released from various combustible sources including e-cigarettes, conventional cigarettes, or scented candles to their concentration levels in a small room with relatively poor ventilation. This simple procedure relies on a mass balance approach by considering the masses of pollutants emitted from source and lost through ventilation under the assumption that mixing occurs instantaneously in the room without chemical reactions or surface sorption. The results of our study provide valuable insights into re-evaluation procedure of chamber data to allow comparison between extrapolated and recommended values to judge the safe use of various combustible products in confined spaces. If two scented candles with a formaldehyde emission rate of 310 µg h(-1) each were lit for 4 h in a small 20 m(3) room with an air change rate of 0.5 h(-1), then the 4-h (candle lit) and 8-h (up to 8 h after candle lighting) TWA [FA] were determined to be 28.5 and 23.5 ppb, respectively. This is clearly above the 8-h NIOSH recommended exposure limit (REL) time weighted average of 16 ppb. PMID:26495830

  4. Modeling of CWM droplet combustion. Final report

    SciTech Connect

    Pandalai, K.; Aggarwal, S.; Sirignano, W.

    1983-10-01

    The objective of the present study was to develop a one-dimensional, unsteady state model for coal-water mixture droplet combustion, and to compare the characteristic times for the various processes, such as water vaporization, devolatilization and char oxidation with available experimental data. A water film surrounding a spherical coal particle is considered to undergo vaporization by heat transfer from the hot air. After the water vaporization is complete, devolatilization begins. This process is assumed to be kinetically controlled. Water vaporization and devolatilization processes are modeled by using a hybrid Eulerian-Lagrangian method to obtain the properties of the gas-phase and the condensed-phase. An explicit finite difference scheme is used to solve the Eulerian gas-phase equation where as a Runga-Kutta scheme is employed to solve the Lagrangian condensed-phase equations. The predicted characteristic times for water vaporization is in good agreement with values proposed in the literature. At the present time there is insufficient data to draw any conclusions on the model. Methods are proposed to refine the simple kinetic model which takes into account pore diffusion and mass transfer for devolatilization and char oxidation. 9 references, 12 figures.

  5. Tripropellant combustion process

    NASA Technical Reports Server (NTRS)

    Kmiec, T. D.; Carroll, R. G.

    1988-01-01

    The addition of small amounts of hydrogen to the combustion of LOX/hydrocarbon propellants in large rocket booster engines has the potential to enhance the system stability. Programs being conducted to evaluate the effects of hydrogen on the combustion of LOX/hydrocarbon propellants at supercritical pressures are described. Combustion instability has been a problem during the development of large hydrocarbon fueled rocket engines. At the higher combustion chamber pressures expected for the next generation of booster engines, the effect of unstable combustion could be even more destructive. The tripropellant engine cycle takes advantage of the superior cooling characteristics of hydrogen to cool the combustion chamber and a small amount of the hydrogen coolant can be used in the combustion process to enhance the system stability. Three aspects of work that will be accomplished to evaluate tripropellant combustion are described. The first is laboratory demonstration of the benefits through the evaluation of drop size, ignition delay and burning rate. The second is analytical modeling of the combustion process using the empirical relationship determined in the laboratory. The third is a subscale demonstration in which the system stability will be evaluated. The approach for each aspect is described and the analytical models that will be used are presented.

  6. Two-chamber model for divertors with plasma recycling

    SciTech Connect

    Langer, W.D.; Singer, C.E.

    1984-11-01

    To model particle and heat loss terms at the edge of a tokamak with a divertor or pumped limiter, a simple two-chamber formulation of the scrapeoff has been constructed by integrating the fluid equations, including sources, along open field lines. The model is then solved for a wide range of density and temperature conditions in the scrapeoff, using geometrical parameters typical of the PDX poloidal divertor. The solutions characterize four divertor operating conditions for beam-heated plasmas: plugged, unplugged, blowthrough, and blowback.

  7. Modelling the combustion of charcoal in a model blast furnace

    NASA Astrophysics Data System (ADS)

    Shen, Yansong; Shiozawa, Tomo; Yu, Aibing; Austin, Peter

    2013-07-01

    The pulverized charcoal (PCH) combustion in ironmaking blast furnaces is abstracting remarkable attention due to various benefits such as lowering CO2 emission. In this study, a three-dimensional CFD model is used to simulate the flow and thermo-chemical behaviours in this process. The model is validated against the experimental results from a pilot-scale combustion test rig for a range of conditions. The typical flow and thermo-chemical phenomena is simulated. The effect of charcoal type, i.e. VM content is examined, showing that the burnout increases with VM content in a linear relationship. This model provides an effective way for designing and optimizing PCH operation in blast furnace practice.

  8. Chemical Kinetic Models for HCCI and Diesel Combustion

    SciTech Connect

    Pitz, W J; Westbrook, C K; Mehl, M; Sarathy, S M

    2010-11-15

    Predictive engine simulation models are needed to make rapid progress towards DOE's goals of increasing combustion engine efficiency and reducing pollutant emissions. These engine simulation models require chemical kinetic submodels to allow the prediction of the effect of fuel composition on engine performance and emissions. Chemical kinetic models for conventional and next-generation transportation fuels need to be developed so that engine simulation tools can predict fuel effects. The objectives are to: (1) Develop detailed chemical kinetic models for fuel components used in surrogate fuels for diesel and HCCI engines; (2) Develop surrogate fuel models to represent real fuels and model low temperature combustion strategies in HCCI and diesel engines that lead to low emissions and high efficiency; and (3) Characterize the role of fuel composition on low temperature combustion modes of advanced combustion engines.

  9. Characteristics modeling for supercritical circulating fluidized bed boiler working in oxy-combustion technology

    NASA Astrophysics Data System (ADS)

    Balicki, Adrian; Bartela, ?ukasz

    2014-06-01

    Among the technologies which allow to reduce greenhouse gas emission, mainly carbon dioxide, special attention deserves the idea of `zeroemission' technology based on boilers working in oxy-combustion technology. In the paper the results of analyses of the influence of changing two quantities, namely oxygen share in oxidant produced in the air separation unit, and oxygen share in oxidant supplied to the furnace chamber on the selected characteristics of a steam boiler including the degree of exhaust gas recirculation, boiler efficiency and adiabatic flame temperature, was examined. Due to the possibility of the integration of boiler model with carbon dioxide capture, separation and storage installation, the subject of the analysis was also to determine composition of the flue gas at the outlet of a moisture condensation installation. Required calculations were made using a model of a supercritical circulating fluidized bed boiler working in oxy-combustion technology, which was built in a commercial software and in-house codes.

  10. Computational experience with a three-dimensional rotary engine combustion model

    NASA Technical Reports Server (NTRS)

    Raju, M. S.; Willis, E. A.

    1990-01-01

    A new computer code was developed to analyze the chemically reactive flow and spray combustion processes occurring inside a stratified-charge rotary engine. Mathematical and numerical details of the new code were recently described by the present authors. The results are presented of limited, initial computational trials as a first step in a long-term assessment/validation process. The engine configuration studied was chosen to approximate existing rotary engine flow visualization and hot firing test rigs. Typical results include: (1) pressure and temperature histories, (2) torque generated by the nonuniform pressure distribution within the chamber, (3) energy release rates, and (4) various flow-related phenomena. These are discussed and compared with other predictions reported in the literature. The adequacy or need for improvement in the spray/combustion models and the need for incorporating an appropriate turbulence model are also discussed.

  11. Modeling smog chamber measurements of vehicle exhaust VOC reactivities

    SciTech Connect

    Chang, T.Y.; Nance, B.I.; Kelly, N.A.

    1997-12-31

    Vehicle exhaust VOC reactivities, measured at GM`s smog chamber facility, have been modeled using the SAPRC93 photochemical mechanism. The vehicle exhaust mixtures were generated by a single vehicle run over a portion of the Federal Test Procedure using three Auto/Oil reformulated test gasolines. For each run, up to 156 individual VOC species were identified. Initial HONO concentrations are needed to simulate reactivity measurement runs. (HONO is expected to be generated in a Tedlar bag holding the exhaust sample prior to its transfer to the smog chambers.) Measured and simulated relative incremental reactivities for the three exhaust mixtures are highly consistent. However, measured relative incremental reactivities are more sensitive to fuel effects than simulated ones. The maximum incremental reactivity (MIR)-based relative incremental reactivities, derived from individual species concentrations and MIR factors, are very close to simulated ones. A number of sensitivity simulation runs have been carried out to investigate the impact of HONO and other variables. Results show that relative reactivities of actual vehicle exhaust emissions can be measured by chamber runs in spite of the HONO effect.

  12. Active combustion control : modeling, design and implementation

    E-print Network

    Park, Sungbae, 1973-

    2004-01-01

    Continuous combustion systems common in propulsion and power generation applications are susceptible to thermoacoustic instability, which occurs under lean burn conditions close to the flammability where most emissions and ...

  13. Tetra-ol Glycidyl Azide Polymer Combustion Modeling

    NASA Astrophysics Data System (ADS)

    Wada, Yutaka; Tsutsumi, Akimasa; Seike, Yoshio; Nishioka, Makihito; Shimada, Toru; Hasegawa, Katsuya; Kobayashi, Kiyokazu; Hori, Keiichi

    Tetra-ol glycidyl azide polymer (GAP) is one of the best candidates for the solid fuel of gas hybrid rocket system because of self-combustibility and high heat of formation. Combustion model of GAP was developed by Beckstead et al. and they applied it to tri-ol GAP successfully. We have applied this model to tetra-ol GAP as an initial attempt, and numerical simulation showed that maximum temperatures in the gas phase exceeded those of experimental results significantly, and calculated burning rates were much higher than strand burner data, thus, modification of the model taking account of combustion incompleteness was found to be necessary. Modifications of combustion model were made taking the residue analysis results into account as Blow Off Mechanism. Simulated final temperature in the gas phase and burning rate are lowered effectively and coincide well with experimental data adjusting kinetic parameters.

  14. Computational Model of Forward and Opposed Smoldering Combustion in Microgravity 

    E-print Network

    Rein, Guillermo; Fernandez-Pello, Carlos; Urban, David

    2006-08-06

    A novel computational model of smoldering combustion capable of predicting both forward and opposed propagation is developed. This is accomplished by considering the one-dimensional, transient, governing equations for ...

  15. Double-distribution-function discrete Boltzmann model for combustion

    E-print Network

    Chuandong Lin; Aiguo Xu; Guangcai Zhang; Yingjun Li

    2015-11-11

    A 2-dimensional discrete Boltzmann model for combustion is presented. Mathematically, the model is composed of two coupled discrete Boltzmann equations for two species and a phenomenological equation for chemical reaction process. Physically, the model is equivalent to a reactive Navier-Stokes model supplemented by a coarse-grained model for the thermodynamic nonequilibrium behaviours. This model adopts 16 discrete velocities. It works for both subsonic and supersonic combustion phenomena with flexible specific heat ratio. To discuss the physical accuracy of the coarse-grained model for nonequilibrium behaviours, three other discrete velocity models are used for comparisons. Numerical results are compared with analytical solutions based on both the first-order and second-order truncations of the distribution function. It is confirmed that the physical accuracy increases with the increasing moment relations needed by nonequlibrium manifestations. Furthermore, compared with the single distribution function model, this model can simulate more details of combustion.

  16. Turbulence modelling of flow fields in thrust chambers

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Kim, Y. M.; Shang, H. M.

    1993-01-01

    Following the consensus of a workshop in Turbulence Modelling for Liquid Rocket Thrust Chambers, the current effort was undertaken to study the effects of second-order closure on the predictions of thermochemical flow fields. To reduce the instability and computational intensity of the full second-order Reynolds Stress Model, an Algebraic Stress Model (ASM) coupled with a two-layer near wall treatment was developed. Various test problems, including the compressible boundary layer with adiabatic and cooled walls, recirculating flows, swirling flows, and the entire SSME nozzle flow were studied to assess the performance of the current model. Detailed calculations for the SSME exit wall flow around the nozzle manifold were executed. As to the overall flow predictions, the ASM removes another assumption for appropriate comparison with experimental data to account for the non-isotropic turbulence effects.

  17. A model for steady-state HNF combustion

    SciTech Connect

    Louwers, J.; Gadiot, G.M.H.J.L.; Brewster, M.Q.; Son, S.F.

    1997-09-01

    A simple model for the combustion of solid monopropellants is presented. The condensed phase is treated by high activation energy asymptotics. The gas phase is treated by two limit cases: high activation energy, and low activation energy. This results in simplification of the gas phase energy equation, making an (approximate) analytical solution possible. The results of the model are compared with experimental results of Hydrazinium Nitroformate (HNF) combustion.

  18. Operating manual for coaxial injection combustion model. [for the space shuttle main engine

    NASA Technical Reports Server (NTRS)

    Sutton, R. D.; Schuman, M. D.; Chadwick, W. D.

    1974-01-01

    An operating manual for the coaxial injection combustion model (CICM) is presented as the final report for an eleven month effort designed to provide improvement, to verify, and to document the comprehensive computer program for analyzing the performance of thrust chamber operation with gas/liquid coaxial jet injection. The effort culminated in delivery of an operation FORTRAN IV computer program and associated documentation pertaining to the combustion conditions in the space shuttle main engine. The computer program is structured for compatibility with the standardized Joint Army-Navy-NASA-Air Force (JANNAF) performance evaluation procedure. Use of the CICM in conjunction with the JANNAF procedure allows the analysis of engine systems using coaxial gas/liquid injection.

  19. Kinetic data base for combustion modeling

    SciTech Connect

    Tsang, W.; Herron, J.T.

    1993-12-01

    The aim of this work is to develop a set of evaluated rate constants for use in the simulation of hydrocarbon combustion. The approach has been to begin with the small molecules and then introduce larger species with the various structural elements that can be found in all hydrocarbon fuels and decomposition products. Currently, the data base contains most of the species present in combustion systems with up to four carbon atoms. Thus, practically all the structural grouping found in aliphatic compounds have now been captured. The direction of future work is the addition of aromatic compounds to the data base.

  20. Thermodynamic Model of Aluminum Combustion in SDF Explosions

    SciTech Connect

    Kuhl, . L

    2006-06-19

    Thermodynamic states encountered during combustion of Aluminum powder in Shock-Dispersed-Fuel (SDF) explosions were analyzed with the Cheetah code. Results are displayed in the Le Chatelier diagram: the locus of states of specific internal energy versus temperature. Accuracy of the results was confirmed by comparing the fuel and products curves with the heats of detonation and combustion, and species composition as measured in bomb calorimeter experiments. Results were fit with analytic functions u = f(T) suitable for specifying the thermodynamic properties required for gas-dynamic models of combustion in explosions.

  1. Combustor nozzle for a fuel-flexible combustion system

    DOEpatents

    Haynes, Joel Meier (Niskayuna, NY); Mosbacher, David Matthew (Cohoes, NY); Janssen, Jonathan Sebastian (Troy, NY); Iyer, Venkatraman Ananthakrishnan (Mason, OH)

    2011-03-22

    A combustor nozzle is provided. The combustor nozzle includes a first fuel system configured to introduce a syngas fuel into a combustion chamber to enable lean premixed combustion within the combustion chamber and a second fuel system configured to introduce the syngas fuel, or a hydrocarbon fuel, or diluents, or combinations thereof into the combustion chamber to enable diffusion combustion within the combustion chamber.

  2. Up the Technology Readiness Level (TRL) Scale to Demonstrate a Robust, Long Life, Liquid Rocket Engine Combustion Chamber, or...Up the Downstairs

    NASA Technical Reports Server (NTRS)

    Holmes, Richard; Elam, Sandra; McKechnie, Timothy; Power, Christopher

    2008-01-01

    Advanced vacuum plasma spray (VPS) technology, utilized to successfully apply thermal barrier coatings to space shuttle main engine turbine blades, was further refined as a functional gradient material (FGM) process for space furnace cartridge experiments at 1600 C and for robust, long life combustion chambers for liquid rocket engines. A VPS/FGM 5K (5,000 lb. thrust) thruster has undergone 220 hot firing tests, in pristine condition, showing no wear, blanching or cooling channel cracks. Most recently, this technology has been applied to a 40K thruster, with scale up planned for a 194K Ares I, J-2X engine.

  3. Thermophysics Characterization of Kerosene Combustion

    NASA Technical Reports Server (NTRS)

    Wang, Ten-See

    2001-01-01

    A one-formula surrogate fuel formulation and its quasi-global combustion kinetics model are developed to support the design of injectors and thrust chambers of kerosene-fueled rocket engines. This surrogate fuel model depicts a fuel blend that properly represents the general physical and chemical properties of kerosene. The accompanying gaseous-phase thermodynamics of the surrogate fuel is anchored with the heat of formation of kerosene and verified by comparing a series of one-dimensional rocket thrust chamber calculations. The quasi-global combustion kinetics model consists of several global steps for parent fuel decomposition, soot formation, and soot oxidation and a detailed wet-CO mechanism to complete the combustion process. The final thermophysics formulations are incorporated with a computational fluid dynamics model for prediction of the combustion efficiency of an unielement, tripropellant combustor and the radiation of a kerosene-fueled thruster plume. The model predictions agreed reasonably well with those of the tests.

  4. An Experimental and Kinetic Modeling Study of Methyl Decanoate Combustion

    SciTech Connect

    Sarathy, S M; Thomson, M J; Pitz, W J; Lu, T

    2010-02-19

    Biodiesel is typically a mixture of long chain fatty acid methyl esters for use in compression ignition engines. Improving biofuel engine performance requires understanding its fundamental combustion properties and the pathways of combustion. This research study presents new combustion data for methyl decanoate in an opposed-flow diffusion flame. An improved detailed chemical kinetic model for methyl decanoate combustion is developed, which serves as the basis for deriving a skeletal mechanism via the direct relation graph method. The novel skeletal mechanism consists of 648 species and 2998 reactions. This mechanism well predicts the methyl decanoate opposed-flow diffusion flame data. The results from the flame simulations indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular weight oxygenated compounds such as carbon monoxide, formaldehyde, and ketene.

  5. Theory and modeling in combustion chemistry

    SciTech Connect

    Miller, J.A.

    1996-10-01

    This paper discusses four important problems in combustion chemistry. In each case, resolution of the problem focuses on a single elementary reaction. Theoretical analysis of this reaction is discussed in some depth, with emphasis on its unusual features. The four combustion problems and their elementary reactions are: (1) Burning velocities, extinction limits, and flammability limits: H+O{sub 2}{leftrightarrow}OH+O, (2) Prompt NO: CH+N{sub 2}{leftrightarrow}HCN+N, (3) the Thermal De-NO{sub x} Process: NH{sub 2}+NO{leftrightarrow}products, and (4) ``Ring`` formation in flames of aliphatic fuels and the importance of resonantly stabilized free radicals: C{sub 3}H{sub 3}{leftrightarrow}products.

  6. 3-DIMENSIONAL Numerical Modeling on the Combustion and Emission Characteristics of Biodiesel in Diesel Engines

    NASA Astrophysics Data System (ADS)

    Yang, Wenming; An, Hui; Amin, Maghbouli; Li, Jing

    2014-11-01

    A 3-dimensional computational fluid dynamics modeling is conducted on a direct injection diesel engine fueled by biodiesel using multi-dimensional software KIVA4 coupled with CHEMKIN. To accurately predict the oxidation of saturated and unsaturated agents of the biodiesel fuel, a multicomponent advanced combustion model consisting of 69 species and 204 reactions combined with detailed oxidation pathways of methyl decenoate (C11H22O2), methyl-9-decenoate (C11H20O2) and n-heptane (C7H16) is employed in this work. In order to better represent the real fuel properties, the detailed chemical and thermo-physical properties of biodiesel such as vapor pressure, latent heat of vaporization, liquid viscosity and surface tension were calculated and compiled into the KIVA4 fuel library. The nitrogen monoxide (NO) and carbon monoxide (CO) formation mechanisms were also embedded. After validating the numerical simulation model by comparing the in-cylinder pressure and heat release rate curves with experimental results, further studies have been carried out to investigate the effect of combustion chamber design on flow field, subsequently on the combustion process and performance of diesel engine fueled by biodiesel. Research has also been done to investigate the impact of fuel injector location on the performance and emissions formation of diesel engine.

  7. INSTITUTE OF PHYSICS PUBLISHING COMBUSTION THEORY AND MODELLING Combust. Theory Modelling 8 (2004) 593606 PII: S1364-7830(04)71644-7

    E-print Network

    Long, Marshall B.

    2004-01-01

    INSTITUTE OF PHYSICS PUBLISHING COMBUSTION THEORY AND MODELLING Combust. Theory Modelling 8 (2004 size limit to the primary particle size; and (iv) estimates of radiative optical thickness corrections to computed flame temperatures. 1. Introduction Combustion-generated soot particles from land-based sources

  8. Comparison of numerical methods and combustion models for LES of a ramjet

    NASA Astrophysics Data System (ADS)

    Roux, A.; Reichstadt, S.; Bertier, N.; Gicquel, L.; Vuillot, F.; Poinsot, T.

    2009-06-01

    Ramjets are very sensitive to instabilities and their numerical predictions can only be addressed adequately by Large Eddy Simulation (LES). With this technique, solvers can be implicit or explicit and handle structured, unstructured or hybrid meshes, etc. Turbulence and combustion models are other sources of differences. The impact of these options is here investigated for the ONERA ramjet burner. To do so, two LES codes developed by ONERA and CERFACS compute one stable operating condition. Preliminary LES results of the two codes underline the overall robustness of LES. Mean flow features at the various critical sections are reasonably well predicted by both codes. Disagreement mainly appear in the chamber where combustion positions differ pointing to the importance of the combustion and subgrid mixing models. The two LES produce different energy containing motions. With CEDRE, a low frequency dominates while AVBP produces different ranges of low frequencies that can be linked with acoustic modes of the configuration. To cite this article: A. Roux et al., C. R. Mecanique 337 (2009).

  9. OUTDOOR SMOG CHAMBER EXPERIMENTS TO TEST PHOTOCHEMICAL MODELS

    EPA Science Inventory

    The smog chamber facility of the University of North Carolina was used in a study to provide experimental data for developing and testing kinetic mechanisms of photochemical smog formation. The smog chamber, located outdoors in rural North Carolina, is an A-frame structure covere...

  10. Free surface modeling in OWC chamber with parabolic side walls using 3D BEM

    SciTech Connect

    Hasanabad, Madjid Ghodsi

    2015-03-10

    In this paper, BEM was used for free surface modeling in OWC chamber and out of it. Linear kinematic and dynamic boundary conditions were used for free surface out of OWC chamber and nonlinear forms were used for free surface in the chamber. These boundary conditions were discretized by finite differences method. Also, some thermodynamics relations were applied for trapped air behavior modeling in OWC chamber. Wave specifications in Chabahar region were used in modeling because these waves have an acceptable power for electricity generation. The results show a good agreement with results of other researches.

  11. Modeling of Transient Flow Mixing of Streams Injected into a Mixing Chamber

    NASA Technical Reports Server (NTRS)

    Voytovych, Dmytro M.; Merkle, Charles L.; Lucht, Robert P.; Hulka, James R.; Jones, Gregg W.

    2006-01-01

    Ignition is recognized as one the critical drivers in the reliability of multiple-start rocket engines. Residual combustion products from previous engine operation can condense on valves and related structures thereby creating difficulties for subsequent starting procedures. Alternative ignition methods that require fewer valves can mitigate the valve reliability problem, but require improved understanding of the spatial and temporal propellant distribution in the pre-ignition chamber. Current design tools based mainly on one-dimensional analysis and empirical models cannot predict local details of the injection and ignition processes. The goal of this work is to evaluate the capability of the modern computational fluid dynamics (CFD) tools in predicting the transient flow mixing in pre-ignition environment by comparing the results with the experimental data. This study is a part of a program to improve analytical methods and methodologies to analyze reliability and durability of combustion devices. In the present paper we describe a series of detailed computational simulations of the unsteady mixing events as the cold propellants are first introduced into the chamber as a first step in providing this necessary environmental description. The present computational modeling represents a complement to parallel experimental simulations' and includes comparisons with experimental results from that effort. A large number of rocket engine ignition studies has been previously reported. Here we limit our discussion to the work discussed in Refs. 2, 3 and 4 which is both similar to and different from the present approach. The similarities arise from the fact that both efforts involve detailed experimental/computational simulations of the ignition problem. The differences arise from the underlying philosophy of the two endeavors. The approach in Refs. 2 to 4 is a classical ignition study in which the focus is on the response of a propellant mixture to an ignition source, with emphasis on the level of energy needed for ignition and the ensuing flame propagation issues. Our focus in the present paper is on identifying the unsteady mixing processes that provide the propellant mixture in which the ignition source is to be placed. In particular, we wish to characterize the spatial and temporal mixture distribution with a view toward identifying preferred spatial and temporal locations for the ignition source. As such, the present work is limited to cold flow (pre-ignition) conditions

  12. Spectral optimization and uncertainty quantification in combustion modeling

    NASA Astrophysics Data System (ADS)

    Sheen, David Allan

    Reliable simulations of reacting flow systems require a well-characterized, detailed chemical model as a foundation. Accuracy of such a model can be assured, in principle, by a multi-parameter optimization against a set of experimental data. However, the inherent uncertainties in the rate evaluations and experimental data leave a model still characterized by some finite kinetic rate parameter space. Without a careful analysis of how this uncertainty space propagates into the model's predictions, those predictions can at best be trusted only qualitatively. In this work, the Method of Uncertainty Minimization using Polynomial Chaos Expansions is proposed to quantify these uncertainties. In this method, the uncertainty in the rate parameters of the as-compiled model is quantified. Then, the model is subjected to a rigorous multi-parameter optimization, as well as a consistency-screening process. Lastly, the uncertainty of the optimized model is calculated using an inverse spectral optimization technique, and then propagated into a range of simulation conditions. An as-compiled, detailed H2/CO/C1-C4 kinetic model is combined with a set of ethylene combustion data to serve as an example. The idea that the hydrocarbon oxidation model should be understood and developed in a hierarchical fashion has been a major driving force in kinetics research for decades. How this hierarchical strategy works at a quantitative level, however, has never been addressed. In this work, we use ethylene and propane combustion as examples and explore the question of hierarchical model development quantitatively. The Method of Uncertainty Minimization using Polynomial Chaos Expansions is utilized to quantify the amount of information that a particular combustion experiment, and thereby each data set, contributes to the model. This knowledge is applied to explore the relationships among the combustion chemistry of hydrogen/carbon monoxide, ethylene, and larger alkanes. Frequently, new data will become available, and it will be desirable to know the effect that inclusion of these data has on the optimized model. Two cases are considered here. In the first, a study of H2/CO mass burning rates has recently been published, wherein the experimentally-obtained results could not be reconciled with any extant H2/CO oxidation model. It is shown in that an optimized H2/CO model can be developed that will reproduce the results of the new experimental measurements. In addition, the high precision of the new experiments provide a strong constraint on the reaction rate parameters of the chemistry model, manifested in a significant improvement in the precision of simulations. In the second case, species time histories were measured during n-heptane oxidation behind reflected shock waves. The highly precise nature of these measurements is expected to impose critical constraints on chemical kinetic models of hydrocarbon combustion. The results show that while an as-compiled, prior reaction model of n-alkane combustion can be accurate in its prediction of the detailed species profiles, the kinetic parameter uncertainty in the model remains to be too large to obtain a precise prediction of the data. Constraining the prior model against the species time histories within the measurement uncertainties led to notable improvements in the precision of model predictions against the species data as well as the global combustion properties considered. Lastly, we show that while the capability of the multispecies measurement presents a step-change in our precise knowledge of the chemical processes in hydrocarbon combustion, accurate data of global combustion properties are still necessary to predict fuel combustion.

  13. High Temperature Chemical Kinetic Combustion Modeling of Lightly Methylated Alkanes

    SciTech Connect

    Sarathy, S M; Westbrook, C K; Pitz, W J; Mehl, M

    2011-03-01

    Conventional petroleum jet and diesel fuels, as well as alternative Fischer-Tropsch (FT) fuels and hydrotreated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed high temperature chemical kinetic mechanism for n-octane and three lightly branched isomers octane (i.e., 2-methylheptane, 3-methylheptane, and 2,5-dimethylhexane). The model is validated against experimental data from a variety of fundamental combustion devices. This new model is used to show how the location and number of methyl branches affects fuel reactivity including laminar flame speed and species formation.

  14. STRUCTURE-BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION

    SciTech Connect

    CHRISTOPHER M. HADAD; JOSEPH M. CALO; ROBERT H. ESSENHIGH; ROBERT H. HURT

    1998-09-11

    Progress was made this period on a number of tasks. A significant advance was made in the incorporation of macrostructural ideas into high temperature combustion models. Work at OSU by R. Essenhigh in collaboration with the University of Stuttgart has led to a theory that the zone I / II transition in char combustion lies within the range of conditions of interest for pulverized char combustion. The group has presented evidence that some combustion data, previously interpreted with zone II models, in fact takes place in the transition from zone II to zone 1. This idea was used at Brown to make modifications to the CBK model (a char kinetics package specially designed for carbon burnout prediction, currently used by a number of research and furnace modeling groups in academia and industry). The resulting new model version, CBK8, shows improved ability to predict extinction behavior in the late stages of combustion, especially for particles with low ash content. The full development and release of CBK8, along with detailed descriptions of the role of the zone 1/2 transition will be reported on in subsequent reports. ABB-CE is currently implementing CBK7 into a special version of the CFD code Fluent for use in the modeling and design of their boilers. They have been appraised of the development, and have expressed interest in incorporating the new feature, realizing full CBK8 capabilities into their combustion codes. The computational chemistry task at OSU continued to study oxidative pathways for PAH, with emphasis this period on heteroatom containing ring compounds. Preliminary XPS studies were also carried out. Combustion experiments were also carried out at OSU this period, leading to the acquisition of samples at various residence times and the measurement of their oxidation reactivity by nonisothermal TGA techniques. Several members of the project team attended the Carbon Conference this period and made contacts with representatives from the new FETC Consortium for Premium Carbon Products from Coal. Possibilities for interactions with this new center will be explored. Also this period, an invited review paper was prepared for the 27th International Symposium on Combustion, to be held in Boulder, Colorado in August. The paper is entitled; "Structure, Properties, and Reactivity of Solid Fuels," and reports on a number of advances made in this collaborative project.

  15. A Nonlinear Model for Fuel Atomization in Spray Combustion

    NASA Technical Reports Server (NTRS)

    Liu, Nan-Suey (Technical Monitor); Ibrahim, Essam A.; Sree, Dave

    2003-01-01

    Most gas turbine combustion codes rely on ad-hoc statistical assumptions regarding the outcome of fuel atomization processes. The modeling effort proposed in this project is aimed at developing a realistic model to produce accurate predictions of fuel atomization parameters. The model involves application of the nonlinear stability theory to analyze the instability and subsequent disintegration of the liquid fuel sheet that is produced by fuel injection nozzles in gas turbine combustors. The fuel sheet is atomized into a multiplicity of small drops of large surface area to volume ratio to enhance the evaporation rate and combustion performance. The proposed model will effect predictions of fuel sheet atomization parameters such as drop size, velocity, and orientation as well as sheet penetration depth, breakup time and thickness. These parameters are essential for combustion simulation codes to perform a controlled and optimized design of gas turbine fuel injectors. Optimizing fuel injection processes is crucial to improving combustion efficiency and hence reducing fuel consumption and pollutants emissions.

  16. MULTIGRID METHOD FOR MODELING MULTIDIMENSIONAL COMBUSTION WITH DETAILED CHEMISTRY

    E-print Network

    part and fluid flow part are treated separately. For the flow part, the mass, momentumand energy equations can be solved by using the existing CFD code, therefore most efforts towards modeling combustion(Liao, 1995, Liu, 1995), very efficient CFD methods will greatly reduce the iteration numbers of the reaction

  17. Geometric and number effect on damping capacity of Helmholtz resonators in a model chamber

    NASA Astrophysics Data System (ADS)

    Kim, H. J.; Cha, J.-P.; Song, J.-K.; Ko, Y. S.

    2010-08-01

    An acoustic cavity was selected as a stabilization device to control high-frequency combustion instabilities in gas turbines or liquid rocket engine combustors, and the acoustic damping capacity of the acoustic cavity was investigated for various geometric configurations under atmospheric non-reacting conditions. The tuning frequency of the acoustic cavity and the acoustic responses of a model chamber with a single acoustic cavity were studied first. Damping capacity was initially quantified through the frequency width of two split modes and the amplitude-damped ratio. The results showed that the cavity with the largest orifice area or the shortest orifice length was the most effective in acoustic damping of the harmful resonant mode. The effect of the number of cavities on acoustic damping capacity was also studied. Damping capacity was improved by increasing the number of cavities. For a better evaluation of acoustic damping capacity, two quantified parameters; the acoustic absorption, meaning the damping efficiency, and acoustic conductance, meaning the acoustic power loss, were introduced. The case was observed that has had insufficient loss of acoustic power in spite of having the highest absorption efficiency. As a result, fine geometric tuning for the acoustic cavity is required for the sufficient passive control. Also, the choice of the number of cavities is important to optimize the damping efficiency and absolute damping loss in consideration of the restriction of the cavity volume.

  18. A regenerative multiple zone model for HCCI combustion

    SciTech Connect

    Hamosfakidis, Vasileios; Im, Hong G.; Assanis, Dennis N.

    2009-04-15

    A new conserved scalar approach, the so-called regenerative multiple zone (RMZ) model, is introduced to simulate combustion in homogeneous charge compression ignition (HCCI) engines with significant products of combustion. In this approach, two conserved scalars are introduced, the mixture fraction Z and the initial exhaust gas fraction J, to determine uniquely the state of the reactive system as a function of the two conserved scalars and time. For the numerical solution of the HCCI combustion, the conserved scalar plane is divided into different zones, which represent homogeneous reactors with constant initial exhaust gas level. Particularly, the zones are created based on the distribution of the initial exhaust gases and are mixed and regenerated at every time step during combustion in order to account for the history effects which are due to the finite rate chemistry. A proper methodology to create and initialize the new zones during the combustion, the so-called zone creation strategy (ZCS), is also proposed. For validation, the RMZ model is implemented in the 2DRD code, which is a computational fluid dynamics code that solves the governing equations for a two-dimensional reaction-diffusion problem. Initially, the consistency of the new model is validated in a one-dimensional reaction-diffusion (RD) case. Subsequently, the necessity for a proper zone creation strategy is demonstrated by a two-dimensional RD case. Next, a parametric study is performed to investigate the sensitivity of the new model on the maximum number of zones that is used. Finally, the limitations as well as the advantages of the RMZ model are discussed. (author)

  19. Develop an alternate energy source thru use of a poultry litter pelletizer and a combustion chamber to heat poultry houses. Final technical project report

    SciTech Connect

    Gonthier, M.W.; Mercier, R.A.

    1984-01-01

    Poultry litter in a pelletized form is an acceptable energy source. The machinery and mechanism to process the litter, the combustion chamber with supporting controls and equipment, is practical and marketable. The controlling factor is economic demand. With the price of fossil fuel diminishing and with the labor cost and energy cost to process the litter, it is not economically desirable to pay the equivalent of $1.50 per gallon. It would not be economically competitive with present heating power plants because of its high initial cost, the cost of labor to maintain a pellet supply and the undesirable feature of solid fuel versus liquid fuel. This system could not be fully competitive with present systems until fuel pric

  20. Three-dimensional modeling of diesel engine intake flow, combustion and emissions-II

    SciTech Connect

    Reitz, R.D.; Rutland, C.J.

    1993-09-01

    A three-dimensional computer code, KIVA, is being modified to include state-of-the-art submodels for diesel engine flow and combustion. Improved and/or new submodels which have already been implemented and previously reported are: Wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo`vich NO{sub x}, and spray/wall impingement with rebounding and sliding drops. Progress on the implementation of improved spray drop drag and drop breakup models, the formulation and testing of a multistep kinetics ignition model and preliminary soot modeling results are described in this report. In addition, the use of a block structured version of KIVA to model the intake flow process is described. A grid generation scheme has been developed for modeling realistic (complex) engine geometries, and computations have been made of intake flow in the ports and combustion chamber of a two-intake-valve engine. The research also involves the use of the code to assess the effects of subprocesses on diesel engine performance. The accuracy of the predictions is being tested by comparisons with engine experiments. To date, comparisons have been made with measured engine cylinder pressure, temperature and heat flux data, and the model results are in good agreement with the experiments. Work is in progress that will allow validation of in-cylinder flow and soot formation predictions. An engine test facility is described that is being used to provide the needed validation data. Test results have been obtained showing the effect of injection rate and split injections on engine performance and emissions.

  1. Three-dimensional modeling of diesel engine intake flow, combustion and emissions-2

    NASA Technical Reports Server (NTRS)

    Reitz, R. D.; Rutland, C. J.

    1993-01-01

    A three-dimensional computer code, KIVA, is being modified to include state-of-the-art submodels for diesel engine flow and combustion. Improved and/or new submodels which have already been implemented and previously reported are: wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo'vich NO(x), and spray/wall impingement with rebounding and sliding drops. Progress on the implementation of improved spray drop drag and drop breakup models, the formulation and testing of a multistep kinetics ignition model, and preliminary soot modeling results are described. In addition, the use of a block structured version of KIVA to model the intake flow process is described. A grid generation scheme was developed for modeling realistic (complex) engine geometries, and computations were made of intake flow in the ports and combustion chamber of a two-intake-value engine. The research also involves the use of the code to assess the effects of subprocesses on diesel engine performance. The accuracy of the predictions is being tested by comparisons with engine experiments. To date, comparisons were made with measured engine cylinder pressure, temperature and heat flux data, and the model results are in good agreement with the experiments. Work is in progress that will allow validation of in-cylinder flow and soot formation predictions. An engine test facility is described that is being used to provide the needed validation data. Test results were obtained showing the effect of injection rate and split injections on engine performance and emissions.

  2. Disappearance of fuel hydrazine vapors in fluorocarbon-film environmental chambers. Experimental observations and kinetic modeling

    SciTech Connect

    Stone, D.A.; Wiseman, F.L.; Kilduff, J.E.; Koontz, S.L.; Davis, D.D.

    1989-03-01

    Fluorocarbon-film environmental chambers, of the type often employed in air pollution studies, have been used to investigate the stability of the fuel hydrazines (hydrazine, methylhydrazine, and 1,1-dimethylhydrazine) with respect to atmospheric oxidation. These studies have shown that the observed disappearance of fuel hydrazine vapors in these chambers is caused by physical loss processes rather than oxidation. Vapor-phase decay is affected by chamber size, water content of the matrix gas, and previous chamber experiments. A kinetic model has been developed that incorporates adsorption, permeation, and surface site concentration to fit the observed decay data.

  3. Numerical Modelling of a Pulse Combustion Burner: Limiting Conditions of Stable

    E-print Network

    Vuik, Kees

    a mathematical analysis of a simple model for thermal pulse combustion and determines conditions under which analysis. 2 Thermal Pulse Combustion: A Mathematical Model Richards et al. [3] introduced a mathematicalNumerical Modelling of a Pulse Combustion Burner: Limiting Conditions of Stable Operation P.A. van

  4. Neural Transplantation Model Using Integration Co-culture Chamber

    NASA Astrophysics Data System (ADS)

    Shimba, Kenta; Saito, Atsushi; Takeuchi, Akimasa; Takayama, Yuzo; Kotani, Kiyoshi; Jimbo, Yasuhiko

    Regenerative medicine is a promising therapy for injuries and diseases of the central nervous system (CNS). Implantation of stem cell-derived neurons into the recipient tissue is one of the key processes of the therapy. How the implanted cells establish functional connections with the intact neurons, and whether the established connections are maintained stably for a long time, remain unknown. Here, we report a novel co-culture device for visualizing interconnections between primary and differentiated neuronal cultures, and long-term monitoring of neuronal activity. A circular micro-chamber surrounded by another chamber is aligned on a microelectrode array (MEA). These chambers are interconnected through 36 micro-tunnels. Stem cell-derived neurons were cultured in the inner circular chamber, and primary neurons taken from mouse cortices were cultured in the surrounding chamber. Neurites outgrew into the micro-tunnels from both primary and differentiated neurons. The immunofluorescence images indicate that synaptic connections are formed between them. Propagation of electrical activity was observed 6 days after starting co-culture. More than half of the spontaneous activity was initiated from primary neurons, and probability of activity propagation to the stem cell-derived neurons gradually increased with culture days. These results suggest that our device is feasible for long-term monitoring of interaction between stem cell-derived cells and the recipient tissue.

  5. Modeling of Nitrogen Oxides Emissions from CFB Combustion

    NASA Astrophysics Data System (ADS)

    Kallio, S.; Keinonen, M.

    In this work, a simplified description of combustion and nitrogen oxides chemistry was implemented in a 1.5D model framework with the aim to compare the results with ones earlier obtained with a detailed reaction scheme. The simplified chemistry was written using 12 chemical components. Heterogeneous chemistry is given by the same models as in the earlier work but the homogeneous and catalytic reactions have been altered. The models have been taken from the literature. The paper describes the numerical model with emphasis on the chemistry submodels. A simulation of combustion of bituminous coal in the Chalmers 12 MW boiler is conducted and the results are compared with the results obtained earlier with the detailed chemistry description. The results are also compared with measured O2, CO, NO and N2O profiles. The simplified reaction scheme produces equally good results as earlier obtained with the more elaborate chemistry description.

  6. COMPENSATING FOR WALL EFFECTS IN IAQ (INDOOR AIR QUALITY) CHAMBER TESTS BY MATHEMATICAL MODELING

    EPA Science Inventory

    The paper presents mechanistic mathematical models that account for two phenomena: interior surfaces of a state-of-the-art emissions test chamber acting as a transient sink for organic emissions; the effect of increasing chamber concentration on the emission rate of the source. A...

  7. COMPENSATING FOR SINK EFFECTS IN EMISSIONS TEST CHAMBERS BY MATHEMATICAL MODELING

    EPA Science Inventory

    The paper presents mechanistic mathematical models that account for two phenomena: (1) interior surfaces of a state-of-the-art emissions test chamber acting as a transient sink for organic emissions; and (2) the effect of increasing chamber concentration on the emission rate of t...

  8. Chemical Looping Combustion System-Fuel Reactor Modeling

    SciTech Connect

    Gamwo, I.K.; Jung, J.; Anderson, R.R.; Soong, Y.

    2007-04-01

    Chemical looping combustion (CLC) is a process in which an oxygen carrier is used for fuel combustion instead of air or pure oxygen as shown in the figure below. The combustion is split into air and fuel reactors where the oxidation of the oxygen carrier and the reduction of the oxidized metal occur respectively. The CLC system provides a sequestration-ready CO2 stream with no additional energy required for separation. This major advantage places combustion looping at the leading edge of a possible shift in strict control of CO2 emissions from power plants. Research in this novel technology has been focused in three distinct areas: techno-economic evaluations, integration of the system into power plant concepts, and experimental development of oxygen carrier metals such as Fe, Ni, Mn, Cu, and Ca. Our recent thorough literature review shows that multiphase fluid dynamics modeling for CLC is not available in the open literature. Here, we have modified the MFIX code to model fluid dynamic in the fuel reactor. A computer generated movie of our simulation shows bubble behavior consistent with experimental observations.

  9. Experimental and analytical study to model temperature profiles and stoichiometry in oxygen-enriched in-situ combustion 

    E-print Network

    Rodriguez, Jose Ramon

    2004-09-30

    A new combustion zone analytical model has been developed in which the combustion front temperature may be calculated. The model describes in the combustion zone, the amount of fuel burned based on reaction kinetics, the fuel concentration...

  10. Modeling of pulverized coal combustion in cement rotary kiln

    SciTech Connect

    Shijie Wang; Jidong Lu; Weijie Li; Jie Li; Zhijuan Hu

    2006-12-15

    In this paper, based on analysis of the chemical and physical processes of clinker formation, a heat flux function was introduced to take account of the thermal effect of clinker formation. Combining the models of gas-solid flow, heat and mass transfer, and pulverized coal combustion, a set of mathematical models for a full-scale cement rotary kiln were established. In terms of commercial CFD code (FLUENT), the distributions of gas velocity, gas temperature, and gas components in a cement rotary kiln were obtained by numerical simulation of a 3000 t/d rotary kiln with a four-channel burner. The predicted results indicated that the improved model accounts for the thermal enthalpy of the clinker formation process and can give more insight (such as fluid flow, temperature, etc,) from within the cement rotary kiln, which is a benefit to better understanding of combustion behavior and an improvement of burner and rotary kiln technology. 25 refs., 12 figs., 5 tabs.

  11. Turbulent hydrocarbon combustions kinetics - Stochastic modeling and verification

    NASA Technical Reports Server (NTRS)

    Wang, T. S.; Farmer, R. C.; Tucker, Kevin

    1989-01-01

    Idealized reactors, that are designed to ensure perfect mixing and are used to generate the combustion kinetics for complex hydrocarbon fuels, may depart from the ideal and influence the kinetics model performance. A complex hydrocarbon kinetics model that was established by modeling a jet-stirred combustor (JSC) as a perfectly stirred reactor (PSR), is reevaluated with a simple stochastic process in order to introduce the unmixedness effect quantitatively into the reactor system. It is shown that the comparisons of the predictions and experimental data have improved dramatically with the inclusion of the unmixedness effect in the rich combustion region. The complex hydrocarbon kinetics is therefore verified to be mixing effect free and be applicable to general reacting flow calculations.

  12. A filtered tabulated chemistry model for LES of premixed combustion

    SciTech Connect

    Fiorina, B.; Auzillon, P.; Darabiha, N.; Gicquel, O.; Veynante, D.; Vicquelin, R.

    2010-03-15

    A new modeling strategy called F-TACLES (Filtered Tabulated Chemistry for Large Eddy Simulation) is developed to introduce tabulated chemistry methods in Large Eddy Simulation (LES) of turbulent premixed combustion. The objective is to recover the correct laminar flame propagation speed of the filtered flame front when subgrid scale turbulence vanishes as LES should tend toward Direct Numerical Simulation (DNS). The filtered flame structure is mapped using 1-D filtered laminar premixed flames. Closure of the filtered progress variable and the energy balance equations are carefully addressed in a fully compressible formulation. The methodology is first applied to 1-D filtered laminar flames, showing the ability of the model to recover the laminar flame speed and the correct chemical structure when the flame wrinkling is completely resolved. The model is then extended to turbulent combustion regimes by including subgrid scale wrinkling effects in the flame front propagation. Finally, preliminary tests of LES in a 3-D turbulent premixed flame are performed. (author)

  13. Modeling chamber transport for heavy-ion fusion

    SciTech Connect

    Sharp, W.M.; Callahan, D.A.; Tabak, M.; Yu, S.S.; Peterson, P.F.; Welch, D.R.; Rose, D.V.; Olson, C.L.

    2002-10-01

    In a typical thick-liquid-wall scenario for heavy-ion fusion (HIF), between seventy and two hundred high-current beams enter the target chamber through ports and propagate about three meters to the target. Since molten-salt jets are planned to protect the chamber wall, the beams move through vapor from the jets, and collisions between beam ions and this background gas both strip the ions and ionize the gas molecules. Radiation from the preheated target causes further beam stripping and gas ionization. Due to this stripping, beams for heavy-ion fusion are expected to require substantial neutralization in a target chamber. Much recent research has, therefore, focused on beam neutralization by electron sources that were neglected in earlier simulations, including emission from walls and the target, photoionization by the target radiation, and pre-neutralization by a plasma generated along the beam path. When these effects are included in simulations with practicable beam and chamber parameters, the resulting focal spot is approximately the size required by a distributed radiator target.

  14. OUTDOOR SMOG CHAMBER EXPERIMENTS TO TEST PHOTOCHEMICAL MODELS: PHASE 2

    EPA Science Inventory

    The smog chamber facility of the University of North Carolina was used to provide experimental data for developing and testing kinetic mechanisms of photochemical smog formation. In this study, 128 pairs of experiments were performed using NOx and various hydrocarbons and hydroca...

  15. Combustion Characteristics of Liquid Normal Alkane Fuels in a Model Combustor of Supersonic Combustion Ramjet Engine

    NASA Astrophysics Data System (ADS)

    ??, ?; ??, ??; ??, ??; ??, ???; ??, ??; ??, ??; ??, ??

    Effect of kinds of one-component n-alkane liquid fuels on combustion characteristics was investigated experimentally using a model combustor of scramjet engine. The inlet condition of a model combustor is 2.0 of Mach number, up to 2400K of total temperature, and 0.38MPa of total pressure. Five kinds of n-alkane are tested, of which carbon numbers are 7, 8, 10, 13, and 16. They are more chemically active and less volatile with an increase of alkane carbon number. Fuels are injected to the combustor in the upstream of cavity with barbotage nitrogen gas and self-ignition performance was investigated. The result shows that self-ignition occurs with less equivalence ratio when alkane carbon number is smaller. This indicates that physical characteristic of fuel, namely volatile of fuel, is dominant for self-ignition behavior. Effect on flame-holding performance is also examined with adding pilot hydrogen and combustion is kept after cutting off pilot hydrogen with the least equivalence ratio where alkane carbon number is from 8 to 10. These points are discussed qualitatively from the conflict effect of chemical and physical properties on alkane carbon number.

  16. SAE Paper 04P-273 Modeling of Diesel Combustion and NO Emissions Based on a

    E-print Network

    Im, Hong G.

    is controlled by the rates #12;of fuel injection and fuel-air mixing. The chemical delay is due to pre-combustionSAE Paper 04P-273 Modeling of Diesel Combustion and NO Emissions Based on a Modified Eddy of Automotive Engineers, Inc. ABSTRACT This paper reports the development of a model of diesel combustion

  17. Control-relevant Modelling and Linear Analysis of Instabilities in Oxy-fuel Combustion

    E-print Network

    Foss, Bjarne A.

    Control-relevant Modelling and Linear Analysis of Instabilities in Oxy-fuel Combustion Dagfinn (compared to conventional combustion control). Analysis on the developed model show that secondary injection combustion have been proposed as an alternative to conventional gas turbine cycles for achieving CO2-capture

  18. Bubble Combustion

    NASA Technical Reports Server (NTRS)

    Corrigan, Jackie

    2004-01-01

    A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM, a computational model developed at Glenn, that simulates the cavitational collapse of a single bubble in a liquid (water) and the subsequent combustion of the gaseous contents inside the bubble. The model solves the time-dependent, compressible Navier-Stokes equations in one-dimension with finite-rate chemical kinetics using the CHEMKIN package. Specifically, parameters such as frequency, pressure, bubble radius, and the equivalence ratio were varied while examining their effect on the maximum temperature, radius, and chemical species. These studies indicate that the radius of the bubble is perhaps the most critical parameter governing bubble combustion dynamics and its efficiency. Based on the results of the parametric studies, we plan on conducting experiments to study the effect of ultrasonic perturbations on the bubble generation process with respect to the bubble radius and size distribution.

  19. Surrogate Model Development for Fuels for Advanced Combustion Engines

    SciTech Connect

    Anand, Krishnasamy; Ra, youngchul; Reitz, Rolf; Bunting, Bruce G

    2011-01-01

    The fuels used in internal-combustion engines are complex mixtures of a multitude of different types of hydrocarbon species. Attempting numerical simulations of combustion of real fuels with all of the hydrocarbon species included is highly unrealistic. Thus, a surrogate model approach is generally adopted, which involves choosing a few representative hydrocarbon species whose overall behavior mimics the characteristics of the target fuel. The present study proposes surrogate models for the nine fuels for advanced combustion engines (FACE) that have been developed for studying low-emission, high-efficiency advanced diesel engine concepts. The surrogate compositions for the fuels are arrived at by simulating their distillation profiles to within a maximum absolute error of 4% using a discrete multi-component (DMC) fuel model that has been incorporated in the multi-dimensional computational fluid dynamics (CFD) code, KIVA-ERC-CHEMKIN. The simulated surrogate compositions cover the range and measured concentrations of the various hydrocarbon classes present in the fuels. The fidelity of the surrogate fuel models is judged on the basis of matching their specific gravity, lower heating value, hydrogen/carbon (H/C) ratio, cetane number, and cetane index with the measured data for all nine FACE fuels.

  20. INVESTIGATION OF THE FATE OF MERCURY IN A COAL COMBUSTION PLUME USING A STATIC PLUME DILUTION CHAMBER

    SciTech Connect

    Dennis L. Laudal

    2001-11-01

    The overall goal of the project was to further develop and then verify SPDC's ability to determine the physical and chemical transformations of mercury in combustion stack plumes. Specific objectives of the project were to perform controlled tests at the pilot scale using dynamic spiking of known mercury compounds (i.e., Hg{sup 0} and HgCl{sub 2}) to prove the ability of the SPDC to determine the following: whether mercury condenses onto particulate matter in a cooling plume; whether there is reduction of Hg{sup 2+} to Hg{sup 0} occurring in hygroscopic aerosols; whether condensed Hg{sup 2+} on particles is photochemically reduced to Hg{sup 0}; and whether or not the Solid Ontario Hydro mercury speciation method (SOH) provides the same results as the Ontario Hydro (OH) mercury speciation method.

  1. Chemical Kinetic Modeling of Hydrogen Combustion Limits

    SciTech Connect

    Pitz, W J; Westbrook, C K

    2008-04-02

    A detailed chemical kinetic model is used to explore the flammability and detonability of hydrogen mixtures. In the case of flammability, a detailed chemical kinetic mechanism for hydrogen is coupled to the CHEMKIN Premix code to compute premixed, laminar flame speeds. The detailed chemical kinetic model reproduces flame speeds in the literature over a range of equivalence ratios, pressures and reactant temperatures. A series of calculation were performed to assess the key parameters determining the flammability of hydrogen mixtures. Increased reactant temperature was found to greatly increase the flame speed and the flammability of the mixture. The effect of added diluents was assessed. Addition of water and carbon dioxide were found to reduce the flame speed and thus the flammability of a hydrogen mixture approximately equally well and much more than the addition of nitrogen. The detailed chemical kinetic model was used to explore the detonability of hydrogen mixtures. A Zeldovich-von Neumann-Doring (ZND) detonation model coupled with detailed chemical kinetics was used to model the detonation. The effectiveness on different diluents was assessed in reducing the detonability of a hydrogen mixture. Carbon dioxide was found to be most effective in reducing the detonability followed by water and nitrogen. The chemical action of chemical inhibitors on reducing the flammability of hydrogen mixtures is discussed. Bromine and organophosphorus inhibitors act through catalytic cycles that recombine H and OH radicals in the flame. The reduction in H and OH radicals reduces chain branching in the flame through the H + O{sub 2} = OH + O chain branching reaction. The reduction in chain branching and radical production reduces the flame speed and thus the flammability of the hydrogen mixture.

  2. Internal combustion engine

    DOEpatents

    Baker, Quentin A. (P.O. Box 6477, San Antonio, TX 78209); Mecredy, Henry E. (1630-C W. 6th, Austin, TX 78703); O'Neal, Glenn B. (6503 Wagner Way, San Antonio, TX 78256)

    1991-01-01

    An improved engine is provided that more efficiently consumes difficult fuels such as coal slurries or powdered coal. The engine includes a precombustion chamber having a portion thereof formed by an ignition plug. The precombustion chamber is arranged so that when the piston is proximate the head, the precombustion chamber is sealed from the main cylinder or the main combustion chamber and when the piston is remote from the head, the precombustion chamber and main combustion chamber are in communication. The time for burning of fuel in the precombustion chamber can be regulated by the distance required to move the piston from the top dead center position to the position wherein the precombustion chamber and main combustion chamber are in communication.

  3. Fluids and Combustion Facility: Fluids Integrated Rack Modal Model Correlation

    NASA Technical Reports Server (NTRS)

    McNelis, Mark E.; Suarez, Vicente J.; Sullivan, Timothy L.; Otten, Kim D.; Akers, James C.

    2005-01-01

    The Fluids Integrated Rack (FIR) is one of two racks in the Fluids and Combustion Facility on the International Space Station. The FIR is dedicated to the scientific investigation of space system fluids management supporting NASA s Exploration of Space Initiative. The FIR hardware was modal tested and FIR finite element model updated to satisfy the International Space Station model correlation criteria. The final cross-orthogonality results between the correlated model and test mode shapes was greater than 90 percent for all primary target modes.

  4. Kinetic Modeling of Low-Temperature Plasma Assisted Combustion

    NASA Astrophysics Data System (ADS)

    Adamovich, Igor

    2013-11-01

    Quantitative insight into kinetics of low-temperature plasma assisted fuel oxidation and ignition would be impossible without kinetic modeling. The principal challenges in development of a predictive kinetic model of nonequilibrium plasmas sustained in fuel-air mixtures include (i) lack of ``conventional'' chemical kinetics mechanisms validated at low temperatures, (ii) lack of data on rates and products of reactions of excited species generated in the plasma, some of which are not well understood, and their coupling with fuel-air plasma chemistry, and (iii) scarcity of data obtained in well-characterized plasma-assisted combustion experiments, which can be used for model validation. ``Conventional'' combustion chemistry mechanisms have been developed for relatively high temperature conditions. Their applicability at temperatures below ignition temperature, common in plasma assisted combustion environments, needs to be assessed to determine if they can be used as a basis for a plasma-assisted combustion chemistry mechanism. This requires time-resolved measurements of radical species concentrations during low-temperature fuel oxidation, when an initial pool of primary radicals (O, H, and OH) is generated in the plasma, such as in the late afterglow of an electric discharge. This allows isolating relatively slow ``conventional'' low-temperature fuel oxidation reactions triggered by the radicals from the reactions of excited species generated in the discharge, which decay relatively rapidly. Kinetic modeling calculations demonstrated that some of the existing combustion mechanisms provide good agreement with the experimental data taken in lean H2-, CH4-, and C2H4-air mixtures at low temperatures, while data taken in C3H8-air are not reproduced by any of the mechanisms tested. A complementary approach is to focus on kinetics of ``rapid'' reactions of electronically and vibrationally excited species in the electric discharge, as well as oxygen dissociation by electron impact, and their effect on production of radicals in the early afterglow. These experiments provide key data on coupling of molecular energy transfer processes in the plasma with ``conventional'' chemical reactions. Time-resolved and spatially-resolved measurements of temperature, vibrational and electronic levels populations, and radical species concentrations are critical for characterization of the nonequilibrium reacting mixture at these conditions. Kinetic modeling of recent experiments in a diffuse filament, nanosecond pulse electric discharges in air suggest that the role of electronically excited N2* molecules on chemical reactions in the afterglow, such as NO generation reactions, has been significantly underestimated in the past. Further experiments in fuel-air mixtures are expected to provide additional data on the role of these excited species on low-temperature fuel-air chemistry.

  5. Development of Supersonic Combustion Experiments for CFD Modeling

    NASA Technical Reports Server (NTRS)

    Baurle, Robert; Bivolaru, Daniel; Tedder, Sarah; Danehy, Paul M.; Cutler, Andrew D.; Magnotti, Gaetano

    2007-01-01

    This paper describes the development of an experiment to acquire data for developing and validating computational fluid dynamics (CFD) models for turbulence in supersonic combusting flows. The intent is that the flow field would be simple yet relevant to flows within hypersonic air-breathing engine combustors undergoing testing in vitiated-air ground-testing facilities. Specifically, it describes development of laboratory-scale hardware to produce a supersonic combusting coaxial jet, discusses design calculations, operability and types of flames observed. These flames are studied using the dual-pump coherent anti- Stokes Raman spectroscopy (CARS) - interferometric Rayleigh scattering (IRS) technique. This technique simultaneously and instantaneously measures temperature, composition, and velocity in the flow, from which many of the important turbulence statistics can be found. Some preliminary CARS data are presented.

  6. Modeling and simulation of combustion dynamics in lean-premixed swirl-stabilized gas-turbine engines

    NASA Astrophysics Data System (ADS)

    Huang, Ying

    This research focuses on the modeling and simulation of combustion dynamics in lean-premixed gas-turbines engines. The primary objectives are: (1) to establish an efficient and accurate numerical framework for the treatment of unsteady flame dynamics; and (2) to investigate the parameters and mechanisms responsible for driving flow oscillations in a lean-premixed gas-turbine combustor. The energy transfer mechanisms among mean flow motions, periodic motions and background turbulent motions in turbulent reacting flow are first explored using a triple decomposition technique. Then a comprehensive numerical study of the combustion dynamics in a lean-premixed swirl-stabilized combustor is performed. The analysis treats the conservation equations in three dimensions and takes into account finite-rate chemical reactions and variable thermophysical properties. Turbulence closure is achieved using a large-eddy-simulation (LES) technique. The compressible-flow version of the Smagorinsky model is employed to describe subgrid-scale turbulent motions and their effect on large-scale structures. A level-set flamelet library approach is used to simulate premixed turbulent combustion. In this approach, the mean flame location is modeled using a level-set G-equation, where G is defined as a distance function. Thermophysical properties are obtained using a presumed probability density function (PDF) along with a laminar flamelet library. The governing equations and the associated boundary conditions are solved by means of a four-step Runge-Kutta scheme along with the implementation of the message passing interface (MPI) parallel computing architecture. The analysis allows for a detailed investigation into the interaction between turbulent flow motions and oscillatory combustion of a swirl-stabilized injector. Results show good agreement with an analytical solution and experimental data in terms of acoustic properties and flame evolution. A study of flame bifurcation from a stable state to an unstable state indicates that the inlet flow temperature and equivalence ratio are the two most important variables determining the stability characteristics of the combustor. Under unstable operating conditions, several physical processes responsible for driving combustion instabilities in the chamber have been identified and quantified. These processes include vortex shedding and acoustic interaction, coupling between the flame evolution and local flow oscillations, vortex and flame interaction and coupling between heat release and acoustic motions. The effects of inlet swirl number on the flow development and flame dynamics in the chamber are also carefully studied. In the last part of this thesis, an analytical model is developed using triple decomposition techniques to model the combustion response of turbulent premixed flames to acoustic oscillations.

  7. Combustion-gas recirculation system

    DOEpatents

    Baldwin, Darryl Dean (Lacon, IL)

    2007-10-09

    A combustion-gas recirculation system has a mixing chamber with a mixing-chamber inlet and a mixing-chamber outlet. The combustion-gas recirculation system may further include a duct connected to the mixing-chamber inlet. Additionally, the combustion-gas recirculation system may include an open inlet channel with a solid outer wall. The open inlet channel may extend into the mixing chamber such that an end of the open inlet channel is disposed between the mixing-chamber inlet and the mixing-chamber outlet. Furthermore, air within the open inlet channel may be at a pressure near or below atmospheric pressure.

  8. Evaluation of a hybrid kinetics/mixing-controlled combustion model for turbulent premixed and diffusion combustion using KIVA-2

    NASA Technical Reports Server (NTRS)

    Nguyen, H. Lee; Wey, Ming-Jyh

    1990-01-01

    Two dimensional calculations were made of spark ignited premixed-charge combustion and direct injection stratified-charge combustion in gasoline fueled piston engines. Results are obtained using kinetic-controlled combustion submodel governed by a four-step global chemical reaction or a hybrid laminar kinetics/mixing-controlled combustion submodel that accounts for laminar kinetics and turbulent mixing effects. The numerical solutions are obtained by using KIVA-2 computer code which uses a kinetic-controlled combustion submodel governed by a four-step global chemical reaction (i.e., it assumes that the mixing time is smaller than the chemistry). A hybrid laminar/mixing-controlled combustion submodel was implemented into KIVA-2. In this model, chemical species approach their thermodynamics equilibrium with a rate that is a combination of the turbulent-mixing time and the chemical-kinetics time. The combination is formed in such a way that the longer of the two times has more influence on the conversion rate and the energy release. An additional element of the model is that the laminar-flame kinetics strongly influence the early flame development following ignition.

  9. Evaluation of a hybrid kinetics/mixing-controlled combustion model for turbulent premixed and diffusion combustion using KIVA-II

    NASA Technical Reports Server (NTRS)

    Nguyen, H. Lee; Wey, Ming-Jyh

    1990-01-01

    Two-dimensional calculations were made of spark ignited premixed-charge combustion and direct injection stratified-charge combustion in gasoline fueled piston engines. Results are obtained using kinetic-controlled combustion submodel governed by a four-step global chemical reaction or a hybrid laminar kinetics/mixing-controlled combustion submodel that accounts for laminar kinetics and turbulent mixing effects. The numerical solutions are obtained by using KIVA-2 computer code which uses a kinetic-controlled combustion submodel governed by a four-step global chemical reaction (i.e., it assumes that the mixing time is smaller than the chemistry). A hybrid laminar/mixing-controlled combustion submodel was implemented into KIVA-2. In this model, chemical species approach their thermodynamics equilibrium with a rate that is a combination of the turbulent-mixing time and the chemical-kinetics time. The combination is formed in such a way that the longer of the two times has more influence on the conversion rate and the energy release. An additional element of the model is that the laminar-flame kinetics strongly influence the early flame development following ignition.

  10. Structure-Based Predictive model for Coal Char Combustion.

    SciTech Connect

    Hurt, R.; Colo, J; Essenhigh, R.; Hadad, C; Stanley, E.

    1997-09-24

    During the third quarter of this project, progress was made on both major technical tasks. Progress was made in the chemistry department at OSU on the calculation of thermodynamic properties for a number of model organic compounds. Modelling work was carried out at Brown to adapt a thermodynamic model of carbonaceous mesophase formation, originally applied to pitch carbonization, to the prediction of coke texture in coal combustion. This latter work makes use of the FG-DVC model of coal pyrolysis developed by Advanced Fuel Research to specify the pool of aromatic clusters that participate in the order/disorder transition. This modelling approach shows promise for the mechanistic prediction of the rank dependence of char structure and will therefore be pursued further. Crystalline ordering phenomena were also observed in a model char prepared from phenol-formaldehyde carbonized at 900{degrees}C and 1300{degrees}C using high-resolution TEM fringe imaging. Dramatic changes occur in the structure between 900 and 1300{degrees}C, making this char a suitable candidate for upcoming in situ work on the hot stage TEM. Work also proceeded on molecular dynamics simulations at Boston University and on equipment modification and testing for the combustion experiments with widely varying flame types at Ohio State.

  11. Multiple-relaxation-time lattice Boltzmann kinetic model for combustion

    E-print Network

    Aiguo Xu; Chuandong Lin; Guangcai Zhang; Yingjun Li

    2015-03-13

    To probe both the Hydrodynamic Non-Equilibrium (HNE) and Thermodynamic Non-Equilibrium (TNE) in the combustion process, a two-dimensional Multiple-Relaxation-Time (MRT) version of Lattice Boltzmann Kinetic Model(LBKM) for combustion phenomena is presented. The chemical energy released in the progress of combustion is dynamically coupled into the system by adding a chemical term to the LB kinetic equation. Beside describing the evolutions of the conserved quantities, the density, momentum and energy, which are what the Navier-Stokes model describes, the MRT-LBKM presents also a coarse-grained description on the evolutions of some non-conserved quantities. The current model works for both subsonic and supersonic flows with or without chemical reaction. In this model both the specific-heat ratio and the Prandtl number are flexible, the TNE effects are naturally presented in each simulation step. The model is verified and validated via well-known benchmark tests. As an initial application, various non-equilibrium behaviours, including the complex interplays between various HNEs, between various TNEs and between the HNE and TNE, around the detonation wave in the unsteady and steady one-dimensional detonation processes are preliminarily probed. It is found that the system viscosity (or heat conductivity) decreases the local TNE, but increase the global TNE around the detonation wave, that even locally, the system viscosity (or heat conductivity) results in two kinds of competing trends, to increase and to decrease the TNE effects. The physical reason is that the viscosity (or heat conductivity) takes part in both the thermodynamic and hydrodynamic responses.

  12. Multiple-relaxation-time lattice Boltzmann kinetic model for combustion

    NASA Astrophysics Data System (ADS)

    Xu, Aiguo; Lin, Chuandong; Zhang, Guangcai; Li, Yingjun

    2015-04-01

    To probe both the hydrodynamic nonequilibrium (HNE) and thermodynamic nonequilibrium (TNE) in the combustion process, a two-dimensional multiple-relaxation-time (MRT) version of lattice Boltzmann kinetic model (LBKM) for combustion phenomena is presented. The chemical energy released in the progress of combustion is dynamically coupled into the system by adding a chemical term to the LB kinetic equation. Aside from describing the evolutions of the conserved quantities, the density, momentum, and energy, which are what the Navier-Stokes model describes, the MRT-LBKM presents also a coarse-grained description on the evolutions of some nonconserved quantities. The current model works for both subsonic and supersonic flows with or without chemical reaction. In this model, both the specific-heat ratio and the Prandtl number are flexible, the TNE effects are naturally presented in each simulation step. The model is verified and validated via well-known benchmark tests. As an initial application, various nonequilibrium behaviors, including the complex interplays between various HNEs, between various TNEs, and between the HNE and TNE, around the detonation wave in the unsteady and steady one-dimensional detonation processes are preliminarily probed. It is found that the system viscosity (or heat conductivity) decreases the local TNE, but increases the global TNE around the detonation wave, that even locally, the system viscosity (or heat conductivity) results in two kinds of competing trends, to increase and to decrease the TNE effects. The physical reason is that the viscosity (or heat conductivity) takes part in both the thermodynamic and hydrodynamic responses.

  13. Multiple-relaxation-time lattice Boltzmann kinetic model for combustion.

    PubMed

    Xu, Aiguo; Lin, Chuandong; Zhang, Guangcai; Li, Yingjun

    2015-04-01

    To probe both the hydrodynamic nonequilibrium (HNE) and thermodynamic nonequilibrium (TNE) in the combustion process, a two-dimensional multiple-relaxation-time (MRT) version of lattice Boltzmann kinetic model (LBKM) for combustion phenomena is presented. The chemical energy released in the progress of combustion is dynamically coupled into the system by adding a chemical term to the LB kinetic equation. Aside from describing the evolutions of the conserved quantities, the density, momentum, and energy, which are what the Navier-Stokes model describes, the MRT-LBKM presents also a coarse-grained description on the evolutions of some nonconserved quantities. The current model works for both subsonic and supersonic flows with or without chemical reaction. In this model, both the specific-heat ratio and the Prandtl number are flexible, the TNE effects are naturally presented in each simulation step. The model is verified and validated via well-known benchmark tests. As an initial application, various nonequilibrium behaviors, including the complex interplays between various HNEs, between various TNEs, and between the HNE and TNE, around the detonation wave in the unsteady and steady one-dimensional detonation processes are preliminarily probed. It is found that the system viscosity (or heat conductivity) decreases the local TNE, but increases the global TNE around the detonation wave, that even locally, the system viscosity (or heat conductivity) results in two kinds of competing trends, to increase and to decrease the TNE effects. The physical reason is that the viscosity (or heat conductivity) takes part in both the thermodynamic and hydrodynamic responses. PMID:25974611

  14. Structure Based Predictive Model for Coal Char Combustion

    SciTech Connect

    Robert Hurt; Joseph Calo; Robert Essenhigh; Christopher Hadad

    2000-12-30

    This unique collaborative project has taken a very fundamental look at the origin of structure, and combustion reactivity of coal chars. It was a combined experimental and theoretical effort involving three universities and collaborators from universities outside the U.S. and from U.S. National Laboratories and contract research companies. The project goal was to improve our understanding of char structure and behavior by examining the fundamental chemistry of its polyaromatic building blocks. The project team investigated the elementary oxidative attack on polyaromatic systems, and coupled with a study of the assembly processes that convert these polyaromatic clusters to mature carbon materials (or chars). We believe that the work done in this project has defined a powerful new science-based approach to the understanding of char behavior. The work on aromatic oxidation pathways made extensive use of computational chemistry, and was led by Professor Christopher Hadad in the Department of Chemistry at Ohio State University. Laboratory experiments on char structure, properties, and combustion reactivity were carried out at both OSU and Brown, led by Principle Investigators Joseph Calo, Robert Essenhigh, and Robert Hurt. Modeling activities were divided into two parts: first unique models of crystal structure development were formulated by the team at Brown (PI'S Hurt and Calo) with input from Boston University and significant collaboration with Dr. Alan Kerstein at Sandia and with Dr. Zhong-Ying chen at SAIC. Secondly, new combustion models were developed and tested, led by Professor Essenhigh at OSU, Dieter Foertsch (a collaborator at the University of Stuttgart), and Professor Hurt at Brown. One product of this work is the CBK8 model of carbon burnout, which has already found practical use in CFD codes and in other numerical models of pulverized fuel combustion processes, such as EPRI's NOxLOI Predictor. The remainder of the report consists of detailed technical discussion organized into chapters whose organization is dictated by the nature of the research performed. Chapter 2 is entitled 'Experimental Work on Char Structure, Properties, and Reactivity', and focuses on fundamental structural studies at Brown using both phenollformaldehyde resin chars as model carbons and real coal chars. This work includes the first known in site high resolution TEM studies of carbonization processes, and some intriguing work on 'memory loss', a form of interaction between annealing and oxidation phenomena in chars. Chapter 3 entitled 'Computational Chemistry of Aromatic Oxidation Pathways' presents in detail the OSU work targeted at understanding the elementary molecular pathways of aromatic oxidation. Chapter 4 describes the 'Mesoscale Structural Models', using a combination of thermodynamic (equilibrium) approaches based on liquid crystal theory and kinetic simulations accounting for the effects of limited layer mobility in many fossil fuel derived carbons containing cross-linking agents. Chapter 5 entitled 'Combustion Modeling' presents work on extinction in the late stages of combustion and the development and features of the CBK8 model.

  15. Analysis of Combustion Trajectories of Advanced Combustion Modes in a CIDI Engine with a Two-Zone Phenomenological Model

    SciTech Connect

    Gao, Zhiming; Daw, C Stuart; Wagner, Robert M; Sluder, Scott; Green Jr, Johney Boyd

    2011-01-01

    We describe a two-zone phenomenological model for simulating in-cylinder details in conventional, highdilution, and high-efficiency clean combustion in a diesel engine. Using this model we characterize the differences in these combustion modes in terms of 3D trajectories involving equivalence ratio, flame temperature, and oxygen mass fraction. These trajectories in turn make it possible to better understand the relative NOx and particulate emissions of the different modes. The two-zone model predictions are shown to be consistent with more detailed CFD simulations and provide the benefit of very rapid simulation.

  16. Assessment of Turbulence-Chemistry Interaction Models in the National Combustion Code (NCC) - Part I

    NASA Technical Reports Server (NTRS)

    Wey, Thomas Changju; Liu, Nan-suey

    2011-01-01

    This paper describes the implementations of the linear-eddy model (LEM) and an Eulerian FDF/PDF model in the National Combustion Code (NCC) for the simulation of turbulent combustion. The impacts of these two models, along with the so called laminar chemistry model, are then illustrated via the preliminary results from two combustion systems: a nine-element gas fueled combustor and a single-element liquid fueled combustor.

  17. Towards cleaner combustion engines through groundbreaking detailed chemical kinetic models

    PubMed Central

    Battin-Leclerc, Frédérique; Blurock, Edward; Bounaceur, Roda; Fournet, René; Glaude, Pierre-Alexandre; Herbinet, Olivier; Sirjean, Baptiste; Warth, V.

    2013-01-01

    In the context of limiting the environmental impact of transportation, this paper reviews new directions which are being followed in the development of more predictive and more accurate detailed chemical kinetic models for the combustion of fuels. In the first part, the performance of current models, especially in terms of the prediction of pollutant formation, is evaluated. In the next parts, recent methods and ways to improve these models are described. An emphasis is given on the development of detailed models based on elementary reactions, on the production of the related thermochemical and kinetic parameters, and on the experimental techniques available to produce the data necessary to evaluate model predictions under well defined conditions. PMID:21597604

  18. Evaluation of a locally homogeneous flow model of spray combustion

    NASA Technical Reports Server (NTRS)

    Mao, C. P.; Szekely, G. A., Jr.; Faeth, G. M.

    1980-01-01

    A model of spray combustion which employs a second-order turbulence model was developed. The assumption of locally homogeneous flow is made, implying infinitely fast transport rates between the phase. Measurements to test the model were completed for a gaseous n-propane flame and an air atomized n-pentane spray flame, burning in stagnant air at atmospheric pressure. Profiles of mean velocity and temperature, as well as velocity fluctuations and Reynolds stress, were measured in the flames. The predictions for the gas flame were in excellent agreement with the measurements. The predictions for the spray were qualitatively correct, but effects of finite rate interphase transport were evident, resulting in a overstimation of the rate development of the flow. Predictions of spray penetration length at high pressures, including supercritical combustion conditions, were also completed for comparison with earlier measurements. Test conditions involved a pressure atomized n-pentane spray, burning in stagnant air at pressures of 3, 5, and 9 MPa. The comparison between predictions and measurements was fair. This is not a very sensitive test of the model, however, and further high pressure experimental and theoretical results are needed before a satisfactory assessment of the locally homogeneous flow approximation can be made.

  19. Examination of various turbulence models for application in liquid rocket thrust chambers

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1991-01-01

    There is a large variety of turbulence models available. These models include direct numerical simulation, large eddy simulation, Reynolds stress/flux model, zero equation model, one equation model, two equation k-epsilon model, multiple-scale model, etc. Each turbulence model contains different physical assumptions and requirements. The natures of turbulence are randomness, irregularity, diffusivity and dissipation. The capabilities of the turbulence models, including physical strength, weakness, limitations, as well as numerical and computational considerations, are reviewed. Recommendations are made for the potential application of a turbulence model in thrust chamber and performance prediction programs. The full Reynolds stress model is recommended. In a workshop, specifically called for the assessment of turbulence models for applications in liquid rocket thrust chambers, most of the experts present were also in favor of the recommendation of the Reynolds stress model.

  20. CARS study of linewidths of the Q-branch of hydrogen molecules at high temperatures in a pulsed high-pressure H{sub 2}-O{sub 2} combustion chamber

    SciTech Connect

    Vereschagin, Konstantin A; Vereschagin, Alexey K; Smirnov, Valery V; Stelmakh, O M; Fabelinskii, V I; Clauss, W; Klimenko, D N; Oschwald, M

    2005-03-31

    The results of measurements of individual line widths of the Q-branch of a hydrogen molecule and the corresponding coefficients of broadening caused by collisions with water molecules at T = 2700 K in a repetitively pulsed high-pressure (50-200 atm) hydrogen-oxygen combustion chamber are presented. CARS spectra of individual Q{sub 1}-Q{sub 7} hydrogen lines, pressure pulses, and the broadband CARS spectra of the entire Q-branch of hydrogen are recorded simultaneously during a single laser pulse. The shape of line profiles was analysed using a Fabry-Perot interferometer. The temperature in the volume being probed was determined from the 'broadband' CARS spectra. The entire body of the experimental results gives information on the spectral linewidths, temperature and pressure in the combustion chamber during CARS probing. (laser applications and other topics in quantum electronics)

  1. Numerical modeling of spray combustion with an advanced VOF method

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen; Shang, Huan-Min; Shih, Ming-Hsin; Liaw, Paul

    1995-01-01

    This paper summarizes the technical development and validation of a multiphase computational fluid dynamics (CFD) numerical method using the volume-of-fluid (VOF) model and a Lagrangian tracking model which can be employed to analyze general multiphase flow problems with free surface mechanism. The gas-liquid interface mass, momentum and energy conservation relationships are modeled by continuum surface mechanisms. A new solution method is developed such that the present VOF model can be applied for all-speed flow regimes. The objectives of the present study are to develop and verify the fractional volume-of-fluid cell partitioning approach into a predictor-corrector algorithm and to demonstrate the effectiveness of the present approach by simulating benchmark problems including laminar impinging jets, shear coaxial jet atomization and shear coaxial spray combustion flows.

  2. Solid Rocket Motor Combustion Instability Modeling in COMSOL Multiphysics

    NASA Technical Reports Server (NTRS)

    Fischbach, Sean R.

    2015-01-01

    Combustion instability modeling of Solid Rocket Motors (SRM) remains a topic of active research. Many rockets display violent fluctuations in pressure, velocity, and temperature originating from the complex interactions between the combustion process, acoustics, and steady-state gas dynamics. Recent advances in defining the energy transport of disturbances within steady flow-fields have been applied by combustion stability modelers to improve the analysis framework [1, 2, 3]. Employing this more accurate global energy balance requires a higher fidelity model of the SRM flow-field and acoustic mode shapes. The current industry standard analysis tool utilizes a one dimensional analysis of the time dependent fluid dynamics along with a quasi-three dimensional propellant grain regression model to determine the SRM ballistics. The code then couples with another application that calculates the eigenvalues of the one dimensional homogenous wave equation. The mean flow parameters and acoustic normal modes are coupled to evaluate the stability theory developed and popularized by Culick [4, 5]. The assumption of a linear, non-dissipative wave in a quiescent fluid remains valid while acoustic amplitudes are small and local gas velocities stay below Mach 0.2. The current study employs the COMSOL multiphysics finite element framework to model the steady flow-field parameters and acoustic normal modes of a generic SRM. The study requires one way coupling of the CFD High Mach Number Flow (HMNF) and mathematics module. The HMNF module evaluates the gas flow inside of a SRM using St. Robert's law to model the solid propellant burn rate, no slip boundary conditions, and the hybrid outflow condition. Results from the HMNF model are verified by comparing the pertinent ballistics parameters with the industry standard code outputs (i.e. pressure drop, thrust, ect.). These results are then used by the coefficient form of the mathematics module to determine the complex eigenvalues of the Acoustic Velocity Potential Equation (AVPE). The mathematics model is truncated at the nozzle sonic line, where a zero flux boundary condition is self-satisfying. The remaining boundaries are modeled with a zero flux boundary condition, assuming zero acoustic absorption on all surfaces. The results of the steady-state CFD and AVPE analyses are used to calculate the linear acoustic growth rate as is defined by Flandro and Jacob [2, 3]. In order to verify the process implemented within COMSOL we first employ the Culick theory and compare the results with the industry standard. After the process is verified, the Flandro/Jacob energy balance theory is employed and results displayed.

  3. Hydrodynamic model of advanced pressurized fluidized bed combustion

    SciTech Connect

    Horio, Masayuki; Lei, H.W.

    1997-12-31

    A hydrodynamic model was developed for the advanced pressurized fluidized bed combustion (A-PFBC) process. The particular system investigated here is composed of a pressurized circulating fluidized bed (PCFB) for coal gasification/desulfurization and a PCFB for combustion with the gas-solid counter-current flow through the two PCFBs. One of the most important parameters may be the material seal height (MSH) in the downcomer connecting the gasifier/desulfurizer and the combustor, which is thought to strongly influence the safe and stable operation of the process. In this mode, MSH was determined according to the pressure balance between the gasifier/desulfurizer and the combustor. The solid flux in the lower dense region of the two PCFBs was estimated by considering the clustering suspension and core-annulus flow. The mean cluster size and voidage in the cluster phase were predicted by the cluster size model of Horio-Ito (1996). Solid flux of the gasifier and combustor was calculated based on mass balances of limestone, char and ash in the system. Based on this model, the whole pressure profile loop in the system was predicted, and the effects of operating conditions on MSH between the gasifier and the combustor were investigated. The feasibility of the A-PCFB system with PCFBs both for the gasifier/desulfurizer and for the combustor was successfully confirmed.

  4. Characterization of Low-Frequency Combustion Stability of the Fastrac Engine

    NASA Technical Reports Server (NTRS)

    Rocker, Marvin; Jones, Preston (Technical Monitor)

    2002-01-01

    A series of tests were conducted to measure the combustion performance of the Fastrac engine thrust chamber. During mainstage, the thrust chamber exhibited no large-amplitude chamber pressure oscillations that could be identified as low-frequency combustion instability or 'chug'. However, during start-up and shutdown, the thrust chamber very briefly exhibited large-amplitude chamber pressure oscillations that were identified as chug. These instabilities during start-up and shutdown were regarded as benign due to their brevity. Linear models of the thrust chamber and the propellant feed systems were formulated for both the thrust chamber component tests and the flight engine tests. These linear models determined the frequency and decay rate of chamber pressure oscillations given the design and operating conditions of the thrust chamber and feed system. The frequency of chamber pressure oscillations determined from the model closely matched the frequency of low-amplitude, low-frequency chamber pressure oscillations exhibited in some of the later thrust chamber mainstage tests. The decay rate of the chamber pressure oscillations determined from the models indicated that these low-frequency oscillations were stable. Likewise, the decay rate, determined from the model of the flight engine tests indicated that the low-frequency chamber pressure oscillations would be stable.

  5. Advanced computational simulation of transient, multiphase combustion

    SciTech Connect

    Hosangadi, A.; Sinha, N.; Dash, S.M.

    1995-12-31

    In recent activities involving combustion chamber simulation of next-generation guns (Liquid Propellant Gun, Electrothermal-Chemical Gun, Ram Accelerator), a three-dimensional upwind/implicit Navier-Stokes code, CRAFT, has been extended to analyze very complex multiphase combustion problems. The extensions have included: (1) gas/bulk liquid interaction modeling; (2) droplet combustion of liquid propellants; and (3) fluidized bed combustion of solid (balled) propellants. The computational framework utilizes Reimann-based Roe/TVD upwind numerics with strongly coupled, fully-implicit numerics (all equations and source terms are strongly coupled) which permits the accurate analysis of complex transient processes including combustion instabilities. A large eddy simulation (LES) framework is used to represent the turbulence with simplified subgrid stress (SGS) modeling. While problem specific details of next-generation gun models are restricted (details have been presented at JANNAF Combustion meetings), the basic methodology is not and is being extended to several non-DoD arenas. This paper will present an overview of the new methodology developed and will describe fundamental studies of varied transient, multiphase combusting flows. Details of the physics will be emphasized including large eddy turbulent behavior in complex multiphase environments. Analyses performed have involved detailed spectral processing in situations where chamber acoustics strongly interact with combustion processes.

  6. Thermophysics Characterization of Kerosene Combustion

    NASA Technical Reports Server (NTRS)

    Wang, Ten-See

    2000-01-01

    A one-formula surrogate fuel formulation and its quasi-global combustion kinetics model are developed to support the design of injectors and thrust chambers of kerosene-fueled rocket engines. This surrogate fuel model depicts a fuel blend that properly represents the general physical and chemical properties of kerosene. The accompanying gaseous-phase thermodynamics of the surrogate fuel is anchored with the heat of formation of kerosene and verified by comparing a series of one-dimensional rocket thrust chamber calculations. The quasi-global combustion kinetics model consists of several global steps for parent fuel decomposition, soot formation, and soot oxidation, and a detailed wet-CO mechanism. The final thermophysics formulations are incorporated with a computational fluid dynamics model for prediction of the combustor efficiency of an uni-element, tri-propellant combustor and the radiation of a kerosene-fueled thruster plume. The model predictions agreed reasonably well with those of the tests.

  7. Kinetic Modeling of Combustion Characteristics of Real Biodiesel Fuels

    SciTech Connect

    Naik, C V; Westbrook, C K

    2009-04-08

    Biodiesel fuels are of much interest today either for replacing or blending with conventional fuels for automotive applications. Predicting engine effects of using biodiesel fuel requires accurate understanding of the combustion characteristics of the fuel, which can be acquired through analysis using reliable detailed reaction mechanisms. Unlike gasoline or diesel that consists of hundreds of chemical compounds, biodiesel fuels contain only a limited number of compounds. Over 90% of the biodiesel fraction is composed of 5 unique long-chain C{sub 18} and C{sub 16} saturated and unsaturated methyl esters. This makes modeling of real biodiesel fuel possible without the need for a fuel surrogate. To this end, a detailed chemical kinetic mechanism has been developed for determining the combustion characteristics of a pure biodiesel (B100) fuel, applicable from low- to high-temperature oxidation regimes. This model has been built based on reaction rate rules established in previous studies at Lawrence Livermore National Laboratory. Computed results are compared with the few fundamental experimental data that exist for biodiesel fuel and its components. In addition, computed results have been compared with experimental data for other long-chain hydrocarbons that are similar in structure to the biodiesel components.

  8. High fidelity chemistry and radiation modeling for oxy -- combustion scenarios

    NASA Astrophysics Data System (ADS)

    Abdul Sater, Hassan A.

    To account for the thermal and chemical effects associated with the high CO2 concentrations in an oxy-combustion atmosphere, several refined gas-phase chemistry and radiative property models have been formulated for laminar to highly turbulent systems. This thesis examines the accuracies of several chemistry and radiative property models employed in computational fluid dynamic (CFD) simulations of laminar to transitional oxy-methane diffusion flames by comparing their predictions against experimental data. Literature review about chemistry and radiation modeling in oxy-combustion atmospheres considered turbulent systems where the predictions are impacted by the interplay and accuracies of the turbulence, radiation and chemistry models. Thus, by considering a laminar system we minimize the impact of turbulence and the uncertainties associated with turbulence models. In the first section of this thesis, an assessment and validation of gray and non-gray formulations of a recently proposed weighted-sum-of-gray gas model in oxy-combustion scenarios was undertaken. Predictions of gas, wall temperatures and flame lengths were in good agreement with experimental measurements. The temperature and flame length predictions were not sensitive to the radiative property model employed. However, there were significant variations between the gray and non-gray model radiant fraction predictions with the variations in general increasing with decrease in Reynolds numbers possibly attributed to shorter flames and steeper temperature gradients. The results of this section confirm that non-gray model predictions of radiative heat fluxes are more accurate than gray model predictions especially at steeper temperature gradients. In the second section, the accuracies of three gas-phase chemistry models were assessed by comparing their predictions against experimental measurements of temperature, species concentrations and flame lengths. The chemistry was modeled employing the Eddy Dissipation Concept (EDC) employing a 41-step detailed chemistry mechanism, the non-adiabatic extension of the equilibrium Probability Density Function (PDF) based mixture-fraction model and a two-step global finite rate chemistry model with modified rate constants proposed to work well in oxy-methane flames. Based on the results from this section, the equilibrium PDF model in conjunction with a high-fidelity non-gray model for the radiative properties of the gas-phase may be deemed as accurate to capture the major gas species concentrations, temperatures and flame lengths in oxy-methane flames. The third section examines the variations in radiative transfer predictions due to the choice of chemistry and gas-phase radiative property models. The radiative properties were estimated employing four weighted-sum-of-gray-gases models (WSGGM) that were formulated employing different spectroscopic/model databases. An average variation of 14 -- 17% in the wall incident radiative fluxes was observed between the EDC and equilibrium mixture fraction chemistry models, due to differences in their temperature predictions within the flame. One-dimensional, line-of-sight radiation calculations showed a 15 -- 25 % reduction in the directional radiative fluxes at lower axial locations as a result of ignoring radiation from CO and CH4. Under the constraints of fixed temperature and species distributions, the flame radiant power estimates and average wall incident radiative fluxes varied by nearly 60% and 11% respectively among the different WSGG models.

  9. Thermal analysis simulation for a spin-motor used in the advanced main combustion chamber vacuum plasma spray project using the SINDA computer program

    NASA Technical Reports Server (NTRS)

    Mcdonald, Gary H.

    1990-01-01

    One of the many design challenges of this project is predicting the thermal effects due to the environment inside the vacuum chamber on the turntable and spin motor spindle assembly. The objective of the study is to model the spin motor using the computer program System Improved Numerical Differencing Analyzer (SINDA). By formulating the appropriate input information concerning the motor's geometry, coolant flow path, material composition, and bearing and motor winding characteristics, SINDA should predict temperatures at various predefined nodes. From these temperatures, hopefully, one can predict if the coolant flow rate is sufficient or if certain mechanical elements such as bearings, O ring seals, or motor windings will exceed maximum design temperatures.

  10. A model for the emergence of pillars, walls and royal chambers in termite nests

    E-print Network

    Theraulaz, Guy

    A model for the emergence of pillars, walls and royal chambers in termite nests Eric Bonabeau1, 31062 Toulouse Ce¨ dex, France A simple model of the emergence of pillars in termite nests by Deneubourg, and that this transformation may not be driven by any change in the termites' behaviour. Because the same type of response

  11. MODELS AND STATISTICAL METHODS FOR GASEOUS EMISSION TESTING OF FINITE SOURCES IN WELL-MIXED CHAMBERS

    EPA Science Inventory

    The paper proposes two families of mathematical models to represent either the concentration of a gaseous emission in (or the accumulated amount exiting from) a well-mixed, environmentally controlled test chamber. A thin film model, which seems applicable to such sources as carpe...

  12. Comparing simple respiration models for eddy flux and dynamic chamber data

    E-print Network

    Richardson, Andrew D.

    Comparing simple respiration models for eddy flux and dynamic chamber data Andrew D. Richardson a October 2006; accepted 20 October 2006 Abstract Selection of an appropriate model for respiration (R exchange (NEE) to respiration and gross ecosystem exchange (GEE). Using cross-validation methods

  13. Spray Combustion Modeling with VOF and Finite-Rate Chemistry

    NASA Technical Reports Server (NTRS)

    Chen, Yen-Sen; Shang, Huan-Min; Liaw, Paul; Wang, Ten-See

    1996-01-01

    A spray atomization and combustion model is developed based on the volume-of-fluid (VOF) transport equation with finite-rate chemistry model. The gas-liquid interface mass, momentum and energy conservation laws are modeled by continuum surface force mechanisms. A new solution method is developed such that the present VOF model can be applied for all-speed range flows. The objectives of the present study are: (1) to develop and verify the fractional volume-of-fluid (VOF) cell partitioning approach into a predictor-corrector algorithm to deal with multiphase (gas-liquid) free surface flow problems; (2) to implement the developed unified algorithm in a general purpose computational fluid dynamics (CFD) code, Finite Difference Navier-Stokes (FDNS), with droplet dynamics and finite-rate chemistry models; and (3) to demonstrate the effectiveness of the present approach by simulating benchmark problems of jet breakup/spray atomization and combustion. Modeling multiphase fluid flows poses a significant challenge because a required boundary must be applied to a transient, irregular surface that is discontinuous, and the flow regimes considered can range from incompressible to highspeed compressible flows. The flow-process modeling is further complicated by surface tension, interfacial heat and mass transfer, spray formation and turbulence, and their interactions. The major contribution of the present method is to combine the novel feature of the Volume of Fluid (VOF) method and the Eulerian/Lagrangian method into a unified algorithm for efficient noniterative, time-accurate calculations of multiphase free surface flows valid at all speeds. The proposed method reformulated the VOF equation to strongly couple two distinct phases (liquid and gas), and tracks droplets on a Lagrangian frame when spray model is required, using a unified predictor-corrector technique to account for the non-linear linkages through the convective contributions of VOF. The discontinuities within the sharp interface will be modeled as a volume force to avoid stiffness. Formations of droplets, tracking of droplet dynamics and modeling of the droplet breakup/evaporation, are handled through the same unified predictor-corrector procedure. Thus the new algorithm is non-iterative and is flexible for general geometries with arbitrarily complex topology in free surfaces. The FDNS finite-difference Navier-Stokes code is employed as the baseline of the current development. Benchmark test cases of shear coaxial LOX/H2 liquid jet with atomization/combustion and impinging jet test cases are investigated in the present work. Preliminary data comparisons show good qualitative agreement between data and the present analysis. It is indicative from these results that the present method has great potential to become a general engineering design analysis and diagnostics tool for problems involving spray combustion.

  14. Test plan pressure fed thrust chamber technology

    NASA Technical Reports Server (NTRS)

    Dunn, Glenn

    1990-01-01

    Aerojet is developing the technology for the design of a reliable, low cost, efficient, and lightweight LOX/RP-1 pressure fed engine. This technology program is a direct result of Aerojet's liquid rocket booster (LRB) study and previous NASA studies that identified liquid engines using high bulk density hydrocarbon fuels as very attractive for a space transportation system (STS). Previous large thrust LOX/RP-1 engine development programs were characterized by costly development problems due to combustion instability damage. The combustion stability solution was typically obtained through trial and error methods of minimizing instability damage by degrading engine performance. The approach to this program was to utilize existing and newly developed combustion analysis models and design methodology to create a thrust chamber design with features having the potential of producing reliable and efficient operation. This process resulted in an engine design with a unique high thrust-per-element OFO triplet injector utilizing a low cost modular approach. Cost efficient ablative materials are baselined for the injector face and chamber. Technology demonstration will be accomplished through a hot fire test program using appropriately sized subscale hardware. This subscale testing will provide a data base to supplement the current industry data bank and to anchor and validate the applied analysis models and design methodology. Once anchored and validated, these analysis models and design methodology can be applied with greatly increased confidence to design and characterize a large scale pressure fed LOX/RP-1 thrust chamber. The objective of this test program is to generate a data base that can be used to anchor and validate existing analysis models and design methodologies and to provide early concept demonstration of a low cost, efficient LOX/RP-1 thrust chamber. Test conditions and hardware instrumentation were defined to provide data sufficient to characterize combustion stability, performance, and thermal operation over a wide thrust chamber throttling range.

  15. A model for the origin of large silicic magma chambers: precursors of caldera-forming eruptions

    SciTech Connect

    Jellinek, A. Mark; DePaolo, Donald J.

    2002-01-02

    The relatively low rates of magma production in island arcs and continental extensional settings require that the volume of silicic magma involved in large catastrophic caldera-forming (CCF) eruptions must accumulate over periods of 10(5) to 10(6) years. We address the question of why buoyant and otherwise eruptible high silica magma should accumulate for long times in shallow chambers rather than erupt more continuously as magma is supplied from greater depths. Our hypothesis is that the viscoelastic behavior of magma chamber wall rocks may prevent an accumulation of overpressure sufficient to generate rhyolite dikes that can propagate to the surface and cause an eruption. The critical overpressure required for eruption is based on the model of Rubin (1995a). An approximate analytical model is used to evaluate the controls on magma overpressure for a continuously or episodically replenished spherical magma chamber contained in wall rocks with a Maxwell viscoelastic rheology. The governing parameters are the long-term magma supply, the magma chamber volume, and the effective viscosity of the wall rocks. The long-term magma supply, a parameter that is not typically incorporated into dike formation models, can be constrained from observations and melt generation models. For effective wall-rock viscosities in the range 10(18) to 10(20) Pa s(-1), dynamical regimes are identified that lead to the suppression of dikes capable of propagating to the surface. Frequent small eruptions that relieve magma chamber overpressure are favored when the chamber volume is small relative to the magma supply and when the wall rocks are cool. Magma storage, leading to conditions suitable for a CCF eruption, is favored for larger magma chambers (>10(2) km(3)) with warm wall rocks that have a low effective viscosity. Magma storage is further enhanced by regional tectonic extension, high magma crystal contents, and if the effective wall-rock viscosity is lowered by microfracturing, fluid infiltration, or metamorphic reactions. The long-term magma supply rate and chamber volume are important controls on eruption frequency for all magma chamber sizes. The model can explain certain aspects of the frequency, volume, and spatial distribution of small-volume silicic eruptions in caldera systems, and helps account for the large size of granitic plutons, their association with extensional settings and high thermal gradients, and the fact that they usually post-date associated volcanic deposits. [References: 139

  16. Thrust Chamber Modeling Using Navier-Stokes Equations: Code Documentation and Listings. Volume 2

    NASA Technical Reports Server (NTRS)

    Daley, P. L.; Owens, S. F.

    1988-01-01

    A copy of the PHOENICS input files and FORTRAN code developed for the modeling of thrust chambers is given. These copies are contained in the Appendices. The listings are contained in Appendices A through E. Appendix A describes the input statements relevant to thrust chamber modeling as well as the FORTRAN code developed for the Satellite program. Appendix B describes the FORTRAN code developed for the Ground program. Appendices C through E contain copies of the Q1 (input) file, the Satellite program, and the Ground program respectively.

  17. Modeling the Temporal Evolution of the Magma Chamber at Mount Hood (Oregon, USA)

    NASA Astrophysics Data System (ADS)

    Degruyter, W.; Huber, C.; Cooper, K. M.; Kent, A. J.

    2014-12-01

    The evolution of shallow magma reservoirs is complex as new mass is added intermittently and phase proportions (crystals, melt and bubbles) vary because of cooling or mass removal (eruptions). One requirement for eruptions to occur is that the crystal content during storage is low enough (< 0.4-0.6) such that the magma is mobile. Thermal modeling and geochemical data suggest these chambers are mobile only a very small fraction of their lifetime. Data from uranium-series disequilibria, crystal size distributions, and zoning of trace elements in crystals collected at Mount Hood (Oregon, USA) provide constraints on the thermal evolution of this system over the past 21 kyrs years and suggest <10% of this time the magma was mobile. This system also produced at least 3 significant eruptions over the last 10 kyrs based on the stratigraphic record (~220 and ~1500, and ~7700 years ago). Here we investigate the physical conditions of an open-system magma chamber that are in agreement with the thermal history inferred from the crystal record and with the eruption sequence. What are the magma recharge fluxes that are required to keep a system such as Mount Hood active but predominantly crystal-rich over the last 21 kyrs and what combination of processes produces the observed eruption frequency? To answer these questions we use an idealized magma chamber model to solve for the evolution of the thermodynamical state of the chamber (pressure, temperature, gas and crystal content) as new magma is injected into the chamber. Heat is lost to the surrounding colder crust, which responds visco-elastically to the pressure accumulated during recharge and volatile exsolution. If the crystal volume fraction is lower than 0.5 and chamber overpressure reaches 20 MPa we assume an eruption occurs. We analyze what type of injection (constant, periodic, magma lensing), injection rate, and magma chamber volume yields trends consistent with the timescales found at Mount Hood.

  18. Optical combustion diagnostics applied to a flameproof enclosure model

    NASA Astrophysics Data System (ADS)

    Beyer, Michael

    1995-09-01

    The propagation of an explosion caused by an error can be successfully prevented by flameproof enclosures. This paper describes investigations applying different nonintrusive diagnostic methods to the combustion process in a turbulent jet emerging from the joint gap of a flameproof enclosure model. Experiments are carried out using a tuneable excimer laser operated either with ArF (193 nm) or KrF (248 nm). Rayleigh scattering is used to determine temperature distribution in the free jet, and laser-induced fluorescence of OH is used to observe the combustion and flow processes. The enclosure consists of two explosion vessels which are connected via a nozzle of variable dimensions. H2/O2/N2 mixtures with a stoichiometric H2/O2 ratio are investigated. The position of the ignition source in the smaller vessel is made use of to vary the explosion pressure prevailing in the enclosure at the moment when the flame front enters the joint. Prevention of an outside explosion depends on both the nozzle dimensions and the upstream explosion pressure at the moment when the flame front enters the joint. In the range of application of flameproof enclosures, the outside ignition takes place as a result of a flame quenching process in the nozzle and subsequent re- ignition in the turbulent mixing zone of fresh and exhaust gas that has escaped from the joint gap into the environment.

  19. Liquid rocket combustion computer model with distributed energy release. DER computer program documentation and user's guide, volume 1

    NASA Technical Reports Server (NTRS)

    Combs, L. P.

    1974-01-01

    A computer program for analyzing rocket engine performance was developed. The program is concerned with the formation, distribution, flow, and combustion of liquid sprays and combustion product gases in conventional rocket combustion chambers. The capabilities of the program to determine the combustion characteristics of the rocket engine are described. Sample data code sheets show the correct sequence and formats for variable values and include notes concerning options to bypass the input of certain data. A seperate list defines the variables and indicates their required dimensions.

  20. Construction of combustion models for rapeseed methyl ester bio-diesel fuel for internal combustion engine applications.

    PubMed

    Golovitchev, Valeri I; Yang, Junfeng

    2009-01-01

    Bio-diesel fuels are non-petroleum-based diesel fuels consisting of long chain alkyl esters produced by the transesterification of vegetable oils, that are intended for use (neat or blended with conventional fuels) in unmodified diesel engines. There have been few reports of studies proposing theoretical models for bio-diesel combustion simulations. In this study, we developed combustion models based on ones developed previously. We compiled the liquid fuel properties, and the existing detailed mechanism of methyl butanoate ester (MB, C(5)H(10)O(2)) oxidation was supplemented by sub-mechanisms for two proposed fuel constituent components, C(7)H(16) and C(7)H(8)O (and then, by mp2d, C(4)H(6)O(2) and propyne, C(3)H(4)) to represent the combustion model for rapeseed methyl ester described by the chemical formula, C(19)H(34)O(2) (or C(19)H(36)O(2)). The main fuel vapor thermal properties were taken as those of methyl palmitate C(19)H(36)O(2) in the NASA polynomial form of the Burcat database. The special global reaction was introduced to "crack" the main fuel into its constituent components. This general reaction included 309 species and 1472 reactions, including soot and NO(x) formation processes. The detailed combustion mechanism was validated using shock-tube ignition-delay data under diesel engine conditions. For constant volume and diesel engine (Volvo D12C) combustion modeling, this mechanism could be reduced to 88 species participating in 363 reactions. PMID:19409477

  1. A numerical model for coupling between atomization and spray dynamics in liquid rocket thrust chambers

    NASA Technical Reports Server (NTRS)

    Giridharan, M. G.; Lee, J. G.; Krishnan, A.; Przekwas, A. J.; Gross, Klaus

    1992-01-01

    This paper describes a novel method of coupling the atomization and spray combustion processes encountered in coaxial injection elements of liquid rocket engine thrust chambers. This method is based on the Jet-Embedding technique in which the liquid jet core equations and the gas phase equations are solved separately. The liquid and gas phase solutions, however, are coupled through the boundary conditions at the interface between the phases. The computational grid for the gas phase calculations are adapted to the shape of the liquid jet core. The axial variation of droplet sizes are calculated using a stability analysis appropriate for the atomization regime of liquid jet breakup. The predictions of this method have been validated with experimental data on low speed water jets. Using this method, calculations are performed for the SSME fuel preburner single injector flow field. The results obtained are in good agreement with the predictions of the volume-of-fluid method.

  2. Analysis of Bifurcations in Low-Dimensional Models of Turbulent Combustion J. M. McDonough

    E-print Network

    McDonough, James M.

    Analysis of Bifurcations in Low-Dimensional Models of Turbulent Combustion J. M. Mc points in parameter space are crossed. In the present study an analysis technique based on construction of bifurcation diagrams is described and employed to analyze a specific class of such models for H2­O2 combustion

  3. Application of Supervised Learning to Quantify Uncertainties in Turbulence and Combustion Modeling

    E-print Network

    Alonso, Juan J.

    Application of Supervised Learning to Quantify Uncertainties in Turbulence and Combustion Modeling design and analysis. In this paper, we introduce a methodology aimed at improving low-fidelity models of turbulence and combustion and obtaining error bounds. Towards this end, we first develop a new machine

  4. Modeling autoignition in non-premixed turbulent combustion using a stochastic

    E-print Network

    Pitsch, Heinz

    .elsevier.com/locate/proci Proceedings of the Combustion Institute #12;These involve 3D isotropic decaying turbulence [1,2], counterflowModeling autoignition in non-premixed turbulent combustion using a stochastic flamelet approach 94305, USA Abstract In this paper, a stochastic flamelet approach is used to model autoignition

  5. Tissue Engineering Chamber Promotes Adipose Tissue Regeneration in Adipose Tissue Engineering Models Through Induced Aseptic Inflammation

    PubMed Central

    Peng, Zhangsong; Dong, Ziqing; Chang, Qiang; Zhan, Weiqing; Zeng, Zhaowei; Zhang, Shengchang

    2014-01-01

    Tissue engineering chamber (TEC) makes it possible to generate significant amounts of mature, vascularized, stable, and transferable adipose tissue. However, little is known about the role of the chamber in tissue engineering. Therefore, to investigate the role of inflammatory response and the change in mechanotransduction started by TEC after implantation, we placed a unique TEC model on the surface of the groin fat pads in rats to study the expression of cytokines and tissue development in the TEC. The number of infiltrating cells was counted, and vascular endothelial growth factor (VEGF) and monocyte chemotactic protein-1 (MCP-1) expression levels in the chamber at multiple time points postimplantation were analyzed by enzyme-linked immunosorbent assay. Tissue samples were collected at various time points and labeled for specific cell populations. The result showed that new adipose tissue formed in the chamber at day 60. Also, the expression of MCP-1 and VEGF in the chamber decreased slightly from an early stage as well as the number of the infiltrating cells. A large number of CD34+/perilipin? perivascular cells could be detected at day 30. Also, the CD34+/perilipin+ adipose precursor cell numbers increased sharply by day 45 and then decreased by day 60. CD34?/perilipin+ mature adipocytes were hard to detect in the chamber content at day 30, but their number increased and then peaked at day 60. Ki67-positive cells could be found near blood vessels and their number decreased sharply over time. Masson's trichrome showed that collagen was the dominant component of the chamber content at early stage and was replaced by newly formed small adipocytes over time. Our findings suggested that the TEC implantation could promote the proliferation of adipose precursor cells derived from local adipose tissue, increase angiogenesis, and finally lead to spontaneous adipogenesis by inducing aseptic inflammation and changing local mechanotransduction. PMID:24559078

  6. Spatial Analysis of Emissions Sources for HCCI Combustion at Low Loads Using a Multi-Zone Model

    SciTech Connect

    Aceves, S M; Flowers, D L; Espinosa-Loza, F; Martinez-Frias, J; Dec, J E; Sjoberg, M; Dibble, R W; Hessel, R P

    2004-02-20

    We have conducted a detailed numerical analysis of HCCI engine operation at low loads to investigate the sources of HC and CO emissions and the associated combustion inefficiencies. Engine performance and emissions are evaluated as fueling is reduced from typical HCCI conditions, with an equivalence ratio f = 0.26 to very low loads (f = 0.04). Calculations are conducted using a segregated multi-zone methodology and a detailed chemical kinetic mechanism for iso-octane with 859 chemical species. The computational results agree very well with recent experimental results. Pressure traces, heat release rates, burn duration, combustion efficiency and emissions of hydrocarbon, oxygenated hydrocarbon, and carbon monoxide are generally well predicted for the whole range of equivalence ratios. The computational model also shows where the pollutants originate within the combustion chamber, thereby explaining the changes in the HC and CO emissions as a function of equivalence ratio. The results of this paper contribute to the understanding of the high emission behavior of HCCI engines at low equivalence ratios and are important for characterizing this previously little explored, yet important range of operation.

  7. Using a Phenomenological Computer Model to Investigate Advanced Combustion Trajectories in a CIDI Engine

    SciTech Connect

    Gao, Zhiming; Wagner, Robert M; Sluder, Scott; Daw, C Stuart; Green Jr, Johney Boyd

    2011-01-01

    This paper summarizes results from simulations of conventional, high-dilution, and high-efficiency clean combustion in a diesel engine based on a two-zone phenomenological model. The two-zone combustion model is derived from a previously published multi-zone model, but it has been further simplified to increase computational speed by a factor of over 100. The results demonstrate that this simplified model is still able to track key aspects of the combustion trajectory responsible for NOx and soot production. In particular, the two-zone model in combination with highly simplified global kinetics correctly predicts the importance of including oxygen mass fraction (in addition to equivalence ratio and temperature) in lowering emissions from high-efficiency clean combustion. The methodology also provides a convenient framework for extracting information directly from in-cylinder pressure measurements. This feature is likely to be useful for on-board combustion diagnostics and controls. Because of the possibility for simulating large numbers of engine cycles in a short time, models of this type can provide insight into multi-cycle and transient combustion behavior not readily accessible to more computationally intensive models. Also the representation of the combustion trajectory in 3D space corresponding to equivalence ratio, flame temperature, and oxygen fraction provides new insight into optimal combustion management.

  8. Computational Combustion

    SciTech Connect

    Westbrook, C K; Mizobuchi, Y; Poinsot, T J; Smith, P J; Warnatz, J

    2004-08-26

    Progress in the field of computational combustion over the past 50 years is reviewed. Particular attention is given to those classes of models that are common to most system modeling efforts, including fluid dynamics, chemical kinetics, liquid sprays, and turbulent flame models. The developments in combustion modeling are placed into the time-dependent context of the accompanying exponential growth in computer capabilities and Moore's Law. Superimposed on this steady growth, the occasional sudden advances in modeling capabilities are identified and their impacts are discussed. Integration of submodels into system models for spark ignition, diesel and homogeneous charge, compression ignition engines, surface and catalytic combustion, pulse combustion, and detonations are described. Finally, the current state of combustion modeling is illustrated by descriptions of a very large jet lifted 3D turbulent hydrogen flame with direct numerical simulation and 3D large eddy simulations of practical gas burner combustion devices.

  9. Solid Rocket Motor Combustion Instability Modeling in COMSOL Multiphysics

    NASA Technical Reports Server (NTRS)

    Fischbach, S. R.

    2015-01-01

    Combustion instability modeling of Solid Rocket Motors (SRM) remains a topic of active research. Many rockets display violent fluctuations in pressure, velocity, and temperature originating from the complex interactions between the combustion process, acoustics, and steady-state gas dynamics. Recent advances in defining the energy transport of disturbances within steady flow-fields have been applied by combustion stability modelers to improve the analysis framework. Employing this more accurate global energy balance requires a higher fidelity model of the SRM flow-field and acoustic mode shapes. The current industry standard analysis tool utilizes a one dimensional analysis of the time dependent fluid dynamics along with a quasi-three dimensional propellant grain regression model to determine the SRM ballistics. The code then couples with another application that calculates the eigenvalues of the one dimensional homogenous wave equation. The mean flow parameters and acoustic normal modes are coupled to evaluate the stability theory developed and popularized by Culick. The assumption of a linear, non-dissipative wave in a quiescent fluid remains valid while acoustic amplitudes are small and local gas velocities stay below Mach 0.2. The current study employs the COMSOL Multiphysics finite element framework to model the steady flow-field parameters and acoustic normal modes of a generic SRM. This work builds upon previous efforts to verify the use of the acoustic velocity potential equation (AVPE) laid out by Campos. The acoustic velocity potential (psi) describing the acoustic wave motion in the presence of an inhomogeneous steady high-speed flow is defined by, del squared psi - (lambda/c) squared psi - M x [M x del((del)(psi))] - 2((lambda)(M)/c + M x del(M) x (del)(psi) - 2(lambda)(psi)[M x del(1/c)] = 0. with M as the Mach vector, c as the speed of sound, and ? as the complex eigenvalue. The study requires one way coupling of the CFD High Mach Number Flow (HMNF) and mathematics module. The HMNF module evaluates the gas flow inside of a SRM using St. Robert's law to model the solid propellant burn rate, slip boundary conditions, and the supersonic outflow condition. Results from the HMNF model are verified by comparing the pertinent ballistics parameters with the industry standard code outputs (i.e. pressure drop, axial velocity, exit velocity). These results are then used by the coefficient form of the mathematics module to determine the complex eigenvalues of the AVPE. The mathematics model is truncated at the nozzle sonic line, where a zero flux boundary condition is self-satisfying. The remaining boundaries are modeled with a zero flux boundary condition, assuming zero acoustic absorption on all surfaces. The one way coupled analysis is perform four times utilizing geometries determined through traditional SRM modeling procedures. The results of the steady-state CFD and AVPE analyses are used to calculate the linear acoustic growth rate as is defined by Flandro and Jacob. In order to verify the process implemented within COMSOL we first employ the Culick theory and compare the results with the industry standard. After the process is verified, the Flandro/Jacob energy balance theory is employed and results displayed.

  10. Outdoor smog chamber experiments to test photochemical models. Final report May 78-May 81

    SciTech Connect

    Feffries, H.E.; Kamens, R.M.; Sexron, K.G.; Gerhardt, A.A.

    1982-04-01

    The smog chamber facility of the University of North Carolina was used in a study to provide experimental data for developing and testing kinetic mechanisms of photochemical smog formation. The smog chamber, located outdoors in rural North Carolina, is an A-frame structure covered with Teflon film. Because the chamber is partitioned into two sections, each with a volume of 156 cu m, two experiments can be conducted simultaneously. The dual chamber is operated under natural conditions of solar radiation, temperature, and relative humidity. In this study, 115 dual all-day experiments were conducted using NOx and a variety of organic species. The organic compounds investigated included various paraffins, olefins, aromatics and oxygenates, both singly and in mixtures of two or more components. In this report the data collected over the three-year period of the study are described. The experimental procedures and analytical methods used in this study and the limitations and uncertainties of the data are discussed. Guidance for modeling of the data is also given, including a detailed discussion of how to estimate photolytic rate constants from the available UV and total solar radiation data and how to treat such chamber artifacts as dilution, wall sources and losses of pollutants, and reactivity of the background air.

  11. STRUCTURE-BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION

    SciTech Connect

    Robert H. Hurt; Eric M. Suuberg

    2000-05-03

    This report is part on the ongoing effort at Brown University and Ohio State University to develop structure based models of coal combustion. A very fundamental approach is taken to the description of coal chars and their reaction processes, and the results are therefore expected to have broad applicability to the spectrum of carbon materials of interest in energy technologies. This quarter, our work on structure development in carbons continued. A combination of hot stage in situ and ex situ polarized light microscopy was used to identify the preferred orientational of graphene layers at gas interfaces in pitches used as carbon material precursors. The experiments show that edge-on orientation is the equilibrium state of the gas/pitch interface, implying that basal-rich surfaces have higher free energies than edge-rich surfaces in pitch. This result is in agreement with previous molecular modeling studies and TEM observations in the early stages of carbonization. The results may have important implications for the design of tailored carbons with edge-rich or basal-rich surfaces. In the computational chemistry task, we have continued our investigations into the reactivity of large aromatic rings. The role of H-atom abstraction as well as radical addition to monocyclic aromatic rings has been examined, and a manuscript is currently being revised after peer review. We have also shown that OH radical is more effective than H atom in the radical addition process with monocyclic rings. We have extended this analysis to H-atom and OH-radical addition to phenanthrene. Work on combustion kinetics focused on the theoretical analysis of the data previously gathered using thermogravametric analysis.

  12. MODELING OF AUTO EXHAUST SMOG CHAMBER DATA FOR EKMA DEVELOPMENT

    EPA Science Inventory

    A new generalized mechanism for photochemical smog has been developed. The mechanism is suitable for use in the Empirical Kinetics Modeling Approach (EKMA) to estimate the control of volatile organic compounds that is needed to achieve the National Ambient Air Quality Standard fo...

  13. Solid waste combustion for alpha waste incineration

    SciTech Connect

    Orloff, D.I.

    1981-02-01

    Radioactive waste incinerator development at the Savannah River Laboratory has been augmented by fundamental combustion studies at the University of South Carolina. The objective was to measure and model pyrolysis and combustion rates of typical Savannah River Plant waste materials as a function of incinerator operating conditions. The analytical models developed in this work have been incorporated into a waste burning transient code. The code predicts maximum air requirement and heat energy release as a function of waste type, package size, combustion chamber size, and temperature. Historically, relationships have been determined by direct experiments that did not allow an engineering basis for predicting combustion rates in untested incinerators. The computed combustion rates and burning times agree with measured values in the Savannah River Laboratory pilot (1 lb/hr) and full-scale (12 lb/hr) alpha incinerators for a wide variety of typical waste materials.

  14. Numerical investigation of high-pressure combustion in rocket engines using Flamelet/Progress-variable models

    E-print Network

    Coclite, A; De Palma, P; Pascazio, G

    2015-01-01

    The present paper deals with the numerical study of high pressure LOx/H2 or LOx/hydrocarbon combustion for propulsion systems. The present research effort is driven by the continued interest in achieving low cost, reliable access to space and more recently, by the renewed interest in hypersonic transportation systems capable of reducing time-to-destination. Moreover, combustion at high pressure has been assumed as a key issue to achieve better propulsive performance and lower environmental impact, as long as the replacement of hydrogen with a hydrocarbon, to reduce the costs related to ground operations and increase flexibility. The current work provides a model for the numerical simulation of high- pressure turbulent combustion employing detailed chemistry description, embedded in a RANS equations solver with a Low Reynolds number k-omega turbulence model. The model used to study such a combustion phenomenon is an extension of the standard flamelet-progress-variable (FPV) turbulent combustion model combined ...

  15. SOYCHMBR.I - A model designed for the study of plant growth in a closed chamber

    NASA Technical Reports Server (NTRS)

    Reinhold, C.

    1982-01-01

    The analytical model SOYCHMBER.I, an update and alteration of the SOYMOD/OARDC model, for describing the total processes experienced by a plant in a controlled mass environment is outlined. The model is intended for use with growth chambers for examining plant growth in a completely controlled environment, leading toward a data base for the design of spacecraft food supply systems. SOYCHMBER.I accounts for the assimilation, respiration, and partitioning of photosynthate and nitrogen compounds among leaves, stems, roots, and potentially, flowers of the soybean plant. The derivation of the governing equations is traced, and the results of the prediction of CO2 dynamics for a seven day experiment with rice in a closed chamber are reported, together with data from three model runs for soybean. It is concluded that the model needs expansion to account for factors such as relative humidity.

  16. Engine Combustion Network Experimental Data

    DOE Data Explorer

    Maintained by the Engine Combustion Department of Sandia National Laboratories, data currently available on the website includes reacting and non-reacting sprays in a constant-volume chamber at conditions typical of diesel combustion. The data are useful for model development and validation because of the well-defined boundary conditions and the wide range of conditions employed. A search utility displays data based on experimental conditions such as ambient temperature, ambient density, injection pressure, nozzle size, fuel, etc. Experiment-related visualizations are also available. The search utility for experimental data is located at http://public.ca.sandia.gov/ecn/cvdata/frameset.html (Specialized Interface)

  17. Characterization of complexities in combustion instability in a lean premixed gas-turbine model combustor.

    PubMed

    Gotoda, Hiroshi; Amano, Masahito; Miyano, Takaya; Ikawa, Takuya; Maki, Koshiro; Tachibana, Shigeru

    2012-12-01

    We characterize complexities in combustion instability in a lean premixed gas-turbine model combustor by nonlinear time series analysis to evaluate permutation entropy, fractal dimensions, and short-term predictability. The dynamic behavior in combustion instability near lean blowout exhibits a self-affine structure and is ascribed to fractional Brownian motion. It undergoes chaos by the onset of combustion oscillations with slow amplitude modulation. Our results indicate that nonlinear time series analysis is capable of characterizing complexities in combustion instability close to lean blowout. PMID:23278063

  18. Internal combustion engine using premixed combustion of stratified charges

    DOEpatents

    Marriott, Craig D. (Rochester Hills, MI); Reitz, Rolf D. (Madison, WI

    2003-12-30

    During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.

  19. Modeling extinction and reignition in turbulent nonpremixed combustion using a doubly-conditional moment closure approach

    E-print Network

    Pitsch, Heinz

    Modeling extinction and reignition in turbulent nonpremixed combustion using a doubly variable into the first-moment, singly conditional moment closure model to describe extinction direct numerical simulation experiments exhibiting local extinction/reignition events is described

  20. Flow chamber

    DOEpatents

    Morozov, Victor (Manassas, VA)

    2011-01-18

    A flow chamber having a vacuum chamber and a specimen chamber. The specimen chamber may have an opening through which a fluid may be introduced and an opening through which the fluid may exit. The vacuum chamber may have an opening through which contents of the vacuum chamber may be evacuated. A portion of the flow chamber may be flexible, and a vacuum may be used to hold the components of the flow chamber together.

  1. Interactive computer modeling of combustion chemistry and coalescence-dispersion modeling of turbulent combustion

    NASA Technical Reports Server (NTRS)

    Pratt, D. T.

    1984-01-01

    An interactive computer code for simulation of a high-intensity turbulent combustor as a single point inhomogeneous stirred reactor was developed from an existing batch processing computer code CDPSR. The interactive CDPSR code was used as a guide for interpretation and direction of DOE-sponsored companion experiments utilizing Xenon tracer with optical laser diagnostic techniques to experimentally determine the appropriate mixing frequency, and for validation of CDPSR as a mixing-chemistry model for a laboratory jet-stirred reactor. The coalescence-dispersion model for finite rate mixing was incorporated into an existing interactive code AVCO-MARK I, to enable simulation of a combustor as a modular array of stirred flow and plug flow elements, each having a prescribed finite mixing frequency, or axial distribution of mixing frequency, as appropriate. Further increase the speed and reliability of the batch kinetics integrator code CREKID was increased by rewriting in vectorized form for execution on a vector or parallel processor, and by incorporating numerical techniques which enhance execution speed by permitting specification of a very low accuracy tolerance.

  2. DEVELOPMENT OF THE INDUSTRIAL COMBUSTION EMISSIONS MODEL FOR ACID RAIN ANALYSES

    EPA Science Inventory

    The paper discusses forecasts of industrial combustion emissions being developed by the U.S. EPA as part of the National Acid Precipitation Assessment Program (NAPAP). The Industrial Combustion Emissions (ICE) Model will estimate sulfur dioxide (SO2), nitrogen oxides (NOx), and p...

  3. Thermochemistry of Aluminum Species for Combustion Modeling from Ab Initio Molecular Orbital Calculations

    E-print Network

    Swihart, Mark T.

    Thermochemistry of Aluminum Species for Combustion Modeling from Ab Initio Molecular Orbital initio methods for computational thermochemistry have been applied to aluminum compounds expected to be present during combustion of aluminum particles. The computed enthalpies of formation at 298.15 K agree

  4. A comparison of various models in predicting ignition delay in single-particle coal combustion

    E-print Network

    A comparison of various models in predicting ignition delay in single-particle coal combustion November 2013 Accepted 7 January 2014 Available online xxxx Keywords: Coal Devolatilization Ignition delay a b s t r a c t In this paper, individual coal particle combustion under laminar conditions

  5. A model for eruption frequency of upper crustal silicic magma chambers

    NASA Astrophysics Data System (ADS)

    Degruyter, W.; Huber, C.

    2014-10-01

    Whether a magma body is able to produce eruptions and at what frequency remains a challenging problem in volcanology as it involves the nonlinear interplay of different processes acting over different time scales. Due to their complexity these are often considered independently in spite of their coupled nature. Here we consider an idealized model that focuses on the evolution of the thermodynamic state of the chamber (pressure, temperature, gas and crystal content) as new magma is injected into the chamber. The magma chamber cools in contact with the crust, which responds viscoelastically to the pressure accumulated during recharge and volatile exsolution. The magma is considered eruptible if the crystal volume fraction is smaller than 0.5. If a critical overpressure is reached, mass is released from the magma chamber until the lithostatic pressure is recovered. The setup of the model allows for rapid calculations that provide the opportunity to test the influence of competing processes on the evolution of the magma reservoir. We show how the frequency of eruptions depends on the timescale of injection, cooling, and viscous relaxation and develop a scaling law that relates these timescales to the eruption frequency. Based on these timescales we place different eruption triggering mechanisms (second boiling, mass injection, and buoyancy) in a coherent framework and evaluate the conditions needed to grow large magma reservoirs.

  6. Numerical Modeling of Mixing and Venting from Explosions in Underground Chambers

    NASA Astrophysics Data System (ADS)

    Liu, Benjamin T.; Lomov, Ilya; Glenn, Lewis A.

    2006-07-01

    2D and 3D numerical simulations were performed to study the dynamic interaction of explosion products in an underground concrete chamber with ambient air, barrels of water, and the surrounding walls and structure. The simulations were carried out with GEODYN, a multi-material, Godunov-based Eulerian code that employs adaptive mesh refinement and runs efficiently on massively parallel computer platforms. Tabular equations of state were used to model materials under shock loading. An appropriate constitutive model was used to describe the concrete. Interfaces between materials were either tracked with a volume-of-fluid method that used high-order reconstruction to specify the interface location and orientation, or a capturing approach was employed with the assumption of local thermal and mechanical equilibrium. A major focus of the study was to estimate the extent of water heating that could be obtained prior to venting of the chamber. Parameters investigated included the chamber layout, energy density in the chamber and the yield-to-water mass ratio. Turbulent mixing was found to be the dominant heat transfer mechanism for heating the water.

  7. Measurements of a 1/4-scale model of a 60-kg explosives firing chamber

    SciTech Connect

    Pastrnak, J.W.; Baker, C.F.; Simmons, L.F.

    1995-01-27

    In anticipation of increasingly stringent environmental regulations, Lawrence Livermore National Laboratory (LLNL) proposes to construct a 60-kg firing chamber to provide blast-effects containment for, most of its open-air, high-explosive, firing operations. Even though these operations are within current environmental limits, containment of the blast effects and hazardous debris will further drastically reduce emissions to the environment and minimize the generated hazardous waste. The major design consideration of such a chamber is its overall structural dynamic response in terms of long-term containment of all blast effects from repeated internal detonations of high explosives. Another concern is how much other portions of the facility must be hardened to ensure personnel protection in the event of an accidental detonation. To assess these concerns, a 1/4-scale replica model of the planned contained firing chamber was designed, constructed, and tested with scaled explosive charges ranging from 25 to 125% of the operational explosives limit of 60 kg. From 16 detonations of high explosives, 880 resulting strains, blast pressures, and temperatures within the model were measured. Factors of safety for dynamic yield of the firing chamber structure were calculated and compared to the design criterion of totally elastic response. The rectangular, reinforced-concrete chamber model exhibited a lightly damped vibrational response that placed the structure in alternating cycles of tension and compression. During compression, both the reinforcing steel and the concrete remained elastic. During tension, the reinforcing steel remained elastic, but the concrete elastic limit was exceeded in two areas, the center spans of the ceiling and the north wall, where elastic safety factors as low as 0.66 were obtained, thus indicating that the concrete would be expected to crack in those areas. Indeed, visual post-test inspection of those areas revealed tight cracks in the concrete.

  8. Observing and modeling nonlinear dynamics in an internal combustion engine Engineering Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8088

    E-print Network

    Tennessee, University of

    Observing and modeling nonlinear dynamics in an internal combustion engine C. S. Daw* Engineering motivated, nonlinear map as a model for cyclic combustion variation in spark-ignited internal combustion combustion engines can exhibit substantial cycle-to-cycle variation in combustion energy release

  9. Thermal ignition combustion system

    DOEpatents

    Kamo, R.; Kakwani, R.M.; Valdmanis, E.; Woods, M.E.

    1988-04-19

    The thermal ignition combustion system comprises means for providing walls defining an ignition chamber, the walls being made of a material having a thermal conductivity greater than 20 W/m C and a specific heat greater than 480 J/kg C with the ignition chamber being in constant communication with the main combustion chamber, means for maintaining the temperature of the walls above a threshold temperature capable of causing ignition of a fuel, and means for conducting fuel to the ignition chamber. 8 figs.

  10. Thermal ignition combustion system

    DOEpatents

    Kamo, Roy (Columbus, IN); Kakwani, Ramesh M. (Columbus, IN); Valdmanis, Edgars (Columbus, IN); Woods, Melvins E. (Columbus, IN)

    1988-01-01

    The thermal ignition combustion system comprises means for providing walls defining an ignition chamber, the walls being made of a material having a thermal conductivity greater than 20 W/m.degree. C. and a specific heat greater than 480 J/kg.degree. C. with the ignition chamber being in constant communication with the main combustion chamber, means for maintaining the temperature of the walls above a threshold temperature capable of causing ignition of a fuel, and means for conducting fuel to the ignition chamber.

  11. Simulating Combustion

    NASA Astrophysics Data System (ADS)

    Merker, G.; Schwarz, C.; Stiesch, G.; Otto, F.

    The content spans from simple thermodynamics of the combustion engine to complex models for the description of the air/fuel mixture, ignition, combustion and pollutant formation considering the engine periphery of petrol and diesel engines. Thus the emphasis of the book is on the simulation models and how they are applicable for the development of modern combustion engines. Computers can be used as the engineers testbench following the rules and recommendations described here.

  12. Modelling the Propagation of Forward and Opposed Smouldering Combustion 

    E-print Network

    Rein, Guillermo; Torero, Jose L; Fernandez-Pello, Carlos

    A computational study has been carried out to investigate smouldering ignition and propagation in polyurethane foam. The one-dimensional, transient, governing equations for smouldering combustion in a porous fuel are ...

  13. Gasification and combustion modeling for porous char particles

    E-print Network

    Singer, Simcha Lev

    2012-01-01

    Gasification and combustion of porous char particles occurs in many industrial applications. Reactor-scale outputs of importance depend critically on processes that occur at the particle-scale. Because char particles often ...

  14. Modeling piston skirt lubrication in internal combustion engines

    E-print Network

    Bai, Dongfang, Ph. D. Massachusetts Institute of Technology

    2012-01-01

    Ever-increasing demand for reduction of the undesirable emissions from the internal combustion engines propels broader effort in auto industry to design more fuel efficient engines. One of the major focuses is the reduction ...

  15. Establishing global error bounds for model reduction in combustion

    E-print Network

    Oxberry, Geoffrey Malcolm

    2013-01-01

    In addition to theory and experiment, simulation of reacting flows has become important in policymaking, industry, and combustion science. However, simulations of reacting flows can be extremely computationally demanding ...

  16. Longitudinal-Mode Combustion Instabilities: Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    Cohen, J. M.; Hibshman, J. R.; Proscia, W.; Rosfjord, T. J.; Wake, B. E.; McVey, J. B.; Lovett, J.; Ondas, M.; DeLaat, J.; Breisacher, K.

    2000-01-01

    Combustion instabilities can lead to increased development time and cost for aeroengine gas turbines. This problem has been evident in the development of very-low emissions stationary gas turbines, and will likely be encountered in the newer, more aggressive aeroengine designs. In order to minimize development time and cost, it is imperative that potential combustion dynamics issues be resolved using analyses and smaller-scale experimentation. This paper discusses a methodology through which a problem in a full-scale engine was replicated in a single-nozzle laboratory combustor. Specifically, this approach is valid for longitudinal and "bulk" mode combustion instabilities. An explanation and partial validation of the acoustic analyses that were used to achieve this replication are also included. This approach yields a testbed for the diagnosis of combustion dynamics problems and for their solution through passive and active control techniques.

  17. Modeling aerosol emissions from the combustion of composite materials

    NASA Technical Reports Server (NTRS)

    Roop, J. A.; Caldwell, D. J.; Kuhlmann, K. J.

    1994-01-01

    The use of advanced composite materials (ACM) in the B-2 bomber, composite armored vehicle, and F-22 advanced tactical fighter has rekindled interest concerning the health risk of burned or burning ACM. The objective of this work was to determine smoke production from burning ACM and its toxicity. A commercial version of the UPITT II combustion toxicity method developed at the University of Pittsburgh, and subsequently refined through a US Army-funded basic research project, was used to established controlled combustion conditions which were selected to evaluate real-world exposure scenarios. Production and yield of toxic species varied with the combustion conditions. Previous work with this method showed that the combustion conditions directly influenced the toxicity of the decomposition products from a variety of materials.

  18. Dry low combustion system with means for eliminating combustion noise

    DOEpatents

    Verdouw, Albert J.; Smith, Duane; McCormick, Keith; Razdan, Mohan K.

    2004-02-17

    A combustion system including a plurality of axially staged tubular premixers to control emissions and minimize combustion noise. The combustion system includes a radial inflow premixer that delivers the combustion mixture across a contoured dome into the combustion chamber. The axially staged premixers having a twist mixing apparatus to rotate the fluid flow and cause improved mixing without causing flow recirculation that could lead to pre-ignition or flashback.

  19. A model of smoldering combustion applied to flexible polyurethane foams

    NASA Technical Reports Server (NTRS)

    Ohlemiller, T. J.; Rogers, F.; Bellan, J.

    1979-01-01

    Smoldering combustion, particularly in upholstery and bedding materials, has been proven a serious life hazard. The simplest representation of this hazard situation is one-dimensional downward propagation of a smolder wave against a buoyant upflow (cocurrent smolder); the configuration treated here is identical in all respects to this except for the presence of a forced flow replacing the buoyant one. The complex degradation chemistry of the polyurethanes is here reduced to the two major overall reactions of char formation and char oxidation. The model solutions, which are in reasonable agreement with experimental results, show the smolder process to be oxygen-limited, which leads to some very simple trends. More subtle behavior aspects determine actual propagation velocity, fraction of fuel consumed, and apparent equivalence ratio (all of which are variable). The self-insulating character of the smolder wave makes it viable in a wide-ranging set of conditions if the igniting stimulus is sufficiently long. These results have significant implications regarding the problem of smolder prevention or hindrance.

  20. [Studies of ozone formation potentials for benzene and ethylbenzene using a smog chamber and model simulation].

    PubMed

    Jia, Long; Xu, Yong-Fu

    2014-02-01

    Ozone formation potentials from irradiations of benzene-NO(x) and ethylbenzene-NO(x) systems under the conditions of different VOC/NO(x) ratios and RH were investigated using a characterized chamber and model simulation. The repeatability of the smog chamber experiment shows that for two sets of ethylbenzene-NO(x) irradiations with similar initial concentrations and reaction conditions, such as temperature, relative humidity and relative light intensity, the largest difference in O3 between two experiments is only 4% during the whole experimental run. On the basis of smog chamber experiments, ozone formation of photo-oxidation of benzene and ethylbenzene was simulated in terms of the master chemical mechanism (MCM). The peak ozone values for benzene and ethylbenzene simulated by MCM are higher than the chamber data, and the difference between the MCM-simulated results and chamber data increases with increasing RH. Under the conditions of sunlight irradiations, with benzene and ethylbenzene concentrations being in the range of (10-50) x 10(-9) and NO(x) concentrations in the range of (10-100) x 10(-9), the 6 h ozone contributions of benzene and ethylbenzene were obtained to be (3.1-33) x 10(-9) and (2.6-122) x 10(-9), whereas the peak O3 contributions of benzene and ethylbenzene were (3.5-54) x 10(-9) and (3.8-164) x 10(-9), respectively. The MCM-simulated maximum incremental reactivity (MIR) values for benzene and ethylbenzene were 0.25/C and 0.97/C (per carbon), respectively. The maximum ozone reactivity (MOR) values for these two species were obtained to be 0.73/C and 1.03/C, respectively. The MOR value of benzene from MCM is much higher than that obtained by carter from SAPRC, indicating that SAPRC may underestimate the ozone formation potential of benzene. PMID:24812939

  1. Accuracy Quantification of the Loci-CHEM Code for Chamber Wall Heat Fluxes in a G02/GH2 Single Element Injector Model Problem

    NASA Technical Reports Server (NTRS)

    West, Jeff; Westra, Doug; Lin, Jeff; Tucker, Kevin

    2006-01-01

    A robust rocket engine combustor design and development process must include tools which can accurately predict the multi-dimensional thermal environments imposed on solid surfaces by the hot combustion products. Currently, empirical methods used in the design process are typically one dimensional and do not adequately account for the heat flux rise rate in the near-injector region of the chamber. Computational Fluid Dynamics holds promise to meet the design tool requirement, but requires accuracy quantification, or validation, before it can be confidently applied in the design process. This effort presents the beginning of such a validation process for the Loci- CHEM CPD code. The model problem examined here is a gaseous oxygen (GO2)/gaseous hydrogen (GH2) shear coaxial single element injector operating at a chamber pressure of 5.42 MPa. The GO2/GH2 propellant combination in this geometry represents one the simplest rocket model problems and is thus foundational to subsequent validation efforts for more complex injectors. Multiple steady state solutions have been produced with Loci-CHEM employing different hybrid grids and two-equation turbulence models. Iterative convergence for each solution is demonstrated via mass conservation, flow variable monitoring at discrete flow field locations as a function of solution iteration and overall residual performance. A baseline hybrid grid was used and then locally refined to demonstrate grid convergence. Solutions were also obtained with three variations of the k-omega turbulence model.

  2. Accuracy Quantification of the Loci-CHEM Code for Chamber Wall Heat Transfer in a GO2/GH2 Single Element Injector Model Problem

    NASA Technical Reports Server (NTRS)

    West, Jeff; Westra, Doug; Lin, Jeff; Tucker, Kevin

    2006-01-01

    A robust rocket engine combustor design and development process must include tools which can accurately predict the multi-dimensional thermal environments imposed on solid surfaces by the hot combustion products. Currently, empirical methods used in the design process are typically one dimensional and do not adequately account for the heat flux rise rate in the near-injector region of the chamber. Computational Fluid Dynamics holds promise to meet the design tool requirement, but requires accuracy quantification, or validation, before it can be confidently applied in the design process. This effort presents the beginning of such a validation process for the Loci-CHEM CFD code. The model problem examined here is a gaseous oxygen (GO2)/gaseous hydrogen (GH2) shear coaxial single element injector operating at a chamber pressure of 5.42 MPa. The GO2/GH2 propellant combination in this geometry represents one the simplest rocket model problems and is thus foundational to subsequent validation efforts for more complex injectors. Multiple steady state solutions have been produced with Loci-CHEM employing different hybrid grids and two-equation turbulence models. Iterative convergence for each solution is demonstrated via mass conservation, flow variable monitoring at discrete flow field locations as a function of solution iteration and overall residual performance. A baseline hybrid was used and then locally refined to demonstrate grid convergence. Solutions were obtained with three variations of the k-omega turbulence model.

  3. Multiphase CFD-based models for chemical looping combustion process: Fuel reactor modeling

    SciTech Connect

    Jung, Jonghwun; Gamwo, I.K.

    2008-04-21

    Chemical looping combustion (CLC) is a flameless two-step fuel combustion that produces a pure CO2 stream, ready for compression and sequestration. The process is composed of two interconnected fluidized bed reactors. The air reactor which is a conventional circulating fluidized bed and the fuel reactor which is a bubbling fluidized bed. The basic principle is to avoid the direct contact of air and fuel during the combustion by introducing a highly-reactive metal particle, referred to as oxygen carrier, to transport oxygen from the air to the fuel. In the process, the products from combustion are kept separated from the rest of the flue gases namely nitrogen and excess oxygen. This process eliminates the energy intensive step to separate the CO2 from nitrogen-rich flue gas that reduce the thermal efficiency. Fundamental knowledge of multiphase reactive fluid dynamic behavior of the gas–solid flow is essential for the optimization and operation of a chemical looping combustor. Our recent thorough literature review shows that multiphase CFD-based models have not been adapted to chemical looping combustion processes in the open literature. In this study, we have developed the reaction kinetics model of the fuel reactor and implemented the kinetic model into a multiphase hydrodynamic model, MFIX, developed earlier at the National Energy Technology Laboratory. Simulated fuel reactor flows revealed high weight fraction of unburned methane fuel in the flue gas along with CO2 and H2O. This behavior implies high fuel loss at the exit of the reactor and indicates the necessity to increase the residence time, say by decreasing the fuel flow rate, or to recirculate the unburned methane after condensing and removing CO2.

  4. On precisely modelling surface deformation due to interacting magma chambers and dykes

    NASA Astrophysics Data System (ADS)

    Pascal, Karen; Neuberg, Jurgen; Rivalta, Eleonora

    2014-01-01

    Combined data sets of InSAR and GPS allow us to observe surface deformation in volcanic settings. However, at the vast majority of volcanoes, a detailed 3-D structure that could guide the modelling of deformation sources is not available, due to the lack of tomography studies, for example. Therefore, volcano ground deformation due to magma movement in the subsurface is commonly modelled using simple point (Mogi) or dislocation (Okada) sources, embedded in a homogeneous, isotropic and elastic half-space. When data sets are too complex to be explained by a single deformation source, the magmatic system is often represented by a combination of these sources and their displacements fields are simply summed. By doing so, the assumption of homogeneity in the half-space is violated and the resulting interaction between sources is neglected. We have quantified the errors of such a simplification and investigated the limits in which the combination of analytical sources is justified. We have calculated the vertical and horizontal displacements for analytical models with adjacent deformation sources and have tested them against the solutions of corresponding 3-D finite element models, which account for the interaction between sources. We have tested various double-source configurations with either two spherical sources representing magma chambers, or a magma chamber and an adjacent dyke, modelled by a rectangular tensile dislocation or pressurized crack. For a tensile Okada source (representing an opening dyke) aligned or superposed to a Mogi source (magma chamber), we find the discrepancies with the numerical models to be insignificant (<5 per cent) independently of the source separation. However, if a Mogi source is placed side by side to an Okada source (in the strike-perpendicular direction), we find the discrepancies to become significant for a source separation less than four times the radius of the magma chamber. For horizontally or vertically aligned pressurized sources, the discrepancies are up to 20 per cent, which translates into surprisingly large errors when inverting deformation data for source parameters such as depth and volume change. Beyond 8 radii however, we demonstrate that the summation of analytical sources represents adjacent magma chambers correctly.

  5. Fundamentals of Gas Turbine combustion

    NASA Technical Reports Server (NTRS)

    Gerstein, M.

    1979-01-01

    Combustion problems and research recommendations are discussed in the areas of atomization and vaporization, combustion chemistry, combustion dynamics, and combustion modelling. The recommendations considered of highest priority in these areas are presented.

  6. A hierarchical modeling approach to estimating soil trace gas fluxes from static chambers

    NASA Astrophysics Data System (ADS)

    Ogle, K.; Ryan, E.; Dijkstra, F. A.; Pendall, E.

    2014-12-01

    Static chambers are often employed to measure soil trace gas fluxes. Gas concentrations (C) in the headspace are sampled at different times (t), and for each group of chamber measurements, flux rates are frequently calculated as the slope of linear regressions of C versus t (ultimately, statistical analyses are performed with the flux rate "data"). While non-linear regressions are recognized to be more accurate than linear regressions, a trade-off with precision can arise due to variability in raw data leading to poor curve fits, and groups of data with too few observations or with poor regression fits (i.e., low R2) are often discarded. We solve these problems via a hierarchical Bayesian approach that fits a simple, dynamic non-linear model of C versus t based on Fick's law. Data are from the Prairie Heating and CO2 Enrichment (PHACE) study that involves manipulations of atmospheric CO2, temperature, soil moisture, and vegetation. CO2, CH4, and N2O gas samples were collected from static chambers bi-weekly during five growing seasons, resulting in >12,000 individual gas samples and >3100 groups of samples and associated fluxes. Using these data, we compare flux estimates from our non-linear model to those obtained from a linear model, and we evaluate the effect of conducting independent regressions for each group of samples versus simultaneously estimating the fluxes for all groups within a hierarchical framework motivated by the PHACE experimental design. The CO2 flux estimates from the hierarchical linear and non-linear models fit the observed CO2 data well (R2 = 0.97) and were highly correlated with each other (r = 0.99), but the linear model resulted in estimates that were ~10% lower than the non-linear model. The hierarchical versus non-hierarchical models also produced similar flux estimates (r = 0.94), but the non-hierarchical version yielded notably less precise estimates (the 95% CIs for its fluxes were 1-2 orders of magnitude wider that the hierarchical model). Hence, the hierarchical, non-linear approach to estimating trace gas fluxes from static chambers is a significant improvement upon the non-hierarchical (independent groups) and linear regression approaches, which tend to produce highly uncertain (non-hierarchical models) and biased (underestimated, linear model) flux estimates.

  7. Modelling the photooxidation of ULP, E5 and E10 in the CSIRO smog chamber

    NASA Astrophysics Data System (ADS)

    White, Stephen J.; Azzi, Merched; Angove, Dennys E.; Jamie, Ian M.

    2010-12-01

    The photooxidation of fuel vapour was investigated in a smog chamber and simulated using three chemical mechanisms, the Master Chemical Mechanism (MCMv3.1), SAPRC-99 and the Carbon Bond chemical mechanism (CB05). Three varieties of fuel were used, unleaded petrol (ULP) and two ULP-ethanol blends which contained 5% and 10% ethanol (E5, E10). The fuel vapours were introduced into the chamber using two methods, by injecting the vapours from wholly evaporated fuel directly, and by injecting the headspace vapour from fuel equilibrated at 38 °C. The chamber experiments were simulated using the selected mechanisms and comparisons made with collected experimental data. The SAPRC-99 mechanism reproduced ?(O 3-NO) more accurately for almost all fuel types and injection modes, with negligible model error for both injection modes. The average model error for MCM simulations was -16% and for CB05 the average model error was -34%. The predictions for the CB05 mechanism varied depending on injection mode, the ?(O 3-NO) model error for wholly evaporated experiments was -44%, compared to -24% for headspace vapour experiments. The difference in aromatic content between experiments of different injection modes was likely to be the cause of the difference in model error for CB05. The model error for all headspace experiments was dependent upon the initial carbon monoxide concentrations. The results for ?(O 3-NO) were matched by the prediction of other key products, with formaldehyde predicted to within 20% by both SAPRC and the MCM. The addition of ethanol to the base SAPRC mechanism altered the predictions of ?(O 3-NO) by less than 2%. Changes observed in the concentrations of formaldehyde and acetaldehyde were consistent with the expected yields from ethanol oxidation.

  8. Comprehensive mechanisms for combustion chemistry: Experiment, modeling, and sensitivity analysis

    SciTech Connect

    Dryer, F.L.; Yetter, R.A.

    1993-12-01

    This research program is an integrated experimental/numerical effort to study pyrolysis and oxidation reactions and mechanisms for small-molecule hydrocarbon structures under conditions representative of combustion environments. The experimental aspects of the work are conducted in large diameter flow reactors, at pressures from one to twenty atmospheres, temperatures from 550 K to 1200 K, and with observed reaction times from 10{sup {minus}2} to 5 seconds. Gas sampling of stable reactant, intermediate, and product species concentrations provides not only substantial definition of the phenomenology of reaction mechanisms, but a significantly constrained set of kinetic information with negligible diffusive coupling. Analytical techniques used for detecting hydrocarbons and carbon oxides include gas chromatography (GC), and gas infrared (NDIR) and FTIR methods are utilized for continuous on-line sample detection of light absorption measurements of OH have also been performed in an atmospheric pressure flow reactor (APFR), and a variable pressure flow (VPFR) reactor is presently being instrumented to perform optical measurements of radicals and highly reactive molecular intermediates. The numerical aspects of the work utilize zero and one-dimensional pre-mixed, detailed kinetic studies, including path, elemental gradient sensitivity, and feature sensitivity analyses. The program emphasizes the use of hierarchical mechanistic construction to understand and develop detailed kinetic mechanisms. Numerical studies are utilized for guiding experimental parameter selections, for interpreting observations, for extending the predictive range of mechanism constructs, and to study the effects of diffusive transport coupling on reaction behavior in flames. Modeling using well defined and validated mechanisms for the CO/H{sub 2}/oxidant systems.

  9. Modeling and Simulation of Upset-Inducing Disturbances for Digital Systems in an Electromagnetic Reverberation Chamber

    NASA Technical Reports Server (NTRS)

    Torres-Pomales, Wilfredo

    2014-01-01

    This report describes a modeling and simulation approach for disturbance patterns representative of the environment experienced by a digital system in an electromagnetic reverberation chamber. The disturbance is modeled by a multi-variate statistical distribution based on empirical observations. Extended versions of the Rejection Samping and Inverse Transform Sampling techniques are developed to generate multi-variate random samples of the disturbance. The results show that Inverse Transform Sampling returns samples with higher fidelity relative to the empirical distribution. This work is part of an ongoing effort to develop a resilience assessment methodology for complex safety-critical distributed systems.

  10. Combustion physics

    NASA Astrophysics Data System (ADS)

    Jones, A. R.

    1985-11-01

    Over 90% of our energy comes from combustion. By the year 2000 the figure will still be 80%, even allowing for nuclear and alternative energy sources. There are many familiar examples of combustion use, both domestic and industrial. These range from the Bunsen burner to large flares, from small combustion chambers, such as those in car engines, to industrial furnaces for steel manufacture or the generation of megawatts of electricity. There are also fires and explosions. The bountiful energy release from combustion, however, brings its problems, prominent among which are diminishing fuel resources and pollution. Combustion science is directed towards finding ways of improving efficiency and reducing pollution. One may ask, since combustion is a chemical reaction, why physics is involved: the answer is in three parts. First, chemicals cannot react unless they come together. In most flames the fuel and air are initially separate. The chemical reaction in the gas phase is very fast compared with the rate of mixing. Thus, once the fuel and air are mixed the reaction can be considered to occur instantaneously and fluid mechanics limits the rate of burning. Secondly, thermodynamics and heat transfer determine the thermal properties of the combustion products. Heat transfer also plays a role by preheating the reactants and is essential to extracting useful work. Fluid mechanics is relevant if work is to be performed directly, as in a turbine. Finally, physical methods, including electric probes, acoustics, optics, spectroscopy and pyrometry, are used to examine flames. The article is concerned mainly with how physics is used to improve the efficiency of combustion.

  11. The acoustic model of oscillations of gas combustion in coaxial pipes

    NASA Astrophysics Data System (ADS)

    Semenova, E. V.; Larionov, V. M.; Kazakova, E. I.

    2014-11-01

    Organization of pulse combustion mode is one of the possible solutions to the problem of energy efficiency installations using hydrocarbon fuel. For grate combustion of solid fuels, in particular, solid industrial wastes are considered to be promising coaxial system, allowing the admission of secondary air to the combustion zone. In this paper we proposed an acoustic model of oscillations of gas when burning solid fuel in the system is coaxially arranged pipes with natural air supply. The description of the motion of the gas in the system during one period of oscillation.

  12. Heat exchange model in absorption chamber of water-direct-absorption-typed laser energy meter

    NASA Astrophysics Data System (ADS)

    Feng Wei, Ji; Qun Sun, Li; Zhang, Kai; Hu, XiaoYang; Zhou, Shan

    2015-04-01

    The interaction between laser and water flow is very complicated in the absorption chamber of a high energy laser (HEL) energy meter which directly uses water as an absorbing medium. Therefore, the heat exchange model cannot be studied through traditional methods, but it is the most important factor to improve heat exchange efficiency in the absorption chamber. After the exchanges of heat and mass were deeply analyzed, experimental study and numerical fitting were brought out. The original testing data of laser power and water flow temperature at one moment were utilized to calculate those at the next moment, and then the calculated temperature curve was compared with the measured one. If the two curves matched well, the corresponding coefficient was obtained. Meanwhile, numerous experiments were performed to study the effects of laser power, duration, focal spot scale, and water flow rate on heat exchange coefficient. In addition, the relationship between water phase change and heat exchange was analyzed. The heat exchange coefficient was increased by optimizing the construction of the absorption chamber or increasing water flow rate. The results provide the reference for design of water-direct-absorption-typed HEL energy meters, as well as for analysis of the interaction between other similar lasers and water flow.

  13. Numerical modelling by the Stokes--DEM coupled simulation for a roof at hot magma chamber

    NASA Astrophysics Data System (ADS)

    Furuichi, M.; Nishiura, D.

    2014-12-01

    The dynamics of a granular media has been suggested to play an important role in a reheated magma chamber by a hot intrusion (e.g. Burgisser and Bergantz, 2011). Although several mechanisms, such as Rayleigh Taylor instability, unzipping, and rhythmic convection (e.g. Shibano et.al. 2012, 2013), have been proposed for characterizing upward migration process in a crystalline magma chamber, their contributions in the long geodynamical time scale are not clear yet. Thus we perform numerical simulations to investigate the thermal evolution of the magma chamber with basal intrusion in three dimensions. In order to solve high-viscosity fluid and particle dynamics for modelling a melt--crystal jammed state of the magma, we have developed a coupled Stokes--DEM simulation code with two key techniques: formulation of particle motion without inertia and semi-implicit treatment of particle motion in the fluid equation (Furuichi and Nishiura 2014). Our simulation can successfully handle sinking particles in a high-viscosity fluid. We examine different types of the granular media heated from the bottom with varying parameters. We especially focus on pattern of the settling particles against the melt density contrast between upper and lower region.

  14. Standard formaldehyde source for chamber testing of material emissions: model development, experimental evaluation, and impacts of environmental factors.

    PubMed

    Wei, Wenjuan; Howard-Reed, Cynthia; Persily, Andrew; Zhang, Yinping

    2013-07-16

    Formaldehyde, which is recognized as a harmful indoor air pollutant for human health, is emitted mainly from urea-formaldehyde resin in wood products. Chamber tests are used to evaluate formaldehyde emission rates from these products. However, there is no available formaldehyde standard reference emission source to assess the performance of chamber testing systems. In this work, a LIFE (liquid-inner tube diffusion-film-emission) formaldehyde reference is described. The formaldehyde source consists of a polytetrafluoroethene (PTFE) tube that holds a formaldehyde-water solution with a concentration of 16 g formaldehyde per 100 mL water, with a thin polydimethylsiloxane (PDMS) film cover. Formaldehyde emission parameters for the PDMS film (diffusion coefficient and partition coefficient) were determined experimentally, thereby enabling the prediction of the formaldehyde emissions from the source for use as a reference value in a chamber. Chamber tests were conducted in a 51 L stainless steel ventilated chamber. The impacts of temperature and relative humidity on the emissions were investigated. Results show the LIFE's chamber test results match those predicted by a mass transfer model. As a result, this formaldehyde source may be used to generate a reference concentration in product emission testing chambers, thereby providing a powerful tool to evaluate the performance of the chamber testing systems. PMID:23802904

  15. Ultrafast Structural Dynamics in Combustion Relevant Model Systems

    SciTech Connect

    Weber, Peter M.

    2014-03-31

    The research project explored the time resolved structural dynamics of important model reaction system using an array of novel methods that were developed specifically for this purpose. They include time resolved electron diffraction, time resolved relativistic electron diffraction, and time resolved Rydberg fingerprint spectroscopy. Toward the end of the funding period, we also developed time-resolved x-ray diffraction, which uses ultrafast x-ray pulses at LCLS. Those experiments are just now blossoming, as the funding period expired. In the following, the time resolved Rydberg Fingerprint Spectroscopy is discussed in some detail, as it has been a very productive method. The binding energy of an electron in a Rydberg state, that is, the energy difference between the Rydberg level and the ground state of the molecular ion, has been found to be a uniquely powerful tool to characterize the molecular structure. To rationalize the structure sensitivity we invoke a picture from electron diffraction: when it passes the molecular ion core, the Rydberg electron experiences a phase shift compared to an electron in a hydrogen atom. This phase shift requires an adjustment of the binding energy of the electron, which is measurable. As in electron diffraction, the phase shift depends on the molecular, geometrical structure, so that a measurement of the electron binding energy can be interpreted as a measurement of the molecule’s structure. Building on this insight, we have developed a structurally sensitive spectroscopy: the molecule is first elevated to the Rydberg state, and the binding energy is then measured using photoelectron spectroscopy. The molecule’s structure is read out as the binding energy spectrum. Since the photoionization can be done with ultrafast laser pulses, the technique is inherently capable of a time resolution in the femtosecond regime. For the purpose of identifying the structures of molecules during chemical reactions, and for the analysis of molecular species in the hot environments of combustion processes, there are several features that make the Rydberg ionization spectroscopy uniquely useful. First, the Rydberg electron’s orbit is quite large and covers the entire molecule for most molecular structures of combustion interest. Secondly, the ionization does not change vibrational quantum numbers, so that even complicated and large molecules can be observed with fairly well resolved spectra. In fact, the spectroscopy is blind to vibrational excitation of the molecule. This has the interesting consequence for the study of chemical dynamics, where the molecules are invariably very energetic, that the molecular structures are observed unobstructed by the vibrational congestion that dominates other spectroscopies. This implies also that, as a tool to probe the time-dependent structural dynamics of chemically interesting molecules, Rydberg spectroscopy may well be better suited than electron or x-ray diffraction. With recent progress in calculating Rydberg binding energy spectra, we are approaching the point where the method can be evolved into a structure determination method. To implement the Rydberg ionization spectroscopy we use a molecular beam based, time-resolved pump-probe multi-photon ionization/photoelectron scheme in which a first laser pulse excites the molecule to a Rydberg state, and a probe pulse ionizes the molecule. A time-of-flight detector measures the kinetic energy spectrum of the photoelectrons. The photoelectron spectrum directly provides the binding energy of the electron, and thereby reveals the molecule’s time-dependent structural fingerprint. Only the duration of the laser pulses limits the time resolution. With a new laser system, we have now reached time resolutions better than 100 fs, although very deep UV wavelengths (down to 190 nm) have slightly longer instrument functions. The structural dynamics of molecules in Rydberg-excited states is obtained by delaying the probe ionization photon from the pump photon; the structural dynamics of molecules in their ground state or e

  16. Robust Feedback Control of Combustion Instability with Modeling Uncertainty

    E-print Network

    Ray, Asok

    in frequency domain T Temperature t Time u Control output of secondary-fuel injector V Volume of combustion Park, Pennsylvania 16802 This paper presents the design of a robust feedback controller for suppressing plant a Speed of sound in mixture bk Spatial distribution of burning of control fuel at kth location Cv

  17. Testing of the Engineering Model Electrical Power Control Unit for the Fluids and Combustion Facility

    NASA Technical Reports Server (NTRS)

    Kimnach, Greg L.; Lebron, Ramon C.; Fox, David A.

    1999-01-01

    The John H. Glenn Research Center at Lewis Field (GRC) in Cleveland, OH and the Sundstrand Corporation in Rockford, IL have designed and developed an Engineering Model (EM) Electrical Power Control Unit (EPCU) for the Fluids Combustion Facility, (FCF) experiments to be flown on the International Space Station (ISS). The EPCU will be used as the power interface to the ISS power distribution system for the FCF's space experiments'test and telemetry hardware. Furthermore. it is proposed to be the common power interface for all experiments. The EPCU is a three kilowatt 12OVdc-to-28Vdc converter utilizing three independent Power Converter Units (PCUs), each rated at 1kWe (36Adc @ 28Vdc) which are paralleled and synchronized. Each converter may be fed from one of two ISS power channels. The 28Vdc loads are connected to the EPCU output via 48 solid-state and current-limiting switches, rated at 4Adc each. These switches may be paralleled to supply any given load up to the 108Adc normal operational limit of the paralleled converters. The EPCU was designed in this manner to maximize allocated-power utilization. to shed loads autonomously, to provide fault tolerance. and to provide a flexible power converter and control module to meet various ISS load demands. Tests of the EPCU in the Power Systems Facility testbed at GRC reveal that the overall converted-power efficiency, is approximately 89% with a nominal-input voltage of 12OVdc and a total load in the range of 4O% to 110% rated 28Vdc load. (The PCUs alone have an efficiency of approximately 94.5%). Furthermore, the EM unit passed all flight-qualification level (and beyond) vibration tests, passed ISS EMI (conducted, radiated. and susceptibility) requirements. successfully operated for extended periods in a thermal/vacuum chamber, was integrated with a proto-flight experiment and passed all stability and functional requirements.

  18. Regularities of heat transfer in the gas layers of a steam boiler furnace flame. Part II. Gas layer radiation laws and the procedure for calculating heat transfer in furnaces, fire boxes, and combustion chambers developed on the basis of these laws

    NASA Astrophysics Data System (ADS)

    Makarov, A. N.

    2014-10-01

    The article presents the results stemming from the scientific discovery of laws relating to radiation from the gas layers generated during flame combustion of fuel and when electric arc burns in electric-arc steel-melting furnaces. The procedure for calculating heat transfer in electric-arc and torch furnaces, fire-boxes, and combustion chambers elaborated on the basis of this discovery is described.

  19. Nonisothermal particle modeling of municipal solid waste combustion with heavy metal vaporization

    SciTech Connect

    Mazza, G.; Falcoz, Q.; Gauthier, D.; Flamant, G.; Soria, J.

    2010-12-15

    A particulate model was developed for municipal solid-waste incineration in a fluidized bed combining solid-waste-particle combustion and heavy metal vaporization from the burning particles. Based on a simpler, isothermal version presented previously, this model combines an asymptotic-combustion model for carbonaceous-solid combustion and a shrinking-core model to describe the heavy metal vaporization phenomenon, in which the particle is now considered nonisothermal. A parametric study is presented that shows the influence of temperature on the global metal-vaporization process. The simulation results are compared to experimental data obtained with a lab-scale fluid bed incinerator and to the results of the simpler isothermal model. It is shown that conduction in the particle strongly affects the variation of the vaporization rate with time and that the present version of the model well fits both the shape of the plots and the maximum heavy metal vaporization rates for all bed temperatures. (author)

  20. An integrated model of magma chamber, conduit and column for the analysis of sustained explosive eruptions

    NASA Astrophysics Data System (ADS)

    Colucci, S.; de'Michieli Vitturi, M.; Neri, A.; Palladino, D. M.

    2014-10-01

    Explosive volcanic eruptions comprise a complex series of processes involving withdrawal from the magma chamber, magma ascent along the conduit and eruption column dynamics. Numerous studies have modeled the different sub-domains of a volcanic system, but their interplay has seldom been analyzed. To this end, we developed C3 (C-cubed, that stands for Chamber, Conduit and Column), a new integrated model that describes the dynamics of an explosive eruption as a series of steady state regimes and as a function of geometry and initial conditions of the magma reservoir. We used Global Sensitivity Analysis to quantify the role of the relevant model parameters and describe the interplay between the different volcanic sub-domains. In particular, we analyzed the evolution of a sustained explosive eruption in order to identify the conditions for buoyant, super-buoyant and collapsing columns. Input data were based on field reconstructions of Quaternary explosive eruptions in the Vulsini Volcanic District (Roman Province, central Italy). Model results show that: 1) the column regime, although affected by complex interactions among several factors, mostly depends on the conduit radius, the volatile content (i.e. supersaturation concentration at the top of the chamber) and length of the conduit, in decreasing level of importance; 2) the amount of mass erupted is independent of the conduit radius and depends mostly on volatile supersaturation, the radius of the magma chamber, the length of the conduit and the overpressure at the conduit inlet; 3) the mass flow-rate, column height and duration of the eruption are largely controlled by the conduit radius; 4) the flow pressure and density at the conduit exit are mostly controlled by the conduit inlet overpressure at the onset of the eruption, and by the length of the conduit at the end of the eruption; 5) the exit velocity from the conduit is mostly controlled by the volatile content, the length of the conduit and the inlet overpressure. In this model framework, and with specific reference to selected Plinian events of the Vulsini Volcanic District, simulation results show that column collapse is not achieved for reasonable eruption durations (order of hours) and conduit widths (tens of meters). This is consistent with field reconstructions suggesting that column collapse did not likely occur and that pyroclastic flows were therefore generated by independent mechanisms from ring fissures and/or multiple vents concomitant to caldera collapse.

  1. Modelling Contribution of Biogenic VOCs to New Particle Formation in the Jülich Plant Atmosphere Chamber

    NASA Astrophysics Data System (ADS)

    Liao, L.; Boy, M.; Mogensen, D.; Mentel, T. F.; Kleist, E.; Kiendler-Scharr, A.; Tillman, R.; Kulmala, M. T.; Dal Maso, M.

    2012-12-01

    Biogenic VOCs are substantially emitted from vegetation to atmosphere. The oxidation of BVOCs by OH, O3, and NO3 in air generating less volatile compounds may lead to the formation and growth of secondary organic aerosol, and thus presents a link to the vegetation, aerosol, and climate interaction system (Kulmala et al, 2004). Studies including field observations, laboratory experiments and modelling have improved our understanding on the connection between BVOCs and new particle formation mechanism in some extent (see e.g. Tunved et al., 2006; Mentel et al., 2009). Nevertheless, the exact formation process still remains uncertain, especially from the perspective of BVOC contributions. The purpose of this work is using the MALTE aerosol dynamics and air chemistry box model to investigate aerosol formation from reactions of direct tree emitted VOCs in the presence of ozone, UV light and artificial solar light in an atmospheric simulation chamber. This model employs up to date air chemical reactions, especially the VOC chemistry, which may potentially allow us to estimate the contribution of BVOCs to secondary aerosol formation, and further to quantify the influence of terpenes to the formation rate of new particles. Experiments were conducted in the plant chamber facility at Forschungszentrum Jülich, Germany (Jülich Plant Aerosol Atmosphere Chamber, JPAC). The detail regarding to the chamber facility has been written elsewhere (Mentel et al., 2009). During the experiments, sulphuric acid was measured by CIMS. VOC mixing ratios were measured by two GC-MS systems and PTR-MS. An Airmodus Particle size magnifier coupled with a TSI CPC and a PH-CPC were used to count the total particle number concentrations with a detection limit close to the expected size of formation of fresh nanoCN. A SMPS measured the particle size distribution. Several other parameters including ozone, CO2, NO, Temperature, RH, and flow rates were also measured. MALTE is a modular model to predict new aerosol formation in the lower troposphere, developed by Boy, et al. (2006). We first evaluate the modelled results with measurements, and further we investigate the influence of different order of magnitude of terpene mixing ratios, especially isoprene and monoterpenes to the most important parameter of new particles formation, i.e. the formation rate (J1). Also, the influence of varying organic source rates on the sulphuric acid concentration available for particle formation is discussed. M. Boy et al., (2006). Atmos. Chem. Phys., 6, 4499-4517. M. Kulmala et al., (2004). Atmos. Chem. Phys., 4, 557-562. P. Tunved et al., (2006). Science, 14, 261-263. Th. F. Mentel et al., (2009). Atmos. Chem. Phys., 9, 4387-4406.

  2. Three-dimensional modeling of diesel engine intake flow, combustion and emissions

    NASA Technical Reports Server (NTRS)

    Reitz, R. D.; Rutland, C. J.

    1992-01-01

    A three-dimensional computer code (KIVA) is being modified to include state-of-the-art submodels for diesel engine flow and combustion: spray atomization, drop breakup/coalescence, multi-component fuel vaporization, spray/wall interaction, ignition and combustion, wall heat transfer, unburned HC and NOx formation, soot and radiation, and the intake flow process. Improved and/or new submodels which were completed are: wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo'vich NOx, and spray/wall impingement with rebounding and sliding drops. Results to date show that adding the effects of unsteadiness and compressibility improves the accuracy of heat transfer predictions; spray drop rebound can occur from walls at low impingement velocities (e.g., in cold-starting); larger spray drops are formed at the nozzle due to the influence of vaporization on the atomization process; a laminar-and-turbulent characteristic time combustion model has the flexibility to match measured engine combustion data over a wide range of operating conditions; and finally, the characteristic time combustion model can also be extended to allow predictions of ignition. The accuracy of the predictions is being assessed by comparisons with available measurements. Additional supporting experiments are also described briefly. To date, comparisons with measured engine cylinder pressure and heat flux data were made for homogeneous charge, spark-ignited and compression-ignited engines. The model results are in good agreement with the experiments.

  3. An experimental validation of a turbulence model for air flow in a mining chamber

    NASA Astrophysics Data System (ADS)

    Branny, M.; Karch, M.; Wodziak, W.; Jaszczur, M.; Nowak, R.; Szmyd, J. S.

    2014-08-01

    In copper mines, excavation chambers are ventilated by jet fans. A fan is installed at the inlet of the dead-end chamber, which is usually 20-30m long. The effectiveness of ventilation depends on the stream range generated by the fan. The velocity field generated by the supply air stream is fully three-dimensional and the flow is turbulent. Currently, the parameters of 3D air flows are determined using the CFD approach. This paper presents the results of experimental testing and numerical simulations of airflow in a laboratory model of a blind channel, aired by a forced ventilation system. The aim of the investigation is qualitative and quantitative verification of computer modelling data. The analysed layout is a geometrically re-scaled and simplified model of a real object. The geometrical scale of the physical model is 1:10. The model walls are smooth, the channel cross-section is rectangular. Measurements were performed for the average airflow velocity in the inlet duct equal 35.4m/s, which gives a Reynolds number of about 180 000. The components of the velocity vector were measured using the Particle Image Velocimetry approach. The numerical procedures presented in this paper use two turbulence models: the standard k-? model and the Reynolds Stress model. The experimental results have been compared against the results of numerical simulations. In the investigated domain of flow - extending from the air inlet to the blind wall of the chamber - we can distinguish two zones with recirculating flows. The first, reaching a distance of about lm from the inlet is characterized by intense mixing of air. A second vortex is formed into a distance greater than lm from the inlet. Such an image of the velocity field results from both the measurements and calculations. Based on this study, we can conclude that the RSM model provides better predictions than the standard k-? model. Good qualitative agreement is achieved between Reynolds Stress model predictions and measured components of the velocity.

  4. One Dimensional Analysis Model of a Condensing Spray Chamber Including Rocket Exhaust Using SINDA/FLUINT and CEA

    NASA Technical Reports Server (NTRS)

    Sakowski, Barbara A.; Edwards, Daryl; Dickens, Kevin

    2014-01-01

    Modeling droplet condensation via CFD codes can be very tedious, time consuming, and inaccurate. CFD codes may be tedious and time consuming in terms of using Lagrangian particle tracking approaches or particle sizing bins. Also since many codes ignore conduction through the droplet and or the degradating effect of heat and mass transfer if noncondensible species are present, the solutions may be inaccurate. The modeling of a condensing spray chamber where the significant size of the water droplets and the time and distance these droplets take to fall, can make the effect of droplet conduction a physical factor that needs to be considered in the model. Furthermore the presence of even a relatively small amount of noncondensible has been shown to reduce the amount of condensation. It is desirable then to create a modeling tool that addresses these issues. The path taken to create such a tool is illustrated. The application of this tool and subsequent results are based on the spray chamber in the Spacecraft Propulsion Research Facility (B2) located at NASA's Plum Brook Station that tested an RL-10 engine. The platform upon which the condensation physics is modeled is SINDAFLUINT. The use of SINDAFLUINT enables the ability to model various aspects of the entire testing facility, including the rocket exhaust duct flow and heat transfer to the exhaust duct wall. The ejector pumping system of the spray chamber is also easily implemented via SINDAFLUINT. The goal is to create a transient one dimensional flow and heat transfer model beginning at the rocket, continuing through the condensing spray chamber, and finally ending with the ejector pumping system. However the model of the condensing spray chamber may be run independently of the rocket and ejector systems detail, with only appropriate mass flow boundary conditions placed at the entrance and exit of the condensing spray chamber model. The model of the condensing spray chamber takes into account droplet conduction as well as the degrading effect of mass and heat transfer due to the presence of noncondensibles. The one dimension model of the condensing spray chamber makes no presupposition on the pressure profile within the chamber, allowing the implemented droplet physics of heat and mass transfer coupled to the SINDAFLUINT solver to determine a transient pressure profile of the condensing spray chamber. Model results compare well to the RL-10 engine pressure test data.

  5. One Dimensional Analysis Model of a Condensing Spray Chamber Including Rocket Exhaust Using SINDA/FLUINT and CEA

    NASA Technical Reports Server (NTRS)

    Sakowski, Barbara; Edwards, Daryl; Dickens, Kevin

    2014-01-01

    Modeling droplet condensation via CFD codes can be very tedious, time consuming, and inaccurate. CFD codes may be tedious and time consuming in terms of using Lagrangian particle tracking approaches or particle sizing bins. Also since many codes ignore conduction through the droplet and or the degradating effect of heat and mass transfer if noncondensible species are present, the solutions may be inaccurate. The modeling of a condensing spray chamber where the significant size of the water droplets and the time and distance these droplets take to fall, can make the effect of droplet conduction a physical factor that needs to be considered in the model. Furthermore the presence of even a relatively small amount of noncondensible has been shown to reduce the amount of condensation [Ref 1]. It is desirable then to create a modeling tool that addresses these issues. The path taken to create such a tool is illustrated. The application of this tool and subsequent results are based on the spray chamber in the Spacecraft Propulsion Research Facility (B2) located at NASA's Plum Brook Station that tested an RL-10 engine. The platform upon which the condensation physics is modeled is SINDAFLUINT. The use of SINDAFLUINT enables the ability to model various aspects of the entire testing facility, including the rocket exhaust duct flow and heat transfer to the exhaust duct wall. The ejector pumping system of the spray chamber is also easily implemented via SINDAFLUINT. The goal is to create a transient one dimensional flow and heat transfer model beginning at the rocket, continuing through the condensing spray chamber, and finally ending with the ejector pumping system. However the model of the condensing spray chamber may be run independently of the rocket and ejector systems detail, with only appropriate mass flow boundary conditions placed at the entrance and exit of the condensing spray chamber model. The model of the condensing spray chamber takes into account droplet conduction as well as the degrading effect of mass and heat transfer due to the presence of noncondensibles. The one dimension model of the condensing spray chamber makes no presupposition on the pressure profile within the chamber, allowing the implemented droplet physics of heat and mass transfer coupled to the SINDAFLUINT solver to determine a transient pressure profile of the condensing spray chamber. Model results compare well to the RL-10 engine pressure test data.

  6. Multimodality pH imaging in a mouse dorsal skin fold window chamber model

    NASA Astrophysics Data System (ADS)

    Leung, Hui Min; Schafer, Rachel; Pagel, Mark M.; Robey, Ian F.; Gmitro, Arthur F.

    2013-03-01

    Upregulate levels of expression and activity of membrane H+ ion pumps in cancer cells drives the extracellular pH (pHe,) to values lower than normal. Furthermore, disregulated pH is indicative of the changes in glycolytic metabolism in tumor cells and has been shown to facilitate extracellular tissue remodeling during metastasis Therefore, measurement of pHe could be a useful cancer biomarker for diagnostic and therapy monitoring evaluation. Multimodality in-vivo imaging of pHe in tumorous tissue in a mouse dorsal skin fold window chamber (DSFWC) model is described. A custom-made plastic window chamber structure was developed that is compatible with both imaging optical and MR imaging modalities and provides a model system for continuous study of the same tissue microenvironment on multiple imaging platforms over a 3-week period. For optical imaging of pHe, SNARF-1 carboxylic acid is injected intravenously into a SCID mouse with an implanted tumor. A ratiometric measurement of the fluorescence signal captured on a confocal microscope reveals the pHe of the tissue visible within the window chamber. This imaging method was used in a preliminary study to evaluate sodium bicarbonate as a potential drug treatment to reverse tissue acidosis. For MR imaging of pHe the chemical exchange saturation transfer (CEST) was used as an alternative way of measuring pHe in a DSFWC model. ULTRAVIST®, a FDA approved x-ray/CT contrast agent has been shown to have a CEST effect that is pH dependent. A ratiometric analysis of water saturation at 5.6 and 4.2 ppm chemical shift provides a means to estimate the local pHe.

  7. Fluorescence and reflectance spectral imaging system for a murine mammary window chamber model.

    PubMed

    Leung, Hui Min; Gmitro, Arthur F

    2015-08-01

    A spectral imaging system was developed to study the development of breast cancer xenografts in a murine mammary window chamber model. The instrument is configured to work with either a laser to excite fluorescence or a broadband light source for diffuse reflectance imaging. Two applications were demonstrated. First, spectral imaging of fluorescence signals was demonstrated with a GFP-breast cancer tumor and fluorescein injection. Second, based on the principles of broadband reflectance spectroscopy, the instrument was used to monitor dynamic changes of tissue absorbance to yield tissue oxygenation maps at different time points during tumor progression. PMID:26309753

  8. Fluorescence and reflectance spectral imaging system for a murine mammary window chamber model

    PubMed Central

    Leung, Hui Min; Gmitro, Arthur F.

    2015-01-01

    A spectral imaging system was developed to study the development of breast cancer xenografts in a murine mammary window chamber model. The instrument is configured to work with either a laser to excite fluorescence or a broadband light source for diffuse reflectance imaging. Two applications were demonstrated. First, spectral imaging of fluorescence signals was demonstrated with a GFP-breast cancer tumor and fluorescein injection. Second, based on the principles of broadband reflectance spectroscopy, the instrument was used to monitor dynamic changes of tissue absorbance to yield tissue oxygenation maps at different time points during tumor progression. PMID:26309753

  9. Chemical kinetics modeling and LES combustion model effects on a perfectly premixed burner

    NASA Astrophysics Data System (ADS)

    Albouze, Guillaume; Poinsot, Thierry; Gicquel, Laurent

    2009-06-01

    Chemical kinetics modeling and coupling with turbulent combustion models for compressible Large Eddy Simulations (LES) is a critical issue. Accurate flow predictions can only be guaranteed if the coupling is well mastered. In a first attempt to qualify the effect of each model, the case of a lean premixed swirled combustor with comprehensive measures is targeted (species mass fractions and temperature fields). For the investigation, two turbulent combustion models are considered. The first model relies on a presumed PDF approach coupled to a look-up chemistry table obtained with a reduced chemical scheme. The second model makes use of the thickened flame approach using the same reduced chemical scheme but with reaction rates computed explicitly as the computation advances. Then, to estimate kinetic schemes reduction effects, the first model is compared to a third one, with the same PDF approach, but coupled to a look-up chemistry table obtained with a complete chemical scheme. All LES are very close to each other. The main difference between the different predictions relies on CO mass fractions. Although they are all able to return good outlet mass fractions, CO values inside the flame are different depending on the model used. To cite this article: G. Albouze et al., C. R. Mecanique 337 (2009).

  10. V CONGRESO NACIONAL DE PILAS DE COMBUSTIBLE DISTRIBUTED PARAMETER MODEL SIMULATION TOOL

    E-print Network

    Batlle, Carles

    and achieve a high performance and long life of the cells. Variations in the concentrations of hydrogen, water distributed parameter model to be used in model-based controllers. The paper is organized as follows. SectionV CONGRESO NACIONAL DE PILAS DE COMBUSTIBLE DISTRIBUTED PARAMETER MODEL SIMULATION TOOL FOR PEM

  11. Evaluation of chemical-kinetics models for n-heptane combustion using a multidimensional CFD code

    E-print Network

    Aggarwal, Suresh K.

    Evaluation of chemical-kinetics models for n-heptane combustion using a multidimensional CFD code Chemical kinetics Modeling Diffusion flames Premixed flames a b s t r a c t Computational fluid dynamics-heptane fuel. Three state-of-the-art chemical kinetics models are incorporated into a time-dependent, two

  12. Physical aspects and modelling of turbulent MILD combustion

    E-print Network

    Minamoto, Yuki

    2014-02-04

    explored to meet these requirements. Fuel lean premixed combustion is a potential method to meet these demands, but it is highly susceptible to thermo-acoustic instability. One method to avoid the in- stabilities is to preheat the reactant mixture by using... . Furthermore, MILD conditions are achieved relatively straightforwardly in practical devices using conventional tech- niques such as exhaust or flue gas recirculation (EGR or FGR) or staged fuel injection (Wu¨nning & Wu¨nning, 1997; Cavaliere & de Joannon, 2004...

  13. Modelling Of Hindered Crystal Settling-Floating Process In A Magma Chamber

    NASA Astrophysics Data System (ADS)

    Berres, S.; Forien, M.; Bagdassarov, N. S.; Dingwell, D. B.

    2011-12-01

    In interior of magma chamber during the fractional crystallisation, the separation of the minerals can be done by a simple density contrast. The denser minerals sank to the bottom of magma chamber and can formed, later, a cumulate layer. In order to better understand the relations between cumulus texture and evolution of the chemical composition at grain boundaries during the crystal-melt settling-floating process, a series of centrifuge experiments have been carried out. The experiments were conducted in a centrifuging furnace at 1235°C under atmospheric pressure during 6 hours and with an acceleration range between 1g to 1000g of partially molten gabbro samples with the grain size 100?m. Crystals during the centrifuging process have been segregated according to their buoyancy: plagioclase crystals floated to the top and magnetite crystals sank to the bottom of container. The chemical evolution of melt, vertical and horizontal distribution of crystals and melt in the experiments at 100g and 200g is similar. The segregation realized in experiments at 500g and 1000g revealed much worse separation of heavy and light crystals and the melt phase. The vertical evolution of the major and trace elements in the melt phase shows that close to the cumulate layer (between 0 to 2 mm from the bottom) the variation of these elements depends on the distance from the container wall, and becomes constant in the interior of sample. The horizontal evolution shows some variations which appear close to the walls of the capsule and which are due to the wall effect during the centrifuging runs. In order to describe the compaction evolution with time, a numerical modelling of the sedimentation process of the crystals has been build and then compared with the centrifuge modelling. The numerical and centrifuge modelling results agree quite well: the stratification of the compacted layer in the runs is reproduced in numerical models. The settling model of a concentrated suspension can predict a realistic evolution of the cumulus layer compaction for a time scale of several years. The combination of centrifuge experiments and numerical modelling demonstrates that in magma chambers there are correlations between cumulus textures and the evolution of chemical composition at grain boundaries during the stage when crystals come into mechanical contact with each other in a cumulus layer. Finally, formation time and melt fraction evolution of Muskox layered intrusion have been revisited using the hindered sedimentation model calculations. The results on the time formation of the intrusion as well as the porosity loss with time are in agreement with previous results of the compaction model.

  14. Automated modeling of ecosystem CO2 fluxes based on closed chamber measurements: A standardized conceptual and practical approach

    NASA Astrophysics Data System (ADS)

    Hoffmann, Mathias; Jurisch, Nicole; Albiac Borraz, Elisa; Hagemann, Ulrike; Sommer, Michael; Augustin, Jürgen

    2015-04-01

    Closed chamber measurements are widely used for determining the CO2 exchange of small-scale or heterogeneous ecosystems. Among the chamber design and operational handling, the data processing procedure is a considerable source of uncertainty of obtained results. We developed a standardized automatic data processing algorithm, based on the language and statistical computing environment R© to (i) calculate measured CO2 flux rates, (ii) parameterize ecosystem respiration (Reco) and gross primary production (GPP) models, (iii) optionally compute an adaptive temperature model, (iv) model Reco, GPP and net ecosystem exchange (NEE), and (v) evaluate model uncertainty (calibration, validation and uncertainty prediction). The algorithm was tested for different manual and automatic chamber measurement systems (such as e.g. automated NEE-chambers and the LI-8100A soil CO2 Flux system) and ecosystems. Our study shows that even minor changes within the modelling approach may result in considerable differences of calculated flux rates, derived photosynthetic active radiation and temperature dependencies and subsequently modeled Reco, GPP and NEE balance of up to 25%. Thus, certain modeling implications will be given, since automated and standardized data processing procedures, based on clearly defined criteria, such as statistical parameters and thresholds are a prerequisite and highly desirable to guarantee the reproducibility, traceability of modelling results and encourage a better comparability between closed chamber based CO2 measurements.

  15. Numerical study of premixed HCCI engine combustion and its sensitivity to computational mesh and model uncertainties

    NASA Astrophysics Data System (ADS)

    Kong, Song-Charng; Reitz, Rolf D.

    2003-06-01

    This study used a numerical model to investigate the combustion process in a premixed iso-octane homogeneous charge compression ignition (HCCI) engine. The engine was a supercharged Cummins C engine operated under HCCI conditions. The CHEMKIN code was implemented into an updated KIVA-3V code so that the combustion could be modelled using detailed chemistry in the context of engine CFD simulations. The model was able to accurately simulate the ignition timing and combustion phasing for various engine conditions. The unburned hydrocarbon emissions were also well predicted while the carbon monoxide emissions were under predicted. Model results showed that the majority of unburned hydrocarbon is located in the piston-ring crevice region and the carbon monoxide resides in the vicinity of the cylinder walls. A sensitivity study of the computational grid resolution indicated that the combustion predictions were relatively insensitive to the grid density. However, the piston-ring crevice region needed to be simulated with high resolution to obtain accurate emissions predictions. The model results also indicated that HCCI combustion and emissions are very sensitive to the initial mixture temperature. The computations also show that the carbon monoxide emissions prediction can be significantly improved by modifying a key oxidation reaction rate constant.

  16. A numerical model of initial recombination for high-LET irradiation: Application to liquid-filled ionization chambers

    NASA Astrophysics Data System (ADS)

    Aguiar, P.; Pardo-Montero, J.

    2016-02-01

    In this paper we present a numerical model of initial recombination in media irradiated with high linear energy transfer (LET) ions, which relies on an amorphous track model of ionization of high LET particles, and diffusion, drift and recombination of ionized charge carriers. The model has fundamental applications for the study of recombination in non-polar liquids, as well as practical ones, like in modelling hadrontherapy dosimetry with ionization chambers. We have used it to study the response of liquid-filled ionization chambers to hadrontherapy beams: dependence of initial recombination on ion species, energy and applied external electric field.

  17. Combustion Fundamentals Research

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Increased emphasis is placed on fundamental and generic research at Lewis Research Center with less systems development efforts. This is especially true in combustion research, where the study of combustion fundamentals has grown significantly in order to better address the perceived long term technical needs of the aerospace industry. The main thrusts for this combustion fundamentals program area are as follows: analytical models of combustion processes, model verification experiments, fundamental combustion experiments, and advanced numeric techniques.

  18. PARTICULATE EMISSIONS AND CONTROL IN FLUIDIZED-BED COMBUSTION: MODELING AND PARAMETRIC PERFORMANCE

    EPA Science Inventory

    The report discusses a model, developed to describe the physical characteristics of the particulates emitted from fluidized-bed combustion (FBC) systems and to evaluate data on FBC particulate control systems. The model, which describes the particulate emissions profile from FBC,...

  19. REVISION OF THE INDUSTRIAL COMBUSTION EMISSIONS MODEL TO A BASE YEAR OF 1980

    EPA Science Inventory

    The report describes the development of an updated 1980 base year fuel consumption and air pollution emissions estimates data base by state. These 1980 base year data have been incorporated into industrial combustion emissions (ICE) model Versions 4.0, 5.0, and 6.0. The model is ...

  20. INDUSTRIAL COMBUSTION EMISSIONS (ICE) MODEL, VERSION 6.0. SOFTWARE DESCRIPTION

    EPA Science Inventory

    The report describes the software of the Industrial Combustion Emissions (ICE) model, developed to support the EPA's analysis of acid deposition control alternatives. The model projects industrial fossil-fuel-fired boiler fuels, air emissions, and costs by state for 1985, 1990, 1...

  1. Plant growth modeling at the JSC variable pressure growth chamber - An application of experimental design

    NASA Technical Reports Server (NTRS)

    Miller, Adam M.; Edeen, Marybeth; Sirko, Robert J.

    1992-01-01

    This paper describes the approach and results of an effort to characterize plant growth under various environmental conditions at the Johnson Space Center variable pressure growth chamber. Using a field of applied mathematics and statistics known as design of experiments (DOE), we developed a test plan for varying environmental parameters during a lettuce growth experiment. The test plan was developed using a Box-Behnken approach to DOE. As a result of the experimental runs, we have developed empirical models of both the transpiration process and carbon dioxide assimilation for Waldman's Green lettuce over specified ranges of environmental parameters including carbon dioxide concentration, light intensity, dew-point temperature, and air velocity. This model also predicts transpiration and carbon dioxide assimilation for different ages of the plant canopy.

  2. A model for the emergence of pillars, walls and royal chambers in termite nests

    PubMed Central

    Bonabeau, E.

    1998-01-01

    A simple model of the emergence of pillars in termite nests by Deneubourg is modified to include several additional features that break the homogeneity of the original model: (i) a convection air stream that drives molecules of pheromone along a given direction; (ii) a net flux of individuals in a specific direction; (iii) a well-defined self-maintained pheromone trail; and (iv) a pheromonal template representing the effect of the presence of a queen that continuously emits pheromone. It is shown that, under certain conditions, pillars are transformed into walls or galleries or chambers, and that this transformation may not be driven by any change in the termites' behaviour. Because the same type of response at the individual level can generate different patterns under different conditions, and because previous construction modifies current building conditions, we hypothesize that nest complexity can result from the unfolding of a morphogenetic process that progressively generates a diversity of history-dependent structures.

  3. High-Resolution In Vivo Imaging of Fluorescent Proteins Using Window Chamber Models

    PubMed Central

    Palmer, Gregory M.; Fontanella, Andrew N.; Shan, Siqing; Dewhirst, Mark W.

    2013-01-01

    Fluorescent proteins enable in vivo characterization of a wide and growing array of morphological and functional biomarkers. To fully capitalize on the spatial and temporal information afforded by these reporter proteins, a method for imaging these proteins at high resolution longitudinally is required. This chapter describes the use of window chamber models as a means of imaging fluorescent proteins and other optical parameters. Such models essentially involve surgically implanting a window through which tumor or normal tissue can be imaged using existing microscopy techniques. This enables acquisition of high-quality images down to the cellular or subcellular scale, exploiting the diverse array of optical contrast mechanisms, while also maintaining the native microenvironment of the tissue of interest. This makes these techniques applicable to a wide array of problems in the biomedical sciences. PMID:22700402

  4. Modeling coal combustion behavior in an ironmaking blast furnace raceway: model development and applications

    SciTech Connect

    Maldonado, D.; Austin, P.R.; Zulli, P.; Guo B.

    2009-03-15

    A numerical model has been developed and validated for the investigation of coal combustion phenomena under blast furnace operating conditions. The model is fully three-dimensional, with a broad capacity to analyze significant operational and equipment design changes. The model was used in a number of studies, including: Effect of cooling gas type in coaxial lance arrangements. It was found that oxygen cooling improves coal burnout by 7% compared with natural gas cooling under conditions that have the same amount of oxygen enrichment in the hot blast. Effect of coal particle size distribution. It was found that during two similar periods of operation at Port Kembla's BF6, a difference in PCI capability could be attributed to the difference in coal size distribution. Effect of longer tuyeres. Longer tuyeres were installed at Port Kembla's BF5, leading to its reline scheduled for March 2009. The model predicted an increase in blast velocity at the tuyere nose due to the combustion of volatiles within the tuyere, with implications for tuyere pressure drop and PCI capability. Effect of lance tip geometry. A number of alternate designs were studied, with the best-performing designs promoting the dispersion of the coal particles. It was also found that the base case design promoted size segregation of the coal particles, forcing smaller coal particles to one side of the plume, leaving larger coal particles on the other side. 11 refs., 15 figs., 4 tabs.

  5. Carbon deposition model for oxygen-hydrocarbon combustion

    NASA Technical Reports Server (NTRS)

    Bossard, John A.

    1988-01-01

    The objectives are to use existing hardware to verify and extend the database generated on the original test programs. The data to be obtained are the carbon deposition characteristics when methane is used at injection densities comparable to full scale values. The database will be extended to include liquid natural gas (LNG) testing at low injection densities for gas generator/preburner conditions. The testing will be performed at mixture ratios between 0.25 and 0.60, and at chamber pressures between 750 and 1500 psi.

  6. Modeling the optical coupling across the anterior chamber of the eye towards polarimetric glucose sensing

    NASA Astrophysics Data System (ADS)

    Pirnstill, Casey W.; Coté, Gerard L.

    2014-02-01

    Millions of people worldwide are affected by diabetes. While glucose sensing technology has come a long way over the past several decades, the current commercially available techniques are still invasive, often leading to poor patient compliance. To minimize invasiveness, focus has been placed on optical techniques to ascertain blood glucose concentrations. Optical polarimetry has shown promise and progress as a viable technique for glucose sensing. Recent developments in polarimetric glucose sensing have been focused on overcoming time varying corneal birefringence due to motion artifacts. Beyond corneal birefringence, the next hurdle toward making this approach viable is the ability to couple polarized light across the eye's anterior chamber. The eye is ideally suited to couple light to the retina. The index mismatch between the air and cornea is partially responsible for the beam bending toward the retina and, while good for vision, it complicates our ability to couple light across the anterior chamber without using an index matching device when performing polarimetric glucose monitoring. In this report, we have designed and modeled a non-index matched coupling scheme constructed with commercially available optics. The optical ray tracing model was performed using CODE V to verify the feasibility of a reflective based non-index matched coupling scheme with respect to index of refraction and anatomical restraints. The ray tracing model was developed for a dual-wavelength system and the effect of refraction and reflection at each optical interface within the setup was evaluated. The modeling results indicate a reflective based optical coupling design could be added to existing polarimetric glucose systems thus removing the need for placing an index matched eye-coupling mechanism over the eye prior to data collection.

  7. Modeling of single char combustion, including CO oxidation in its boundary layer

    SciTech Connect

    Lee, C.H.; Longwell, J.P.; Sarofim, A.F.

    1994-10-25

    The combustion of a char particle can be divided into a transient phase where its temperature increases as it is heated by oxidation, and heat transfer from the surrounding gas to an approximately constant temperature stage where gas phase reaction is important and which consumes most of the carbon and an extinction stage caused by carbon burnout. In this work, separate models were developed for the transient heating where gas phase reactions were unimportant and for the steady temperature stage where gas phase reactions were treated in detail. The transient char combustion model incorporates intrinsic char surface production of CO and CO{sub 2}, internal pore diffusion and external mass and heat transfer. The model provides useful information for particle ignition, burning temperature profile, combustion time, and carbon consumption rate. A gas phase reaction model incorporating the full set of 28 elementary C/H/O reactions was developed. This model calculated the gas phase CO oxidation reaction in the boundary layer at particle temperatures of 1250 K and 2500 K by using the carbon consumption rate and the burning temperature at the pseudo-steady state calculated from the temperature profile model but the transient heating was not included. This gas phase model can predict the gas species, and the temperature distributions in the boundary layer, the CO{sub 2}/CO ratio, and the location of CO oxidation. A mechanistic heat and mass transfer model was added to the temperature profile model to predict combustion behavior in a fluidized bed. These models were applied to data from the fluidized combustion of Newlands coal char particles. 52 refs., 60 figs.

  8. Analysis of cyclic combustion of the coal-water suspension

    NASA Astrophysics Data System (ADS)

    Kijo-Kleczkowska, Agnieszka

    2011-04-01

    Combustion technology of the coal-water suspension creates a number of new possibilities to organize the combustion process fulfilling contemporary requirements, e.g. in the environment protection. Therefore the in-depth analysis is necessary to examine the technical application of coal as a fuel in the form of suspension. The research undertakes the complex investigations of the continuous coal-water suspension as well as cyclic combustion. The cyclic nature of fuel combustion results from the movement of the loose material in the flow contour of the circulating fluidized bed (CFB): combustion chamber, cyclone and downcomer. The experimental results proved that the cyclic change of oxygen concentration around fuel, led to the vital change of both combustion mechanisms and combustion kinetics. The mathematical model of the process of fuel combustion has been presented. Its original concept is based on the allowance for cyclic changes of concentrations of oxygen around the fuel. It enables the prognosis for change of the surface and the centre temperatures as well as mass loss of the fuel during combustion in air, in the fluidized bed and during the cyclic combustion.

  9. Experimental and Modeling Studies of the Characteristics of Liquid Biofuels for Enhanced Combustion

    SciTech Connect

    E. Meeks; A. U. Modak; C.V. Naik; K. V. Puduppakkam; C. Westbrook; F. N. Egolfopoulos; T. Tsotsis; S. H. Roby

    2009-07-01

    The objectives of this project have been to develop a comprehensive set of fundamental data regarding the combustion behavior of biodiesel fuels and appropriately associated model fuels that may represent biodiesels in automotive engineering simulation. Based on the fundamental study results, an auxiliary objective was to identify differentiating characteristics of molecular fuel components that can be used to explain different fuel behavior and that may ultimately be used in the planning and design of optimal fuel-production processes. The fuels studied in this project were BQ-9000 certified biodiesel fuels that are certified for use in automotive engine applications. Prior to this project, there were no systematic experimental flame data available for such fuels. One of the key goals has been to generate such data, and to use this data in developing and verifying effective kinetic models. The models have then been reduced through automated means to enable multi-dimensional simulation of the combustion characteristics of such fuels in reciprocating engines. Such reliable kinetics models, validated against fundamental data derived from laminar flames using idealized flow models, are key to the development and design of optimal engines, engine operation and fuels. The models provide direct information about the relative contribution of different molecular constituents to the fuel performance and can be used to assess both combustion and emissions characteristics. During this project, we completed a major and thorough validation of a set of biodiesel surrogate components, allowing us to begin to evaluate the fundamental combustion characteristics for B100 fuels.

  10. SU-E-T-17: A Mathematical Model for PinPoint Chamber Correction in Measuring Small Fields

    SciTech Connect

    Li, T; Zhang, Y; Li, X; Heron, D.E.; Huq, M.Saiful

    2014-06-01

    Purpose: For small field dosimetry, such as measuring the cone output factor for stereotactic radiosurgery, ion chambers often result in underestimation of the dose, due to both the volume averaging effect and the lack of electron equilibrium. The purpose of this work is to develop a mathematical model, specifically for the pinpoint chamber, to calculate the correction factors corresponding to different type of small fields, including single cone-based circular field and non-standard composite fields. Methods: A PTW 0.015cc PinPoint chamber was used in the study. Its response in a certain field was modeled as the total contribution of many small beamlets, each with different response factor depending on the relative strength, radial distance to the chamber axis, and the beam angle. To get these factors, 12 cone-shaped circular fields (5mm,7.5mm, 10mm, 12.5mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 50mm, 60mm) were irradiated and measured with the PinPoint chamber. For each field size, hundreds of readings were recorded for every 2mm chamber shift in the horizontal plane. These readings were then compared with the theoretical doses as obtained with Monte Carlo calculation. A penalized-least-square optimization algorithm was developed to find out the beamlet response factors. After the parameter fitting, the established mathematical model was validated with the same MC code for other non-circular fields. Results: The optimization algorithm used for parameter fitting was stable and the resulted response factors were smooth in spatial domain. After correction with the mathematical model, the chamber reading matched with the Monte Carlo calculation for all the tested fields to within 2%. Conclusion: A novel mathematical model has been developed for the PinPoint chamber for dosimetric measurement of small fields. The current model is applicable only when the beam axis is perpendicular to the chamber axis. It can be applied to non-standard composite fields. Further validation with other type of detectors is being conducted.

  11. Combustion Stability Analyses for J-2X Gas Generator Development

    NASA Technical Reports Server (NTRS)

    Hulka, J. R.; Protz, C. S.; Casiano, M. J.; Kenny, R. J.

    2010-01-01

    The National Aeronautics and Space Administration (NASA) is developing a liquid oxygen/liquid hydrogen rocket engine for upper stage and trans-lunar applications of the Ares vehicles for the Constellation program. This engine, designated the J-2X, is a higher pressure, higher thrust variant of the Apollo-era J-2 engine. Development was contracted to Pratt & Whitney Rocketdyne in 2006. Over the past several years, development of the gas generator for the J-2X engine has progressed through a variety of workhorse injector, chamber, and feed system configurations. Several of these configurations have resulted in injection-coupled combustion instability of the gas generator assembly at the first longitudinal mode of the combustion chamber. In this paper, the longitudinal mode combustion instabilities observed on the workhorse test stand are discussed in detail. Aspects of this combustion instability have been modeled at the NASA Marshall Space Flight Center with several codes, including the Rocket Combustor Interaction Design and Analysis (ROCCID) code and a new lumped-parameter MatLab model. To accurately predict the instability characteristics of all the chamber and injector geometries and test conditions, several features of the submodels in the ROCCID suite of calculations required modification. Finite-element analyses were conducted of several complicated combustion chamber geometries to determine how to model and anchor the chamber response in ROCCID. A large suite of sensitivity calculations were conducted to determine how to model and anchor the injector response in ROCCID. These modifications and their ramification for future stability analyses of this type are discussed in detail. The lumped-parameter MatLab model of the gas generator assembly was created as an alternative calculation to the ROCCID methodology. This paper also describes this model and the stability calculations.

  12. A comprehensive study on different modelling approaches to predict platelet deposition rates in a perfusion chamber

    PubMed Central

    Pallarès, Jordi; Senan, Oriol; Guimerà, Roger; Vernet, Anton; Aguilar-Mogas, Antoni; Vilahur, Gemma; Badimon, Lina; Sales-Pardo, Marta; Cito, Salvatore

    2015-01-01

    Thrombus formation is a multiscale phenomenon triggered by platelet deposition over a protrombotic surface (eg. a ruptured atherosclerotic plaque). Despite the medical urgency for computational tools that aid in the early diagnosis of thrombotic events, the integration of computational models of thrombus formation at different scales requires a comprehensive understanding of the role and limitation of each modelling approach. We propose three different modelling approaches to predict platelet deposition. Specifically, we consider measurements of platelet deposition under blood flow conditions in a perfusion chamber for different time periods (3, 5, 10, 20 and 30?minutes) at shear rates of 212?s?1, 1390?s?1 and 1690?s?1. Our modelling approaches are: i) a model based on the mass-transfer boundary layer theory; ii) a machine-learning approach; and iii) a phenomenological model. The results indicate that the three approaches on average have median errors of 21%, 20.7% and 14.2%, respectively. Our study demonstrates the feasibility of using an empirical data set as a proxy for a real-patient scenario in which practitioners have accumulated data on a given number of patients and want to obtain a diagnosis for a new patient about whom they only have the current observation of a certain number of variables. PMID:26391513

  13. A comprehensive study on different modelling approaches to predict platelet deposition rates in a perfusion chamber.

    PubMed

    Pallarès, Jordi; Senan, Oriol; Guimerà, Roger; Vernet, Anton; Aguilar-Mogas, Antoni; Vilahur, Gemma; Badimon, Lina; Sales-Pardo, Marta; Cito, Salvatore

    2015-01-01

    Thrombus formation is a multiscale phenomenon triggered by platelet deposition over a protrombotic surface (eg. a ruptured atherosclerotic plaque). Despite the medical urgency for computational tools that aid in the early diagnosis of thrombotic events, the integration of computational models of thrombus formation at different scales requires a comprehensive understanding of the role and limitation of each modelling approach. We propose three different modelling approaches to predict platelet deposition. Specifically, we consider measurements of platelet deposition under blood flow conditions in a perfusion chamber for different time periods (3, 5, 10, 20 and 30 minutes) at shear rates of 212 s(-1), 1390 s(-1) and 1690 s(-1). Our modelling approaches are: i) a model based on the mass-transfer boundary layer theory; ii) a machine-learning approach; and iii) a phenomenological model. The results indicate that the three approaches on average have median errors of 21%, 20.7% and 14.2%, respectively. Our study demonstrates the feasibility of using an empirical data set as a proxy for a real-patient scenario in which practitioners have accumulated data on a given number of patients and want to obtain a diagnosis for a new patient about whom they only have the current observation of a certain number of variables. PMID:26391513

  14. Transient and translating gas jet modeling for pressure gain combustion applications

    NASA Astrophysics Data System (ADS)

    Wijeyakulasuriya, Sameera Devsritha

    Major mechanisms governing the mixing process of a gas injected into a long confined chamber is analyzed when there's a relative motion between the two. Such applications arise in a wave rotor combustor (WRCVC) where the moving combustion chambers receive gas from stationary injectors for fueling and ignition. Counter rotating vortices govern the mixing process in such problems, which moves across the channel enhancing mixing. The actions of vortices were seen to localize the injected gas in the vicinity of the injector end wall which can prove advantages during fueling to make a rich mixture near the ignition source and during hot gas injection for ignition to minimize the drop of temperature. The vortex structures can alter the exit conditions of the injector due to its strong near field interactions. The confinement is also important in which it suppresses the development and motion of such vortices and hence affect mixing. The thesis discusses several important features in a WRCVC. Namely, the effect of a combustion channel being opened to the preceding exit port prior to its opening to the gas injectors, on mixing of injected gas with channel gases. This prior opening was seen to deposit vorticity on the channel wall which gets convected along them. This convecting vorticity resulted in enhanced jet penetration. The effect of combustible mixture non-uniformity on ignition success of a WRCVC was also analyzed using 2D and 1D computations. The predictions are validated against measured data from a WRCVC test rig. Ignition locations and combustion pressures were successfully predicted. Limited 3D computations of the hot gas jet mixing with the channel gases were carried out and measure temperature data from the WRCVC test rig was used to verify the axial penetration predictions of the jet. A methodology is proposed to quantify the level of mixing and ignition success by comparing the amount of injected gas inside the channel which is above a certain threshold temperature and mass fraction limits, to the total amount of injected mass trapped inside it at that particular time. Conclusions were made on the level of mixing and the 'ignitability' of the mixture by looking at the time variation of these defined quantities.

  15. Updating the conceptual model for fine particle mass emissions from combustion systems.

    PubMed

    Robinson, Allen L; Grieshop, Andrew P; Donahue, Neil M; Hunt, Sherri W

    2010-10-01

    Atmospheric transformations determine the contribution of emissions from combustion systems to fine particulate matter (PM) mass. For example, combustion systems emit vapors that condense onto existing particles or form new particles as the emissions are cooled and diluted. Upon entering the atmosphere, emissions are exposed to atmospheric oxidants and sunlight, which causes them to evolve chemically and physically, generating secondary PM. This review discusses these transformations, focusing on organic PM. Organic PM emissions are semi-volatile at atmospheric conditions and thus their partitioning varies continuously with changing temperature and concentration. Because organics contribute a large portion of the PM mass emitted by most combustion sources, these emissions cannot be represented using a traditional, static emission factor. Instead, knowledge of the volatility distribution of emissions is required to explicitly account for changes in gas-particle partitioning. This requires updating how PM emissions from combustion systems are measured and simulated from combustion systems. Secondary PM production often greatly exceeds the direct or primary PM emissions; therefore, secondary PM must be included in any assessment of the contribution of combustion systems to ambient PM concentrations. Low-volatility organic vapors emitted by combustion systems appear to be very important secondary PM precursors that are poorly accounted for in inventories and models. The review concludes by discussing the implications that the dynamic nature of these PM emissions have on source testing for emission inventory development and regulatory purposes. This discussion highlights important linkages between primary and secondary PM, which could lead to simplified certification test procedures while capturing the emission components that contribute most to atmospheric PM mass. PMID:21090549

  16. Combustion Characteristics of Oxy-fuel Burners for CO2 Capturing Boilers

    NASA Astrophysics Data System (ADS)

    Ahn, Joon; Kim, Hyouck Ju; Choi, Kyu Sung

    Oxy-fuel boilers have been developed to capture CO2 from the exhaust gas. A 50 kW class model burner has been developed and tested in a furnace type boiler. The burner has been scaled up to 0.5 and 3 MW class for fire-tube type boilers. The burners are commonly laid out in a coaxial type to effectively heat the combustion chamber of boilers. Burners are devised to support air and oxy-fuel combustion modes for the retrofitting scenario. FGR (flue gas recirculation) has been tried during the scale-up procedure. Oxy-fuel combustion yields stretched flame to uniformly heat the combustion chamber. It also provides the high CO2 concentration, which is over 90% in dry base. However, pure oxy-fuel combustion increases NO concentration, because of the reduced flow rate. The FGR can suppress the thermal NOx induced by the infiltration of the air.

  17. A Two-Dimensional Multiphase Model of Biofilm Formation in Microfluidic Chambers.

    PubMed

    Whidden, Mark; Cogan, Nick; Donahue, Matt; Navarrete, Fernando; De La Fuente, Leonardo

    2015-12-01

    The bacterial pathogen Xylella fastidiosa is the causal agent of many pathological conditions of economically important agricultural crops. There is no known cure for X. fastidiosa diseases, and management of the problem is based solely in controlling the population of insect vectors, which is somewhat effective. The bacterium causes disease by forming biofilms inside the vascular system of the plant, a process that is poorly understood. In microfluidic chambers, used as artificial xylem vessels, this bacterium has been observed to reproducibly cluster into a distinct, regular pattern of aggregates, spatially separated by channels of non-biofilm components. We develop a multiphase model in two dimensions, which recapitulates this spatial patterning, suggesting that bacterial growth and attachment/detachment processes are strongly influential modulators of these patterns. This indicates plausible strategies, such as the addition of metals and chelators, for mitigating the severity of diseases induced by this bacterial pathogen. PMID:26621357

  18. Temperature field simulation with stratification model of magma chamber under Los Humeros Caldera, Puebla, Mexico

    SciTech Connect

    Verma, M.P.; Verma, S.P.; Sanvicente, H. )

    1990-01-01

    A simulation of the temperature field underlying Los Humeros caldera is obtained through numerical solution of the energy-conservation equation for a conductive heat flow process. The up-date information on geological, geochemical, geophysical and geochronological studies is used to estimate the parameters of the internal structure of the caldera. The simulation is carried out under a model of the stratification of a magma chamber. The existence of such a stratification is supported by geological and geochemical evidence. The boundary conditions, the equality of temperature and heat flux are programmed in the numeric solution of the energy-conservation equation by considering the boundary of a very small, finite thickness and smoothing the temperature curve at every step of calculation.

  19. STE thrust chamber technology: Main injector technology program and nozzle Advanced Development Program (ADP)

    NASA Technical Reports Server (NTRS)

    1993-01-01

    The purpose of the STME Main Injector Program was to enhance the technology base for the large-scale main injector-combustor system of oxygen-hydrogen booster engines in the areas of combustion efficiency, chamber heating rates, and combustion stability. The initial task of the Main Injector Program, focused on analysis and theoretical predictions using existing models, was complemented by the design, fabrication, and test at MSFC of a subscale calorimetric, 40,000-pound thrust class, axisymmetric thrust chamber operating at approximately 2,250 psi and a 7:1 expansion ratio. Test results were used to further define combustion stability bounds, combustion efficiency, and heating rates using a large injector scale similar to the Pratt & Whitney (P&W) STME main injector design configuration including the tangential entry swirl coaxial injection elements. The subscale combustion data was used to verify and refine analytical modeling simulation and extend the database range to guide the design of the large-scale system main injector. The subscale injector design incorporated fuel and oxidizer flow area control features which could be varied; this allowed testing of several design points so that the STME conditions could be bracketed. The subscale injector design also incorporated high-reliability and low-cost fabrication techniques such as a one-piece electrical discharged machined (EDMed) interpropellant plate. Both subscale and large-scale injectors incorporated outer row injector elements with scarfed tip features to allow evaluation of reduced heating rates to the combustion chamber.

  20. Coal-water slurry fuel internal combustion engine and method for operating same

    DOEpatents

    McMillian, Michael H. (Fairmont, WV)

    1992-01-01

    An internal combustion engine fueled with a coal-water slurry is described. About 90 percent of the coal-water slurry charge utilized in the power cycle of the engine is directly injected into the main combustion chamber where it is ignited by a hot stream of combustion gases discharged from a pilot combustion chamber of a size less than about 10 percent of the total clearance volume of main combustion chamber with the piston at top dead center. The stream of hot combustion gases is provided by injecting less than about 10 percent of the total coal-water slurry charge into the pilot combustion chamber and using a portion of the air from the main combustion chamber that has been heated by the walls defining the pilot combustion chamber as the ignition source for the coal-water slurry injected into the pilot combustion chamber.

  1. Combustion & Health 

    E-print Network

    Hamilton, W.

    2012-01-01

    Winifred J. Hamilton, PhD, SM Clear Air Through Energy Efficiency (CATEE) Galveston, TX October 9?11, 2012 FFCOMBUSTION & HEALTH FFCOMBUSTION: THE THREAT ? Biggest threat to world ecosystems (and to human health) ? Combustion of fossil fuels... and strategies to reduce GHG ? Reduce CO2 emissions by 50% by 2030 ? Reduction in PM2.5 deaths greatly offset costs in all models FFCOMBUSTION & HEALTH FFCOMBUSTION: PM EXPOSURE ? Combustion is source of most concern ? Health considerations ? Size...

  2. Compensating for wall effects in IAQ (indoor air quality) chamber tests by mathematical modeling. Report for June 1986-February 1987

    SciTech Connect

    Dunn, J.E.; Tichenor, B.A.

    1987-04-01

    The paper presents mechanistic mathematical models that account for two phenomena: interior surfaces of a state-of-the-art emissions test chamber acting as a transient sink for organic emissions; and the effect of increasing chamber concentration on the emission rate of the source. As a consequence of this mathematical development, a source emission rate as a function of time and a steady-state emission rate factor are given precise definitions. Applications involve modeling 1,4 dichlorobenzene emission from moth crystals, and mixed emissions from latex caulk.

  3. Analytical Model for the Diffusion Process in a In-Situ Combustion Tube

    NASA Astrophysics Data System (ADS)

    Gutierrez, Patricia; Reyes, Adrian

    2015-03-01

    The in-situ combustion process (ISC) is basically an air or oxygen enriched gas injection oil recovery process, inside an extraction well. In contrast to a conventional gas injection process, an ISC process consists in using heat to create a combustion front that raises the fuel temperature, decreasing its viscosity, making extraction easier. The oil is taken toward the productor by means of a vigorous gas thrust as well as a water thrust. To improve and enhance this technique in the field wells, it has been widely perform experimental laboratory tests, in which an in-situ combustion tube is designed to simulate the extraction process. In the present work we propose to solve analytically the problem, with a parabolic partial differential equation associated to the convection-diffusion phenomenon, equation which describes the in-situ combustion process. The whole mathematical problem is established by completing this equation with the correspong boundary and initial conditions, the thickness of the combustion zone, flow velocity, and more parameters. The theoretically obtained results are compared with those reported in literature. We further, fit the parameter of our model to the mentioned data taken from the literature.

  4. Modelling Residential-Scale Combustion-Based Cogeneration in Building Simulation

    SciTech Connect

    Ferguson, A.; Kelly, N.; Weber, A.; Griffith, B.

    2009-03-01

    This article describes the development, calibration and validation of a combustion-cogeneration model for whole-building simulation. As part of IEA Annex 42, we proposed a parametric model for studying residentialscale cogeneration systems based on both Stirling and internal combustion engines. The model can predict the fuel use, thermal output and electrical generation of a cogeneration device in response to changing loads, coolant temperatures and flow rates, and control strategies. The model is now implemented in the publicly-available EnergyPlus, ESP-r and TRNSYS building simulation programs. We vetted all three implementations using a comprehensive comparative testing suite, and validated the model's theoretical basis through comparison to measured data. The results demonstrate acceptable-to-excellent agreement, and suggest the model can be used with confidence when studying the energy performance of cogeneration equipment in non-condensing operation.

  5. Comparison of direct and indirect combustion noise mechanisms in a model combustor

    E-print Network

    Nicoud, Franck

    aircraft design in order to meet the increasingly restrictive rules about noise reduction. While drastic reComparison of direct and indirect combustion noise mechanisms in a model combustor M. Leyko SNECMA, France Core-noise in aero-engines is due to two main mechanisms: direct com- bustion noise, which

  6. Dynamic Modeling of Combustion and Gas Exchange Processes for Controlled Auto-Ignition Engines

    E-print Network

    Cambridge, University of

    combustion such as intake air heating, increased compres- sion ratios and Exhaust Gas Recirculation [6]. All-zone models and it persists between multiple cycles, enabling the capture of the cycle-to-cycle exhaust gas was found. Con- trolled Auto-Ignition was attained by diluting the mixture with exhaust gas trapped

  7. Modeling of Diesel Combustion, Soot and NO Emissions Based on a Modified Eddy Dissipation Concept

    E-print Network

    Im, Hong G.

    and soot emissions modeling, computational diesel engine simulations, eddy dissipation concept #12 ignition, combustion, NOx and soot emissions over a wide range of operating conditions in a diesel engine simulations of physical and chemical processes within a diesel engine remain a challenge due to the many

  8. Full System Model of Magnetron Sputter Chamber - Proof-of-Principle Study

    SciTech Connect

    Walton, C; Gilmer, G; Zepeda-Ruiz, L; Wemhoff, A; Barbee, T

    2007-05-04

    The lack of detailed knowledge of internal process conditions remains a key challenge in magnetron sputtering, both for chamber design and for process development. Fundamental information such as the pressure and temperature distribution of the sputter gas, and the energies and arrival angles of the sputtered atoms and other energetic species is often missing, or is only estimated from general formulas. However, open-source or low-cost tools are available for modeling most steps of the sputter process, which can give more accurate and complete data than textbook estimates, using only desktop computations. To get a better understanding of magnetron sputtering, we have collected existing models for the 5 major process steps: the input and distribution of the neutral background gas using Direct Simulation Monte Carlo (DSMC), dynamics of the plasma using Particle In Cell-Monte Carlo Collision (PIC-MCC), impact of ions on the target using molecular dynamics (MD), transport of sputtered atoms to the substrate using DSMC, and growth of the film using hybrid Kinetic Monte Carlo (KMC) and MD methods. Models have been tested against experimental measurements. For example, gas rarefaction as observed by Rossnagel and others has been reproduced, and it is associated with a local pressure increase of {approx}50% which may strongly influence film properties such as stress. Results on energies and arrival angles of sputtered atoms and reflected gas neutrals are applied to the Kinetic Monte Carlo simulation of film growth. Model results and applications to growth of dense Cu and Be films are presented.

  9. Experimental study and modelling of char combustion under fluidized bed conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Yongzhe; Xu, Xiangdong; Wirsum, Manfred C.; Hamel, Stefan; Fett, Franz N.

    1998-12-01

    The combustion behavior of chars from two Chinese coals has been investigated in a laboratory scale bubbling fluidized bed system in Siegen University, Germany. Experimental equipment and method are introduced. The ‘shrinking-core’ model and the ‘shrinking-particle’ model were employed to evaluate the kinetic parameters. The results indicated that the char conversion process of these two coals can be well described by the two models.

  10. Measurement and analysis of combustion response to transverse combustion instability

    NASA Astrophysics Data System (ADS)

    Pomeroy, Brian R.

    This research aimed to gain a better understanding of the response of a gas-centered swirl coaxial injector to transverse combustion instability. The goals of the research were to develop a combustion chamber that would be able to spontaneously produce transverse combustion instability at elevated pressures and temperatures. Methods were also developed to analyze high-speed video images to understand the response of the injector. A combustion chamber was designed that produced high levels of instabilities. The chamber was capable of pressures as high as 1034 kPa (150 psi) and operated using decomposed 90% hydrogen peroxide and JP-8. The chamber used an array of seven gas-centered swirl coaxial injectors that exhibited linear instability to drive the transverse oscillations. The injector elements would operate in a monopropellant configuration flowing only decomposed hydrogen peroxide or in a bipropellant configuration. The location of the bipropellant injectors could be varied to change the level of the instability in the chamber from 10% of the chamber pressure up to 70% of the chamber pressure. A study element was placed in the center of the chamber where it was observed simultaneously by two high-speed video cameras which recorded a backlit video to show the location of the fuel spray and the location of the emitted CH* chemiluminescence. The videos were synchronized with high frequency pressure measurements to gain a full understanding of the physics in the combustion chamber. Results showed that the study element was coupled with the first mode velocity wave. This was expected due to the first mode velocity anti-node being located in the center of the chamber. The velocity is an absolute maximum twice during each cycle so the coupling with the second mode pressure was also investigated showing a possible coupling with both the velocity and pressure. The results of the first mode velocity showed that, as the velocity wave traveled through the chamber, the fuel spray was first displaced into an oxidizer rich region and secondly followed by a reaction in the direction of travel of the velocity wave as the peak velocity traveled through the region. The deflection into the oxidizer rich region was especially apparent in high-level instabilities. In low-level instabilities, the velocity wave was not strong enough to fully displace the fuel, and instead the oxidizer core was deflected into the fuel annulus causing a reaction in the direction of travel of the velocity wave. Neighboring oxidizer only injectors caused a lower reaction upstream as the neighboring oxidizer was deflected into the fuel annulus. The region of the fluctuating emitted light agreed well in size, shape and location with a correlation between the first mode velocity and combustion leading to the conclusion that the first mode is highly coupled with velocity. The second mode variance did not agree well with either the velocity or pressure correlation leading to a conclusion that it is coupled with both velocity and pressure. When comparing the variance to the pressure or velocity correlation, parts of the variance compared in shape and location to the pressure or velocity correlation, however, this was not true for all regions of response. This leads to a conclusion that both the pressure and velocity can be affecting the second mode. The second mode chemiluminescence emission occurs when the velocity is nearly zero in the chamber leading to the reaction to not be deflected and occurring downstream of the injector. At the same time, the second mode pressure is a minimum so an increase in mass flow could be responsible for the increased reaction. The methods and combustion chamber used to study the response of an injector can be used in the future to study any injector or combination of injectors placed at various locations in the chamber to study pressure or velocity coupling. The chemiluminescence data can be used to develop transfer functions for use in low fidelity computational models and can be used to validate high fidelity CFD.

  11. TRACE GAS EMISSIONS IN CHAMBERS: A NON-STEADY-STATE DIFFUSION MODEL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Non-steady-state (NSS) chambers are widely used to measure trace gas emissions from the Earth’s surface in the atmosphere. Unfortunately, traditional interpretations of time-dependent chamber concentrations often systematically underestimate predeployment exchange rates because they do not accuratel...

  12. Measurement and modelling of oxygenated organic compounds from smoldering combustion of biomass

    SciTech Connect

    McKenzie, L.M.; Richards, G.N.

    1995-12-01

    Biomass fires emit a myriad of compounds, some of which are toxic and/or globally significant as photochemically reactive, tropospheric trace gases, greenhouse gases and precursors to stratospheric ozone-destroying radicals. 35 oxygenated organic compounds in condensed (-45{degrees}C) smoke from 29 bench scale fires of ponderosa pine sapwood, needles, bark, litter, duff, and humus have been identified and quantified. These fires ranged from flaming to low intensity smoldering. In addition, five low intensity fires of intact ponderosa pine forest floor (litter, duff, and humus) were carried out on a larger scale in a combustion chamber. The condensates were analyzed by gas chromatography/mass spectrometry and the gas phase was analyzed by gas chromatography/flame ionization detection. Acetic acid, vinyl acetate and acetol were major condensable emissions. The dependence of oxygenated organic emissions on fuel chemistry and combustion efficiency has been investigated, along with correlations between emissions. Molar emission ratios of individual compounds to CO have been calculated and used to estimate possible exposure levels for wildland firefighters.

  13. Development of an Efficient CFD Model for Nuclear Thermal Thrust Chamber Assembly Design

    NASA Technical Reports Server (NTRS)

    Cheng, Gary; Ito, Yasushi; Ross, Doug; Chen, Yen-Sen; Wang, Ten-See

    2007-01-01

    The objective of this effort is to develop an efficient and accurate computational methodology to predict both detailed thermo-fluid environments and global characteristics of the internal ballistics for a hypothetical solid-core nuclear thermal thrust chamber assembly (NTTCA). Several numerical and multi-physics thermo-fluid models, such as real fluid, chemically reacting, turbulence, conjugate heat transfer, porosity, and power generation, were incorporated into an unstructured-grid, pressure-based computational fluid dynamics solver as the underlying computational methodology. The numerical simulations of detailed thermo-fluid environment of a single flow element provide a mechanism to estimate the thermal stress and possible occurrence of the mid-section corrosion of the solid core. In addition, the numerical results of the detailed simulation were employed to fine tune the porosity model mimic the pressure drop and thermal load of the coolant flow through a single flow element. The use of the tuned porosity model enables an efficient simulation of the entire NTTCA system, and evaluating its performance during the design cycle.

  14. Modeling engine oil vaporization and transport of the oil vapor in the piston ring pack on internal combustion engines

    E-print Network

    Cho, Yeunwoo, 1973-

    2004-01-01

    A model was developed to study engine oil vaporization and oil vapor transport in the piston ring pack of internal combustion engines. With the assumption that the multi-grade oil can be modeled as a compound of several ...

  15. Rotating Detonation Combustion: A Computational Study for Stationary Power Generation

    NASA Astrophysics Data System (ADS)

    Escobar, Sergio

    The increased availability of gaseous fossil fuels in The US has led to the substantial growth of stationary Gas Turbine (GT) usage for electrical power generation. In fact, from 2013 to 2104, out of the 11 Tera Watts-hour per day produced from fossil fuels, approximately 27% was generated through the combustion of natural gas in stationary GT. The thermodynamic efficiency for simple-cycle GT has increased from 20% to 40% during the last six decades, mainly due to research and development in the fields of combustion science, material science and machine design. However, additional improvements have become more costly and more difficult to obtain as technology is further refined. An alternative to improve GT thermal efficiency is the implementation of a combustion regime leading to pressure-gain; rather than pressure loss across the combustor. One concept being considered for such purpose is Rotating Detonation Combustion (RDC). RDC refers to a combustion regime in which a detonation wave propagates continuously in the azimuthal direction of a cylindrical annular chamber. In RDC, the fuel and oxidizer, injected from separated streams, are mixed near the injection plane and are then consumed by the detonation front traveling inside the annular gap of the combustion chamber. The detonation products then expand in the azimuthal and axial direction away from the detonation front and exit through the combustion chamber outlet. In the present study Computational Fluid Dynamics (CFD) is used to predict the performance of Rotating Detonation Combustion (RDC) at operating conditions relevant to GT applications. As part of this study, a modeling strategy for RDC simulations was developed. The validation of the model was performed using benchmark cases with different levels of complexity. First, 2D simulations of non-reactive shock tube and detonation tubes were performed. The numerical predictions that were obtained using different modeling parameters were compared with analytical solutions in order to quantify the numerical error in the simulations. Additionally, experimental data from laboratory scale combustors was used to validate 2D and 3D numerical simulations. The effects of different modeling parameters on RDC predictions was also studied. The validated simulation strategy was then used to assess the performance of RDC for different combustion chamber geometries and operating conditions relevant to GT applications. As a result, the limiting conditions for which continuous detonation and pressure gain combustion can be achieved were predicted and the effect of operating conditions on flow structures and RDC performance was assessed. The modeling strategy and the results from this study could be further used to design more efficient and more stable RDC systems.

  16. Effects of primary breakup modeling on spray and combustion characteristics of compression ignition engines

    SciTech Connect

    Som, S.; Aggarwal, S.K.

    2010-06-15

    Injector flow dynamics and primary breakup processes are known to play a pivotal role in determining combustion and emissions in diesel engines. In the present study, we examine the effects of primary breakup modeling on the spray and combustion characteristics under diesel engine conditions. The commonly used KH model, which considers the aerodynamically induced breakup based on the Kelvin-Helmholtz instability, is modified to include the effects of cavitation and turbulence generated inside the injector. The KH model and the new (KH-ACT) model are extensively evaluated by performing 3-D time-dependent simulations with detailed chemistry under diesel engine conditions. Results indicate that the inclusion of cavitation and turbulence enhances primary breakup, leading to smaller droplet sizes, decrease in liquid penetration, and increase in the radial dispersion of spray. Predictions are compared with measurements for non-evaporating and evaporating sprays, as well as with flame measurements. While both the models are able to reproduce the experimentally observed global spray and combustion characteristics, predictions using the KH-ACT model exhibit closer agreement with measurements in terms of liquid penetration, cone angle, spray axial velocity, and liquid mass distribution for non-evaporating sprays. Similarly, the KH-ACT model leads to better agreement with respect to the liquid length and vapor penetration distance for evaporating sprays, and with respect to the flame lift-off location for combusting sprays. The improved agreement is attributed to the ability of the new model to account for the effects of turbulence and cavitation generated inside the injector, which enhance the primary breakup. Results further indicate that the combustion under diesel engine conditions is characterized by a double-flame structure with a rich premixed reaction zone near the flame stabilization region and a non-premixed reaction zone further downstream. This flame structure is consistent with the Dec's model for diesel engine combustion (Dec, 1997), and well captured by a newly developed flame index based on the scalar product of CO and O{sub 2} mass fraction gradients. (author)

  17. Exposure chamber

    DOEpatents

    Moss, Owen R. (Kennewick, WA)

    1980-01-01

    A chamber for exposing animals, plants, or materials to air containing gases or aerosols is so constructed that catch pans for animal excrement, for example, serve to aid the uniform distribution of air throughout the chamber instead of constituting obstacles as has been the case in prior animal exposure chambers. The chamber comprises the usual imperforate top, bottom and side walls. Within the chamber, cages and their associated pans are arranged in two columns. The pans are spaced horizontally from the walls of the chamber in all directions. Corresponding pans of the two columns are also spaced horizontally from each other. Preferably the pans of one column are also spaced vertically from corresponding pans of the other column. Air is introduced into the top of the chamber and withdrawn from the bottom. The general flow of air is therefore vertical. The effect of the horizontal pans is based on the fact that a gas flowing past the edge of a flat plate that is perpendicular to the flow forms a wave on the upstream side of the plate. Air flows downwardly between the chamber walls and the outer edges of the pan. It also flows downwardly between the inner edges of the pans of the two columns. It has been found that when the air carries aerosol particles, these particles are substantially uniformly distributed throughout the chamber.

  18. Computational Model Tracking Primary Electrons, Secondary Electrons, and Ions in the Discharge Chamber of an Ion Engine

    NASA Technical Reports Server (NTRS)

    Mahalingam, Sudhakar; Menart, James A.

    2005-01-01

    Computational modeling of the plasma located in the discharge chamber of an ion engine is an important activity so that the development and design of the next generation of ion engines may be enhanced. In this work a computational tool called XOOPIC is used to model the primary electrons, secondary electrons, and ions inside the discharge chamber. The details of this computational tool are discussed in this paper. Preliminary results from XOOPIC are presented. The results presented include particle number density distributions for the primary electrons, the secondary electrons, and the ions. In addition the total number of a particular particle in the discharge chamber as a function of time, electric potential maps and magnetic field maps are presented. A primary electron number density plot from PRIMA is given in this paper so that the results of XOOPIC can be compared to it. PRIMA is a computer code that the present investigators have used in much of their previous work that provides results that compare well to experimental results. PRIMA only models the primary electrons in the discharge chamber. Modeling ions and secondary electrons, as well as the primary electrons, will greatly increase our ability to predict different characteristics of the plasma discharge used in an ion engine.

  19. Reduced-order modeling and active control of dry-low-emission combustion

    NASA Astrophysics Data System (ADS)

    Yi, Tongxun

    This dissertation is a complementary experimental and theoretical investigation of combustion instability and lean blowout (LBO) in dry-low-emission (DLE) gas turbine engines, aiming to understand the fundamental mechanisms and shed light on active combustion control. Combustion instability involves complicated physicochemical processes, and many of the underlying mechanisms remain unknown, despite extensive research in the past several decades. A practical control system must be able to achieve satisfactory control performances in the presence of large uncertainties, large variations, and even unknown system dynamics. Toward this goal, an observer-based controller, capable of attenuating multiple unstable modes with unknown characteristics, is developed. A mechanism suitable for online prediction of the safety margin to the onset of combustion instability is presented, which does not require knowing the unstable frequencies. The shortage of a reliable, high-frequency, proportional fuel actuator is a major technical challenge for active combustion control. A complementary theoretical and experimental study is performed on a pump-style, high-frequency, magnetostrictive fuel actuator. Improvements to the fuel setup have been made according to the model predictions, which have been experimentally shown to be beneficial to combustion instability control. The second part of this dissertation is about modeling, prediction, and control of lean blowout. The experimentally observed, "intensified", low frequency, near-LBO combustion oscillations have been used as incipient LBO precursors, and are characterized as low-dimension chaotic behavior in the present study. The normalized chemiluminescence RMS and the normalized cumulative duration of LBO precursor events are recommended for LBO prediction in generic gas turbine engines. Linear stability analysis shows that, with decreasing equivalence ratios, a complex conjugate pair of eigenvalues emerges from three negative real ones, moves left toward the right half phase plane, and finally crosses the imaginary axis. Model predictions qualitatively and even quantitatively match the experiments. Simulation of the nonlinear WSR models shows the "triggered instability" which is similar to that in rocket motors. It is numerically demonstrated that zero-mean small-amplitude fuel modulations based on modern feedback control principles, can be very effective in strengthening the flame's robustness to external disturbances without exacerbating the overall emissions. Experimental demonstrations are suggested for future research.

  20. Flame structure measurements and modeling analysis of isolated aluminum particle combustion

    NASA Astrophysics Data System (ADS)

    Bucher, Paulus

    1998-12-01

    With the goal of understanding the behavior of aluminum in solid propellant combustion, the flame structure of isolated aluminum particles burning in a variety of controlled environments has been examined experimentally and computationally. Spherical aluminum particles of 220 mum diameter were generated continuously by mechanical chopping of wire strands and Co2 laser heating, and were released into cold, quiescent environments consisting of pure CO2,H2O, N2O,CO, and mixtures of 21% O2/Ar, 50% O2/Ar and 21% O2/N2. Spatially resolved species and temperature measurements were carried out during a quasi-steady, near spherically symmetric burning period using an in situ two-excitation-line ratiometric planar laser-induced fluorescence (PLIF) technique. The radial distributions of the condensed-phase products formed in the flame, and the composition within quenched particles, were measured using off-line electron probe microanalysis (EPMA). To aid the interpretation of the experimental results, a detailed local equilibrium numerical model of aluminum particle combustion has been developed. The important aspect of the model is that neither thin flame sheet, nor thin condensation sheet assumptions were invoked. In accord with Glassman's Criterion for the vapor-phase combustion of metals, aluminum particles burned with an intensely luminous, detached flame in all atmospheres studied, with the exception of CO. During quasi-steady particle combustion, AlO was a gas-phase intermediate with non-zero concentrations on the particle surface. The 21% O2/Ar, 21% O2/N2 and N2O combustion systems attained a nearly constant flame temperature over significant radial distances. These systems were thermodynamically expected to reach a "limit" temperature because the heat of combustion is sufficient to partially decompose Al2O3. In contrast, the temperature profile for combustion in CO2 did not exhibit a plateau, but had the shape of a classical diffusion flame. Except in the CO atmosphere, spherical particles between 100--200 nm, consisting of stoichiometric Al2O3, were produced in the detached envelope at r/rs > 2. The presence of N in the combustion gases significantly altered the flame structure, and also promoted the formation of large (5--60 mum) residual particles. Qualitatively, model and experiment were in excellent agreement for combustion in an air-equivalent mixture of O2 and Ar. The model predicted a distributed reaction zone in which the flame temperature was controlled by the decomposing condensed-phase product. The model also predicted the pressure dependence of the mass burning rate found in the literature. Contrary to previous explanations, however, this pressure sensitivity was found to originate from the pressure dependence of the gasification temperature of Al and decomposition temperature of Al2O3 l . Model results obtained for aluminum combustion in pure CO2 agreed less well with the experimental data, and hence indicated the importance of sub-processes such as the nucleation, coagulation, growth and migration of condensed-phase oxides.

  1. Combustion Instability in an Acid-Heptane Rocket with a Pressurized-Gas Propellant Pumping System

    NASA Technical Reports Server (NTRS)

    Tischler, Adelbert O.; Bellman, Donald R.

    1951-01-01

    Results of experimental measurements of low-frequency combustion instability of a 300-pound thrust acid-heptane rocket engine were compared to the trends predicted by an analysis of combustion instability in a rocket engine with a pressurized-gas propellant pumping system. The simplified analysis, which assumes a monopropellant model, was based on the concept of a combustion the delay occurring from the moment of propellant injection to the moment of propellant combustion. This combustion time delay was experimentally measured; the experimental values were of approximately half the magnitude predicted by the analysis. The pressure-fluctuation frequency for a rocket engine with a characteristic length of 100 inches and operated at a combustion-chamber pressure of 280 pounds per square inch absolute was 38 cycles per second; the analysis indicated. a frequency of 37 cycles per second. Increasing combustion-chamber characteristic length decreased the pressure-fluctuation frequency, in conformity to the analysis. Increasing the chamber operating pressure or increasing the injector pressure drop increased the frequency. These latter two effects are contrary to the analysis; the discrepancies are attributed to the conflict between the assumptions made to simplify the analysis and the experimental conditions. Oxidant-fuel ratio had no apparent effect on the experimentally measured pressure-fluctuation frequency for acid-heptane ratios from 3.0 to 7.0. The frequencies decreased with increased amplitude of the combustion-chamber pressure variations. The analysis indicated that if the combustion time delay were sufficiently short, low-frequency combustion instability would be eliminated.

  2. PROGRESS IN DETAILED KINETIC MODELING OF THE COMBUSTION OF OXYGENATED COMPONENTS OF BIOFUELS

    PubMed Central

    Sy Tran, Luc; Sirjean, Baptiste; Glaude, Pierre-Alexandre; Fournet, René; Battin-Leclerc, Frédérique

    2013-01-01

    Due to growing environmental concerns and diminishing petroleum reserves, a wide range of oxygenated species has been proposed as possible substitutes to fossil fuels: alcohols, methyl esters, acyclic and cyclic ethers. After a short review the major detailed kinetic models already proposed in the literature for the combustion of these molecules, the specific classes of reactions considered for modeling the oxidation of acyclic and cyclic oxygenated molecules respectively, are detailed. PMID:23700355

  3. Nuclear, optical, and magnetic resonance imaging in a mouse mammary window chamber model

    NASA Astrophysics Data System (ADS)

    Leung, Hui Min; Schafer, Rachel; Gmitro, Arthur F.

    2014-09-01

    An orthotopic mouse mammary window chamber (MWC) model has been developed for multimodal in-vivo functional and anatomical imaging of breast cancer xenografts. Capabilities to image numerous physiological aspects of the same tumor microenvironment over time has important applications such as in experiments studying the efficacies of therapeutic interventions, improvement of cancer detection and investigating basic cancer biology. The compatibility of this MWC model with optical, nuclear and magnetic resonance imaging (MRI) makes it possible to perform a multitude of studies ranging from cellular imaging to whole body imaging. Thus, the MWC represents a powerful tool for breast cancer research. Here, two imaging applications are highlighted, namely the nuclear imaging of glycolytic metabolism with 18FFDG and MRI of tissue perfusion. Nuclear imaging is performed with the use of a 3?m thin phosphor scintillator placed directly in contact with the tissue and visible light from the scintillation is directly detected in a low noise, light tight imaging system. Tissue perfusion is imaged either qualitatively with a dynamic contrast enhancement (DCE) MRI technique or quantitatively with an arterial spin labeling flow-sensitive alternating inversion recovery-rapid acquisition with relaxation enhancement (FAIR-RARE) technique.

  4. Effects of Geometric Variations on Lift Augmentation of Simple-plenum-chamber Ground-effect Models

    NASA Technical Reports Server (NTRS)

    Davenport, Edwin E.

    1961-01-01

    Considerable interest has been shown during recent years in ground-effect vehicles. Of the various types proposed, the simple-plenum-chamber vehicle has indicated promise because, although the lift augmentation obtainable appears to be less than that of an annular jet, it may be somewhat less complicated structurally. The present investigation was undertaken to study the effects of some geometric variations upon lift augmentation of a simple plenum chamber within ground proximity. The variables included the ratio inlet area to exit area, plenum-chamber depth, and entrance configuration. An optimum plenum-chamber depth appeared to be between 3 and 10 percent of the plenum-chamber diameter with a ratio of inlet diameter to plenum-chamber diameter of 0.15 for the range of plenum-chamber depths investigated. The most important effect of multiple inlets was the elimination of negative lift augmentation, which was experienced with single sharp-edged inlets, at intermediate heights. Installation of a flared inlet and a turning-vane assembly improved lift augmentation of a single-inlet configuration at intermediate heights.

  5. Improved Modeling of Finite-Rate Turbulent Combustion Processes in Research Combustors

    NASA Technical Reports Server (NTRS)

    VanOverbeke, Thomas J.

    1998-01-01

    The objective of this thesis is to further develop and test a stochastic model of turbulent combustion in recirculating flows. There is a requirement to increase the accuracy of multi-dimensional combustion predictions. As turbulence affects reaction rates, this interaction must be more accurately evaluated. In this work a more physically correct way of handling the interaction of turbulence on combustion is further developed and tested. As turbulence involves randomness, stochastic modeling is used. Averaged values such as temperature and species concentration are found by integrating the probability density function (pdf) over the range of the scalar. The model in this work does not assume the pdf type, but solves for the evolution of the pdf using the Monte Carlo solution technique. The model is further developed by including a more robust reaction solver, by using accurate thermodynamics and by more accurate transport elements. The stochastic method is used with Semi-Implicit Method for Pressure-Linked Equations. The SIMPLE method is used to solve for velocity, pressure, turbulent kinetic energy and dissipation. The pdf solver solves for temperature and species concentration. Thus, the method is partially familiar to combustor engineers. The method is compared to benchmark experimental data and baseline calculations. The baseline method was tested on isothermal flows, evaporating sprays and combusting sprays. Pdf and baseline predictions were performed for three diffusion flames and one premixed flame. The pdf method predicted lower combustion rates than the baseline method in agreement with the data, except for the premixed flame. The baseline and stochastic predictions bounded the experimental data for the premixed flame. The use of a continuous mixing model or relax to mean mixing model had little effect on the prediction of average temperature. Two grids were used in a hydrogen diffusion flame simulation. Grid density did not effect the predictions except for peak temperature and tangential velocity. The hybrid pdf method did take longer and required more memory, but has a theoretical basis to extend to many reaction steps which cannot be said of current turbulent combustion models.

  6. Experimental and Modeling Studies of the Combustion Characteristics of Conventional and Alternative Jet Fuels. Final Report

    NASA Technical Reports Server (NTRS)

    Meeks, Ellen; Naik, Chitral V.; Puduppakkam, Karthik V.; Modak, Abhijit; Egolfopoulos, Fokion N.; Tsotsis, Theo; Westbrook, Charles K.

    2011-01-01

    The objectives of this project have been to develop a comprehensive set of fundamental data regarding the combustion behavior of jet fuels and appropriately associated model fuels. Based on the fundamental study results, an auxiliary objective was to identify differentiating characteristics of molecular fuel components that can be used to explain different fuel behavior and that may ultimately be used in the planning and design of optimal fuel-production processes. The fuels studied in this project were Fischer-Tropsch (F-T) fuels and biomass-derived jet fuels that meet certain specifications of currently used jet propulsion applications. Prior to this project, there were no systematic experimental flame data available for such fuels. One of the key goals has been to generate such data, and to use this data in developing and verifying effective kinetic models. The models have then been reduced through automated means to enable multidimensional simulation of the combustion characteristics of such fuels in real combustors. Such reliable kinetic models, validated against fundamental data derived from laminar flames using idealized flow models, are key to the development and design of optimal combustors and fuels. The models provide direct information about the relative contribution of different molecular constituents to the fuel performance and can be used to assess both combustion and emissions characteristics.

  7. An extended supersonic combustion model for the dynamic analysis of hypersonic vehicles

    NASA Technical Reports Server (NTRS)

    Bossard, J. A.; Peck, R. E.; Schmidt, D. K.

    1993-01-01

    The development of an advanced dynamic model for aeroelastic hypersonic vehicles powered by air breathing engines requires an adequate engine model. This report provides a discussion of some of the more important features of supersonic combustion and their relevance to the analysis and design of supersonic ramjet engines. Of particular interest are those aspects of combustion that impact the control of the process. Furthermore, the report summarizes efforts to enhance the aeropropulsive/aeroelastic dynamic model developed at the Aerospace Research Center of Arizona State University by focusing on combustion and improved modeling of this flow. The expanded supersonic combustor model described here has the capability to model the effects of friction, area change, and mass addition, in addition to the heat addition process. A comparison is made of the results from four cases: (1) heat addition only; (2) heat addition plus friction; (3) heat addition, friction, and area reduction, and (4) heat addition, friction, area reduction, and mass addition. The relative impact of these effects on the Mach number, static temperature, and static pressure distributions within the combustor are then shown. Finally, the effects of frozen versus equilibrium flow conditions within the exhaust plume is discussed.

  8. Stabilization Of Combustion Of Sprayed Fuel

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E.; Jan, Darrell L.

    1995-01-01

    Several modifications of nozzle spraying liquid propellant into combustion chamber proposed to stabilize combustion. Proposed changes in design of nozzle alter flow field in combustion chamber, according to fluid-mechanical principles, in such way as to suppress oscillations. Various alternative nozzle configurations include bluff or toroidal body to generate turbulence. Other features helping to suppress oscillations include down-stream recirculation zones, baffles, and damping cavities. Similar modifications help to suppress oscillations in industrial combustion chambers and in commercial and domestic oil-burning furnaces.

  9. Wire chamber

    DOEpatents

    Atac, Muzaffer (Wheaton, IL)

    1989-01-01

    A wire chamber or proportional counter device, such as Geiger-Mueller tube or drift chamber, improved with a gas mixture providing a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor.

  10. Ignition and combustion characteristics of metallized propellants, phase 2

    NASA Technical Reports Server (NTRS)

    Mueller, D. C.; Turns, Stephen R.

    1994-01-01

    Secondary atomization and ignition characteristics of aluminum/hydrocarbon gel propellants were investigated. Models of gel droplet shell formation were applied to aluminum/liquid hydrocarbon propellants to examine the effects of solid loading and ultimate particle size on the minimum droplet diameter permitting secondary atomization. A one-dimensional model of a gel-fueled rocket combustion chamber was developed. A model for radiant heat transfer from hot aluminum oxide particles to the chamber walls is included. A two-dimensional, two-phase nozzle code was used to estimate nozzle two-phase losses and overall engine performance.

  11. Combustion performance and scale effect from N2O/HTPB hybrid rocket motor simulations

    NASA Astrophysics Data System (ADS)

    Shan, Fanli; Hou, Lingyun; Piao, Ying

    2013-04-01

    HRM code for the simulation of N2O/HTPB hybrid rocket motor operation and scale effect analysis has been developed. This code can be used to calculate motor thrust and distributions of physical properties inside the combustion chamber and nozzle during the operational phase by solving the unsteady Navier-Stokes equations using a corrected compressible difference scheme and a two-step, five species combustion model. A dynamic fuel surface regression technique and a two-step calculation method together with the gas-solid coupling are applied in the calculation of fuel regression and the determination of combustion chamber wall profile as fuel regresses. Both the calculated motor thrust from start-up to shut-down mode and the combustion chamber wall profile after motor operation are in good agreements with experimental data. The fuel regression rate equation and the relation between fuel regression rate and axial distance have been derived. Analysis of results suggests improvements in combustion performance to the current hybrid rocket motor design and explains scale effects in the variation of fuel regression rate with combustion chamber diameter.

  12. A particulate model of solid waste incineration in a fluidized bed combining combustion and heavy metal vaporization

    SciTech Connect

    Mazza, G.; Falcoz, Q.; Gauthier, D.; Flamant, G.

    2009-11-15

    This study aims to develop a particulate model combining solid waste particle combustion and heavy metal vaporization from burning particles during MSW incineration in a fluidized bed. The original approach for this model combines an asymptotic combustion model for the carbonaceous solid combustion and a shrinking core model to describe the heavy metal vaporization. A parametric study is presented. The global metal vaporization process is strongly influenced by temperature. Internal mass transfer controls the metal vaporization rate at low temperatures. At high temperatures, the chemical reactions associated with particle combustion control the metal vaporization rate. A comparison between the simulation results and experimental data obtained with a laboratory-scale fluid bed incinerator and Cd-spiked particles shows that the heavy metal vaporization is correctly predicted by the model. The predictions are better at higher temperatures because of the temperature gradient inside the particle. Future development of the model will take this into account. (author)

  13. Heat regenerative external combustion engine

    NASA Astrophysics Data System (ADS)

    Duva, Anthony W.

    1993-03-01

    It is an object of the invention to provide an external combustion expander-type engine having improved efficiency. It is another object of the invention to provide an external combustion engine in which afterburning in the exhaust channel is substantially prevented. Yet another object of the invention is to provide an external combustion engine which is less noisy than an external combustion engine of conventional design. These and other objects of the invention will become more apparent from the following description. The above objects of the invention are realized by providing a heat regenerative external combustion engine. The heat regenerative external combustion engine of the invention comprises a combustion chamber for combusting a monopropellant fuel in order to form an energized gas. The energized gas is then passed through a rotary valve to a cylinder having a reciprocating piston disposed therein. The gas is spent in moving the piston, thereby driving a drive shaft.

  14. Modeling Vortex Cavitation Inception Delay in a Swirl Chamber by Polymer Injection

    NASA Astrophysics Data System (ADS)

    Ma, J.; Zhang, Q.; Hsiao, C. T.; Chahine, G. L.

    2011-11-01

    Experimental studies have shown tip vortex cavitation can be delayed with injection of drag reducing dilute polymer solutions. We present here numerical simulations conducted to understand the mechanisms responsible for cavitation suppression with local polymer injection. A canonical flow in a linear vortex chamber was simulated by using the NS solver, 3DYNAFS-VIS, equipped with a FENE-P viscoelastic model for the polymer solution and a transport equation to track its concentration. The simulation showed that injection of dilute polymer can delay cavitation inception at a much lower injection flow rate than needed with massive injection of water or a higher viscosity liquid. Injection of polymer increases the pressure along the vortex axis and a much earlier vortex breakdown created by the elasticity of the polymers appears to be responsible for the strong modification of the flow character. This results in a fast reduction of the rotational velocity, increase of the pressure, and delay of cavitation inception. The dependency of polymer effects on the injection flow rate and polymer concentration was also investigated, finding good consistency with experimental observations. ONR Contract N00014-04-C-0110, monitored by Dr. Ki-Han Kim.

  15. Assessment of the GECKO-A modeling tool using chamber observations for C12 alkanes

    NASA Astrophysics Data System (ADS)

    Aumont, B.; La, S.; Ouzebidour, F.; Valorso, R.; Mouchel-Vallon, C.; Camredon, M.; Lee-Taylor, J. M.; Hodzic, A.; Madronich, S.; Yee, L. D.; Loza, C. L.; Craven, J. S.; Zhang, X.; Seinfeld, J.

    2013-12-01

    Secondary Organic Aerosol (SOA) production and ageing is the result of atmospheric oxidation processes leading to the progressive formation of organic species with higher oxidation state and lower volatility. Explicit chemical mechanisms reflect our understanding of these multigenerational oxidation steps. Major uncertainties remain concerning the processes leading to SOA formation and the development, assessment and improvement of such explicit schemes is therefore a key issue. The development of explicit mechanism to describe the oxidation of long chain hydrocarbons is however a challenge. Indeed, explicit oxidation schemes involve a large number of reactions and secondary organic species, far exceeding the size of chemical schemes that can be written manually. The chemical mechanism generator GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) is a computer program designed to overcome this difficulty. GECKO-A generates gas phase oxidation schemes according to a prescribed protocol assigning reaction pathways and kinetics data on the basis of experimental data and structure-activity relationships. In this study, we examine the ability of the generated schemes to explain SOA formation observed in the Caltech Environmental Chambers from various C12 alkane isomers and under high NOx and low NOx conditions. First results show that the model overestimates both the SOA yields and the O/C ratios. Various sensitivity tests are performed to explore processes that might be responsible for these disagreements.

  16. New model of Mars surface irradiation for the climate simulation chamber 'Artificial Mars'

    NASA Astrophysics Data System (ADS)

    Tarasashvili, M. V.; Sabashvili, Sh. A.; Tsereteli, S. L.; Aleksidze, N. G.

    2013-04-01

    A new model of the Mars surface irradiation has been developed for the imitation of radiation-temperature parameters within Mars Climate Simulation Chamber (MCSC). In order to determine the values of annual and diurnal variations of the irradiance on the Martian surface, the Solar illumination E has been expressed by the distance r between the Sun and Mars and the Sun's altitude z in the Martian sky, along with its midday zenith distance z min. The arrangements of spring and autumn equinoxes as well as summer and winter solstice points in the Martian sky are discussed regarding the perihelion of Mars. Annual orbital points and variability of Solar z min for different planetary latitudes have been calculated for the 15 selected values of Mars's true anomaly, along with the illumination E for 12 hourly moments of Martian daytime on the Martian equator. These original calculations and the data which have been obtained are used for the construction of technical tools imitating variations of the surface irradiation and temperature within MCSC, programming of the supporting computer and the electric scheme, which provide proper remote control and set the environmental parameters that are analogues to the 24 hours 39 minutes circadian cycle on planet Mars. Spectral distribution as monochromatic irradiance, humidity control, atmospheric composition and other environmental parameters of planet Mars are also imitated and remotely controlled within MCSC, however, are not discussed in this particular article.

  17. Composition of fibrin glues significantly influences axial vascularization and degradation in isolation chamber model.

    PubMed

    Arkudas, Andreas; Pryymachuk, Galyna; Hoereth, Tobias; Beier, Justus P; Polykandriotis, Elias; Bleiziffer, Oliver; Gulle, Heinz; Horch, Raymund E; Kneser, Ulrich

    2012-07-01

    In this study, different fibrin sealants with varying concentrations of the fibrin components were evaluated in terms of matrix degradation and vascularization in the arteriovenous loop (AVL) model of the rat. An AVL was placed in a Teflon isolation chamber filled with 500 ?l fibrin gel. The matrix was composed of commercially available fibrin gels, namely Beriplast (Behring GmbH, Marburg, Germany) (group A), Evicel (Omrix Biopharmaceuticals S.A., Somerville, New Jersey, USA) (group B), Tisseel VH S/D (Baxter, Vienna, Austria) with a thrombin concentration of 4?IU/ml and a fibrinogen concentration of 80 mg/ml [Tisseel S F80 (Baxter), group C] and with an fibrinogen concentration of 20 mg/ml [Tisseel S F20 (Baxter), group D]. After 2 and 4 weeks, five constructs per group and time point were investigated using micro-computed tomography, and histological and morphometrical analysis techniques. The aprotinin, factor XIII and thrombin concentration did not affect the degree of clot degradation. An inverse relationship was found between fibrin matrix degradation and sprouting of blood vessels. By reducing the fibrinogen concentration in group D, a significantly decreased construct weight and an increased generation of vascularized connective tissue were detected. There was an inverse relationship between matrix degradation and vascularization detectable. Fibrinogen as the major matrix component showed a significant impact on the matrix properties. Alteration of fibrin gel properties might optimize formation of blood vessels. PMID:22576289

  18. Combustion Theory and Modelling Vol. 14, No. 1, 2010, 4167

    E-print Network

    DesJardin, Paul E.

    elevators and coal mines) [5, 6], and the fundamental issues of deflagration-to-detonation-transition (DDT condensed phase deflagration-to-detonation- transition (DDT) [13]. In their formulation mesoscale models to determine the post- detonation shock-focusing ignition and burning of aluminum particle mixtures. A model

  19. Some effects of thermal-cycle-induced deformation in rocket thrust chambers

    NASA Technical Reports Server (NTRS)

    Hannum, N. P.; Price, R. G., Jr.

    1981-01-01

    The deformation process observed in the hot gas side wall of rocket combustion chambers was investigaged for three different liner materials. Five thrust chambers were cycled to failure by using hydrogen and oxygen as propellants at a chamber pressure of 4.14 MN/cu m. The deformation was observed nondestructively at midlife points and destructively after failure occurred. The cyclic life results are presented with an accompanying discussion about the problems of life prediction associated with the types of failures encountered in the present work. Data indicating the deformation of the thrust chamber liner as cycles are accumulated are presented for each of the test thrust chambers. From these deformation data and observation of the failure sites it is evident that modeling the failure process as classic low cycle thermal fatigue is inadequate as a life prediction method.

  20. Flamelet Model Application for Non-Premixed Turbulent Combustion

    NASA Technical Reports Server (NTRS)

    Secundov, A.; Bezgin, L.; Buriko, Yu.; Guskov, O.; Kopchenov, V.; Laskin, I.; Lomkov, K.; Tshepin, S.; Volkov, D.; Zaitsev, S.

    1996-01-01

    The current Final Report contains results of the study which was performed in Scientific Research Center 'ECOLEN' (Moscow, Russia). The study concerns the development and verification of non-expensive approach for modeling of supersonic turbulent diffusion flames based on flamelet consideration of the chemistry/turbulence interaction (FL approach). Research work included: development of the approach and CFD tests of the flamelet model for supersonic jet flames; development of the simplified procedure for solution of the flamelet equations based on partial equilibrium chemistry assumption; study of the flame ignition/extinction predictions provided by flamelet model. The performed investigation demonstrated that FL approach allowed to describe satisfactory main features of supersonic H 2/air jet flames. Model demonstrated also high capabilities for reduction of the computational expenses in CFD modeling of the supersonic flames taking into account detailed oxidation chemistry. However, some disadvantages and restrictions of the existing version of approach were found in this study. They were: (1) inaccuracy in predictions of the passive scalar statistics by our turbulence model for one of the considered test cases; and (2) applicability of the available version of the flamelet model to flames without large ignition delay distance only. Based on the results of the performed investigation, we formulated and submitted to the National Aeronautics and Space Administration our Project Proposal for the next step research directed toward further improvement of the FL approach.

  1. Chemical kinetic models for combustion of hydrocarbons and formation of nitric oxide

    NASA Technical Reports Server (NTRS)

    Jachimowski, C. J.; Wilson, C. H.

    1980-01-01

    The formation of nitrogen oxides NOx during combustion of methane, propane, and a jet fuel, JP-4, was investigated in a jet stirred combustor. The results of the experiments were interpreted using reaction models in which the nitric oxide (NO) forming reactions were coupled to the appropriate hydrocarbon combustion reaction mechanisms. Comparison between the experimental data and the model predictions reveals that the CH + N2 reaction process has a significant effect on NO formation especially in stoichiometric and fuel rich mixtures. Reaction models were assembled that predicted nitric oxide levels that were in reasonable agreement with the jet stirred combustor data and with data obtained from a high pressure (5.9 atm (0.6 MPa)), prevaporized, premixed, flame tube type combustor. The results also suggested that the behavior of hydrocarbon mixtures, like JP-4, may not be significantly different from that of pure hydrocarbons. Application of the propane combustion and nitric oxide formation model to the analysis of NOx emission data reported for various aircraft gas turbines showed the contribution of the various nitric oxide forming processes to the total NOx formed.

  2. Submersible chamber water heater

    SciTech Connect

    Eising, J.P.

    1987-08-11

    A high efficiency water heating apparatus is described comprising a tank to contain water to be heated, means for withdrawing heated water from the upper end of the tank, heating means for heating water in the tank and comprising a tubular member disposed in an opening in the side wall of the tank and extending across the tank, a burner disposed in the tubular member, fuel supply means for supplying a combustible fuel to the burner, means for supplying air to the burner to provide a combustible fuel-air mixture, pilot light means for igniting the mixture and generating waste gases of combustion, a heat exchanger located beneath the tubular member, conduit means for conducting waste gases from the tubular member to the heat exchanger, a stack communicating with the heat exchanger for discharging the waste gases from the apparatus, means for flowing the waste gases from the combustion chamber through the heat exchanger to the stack, a vent tube separate from the stack, one end of the vent tube being disposed adjacent the pilot light means and extending along the outside of the tank and communicating with the atmosphere. The vent tube serves to vent gases generated by burning of the pilot light means.

  3. Method of combustion for dual fuel engine

    DOEpatents

    Hsu, Bertrand D. (Erie, PA); Confer, Gregory L. (Erie, PA); Shen, Zujing (Erie, PA); Hapeman, Martin J. (Edinboro, PA); Flynn, Paul L. (Fairview, PA)

    1993-12-21

    Apparatus and a method of introducing a primary fuel, which may be a coal water slutty, and a high combustion auxiliary fuel, which may be a conventional diesel oil, into an internal combustion diesel engine comprises detecting the load conditions of the engine, determining the amount of time prior to the top dead center position of the piston to inject the main fuel into the combustion chamber, and determining the relationship of the timing of the injection of the auxiliary fuel into the combustion chamber to achieve a predetermined specific fuel consumption, a predetermined combustion efficiency, and a predetermined peak cylinder firing pressure.

  4. Method of combustion for dual fuel engine

    DOEpatents

    Hsu, B.D.; Confer, G.L.; Zujing Shen; Hapeman, M.J.; Flynn, P.L.

    1993-12-21

    Apparatus and a method of introducing a primary fuel, which may be a coal water slurry, and a high combustion auxiliary fuel, which may be a conventional diesel oil, into an internal combustion diesel engine comprises detecting the load conditions of the engine, determining the amount of time prior to the top dead center position of the piston to inject the main fuel into the combustion chamber, and determining the relationship of the timing of the injection of the auxiliary fuel into the combustion chamber to achieve a predetermined specific fuel consumption, a predetermined combustion efficiency, and a predetermined peak cylinder firing pressure. 19 figures.

  5. The Mobile Chamber

    NASA Technical Reports Server (NTRS)

    Scharfstein, Gregory; Cox, Russell

    2012-01-01

    A document discusses a simulation chamber that represents a shift from the thermal-vacuum chamber stereotype. This innovation, currently in development, combines the capabilities of space simulation chambers, the user-friendliness of modern-day electronics, and the modularity of plug-and-play computing. The Mobile Chamber is a customized test chamber that can be deployed with great ease, and is capable of bringing payloads at temperatures down to 20 K, in high vacuum, and with the desired metrology instruments integrated to the systems control. Flexure plans to lease Mobile Chambers, making them affordable for smaller budgets and available to a larger customer base. A key feature of this design will be an Apple iPad-like user interface that allows someone with minimal training to control the environment inside the chamber, and to simulate the required extreme environments. The feedback of thermal, pressure, and other measurements is delivered in a 3D CAD model of the chamber's payload and support hardware. This GUI will provide the user with a better understanding of the payload than any existing thermal-vacuum system.

  6. A computational model for coal transport and combustion

    SciTech Connect

    Ahmadi, G.

    1992-06-02

    In the period of March 1, 1992 to May 30, 1992 considerable progress has been made in the development of the stress transport model for rapid granular flows in a rotating frame of reference. The derivation of thermodynamically consistent constitutive equations were complete. It was shown that the model contains the existing kinetics theories as special limiting cases. The model predictions for the special case of rapid simple shear flows were evaluated and the results are compared with the simulation data. Progress also has been made in formulation of the thermodynamically consistent rate dependent model for turbulent two-phase flows. The thermodynamically admissible constitutive equations were derived, and the case of a simple shear flow was also studied. The kinetic model for rapid flows of granular materials, which includes frictional losses, was used and the special case of gravity flows down an inclined chute was studied. The computational modeling for rapid granular flows in complex geometries was further developed. The design for the experimental simple shear flow device was further improved, and the construction of the device has started.

  7. Modeling of devolatilization in circulating fluidized bed combustion

    SciTech Connect

    Stenseng, M.; Lin, W.; Johnsson, J.E.; Dam-Johansen, K.

    1997-12-31

    A mathematical model is developed to describe the devolatilization process in a circulating fluidized bed combustor. The model is a combination of two submodels: single particle devolatilization and fluid dynamics. The single particle model includes the influence of both chemical kinetics and heat transfer on the rate of devolatilization. The results show a good agreement with literature data. The fluid dynamic model describes the main characteristics of a CFB: a dense zone in the bottom, followed by a splash zone and a dilute zone with a core-annulus structure. Each zone is modeled as a number of CSTR`s and the size and number of CSTR`s has been estimated from tracer experiments in an 80 MW{sub th} CFB boiler. It was not possible to evaluate the model against experimental data, but the dependence of particle size on the degree of devolatilization in the dense bed agrees qualitative with the expected behavior. The mode4l shows that the devolatilization mainly occurs in the dense bed.

  8. Large eddy simulation of a premixed combustion flow in a gas turbine combustor

    SciTech Connect

    Taniguchi, Nobuyuki; Kobayashi, Toshio; Ko, Sancheol; Ikegawa, Masahiro

    1999-07-01

    An aim of this research is to develop a numerical prediction of turbulent combustion flows with a large eddy simulation (LES) for a systematical design of the clean and highly-efficient combustion equipment. A numerical method and a model for turbulent combustion are developed for the LES of the premixed combustion flows and validated with a test chamber which examines a practical combustion equipment in a gas-turbine system. A comparison with the experiment indicates that the present method can predict a turbulence velocity field and also capture a instantaneous three-dimensional flame structure. An applicability to the variable combustion design are also investigated through some trials of the numerical simulations.

  9. A Simplified Model for the Investigation of Acoustically Driven Combustion Instabilities

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.; Quinn, D. Dane

    1998-01-01

    A simplified one-dimensional model of reactive flow is presented which captures features of aeropropulsion systems, including acoustically driven combustion instabilities. Although the resulting partial differential equations are one dimensional, they qualitatively describe observed phenomena, including, resonant frequencies and the admission of both steady and unsteady behavior. A number of simulations are shown which exhibit both steady and unsteady behavior, including flame migration and thermo acoustic instabilities. Finally, we present examples of unsteady flow resulting from fuel modulation.

  10. A flamelet model for supersonic non-premixed combustion with pressure variation

    NASA Astrophysics Data System (ADS)

    Zhao, Guo-Yan; Sun, Ming-Bo; Wu, Jin-Shui; Wang, Hong-Bo

    2015-08-01

    A modified flamelet model is proposed for studying supersonic combustion with pressure variation considering that pressure is far from homogenous in a supersonic combustor. In this model, the flamelet database are tabulated at a reference pressure, while quantities at other pressure are obtained using a sixth-order polynomial in pressure. Attributed to merit of the modified model which compute coefficients for the expansion only. And they brought less requirements for memory and table lookup time, expensive cost is avoided. The performance of modified model is much better than the approach of using a flamelet model-based method with tabulation at different pressure values. Two types of hydrogen fueled scramjet combustors were introduced to validate the modified flamelet model. It was observed that the temperature is sensitive to the choice of model in combustion area, which in return will significantly affect the pressure. It was found that the results of modified model were in good agreement with the experimental data compared with the isobaric flamelet model, especially for temperature, whose value is more accurately predicted. It is concluded that the modified flamelet model was more effective for cases with a wide range of pressure variation.

  11. Modeling the behavior of selenium in Pulverized-Coal Combustion systems

    SciTech Connect

    Senior, Constance; Otten, Brydger Van; Wendt, Jost O.L.; Sarofim, Adel

    2010-11-15

    The behavior of Se during coal combustion is different from other trace metals because of the high degree of vaporization and high vapor pressures of the oxide (SeO{sub 2}) in coal flue gas. In a coal-fired boiler, these gaseous oxides are absorbed on the fly ash surface in the convective section by a chemical reaction. The composition of the fly ash (and of the parent coal) as well as the time-temperature history in the boiler therefore influences the formation of selenium compounds on the surface of the fly ash. A model was created for interactions between selenium and fly ash post-combustion. The reaction mechanism assumed that iron reacts with selenium at temperatures above 1200 C and that calcium reacts with selenium at temperatures less than 800 C. The model also included competing reactions of SO{sub 2} with calcium and iron in the ash. Predicted selenium distributions in fly ash (concentration versus particle size) were compared against measurements from pilot-scale experiments for combustion of six coals, four bituminous and two low-rank coals. The model predicted the selenium distribution in the fly ash from the pilot-scale experiments reasonably well for six coals of different compositions. (author)

  12. Energy and cost analysis model to evaluate the combustion of food processing wastes

    SciTech Connect

    Sargent, S.A.

    1984-01-01

    Technical and economic factors pertinent to conversion of food processing wastes into recoverable energy were investigated. Combustion characteristics for a variety of wastes were defined, leading to the selection of components for an in-plant waste handling system for use in conjunction with each of three boiler systems representing pile burning, fluidized-bed combustion and suspension-firing technologies. Life cyle costing techniques were chosen to determine the total costs of the handling/combustion systems that would be incurred over a fixed payback period. Energy and cost calculations were incorporated into an interactive computer model for analysis of individual food processing firms. The model prompts the user for input regarding the processing plant schedule, operating and loan parameters, and fossil and waste fuel characteristics. Projected annual savings in fuel and disposal costs are compared with average annual costs to determine the breakeven point for cost-effective investment. The model was validated with conservative parameters representing two sizes of Michigan apple juice processors. Apple pomace was substituted for natural gas and number2 fuel oil.

  13. Hydrazine decay in the atmosphere: Controlled-environment chamber studies and kinetic modeling. Final report, October 1987-September 1990

    SciTech Connect

    Stone, D.A.; Long, J.R.

    1992-02-01

    This report documents a series of experiments conducted to shed additional light on the role of surface-catalyzed reactions on the atmospheric oxidation of hydrazine vapor. The experiments were conducted in a controlled-environment chamber consisting of a one-meter diameter stainless steel sphere which is Teflon coated. Vapor-phase hydrazine was introduced into the chamber at the 50-100 ppm concentration level. It was combined with four different synthetic atmospheric mixtures (all at one atmosphere total pressure): dry helium, humid (approx. 75 percent R.H.) helium, 80 percent dry helium plus 20 percent oxygen and 80 percent humid helium plus 20 percent oxygen. A series of experiments were conducted, using the same four synthetic atmospheres listed above, with several types of plates which were placed into a rack in the chamber. These plates included: Teflon-coated aluminum (TCA), black iron (BI), corroded aluminum (CA), and F-16 painted aluminum (PA). The reactivity of the plates towards hydrazine decay was: TAC < BI approx. PA < CA.... Hydrazine, Controlled-environment chamber, FT-IR Spectroscopy, Kinetic modeling, Surface-catalyzed reactions.

  14. Computer model of catalytic combustion/Stirling engine heater head

    NASA Technical Reports Server (NTRS)

    Chu, E. K.; Chang, R. L.; Tong, H.

    1981-01-01

    The basic Acurex HET code was modified to analyze specific problems for Stirling engine heater head applications. Specifically, the code can model: an adiabatic catalytic monolith reactor, an externally cooled catalytic cylindrical reactor/flat plate reactor, a coannular tube radiatively cooled reactor, and a monolithic reactor radiating to upstream and downstream heat exchangers.

  15. Flowfield measurements in a model scramjet combustion using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Mcdaniel, J. C., Jr.

    1984-01-01

    Preliminary designs were completed for an iodine mixing chamber and the optical setup to be used with a modified wind tunnel in obtaining accurate, spatially resolved measurements of variables in the flowfield of a model nonreacting scramjet combustor. Schematics of the iodine-seeded wind tunnel and a sketch of the charcoal filter for removing the iodine are included along with a cutaway section of the laboratory.

  16. Experiments and Model Development for the Investigation of Sooting and Radiation Effects in Microgravity Droplet Combustion

    NASA Technical Reports Server (NTRS)

    Choi, Mun Young; Yozgatligil, Ahmet; Dryer, Frederick L.; Kazakov, Andrei; Dobashi, Ritsu

    2001-01-01

    Today, despite efforts to develop and utilize natural gas and renewable energy sources, nearly 97% of the energy used for transportation is derived from combustion of liquid fuels, principally derived from petroleum. While society continues to rely on liquid petroleum-based fuels as a major energy source in spite of their finite supply, it is of paramount importance to maximize the efficiency and minimize the environmental impact of the devices that burn these fuels. The development of improved energy conversion systems, having higher efficiencies and lower emissions, is central to meeting both local and regional air quality standards. This development requires improvements in computational design tools for applied energy conversion systems, which in turn requires more robust sub-model components for combustion chemistry, transport, energy transport (including radiation), and pollutant emissions (soot formation and burnout). The study of isolated droplet burning as a unidimensional, time dependent model diffusion flame system facilitates extensions of these mechanisms to include fuel molecular sizes and pollutants typical of conventional and alternative liquid fuels used in the transportation sector. Because of the simplified geometry, sub-model components from the most detailed to those reduced to sizes compatible for use in multi-dimensional, time dependent applied models can be developed, compared and validated against experimental diffusion flame processes, and tested against one another. Based on observations in microgravity experiments on droplet combustion, it appears that the formation and lingering presence of soot within the fuel-rich region of isolated droplets can modify the burning rate, flame structure and extinction, soot aerosol properties, and the effective thermophysical properties. These observations led to the belief that perhaps one of the most important outstanding contributions of microgravity droplet combustion is the observation that in the absence of asymmetrical forced and natural convection, a soot shell is formed between the droplet surface and the flame, exerting an influence on the droplet combustion response far greater than previously recognized. The effects of soot on droplet burning parameters, including burning rate, soot shell dynamics, flame structure, and extinction phenomena provide significant testing parameters for studying the structure and coupling of soot models with other sub-model components.

  17. Structure-Based Predictive Model for Coal Char Combustion

    SciTech Connect

    Christopher Hadad; Joseph Calo; Robert Essenhigh; Robert Hurt

    1998-04-08

    Progress was made this period on a number of separate experimental and modelling activities. At Brown, the models of carbon nanostructure evolution were expanded to consider high-rank materials with initial anisotropy. The report presents detailed results of Monte Carlo simulations with non-zero initial layer length and with statistically oriented initial states. The expanded simulations are now capable of describing the development of nanostructure during carbonization of most coals. Work next quarter will address the remaining challenge of isotropic coke-forming coals. Experiments at Brown yielded important data on the "memory loss" phenomenon in carbon annealing, and on the effect of mineral matter on high-temperature reactivity. The experimental aspects of the Brown work will be discussed in detail in the next report.

  18. Low Order Modeling Tools for Preliminary Pressure Gain Combustion Benefits Analyses

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    2012-01-01

    Pressure gain combustion (PGC) offers the promise of higher thermodynamic cycle efficiency and greater specific power in propulsion and power systems. This presentation describes a model, developed under a cooperative agreement between NASA and AFRL, for preliminarily assessing the performance enhancement and preliminary size requirements of PGC components either as stand-alone thrust producers or coupled with surrounding turbomachinery. The model is implemented in the Numerical Propulsion Simulation System (NPSS) environment allowing various configurations to be examined at numerous operating points. The validated model is simple, yet physics-based. It executes quickly in NPSS, yet produces realistic results.

  19. Modeling SOA formation from alkanes and alkenes in chamber experiments: effect of gas/wall partitioning of organic vapors.

    NASA Astrophysics Data System (ADS)

    Stéphanie La, Yuyi; Camredon, Marie; Ziemann, Paul; Ouzebidour, Farida; Valorso, Richard; Madronich, Sasha; Lee-Taylor, Julia; Hodzic, Alma; Aumont, Bernard

    2014-05-01

    Oxidation products of Intermediate Volatility Organic Compounds (IVOC) are expected to be the major precursors of secondary organic aerosols (SOA). Laboratory experiments were conducted this last decade in the Riverside APRC chamber to study IVOC oxidative mechanisms and SOA formation processes for a large set of linear, branched and cyclic aliphatic hydrocarbons (Ziemann, 2011). This dataset are used here to assess the explicit oxidation model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) (Aumont et al., 2005). The simulated SOA yields agree with the general trends observed in the chamber experiments. They are (i) increasing with the increasing carbon number; (ii) decreasing with increasing methyl branch number; and (iii) increasing for cyclic compounds compared to their corresponding linear analogues. However, simulated SOA yields are systematically overestimated regardless of the precursors, suggesting missing processes in the model. In this study, we assess whether gas-to-wall partitioning of organic vapors can explain these model/observation mismatches (Matsunaga and Ziemann, 2010). First results show that GECKO-A outputs better match the observations when wall uptake of organic vapors is taken into account. Effects of gas/wall partitioning on SOA yields and composition will be presented. Preliminary results suggest that wall uptake is a major process influencing SOA production in the Teflon chambers. References Aumont, B., Szopa, S., Madronich, S.: Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach. Atmos.Chem.Phys., 5, 2497-2517 (2005). P. J. Ziemann: Effects of molecular structure on the chemistry of aerosol formation from the OH-radical-initiated oxidation of alkanes and alkenes, Int. Rev.Phys.Chem., 30:2, 161-195 (2011). Matsunaga, A., Ziemann, P. J.: Gas-wall partitioning of organic compounds in a Teflon film chamber and potential effects on reaction product and aerosol yield measurements, Aerosol Sci. Technol., 44:10, 881-892 (2010).

  20. Modeling of the saturation current of a fission chamber taking into account the distorsion of electric field due to space charge effects

    NASA Astrophysics Data System (ADS)

    Poujade, O.; Lebrun, A.

    1999-09-01

    Fission chambers were first made 50 years ago for neutron detection. Presently, the French Atomic Energy Commission (CEA-Cadarache) is developing a sub-miniature fission chamber technology with a diameter of 1.5 mm working in the current mode [1]. To be able to measure intense fluxes, it is necessary to adjust the chamber geometry and the gas pressure before testing it under real neutron flux. In the present paper, we describe a theoretical method to foresee the current-voltage characteristics (sensitivity and saturation plateau) of a fission chamber whose geometrical features are given, taking into account the neutron flux to be measured (spectrum and intensity). The proposed theoretical model describes electric field distortion resulting from charge collection effect. A computer code has been developed on this model basis. Its application to 3 kinds of fission chambers indicates excellent agreement between theoretical model and measured characteristics.

  1. Modeling of the saturation current of a fission chamber taking into account the distorsion of electric field due to space charge effects

    E-print Network

    Olivier Poujade; Alain Lebrun

    2002-02-08

    Fission chambers were first made fifty years ago for neutron detection. At the moment, the French Atomic Energy Commission \\textsf{(CEA-Cadarache)} is developing a sub-miniature fission chamber technology with a diameter of 1.5 mm working in the current mode (Bign). To be able to measure intense fluxes, it is necessary to adjust the chamber geometry and the gas pressure before testing it under real neutron flux. In the present paper, we describe a theoretical method to foresee the current-voltage characteristics (sensitivity and saturation plateau) of a fission chamber whose geometrical features are given, taking into account the neutron flux to be measured (spectrum and intensity). The proposed theoretical model describes electric field distortion resulting from charge collection effect. A computer code has been developed on this model basis. Its application to 3 kinds of fission chambers indicates excellent agreement between theoretical model and measured characteristics.

  2. A Model Parameter Extraction Method for Dielectric Barrier Discharge Ozone Chamber using Differential Evolution

    NASA Astrophysics Data System (ADS)

    Amjad, M.; Salam, Z.; Ishaque, K.

    2014-04-01

    In order to design an efficient resonant power supply for ozone gas generator, it is necessary to accurately determine the parameters of the ozone chamber. In the conventional method, the information from Lissajous plot is used to estimate the values of these parameters. However, the experimental setup for this purpose can only predict the parameters at one operating frequency and there is no guarantee that it results in the highest ozone gas yield. This paper proposes a new approach to determine the parameters using a search and optimization technique known as Differential Evolution (DE). The desired objective function of DE is set at the resonance condition and the chamber parameter values can be searched regardless of experimental constraints. The chamber parameters obtained from the DE technique are validated by experiment.

  3. Analytical flow/thermal modeling of combustion gas flows in Redesigned Solid Rocket Motor test joints

    NASA Technical Reports Server (NTRS)

    Woods, G. H.; Knox, E. C.; Pond, J. E.; Bacchus, D. L.; Hengel, J. E.

    1992-01-01

    A one-dimensional analytical tool, TOPAZ (Transient One-dimensional Pipe flow AnalyZer), was used to model the flow characteristics of hot combustion gases through Redesigned Solid Rocket Motor (RSRM) joints and to compute the resultant material surface temperatures and o-ring seal erosion of the joints. The capabilities of the analytical tool were validated with test data during the Seventy Pound Charge (SPC) motor test program. The predicted RSRM joint thermal response to ignition transients was compared with test data for full-scale motor tests. The one-dimensional analyzer is found to be an effective tool for simulating combustion gas flows in RSRM joints and for predicting flow and thermal properties.

  4. Theoretical Performance of Hydrogen-Oxygen Rocket Thrust Chambers

    NASA Technical Reports Server (NTRS)

    Sievers, Gilbert K.; Tomazic, William A.; Kinney, George R.

    1961-01-01

    Data are presented for liquid-hydrogen-liquid-oxygen thrust chambers at chamber pressures from 15 to 1200 pounds per square inch absolute, area ratios to approximately 300, and percent fuel from about 8 to 34 for both equilibrium and frozen composition during expansion. Specific impulse in vacuum, specific impulse, combustion-chamber temperature, nozzle-exit temperature, characteristic velocity, and the ratio of chamber-to-nozzle-exit pressure are included. The data are presented in convenient graphical forms to allow quick calculation of theoretical nozzle performance with over- or underexpansion, flow separation, and introduction of the propellants at various initial conditions or heat loss from the combustion chamber.

  5. A semi-analytical variable property droplet combustion model

    NASA Astrophysics Data System (ADS)

    Sisti, John

    A multizone droplet burn model is developed to account for changes in the thermal and transport properties as a function of droplet radius. The formulation is semi-analytical---allowing for accurate and computationally efficient estimates of flame structure and burn rates. Zonal thermal and transport properties are computed using the Cantera software and pre-tabulated for rapid evaluation during run-time. Model predictions are compared to experimental measurements of burning n-heptane, ethanol and methanol droplets. An adaptive zone refinement algorithm is developed that minimizes the number of zones required to provide accurate estimates of burn time without excess zones. A sensitivity study of burn rate and flame stand-off with far-field oxygen concentration is conducted with comparisons to experimental data. Overall agreement to data is encouraging with errors typically less than 20% for predictions of burn rates, stand-off ratio and flame temperature for the fuels considered. The quiescent quasi-steady solution is extended to a convective transient solution without the need to solve an eigenvalue solution in time. The time history of the burning droplets show good comparison with experimental data. To further decrease computational cost, the source terms for the transient solution are linearized for an explicit time marching solution. An error convergence study was performed to show a time-step independent solution exists at a reasonable Delta t.

  6. Combustion of CNG in Charged Spark Ignition Engines

    NASA Astrophysics Data System (ADS)

    Mitianiec, Wladyslaw

    2009-12-01

    The paper describes mixing of injected CNG with air and combustion process in spark ignition internal combustion engine. Because of higher ignition temperature of CNG the SI engines have more effective ignition system than conventional engines. The gas motion, turbulence, charge temperature and obviously electrical energy of the ignition coil have a big influence on the ignition and burning process in the combustion chamber. The paper includes theoretical and experimental investigations of ignition process in the high charged SI engines with direct CNG injection by using LES technique in KIVA program. Simulation of CNG combustion in the caloric chamber was carried in the environment of OpenFOAM program with LES model and also the experimental test was carried out for comparison of results in the chamber with the same geometry. The influence of the "tumble" and "swirl" on the sparking is shown by modelling of this process in premixed charge by using LES technique. The charge motion and also considerably turbulence effect influence strongly on the ignition process.

  7. Analyses of Longitudinal Mode Combustion Instability in J-2X Gas Generator Development

    NASA Technical Reports Server (NTRS)

    Hulka, J. R.; Protz, C. S.; Casiano, M. J.; Kenny, R. J.

    2011-01-01

    The National Aeronautics and Space Administration (NASA) and Pratt & Whitney Rocketdyne are developing a liquid oxygen/liquid hydrogen rocket engine for future upper stage and trans-lunar applications. This engine, designated the J-2X, is a higher pressure, higher thrust variant of the Apollo-era J-2 engine. The contract for development was let to Pratt & Whitney Rocketdyne in 2006. Over the past several years, development of the gas generator for the J-2X engine has progressed through a variety of workhorse injector, chamber, and feed system configurations on the component test stand at the NASA Marshall Space Flight Center (MSFC). Several of the initial configurations resulted in combustion instability of the workhorse gas generator assembly at a frequency near the first longitudinal mode of the combustion chamber. In this paper, several aspects of these combustion instabilities are discussed, including injector, combustion chamber, feed system, and nozzle influences. To ensure elimination of the instabilities at the engine level, and to understand the stability margin, the gas generator system has been modeled at the NASA MSFC with two techniques, the Rocket Combustor Interaction Design and Analysis (ROCCID) code and a lumped-parameter MATLAB(TradeMark) model created as an alternative calculation to the ROCCID methodology. To correctly predict the instability characteristics of all the chamber and injector geometries and test conditions as a whole, several inputs to the submodels in ROCCID and the MATLAB(TradeMark) model were modified. Extensive sensitivity calculations were conducted to determine how to model and anchor a lumped-parameter injector response, and finite-element and acoustic analyses were conducted on several complicated combustion chamber geometries to determine how to model and anchor the chamber response. These modifications and their ramification for future stability analyses of this type are discussed.

  8. 40 CFR Table 2 to Subpart Bbbb of... - Model Rule-Class I Emission Limits for Existing Small Municipal Waste Combustion Units a

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Existing Small Municipal Waste Combustion Units a 2 Table 2 to Subpart BBBB of Part 60 Protection of... NEW STATIONARY SOURCES Emission Guidelines and Compliance Times for Small Municipal Waste Combustion... Part 60—Model Rule—Class I Emission Limits for Existing Small Municipal Waste Combustion Units a...

  9. High-pressure combustion of binary fuel sprays

    NASA Technical Reports Server (NTRS)

    Mikami, Masato; Kono, Michikata; Sato, Jun'ichi; Dietrich, Daniel L.; Williams, Forman A.

    1995-01-01

    The ultimate objective of this study is to obtain fundamental information relevant to combustion processes that occur in fuel sprays of practical interest at high pressures in internal combustion engines. Since practical fuels are multicomponent and derived from petroleum, the present work involves the model alkane mixture of n-heptane and n-hexadecane. Since burning droplets in sprays can interact with each other, the present work involves investigation of the effects of this interaction on flame shapes and droplet burning times. The small droplets in practical combustion chambers are not significantly influenced by buoyancy. Since such small droplets are difficult to study experimentally, the present work takes advantage of microgravity to lessen buoyancy and enable information about droplet interactions to be obtained by studying larger droplets. The results are intended to provide fundamental understanding that can be used in improving descriptions of practical spray combustion.

  10. Agglomerate formation during coal combustion; A mechanistic model

    SciTech Connect

    Sarofim, A.F.; Beer, J.M.; Kang, S.W. )

    1991-08-01

    This paper reports that during the plastic stage of coal pyrolysis, there is competition between centrifugal force, which favors the breakup of coal agglomerates, and adhesive force between coal particles. A theoretical model of agglomeration was developed to investigate the adhesive force between contiguous coal particles in an agglomerate. The adhesive force in the process of agglomeration of coal particles was found to be proportional to the duration of plasticity of the particles. It was also found that rapid heating reduces the tendency of coal particles to form agglomerates during the plastic stage of coal pyrolysis. Therefore, whether particles burn individually or as agglomerates can be influenced by the temperature history of the coal or coal-water fuel (CWF) particles and hence by burner design.

  11. Modelling the contribution of biogenic volatile organic compounds to new particle formation in the Jülich plant atmosphere chamber

    NASA Astrophysics Data System (ADS)

    Roldin, P.; Liao, L.; Mogensen, D.; Dal Maso, M.; Rusanen, A.; Kerminen, V.-M.; Mentel, T. F.; Wildt, J.; Kleist, E.; Kiendler-Scharr, A.; Tillmann, R.; Ehn, M.; Kulmala, M.; Boy, M.

    2015-09-01

    We used the Aerosol Dynamics gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM) to simulate the contribution of BVOC plant emissions to the observed new particle formation during photooxidation experiments performed in the Jülich Plant-Atmosphere Chamber and to evaluate how well smog chamber experiments can mimic the atmospheric conditions during new particle formation events. ADCHAM couples the detailed gas-phase chemistry from Master Chemical Mechanism with a novel aerosol dynamics and particle phase chemistry module. Our model simulations reveal that the observed particle growth may have either been controlled by the formation rate of semi- and low-volatility organic compounds in the gas phase or by acid catalysed heterogeneous reactions between semi-volatility organic compounds in the particle surface layer (e.g. peroxyhemiacetal dimer formation). The contribution of extremely low-volatility organic gas-phase compounds to the particle formation and growth was suppressed because of their rapid and irreversible wall losses, which decreased their contribution to the nano-CN formation and growth compared to the atmospheric situation. The best agreement between the modelled and measured total particle number concentration (R2 > 0.95) was achieved if the nano-CN was formed by kinetic nucleation involving both sulphuric acid and organic compounds formed from OH oxidation of BVOCs.

  12. Model of Non-premixed Combustion of Aluminium---Air Mixtures

    NASA Astrophysics Data System (ADS)

    Khasainov, Boris; Kuhl, Allen; Victorov, Sergey; Neuwald, Peter

    2005-07-01

    For solving the problem of shock-induced dissemination and burning of aluminium particles in air, we have developed a new solver based on equilibrium equation of states (EOS) of 2-phase reactive mixtures. The solver uses two pre-calculated tables; the larger one describes the equilibrium states of reaction products and the smaller one describes states of fresh air. Being linked with gas-dynamics equations, the solver finds iteratively the mixture pressure and temperature; in addition it furnishes a complete description of chemical and physical transformations. 2D numerical simulations give encouraging agreement with experimental pressure histories recorded on the chamber wall. It is shown that multiple blast wave reflections from the walls of the chamber strongly accelerate particle burning. The results demonstrate the advantages of the equilibrium EOS model and appeal for 3D AMR calculations on massively-parallel computers, which should better define the initial stage of turbulent particle dissemination.

  13. Combustion of liquid fuels in a flowing combustion gas environment at high pressures

    NASA Technical Reports Server (NTRS)

    Canada, G. S.; Faeth, G. M.

    1975-01-01

    The combustion of fuel droplets in gases which simulate combustion chamber conditions was considered both experimentally and theoretically. The fuel droplets were simulated by porous spheres and allowed to gasify in combustion gases produced by a burner. Tests were conducted for pressures of 1-40 atm, temperatures of 600-1500 K, oxygen concentrations of 0-13% (molar) and approach Reynolds numbers of 40-680. The fuels considered in the tests included methanol, ethanol, propanol-1, n-pentane, n-heptane and n-decane. Measurements were made of both the rate of gasification of the droplet and the liquid surface temperature. Measurements were compared with theory, involving various models of gas phase transport properties with a multiplicative correction for the effect of forced convection.

  14. A level set based flamelet model for the prediction of combustion in spark ignition engines

    NASA Astrophysics Data System (ADS)

    Ewald, J.; Peters, N.

    2005-08-01

    A Flamelet Model based on the Level Set approach for turbulent premixed combustion is presented. The original model is enhanced in order to consistently model the evolution of the premixed flame from laminar into a fully developed turbulent flame. This is accomplished by establishing a linear relationship between the thickness of the turbulent flame brush and the turbulent burning velocity. Starting from there a model for the initial flame propagation of a spherical spark kernel immediately after ignition and for the flame propagation in 3D space is derived. In contrast to other models, the same physical modeling assumptions are employed for the phase initially after spark ignition and for the later phases of flame propagation. The model is applied to a test case in an homogeneous charge Spark Ignition (SI) engine.

  15. Reliable and efficient numerical simulation of a model of tissue differentiation in a bone chamber1

    E-print Network

    of peri-implant tissue differentiation, a repeated sampling bone chamber has been developed. Mathematical fractures and the osseointegration of implants, alongside its importance in unravelling aspects), a teflon bearing (5) and an implant (6). Tissue can grow through the perforations (2)

  16. A CHAMBER AND MODELING STUDY TO ASSESS THE PHOTOCHEMISTRY OF FORMALDEHYDE

    EPA Science Inventory

    A new analytical method for formaldehyde (HCHO) was implemented for use in the UNC outdoor smog chamber. CHO measurements obtained with this method were compared with those obtained using other analytical techniques. ix different calibration standards for HCHO were found to agree...

  17. OUTDOOR SMOG CHAMBER EXPERIMENTS TO TEST PHOTOCHEMICAL MODELS: MICROFICHE OF DATA COLLECTED IN THE STUDY

    EPA Science Inventory

    The smog chamber facility of the University of North Carolina was used in a study to collect experimental data for developing and testing kinetic mechanisms of photochemical smog formation. Listings and plots of the 115 dual all-day experiments conducted in the study are containe...

  18. Modeling of fluidized-bed combustion of coal: Phase II, final reports. Volume V. Appendix: stability and instability in fluidized-bed combustion

    SciTech Connect

    Louis, J.F.; Tung, S.E.

    1980-10-01

    This document is the fifth of the seven volumes series of our Phase II Final Report. The material developed in this volume has not been incorporated into the system model. It will be used as a precursor of a transient model to be developed in the next phase of our model work. There have been various fluidized combustor models of differing complexity and scope published in the literature. Most of these models have identified and predicted - often in satisfactory agreement with results from pilot units - the key steady state combustor characteristics such as the mass of carbon in the bed (carbon loading), the combustion efficiency, the sulfur retention by the solid sorbent and the pollutant (mainly NO/sub x/) emissions. These models, however, cannot be in most instances successfully used to study the extinction and ignition characteristics of the combustor because they are isothermal in structure in the sense that the bed temperature is not an output variable but rather an input one and must be a priori specified. In order to remedy these inadequacies of the previous models, we here present a comprehensive account of the formulation and some typical results of a new nonisothermal model which has been developed in order to study, among other things, the ignition and extinction characteristics of the AFBC units. This model is able to predict the temperature patterns in the bed, the carbon loading, the combustion efficiency and the O/sub 2/ and CO concentration profiles in the combustor for the different design or operational characteristics.

  19. Subfilter Scale Modelling for Large Eddy Simulation of Lean Hydrogen-Enriched Turbulent Premixed Combustion

    NASA Astrophysics Data System (ADS)

    Hernandez Perez, Francisco Emanuel

    Hydrogen (H2) enrichment of hydrocarbon fuels in lean premixed systems is desirable since it can lead to a progressive reduction in greenhouse-gas emissions, while paving the way towards pure hydrogen combustion. In recent decades, large-eddy simulation (LES) has emerged as a promising tool to computationally describe and represent turbulent combustion processes. However, a considerable complication of LES for turbulent premixed combustion is that chemical reactions occur in a thin reacting layer at small scales which cannot be entirely resolved on computational grids and need to be modelled. In this thesis, subfilter-scale (SFS) modelling for LES of lean H 2-enriched methane-air turbulent premixed combustion was investigated. Two- and three-dimensional fully-compressible LES solvers for a thermally perfect reactive mixture of gases were developed and systematically validated. Two modelling strategies for the chemistry-turbulence interaction were pursued: the artificially thickened flame model with a power-law SFS wrinkling approach and the presumed conditional moment (PCM) coupled with the flame prolongation of intrinsic low-dimensional manifold (FPI) chemistry tabulation technique. Freely propagating and Bunsen-type flames corresponding to stoichiometric and lean premixed mixtures were considered. Validation of the LES solvers was carried out by comparing predicted solutions with experimental data and other published numerical results. Head-to-head comparisons of different SFS approaches, including a transported flame surface density (FSD) model, allowed to identify weaknesses and strengths of the various models. Based on the predictive capabilities of the models examined, the PCM-FPI model was selected for the study of hydrogen-enrichment of methane. A new progress of reaction variable was proposed to account for NO. The importance of transporting species with different diffusion coefficients was demonstrated, in particular for H2. The proposed approach was applied to a Bunsen-type configuration, reproducing key features observed in the experiments: the enriched flame was shorter, which is attributed to a faster consumption of the blended fuel; and the enriched flame displayed a broader two-dimensional curvature probability density function. Furthermore, reduced levels of carbon dioxide (CO2), increased levels of nitrogen monoxide (NO), and a slight increase in the carbon monoxide (CO) levels in areas of fully burned gas were predicted for the enriched flame.

  20. Science Support for Space-Based Droplet Combustion: Drop Tower Experiments and Detailed Numerical Modeling

    NASA Technical Reports Server (NTRS)

    Marchese, Anthony J.; Dryer, Frederick L.

    1997-01-01

    This program supports the engineering design, data analysis, and data interpretation requirements for the study of initially single component, spherically symmetric, isolated droplet combustion studies. Experimental emphasis is on the study of simple alcohols (methanol, ethanol) and alkanes (n-heptane, n-decane) as fuels with time dependent measurements of drop size, flame-stand-off, liquid-phase composition, and finally, extinction. Experiments have included bench-scale studies at Princeton, studies in the 2.2 and 5.18 drop towers at NASA-LeRC, and both the Fiber Supported Droplet Combustion (FSDC-1, FSDC-2) and the free Droplet Combustion Experiment (DCE) studies aboard the shuttle. Test matrix and data interpretation are performed through spherically-symmetric, time-dependent numerical computations which embody detailed sub-models for physical and chemical processes. The computed burning rate, flame stand-off, and extinction diameter are compared with the respective measurements for each individual experiment. In particular, the data from FSDC-1 and subsequent space-based experiments provide the opportunity to compare all three types of data simultaneously with the computed parameters. Recent numerical efforts are extending the computational tools to consider time dependent, axisymmetric 2-dimensional reactive flow situations.

  1. Combustion products generating and metering device

    NASA Technical Reports Server (NTRS)

    Wiberg, R. E.; Klisch, J. A. (inventors)

    1971-01-01

    An apparatus for generating combustion products at a predetermined fixed rate, mixing the combustion products with air to achieve a given concentration, and distributing the resultant mixture to an area or device to be tested is described. The apparatus is comprised of blowers, a holder for the combustion product generating materials (which burn at a predictable and controlled rate), a mixing plenum chamber, and a means for distributing the air combustion product mixture.

  2. Measuring oxygen tension modulation, induced by a new pre-radiotherapy therapeutic, in a mammary window chamber mouse model

    NASA Astrophysics Data System (ADS)

    Schafer, Rachel; Gmitro, Arthur F.

    2015-03-01

    Tumor regions under hypoxic or low oxygen conditions respond less effectively to many treatment strategies, including radiation therapy. A novel investigational therapeutic, NVX-108 (NuvOx Pharma), has been developed to increase delivery of oxygen through the use of a nano-emulsion of dodecofluoropentane. By raising pO2 levels prior to delivering radiation, treatment efficacy may be improved. To aid in evaluating the novel drug, oxygen tension was quantitatively measured, spatially and temporally, to record the effect of administrating NVX-108 in an orthotopic mammary window chamber mouse model of breast cancer. The oxygen tension was measured through the use of an oxygen-sensitive coating, comprised of phosphorescent platinum porphyrin dye embedded in a polystyrene matrix. The coating, applied to the surface of the coverslip of the window chamber through spin coating, is placed in contact with the mammary fat pad to record the oxygenation status of the surface tissue layer. Prior to implantation of the window chamber, a tumor is grown in the SCID mouse model by injection of MCF-7 cells into the mammary fat pad. Two-dimensional spatial distributions of the pO2 levels were obtained through conversion of measured maps of phosphorescent lifetime. The resulting information on the spatial and temporal variation of the induced oxygen modulation could provide valuable insight into the optimal timing between administration of NVX-108 and radiation treatment to provide the most effective treatment outcome.

  3. Turbulent combustion

    SciTech Connect

    Talbot, L.; Cheng, R.K.

    1993-12-01

    Turbulent combustion is the dominant process in heat and power generating systems. Its most significant aspect is to enhance the burning rate and volumetric power density. Turbulent mixing, however, also influences the chemical rates and has a direct effect on the formation of pollutants, flame ignition and extinction. Therefore, research and development of modern combustion systems for power generation, waste incineration and material synthesis must rely on a fundamental understanding of the physical effect of turbulence on combustion to develop theoretical models that can be used as design tools. The overall objective of this program is to investigate, primarily experimentally, the interaction and coupling between turbulence and combustion. These processes are complex and are characterized by scalar and velocity fluctuations with time and length scales spanning several orders of magnitude. They are also influenced by the so-called {open_quotes}field{close_quotes} effects associated with the characteristics of the flow and burner geometries. The authors` approach is to gain a fundamental understanding by investigating idealized laboratory flames. Laboratory flames are amenable to detailed interrogation by laser diagnostics and their flow geometries are chosen to simplify numerical modeling and simulations and to facilitate comparison between experiments and theory.

  4. Modeling of electron behaviors under microwave electric field in methane and air pre-mixture gas plasma assisted combustion

    NASA Astrophysics Data System (ADS)

    Akashi, Haruaki; Sasaki, K.; Yoshinaga, T.

    2011-10-01

    Recently, plasma-assisted combustion has been focused on for achieving more efficient combustion way of fossil fuels, reducing pollutants and so on. Shinohara et al has reported that the flame length of methane and air premixed burner shortened by irradiating microwave power without increase of gas temperature. This suggests that electrons heated by microwave electric field assist the combustion. They also measured emission from 2nd Positive Band System (2nd PBS) of nitrogen during the irradiation. To clarify this mechanism, electron behavior under microwave power should be examined. To obtain electron transport parameters, electron Monte Carlo simulations in methane and air mixture gas have been done. A simple model has been developed to simulate inside the flame. To make this model simple, some assumptions are made. The electrons diffuse from the combustion plasma region. And the electrons quickly reach their equilibrium state. And it is found that the simulated emission from 2nd PBS agrees with the experimental result. Recently, plasma-assisted combustion has been focused on for achieving more efficient combustion way of fossil fuels, reducing pollutants and so on. Shinohara et al has reported that the flame length of methane and air premixed burner shortened by irradiating microwave power without increase of gas temperature. This suggests that electrons heated by microwave electric field assist the combustion. They also measured emission from 2nd Positive Band System (2nd PBS) of nitrogen during the irradiation. To clarify this mechanism, electron behavior under microwave power should be examined. To obtain electron transport parameters, electron Monte Carlo simulations in methane and air mixture gas have been done. A simple model has been developed to simulate inside the flame. To make this model simple, some assumptions are made. The electrons diffuse from the combustion plasma region. And the electrons quickly reach their equilibrium state. And it is found that the simulated emission from 2nd PBS agrees with the experimental result. This work was supported by KAKENHI (22340170).

  5. Space shuttle maneuvering engine reusable thrust chamber program. Task 11: Stability analyses and acoustic model testing data dump

    NASA Technical Reports Server (NTRS)

    Oberg, C. L.

    1974-01-01

    The combustion stability characteristics of engines applicable to the Space Shuttle Orbit Maneuvering System and the adequacy of acoustic cavities as a means of assuring stability in these engines were investigated. The study comprised full-scale stability rating tests, bench-scale acoustic model tests and analysis. Two series of stability rating tests were made. Acoustic model tests were made to determine the resonance characteristics and effects of acoustic cavities. Analytical studies were done to aid design of the cavity configurations to be tested and, also, to aid evaluation of the effectiveness of acoustic cavities from available test results.

  6. Utilizing ARC EMCS Seedling Cassettes as Highly Versatile Miniature Growth Chambers for Model Organism Experiments

    NASA Technical Reports Server (NTRS)

    Freeman, John L.; Steele, Marianne K.; Sun, Gwo-Shing; Heathcote, David; Reinsch, S.; DeSimone, Julia C.; Myers, Zachary A.

    2014-01-01

    The aim of our ground testing was to demonstrate the capability of safely putting specific model organisms into dehydrated stasis, and to later rehydrate and successfully grow them inside flight proven ARC EMCS seedling cassettes. The ARC EMCS seedling cassettes were originally developed to support seedling growth during space flight. The seeds are attached to a solid substrate, launched dry, and then rehydrated in a small volume of media on orbit to initiate the experiment. We hypothesized that the same seedling cassettes should be capable of acting as culture chambers for a wide range of organisms with minimal or no modification. The ability to safely preserve live organisms in a dehydrated state allows for on orbit experiments to be conducted at the best time for crew operations and more importantly provides a tightly controlled physiologically relevant growth experiment with specific environmental parameters. Thus, we performed a series of ground tests that involved growing the organisms, preparing them for dehydration on gridded Polyether Sulfone (PES) membranes, dry storage at ambient temperatures for varying periods of time, followed by rehydration. Inside the culture cassettes, the PES membranes were mounted above blotters containing dehydrated growth media. These were mounted on stainless steel bases and sealed with plastic covers that have permeable membrane covered ports for gas exchange. The results showed we were able to demonstrate acceptable normal growth of C.elegans (nematodes), E.coli (bacteria), S.cerevisiae (yeast), Polytrichum (moss) spores and protonemata, C.thalictroides (fern), D.discoideum (amoeba), and H.dujardini (tardigrades). All organisms showed acceptable growth and rehydration in both petri dishes and culture cassettes initially, and after various time lengths of dehydration. At the end of on orbit ISS European Modular Cultivation System experiments the cassettes could be frozen at ultra-low temperatures, refrigerated, or chemically preserved before being returned to Earth for analyses. Our results suggest that with protocol modifications and future verification testing we can utilize the versatile EMCS to conduct tightly controlled experiments inside our culture cassettes for a wide variety of organisms. These physiological experiments would be designed to answer questions at the molecular level about the specific stress responses of space flight.

  7. Calculations of radiative exchange by the Monte-Carlo method. Theory and applications to industrial combustion systems

    SciTech Connect

    Goerner, K. . Inst. fuer Verfahrenstechnik und Dampfkesselwesen); Dietz, U. )

    1993-04-01

    The application of the Monte-Carlo method to the calculation of radiation exchange processes in combustion systems is discussed. After a brief introduction, the modeling of radiation exchange and the optical properties of the combustion-chamber suspension are described. The application of the method of technical-scale systems is illustrated for large-scale coal- and lignite-fired combustion plants. Flow and heat release are approximated to reduce the computational effort, and to achieve industrial relevance. The simulated results are in good agreement with available data. Coupling with complete flame and combustion-chamber models, in which the turbulent two-phase flow and local heat release are calculated, is discussed, and found to be feasible.

  8. Experimental and simulation study of a Gaseous oxygen/Gaseous hydrogen vortex cooling thrust chamber

    NASA Astrophysics Data System (ADS)

    Yu, Nanjia; Zhao, Bo; Li, Gongnan; Wang, Jue

    2016-01-01

    In this paper, RNG k-? turbulence model and PDF non-premixed combustion model are used to simulate the influence of the diameter of the ring of hydrogen injectors and oxidizer-to-fuel ratio on the specific impulse of the vortex cooling thrust chamber. The simulation results and the experimental tests of a 2000 N Gaseous oxygen/Gaseous hydrogen vortex cooling thrust chamber reveal that the efficiency of the specific impulse improves significantly with increasing of the diameter of the ring of hydrogen injectors. Moreover, the optimum efficiency of the specific impulse is obtained when the oxidizer-to-fuel ratio is near the stoichiometric ratio.

  9. Combustion Model of Supersonic Rocket Exhausts in an Entrained Flow Enclosure

    NASA Technical Reports Server (NTRS)

    Vu, Bruce T.; Oliveira, Justin

    2011-01-01

    This paper describes the Computational Fluid Dynamics (CFD) model developed to simulate the supersonic rocket exhaust in an entrained flow cylinder. The model can be used to study the plume-induced environment due to static firing tests of the Taurus-II launch vehicle. The finite-rate chemistry is used to model the combustion process involving rocket propellant (RP-1) and liquid oxidizer (LOX). A similar chemical reacting model is also used to simulate the mixing of rocket plume and ambient air. The model provides detailed information on the gas concentration and other flow parameters within the enclosed region, thus allowing different operating scenarios to be examined in an efficient manner. It is shown that the real gas influence is significant and yields better agreement with the theory.

  10. Combustion Model of Supersonic Rocket Exhausts in an Entrained Flow Enclosure

    NASA Technical Reports Server (NTRS)

    Vu, Bruce; Oliveira, Justin

    2011-01-01

    This paper describes the Computation Fluid Dynamics (CFD) model developed to simulate the supersonic rocket exhaust in an entrained flow cylinder. The model can be used to study the plume-induced environment due to static firing test of the Taurus II launch vehicle. The finite rate chemistry is used to model the combustion process involving rocket propellant (RP 1) and liquid oxidizer (LOX). A similar chemical reacting model is also used to simulate the mixing of rocket plume and ambient air. The model provides detailed information on the gas concentration and other flow parameters within the enclosed region thus allowing different operating scenarios to be examined in an efficient manner. It is shown that the real gas influence is significant and yields better agreement with the theory.

  11. IFE Final Optics and Chamber Dynamics Modeling and Experiments Final Technical Report

    SciTech Connect

    F. Najmabadi; M. S. Tillack

    2006-01-11

    Our OFES-sponsored research on IFE technology originally focused on studies of grazing-incidence metal mirrors (GIMM's). After the addition of GIMM research to the High Average Power Laser (HAPL) program, our OFES-sponsored research evolved to include laser propagation studies, surface material evolution in IFE wetted-wall chambers, and magnetic intervention. In 2003, the OFES IFE Technology program was terminated. We continued to expend resources on a no-cost extension in order to complete student research projects in an orderly way and to help us explore new research directions. Those explorations led to funding in the field of extreme ultraviolet lithography, which shares many issues in common with inertial fusion chambers, and the field of radiative properties of laser-produced plasma.

  12. Compare pilot-scale and industry-scale models of pulverized coal combustion in an ironmaking blast furnace

    NASA Astrophysics Data System (ADS)

    Shen, Yansong; Yu, Aibing; Zulli, Paul

    2013-07-01

    In order to understand the complex phenomena of pulverized coal injection (PCI) process in blast furnace (BF), mathematical models have been developed at different scales: pilot-scale model of coal combustion and industry-scale model (in-furnace model) of coal/coke combustion in a real BF respectively. This paper compares these PCI models in aspects of model developments and model capability. The model development is discussed in terms of model formulation, their new features and geometry/regions considered. The model capability is then discussed in terms of main findings followed by the model evaluation on their advantages and limitations. It is indicated that these PCI models are all able to describe PCI operation qualitatively. The in-furnace model is more reliable for simulating in-furnace phenomena of PCI operation qualitatively and quantitatively. These models are useful for understanding the flow-thermo-chemical behaviors and then optimizing the PCI operation in practice.

  13. Black liquor combustion validated recovery boiler modeling: Final year report. Volume 4 (Appendix IV)

    SciTech Connect

    Grace, T.M.; Frederick, W.J.; Salcudean, M.; Wessel, R.A.

    1998-08-01

    This project was initiated in October 1990, with the objective of developing and validating a new computer model of a recovery boiler furnace using a computational fluid dynamics (CFD) code specifically tailored to the requirements for solving recovery boiler flows, and using improved submodels for black liquor combustion based on continued laboratory fundamental studies. The key tasks to be accomplished were as follows: (1) Complete the development of enhanced furnace models that have the capability to accurately predict carryover, emissions behavior, dust concentrations, gas temperatures, and wall heat fluxes. (2) Validate the enhanced furnace models, so that users can have confidence in the predicted results. (3) Obtain fundamental information on aerosol formation, deposition, and hardening so as to develop the knowledge base needed to relate furnace model outputs to plugging and fouling in the convective sections of the boiler. (4) Facilitate the transfer of codes, black liquid submodels, and fundamental knowledge to the US kraft pulp industry. Volume 4 contains the following appendix sections: Radiative heat transfer properties for black liquor combustion -- Facilities and techniques and Spectral absorbance and emittance data; and Radiate heat transfer determination of the optical constants of ash samples from kraft recovery boilers -- Calculation procedure; Computation program; Density determination; Particle diameter determination; Optical constant data; and Uncertainty analysis.

  14. A novel convolution-based approach to address ionization chamber volume averaging effect in model-based treatment planning systems

    NASA Astrophysics Data System (ADS)

    Barraclough, Brendan; Li, Jonathan G.; Lebron, Sharon; Fan, Qiyong; Liu, Chihray; Yan, Guanghua

    2015-08-01

    The ionization chamber volume averaging effect is a well-known issue without an elegant solution. The purpose of this study is to propose a novel convolution-based approach to address the volume averaging effect in model-based treatment planning systems (TPSs). Ionization chamber-measured beam profiles can be regarded as the convolution between the detector response function and the implicit real profiles. Existing approaches address the issue by trying to remove the volume averaging effect from the measurement. In contrast, our proposed method imports the measured profiles directly into the TPS and addresses the problem by reoptimizing pertinent parameters of the TPS beam model. In the iterative beam modeling process, the TPS-calculated beam profiles are convolved with the same detector response function. Beam model parameters responsible for the penumbra are optimized to drive the convolved profiles to match the measured profiles. Since the convolved and the measured profiles are subject to identical volume averaging effect, the calculated profiles match the real profiles when the optimization converges. The method was applied to reoptimize a CC13 beam model commissioned with profiles measured with a standard ionization chamber (Scanditronix Wellhofer, Bartlett, TN). The reoptimized beam model was validated by comparing the TPS-calculated profiles with diode-measured profiles. Its performance in intensity-modulated radiation therapy (IMRT) quality assurance (QA) for ten head-and-neck patients was compared with the CC13 beam model and a clinical beam model (manually optimized, clinically proven) using standard Gamma comparisons. The beam profiles calculated with the reoptimized beam model showed excellent agreement with diode measurement at all measured geometries. Performance of the reoptimized beam model was comparable with that of the clinical beam model in IMRT QA. The average passing rates using the reoptimized beam model increased substantially from 92.1% to 99.3% with 3%/3?mm and from 79.2% to 95.2% with 2%/2?mm when compared with the CC13 beam model. These results show the effectiveness of the proposed method. Less inter-user variability can be expected of the final beam model. It is also found that the method can be easily integrated into model-based TPS.

  15. Review of wire chamber aging

    SciTech Connect

    Va'Vra, J.

    1986-02-01

    This paper makes an overview of the wire chamber aging problems as a function of various chamber design parameters. It emphasizes the chemistry point of view and many examples are drawn from the plasma chemistry field as a guidance for a possible effort in the wire chamber field. The paper emphasizes the necessity of variable tuning, the importance of purity of the wire chamber environment, as well as it provides a practical list of presently known recommendations. In addition, several models of the wire chamber aging are qualitatively discussed. The paper is based on a summary talk given at the Wire Chamber Aging Workshop held at LBL, Berkeley on January 16-17, 1986. Presented also at Wire Chamber Conference, Vienna, February 25-28, 1986. 74 refs., 18 figs., 11 tabs.

  16. A Spinal Cord Window Chamber Model for In Vivo Longitudinal Multimodal Optical and Acoustic Imaging in a Murine Model

    PubMed Central

    Maeda, Azusa; Conroy, Leigh; McMullen, Jesse D.; Silver, Jason I.; Stapleton, Shawn; Vitkin, Alex; Lindsay, Patricia; Burrell, Kelly; Zadeh, Gelareh; Fehlings, Michael G.; DaCosta, Ralph S.

    2013-01-01

    In vivo and direct imaging of the murine spinal cord and its vasculature using multimodal (optical and acoustic) imaging techniques could significantly advance preclinical studies of the spinal cord. Such intrinsically high resolution and complementary imaging technologies could provide a powerful means of quantitatively monitoring changes in anatomy, structure, physiology and function of the living cord over time after traumatic injury, onset of disease, or therapeutic intervention. However, longitudinal in vivo imaging of the intact spinal cord in rodent models has been challenging, requiring repeated surgeries to expose the cord for imaging or sacrifice of animals at various time points for ex vivo tissue analysis. To address these limitations, we have developed an implantable spinal cord window chamber (SCWC) device and procedures in mice for repeated multimodal intravital microscopic imaging of the cord and its vasculature in situ. We present methodology for using our SCWC to achieve spatially co-registered optical-acoustic imaging performed serially for up to four weeks, without damaging the cord or induction of locomotor deficits in implanted animals. To demonstrate the feasibility, we used the SCWC model to study the response of the normal spinal cord vasculature to ionizing radiation over time using white light and fluorescence microscopy combined with optical coherence tomography (OCT) in vivo. In vivo power Doppler ultrasound and photoacoustics were used to directly visualize the cord and vascular structures and to measure hemoglobin oxygen saturation through the complete spinal cord, respectively. The model was also used for intravital imaging of spinal micrometastases resulting from primary brain tumor using fluorescence and bioluminescence imaging. Our SCWC model overcomes previous in vivo imaging challenges, and our data provide evidence of the broader utility of hybridized optical-acoustic imaging methods for obtaining multiparametric and rich imaging data sets, including over extended periods, for preclinical in vivo spinal cord research. PMID:23516432

  17. Transient Numerical Modeling of the Combustion of Bi-Component Liquid Droplets: Methanol/Water Mixture

    NASA Technical Reports Server (NTRS)

    Marchese, A. J.; Dryer, F. L.

    1994-01-01

    This study shows that liquid mixtures of methanol and water are attractive candidates for microgravity droplet combustion experiments and associated numerical modeling. The gas phase chemistry for these droplet mixtures is conceptually simple, well understood and substantially validated. In addition, the thermodynamic and transport properties of the liquid mixture have also been well characterized. Furthermore, the results obtained in this study predict that the extinction of these droplets may be observable in ground-based drop to tower experiments. Such experiments will be conducted shortly followed by space-based experiments utilizing the NASA FSDC and DCE experiments.

  18. Numerical studies of integral equation and rod models of solid fuel combustion

    NASA Astrophysics Data System (ADS)

    Park, Jang Hoon

    We consider modes of solid flame propagation associated with the SHS (Self Propagating High Temperature Synthesis) process of materials synthesis. In this process reactants are ground into a powder, cold pressed into a solid sample, typically a cylinder, and ignited at one end. Synthesis ensues as a high temperature self-sustaining combustion wave propagates through the sample converting reactants to products. When gas plays no significant role in the process the resulting gasless combustion wave is referred to as a "solid flame". First we consider nonadiabatic gasless solid fuel combustion employing a reaction sheet model. We derive an integrodifferential equation for the location of the interface separating the fresh fuel from the burned products. For all values of the scaled activation energy, Z, and heat loss parameter, Gamma, the model admits a uniformly propagating combustion wave. This solution is subject to a pulsating instability for Z sufficiently large. We find that for Z slightly below the adiabatic stability limit, the effect of heat loss is to promote a period doubling cascade leading to chaotic behavior prior to extinction. We also find an interval of laminar behavior within the chaotic window, corresponding to a secondary period doubling sequence. We next consider an array of interacting rods, each of which supports propagating waves. Thus, we employ an array of interacting 1D rods connected via heat transfer. The heat transfer terms correspond to a discretization of the transverse Laplacian. We consider first a rod model consisting of an outer ring of 3 rods equally spaced along the ring, together with an axial rod. We find a multitude of solutions including spinning, radial, and quasiperiodic solutions. We next consider an 8/8/1 rod model in which 8 equally spaced rods are located at the surface of the cylinder, another 8 equally spaced rods are on a concentric circle located halfway inside the cylinder, and an axial rod is located on the axis. Neighboring rods are connected to one another via heat transfer. We find numerous spin, radial, periodic, and quasiperiodic solutions and compare these solutions with possible 3D analogues.

  19. Checking the validity of superimposing analytical deformation models and implications for numerical modelling of dikes and magma chambers

    NASA Astrophysics Data System (ADS)

    Pascal, K.; Neuberg, J. W.; Rivalta, E.

    2011-12-01

    The displacement field due to magma movements in the subsurface is commonly modelled using the solutions for a point source (Mogi, 1958), a finite spherical source (McTigue, 1987), or a dislocation source (Okada, 1992) embedded in a homogeneous elastic half-space. When the magmatic system is represented by several sources, their respective deformation fields are summed, and the assumption of homogeneity in the half-space is violated. We have investigated the effects of neglecting the interaction between sources on the surface deformation field. To do so, we calculated the vertical and horizontal displacements for models with adjacent sources and we tested them against the solutions of corresponding numerical 3D finite element models. We implemented several models combining spherical pressure sources and dislocation sources, varying the pressure or opening of the sources and their relative position. We also investigated various numerical methods to model a dike as a dislocation tensile source or as a pressurized tabular crack. In the former case, the dike opening was either defined as two boundaries displaced from a central location, or as one boundary displaced relative to the other. We finally considered two case studies based on Soufrière Hills Volcano (Montserrat, West Indies) and the Dabbahu rift segment (Afar, Ethiopia) magmatic systems. We found that the discrepancies between simple superposition of the displacement field and a fully interacting numerical solution depend mostly on the source types and on their spacing. Their magnitude may be comparable with the errors due to neglecting the topography, the inhomogeneities in crustal properties or more realistic rheologies. In the models considered, the errors induced when neglecting the source interaction can be neglected (<5%) when the sources are separated by at least 4 radii for two combined Mogi sources and by at least 3 radii for juxtaposed Mogi and Okada sources. Furthermore, this study underlines fundamental issues related to the numerical method chosen to model a dike or a magma chamber. It clearly demonstrates that, while the magma compressibility can be neglected to model the deformation due to one source or distant sources, it is necessary to take it into account in models combining close sources.

  20. Ambient PM 10 concentrations from wood combustion - Emission modeling and dispersion calculation for the city area of Augsburg, Germany

    NASA Astrophysics Data System (ADS)

    Brandt, Christian; Kunde, Robert; Dobmeier, Bernhard; Schnelle-Kreis, Jürgen; Orasche, Jürgen; Schmoeckel, Gerhard; Diemer, Jürgen; Zimmermann, Ralf; Gaderer, Matthias

    2011-07-01

    Ambient PM 10 concentration monitoring as well as dispersion calculations were conducted to determine the influence of emissions from domestic heating on ambient PM 10 concentrations in Augsburg, Germany. Based on the Augsburg emission inventory for domestic heating an average emission factor for particulate emissions from the combustion of different solid fuels (wood logs, pellets, briquettes) in different types of stoves under various combustion conditions was found to be 120 mg MJ -1 related to energy input. Hence an emission model as well as a wind field model were created for dispersion calculation of the emitted PM from wood combustion within Augsburg. The results of the dispersion calculation concurred with the ambient PM 10 monitoring data measured during the heating period 2007/2008. One result found that in residential areas with a high density of stoves the observed maximum concentration value of 9 ?g m -3 from wood combustion was up to 50% higher than in the city center. Ambient monitoring as well as dispersion calculation have shown a significant influence of wood combustion on ambient PM 10 concentrations in Augsburg. Based on these results the impact of wood combustion in a city can be estimated.