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1

Comprehensive modeling of a liquid rocket combustion chamber  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

2

Flow measurements in a model ramjet secondary combustion chamber  

SciTech Connect

Experimental studies were conducted on a typical secondary combustion chamber of a ramjet to understand the influence of various inlet parameters such as primary nozzle configuration, secondary air injection angle, and flow Reynolds numbers on the secondary combustion chamber (SCC) performance. Cold flow studies were made with air as the flow medium for both primary and secondary jets followed by similar studies with hot primary jets. The general flow structure in the SCC obtained from surface oil film technique showed recirculation zones near the head end. The combustor length required for jet mixing was found to be unrelated to recirculation zone length confirmed by selective temperature and total pressure profile measurements. The calculated frictional loss from the momentum balance consideration was found to be small. That significant improvement in mixing can be achieved by a choice of multiple-hole primary nozzle configuration has been demonstrated. 11 refs.

Chittilapilly, L.T.; Venkateswaran, S.; Paul, P.J.; Mukunda, H.S. (ISRO, Vikram Sarabhai Space Centre, Trivandrum (India) Indian Institute of Science, Bangalore (India))

1990-12-01

3

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...

4

Antipollution combustion chamber  

SciTech Connect

The invention concerns a combustion chamber for turbojet engines. The combustion chamber is of the annular type and consists of two coaxial flame tubes opening into a common dilution and mixing zone. The inner tube is designed for low operating ratings of the engine, the outer tube for high ratings. Air is injected as far upstream as possible into the dilution zone, to enhance the homogenization of the gaseous flow issuing from the two tubes prior to their passage into the turbine and to assure the optimum radial distribution of temperatures. The combustion chamber according to the invention finds application in a particularly advantageous manner in turbojet engines used in aircraft propulsion because of the reduced emission of pollutants it affords.

Caruel, J.E.; Gastebois, P.M.

1981-01-27

5

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

NASA Astrophysics Data System (ADS)

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.

Pitalo, Gerald Alexander

2000-10-01

6

Modeling and simulation of combustion chamber and propellant dynamics and issues in active control of combustion instabilities  

NASA Astrophysics Data System (ADS)

A method for a comprehensive approach to analysis of the dynamics of an actively controlled combustion chamber, with detailed analysis of the combustion models for the case of a solid rocket propellant, is presented here. The objective is to model the system as interconnected blocks describing the dynamics of the chamber, combustion and control. The analytical framework for the analysis of the dynamics of a combustion chamber is based on spatial averaging, as introduced by Culick. Combustion dynamics are analyzed for the case of a solid propellant. Quasi-steady theory is extended to include the dynamics of the gas-phase and also of a surface layer. The models are constructed so that they produce a combustion response function for the solid propellant that can be immediately introduced in the our analytical framework. The principal objective mechanisms responsible for the large sensitivity, observed experimentally, of propellant response to small variations. We show that velocity coupling, and not pressure coupling, has the potential to be the mechanism responsible for that high sensitivity. We also discuss the effect of particulate modeling on the global dynamics of the chamber and revisit the interpretation of the intrinsic stability limit for burning of solid propellants. Active control is also considered. Particular attention is devoted to the effect of time delay (between sensing and actuation); several methods to compensate for it are discussed, with numerical examples based on the approximate analysis produced by our framework. Experimental results are presented for the case of a Dump Combustor. The combustor exhibits an unstable burning mode, defined through the measurement of the pressure trace and shadowgraph imaging. The transition between stable and unstable modes of operation is characterized by the presence of hysteresis, also observed in other experimental works, and hence not a special characteristic of this combustor. Control is introduced in the form of pulsed secondary fuel. We show the capability of forcing the transition from unstable to stable burning, hence extending the stable operating regime of the combustor. The transition, characterized by the use of a shadowgraph movie sequence, is attributed to a combined fluid-mechanic and combustion mechanism.

Isella, Giorgio Carlo

7

Evaporation and ignition of droplets in combustion chambers modeling and simulation  

NASA Astrophysics Data System (ADS)

Computer simulation of liquid fuel jet injection into heated atmosphere of combustion chamber, mixture formation, ignition and combustion need adequate modeling of evaporation, which is extremely important for the curved surfaces in the presence of strong heat and mass diffusion fluxes. Combustion of most widely spread hydrocarbon fuels takes place in a gas-phase regime. Thus, evaporation of fuel from the surface of droplets turns to be one of the limiting factors of the process as well. The problems of fuel droplets atomization, evaporation being the key factors for heterogeneous reacting mixtures, the non-equilibrium effects in droplets atomization and phase transitions will be taken into account in describing thermal and mechanical interaction of droplets with streaming flows. In the present paper processes of non-equilibrium evaporation of small droplets will be discussed. As it was shown before, accounting for non-equilibrium effects in evaporation for many types of widely used liquids is crucial for droplet diameters less than 100 ?m, while the surface tension effects essentially manifest only for droplets below 0.1 ?m. Investigating the behavior of individual droplets in a heated air flow allowed to distinguish two scenarios for droplet heating and evaporation. Small droplets undergo successively heating, then cooling due to heat losses for evaporation, and then rapid heating till the end of their lifetime. Larger droplets could directly be heated up to a critical temperature and then evaporate rapidly. Droplet atomization interferes the heating, evaporation and combustion scenario. The scenario of fuel spray injection and self-ignition in a heated air inside combustion chamber has three characteristic stages. At first stage of jet injection droplets evaporate very rapidly thus cooling the gas at injection point, the liquid jet is very short and changes for a vapor jet. At second stage liquid jet is becoming longer, because evaporation rate decreases due to decrease of temperature. But combustion of fuel vapor begins which brings to increase of heat flux to droplets and accelerates evaporation. The length of the liquid jet decreases again and remains constant slightly oscillating.

Betelin, V. B.; Smirnov, N. N.; Nikitin, V. F.; Dushin, V. R.; Kushnirenko, A. G.; Nerchenko, V. A.

2012-01-01

8

Modeling of Solid Waste Flow and Mixing on the Traveling Grate of a Waste-to- energy Combustion Chamber  

Microsoft Academic Search

Mixing of the highly non-homogeneous municipal solid wastes (MSW) on the traveling grate of mass-burn combustion chambers assists the combustion process in waste-to-energy (WTE) facilities. A matrix-based Markov chain model was developed to simulate particle flow and mixing as the solid waste particles travel over a reverse acting Martin grate. The model was used to project the pathway of a

MASATO NAKAMURA; N. J. THEMELIS

9

Study of trajectories and combustion of fuel-oil droplets in the combustion chamber of a power-plant boiler with the use of a mathematical model  

NASA Astrophysics Data System (ADS)

A mathematical model is developed to permit study of the behavior of fuel-oil droplets in a combustion chamber, and results are presented from a computer calculation performed for the 300-MW model TGMP-314P boiler of a power plant.

Enyakin, Yu. P.; Usman, Yu. M.

1987-09-01

10

Combustion chamber analysis code  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

11

Iridium-Coated Rhenium Combustion Chamber  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

12

Internal flow-field measurements in a model can-type gas-turbine combustion chamber  

NASA Astrophysics Data System (ADS)

LDA measurements of the three mean velocity components and the corresponding turbulence intensities have been made to provide qualitative and quantitative information on the flow-field in a water model of a can-type gas turbine combustion chamber. The combustor geometry comprised a swirl driven primary zone, annulus fed rows of primary and secondary jets and an exit contraction nozzle. Flow visualization revealed a stable and symmetric vortex established within the primary zone via the combined effects of the inlet swirl and primary jet impingement. High levels of turbulence kinetic energy were generated within the vortex as well as near the location where the jets impinged. Large streamline curvature, anisotropy of the turbulence structure and very rapid transfer of momentum from the radial to the axial direction were associated with this primary region. In the downstream dilution zone a shallower jet trajectory was observed and the larger turbulence kinetic energy levels could be identified in this region with the shear layers formed between the bulk flow emerging from the primary zone and the incoming secondary jets. Moderate levels of spatial non-uniformities were measured at the exit from the nozzle.

Koutmos, P.; McQuirk, J. J.; Vafidis, C.

13

Formation mechanisms of combustion chamber deposits  

E-print Network

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 ...

O'Brien, Christopher J. (Christopher John)

2001-01-01

14

A simple analytical model to study and control azimuthal instabilities in annular combustion chambers  

E-print Network

today because fundamental issues in terms of mechanisms and modeling are not mastered yet. The first corresponding to an annular helicopter chamber using LES [6] but this may not be true in general: in liquid-fueled rocket en- gines or more generally in burners containing multiple jets [7], the interaction between

Nicoud, Franck

15

Modelling of turbulent reacting flows with gaseous fuels in a combustion chamber  

Microsoft Academic Search

The object of this study was to develop an efficient mathematical model of turbulent, chemically reacting gas-phase flows under two-dimensional steady-state conditions. The solution of the Navier-Stokes equations incorporating physical modelling for turbulence, combustion and thermal radiation was obtained by combining several computer codes previously developed. Numerical results for quantities such as temperature, stream function and species mole number distributions

Celalettin Çelik; Ahimet Arisoy; Osman F. Genceli

1996-01-01

16

External combustion engine having a combustion expansion chamber  

NASA Astrophysics Data System (ADS)

This patent application discloses an external combustion engine having a combustion expansion chamber. The engine includes a combustion chamber for generating a high-pressure, energized gas from a monopropellant fuel, and a cylinder for receiving the energized gas through a rotary valve to perform work on a cylinder disposed therein. A baffle plate is positioned between the combustion area and expansion area for reducing the pressure of the gas. The combustion area and expansion area are separated by a baffle plate having a flow area which is sufficiently large to eliminate the transmission of pressure pulsations from the combustion area to the expansion area while being small enough to provide for substantially complete combustion in the combustion area. The engine is particularly well suited for use in a torpedo.

Duva, Anthony W.

1993-03-01

17

Development of global mixing, combustion, and ignition models for quiescent chamber direct-injection diesel engines  

NASA Astrophysics Data System (ADS)

A large scale mixing and combustion model has been developed and studied through testing of two separate direct injection diesel engines. As a corollary, a shear layer ignition model was also developed for estimating the effects of key engine-related parameters on autoignition. Both models were developed for eventual inclusion into an engine cycle simulation for studying the effect of various key engine design parameters on overall power plant performance. The combustion model is comprised of two phases whose general behavior is characterized by a transient, representative time scale indicative of global mixing rate, mixing length scale, in-cylinder thermodynamic condition, and fuel properties. During the initial premixed phase, a mixing layer located on the injected fuel jet periphery is allowed to ignite and subsequently burn as controlled by the flame spread entrainment rate. After a determined delay, the second or mixing controlled phase is initiated and burns at a rate controlled by mixing, air utilization, impingement, and jet expansion. The shear layer ignition model is a transient, one-dimensional approach which accounts for fuel-air ratio stratification in the aforementioned mixing layer through assumed temperature and fuel specie profiles whose general shape is dictated by the conservation of energy. The first engine employed in this study was a Cummins VTA903 while the second engine was a heavy duty, Detroit Diesel (DDC) Series 60. In-cylinder pressure data was acquired for each engine and further analyzed using a commercially available thermodynamic engine cycle analysis code for net heat release rate analysis. Each engine was also instrumented to provide key details about the injection event such that reasonable estimates for autoignition were available for comparison with the proposed shear layer ignition model. Over a broad range of operating conditions for both engines, the mixing and combustion model exhibited predictive capability compared to experimentally determined net heat release rate profiles. Similarly, the shear layer ignition performed in an acceptable manner demonstrating superior performance compared to published empirical ignition delay models for diesel engines.

Schihl, Peter Joseph

18

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

NASA Technical Reports Server (NTRS)

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.

Petersen, Hans

1938-01-01

19

Numerical modelling of air supply and air flow pattern of a room that contains a gas appliance with open combustion chamber  

Microsoft Academic Search

SUMMARY In the last decade, quite a few carbon-monoxide intoxications occurred in Hungary due to the inadequate operation of gas appliances with open combustion chamber, connected to chimneys. These cases emphasized the importance of faultless air supply of the appliances and the safe removal of the incipient flue gases. This problem gave reason for the modelling of air supply, temperature

Lajos Barn; Róbert God

20

Heat-barrier coatings for combustion chambers  

NASA Technical Reports Server (NTRS)

Arc-plasma-sprayed layered coating of graded Inconel and zirconia protects film-coolant ring below injector plate of rocket engine combustion chamber. Interfacial temperature is designed for minimum buildup of stress and to avoid melting of the metal phase in the graded layers.

Carpenter, H. W.

1970-01-01

21

30 CFR 56.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2011 CFR

...Piercing § 56.7807 Flushing the combustion chamber. The combustion chamber of a jet drill stem which has been sitting unoperated in a drill hole shall be flushed with a suitable solvent after the stem is pulled...

2011-07-01

22

30 CFR 56.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2010 CFR

...Piercing § 56.7807 Flushing the combustion chamber. The combustion chamber of a jet drill stem which has been sitting unoperated in a drill hole shall be flushed with a suitable solvent after the stem is pulled...

2010-07-01

23

Internal chamber modeling of a solid rocket motor: Effects of coupled structural and acoustic oscillations on combustion  

NASA Astrophysics Data System (ADS)

This paper outlines modeling considerations for the internal ballistics of solid rocket motors. The simulation model consists of three coupled physical components, including the combined propellant and motor structure, the core fluid flow and the propellant combustion. A coupling component is also employed to control the fluid-structure-combustion interaction during the simulations. The results of simulating a motor firing illustrate the coupled effects of the structural and acoustic oscillations with the combustion model. Comparisons of the predicted results with experimental test results indicate a good correlation exists, providing support for the present simulation model.

Montesano, John; Behdinan, Kamran; Greatrix, David R.; Fawaz, Zouheir

2008-03-01

24

High-pressure promoted combustion chamber  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

25

Study of vortex core precession in combustion chambers  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

26

Prediction of temperature front in a gas turbine combustion chamber  

Microsoft Academic Search

Numerical computation has been applied to investigate the temperature field in a gas turbine combustion chamber. The simulation assumed that pressure imbalance conditions of air flow between primary and secondary inlets occur. The combustion chamber under study is part of a 70MW gas turbine from an operating combined cycle power plant. The combustion was simulated with normal fuel–air flow rate

F. Z. Sierra; J. Kubiak; G. González; G. Urquiza

2005-01-01

27

Design handbook for gaseous fuel engine injectors and combustion chambers  

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

28

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

NASA Technical Reports Server (NTRS)

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.

Mcdonald, G. H.

1979-01-01

29

Combustion chamber struts can be effectively transpiration cooled  

NASA Technical Reports Server (NTRS)

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.

Palmer, G. H.

1966-01-01

30

Fabrication of Composite Combustion Chamber/Nozzle for Fastrac Engine  

NASA Technical Reports Server (NTRS)

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.

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

31

Fabrication of Composite Combustion Chamber/Nozzle for Fastrac Engine  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

32

Fastrac Rocket Engine Combustion Chamber Acoustic Cavities  

NASA Technical Reports Server (NTRS)

A three dimensional modal analysis was performed using finite fluid elements. The analysis shows four distinct modes of the Fastrac chamber plus cavities near the frequency of the chamber first tangential mode. The mode shapes illustrate the complexity of fluid oscillations in a three dimensional chamber and acoustic cavity. In addition, a first tangential forcing function was applied to the chamber with three different acoustic cavity fluid temperatures. It was observed that the acoustic cavity fluid temperature has a significant effect on the response of the chamber to first tangential mode oscillations.

Christensen, Eric; Nesman, Tom

1998-01-01

33

Performance of Several Combustion Chambers Designed for Aircraft Oil Engines  

NASA Technical Reports Server (NTRS)

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)

Joachim, William F; Kemper, Carlton

1928-01-01

34

Pyrolysis reactor and fluidized bed combustion chamber  

DOEpatents

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.

Green, Norman W. (Upland, CA)

1981-01-06

35

Fabrication process for combustion chamber/nozzle assembly  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

36

Combustion Chamber/Nozzle Assembly and Fabrication Process Therefor  

NASA Technical Reports Server (NTRS)

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 larger end with a rocket body, and terminates at its smaller end in a tube of generally cylindrical 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.

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

2000-01-01

37

Hot fire fatigue testing results for the compliant combustion chamber  

NASA Technical Reports Server (NTRS)

A hydrogen-oxygen subscale rocket combustion chamber was designed incorporating an advanced design concept to reduce strain and increase life. The design permits unrestrained thermal expansion of a circumferential direction and, thereby, provides structural compliance during the thermal cycling of hot-fire testing. The chamber was built and test fired at a chamber pressure of 4137 kN/sq m (600 psia) and a hydrogen-oxygen mixture ratio of 6.0. Compared with a conventional milled-channel configuration, the new structurally compliant chamber had a 134 or 287 percent increase in fatigue life, depending on the life predicted for the conventional configuration.

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

1992-01-01

38

PROCESS SIMULATION AND CFD CALCULATIONS FOR THE DEVELOPMENT OF AN INNOVATIVE BALED BIOMASS-FIRED COMBUSTION CHAMBER  

Microsoft Academic Search

The present work shows that process simulation and CFD calculations are helpful tools for the development of a new and innovative combustion chamber for baled biomass. In addition experimental data were collected at a pilot plant and used for adjusting the simulation models and parameters. With this validated modelling approach the optimisation of combustion parameters as well as the combustion

MILTNER Martin

39

Wave instabilities in combustion and thrust chambers  

Microsoft Academic Search

A new theory and computations for combustion instability analysis are presented. The basic theoretical foundation stems from the concept of entropy-controlled energy growth or decay. Third order perturbation expansion is performed on the entropy-controlled acoustic energy equation to obtain the stability integrodifferential equation for the energy growth factor in terms of the linear, second, and third order energy growth rate

W. S. Yoon; T. J. Chung

1990-01-01

40

Liquid rocket engine self-cooled combustion chambers  

NASA Technical Reports Server (NTRS)

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.

1977-01-01

41

Experimental biomass burning emission assessment by combustion chamber  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

42

Corrosion fatigue causes failure of gas turbine combustion chamber  

SciTech Connect

Plates in the combustion chamber case of a gas turbine made of welded alloy 617 (UNS NO6617) and alloy Nimonic 75 (UNS N06075) failed by complete circumferential fracturing at the matrix-welding interface in the UNS N06075 plate. Fatigue cracks were first initiated at the outer subsurface within the intergranularly cracked coarse grains adjacent to the weld and then propagated because of combustion vibration during start-up operation conditions.

Elshawesh, F.; Elhoud, A.; Elmendelsi, T. [Petroleum Research Center, Tripoli (Libyan Arab Jamahiriya); Elwaer, A. [General Electricity Co., Tripoli (Libyan Arab Jamahiriya). Planning and Project Dept.

1997-07-01

43

Pulsating combustion of gas fuel in the combustion chamber with closed resonant circuit  

NASA Astrophysics Data System (ADS)

In the combustion chambers of the pulsation of gas flow oscillation greatly accelerate heat dissipation to the walls of the combustion chamber and improve combustion efficiency as compared with a uniform combustion mode. This allows you to effectively solve a number of problems of industrial power, including an environmentally friendly combustion products. Significant drawback of such systems - the emitted noise exceeding the permissible requirements. One solution to this problem - the separation of the resonance tube into 2 parts connected at the output to the interference of sound waves. The results of theoretical studies pulsating combustion technical mixture of propane in the system, consisting of a combustion chamber and two resonance tubes forming a closed resonant circuit. Resonators have a variable length. Calculations have shown that under certain oscillation of the resonator length to the first resonant frequency of the system is achieved by reducing SPL more than 15 dB. For oscillations at a second resonant frequency is the complete elimination of noise while maintaining intense oscillations in the combustion chamber.

Yallina, E. V.; Larionov, V. M.; Iovleva, O. V.

2013-12-01

44

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...

45

Optical Power Source Derived from Engine Combustion Chambers  

NASA Technical Reports Server (NTRS)

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.

Baumbick, Robert J. (Inventor)

1999-01-01

46

Heat transfer in rocket engine combustion chambers and nozzles  

NASA Technical Reports Server (NTRS)

Complexities of liquid rocket engine heat transfer which involve the injector faceplate and regeneratively and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis will be used to describe localized heating phenomena associated with particular injector configurations and coolant channels and film coolant dumps. These components are being analyzed, and the analyses verified with appropriate test data. Finally, the component analyses will be synthesized into an overall flowfield/heat transfer model. The FDNS code is being used to make the component analyses. Particular attention is being given to the representation of the thermodynamic properties of the fluid streams and to the method of combining the detailed models to represent overall heating. Unit flow models of specific coaxial injector elements have been developed and will be described. Since test data from the NLS development program are not available, new validation heat transfer data have been sought. Suitable data were obtained from a Rocketdyne test program on a model hydrocarbon/oxygen engine. Simulations of these test data will be presented. Recent interest in the hybrid motor have established the need for analyses of ablating solid fuels in the combustion chamber. Analysis of a simplified hybrid motor will also be presented.

Anderson, P. G.; Cheng, G. C.; Farmer, R. C.

1993-01-01

47

Explosion-induced combustion of hydrocarbon clouds in a chamber  

SciTech Connect

The interaction of the detonation of a solid HE-charge with a non-premixed cloud of hydro-carbon fuel in a chamber was studied in laboratory experiments. Soap bubbles filled with a flammable gas were subjected to the blast wave created by the detonation of PETN-charges (0.2 g < mass < 0.5 g). The dynamics of the combustion system were investigated by means of high-speed photography and measurement of the quasi-static chamber pressure.

Neuwald, P; Reichenbach, H; Kuhl, A L

2001-02-06

48

Formed platelets for low cost regeneratively cooled rocket combustion chambers  

NASA Technical Reports Server (NTRS)

Formed platelet technology can be used to fabricate LO2/LH2-fueled rocket propulsion chambers with higher heat capacity, higher cycle life, and lower pressure drops, in conjunction with lower costs due to the application of high volume production methods. The formed-platelet combustor liner is an assembly of identical platelets, each of which is composed of diffusion-bonded, photoetched laminae with coolant flow passages; the platelets are also joined by diffusion bonding to form the combustor's circumference. Attention is given to the fabrication of a platelet combustion chamber generating 40 Klbf of thrust.

Burkhardt, W. M.; Hayes, W. A.

1992-01-01

49

Effects of high combustion chamber pressure on rocket noise environment  

NASA Technical Reports Server (NTRS)

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.

Pao, S. P.

1972-01-01

50

Heat exchanger. [rocket combustion chambers and cooling systems  

NASA Technical Reports Server (NTRS)

A heat exchanger, as exemplified by a rocket combustion chamber, is constructed by stacking thin metal rings having microsized openings therein at selective locations to form cooling passages defined by an inner wall, an outer wall and fins. Suitable manifolds are provided at each end of the rocket chamber. In addition to the cooling channel openings, coolant feed openings may be formed in each of rings. The coolant feed openings may be nested or positioned within generally U-shaped cooling channel openings. Compression on the stacked rings may be maintained by welds or the like or by bolts extending through the stacked rings.

Sokolowski, D. E. (inventor)

1978-01-01

51

Heat transfer in rocket combustion chambers  

NASA Technical Reports Server (NTRS)

Complexities of liquid rocket engine heat transfer which involve the injector faceplate and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis was used to describe localized heating phenomena associated with particular injector configurations and film coolant flows. These components were analyzed, and the analyses verified when appropriate test data were available. The component analyses are being synthesized into an overall flowfield/heat transfer model. A Navier-Stokes flow solver, the FDNS code, was used to make the analyses. Particular attention was given to the representation of the thermodynamic properties of the fluid streams. Unit flow models of specific coaxial injector elements have been developed and are being used to describe the flame structure near the injector faceplate.

Anderson, P.; Cheng, G.; Farmer, R.

1993-01-01

52

Progress in Fabrication of Rocket Combustion Chambers by VPS  

NASA Technical Reports Server (NTRS)

Several documents in a collection describe aspects of the development of advanced materials and fabrication processes intended to enable the manufacture of advanced rocket combustion chambers and nozzles at relatively low cost. One concept discussed in most of the documents is the fabrication of combustion-chamber liners by vacuum plasma spraying (VPS) of an alloy of 88Cu/8Cr/4Nb (numbers indicate atomic percentages) -- a concept that was reported in "Improved Alloy for Fabrication of Combustion Chambers by VPS" (MFS-26546). Another concept is the deposition of graded-composition wall and liner structures by VPS in order to make liners integral parts of wall structures and to make oxidation- and thermal-protection layers integral parts of liners: The VPS process is started at 100 percent of a first alloy, then the proportion of a second alloy is increased gradually from zero as deposition continues, ending at 100 percent of the second alloy. Yet another concept discussed in one of the documents is the VPS of oxidation-protection coats in the forms of nickel-and-chromium-containing refractory alloys on VPS-deposited 88Cu/8Cr/4Nb liners.

Holmes, Richard R.; McKechnie, Timothy N.

2004-01-01

53

Spray and Combustion Characteristics of Butanol-Biodiesel-Diesel in a Constant Volume Combustion Chamber  

Microsoft Academic Search

The spray and combustion characteristics of ternary blends of butanol-biodiesel-diesel fuel were experimentally investigated in a constant volume combustion chamber under various ambient temperatures. The blends were mixed in three different volumetric ratios and the biofuels additive is lower than 20% in volume. The results indicate that the spray tip penetration reduced with the increase of ambient temperature and n-butanol

Yu Liu; Haifeng Liu; Ming Huo; Chia-fon F. Lee; Jun Li

2012-01-01

54

Effect of combustion chamber shape on air flow field in a D. I. diesel engine  

Microsoft Academic Search

The behaviour of two combustion chambers, a toroidal and a turbulent one, has been compared. The engine performance in terms of imep and exhaust emissions were measured. Laser Doppler Anemometry technique was used to characterize the fluids dynamic aspect of combustion system. The axial asymmetry introduced in combustion chamber shape causes strong differences in the air flow field at the

C. Bertoli; F. E. Corcione; G. Police; G. Valentino

1987-01-01

55

Slag monitoring system for combustion chambers of steam boilers  

SciTech Connect

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.

Taler, J.; Taler, D. [Cracow University of Technology, Krakow (Poland)

2009-07-01

56

Heat transfer in rocket engine combustion chambers and regeneratively cooled nozzles  

NASA Technical Reports Server (NTRS)

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.

1993-01-01

57

Comparison of LES, RANS and experiments in an aeronautical gas turbine combustion chamber  

Microsoft Academic Search

Although Large Eddy Simulations (LES) have demonstrated their potential in simple academic combustion chambers, their application to real gas turbine chambers requires specific developments and validations. In this study, three specific aspects of such chambers are discussed: multiple inlets, multi-perforated plates and film cooling. LES are used in an industry-like chamber and results are compared with predictions provided by Reynolds

G. Boudier; L. Y. M. Gicquel; T. Poinsot; D. Bissières; C. Bérat

2007-01-01

58

Reduction of the NOx emission of a closed combustion chamber by changing to air flows with swirl  

Microsoft Academic Search

From a study of NOx production in flames it follows that NOx emission differs for various combustion chambers. In addition to increasing the combustion chamber temperature or the volume flow into the combustion chamber, it is essential to find another way of reducing the production of NOx in the combustion process. In this paper the effect of swirl on NOx

R. Hatami

1981-01-01

59

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

60

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

61

NiAl-Based Approach For Rocket Combustion Chambers  

NASA Technical Reports Server (NTRS)

A multi-layered component, such as a rocket engine combustion chamber, includes NiAl or NiAl-based alloy as a structural layer on the hot side of the component. A second structural layer is formed of material selected form Ni-based superalloys, Co-based alloys, Fe-based alloys, Cu, and Cu-based alloys. The second material is more ductile than the NiAl and imparts increased toughness to the component. The second material is selected to enhance one or more predetermined physical properties of the component. Additional structural layers may be included with the additional material(s) being selected for their impact on physical properties of the component.

Nathal, Michael V. (Inventor); Gayda, John (Inventor); Noebe, Ronald D. (Inventor)

2005-01-01

62

NiAl-based approach for rocket combustion chambers  

NASA Technical Reports Server (NTRS)

A multi-layered component, such as a rocket engine combustion chamber, includes NiAl or NiAl-based alloy as a structural layer on the hot side of the component. A second structural layer is formed of material selected from Ni-based superalloys, Co-based alloys, Fe-based alloys, Cu, and Cu-based alloys. The second material is more ductile than the NiAl and imparts increased toughness to the component. The second material is selected to enhance one or more predetermined physical properties of the component. Additional structural layers may be included with the additional material(s) being selected for their impact on physical properties of the component.

Nathal, Michael V. (Inventor); Gayda, John (Inventor); Noebe, Ronald D. (Inventor)

2005-01-01

63

Modifications of a Composite-Material Combustion Chamber  

NASA Technical Reports Server (NTRS)

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.

Williams, Brian E.; McNeal, Shawn R.

2005-01-01

64

Determination of ram-jet combustion-chamber temperatures by means of total-pressure surveys  

NASA Technical Reports Server (NTRS)

A method is described by which the total temperature of the gases at the combustion-chamber outlet of a ram-jet engine may be determined from the loss in total pressure measured across the combustion chamber. A working chart is presented by means of which the ratio of the total temperature of the gases at the combustion-chamber outlet to the total temperature of the gases at the combustion-chamber inlet may be determined from the measured loss of total pressure across the combustion chamber and the known values of air flow, total pressure, and total temperature at the combustion-chamber inlet. Values of total-temperature ratio across the combustion chamber of a 20-inch ram jet were obtained in the Cleveland altitude wind tunnel over a range of pressure altitudes from 6000 to 15,000 feet. The difference between the temperature ratio across the combustion chamber determined from the chart and that obtained from the thermocouple measurement was within 6.2 percent of the thermocouple-temperature ratio and was within the accuracy of the thermocouple measurements.

Pinkel, I Irving

1947-01-01

65

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

Microsoft Academic Search

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

J. D. Lackey; W. N. Myers

1992-01-01

66

Development of a Rate of Injection Bench and Constant Volume Combustion Chamber for Diesel Spray Diagnostics  

Microsoft Academic Search

To help understand the complex fuel spray combustion phenomena in modern diesel engine using high injection pressure, a fuel injection test bench and a constant volume combustion chamber were developed and demonstrated in this study for diesel spray diagnostics. Both facilities are significant when linking between spray injection and combustion dynamics and engine performance. This link is important to determine

Anthony Phan

2009-01-01

67

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

NASA Astrophysics Data System (ADS)

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.

Maqsood, Omar Shahzada

68

Thermodynamics and combustion modeling  

NASA Technical Reports Server (NTRS)

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.

Zeleznik, Frank J.

1986-01-01

69

Structural Benchmark Tests of Composite Combustion Chamber Support Completed  

NASA Technical Reports Server (NTRS)

A series of mechanical load tests was completed on several novel design concepts for extremely lightweight combustion chamber support structures at the NASA Glenn Research Center (http://www.nasa.gov/glenn/). The tests included compliance evaluation, preliminary proof loadings, high-strain cyclic testing, and finally residual strength testing of each design (see the photograph on the left). Loads were applied with single rollers (see the photograph on the right) or pressure plates (not shown) located midspan on each side to minimize the influence of contact stresses on corner deformation measurements. Where rollers alone were used, a more severe structural loading was produced than the corresponding equal-force pressure loading: the maximum transverse shear force existed over the entire length of each side, and the corner bending moments were greater than for a distributed (pressure) loading. Failure modes initiating at the corner only provided a qualitative indication of the performance limitations since the stress state was not identical to internal pressure. Configurations were tested at both room and elevated temperatures. Experimental results were used to evaluate analytical prediction tools and finite-element methodologies for future work, and they were essential to provide insight into the deformation at the corners. The tests also were used to assess fabrication and bonding details for the complicated structures. They will be used to further optimize the design of the support structures for weight performance and the efficacy of corner reinforcement.

Krause, David L.; Thesken, John C.; Shin, E. Eugene; Sutter, James K.

2005-01-01

70

SSME Main Combustion Chamber (MCC) hot oil dewaxing  

NASA Technical Reports Server (NTRS)

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.

Akpati, Anthony U.

1995-01-01

71

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

NASA Technical Reports Server (NTRS)

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.

Akpati, Anthony U.

1994-01-01

72

Combustion of liquid fuel in the counter-swirled jets of a gas turbine plant annular combustion chamber  

NASA Astrophysics Data System (ADS)

Tests were carried out on an annular combustion chamber rig with a stabilizer of the type used in the GTN-25 gas turbine plant to determine the feasibility of burning a liquid fuel (diesel fuel, GOST 4749-73) in a combustion chamber of this type. Very high performance was obtained for a number of important characteristics of the microflame combustion process in counterswirled jets where all the air was supplied through the front unit of the chamber. However, the tests did not make it possible to solve some of the problems which arise when operating under full-scale conditions, such as the required high combustion efficiency under variable operating conditions of a gas turbine plant; elimination of soot formation at the walls of the stabilizer and the internal surfaces of the pipes supplying fuel to the atomizers; and a decrease in smoking under conditions of excess air factor.

Tumanovskii, A. G.; Semichastnyi, N. N.; Sokolov, K. Iu.

1986-03-01

73

Simulation of Turbulent Combustion Using Various Turbulent Combustion Models  

Microsoft Academic Search

The reynolds-averaged navier-stokes (RANS) method nowadays still is the major tool for gas turbine chamber (GTC) designers, but there is not a universal method in RANS GTC spray combustion simulation at present especially for the two- phase turbulent combustion. Usually there are two main steps in two-phase combustion: the liquid fuel evaporation and the gas mixture combustion. Thus, two widely

Fang Wang; Yong Huang; Tian Deng

2009-01-01

74

An experimental and computational evaluation of two dual-intake-valve combustion chambers  

SciTech Connect

This paper reports on multi-dimensional computations that wle made of spark-ignited premixed-charge combustion in two engines having pent-roof-shaped combustion chambers and two intake valves per cylinder, one with a central spark plug and the other with dual lateral spark plugs. The basic specifications for the two engines were the same except for differences in the number of spark plugs and exhaust valves. The effects of swirl and equivalence ratio on combustion, wall heat transfer, and nitric oxide emission characteristics were examined using a global combustion model that accounts for laminar-kinetics and turbulent-mixing effects. The initial conditions on both mean-flow and turbulence parameters at intake valve closing (IVC) were estimated in order to simulate engine operation either with both intake valves active or with one valve deactivated. The predictions were compared with experimentally derived pressure-time, heat loss, and nitric oxide emission data. The model, consistent with experimental data, indicates that the dual lateral ignition engine responds more favorably to valve deactivation as charge dilution is increased, and shows flame convection to be the source of the dual lateral ignition engine's superior that when the effects of flame convection are considered, the model predicted top dead center (TDC) turbulence intensities are in good agreement with experimentally derived apparent TDC turbulence intensities for both engines with the without valve deactivation.

Najt, P.M.; Kuo, T.W.

1990-01-01

75

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

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

76

Fluids and Combustion Facility: Combustion Integrated Rack Modal Model Correlation  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

77

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

NASA Technical Reports Server (NTRS)

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.

Campbell, Carl E

1951-01-01

78

Experimental and theoretical investigation of a research atomizer/combustion chamber configuration  

NASA Astrophysics Data System (ADS)

A mathematical model of two-phase flows in gas turbine combustors is presently validated in light of an experimental airblast atomizer/combustion chamber configuration. Inlet boundary conditions were measured within the nozzle by laser two-focus velocimetry, and the starting velocities and mass fluxes for the spray's droplet sizes were determined by phase-Doppler anemometry. The spray exhibits the structure of an axial acceleration of all drop sizes, as well as a subsequent dispersion of the droplets and radial separation by centrifugal force according to size.

Hassa, C.; Bluemcke, E.; Brandt, M.; Eickoff, H.

1992-06-01

79

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

NASA Technical Reports Server (NTRS)

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.

Zimmerman, Frank

2003-01-01

80

Investigation of combustion chamber acoustics and its interaction with LOX/H2 spray flames  

NASA Astrophysics Data System (ADS)

Acoustics of combustion chambers is investigated experimentally in cold flow and hot fire tests. The performance of absorber elements is analyzed in respect to their effect on combustion chamber eigenfrequencies as well as to their damping characteristics. It is shown that predictions of numerical modal analysis of chamber acoustics are in very good agreement with measurements. In hot fire tests, a burning LOX/H2 spray is acoustically excited with a siren wheel and combustion response is recorded with dynamic pressure sensors and by high-speed visualization of the spray and the flame. Although no combustion instability could be observed, analyzing the temporal and spatial distribution of flame response allowed addressing the question, whether the coupling of acoustics to combustion is via pressure or velocity sensitive processes.

Oschwald, M.; Knapp, B.

2009-09-01

81

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

82

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

83

MODELLING PULVERISED COAL COMBUSTION USING A DETAILED COAL COMBUSTION MODEL  

Microsoft Academic Search

The ability to assess the combustion behaviour of internationally traded coals and accurately predict flame characteristics, stable species concentration, unburned carbon and pollutant emissions is of importance to the power generating industry. Despite recent advances in coal combustion modelling detailed understanding is still lacking on the exact role of the coal maceral content on the combustion process. Here, a CFD-based

R. I. BACKREEDY; L. M. FLETCHER; L. MA; M. POURKASHANIAN; A. WILLIAMS

2006-01-01

84

Radiative heat exchange in the combustion chamber of an MHD electric power plant using methane gas  

Microsoft Academic Search

A method is proposed for calculating radiative thermal fluxes on the wall of the combustion chamber of an MHD electric power plant operating with methane gas. The calculations are performed on the basis of spectral characteristics of the molecular components of the combustion products and ionizing potassium impurity, with allowance for multiple reflection of radiation from the wall of the

L. M. Biberman; M. B. Zhelezniak; A. Kh. Mnatsakanian; A. G. Rotinov; S. A. Tager

1980-01-01

85

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

Microsoft Academic Search

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

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

1993-01-01

86

An Extended Combustion Model for the Aircraft Turbojet Engine  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

87

Considerations of Air Flow in Combustion Chambers of High-Speed Compression-Ignition Engines  

NASA Technical Reports Server (NTRS)

The air flow in combustion chambers is divided into three fundamental classes - induced, forced, and residual. A generalized resume is given of the present status of air flow investigations and of the work done at this and other laboratories to determine the direction and velocity of air movement in auxiliary and integral combustion chambers. The effects of air flow on engine performance are mentioned to show that although air flow improves the combustion efficiency, considerable induction, friction, and thermal losses must be guarded against.

Spanogle, J A; Moore, C S

1932-01-01

88

Characteristics of the thermal regime of circular tube combustion chambers with combined wall cooling  

NASA Astrophysics Data System (ADS)

The thermal characteristics of circular tube gas turbine engine combustion chambers cooled by external blowing and the creation of an internal air-enclosed sheet are investigated. Combustion chamber wall temperatures were measured as a function of air flow parameters and fuel type (kerosene or natural gas) for two flame tube configurations. It is found that kerosene combustion leads to a higher wall temperature than natural gas, while increased air temperature increases wall temperature and air pressure is observed to have no effect in the range studied. It is also observed that the gas delivery scheme has little influence on wall temperature, while the influence of the air excess coefficient and the entrance velocity are shown to depend on flame tube air intake geometry. Results indicate that local combustion chamber wall temperatures may be lowered by creating additional flame tube openings or by drilling existing ones.

Didenko, V. I.; Khristich, V. A.; Liubchik, G. N.; Shevchenko, A. M.

1980-03-01

89

Status on the Verification of Combustion Stability for the J-2X Engine Thrust Chamber Assembly  

NASA Technical Reports Server (NTRS)

Development is underway of the J -2X engine, a liquid oxygen/liquid hydrogen rocket engine for use on the Space Launch System. The Engine E10001 began hot fire testing in June 2011 and testing will continue with subsequent engines. The J -2X engine main combustion chamber contains both acoustic cavities and baffles. These stability aids are intended to dampen the acoustics in the main combustion chamber. Verification of the engine thrust chamber stability is determined primarily by examining experimental data using a dynamic stability rating technique; however, additional requirements were included to guard against any spontaneous instability or rough combustion. Startup and shutdown chug oscillations are also characterized for this engine. This paper details the stability requirements and verification including low and high frequency dynamics, a discussion on sensor selection and sensor port dynamics, and the process developed to assess combustion stability. A status on the stability results is also provided and discussed.

Casiano, Matthew; Hinerman, Tim; Kenny, R. Jeremy; Hulka, Jim; Barnett, Greg; Dodd, Fred; Martin, Tom

2013-01-01

90

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

NASA Technical Reports Server (NTRS)

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.

Zimmerman, Frank

2000-01-01

91

Study on Combustion Chamber Geometry Effects in an HCCI Engine using High-Speed Cycle-Resolved Chemiluminescence Imaging  

Microsoft Academic Search

The aim of this study is to see how geometry generated turbulence affects the Rate of Heat Release (ROHR) in an HCCI engine. HCCI combustion is limited in load due to high peak pressures and too fast combustion. If the speed of combustion can be decreased the load range can be extended. Therefore two different combustion chamber geometries were investigated,

Andreas Vressner; Anders Hultqvist; Bengt Johansson

2007-01-01

92

Effect of radiative heat transfer on combustion chamber flows  

Microsoft Academic Search

The importance of radiative heat transfer in the hydrodynamics of a parabolic combusting flow has been explored. Numerical studies have been performed of turbulent, nonpremixed flames confined within cylindrical and two-dimensional enclosures in order to produce a definitive answer to the question as to when radiation is important in determining the flow properties. A new method, called the effective angle

S. Bhattacharjee; W. L. Grosshandler

1989-01-01

93

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

94

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

95

Atmospheric behaviour of oil-shale combustion fly ash in a chamber study  

Microsoft Academic Search

There are huge world deposits of oil shale, however, little is known about the fate of atmospheric oil-shale combustion fly ash. In the present work, oil-shale combustion fly-ash aerosol was investigated under simulated daytime and nighttime conditions. Fly-ash particles collected from the Baltic Power Plant (Estonia) were injected directly to a 190m3 outdoor Teflon film chamber. The initial concentration of

Erik Teinemaa; Uuve Kirso; Michael R. Strommen; Richard M. Kamens

2002-01-01

96

An experimental and computational evaluation of two dual-intake-valve combustion chambers  

Microsoft Academic Search

This paper reports on multi-dimensional computations that wle made of spark-ignited premixed-charge combustion in two engines having pent-roof-shaped combustion chambers and two intake valves per cylinder, one with a central spark plug and the other with dual lateral spark plugs. The basic specifications for the two engines were the same except for differences in the number of spark plugs and

P. M. Najt; T. W. Kuo

1990-01-01

97

Formed platelets for low cost regeneratively cooled rocket combustion chambers  

Microsoft Academic Search

Formed platelet technology can be used to fabricate LO2\\/LH2-fueled rocket propulsion chambers with higher heat capacity, higher cycle life, and lower pressure drops, in conjunction with lower costs due to the application of high volume production methods. The formed-platelet combustor liner is an assembly of identical platelets, each of which is composed of diffusion-bonded, photoetched laminae with coolant flow passages;

W. M. Burkhardt; W. A. Hayes

1992-01-01

98

Coal-feeding mechanism for a fluidized bed combustion chamber  

DOEpatents

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.

Gall, Robert L. (Morgantown, WV)

1981-01-01

99

Design of a pyrometer for temperature measurements on the solid fuel combustion chamber  

Microsoft Academic Search

A pyrometer was developed for the measurement of the flame temperature of the solid fuel combustion chamber. The principle of the design is based on the measurement of the spectral intensity at two wavelengths, 577 and 830 nm, emitted by the soot in the flame. The ratio of the intensities is a univocal measure of the color temperature at these

W. J. A. M. Aarts; T. Wijchers

1987-01-01

100

Experimental determination of turbulence in a GH2-GOX rocket combustion chamber  

NASA Technical Reports Server (NTRS)

The intensity of turbulence and the Lagrangian correlation coefficient for a gaseous rocket combustion chamber have been determined from the experimental measurements of the tracer gas diffusion. A combination of Taylor's turbulent diffusion theory and Spalding's numerical method for solving the conservation equations of fluid mechanics was used to calculate these quantities. Taylor's theory was extended to consider the inhomogeneity of the turbulence field in the axial direction of the combustion chamber. An exponential function was used to represent the Lagrangian correlation coefficient. The results indicate that the maximum value of the intensity of turbulence is about 15% and the Lagrangian correlation coefficient drops to about 0.12 in one inch of the chamber length.

Tou, P.; Russell, R.; Ohara, J.

1974-01-01

101

Lean stability augmentation study. [on gas turbine combustion chambers  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

102

Hydrocarbon-fuel/combustion-chamber-liner materials compatibility  

NASA Technical Reports Server (NTRS)

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.

Homer, G. David

1991-01-01

103

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

104

Effect of Triangular Fins on Critical Heat Flux in Ethanol-cooled Combustion Chamber  

NASA Astrophysics Data System (ADS)

A pressure-fed engine with a regeneratively-cooled combustion chamber is studied in JAXA. Operation chamber pressure is approximately 1 MPa. A proposed propellant combination is liquid oxygen and ethanol. However, it is necessary to understand the critical heat flux when ethanol is used as a coolant for regeneratively-cooled combustion chamber because the saturation pressure of it is 6.3 MPa. In general, it is known that the cooling wall with fins improves the cooling performance. In this study, the effect of triangular fins on critical heat flux of ethanol in ethanol-cooled combustion chamber was investigated. As the result, it was found that the critical heat flux of cooling wall with triangular fins was 23 % higher than that of that without fin in the same velocity condition of the coolant. The critical heat flux increases by the triangular fins on the cooling surface due to the effect of the combination cooling with film boiling and nucleate boiling.

Takegoshi, Masao; Suzuki, Ryosuke; Saito, Toshihito; Ono, Fumiei; Hiraiwa, Tetsuo; Tomioka, Sadatake

105

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

NASA Technical Reports Server (NTRS)

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.

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

2014-01-01

106

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

NASA Technical Reports Server (NTRS)

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.

Holmes, Richard; Ellis, David; McKechnie

1999-01-01

107

Experimental and numerical investigation of gaseous fuel combustion in swirl chamber  

Microsoft Academic Search

In this paper the results of experimental and numerical investigations of swirl burner were presented. Mathematical model for prediction of velocity, temperature and concentration fields of axisymmetrical confined swirl turbulent flame was developed. Model consists of few mutually coupled segments related to basic processes in turbulent flows with combustion. The original combustion rate model based on the ideal reacting hypothesis

Stevan Nemoda; Vukman Baki?; Simeon Oka; Goran Zivkovi?; Nenad Crnomarkovi?

2005-01-01

108

Analysis of Combustion Chamber Deposits by ESI-TOF-MS and MALDI-TOF-MS  

SciTech Connect

Combustion chamber deposits (CCDs) in internal combustion engines have been studied by various techniques to understand the relationship of performance degradation with deposit quantity and structure. XPS, XAS, NMR, and elemental analysis have offered insight into the bulk structure of C, H, N, O and metal components [1]. MS has offered some information about compound structure, but results are limited due to the insolubility and complexity of the materials. Recent advances in MS have opened new possibilities for analysis of CCDs. Here we report initial findings on the carbon structure of these deposits determined by ESI-TOF-MS and MADLI-TOF-MS.

Reynolds, J G; Shields, S J; Roos, J W

2001-06-14

109

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

NASA Technical Reports Server (NTRS)

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.

Spanogle, J A; Buckley, E C

1933-01-01

110

Turbulence in a gaseous hydrogen-liquid oxygen rocket combustion chamber  

NASA Technical Reports Server (NTRS)

The intensity of turbulence and the Lagrangian correlation coefficient for a LOX-GH2 rocket combustion chamber was determined from experimental measurements of tracer gas diffusion. A combination of Taylor's turbulent diffusion theory and a numerical method for solving the conservation equations of fluid mechanics was used to calculate these quantities. Taylor's theory was extended to consider the inhomogeneity of the turbulence field in the axial direction of the combustion chamber, and an exponential function was used to represent the Lagrangian correlation coefficient. The results indicate that the value of the intensity of turbulence reaches a maximum of 14% at a location about 7" downstream from the injector. The Lagrangian correlation coefficient associated with this value is given by the above exponential expression where alpha = 10,000/sec.

Lebas, J.; Tou, P.; Ohara, J.

1975-01-01

111

Radiative heat exchange in the combustion chamber of an MHD electric power plant using methane gas  

NASA Astrophysics Data System (ADS)

A method is proposed for calculating radiative thermal fluxes on the wall of the combustion chamber of an MHD electric power plant operating with methane gas. The calculations are performed on the basis of spectral characteristics of the molecular components of the combustion products and ionizing potassium impurity, with allowance for multiple reflection of radiation from the wall of the chamber. It is shown that the effect of particles of vaporizing impurity on the optical properties of the working medium is insignificant. It follows from the calculations that emission from the potassium impurity atoms amounts to about one half the radiative thermal flux density received on the wall, the magnitude of which reaches 2-3 MW/sq m.

Biberman, L. M.; Zhelezniak, M. B.; Mnatsakanian, A. Kh.; Rotinov, A. G.; Tager, S. A.

1980-09-01

112

Heat transfer in rocket engine combustion chambers and nozzles  

NASA Technical Reports Server (NTRS)

The complexities of liquid rocket engine heat transfer which involve the injector faceplate and regeneratively and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis will be used to describe localized heating phenomena associated with particular injector configurations and coolant channels and film coolant dumps. These components are being analyzed, and the analysis verified with appropriate test data. Finally, the component analysis will be synthesized into an overall flowfield/heat transfer model. The FDNS code is being used to make the component analyses. Particular attention is being given to the representation of the thermodynamic properties of the fluid streams and to the method of combining the detailed models to represent overall heating. Unit flow models of specific coaxial injector elements have been developed and will be described. Film cooling simulations of film coolant flows typical of the subscale Space Transportation Main Engine (STME) being experimentally studied by Pratt and Whitney have been made, and these results will be presented. Other film coolant experiments have also been simulated to verify the CFD heat transfer model being developed. The status of the study and its relevance as a new design tool are covered. Information is given in viewgraph form.

Anderson, P. G.; Chen, Y. S.; Farmer, R. C.

1992-01-01

113

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

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

114

Chemical kinetics and combustion modeling  

SciTech Connect

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.

Miller, J.A. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

115

Problems of providing completeness of the methane-containing block-jet combustion in a rocket-ramjet engine's combustion chamber  

NASA Astrophysics Data System (ADS)

Some problems of methane-containing hydrocarbon fuel combustion are discussed. It seems that reduction of methane burnout zone length is one from main problems of designing new type engine. It is very important at the creation of combustion chambers of a rocket-ramjet engine for prospective space shuttle launch vehicles.

Timoshenko, Valeriy I.; Belotserkovets, Igor S.; Gusinin, Vjacheslav P.

2009-11-01

116

Combustion instability modeling and analysis  

SciTech Connect

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.

Santoro, R.J.; Yang, V.; Santavicca, D.A. [Pennsylvania State Univ., University Park, PA (United States); Sheppard, E.J. [Tuskeggee Univ., Tuskegee, AL (United States). Dept. of Aerospace Engineering

1995-12-31

117

Altitude-test-chamber Investigation of Performance of a 28-inch Ram-jet Engine I : Combustion and Operational Performance of Four Combustion-chamber Configurations  

NASA Technical Reports Server (NTRS)

An altitude-test-chamber investigation of a 28-inch-diameter ram-jet engine at a simulated flight Mach number of approximately 2.0 for altitudes of 40,000 to 50,000 feet was conducted at the NACA Lewis laboratory. Three different flame holders, varying in the number and size of the annular gutters, in conjunction with several fuel-injection systems were investigated. The combustion efficiency for the flame-holder fuel-injection system that provided the best over-all operational fuel-air-ratio range (0.03 to 0.075) was over 0.9 at a fuel-air ratio of about 0.065 for the altitude range investigated.

Shillito, T B; Jones, W L; Henzel, J G , Jr

1950-01-01

118

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

119

Modeling the internal combustion engine  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

120

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

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

121

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

NASA Technical Reports Server (NTRS)

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.

Wadel, Mary F.

1997-01-01

122

Measurement of regression rate in hybrid rocket using combustion chamber pressure  

NASA Astrophysics Data System (ADS)

An attempt was made in this paper to determine the regression rate of a hybrid fuel by using combustion chamber pressure. In this method, the choked flow condition at the nozzle throat of the hybrid rocket was used to obtain the mass of fuel burnt and in turn the regression rate. The algorithm used here is better than those reported in the literature as the results obtained were compared with the results obtained using the weight loss method and was demonstrated to be in good agreement with the results obtained using the weight loss method using the same motor and the same fuel and oxidizer combination. In addition, the O/F ratio obtained was in good agreement with those obtained using the weight loss method. The combustion efficiencies obtained were in good agreement with the average values.

Kumar, Rajiv; Ramakrishna, P. A.

2014-10-01

123

Analysis of Combustion Chamber Deposits by ESI-TOF-MS and MALDI-TOF-MS  

SciTech Connect

Combustion chamber deposits (CCD) in internal combustion engines have been studied by various techniques to understand the relationship of performance degradation with deposit quantity and structure. XPS, XAS, NMR, and elemental analysis have offered insight into the bulk structure of C, H, N, O and metal components. MS has offered some information about compound structure, but results are limited due to the insolubility and complexity of the materials. Recently, we have reported on the metal structure by XPS and XAS of several deposits from a GM 3800 engine generated using a standard fuel and one that contains low levels of the gasoline anti-knock additive, MMT. Here we report the initial findings on the carbon structure of these deposits determined by ESI-TOF-MS and MADLI-TOF-MS.

Reynolds, J G; Shields, S J; Roos, J W

2001-06-14

124

Modeling of microgravity combustion experiments  

NASA Technical Reports Server (NTRS)

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.

Buckmaster, John

1993-01-01

125

Experimental investigation of fuel evaporation in the vaporizing elements of combustion chambers  

NASA Technical Reports Server (NTRS)

A description is given of the experimental apparatus and the methods used in the investigation of the degree of fuel (kerosene) evaporation in two types of vaporizing elements in combustion chambers. The results are presented as dependences of the degree of fuel evaporation on the factors which characterize the functioning of the vaporizing elements: the air surplus coefficient, the velocity of flow and temperature of the air at the entrance to the vaporizing element and the temperature of the wall of the vaporizing element.

Vezhba, I.

1979-01-01

126

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

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

127

Design of a pyrometer for temperature measurements on the solid fuel combustion chamber  

NASA Astrophysics Data System (ADS)

A pyrometer was developed for the measurement of the flame temperature of the solid fuel combustion chamber. The principle of the design is based on the measurement of the spectral intensity at two wavelengths, 577 and 830 nm, emitted by the soot in the flame. The ratio of the intensities is a univocal measure of the color temperature at these wavelengths. The apparatus is small, robust and user friendly. Calibration currents which imitate the output of the detectors are used to control the electronic circuits. The preliminary measuring accuracy between 1400 and 2800 K is about 20 K if the pyrometer is calibrated every 4 months using a qualified tungsten ribbon lamp.

Aarts, W. J. A. M.; Wijchers, T.

1987-10-01

128

Particle-Bound PAH Emission from the Exhaust of Combustion Chamber  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

129

Measurement of the flow field in a diesel engine combustion chamber after combustion by cross-correlation of high-speed photographs  

NASA Astrophysics Data System (ADS)

A cellular cross-correlation technique is applied to high-speed photographs of the luminous phase of combustion in a high-speed direct-injection diesel engine. The method enables the velocity and vorticity distributions in the combustion chamber to be evaluated. The results obtained from the basic technique are refined to remove spurious results and to complete the definition of the flow field by applying data validation, interpolation, and smoothing. The velocity and vorticity fields evaluated at two swirl ratios show the way in which the basically solid body swirl motion interacts with the fuel jets in the combustion chamber. A better understanding of the post-combustion fluid motion is obtained, and this should be of help in validating CFD codes and also the design of engines.

Sun, J. H.; Yates, D. A.; Winterbone, D. E.

1996-03-01

130

Modeling of Laser-Induced Metal Combustion  

SciTech Connect

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.

Boley, C D; Rubenchik, A M

2008-02-20

131

Combustion behaviors and flame structure of methane/coal dust hybrid in a vertical rectangle chamber  

SciTech Connect

Methane/coal dust hybrid flame propagating in a vertical rectangle chamber was examined experimentally. In these experiments, the coal dusts were dispersed into the chamber by premixed methane/air mixture flow to form a methane/coal dust/air hybrid and the hybrid was ignited by an electrode spark. A high-speed video camera was used to record the images of the propagating flame, and a photodiode was used to study the emitting light characteristics of the flame. Micro-thermocouples and ion current probes were used to obtain temperature profiles and reaction behaviors of the combustion zone, respectively. Based on experimental results, combustion behaviors and flame structure of methane/coal dust hybrid propagating flame were analyzed. After the methane/coal dust hybrid is ignited by the electrode spark, the flame begins to propagate in the chamber. The flame front propagates downwards in the initial 20ms, and then propagates upwards. The flame emits strong yellow light and the luminous zone length increases during propagation. The measured temperature starts to increase at a position about 2.15cm ahead of the reaction zone, then to a maximum value near the end of the reaction zone and then subsequently decreases. The chemical reaction begins while the temperature is about 200{sup o}C, and the reaction intensity increases quickly with the temperature increasing. The reaction intensity increases to the maximum value while the temperature is about 500 {sup o}C and then decreases gradually. According to the measured temperature and ion current curves, the preheated zone of the methane/coal dust hybrid is about 2.15cm in width.

Chen, D.L.; Sun, J.H.; Wang, Q.S.; Liu, Y. [University of Science & Technology China, Hefei (China)

2008-07-01

132

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)

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.

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

2006-01-01

133

Modeling Combustion in Supersonic Flows  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

134

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)

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.

Boyd, Bemrose

1948-01-01

135

New technique of the local heat flux measurement in combustion chambers of steam boilers  

NASA Astrophysics Data System (ADS)

A new method for measurement of local heat flux to water-walls of steam boilers was developed. A flux meter tube was made from an eccentric tube of short length to which two longitudinal fins were attached. These two fins prevent the boiler setting from heating by a thermal radiation from the combustion chamber. The fins are not welded to the adjacent water-wall tubes, so that the temperature distribution in the heat flux meter is not influenced by neighbouring water-wall tubes. The thickness of the heat flux tube wall is larger on the fireside to obtain a greater distance between the thermocouples located inside the wall which increases the accuracy of heat flux determination. Based on the temperature measurements at selected points inside the heat flux meter, the heat flux absorbed by the water-wall, heat transfer coefficient on the inner tube surface and temperature of the water-steam mixture was determined.

Taler, Jan; Taler, Dawid; Sobota, Tomasz; Dzierwa, Piotr

2011-12-01

136

Effects of combustion chamber deposit location and composition. [MMT is the antiknock fuel additive methylcyclopentadienylmanganese tricarbonyl  

SciTech Connect

Combustion chamber deposit samples were taken from two vehicles from an octane requirement increase (ORI) fleet and six vehicles from a three-way catalyst (TWC) durability fleet. This selection allowed a comparison of engine type, driving cycle, and the antiknock fuel additive methycyclopentadienylmanganese tricarbonyl (MMT). Selected samples were characterized by quantitative elemental analyses, emission spectroscopy, and by x-ray diffraction. Results of the study are: (1) combustion chamber deposits consist mainly of carbonaceous material with inorganic compounds from both the fuel and the oil; (2) in most cases the H/C ratio is higher for deposits removed from the end gas region; (3) deposits removed from the exhaust valve are almost entirely inorganic compounds, metal phosphates from the oil and manganese oxide if the fuel contains MMT; (4) the cylinder with the highest octane requirement, and hence the first cylinder to knock, cannot be distinguished from the other cylinders by chemical composition of the deposits; (5) cylinders with high oil consumption could be identified by the high concentration of oil inorganics and low concentration of fuel inorganics compared to the other cylinders; (6) differences in deposit composition were observed between engine families and between driving cycles with the same engine family. The source of these differences is believed to be the engine operating conditions but a specific relation has not been established; (7) Mn/sub 3/O/sub 4/ was present in the deposits when MMT was used in the fuel; and (8) deposit accumulation and stabilization involve more than a single mechanism.

Adams, K.M.; Baker, R.E.

1981-03-01

137

Altitude-chamber Performance of British Roll-royce Nene II Engine IV : Effect of Operational Variables on Temperature Distribution at Combustion-chamber Outlets  

NASA Technical Reports Server (NTRS)

Temperature surveys were made at the combustion-chamber outlets of a British Rolls-Royce Nene II engine. The highest mean nozzle-vane and mean gas temperatures were found to occur at a radius approximately 75% of the nozzle-vane length from the inner ring of the nozzle-vane assembly. Variations in engine speed, jet-nozzle area, simulated altitude, and simulated flight speed altered the temperature level but did not materially affect the pattern of radial temperature distribution.

Huntley, Sidney C

1950-01-01

138

Modelling of Non-Premixed Turbulent Combustion of Hydrogen using Conditional Moment Closure Method  

NASA Astrophysics Data System (ADS)

Most of the electricity generation and energy for transport is still generated by the conversion of chemical to mechanical energy by burning the fuels in the combustion chamber. Regulation for pollution and the demand for more fuel economy had driven worldwide researcher to focus on combustion efficiency. In order to reduce experimental cost, accurate modelling and simulation is very critical step. Taylor series expansion was utilised to reduce the error term for the discretization. FORTRAN code was used to execute the discretized partial differential equation. Hydrogen combustion was simulated using Conditional Moment Closure (CMC) model. Combustion of hydrogen with oxygen was successfully simulated and reported in this paper.

Noor, M. M.; Aziz Hairuddin, A.; Wandel, Andrew P.; Yusaf, T. F.

2012-09-01

139

Numerical calculation of the NO formation in a multi-point combustion chamber and results of the associated validation experiments  

Microsoft Academic Search

This paper presents some numerical simulations of a multi-point combustion chamber including the calculation of the NO formation by a lagrangian method well adapted to take into account the turbulence-chemistry interaction. The simplifying assumption of axial symmetry was used to limit the computation time and made it possible to obtain numerically the influence of a geometrical parameter, the direction of

Lionel Matuszewski; Francis Dupoirieux; Christian Guin; Frederic Grisch

140

Subgrid Combustion Modeling for the Next Generation National Combustion Code  

NASA Technical Reports Server (NTRS)

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.

Menon, Suresh; Sankaran, Vaidyanathan; Stone, Christopher

2003-01-01

141

Altitude-wind-tunnel investigation of a 4000-pound-thrust axial-flow turbojet engine VI : combustion-chamber performance  

NASA Technical Reports Server (NTRS)

An analysis of the performance of the types A, B, and C combustion chambers of the 4000-pound-thrust axial-flow turbojet engine is presented. The data were obtained from investigations of the complete engine over a range of pressure altitudes from 5000 to 40,000 feet and ram pressure ratios from 1.00 to 1.86. The combustion-chamber pressure losses, the effect of the losses on cycle efficiency, and the combustion efficiency are discussed.

Pinkel, I Irving; Shames, Harold

1948-01-01

142

A model for premixed combustion oscillations  

SciTech Connect

This paper describes a simulation based on a time dependent, nonlinear control volume analysis. The combustion is modeled as a well-stirred reactor having finite kinetics. Flow properties and species in the nozzle, combustion, and tailpipe regions are determined using a control volume formulation of the conservation equation.

Janus, M.C.; Richards, G.A.

1996-09-01

143

Utilizing Chamber Data for Developing and Validating Climate Change Models  

NASA Technical Reports Server (NTRS)

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.

Monje, Oscar

2012-01-01

144

1025:1 Area Ratio Nozzle Evaluated at High Combustion Chamber Pressure  

NASA Technical Reports Server (NTRS)

A recently completed experimental test program obtained performance data on an optimally contoured nozzle with an exit-to-throat 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 12.4 to 16.5 mPa (1800 to 2400 psia). Testing was conducted in the altitude test capsule at the NASA Lewis Research Center's Rocket Engine Test Facility (RETF), and results were compared with analytical performance predictions. This testing builds on previous work with this nozzle at Lewis, where testing was completed at nominal chamber pressure of 350 psia. High-area-ratio nozzles have long been sought as a means to increase the performance of spacebased rocket engines. However, as the area ratio increases, the physical size and weight of the nozzle also increase. As a result, engine and vehicle designers must make tradeoffs between nozzle size and performance enhancement. Until this test program, very little experimental data existed on the performance of the high-area-ratio nozzles used in rocket engine designs. The computer codes being used by rocket engine designers rely on data extrapolated from tests of low-area-ratio nozzles, and these extrapolations do not always provide the accuracy needed for a reliable design assessment. Therefore, we conducted this high-area-ratio nozzle testing program to provide performance data for use in rocket engine design and analysis computer codes. The nozzle had a nominal 2.54-cm- (1-in.-) diameter throat, an exit diameter of 81.3-cm (32.0-in.) at an exit-to-throat area ratio of 1025, and a length of 128.6 cm (50.6 in.). Testing was conducted in an altitude test capsule to simulate the static pressure at altitude by vacuum pumping. Data such as propellant mass flow, oxidizer-to-fuel mixture, and thrust were measured. These measurements were then used to calculate performance factors such as the thrust coefficient, the characteristic exhaust velocity efficiency, and the vacuum specific impulse. In addition, the nozzle temperature was measured to calculate the amount of heat transferred from the combustion gases to the nozzle.

1995-01-01

145

Predictive modeling of combustion processes  

E-print Network

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 ...

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

2009-01-01

146

Particle size distribution and PAH concentrations of incense smoke in a combustion chamber.  

PubMed

The particle size distribution and the concentrations of polycyclic aromatic hydrocarbons (PAHs) in incense smoke were studied using a custom-designed combustion chamber. Among the nine types of incense investigated, the particle and the total PAH emission factors varied significantly. The average mass median aerodynamic diameter (MMAD) of the smoke aerosol was 262+/-49nm, which positively correlated to particle emission factor (mg/stick, p<0.05). Coagulation was a major mechanism that dictates the MMAD of the smoke. The total toxic equivalency (the sum of the benzo[a]pyrene equivalent concentration) of the solid-phase PAHs (S-PAHs) was over 40 times higher than that of the corresponding gas-phase PAHs, indicating that the S-PAHs in incense smoke may pose potential health risk. Experiments show that each lowered percentage of total carbon content in the raw incense helped decrease the particle emission factor by 2.6mg/g-incense, and the reduction of S-PAH emission factor ranged from 8.7 to 26% when the carbon content was lowered from 45 to 40%. PMID:17014940

Yang, Chi-Ru; Lin, Ta-Chang; Chang, Feng-Hsiang

2007-01-01

147

Spray combustion model improvement study, 1  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

148

Modeling the combustion of propellant sandwiches  

Microsoft Academic Search

A two-dimensional, steady-state model of a burning composite solid propellant is developed to study the characteristics of the combustion process. The solid composite is a periodic sandwich unit comprised of two oxidizer laminates (ammonium perchlorate, AP) separated by a fuel binder layer (hydroxyl-terminated polybutadiene, HTPB). Included in the model are essential features for simulating composite propellant combustion: (1) a free

G. M. Knott; M. Q. Brewster

2002-01-01

149

The composition of combustion products formed from gasoline-hydrogen-air mixtures in a constant-volume spherical chamber  

Microsoft Academic Search

The experimental unit, procedure for testing, and the results and reliability of the determination of the composition of combustion\\u000a products formed from gasoline-hydrogen-air (containing 0–100% hydrogen), gasoline-air, and isooctane-hydrogen-air mixtures\\u000a in a constant-volume chamber are described. Studies were performed at initial mixture temperatures of 20–70°C and a 0.1 MPa\\u000a pressure.

L. N. Bortnikov; D. A. Pavlov; M. M. Rusakov; A. P. Shaikin

2011-01-01

150

Modeling of Waste-to-Energy Combustion with Continuous Variation of the Solid Waste Fuel  

Microsoft Academic Search

A mathematical model of a mass-burn, waste-to-energy combustion chamber has been developed that includes stochastic representation of the variability of the fuel (municipal solid waste, MSW). The drying, pyrolysis, gasification and combustion processes on the moving grate are governed by several factors such as proximate and ultimate analysis, particle size, moisture, heating value, and bulk density, all of which change

MASATO NAKAMURA; HANWEI ZHANG; KARSTEN MILLRATH; NICKOLAS J. THEMELIS

151

Modelling Spontaneous Combustion of Coal  

Microsoft Academic Search

Spontaneous combustion of coal is an important problem in mining and storage, in terms of both safety and economics. This is because coal reacts with oxygen in the air and an exothermic reaction occurs, even in ambient conditions. The heat of the reaction accumulates and the reaction becomes progressively faster and thermal runaway may take place to the point of

Ahmet ARISOY; B. Basil BEAMISH

152

Flow, spray and combustion analysis by laser techniques in the combustion chamber of a direct-injection diesel engine  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to show how the analysis of in -cylinder flow, fuel injection, and combustion by means of state-of-the-art optical techniques, as laser light-sheet, laser doppler anemometry and laser shadowgraphy, can help to support the understanding of the interaction of swirl flow development, spray formation, auto-ignition and combustion in near production-line direct-injection diesel engines and thus advances the development of engines with lower fuel consumption and emissions.

Hentschel, W.; Schindler, K.-P.

1996-12-01

153

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

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

154

Discharge Chamber Primary Electron Modeling Activities in Three-Dimensions  

NASA Technical Reports Server (NTRS)

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.

Steuber, Thomas J.

2004-01-01

155

Development of Electrophoretic Process for Coating T-53 Air Diffuser, Exhaust Diffuser, and Combustion Chamber Housing with 'Sermetel W' (Trade Name).  

National Technical Information Service (NTIS)

The report covers activities accomplished to develop an electrophoretic coating method for the application of 'SERMETEL W' to all critical surfaces of the exhaust diffuser, air diffuser and combustion chamber housing of the T-53 engine. 'SERMETEL W' has b...

K. A. Gebler

1967-01-01

156

Spray combustion modeling. Final report  

SciTech Connect

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.

Bellan, J. [Jet Propulsion Lab., Pasadena, CA (United States)

1997-03-01

157

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

NASA Technical Reports Server (NTRS)

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.

Wadel, Mary F.; Meyer, Michael L.

1996-01-01

158

MODEL IV-GRAPHITE, CARBON DIOXIDE 4CC IONIZATION CHAMBER  

Microsoft Academic Search

The Model IV 4-cc ionization chamber, a graphite-COâ chamber ; filled with 99.99% pure COâ to a pressure of 30 in. Hg, was designed to ; withstand mechanical vibration as well as high gamma dose rates. The materials ; used were selected for long life in high radiation fields and for low neutron ; activation. To determine saturation characteristics, the

C. C. Hall; S. D. Johnson

1960-01-01

159

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)

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.

Bartrand, Timothy A.

1988-01-01

160

Thermal load in D.I. diesel engine under EGR operation— measurements of steady state temperature of combustion chamber wall surface and intake gas temperature  

Microsoft Academic Search

The combustion temperature drops with exhaust gas recirculation (EGR), but the mean gas temperature in the combustion chamber may rise due to the rise of intake gas temperature and the drop of excess air ratio. For the verification of these effects, narrow J-type thermocouples were embedded in the piston and cylinder liner of an automobile D.I. diesel engine, and accurate

Yoshiteru Enomoto; Hiroshi Nagano; Yuji Hagihara; Takeshi Koyama

1997-01-01

161

Numerical modeling of straw combustion in a fixed bed  

Microsoft Academic Search

Straw is being used as main renewable energy source in grate boilers in Denmark. For optimizing operating conditions and design parameters, a one-dimensional unsteady heterogeneous mathematical model has been developed and experiments have been carried out for straw combustion in a fixed bed. The straw combustion processes include moisture evaporation, straw pyrolysis, gas combustion, and char combustion. The model provides

H. Zhou; A. D. Jensen; P. Glarborg; P. A. Jensen; A. Kavaliauskas

2005-01-01

162

Challenges of oxyfuel combustion modeling for carbon capture  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

163

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

164

Atomization data for spray combustion modeling  

NASA Technical Reports Server (NTRS)

Computer models that simulate the energy release processes in spray combustion are highly dependent upon the quality of atomization data utilized. This paper presents results of analyses performed with a state-of-the-art rocket combustion code, demonstrating the important effects of initial droplet sizes and size distributions on combustion losses. Also, the questionable aspects and inapplicability of the generally available atomization data are discussed. One important and misunderstood aspect of the atomization process is the difference between spatial (concentration) and flux (temporal) droplet size distributions. These are addressed, and a computer model developed to assess this difference is described and results presented. Finally, experimental results are shown that demonstrate the often neglected effects of the local gas velocity field on the atomization process.

Ferrenberg, A. J.; Varma, M. S.

1985-01-01

165

A model for premixed combustion oscillations  

SciTech Connect

Combustion oscillations are receiving renewed research interest due to increasing application of lean premix (LPM) combustion to gas turbines. A simple, nonlinear model for premixed combustion is described; it was developed to explain experimental results and to provide guidance for developing active control schemes based on nonlinear concepts. The model can be used to quickly examine instability trends associated with changes in equivalence ratio, mass flow rate, geometry, ambient conditions, etc. The model represents the relevant processes occurring in a fuel nozzle and combustor analogous to current LPM turbine combustors. Conservation equations for the nozzle and combustor are developed from simple control volume analysis, providing ordinary differential equations that can be solved on a PC. Combustion is modeled as a stirred reactor, with bimolecular reaction between fuel and air. Although focus is on the model, it and experimental results are compared to understand effects of inlet air temperature and open loop control schemes. The model shows that both are related to changes in transport time.

Janus, M.C.; Richards, G.A.

1996-03-01

166

An infrared technique for measuring cycle-resolved transient combustion-chamber surface temperatures in a fired engine  

SciTech Connect

An optical technique for measuring transient combustion chamber surface temperatures in a fired engine has been developed. The spectral region from 3.6 to 4.0 microns was found to be suitable for making optical measurements through the methane-air flame. The experimental apparatus was capable of making simultaneous time-resolved measurements of infrared gas absorption, gas emission and surface radiation during a single engine cycle. The effects of engine operating conditions on gas absorption and gas emission were investigated. Measurements of ''simulated'' deposits at temperatures ranging from 569 K to 944 K indicated that the technique was accurate within 7 K at the higher temperatures.

Bethel, S.; Anderson, C.L.

1986-01-01

167

Combustion modeling in advanced gas turbine systems  

SciTech Connect

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.

Smoot, L.D.; Hedman, P.O.; Fletcher, T.H.; Brewster, B.S.; Kramer, S.K. [Brigham Young Univ., Provo, UT (United States). Advanced Combustion Engineering Research Center

1995-12-31

168

Modeling LiH Combustion in Solid Fuelled Scramjet Engine  

NASA Astrophysics Data System (ADS)

Lithium Hydride is a hydrogen-rich compound with potential application as fuel, thanks to its high density and low molecular weight. It reacts exothermically with many substances and contains H2, suggesting its use where a much higher density (compared to that of LH2) would be beneficial. In this work LiH (solid at STP) has thus investigated as potential candidate for solid fuelled scramjets (SFSCRJ). Its thermochemical properties and issues associated to its combustion in a hot supersonic stream have been investigated; results show clearly that Li, released by thermal decomposition, plays a key role in the LiH performance. In fact, above the auto-ignition point liquid Li combustion with air increases local temperature and promotes LiH decomposition. To understand quantitatively these effects, a simplified physical model describing LiH “vaporization” and combustion was built and used in simulations of a notional SCRJ chamber by means of a CFD code. Results are intriguing: an intense and stable flame zone is predicted to be present over and downstream of the grain and high temperatures (of order 2900 K) are obtainable. Moreover, specific impulse and thrust density predicted at a flight Mach = 7 are also interesting, being 10,000 m/s and 200-300 m/s, respectively.

Simone, Domenico; Bruno, Claudio

169

Chemical Kinetic Modeling of Biofuel Combustion  

NASA Astrophysics Data System (ADS)

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.

Sarathy, Subram Maniam

170

Modeling Decomposing Objects under Combustion Texas A&M University  

E-print Network

the heat distribution and fuel gas mo- tion required by the model. The heat produced by combustion af to flow enables us to model heat distribution inside the computational domain. We simulate the combustion

Keyser, John

171

Combustion response modeling for composite solid propellants  

NASA Technical Reports Server (NTRS)

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.

1977-01-01

172

Advanced Combustion Modeling for Complex Turbulent Flows  

NASA Technical Reports Server (NTRS)

The next generation of aircraft engines will need to pass stricter efficiency and emission tests. NASA's Ultra-Efficient Engine Technology (UEET) program has set an ambitious goal of 70% reduction of NO(x) emissions and a 15% increase in fuel efficiency of aircraft engines. We will demonstrate the state-of-the-art combustion tools developed a t Stanford's Center for Turbulence Research (CTR) as part of this program. In the last decade, CTR has spear-headed a multi-physics-based combustion modeling program. Key technologies have been transferred to the aerospace industry and are currently being used for engine simulations. In this demo, we will showcase the next-generation combustion modeling tools that integrate a very high level of detailed physics into advanced flow simulation codes. Combustor flows involve multi-phase physics with liquid fuel jet breakup, evaporation, and eventual combustion. Individual components of the simulation are verified against complex test cases and show excellent agreement with experimental data.

Ham, Frank Stanford

2005-01-01

173

Modeling of combustion noise spectrum from turbulent premixed flames  

E-print Network

of jet noise in non-reacting flows [11], the source mechanisms of combustion noise are more complicatedModeling of combustion noise spectrum from turbulent premixed flames Y. Liu, A. P. Dowling, T. D, this temporal correlation and its role in the modeling of combustion noise spectrum are studied by analyzing

Paris-Sud XI, Université de

174

Modeling of Injection-Rate Shaping in Diesel Engine Combustion  

E-print Network

Modeling of Injection-Rate Shaping in Diesel Engine Combustion Vivak Luckhchoura #12;#12;Modeling of Injection-Rate Shaping in Diesel Engine Combustion Von der Fakult¨at f¨ur Maschinenwesen der Rheinisch . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Literature Survey 5 2.1 Combustion in Direct Injection Diesel Engines . . . . . . . . . . . . 5

Peters, Norbert

175

Structure analysis and size distribution of particulate matter from candles and kerosene combustion in burning chamber  

NASA Astrophysics Data System (ADS)

Burning of candles generates particulate matter of fine dimensions that produces poor indoor air quality, so it may cause harmful impact on human health. In this study solid aerosol particles of burning of candles of different composition and kerosene combustion were collected in a closed laboratory system. Present work describes particulate matter collection for structure analysis and the relationship between source and size distribution of particulate matter. The formation mechanism of particulate matter and their tendency to agglomerate also are described. Particles obtained from kerosene combustion have normal size distribution. Whereas, particles generated from the burning of stearin candles have distribution shifted towards finer particle size range. If an additive of stearin to paraffin candle is used, particle size distribution is also observed in range of towards finer particles. A tendency to form agglomerates in a short time is observed in case of particles obtained from kerosene combustion, while in case of particles obtained from burning of candles of different composition such a tendency is not observed. Particles from candles and kerosene combustion are Aitken and accumulation mode particles

Baitimirova, M.; Osite, A.; Katkevics, J.; Viksna, A.

2012-08-01

176

RSRM Chamber Pressure Oscillations: Transit Time Models and Unsteady CFD  

NASA Technical Reports Server (NTRS)

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.

Nesman, Tom; Stewart, Eric

1996-01-01

177

Combustion  

NASA Technical Reports Server (NTRS)

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.

Bulzan, Dan

2007-01-01

178

Engine Hydraulic Stability. [injector model for analyzing combustion instability  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

179

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

NASA Technical Reports Server (NTRS)

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.

Wadel, Mary F.

1998-01-01

180

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

E-print Network

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 ...

Chen, Haijie

2011-01-01

181

A GENERALIZED MODEL OF ACOUSTIC RESPONSE OF TURBULENT PREMIXED FLAME AND ITS APPLICATION TO GAS-TURBINE COMBUSTION INSTABILITY ANALYSIS  

Microsoft Academic Search

An analytical model is developed to study the combustion response of turbulent premixed flames to acoustic oscillations. The analysis is based on a level-set flamelet model, and accommodates spatial variations in chamber geometry and mean-flow properties. All known factors affecting the flame response to local flow disturbances are analyzed. A triple decomposition technique, which expresses each flow variable as the

DANNING YOU; YING HUANG; VIGOR YANG

2005-01-01

182

Proceedings of air toxic reduction and combustion modeling  

SciTech Connect

This book contains proceedings of Air Toxic Reduction and Combustion Modelling. Topics include modeling of furnaces, burners, combustors, gaseous flames, spray combustion, coal and coal slurry combustion. Both fundamental and applied studies in the area of pollution control, including NO[sub x], and efficiency are of interest. Systems of special interest included furnaces and boilers, gas turbine combustion, internal combustion engines and other power generation systems. Fundamental and applied, as well as numerical and experimental studies were of interest, with emphasis on the evolution of toxic metals and the modeling of rotary-kiln and fluidized-bed incinerators.

Gupta, A.K. (Univ. of Maryland, MD (United States)); Presser, G. (National Inst. of Standards and Technology (United States)); Axelbaum, R.L. (Washington Univ. (United States))

1992-01-01

183

Design and testing of a model CELSS chamber robot  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

184

Robust Feedback Control of Combustion Instability with Modeling Uncertainty  

E-print Network

Eni Linear parameters, Eq. (12) e Internal energy Hc Heat of combustion of control fuel h Source term chamber Input vector associated with distributed control source Un Control input of nth mode vg Velocity output vector z Objective variable; z [zs T zp T zu z ]T zs Stability variable associated with plant

Ray, Asok

185

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

186

Combustion chamber heat transfer characterization of LOX/hydrocarbon-type propellants  

NASA Technical Reports Server (NTRS)

The gas-side heat transfer rates for LOX/propane and LOX/ethanol are experimentally characterized using a 1000 lb thrust water-cooled calorimeter chamber. The effects of injector element type and fuel film cooling are defined as a function of mixture ratio. The interaction of fuel injected through the resonator cavities on heat transfer and wall soot buildup are displayed as a function of time, axial distance, fuel coolant flow rate, and mixture ratio. Comparisons between clean-burning ethanol and sooting propane show a large difference between the two fuels and significantly higher than expected heat flux levels for ethanol in the throat region.

Schoenman, Leonard

1987-01-01

187

Altitude-Wind-Tunnel Investigation of a 3000-Pound-Thrust Axial-Flow Turbojet Engine. 3; Analysis of Combustion-Chamber Performance  

NASA Technical Reports Server (NTRS)

Combustion chamber performance properties of a 3000-pound-thrust axial-flow turbojet engine were determined. Data are presented for a range of simulated altitudes from 15,000 to 45,0000 feet and a range of Mach numbers from 0.23 to 1.05 for various modifications of the engine.

Campbell, Carl E.

1948-01-01

188

Carbon Deposition Model for Oxygen-Hydrocarbon Combustion, Volume 2  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

189

Characterization of combustion chamber products by core-level photoabsorption spectroscopy  

SciTech Connect

The lubricating performance of motor oil is adversely affected by the carbon soot contamination that is a natural by-product of the combustion process. Particularly in diesel engines, {open_quote}blow-by{close_quote} is a problem that greatly decreases the longevity of the engine-lubricating oil. Motor oil manufacturers spend considerable resources developing new oil formulations that counteract the adverse affects of this combustion soot. At present, the only effective way to test new formulations is in a working engine. This process is obviously expensive and not especially efficient. In this ongoing work in collaboration with Chevron Research and Technology, the authors goal is to find a form of carbon that chemically resembles the soot created by the {open_quote}blow-by{close_quote} in a diesel engine. The chemically correct soot substitute can be used in bench tests to replace the expensive full motor testing for new formulations. The final testing would still be done in the test motors but only with promising candidates. To these ends, Near Edge X-ray Adsorption spectroscopy Extended Fine Structure (NEXAFS) is an attractive technique in that it has chemical specificity through the core-level binding energy and because it probes the chemically important unoccupied molecular orbitals of the material. Core-level photoabsorption has been used to characterize the empty electronic states of a wide variety of materials. Specifically, the near-edge region of the photoabsorption process has been used to determine the relative quantity of sp{sup 2} and sp{sup 3}bonding in carbon films. The samples were fine grained powders pressed into pellets. The C(1s) absorption spectra were collected from each sample by measuring the total electron yield from the sample as a function of photon energy. The absorption intensity was normalized to the incoming photon flux by measuring the photoyield from a fine gold mesh.

Kellar, S.A.; Huff, W.R.A.; Moler, E.J. [Univ. of California, Berkeley, CA (United States); [Lawrence Berkeley National Lab., CA (United States)] [and others

1997-04-01

190

Numerical Modeling of Spray Combustion with an Unstructured-Grid Method  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

191

Numerical Modeling of Single-Chamber SOFCs with Hydrocarbon Fuels  

Microsoft Academic Search

A two-dimensional numerical model of a single-chamber solid oxide fuel cell SCFC operating on hydrocarbon fuels is devel- oped. The SCFC concept is a simplification of a conventional solid oxide fuel cell in which the anode and cathode are both exposed to the same premixed fuel-air mixture, and selective catalysts promote electrochemical oxidation of the fuel at the anode and

Y. Hao; D. G. Goodwin

2007-01-01

192

Chemical Kinetic Models for HCCI and Diesel Combustion  

SciTech Connect

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.

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

2008-10-30

193

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

DOEpatents

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.

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

2013-12-17

194

Carbon deposition model for oxygen-hydrocarbon combustion, volume 1  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

195

Modeling complex chemical effects in turbulent nonpremixed combustion  

NASA Technical Reports Server (NTRS)

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.

Smith, Nigel S. A.

1995-01-01

196

Components, formulations, solutions, evaluation, and application of comprehensive combustion models  

Microsoft Academic Search

Development and application of comprehensive, multidimensional, computational combustion models are increasing at a significant pace across the world. While once confined to specialized research computer codes, these combustion models are becoming more readily accessible as features in commercially available computational fluid dynamics (CFD) computer codes. Simulations made with such computer codes offer great potential for use in analyzing, designing, retrofitting,

A. M. Eaton; L. D. Smoot; S. C. Hill; C. N. Eatough

1999-01-01

197

Integrated modelling of process heat transfer with combustion and fouling  

Microsoft Academic Search

This paper provides a summary of the main project topics which contribute to a major study aimed at integrating fouling and combustion activities. Brief outlines of the aims of the 14 main activities are provided along with examples of results from work on time-dependent fouling, industrial measurements, particle deposition tests, engineering combustion modelling, CFB modelling, sonic control and optimisation tests.

J. D. Isdale; P. Mercier; J. M. Grillot; A. Mulholland; J. Gomatam

1997-01-01

198

Combustion system CFD modeling at GE Aircraft Engines  

NASA Technical Reports Server (NTRS)

This viewgraph presentation discusses key features of current combustion system CFD modeling capabilities at GE Aircraft Engines provided by the CONCERT code; CONCERT development history; modeling applied for designing engine combustion systems; modeling applied to improve fundamental understanding; CONCERT3D results for current production combustors; CONCERT3D model of NASA/GE E3 combustor; HYBRID CONCERT CFD/Monte-Carlo modeling approach; and future modeling directions.

Burrus, D.; Mongia, H.; Tolpadi, Anil K.; Correa, S.; Braaten, M.

1995-01-01

199

Consideration of real gas effects and condensation in a spray-combustion rocket-thrust-chamber design tool  

NASA Astrophysics Data System (ADS)

For the prediction of hot gas side heat transfer in rocket thrust chambers, Astrium Space Transportation (ST) uses the second generation multiphase Navier-Stokes solver Rocflam-II. To account for real-gas and condensation effects, pressure-dependent and even multiphase fluid data are included in the chemistry tables used by the code. Thus, the changing fluid properties near the two-phase region as well as transformation from gaseous to liquid and even solid state are reflected properly. Heat flux measurements for a dedicated subscale test campaign with strongly cooled walls show a clearly increasing heat load as soon as the combustion gases condense at the wall, due to the released latent heat of condensation. Corresponding coupled Rocflam-II/CFX simulations show a good quantitative agreement in heat flux for load cases with and without condensation, showing the ability of the code to correctly simulate flows in the real-gas and even inside the two-phase region.

Frey, M.; Kniesner, B.; Knab, O.

2011-10-01

200

Microtubular, single-chamber solid oxide fuel cell (MT–SC-SOFC) stacks: Model development  

Microsoft Academic Search

Our previously developed numerical model has been used to study the flow, species and temperature distribution in a micro-tubular, single-chamber solid oxide fuel cell stack. The stack consists of three cells, spaced equally inside the gas-chamber. Two different configurations of the gas-chamber have been investigated, i.e., a bare gas-chamber and a porous material filled gas-chamber. The results show that the

N. Akhtar

201

Modeling smog chamber measurements of vehicle exhaust VOC reactivities  

SciTech Connect

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.

Chang, T.Y.; Nance, B.I. [Ford Motor Co., Dearborn, MI (United States). Ford Research Lab.; Kelly, N.A. [General Motors R and D Center, Warren, MI (United States)

1997-12-31

202

Influence of resonators on the acoustic and propulsion performance characteristics of a ramjet ejector chamber under conditions with vibration hydrogen combustion  

NASA Astrophysics Data System (ADS)

The influence of acoustic resonators on the acoustic and propulsion performance characteristics of a ramjet ejector chamber under conditions with vibration hydrogen combustion was experimentally examined. In the study, resonators having identical throats and different cavity diameters were used. For fixed-volume resonators the best propulsion performance characteristics were achieved in the case in which the cavity diameter differed little from the resonator throat diameter.

Potapkin, A. V.; Moskvichev, D. Yu.

2008-09-01

203

Combustion Theory and Modelling Vol. 14, No. 1, 2010, 4167  

E-print Network

Combustion Theory and Modelling Vol. 14, No. 1, 2010, 41­67 Modeling of particle compressibility of these studies the compressibility of the solid particulate is not considered. Baer and Nunziato (BN) first

DesJardin, Paul E.

204

Influence of the inlet port and combustion chamber configuration on the lean-burn behavior of a spark-ignition gasoline engine  

SciTech Connect

The influence of different port designs on the generation of a swirl flow is described on the basis of stationary and non-stationary flow analyses. Subsequently, engine test bench analyses with a 3-valve one-cylinder engine were performed to assess the aforementioned port configurations with respect to their influence on the lean-burn behavior. The most favorable port design was then used to analyze various combustion chamber shapes in order to further improve the engine behavior during lean-burn operation and to select the most promising combustion chamber variant. Finally, the port and combustion chamber configurations thus identified were applied in vehicle simulation tests with lean-burn and EGR-burn operation to check the emission behavior for compliance with the future European level 3 emission limits. These findings allowed a requirements specification to be drawn up for the conversion rate of a DENOX catalyst to be used for this purpose and also enabled the authors to assess the risks associated with the use of a lean-burn or an EGR burn technique.

Kuehn, M.; Abthoff, J.; Kemmler, R.; Kaiser, T.

1996-09-01

205

Modeling of Nonacoustic Combustion Instability in Simulations of Hybrid Motor Tests  

NASA Technical Reports Server (NTRS)

A transient model of a hybrid motor was formulated to study the cause and elimination of nonacoustic combustion instability. The transient model was used to simulate four key tests out of a series of seventeen hybrid motor tests conducted by Thiokol, Rocketdyne, and Martin Marietta at NASA Marshall Space Flight Center (MSFC). These tests were performed under the Hybrid Propulsion Technology for Launch Vehicle Boosters (HPTLVB) program. The first test resulted in stable combustion. The second test resulted in large-amplitude, 6.5-Hz chamber pressure oscillations that gradually damped away by the end of the test. The third test resulted in large-amplitude, 7.5-Hz chamber pressure oscillations that were sustained throughout the test. The seventh test resulted in elimination of combustion instability with the installation of an orifice immediately upstream of the injector. Formulation and implementation of the model are the scope of this presentation. The current model is an independent continuation of modeling presented previously by joint Thiokol-Rocketdyne collaborators Boardman, Hawkins, Wassom. and Claflin. The previous model simulated an unstable independent research and development (IR&D) hybrid motor test performed by Thiokol. There was very good agreement between the model and test data. Like the previous model, the current model was developed using Matrix-x simulation software. However, tests performed at MSFC under the HPTLVB program were actually simulated. ln the current model, the hybrid motor, consisting of the liquid oxygen (lox) injector, the multiport solid fuel grain, and nozzle, was simulated. The lox feedsystem, consisting of the tank, venturi. valve, and feed lines, was also simulated in the model. All components of the hybrid motor and lox feedsystem are treated by a lumped-parameter approach. Agreement between the results of the transient model and actual test data was very good. This agreement between simulated and actual test data indicated that the combustion instability in the hybrid motor was due to two causes: 1. a lox feed system of insufficient stiffness, and 2. a lox injector with an impedance (it pressure drop that was too low to provide damping against the feed system oscillations. Also, it was discovered that testing with a new grain of solid fuel sustained the combustion instability. However, testing with a used grain of solid fuel caused the combustion instability to gradually decay.

Rocker, M.

2000-01-01

206

Active combustion control : modeling, design and implementation  

E-print Network

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 ...

Park, Sungbae, 1973-

2004-01-01

207

Numerical Modeling of Diesel Spray Formation and Combustion  

Microsoft Academic Search

A study is presented on the modeling of fuel sprays in diesel engines. The objective of this study is in the first place to accurately and efficiently model non-reacting diesel spray formation, and secondly to include ignition and combustion. For that an efficient 1D Euler-Euler spray model (21) is implemented and applied in 3D CFD simulations. Concerning combustion, a detailed

C. Bekdemir; L. M. T. Somers; L. P. H. de Goey

2009-01-01

208

Computational experience with a three-dimensional rotary engine combustion model  

SciTech Connect

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.

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

1990-04-01

209

Tripropellant combustion process  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

210

Modelling and experiments of straw combustion in a grate furnace  

Microsoft Academic Search

A two-dimensional mathematical model for the combustion of straw in a cross-current, moving bed was developed as part of a tool for optimizing operating conditions and design parameters. To verify the model and to increase the understanding of straw bed combustion, laboratory fixed-bed experiments were performed in a 15cm diameter and 137cm long vertical reactor. Air was introduced through the

R. P van der Lans; L. T Pedersen; A Jensen; P Glarborg; K Dam-Johansen

2000-01-01

211

A model for steady-state HNF combustion  

SciTech Connect

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.

Louwers, J.; Gadiot, G.M.H.J.L. [TNO Prins Maurits Lab., Rijswijk (Netherlands); Brewster, M.Q. [Univ. of Illinois, Urbana, IL (United States); Son, S.F. [Los Alamos National Lab., NM (United States)

1997-09-01

212

Influence of intraparticle gradients in modeling of fixed bed combustion  

Microsoft Academic Search

The impact of using a porous media approximation, neglecting intraparticle gradients, for modeling fixed bed combustion has been investigated. This has been done by comparing the results from a bed model using the porous media approximation with the results from the same model, where the intraparticle gradients have been taken into account by a two-dimensional particle model. The particle model

R. Johansson; H. Thunman; B. Leckner

2007-01-01

213

Kinetic data base for combustion modeling  

SciTech Connect

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.

Tsang, W.; Herron, J.T. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

1993-12-01

214

Distinctive features of the intrachamber instability of combustion in liquid-propellant rocket engines  

NASA Astrophysics Data System (ADS)

Self-oscillations and certain of their regularities determined by solution of a degenerate system of differential equations that is used in considering combustion instability in combustion chambers of liquid-propellant rocket engines are modeled mathematically.

Gotsulenko, V. V.

2008-09-01

215

Thermodynamic Model of Aluminum Combustion in SDF Explosions  

SciTech Connect

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.

Kuhl, . L

2006-06-19

216

Boiler Modelling of Simple Combustion Processes  

Microsoft Academic Search

The aim of the work is to investigate coal combustion in fixed bed reactor. The experimental results were worked out in the form of approximation functions describing gas composition at the exit of fixed bed reactor. Furthermore, developed functions were applied for defining the boundary conditions at the interface between the fixed bed and gas phase using FLUENT. The simulations

Radovan Nosek; Jozef Jandacka; Andrzej Szlek

2012-01-01

217

A digital simulation of the exhaust nitric oxide and soot formation histories in the combustion chambers of a swirl chamber diesel engine  

Microsoft Academic Search

This work presents a computer simulation of the exhaust nitric oxide and soot emission histories from a four stroke, naturally\\u000a aspirated, Diesel engine with a swirl prechamber (divided chamber). The simulation is based on a thermodynamic analysis, which\\u000a was validated successfully concerning the performance of the engine (load, fuel consumption, maximum pressures, etc). The\\u000a analysis includes the calculation of the

Dimitrios A. Kouremenos; Constantine D. Rakopoulos; Dimitrios Hountalas; Petros Kotsiopoulos

1990-01-01

218

Results of a model for premixed combustion oscillation  

SciTech Connect

Combustion oscillations are receiving renewed research interest due to the increasing application of lean premix (LPM) combustion to gas turbines. A simple, nonlinear model for premixed combustion is described in this paper. The model was developed to help explain specific experimental observations, and to provide guidance for the development of active control schemes based on nonlinear concepts. The model can be used to quickly examine instability trends associated with changes in equivalence ratio, mass flow rate, geometry, ambient conditions, and other pertinent factors. The model represents the relevant processes occurring in a fuel nozzle and combustor which are analogous to current LPM turbine combustors. Conservation equations for the fuel nozzle and combustor are developed from simple control volume analysis, providing a set of ordinary differential equations that can be solved on a personal computer. Combustion is modeled as a stirred reactor, with a bi- molecular reaction rate between fuel and air. A variety of numerical results and comparisons to experimental data are presented to demonstrate the utility of the model. Model results are used to understand the fundamental mechanisms which drive combustion oscillations, the effects of inlet air temperature and nozzle geometry on instability, and the effectiveness of active control schemes. The technique used in the model may also be valuable to understand oscillations in low NO{sub x} industrial burners.

Janus, M.C.; Richards, G.A.

1996-12-31

219

Laser Diagnostic Study of the Mechanism of a Periodic Combustion Instability in a Gas Turbine Model Combustor  

Microsoft Academic Search

To investigate the mechanisms leading to sustained thermoacoustic oscillations in swirl flames, a gas turbine model combustor was equipped with an optically accessible combustion chamber allowing the application of various laser techniques. The flame investigated was a swirled CH4\\/air diffusion flame (thermal power 10 kW, global equivalence ratio ? = 0.75) at atmospheric pressure which exhibited self-excited thermoacoustic oscillations at

P. Weigand; W. Meier; X. R. Duan; R. Giezendanner-Thoben; U. Meier

2005-01-01

220

Results of a model for premixed combustion oscillations  

SciTech Connect

Combustion oscillations are receiving renewed research interest due to increasing use of lean premix (LPM) combustion to gas turbines. A simple, nonlinear model for premixed combustion is described in this paper. The model was developed to help explain specific experimental observations and to provide guidance for development of active control schemes based on nonlinear concepts. The model can be used to quickly examine instability trends associated with changes in equivalence ratio, mass flow rate, geometry, ambient conditions, etc. The model represents the relevant processes occurring in a fuel nozzle and combustor which are analogous to current LPM turbine combustors. Conservation equations for the fuel nozzle and combustor are developed from simple control volume analysis, providing a set of ordinary differential equations that can be solved on a personal computer. Combustion is modeled as a stirred reactor, with a bimolecular reaction rate between fuel and air. A variety of numerical results and comparisons to experimental data are presented to demonstrate the utility of the model. Model results are used to understand the fundamental mechanisms which drive combustion oscillations, effects of inlet air temperature and nozzle geometry on instability, and effectiveness of open loop control schemes.

Janus, M.C.; Richards, G.A.

1996-09-01

221

Assessment of pulverized-coal-fired combustor performance. Parametric screening studies for the calculation of heat transfer in combustion chambers. Topical report  

SciTech Connect

The screening studies performed to identify those parameters most influencing the thermal performance of full-scale combustion chambers, such as those of industrial furnaces or utility boilers are presented. Special attention is given to pulverized-coal (p.f.) firing. The report consists basically of two parts. Part one deals with overall thermal behavior, expressed in terms of a furnace efficiency and a furnace exit temperature. In part two, local heat transfer, characterized by local temperature and heat flux distributions, is investigated. It is also shown how these local inhomogeneities may influence the overall performance. The screening studies are carried out analytically.

Richter, W.

1982-01-01

222

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)

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.

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

2008-01-01

223

Statistical model for combustion of high-metal magnesium-based hydro-reactive fuel  

NASA Astrophysics Data System (ADS)

We investigate experimentally and analytically the combustion behavior of a high-metal magnesium-based hydro-reactive fuel under high temperature gaseous atmosphere. The fuel studied in this paper contains 73% magnesium powders. An experimental system is designed and experiments are carried out in both argon and water vapor atmospheres. It is found that the burning surface temperature of the fuel is higher in water vapor than that in argon and both of them are higher than the melting point of magnesium, which indicates the molten state of magnesium particles in the burning surface of the fuel. Based on physical considerations and experimental results, a mathematical one-dimensional model is formulated to describe the combustion behavior of the high-metal magnesium-based hydro-reactive fuel. The model enables the evaluation of the burning surface temperature, the burning rate and the flame standoff distance each as a function of chamber pressure and water vapor concentration. The results predicted by the model show that the burning rate and the surface temperature increase when the chamber pressure and the water vapor concentration increase, which are in agreement with the observed experimental trends.

Hu, Jian-Xin; Han, Chao; Xia, Zhi-Xun; Huang, Li-Ya; Huang, Xu

2012-12-01

224

Theory and modeling in combustion chemistry  

SciTech Connect

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.

Miller, J.A.

1996-10-01

225

Large eddy simulation modelling of combustion for propulsion applications.  

PubMed

Predictive modelling of turbulent combustion is important for the development of air-breathing engines, internal combustion engines, furnaces and for power generation. Significant advances in modelling non-reactive turbulent flows are now possible with the development of large eddy simulation (LES), in which the large energetic scales of the flow are resolved on the grid while modelling the effects of the small scales. Here, we discuss the use of combustion LES in predictive modelling of propulsion applications such as gas turbine, ramjet and scramjet engines. The LES models used are described in some detail and are validated against laboratory data-of which results from two cases are presented. These validated LES models are then applied to an annular multi-burner gas turbine combustor and a simplified scramjet combustor, for which some additional experimental data are available. For these cases, good agreement with the available reference data is obtained, and the LES predictions are used to elucidate the flow physics in such devices to further enhance our knowledge of these propulsion systems. Particular attention is focused on the influence of the combustion chemistry, turbulence-chemistry interaction, self-ignition, flame holding burner-to-burner interactions and combustion oscillations. PMID:19531515

Fureby, C

2009-07-28

226

An Experimental and Kinetic Modeling Study of Methyl Decanoate Combustion  

SciTech Connect

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.

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

2010-02-19

227

Combustion  

NSDL National Science Digital Library

In this chemistry activity, learners discover that the weight of the product of combustion is greater than that of the starting material. Learners will compare the weight of steel wool before and after it is heated. Learners are asked to consider why the steel wool weighs more (oxidation) as well as write the balanced chemical equation for the burning of steel. This activity uses an open flame; adult supervision is recommended. The resource includes notes for educators and extension ideas.

House, The S.

2014-01-28

228

Modeling the effects of auxiliary gas injection and fuel injection rate shape on diesel engine combustion and emissions  

NASA Astrophysics Data System (ADS)

The effect of auxiliary gas injection and fuel injection rate-shaping on diesel engine combustion and emissions was studied using KIVA a multidimensional computational fluid dynamics code. Auxiliary gas injection (AGI) is the injection of a gas, in addition to the fuel injection, directly into the combustion chamber of a diesel engine. The objective of AGI is to influence the diesel combustion via mixing to reduce emissions of pollutants (soot and NO x). In this study, the accuracy of modeling high speed gas jets on very coarse computational grids was addressed. KIVA was found to inaccurately resolve the jet flows near walls. The cause of this inaccuracy was traced to the RNG k - ? turbulence model with the law-of-the-wall boundary condition used by KIVA. By prescribing the lengthscale near the nozzle exit, excellent agreement between computed and theoretical jet penetration was attained for a transient gas jet into a quiescent chamber at various operating conditions. The effect of AGI on diesel engine combustion and emissions was studied by incorporating the coarse grid gas jet model into a detailed multidimensional simulation of a Caterpillar 3401 heavy-duty diesel engine. The effects of AGI timing, composition, amount, orientation, and location were investigated. The effects of AGI and split fuel injection were also investigated. AGI was found to be effective at reducing soot emissions by increasing mixing within the combustion chamber. AGI of inert gas was found to be effective at reducing emissions of NOx by depressing the peak combustion temperatures. Finally, comparison of AGI simulations with experiments were conducted for a TACOM-LABECO engine. The results showed that AGI improved soot oxidation throughout the engine cycle. Simulation of fuel injection rate-shaping investigated the effects of three injection velocity profiles typical of unit-injector type, high-pressure common-rail type, and accumulator-type fuel injectors in the Caterpillar 3401 heavy-duty diesel engine. Pollutant emissions for the engine operating with different injection velocity profiles reflected the sensitivity of diesel engines to the location of pollutants within the combustion chamber, as influenced by the fuel injection.

Mather, Daniel Kelly

1998-11-01

229

Combustor nozzle for a fuel-flexible combustion system  

DOEpatents

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.

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

2011-03-22

230

Modeling chemical flame structure and combustion dynamics in LES  

Microsoft Academic Search

In turbulent premixed combustion, the instantaneous flame thickness is typically thinner that the grid size usually retained in Large Eddy Simulations (LES), requiring adapted models. Two alternatives to couple chemical databases with LES balance equations, the Thickened Flame (TFLES) and the Filtered Tabulated Chemistry (F-TACLES) models, are investigated here and compared in terms of chemical flame structure and dynamics. To

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

2011-01-01

231

Neural Transplantation Model Using Integration Co-culture Chamber  

NASA Astrophysics Data System (ADS)

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.

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

232

Numerical modeling of hydrogen-fueled internal combustion engines  

SciTech Connect

Major progress was achieved in the last year in advancing the modeling capabilities of hydrogen-fueled engines, both in support of the multi-laboratory project with SNL and LLNL to develop a high-efficiency, low emission powerplant and to provide the engine design tools to industry and research laboratories for hydrogen-fueled engines and stationary power generators. The culmination of efforts on many fronts was the excellent comparison of the experimental data from the Onan engine, operated by SNL.These efforts include the following. An extensive study of the intake flow culminated in a major understanding of the interdependence of the details of the intake port design and the engine operating condition on the emissions and efficiency. This study also resulted in design suggestions for future engines and general scaling laws for turbulence that enables the KIVA results to be applied to a wide variety of operating conditions. The research on the turbulent combustion of hydrogen brought into perspective the effect of the unique aspects of hydrogen combustion and their influence on possible models of turbulent combustion. The effort culminated in a proposed model for turbulent hydrogen combustion that is in agreement with available literature. Future work will continue the development in order to provide a generally predictive model for hydrogen combustion. The application of the combustion model to the Onan experiments elucidated the observed improvement of the efficiency of the engine with the addition of a shroud on the intake valve. This understanding will give guidance to future engine design for optimal efficiency. Finally, a brief summary is given of the extensions and refinements of the KIVA-3 code, in support of future designers of hydrogen-fueled engines.

Johnson, N.L.; Amsden, A.A.; Butler, T.D. [Los Alamos National Lab., NM (United States). Theoretical Div.

1996-07-01

233

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

NASA Astrophysics Data System (ADS)

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).

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

2009-06-01

234

High Temperature Chemical Kinetic Combustion Modeling of Lightly Methylated Alkanes  

SciTech Connect

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.

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

2011-03-01

235

STRUCTURE-BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION  

SciTech Connect

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.

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

1998-09-11

236

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

SciTech Connect

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.

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

1989-03-01

237

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...

238

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...

239

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...

240

Reliable and efficient numerical simulation of a model of tissue differentiation in a bone chamber1  

E-print Network

, in postnatal bone growth, and in fracture healing (in case of moderate fracture gap size and stabilityReliable and efficient numerical simulation of a model of tissue differentiation in a bone chamber1 of peri-implant tissue differentiation, a repeated sampling bone chamber has been developed. Mathematical

241

Effect of fuel and engine operational characteristics on the heat loss from combustion chamber surfaces of SI engines  

Microsoft Academic Search

Understanding of engine heat transfer is important because of its influence on engine efficiency, exhaust emissions and component thermal stresses. In this paper, the effect of various parameters such as compression ratio, equivalence ratio, spark timing, engine speed, inlet mixture temperature and swirl ratio as well as fuel type on the heat transfer through the chamber walls of a spark

Ali Jafari; Siamak Kazemzadeh Hannani

2006-01-01

242

Exact solutions for modeling sound propagation through a combustion zone.  

PubMed

Exact analytical solutions for one-dimensional sound propagation through a combustion zone, taking the effects of mean temperature gradient and oscillatory heat release into account, are presented in this paper. The wave equation is derived starting from the momentum and energy equations. Using appropriate transformations, solutions are derived for the case of an exponential mean temperature gradient in terms of Bessel functions. For the case of a linear mean temperature profile, solutions are derived in terms of confluent hypergeometric functions. Example calculations show that the accuracy in modeling combustion-acoustics interactions can be significantly increased by the use of these solutions. PMID:11681365

Sujith, R I

2001-10-01

243

Numerical modeling of hydrogen-fueled internal combustion engines  

SciTech Connect

The planned use of hydrogen as the energy carrier of the future introduces new challenges and opportunities, especially to the engine design community. Hydrogen is a bio-friendly fuel that can be produced from renewable resources and has no carbon dioxide combustion products; and in a properly designed ICE, almost zero NO{sub x} and hydrocarbon emissions can be achieved. Because of the unique properties of hydrogen combustion - in particular the highly wrinkled nature of the laminar flame front due to the preferential diffusion instability - modeling approaches for hydrocarbon gaseous fuels are not generally applicable to hydrogen combustion. This paper reports on the current progress to develop a engine design capability based on KIVA family of codes for hydrogen-fueled, spark-ignited engines in support of the National Hydrogen Program. A turbulent combustion model, based on a modified eddy-turnover model in conjunction with an intake flow valve model, is found to describe well the efficiency and NO{sub x} emissions of this engine satisfy the Equivalent Zero Emission Vehicle (EZEV) standard established by the California Resource Board. 26 refs., 10 figs., 1 tab.

Johnson, N.L.; Amsden, A.A.

1996-12-31

244

A filtered tabulated chemistry model for LES of premixed combustion  

E-print Network

and the correct chemical structure when the flame wrinkling is completely resolved. The model is then extended analysis of the dynamic behavior of the chemical system response. Alterna- tive approaches are Flame that the chemical flame structure can be described in a reduced phase subspace from elemen- tary combustion

Paris-Sud XI, Université de

245

A Nonlinear Model for Fuel Atomization in Spray Combustion  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

246

Modeling of combustion processes in a solid fuel particle  

SciTech Connect

During the production of granules of uranium oxide, granules of ion exchange resin, loaded with uranium ions, are burned to remove the resin matrix and leave a uranium oxide ash''. Under some conditions of combustion, the oxide granules are produced in a highly fractured, porous state, while other conditions result in hard, dense, solid granules. ABAQUS, a commercial finite-element code, run on an IBM 3090, was used to model the physical processes occurring during combustion: heat transfer with a very nonlinear temperature-dependent rate of heat generation, diffusion of reactants and products, and stress/strain resulting from the differential temperatures and from the phase changes during the combustion. The ABAQUS simulation successfully explained the differences in morphology of the granules under different conditions, and lead to control strategies to produce the desired morphology. 10 figs.

Howard, D.W.

1990-01-01

247

A regenerative multiple zone model for HCCI combustion  

SciTech Connect

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)

Hamosfakidis, Vasileios; Im, Hong G.; Assanis, Dennis N. [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)

2009-04-15

248

Hydrogen program combustion research: Three dimensional computational modeling  

SciTech Connect

We have significantly increased our computational modeling capability by the addition of a vertical valve model in KIVA-3, code used internationally for engine design. In this report the implementation and application of the valve model is described. The model is shown to reproduce the experimentally verified intake flow problem examined by Hessel. Furthermore, the sensitivity and performance of the model is examined for the geometry and conditions of the hydrogen-fueled Onan engine in development at Sandia National Laboratory. Overall the valve model is shown to have comparable accuracy as the general flow simulation capability in KIVA-3, which has been well validated by past comparisons to experiments. In the exploratory simulations of the Onan engine, the standard use of the single kinetic reaction for hydrogen oxidation was found to be inadequate for modeling the hydrogen combustion because of its inability to describe both the observed laminar flame speed and the absence of autoignition in the Onan engine. We propose a temporary solution that inhibits the autoignition without sacrificing the ability to model spark ignition. In the absence of experimental data on the Onan engine, a computational investigation was undertaken to evaluate the importance of modeling the intake flow on the combustion and NO{sub x} emissions. A simulation that began with the compression of a quiescent hydrogen-air mixture was compared to a simulation of the full induction process with resolved opening and closing of the intake valve. Although minor differences were observed in the cylinder-averaged pressure, temperature, bulk-flow kinetic energy and turbulent kinetic energy, large differences where observed in the hydrogen combustion rate and NO{sub x} emissions. The flow state at combustion is highly heterogeneous and sensitive to the details of the bulk and turbulent flow and that an accurate simulation of the Onan engine must include the modeling of the air-fuel induction.

Johnson, N.L.; Amsden, A.A.; Butler, T.D.

1995-05-01

249

Quasiglobal reaction model for ethylene combustion  

NASA Technical Reports Server (NTRS)

The objective of this study is to develop a reduced mechanism for ethylene oxidation. The authors are interested in a model with a minimum number of species and reactions that still models the chemistry with reasonable accuracy for the expected combustor conditions. The model will be validated by comparing the results to those calculated with a detailed kinetic model that has been validated against the experimental data.

Singh, D. J.; Jachimowski, Casimir J.

1994-01-01

250

A model for double base propellant combustion  

Microsoft Academic Search

Several models have been developed to predict the burning rate of double base propellant as a function of pressure and initial temperature. The increasingly numerous experimental results (most from Kubota) provide a well established data base which allows one to verify the reliability of the numerical models. A complete model must determine the burning rate vs. pressure, initial temperature, and

Bizot

1987-01-01

251

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

252

Canards and critical behavior in autocatalytic combustion models  

Microsoft Academic Search

The basic elements of the theory of slow invariant manifolds and canard phenomena of singularly perturbed nonlinear differential\\u000a equations in the context of thermal-explosion problems are outlined. The mathematical results are applied to the investigation\\u000a of the critical phenomena in autocatalytic combustion models described by singularly perturbed differential equations with\\u000a lumped and distributed parameters. Critical regimes are modeled by canards

G. N. Gorelov; E. A. Shchepakina; V. A. Sobolev

2006-01-01

253

Finite element model for turbulent spray combustion  

Microsoft Academic Search

A finite element model for the prediction of spray flame field is presented. An Eulerian-Lagrangian approach is employed to model the reacting flow field of a spray combustor. The unsteady axisymmetric gas-phase equations are presented in Eulerian coordinates and the liquid-phase equations are formulated in Lagrangian coordinates. Turbulence is represented by the k-sigma model, and the reaction rate is determined

Y. M. Kim; T. J. Chung; K. S. Chang

1990-01-01

254

Combustion turbine dynamic model validation from tests  

Microsoft Academic Search

Studies have been conducted on the Alaskan Railbelt System to examine the hydrothermal power system response after the hydroelectric power units at Bradley Lake are installed. The models and data for the generating units for the initial studies were not complete. Typical models were used, but their response appeared to be faster than judged by operating experience. A testing program

L. N. Hannett; Afzal Khan

1993-01-01

255

Fluids & Combustion Seminar "Multiscale modeling of heterogeneous  

E-print Network

- solved at the macro-scale where the shock dynamics modeling is performed. Sub- grid scale dynamics can -material intraction are presented, namely particle-laden gas flows and porous sol- id dynamics. Biosketch, AFOSR and AFRL (Eglin AFB, FL). His current work is in modeling of blood flow in heart valves, high

Ponce, V. Miguel

256

Turbulent hydrocarbon combustions kinetics - Stochastic modeling and verification  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

257

A filtered tabulated chemistry model for LES of premixed combustion  

SciTech Connect

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)

Fiorina, B.; Auzillon, P.; Darabiha, N.; Gicquel, O.; Veynante, D. [EM2C - CNRS, Ecole Centrale Paris, 92295 Chatenay Malabry (France); Vicquelin, R. [EM2C - CNRS, Ecole Centrale Paris, 92295 Chatenay Malabry (France); GDF SUEZ, Pole CHENE, Centre de Recherche et d'Innovation Gaz et Energies Nouvelles, 93211 Saint-Denis la Plaine (France)

2010-03-15

258

Quasi-steady combustion modeling of homogeneous solid propellants  

SciTech Connect

Classical, linearized quasi-steady (QS) theory of unsteady combustion of homogeneous solid propellants (both pressure- and radiation-driven) is reexamined. Zeroth order, high activation energy (E/RT {much_gt} 1), decomposition is assumed. Many prevailing ideas about condensed-phase pyrolysis are challenged and several misconceptions are corrected. The results show the following: (1) the inadequacy of simple Arrhenius surface pyrolysis; (2) that the common assumption of zero Jacobian ({delta} or n{sub s}) parameter is physically unrealistic for pressure-driven combustion except perhaps in plateau regions; (3) that classical quasi-steady theory is not necessarily incompatible with observed pressure instability [Re{l_brace}R{sub p}{r_brace} > 0] in mesa propellants; (4) that measured steady-state combustion parameters (e.g., E{sub c} = 2E{sub s} = 40 kcal/mol for double base propellant) and quasi-steady theory can model T-burner data reasonably well; (5) that the preexponential parameters in the pyrolysis expression play a critical role in the dynamic response (particularly T{sub 0} and Q{sub c}); (6) that thermal radiation also plays an important role through its effect on the steady state sensitivity parameters, particularly the k (or {sigma}{sub p}) parameter. An approach is outlined for modeling dynamic combustion response based on zeroth order pyrolysis which allows difficult parameters, such as r and {delta} (or A and n{sub s}) to be obtained from relatively easily measured ones, k and v (or B and n), E{sub c}, Q{sub c}, and T{sub s}. An approach for determining these fundamental combustion parameters using radiation-driven unsteady burning tests is described.

Brewster, Q. [Univ. of Illinois, Urbana, IL (United States). Dept. of Mechanical and Industrial Engineering] [Univ. of Illinois, Urbana, IL (United States). Dept. of Mechanical and Industrial Engineering; Son, S.F. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States)

1995-10-01

259

Modelling wood combustion under fixed bed conditions  

Microsoft Academic Search

A computer model describing the conversion of wood under packed-bed conditions is presented. The packed bed is considered to be an arrangement of a finite number of particles, typically sized between 5 and 25mm, with a void space left between them. Each particle is undergoing a thermal conversion process, which is described by a one-dimensional and transient model.Within the single-particle

Christian Bruch; Bernhard Peters; Thomas Nussbaumer

2003-01-01

260

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.

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

261

Modelling NOx emissions of single droplet combustion  

Microsoft Academic Search

An approach for modelling and simulation of the generation of nitrogen oxide (NOx) in the gas phase surrounding single burning droplets is presented. Assuming spherical symmetry (no gravity, no forced convection), the governing equations are derived first. Then simplifications are introduced and it is proven that they are appropriate. The influences of the initial droplet diameter, the ambient conditions, and

Klaus G. Moesl; Joachim E. Schwing; Thomas Sattelmayer

2011-01-01

262

Modelling NOx emissions of single droplet combustion  

Microsoft Academic Search

An approach for modelling and simulation of the generation of nitrogen oxide (NOx) in the gas phase surrounding single burning droplets is presented. Assuming spherical symmetry (no gravity, no forced convection), the governing equations are derived first. Then simplifications are introduced and it is proven that they are appropriate. The influences of the initial droplet diameter, the ambient conditions, and

Klaus G. Moesl; Joachim E. Schwing; Thomas Sattelmayer

2012-01-01

263

Combustion-gas recirculation system  

Microsoft Academic Search

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

Darryl Dean

2007-01-01

264

Modeling and Simulation of Combustion in PDE using simplified Chemical Mechanisms  

NASA Astrophysics Data System (ADS)

The detonation phenomenon has been studied for nearly a century for its use in a Pulse Detonation Engine (PDE). It is attractive since it is a fast, constant-volume process, which is more efficient than deflagration, in converting chemical energy to mechanical energy. The combustion phenomenon inside a PDE is being modeled with single-step and simplified multi-step finite-rate reaction mechanisms. Detonation is initiated using two techniques, namely, i) Deflagration to Detonation Transition (DDT) and ii) Direct initiation. Both of these approaches are studied using mixtures of ethylene-oxygen and hydrogen-oxygen. A second-order accurate, finite-volume flow solver with capabilities to model chemical reactions (FLUENT) is used for this purpose. The computational simulation allows for proper visualization of the flame propagation, and provides additional insight into the onset of detonation and its structure. The pressure and temperature time-histories at various points in the combustion chamber are examined in detail. The computational results for ethylene-oxygen mixture are validated with the work of Li and Kailasanath. These results show comparable trends in the pressure profiles inside the tube at various time instants.

Raghupathy, Arun P.; Ghia, Karman; Ghia, Urmila

2004-11-01

265

Fluids and Combustion Facility: Fluids Integrated Rack Modal Model Correlation  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

266

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

NASA Technical Reports Server (NTRS)

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.

Hung, R. J.

1991-01-01

267

Aeroelasticity Analysis of AN Industrial Gas Turbine Combustor Using a Simplified Combustion Model  

NASA Astrophysics Data System (ADS)

Lean premixed industrial gas turbine combustors are susceptible to flame instabilities, resulting in large unsteady pressure waves that may cause the discharge nozzle to experience excessive vibration levels. A detailed aeroelasticity analysis, aimed at investigating possible structural failure mechanisms, was undertaken using a time-accurate unsteady flow representation, a simplified combustion disturbance and a structural model of the discharge nozzle. The computational domain included the lower part of the combustor geometry as well as the nozzle guide vanes (NGVs) at the HP turbine inlet. A pressure perturbation, representing the unsteadiness due to the combustion process, was applied below the tertiary fuel inlet and its frequency was set to each structural natural frequency in turn. The propagation of the pressure perturbation through the combustor nozzle, its reflection from the NGVs and further reflections were monitored using two different models. The first one, the so-called ``open'' system, ignored the reflections from the upper part of the combustion chamber while the second one, the ``closed'' system, assumed full reflection with an appropriate time shift. The calculations have shown that the imposed excitation could generate unsteady pressure shapes that were correlated with the ``flap'' modes of the discharge nozzle. In addition, an acoustic resonance condition was observed when the forcing pressure wave had a frequency close to 550 Hz, the experimentally observed failure frequency of the nozzle. The co-existence of these two factors, i.e., excitation/structural-mode match and the possibility of acoustic resonance, was thought to have the potential of producing very high vibration response.

Bréard, C.; Sayma, A. I.; Vahdati, M.; Imregun, M.

2002-12-01

268

The effects of topography on magma chamber deformation models: Application to Mt. Etna and radar interferometry  

Microsoft Academic Search

We have used a three-dimensional elastic finite element model to examine the effects of topography on the surface deformation predicted by models of magma chamber deflation. We used the topography of Mt. Etna to control the geometry of our model, and compared the finite element results to those predicted by an analytical solution for a pressurized sphere in an elastic

Charles A. Williams; Geoff Wadge

1998-01-01

269

Advanced modeling of large-scale oxy-fuel combustion processes  

E-print Network

radiative heat transfer and combustion chemistry are two of the fundamental issues. Efforts are made in bothAdvanced modeling of large-scale oxy-fuel combustion processes Chungen Yin Department of Energy Technology, Aalborg University, DK-9220 Aalborg, Denmark, chy@et.aau.dk Introduction Oxy-fuel combustion

Yin, Chungen

270

Filifactor alocis infection and inflammatory responses in the mouse subcutaneous chamber model.  

PubMed

Recent microbiome studies have implicated a role for Filifactor alocis in periodontal disease. In this study, we investigated the colonization and survival properties of F. alocis in a mouse subcutaneous chamber model of infection and characterized host innate immune responses. An infection of 10(9) F. alocis successfully colonized all chambers; however, the infection was cleared after 72 h. F. alocis elicited a local inflammatory response with neutrophils recruited into the chambers at 2 h postinfection along with an increase in levels of the proinflammatory cytokines interleukin 1? (IL-1?), IL-6, and tumor necrosis factor (TNF). F. alocis also induced apoptosis in chamber epithelial cells and neutrophils. Consistent with resolution of infection, neutrophil numbers and cytokine levels returned to baseline by 72 h. Fluorescent in situ hybridization (FISH) and quantitative PCR demonstrated that F. alocis exited the chambers and spread to the spleen, liver, lung, and kidney. Massive neutrophil infiltration was observed in the spleen and lungs, and the recruited neutrophils were in close proximity to the infecting bacteria. Significant epithelial injury was observed in the kidneys. Infection of all tissues was resolved after 7 days. This first in vivo study of the pathogenicity of F. alocis shows that in the chamber model the organism can establish a proinflammatory, proapoptotic local infection which is rapidly resolved by the host concordant with neutrophil influx. Moreover, F. alocis can spread to, and transiently infect, remote tissues where neutrophils can also be recruited. PMID:24379289

Wang, Qian; Jotwani, Ravi; Le, Junyi; Krauss, Jennifer L; Potempa, Jan; Coventry, Susan C; Uriarte, Silvia M; Lamont, Richard J

2014-03-01

271

Progress in the development of PDF turbulence models for combustion  

NASA Technical Reports Server (NTRS)

A combined Monte Carlo-computational fluid dynamic (CFD) algorithm was developed recently at Lewis Research Center (LeRC) for turbulent reacting flows. In this algorithm, conventional CFD schemes are employed to obtain the velocity field and other velocity related turbulent quantities, and a Monte Carlo scheme is used to solve the evolution equation for the probability density function (pdf) of species mass fraction and temperature. In combustion computations, the predictions of chemical reaction rates (the source terms in the species conservation equation) are poor if conventional turbulence modles are used. The main difficulty lies in the fact that the reaction rate is highly nonlinear, and the use of averaged temperature produces excessively large errors. Moment closure models for the source terms have attained only limited success. The probability density function (pdf) method seems to be the only alternative at the present time that uses local instantaneous values of the temperature, density, etc., in predicting chemical reaction rates, and thus may be the only viable approach for more accurate turbulent combustion calculations. Assumed pdf's are useful in simple problems; however, for more general combustion problems, the solution of an evolution equation for the pdf is necessary.

Hsu, Andrew T.

1991-01-01

272

CFD modeling of oxy-coal combustion in circulating fluidized bed  

Microsoft Academic Search

Based on the Computational Fluid Dynamics (CFD) method, the previously established and validated 2-dimensional model was employed to predict the oxy-coal combustion processes in a 50kW circulating fluidized bed (CFB) at Southeast University, China. The simulated processes of coal conversion in our CFB combustion system included particle drying, dry coal devolatilization, volatile combustion, char combustion, char gasification and SO2 emission.

Wu Zhou; Changsui Zhao; Lunbo Duan; Daoyin Liu; Xiaoping Chen

273

Towards cleaner combustion engines through groundbreaking detailed chemical kinetic models  

PubMed Central

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

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

2013-01-01

274

Evaluation of a locally homogeneous flow model of spray combustion  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

275

Econometric modeling of industries: Semiconductors and internal-combustion engines  

SciTech Connect

A small-scale econometric model of an industry is developed as a tool to analyze the impact of government purchases and other exogenous variables on the output, capital expenditures, and employment of the semiconductor industry in the United States. The model is also applied to the internal-combustion-engine industry in order to examine its performance on an alternative industry. The model consists of an equation for the industry's output, an investment and a man hour equation for the industry's input, and an equation for the shipments of the industries that use the industry's outputs as an intermediate input. An historical simulation is conducted for both industries on a microcomputer to test the accuracy of the model over the estimation periods. Results indicate that government defense purchases have significant impact on the information industries, which in turn influence the semiconductor industry. Government defense purchases, however, do not show any significant effect on the shipments of the primary purchasers of the internal-combustion engines.

Torbat-Esfahani, A.

1987-01-01

276

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...

277

Measurements of a 1/4-scale model of an explosives firing chamber  

SciTech Connect

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 outside the firing chamber must be hardened to ensure personnel protection in the event of an accidental detonation while the chamber door is open. 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 to provide information for the final design. 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.

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

1995-01-27

278

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

SciTech Connect

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

Jellinek, A. Mark; DePaolo, Donald J.

2002-01-02

279

Numerical modeling of spray combustion with an advanced VOF method  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

280

A magma chamber model beneath Unzen Volcano inferred from geodetic and seismic data using FEM  

NASA Astrophysics Data System (ADS)

A supplying system of the magma beneath Unzen volcano has been proposed using both geodetic and seismic data simultaneously. Spatial variation of geodetic data is affected by change of magma body in both of shape and pressure. In most cases, relative stress field is able to be inferred from focal mechanisms of earthquakes. This changing also disturbs stress field in the region around the magma chamber. A model about shape and internal pressure of magma chamber is constrained by mean of both grounds deformation and focal mechanism. Unzen Volcano is the massive volcanic complex, located in the middle part of Kyushu Island, Japan, erupted accompanying by pyroclastic flows and formed a huge lava dome at the summit during 1990-1995. Based on geodetic data during period 1991-2004, a magma chamber model composed of four pressure sources was constructed by grid search method (Kohno et al., 2008). For the data with greater crustal deformation observed in 1992-93 and 1993-94, we applied finite element method (FEM) to model the magma chamber. Especially, shape of a pressure source at a depth of 7 km (C-source) was also estimated in this searching process. C-source during 1992-93 has an oblate spheroid with south-southwest dip oriented made good correlation with observation data. Regards only from ground deformation data, the length of the major axis is smaller than 3km. The shape sustains to an idea that magma ascends easily toward the shallower chamber. The best solution of C-source in 1993-94 was obtained as a prolate spheroid source with north dip oriented. This latter source is smaller size and dipping to opposite side with the previous one. Although they are separated at distance of 1 km, this is not far to call different magma chamber each other. Different shape indicated that inhomogeneous structure of magma chamber. From this arrangement of the sources, we considered a model that the magma chamber at a depth of about 7 km could be composed of small magma chambers like pocket. These shapes are parallel to distribution of seismic epicenters, which means there is some correlation with magma chamber. We also estimated deviatoric stress tensors for the focal region beneath Unzen Volcano using stress tensor inversion method through 1986-88 the deviatoric stress field in depth beneath Chijiwa bay, west next of Shimabara peninsula, drastically changed in the directions of principal stresses. It is interpreted that the phenomenon was caused by overpressure of numerous dikes having dimension long oriented in vertical direction. In the other period, that the principal stress did not change, which means that the inflation of deflation of the magma chambers did not make any stress change in the focal area in spite of high volcanic activity accompanied with eruption. Comparing the stress using the optimal solution inferred from geodetic data, stress tensors were calculated by FEM, and there is stress disturbance induced from increasing or decreasing pressure of magma chamber only in the region which close to the chamber. From these facts we can say the body of magma chamber did not reach at the focal area, thus earthquake swarm was generated by volatile substance which can make weaken the bed rock when they soak into the rocks. By combining geodetic data and stress field from seismic data, we obtained more reliable shape for magma bodies. It allows us to evaluate quantitatively process of volcanic activity.

Kohno, Y.; Matsumoto, S.; Matsushima, T.; Uehira, K.; Umakoshi, K.; Shimizu, H.

2008-12-01

281

The study of PDF turbulence models in combustion  

NASA Technical Reports Server (NTRS)

In combustion computations, it is known that the predictions of chemical reaction rates are poor if conventional turbulence models are used. The probability density function (pdf) method seems to be the only alternative that uses local instantaneous values of the temperature, density, etc., in predicting chemical reaction rates, and thus is the only viable approach for more accurate turbulent combustion calculations. The fact that the pdf equation has a very large dimensionality renders finite difference schemes extremely demanding on computer memories and thus impractical. A logical alternative is the Monte Carlo scheme. Since CFD has a certain maturity as well as acceptance, it seems that the use of a combined CFD and Monte Carlo scheme is more beneficial. Therefore, a scheme is chosen that uses a conventional CFD flow solver in calculating the flow field properties such as velocity, pressure, etc., while the chemical reaction part is solved using a Monte Carlo scheme. The discharge of a heated turbulent plane jet into quiescent air was studied. Experimental data for this problem shows that when the temperature difference between the jet and the surrounding air is small, buoyancy effect can be neglected and the temperature can be treated as a passive scalar. The fact that jet flows have a self-similar solution lends convenience in the modeling study. Futhermore, the existence of experimental data for turbulent shear stress and temperature variance make the case ideal for the testing of pdf models wherein these values can be directly evaluated.

Hsu, Andrew T.

1991-01-01

282

Combustion-gas recirculation system  

DOEpatents

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.

Baldwin, Darryl Dean (Lacon, IL)

2007-10-09

283

Multidimensional Modeling of Diesel Ignition and Combustion Usinga Multistep Kinetics Model  

Microsoft Academic Search

Ignition and combustion mechanisms in diesel engines were studied\\u000d\\u000a\\u0009using the KIVA code, with modifications to the combustion, heat transfer,\\u000d\\u000a\\u0009crevice flow, and spray models. A laminar-and-turbulent characteristic-time\\u000d\\u000a\\u0009combustion model that has been used successfully for spark-ignited\\u000d\\u000a\\u0009engine studies was extended to allow predictions of ignition and\\u000d\\u000a\\u0009combustion in diesel engines. A more accurate prediction of ignition\\u000d\\u000a\\u0009delay was achieved

S.-C. Kong; R. D. Reitz

1993-01-01

284

Lessons from patient-specific 3D models of the cardiac chambers after the Mustard operation  

PubMed Central

The recent ability to create detailed 3D models of the atrial and ventricular chambers using CT, MRI and rapid prototyping offers unique opportunities to study the size and shape of the different cardiac chambers both before and following operation for complex cardiac anomalies. We here describe the techniques for creating detailed 3D models of the heart and demonstrate the utility of these techniques in a patient studied after the Mustard operation. This can give important insights into the changes in size and shape of the different chambers and the patterns of blood flow from the pulmonary and systemic veins to the ‘appropriate’ ventricle. This information in turn could be extremely helpful in understanding and optimizing the overall hemodynamic function after the Mustard operation. PMID:24749115

Chapron, Julien; Hosny, Hatem; Torii, Ryo; Sedky, Yasser; Donya, Mohamed; Yacoub, Magdi H

2013-01-01

285

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

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)

Vereschagin, Konstantin A; Vereschagin, Alexey K; Smirnov, Valery V; Stelmakh, O M; Fabelinskii, V I [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Clauss, W; Klimenko, D N; Oschwald, M [German Aerospace Research Centre, DLR, Hardthausen (Germany)

2005-03-31

286

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...

287

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

288

Tissue engineering chamber promotes adipose tissue regeneration in adipose tissue engineering models through induced aseptic inflammation.  

PubMed

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

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

2014-11-01

289

Spray Combustion Modeling with VOF and Finite-Rate Chemistry  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

290

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)

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.

Mcdonald, Gary H.

1990-01-01

291

Influence of intraparticle gradients in modeling of fixed bed combustion  

SciTech Connect

The impact of using a porous media approximation, neglecting intraparticle gradients, for modeling fixed bed combustion has been investigated. This has been done by comparing the results from a bed model using the porous media approximation with the results from the same model, where the intraparticle gradients have been taken into account by a two-dimensional particle model. The particle model provides information on the internal heating of the solid particles and the internal rate of drying and devolatilization. The surface temperature of the particles, given by the porous bed model, is the boundary condition for the particle model. Fuel particles of sizes between 5 and 40 mm, consisting of wood, and inlet gas velocities ranging from 0.05 to 0.2 m/s are used. For large bed particles there are considerable differences between the two modeling approaches in the rates of release of volatiles and moisture. The temperature profile in the bed is also affected. For the smaller bed particles in the size range investigated, the differences are small. However, the difference in ignition rate and maximum temperature are small even for the largest particles, compared to uncertainties in the models and scattering of experimental data. (author)

Johansson, R.; Thunman, H.; Leckner, B. [Department of Energy and Environment, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden)

2007-04-15

292

Comparison of different methods of modeling turbulent combustion in a boundary layer  

Microsoft Academic Search

Three methods of modeling a chemical reaction in the combustion of ethanol injected into the boundary layer through a porous plate are compared. In calculations of the average velocity and temperature and also heat-transfer coefficients, simple models of combustion are shown to be close in accuracy to a model that takes into complete account the kinetics of all reactions occurring

É. P. Volchkov; N. A. Dvornikov; L. N. Perepechko

1996-01-01

293

3D MODELING FROM LARGE CHAMBER SEM IMAGES FOR MICRO-SCALE MATERIAL CHARACTERIZATION  

E-print Network

3D MODELING FROM LARGE CHAMBER SEM IMAGES FOR MICRO-SCALE MATERIAL CHARACTERIZATION *S. Huq, *B Electron Microscope (LC-SEM), a one of a kind microscope in the US. By applying an annealing based two of great value to first responders and security personnel. In this regard, LC-SEM plays a significant role

Abidi, Mongi A.

294

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

SciTech Connect

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.

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

1982-04-01

295

A spray-suppression model for turbulent combustion  

SciTech Connect

A spray-suppression model that captures the effects of liquid suppressant on a turbulent combusting flow is developed and applied to a turbulent diffusion flame with water spray suppression. The spray submodel is based on a stochastic separated flow approach that accounts for the transport and evaporation of liquid droplets. Flame extinguishment is accounted for by using a perfectly stirred reactor (PSR) submodel of turbulent combustion. PSR pre-calculations of flame extinction times are determined using CHEMKIN and are compared to local turbulent time scales of the flow to determine if local flame extinguishment has occurred. The PSR flame extinguishment and spray submodels are incorporated into Sandia's flow fire simulation code, VULCAN, and cases are run for the water spray suppression studies of McCaffrey for turbulent hydrogen-air jet diffusion flames. Predictions of flame temperature decrease and suppression efficiency are compared to experimental data as a function of water mass loading using three assumed values of drop sizes. The results show that the suppression efficiency is highly dependent on the initial droplet size for a given mass loading. A predicted optimal suppression efficiency was observed for the smallest class of droplets while the larger drops show increasing suppression efficiency with increasing mass loading for the range of mass loadings considered. Qualitative agreement to the experiment of suppression efficiency is encouraging, however quantitative agreement is limited due to the uncertainties in the boundary conditions of the experimental data for the water spray.

DESJARDIN,PAUL E.; TIESZEN,SHELDON R.; GRITZO,LOUIS A.

2000-02-14

296

Insights of magma chamber evolution from multiscale physical modeling (Invited)  

NASA Astrophysics Data System (ADS)

The evolution of shallow magma reservoirs has a profound effect on volcanic activity and plays a significant role in crustal differentiation. However, our understanding of their physical state remains inadequate. Here, we discuss the evolution of silicic magma reservoir in the light of observations made on large ignimbrites, which typically group into: (1) crystal-rich (>30%) and (2) crystal-poor deposits. The crystal-rich deposits appear to be homogeneous in crystallinity and major element composition throughout the deposit, while crystal-poor ignimbrites can be either homogeneous or conspicuously zoned in composition, mineralogy and temperature. We propose a thermomechanical model for the evolution of mature silicic magmas interacting with new recharges and discuss how the reactivation of crystal-rich mushes by reheating and partial melting can explain the difference of deposits observed for crystal-rich and crystal-poor systems. We also discuss the role of exsolved volatiles on the thermal evolution of crystal-rich magma bodies during recharge episodes.

Huber, C.; Bachmann, O.; Parmigiani, A.; Dufek, J.

2013-12-01

297

Numerical modelling of dykes deflected into sills to form a magma chamber  

NASA Astrophysics Data System (ADS)

Most shallow magma chambers are thought to evolve from sills. For this to happen, several conditions must be met. (1) There must be a discontinuity, normally a contact, that deflects a dyke (or an inclined sheet) into a sill. (2) The initial sill must have a considerable thickness, normally (depending on dyke injection rates) not less than some tens of metres. (3) The resulting sill must receive magma (through dykes) frequently enough so as to stay liquid and expand into a chamber. (4) The resulting magma chamber must remain at least partially molten and receive multiple magma injections over a given period of time to build up a volcano on the surface above. In this paper we present numerical models based upon field data and geophysical data as to how sills are emplaced and may subsequently evolve into shallow magma chambers. We suggest that most sills form when dykes meet contacts, particularly weak ones, which are unfavourable to dyke propagation. A contact may halt (arrest) a dyke altogether or, alternatively, deflect the dyke into the contact. The three main mechanisms for dyke deflection into a contact are (1) the Cook-Gordon debonding or delamination, (2) rotation of the principal stresses, generating a stress barrier, and (3) an elastic mismatch across a contact between adjacent layers. Elastic mismatch means that the layers have contrasting Young's moduli and varying material toughness. Once a sill is initiated, the developing magma chamber may take various forms. Many shallow magma chambers, however, tend to maintain a straight sill-like or somewhat flat (oblate) ellipsoidal geometry during their lifetimes. For a sill to evolve into a magma chamber there must be elastic-plastic deformation of the overburden and, to some extent, of the underburden. So long as the sill stays liquid, subsequent dyke injections become arrested on meeting the sill. Some magma chambers develop from sill complexes. For the sill complex to remain partially molten it must receive a constant replenishment of magma, implying a high dyke-injection rate. Alternatively, an initial comparatively thick sill may absorb much of the magma of the dykes that meet it and evolve into a single shallow magma chamber.

Barnett, Zoe A.; Gudmundsson, Agust

2014-06-01

298

A simplified model to tie magma chamber evolution to eruption frequency  

NASA Astrophysics Data System (ADS)

Whether a magma body is able to produce eruptions and at what frequency remains a challenging problem in volcanology as it involves the non-linear interplay of different processes acting over different time scales. Due to their complexity they are often considered independently in spite of their coupled nature. Here we consider a simplified model that focuses on the evolution of the thermodynamical state of the chamber (pressure, temperature, gas and crystal content) as new magma is injected into the chamber. The crust heats up in contact with the magma chamber and is allowed to respond visco-elastically to the stress 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 in the form of dikes until the lithostatic pressure is recovered. Using scaling of dike propagation and thermal viability arguments, we assess whether the released mass can reach the surface or remains intruded in the crust. Our model also includes passive degassing, which is parameterized as a multiphase porous flow model that becomes active when the crystal fraction exceeds 0.5 and the fluid volume fraction of exsolved volatiles exceeds 0.2 (percolation threshold). Using this model, we study the effect of various scenarios for the magma recharge on the periodicity of eruptions, the volume of magma erupted (and its gas and crystal content), and whether the magma in the reservoir is headed to form eruptions or plutons. These recharge scenarios include (i) constant injection, (ii) periodic injection, and (iii) magmatic lensing through which magma chamber overpressure increases injection rate due to dike focusing. The modularity and the simplicity of the model allow for rapid calculations and offer the flexibility to add different and sometimes competing processes and test their influence on the evolution of the magma reservoir.

Degruyter, W.; Huber, C.

2013-12-01

299

Two-Fluid Models for Simulating Reacting Gas-Particle Flows, Coal Combustion and NOx Formation  

Microsoft Academic Search

Unlike the widely used Eulenan gas-Lagrangian particle models (particle trajectory models), two versions of two-fluid models—a pure two-fluid (FTF) model and a two-fluid-trajectory (continuum-trajectory, CT) model are proposed for simulating turbulent reacting gas-particle flows and coal combustion. Both of diem are based on Eulerian gas-phase equations, Eulenan particle-phase continuity and momentum equations, ?-?-? two-phase turbulence model, EBU-Arrhenius turbulent combustion model,

L. X. ZHOU; Y. C. GUO; W. Y. LIN

2000-01-01

300

Influence of immunization on Porphyromonas gingivalis colonization and invasion in the mouse chamber model.  

PubMed Central

The effects of immunization with invasive or noninvasive Porphyromonas (Bacteroides) gingivalis strains on the pathogenesis of infection in a mouse chamber model were examined. BALB/c mice were immunized by a single injection of heat-killed P. gingivalis invasive strain A7436 or W83 or noninvasive strain 33277, HG405, or 381 directly into subcutaneous chambers. P. gingivalis-specific antibody was detected in chamber fluid 21 days postimmunization, and mice were subsequently challenged by injection of exponential-phase P. gingivalis into chambers. Immunization with A7436 or W83 followed by challenge with A7436 protected mice against secondary abscess formation and death; however, P. gingivalis persisted in chambers for up to 14 days postchallenge. Immunization with noninvasive strain 33277, HG405, or 381 followed by challenge with invasive strain A7436 or W83 protected mice against secondary lesion formation and death. P. gingivalis was cultured from 33277- or HG405-immunized and nonimmunized animals to day 14. All P. gingivalis strains induced an immunoglobulin G response, as measured by an enzyme-linked immunosorbent assay and Western immunoblotting of P. gingivalis whole-cell and outer membrane protein preparations. Western blot analyses indicated that sera from mice immunized with different invasive and noninvasive strains recognized common P. gingivalis antigens. In summary, immunization with invasive P. gingivalis A7436 and W83 or noninvasive P. gingivalis 33277, HG405, and 381 protected mice from secondary lesion formation and death after challenge with invasive P. gingivalis A7436 or W83. P. gingivalis-specific antibody did not, however, inhibit the colonization of P. gingivalis within chambers. Images PMID:1312515

Genco, C A; Kapczynski, D R; Cutler, C W; Arko, R J; Arnold, R R

1992-01-01

301

Numerical modeling of flow in a differential chamber of the gas-dynamic interface of a portable mass-spectrometer  

NASA Astrophysics Data System (ADS)

Mathematical modeling of flow in the differential chamber of the gas-dynamic interface of a portable mass-spectrometer was carried out to comprehensively study the flow structure and make recommendations for the optimization of the gas-dynamic interface. Modeling was performed using an OpenFOAM open computational platform. Conditions for an optimal operating mode of the differential chamber were determined.

Pivovarova, E. A.; Smirnovsky, A. A.; Schmidt, A. A.

2013-11-01

302

Validation of a Three-Dimensional Transmission Line Matrix (TLM) Model Implementation of a Mode-Stirred Reverberation Chamber  

Microsoft Academic Search

Reverberation chambers are attractive electromagnetic compatibility test facilities, both economically and technically. Careful design and analysis of these facilities are important, if the results obtained are to be treated with a high level of confidence. Numerical modeling is an important part of the process of reverberation chamber design and analysis. Hence, it is important that the modeling techniques to be

Alyse Coates; Hugh G. Sasse; Dawn E. Coleby; Alistair P. Duffy; Antonio Orlandi

2007-01-01

303

Modeling of Diesel Combustion, Soot and NO Emissions Based on a Modified Eddy Dissipation Concept  

E-print Network

1 Modeling of Diesel Combustion, Soot and NO Emissions Based on a Modified Eddy Dissipation Concept 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

Im, Hong G.

304

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

E-print Network

SAE 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 about global warming and hazardous emissions bring about a need for an improved understanding of diesel

Im, Hong G.

305

Numerical Modeling of Mixing and Venting from Explosions in Underground Chambers  

NASA Astrophysics Data System (ADS)

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.

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

2006-07-01

306

A model for eruption frequency of upper crustal silicic magma chambers  

NASA Astrophysics Data System (ADS)

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.

Degruyter, W.; Huber, C.

2014-10-01

307

Model predictive control as a tool for improving the process operation of MSW combustion plants.  

PubMed

In this paper a feasibility study is presented on the application of the advanced control strategy called model predictive control (MPC) as a tool for obtaining improved process operation performance for municipal solid waste (MSW) combustion plants. The paper starts with a discussion of the operational objectives and control of such plants, from which a motivation follows for applying MPC to them. This is followed by a discussion on the basic idea behind this advanced control strategy. After that, an MPC-based combustion control system is proposed aimed at tackling a typical MSW combustion control problem and, using this proposed control system, an assessment is made of the improvement in performance that an MPC-based MSW combustion control system can provide in comparison to conventional MSW combustion control systems. This assessment is based on simulations using an experimentally obtained process and disturbance model of a real-life large-scale MSW combustion plant. PMID:15896951

Leskens, M; van Kessel, L B M; Bosgra, O H

2005-01-01

308

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

SciTech Connect

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.

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

1995-01-27

309

Flow chamber  

DOEpatents

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.

Morozov, Victor (Manassas, VA)

2011-01-18

310

Modeling the combustion behavior of hazardous waste in a rotary kiln incinerator.  

PubMed

Hazardous wastes have complex physical forms and chemical compositions and are normally incinerated in rotary kilns for safe disposal and energy recovery. In the rotary kiln, the multifeed stream and wide variation of thermal, physical, and chemical properties of the wastes cause the incineration system to be highly heterogeneous, with severe temperature fluctuations and unsteady combustion chemistry. Incomplete combustion is often the consequence, and the process is difficult to control. In this article, modeling of the waste combustion is described by using computational fluid dynamics (CFD). Through CFD simulation, gas flow and mixing, turbulent combustion, and heat transfer inside the incinerator were predicted and visualized. As the first step, the waste in various forms was modeled to a hydrocarbon-based virtual fuel mixture. The combustion of the simplified waste was then simulated with a seven-gas combustion model within a CFD framework. Comparison was made with previous global three-gas combustion model with which no chemical behavior can be derived. The distribution of temperature and chemical species has been investigated. The waste combustion model was validated with temperature measurements. Various operating conditions and the influence on the incineration performance were then simulated. Through this research, a better process understanding and potential optimization of the design were attained. PMID:16194906

Yang, Yongxiang; Pijnenborg, Marc J A; Reuter, Markus A; Verwoerd, Joep

2005-01-01

311

A numerical model for atomization-spray coupling in liquid rocket thrust chambers  

NASA Technical Reports Server (NTRS)

The physical process of atomization is an important consideration in the stable operation of liquid rocket engines. Many spray combustion computational fluid dynamics (CFD) codes do not include an atomization sub-model but assume arbitrary drop size distributions, drop initial locations, and velocities. A method of coupling an atomization model with the spray model in a REFLEQS CFD code is presented. This method is based on a jet-embedding technique in which the equations governing the liquid jet core are solved separately using the surrounding gas phase conditions. The droplet initial conditions are calculated using a stability analysis appropriate for the atomization regime of liquid jet break-up.

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

1992-01-01

312

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

E-print Network

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

Pitsch, Heinz

313

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

PubMed

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

Jia, Long; Xu, Yong-Fu

2014-02-01

314

Overfeed fixed-bed combustion of wood  

Microsoft Academic Search

Research on the combustion of wood on a fixed grate with a separate supply of combustion air is described in this paper. From the layer of the wood on the grate, only fixed carbon was burned in the primary combustion chamber in the presence of primary air, whereas the volatiles were burned subsequently in the secondary combustion chamber in the

Janez Oman; Matija Tuma

1999-01-01

315

Computational Modeling of CO/CO2 Ratio Inside Single Char Particles during Pulverized Coal Combustion  

E-print Network

of submicrometer-sized ash in coal combustion systems affects the emissions of toxic metals and the formation of boiler deposits. The formation of submicrometer-sized aerosol during coal combustion is known to be dueComputational Modeling of CO/CO2 Ratio Inside Single Char Particles during Pulverized Coal

Utah, University of

316

Computing combustion noise by combining Large Eddy Simulations with analytical models for the propagation of waves  

E-print Network

airplanes as the noise generated by other sources such as jet and fan noise have been reduced. This noiseComputing combustion noise by combining Large Eddy Simulations with analytical models +++++ Presented by Ignacio Duran Abstract Two mechanisms control combustion noise generation as shown by Marble

Paris-Sud XI, Université de

317

Explicit Stochastic Predictive Control of Combustion Plants Based on Gaussian Process Models  

E-print Network

Energy production is one of the largest sources of air pollution. A feasible method to reduce the harmful). The objectives for the improvement of the power plant combustion process are energy saving, pollution reduction1 Explicit Stochastic Predictive Control of Combustion Plants Based on Gaussian Process Models

Johansen, Tor Arne

318

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...

319

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

NASA Astrophysics Data System (ADS)

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.

Pascal, Karen; Neuberg, Jurgen; Rivalta, Eleonora

2014-01-01

320

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)

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.

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

2006-01-01

321

Solid waste combustion for alpha waste incineration  

SciTech Connect

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.

Orloff, D.I.

1981-02-01

322

Establishing global error bounds for model reduction in combustion  

E-print Network

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 ...

Oxberry, Geoffrey Malcolm

2013-01-01

323

Modeling piston skirt lubrication in internal combustion engines  

E-print Network

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 ...

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

2012-01-01

324

Longitudinal-Mode Combustion Instabilities: Modeling and Experiments  

NASA Technical Reports Server (NTRS)

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.

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

325

Gasification and combustion modeling for porous char particles  

E-print Network

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 ...

Singer, Simcha Lev

2012-01-01

326

Modelling fly ash generation for pulverised coal combustion  

Microsoft Academic Search

An in-depth characterisation was made of three U.K. bituminous coals and the combustion products from these coals when burned at a power station and on a range of experimental combustion facilities. CCSEM analysis of pulverised coals was performed to provide quantitative data on the size and chemical composition of individual mineral occurrences, and to determine the nature of the mineral-mineral

F. Wigley; J. Williamson

1998-01-01

327

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

SciTech Connect

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.

Jung, Jonghwun (ANL); Gamwo, I.K.

2008-04-21

328

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)

329

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

NASA Technical Reports Server (NTRS)

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.

Torres-Pomales, Wilfredo

2014-01-01

330

A Polyethylene Chamber for Use in Physical Modelling of the Heat Exchange on Surfaces Exposed to a Radiation Regime  

NASA Astrophysics Data System (ADS)

Bodies located in outdoor environments are radiatively heated in the daytime and cooled at night. Convective heat transfer is subsequently activated between the body surface and the surrounding air. To investigate these heat-exchange processes, we developed a new apparatus, referred to as a "polyethylene chamber", for use in physical model experiments. The chamber is a 1.51-m-long tube with the ends serving as the air inlet and outlet, and is ventilated in the longitudinal direction by using an exhaust fan. The measurement section of the chamber is open but otherwise the device is covered with 0.02-mm-thick polyethylene film. Because such thin polyethylene film transmits approximately 85 % of both shortwave and longwave radiation, the model surface in the chamber is exposed to a radiation level almost equivalent to the outdoor radiation level. For example, at night the surface of the model is cooled by radiation, and subsequently, the air inside the chamber is cooled by the surface. Consequently, the outlet air temperature becomes lower than the inlet air temperature. The use of this temperature difference between the air inlet and outlet, together with other heat balance components, is a unique approach to the chamber technique for evaluating the heat exchange rate at a model's surface. This report describes the design and heat balance of the chamber, and compares the heat-balance-based approach with another approach based on the radiation-convection balance on the model surface. To demonstrate the performance of the polyethylene chamber, two chambers were exposed to outdoor radiation on a clear night; one contained a leaf model. Air and surface temperatures were measured and the convective heat flux at the surfaces of the model and floor surface were calculated from the heat balance components of the chambers by assuming steady-state heat transfer. The fluxes agreed closely with those obtained from the radiation-convection balance at the model or floor surface. The results also clearly showed that the air flowing in the polyethylene chamber was cooled more efficiently when the model surface was installed in the chamber, even though the model surface temperature was high.

Okada, Maki; Okada, Masumi; Kusaka, Hiroyuki

2014-07-01

331

Internal combustion engine using premixed combustion of stratified charges  

DOEpatents

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.

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

2003-12-30

332

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

NASA Astrophysics Data System (ADS)

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.

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

333

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

334

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

335

Modeling of the reaction-front propagation during the fixed-bed combustion of solid fuel  

Microsoft Academic Search

A one-dimensional, steady-state mathematical model of solid-fuel combustion in a fixed bed is presented. The model equations and boundary conditions as well as the solution method are presented. Calculation results are shown to agree very well with the experimental data. Calculations indicate that during fixed-bed cocurrent flow combustion a reaction front is formed that propagates in the direction opposite to

2003-01-01

336

Thermal ignition combustion system  

DOEpatents

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.

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

1988-04-19

337

Thermal ignition combustion system  

DOEpatents

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.

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

1988-01-01

338

Simplified Combustion Modeling of Double Base Propellant: Gas Phase Chain Reaction Vs. Thermal Decomposition  

Microsoft Academic Search

Simplified combustion modeling of nitrocellulose (NC), nitroglycerin (NG) double base propellant is considered. Two models with simple but rational chemistry are compared: the classical thermal decomposition, high gas activation energy (Eg\\/RT> > 1) Denison-Baum-Williams (DBW) model, and a new chain reaction, low gas activation energy (Eg\\/RT < < 1) model recently proposed by Ward, Son, and Brewster (WSB). Both models

M. Q. BREWSTER; M. J. WARD; S. F. SON

2000-01-01

339

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

340

Longitudinal Mode Aeroengine Combustion Instability: Model and Experiment  

NASA Technical Reports Server (NTRS)

Combustion instabilities in gas turbine engines are most frequently encountered during the late phases of engine development, at which point they are difficult and expensive to fix. The ability to replicate an engine-traceable combustion instability in a laboratory-scale experiment offers the opportunity to economically diagnose the problem more completely (to determine the root cause), and to investigate solutions to the problem, such as active control. The development and validation of active combustion instability control requires that the casual dynamic processes be reproduced in experimental test facilities which can be used as a test bed for control system evaluation. This paper discusses the process through which a laboratory-scale experiment and be designed to replicate an instability observed in a developmental engine. The scaling process used physically-based analyses to preserve the relevant geometric, acoustic, and thermo-fluid features, ensuring that results achieved in the single-nozzle experiment will be scalable to the engine.

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.

2001-01-01

341

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

SciTech Connect

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.

Dryer, F.L.; Yetter, R.A. [Princeton Univ., NJ (United States)

1993-12-01

342

Automated computation of functional vascular density using laser speckle imaging in a rodent window chamber model.  

PubMed

We report a methodology for computing functional vascular density within a rodent dorsal window chamber model based on long-exposure laser speckle imaging (LSI). This technique relies on the presence of flow to create detailed vasculature maps. Employing this contrast mechanism is not possible using conventional imaging methods. Additionally, a freeware algorithm for computing functional vascular density (FVD) from images acquired using long-exposure LSI is also described to facilitate ease in adopting this method. We demonstrate that together these tools can be used to compute FVD nearly twelve times faster than manual computation, yet with comparable accuracy. PMID:21419785

White, Sean M; George, Steven C; Choi, Bernard

2011-07-01

343

Model calculations for the airborne Fast Ice Nuclei CHamber FINCH-HALO  

NASA Astrophysics Data System (ADS)

Ice nuclei (IN) initiate the formation of primary ice in tropospheric clouds. In mixed phase clouds the primary ice crystals can grow very fast by the Bergeron-Findeisen process (Findeisen, 1938) at the expense of evaporating water droplets, and form precipitation. Thus, IN are essential for the development of precipitation in mixed phase clouds in the middle latitude. However, the role of IN in the development of clouds is still poorly understood and needs to be studied (Levin and Cotton, 2007). A Fast Ice Nuclei CHamber (FINCH-HALO) for airborne operation on the High And LOng Range research aircraft (HALO) is under development at the Institute for Atmosphere and Environment University Frankfurt. IN particles are activated within the chamber at certain ice super-saturation and temperature by mixing three gas flows, a warm moist, a cold dry, and an aerosol flow. After activation the particles will grow within a processing chamber. In an optical depolarisation detector droplets and ice crystals are detected separately. The setup of the new FINCH-HALO instrument is based on the ground based IN counter FINCH (Bundke, 2008). In FINCH-HALO a new cooling unit is used. Thus, measurements down to -40°C are possible. Furthermore minor changes of the inlet section where the mixing occurs were done. The contribution will present 3D model calculations with FLUENT of the flow conditions in the new inlet section for different pressure levels during a flight typical for HALO. Growth rates of ice crystals in the chamber at different temperature and super-saturation will be shown. References: Bundke U., B. Nillius, R. Jaenicke, T. Wetter, H. Klein, H. Bingemer, (2008). The Fast Ice Nucleus Chamber FINCH, Atmospheric Research, doi:10.1016/j.atmosres.2008.02.008 Findeisen, R., (1938). Meteorologisch-physikalische Begebenheiten der Vereisung in der Atmosphäre. Hauptversammlung 1938 der Lilienthal-Gesellschaft. Levin, Z., W. Cotton, (2007). Aerosol pollution impact on precipitation: a scientific review. The WMO/IUGG International Aerosol Precipitation Science Assessment Group (IAPSAG). World Meteorological Organization, Geneva. Acknowledgements: This work was supported by the German Research Foundation, SFB 641 "Tropospheric Ice Phase" TP A1, SPP 1294, BU 1432/3-1, JA 344/12-1, by the Helmholtz Association, VI-233 "Aerosol Cloud Interactions" and by the EU FP6 Infrastructure Project EUSAAR.

Nillius, B.; Bingemer, H.; Bundke, U.; Jaenicke, R.; Reimann, B.; Wetter, T.

2009-04-01

344

HCCI Combustion: Analysis and Experiments  

SciTech Connect

Homogeneous charge compression ignition (HCCI) is a new combustion technology that may develop as an alternative to diesel engines with high efficiency and low NOx and particulate matter emissions. This paper describes the HCCI research activities being currently pursued at Lawrence Livermore National Laboratory and at the University of California Berkeley. Current activities include analysis as well as experimental work. On analysis, we have developed two powerful tools: a single zone model and a multi-zone model. The single zone model has proven very successful in predicting start of combustion and providing reasonable estimates for peak cylinder pressure, indicated efficiency and NOX emissions. This model is being applied to develop detailed engine performance maps and control strategies, and to analyze the problem of engine startability. The multi-zone model is capable of very accurate predictions of the combustion process, including HC and CO emissions. The multi-zone model h as applicability to the optimization of combustion chamber geometry and operating conditions to achieve controlled combustion at high efficiency and low emissions. On experimental work, we have done a thorough evaluation of operating conditions in a 4-cylinder Volkswagen TDI engine. The engine has been operated over a wide range of conditions by adjusting the intake temperature and the fuel flow rate. Satisfactory operation has been obtained over a wide range of operating conditions. Cylinder-to-cylinder variations play an important role in limiting maximum power, and should be controlled to achieve satisfactory performance.

Salvador M. Aceves; Daniel L. Flowers; Joel Martinez-Frias; J. Ray Smith; Robert Dibble; Michael Au; James Girard

2001-05-14

345

Master Equation Models for Chemical Reactions of Importance in Combustion  

Microsoft Academic Search

The master equation provides a quantitative description of the interaction between collisional energy transfer and chemical reaction for dissociation, isomerization, and association processes. The approach is outlined for both irreversible and reversible dissociation, isomerization, and association reactions. There is increasing interest, especially in combustion, in association reactions that involve several linked potential wells, with the possibility of isomerization, collisional stabilization,

Michael J. Pilling; Struan H. Robertson

2003-01-01

346

Advanced laser diagnostics in combustion for prototype and modelling development  

Microsoft Academic Search

This paper addresses the questions of how advanced laser diagnostics for the measurement and imaging of scalar quantities are helping in the development of new high-performance combustors and engines. Such diagnostics have greatly improved our understanding of combustion processes but their early promise for aiding more directly the development process are perhaps unfulfilled as yet. Some examples of the direct

Robert W. Bilger

347

Carbon black enriched combustion  

SciTech Connect

A process for combustion of carbon black enriched gaseous hydrocarbon fuels is described comprising: entraining a plurality of carbon black particles in a carrier fluid, forming a carbon black/carrier fluid mixture; injecting said carbon black/carrier fluid mixture through a center nozzle of a fluid injector into a combustion chamber, said fluid injector having an outer nozzle concentrically disposed around said center nozzle forming an annular chamber between said center nozzle and said outer nozzle; injecting at least a first portion of a gaseous hydrocarbon fuel through said annular chamber into said combustion chamber forming a carbon black enriched gaseous hydrocarbon fuel; mixing said carbon black enriched gaseous hydrocarbon fuel with combustion air, forming a fuel/air mixture; and igniting said fuel/air mixture.

Joshi, M.L.; Tester, M.E.

1993-06-29

348

INSTITUTE OF PHYSICS PUBLISHING COMBUSTION THEORY AND MODELLING Combust. Theory Modelling 8 (2004) 721743 PII: S1364-7830(04)69216-3  

E-print Network

into a number of burnt gas zones. For the methane­air mixture the model is used to determine the temperature, the variation of the combustion products with temperature and pressure, the spatial distribution of the gas gradient in the burnt gas due to the consecutive nature of burning inside the closed vessel. O

349

DESCRIPTION OF THE INDUSTRIAL COMBUSTION EMISSIONS MODEL (VERSION 6.0)  

EPA Science Inventory

The report describes the model methodology, key assumptions, data sources, and user options for Version 6 of the Industrial Combustion Emissions (ICE) Model, one of a number of National Acid Precipitation Assessment Program emission forecasting models. Future ICE Model runs may i...

350

Analysis of the dynamics of coal char combustion with ignition and extinction phenomena: Shrinking core model  

SciTech Connect

Single-particle combustion of coal char is analyzed using a generalized shrinking core model. Finite volume method, which was earlier employed by the authors in solving moving boundary problems involving fluid-solid noncatalytic reactions in general, is used to solve fully transient mass and energy equations. The model takes into account convection and diffusion inside the particle as well as in the boundary layer. The computed results are compared with the experimental data of the authors for combustion of coal char in a fluidized bed combustor. The effects of parameters such as bulk temperature and initial particle radius on the combustion dynamics are examined. The phenomena of ignition and extinction are also investigated. Finally, the importance of Stefan flow, originating due to nonequimolar counterdiffusion, on combustion of coal char is analyzed.

Sadhukhan, A.K.; Gupta, P.; Saha, R.K. [National Institute for Technology, Durgapur (India). Dept. of Chemical Engineering

2008-09-15

351

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

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

352

Numerical modeling of the combustion of densified wood under fixed-bed conditions  

Microsoft Academic Search

This paper presents a three-dimensional model for the simulation of fixed-bed combustion systems. These generally involve two main zones, namely, bed and freeboard. Although commercially available CFD codes have extensively demonstrated their ability to simulate the behavior of the freeboard region, difficulties are found in the simulation of heterogeneous combustion and in the mass–energy interaction between the zones. A unified

J. Collazo; J. Porteiro; D. Patiño; E. Granada

353

Self-ignition and combustion modeling of initially nonpremixed turbulent systems  

Microsoft Academic Search

A model to simulate numerically self-ignition and combustion of initially non-premixed turbulent systems is proposed. Its development is based on Direct Numerical Simulations (DNS) of turbulent mixing layers between cold fuel and a hot oxidizer. The direct numerical simulations are used to better understand the physical mechanisms controlling mixing, self-ignition, and establishment of combustion inside turbulent mixing layers. They are

A. Pires da Cruz; T. A. Baritaud; T. J. Poinsot

2001-01-01

354

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

SciTech Connect

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)

Mazza, G. [Facultad de Ingenieria, Departamento de Quimica, Universidad Nacional del Comahue, IDEPA (CONICET - UNCo), Buenos Aires 1400, 8300 Neuquen (Argentina); Falcoz, Q.; Gauthier, D.; Flamant, G. [Laboratoire Procedes et Materiaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu Cedex (France); Soria, J. [Facultad de Ingenieria, Departamento de Quimica, Universidad Nacional del Comahue, IDEPA (CONICET - UNCo), Buenos Aires 1400, 8300 Neuquen (Argentina); Laboratoire Procedes et Materiaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu Cedex (France)

2010-12-15

355

High-Resolution In Vivo Imaging of Fluorescent Proteins Using Window Chamber Models  

PubMed Central

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

Palmer, Gregory M.; Fontanella, Andrew N.; Shan, Siqing; Dewhirst, Mark W.

2013-01-01

356

Plant growth modeling at the JSC variable pressure growth chamber - An application of experimental design  

NASA Technical Reports Server (NTRS)

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.

Miller, Adam M.; Edeen, Marybeth; Sirko, Robert J.

1992-01-01

357

Modeling the optical coupling across the anterior chamber of the eye towards polarimetric glucose sensing  

NASA Astrophysics Data System (ADS)

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.

Pirnstill, Casey W.; Coté, Gerard L.

2014-02-01

358

Use of a Rabbit Soft Tissue Chamber Model to Investigate Campylobacter Jejuni-Host Interactions  

PubMed Central

Despite the prevalence of Campylobacter jejuni as an important food borne pathogen, the microbial factors governing its infection process are poorly characterized. In this study, we developed a novel rabbit soft tissue chamber model to investigate C. jejuni interactions with its host. The in vivo transcriptome profile of C. jejuni was monitored as a function of time post-infection by competitive microarray hybridization with cDNA obtained from C. jejuni grown in vitro. Genome-wide expression analysis identified 449 genes expressed at significantly different levels in vivo. Genes implicated to play important roles in early colonization of C. jejuni within the tissue chamber include up-regulation of genes involved in ribosomal protein synthesis and modification, heat shock response, and primary adaptation to the host environment (DccSR regulon). Genes encoding proteins involved in the TCA cycle and flagella related components were found to be significantly down-regulated during early colonization. Oxidative stress defense and stringent response genes were found to be maximally induced during the acute infectious phase. Overall, these findings reveal possible mechanisms involved in adaptation of Campylobacter to the host. PMID:21687769

Flint, Annika; Butcher, James; Clarke, Cyril; Marlow, Denver; Stintzi, Alain

2010-01-01

359

From elementary reactions to evaluated chemical mechanisms for combustion models  

Microsoft Academic Search

Methods of determining rate data for elementary reactions for combustion applications, using experimental and theoretical methods, are briefly reviewed. The approaches are illustrated by reference to recent research in three areas: (i) reactions of OH with C2H4 and C2H2, where theory, tuned by reference to experiment, has provided a substantial contribution to the determination of rate data for these complex

Michael J. Pilling

2009-01-01

360

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)

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.

Makarov, A. N.

2014-10-01

361

Experiments on Spray Combustion in a Gas Turbine Model Combustor  

Microsoft Academic Search

A hollow-cone kerosene spray with a nominal cone angle of 30 degrees from a pressure-swirl fuel atomizer was used in a swirl-stabilized combustor. Swirling air flow with a calculated swirl number of 0.36 is generated with a swirl plate having an exit air velocity vector of 30 degrees with respect to the chamber axis. Effects of swirl and dilution air

M. GHAFFARPOUR; B. CHEHROUDI

1993-01-01

362

Simulated Altitude Investigation of Stewart-Warner Model 906-B Combustion Heater  

NASA Technical Reports Server (NTRS)

An investigation has been conducted to determine thermal and pressure-drop performance and the operational characteristics of a Stewart-Warner model 906-B combustion heater. The performance tests covered a range of ventilating-air flows from 500 to 3185 pounds per hour, combustion-air pressure drops from 5 to 35 inches of water, and pressure altitudes from sea level to 41,000 feet. The operational characteristics investigated were the combustion-air flows for sustained combustion and for consistent ignition covering fuel-air ratios ranging from 0.033 to 0.10 and pressure altitudes from sea level to 45,000 feet. Rated heat output of 50,000 Btu per hour was obtained at pressure altitudes up to 27,000 feet for ventilating-air flows greater than 800 pounds per hour; rated output was not obtained at ventilating-air flow below 800 pounds per hour at any altitude. The maximum heater efficiency was found to be 60.7 percent at a fuel-air ratio of 0.050, a sea-level pressure altitude, a ventilating-air temperature of 0 F, combustion-air temperature of 14 F, a ventilating-air flow of 690 pounds per hour, and a combustion-air flow of 72.7 pounds per hour. The minimum combustion-air flow for sustained combustion at a pressure altitude of 25,000 feet was about 9 pounds per hour for fuel-air ratios between 0.037 and 0.099 and at a pressure altitude of 45,000 feet increased to 18 pounds per hour at a fuel-air ratio of 0.099 and 55 pounds per hour at a fuel-air ratio of 0.036. Combustion could be sustained at combustion-air flows above values of practical interest. The maximum flow was limited, however, by excessively high exhaust-gas temperature or high pressure drop. Both maximum and minimum combustion-air flows for consistent ignition decrease with increasing pressure altitude and the two curves intersect at a pressure altitude of approximately 25,000 feet and a combustion-air flow of approximately 28 pounds per hour.

Ebersbach, Frederick R.; Cervenka, Adolph J.

1947-01-01

363

A novel cardiac MR chamber volume model for mechanical dyssynchrony assessment  

NASA Astrophysics Data System (ADS)

A novel cardiac chamber volume model is proposed for the assessment of left ventricular mechanical dyssynchrony. The tool is potentially useful for assessment of regional cardiac function and identification of mechanical dyssynchrony on MRI. Dyssynchrony results typically from a contraction delay between one or more individual left ventricular segments, which in turn leads to inefficient ventricular function and ultimately heart failure. Cardiac resynchronization therapy has emerged as an electrical treatment of choice for heart failure patients with dyssynchrony. Prior MRI techniques have relied on assessments of actual cardiac wall changes either using standard cine MR images or specialized pulse sequences. In this abstract, we detail a semi-automated method that evaluates dyssynchrony based on segmental volumetric analysis of the left ventricular (LV) chamber as illustrated on standard cine MR images. Twelve sectors each were chosen for the basal and mid-ventricular slices and 8 sectors were chosen for apical slices for a total of 32 sectors. For each slice (i.e. basal, mid and apical), a systolic dyssynchrony index (SDI) was measured. SDI, a parameter used for 3D echocardiographic analysis of dyssynchrony, was defined as the corrected standard deviation of the time at which minimal volume is reached in each sector. The SDI measurement of a healthy volunteer was 3.54%. In a patient with acute myocardial infarction, the SDI measurements 10.98%, 16.57% and 1.41% for basal, mid-ventricular and apical LV slices, respectively. Based on published 3D echocardiogram reference threshold values, the patient's SDI corresponds to moderate basal dysfunction, severe mid-ventricular dysfunction, and normal apical LV function, which were confirmed on echocardiography. The LV chamber segmental volume analysis model and SDI is feasible using standard cine MR data and may provide more reliable assessment of patients with dyssynchrony especially if the LV myocardium is thin or if the MR images have spatial resolution insufficient for proper resolution of wall thickness-features problematic for dyssynchrony assessment using existing MR techniques.

Song, Ting; Fung, Maggie; Stainsby, Jeffrey A.; Hood, Maureen N.; Ho, Vincent B.

2009-02-01

364

Modeling coal combustion behavior in an ironmaking blast furnace raceway: model development and applications  

SciTech Connect

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.

Maldonado, D.; Austin, P.R.; Zulli, P.; Guo B. [BlueScope Steel Research Laboratories, Port Kembla, NSW (Australia)

2009-03-15

365

Recent Developments in Spray Combustion: Experiments and Modeling  

NASA Technical Reports Server (NTRS)

The current research program under NASA sponsorship (NAG3-1688) focuses on the study of fundamental aspects of spray diffusion flames at normal and reduced gravity. The objective of this program is to bridge the gap between classical single droplet burning studies and practical spray flames, by using a variety of well-defined configurations, encompassing both laminar and turbulent spray diffusion flames. In the remainder of this article the main accomplishments in the two-year period (3-15-95 to 3-14-97) since the last International Microgravity Combustion Conference will be reviewed. A detailed account of the research activity is given in.

Gomez, Alessandro; Smooke, Mitchell D.; Chen, Gung; Karpetis, Adonis; Gao, Ling-Ping

1997-01-01

366

Description of fluid dynamics and coupled transports in models of a laminar flow diffusion chamber  

NASA Astrophysics Data System (ADS)

The aim of this study is to assess how much the results of nucleation experiments in a laminar flow diffusion chamber (LFDC) are influenced by the complexity of the model of the transport properties. The effects of the type of fluid dynamic model (the steady state compressible Navier-Stokes system for an ideal gas/parabolic profile approximation) and the contributions of the coupled terms describing the Dufour effects and thermodiffusion on the predicted magnitude of the nucleation maxima and its location were investigated. This study was performed on the model of the homogeneous nucleation of an n-butanol-He vapor mixture in a LFDC. The isothermal dependencies of the nucleation rate on supersaturation were determined at three nucleation temperatures: 265 K, 270 K, and 280 K. For this purpose, the experimental LFDC data measured by A. P. Hyvärinen et al. [J. Chem. Phys. 124, 224304 (2006)] were reevaluated using transport models at different levels of complexity. Our results indicate that the type of fluid dynamical model affects both the position of the nucleation maxima in the LFDC and the maximum value of the nucleation rate. On the other hand, the Dufour effects and thermodiffusion perceptibly influence only the value of the maximal nucleation rate. Its position changes only marginally. The dependence of the maximum experimental nucleation rate on the saturation ratio and nucleation temperature was acquired for each case. Based on this dependence, we presented a method for the comparison and evaluation of the uncertainties of simpler models' solutions for the results, where we assumed that the model with Navier-Stokes equations and both coupled effects taken into account was the basis. From this comparison, it follows that an inappropriate choice of mathematical models could lead to relative errors of the order of several hundred percent in the maximum experimental nucleation rate. In the conclusion of this study, we also provide some general recommendations concerning the proper choice and setting of the mathematical model of transport processes in the LFDC.

Trávní?ková, Tereza; Havlica, Jaromír; Ždímal, Vladimír

2013-08-01

367

Atmospheric photochemical modeling of turbine engine fuels. Phase 1: Experimental studies. Volume 2: Environmental chamber data tabulations  

NASA Astrophysics Data System (ADS)

This report documents the results of the first phase of a two-phase program aimed at developing for the U.S. Air Force experimentally tested computer models to predict worst-case potentials for air quality degradation resulting from use of current and potential future turbine engine (jet) fuels. The development and testing of such models requires an adequate data base derived from appropriate environmental chamber experiments and laboratory studies. In Phase I of this two-phase program, a total of 131 environmental chamber experiments were carried out in a approx. 640000-liter, all Teflon indoor environmental chamber and several kinetic measurements were made in order to obtain data required for model development. The chamber experiments included 47 single component-NOx-air irradiations of various representative fuel constituents and potential future fuel impurities, 15 fuel-NOx-air irradiations of various representative fuel constituents and potential future fuel impurities, 15 fuel--NOx-air irradiations employing one whole and six synthetic surrogate fuels, and 69 control or characterization runs. Volume II contains a tabulation of the environmental chamber data gathered during the course of the experimental phase of this program.

Carter, W. P. L.; Winer, A. M.; Atkinson, R.; Dodd, M. C.; Long, W. D.

1984-09-01

368

Numerical modeling of combustion and pyrolysis of cellulosic biomass in thermogravimetric systems  

Microsoft Academic Search

A two-dimensional axisymmetrical numerical model for pyrolysis and combustion of cellulosic biomass in a thermogravimetric system is presented. Both chemical reactions and physical phenomena are considered, using fundamental principles. This mathematical model has combined the transient mass, species and energy conservation equation, Darcy momentum equation and a global Arrhenius decomposition for a porous reacting biomass. It can predict weight loss

X. H. Liang; J. A. Kozinski

2000-01-01

369

CFD modelling of bed shrinkage and channelling in fixed-bed combustion  

Microsoft Academic Search

Combustion of fixed fuel beds in grate furnaces is common within production of heat and power from solid fuels. Available theoretical and experimental experience provides a solid base of knowledge on how a conversion model of a fuel bed, using Computational Fluid Dynamics (CFD), needs to be structured and solved. Most existing models, however, handle the conversion in one single

Sven Hermansson; Henrik Thunman

2011-01-01

370

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

E-print Network

- quence, some of these species have never been introduced into kinetic models. Such species mustThermochemistry of Aluminum Species for Combustion Modeling from Ab Initio Molecular Orbital thermochemical data are also presented for several species never studied experimentally, including AlH2, AlH3, Al

Swihart, Mark T.

371

Combustion of wood particles—a particle model for eulerian calculations  

Microsoft Academic Search

A simplified model for the combustion of solid fuel particles is derived, relevant for particle sizes and shapes used in fluidized and fixed-bed combustors and gasifiers. The model operates with a small number of variables and treats the most essential features of the conversion of solid fuel particles, such as temperature gradients inside the particle, the release of volatiles, shrinkage,

H. Thunman; B. Leckner; F. Niklasson; F. Johnsson

2002-01-01

372

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,...

373

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...

374

Supersonic combustion studies using a multivariate quadrature based method for combustion modeling  

E-print Network

for studying the effect of various model parameters in an experimental supersonic hydrogen jet. Development is the transported probability density function (PDF) method. Here, the joint-PDF of the gas phase thermochemical statistical error. Second, high-speed problems involving complex shock-turbulence interaction and strong wall

Raman, Venkat

375

Modeling of single char combustion, including CO oxidation in its boundary layer  

SciTech Connect

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.

Lee, C.H.; Longwell, J.P.; Sarofim, A.F.

1994-10-25

376

14 CFR 29.859 - Combustion heater fire protection.  

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate in the combustion chamber or the heat exchanger. In...

2014-01-01

377

14 CFR 25.859 - Combustion heater fire protection.  

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate within the combustion chamber or the heat exchanger. In...

2014-01-01

378

14 CFR 29.859 - Combustion heater fire protection.  

Code of Federal Regulations, 2010 CFR

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate in the combustion chamber or the heat exchanger. In...

2010-01-01

379

14 CFR 29.859 - Combustion heater fire protection.  

Code of Federal Regulations, 2011 CFR

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate in the combustion chamber or the heat exchanger. In...

2011-01-01

380

14 CFR 25.859 - Combustion heater fire protection.  

Code of Federal Regulations, 2012 CFR

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate within the combustion chamber or the heat exchanger. In...

2012-01-01

381

14 CFR 25.859 - Combustion heater fire protection.  

Code of Federal Regulations, 2013 CFR

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate within the combustion chamber or the heat exchanger. In...

2013-01-01

382

14 CFR 29.859 - Combustion heater fire protection.  

Code of Federal Regulations, 2012 CFR

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate in the combustion chamber or the heat exchanger. In...

2012-01-01

383

14 CFR 25.859 - Combustion heater fire protection.  

Code of Federal Regulations, 2011 CFR

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate within the combustion chamber or the heat exchanger. In...

2011-01-01

384

14 CFR 25.859 - Combustion heater fire protection.  

Code of Federal Regulations, 2010 CFR

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate within the combustion chamber or the heat exchanger. In...

2010-01-01

385

14 CFR 29.859 - Combustion heater fire protection.  

Code of Federal Regulations, 2013 CFR

... (i) The heat exchanger temperature... (iii) The combustion airflow becomes...any heater whose heat output is essential...intakes. Each combustion and ventilating...accumulate in the combustion chamber or the heat exchanger. In...

2013-01-01

386

Development of an Efficient CFD Model for Nuclear Thermal Thrust Chamber Assembly Design  

NASA Technical Reports Server (NTRS)

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.

Cheng, Gary; Ito, Yasushi; Ross, Doug; Chen, Yen-Sen; Wang, Ten-See

2007-01-01

387

IEEE TRANSACTIONS ON MEDICAL IMAGING 1 Four-Chamber Heart Modeling and Automatic  

E-print Network

-chamber heart seg- mentation system for the quantitative functional analysis of the heart from cardiac computed about the heart chambers, large vessels, and coronary arter- ies [1]. Therefore, CT is an important must be obtained from the IEEE by sending a request to pubs-permissions@ieee.org. quantitative

Barbu, Adrian

388

Experimental and Modeling Studies of the Characteristics of Liquid Biofuels for Enhanced Combustion  

SciTech Connect

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.

E. Meeks; A. U. Modak; C.V. Naik; K. V. Puduppakkam; C. Westbrook; F. N. Egolfopoulos; T. Tsotsis; S. H. Roby

2009-07-01

389

Phase transition model of water flow irradiated by high-energy laser in a chamber  

NASA Astrophysics Data System (ADS)

In the absorption chamber of a high-energy laser energy meter, water is directly used as an absorbing medium and the interaction of the high-power laser and the water flow can produce a variety of physical phenomena such as phase transitions. The unit difference method is adopted to deduce the phase transition model for water flow irradiated by a high-energy laser. In addition, the model is simulated and verified through experiments. Among them, the experimental verification uses the photographic method, shooting the distribution and the form of the air mass of water flow in different operating conditions, which are compared with the simulation results. The research shows that it is achievable to reduce the intensity of the phase transition by increasing the water flow, reducing the power intensity of the beam, shortening the distance the beam covers, reducing the initial water temperature or adopting a shorter wavelength laser. The study's results will provide the reference for the design of a water-direct-absorption-type high-energy laser energy meter as well as an analysis of the interaction processes of other similar high-power lasers and water flow.

Wei, Ji-Feng; Sun, Li-Qun; Zhang, Kai; Hu, Xiao-Yang

2014-07-01

390

Combustion Fundamentals Research  

NASA Technical Reports Server (NTRS)

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.

1983-01-01

391

Computational Model Tracking Primary Electrons, Secondary Electrons, and Ions in the Discharge Chamber of an Ion Engine  

NASA Technical Reports Server (NTRS)

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.

Mahalingam, Sudhakar; Menart, James A.

2005-01-01

392

Volcano-tectonic modelling of magma chambers, ring-faults, unrest, and eruptions in the Tianchi Volcano, China  

E-print Network

Volcano-tectonic modelling of magma chambers, ring-faults, unrest, and eruptions in the Tianchi Volcano, China Supervisor: Agust Gudmundsson Project Description: The Tianchi (Changbaishan) Volcano, located at the boundary between China and North Korea, is widely regarded as the most dangerous volcano

Sheldon, Nathan D.

393

Modelling Residential-Scale Combustion-Based Cogeneration in Building Simulation  

SciTech Connect

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.

Ferguson, A.; Kelly, N.; Weber, A.; Griffith, B.

2009-03-01

394

Micro-chamber filling experiments for validation of macro models with applications in capillary driven microfluidics  

E-print Network

with side walls L 1 length of micro-chamber L 2 width of micro-chamber L e1 Scan Length at Top of Microchamber L e2 Scan Length at Bottom of Microchamber l s1 Meniscus Position along L 1 Direction l s2 Meniscus Position along L 2... Direction l m Position along central portion of the meniscus viii ?l s1 Measurement Error of l s1 ?l s2 Measurement Error of l s2 ?l m Measurement Error of l m h depth of micro-chamber Q volumetric flow rate t time w region...

Gauntt, Stephen Byron

2009-05-15

395

Methodology of a combined ground based testing and numerical modelling analysis of supersonic combustion flow paths  

NASA Astrophysics Data System (ADS)

In the framework of the European Commission co-funded LAPCAT (Long-Term Advanced Propulsion Concepts and Technologies) project, the methodology of a combined ground-based testing and numerical modelling analysis of supersonic combustion flow paths was established. The approach is based on free jet testing of complete supersonic combustion ramjet (scramjet) configurations consisting of intake, combustor and nozzle in the High Enthalpy Shock Tunnel Göttingen (HEG) of the German Aerospace Center (DLR) and computational fluid dynamics studies utilising the DLR TAU code. The capability of the established methodology is demonstrated by applying it to the flow path of the generic HyShot II scramjet flight experiment configuration.

Hannemann, Klaus; Karl, Sebastian; Martinez Schramm, Jan; Steelant, Johan

2010-10-01

396

Hydrogen program combustion research: Three dimensional computational modeling  

Microsoft Academic Search

We have significantly increased our computational modeling capability by the addition of a vertical valve model in KIVA-3, code used internationally for engine design. In this report the implementation and application of the valve model is described. The model is shown to reproduce the experimentally verified intake flow problem examined by Hessel. Furthermore, the sensitivity and performance of the model

N. L. Johnson; A. A. Amsden; T. D. Butler

1995-01-01

397

A Multi-FhJid CFD Turbulent Entrainment Combustion Model: Formulation and One-Dimensional Results  

E-print Network

~. 2. 2.r 972880 A Multi-FhJid CFD Turbulent Entrainment Combustion Model: Formulation and One is formulated in a manner suitable for coupling with CFD solvers in one or more spatial dimensions. The existing (CFD) techniques have seen increasing popularity in recent years due to advances in computational

398

Supersonic Combustion of Kerosene\\/H2Mixtures in a Model Scramjet Combustor  

Microsoft Academic Search

Liquid hydrocarbon supersonic combustion has been experimentally investigated. Kerosene was burnt in a steady. vitiated Mach 2.15 - air flow of a model scramjet combustor. The fuel is injected into the supersonic air stream by means of pylons. The effervescent atomisation method has been employed such that the liquid fuel is injected as a spray. By means of the Mie

C. Gruenig; F. Mayinger

1999-01-01

399

Combustion Timing Control of Natural Gas HCCI Engines Using Physics-Based Modeling and LQR Controller  

E-print Network

to control its combustion timing. The aim of this research project is to model and control a natural gas HCCI engine. Since HCCI depends primarily on temperature and chemical composition of the mixture, Exhaust Gas Recirculation (EGR) is used to control...

Abdelgawad, Marwa

2012-07-16

400

Comparison of direct and indirect combustion noise mechanisms in a model combustor  

E-print Network

's method I. Introduction Over the last five decades, jet and external aerodynamic noises of aircraft have been achieved on fan and jet noise, the relative importance of other noise sources has increasedComparison of direct and indirect combustion noise mechanisms in a model combustor M. Leyko SNECMA

Paris-Sud XI, Université de

401

Predictive Modeling of Mercury Speciation in Combustion Flue Gases Using GMDH-Based Abductive Networks  

E-print Network

Predictive Modeling of Mercury Speciation in Combustion Flue Gases Using GMDH-Based Abductive Networks R. E. Abdel-Aal Department of Computer Engineering, King Fahd University of Petroleum and Minerals to develop. The use of modern data-based machine learning techniques has been recently introduced, including

Abdel-Aal, Radwan E.

402

Combustion Theory and Modelling Vol. 11, No. 5, October 2007, 697714  

E-print Network

scales of the flow-field can have significant effects on the flame, see, e.g. [3, 4]. The present invCombustion Theory and Modelling Vol. 11, No. 5, October 2007, 697­714 Flame propagation in a small flames in the presence of a parallel flow whose scale is smaller than the laminar flame thickness

Heil, Matthias

403

A thickened flame model for large eddy simulations of turbulent premixed combustion  

Microsoft Academic Search

A subgrid scale model for large eddy simulations of turbulent premixed combustion is developed and validated. The approach is based on the concept of artificially thickened flames, keeping constant the laminar flame speed sl0. This thickening is simply achieved by decreasing the pre-exponential factor of the chemical Arrhenius law whereas the molecular diffusion is enhanced. When the flame is thickened,

O. Colin; F. Ducros; D. Veynante; T. Poinsot

2000-01-01

404

Modeling chemical flame structure and combustion dynamics in LES P. Auzillona,  

E-print Network

Modeling chemical flame structure and combustion dynamics in LES P. Auzillona, , B. Fiorinaa , R and compared in terms of chemical flame structure and dynamics. To avoid the uncertainties related.ecp.fr [3, 5], the chemical subspace of a turbulent premixed flame can be approximated by a collection of 1

Paris-Sud XI, Université de

405

Problems of modeling gas-particle turbulent flows with combustion and phase transitions. Review  

Microsoft Academic Search

The basic theoretical problems connected with the modeling of gas-particle and vapor-droplet turbulent flows with combustion or phase transitions are considered. Methods of solving these problems are discussed and examples of realization of the solutions are given.

L. I. Zaichik; V. A. Pershukov

1996-01-01

406

Industry Motivated Advancements of Current Combustion Instability Model: The Conversion of  

E-print Network

demonstrated that, by incorporating unsteady rotational sources and sinks in the acoustic energy assessmentIndustry Motivated Advancements of Current Combustion Instability Model: The Conversion of Volume, a more precise formulation of the acoustic instability in rocket motors can be achieved. The new

Flandro, Gary A.

407

A model of large heat transfer surface combustion with radiant heat emission  

Microsoft Academic Search

A model is formulated for the surface combustion of a premixed gas mixture near the downstream surface of a porous solid. Large heat transfer occurs between the gas and porous solid, and there is significant radiant heat emission from the heated surface of the solid. Using large-activation-energy asymptotic methods an analytical solution is derived for the gas and solid temperature

A McIntosh

1991-01-01

408

An improved model for fixed-bed coal combustion and gasification: sensitivity analysis and applications  

Microsoft Academic Search

Detailed sensitivity analysis and applications of an improved, comprehensive, one-dimensional model for combustion and gasification of coal in fixed beds, FBED-1, are presented. The effects of the devolatilization, oxidation and gasification submodels on the model predictions are discussed. The product gas compositions predicted by various options for gas-phase chemistry are shown. The effects of five model parameters and one operational

M. Usman Ghani; Predrag T. Radulovic; L. Douglas Smoot

1996-01-01

409

Calculations of radiative exchange by the Monte-Carlo method. Theory and applications to industrial combustion systems  

Microsoft Academic Search

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

K. Goerner; U. Dietz

1993-01-01

410

STE thrust chamber technology: Main injector technology program and nozzle Advanced Development Program (ADP)  

NASA Technical Reports Server (NTRS)

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.

1993-01-01

411

Evaluation of the UNC toluene-SOA mechanism with respect to other chamber studies and key model parameters  

NASA Astrophysics Data System (ADS)

In a companion paper by Hu et al. [2007. A kinetic mechanism for predicting secondary organic aerosol formation from toluene oxidation in the presence of NO x and natural sunlight. Atmospheric Environment, doi:10.1016/j.atmosenv.2007.04.025], a kinetic mechanism was developed from data generated in the University of North Carolina's (UNC) 270 m 3 dual outdoor aerosol smog chamber, to predict secondary organic aerosol (SOA) formation from toluene oxidation in the atmosphere. In this paper, experimental data sets from European Photoreactor (EUPHORE), smog chambers at the California Institute of Technology (Caltech), and the UNC 300 m 3 dual-outdoor gas phase chamber were used to evaluate the toluene mechanism. The model simulates SOA formation for the 'low-NO x' and 'mid-NO x' experiments from EUPHORE chambers reasonably well, but over-predicts SOA mass concentrations for the 'high-NO x' run. The model well simulates the SOA mass concentrations observed from the Caltech chambers. Experiments with the three key toluene products, 1,4-butenedial, 4-oxo-2-pentenal and o-cresol in the presence of oxides of nitrogen (NO x) are also simulated by the developed mechanism. The model well predicts the NO x time-concentration profiles and the decay of these two carbonyls, but underestimates ozone (O 3) formation for 4-oxo-2-pentenal. It well simulates SOA formation from 1,4-butenedial but overestimates (possibly due to experimental problems) the measured aerosol mass concentrations from 4-oxo-2-pentenal. The model underestimates SOA production from o-cresol, mostly due to its under-prediction of o-cresol decay. The effects of varying temperature, relative humidity, glyoxal uptake, organic nitrate yields, and background seed aerosol concentrations, were also investigated.

Hu, Di; Kamens, Richard M.

412

Analysis of cyclic combustion of the coal-water suspension  

NASA Astrophysics Data System (ADS)

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.

Kijo-Kleczkowska, Agnieszka

2011-04-01

413

Measurement and modelling of oxygenated organic compounds from smoldering combustion of biomass  

SciTech Connect

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.

McKenzie, L.M.; Richards, G.N. [Univ. of Montana, Missoula, MT (United States)

1995-12-01

414

Wire chamber  

DOEpatents

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.

Atac, Muzaffer (Wheaton, IL)

1989-01-01

415

Numerical modeling of deformation and stress fields around a magma chamber: Constraints on failure conditions and rheology  

NASA Astrophysics Data System (ADS)

We present a stress-strain analysis using the Finite Element Method to investigate failure conditions of pressured magma chambers embedded in an inelastic domain. The pressure build-up induces variations in the stress field until failure conditions are reached. Therefore, the definition of the failure conditions could have a significant impact on the volcano hazard assessment. Using a numerical approach, we analyze the stresses in a gravitationally loaded model assuming a brittle failure criterion, to determine the favorable conditions for magma chamber failure in different source geometries, reference stress states, pore fluid pressures, rock rheologies and topographic profiles. The numerical results allow us to pinpoint the conditions promoting seismicity near the magma chamber. The methodology places a limit on the pressure that a magma chamber can sustain before failing and provides a quantitative estimate of the uplift expected at the ground surface. Thermally-activated ductile regimes, which may develop in the region surrounding a heated magma chamber, are also investigated. The stress relaxation in a ductile shell may prevent the wall rupture, favoring the growth of large overpressured chambers, which could lead to considerable deformation at the ground surface without significant seismicity. The numerical results suggest that a spherical source, compressive regime, gentle edifice topography, and growth of a ductile shell are important factors for the initial formation and the mechanical stability of magma storage systems. On the other hand, an elongated ellipsoidal source, extensional regime, steep volcano topography and high pore fluid pressure lower the overpressure necessary for inducing failure. These findings could help in gaining insights on the internal state of the volcano and, hence, in advancing the assessment of the likelihood of volcano unrest.

Currenti, Gilda; Williams, Charles A.

2014-01-01

416

Combustion Stability Analyses for J-2X Gas Generator Development  

NASA Technical Reports Server (NTRS)

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.

Hulka, J. R.; Protz, C. S.; Casiano, M. J.; Kenny, R. J.

2010-01-01

417

Effects of primary breakup modeling on spray and combustion characteristics of compression ignition engines  

SciTech Connect

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)

Som, S.; Aggarwal, S.K. [Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL 60607 (United States)

2010-06-15

418

Modeling engine oil vaporization and transport of the oil vapor in the piston ring pack on internal combustion engines  

E-print Network

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 ...

Cho, Yeunwoo, 1973-

2004-01-01

419

Modeling Ignition and Combustion in Direct Injection Compression Ignition Engines Employing Very Early Injection Timing  

NASA Astrophysics Data System (ADS)

An ignition and combustion model has been developed to predict the heat release rate in direct injection compression ignition engines employing very early injection timing. The model describes the chemical reactions, including low-temperature oxidation. The KIVA II computer code was modified with the present ignition and combustion model. The numerical results indicate that the model developed in this work reproduces major features of two-stage autoignition, as well as experimentally observed trends in NOx and unburned fuel emissions. The computational results show that fuel injection timing significantly influences NOx emissions. Results also indicate that fuel droplets that enter the squish region possibly become unburned fuel emissions. Some graphical results demonstrate the relationships among the in-cylinder fuel spray distributions, fuel-air equivalence ratio, temperature, and mass fractions of NO and unburned fuel.

Miyamoto, Takeshi; Tsurushima, Tadashi; Shimazaki, Naoki; Harada, Akira; Sasaki, Satoru; Hayashi, Koichi; Asaumi, Yasuo; Aoyagi, Yuzo

420

PSR-based microstructural modeling for turbulent combustion processes and pollutant formation in double swirler combustors  

Microsoft Academic Search

The present study numerically investigates the fuel-air mixing characteristics, flame structure, and pollutant emission inside\\u000a a double-swirler combustor. A PSR (Perfectly Stirred Reactor) based microstructural model is employed to account for the effects\\u000a of finite rate chemistry on the flame structure and NO formation. The turbulent combustion model is extended to nonadiabatic\\u000a flame condition with radiation by introducing an enthalpy

Seong-Ku Kim; Sung-Mo Kang; Yong-Mo Kim; Jeong-Lak Sohn

2001-01-01

421

Modeling Effects of Soot and Turbulence-Radiation Coupling on Radiative Transfer in Turbulent Gaseous Combustion  

Microsoft Academic Search

A three-dimensional combustion model which couples turbulent flow statistics with chemical reactions and radiative heat transfer is used to evaluate the effect of soot and turbulence-radiation coupling on radiative transfer in an industrial-scale furnace. Radiation and soot formation models are presented which include the nonlinear dependencies between fluid turbulence effects, soot formation and radiative absorption and emission in the participating

B. R. ADAMS; P. J. SMITH

1995-01-01

422

Modeling of a conceptual self-sustained liquid fuel vaporization – combustion system with radiative output using inert porous media  

Microsoft Academic Search

The present model is based on a combined self-sustained liquid fuel vaporization – combustion system, where the liquid fuel vaporization occurs on a wetted wall plate with energy transferred through the plate from the combustion of vaporized oil. The vaporization energy has been derived through the radiative interaction of the vaporizing plate and an upstream end surface of the porous

Tarun K. Kayal; Mithiles Chakravarty

2007-01-01

423

An extended supersonic combustion model for the dynamic analysis of hypersonic vehicles. Interim Task Report  

SciTech Connect

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.

Bossard, J.A.; Peck, R.E.; Schmidt, D.K.

1993-03-01

424

Multiple-distribution-function lattice Boltzmann kinetic model for combustion phenomena  

E-print Network

A hybrid kinetic model for combustion phenomena is proposed. The chemical reaction process is described by a phenomenological rate function. The flow behavior is described by a Lattice Boltzmann Kinetic Model (LBKM) with any number of distribution functions. As an example, we illustrate the case with only two distribution functions. One distribution function is used to describe the reactant, and the other one is used to describe the reaction product. Compared with the traditional fluid model for combustion, the new model can be used to study simultaneously both the hydrodynamic and the thermodynamic nonequilibrium behaviors. Compared with the previous LBKM-hybrid models with single distribution function, the new model can be used to study more carefully the combustion process, for example, the variations of the particle number densities, particle mass densities, flow velocities, internal energies per unit volume, internal energies per unit mass, temperatures, and pressures of each species and the whole of the system. It is found that both of chemical reactant and reaction product have different levels of deviation from their equilibrium state in different degrees of freedom. For a special degree of freedom, the deviation of chemical reactant from its equilibrium state is different from that of reaction product from its equilibrium state.

Chuandong Lin; Aiguo Xu; Guangcai Zhang; Yingjun Li

2014-05-21

425

An extended supersonic combustion model for the dynamic analysis of hypersonic vehicles  

NASA Technical Reports Server (NTRS)

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.

Bossard, J. A.; Peck, R. E.; Schmidt, D. K.

1993-01-01

426