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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

IDENTIFICATION OF AN IDEAL REACTOR MODEL IN A SECONDARY COMBUSTION CHAMBER  

EPA Science Inventory

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

3

Winged reentrant electromagnetic combustion chamber  

Microsoft Academic Search

An internal combustion engine combustion chamber suitable for electromagnetic stimulation of combustion which has been improved by the addition of combustion chamber periphery extensions (wings) filled with dielectric material. The wing dimensions and filler dielectric material are chosen to allow for specification of the chamber EM resonant frequency, preferably at a frequency in the UHF range (where low cost DC

M. A. V

1985-01-01

4

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

5

Internal combustion engine with rotary combustion chamber  

Microsoft Academic Search

This patent describes an internal combustion engine comprising: a block having at least one cylindrical wall surrounding a piston chamber, piston means located in the piston chamber means operable to reciprocate the piston means in the chamber, head means mounted on the block covering the chamber. The head means has an air and fuel intake passage, and exhaust gas passage,

C. N. Hansen; P. C. Cross

1986-01-01

6

Internal combustion engine with rotary combustion chamber  

Microsoft Academic Search

This patent describes an internal combustion engine comprising: a block having at least one cylindrical wall surrounding a piston chamber, piston means located in the piston chamber, means operable to reciprocate the piston means in the chamber, head means mounted on the block covering the chamber. The head means having an air and fuel intake passage, an exhaust gas passage,

C. N. Hansen; P. C. Cross

1988-01-01

7

CFD Analysis of Radiative Heat Transfer in the SSME Main Combustion Chamber Using Advanced Spectral Models  

NASA Astrophysics Data System (ADS)

In this work, enhanced Weighted Sum of Gray Gases Models for spectral integration of radiative heat transfer are identified and implemented in the Computational Fluid Dynamics solver ANSYS CFX. The models are applicable to both homogeneous and nonhomogeneous conditions in temperature, pressure and molar fraction of radiating species. A simulation of the Space Shuttle Main Engine Main Combustion Chamber is done using these models combined with the P1 Model and the Discrete Transfer Model. Results in Radiative Wall Heat Flux are then compared to benchmark solutions. The results show that the model by Denison & Webb comes close to the benchmark results with vanishing difference between its applications for homogeneous and nonhomogeneous conditions. Both models by Modest predict a smaller radiative wall heat flux than the benchmarks, whereas the results of the nonhomogeneous Full- pectrum-Correlated-k- Distribution-Model are closer to the benchmarks than those of the homogeneous Full-Spectrum-k- Distribution-Model.

Göbel, F.; Mundt, C.

2011-08-01

8

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

9

Structure of divided combustion chamber for internal combustion engine  

Microsoft Academic Search

This patent describes a structure defining a divided combustion chamber of an internal combustion engine, comprising an upper ceramic member, and a lower ceramic member having a transfer passage which communicates with a main combustion chamber of the engine. The upper and lower ceramic members meet with each other at an interface to form divided combustion chamber such that it

Y. Ogawa; T. Ogasawara; S. Hanzawa

1987-01-01

10

Mathematical modeling and experimental investigations of oxygen-methane fuel combustion at coaxial-jet supply into the combustion chamber of liquid-propellant rocket engine  

Microsoft Academic Search

The numerical results are presented for the case of coaxial-jet supply at the different ratio of mass component velocities\\u000a at the combustion chamber inlet with the constant and variable relationship of oxygen-methane components. The experimental\\u000a investigations of coaxial-jet mixing elements as part of the model setup chamber operating on corrosive producer gas and gaseous\\u000a methane were carried out. A qualitative

V. R. Rubinskii; S. P. Khrisanfov; V. Yu. Klimov; A. V. Kretinin

2010-01-01

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

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

13

Method of regulating combustion in the combustion chambers of an internal combustion engine  

Microsoft Academic Search

A method is proposed for regulating the combustion of operating mixtures in the combustion chambers of internal combustion engines. The course of the light intensity of the light resulting from combustion in the combustion chamber is detected and evaluated over the course of combustion; reference control variables derived therefrom are formed for use by subsequently disposed closed-loop control devices of

R. Burkel; K. Eckert; H. Franke; E. Linder; H. Maurer; W. Moser; K. Muller; C. Peter; F. Rieger

1983-01-01

14

Non-grey radiation in a liquid rocket combustion chamber  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

15

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

16

Engine Knock and Combustion Chamber Form  

NASA Technical Reports Server (NTRS)

The present report is confined to the effect of the combustion chamber shape on engine knock from three angles, namely: 1) The uniformity of flame-front movement as affected by chamber design and position of the spark plug; 2) The speed of advance of the flame as affected by turbulence and vibrations; 3) The reaction processes in the residual charge as affected by the walls.

Zinner, Karl

1939-01-01

17

The effect of turbulence model variation on flame propagation in a particular 4-valve engine combustion chamber  

NASA Astrophysics Data System (ADS)

In this paper some initial results concerning the evolution of flame propagation in 4-valve engines with tilted valves were presented. Results were obtained by dint of multidimensional modeling of reactive flows in arbitrary geometry with moving boundaries. During induction fluid flow pattern was characterized with organized tumble motion followed by small but clearly legible deterioration in the vicinity of BDC. During compression the fluid flow pattern is entirely three-dimensional and fully controlled by vortex motion located in the central part of the chamber. The effect of turbulence model variation on flame propagation was tackled as well. Namely, some results obtained with eddy-viscosity model i.e. standard k-? model were compared with results obtained with k-?-f model of turbulence in domain of 4-valve engine in-cylinder flow. Some interesting results emerged rendering impetus for further quest in the near future. In the case of combustion all differences ensuing from turbulence model variation, encountered in the case of non-reactive flow were annihilated entirely. Namely the interplay between fluid flow pattern and flame propagation is invariant as regards both turbulence models applied.

Jovanovic, Z.; Masonicic, Z.

2012-11-01

18

Radiation Effects on Flow Characteristics in Combustion Chambers  

NASA Technical Reports Server (NTRS)

A JANNAF sponsored workshop was held to discuss the importance and role of radiative heat transfer in rocket combustion chambers. The potential impact of radiative transfer on hardware design, reliability, and performance was discussed. The current state of radiative transfer prediction capability in CFD modeling was reviewed and concluded to be substantially lacking in both the physical models used and the radiative property data available. There is a clear need to begin to establish a data base for making radiation calculations in rocket combustion chambers. A natural starting point for this effort would be the NASA thermochemical equilibrium code (CEC).

Brewster, M. Q.; Gross, Klaus W.

1989-01-01

19

30 CFR 57.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2013 CFR

...AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Rotary Jet Piercing-Surface Only § 57.7807 Flushing the combustion chamber. The combustion chamber of a jet drill...

2013-07-01

20

30 CFR 57.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2014 CFR

...AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Rotary Jet Piercing-Surface Only § 57.7807 Flushing the combustion chamber. The combustion chamber of a jet drill...

2014-07-01

21

30 CFR 56.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2011 CFR

...SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Rotary Jet Piercing § 56.7807 Flushing the combustion chamber. The combustion chamber of a jet drill stem which has...

2011-07-01

22

30 CFR 56.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2014 CFR

...SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Rotary Jet Piercing § 56.7807 Flushing the combustion chamber. The combustion chamber of a jet drill stem which has...

2014-07-01

23

30 CFR 56.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2012 CFR

...SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Rotary Jet Piercing § 56.7807 Flushing the combustion chamber. The combustion chamber of a jet drill stem which has...

2012-07-01

24

30 CFR 57.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2012 CFR

...AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Rotary Jet Piercing-Surface Only § 57.7807 Flushing the combustion chamber. The combustion chamber of a jet drill...

2012-07-01

25

30 CFR 57.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2011 CFR

...AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Rotary Jet Piercing-Surface Only § 57.7807 Flushing the combustion chamber. The combustion chamber of a jet drill...

2011-07-01

26

30 CFR 56.7807 - Flushing the combustion chamber.  

Code of Federal Regulations, 2013 CFR

...SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Drilling and Rotary Jet Piercing Rotary Jet Piercing § 56.7807 Flushing the combustion chamber. The combustion chamber of a jet drill stem which has...

2013-07-01

27

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

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

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.

2014-12-01

30

3-D flow field in combustion chamber under moving boundaries  

NASA Astrophysics Data System (ADS)

3D flow calculations for the combustion chamber of a solid propellant rocket motor are carried out using the SIMPLE method. The moving boundaries of the burning surface are treated by using a tracking technique with a marked grid. The analysis uses 3D continuity equations, momentum and energy equations, k-epsilon model equations, and 3D flux equations of heat radiation. The principal physical factors considered and the results obtained are discussed.

He, Hongqing; Liu, Yu; Wu, Xinping; Cai, Timin

1993-06-01

31

3-D flow field in combustion chamber under moving boundaries  

Microsoft Academic Search

3D flow calculations for the combustion chamber of a solid propellant rocket motor are carried out using the SIMPLE method. The moving boundaries of the burning surface are treated by using a tracking technique with a marked grid. The analysis uses 3D continuity equations, momentum and energy equations, k-epsilon model equations, and 3D flux equations of heat radiation. The principal

Hongqing He; Yu Liu; Xinping Wu; Timin Cai

1993-01-01

32

3D calculations of reacting flows within aircraft engine combustion chambers  

Microsoft Academic Search

Some three-dimensional calculations have been worked out in the case of an aircraft engine combustion chamber containing one swirling fuel-air injector and four primary holes. The influence of the grid size and of some parameters of the combustion and turbulence models has been investigated. The combustion efficiency is relatively unsensitive to the grid size unlike the maximum wall temperature and

F. Pit; H. Tichtinsky; F. Dupoirieux

1989-01-01

33

A novel approach to predict the stability limits of combustion chambers with large eddy simulation  

Microsoft Academic Search

Lean premixed combustion, which allows for reducing the production of thermal NOx, is prone to combustion instabilities. There\\u000a is an extensive research to develop a reduced physical model, which allows — without time-consuming measurements — to calculate\\u000a the resonance characteristics of a combustion system consisting of Helmholtz resonator type components (burner plenum, combustion\\u000a chamber). For the formulation of this model

B. Pritz; F. Magagnato; M. Gabi

2010-01-01

34

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

35

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

36

Combustion chamber inlet manifold separates vapor from liquid  

NASA Technical Reports Server (NTRS)

Circular manifold with tangential orifices at the inner circumference provides for the vapor constituent of a vaporized cryogenic propellant to enter a rocket combustion chamber before the liquid constituent. The vapor is separated from the liquid by centrifugal action and precedes it into the chamber through carefully positioned orifices.

Baker, D. I.

1966-01-01

37

Liquid rocket engine fluid-cooled combustion chambers  

NASA Technical Reports Server (NTRS)

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

1972-01-01

38

Structurally compliant rocket engine combustion chamber: Experimental and analytical validation  

NASA Technical Reports Server (NTRS)

A new, structurally compliant rocket engine combustion chamber design has been validated through analysis and experiment. Subscale, tubular channel chambers have been cyclically tested and analytically evaluated. Cyclic lives were determined to have a potential for 1000 percent increase over those of rectangular channel designs, the current state of the art. Greater structural compliance in the circumferential direction gave rise to lower thermal strains during hot firing, resulting in lower thermal strain ratcheting and longer predicted fatigue lives. Thermal, structural, and durability analyses of the combustion chamber design, involving cyclic temperatures, strains, and low-cycle fatigue lives, have corroborated the experimental observations.

Jankovsky, Robert S.; Arya, Vinod K.; Kazaroff, John M.; Halford, Gary R.

1994-01-01

39

Oxide Protective Coats for Ir/Re Rocket Combustion Chambers  

NASA Technical Reports Server (NTRS)

An improved material system has been developed for rocket engine combustion chambers for burning oxygen/ hydrogen mixtures or novel monopropellants, which are highly oxidizing at operating temperatures. The baseline for developing the improved material system is a prior iridium/rhenium system for chambers burning nitrogen tetroxide/monomethyl hydrazine mixtures, which are less oxidizing. The baseline combustion chamber comprises an outer layer of rhenium that provides structural support, plus an inner layer of iridium that acts as a barrier to oxidation of the rhenium. In the improved material system, the layer of iridium is thin and is coated with a thermal fatigue-resistant refractory oxide (specifically, hafnium oxide) that serves partly as a thermal barrier to decrease the temperature and thus the rate of oxidation of the rhenium. The oxide layer also acts as a barrier against the transport of oxidizing species to the surface of the iridium. Tests in which various oxygen/hydrogen mixtures were burned in iridium/rhenium combustion chambers lined with hafnium oxide showed that the operational lifetimes of combustion chambers of the improved material system are an order of magnitude greater than those of the baseline combustion chambers.

Fortini, Arthur; Tuffias, Robert H.

2003-01-01

40

Rocket combustion chamber life-enhancing design concepts  

NASA Technical Reports Server (NTRS)

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

Quentmeyer, Richard J.

1990-01-01

41

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

42

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

43

Rocket combustion chamber life-enhancing design concepts  

SciTech Connect

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

Quentmeyer, R.J.

1990-07-01

44

3D calculations of reacting flows within aircraft engine combustion chambers  

NASA Astrophysics Data System (ADS)

Some three-dimensional calculations have been worked out in the case of an aircraft engine combustion chamber containing one swirling fuel-air injector and four primary holes. The influence of the grid size and of some parameters of the combustion and turbulence models has been investigated. The combustion efficiency is relatively unsensitive to the grid size unlike the maximum wall temperature and depends slightly on the treatment of the k-epsilon equations near the wall.

Pit, F.; Tichtinsky, H.; Dupoirieux, F.

45

Mathematical modeling of heat transfer processes of coal waste combustion in a chamber of automated energy generating complex  

NASA Astrophysics Data System (ADS)

The automated energy generating complex allows obtaining heat energy from waste coal-water slurry fuel (WCF) that is a mixture of fine coal particles from coal enrichment wastes with water. The mixture is blown into the swirl chamber under the pressure through the special sprayers. The received heat energy is used in different ways. One of the important issues is to estimate the heat losses through the walls of this chamber. In this paper we solved the boundary problem of mathematical physics to estimate the temperature fields in the walls of the swirl chamber. The obtained solution allows us to estimate the heat losses through the walls of the swirl chamber. The task of the mathematical physics has been solved by a numerical finite-difference method. The method for solving this problem can be used in the calculation of temperature fields and evaluation of heat losses in other thermal power units.

Mochalov, Sergey P.; Kalashnikov, Sergey N.; Mochalov, Pavel S.; Song, Guolin; Tang, Guoyi

2013-04-01

46

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

47

Physical mechanism for deposit formation in a combustion chamber  

Microsoft Academic Search

Combustion chamber deposits in an internal combustion engine are known to impair engine performance. Using a variable temperature probe and retrievable sampling coupons, this study shows that the deposit-forming rate is inversely related to surface temperature, and directly related to the stabilized deposit weight. Together with the well-recognized fact that deposits are good thermal insulators, a deposit-forming mechanism is proposed.

S. W. S

1994-01-01

48

Orifices For Fuel-Film Cooling Of Combustion Chamber  

NASA Technical Reports Server (NTRS)

Boundary-layer film of fuel flows along wall of combustion chamber mentioned in article, "Rhenium-Foil Witness Cylinders" (NPO-18224), cooling wall and neutralizing excess of oxidizer in vicinity of wall. Enters chamber through 16 small, replaceable nozzles placed around periphery of fuel-and-oxidizer injector. Adjusted, independently of main injected flow of fuel and oxidizer, by selection of nozzle passing larger or smaller flow.

Knight, B. L.

1992-01-01

49

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...

50

Promoted-Combustion Chamber with Induction Heating Coil  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

51

Effect of mirror-finished combustion chamber on heat loss  

SciTech Connect

The use of ceramic insulation to reduce engine heat loss and thus improve fuel economy was examined but found to be detrimental rather than advantageous. This paper analyzes the reasons and presents an alternative approach, namely minimizing the heat transfer area. This paper reports on experiments conducted to determine the effects of surface smoothness on BSFC, output torque, heat release rate and piston temperature. It was found that with a mirror-finished combustion chamber, heat loss is decreased and consequently engine output is raised, while fuel consumption is lowered. The percentage reduction in heat loss was ascertained by numerically simulating combustion and was confirmed by FEM analysis of piston thermal distribution.

Tsutsumi, Y.; Nomura, K.; Nakamura, N.

1990-01-01

52

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

53

Optical Pressure-Temperature Sensor for a Combustion Chamber  

NASA Technical Reports Server (NTRS)

A compact sensor for measuring temperature and pressure in a combusti on chamber has been proposed. The proposed sensor would include two optically birefringent, transmissive crystalline wedges: one of sapph ire (Al2O3) and one of magnesium oxide (MgO), the optical properties of both of which vary with temperature and pressure. The wedges wou ld be separated by a vapor-deposited thin-film transducer, which wou ld be primarily temperaturesensitive (in contradistinction to pressur e- sensitive) when attached to a crystalline substrate. The sensor w ould be housed in a rugged probe to survive the extreme temperatures and pressures in a combustion chamber.

Wiley, John; Korman, Valentin; Gregory, Don

2008-01-01

54

Hydrocarbon-fuel/combustion-chamber-liner materials compatibility  

NASA Technical Reports Server (NTRS)

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

Gage, Mark L.

1990-01-01

55

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

NASA Technical Reports Server (NTRS)

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

Mcdonald, G. H.

1978-01-01

56

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

57

Self-oscillations of an unstable fuel combustion in the combustion chamber of a liquid-propellant rocket engine  

NASA Astrophysics Data System (ADS)

The form of the self-oscillations of a vibrating combustion of a fuel in the combustion chamber of a liquidpropellant rocket engine, caused by the fuel-combustion lag and the heat release, was determined. The character of change in these self-oscillations with increase in the time of the fuel-combustion lag was investigated.

Gotsulenko, V. V.; Gotsulenko, V. N.

2013-01-01

58

Toward the Impact of Fuel Evaporation-Combustion Interaction on Spray Combustion in Gas Turbine Combustion Chambers. Part I: Effect of Partial Fuel Vaporization on Spray Combustion  

Microsoft Academic Search

\\u000a This work aims at investigating the impact of the interaction between evaporation process and combustion on spray combustion\\u000a characteristics in gas turbine combustion chambers. It is subdivided into two parts. The first part studies how the evaporation\\u000a process affects the behavior of partially pre-vaporized spray combustion. The second part attempts to answer the question\\u000a how the fuel evaporation process behaves

Amsini Sadiki; W. Ahmadi; Mouldi Chrigui; J. Janicka

59

Liquid fuel vaporizer and combustion chamber having an adjustable thermal conductor  

DOEpatents

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

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

2014-03-04

60

Effect of Chamber Pressurization Rate on Combustion and Propagation of Solid Propellant Cracks  

NASA Astrophysics Data System (ADS)

area of the propellant grain satisfies the designed value. But cracks in propellant grain can be generated during manufacture, storage, handing and so on. The cracks can provide additional surface area for combustion. The additional combustion may significantly deviate the performance of the rocket motor from the designed conditions, even lead to explosive catastrophe. Therefore a thorough study on the combustion, propagation and fracture of solid propellant cracks must be conducted. This paper takes an isolated propellant crack as the object and studies the effect of chamber pressurization rate on the combustion, propagation and fracture of the crack by experiment and theoretical calculation. deformable, the burning inside a solid propellant crack is a coupling of solid mechanics and combustion dynamics. In this paper, a theoretical model describing the combustion, propagation and fracture of the crack was formulated and solved numerically. The interaction of structural deformation and combustion process was included in the theoretical model. The conservation equations for compressible fluid flow, the equation of state for perfect gas, the heat conducting equation for the solid-phase, constitutive equation for propellant, J-integral fracture criterion and so on are used in the model. The convective burning inside the crack and the propagation and fracture of the crack were numerically studied by solving the set of nonlinear, inhomogeneous gas-phase governing equations and solid-phase equations. On the other hand, the combustion experiments for propellant specimens with a precut crack were conducted by RTR system. Predicted results are in good agreement with experimental data, which validates the reasonableness of the theoretical model. Both theoretical and experimental results indicate that the chamber pressurization rate has strong effects on the convective burning in the crack, crack fracture initiation and fracture pattern.

Yuan, Wei-Lan; Wei, Shen; Yuan, Shu-Shen

2002-01-01

61

Combustion Modeling in Internal Combustion Engines  

Microsoft Academic Search

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

FRANK J. ZELEZNIK

1976-01-01

62

Effects of fuel and additives on combustion chamber deposits  

SciTech Connect

The effects of gasoline composition, as represented in typical regular and premium unleaded gasolines and fuel additives, on Combustion Chamber Deposits (CCD) were investigated in BMW and Ford tests. In addition, the influences of engine lubricant oil and ethanol oxygenate on CCD were examined in Ford 2.3L engine dynamometer tests. Also, additive effects of packages based on mineral oil fluidizers versus synthetic fluidizers were studied in several different engines for CCD. Finally, a new method for evaluating the effect of fluidizers on valve sticking is introduced. 6 refs., 16 figs., 14 tabs.

Jackson, M.M.; Pocinki, S.B.

1994-10-01

63

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

64

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

65

Elimination of High-Frequency Combustion Instability in the Fastrac Engine Thrust Chamber  

NASA Technical Reports Server (NTRS)

A series of tests were conducted to stabilize the combustion of the Fastrac engine thrust chamber. The first few stability tests resulted in unstable combustion due ineffective acoustic cavity designs. The thrust chamber exhibited unstable combustion in the first-tangential mode and its harmonics. Combustion was stabilized by increasing the volume of the acoustic cavities and by plugging the dump-cooling orifices so that the cavities were uncooled. Although the first few stability tests resulted in unstable combustion, prior and subsequent long-duration performance tests of the Fastrac thrust chamber were spontaneously stable. Stability considerations during the injector faceplate design were based on the Hewitt correlation.

Rocker, Marvin; Nesman, Tomas E.

1999-01-01

66

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

67

Internal combustion engine in which compressed fuel mixture is combusted externally of the cylinders of the engine in a rotating combustion chamber  

SciTech Connect

An internal combustion engine is described comprising a cylinder body having a pair of adjoining first and second cylinders, a reciprocable piston in each cylinder, first valve means for introducing a fuel mixture in the first cylinder, second valve means for discharge of exhaust gases from the second cylinder, a combustion chamber mounted adjacent the cylinder body for movement between the cylinders and communicating in one position with the first cylinder and in a second position with the second cylinder, the combustion chamber receiving compressed fuel mixture from the first cylinder in the one position, and means for igniting the compressed fuel mixture in the combustion chamber as the chamber moves from the first to the second position, the combustion chamber delivering combusted fuel mixture to the second cylinder in the second position.

Staheli, A.A.

1988-04-26

68

Combustion modeling in internal combustion engines  

NASA Technical Reports Server (NTRS)

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

Zeleznik, F. J.

1976-01-01

69

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

70

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

71

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

NASA Astrophysics Data System (ADS)

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.

1993-11-01

72

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

73

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

74

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

75

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

76

Evaluation of the Migrating Combustion Chamber (MCC) engine  

NASA Astrophysics Data System (ADS)

The Belvoir Research, Development and Engineering Center (BRDEC) tested three Migrating Combustion Chamber (MCC) engines built by Engine Research Associates (ERA) for Natick RD and E Center. The MCC concept attempts to provide a lightweight, quiet engine having a cool exhaust gas stream. The cool exhaust is attained by capturing additional energy from expansion beyond that achievable in conventional engines by the use of gas porting to multiple expansion chambers; this provides a more efficient engine operation than is otherwise attainable for the configuration. The testing included determining the engine torque-speed-power characteristics and the Brake Specific Fuel Consumption (BSFC) under a variety of load conditions. Startability and operability were concerns; starting under normal ambient conditions was difficult. All testing was performed using a 10:1 fuel/oil mixture of low lead gasoline with AMZOIL synthetic lubricating oil for two-stroke engines. The maximum power achieved was 0.25 horsepower at 4,400 rpm. The peak torque observed was 69 oz.-in. at 3,200 rpm. It was not possible to make noise and vibration measurements during the testing cycle, but they appeared to be low. The MCC engines tested had relatively short lives, operating for less than 25 hours. Performance and durability improvements are necessary before this MCC design can be considered as a viable alternative to commercially available two-cycle engines.

Miller, K. M.; Morar, Dorin

1993-01-01

77

Prevention of Over-Pressurization During Combustion in a Sealed Chamber  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

78

CFD Analysis of Spray Combustion and Radiation in OMV Thrust Chamber  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

79

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

80

Development of ceramic pre-combustion chamber for the automotive diesel engine  

Microsoft Academic Search

A precombustion chamber (hot plug) made of the silicon nitride ceramics has been developed. The hot plug constitutes a component of the combustion chamber of swirl chamber diesel engines. It is subjected to the severest thermal load of all the diesel engine operating components. Unlike metal hot plugs, the ceramic hot plug application requires a unique design approach to meet

H. Matsuoka; H. Kawamura; S. Toeda

1984-01-01

81

THERMAL LOADING AND TEMPEARTURE DISTRIBUTION OF A PRE COMBUSTION CHAMBER DIESEL ENGINE RUNNING ON GASOIL \\/ NATURAL GAS  

Microsoft Academic Search

Heat flux and temperature distribution were carried out in the combustion chamber of a pre-combustion chamber diesel engine running on dual fuel of diesel and natural gas. The test rig consists of a pre- combustion chamber single cylinder diesel engine fully equipped for temperature measurements across different points in the cylinder head, cylinder liner and other critical areas of the

Mohamed Y. E. Selim

82

Transpiring Cooling of a Scram-Jet Engine Combustion Chamber  

NASA Technical Reports Server (NTRS)

The peak cold-wall heating rate generated in a combustion chamber of a scram-jet engine can exceed 2000 Btu/sq ft sec (approx. 2344 W/sq cm). Therefore, a very effective heat dissipation mechanism is required to sustain such a high heating load. This research focused on the transpiration cooling mechanism that appears to be a promising approach to remove a large amount of heat from the engine wall. The transpiration cooling mechanism has two aspects. First, initial computations suggest that there is a reduction, as much as 75%, in the heat flux incident on the combustion chamber wall due to the transpirant modifying the combustor boundary layer. Secondly, the heat reaching the combustor wall is removed from the structure in a very effective manner by the transpirant. It is the second of these two mechanisms that is investigated experimentally in the subject paper. A transpiration cooling experiment using a radiant heating method, that provided a heat flux as high as 200 Btu/sq ft sec ( approx. 234 W/sq cm) on the surface of a specimen, was performed. The experiment utilized an arc-lamp facility (60-kW radiant power output) to provide a uniform heat flux to a test specimen. For safety reasons, helium gas was used as the transpirant in the experiments. The specimens were 1.9-cm diameter sintered, powdered-stainless-steel tubes of various porosities and a 2.54cm square tube with perforated multi-layered walls. A 15-cm portion of each specimen was heated. The cooling effectivenes and efficiencies by transpiration for each specimen were obtained using the experimental results. During the testing, various test specimens displayed a choking phenomenon in which the transpirant flow was limited as the heat flux was increased. The paper includes a preliminary analysis of the transpiration cooling mechanism and a scaling conversion study that translates the results from helium tests into the case when a hydrogen medium is used.

Choi, Sang H.; Scotti, Stephen J.; Song, Kyo D.; Ries,Heidi

1997-01-01

83

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

84

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

85

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

86

Internal combustion engine in which compressed fuel mixture is combusted externally of the cylinders of the engine in a rotating combustion chamber  

Microsoft Academic Search

An internal combustion engine is described comprising a cylinder body having a pair of adjoining first and second cylinders, a reciprocable piston in each cylinder, first valve means for introducing a fuel mixture in the first cylinder, second valve means for discharge of exhaust gases from the second cylinder, a combustion chamber mounted adjacent the cylinder body for movement between

Staheli

1988-01-01

87

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

88

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

NASA Technical Reports Server (NTRS)

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

Schock, H. J.

1984-01-01

89

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

90

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

91

Liquid oxygen/hydrogen testing of a single swirl coaxial injector element in a windowed combustion chamber  

NASA Astrophysics Data System (ADS)

A modular, high pressure, liquid rocket single element combustion chamber was developed at Aerojet for use with nonintrusive combustion diagnostics. The hardware is able to accommodate full-size injection elements and includes a recessed annular injector around the single element to provide a source for hot gas background flow, which reduces recirculation in the chamber and provides additional injection mass to elevate chamber pressure. Experiments are being conducted to develop the diagnostics required to characterize a single-element combustion spray field for combustion modeling, benchmark data for CFD model validation, and development of the transfer functions between single element cold flow and multielement hot fire. The latter task is being pursued using an injector element identical to elements that had been previously cold-flow tested in single element tests to ambient backpressure and hot fire tested in a multielement injector. Preliminary tests conducted to date without hydrogen flowing through the annular coaxial orifice of the single element show the general flow characteristics of a reacting, unconfined, liquid oxygen hollow cone swirl spray.

Hulka, J.; Makel, D.

1993-06-01

92

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

NASA Technical Reports Server (NTRS)

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

Schock, H. J.

1984-01-01

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

Composite propellant combustion modeling studies  

NASA Technical Reports Server (NTRS)

A review is presented of theoretical and experimental studies of composite propellant combustion. The theoretical investigations include a model of the combustion of a nonmetallized ammonium perchlorate (AP) propellant (noting time scales for vapor-phase combustion and the condensed phase) and response functions in pressure-coupled oscillations. The experimental studies are discussed with reference to scale-modeling apparatus, flame standoff distance versus velocity as a function of pressure, and results from T-burner firings of a nonmetallized AP/polysulfide propellant. Research applications including problems with nitramine propellants, the feasibility of stop-restart rockets with salt quench, and combustion problems in large boosters are outlined.

Ramohalli, K.

1977-01-01

95

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

96

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

97

Linear and non-linear pressure oscillations in baffled combustion chambers  

Microsoft Academic Search

Linear and non-linear analyses of acoustic waves in baffled combustion chambers have been developed by means of perturbation-expansion techniques. The formulation is based on a generalized wave equation derived from the conservation equations for a two-phase mixture, and accommodates all influences of non-linear gas dynamics and combustion responses. Several specific effects of baffles are presented as mechanisms by which baffles

J. M. Wicker; M. W. Yoon; V. Yang

1995-01-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

99

Numerical investigation of the flow inside the combustion chamber of a plant oil stove  

NASA Astrophysics Data System (ADS)

Recently a low cost cooking device for developing and emerging countries was developed at KIT in cooperation with the company Bosch und Siemens Hausgeräte GmbH. After constructing an innovative basic design further development was required. Numerical investigations were conducted in order to investigate the flow inside the combustion chamber of the stove under variation of different geometrical parameters. Beyond the performance improvement a further reason of the investigations was to rate the effects of manufacturing tolerance problems. In this paper the numerical investigation of a plant oil stove by means of RANS simulation will be presented. In order to reduce the computational costs different model reduction steps were necessary. The simulation results of the basic configuration compare very well with experimental measurements and problematic behaviors of the actual stove design could be explained by the investigation.

Pritz, B.; Werler, M.; Wirbser, H.; Gabi, M.

2013-10-01

100

Numerical analysis of bipropellant combustion in orbit maneuvering vehicle thrust chamber  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

101

Liquid oxygen\\/hydrogen testing of a single swirl coaxial injector element in a windowed combustion chamber  

Microsoft Academic Search

A modular, high pressure, liquid rocket single element combustion chamber was developed at Aerojet for use with nonintrusive combustion diagnostics. The hardware is able to accommodate full-size injection elements and includes a recessed annular injector around the single element to provide a source for hot gas background flow, which reduces recirculation in the chamber and provides additional injection mass to

J. Hulka; D. Makel

1993-01-01

102

Modelling paradigms for MILD combustion  

E-print Network

, CB2 1PZ, UK. E-mail: ns341@cam.ac.uk. Phone: +44(0)1223 332586. Fax: +44(0)1223 339906. Running Title: Modelling of MILD combustion Submitted to International Journal of Advances in Engineering Sciences and Applied Mathematics (Special Issue... Modelling paradigms for MILD combustion Y. Minamoto and N. Swaminathan? Department of Engineering, Cambridge University, Cambridge, CB2 1PZ, UK. ?Corresponding author: Department of Engineering, Cambridge University, Trumpington Street, Cambridge...

Minamoto, Y.; Swaminathan, N.

2014-04-26

103

Hierarchical Modeling of Combustion Processes  

Microsoft Academic Search

\\u000a Combustion processes are governed by a strong coupling of chemical kinetics, molecular transport processes and flow. Mathematical\\u000a modeling is complicated by the existence of scaling problems (time-, velocity- and length scales). In order to allow a reliable\\u000a numerical simulation of practical combustion systems, models have to be devised which do not neglect or over-simplify the\\u000a underlying physical and chemical processes.

Ulrich Maas; Viatcheslav Bykov; Andriy Rybakov; Rainer Stauch

104

Hypergolic bipropellant spray combustion and flow modelling in rocket engines  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

105

Three-dimensional computer modeling of hydrogen injection and combustion  

SciTech Connect

The hydrodynamics of hydrogen gas injection into a fixed-volume combustion chamber is analyzed and simulated using KIVA-3, a three-dimensional, reactive flow computer code. Comparisons of the simulation results are made to data obtained at the Combustion Research Facility at Sandia National Laboratory-California (SNL-CA). Simulation of the gas injection problem is found to be of comparable difficulty as the liquid fuel injection in diesel engines. The primary challenge is the large change of length scale from the flow of gas in the orifice to the penetration in the combustion chamber. In the current experiments, the change of length scale is about 4,000. A reduction of the full problem is developed that reduces the change in length scale in the simulation to about 400, with a comparable improvement in computational times. Comparisons of the simulation to the experimental data shows good agreement in the penetration history and pressure rise in the combustion chamber. At late times the comparison is sensitive to the method of determination of the penetration in the simulations. In a comparison of the combustion modeling of methane and hydrogen, hydrogen combustion is more difficult to model, and currently available kinetic models fail to predict the observed autoignition delay at these conditions.

Johnson, N.L.; Amsden, A.A. [Los Alamos National Lab., NM (United States). Theoretical Division; Naber, J.D.; Siebers, D.L. [Sandia National Lab., Livermore, CA (United States)

1995-02-01

106

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

107

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

108

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

109

Combustion modeling in waste tanks  

SciTech Connect

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

Mueller, C.; Unal, C. [Los Alamos National Lab., NM (United States); Travis, J.R. [Los Alamos National Lab., NM (United States)]|[Forschungszentrum Karlsruhe (Germany). Inst. fuer Reaktorsicherheit

1997-08-01

110

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

111

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

112

Large Eddy Simulation of the Fuel Injection in Scramjet Combustion Chambers  

NASA Astrophysics Data System (ADS)

Fuel injection in a typical scramjet combustion chamber is a very challenging flow to characterise either in ex- perimental or computational studies. It involves multi- species compressible turbulent features with complex coherent flow structures arising as a result of sonic fuel injection transverse or inclined to the free-stream supersonic flow. In this paper the fuel injection in the HyShot- II combustion chamber is studied using an Implicit LES method employing a modified very high order accurate numerical method. To gain accurate mean inflow boundary conditions, a thermally perfect gas formulation has been employed in preliminary simulations of the inlet ramp and cowl configuration. The results of these simulations are presented and validated against wind tunnel data.

Rana, Z. A.; Thornber, B. J. R.; Drikakis, D.

2011-08-01

113

Full-Scale GRCop-84 Combustion Chamber Liner Preform Fabricated Successfully  

NASA Technical Reports Server (NTRS)

GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) has been under development at the NASA Glenn Research Center for several years. The alloy possesses a unique combination of good thermal conductivity, high elevated temperature strength, long creep life, and long low-cycle- fatigue. The alloy is also more oxidation resistant than pure copper and most competitive alloys. The combination of properties has attracted attention from major rocket engine manufacturers who are interested in the alloy for the combustion chamber liner in their next generation of regeneratively cooled engines. Before GRCop-84 can be used in a main combustion chamber application, it must be demonstrated that the alloy can be made successfully to the large sizes and proper shape needed and that it retain useful properties. Recent efforts have successfully demonstrated the ability to fabricate a liner preform via metal spinning that retains the alloy s strength even in the welded sections.

Ellis, David L.; Russell, Carolyn K.; Goudy, Rick

2005-01-01

114

Spray combustion modeling  

NASA Technical Reports Server (NTRS)

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.

1997-01-01

115

On the method for hot-fire modeling of high-frequency combustion instability in liquid rocket engines  

Microsoft Academic Search

This study presents the methodological aspects of combustion instability modeling and pro-vides the numerical results of the\\u000a model (sub-scale) combustion chamber, regarding geometrical dimensions and operating conditions, which are for determining\\u000a the combustion stability boundaries using the model chamber. An approach to determine the stability limits and acoustic characteristics\\u000a of injectors is described intensively. Procedures for extrapolation of the model

Chae Hoon Sohn; Woo-Seok Seol; Alexander A. Shibanov; Valery P. Pikalov

2004-01-01

116

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

117

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

118

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

119

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

120

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

121

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

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

Steady state HNG combustion modeling  

SciTech Connect

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

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); Parr, T.; Hanson-Parr, D. [Naval Air Warfare Center, China Lake, CA (United States)

1998-04-01

124

In-situ vibrational spectroscopy of real-time combustion chamber deposit formation  

SciTech Connect

This paper describes the development of two novel experimental approaches for characterizing combustion chamber deposit formation and discusses the associated results. The first approach is a custom designed sampling technique for the mid-infrared spectroscopy of deposit formation; and the second, is real-time infrared emission spectroscopy of deposit formation in an optically accessible engine. The data shows that the characterization can follow changes in fuel consumption from evaporation, gum and varnish formation, to the solid deposit formation and aging at elevated temperature. In addition, it will show the design was chosen to preserve the sample geometry and environmental conditions as much as possible.

DeBlase, F.J.; Swindal, C.; Acker, W.P. [Texaco Research Center, Beacon, NY (United States)

1996-10-01

125

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

126

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

127

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

SciTech Connect

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

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

1995-12-31

128

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

NASA Technical Reports Server (NTRS)

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

Rothrock, A M; Biermann, Arnold E

1940-01-01

129

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

130

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

131

The FLAME Deluge: organic aerosol emission ratios from combustion chamber experiments  

NASA Astrophysics Data System (ADS)

A high level of variability has been identified amongst organic aerosol (OA) emission ratios (ER) from biomass burning (BB) under ambient conditions. However, it is difficult to assess the influences of potential drivers for this variability, given the wide range of conditions associated with wildfire measurements. Chamber experiments performed under controlled conditions provide a means of examining the effects of different fuel types and combustion conditions on OA emissions from biomass fuels. ERs have been characterised for 67 burns during the second Fire Laboratory at Missoula Experiment (FLAME II), involving 19 different species from 6 fuel types widely consumed in BB events in the US each year. Average normalised dOA/dCO ratios show a high degree of variability, both between and within different fuel types and species, typically exceeding variability between separate plumes in ambient measurements. Relationships with source conditions were found to be complex, with little consistent influence from fuel properties and combustion conditions for the entire range of experiments. No strong correlation across all fires was observed between dOA/dCO and modified combustion efficiency (MCE), which is used as an indicator of the proportional contributions of flaming and smouldering combustion phases throughout each burn. However, a negative correlation exists between dOA/dCO and MCE for some coniferous species, most notably Douglas fir, for which there is also an apparent influence from fuel moisture content. Significant contrasts were also identified between combustion emissions from different fuel components of additional coniferous species. Changes in fire efficiency were also shown to dramatically alter emissions for fires with very similar initial conditions. Although the relationship with MCE is variable between species, there is greater consistency with the level of oxygenation in OA. The ratio of the m/z 44 fragment to total OA mass concentration (f44) as measured by aerosol mass spectrometer (AMS) provides an indication of oxygenation as influenced by combustion processes at source, with dOA/dCO decreasing with increasing f44 for all fuel types. Inconsistencies in the magnitude of the effects associated with each potential influence on dOA/dCO emphasise the lack of a single dominant control on fire emissions, and a dependency on both fuel properties and combustion conditions.

Jolleys, Matthew; Coe, Hugh; McFiggans, Gordon; McMeeking, Gavin; Lee, Taehyoung; Sullivan, Amy; Kreidenweis, Sonia; Collett, Jeff

2014-05-01

132

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

133

Chemical kinetics and modeling of combustion processes  

Microsoft Academic Search

Chemical kinetic modeling is an important tool in the analysis of many combustion systems. The use of detailed kinetic models in the interpretation of fundamental kinetics experiments in shock tubes and plug flow reactors is widespread. Recently these models, coupled with fluid mechanical models, have become valuable in helping to understand complex phenomena in practical combustion devices. This study reviews

C. K. Westbrook; F. L. Dryer

1981-01-01

134

Radiative heat transfer, Favre-averaging and turbulence closure models for combustion applications  

NASA Astrophysics Data System (ADS)

Flow through a solid fuel combustion chamber (SFCC) was analyzed. Radiative heat transfer, Favre averaging of the conservation equations, and turbulence closure models for a computational model describing the flow through an SFCC were studied. A k-epsilon turbulence model is recommended.

Vos, J. B.

1983-05-01

135

Resistive Plate Chambers: electron transport and modeling  

NASA Astrophysics Data System (ADS)

We study the electron transport in gas mixtures used by Resistive Plate Chambers (RPCs) in high energy physics experiments at CERN. Calculations are performed using a multi term theory for solving the Boltzmann equation. We identify the effects induced by non-conservative nature of electron attachment, including attachment heating of electrons and negative differential conductivity (NDC). NDC was observed only in the bulk component of drift velocity. Using our Monte Carlo technique, we calculate the spatially resolved transport properties in order to investigate the origin of these effects. We also present our microscopic approach to modeling of RPCs which is based on Monte Carlo method. Calculated results for a timing RPC show good agreement with an analytical model and experimental data. Different cross section sets for electron scattering in C2H2F4 are used for comparison and analysis.

Bošnjakovi?, D.; Petrovi?, Z. Lj; Dujko, S.

2014-12-01

136

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

137

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

138

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

139

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

140

Gasdynamic Model of Turbulent Combustion in TNT Explosions  

SciTech Connect

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

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

2010-01-08

141

Hydrocarbon-fuel/combustion-chamber-liner materials compatibility. Interim final report, 7 November 1986-31 October 1989  

SciTech Connect

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

Gage, M.L.

1990-04-01

142

Large-eddy simulation of turbulent combustion using different combustion models  

Microsoft Academic Search

The second-order moment (SOM) combustion model proposed by the present authors is compared with eddy-break-up (EBU) and presumed probability density function (PDF) combustion models in large-eddy simulation of jet diffusion combustion, swirling diffusion combustion and premixed combustion behind a bluff body. The statistical results for time-averaged and RMS fluctuation temperatures are validated by experimental results. It is seen that the

L. X. Zhou; L. Y. Hu; F. Wang

2008-01-01

143

Control of heat release in engine combustion chamber by multiple flames (A research on the reduction of NOx by controlling the heat release process)  

SciTech Connect

Combustion in the cylinder of an internal combustion engine requires a short but finite time to occur. Since the combustion is usually controlled by a fuel mixture supply and an ignition timing depending on the required load, the combustion characteristics cannot actively be changed once ignited. However, if the combustion is achieved in several zones in the combustion chamber, and the ignition of each zone is independently controlled by either the multiple direct injections coupled with an individual ignition or the multiple ignitions in a premixed charge, the process may positively be changed during combustion period. The effect of ignition timing control by the multiple flames on the combustion process of the test engine is investigated in the present study. The multiple flames are initiated from two ignition sources located around the disk type combustion chamber or by the sequential ignition from one ignition source. Depending on the separately controlled ignition timing of each electrode and the swirling speed at the ignition point, a growth of flame area and a separation between flames can be controlled using the single combustion test engine fueled with methane. The ignition timing retard is effective for reducing NOx at the sacrifice of a fuel economy, when the combustion process after ignition is not properly adjusted. A qualitative evaluation of the cycle performance related to the combustion process, using the simulator reformed for the purpose of the present case, and an approximated Wiebe function for the experimental heat release rate, shows that the optimum processes under these combustion control may exist.

Ono, Shinsuke; Murase, Eiichi; Hirayama, Yoshinori; Xuan, Qiwu; Yoshizawa, Hisashi

1999-07-01

144

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

145

Modeling and identification of the combustion pressure process in internal combustion engines  

Microsoft Academic Search

We present new models relating combustion pressure to crankshaft velocity in an internal combustion engine. There are three aspects to this model. First, by changing the independent variable from time to crankshaft angle, a nonlinear differential equation model becomes a linear first-order differential equation. Second, a new stochastic signal model for combustion pressure uses the sum of a deterministic waveform

Francis T. Connolly; Andrew E. Yagle

1993-01-01

146

High-pressure calorimeter chamber tests for liquid oxygen/kerosene (LOX/RP-1) rocket combustion  

SciTech Connect

An experimental program was conducted to investigate the rocket combustion and heat transfer characteristics of liquid oxygen/kerosene (LOX/RP-1) mixtures at high chamber pressures. Two water-cooled calorimeter chambers of different combustion lengths were tested using 37- and 61-element oxidizer-fuel-oxidizer triplet injectors. The tests were conducted at nominal chamber pressures of 4.1, 8.3, and 13.8 MPa abs (600, 1200, and 2000 psia). Heat flux Q/A data were obtained for the entire calorimeter length for oxygen/fuel mixture ratios of 1.8 to 3.3. Test data at 4.1 MPa abs compared favorably with previous test data from another source. Using an injector with a fuel-rich outer zone reduced the throat heat flux by 47 percent with only a 4.5 percent reduction in the characteristic exhaust velocity efficiency C* sub eff. The throat heat transfer coefficient was reduced approximately 40 percent because of carbon deposits on the chamber wall.

Masters, P.A.; Armstrong, E.S.; Price, H.G.

1988-12-01

147

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

148

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

149

Combustion instability modeling and analysis  

Microsoft Academic Search

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 NOâ 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

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

1995-01-01

150

Modeling the unsteady combustion of solid propellants with detailed chemistry  

NASA Astrophysics Data System (ADS)

Unsteady combustion phenomena are of great interest to the solid propellant community and have been studied for many years. One area of particular interest is the relation between fluctuating pressure and propellant combustion. Pressure fluctuations, such as acoustics, naturally occur inside solid rocket combustion chambers during motor firing. Coupling between these pressure waves and the burning propellant can lead to changes in burning characteristics, a loss of performance, or even motor failure. During the past several years, various researchers have employed detailed chemical reaction mechanisms for modeling steady-state propellant combustion. The current work extends steady-state modeling into the unsteady domain and is particularly focused on the pressure-coupled phenomena. A numerical model was developed to calculate homogeneous propellant combustion under steady or unsteady conditions. The model was separated into two regions: the condensed and gas phases. Variable properties, distributed decomposition and evaporation were included in the condensed phase. The gas phase included detailed chemistry and the solution of the continuity, species, momentum and energy equations. Application was made to the cyclic nitramines, RDX and HMX. Modeling results were obtained for a wide variety of conditions including (1) steady-state; (2) quasi-steady gas phase, unsteady condensed phase; and (3) fully unsteady gas phase, unsteady condensed phase. The effects of pressure and radiant heat flux oscillations were examined through model simulations. It is believed that this work represents the first successful effort to implement both detailed kinetics and a fully unsteady gas phase for oscillatory propellant combustion. Reasonable agreement with steady-state experimental data was achieved for many combustion parameters including burning rate, surface temperature, melt layer thickness, and species concentration profiles. Pressure and heat flux responses (Rp and Rq) were obtained through numerical simulations. Reasonable agreement with experimental data was attained for many cases. In cases where the model failed to predict experimental results, explanations are given. The quasi-steady gas phase assumption was evaluated by comparing quasi-steady simulations with fully unsteady simulations at the same conditions. At low frequencies, the results coincide, but deviations begin to occur above about 100 Hz at atmospheric pressure and above about 1000 Hz for 1000 psi.

Erikson, William W.

151

A mathematical model for pressurized circulating fluidized bed combustion  

SciTech Connect

Pressurized fluidized bed combustion is one of the most promising techniques for high efficiency and low emission power generation from hard and brown coal. Mathematical modeling and simulations may facilitate understanding, development and operation of this new process. Since 1980 at the Institute of Energy Technology of the University of Siegen, work has been carried out upon mathematical models for the simulation of fluidized bed coal combustion. This work comprises the simulation of steady state and transient behavior of atmospheric bubbling and circulating fluidized bed combustors based on hard and brown coal as well as the steam generator and the control system. This work has been extended to combined cycle processes by modeling the steady state behavior of a pressurized circulating fluidized bed combustor (PCFBC) for hard coal. In continuation of the former work it is intended to construct a comprehensive model from submodels based on physical and chemical principles and to avoid correlations for a certain plant. Based on recent publications from utility companies concerning the design of a PCFBC, a comparison of the steady state behavior of an atmospheric circulating fluidized bed combustor and pressurized circulating fluidized bed combustors at pressures of 5, 10, 15 and 20 bar was carried out. The simulation elucidates the influence of pressure on the axial temperature profile and the solid distribution in the combustion chamber, on CO-, NO- and SO{sub 2}-emissions and on the energy balance for the whole plant.

Heinbockel, I.; Fett, F.N. [Univ. of Siegen (Germany). Inst. of Energy Technology

1995-12-31

152

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

153

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

154

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

155

Fluids & Combustion Seminar "Multiscale modeling of heterogeneous  

E-print Network

Fluids & Combustion Seminar "Multiscale modeling of heterogeneous materials in shocked flows of a material with internal structure (micro- or macro-) to loading delivered by shock waves is a challenging materials. Friday Feb 17, 2012 2:00 P.M. Engineering Bldg. Room 328 5500 Campanile Drive Mail Code 1308 San

Ponce, V. Miguel

156

Spectral modeling of radiation in combustion systems  

Microsoft Academic Search

Radiation calculations are important in combustion due to the high temperatures encountered but has not been studied in sufficient detail in the case of turbulent flames. Radiation calculations for such problems require accurate, robust, and computationally efficient models for the solution of radiative transfer equation (RTE), and spectral properties of radiation. One more layer of complexity is added in predicting

Gopalendu Pal

2010-01-01

157

Recent progress in modeling solid propellant combustion  

Microsoft Academic Search

Tremendous progress has been achieved in the last ten years with respect to modeling the combustion of solid propellants.\\u000a The vastly increased performance of computing capabilities has allowed utilization of calculation approaches that were previously\\u000a only conceptual. The paper will discuss three areas of emphasis: first, numerical modeling of premixed flames using detailed\\u000a kinetic mechanisms; second, development of packing models

M. W. Beckstead

2006-01-01

158

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

159

A hybrid 2-zone/WAVE engine combustion model for simulating combustion instabilities during dilute operation  

SciTech Connect

Internal combustion engines are operated under conditions of high exhaust gas recirculation (EGR) to reduce NO x emissions and promote enhanced combustion modes such as HCCI. However, high EGR under certain conditions also promotes nonlinear feedback between cycles, leading to the development of combustion instabilities and cyclic variability. We employ a two-zone phenomenological combustion model to simulate the onset of combustion instabilities under highly dilute conditions and to illustrate the impact of these instabilities on emissions and fuel efficiency. The two-zone in-cylinder combustion model is coupled to a WAVE engine-simulation code through a Simulink interface, allowing rapid simulation of several hundred successive engine cycles with many external engine parametric effects included. We demonstrate how this hybrid model can be used to study strategies for adaptive feedback control to reduce cyclic combustion instabilities and, thus, preserve fuel efficiency and reduce emissions.

Edwards, Kevin Dean [ORNL; Wagner, Robert M [ORNL; Chakravarthy, Veerathu K [ORNL; Daw, C Stuart [ORNL; Green Jr, Johney Boyd [ORNL

2006-01-01

160

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

161

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

162

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

163

Internal combustion engine with one or more compression caps between piston and cylinder head and deflection means in the combustion chamber through which rotary flow is induced in the charge  

Microsoft Academic Search

This patent describes an internal combustion engine cylinder construction for providing a vertically oriented rotational swirl of a gas fuel charge in a combustion chamber immediately before ignition. It consists of: (A) an engine cylinder having a repicrocable piston disposed and closed at its upper end by a cylinder head having side-by-side intake and exhaust valves; (B) a recessed, oval-shaped

1986-01-01

164

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

165

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

166

Modeling and identification of the combustion pressure process in internal combustion engines; 2: Experimental results  

Microsoft Academic Search

In Connolly and Yagle they presented a new model relating cylinder combustion pressure to crankshaft angular velocity in an internal combustion engine, primarily the fluctuations in velocity near the cylinder firing frequency. There are three aspects to this model. First, by changing the independent variable from time to crankshaft angle, a nonlinear differential equation becomes a linear first-order differential equation.

F. T. Connolly; A. E. Yagle

1993-01-01

167

Turbulence modeling in supersonic combusting flows  

NASA Technical Reports Server (NTRS)

To support the National Aerospace Plane project, the RPLUS3D CFD code has been developed at NASA Lewis. The code has the ability to solve three-dimensional flowfields with finite rate combustion of hydrogen and air. The combustion processes of the hydrogen-air system are simulated by an 18-reaction path, 8-species chemical kinetic mechanism. The code uses a Lower-Upper (LU) decomposition numerical algorithm as its basis, making it a very efficient and robust code. Except for the Jacobian matrix for the implicit chemistry source terms, there is no inversion of a matrix even though it uses a fully implicit numerical algorithm. A k-epsilon (two equation) turbulence model is incorporated into the RPLUS3D code.

Chitsomboon, Tawit

1991-01-01

168

Dynamic Modelling and Control Design of Pre-combustion Power  

E-print Network

and control design of two pre-combustion power cycles, i.e., a hydro- gen membrane reformer (HMR) based powerLei Zhao Dynamic Modelling and Control Design of Pre-combustion Power Cycles Thesis for the degree than current post combustion technologies. For this type of reforming to be competitive for power

Foss, Bjarne A.

169

Stove with multiple chambers  

SciTech Connect

A stove is described for burning a solid fuel such as wood. The wall means defines a main air inlet, a combustion gas outlet, and four chambers through which gas passes sequentially from the main air inlet to the combustion gas outlet. The chambers comprises a pre-heat plenum chamber into which the main air inlet opens. A main combustion chamber contains solid fuel to be burned into which gas passes from the pre-heat plenum chamber, a second combustion chamber which is downstream of the main combustion chamber with respect to the flow of gas from the main air inlet to the combustion gas outlet, and a third combustion chamber from which the combustion gas outlet opens. The stove also comprises a plate having a restricted opening for providing communication between the second and third combustion chambers. And a catalytic converter comprises a body of solid material formed with passageways, the body of solid material being fitted in the restricted opening so that gas passes from the second combustion chamber to the third combustion chamber by way of the passageways in the body.

Black, A.

1987-04-21

170

Modelling auto ignition of hydrogen in a jet ignition pre-chamber  

Microsoft Academic Search

Spark-less jet ignition pre-chambers are enablers of high efficiencies and load control by quantity of fuel injected when coupled with direct injection of main chamber fuel, thus permitting always lean burn bulk stratified combustion. Towards the end of the compression stroke, a small quantity of hydrogen is injected within the pre-chamber, where it mixes with the air entering from the

Alberto A. Boretti

2010-01-01

171

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

NASA Technical Reports Server (NTRS)

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

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

1950-01-01

172

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

173

Design and testing of a model CELSS chamber robot  

NASA Astrophysics Data System (ADS)

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

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

1994-08-01

174

Simplified combustion modeling of composite propellants  

NASA Astrophysics Data System (ADS)

A two-dimensional, steady state model of a burning composite propellant is developed to study the characteristics of the combustion process. The solid composite is a periodic sandwich unit comprised of two oxidizer laminates separated by a fuel binder layer. Included in the model are essential features for simulating composite propellant combustion: (1) a free surface boundary, (2) gas- and condensed-phase heat release distributions based on simplified chemical kinetics, and (3) an implicit surface regression rate (unique burning rate) determined by coupled gas-solid energy/species transport analysis. Comparisons of the model with experimental observations focus on surface geometry, flame structure and the burning rate for variations in pressure, particle size, binder width and propellant formulation. Experimentally observed trends for typical composite propellants are replicated. For example, the relative protrusion/recession of oxidizer and binder, recognized as an important feature of propellant surface topography, is correctly predicted. The simulation demonstrates the relation between gas-phase heat release and the heat-feedback driving the solid phase pyrolysis. This information is critical to predicting surface geometry and regression rate. Success was also achieved in predicting the experimental burning rate pressure sensitivity without the use of arbitrary non-integer reaction orders. The model provides a framework for future studies with more complex kinetic mechanisms, transient phenomena, and three-dimensional particulate propellants.

Knott, Gregory Matthew

2001-10-01

175

Multiphysics Thrust Chamber Modeling for Nuclear Thermal Propulsion  

NASA Technical Reports Server (NTRS)

The objective of this effort is to develop an efficient and accurate thermo-fluid computational methodology to predict environments for a solid-core, nuclear thermal engine thrust chamber. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation. A two-pronged approach is employed in this effort: A detailed thermo-fluid analysis on a multi-channel flow element for mid-section corrosion investigation; and a global modeling of the thrust chamber to understand the effect of heat transfer on thrust performance. Preliminary results on both aspects are presented.

Wang, Ten-See; Cheng, Gary; Chen, Yen-Sen

2006-01-01

176

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

177

Modeling Propellant Combustion Using Molecular Dynamics Simulations  

NASA Astrophysics Data System (ADS)

Currently, a first-principles theoretical model of self-sustained combustion of solid energetic materials does not exist and consequently the development of new propellants has to be approached from a strictly empirical viewpoint. Without a theoretical framework to guide it, this method remains expensive and time consuming and therefore inefficient. The benefits of a theoretical model are numerous. Primarily, it would offer a systematic way of understanding the seemingly unapproachable combination of physical and chemical reactions inherent in all combustion phenomena. The resulting predictive capabilities would serve as the underlying methods in the development of new propellants. Our model involves the three states of matter as frozen ozone(M.S. Miller, Materials Research Society, Fall meeting (1995).) melts and eventually vaporizes giving oxygen upon decomposition. However, much of the needed thermodynamic and transport properties are unavailable from experiments and therefore, we have appealed to molecular dynamics simulations. Using a Lennard-Jones potential we have been able to obtain thermodynamic and transport properties about the pure components and various mixtures of ozone and oxygen in each phase as well as at the interfaces.

Bembenek, Scott D.; Rice, Betsy M.; Miller, Martin S.

1998-03-01

178

ZMOTTO- MODELING THE INTERNAL COMBUSTION ENGINE  

NASA Technical Reports Server (NTRS)

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

Zeleznik, F. J.

1994-01-01

179

Finite difference seismic modeling of axial magma chambers  

SciTech Connect

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

Swift, S.A.; Dougherty, M.E.; Stephen, R.A. (Woods Hole Oceanographic Institution, MA (USA))

1990-11-01

180

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

181

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

182

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

183

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

E-print Network

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

Bittle, Joshua A

2014-04-18

184

Nonlinear structural analysis of cylindrical thrust chambers using viscoplastic models  

NASA Technical Reports Server (NTRS)

The results are presented of a viscoplastic stress-strain analysis of a cylindrical thrust chamber used in experiments that were designed to simulate the SSME operating conditions. The inelastic strain was calculated by using a viscoplastic model, and a quasi-three-dimensional structural analysis was performed by using a finite element program MARC. The temperatures and pressures were calculated by using the loading cycles of experiments, and these temperatures and pressures were used in the computations. The deformed shape of the component was predicted after the end of each loading cycle. The predicted shape qualitatively replicated the deformed shape of the component as observed in experiments. The results indicate that the use of viscoplastic models for structural analysis may lead to more realistic life assessments of experimental thrust chambers.

Arya, Vinod K.

1991-01-01

185

Modeling of RDX\\/GAP\\/BTTN pseudo-propellant combustion  

Microsoft Academic Search

A comprehensive numerical analysis has been developed to predict the burning characteristics and detailed combustion wave structure of RDX\\/GAP\\/BTTN pseudo-propellant over a broad range of pressures. The present work extends an existing model for the steady-state combustion of RDX\\/GAP pseudo-propellant to include the salient features of BTTN, a commonly used plasticizer for practical solid propellants. The entire combustion zone is

Jae-Kun Yoon; Piyush Thakre; Vigor Yang

2006-01-01

186

Observing and modeling nonlinear dynamics in an internal combustion engine  

Microsoft Academic Search

We propose a low-dimensional, physically motivated, nonlinear map as a model for cyclic combustion variation in spark-ignited internal combustion engines. A key feature is the interaction between stochastic, small-scale fluctuations in engine parameters and nonlinear deterministic coupling between successive engine cycles. Residual cylinder gas from each cycle alters the in-cylinder fuel-air ratio and thus the combustion efficiency in succeeding cycles.

C. S. Daw; M. B. Kennel; C. E. Finney; F. T. Connolly

1998-01-01

187

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

188

LDV measurements of the flow inside the combustion chamber of a 4-valve D.I. diesel engine with axisymmetric piston-bowls  

Microsoft Academic Search

LDV measurements of the tangential and radial velocity components have been performed to investigate the flow patterns inside\\u000a a 4-valve single cylinder diesel engine for various engine speeds, swirl numbers and piston-bowl geometries, under conditions\\u000a similar to those of a production engine. The work focused on the near-wall region of the axisymmetric combustion chambers\\u000a where the strong swirl-squish and spray-wall

F. Payri; J. M. Desantes; J. V. Pastor

1996-01-01

189

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

SciTech Connect

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

Ra, Youngchul; Reitz, Rolf D. [Engine Research Center, University of Wisconsin-Madison (United States)

2011-01-15

190

Scale-up and advanced performance analysis of boiler combustion chambers  

SciTech Connect

This paper discusses methods for evaluation of thermal performance of large boiler furnaces. Merits and limitations of pilot-scale testing and mathematical modeling are pointed out. Available computer models for furnace performance predictions are reviewed according to their classification into finite-difference methods and zone methods. Current state of the art models for industrial application are predominantly zone methods based on advanced Monte-Carlo type techniques for calculation of radiation heat transfer. A representation of this model type is described in more detail together with examples of its practical application. It is also shown, how pilot-scale results can be scaled-up with help of the model to predict full-scale performance of particular boiler furnaces.

Richter, W.

1985-12-31

191

Simulations of Turbulent Spray Combustion in a Constant-Volume Chamber for Diesel-Engine-Like Conditions  

NASA Astrophysics Data System (ADS)

In-cylinder aero-thermal-chemical processes in piston engines are rich and complex, and modern engines are already at a high level of refinement. Further increases in performance, reductions in fuel consumption and emissions, and accommodation of nontraditional fuels will require the effective use of high-spatial-and-temporal-resolution optical diagnostics and numerical simulations. In this research, computational fluid dynamics tools are being developed to explore the influences of fuel properties on autoignition, combustion, and pollutant emissions in compression-ignition engines. The modeling includes a transported probability density function method to account for turbulent fluctuations in composition and temperature, detailed soot models with a method of moments for soot aerosol dynamics, a stochastic photon Monte Carlo method for participating-medium radiation heat transfer, and line-by-line spectral properties for mixtures of molecular gases and soot. The models are applied to a constant-volume spray combustion bomb where measurements are available for a range of thermochemical conditions and for a variety of fuels. Parametric studies of the influences of key physical and numerical parameters are performed to determine sensitivities and to establish best practices to be carried forward into subsequent modeling studies of real engines.

Zhang, H.; Haworth, D. C.

2010-11-01

192

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

193

INDUSTRIAL COMBUSTION EMISSIONS (ICE) MODEL, VERSION 6.0  

EPA Science Inventory

The Industrial Combustion Emissions (ICE) Model was developed by the Environmental Protection Agency for use by the National Acid Precipitation Assessment Program (NAPAP) in preparing future assessments of industrial boiler emissions. The ICE Model user's manual includes a summar...

194

Modeling and control of internal combustion engines using intelligent techniques  

Microsoft Academic Search

This article will compare two different fuzzy-derived techniques for controlling small internal combustion engine and modeling fuel spray penetration in the cylinder of a diesel internal combustion engine. The first case study is implemented using conventional fuzzy-based paradigm, where human expertise and operator knowledge were used to select the parameters for the system. The second case study used an adaptive

Shaun H. Lee; Robert J. Howlett; Simon D. Walters; Cyril Crua

2007-01-01

195

Robust Feedback Control of Combustion Instability with Modeling Uncertainty  

E-print Network

uncertainty bounds by taking into account the effects of unmodeled dynamics, sensor noise, and parametricRobust Feedback Control of Combustion Instability with Modeling Uncertainty BOE-SHONG HONG, VIGOR in frequency domain T Temperature t Time u Control output of secondary-fuel injector V Volume of combustion

Ray, Asok

196

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

197

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

198

Modelling the combustion of charcoal in a model blast furnace  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

199

Chemical Kinetic Models for HCCI and Diesel Combustion  

SciTech Connect

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

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

2010-11-15

200

Computational experience with a three-dimensional rotary engine combustion model  

NASA Technical Reports Server (NTRS)

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.

1990-01-01

201

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

NASA Astrophysics Data System (ADS)

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

Balicki, Adrian; Bartela, ?ukasz

2014-06-01

202

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

203

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

Microsoft Academic Search

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

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

1992-01-01

204

Survey of physical modelling in Resistive Plate Chambers  

NASA Astrophysics Data System (ADS)

Apparently simple detectors, Resistive Plate Chambers actually incorporate a range of physical situations somewhat more complex than those found in most other gaseous detectors. These include the interplay between materials with different electrical characteristics, space-charge dominated avalanches evolving in very high electric fields and the propagation of fast signals on heterogeneous multiconductor transmission lines. In this article the state-of-the-art of physical modelling of many of these aspects is reviewed and sometimes expanded, while aspects still requiring further work are highlighted.

Fonte, P.

2013-11-01

205

Turbulence modelling of flow fields in thrust chambers  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

206

Numerical Modelling of Non-premixed Turbulent Combustion  

Microsoft Academic Search

Non-premixed turbulent flames control many practical applications of combustion. Studying these mechanisms has been the objective of numerous theoretical and experimental works, numerical simulation is also widely used to understand these flames. A brief review of numerical models for non-premixed turbulent combustion is given. This research work focuses on the coupling of Beta-PDF approach with LES model. In this study,

Fethi BOURAS; Azeddine SOUDANI; Mohamed SI-AMEUR

207

Theoretic computing model of combustion process of asphalt smoke  

Microsoft Academic Search

Based on the data and methods provided by research literature, dispersing mathematical model of combustion process of asphalt\\u000a smoke is set by theoretic analysis. Through computer programming, the dynamic combustion process of asphalt smoke is calculated\\u000a to simulate an experimental model. The computing result shows that the temperature and the concentration of asphalt smoke\\u000a influence its burning temperature in approximatively

Rui Huang; Li-yuan Chai; De-wen He; Bing Peng; Yun-yan Wang

2005-01-01

208

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

209

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

210

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

211

The study of PDF turbulence models in combustion  

NASA Technical Reports Server (NTRS)

The accurate prediction of turbulent combustion is still beyond reach for today's computation techniques. It is the consensus of the combustion profession that the predictions of chemically reacting flow were poor if conventional turbulence models were used. The main difficulty lies in the fact that the reaction rate is highly nonlinear, and the use of averaged temperature, pressure, and density produces excessively large errors. The probability density function (PDF) method is the only alternative at the present time that uses local instant values of the temperature, density, etc. in predicting chemical reaction rate, and thus it is the only viable approach for turbulent combustion calculations.

Hsu, Andrew T.

1991-01-01

212

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

213

Analysis of unsteady solid-propellant combustion models (review)  

Microsoft Academic Search

Recent studies of solid-propellant combustion models are briefly analyzed. The models are divided into purely one-dimensional\\u000a (classical and phenomenological models with various generalizations of the Zel’dovich approach) and non-one-dimensional. The\\u000a latter include models with local non-one-dimensionality, which is always accompanied by local unsteadiness. This all can be\\u000a eliminated by averaging. The main disadvantage of unsteady solid-propellant combustion models, which is

L. K. Gusachenko; V. E. Zarko

2008-01-01

214

Modeling of HMX\\/GAP pseudo-propellant combustion  

Microsoft Academic Search

A comprehensive numerical analysis of HMX\\/GAP pseudo-propellant combustion has been established to predict the propellant burning rate and detailed combustion wave structure over a broad range of ambient pressure, laser intensity, and propellant composition. The model takes into account various fundamental processes at scales sufficient to resolve the microscopic flame-zone physiochemistry. The thermochemical parameters of HMX and GAP are deduced

E. S. Kim; V. Yang; Y.-C. Liau

2002-01-01

215

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.

2014-01-28

216

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

217

Towards a detailed soot model for internal combustion engines  

Microsoft Academic Search

In this work, we present a detailed model for the formation of soot in internal combustion engines describing not only bulk quantities such as soot mass, number density, volume fraction, and surface area but also the morphology and chemical composition of soot aggregates. The new model is based on the Stochastic Reactor Model (SRM) engine code, which uses detailed chemistry

Sebastian Mosbach; Matthew S. Celnik; Abhijeet Raj; Markus Kraft; Hongzhi R. Zhang; Shuichi Kubo; Kyoung-Oh Kim

2009-01-01

218

Modeling of an internal combustion engine for control analysis  

Microsoft Academic Search

Recent activity in nonthermodynamic modeling of automotive internal combustion engines with spark ignition, which are inherently nonlinear, is reviewed. A fundamental nonlinear model of the engine is presented, and a linear control-oriented model is derived from the nonlinear process. Techniques for experimental verification are examined, and a practical linear engine example incorporating multirate sampling is illustrated

Jeffrey A. Cook; Barry K. Powell

1988-01-01

219

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

220

Modeling of pulverized coal combustion in cement rotary kiln  

Microsoft Academic Search

In this paper, based on analysis of the chemical and physical processes of clinker formation, a heat flux function was introduced to take account of the thermal effect of clinker formation. Combining the models of gas-solid flow, heat and mass transfer, and pulverized coal combustion, a set of mathematical models for a full-scale cement rotary kiln were established. In terms

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

2006-01-01

221

KINETIC MODELING OF NOX FORMATION AND DESTRUCTION AND COMBUSTIBLES BURNOUT  

EPA Science Inventory

The report describes a model of the gas-phase chemistry involved in the combustion of simple hydrocarbon fuels and the interconversion of fixed nitrogen species. One focus of the work was on modeling the chemistry involved in reburning and other advanced NOx control strategies. A...

222

Spectral optimization and uncertainty quantification in combustion modeling  

NASA Astrophysics Data System (ADS)

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

Sheen, David Allan

223

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

224

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

225

Research on theoretical calculation model for dynamic stiffness of air spring with auxiliary chamber  

Microsoft Academic Search

Based on the theory of thermomechanics and fluid dynamics, the dynamic equations of air spring, auxiliary chamber and orifice were established, and then the calculation model for dynamic stiffness of air spring with auxiliary chamber was deduced. The model indicates that the dynamic stiffness of air spring is caused by the air spring effect area variation with air spring deformation,

Zhu Sihong; Wang Jiasheng; Zhang Ying

2008-01-01

226

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

227

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

228

A reduced order full plant model for oxyfuel combustion  

Microsoft Academic Search

The linkage of models generated in different commercial and\\/or proprietary software packages is becoming the state-of-the-art for the investigation of power generation applications. Here, a sophisticated process modelling software package, gPROMS, has been linked with a commercial CFD code, ANSYS FLUENT version 12, in order to create a reduced order model (ROM) for oxyfuel combustion. This is the first such

P. J. Edge; P. J. Heggs; M. Pourkashanian; P. L. Stephenson; A. Williams

229

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

230

Theoretical models for the combustion of alloyable materials  

NASA Astrophysics Data System (ADS)

The purpose of this work is to extend a theoretical model of layered (laminar) media for SHS combustion presented in an earlier article [1] to explore possible mechanisms for after-burning in SHS ( i.e., gasless) combustion. As before, our particular interest is how the microscopic geometry of the solid reactants is reflected in the combustion wave and in the reaction product. The model is constructed from alternating lamina of two pure reactants that interdiffuse exothermically to form a product. Here, the laminar model is extended to contain layers of differing thicknesses. Using asymptotic theory, it was found that under certain conditions, the combustion wave can become “detached,” and an initial thin flame propagates through the media, leaving a slower, thicker flame following behind ( i.e., afterburning). Thin laminae are consumed in the initial flame and are thick in the secondary. The thin flame has a width determined by the inverse of the activation energy of diffusion, as found previously. The width of the afterburning zone, however, is determined by the absolute time of diffusion for the thicker laminae. Naturally, when the laminae are all the same thickness, there is only one thin flame. The condition for the appearance of afterburning is found to be contingent on the square of the ratio of smallestto-largest thicknesses being considerably less than unity.

Armstrong, Robert

1992-09-01

231

Concerning the problem of dynamic damping of the vibration combustion self-oscillations in a liquid-propellant rocket engine  

NASA Astrophysics Data System (ADS)

The reason for the decrease in the amplitude of longitudinal vibration combustion self-oscillations in the combustion chamber of a liquid-propellant rocket engine by means of antipulse partitions has been justified. A mathematical model of the development of combustion instability in such a chamber on attachment of a Helmholtz resonator to it has been obtained. The character of the damping of vibration combustion self-oscillations excited by the action of the Crocco mechanisms and negative thermal resistance, when varying the acoustic parameters of the resonator and of the pressure head characteristics of combustion chamber is established.

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

2012-11-01

232

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

233

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...

234

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...

235

A comprehensive combustion model for biodiesel-fueled engine simulations  

NASA Astrophysics Data System (ADS)

Engine models for alternative fuels are available, but few are comprehensive, well-validated models that include accurate physical property data as well as a detailed description of the fuel chemistry. In this work, a comprehensive biodiesel combustion model was created for use in multi-dimensional engine simulations, specifically the KIVA3v R2 code. The model incorporates realistic physical properties in a vaporization model developed for multi-component fuel sprays and applies an improved mechanism for biodiesel combustion chemistry. A reduced mechanism was generated from the methyl decanoate (MD) and methyl-9-decenoate (MD9D) mechanism developed at Lawrence Livermore National Laboratory. It was combined with a multi-component mechanism to include n-heptane in the fuel chemistry. The biodiesel chemistry was represented using a combination of MD, MD9D and n-heptane, which varied for a given fuel source. The reduced mechanism, which contained 63 species, accurately predicted ignition delay times of the detailed mechanism over a range of engine-specific operating conditions. Physical property data for the five methyl ester components of biodiesel were added to the KIVA library. Spray simulations were performed to ensure that the models adequately reproduce liquid penetration observed in biodiesel spray experiments. Fuel composition impacted liquid length as expected, with saturated species vaporizing more and penetrating less. Distillation curves were created to ensure the fuel vaporization process was comparable to available data. Engine validation was performed against a low-speed, high-load, conventional combustion experiments and the model was able to predict the performance and NOx formation seen in the experiment. High-speed, low-load, low-temperature combustion conditions were also modeled, and the emissions (HC, CO, NOx) and fuel consumption were well-predicted for a sweep of injection timings. Finally, comparisons were made between the results of biodiesel composition (palm vs. soy) and fuel blends (neat vs. B20). The model effectively reproduced the trends observed in the experiments.

Brakora, Jessica L.

236

Modeling chamber transport for heavy-ion fusion  

SciTech Connect

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

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

2002-10-01

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

Nonlinear Heterogeneous Model of Composite Solid-Propellant Combustion  

Microsoft Academic Search

A computational model of composite solid-propellant combustion that combines three important properties is described. First, the model is heterogeneous, in that it incorporates a multilevel è ame structure similar to the Beckstead-Derr-Price proposition. Second, it is nonsteady, and its main purpose is to predict pressure-coupled frequency response.Third,itisfullynonlinear,wherethermalcapacitancecalculationscomefrom a computational solution of the transient heat-conduction equation separately in the oxidizer and

B. Rasmussenand; R. A. Frederick Jr

2002-01-01

239

Effective modeling and simulation of internal combustion engine control systems  

Microsoft Academic Search

The paper presents an integrated software-hardware solution to effectively model and simulate internal combustion engine control systems. The solution is based on RT-LABTM. The characteristics of the proposed modeling and simulation approach are the preservation of accuracy in the face of relatively large fixed simulation steps and the achievement of real-time and faster than real-time simulation execution. The results of

C. A. Rabbath; H. Desira; K. Butts

2001-01-01

240

Multiple Mapping Conditioning: A New Modelling Framework for Turbulent Combustion  

Microsoft Academic Search

\\u000a Multiple mapping conditioning (MMC) is a relatively new addition to the list of models for turbulent combustion that unifies\\u000a the features of the probability density function, conditional moment closure and mapping closure models. This chapter presents\\u000a the major concepts and theory of MMC without the detailed derivations which can be found in the cited literature. While the\\u000a fundamental basis remains

M. J. Cleary; A. Y. Klimenko

241

Assessment of turbulent combustion submodels using the linear Eddy model  

Microsoft Academic Search

Linear Eddy Model (LEM) simulations are conducted in order to study turbulence-chemistry interactions in a homogeneous, incompressible, stationary turbulent flow with non-premixed reactants. The chemical kinetics model used in this work involves single- and multi-step, reversible and irreversible isothermal reactions. The simulation results are employed to investigate flame structure and statistics and comparisons are made to several other turbulent combustion

Paul E. Desjardin; Steven H. Frankel

1996-01-01

242

Modeling Interface Motion Of Combustion (MINOC). A computer code for two-dimensional, unsteady turbulent combustion  

NASA Technical Reports Server (NTRS)

A computer code for calculating the flow field and flame propagation in a turbulent combustion tunnel is described. The model used in the analysis is the random vortex model, which allows the turbulent field to evolve as a fundamental solution to the Navier-Stokes equations without averaging or closure modeling. The program was used to study the flow field in a model combustor, formed by a rearward-facing step in a channel, in terms of the vorticity field, the turbulent shear stresses, the flame contours, and the concentration field. Results for the vorticity field reveal the formation of large-scale eddy structures in the turbulent flow downstream from the step. The concentration field contours indicate that most burning occurred around the outer edges of the large eddies of the shear layer.

Ghoneim, A. F.; Marek, C. J.; Oppenheim, A. K.

1983-01-01

243

Assessment of RANS-Based Turbulent Combustion Models for Prediction of Emissions from Lean Premixed Combustion of Methane  

Microsoft Academic Search

Reynolds-Averaged Navier-Stokes (RANS) simulations of Lean Premixed Combustion (LPC) of methane–air in a bluff-body stabilized combustor were performed with several widely used turbulent combustion methodologies in order to assess their prediction capabilities. The methods employed are the Eddy Dissipation Concept (EDC), the Composition Probability Density Function (CPDF) and the Joint Velocity–Frequency-Composition PDF (VFCPDF) models. Where needed, two different models were

J. R. Nanduri; D. R. Parsons; S. L. Yilmaz; I. B. Celik; P. A. Strakey

2010-01-01

244

On two-fluid model of turbulent combustion phenomena  

SciTech Connect

Flow characteristics of turbulent combustion in premixed ducted flames are investigated with a two-fluid model. The fluids are defined as the cold premixed, unburned mixture and the hot burned gas mixture. The model involves solution of separate transport equations for zone-averaged variable of each fluid with allowance for interface transfer of mass, momentum and energy. Combustion is assumed to be controlled by the turbulence transport and a simple Arrhenius type of chemical reaction model has been employed. The fragment size which affects interfluid transfer terms and the transport properties is deduced from a transport equation that accounts for growth by entrainment and diminution by shear distortion. The growth and diminution constants of the length-scale equation are parametrically established. Predictions generally agree well with the experimental data. Effects of inlet flow rate and aspect ratio are also investigated.

Ilegbusi, O.J. [Northeastern Univ., Boston, MA (United States). Dept. of Mechanical, Industrial and Manufacturing Engineering

1996-12-31

245

Modeling of pulverized coal combustion in cement rotary kiln  

SciTech Connect

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

Shijie Wang; Jidong Lu; Weijie Li; Jie Li; Zhijuan Hu [Huazhong University of Science and Technology, Wuhan (China). State Key Laboratory of Coal Combustion

2006-12-15

246

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

E-print Network

regulations for spark· ignited (SI) internal combustion engines requires understanding the complex chemical models for combustion have provided a framework for investigating modifications to existing engines it become feasible to apply these simulation tools to model the combustion portion of the engine cycle

247

Two Asymptotic Models for Solid Propellant Combustion  

Microsoft Academic Search

—We derive two different asymptotic models which describe the nonsteady, nonplanar burning of certain types of homogeneous solid propellants. Motivated in part by recent work on ammonium perchlorate deflagration, we assume, in the first model, that a fraction of the pro-pellant is pyrolyzed directly to product gases at a solid\\/gas interface, while the remainder sublimes and burns in the gas

Stephen B. Margolis; Robert C. Armstrong

1986-01-01

248

Surrogate Model Development for Fuels for Advanced Combustion Engines  

SciTech Connect

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

Anand, Krishnasamy [University of Wisconsin, Madison; Ra, youngchul [University of Wisconsin, Madison; Reitz, Rolf [University of Wisconsin; Bunting, Bruce G [ORNL

2011-01-01

249

Bubble Combustion  

NASA Technical Reports Server (NTRS)

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

Corrigan, Jackie

2004-01-01

250

A model for double base propellant combustion  

SciTech Connect

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 heat of explosion, in addition, to the temperature profile in both the condensed and gas phases. For example, it is very well known that the DB propellant gas phase sustains two flames. They are separated by a dark zone at low pressure. At high pressure, the secondary flame merges into the primary flame eliminating the dark zone. It is important to take this phenomenon into account in a DB model. The solution of the temperature profile in the gas phase is quite complex. One generally uses a transient numerical method since it is often convenient to determine the steady solution by first solving the transient equations. However, the process can be very cumbersome (especially if the flame is separated or is about to merge). The purpose of this study is to prove that it is possible to simplify the equations of the steady model in order to avoid a very lengthy resolution especially because the computation shows that it is necessary to adjust several parameters to calculate the correct temperature profiles.

Bizot, A.

1987-01-01

251

Chemical Kinetic Modeling of Hydrogen Combustion Limits  

SciTech Connect

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

Pitz, W J; Westbrook, C K

2008-04-02

252

Model of high-current breakdown from cathode field emission in aged wire chambers  

NASA Astrophysics Data System (ADS)

Observing single electron pulses provides insight into the mechanism that leads to sudden high-current jumps (breakdown) in aged wire chambers. This single electron activity is found to be consistent with the Fowler-Nordheim (FN) equation for field emission of electrons from a cathode surface in a high electric field. The high electric field arises from the positive ion buildup on a very thin insulating layer on the cathode surface. A model is presented to explain the transient behavior of single electron pulses in response to abrupt changes in chamber ionization, as well as the steady-state rate during a long-term aging run. The model is based on properties of the insulating layer (dielectric constant, conductivity, and hole-mobility) as well as the FN equation. This model also applies to other avalanche type chambers such as microstrip gas chambers and gas electron multipliers.

Boyarski, Adam M.

2004-12-01

253

Analytical model of the combustion of multicomponent solid propellants  

NASA Technical Reports Server (NTRS)

Multiple flame models derived for simple composite propellants are extended to describe the combustion of propellants containing multimodal particle sizes, mixed oxidizers and monopropellant binders. Models combining the component contributions to propellant surface structure, flame structure and energy distribution are based in part upon experimental observations and in part upon hypotheses constrained to provide reasonable agreement with measured burning rate characteristics. The methods employed consist of superposition, interaction and iteration. The computerized model is applied to explain the effects of multiple ingredients and to discuss burning rate tailoring problems of current interest.

Cohen, N. S.; Price, C. F.; Strand, L. D.

1977-01-01

254

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

255

Internal combustion engine  

DOEpatents

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

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

1991-01-01

256

Modeling propellant combustion interacting with an eroding solid surface  

SciTech Connect

A computatonal model of turbulent combustion flow acting on and influenced by an eroding wall surface is introduced. The combustion flow field is particle laden. Significant particulate mass loading occurs in the immediate neighborhood of the wall as a result of erosion products issuing from the deteriorating solid surface. In addition, cases are considered in which a substantial particle mass loading develops near the wall as a result of finely divided (sub micron diameter) particulates such as TiO/sub 2/ and talcum powder which are added to suppress erosion. In addition to statistical turbulent field particle flow interaction, the model includes multi-component molecular diffusion processes, and gas phase, gas/surface and or solid surface chemical reactions. Results indicate that despite the unsteady flow conditions, a limiting erosion rate is approached. This occurs as a result of the effective blowing off of the issing vapor phase products. The blowing reduces the gradients driving the incident combustion heat and mass transfer. An analogy is drawn to unsteady, ablative, heat transfer and thermal/material response in hypersonic aerodynamics. Surfaces investigated, at present, include bare steel and refractory metal coated steel walls.

Buckingham, A.C.

1980-05-06

257

Modeling of combustion of a gaseous sphere using mathematica  

NASA Astrophysics Data System (ADS)

Transient combustion of a gaseous sphere of fuel is examined in the flamesheet limit. The gas is considered thermally expandable, the Lewis numbers are taken as unity and a temperature-dependent thermal diffusivity is allowed. Evaluation of some approximations used in forming the model are evaluated by examining a spherical, nonlinear thermal conduction problem first. Mathematica is used to solve the PDEs arising from both problems by a Method of Lines. The solutions for the combustion problem show the expansion and subsequent collapse of the flame-sheet trajectory, the sharp initial temperature spike at the flame front and its later diffusive spreading, and the early peaked expansion velocity, followed by a double humped velocity profile.

Rehm, R. G.; Baum, H. R.

258

Development of Supersonic Combustion Experiments for CFD Modeling  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

259

Subgrid scale modelling for MILD combustion  

E-print Network

. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) small portion creating non-uniform reaction rate field for low cT value which occurs near the inflow boundary of the DNS... simple closure for filtered reaction rate. This modelled reaction rate field and that obtained by filtering the DNS result agree reason- ably well for filter size of DP 3dth. Acknowledgements Y. M. acknowledges the financial support of Nippon Keidanren...

Minamoto, Y.; Swaminathan, N.

2014-07-27

260

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

NASA Technical Reports Server (NTRS)

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

Nguyen, H. Lee; Wey, Ming-Jyh

1990-01-01

261

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

SciTech Connect

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

Nguyen, H.L.; Wey, Mingjyh.

1990-01-01

262

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

263

Structure-Based Predictive model for Coal Char Combustion.  

SciTech Connect

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

Hurt, R.; Colo, J [Brown Univ., Providence, RI (United States). Div. of Engineering; Essenhigh, R.; Hadad, C [Ohio State Univ., Columbus, OH (United States). Dept. of Chemistry; Stanley, E. [Boston Univ., MA (United States). Dept. of Physics

1997-09-24

264

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

265

Structure Based Predictive Model for Coal Char Combustion  

SciTech Connect

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

Robert Hurt; Joseph Calo; Robert Essenhigh; Christopher Hadad

2000-12-30

266

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

SciTech Connect

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

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

2011-01-01

267

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

NASA Technical Reports Server (NTRS)

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

Wey, Thomas Changju; Liu, Nan-suey

2011-01-01

268

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

2013-01-01

269

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

270

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

271

Carbon deposition model for oxygen-hydrocarbon combustion, volume 2. Interim final report  

SciTech Connect

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.

1987-09-01

272

STRUCTURE BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION  

SciTech Connect

This report is part on the ongoing effort at Brown University and Ohio State University to develop structure based models of coal combustion. A very fundamental approach is taken to the description of coal chars and their reaction processes, and the results are therefore expected to have broad applicability to the spectrum of carbon materials of interest in energy technologies. This quarter, the project was in a period no-cost extension and discussions were held about the end phase of the project and possible continuations. The technical tasks were essentially dormant this period, but presentations of results were made, and plans were formulated for renewed activity in the fiscal year 2001.

Robert Hurt; Joseph Calo; Robert Essenhigh; Christopher Hadad

2001-06-15

273

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

274

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

275

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

276

Modified aspirated internal combustion engine  

Microsoft Academic Search

An internal combustion engine is described, comprising: an engine block; at least one cylinder; at least one piston, each piston being reciprocally movable in the cylinder; a head connected with the engine block so as to form a combustion chamber above each piston; aspiration means for providing gas entry into and gas exit from the combustion chamber of each cylinder;

1993-01-01

277

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

E-print Network

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

Theraulaz, Guy

278

Two-chamber lattice model for thermodiffusion in polymer solutions Jutta Luettmer-Strathmanna)  

E-print Network

Two-chamber lattice model for thermodiffusion in polymer solutions Jutta Luettmer 2003 When a temperature gradient is applied to a polymer solution, the polymer typically migrates model approach to investigate thermodiffusion in dilute polymer solutions. For a short polymer chain

Luettmer-Strathmann, Jutta

279

Comparing simple respiration models for eddy flux and dynamic chamber data  

E-print Network

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

Richardson, Andrew D.

280

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...

281

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

282

Kinetic Modeling of Combustion Characteristics of Real Biodiesel Fuels  

SciTech Connect

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

Naik, C V; Westbrook, C K

2009-04-08

283

A stochastic model for the indicated pressure process and the dynamics of the internal combustion engine  

Microsoft Academic Search

Some of the research problems pertaining to cyclic combustion variability are reformulated from a perspective markedly different from the fluid dynamic and thermodynamic models which traditionally characterize this research: a system viewpoint is embraced to construct a stochastic model for the cylinder pressure process and the dynamics of the internal combustion engine. A deterministic model for the dynamics of the

G. Rizzoni

1989-01-01

284

Towards a detailed soot model for internal combustion engines  

SciTech Connect

In this work, we present a detailed model for the formation of soot in internal combustion engines describing not only bulk quantities such as soot mass, number density, volume fraction, and surface area but also the morphology and chemical composition of soot aggregates. The new model is based on the Stochastic Reactor Model (SRM) engine code, which uses detailed chemistry and takes into account convective heat transfer and turbulent mixing, and the soot formation is accounted for by SWEEP, a population balance solver based on a Monte Carlo method. In order to couple the gas-phase to the particulate phase, a detailed chemical kinetic mechanism describing the combustion of Primary Reference Fuels (PRFs) is extended to include small Polycyclic Aromatic Hydrocarbons (PAHs) such as pyrene, which function as soot precursor species for particle inception in the soot model. Apart from providing averaged quantities as functions of crank angle like soot mass, volume fraction, aggregate diameter, and the number of primary particles per aggregate for example, the integrated model also gives detailed information such as aggregate and primary particle size distribution functions. In addition, specifics about aggregate structure and composition, including C/H ratio and PAH ring count distributions, and images similar to those produced with Transmission Electron Microscopes (TEMs), can be obtained. The new model is applied to simulate an n-heptane fuelled Homogeneous Charge Compression Ignition (HCCI) engine which is operated at an equivalence ratio of 1.93. In-cylinder pressure and heat release predictions show satisfactory agreement with measurements. Furthermore, simulated aggregate size distributions as well as their time evolution are found to qualitatively agree with those obtained experimentally through snatch sampling. It is also observed both in the experiment as well as in the simulation that aggregates in the trapped residual gases play a vital role in the soot formation process. (author)

Mosbach, Sebastian; Celnik, Matthew S.; Raj, Abhijeet; Kraft, Markus [Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA (United Kingdom); Zhang, Hongzhi R. [Department of Chemical Engineering, University of Utah, 1495 East 100 South, Kennecott Research Building, Salt Lake City, UT 84112 (United States); Kubo, Shuichi [Frontier Research Center, Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan); Kim, Kyoung-Oh [Higashifuji Technical Center, Toyota Motor Corporation, Mishuku 1200, Susono, Shizuoka 480-1193 (Japan)

2009-06-15

285

Characterization of Low-Frequency Combustion Stability of the Fastrac Engine  

NASA Technical Reports Server (NTRS)

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

Rocker, Marvin; Jones, Preston (Technical Monitor)

2002-01-01

286

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

287

Carbon deposition model for oxygen-hydrocarbon combustion, volume 1. Interim final report  

SciTech Connect

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.

1987-09-01

288

Mixing and chemical reaction in an idealied swirl chamber  

Microsoft Academic Search

A vorticity-based, low-Mach-number model for simulating combustion in closed chambers is constructed. Numerical scheme is based on a mixed finite-difference pseudo-spectral discretization of the governing equations. Discrete evolution equations are integrated in time using a predictor-corrector scheme, while discrete elliptic systems are inverted with the help of fast-Poisson solver. Scheme is applied to analyze mixing and combustion in an idealized

Habib N. Najm; A. S. Worlikar

1996-01-01

289

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

NASA Astrophysics Data System (ADS)

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

1992-07-01

290

Composite propellant combustion modeling with a porous plate burner  

NASA Technical Reports Server (NTRS)

A burner is designed to model on a large scale (millimeters) the complex vapor phase processes that take place on awkwardly small scales (about a hundred microns) in the combustion of practical AP/ composite propellants at conventional pressures. Binder vapor evolution is modeled with gaseous fuel (ethane in the experiments reported) flow through a porous plate and oxidizer vapor with the flow of a gaseous oxidizer (air and enriched air in the experiments reported) through discrete holes in the porous plate. Measured flame standoff distance and surface temperature variations are consistent with theoretical predictions at atmospheric pressure. Data obtained at several atmospheres are discussed in the light of the current theories of propellant burning that place varying emphasis on the roles of chemical kinetics and fluid dynamic diffusion/mixing in the vapor phase of a burning composite propellant. The potential and proposed future applications of the burner are indicated.

Kumar, R. N.; Strand, L. D.; Mcnamara, R. P.

1976-01-01

291

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

292

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

NASA Technical Reports Server (NTRS)

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

Combs, L. P.

1974-01-01

293

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

294

Modeling of scalar dissipation rates in flamelet models for low temperature combustion engine simulations  

E-print Network

The flamelet approach offers a viable framework for combustion modeling of homogeneous charge compression ignition (HCCI) engines under stratified mixture conditions. Scalar dissipation rate acts as a key parameter in flamelet-based combustion models which connects the physical mixing space to the reactive space. The aim of this paper is to gain fundamental insights into turbulent mixing in low temperature combustion (LTC) engines and investigate the modeling of scalar dissipation rate. Three direct numerical simulation (DNS) test cases of two-dimensional turbulent auto-ignition of a hydrogen-air mixture with different correlations of temperature and mixture fraction are considered, which are representative of different ignition regimes. The existing models of mean and conditional scalar dissipation rates, and probability density functions (PDFs) of mixture fraction and total enthalpy are a priori validated against the DNS data.

Gupta, Saurabh; Pal, Pinaki; Im, Hong G

2014-01-01

295

Emissions modeling of fluidised bed co-combustion of poultry litter and peat.  

PubMed

Gaseous emissions from the fluidised bed co-combustion of 50% w/w chicken litter and peat were monitored and recorded. Emission data were used to create a dispersion model for a proposed site on a poultry farm in Ireland. Variables within the combustion unit influenced both combustion and emission levels of pollutants such as SO(2) and NO(x), CO. Concentrations of atmospheric pollutants decreased with use of the correct ratio between fluidising and secondary air. Dispersion modelling of combustion at a proposed poultry unit predicted that ground level concentrations for the set of emissions data would be below the limits and guidelines set by air quality standards. PMID:12507869

Henihan, A M; Leahy, M J; Leahy, J J; Cummins, E; Kelleher, B P

2003-05-01

296

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

PubMed

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

Golovitchev, Valeri I; Yang, Junfeng

2009-01-01

297

Modeling of Evaporation and Combustion of Droplets in a Spray using Unit Cell Approach: A Review  

Microsoft Academic Search

A comprehensive review of modeling of evaporation and combustion of liquid fuel droplets using “unit cell” approach has been presented. The review starts with a general introduction to the different regimes of droplet combustion and a brief overview of other techniques used for evaluating mutual interaction of droplets before presenting the cell model in detail. In this review, the major

Achintya Mukhopadhyay; Dipankar Sanyal

2011-01-01

298

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...

299

Modeling and Verification of a Dual Chamber Implantable Pacemaker  

E-print Network

design and certification of software for medical devices. Keywords: Medical Devices, Implantable. The design and implementation of software for medical de- vices is challenging due to their rapidly pace- maker as a case study for modeling and verification of control algorithms for medical devices

Alur, Rajeev

300

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

301

Hypersonic combustion of hydrogen in a shock tunnel  

NASA Technical Reports Server (NTRS)

Results are reported on shock-tunnel experiments testing the feasibility of hypersonic combustion and thrust generation in a hydrogen scramjet model. Tests with a constant-area duct show that hypersonic combustion is possible with a central injection at static intake pressures of about 20 kPa. The results of a comparison made between model configurations with nominal combustion-chamber intake Mach numbers of 4 and 6 indicated that the hypersonic duct gives a better performance at flight enthalpies above 7 mJ/kg. It is argued that the lower temperatures associated with hypersonic flow produce more efficient combustion.

Morgan, R. G.; Stalker, R. J.

1989-01-01

302

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

303

Modeling Premixed Combustion?Acoustic Wave Interactions: A Review  

Microsoft Academic Search

The interactions between acoustic waves and a premixed combustion process can play an important role in the characteristicunsteadinessofcombustiondevices.Inparticular,theyareoftenresponsiblefortheoccurrenceofself- excited, combustion-driven oscillations that are detrimental to combustor life and performance. A tutorial review is provided of current understanding of these interactions. First, the mutual interaction mechanisms between the combustion process and acoustic, vorticity, and entropy waves are described. Then, the acoustic-

T. Lieuwen

2003-01-01

304

PDF modeling and simulation of premixed turbulent combustion  

Microsoft Academic Search

The use of probability density function (PDF) methods for turbulent combustion simulations is very attractive because arbitrary finite-rate chemistry can be exactly taken into account. PDF methods are well developed for non-premixed turbulent combustion. However, many real flames involve a variety of mixing regimes (non-premixed, partially-premixed and premixed turbulent combustion), and the development of PDF methods for partially-premixed and premixed

Michael Stöllinger; Stefan Heinz

2008-01-01

305

Structure-Based Predictive model for Coal Char Combustion.  

SciTech Connect

During the second quarter of this project, progress was made on both major technical tasks. Three parallel efforts were initiated on the modeling of carbon structural evolution. Structural ordering during carbonization was studied by a numerical simulation scheme proposed by Alan Kerstein involving molecular weight growth and rotational mobility. Work was also initiated to adapt a model of carbonaceous mesophase formation, originally developed under parallel NSF funding, to the prediction of coke texture. This latter work makes use of the FG-DVC model of coal pyrolysis developed by Advanced Fuel Research to specify the pool of aromatic clusters that participate in the order/disorder transition. Boston University has initiated molecular dynamics simulations of carbonization processes and Ohio State has begun theoretical treatment of surface reactions. Experimental work has also begun on model compound studies at Brown and on pilot-scale combustion systems with widely varying flame types at OSE. The work on mobility / growth models shows great promise and is discussed in detail in the body of the report.

Hurt, R.; Calo, J. [Brown Univ., Providence, RI (United States). Div. of Engineering; Essenhigh, R.; Hadad, C. [Ohio State Univ., Columbus, OH (United States). Dept. of Chemistry; Stanley, E. [Boston Univ., MA (United States). Dept. of Physics

1997-06-25

306

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

307

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

308

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)

309

Multi-Zone DI Diesel Spray Combustion Model for Cycle Simulation Studies of Engine Performance and Emissions  

Microsoft Academic Search

A quasi -dimensional, multi-zone, direct injection (DI) diesel combustion model has been developed and implemented in a full cycle simulation of a turbocharged engine. The combustion model accounts for transient fuel spray evolution, fuel-air mixing, ignition, combustion and NO and soot pollutant formation. In the model, the fuel spray is divided into a number of zones, which are treated as

Dohoy Jung; Dennis N. Assanis

2001-01-01

310

Mathematics of combustion  

Microsoft Academic Search

The applications of numerical techniques to the study of combustion processes is considered. The basic equations governing combustion processes are introduced, and some novel approaches to combustion reaction modelling are described. Among the specific applications discussed are: the Burger and Korteweg-de Vries equations of detonation processes; turbulent combustion modelling; and analysis of finite amplitude waves in combustible gases.

J. D. Buckmaster; H. Rabitz; F. A. Williams; W. Fickett; J. F. Clarke

1985-01-01

311

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

E-print Network

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

Swihart, Mark T.

312

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

E-print Network

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

313

A non linear model for combustion instability : analysis and quenching of the oscillations  

E-print Network

- ing the oscillations. 1 Introduction Combustion instabilities phenomena in gas turbine are the focus to predict, but in most cases it can be explained by an unsteady flame generating pressure waves whichA non linear model for combustion instability : analysis and quenching of the oscillations Ioan D

Boyer, Edmond

314

Computer Modelling as an Aid to Teaching in an Internal Combustion Engineering Course  

Microsoft Academic Search

The computer has been used as a laboratory substitute in an Internal Combustion Engineering course. Computer programs have been used to model internal combustion engines and engine systems, allowing the effects of ambient conditions, and internal parameters, to be demonstrated. The programs have been in use for two years and have been developed over that time both to improve student

P. R. Cave

1974-01-01

315

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...

316

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

317

Combustion control system for internal combustion engines  

Microsoft Academic Search

This patent describes a modified spark plug for internal combustion engines comprising: a base made of an electrically conductive material and adapted to be installed in the engine; an insulator disposed within the base and having a precombustion chamber formed therein; a central electrode passing through the insulator, extending into the precombustion chamber and defining a passageway in communication with

1988-01-01

318

Hydrodynamic Modeling of Oxidizer-Rich Staged Combustion Injector Flow  

NASA Technical Reports Server (NTRS)

The main objective of this work is to determine the unsteady hydrodynamic characteristics of coaxial swirl atomizers of interest in oxidizer-rich staged combustion (ORSC) liquid rocket engines. To this end, the pseudo-density (homogeneous flow) treatment combined with the Marker-and-Cell (MAC) numerical algorithm has been used to develop an axisymmetric with swirl, two-phase, unsteady model. The numerical model is capable of assessing the time-dependent orifice exit conditions and internal mixing for arbitrary fuel and oxidizer gas injection conditions. Parametric studies have been conducted to determine the effect of geometry, gas properties, and liquid properties on the exit massflow rate and velocity. It has been found that the frequency at which the liquid film oscillates increases as the density ratio and thickness increase, decreases as film thickness and liquid swirl velocity increase, and is unaffected by the mixing length. Additionally, it has been determined that the variation in the massflow rate increases as the liquid swirl velocity and liquid film thickness increase, and decreases as the density ratio, collar thickness, and mixing length increase.

Harper, Brent (Technical Monitor); Canino, J. V.; Heister, S. D.; Garrison, L. A.

2004-01-01

319

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

320

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

321

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

322

Modeling of internal combustion engine based cogeneration systems for residential applications  

Microsoft Academic Search

A parametric model that can be used in the design and techno-economic evaluation of internal combustion engine (ICE) based cogeneration systems for residential use is presented. The model, which is suitable to be incorporated into a building simulation program, includes sub-models for internal combustion engines and generators, electrical\\/thermal storage systems, and secondary system components (e.g. controllers), and is capable of

Hycienth I. Onovwiona; V. Ismet Ugursal; Alan S. Fung

2007-01-01

323

[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

324

Evaluation of char combustion models: measurement and analysis of variability in char particle size and density  

SciTech Connect

Char samples representing a range of combustion conditions and extents of burnout were obtained from a well-characterized laminar flow combustion experiment. Individual particles from the parent coal and char samples were characterized to determine distributions in particle volume, mass, and density at different extent of burnout. The data were then compared with predictions from a comprehensive char combustion model referred to as the char burnout kinetics model (CBK). The data clearly reflect the particle- to-particle heterogeneity of the parent coal and show a significant broadening in the size and density distributions of the chars resulting from both devolatilization and combustion. Data for chars prepared in a lower oxygen content environment (6% oxygen by vol.) are consistent with zone II type combustion behavior where most of the combustion is occurring near the particle surface. At higher oxygen contents (12% by vol.), the data show indications of more burning occurring in the particle interior. The CBK model does a good job of predicting the general nature of the development of size and density distributions during burning but the input distribution of particle size and density is critical to obtaining good predictions. A significant reduction in particle size was observed to occur as a result of devolatilization. For comprehensive combustion models to provide accurate predictions, this size reduction phenomenon needs to be included in devolatilization models so that representative char distributions are carried through the calculations.

Daniel J. Maloney; Esmail R. Monazam; Kent H. Casleton; Christopher R. Shaddix

2008-08-01

325

Discrete model of gas-free spin combustion of a powder mixture  

NASA Astrophysics Data System (ADS)

We propose a discrete model of gas-free combustion of a cylindrical sample which reproduces in detail a spin combustion mode. It is shown that a spin combustion, in its classical sense as a continuous spiral motion of heat release zones on the surface of the sample, does not exist. Such a concept has arisen due to the misinterpretation of the experimental data. This study shows that in fact a spinlike combustion is realized, at which two energy release zones appear on the lateral surface of the sample and propagate circumferentially in the opposite directions. After some time two new heat release zones are formed on the next layer of the cylinder surface and make the same counter-circular motion. This process continues periodically and from a certain angle it looks like a spiral movement of the luminous zone along the lateral surface of the sample. The model shows that on approaching the combustion limit the process becomes more complicated and the spinlike combustion mode shifts to a more complex mode with multiple zones of heat release moving in different directions along the lateral surface. It is shown that the spin combustion mode appears due to asymmetry of initial conditions and always transforms into a layer-by-layer combustion mode with time.

Klimenok, Kirill L.; Rashkovskiy, Sergey A.

2015-01-01

326

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

327

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

328

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

329

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

330

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

331

RANS and LES Modelling of Premixed Turbulent Combustion  

Microsoft Academic Search

\\u000a Premixed combustion is becoming more common in practical combustion systems in response to increasing regulatory pressure\\u000a to reduce unwanted emissions. The inherent ability of premixed flames to propagate into the unburned mixture leads to a more\\u000a active response to turbulence by comparison with non-premixed flames. It is clear that the sheet-like reaction zone within\\u000a the premixed flame is highly resistant

Stewart Cant

332

A Kinetic Model of Carbon Burnout in Pulverized Coal Combustion  

Microsoft Academic Search

The degree of carbon burnout is an important operating characteristic of full-scale suspension-fired coal combustion systems. Prediction of carbon loss requires special char combustion kinetics valid through the very high conversions targeted in industry (typically >99.5%), and valid for a wide range of particle temperature histories occurring in full-scale furnaces. The present paper presents high-temperature kinetic data for five coal

Robert Hurt; Jian-Kuan Sun; Melissa Lunden

1998-01-01

333

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

334

A model of smoldering combustion applied to flexible polyurethane foams  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

335

Chemistry and radiation in oxy-fuel combustion: A computational fluid dynamics modeling study  

Microsoft Academic Search

In order to investigate the role of combustion chemistry and radiation heat transfer in oxy-fuel combustion modeling, a computational fluid dynamics (CFD) modeling study has been performed for two different oxy-fuel furnaces. One is a lab-scale 0.8MW oxy-natural gas flame furnace whose detailed in-flame measurement data are available; the other is a conventional 609MW utility boiler which is assumed to

Chungen Yin; Lasse A. Rosendahl; Søren K. Kær

2011-01-01

336

Gasdynamic modeling and parametric study of mesoscale internal combustion swing engine\\/generator systems  

Microsoft Academic Search

The demand of portable power generation systems for both domestic and military applications has driven the advances of mesoscale internal combustion engine systems. This dissertation was devoted to the gasdynamic modeling and parametric study of the mesoscale internal combustion swing engine\\/generator systems. First, the system-level thermodynamic modeling for the swing engine\\/generator systems has been developed. The system performance as well

Yongxian Gu

2006-01-01

337

Fundamentals of Gas Turbine combustion  

NASA Technical Reports Server (NTRS)

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

Gerstein, M.

1979-01-01

338

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

339

Magma chambers  

NASA Technical Reports Server (NTRS)

Recent observational and theoretical investigations of terrestrial magma chambers (MCs) are reviewed. Consideration is given to the evidence for MCs with active convection and crystal sorting, problems of direct MC detection, theoretical models of MC cooling, the rheology and dynamics of solidification fronts, crystal capture and differentiation, convection with solidification, MC wall flows, and MC roof melting. Diagrams, graphs, and a list of problems requiring further research are provided.

Marsh, Bruce D.

1989-01-01

340

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

341

Stochastic modeling of CO and NO in premixed methane combustion  

SciTech Connect

The ability to use reduced CH{sub 4}-air chemical mechanisms to predict CO and NO emissions in premixed turbulent combustion has been evaluated in a Partially Stirred Reactor (PaSR) model. CO emissions were described with reduced 4-, 5-, and 9-step mechanisms and a detailed 276-step mechanism. NO emissions from thermal, N{sub 2}O-intermediate, and prompt pathways were included in the 5-, 9-, and 276-step mechanisms. Molecular mixing was described with a deterministic, Interaction-by-Exchange-with-the-Mean (IEM) submodel. Random selection and replacement (without repetition) of fluid particles were used to simulate through-flow. The evolution of mean and root mean square (rms) temperature, CO, and NO in the PaSR was accurately described with the 9-step mechanism over a wide range in mixing frequency and equivalence ratio. Also, the 9-step mechanism provided accurate instantaneous reaction rates and concentrations for a broad region of the accessed composition space in the PaSR. The 5-step mechanism performed less reliably than the 9-step mechanism at {psi} = 1.0 but performed similarly to the 9-step mechanism at {psi} = 0.65. The 4-step mechanism underpredicted mean CO values and overpredicted instantaneous temperature reaction rates, most likely due to its inferior parent mechanism, partial equilibrium assumption for OH, and unallowed dissociation of neglected radical species. The detailed and reduced mechanism predictions of the accessed composition space in the PaSR covered only a small fraction of the allowable composition space, thus facilitating the use of an efficient in situ chemical look-up table for multidimensional, pdf-method calculations.

Cannon, S.M.; Brewster, B.S.; Smoot, L.D. [Brigham Young Univ., Provo, UT (United States). Advanced Combustion Engineering Research Center] [Brigham Young Univ., Provo, UT (United States). Advanced Combustion Engineering Research Center

1998-04-01

342

The acoustic model of oscillations of gas combustion in coaxial pipes  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

343

Rotary valve for internal combustion engine  

Microsoft Academic Search

This patent describes a rotary valve apparatus for a cylinder of an internal combustion engine, the cylinder having therein a piston, with the cylinder and the piston defining a combustion chamber at one end of the cylinder and the combustion chamber having an opening thereinto opposite the piston. It comprises a valve housing positioned to cover the opening of the

Buelna

1991-01-01

344

Ignition apparatus for internal combustion engine  

Microsoft Academic Search

An ignition apparatus for an internal combustion engine comprises an intake path supplying a mixture of air and fuel into the combustion chamber of the engine, a particle supplying unit having an ejection port opening into the combustion chamber for supplying minute particles of a material which is not the fuel and has a high light absorption factor, and a

S. Mukainakano; T. Goto; T. Hattori; T. Mizuno; M. Nishida

1984-01-01

345

Internal combustion engine  

Microsoft Academic Search

This patent describes an internal combustion engine of the two-cycle type. It comprises a cylinder, a piston slidable within the cylinder, a cylinder head to seal the cylinder at the top, thereby defining a combustion chamber, a crankshaft means to provide reciprocating motion to the piston, a lubricating means to lubricate the crankshaft, a sealing means around the bottom of

Van Blaricom

1992-01-01

346

An Integrated Model of Coal/Coke Combustion in a Blast Furnace  

NASA Astrophysics Data System (ADS)

A three-dimensional integrated mathematical model of the combustion of pulverized coal and coke is developed. The model is applied to the region of lance-blowpipe-tuyere-raceway-coke bed to simulate the operation of pulverized coal injection in an ironmaking blast furnace. The model integrates two parts: pulverized coal combustion model in the blowpipe-tuyere-raceway-coke bed and the coke combustion model in the coke bed. The model is validated against the measurements in terms of coal burnout and gas composition, respectively. The comprehensive in-furnace phenomena are simulated in the raceway and coke bed, in terms of flow, temperature, gas composition, and coal burning characteristics. In addition, underlying mechanisms for the in-furnace phenomena are analyzed. The model provides a cost-effective tool for understanding and optimizing the in-furnace flow-thermo-chemical characteristics of the PCI process in full-scale blast furnaces.

Shen, Y. S.; Guo, B. Y.; Yu, A. B.; Austin, P.; Zulli, P.

2010-03-01

347

Ultrafast Structural Dynamics in Combustion Relevant Model Systems  

SciTech Connect

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

Weber, Peter M. [Brown University

2014-03-31

348

HEAT RELEASE DYNAMICS MODELING FOR COMBUSTION INSTABILITY ANALYSIS OF KINETICALLY CONTROLLED BURNING  

Microsoft Academic Search

We present a heat release dynamics model which utilizes a well-stirred reactor (WSR) model and one-step kinetics to describe the unsteady combustion process. The model incorporates the linearized mass and energy equations to describe the response of the reactor to external perturbations, and is cast in the form of a first order filter. The model is able to predict the

Anuradha Annaswamy; Ahmed Ghoniem

349

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

350

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

351

Rotary internal combustion engine  

Microsoft Academic Search

This patent describes a rotary internal combustion engine operating on fuel and air, comprising: a housing having a pair of communicating parallel axis rotor chambers; a pair of parallel axis rotors, one in each rotor chamber of the housing, the rotors each having on its outer periphery circumferentially spaced axial teeth with intervening circumferentially spaced axial passages. The rotors are

Kollen

1987-01-01

352

Modeling Decomposing Objects under Combustion Texas A&M University  

E-print Network

. The fluid motion is applied to advect three quantities: fuel gas, exhaust gas, and heat. Allowing heat process by combining fuel and oxidizer in a cell, creating additional exhaust gas and additional heat. We the flame production and generates heat from a combustion pro- cess, which is used to trigger pyrolysis

Keyser, John

353

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

354

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

355

Modeling and Control of Combustion Dynamics in Lean-Premixed Swirl-Stabilized Combustors  

Microsoft Academic Search

A unified investigation, comprising both numerical simulation and analytical modeling, has been conducted to study the combustion dynamics in lean-premixed (LPM) swirl-stabilized combustors. The numerical analysis treats the conservation equations in three dimensions and takes into account finite-rate chemical reactions and variable thermophysical properties. Turbulence closure is achieved by means of a large-eddy simulation technique. Premixed turbulent combustion is treated

Ying Huang; Vigor Yang

2005-01-01

356

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

357

Combustion response to acoustic perturbation in liquid rocket engines  

Microsoft Academic Search

An experimental study of the effect of acoustic perturbations on combustion behavior of a model liquid propellant rocket engine has been carried out. A pair of compression drivers were used to excite transverse and longitudinal acoustic fields at strengths of up to 156.6 dB and 159.5 dB respectively in the combustion chamber of the experimental rocket engine. Propellant simulants were

Akbar Ghafourian

1993-01-01

358

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

359

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

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

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

1992-01-01

360

Assessment of the combustion model in the HECTR (Hydrogen Event: Containment Transient Response) code  

SciTech Connect

HECTR (Hydrogen Event: Containment Transient Response) is a lumped-parameter containment analysis code developed to model the containment atmosphere during a nuclear reactor accident involving the release, transport, and combustion of hydrogen. A new set of flame speed and combustion completeness correlations has been included in HECTR. The combustion model in HECTR was assessed against a simple two-compartment problem, as well as the NTS (Nevada Test Site) and VGES (Variable Geometry Experimental System) experiments. The example using the two-compartments problem demonstrates that the combustion model in the modified HECTR code is capable of locating the flame position in a compartment with a hydrogen burn, and convecting material with the proper composition instead of a mixture gas through flow junctions. HECTR predictions compare reasonably well with the measured peak pressure ratios for 12 NTS premixed hydrogen experiments. It is concluded that the capability of the new correlations for flame speed and combustion completeness is sufficient for the NTS experiments. Based on the analyses of the NTS and VGES experiments, using a single room as a node is recommended for the nodalization in the HECTR combustion calculation. 16 refs., 17 figs., 7 tabs.

Pong, L.T. (Science Applications International Corp., Albuquerque, NM (USA))

1990-11-01

361

Modelling Of Hindered Crystal Settling-Floating Process In A Magma Chamber  

NASA Astrophysics Data System (ADS)

In interior of magma chamber during the fractional crystallisation, the separation of the minerals can be done by a simple density contrast. The denser minerals sank to the bottom of magma chamber and can formed, later, a cumulate layer. In order to better understand the relations between cumulus texture and evolution of the chemical composition at grain boundaries during the crystal-melt settling-floating process, a series of centrifuge experiments have been carried out. The experiments were conducted in a centrifuging furnace at 1235°C under atmospheric pressure during 6 hours and with an acceleration range between 1g to 1000g of partially molten gabbro samples with the grain size 100?m. Crystals during the centrifuging process have been segregated according to their buoyancy: plagioclase crystals floated to the top and magnetite crystals sank to the bottom of container. The chemical evolution of melt, vertical and horizontal distribution of crystals and melt in the experiments at 100g and 200g is similar. The segregation realized in experiments at 500g and 1000g revealed much worse separation of heavy and light crystals and the melt phase. The vertical evolution of the major and trace elements in the melt phase shows that close to the cumulate layer (between 0 to 2 mm from the bottom) the variation of these elements depends on the distance from the container wall, and becomes constant in the interior of sample. The horizontal evolution shows some variations which appear close to the walls of the capsule and which are due to the wall effect during the centrifuging runs. In order to describe the compaction evolution with time, a numerical modelling of the sedimentation process of the crystals has been build and then compared with the centrifuge modelling. The numerical and centrifuge modelling results agree quite well: the stratification of the compacted layer in the runs is reproduced in numerical models. The settling model of a concentrated suspension can predict a realistic evolution of the cumulus layer compaction for a time scale of several years. The combination of centrifuge experiments and numerical modelling demonstrates that in magma chambers there are correlations between cumulus textures and the evolution of chemical composition at grain boundaries during the stage when crystals come into mechanical contact with each other in a cumulus layer. Finally, formation time and melt fraction evolution of Muskox layered intrusion have been revisited using the hindered sedimentation model calculations. The results on the time formation of the intrusion as well as the porosity loss with time are in agreement with previous results of the compaction model.

Berres, S.; Forien, M.; Bagdassarov, N. S.; Dingwell, D. B.

2011-12-01

362

Torsional vibration analysis of a multi-body single cylinder internal combustion engine model  

Microsoft Academic Search

This paper presents a detailed multi-body numerical nonlinear dynamic model of a single cylinder internal combustion engine. The model comprises all rigid body inertial members, support bearings, joints, couplers, and connections between the various engine components, as well as means of vibration damping. The detailed model is parameterised, thus enabling virtual prototype testing of various engine designs, as well as

A. Boysal; H. Rahnejat

1997-01-01

363

Combustion Theory and Modelling Vol. 12, No. 5, October 2008, 857882  

E-print Network

Combustion Theory and Modelling Vol. 12, No. 5, October 2008, 857­882 Lagrangian investigation the local extinction and re-ignition processes observed in flame E reasonably well. The particle behavior produced by the IEM and modified Curl models is different from that produced by the EMST model, i

364

An idealized model of homogeneous solid propellant combustion  

NASA Technical Reports Server (NTRS)

The idealization of solid propellant combustion which consists of a single condensed-phase reaction and a single gas-phase reaction is discussed. A limiting-case solution to the gas-phase conservation equations is developed and tested by comparison with transformed thermocouple data. Closed-form expressions are derived for the burning rate and temperature sensitivity. Both quantities are linked explicitly to the solid and gas activation energies. It is concluded that the combustion phenomenology associated with the above idealization is still not fully understood. It is suggested that a careful study of the various limiting-case solutions tempered by a small set of numerical benchmark calculations might further such understanding.

Miller, M. S.

1980-01-01

365

Modelling the contribution of biogenic VOCs to new particle formation in the Jülich plant atmosphere chamber  

NASA Astrophysics Data System (ADS)

We used the MALTE-BOX model including near-explicit air chemistry and detailed aerosol dynamics to study the mechanisms of observed new particle formation events in the Jülich Plant Atmosphere Chamber. The modelled and measured H2SO4 (sulfuric acid) concentrations agreed within a factor of two. The modelled total monoterpene concentration was in line with PTR-MS observations, and we provided the distributions of individual isomers of terpenes, when no measurements were available. The aerosol dynamic results supported the hypothesis that H2SO4 is one of the critical compounds in the nucleation process. However, compared to kinetic H2SO4 nucleation, nucleation involving OH oxidation products of monoterpenes showed a better agreement with the measurements, with R2 up to 0.97 between modelled and measured total particle number concentrations. The nucleation coefficient for kinetic H2SO4 nucleation was 2.1 × 10-11 cm3 s-1, while the organic nucleation coefficient was 9.0 × 10-14 cm3 s-1. We classified the VOC oxidation products into two sub-groups including extremely low-volatility organic compounds (ELVOCs) and semi-volatile organic compounds (SVOCs). These ELVOCs and SVOCs contributed approximately equally to the particle volume production, whereas only ELVOCs made the smallest particles to grow in size. The model simulations revealed that the chamber walls constitute a major net sink of SVOCs on the first experiment day. However, the net wall SVOC uptake was gradually reduced because of SVOC desorption during the following days. Thus, in order to capture the observed temporal evolution of the particle number size distribution, the model needs to consider reversible gas-wall partitioning.

Liao, L.; Dal Maso, M.; Mogensen, D.; Roldin, P.; Rusanen, A.; Kerminen, V.-M.; Mentel, T. F.; Wildt, J.; Kleist, E.; Kiendler-Scharr, A.; Tillmann, R.; Ehn, M.; Kulmala, M.; Boy, M.

2014-11-01

366

Numerical study of premixed HCCI engine combustion and its sensitivity to computational mesh and model uncertainties  

NASA Astrophysics Data System (ADS)

This study used a numerical model to investigate the combustion process in a premixed iso-octane homogeneous charge compression ignition (HCCI) engine. The engine was a supercharged Cummins C engine operated under HCCI conditions. The CHEMKIN code was implemented into an updated KIVA-3V code so that the combustion could be modelled using detailed chemistry in the context of engine CFD simulations. The model was able to accurately simulate the ignition timing and combustion phasing for various engine conditions. The unburned hydrocarbon emissions were also well predicted while the carbon monoxide emissions were under predicted. Model results showed that the majority of unburned hydrocarbon is located in the piston-ring crevice region and the carbon monoxide resides in the vicinity of the cylinder walls. A sensitivity study of the computational grid resolution indicated that the combustion predictions were relatively insensitive to the grid density. However, the piston-ring crevice region needed to be simulated with high resolution to obtain accurate emissions predictions. The model results also indicated that HCCI combustion and emissions are very sensitive to the initial mixture temperature. The computations also show that the carbon monoxide emissions prediction can be significantly improved by modifying a key oxidation reaction rate constant.

Kong, Song-Charng; Reitz, Rolf D.

2003-06-01

367

Comparison of Navier-Stokes and DSMC Gas Flow Models in Semiconductor Process Chambers  

NASA Astrophysics Data System (ADS)

Validated, fast turnaround simulations of flows in the transition regime are of significant use as computer-aided design tools for the design of vacuum systems in low-pressure semiconductor processing equipment. This work compares a generic Navier-Stokes flow solution (CFD) using slip boundary conditions to previous simulations from a DSMC code and data taken in an instrumented vacuum test cell typical of semiconductor equipment chambers. The CFD solution matched up as well or better than the previous DSMC simulations at pressures and flows between 1 and 5 millitorr and 100 and 500 SCCM of nitrogen, respectively. This good agreement is seen because even though the mean free path at the lowest pressure is about 5 centimeters, the local Knudsen number is smaller than 0.1 in the flow, which is a generally accepted upper limit for applicability of CFD solutions with slip boundary conditions. Since CFD solutions can be obtained an order of magnitude or more faster than corresponding DSMC solutions, the CFD approach can be used to speed up design turnaround times. Additionally, there are no commercially available DSMC codes with the support and ease-of-use features that are seen in many CFD software packages, which are already in common use in the semiconductor equipment industry. Hence, such a validated CFD approach to computing transition regime flows in vacuum chambers can be seen as a preferred design tool in industrial environments, particularly when models need to be three-dimensional and/or require complex geometrical constructs.

Gochberg, Lawrence. A.

2003-05-01

368

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

369

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

370

Computational Fluid Dynamics Modelling of Residual Fuel Oil Combustion in the Context of Marine Diesel Engines  

Microsoft Academic Search

A simplified model is presented for vaporization and combustion of heavy residual based fuel oil in high-pressure sprays, in the context of marine diesel engines. The fuel is considered as a mix of residual base and cutter stock. The model accounts for multiple fuel components as well as limited diffusion rates and thermal decomposition rates within droplets by the use

L Goldsworthy

2006-01-01

371

INDUSTRIAL COMBUSTION EMISSIONS (ICE) MODEL, VERSION 6.0. USER'S MANUAL  

EPA Science Inventory

The report is a user's manual for the Industrial Combustion Emissions (ICE) model. It summarizes user options and software characteristics, and describes both the input data files and procedures for operating the model. It discusses proper formatting of files and creation of job ...

372

Knock prediction for dual fuel engines by using a simplified combustion model.  

PubMed

The present work used a methane-air mixture chemical kinetics scheme consisting of 119 elementary reaction steps and 41 chemical species to develop a simplified combustion model for prediction of the knock in dual fuel engines. Calculated values by the model for natural gas operation showed good agreement with corresponding experimental values over a broad range of operating conditions. PMID:12958720

Fei, Shao-mei; Liu, Zhen-tao; Yan, Zhao-da

2003-01-01

373

Modeling of combustion instabilities and their active control in a gas fueled combustor  

Microsoft Academic Search

This study deals with the development of simplified models for simulation of combustion instabilities and their active control. Modulation of a part of the fuel supply is used to damp instabilities by generating heat release oscillations that are out of phase with the existing pressure oscillations. A model that accounts for mixing using a heuristic source term has been developed,

Rajendran Mohanraj

1998-01-01

374

Modeling and Numerical Solution of Coal and Natural Gas Co-Combustion in a Rotary Kiln  

Microsoft Academic Search

Due to the great importance of rotary kilns in the cement industry and the fact that these systems are known to be high energy consumers, a model was developed for one of the most important phenomena occurring inside of such kilns, i.e., combustion. This model and its numerical solution allow for carrying out process optimization techniques in order to reduce

Cesar L. Barraza; Antonio J. Bula; Argemiro Palencia

2012-01-01

375

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...

376

A crankshaft system model for structural dynamic analysis of internal combustion engines  

Microsoft Academic Search

A system model for analyzing the dynamic behavior of an internal combustion engine crankshaft is described. The model couples the crankshaft structural dynamics, the main bearing hydrodynamic lubrication and the engine block stiffness using a system approach. A two-level dynamic substructuring technique is used to predict the crankshaft dynamic response based on the finite-element method. The dynamic substructuring uses a

Zissimos P. Mourelatos

2001-01-01

377

REVISION OF THE INDUSTRIAL COMBUSTION EMISSIONS MODEL TO A BASE YEAR OF 1980  

EPA Science Inventory

The report describes the development of an updated 1980 base year fuel consumption and air pollution emissions estimates data base by state. These 1980 base year data have been incorporated into industrial combustion emissions (ICE) model Versions 4.0, 5.0, and 6.0. The model is ...

378

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

379

Rotary internal combustion engine  

SciTech Connect

A rotary internal combustion engine having a housing defining a chamber is disclosed. A fixed shaft extends coaxially through the chamber. A plurality of vanes are pinned to a collar which is rotative about the shaft. One vane is rigidly secured to the collar. A cylindrical drum is positioned in the working chamber with the centerline of the drum radially offset from the centerline of the working chamber. The vanes extend through slots or apertures in the rotor to close proximity with the chamber wall. A fuel delivery system communicates with the chamber through approximately 90 degrees of the compression cycle. An exhaust opening communicates with the chamber at the end of the expansion cycle whereby the compression ratio is substantially less than the expansion ratio. In one embodiment means are provided to vary the compression and expansion ratios.

Crutchfield, M.R.

1980-12-30

380

Carbon deposition model for oxygen-hydrocarbon combustion  

NASA Technical Reports Server (NTRS)

The objectives are to use existing hardware to verify and extend the database generated on the original test programs. The data to be obtained are the carbon deposition characteristics when methane is used at injection densities comparable to full scale values. The database will be extended to include liquid natural gas (LNG) testing at low injection densities for gas generator/preburner conditions. The testing will be performed at mixture ratios between 0.25 and 0.60, and at chamber pressures between 750 and 1500 psi.

Bossard, John A.

1988-01-01

381

TORSIONAL VIBRATION REDUCTION IN INTERNAL COMBUSTION ENGINES USING CENTRIFUGAL PENDULUMS  

Microsoft Academic Search

The goal of the present work is to investigate the performance of tautochronic centrifugal pendulum vibration absorbers (CPVA's) for reducing torsional vibration in internal combustion engines. A mathematical model is first built for the torsional dynamics of an in- line, four-stroke, four-cylinder engine, including the consideration of inertia effects of connecting rods and pistons, gas pressure inside the cylinder chambers,

Cheng-Tang Lee; Steven W. Shaw

382

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

383

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

384

Droplet combustion drop tower tests using models of the space flight apparatus  

NASA Technical Reports Server (NTRS)

An engineering model built for droplet combustion drop tower tests is described. The model was built using a design with mechanical and electrical assemblies of the same level of complexity as they will have in flight. The model was tested for functional operation and integrated into a 5-sec drop tower. Test data obtained to date are presented together with model and test cell diagrams.

Haggard, J. B.; Brace, M. H.; Kropp, J. L.; Dryer, F. L.

1989-01-01

385

Modeling, Dynamic Simulation, and Controller Design for an Air-breathing Combustion System  

Microsoft Academic Search

A novel, high-fidelity, low-order model is developed for an air-breathing combustion system designed for supersonic flight with a subsonic combustor. Individual components - intake, combustor, exhaust nozzle - are modeled with detailed models obtained from CFD, quasi-1D, or isentropic analysis, as the case may be. The components are then interlinked by a low-order global model that captures the physics of

P. Bharani; Chandra Kumar; Nitin K. Gupta; N. Ananthkrishnan; V. S. Renganathan

2009-01-01

386

Modeling of Evaporation and Combustion of Droplets in a Spray Using the Unit Cell Approach: A Review  

Microsoft Academic Search

A comprehensive review of modeling of evaporation and combustion of liquid fuel droplets using “unit cell” approach is presented. The review starts with a general introduction to the different regimes of droplet combustion and a brief overview of other techniques used for evaluating mutual interaction of droplets before presenting the cell model in detail. In this review, the major developments

Achintya Mukhopadhyay; Dipankar Sanyal

2012-01-01

387

Identification of a non-linear internal combustion engine model for on-line indicated torque estimation  

Microsoft Academic Search

In recent years considerable interest has been placed on the estimation of internal combustion engine torque both for control and diagnostic applications. This paper discusses a method for the identification of a non-linear model of the dynamics relating combustion pressure to crankshaft angular velocity. Such a model can be useful in the implementation of control strategies that require an estimate

Giorgio Rizzoni; Yuxuan Zhang

1994-01-01

388

Chemical modelling and measurements of the catalytic combustion of CH 4\\/air mixtures on platinum and palladium catalysts  

Microsoft Academic Search

This work reports experimental measurements and a modelling study carried out on palladium and platinum based catalytic monoliths used as methane combustors for heating purposes. It concentrates on the effects of operating conditions on combustion, heat transfer efficiency and pollutant formation. The development of a detailed homogeneous\\/heterogeneous chemical kinetics model for methane–air combustion over palladium using literature data was undertaken

F. Moallemi; G. Batley; V. Dupont; T. J. Foster; M. Pourkashanian; A. Williams

1999-01-01

389

Transient and translating gas jet modeling for pressure gain combustion applications  

NASA Astrophysics Data System (ADS)

Major mechanisms governing the mixing process of a gas injected into a long confined chamber is analyzed when there's a relative motion between the two. Such applications arise in a wave rotor combustor (WRCVC) where the moving combustion chambers receive gas from stationary injectors for fueling and ignition. Counter rotating vortices govern the mixing process in such problems, which moves across the channel enhancing mixing. The actions of vortices were seen to localize the injected gas in the vicinity of the injector end wall which can prove advantages during fueling to make a rich mixture near the ignition source and during hot gas injection for ignition to minimize the drop of temperature. The vortex structures can alter the exit conditions of the injector due to its strong near field interactions. The confinement is also important in which it suppresses the development and motion of such vortices and hence affect mixing. The thesis discusses several important features in a WRCVC. Namely, the effect of a combustion channel being opened to the preceding exit port prior to its opening to the gas injectors, on mixing of injected gas with channel gases. This prior opening was seen to deposit vorticity on the channel wall which gets convected along them. This convecting vorticity resulted in enhanced jet penetration. The effect of combustible mixture non-uniformity on ignition success of a WRCVC was also analyzed using 2D and 1D computations. The predictions are validated against measured data from a WRCVC test rig. Ignition locations and combustion pressures were successfully predicted. Limited 3D computations of the hot gas jet mixing with the channel gases were carried out and measure temperature data from the WRCVC test rig was used to verify the axial penetration predictions of the jet. A methodology is proposed to quantify the level of mixing and ignition success by comparing the amount of injected gas inside the channel which is above a certain threshold temperature and mass fraction limits, to the total amount of injected mass trapped inside it at that particular time. Conclusions were made on the level of mixing and the 'ignitability' of the mixture by looking at the time variation of these defined quantities.

Wijeyakulasuriya, Sameera Devsritha

390

Development and validation of spray models for investigating diesel engine combustion and emissions  

NASA Astrophysics Data System (ADS)

Diesel engines intrinsically generate NOx and particulate matter which need to be reduced significantly in order to comply with the increasingly stringent regulations worldwide. This motivates the diesel engine manufacturers to gain fundamental understanding of the spray and combustion processes so as to optimize these processes and reduce engine emissions. Strategies being investigated to reduce engine's raw emissions include advancements in fuel injection systems, efficient nozzle orifice design, injection and combustion control strategies, exhaust gas recirculation, use of alternative fuels such as biodiesel etc. This thesis explores several of these approaches (such as nozzle orifice design, injection control strategy, and biodiesel use) by performing computer modeling of diesel engine processes. Fuel atomization characteristics are known to have a significant effect on the combustion and emission processes in diesel engines. Primary fuel atomization is induced by aerodynamics in the near nozzle region as well as cavitation and turbulence from the injector nozzle. The breakup models that are currently used in diesel engine simulations generally consider aerodynamically induced breakup using the Kelvin-Helmholtz (KH) instability model, but do not account for inner nozzle flow effects. An improved primary breakup (KH-ACT) model incorporating cavitation and turbulence effects along with aerodynamically induced breakup is developed and incorporated in the computational fluid dynamics code CONVERGE. The spray simulations using KH-ACT model are "quasi-dynamically" coupled with inner nozzle flow (using FLUENT) computations. This presents a novel tool to capture the influence of inner nozzle flow effects such as cavitation and turbulence on spray, combustion, and emission processes. Extensive validation is performed against the non-evaporating spray data from Argonne National Laboratory. Performance of the KH and KH-ACT models is compared against the evaporating and combusting data from Sandia National Laboratory. The KH-ACT model is observed to provide better predictions for spray dispersion, axial velocity decay, sauter mean diameter, and liquid and lift-off length interplay which is attributed to the enhanced primary breakup predicted by this model. In addition, experimentally observed trends with changing nozzle conicity could only be captured by the KH-ACT model. 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. Finally, the differences in inner nozzle flow and spray characteristics of petrodiesel and biodiesel are quantified. The improved modeling capability developed in this work can be used for extensive diesel engine simulations to further optimize injection, spray, combustion, and emission processes.

Som, Sibendu

391

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

392

Compensating for wall effects in IAQ (indoor air quality) chamber tests by mathematical modeling. Report for June 1986-February 1987  

SciTech Connect

The paper presents mechanistic mathematical models that account for two phenomena: interior surfaces of a state-of-the-art emissions test chamber acting as a transient sink for organic emissions; and the effect of increasing chamber concentration on the emission rate of the source. As a consequence of this mathematical development, a source emission rate as a function of time and a steady-state emission rate factor are given precise definitions. Applications involve modeling 1,4 dichlorobenzene emission from moth crystals, and mixed emissions from latex caulk.

Dunn, J.E.; Tichenor, B.A.

1987-04-01

393

Revision of the conceptual model of combustion mechanism in a liquid-propellant rocket on the basis of the results of highly informative experiments. II. Updating of the model  

Microsoft Academic Search

On the basis of the accumulated experimental data, it is established that gas recirculation in the combustion chamber of a\\u000a liquid-propellant rocket is due not to a single factor (ejection by a fuel injection) but two factors; the second factor is\\u000a the nonequilibrium (over the chamber cross section) distribution of the sources and outflows of gases from the combustion\\u000a process.

V. V. Belyi; D. S. Zhuk; V. V. Solov’ev

1998-01-01

394

Rotary internal combustion engine  

SciTech Connect

This patent describes a rotary internal combustion engine operating on fuel and air, comprising: a housing having a pair of communicating parallel axis rotor chambers; a pair of parallel axis rotors, one in each rotor chamber of the housing, the rotors each having on its outer periphery circumferentially spaced axial teeth with intervening circumferentially spaced axial passages. The rotors are positioned with the teeth and passages of one rotor engaging, respectively, the passages and teeth of the other rotor, and each of the rotors further having an internal chamber surrounding axial generally cylindrical oblique helicoid walls forming a mixer means; mean for introducing a mixture of the fuel and air into the mixer chambers of the rotors whereby rotating of the rotors correspondingly rotates and mixer means to homogenize the mixture to produce a fuel/air mist; means for transferring the mist from the mixer chambers to a predetermined injection point in the rotor chambers of the housing such that the mist is disposed in selected passages of the rotors as the selected passages rotate past the predetermined injection point; means for igniting the mist at a predetermined ignition point in the rotor chambers of the housing. The predetermined ignition point is proximate a combustion chamber formed by interengagement of the teeth of the rotors immediately adjacent the selected passages. Exhaust resulting from ignition of the mist urges expansion of the combustion chamber and causes rotation of the rotors; and means for extracting the exhaust as the selected passages rotate past a predetermined exhaust point in the rotor chambers of the housing. The predetermined exhaust point is located in the rotor chambers such that the selected passages of the rotors rotate past the predetermined exhaust point before rotating past the predetermined injection point.

Kollen, R.H.

1987-01-06

395

Super-resolution non-parametric deconvolution in modelling the radial response function of a parallel plate ionization chamber  

NASA Astrophysics Data System (ADS)

The signal of the dosimetric detector is generally dependent on the shape and size of the sensitive volume of the detector. In order to optimize the performance of the detector and reliability of the output signal the effect of the detector size should be corrected or, at least, taken into account. The response of the detector can be modelled using the convolution theorem that connects the system input (actual dose), output (measured result) and the effect of the detector (response function) by a linear convolution operator. We have developed the super-resolution and non-parametric deconvolution method for determination of the cylinder symmetric ionization chamber radial response function. We have demonstrated that the presented deconvolution method is able to determine the radial response for the Roos parallel plate ionization chamber with a better than 0.5 mm correspondence with the physical measures of the chamber. In addition, the performance of the method was proved by the excellent agreement between the output factors of the stereotactic conical collimators (4-20 mm diameter) measured by the Roos chamber, where the detector size is larger than the measured field, and the reference detector (diode). The presented deconvolution method has a potential in providing reference data for more accurate physical models of the ionization chamber as well as for improving and enhancing the performance of the detectors in specific dosimetric problems.

Kulmala, A.; Tenhunen, M.

2012-11-01

396

Coal-water slurry fuel internal combustion engine and method for operating same  

DOEpatents

An internal combustion engine fueled with a coal-water slurry is described. About 90 percent of the coal-water slurry charge utilized in the power cycle of the engine is directly injected into the main combustion chamber where it is ignited by a hot stream of combustion gases discharged from a pilot combustion chamber of a size less than about 10 percent of the total clearance volume of main combustion chamber with the piston at top dead center. The stream of hot combustion gases is provided by injecting less than about 10 percent of the total coal-water slurry charge into the pilot combustion chamber and using a portion of the air from the main combustion chamber that has been heated by the walls defining the pilot combustion chamber as the ignition source for the coal-water slurry injected into the pilot combustion chamber.

McMillian, Michael H. (Fairmont, WV)

1992-01-01

397

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

398

Kinetic Model for Simulating the Evolution of Particle Size Distributions During Char Combustion  

Microsoft Academic Search

The details of a numerical simulation of particle size distribution evolution during ash-free char oxidation are presented. This work represents the first application of the population balance modeling approach to char combustion, and includes the effects of both oxidation and fragmentation. The simulation consists essentially of a transfer function 'hat determines the evolution of the entire char particle size distribution

D. Dunn-Rankin

1988-01-01

399

An Analytical Model of Solid Propellant Combustion in an Acceleration Field  

Microsoft Academic Search

Abstract-An analytical investigation of an acceleration-induced burning rate increase of solid propellants is presented. The analytical model includes the pit formation on an accelerated combustion surface, the growth of agglomerated globules, the heat feedback by an agglomerated globule and the growth of pits. A set of equations expressing these processes is integrated with respect to burning time in order to

Tohur Mitani; Takashi Niioka

1977-01-01

400

A one-dimensional model of aluminum droplet flow, combustion, and radiation in solid propellants  

Microsoft Academic Search

A one-dimensional model has been developed to describe the combustion, flow, and radiant transport processes by aluminum and alumina particles near the surface of a burning aluminized AP composite solid propellant. The equations of mass, momentum, and energy have been solved to obtain the species concentration, velocity, and temperature profiles near the propellant surface. The de-coupled radiative transfer equation has

M. Q. Brewster; D. L. Parry

1987-01-01

401

Modeling Gas Phase RDX Combustion with Intrinsic Low Dimensional Manifolds 1 Sandeep Singh2  

E-print Network

- ated with full models of gas phase RDX combustion, and thus significantly improve computational a wide variety of thermochemical phenomena, the effects of detailed finite rate chemistry must link between traditional collision-based gas phase chemistry and fundamental fluid mechanics. However

402

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

Microsoft Academic Search

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... Turbulence and combustion models are other sources of differences. In the present work, the impact of these options is investigated for the ONERA ramjet

A. Roux; S. Reichtadt; N. Bertier; L. Y. M. Gicquel; F. Vuillot; T. Poinsot

2008-01-01

403

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

404

Soot particle size modelling in 3D simulations of diesel engine combustion  

Microsoft Academic Search

The present work is focused on multi-dimensional simulations of combustion in diesel engines. The primary objective was to test, in a diesel engine framework, a soot particle size model to represent the carbon particle formation and calculate the corresponding size distribution function. Simulations are performed by means of a parallel version of the KIVA3V numerical code, modified to adopt detailed

V. Fraioli; C. Beatrice; M. Lazzaro

2011-01-01

405

Use of Fractal Geometry to Model Turbulent Combustion in SI Engines  

Microsoft Academic Search

Use of fractal geometry to model the effects of turbulence on flame propagation in an engine is explored using a quasidimensional, 4-stroke, homogeneous charge, SI engine code. This application of fractal geometry requires a new interpretation of the effect of turbulence on the combustion process in an engine. Specifically, flame wrinkling, rather than entrainment, is assumed to be the dominant

YOUNG-WOOK CHIN; RONALD DOUGLAS MATTHEWS; STEVEN P. NICHOLS; THOMAS M. KIEHNE

1992-01-01

406

Modelling of a catalytic plate reactor for dehydrogenation–combustion coupling  

Microsoft Academic Search

Coupling an endothermic with an exothermic reaction in a plate heat exchanger having both sides of the plates covered with appropriate catalysts results in a compact and intensified unit known as catalytic plate reactor (CPR). In this work, catalytic ethane dehydrogenation taking place in a CPR having as heat source catalytic methane combustion is modelled. Reactor behaviour is studied utilising

M. Zanfir; A. Gavriilidis

2001-01-01

407

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

E-print Network

premixed during the ignition delay have been consumed, the rate of heat release is controlled by the rate on the normalized fuel mass fraction is implemented to transition between ignition and combustion. The modeling of new engines through experimental testing alone is prohibitively costly and extremely time consuming

Im, Hong G.

408

Method for combustion of gaseous fuels and flue gases  

Microsoft Academic Search

The invention discloses a method for combustion of gaseous fuels and flue gases in which the heat content of the combustion products is partially recycled to the combustion process by heat exchange with combustion air and\\/or gas, and air and gas are fed to a reaction chamber, where a surface combustion takes place separating air and gas regions, and the

1979-01-01

409

TRACE GAS EMISSIONS IN CHAMBERS: A NON-STEADY-STATE DIFFUSION MODEL  

Technology Transfer Automated Retrieval System (TEKTRAN)

Non-steady-state (NSS) chambers are widely used to measure trace gas emissions from the Earth’s surface in the atmosphere. Unfortunately, traditional interpretations of time-dependent chamber concentrations often systematically underestimate predeployment exchange rates because they do not accuratel...

410

Experimental study and modelling of char combustion under fluidized bed conditions  

NASA Astrophysics Data System (ADS)

The combustion behavior of chars from two Chinese coals has been investigated in a laboratory scale bubbling fluidized bed system in Siegen University, Germany. Experimental equipment and method are introduced. The ‘shrinking-core’ model and the ‘shrinking-particle’ model were employed to evaluate the kinetic parameters. The results indicated that the char conversion process of these two coals can be well described by the two models.

Zhang, Yongzhe; Xu, Xiangdong; Wirsum, Manfred C.; Hamel, Stefan; Fett, Franz N.

1998-12-01

411

DNS-LES Validation of an Algebraic Second-Order-Moment Combustion Model  

Microsoft Academic Search

Direct numerical simulation (DNS) of three-dimensional turbulent reacting channel flows with buoyancy is carried out using a spectral method. Statistical results from the DNS database are used to validate an algebraic second-order-moment sub-grid-scale (ASOM-SGS) combustion model and show that the ASOM-SGS model is reasonable. Furthermore, a methane–air jet flame is simulated by large–eddy simulation (LES) using the ASOM-SGS model and

F. Wang; L. X. Zhou; C. X. Xu; C. K. Chan

2009-01-01

412

Predictive zero-dimensional combustion model for DI diesel engine feed-forward control  

Microsoft Academic Search

An innovative zero-dimensional predictive combustion model has been developed for the estimation of HRR (heat release rate) and in-cylinder pressure traces. This model has been assessed and applied to conventional and PCCI (premixed charge compression ignition) DI diesel engines for model-based feed-forward control purposes.The injection rate profile is calculated on the basis of the injected fuel quantities and on the

Andrea Emilio Catania; Roberto Finesso; Ezio Spessa

2011-01-01

413

Secondary combustion device for woodburning stove  

SciTech Connect

This patent describes in a wood burning stove including an exhaust flue opening, a combustion chamber for primary combustion having an access door, a support for wood to be burned and a primary air inlet means for supplying air to support primary combustion of the wood to produce flue gases containing combustible particulate material, plenum means for directing the flue gases in a direction from the combustion chamber to the flue opening in a preselected path, and secondary combustion means for burning the particulate material in the flue gases before flue gases through the exhaust flue opening. The improvement comprising: the combustion chamber having a flue gas exit opening extending laterally across the top of the combustion chamber and communicating the combustion chamber with the plenum means, an elongated manifold extending laterally across and above the combustion chamber substantially coextensively with the flue gas exit opening, a number of air opening spaced longitudinally along the manifold and facing opposite the direction of the flue gases closely adjacent the flue gas exit opening, and an air inlet means for supplying ambient, secondary combustion air to the manifold for counterflow thereof from the openings into the path of the flue gases in a plurality of distinct jets.

Craver, R.D.

1989-08-08

414

Lagrangian modeling of turbulent spray combustion: application to rocket engines cryogenic conditions  

NASA Astrophysics Data System (ADS)

The present work is concerned with the application of a turbulent two-phase flow combustion model to a spray flame of Liquid Oxygen (LOx) and Gaseous Hydrogen (GH2). The proposed strategy relies on a joint Eulerian-Lagrangian framework. The Probability Density Function (PDF) that characterizes the liquid phase is evaluated by simulating the Williams spray equation [1] thanks to the semifluid approach introduced in [2]. The Lagrangian approach provides the classical exchange terms with the gaseous phase and, especially, several vaporization source terms. They are required to describe turbulent combustion but difficult to evaluate from the Eulerian point of view. The turbulent combustion model retained here relies on the consideration of the mixture fraction to evaluate the local fuel-to-oxidizer ratio, and the oxygen mass fraction to follow the deviations from chemical equilibrium. The difficulty associated with the estimation of a joint scalar PDF is circumvented by invoking the sudden chemistry hypothesis [3]. In this manner, the problem reduces to the estimation of the mixture fraction PDF, but with the influence of the terms related to vaporization that are the source of additional fluctuations of composition. Following the early proposal of [4], these terms are easily obtained from the Lagrangian framework adopted to describe the two-phase flows. The resulting computational model is applied to the numerical simulation of LOx-GH2 spray flames. The test case (Mascotte) is representative of combustion in rocket engine conditions. The results of numerical simulations display a satisfactory agreement with available experimental data.

Izard, J.-F.; Mura, A.

2011-10-01

415

Exposure chamber  

DOEpatents

A chamber for exposing animals, plants, or materials to air containing gases or aerosols is so constructed that catch pans for animal excrement, for example, serve to aid the uniform distribution of air throughout the chamber instead of constituting obstacles as has been the case in prior animal exposure chambers. The chamber comprises the usual imperforate top, bottom and side walls. Within the chamber, cages and their associated pans are arranged in two columns. The pans are spaced horizontally from the walls of the chamber in all directions. Corresponding pans of the two columns are also spaced horizontally from each other. Preferably the pans of one column are also spaced vertically from corresponding pans of the other column. Air is introduced into the top of the chamber and withdrawn from the bottom. The general flow of air is therefore vertical. The effect of the horizontal pans is based on the fact that a gas flowing past the edge of a flat plate that is perpendicular to the flow forms a wave on the upstream side of the plate. Air flows downwardly between the chamber walls and the outer edges of the pan. It also flows downwardly between the inner edges of the pans of the two columns. It has been found that when the air carries aerosol particles, these particles are substantially uniformly distributed throughout the chamber.

Moss, Owen R. (Kennewick, WA)

1980-01-01

416

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

417

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

418

Detailed thermokinetic modelling of alkane autoignition as a tool for the optimization of performance of internal combustion engines  

Microsoft Academic Search

The purpose of this paper is to show how detailed chemical models of combustion processes may be applied to the optimal design of internal combustion engines. Despite the complexity of the low-, intermediate- and high-temperature oxidation mechanisms of hydrocarbon fuels, there is a sufficiently quantitative understanding of the elementary reaction steps involved, and satisfactory kinetic schemes are available, especially for

T. Faravelli; P. Gaffuri; E. Ranzi; J. F. Griffiths

1998-01-01

419

Off-site air monitoring following methyl bromide chamber and building fumigations and evaluation of the ISCST air dispersion model  

SciTech Connect

The Department of Pesticide Regulation`s preliminary risk characterization of methyl bromide indicated an inadequate margin of safety for several exposure scenarios. Characterization of the air concentrations associated with common methyl bromide use patterns was necessary to determine specific scenarios that result in an unacceptable margin of safety. Field monitoring data were used in conjunction with the Industrial Source Complex, Short Tenn (ISCST) air dispersion model to characterize air concentrations associated with various types of methyl bromide applications. Chamber and building fumigations were monitored and modelled. For each fumigation the emission rates, chamber or building specifications and on-site meteorological data were input into the ISCST model. The model predicted concentrations were compared to measured air concentrations. The concentrations predicted by the ISCST model reflect both the pattern and magnitude of the measured concentrations. Required buffer zones were calculated using the ISCST output.

Barry, T.; Swgawa, R.; Wofford, P. [Cal EPA, Sacramento, CA (United States)] [and others

1995-12-31

420

Reduced-order modeling and active control of dry-low-emission combustion  

NASA Astrophysics Data System (ADS)

This dissertation is a complementary experimental and theoretical investigation of combustion instability and lean blowout (LBO) in dry-low-emission (DLE) gas turbine engines, aiming to understand the fundamental mechanisms and shed light on active combustion control. Combustion instability involves complicated physicochemical processes, and many of the underlying mechanisms remain unknown, despite extensive research in the past several decades. A practical control system must be able to achieve satisfactory control performances in the presence of large uncertainties, large variations, and even unknown system dynamics. Toward this goal, an observer-based controller, capable of attenuating multiple unstable modes with unknown characteristics, is developed. A mechanism suitable for online prediction of the safety margin to the onset of combustion instability is presented, which does not require knowing the unstable frequencies. The shortage of a reliable, high-frequency, proportional fuel actuator is a major technical challenge for active combustion control. A complementary theoretical and experimental study is performed on a pump-style, high-frequency, magnetostrictive fuel actuator. Improvements to the fuel setup have been made according to the model predictions, which have been experimentally shown to be beneficial to combustion instability control. The second part of this dissertation is about modeling, prediction, and control of lean blowout. The experimentally observed, "intensified", low frequency, near-LBO combustion oscillations have been used as incipient LBO precursors, and are characterized as low-dimension chaotic behavior in the present study. The normalized chemiluminescence RMS and the normalized cumulative duration of LBO precursor events are recommended for LBO prediction in generic gas turbine engines. Linear stability analysis shows that, with decreasing equivalence ratios, a complex conjugate pair of eigenvalues emerges from three negative real ones, moves left toward the right half phase plane, and finally crosses the imaginary axis. Model predictions qualitatively and even quantitatively match the experiments. Simulation of the nonlinear WSR models shows the "triggered instability" which is similar to that in rocket motors. It is numerically demonstrated that zero-mean small-amplitude fuel modulations based on modern feedback control principles, can be very effective in strengthening the flame's robustness to external disturbances without exacerbating the overall emissions. Experimental demonstrations are suggested for future research.

Yi, Tongxun

421

A Pore-Network Model of In-Situ Combustion in Porous Media  

SciTech Connect

This report the use of dual pore networks (pores and solid sites) for modeling the effect of the microstructure on combustion processes in porous media is considered. The model accounts for flow and transport of the gas phase in the porespace, where convection predominates, and for heat transfer by conduction in the solid phase. Gas phase flow in the pore and throats is governed by Darcy's law.

Lu, Chuan; Yortsos, Y.C.

2001-01-29

422

Challenges in understanding and predictive model development of plasma-assisted combustion  

NASA Astrophysics Data System (ADS)

The key challenges to quantitative insight into fuel–air plasma kinetics, as well as plasma-assisted ignition and flameholding, are identified and assessed based on the results of recent experimental and kinetic modeling studies. Experimental and modeling approaches to address these critical issues are discussed. The results have major implications for the fundamental understanding of pulsed electric discharge dynamics, molecular energy transfer in reacting flows, plasma chemical reactions, and development of low-temperature plasma-assisted combustion technologies.

Adamovich, Igor V.; Lempert, Walter R.

2015-01-01

423

Flamelet modelling of non-premixed turbulent combustion with local extinction and re-ignition  

Microsoft Academic Search

Extinction and re-ignition in non-premixed turbulent combustion is investigated. A flamelet formulation accounting for transport along mixture fraction iso-surfaces is developed. A new transport term appears in the flamelet equations, which is modelled by a stochastic mixing approach. The timescale appearing in this model is obtained from the assumption that transport at constant mixture fraction is only caused by changes

Heinz Pitsch; Chong M. Cha; Sergei Fedotov

2003-01-01

424

PROGRESS IN DETAILED KINETIC MODELING OF THE COMBUSTION OF OXYGENATED COMPONENTS OF BIOFUELS  

PubMed Central

Due to growing environmental concerns and diminishing petroleum reserves, a wide range of oxygenated species has been proposed as possible substitutes to fossil fuels: alcohols, methyl esters, acyclic and cyclic ethers. After a short review the major detailed kinetic models already proposed in the literature for the combustion of these molecules, the specific classes of reactions considered for modeling the oxidation of acyclic and cyclic oxygenated molecules respectively, are detailed. PMID:23700355

Sy Tran, Luc; Sirjean, Baptiste; Glaude, Pierre-Alexandre; Fournet, René; Battin-Leclerc, Frédérique

2013-01-01

425

Combustion Instability in an Acid-Heptane Rocket with a Pressurized-Gas Propellant Pumping System  

NASA Technical Reports Server (NTRS)

Results of experimental measurements of low-frequency combustion instability of a 300-pound thrust acid-heptane rocket engine were compared to the trends predicted by an analysis of combustion instability in a rocket engine with a pressurized-gas propellant pumping system. The simplified analysis, which assumes a monopropellant model, was based on the concept of a combustion the delay occurring from the moment of propellant injection to the moment of propellant combustion. This combustion time delay was experimentally measured; the experimental values were of approximately half the magnitude predicted by the analysis. The pressure-fluctuation frequency for a rocket engine with a characteristic length of 100 inches and operated at a combustion-chamber pressure of 280 pounds per square inch absolute was 38 cycles per second; the analysis indicated. a frequency of 37 cycles per second. Increasing combustion-chamber characteristic length decreased the pressure-fluctuation frequency, in conformity to the analysis. Increasing the chamber operating pressure or increasing the injector pressure drop increased the frequency. These latter two effects are contrary to the analysis; the discrepancies are attributed to the conflict between the assumptions made to simplify the analysis and the experimental conditions. Oxidant-fuel ratio had no apparent effect on the experimentally measured pressure-fluctuation frequency for acid-heptane ratios from 3.0 to 7.0. The frequencies decreased with increased amplitude of the combustion-chamber pressure variations. The analysis indicated that if the combustion time delay were sufficiently short, low-frequency combustion instability would be eliminated.

Tischler, Adelbert O.; Bellman, Donald R.

1951-01-01

426

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

427

Solid Propellant Microthrusters on Silicon: Design, Modeling, Fabrication, and Testing  

Microsoft Academic Search

The design, modeling, fabrication, and characterization of solid propellant microthrusters for space application is presented. The operational concept of solid propellant thruster is simply based on the combustion of a solid energetic material stored in a micromachined chamber. Each thruster contains four main parts (nozzle, heater, chamber, seal). Thrusters presented in this paper have a chamber area of 2.25 mm2.

Carole Rossi; Benoît Larangot; Phuong-Quyen Pham; Danick Briand; Nicolass F. de Rooij; Manel Puig-Vidal; Josep Samitier

2006-01-01

428

Improved Modeling of Finite-Rate Turbulent Combustion Processes in Research Combustors  

NASA Technical Reports Server (NTRS)

The objective of this thesis is to further develop and test a stochastic model of turbulent combustion in recirculating flows. There is a requirement to increase the accuracy of multi-dimensional combustion predictions. As turbulence affects reaction rates, this interaction must be more accurately evaluated. In this work a more physically correct way of handling the interaction of turbulence on combustion is further developed and tested. As turbulence involves randomness, stochastic modeling is used. Averaged values such as temperature and species concentration are found by integrating the probability density function (pdf) over the range of the scalar. The model in this work does not assume the pdf type, but solves for the evolution of the pdf using the Monte Carlo solution technique. The model is further developed by including a more robust reaction solver, by using accurate thermodynamics and by more accurate transport elements. The stochastic method is used with Semi-Implicit Method for Pressure-Linked Equations. The SIMPLE method is used to solve for velocity, pressure, turbulent kinetic energy and dissipation. The pdf solver solves for temperature and species concentration. Thus, the method is partially familiar to combustor engineers. The method is compared to benchmark experimental data and baseline calculations. The baseline method was tested on isothermal flows, evaporating sprays and combusting sprays. Pdf and baseline predictions were performed for three diffusion flames and one premixed flame. The pdf method predicted lower combustion rates than the baseline method in agreement with the data, except for the premixed flame. The baseline and stochastic predictions bounded the experimental data for the premixed flame. The use of a continuous mixing model or relax to mean mixing model had little effect on the prediction of average temperature. Two grids were used in a hydrogen diffusion flame simulation. Grid density did not effect the predictions except for peak temperature and tangential velocity. The hybrid pdf method did take longer and required more memory, but has a theoretical basis to extend to many reaction steps which cannot be said of current turbulent combustion models.

VanOverbeke, Thomas J.

1998-01-01

429

A new modeling approach of pressure waves at the inlet of internal combustion engines  

NASA Astrophysics Data System (ADS)

This paper presents a new model used to describe the propagation of pressure waves at the inlet systems of internal combustion engine. In the first part, an analogy is made between the compressible air in a pipe and a mechanical ideal mass damper spring system. A new model is then presented and the parameters of this model are determined by the use of an experimental setup (shock tube test bench). With this model, a transfer function is defined in order to link directly the pressure and the air mass flow rate. In the second part, the model is included into an internal combustion engine simulation code. The results obtained with this code are compared to experimental ones which are measured on a one-cylinder engine test bench. This last one is driven by an electric motor in order to study only the effect of the pressure waves on the engine behavior. A good agreement is obtained between the experimental results and the numerical ones and the new approach is an alternative method for modeling the pressure wave phenomena in an internal combustion engine manifold.

Chalet, David; Mahé, Alexandre; Hétet, Jean-François; Migaud, Jérôme

2011-06-01

430

Combustion noise and combustion instabilities in propulsion systems  

NASA Technical Reports Server (NTRS)

This paper is concerned with some aspects of non-linear behavior of unsteady motions in combustion chambers. The emphasis is on conditions under which organized oscillations having discrete frequencies may exist in the presence of random motions. In order to treat the two types of motions together, and particularly to investigate coupling between noise and combustion instabilities, the unsteady field is represented as a synthesis of acoustic modes having time-varying amplitudes. Each of the amplitudes are written as the sum of two parts, one associated with the random field and the remainder representing the organized oscillations. After spatial averaging, the general problem is reduced to solution of a set of second-order ordinary differential equations whose structure depends on the sorts of nonlinear processes accounted for. This formulation accommodates any physical process; in particular, terms are included to represent noise sources, although only limited modeling is discussed. Our results suggest that random sources of noise have only small effects on combustion instabilities and seem not to be a cause of unstable motions. However, the coupling between the two sorts of unsteady motions may be important as an essential process in a proposed scheme for noise control. It is now a familiar observation that many nonlinear deterministic systems are capable of exhibiting apparently random motions called 'chaos.' This is a particularly interesting possibility for systems which also executed non-deterministic random motions. In combustion chambers, a nonlinear deterministic system (acoustical motions) exists in the presence of noise produced by flow separation, turbulent motions, and energy released by combustion processes. The last part of the paper is directed to the matter of discovering whether or not chaotic motions exist in combustion systems. Analysis has not progressed sufficiently far to answer the question. We report here recent results of processing data taken in one combustor to determine the dimensions of any attractors in the motions. No evidence has been found for chaos in the strict sense, but the method seems to be an important means of investigating the nonlinear behavior of combustion systems.

Culick, F. E. C.; Paparizos, L.; Sterling, J.; Burnley, V.

1992-01-01

431

Combustion noise and combustion instabilities in propulsion systems  

NASA Astrophysics Data System (ADS)

This paper is concerned with some aspects of non-linear behavior of unsteady motions in combustion chambers. The emphasis is on conditions under which organized oscillations having discrete frequencies may exist in the presence of random motions. In order to treat the two types of motions together, and particularly to investigate coupling between noise and combustion instabilities, the unsteady field is represented as a synthesis of acoustic modes having time-varying amplitudes. Each of the amplitudes are written as the sum of two parts, one associated with the random field and the remainder representing the organized oscillations. After spatial averaging, the general problem is reduced to solution of a set of second-order ordinary differential equations whose structure depends on the sorts of nonlinear processes accounted for. This formulation accommodates any physical process; in particular, terms are included to represent noise sources, although only limited modeling is discussed. Our results suggest that random sources of noise have only small effects on combustion instabilities and seem not to be a cause of unstable motions. However, the coupling between the two sorts of unsteady motions may be important as an essential process in a proposed scheme for noise control. It is now a familiar observation that many nonlinear deterministic systems are capable of exhibiting apparently random motions called 'chaos.' This is a particularly interesting possibility for systems which also executed non-deterministic random motions. In combustion chambers, a nonlinear deterministic system (acoustical motions) exists in the presence of noise produced by flow separation, turbulent motions, and energy released by combustion processes. The last part of the paper is directed to the matter of discovering whether or not chaotic motions exist in combustion systems. Analysis has not progressed sufficiently far to answer the question. We report here recent results of processing data taken in one combustor to determine the dimensions of any attractors in the motions. No evidence has been found for chaos in the strict sense, but the method seems to be an important means of investigating the nonlinear behavior of combustion systems.

Culick, F. E. C.; Paparizos, L.; Sterling, J.; Burnley, V.

1992-04-01

432

Assessment of the GECKO-A modeling tool using chamber observations for C12 alkanes  

NASA Astrophysics Data System (ADS)

Secondary Organic Aerosol (SOA) production and ageing is the result of atmospheric oxidation processes leading to the progressive formation of organic species with higher oxidation state and lower volatility. Explicit chemical mechanisms reflect our understanding of these multigenerational oxidation steps. Major uncertainties remain concerning the processes leading to SOA formation and the development, assessment and improvement of such explicit schemes is therefore a key issue. The development of explicit mechanism to describe the oxidation of long chain hydrocarbons is however a challenge. Indeed, explicit oxidation schemes involve a large number of reactions and secondary organic species, far exceeding the size of chemical schemes that can be written manually. The chemical mechanism generator GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) is a computer program designed to overcome this difficulty. GECKO-A generates gas phase oxidation schemes according to a prescribed protocol assigning reaction pathways and kinetics data on the basis of experimental data and structure-activity relationships. In this study, we examine the ability of the generated schemes to explain SOA formation observed in the Caltech Environmental Chambers from various C12 alkane isomers and under high NOx and low NOx conditions. First results show that the model overestimates both the SOA yields and the O/C ratios. Various sensitivity tests are performed to explore processes that might be responsible for these disagreements.

Aumont, B.; La, S.; Ouzebidour, F.; Valorso, R.; Mouchel-Vallon, C.; Camredon, M.; Lee-Taylor, J. M.; Hodzic, A.; Madronich, S.; Yee, L. D.; Loza, C. L.; Craven, J. S.; Zhang, X.; Seinfeld, J.

2013-12-01

433

A comprehensive model for pilot-ignited, coal-water mixture combustion in a direct-injection diesel engine  

SciTech Connect

This paper reports on a combustion model developed for a direct-injected diesel engine fueled with coal-water slurry mixture (CWM) and assisted by diesel pilot injection. The model combines the unique heat and mass transport and chemical kinetic processes of CWM combustion with the normal in-cylinder processes of a diesel engine. It includes a two-stage evaporation submodel for the drying of the CWM droplet, a global kinetic submodel for devolatilization, and a char combustion submodel describing surface gasification by oxygen, carbon dioxide, and water vapor. The combustion volume is discretized into multiple zones, each of whose individual thermochemistry is determined by in-situ equilibrium calculations. This provides an accurate determination of the boundary conditions for the CWM droplet combustion submodels and the gas phases heat release.

Wahiduzzaman, S.; Blumberg, P.N.; Keribar, R.; Rackmil, C.I. (Ricardo-ITI, Inc., Westmont, IL (US))

1990-07-01

434

A flammability and combustion model for integrated accident analysis. [Advanced light water reactors  

SciTech Connect

A model for flammability characteristics and combustion of hydrogen and carbon monoxide mixtures is presented for application to severe accident analysis of Advanced Light Water Reactors (ALWR's). Flammability of general mixtures for thermodynamic conditions anticipated during a severe accident is quantified with a new correlation technique applied to data for several fuel and inertant mixtures and using accepted methods for combining these data. Combustion behavior is quantified by a mechanistic model consisting of a continuity and momentum balance for the burned gases, and considering an uncertainty parameter to match the idealized process to experiment. Benchmarks against experiment demonstrate the validity of this approach for a single recommended value of the flame flux multiplier parameter. The models presented here are equally applicable to analysis of current LWR's. 21 refs., 16 figs., 6 tabs.

Plys, M.G.; Astleford, R.D.; Epstein, M. (Fauske and Associates, Inc., Burr Ridge, IL (USA))

1988-01-01

435

Evaluation of Impinging Stream Vortex Chamber Concepts for Liquid Rocket Engine Applications  

NASA Technical Reports Server (NTRS)

To pursue technology developments for future launch vehicles, NASA/Marshall Space Flight Center (MSFC) is examining vortex chamber concepts for liquid rocket engine applications. Past studies indicated that the vortex chamber schemes potentially have a number of advantages over conventional chamber methods. Due to the nature of the vortex flow, relatively cooler propellant streams tend to flow along the chamber wall. Hence, the thruster chamber can be operated without the need of any cooling techniques. This vortex flow also creates strong turbulence, which promotes the propellant mixing process. Consequently, the subject chamber concepts not only offer system simplicity, but also enhance the combustion performance. Test results have shown that chamber performance is markedly high even at a low chamber length-to-diameter ratio (LD). This incentive can be translated to a convenience in the thrust chamber packaging. Variations of the vortex chamber concepts have been introduced in the past few decades. These investigations include an ongoing work at Orbital Technologies Corporation (ORBITEC). By injecting the oxidizer tangentially at the chamber convergence and fuel axially at the chamber head end, Knuth et al. were able to keep the wall relatively cold. A recent investigation of the low L/D vortex chamber concept for gel propellants was conducted by Michaels. He used both triplet (two oxidizer orifices and one fuel orifice) and unlike impinging schemes to inject propellants tangentially along the chamber wall. Michaels called the subject injection scheme an Impinging Stream Vortex Chamber (ISVC). His preliminary tests showed that high performance, with an Isp efficiency of 9295, can be obtained. MSFC and the U. S. Army are jointly investigating an application of the ISVC concept for the cryogenic oxygen/hydrocarbon propellant system. This vortex chamber concept is currently tested with gel propellants at AMCOM at Redstone Arsenal, Alabama. A version of this concept for the liquid oxygen (LOX) hydrocarbon fuel (RP-1) system has been derived from the one for the gel propellant. An unlike impinging injector was employed to deliver the propellants to the chamber. MSFC is also conducting an alternative injection scheme, called the chasing injector, associated with this vortex chamber concept. In this injection technique, both propellant jets and their impingement point are in the same chamber cross-sectional plane. Long duration tests (approximately up to 15 seconds) will be conducted on the ISVC to study the thermal effects. This paper will report the progress of the subject efforts at NASA Marshall Space Flight Center. Thrust chamber performance and thermal wall compatibility will be evaluated. The chamber pressures, wall temperatures, and thrust will be measured as appropriate. The test data will be used to validate CFD models, which, in turn, will be used to design the optimum vortex chambers. Measurements in the previous tests showed that the chamber pressures vary significantly with radius. This is due to the existence of the vortices in the chamber flow field. Hence, the combustion efficiency may not be easily determined from chamber pressure. For this project, measured thrust data will be collected. The performance comparison will be in terms of specific impulse efficiencies. In addition to the thrust measurements, several pressure and temperature readings at various locations on the chamber head faceplate and the chamber wall will be made. The first injector and chamber were designed and fabricated based on the available data and experience gained during gel propellant system tests by the U.S. Army. The alternate injector for the ISVC was also fabricated. Hot-fire tests of the vortex chamber are about to start and are expected to complete in February of 2003 at the TS115 facility of MSFC.

Trinh, Huu P.; Bullard, Brad; Kopicz, Charles; Michaels, Scott

2002-01-01

436

High velocity combustion furnace and burner  

SciTech Connect

A new high-velocity combustion system for heat-treating or forging furnaces improves upon prior designs in that it needs only a small combustion chamber and that several nozzles can be housed in a common air manifold. The combustion air is sufficiently pressurized to create a high flue-gas velocity that causes a backpressure within the combustion chamber, thus reducing the volume of space required in the chamber, bringing the refractory closer to the work piece, shortening the heat-treating time, and increasing the thermal load on the work pieces.

McElroy, J.G.

1982-01-05

437

A particulate model of solid waste incineration in a fluidized bed combining combustion and heavy metal vaporization  

SciTech Connect

This study aims to develop a particulate model combining solid waste particle combustion and heavy metal vaporization from burning particles during MSW incineration in a fluidized bed. The original approach for this model combines an asymptotic combustion model for the carbonaceous solid combustion and a shrinking core model to describe the heavy metal vaporization. A parametric study is presented. The global metal vaporization process is strongly influenced by temperature. Internal mass transfer controls the metal vaporization rate at low temperatures. At high temperatures, the chemical reactions associated with particle combustion control the metal vaporization rate. A comparison between the simulation results and experimental data obtained with a laboratory-scale fluid bed incinerator and Cd-spiked particles shows that the heavy metal vaporization is correctly predicted by the model. The predictions are better at higher temperatures because of the temperature gradient inside the particle. Future development of the model will take this into account. (author)

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