Note: This page contains sample records for the topic model combustion chamber from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Optimization of Combustion Chamber for Diesel Engine Using Kriging Model  

NASA Astrophysics Data System (ADS)

Diesel engine combustion chamber which reduces exhaust emission has been designed using CFD analysis and optimization techniques. In order to save computational time for design, the Kriging model, one of the response surface models, is adopted here. For a robust exploration, both the estimated function value of the model and its uncertainty are considered at the same time. In the present problem, the k-means method is used to limit the number of additional sample points to a reasonable level. Among the additional sample points, two combustion chamber shapes dominate the baseline configuration in terms of all objective functions. Compared with the previous optimization with the evolutionary algorithm, its computational time for design was cut by 95%. The results indicate that the present method is a practical approach for real-world applications.

Jeong, Shinkyu; Minemura, Youichi; Obayashi, Shigeru

2

Flow measurements in a model ramjet secondary combustion chamber  

Microsoft Academic Search

Experimental studies were conducted on a typical secondary combustion chamber of a ramjet to understand the influence of various inlet parameters such as primary nozzle configuration, secondary air injection angle, and flow Reynolds numbers on the secondary combustion chamber (SCC) performance. Cold flow studies were made with air as the flow medium for both primary and secondary jets followed by

Lazar T. Chittilapilly; S. Venkateswaran; P. J. Paul; H. S. Mukunda

1990-01-01

3

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

4

Flow measurements in a model ramjet secondary combustion chamber  

SciTech Connect

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

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

1990-12-01

5

Evaporation and ignition of droplets in combustion chambers modeling and simulation  

Microsoft Academic Search

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

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

6

Comprehensive Fuel Spray Modeling and Impacts on Chamber Acoustics in Combustion Dynamics Simulations.  

National Technical Information Service (NTIS)

The current study focuses on comprehensive fuel spray modeling and its effects on chamber acoustics in combustion dynamics simulations. The fuel spray is modeled using an Eulerian-Lagrangian approach describing the atomizer internal flow, primary atomizat...

C. Yoon R. Gejji V. Sankaran W. E. Anderson

2013-01-01

7

Rocket Combustion Chamber Coating  

NASA Technical Reports Server (NTRS)

A coating with the ability to protect (1) the inside wall (i.e., lining) of a rocket engine combustion chamber and (2) parts of other apparatuses that utilize or are exposed to combustive or high temperature environments. The novelty of this invention lies in the manner a protective coating is embedded into the lining.

Holmes, Richard R. (Inventor); McKechnie, Timothy N. (Inventor)

2001-01-01

8

Acoustoelastic Interaction in Combustion Chambers: Modeling and Experiments  

Microsoft Academic Search

To decrease NOx emissions from combustion systems, lean premixed combustion is used. A disadvantage is the higher sensitivity to combustion instabilities, leading to increased sound pressure levels in the combustor and resulting in an increased excitation of the surrounding structure: the liner. This causes fatigue, which limits the lifetime of the combustor. This paper presents a joint experimental and numerical

R. A. Huls; Kampen van J. F; Hoogt van der P. J. M; J. B. W. Kok; A. de Boer

2008-01-01

9

Engine combustion chamber structure  

SciTech Connect

This patent describes a combustion chamber structure comprising an upper wall surface which is shaped like a pent-roof and into which an intake passage opens, a piston having on a head portion thereof a bulged portion conforming to the upper wall surface in shape, a first bowl portion which is formed substantially at the center of the bulged portion and which is substantially semispherical in shape, a pair of second bowl portions which respectively extend on opposite sides of the first bowl portion to the corresponding ends of the bulged portion of the piston along the edge of the bulged portion and are in communication with the first bowl portion, a swirl generating means which is adapted to generate a swirl of intake air in the combustion chamber when the engine load is light, and a spark plug disposed to substantially face the center of the first bowl portion from the upper wall surface; the swirl generating means being adapted to generate the swirl of intake air in a tangential direction in the combustion chamber; and the diameter of the first bowl portion being larger than the width of the second bowl portion.

Tanaka, H.

1988-09-13

10

Modeling the Combustion Chamber Dynamics of Selectable-Thrust Rocket Motors  

Microsoft Academic Search

Challenge Project C4C is dedicated to developing and applying high-performance computing capabilities to accelerate the development of hypergolic and hybrid rocket engine concepts. Computational fluid dynamics is employed to model chemically-reacting flows within engine combustion chambers, and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments are presented and discussed.

Michael J. Nusca; Chiung-Chu Chen; Michael J. McQuaid

2010-01-01

11

Modeling of gas dynamics in a pulse combustion chamber to predict initial drying process parameters  

Microsoft Academic Search

A mathematical model of gas-dynamical processes in a pulse combustion chamber for drying of materials is formulated with regard for the second viscosity. Results of numerical solution of the gas-dynamical problem are reported. In particular, it is shown that the time dependences of the gas pressure and velocity represent sinusoidal plots with a phase shift. Introduction of the dissipation term

P. S. Kuts; P. V. Akulich; N. N. Grinchik; C. Strumillo; I. Zbici?ski; E. F. Nogotov

2002-01-01

12

Two-dimensional model for the two-phase flow simulation in a viking rocket engine combustion chamber  

Microsoft Academic Search

We have presented here a two-dimensional model for the two-phase flow simulation in a VIKING rocket engine combustion chamber. This model allows the transient flow description and shows the chamber unsteady response to combustion. Several calculations have been performed and the injection parameters influence on the flow pattern has been studied, as the concentration distribution of droplets, frequency and damping

M. Habiballah; H. Monin

1985-01-01

13

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

NASA Astrophysics Data System (ADS)

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

Isella, Giorgio Carlo

14

Heat transfer in combustion chambers  

NASA Astrophysics Data System (ADS)

This paper is dedicated to reviewing and assessing the various models, embodied in a calculation procedure, that are employed in order to calculate heat transfer characteristics (the flux models, the Spherical Harmonics model, the Discrete Ordinate model, etc). The calculation procedure solves the governing conservation equation of mass, momentum and energy, expressed in a finite difference form, and employs a two-equation turbulence model and a reaction model. Calculated results obtained using the flux and the Discrete Ordinate models were compared with experimental data for three furnaces. The resulting agreement promises greater economy and better performance in furnaces and combustion chambers.

Khalil, E. E.

1984-06-01

15

Internal combustion engine with dual combustion chambers  

Microsoft Academic Search

This patent describes a spark-ignition. The overhead valve type internal combustion engine comprises: a cylinder closed at the top by a semi-spherical cylinder head; a piston reciprocating within the cylinder with the piston; cylinder and cylinder head defining at least one combustion chamber; and wherein the cylinder head includes an intake valve aperture, an exhaust valve aperture, and a spark

Simay

1987-01-01

16

Evaluation of multi-dimensional flux models for radiative transfer in combustion chambers: A review  

NASA Astrophysics Data System (ADS)

In recent years, flux methods have been widely employed as alternative, albeit intrinsically less accurate, procedures to the zone or Monte Carlo methods in complete prediction procedures. Flux models of radiation fields take the form of partial differential equations, which can conveniently and economically be solved simultaneously with the equations representing flow and reaction. The flux models are usually tested and evaluated from the point of view of predictive accuracy by comparing their predictions with "exact' values produced using the zone or Monte Carlo models. Evaluations of various multi-dimensional flux-type models, such as De Marco and Lockwood, Discrete-Ordinate, Schuster-Schwarzschild and moment, are reviewed from the points of view of both accuracy and computational economy. Six-flux model of Schuster-Schwarzschild type with angular subdivisions related to the enclosure geometry is recommended for incorporation into existing procedures for complete mathematical modelling of rectangular combustion chambers.

Selcuk, N.

1984-01-01

17

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

18

Numerical modelization of a combustion chamber by an assembly of elementary reactors  

NASA Astrophysics Data System (ADS)

Present numerical 2D (TEACH) or 3D (DIAMANT) codes, solving average Navier-Stokes equations, give mean flow characterisation within a combustor. This paper presents some developpements using numerical tracers in order to modelize the turbulent internal flow inside a combustor as an association of elementary reactors: Perfectly Stired Reactor (PSR) and Plug Flow Reactor (PFR). By the resolution of a scalar transport equation it was possible to modelize the tracer behaviour. This first step of the study has shown that the scheme used was very important. This transport equation has been used to compute the mean residence time of the gas phase in some zone of interest in different geometries (2D plane, 2D axisymmetric, 3D). These results will be compared with experimental results. Additional techniques have been developped to compute the mass flow rate between elementary reactors. Finally, these techniques will be applied to a real combustion chamber modelization.

Capdeville, D.; Hebrard, P.; Lavergne, G.

19

Internal combustion engine with dual combustion chambers  

SciTech Connect

This patent describes a spark-ignition. The overhead valve type internal combustion engine comprises: a cylinder closed at the top by a semi-spherical cylinder head; a piston reciprocating within the cylinder with the piston; cylinder and cylinder head defining at least one combustion chamber; and wherein the cylinder head includes an intake valve aperture, an exhaust valve aperture, and a spark plug aperture; a spark plug within the spark plug aperture; and an intake valve and an exhaust valve mounted for reciprocation within the intake valve aperture and the exhaust valve aperture, respectively, with the valves having heads seated on the apertures and opening towards the piston.

Simay, S.

1987-06-02

20

Combustion chamber analysis code  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

21

Investigation into the structure of a swirling flow in a model of a vortex combustion chamber by laser doppler anemometry  

NASA Astrophysics Data System (ADS)

The structure of an isothermal swirling flow is investigated experimentally in a model of a vortex combustion chamber with a horizontal rotation axis and a distributed input of air-fuel jets. The averaged and pulsation characteristics of the velocity field in various sections of the model are measured using laser Doppler anemometry. The features of internal aerodynamics of a new design of a steam-generator firebox are analyzed.

Anufriev, I. S.; Anikin, Yu. A.; Fil'kov, A. I.; Loboda, E. L.; Agafontseva, M. V.; Kasymov, D. P.; Tizilov, A. S.; Astanin, A. V.; Pesterev, A. V.; Evtyushkin, E. V.

2013-01-01

22

High-Pressure Promoted-Combustion Chamber  

NASA Technical Reports Server (NTRS)

Proposed combustion-testing chamber burns specimens of materials in fully contained, high-pressure oxygen atmosphere. Test operator uses handles on threaded retaining rings to attach or remove top or bottom plates sealing combustion chamber. Tests conducted in static or flowing oxygen. Oxygen inlet and outlet far enough above burning specimen, little danger of entrainment of burning fragments in oxygen flowing out.

Rucker, Michelle A.; Stoltzfus, Joel M.

1990-01-01

23

External combustion engine having a combustion expansion chamber  

NASA Astrophysics Data System (ADS)

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

Duva, Anthony W.

1993-03-01

24

Gas Turbine Combustion Chambers with Film Evaporation.  

National Technical Information Service (NTIS)

The paper reports on an attempt to apply Meurer's film vaporization combustion method (M-method), originally developed for diesel motors, to the combustion chambers of gas turbines. (In the M-method, instead of distributing the fuel in the air, it is laid...

A. W. Hussmann

1968-01-01

25

Ribbed Coolant Liners for Combustion Chambers  

NASA Technical Reports Server (NTRS)

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

Wagner, W. R.

1984-01-01

26

Uniform Effusion Cooling Method for a Can Combustion Chamber.  

National Technical Information Service (NTIS)

A dome for a combustion chamber may have a plurality of effusion holes therein to provide efficient cooling while preventing carbon formation on the dome and chamber walls of the combustion chamber. Conventional dome cooling designs, using dome louvers, f...

L. D. Nguyen S. Kujala G. Walhhood L. Critchely G. O. Woodcock

2004-01-01

27

Internal combustion engine with multiple combustion chambers  

Microsoft Academic Search

This patent describes a two-cycle compression ignition engine. It comprises one cylinder, a reciprocable piston moveable in the cylinder, a piston connecting rod, a crankshaft for operation of the piston connecting rod, a cylinder head enclosing the cylinder, the upper surface of the piston and the enclosing surface of the cylinder head defining a cylinder clearance volume, a first combustion

Gruenwald

1992-01-01

28

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

29

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

30

GRCop-84 Development for Combustion Chamber Liners  

NASA Technical Reports Server (NTRS)

The development, test, and thermophysical & mechanical properties of a GRCop-84 alloy for combustion chamber liners is discussed. Topics discussed include: History of GRCop-84 development, GRCop-84 thermal expansion, thermal conductivity of GRCop-84, yield strength of GRCop-84, GRCop-84 creep lives, GrCop-84 low cycle fatigue (LCF) lives, and hot fire testing of GRCop-84 spool pieces.

Ellis, David; Nathal, Michael; Yun, Hee Man; Lerch, Bradley; Greenbauer-Seng, Leslie; Thomas-Ogbuji, Linus; Holmes, Richard

2000-01-01

31

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

32

Effect of the mode of combustion on the service life of the combustion chamber material  

Microsoft Academic Search

The effect of the characteristics of intrachamber combustion (the pressure and the temperature of combustion products) on\\u000a the service life of the material of the combustion chamber of a thermal engine is examined. The problem is studied with the\\u000a help of the Zhurkov kinetic approach based on model examples of spherical and cylindrical shells subjected to the action of\\u000a cyclically

I. G. Assovskii; A. G. Istratov

2008-01-01

33

Pressure scaling effects in a scramjet combustion chamber  

NASA Technical Reports Server (NTRS)

The test results obtained for a model scramjet over a range of pressure levels corresponding to different flight altitudes involve enthalpies that vary from the ignition limit, at the low temperature end, to temperatures where the dissociation of combustion products severely limits heat release. The minimum temperature is noted to be highly pressure-sensitive; above the ignition limit, the amount of heat release increased markedly with pressure and with combustion chamber length. A FEM computer code has been used to model the mixing and combustion processes.

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

1987-01-01

34

Heat transfer in combustion chambers  

Microsoft Academic Search

This paper is dedicated to reviewing and assessing the various models, embodied in a calculation procedure, that are employed in order to calculate heat transfer characteristics (the flux models, the Spherical Harmonics model, the Discrete Ordinate model, etc). The calculation procedure solves the governing conservation equation of mass, momentum and energy, expressed in a finite difference form, and employs a

E. E. Khalil

1984-01-01

35

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

36

Evaluation of multi-dimensional flux models for radiative transfer in cylindrical combustion chambers  

Microsoft Academic Search

Four flux-type models for radiative heat transfer in cylindrical configurations were applied to the prediction of radiative flux density and source term of a cylindrical enclosure problem based on data reported previously on a pilot-scale experimental combustor with steep temperature gradients. The models, which are Schuster-Hamaker type four-flux model derived by Lockwood and Spalding, two Schuster-Schwarzschild type four-flux models derived

Nevin Selcuk

1993-01-01

37

Evaluation of multi-dimensional flux models for radiative transfer in cylindrical combustion chambers  

NASA Astrophysics Data System (ADS)

Four flux-type models for radiative heat transfer in cylindrical configurations were applied to the prediction of radiative flux density and source term of a cylindrical enclosure problem based on data reported previously on a pilot-scale experimental combustor with steep temperature gradients. The models, which are Schuster-Hamaker type four-flux model derived by Lockwood and Spalding, two Schuster-Schwarzschild type four-flux models derived by Siddall and Selcuk and Richter and Quack and spherical harmonics approximation, were evaluated from the viewpoint of predictive accuracy by comparing their predictions with exact solutions produced previously. The comparisons showed that spherical harmonics approximation produces more accurate results than the other models with respect to the radiative energy source term and that the four-flux models of Lockwood and Spalding and Siddall and Selcuk for isotropic radiation field are more accurate with respect to the prediction of radiative flux density to the side wall.

Selcuk, Nevin

1993-02-01

38

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

39

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

40

Combustion chambers of gas-turbine plants - Heat transfer  

Microsoft Academic Search

Results of studies concerned with the convective and radiation heat transfer in the combustion chambers of gas turbines are examined. In particular, the existing methods for cooling flame tubes are analyzed, and heat transfer calculations are carried out for highly augmented combustion chambers. A method is also presented for calculating complex heat transfer in the flame zone for various types

A. V. Sudarev; V. I. Antonovskii

1985-01-01

41

Chamber for Continuous Mixing of High Pressure Combustible Gases  

Microsoft Academic Search

A small mixing chamber has been developed for continuous mixing of combustible gases for use in the combustion driver of a hypersonic shock tunnel. The gases are mixed while passing through the chamber and then flow directly into the shock tunnel driver tube. The system ensures immediate uniform mixing of the gases. It eliminates all waiting time needed to allow

Richard A. Oman; Jarvis Leng

1964-01-01

42

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

43

NASA Teams With Army in Vortex Combustion Chamber Engine Test  

NASA Technical Reports Server (NTRS)

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

2003-01-01

44

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

National Technical Information Service (NTIS)

A series of tests were conducted to measure the combustion performance of the Fastrac engine thrust chamber. The thrust chamber exhibited benign, yet marginally unstable combustion. The marginally unstable combustion was characterized by chamber pressure ...

M. Rocker T. E. Nesman

2001-01-01

45

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

Code of Federal Regulations, 2013 CFR

... Stayed furnaces and combustion chambers. 59.15-5 Section 59.15-5... Stayed furnaces and combustion chambers. (a) Where the plate forming...of stayed furnaces or combustion chambers become bulged between...

2013-10-01

46

Pyrolysis of Polymethylmethacrylate during Combustion in a Solid Fuel Combustion Chamber.  

National Technical Information Service (NTIS)

The report deals with the pyrolysis of the polymer polymethylmethacrylate during combustion in a Solid Fuel Combustion Chamber (SFCC). It includes both a literature study and experimental results. The applicability of bulk pyrolysis experiments, for linea...

J. P. de Wilde

1987-01-01

47

Research Program on Reduced Combustion Chamber Heat Loss Effects on Alternative Fuel Combustion.  

National Technical Information Service (NTIS)

A research program was conducted to determine the effects of thermal barriers in the combustion chamber of a diesel engine on the combustion and emissions of selected alternative fuels. Comparison of steady state fuel economy, exhaust emissions, and combu...

E. E. Daby, I. J. Garwin, P. H. Havstad, C. E. Hunter

1988-01-01

48

High Frequency Combustion Instabilities of LOx\\/CH4 Spray Flames in Rocket Engine Combustion Chambers  

Microsoft Academic Search

Ever since the early stages of space transportation in the 1940’s, and the related liquid propellant rocket engine development, combustion instability has been a major issue. High frequency combustion instability (HFCI) is the interaction between combustion and the acoustic field in the combustion chamber. It destroys the thermal boundary layer wall increasing heat transfer and could lead to compromised performance,

M. Sliphorst

2011-01-01

49

Study of a spherical spinning combustion chamber for orbit insertion  

NASA Astrophysics Data System (ADS)

The study of spray dynamics and fuel vapor distributions in a spinning spherical combustion chamber is of great interest to designers of orbital transfer motors, particularly within the context of residual thrust that can be important for the final staging of such vehicles. In this work we present a theoretical investigation of the evolution in droplet size distributions within such a combustor and spatial distribution of fuel vapors, as the droplets vaporize. The modelling of the spray is performed using a sectional approach that provides the means for handling the large number of droplets in any realistic system by dividing them into size-defined sections and dealing with one integral quantity in each section. However, both droplet transfer to the host gaseous phase and inter- and intra-sectional transfer, through droplet vaporization and coalescence, are rigorously accounted for. The governing two-phase flow equations are solved numerically using split-operator finite difference methods. A wide variety of injection conditions are considered. Computed results highlight the effects of these conditions coupled with spinning rates, and vaporization and coalescence rates on the way in which fuel vapors are formed and become distributed in the combustion chamber. Finally, a description is given of an experimental rig that is to be used for analyzing the flow field and the spatial and size distribution of particles in a spinning chamber.

Avital, G.; Greenberg, J. B.; Laredo, D.; Levy, Y.; Tambour, Y.; Timnat, Y. M.

1990-02-01

50

Study of a Spherical Spinning Combustion Chamber for Orbit Insertion.  

National Technical Information Service (NTIS)

The study of spray dynamics and fuel vapor distributions in a spinning spherical combustion chamber is of great interest to designers of orbital transfer motors, particularly within the context of residual thrust that can be important for the final stagin...

G. Avital J. B. Greenberg D. Laredo Y. Levy Y. Tambour

1990-01-01

51

Fabrication of Composite Combustion Chamber/Nozzle for Fastrac Engine  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

52

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

53

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

54

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

55

Fastrac Rocket Engine Combustion Chamber Acoustic Cavities  

NASA Technical Reports Server (NTRS)

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

Christensen, Eric; Nesman, Tom

1998-01-01

56

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

57

The Bajulaz Cycle: A two-chamber internal combustion engine with increased thermal efficiency  

Microsoft Academic Search

A new engine cycle, called the Bajulaz cycle, is introduced. The cycle has the unique characteristic that it utilizes two chambers, an air-heating chamber and combustion chamber. By allowing heat transfer from the combustion chamber to the air-heating chamber, the heat of combustion is used more efficiently leading to a higher thermal efficiency. Utilizing an ideal thermodynamic cycle analysis, the

W. W. Yuen; J. Andon; R. Bujulaz

1986-01-01

58

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

59

Research program on reduced combustion chamber heat loss effects on alternative fuel combustion  

Microsoft Academic Search

A research program was conducted to determine the effects of thermal barriers in the combustion chamber of a diesel engine on the combustion and emissions of selected alternative fuels. Comparison of steady state fuel economy, exhaust emissions, and combustion data of heat insulated, baseline water-cooled, and high compression ratio engines were made using three fuels. Fuels believed to be representative

E. E. Daby; I. J. Garwin; P. H. Havstad; C. E. Hunter

1988-01-01

60

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

61

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

62

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

63

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

64

Hot fire fatigue testing results for the compliant combustion chamber  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

65

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

66

Effect of swirl on combustion in a short cylindrical chamber  

SciTech Connect

Combustion of a swirling, stoichiometric, and homogeneous mixture of natural gas and air in a short cylindrical chamber has been studied experimentally and simulated numerically. Each mixture was given a steady-state swirling motion by a rotating roughened disc before being ignited at the center of the chamber. By using discs of differencing roughness and by varying the disc speed, the intensities of swirl and turbulence could be varied independently so that the effects on combustion of mixture turbulence and swirl-induced buoyancy could be separately examined. Combustion rate and overall chamber heat transfer were inferred from chamber pressure-time records. High-speed schlieren photography showed the effect of swirl on the early flame kernel. With given swirling angular momentum, increased turbulence level always reduced burning duration and increased total heat transfer rate. With given turbulence level, increasing the swirl intensity from zero first decreased, then strongly increased, the burning duration. The swirling Reynolds number (based on chamber radius and peak tangential velocity) at which combustion duration was minimized was in the range 30,000--40,000. At high Reynolds number buoyancy forces appear to have a strongly inhibiting effect on flame propagation.

Zhang, D.; Hill, P.G. [Univ. of British Columbia, Vancouver, British Columbia (Canada). Dept. of Mechanical Engineering] [Univ. of British Columbia, Vancouver, British Columbia (Canada). Dept. of Mechanical Engineering

1996-08-01

67

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

68

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

NASA Technical Reports Server (NTRS)

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

Breisacher, Kevin J.; Priem, Richard J.

1988-01-01

69

Adherent Thermal Barrier For Combustion Chamber  

NASA Technical Reports Server (NTRS)

In improved method, fabrication begins with machining of aluminum mandrel to requisite cylindrical shape. Heat-barrier coating - yttria-stablized zirconia - plasma-sprayed on mandrel to thickness of 0.076 mm. Nickel/chromium layer about 0.025 mm thick sprayed on zirconia. Thin zirconia coating reduces maximum operating temperature of copper wall of chamber from 844 to 334 K. At lower temperature, copper liner stronger and undergoes less strain and less tendency to distort and crack.

Quentmeyer, Richard J.

1989-01-01

70

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...

71

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

72

Effects of fuel and additives on combustion chamber deposits  

Microsoft Academic Search

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

M. M. Jackson; S. B. Pocinki

1994-01-01

73

Study of a spherical spinning combustion chamber for orbit insertion  

Microsoft Academic Search

The study of spray dynamics and fuel vapor distributions in a spinning spherical combustion chamber is of great interest to designers of orbital transfer motors, particularly within the context of residual thrust that can be important for the final staging of such vehicles. In this work we present a theoretical investigation of the evolution in droplet size distributions within such

G. Avital; J. B. Greenberg; D. Laredo; Y. Levy; Y. Tambour; Y. M. Timnat

1990-01-01

74

Effect of flame-tube head structure on combustion chamber performance  

NASA Technical Reports Server (NTRS)

The experimental combustion performance of a premixed, pilot-type flame tube with various head structures is discussed. The test study covers an extensive area: efficiency of the combustion chamber, quality of the outlet temperature field, limit of the fuel-lean blowout, ignition performance at ground starting, and carbon deposition. As a result of these tests, a nozzle was found which fits the premixed pilot flame tube well. The use of this nozzle optimized the performance of the combustion chamber. The tested models had premixed pilot chambers with two types of air-film-cooling structures, six types of venturi-tube structures, and secondary fuel nozzles with two small spray-cone angles.

Gu, Minqqi

1986-01-01

75

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

76

Heat transfer in rocket engine combustion chambers and nozzles  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

77

The effect of fuel and air agitation on the combustion process in a low-emission combustion chamber  

NASA Astrophysics Data System (ADS)

Methods for numerically simulating the working process in low-emission combustion chamber and for testing it are described. A method of using numerical simulation for predicting NO x emission and combustion process stability in a low-emission combustion chamber is proposed.

Bulysova, L. A.; Gorban', V. D.

2013-09-01

78

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

79

Explosion-induced combustion of hydrocarbon clouds in a chamber  

SciTech Connect

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

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

2001-02-06

80

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

81

Method of fabricating a rocket engine combustion chamber  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

82

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

83

Advanced Main Combustion Chamber structural jacket strength analysis  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

84

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

85

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

This paper describes the application of high performance computing to accelerate the development of hypergolic propulsion systems for tactical missiles. Computational fluid dynamics is employed to model the chemically reacting flow within a systempsilas combustion chamber, and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments from the past year are presented and discussed.

Michael J. Nusca; Chiung-Chu Chen; Michael J. McQuaid

2008-01-01

86

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

This paper describes the application of high performance computing to accelerate the development of hypergolic propulsion systems for tactical missiles. Computational fluid dynamics is employed to model the chemically reacting flow within a system's combustion chamber, and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments from the past year are presented and discussed.

Michael J. Nusca; Chiung-Chu Chen; Michael J. McQuaid

2007-01-01

87

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

This paper describes the development and application of high performance computing for the acceleration of tactical missile hypergolic propulsion system development. Computational fluid dynamics is employed to model the chemically reacting flow within a system's combustion chamber, and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments from the past year are presented and discussed

Michael J. Nusca; Michael J. McQuaid

2006-01-01

88

Spray dynamics and fuel vapor distributions in a spinning combustion chamber  

Microsoft Academic Search

The evolution in droplet size distributions within a spinning spherical combustion chamber is investigated theoretically, and the distribution of fuel vapors as the droplets vaporize is presented for heated sprays. The spray is modeled using a sectional approach that provides the means for handling the large number of droplets in any realistic system by dividing them into size-defined sections and

J. B. Greenberg; Y. Tambour; Y. M. Timnat; G. Avital

1991-01-01

89

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

This paper describes the development and application of high performance computing for the acceleration of tactical missile hypergolic propulsion system development. Computational fluid dynamics (CFD) is employed to model the chemically reacting flow within a system?s combustion chamber, and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments from the past year are presented and discussed.

Michael J. Nusca; Michael J. McQuaid

2005-01-01

90

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines  

Microsoft Academic Search

Challenge Project C2N is dedicated to developing and applying high performance computing capabilities to accelerate the development of hypergolic and hybrid rocket engine concepts. Computational fluid dynamics is employed to model chemically reacting flows within engine combustion chambers and computational chemistry is employed to characterize propellant physical and reactive properties. Accomplishments are presented and discussed.

Chiung-Chu Chen; Michael J. Nusca; Anthony J. Kotlar; Michael J. McQuaid

2009-01-01

91

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

Microsoft Academic Search

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

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

2012-01-01

92

SSME main combustion chamber life prediction  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

93

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

94

Numerical simulation of processes in a spherical combustion chamber  

Microsoft Academic Search

A theoretical model of gasdynamic and mechanical processes in a spherical explosion chamber is considered. Comparison of numerical results obtained with this model with calculated and experimental results of other authors shows good agreement.

A. I. Marchenko; G. S. Romanov

1984-01-01

95

Numerical simulation of processes in a spherical combustion chamber  

NASA Astrophysics Data System (ADS)

A theoretical model of gasdynamic and mechanical processes in a spherical explosion chamber is considered. Comparison of numerical results obtained with this model with calculated and experimental results of other authors shows good agreement.

Marchenko, A. I.; Romanov, G. S.

1984-10-01

96

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

97

Combustion efficiency of a porous injector during throttling of a LOx/H2 combustion chamber  

NASA Astrophysics Data System (ADS)

The effect of throttling on combustion efficiency and stability of a porous injector head has been investigated for the LOx/H2 propellant combination. Several pressure ramps (PR) ranging from 30 to 100 bar have been used so that a broad range of possible chamber pressures was covered. Regarding the design pressure of 80 bar, this was equivalent to a throttling range of 37.5% to 125%. The hydrogen injection temperature was varied between 50 and 105 K. The oxygen injection temperature was about 115 ± 5 K. All tests were performed at the P8 test bench using a 50-millimeter diameter modular combustion chamber. The combustion efficiency at a hydrogen injection temperature of 105 K varied between 97.5% and 99% and was nearly independent of pressure. For hydrogen at 50 K, the combustion efficiency increased with chamber pressure and ranged from 94% to 97%. The combustion roughness at 50 K was higher than for the 105-kelvin test cases.

Deeken, J.; Suslov, D.; Haidn, O.; Schlechtriem, S.

2011-10-01

98

Flow and convective heat transfer in cylindrical reversed flow combustion chambers  

SciTech Connect

This paper presents a computational study of the flow and convective heat transfer in cylindrical reversed flow combustion chambers. The computations are performed using an elliptic solver incorporates the {kappa}-{epsilon} turbulence model. Heat production by combustion is simulated by adding heat generation source terms in the energy equation. And it is assumed that heat generation occurs only a section of the furnace. A number of different inlet conditions with different geometries are considered, and the changes of flow structure, temperature distribution, convective heat flux rate are presented and compared. The results show that, in general, heat transfer in the reversed flow combustion chamber can be improved by properly chosen geometry for the required output.

Kilic, M. [Univ. of Uludag, Bursa (Turkey)] [Univ. of Uludag, Bursa (Turkey)

1996-12-01

99

Nonlinear behavior of acoustic waves in combustion chambers  

NASA Technical Reports Server (NTRS)

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

Culick, F. E. C.

1975-01-01

100

The Design and Manufacture of a 6 Inch Diameter Ablative Combustion Chamber.  

National Technical Information Service (NTIS)

A 6 in. diameter ablative combustion chamber has been designed for use in evaluation tests on rocket engine components. This combustion chamber was designed for operation at 1000 psia chamber pressure with the propellant combination N2O4 and 50% N2H4 - 50...

W. Q. Walker

1965-01-01

101

Thermal Model of the Promoted Combustion Test  

NASA Technical Reports Server (NTRS)

Flammability of metals in high pressure, pure oxygen environments, such as rocket engine turbopumps, is commonly evaluated using the Promoted Combustion Test (PCT). The PCT emphasizes the ability of an ignited material to sustain combustion, as opposed to evaluating the sample's propensity to ignite in the first place. A common arrangement is a rod of the sample material hanging in a chamber in which a high pressure, pure oxygen environment is maintained. An igniter of some energetically combusting material is fixed to the bottom of the rod and fired. This initiates combustion, and the sample burns and melts at its bottom tip. A ball of molten material forms, and this ball detaches when it grows too large to be supported by surface tension with the rod. In materials which do not sustain combustion, the combustion then extinguishes. In materials which do sustain combustion, combustion re-initiates from molten residue left on the bottom of the rod, and the melt ball burns and grows until it detaches again. The purpose of this work is development of a PCT thermal simulation model, detailing phase change, melt detachment, and the several heat transfer modes. Combustion is modeled by a summary rate equation, whose parameters are identified by comparison to PCT results. The sensitivity of PCT results to various physical and geometrical parameters is evaluated. The identified combustion parameters may be used in design of new PCT arrangements, as might be used for flammability assessment in flow-dominated environments. The Haynes 214 nickel-based superalloy, whose PCT results are applied here, burns heterogeneously (fuel and oxidizer are of different phases; combustion takes place on the fuel surface). Heterogeneous combustion is not well understood. (In homogeneous combustion, the metal vaporizes, and combustion takes place in an analytically treatable cloud above the surface). Thermal modeling in heterogeneous combustion settings provides a means for linking test results more directly to detailed combustion mechanics, leading to improved data analysis, and improved understanding of heterogeneous combustion phenomena.

Jones, Peter D.

1996-01-01

102

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

103

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

104

Certain Problems of Unstable Combustion in Rocket Engine Chambers Driven by Liquid Fuel.  

National Technical Information Service (NTIS)

The monograph discusses only certain problems of unstable combustion in a rocket engine combustion chamber, namely, the types of instability, their manifestations, causes, and possible results for the drive, stability criteria and conclusions.

H. Krajewski

1966-01-01

105

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

106

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

107

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

108

Spray dynamics and fuel vapor distributions in a spinning combustion chamber  

NASA Astrophysics Data System (ADS)

The evolution in droplet size distributions within a spinning spherical combustion chamber is investigated theoretically, and the distribution of fuel vapors as the droplets vaporize is presented for heated sprays. The spray is modeled using a sectional approach that provides the means for handling the large number of droplets in any realistic system by dividing them into size-defined sections and dealing with one integral quantity in each section. The governing two-phase flow equations are solved numerically using split-operator finite-difference methods. A wide range of injection conditions are considered. Computed results highlight the effects of these conditions coupled with spinning rates, and vaporization and coalescence rates on the way in which fuel vapors are formed and become distributed in the combustion chamber.

Greenberg, J. B.; Tambour, Y.; Timnat, Y. M.; Avital, G.

109

Combustion Chamber Acoustics and Its Interaction with LOX/H2- and LOX/CH4-Spray Flames  

NASA Astrophysics Data System (ADS)

The acoustics of combustion chambers and the interaction of acoustics and combustion is investigated in a model combustor operated with LOX/H2 and LOX/CH4. Acoustic excitations are induced by a siren during hot fire tests and the response of atomization and combustion is recorded with dynamic pressure sensors and high speed OH-imaging is applied. By analyzing the temporal and spatial distribution of the flame response the question is addressed, whether in the experiments the coupling of acoustics to combustion is via pressure or velocity sensitive processes. In the experiments it appeared that the acoustic eigenmodes of the combustor are characteristically deviating from cylinder modes. The results obtained can be explained by a modal analyses of the combustor geometry. These investigations have been extended to study the influence of absorbers and absorber rings on the acoustics of combustion chambers and resonance frequencies predicted by modal analysis and experimental results are presented.

Oschwald, Michael; Knapp, Bernhard; Sliphorst, Mark; Marpert, Mark

110

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

111

Open-Chamber Combustion Study. Topical Report, June 1991-August 1992.  

National Technical Information Service (NTIS)

The test program was undertaken to research trade-offs between engine design and operational parameters on open-chamber, premixed spark-ignited gas engines, with a primary focus on combustion effects. This included combustion chamber designs which are con...

D. P. Meyers R. C. Meyer

1994-01-01

112

Catalytic relight coating for gas turbine combustion chamber and method of application  

SciTech Connect

A gas turbine combustion chamber is described having a wall with an inner surface exposed to the combustion chamber flame, and a coating of a catalytic material on the surface over a large enough area thereof to cause reignition of the fuel-air mixture after flame-out.

Pfefferle, W.C.; Bak, M.J.

1986-08-05

113

Selected Problems from Technical Analysis of Combustion Chamber Deficiencies of Aviation Engines.  

National Technical Information Service (NTIS)

Fundamental problems encountered in combustion chambers and flame tubes of jet engines are discussed. It is recommended that the tightening force on combustion chamber flange bolts should not exceed 0.4 plus or minus 0.025 kgm. Fragment visual inspection ...

S. Andruszkiewicz M. Sikorski

1969-01-01

114

Modifications of a Composite-Material Combustion Chamber  

NASA Technical Reports Server (NTRS)

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

Williams, Brian E.; McNeal, Shawn R.

2005-01-01

115

A Study on the Effect of Stratified Mixture Formation on Combustion Characteristics in a Constant Volume Combustion Chamber  

NASA Astrophysics Data System (ADS)

It is well known that a lean burn engine caused by stratified mixture formation has many kinds of advantages to combustion characteristics, such as higher thermal efficiency and lower CO, NOx levels than conventional homogeneous mixture combustion. Although this combustion can achieve low fuel consumption, it produces much unburned hydrocarbon and soot because of inhomogeneity of the charge mixture in the combustion chamber. Therefore, it is necessary to investigate the effect of mixture formation on combustion characteristics in order to obtain the stable lean combustion. In this paper, fundamental studies for stratified combustion were carried out using a constant volume combustion chamber. The effect of mixture formation on the combustion characteristics in the chamber was examined experimentally. In addition, the effect of turbulence on stratified charge combustion process was observed by schlieren photography. From this study, as the swirl intensity increases, (Sv)max is rapidly enhanced and the period of combustion is shortened. We also find that the stratification degree can be quantified by using burning velocity and it was controlled by induced air pressure and turbulent intensity.

Lee, Kihyung; Lee, Changhee; Jeoung, Haeyoung

116

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

117

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

NASA Technical Reports Server (NTRS)

A series of tests were conducted to measure the combustion performance of the Fastrac engine thrust chamber. The thrust chamber exhibited benign, yet marginally unstable combustion. The marginally unstable combustion was characterized by chamber pressure oscillations with large amplitudes and a frequency that was too low to be identified as acoustic or high-frequency combustion instability and too high to be identified as chug or low-frequency combustion instability. The source of the buzz or intermediate-frequency combustion instability was traced to the fuel venturi whose violently noisy cavitation caused resonance in the feedline downstream. Combustion was stabilized by increasing the throat diameter of the fuel venturi such that the cavitation would occur more quietly.

Rocker, Marvin; Nesman, Tomas E.; Turner, Jim E. (Technical Monitor)

2001-01-01

118

A numerical and experimental study of the squish-jet combustion chamber  

Microsoft Academic Search

The fluid flow characteristics near top dead centre (TDC) were numerically simulated for three different combustion chambers designed to generate squish flow and enhance turbulence generation in spark ignition engines. One of the combustion chambers was a plain bowl-in-piston type while the remaining two were different configurations of the squish-jet chamber, which has a unique geometry for forming jets that

P Lappas; R L Evans

2006-01-01

119

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

120

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

121

Structural Benchmark Tests of Composite Combustion Chamber Support Completed  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

122

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

123

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

SciTech Connect

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

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

1990-01-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

125

Chamber Clearing First Principles Modeling  

SciTech Connect

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

Loosmore, G

2009-06-09

126

Improvement of rich-lean combustion chamber emission at the design stage  

Microsoft Academic Search

Results of numerical simulation and principles of designing a mixer in the secondary zone of the flame tube when adjusting\\u000a the rich-lean combustion chamber emission in the gas turbine engines are presented.

A. A. Inozemtsev; V. G. Avgustinovich; V. V. Tsatiashvili

2010-01-01

127

Effects of Combustion Chamber Deposits on Vehicle Emissions and Fuel Economy.  

National Technical Information Service (NTIS)

A combination of factors has led to increased interest in better understanding the effects of combustion chamber deposits (CCD) on vehicle and engine performance. More recently, the U.S. Environmental Protection Agency and the California Air Resources Boa...

2000-01-01

128

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

NASA Technical Reports Server (NTRS)

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

Zimmerman, Frank

2003-01-01

129

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

NASA Astrophysics Data System (ADS)

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

Oschwald, M.; Knapp, B.

2009-09-01

130

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

131

COLDSTART ENGINE COMBUSTION MODELLING TO CONTROL HYDROCARBON EMISSIONS  

Microsoft Academic Search

Due to the large contribution of the coldstart process to unburned hydrocarbon emissions of an internal combustion engine during FTP cycle tests, we take a new look at the production of hydrocarbons inside the combustion chamber during coldstart. To this end a model is developed which predicts the exhaust port hydrocarbon concentration, exhaust gas temperature and equivalence ratio based on

Byron T. Shaw II; J. Karl Hedrick

132

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

133

Application of moire deflectometry in visualizing flow field in a diesel combustion chamber  

NASA Astrophysics Data System (ADS)

In this paper a technique of visualizing flow field in diesel combustion chamber is presented. It consists of laser source, moire deflectometer and high speed camera. Using this setup to visualize the flow field in a single chamber diesel, we gained the series deflectograms of flow field under different conditions and calculate the temperature distribution of its flow field quantitatively.

You, Haihang; Yan, Dapeng; Wang, Zhengdong; He, Anzhi

1997-11-01

134

Mesh Dependency of Turbulent Reacting Large-Eddy Simulations of a Gas Turbine Combustion Chamber  

NASA Astrophysics Data System (ADS)

Convergence of reacting LES predictions for an aeronautical gas turbine combustion chamber is analysed in terms of mesh resolution. To do so three fully unstructured meshes containing respectively 1.2, 10.6 and 43.9 million tetrahedra are used to compute this fully turbulent reacting flow. Resolution criteria obtained from the mean velocity and reacting fields depict different convergence behaviors. Reacting fields and more specifically combustion regimes are seen to be slightly grid dependent while maintaining mean global combustion quantities.

Boudier, Guillaume; Staffelbach, Gabriel; Gicquel, Laurent Y. M.; Poinsot, Thierry J.

135

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

NASA Astrophysics Data System (ADS)

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.

1984-06-01

136

Structurally-compliant rocket engine combustion chamber: Experimental/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 in life over that of rectangular channel designs, the current state-of-the-art. Greater structural compliance in the circumferential direction gives rise to lower thermal strains during hot firing, resulting in lower thermal strain ratcheting and longer predicted fatigue lives. Thermal/durability analyses of the combustion chamber design, involving cyclic temperatures, strains, and low-cycle fatigue lives have corroborated the experimental observations.

Jankovsky, R. S.; Kazaroff, J. M.; Galford, G. R.; Arya, V. K.

1993-01-01

137

Numerical simulation of operation processes in the combustion chamber and gas generator of oxygen-methane liquid rocket engine  

NASA Astrophysics Data System (ADS)

The results of numerical simulations of processes in gas generators and combustion chambers operating on oxygen and methane are presented. Specific features of mixing, evaporation, and combustion of propellants have been investigated. The degree of combustion completeness in chambers with three types of injectors - coaxial-jet gas-liquid, liquid-liquid monopropellant, and bipropellant impinging-jets injectors - has been estimated.

Kalmykov, G. P.; Larionov, A. A.; Sidlerov, D. A.; Yanchilin, L. A.

2009-09-01

138

Soot prediction by Large-Eddy Simulation of complex geometry combustion chambers  

NASA Astrophysics Data System (ADS)

This article is dedicated to the modeling of soot production in Large-Eddy Simulations (LES) of complex geometries. Such computations impose a trade-off between accuracy and CPU cost which limits the choice of soot models to semi-empirical ones. As the presence of acetylene is a necessary condition for soot inception, the Leung et al. model that accounts for this feature is chosen and used in this work. However, acetylene concentration is not provided by the reduced chemistries used in LES of complex geometries and a methodology has been developed to predict this key species through a tabulation technique. With this methodology, the model of Leung et al. is first tested and validated against measured laminar premixed flames. Then, the soot prediction method is applied to the LES of the combustion chamber of a helicopter engine.

Lecocq, Guillaume; Hernández, Ignacio; Poitou, Damien; Riber, Eléonore; Cuenot, Bénédicte

2013-01-01

139

The Bajulaz Cycle: A two-chamber internal combustion engine with increased thermal efficiency  

SciTech Connect

A new engine cycle, called the Bajulaz cycle, is introduced. The cycle has the unique characteristic that it utilizes two chambers, an air-heating chamber and combustion chamber. By allowing heat transfer from the combustion chamber to the air-heating chamber, the heat of combustion is used more efficiently leading to a higher thermal efficiency. Utilizing an ideal thermodynamic cycle analysis, the thermal efficiency of the Bajulaz cycle is shown to depend only on the compression ratios based on the two chamber volumes and the fractional heat transer between the two chambers. Based on predictions of peak temperature and pressure generated from the ideal cycle analysis, the Bajulaz engine is shown to be thermally more efficient and has lower NO/subX/ emission than the corresponding Otto engine. Combustion is shown to occur over a full 360/sup 0/ of crankshaft rotation in the Bajulaz engine. The Bajulaz engine thus does not have any restrictive requirement on ignition timing (as in an Otto engine) and on the timing and duration of fuel injection (as in a Diesel engine). It can also utilize multiple fuels including those with slow burning rate.

Yuen, W.W.; Andon, J.; Bujulaz, R.

1986-01-01

140

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

NASA Technical Reports Server (NTRS)

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

Zimmerman, Frank

2000-01-01

141

Microgravity Combustion of Dust Suspension in a Spherical Chamber.  

National Technical Information Service (NTIS)

Experiments in constant volume combustion of dust in air in a 4 liter spherical vessel were carried out in 1 g and microgravity environments. The diagnostics involved exclusively piezoelectric pressure transducers to measure the pressure-time history of t...

J. H. S. Lee O. Peraldi R. Knystautas R. Thirsk

1992-01-01

142

Comparative evaluation of gas-turbine engine combustion chamber starting and stalling characteristics for mechanical and air-injection  

NASA Technical Reports Server (NTRS)

The effectiveness of propellant atomization with and without air injection in the combustion chamber nozzle of a gas turbine engine is studied. Test show that the startup and burning performance of these combustion chambers can be improved by using an injection during the mechanical propellant atomization process. It is shown that the operational range of combustion chambers can be extended to poorer propellant mixtures by combined air injection mechanical atomization of the propellant.

Dyatlov, I. N.

1983-01-01

143

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

NASA Astrophysics Data System (ADS)

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.

1984-06-01

144

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

145

Formation of detonation in a pulse combustion chamber with a porous obstacle  

NASA Astrophysics Data System (ADS)

A study has been made of the influence of a porous obstacle on deflagration-to-detonation transition in a pulse combustion chamber of small length. Dependences of the detonation-wave velocity on the distance have been obtained for two samples of a porous material (steel spheres and a ceramic porous body). It has been shown that the use of an insert from a porous material leads to a reduction of 40% in the predetonation distance without changing substantially the structure of the pulse combustion chamber.

Alhussan, Kh.; Assad, M. S.; Penyazkov, O. G.; Sevruk, K. L.

2012-09-01

146

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

147

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

148

Pulse Combustion Engineering Research Laboratory: Combustion Chamber. Annual Report, July 1, 1990-June 30, 1991.  

National Technical Information Service (NTIS)

A pulse combustion research laboratory for low pressure systems was put into operation to investigate and resolve, on a fundamental level, issues affecting practical applications of pulse combustion technology. In the second year of the program, a NOx dat...

F. E. Belles

1991-01-01

149

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

150

A Study of Combustion Process of LOX/Hydrogen Rocket Engine at Supercritical Pressure by Macroscopic Model (Part 2)  

NASA Astrophysics Data System (ADS)

In the Part-2, it is continuing to examine the presenting combustion model to LOX/methane combustion at supercritical pressure. Then the model is expanded to apply for design and evaluation method of actual rocket combustion chamber at supercritical combustion pressure.

Yatsuyanagi, Nobuyuki

151

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

152

Validation of High Aspect Ratio Cooling in a 89 Kn (20,000 Lb(Sub F)) Thrust Combustion Chamber.  

National Technical Information Service (NTIS)

In order to validate the benefits of high aspect ratio cooling channels in a large scale rocket combustion chamber, a high pressure, 89 kN (20,000 lbf) thrust, contoured combustion chamber was tested in the NASA Lewis Research Center Rocket Engine Test Fa...

M. F. Wadel M. L. Meyer

1996-01-01

153

Impact of Introducing Water into the Combustion Chamber of Diesel Engines on Emissions - an Overview  

Microsoft Academic Search

The method of introducing water with the fuel or directly into the combustion chamber of reciprocating engines has proved to be a powerful and, at the same time, economical tool for reducing oxides of nitrogen (NOx) and particulate matter (PM) in the exhaust gases. Research in this area goes back to the early days of development of aircraft piston engines

X. T. Tran; J. I. Ghojel

154

Fault Detection and Isolation of a Cryogenic Rocket Engine Combustion Chamber Using a Parity Space Approach  

Microsoft Academic Search

This paper presents a parity space (PS) approach for fault detection and isolation (FDI) of a cryogenic rocket engine combustion chamber. Nominal and non-nominal simulation data for three engine set points have been provided. The PS approach uses three measurements to generate residuals and a spherical transformation to map these residuals to faults. The radial co-ordinate is used for fault

Paul van Gelder; A. Bos

2009-01-01

155

Effect of Mirror-Finished Combustion Chamber on Heat-Loss.  

National Technical Information Service (NTIS)

In order to improve fuel economy by reducing the heat-loss of engines, many studies on the reduction of the heat-loss of ceramic combustion chamber have been made. The authors conducted similar studies and experiments. As a result, it is made clear that t...

Y. Tsutsumi K. Nomura N. Nakamura

1989-01-01

156

A direct contact heat exchanger with a submerged combustion chamber for water heating  

Microsoft Academic Search

A direct contact heat exchanger with a submerged combustion chamber has been developed for feasibility study. Efficiencies of over 90 percent have been measured based on the higher heating value of the propane fuel used. Recovery of latent heat of vaporization was also achieved. It is found that the system is feasible and of application value but further study is

M. A. Reissig; J. N. Chung

1984-01-01

157

Organization of kerosene combustion in a model hypersonic ramjet engine  

Microsoft Academic Search

We present the results of experiments on the organization of kerosene combustion in a two-dimensional model of a hypersonic ramjet engine in conditions of external blow-out by a flow with parameters M8=6, p8*=(53–55)·105 Pa, T8*=1500 K. We studied the operation of some variants of a rectangular combustion chamber with different kerosine injectors and stabilizing elements when hydrogen is used as

V. A. Vinogradov; S. A. Kobyzhskii; M. D. Petrov

1992-01-01

158

Combined air and fuel nozzle for fluidized bed combustion chamber  

SciTech Connect

A combined nozzle for air and fuel to a fluidized bed comprises two fixed portions mounted at the top and bottom of an air chamber and a movable, withdrawable portion which connects the two fixed portions and is guided by them. The movable portion blocks the lower fixed portion outwardly and conducts air and fuel to the upper fixed portion . Further , there is a device (3, 26) for sealing the lower fixed portion when the movable portion is removed for inspection during operation. (Fig. 2).

Bergkvist, J.

1981-10-06

159

Interaction of the Acoustic Properties of a Combustion Chamber with those of Premixture Supply  

NASA Astrophysics Data System (ADS)

If the response of a flame to acoustic waves is not known, it must be deduced from measurements in a system for which the acoustic impedances can be inferred. Measurements have been made on a simple combustion system in which gaseous propane is mixed with air in a cylindrical chamber of variable length before flowing up a burner tube. At the end of the tube, the premixture flows around a centre-body, behind which a flame is stabilized. When placed in cylindrical combustion chambers of two different lengths, the flame generates self-excited acoustic oscillations. These have been measured with pressure transducers at three different points and with a system for collecting the UV radiation from the whole flame at a wavelength of chemiluminescent emission. The data demonstrate that the acoustic transmission through the premixture supply system and through the combustion chamber can be described by standard one-dimensional acoustic theory, provided an appropriate choice of mean speed of sound in the combustion chamber is made. This then allows the jump in the volumetric acoustic fluxes across the flame to be calculated, and it is shown, by examination of the magnitude and phase of the transfer function, that this jump is proportional to the UV emission over a range of frequencies up to 800 Hz (a frequency corresponding to wavelengths of the order of the combustion chamber length). This relationship is in accordance with thermo-acoustic theory for a “thin” flame, if the UV emission can be taken as proportional to the instantaneous rate of heat release. The observations therefore validate both the experimental technique and the applicability of the theoretical assumptions, and lay the foundation for a more detailed study of the structural response of the flame.

LAWN, C. J.

1999-07-01

160

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

161

Investigation of the flow in the vortex chamber with centrifugal fluidizing bed with and without combustion  

NASA Astrophysics Data System (ADS)

The flow in the vortex chamber with centrifugal fluidized bed of solid particles was studied experimentally and simulated numerically. The chambers of different configurations were considered, and this allowed us to change the ratio of centrifugal and gravity forces. To estimate the hydraulic losses in the vortex chamber, a simple model was suggested.

Volchkov, E. P.; Dvornikov, N. A.; Lukashov, V. V.; Abdrakhmanov, R. Kh.

2014-12-01

162

Smog chamber study on the evolution of fume from residential coal combustion.  

PubMed

Domestic coal stoves are widely used in countryside and greenbelt residents in China for heating and cooking, and emit considerable pollutants to the atmosphere because of no treatment of their exhaust, which can result in deteriorating local air quality. In this study, a dynamic smog chamber was used to investigate the real-time emissions of gaseous and particulate pollutants during the combustion process and a static smog chamber was used to investigate the fume evolution under simulate light irradiation. The real-time emissions revealed that the total hydrocarbon (THC) and CO increased sharply after ignition, and then quickly decreased, indicating volatilization of hydrocarbons with low molecular weight and incomplete combustion at the beginning stage of combustion made great contribution to these pollutants. There was evident shoulder peak around 10 min combustion for both THC and CO, revealing the emissions from vitrinite combustion. Additionally, another broad emission peak of CO after 30 min was also observed, which was ascribed to the incomplete combustion of the inertinite. Compared with THC and CO, there was only one emission peak for NOx, SO2 and particular matters at the beginning stage of combustion. The fume evolution with static chamber simulation indicated that evident consumption of SO2 and NOx as well as new particle formation were observed. The consumption rates for SO2 and NOx were about 3.44% hr(-1) and 3.68% hr(-1), the new particle formation of nuclei particles grew at a rate of 16.03 nm/hr during the first reaction hour, and the increase of the diameter of accumulation mode particles was evident. The addition of isoprene to the diluted mixture of the fume could promote 03 and secondary particle formation. PMID:22783629

Geng, Chunmei; Wang, Kun; Wang, Wei; Chen, Jianhua; Liu, Xiaoyu; Liu, Hongjie

2012-01-01

163

Numerical approaches to combustion modeling  

SciTech Connect

This book presents a series of topics ranging from microscopic combustion physics to several aspects of macroscopic reactive-flow modeling. As the reader progresses into the book, the successive chapters generally include a wider range of physical and chemical processes in the mathematical model. Including more processes, however, usually means that they will be represented phenomenologically at a cruder level. In practice the detailed microscopic models and simulations are often used to develop and calibrate the phenomenologies used in the macroscopic models. The book first describes computations of the most microscopic chemical processes, then considers laminar flames and detonation modeling, and ends with computations of complex, multiphase combustion systems.

Oran, E.S.; Boris, J.P. (Naval Research Lab., Washington, DC (United States))

1991-01-01

164

Modification of diesel engine precombustion chamber to attenuate detonation and improve combustion  

SciTech Connect

The precombustion chamber of a diesel engine is modified to incorporate an acoustical attenuator therein. Since the precombustion chamber is of fixed dimensions (not changed by piston movement), the acoustic nature and modification response are very powerful, to a surprising degree. In one embodiment of this invention, the attenuator is formed by a body of attenuative material, such as sintered metal or porous ceramic, which is placed around the lower portions of the chamber in the vicinity of the connecting passages to the main combustion chamber. In another embodiment, the attenuation is achieved by means of attenuator pockets which are spaced around the precombustion chamber with communication between these passages and the chamber being provided by means of suitable orifices, these pockets having an acoustic response such as to attenuate detonation waves. In a still further embodiment of the invention, the aforementioned pockets are filled with pellets fabricated of a porous material, such as a suitable porous ceramic or metallic ceramic, which are coated with a catalytic material, such as platinum or rhodium, the pellets providing additional acoustical attenuation with the catalytic material operating to facilitate more complete combustion.

Bodine, A. G.

1985-12-24

165

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

166

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

167

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

168

Modeling semi-anechoic electromagnetic measurement chambers  

Microsoft Academic Search

Previous studies developed a model to predict theoretically the low-frequency plane-wave reflection coefficient of an array of pyramid cone absorbers such as those used to line anechoic electromagnetic measurement chambers. The present authors apply this model in a geometrical optics approach to predict the electromagnetic field in a chamber lined with cone absorbers in the frequency range of 30-300 MHz.

Christopher L. Holloway; Edward F. Kuester

1996-01-01

169

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

170

Procedure for multiparametric investigation of the combustion of metallic particles in a freely falling chamber  

SciTech Connect

A new setup based on the observation of the behavior of metal particles burning inside a falling hermetically sealed chamber was created in order to improve the procedures for experimental combustion of metal particles in a freely falling chamber. The main part of the experimental setup, the falling platform, is illustrated. A spherical concave mirror, the optical system, the detachment shoe, and a photodiode 12 are described. The setup permits analyzing the effect of the velocity of the flow past the burning particle on the parameters and permits interrupting the burning of the particle at any time with sampling of the unburned residue for further analysis.

Kolesnikov-Svinarev, V.I.; Kuznetsov, G.P.; Leipunskii, O.I.

1984-01-01

171

Method for detecting a tumble flow in a cylinder chamber of an internal combustion engine  

US Patent & Trademark Office Database

For the purpose of detecting a tumble flow in a cylinder chamber of an internal combustion engine, with a characteristic tumble value being determined as a quotient from an angular velocity .omega..sub.FK of the tumble movement and an angular velocity .omega..sub.Mot of the internal combustion engine, a method is proposed in which the asymmetry of a flow field w.sub.LDA in the cylinder chamber is detected for a predetermined number of measuring points i with a differential measuring method on a flow test stand and the characteristic tumble value is determined as a result of the asymmetry of the flow field w.sub.LDA. Characteristic tumble values can thus be determined in a simple and practical manner.

2002-05-07

172

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

173

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

174

Remarks on entropy production in the one-dimensional approximation to unsteady flow in combustion chambers  

NASA Technical Reports Server (NTRS)

The treatment of unsteady flows in a combustion chamber is discussed. As an example a rocket motor is considered, where material enters through a lateral boundary with its stagnation enthalpy different from the average speed. The equations of motion for unsteady flow within a one-dimensional approximation are analyzed, and the production of entropy is deduced. In the equations, the term representing the dissipative processes are identified by constructing a representation for the production of entropy.

Culick, F. E. C.

1977-01-01

175

Effects of various baffle designs on acoustic characteristics in combustion chamber of liquid rocket engine  

Microsoft Academic Search

Effects of various baffle designs on acoustic characteristics in combustion chamber are numerically investigated by adopting\\u000a linear acoustic analysis. A hub-blade configuration with five blades is selected as a candidate baffle and five variants of\\u000a baffles with various specifications are designed depending on baffle height and hub position. As damping parameters, natural-frequency\\u000a shift and damping factor are considered and the

Chae Hoon Sohn; Seong-Ku Kim; Young-Mog Kim

2004-01-01

176

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

177

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

178

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

179

Aluminum Combustion in Solid Rocket Motor Chamber Environment (Preprint).  

National Technical Information Service (NTIS)

A model for prediction of particle radius and oxide cap size/shape versus time for an aluminum particle tracking a stream-tube through a solid rocket motor port has been developed. Following preliminary calculations leading to a postulated flame structure...

M. K. King

2007-01-01

180

Inverse combustion force estimation based on response measurements outside the combustion chamber and signal processing  

Microsoft Academic Search

Exposure to vibration has various physiological effects on vehicle passengers. Engine is one of the main sources of vehicle vibration. The major causes of engine vibration are combustion forces transmitted through the pistons and connection rods. Evaluation of sources is the first step to attenuate this vibration. Assessment of these sources is not an easy task because internal parts of

Mohammad Hosseini Fouladi; Mohd. Jailani Mohd. Nor; Ahmad Kamal Ariffin; Shahrir Abdullah

2009-01-01

181

Development of a Spherical Combustion Chamber for Measuring Laminar Flame Speeds in Navy Bulk Fuels and Biofuel Blends.  

National Technical Information Service (NTIS)

This thesis presents the results of an experimental study to determine laminar flame speeds using the spherical flame method. An experimental combustion chamber, based on the constant-volume bomb method, was designed, built, and instrumented to conduct th...

O. D. Buckley

2011-01-01

182

Linear and nonlinear acoustics with nonuiform entropy in combustion chambers  

SciTech Connect

A one-dimensional analytical model is presented for calculating the longitudinal acoustic modes of idealized dump-type ramjet engines. A plane flame was studied and incorporated into the combustor model where the flame is allowed to move or oscillate in the combustor. This provides three mechanisms of interaction at the flame sheet: agement to supply the necessary transparency and the ability to transmit data in a lazy fashion. Study of the test-bed system reveals that copy-on-reference address space transmission improves migration effectiveness (performance). Relocations occur up to a thousand times faster, with transfer times independent of process size. Since processes access a small portion of their memory in their lifetimes, the number of bytes transferred between machines drops by up to 96%. Message-handling cost are lowered by up to 94%, and are more evenly distributed across the remote execution. Implementation, instrumentation, and study of the test bed provides more useful information than is possible through a simulation.

Humphrey, J.W.

1987-01-01

183

Modeling the internal combustion engine  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

184

Combustion Instabilities Modeled  

NASA Technical Reports Server (NTRS)

NASA Lewis Research Center's Advanced Controls and Dynamics Technology Branch is investigating active control strategies to mitigate or eliminate the combustion instabilities prevalent in lean-burning, low-emission combustors. These instabilities result from coupling between the heat-release mechanisms of the burning process and the acoustic flow field of the combustor. Control design and implementation require a simulation capability that is both fast and accurate. It must capture the essential physics of the system, yet be as simple as possible. A quasi-one-dimensional, computational fluid dynamics (CFD) based simulation has been developed which may meet these requirements. The Euler equations of mass, momentum, and energy have been used, along with a single reactive species transport equation to simulate coupled thermoacoustic oscillations. A very simple numerical integration scheme was chosen to reduce computing time. Robust boundary condition procedures were incorporated to simulate various flow conditions (e.g., valves, open ends, and choked inflow) as well as to accommodate flow reversals that may arise during large flow-field oscillations. The accompanying figure shows a sample simulation result. A combustor with an open inlet, a choked outlet, and a large constriction approximately two thirds of the way down the length is shown. The middle plot shows normalized, time-averaged distributions of the relevant flow quantities, and the bottom plot illustrates the acoustic mode shape of the resulting thermoacoustic oscillation. For this simulation, the limit cycle peak-to-peak pressure fluctuations were 13 percent of the mean. The simulation used 100 numerical cells. The total normalized simulation time was 50 units (approximately 15 oscillations), which took 26 sec on a Sun Ultra2.

Paxson, Daniel E.

1999-01-01

185

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

186

Laser-assisted homogeneous charge ignition in a constant volume combustion chamber  

NASA Astrophysics Data System (ADS)

Homogeneous charge compression ignition (HCCI) is a very promising future combustion concept for internal combustion engines. There are several technical difficulties associated with this concept, and precisely controlling the start of auto-ignition is the most prominent of them. In this paper, a novel concept to control the start of auto-ignition is presented. The concept is based on the fact that most HCCI engines are operated with high exhaust gas recirculation (EGR) rates in order to slow-down the fast combustion processes. Recirculated exhaust gas contains combustion products including moisture, which has a relative peak of the absorption coefficient around 3 ?m. These water molecules absorb the incident erbium laser radiations ( ?=2.79 ?m) and get heated up to expedite ignition. In the present experimental work, auto-ignition conditions are locally attained in an experimental constant volume combustion chamber under simulated EGR conditions. Taking advantage of this feature, the time when the mixture is thought to "auto-ignite" could be adjusted/controlled by the laser pulse width optimisation, followed by its resonant absorption by water molecules present in recirculated exhaust gas.

Srivastava, Dhananjay Kumar; Weinrotter, Martin; Kofler, Henrich; Agarwal, Avinash Kumar; Wintner, Ernst

2009-06-01

187

Numerical models on shallow magma chamber formation  

NASA Astrophysics Data System (ADS)

A magma chamber can be defined as a body within the crust that is either partially or totally molten which is injected with new magma from a deep-seated reservoir. A shallow magma chamber acts as a sink as it receives magma from the deeper reservoir, and as a source for volcanic eruptions. Most shallow magma chambers appear to develop from sills, and some, such as many mid-ocean ridge magma chambers, maintain the sill geometry through their lifetimes. For a sill to function as a magma chamber, certain conditions must be met: (1) The sill thickness must be in the order of tens of metres. This thickness is reached by either a) when a complex of thinner sills amalgamates or b) magma accumulates due to multiple dyke arrests at the contact with the sill. (2) The sill must receive a fairly constant magma replenishment so the chamber remains partially or (more rarely) totally molten. Here, we present numerical models based on geophysical data on how an individual sill can evolve into a magma chamber. Sills generally exhibit a concave-upward or straight geometry, although they may take other forms e.g. stepped, saucer-shaped, or concave-downward. Seismic studies suggest that many shallow ocean-ridge magma chambers have a moderately smooth geometry (ellipsoidal) rather than an irregular network of dykes and sills. Our numerical results indicate as follows: Firstly, the deflection of dykes into sills is most favoured in the upper crust where there are many layers generating stress barriers/delaminations due to elastic mismatch, that is, contrasting mechanical properties. Secondly, a sill grows primarily by elastic-plastic deformation of the host rock in which it is emplaced, while host rock anatexis/stoping may generate space for some large sills. The elastic-plastic expansion is partly reflected in upward bending of the overburden and partly in downward bending of the underburden. Thirdly, while the initial sill stays liquid or 'soft', subsequent dyke injections become arrested at the contact with the sill and their magmas become partly absorbed into the sill, which thereby grows. Fourthly, the sill must remain totally or at least partially molten, which requires a high injection rate of dykes feeding the sills to have a chance of developing into a shallow magma chamber. A high dyke injection rate is most likely to be reached at high extension rates, such as at fast-spreading ridges. This may be one reason for the common sill-like magma chambers being located at fast-spreading ridges.

Barnett, Zoe; Gudmundsson, Agust

2013-04-01

188

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

189

Gas Turbine Combustion Modeling.  

National Technical Information Service (NTIS)

To effectively use multidimensional models for gas tubine combustor design and development activities, a method is presented to compute aerothermal performance parameters including CO, unburned hydrocarbon, NOx and smoke emissions; lean blowout and igniti...

H. C. Mongia

1988-01-01

190

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

191

Numerical modeling of turbulent combustion  

NASA Technical Reports Server (NTRS)

The work in numerical modeling is focused on the use of the random vortex method to treat turbulent flow fields associated with combustion while flame fronts are considered as interfaces between reactants and products, propagating with the flow and at the same time advancing in the direction normal to themselves at a prescribed burning speed. The latter is associated with the generation of specific volume (the flame front acting, in effect, as the locus of volumetric sources) to account for the expansion of the flow field due to the exothermicity of the combustion process. The model was applied to the flow in a channel equipped with a rearward facing step. The results obtained revealed the mechanism of the formation of large scale turbulent structure in the wake of the step, while it showed the flame to stabilize on the outer edges of these eddies.

Ghoneim, A. F.; Chorin, A. J.; Oppenheim, A. K.

1983-01-01

192

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

NASA Technical Reports Server (NTRS)

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

Wadel, Mary F.

1997-01-01

193

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

194

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

NASA Technical Reports Server (NTRS)

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

Williams, Brian E.; Arrieta, Victor M.

2013-01-01

195

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

196

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

197

Modeling of cyclic-nitramine combustion  

Microsoft Academic Search

The theoretical and experimental data on the combustion of cyclic nitramines published in the past 30 years are systematized\\u000a and critically reviewed. Results of studies of combustion-wave parameters and flame chemical structure are presented. Simplified\\u000a and detailed models of nitramine combustion are examined. Reduction of the chemical mechanism in a flame and general problems\\u000a of the adequate description of nitramine-combustion

N. E. Ermolin; V. E. Zarko

1998-01-01

198

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

199

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

200

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

201

Modeling Combustion in Supersonic Flows  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

202

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

203

Turbulent combustion modelling in a side dump ramjet combustor  

SciTech Connect

Experimental and theoretical studies are reported on the turbulent flow in a side dump rectangular combustor. Hot wire velocimetry was used to measure the axial and transverse mean velocity and turbulence intensity components in the nonreacting case. Flow oscillations in nonreacting case are determined from spectral analysis of the signal. In the presence of combustion, gas analysis (CO, CO2) was carried out in the chamber to obtain the temperature field. Light emission from CH radicals provides additional information which is interpreted as mean rate of heat release per unit volume. Regions where combustion takes place are identified. Measurements are compared with calculations performed with a combustion model relying on the flamelet concept and using a transport equation for the surface density. Good agreement is achieved between the model predictions and experimental results. 26 refs.

Montazel, X.; Samaniego, J.M.; Lacas, F.; Poinsot, T.; Candel, S. (Aerospatiale, Centre des Gatines, Verrieres-le-Buisson (France) Laboratoire d'Energetique Moleculaire et Macroscopique-Combustion, Chatenay-Malabry (France))

1992-07-01

204

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

205

Linear and non-linear pressure oscillations in baffled combustion chambers  

NASA Astrophysics Data System (ADS)

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 eliminate combustion instabilities. Included are longitudinalization of transverse waves inside baffle compartments, restriction of velocity fluctuations near the injector face, and decreased oscillation frequency. A potential destabilizing influence of baffles is found to be the concentration of acoustic pressure at the injector face. Primary aspects of limit cycles are examined by considering second order non-linear acoustics for both two- and three-dimensional cases. Conditions for the existence of limit cycles were obtained, as well as explicit formulas for the oscillation amplitudes and frequencies in terms of linear and non-linear parameters. Important features of the energy cascade among acoustic modes are elucidated, including the energy balance during limit cycles and transfer of energy by non-linear gas dynamics.

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

1995-07-01

206

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

208

Modeling the unsteady combustion of solid propellants with detailed chemistry  

Microsoft Academic Search

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

William W. Erikson

1999-01-01

209

Simulations of Shock-Induced Mixing and Combustion of an Acetylene Cloud in a Chamber.  

National Technical Information Service (NTIS)

In this paper we present numerical simulations of the interaction of a blast wave with an acetylene bubble in a closed chamber. We model the system using the inviscid Euler equations for a mixture of ideal gases. The formulation specifies the thermodynami...

J. B. Bell M. S. Day V. E. Beckner A. L. Kuhl P. Neuwald

2001-01-01

210

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

SciTech Connect

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

NONE

1995-10-09

211

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

NASA Technical Reports Server (NTRS)

NASA's Marshall Space Flight Center(MSFC) has been tasked with developing a 60,000 pound thrust, pump-fed, LOX/RP-1 engine under the Advanced Space Transportation Program(ASTP). This government-led design has been designated the Fastrac engine. The X-34 vehicle will use the Fastrac engine as the main propulsion system. The X-34 will be a suborbital vehicle developed by the Orbital Sciences Corporation. The X-34 vehicle will be launched from an L-1011 airliner. After launch, the X-34 vehicle will be able to climb to altitudes up to 250,000 feet and reach speeds up to Mach 8, over a mission range of 500 miles. The overall length, wingspan, and gross takeoff weight of the X-34 vehicle are 58.3 feet, 27.7 feet and 45,000 pounds, respectively. This report summarizes the plan of achieving a Fastrac thrust chamber assembly(TCA) stable bomb test that meets the JANNAF standards, the Fastrac TCA design, and the combustion instabilities exhibited by the Fastrac TCA during testing at MSFC's test stand 116 as determined from high-frequency fluctuating pressure measurements. This report also summarizes the characterization of the combustion instabilities from the pressure measurements and the steps taken to eliminate the instabilities.

Rocker, Marvin; Nesman, Thomas E.

1998-01-01

212

Observation of nonuniform shrinkage and activation of highly porous chars during combustion in an improved electrodynamic chamber  

Microsoft Academic Search

Combustion of single particles of highly porous synthetic char has been investigated in an electrodynamic chamber (EDC). The main reasons for using the EDC for studying high temperature kinetics of single particles are to (1) sustain the particle without moving at all times at a known point, (2) eliminate heat and mass transfer limitations, (3) observe particle-to-particle differences, (4) fully

Yony Weiss; Ezra Bar-Ziv

1995-01-01

213

ANALYSIS OF THE TURBULENT, NON-PREMIXED COMBUSTION OF NATURAL GAS IN A CYLINDRICAL CHAMBER WITH AND WITHOUT THERMAL RADIATION  

Microsoft Academic Search

This work presents a numerical simulation of the non-premixed combustion of natural gas in atmospheric air in an axis-symmetric cylindrical chamber, focusing on the effect of thermal radiation on the temperature and chemical species concentration fields and the heat transfer. The simulation is based on the solution of the mass, energy, momentum and the chemical species conservation equations. Thermal radiation

C. V. SILVA; F. H. R. FRANÇA; H. A. VIELMO

2007-01-01

214

Subgrid Combustion Modeling for the Next Generation National Combustion Code  

NASA Technical Reports Server (NTRS)

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

Menon, Suresh; Sankaran, Vaidyanathan; Stone, Christopher

2003-01-01

215

Three-dimensional unsteady flow calculations in both intake port and combustion chamber  

Microsoft Academic Search

A numerical scheme using overlapping grids and multigrid methods for calculations of three-dimensional unsteady flows in internal combustion engines is presented. The flow is modeled by the incompressible Navier-Stokes equations incorporating a k-epsilon turbulence model. The main feature of the present scheme is its extended flexibility to deal with three-dimensional complex multicomponent geometries. The multigrid method is used to accelerate

J. Y. Tu; L. Fuchs

1992-01-01

216

A model for premixed combustion oscillations  

SciTech Connect

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

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

1996-09-01

217

Solar Bimodal System with Hydrogen Post-Burning. The Porblems of Combustion Chamber Heat Shield  

NASA Astrophysics Data System (ADS)

The space solar bimodal system (SBS) with the high-temperature heating of hydrogen in the concentrator-absorber system and the heated hydrogen post-burning with oxygen in the combustion chamber is considered. The SBS can provide the interorbital transfers at operation in the propulsion mode, and the power supply at operation in the energy mode. The SBS operation in the propulsion mode permits to increase the delivered (from LEO to GEO) payload mass in 1.5-2 times in comparison with the prospective LH2-LOX liquid rocket engines, or to use the carrier-rocket of more light class with less cost of launch. The SBS operation in the onboard equipment power supply mode can provide the high specific power - 5 kWe per ton or more. The reliability of such SBS prolonged operation is rather high due to usage of the high-effective multi-stage concentrator- absorber system which prevents the SBS optical efficiency decreasing occurring because of the concentrator accuracy reduction at space operation conditions (periodical temperature changing, UV-radiation influence, etc.) One of the principle problems of creation of SBS, as a system of low thrust, is the complexity of cooling of the combustion chamber where the heated hydrogen is post-burned. In the carried-out investigation the possible solution of this problem is considered. The usage of heat shield system including coolant loop with the liquid metal and the tank with thermal accumulating substance is suggested. The results of corresponding investigations concerning the performances of the SBS cooling and specific impulse change are presented. It is shown that specific impulse of the presented SBS can slightly reduce or even increase in some important cases in comparison with the existing solar bimodal systems. In the energy mode the concentrator-absorber assembly provides the high- temperature elements heating in the electric power supply system. The combination of the number of propulsion system thrust and working process parameters in some cases can be of interest of practical realisation of the thermal protection considered method.

Chvanov, Vladimir K.; Finogenov, Sergey L.; Kudrin, Oleg I.; Martynov, Mikhail V.

2002-01-01

218

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

NASA Technical Reports Server (NTRS)

A recently completed experimental test program obtained performance data on an optimally contoured nozzle with an exit-to-throat area ratio of 1025:1 and on a truncated version of this nozzle with an area ratio of 440:1. The nozzles were tested with gaseous hydrogen and liquid oxygen propellants at combustion chamber pressures of 12.4 to 16.5 mPa (1800 to 2400 psia). Testing was conducted in the altitude test capsule at the NASA Lewis Research Center's Rocket Engine Test Facility (RETF), and results were compared with analytical performance predictions. This testing builds on previous work with this nozzle at Lewis, where testing was completed at nominal chamber pressure of 350 psia. High-area-ratio nozzles have long been sought as a means to increase the performance of spacebased rocket engines. However, as the area ratio increases, the physical size and weight of the nozzle also increase. As a result, engine and vehicle designers must make tradeoffs between nozzle size and performance enhancement. Until this test program, very little experimental data existed on the performance of the high-area-ratio nozzles used in rocket engine designs. The computer codes being used by rocket engine designers rely on data extrapolated from tests of low-area-ratio nozzles, and these extrapolations do not always provide the accuracy needed for a reliable design assessment. Therefore, we conducted this high-area-ratio nozzle testing program to provide performance data for use in rocket engine design and analysis computer codes. The nozzle had a nominal 2.54-cm- (1-in.-) diameter throat, an exit diameter of 81.3-cm (32.0-in.) at an exit-to-throat area ratio of 1025, and a length of 128.6 cm (50.6 in.). Testing was conducted in an altitude test capsule to simulate the static pressure at altitude by vacuum pumping. Data such as propellant mass flow, oxidizer-to-fuel mixture, and thrust were measured. These measurements were then used to calculate performance factors such as the thrust coefficient, the characteristic exhaust velocity efficiency, and the vacuum specific impulse. In addition, the nozzle temperature was measured to calculate the amount of heat transferred from the combustion gases to the nozzle.

1995-01-01

219

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

220

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

221

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

222

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

PubMed

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

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

2007-01-01

223

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

Microsoft Academic Search

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

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

224

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

Microsoft Academic Search

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

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

2006-01-01

225

Modeling Secondary Organic Aerosol Formation From Emissions of Combustion Sources  

NASA Astrophysics Data System (ADS)

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

Jathar, Shantanu Hemant

226

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

227

A two-dimensional numerical study of the flow inside the combustion chamber of a motored rotary engine  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

228

An approach to simulate the motion of spherical and non-spherical fuel particles in combustion chambers  

Microsoft Academic Search

The objective of this paper is to identify a numerical method to simulate motion of a packed or fluidized bed of fuel particles\\u000a in combustion chambers, such as a grate furnace and a rotary kiln. Therefore, the various numerical methods applied in the\\u000a areas of granular matter and molecular dynamics were reviewed extensively. As a result, a time driven approach

Algis Džiugys; Bernhard Peters

2001-01-01

229

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

Microsoft Academic Search

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

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

2011-01-01

230

Modeling of Plasma Assisted Combustion  

NASA Astrophysics Data System (ADS)

Recently, many experimental study of plasma-assisted combustion has been done. However, numerous complex reactions in combustion of hydrocarbons are preventing from theoritical study for clarifying inside the plasma-assisted combustion, and the effect of plasma-assist is still not understood. Shinohara and Sasaki [1,2] have reported that the shortening of flame length by irradiating microwave without increase of gas temperature. And they also reported that the same phenomena would occur when applying dielectric barrier discharges to the flame using simple hydrocarbon, methane. It is suggested that these phenomena may result by the electron heating. To clarify this phenomena, electron behavior under microwave and DBD was examined. For the first step of DBD plasma-assisted combustion simulation, electron Monte Carlo simulation in methane, oxygen and argon mixture gas(0.05:0.14:0.81) [2] has been done. Electron swarm parameters are sampled and electron energy distribution function (EEDF)s are also determined. In the combustion, gas temperature is higher(>1700K), so reduced electric field E/N becomes relatively high(>10V/cm/Torr). The electrons are accelerated to around 14 eV. This result agree with the optical emission from argon obtained by the experiment of reference [2]. Dissociation frequency of methane and oxygens are obtained in high. This might be one of the effect of plasma-assist. And it is suggested that the electrons should be high enough to dissociate methane, but plasma is not needed.[4pt] [1] K. Shinohara et al, J. Phys. D:Appl. Phys., 42, 182008 (1-7) (2009).[0pt] [2] K. Sasaki, 64th Annual Gaseous Electronic Conference, 56, 15 CT3.00001(2011).

Akashi, Haruaki

2012-10-01

231

Combustion modeling, scaling and air toxins  

Microsoft Academic Search

This volume contains papers presented at the 1994 International Joint Power Generation Conference which was held October 2--6 in Phoenix, Arizona. The purpose of this conference was to provide a forum for exchange of state-of-the-art information relevant to combustion, pollutants emission, and air toxins. The papers focus on the following broad categories: pollutants emissions and combustion modeling; particle transport and

A. K. Gupta; A. Moussa; C. Presser; M. J. Rini; R. Weber; G. Woodward

1994-01-01

232

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

PubMed

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

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

2001-06-01

233

Measurement of Temperature of Plasma in Mhd-Generators and in Combustion Chambers by the Method of Recording the Absolute Intensities of Spectral Lines.  

National Technical Information Service (NTIS)

A discussion is given of the theory of measuring the temperature of plasmas in combustion chambers and MHD ducts by recording the absolute intensities (AI) of spectral lines with a large spontaneous emission coefficient (Aigi). The accuracy of the method ...

S. Suckewer

1968-01-01

234

Hydrogen-Air Combustion in a Spherical Combustion Chamber with Central Ignition and Comparison of the Results with Kinetic Calculations.  

National Technical Information Service (NTIS)

In order to get information on flame velocities and temperatures during the combustion of a hydrogen-air mixture, one determined pressure cruves of and carried out optical measurements with a spherical, centrally ignited combusition bomb. Details of the m...

W. Sehn

1985-01-01

235

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

NASA Astrophysics Data System (ADS)

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

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

1996-12-01

236

Discharge Chamber Primary Electron Modeling Activities in Three-Dimensions  

NASA Technical Reports Server (NTRS)

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

Steuber, Thomas J.

2004-01-01

237

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

238

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

239

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

NASA Technical Reports Server (NTRS)

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

Wadel, Mary F.; Meyer, Michael L.

1996-01-01

240

Challenges of oxyfuel combustion modeling for carbon capture  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

241

Effects of Oxygen/Hydrogen Combustion Chamber Environment on Copper Alloys.  

National Technical Information Service (NTIS)

Main chamber liner deterioration in the Space Shuttle Main Engine (SSME) is sufficient to cause local chamber wall failures in the form of cracks through the copper alloy chamber wall. This deterioration is termed blanching and is characterized by an incr...

M. Murphy R. E. Anderson D. C. Rousar J. A. Vankleeck

1986-01-01

242

Three-dimensional unsteady flow calculations in both intake port and combustion chamber  

SciTech Connect

A numerical scheme using overlapping grids and multigrid methods for calculations of three-dimensional unsteady flows in internal combustion engines is presented. The flow is modeled by the incompressible Navier-Stokes equations incorporating a k-epsilon turbulence model. The main feature of the present scheme is its extended flexibility to deal with three-dimensional complex multicomponent geometries. The multigrid method is used to accelerate the convergence of the numerical solver. A time-independent grid system is constructed for the moving piston in the engine. The flexibility and potential of the method has been demonstrated by calculating several cases which would be very difficult to be handled by other approaches. Results are compared with published numerical and experimental data. 28 refs.

Tu, J.Y.; Fuchs, L. (Royal Institute of Technology, Stockholm (Sweden))

1992-01-01

243

Multimodality imaging in an orthotopic mammary window chamber model  

NASA Astrophysics Data System (ADS)

Window chamber models have been utilized for many years to investigate cancer development and the tumor microenvironment. Orthotopic mammary window chamber model have been developed for detailed study of breast cancer. Orthotopic window chamber models, due to the native environment, support more realistic growth and tumor behavior than ectopic models. The work by other groups thus far utilizing mammary window chamber models has focused solely on optical imaging techniques, limited to probing the first millimeter or less of tissue. These techniques do not take full advantage of the unrestricted, three-dimensional tumor growth the model supports. We have developed a custom plastic structure compatible with multimodality imaging. We present in this work the implementation of our custom window chamber in a mouse model and the successful imaging of the window chamber cancer model with MRI, nuclear imaging, and optical techniques. MRI provides a full three-dimensional view of the tumor growth and allows for additional, potentially clinically translatable, approaches to be utilized in investigating the cancer microenvironment. Nuclear imaging is accomplished using the Beta Imager, which is a novel approach to nuclear imaging of window chambers. The Beta Imager detects photons after the interaction of a single positron with a scintillator, instead of the coincidence detection of annihilation gamma ray pairs. We utilized the radioisotope glucose analog, 2-deoxy-2- (18F)fluoro-D-glucose or FDG, with the Beta Imager to obtain information on the glycolytic metabolism of the tumor and surrounding region.

Schafer, Rachel; Leung, Hui Min; Gmitro, Arthur F.

2013-02-01

244

Advanced Chemical Modeling for Turbulent Combustion Simulations.  

National Technical Information Service (NTIS)

The goals of this project were the development of new sub-filter models for large eddy simulation of turbulent combustion and of chemical mechanisms for jet fuel surrogates. The sub-filter modeling work focuses on the development of a framework for descri...

H. Pitsch

2012-01-01

245

Compliant Walled Combustion Devices.  

National Technical Information Service (NTIS)

Combustion devices described herein comprise a compliant combustion chamber wall or segment. The compliant segment deforms during combustion in the combustion chamber. Some devices may include a compliant wall configured to stretch responsive to pressure ...

H. Prahlad J. Helm R. E. Pelrine S. Oh S. E. Stanford

2005-01-01

246

Atomization data for spray combustion modeling  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

247

A model for premixed combustion oscillations  

SciTech Connect

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

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

1996-03-01

248

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

249

Combustion modeling in advanced gas turbine systems  

SciTech Connect

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

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

1995-12-31

250

Combustion modeling and burner replacement strategies  

Microsoft Academic Search

This book contains papers presented at the 1990 International Joint Power Generation Conference. Included are the following articles: Combustion system optimization by advanced modeling technology, Experience on conversion of oil-fired to coal-fired boiler, Sources and solutions of burner related rumbling problems in boilers.

R. V. Nayak; N. A. Mousa

1990-01-01

251

THEORETICAL INVESTIGATION OF THE PERFORMANCE OF ALTERNATIVE AVIATION FUELS IN AN AERO-ENGINE COMBUSTION CHAMBER  

Microsoft Academic Search

When considering alternative fuels for aviation, factors such as the overall efficiency of the combustion process and the levels of emissions emitted to the atmosphere, need to be critically evaluated. The physical and chemical properties of a fuel influence the combustion efficiency and emissions and therefore need to be considered. The energy content of a biofuel, which is influenced negatively

I. Uryga; M. Pourkashanian; D. Borman; E. Catalanotti; C. W. Wilson

2009-01-01

252

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

253

Numerical investigations of cooling holes system role in the protection of the walls of a gas turbine combustion chamber  

NASA Astrophysics Data System (ADS)

Numerical simulations in a gas turbine Swirl stabilized combustor were conducted to investigate the effectiveness of a cooling system in the protection of combustor walls. The studied combustion chamber has a high degree of geometrical complexity related to the injection system as well as the cooling system based on a big distribution of small holes (about 3,390 holes) bored on the flame tube walls. Two cases were considered respectively the flame tube without and with its cooling system. The calculations were carried out using the industrial CFD code FLUENT 6.2. The various simulations made it possible to highlight the role of cooling holes in the protection of the flame tube walls against the high temperatures of the combustion products. In fact, the comparison between the results of the two studied cases demonstrated that the walls temperature can be reduced by about 800°C by the mean of cooling holes technique.

Ben Sik Ali, Ahlem; Kriaa, Wassim; Mhiri, Hatem; Bournot, Philippe

2012-05-01

254

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

255

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

NASA Technical Reports Server (NTRS)

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

Culick, F. E. C.

1976-01-01

256

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

SciTech Connect

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

Bethel, S.; Anderson, C.L.

1986-01-01

257

Influence of combustion conditions on the PCDD/F-, PCB-, PCBz- and PAH-concentrations in the post-combustion chamber of a waste incineration pilot plant.  

PubMed

Experiments at a pilot scale waste incinerator (0.5 MW thermal power) showed that the conditions in the post-combustion chamber (650-900 degrees C) are strongly influencing the formation of chlorinated and non-chlorinated aromatics. Non-optimal combustion conditions resulted in increased concentrations of mono- to trichlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and polycyclic aromatic hydrocarbons (PAH), while chlorinated benzenes (PCBz), polychlorinated biphenyls (PCB) and the higher chlorinated PCDD/F are only weakly affected or even decrease. The changes in concentration of the compounds investigated over a time span of hours gave hints on 'memory effects' in this combustion zone. For mono- and dichlorinated benzenes, a high correlation (r2 = 0.80) with the international toxicity equivalent (I-TEQ) value of PCDD/F was observed. As recently has been demonstrated, this correlation can be utilized for an indirect on-line measurement of the I-TEQ by a novel laser mass spectrometric technique (REMPI-TO-FMS). PMID:10739036

Blumenstock, M; Zimmermann, R; Schramm, K W; Kettrup, A

2000-01-01

258

Biomass downdraft gasifier with internal cyclonic combustion chamber: design, construction, and experimental results.  

PubMed

An exploratory downdraft gasifier design with unique biomass pyrolysis and tar cracking mechanism is evolved at Oklahoma State University. This design has an internal separate combustion section where turbulent, swirling high-temperature combustion flows are generated. A series of research trials were conducted using wood shavings as the gasifier feedstock. Maximum tar cracking temperatures were above 1100°C. Average volumetric concentration levels of major combustible components in the product gas were 22% CO and 11% H(2). Hot and cold gas efficiencies were 72% and 66%, respectively. PMID:21463935

Patil, Krushna; Bhoi, Prakash; Huhnke, Raymond; Bellmer, Danielle

2011-05-01

259

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

260

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

NASA Technical Reports Server (NTRS)

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

Gensenheyner, Robert M.; Berdysz, Joseph J.

1947-01-01

261

Experimental verification of computer spray-combustion models  

NASA Technical Reports Server (NTRS)

Analytical model formulation, representing performance of spray-combustion device, is based on understanding of atomization, mixing, vaporization, and combustion which occurs in device. Report lists results of correlations of computed values with values obtained from experiments with rocket combustor. Technique offers excellent method for evaluating validity and ranges of applicability of combustion models.

Nurick, W. H.; Clayton, R. M.; Rupe, J. H.

1973-01-01

262

Visualization of Gas-to-Liquid (GTL) Fuel Liquid Length and Soot Formation in the Constant Volume Combustion Chamber  

NASA Astrophysics Data System (ADS)

In this research, GTL spray combustion was visualized in an optically accessible quiescent constant-volume combustion chamber. The results were compared with the spray combustion of diesel fuel. Fast-speed photography with direct laser sheet illumination was used to determine the fuel liquid-phase length, and shadowgraph photography was used to determine the distribution of the sooting area in the fuel jet. The results showed that the fuel liquid-phase length of GTL fuel jets stabilized at about 20-22mm from the injector orifice and mainly depended on the ambient gas temperature and fuel volatility. GTL had a slightly shorter liquid length than that of the diesel fuel. This tendency was also maintained when multiple injection strategy was applied. The penetration of the tip of the liquid-phase fuel during pilot injection was a little shorter than the penetration during main injection. The liquid lengths during single and main injections were identical. In the case of soot formation, the results showed that soot formation was mainly affected by air-fuel mixing, and had very weak dependence on fuel volatility.

Azimov, Ulugbek; Kim, Ki-Seong

263

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

NASA Astrophysics Data System (ADS)

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

Yatsuyanagi, Nobuyuki

264

Multidimensional Modelling of Diesel Combustion: Review  

Microsoft Academic Search

\\u000a With the exponentially increasing computational power of modern computers, multi-dimensional Computational Fluid Dynamics\\u000a (CFD) has found more and more applications in diesel engine research, design and development since its initiation in the late\\u000a 1970s. Enhanced understandings of the physical processes of diesel combustion and correspondingly improved numerical models\\u000a and methods have both driven simulations using multi-dimensional CFD tools from qualitative

Yu Shi; Rolf D Reitz

265

Combustion model of tetra-ol glycidyl azide polymer  

Microsoft Academic Search

Tetra-ol glycidyl azide polymer (GAP) is one of the best candidates for the solid fuel of gas hybrid rocket system because of self-combustibility, better mechanical property and high heat of formation, and comprehensive understanding of combustion phenomena is indispensable for such an application. Combustion model of GAP, which is one-dimensional three-phase mode combustion model, was developed by Beckstead et al.

Yutaka Wada; Yoshio Seike; Nobuyuki Tsuboi; Katsuya Hasegawa; Kiyokazu Kobayashi; Makihito Nishioka; Keiichi Hori

2009-01-01

266

Engine Hydraulic Stability. [injector model for analyzing combustion instability  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

267

Modeling gas exchange in a closed plant growth chamber  

NASA Astrophysics Data System (ADS)

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

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

1994-11-01

268

Observation of nonuniform shrinkage and activation of highly porous chars during combustion in an improved electrodynamic chamber  

SciTech Connect

Combustion of single particles of highly porous synthetic char has been investigated in an electrodynamic chamber (EDC). The main reasons for using the EDC for studying high temperature kinetics of single particles are to (1) sustain the particle without moving at all times at a known point, (2) eliminate heat and mass transfer limitations, (3) observe particle-to-particle differences, (4) fully characterize the particle prior to combustion, and (5) monitor the important properties of the single particle through its entire combustion history. In this device the particle is heated radiatively by a focused laser beam to the desired temperature. During the heating the particle should not move by more than 1% of its diameter since the waist of the beam is comparable to the particle diameter. A strong proportional-integral-derivative (PID) position controller was developed to maintain the particle at the center of the EDC, with position stability better than 0.6% of its diameter. Further development of the EDC included (1) real time measurement of the particle shape and diameter with a temporal resolution of 0.1 ms and (2) infrared optical pyrometry with wide spectral bands to determine the particle temperature to within {+-} 10 K. Oxidation of synthetic char particles (Spherocarb) was studied in the EDC at temperatures around 900 K. Transients of the particle weight, size, shape, temperature, and position of the particle were measured in real-time. Using the present EDC two new phenomena were observed when highly porous chars were heated (in the range 800--900 K): (1) prior to conversion there was a stage in which mass loss or size change did not occur, this is attributed to activation of the char and was found to depend on the particle temperature; (2) nonuniform shrinkage during combustion--the initially spherical particles were consumed nonuniformly in all the numerous experiments. Quantitative results are presented for both phenomena.

Weiss, Y. [Ben-Gurion Univ. of the Negev, Beer-Sheva (Israel). Dept. of Mechanical Engineering] [Ben-Gurion Univ. of the Negev, Beer-Sheva (Israel). Dept. of Mechanical Engineering; Bar-Ziv, E. [Ben-Gurion Univ. of the Negev, Beer-Sheva (Israel). Dept. of Mechanical Engineering] [Ben-Gurion Univ. of the Negev, Beer-Sheva (Israel). Dept. of Mechanical Engineering; [Nuclear Research Center, Beer-Sheva (Israel)

1995-06-01

269

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

NASA Technical Reports Server (NTRS)

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

Geisenheyner, Robert M.; Berdysz, Joseph J.

1948-01-01

270

High turbulence combustion chamber for turbocharged lean burn gaseous fueled engine  

Microsoft Academic Search

This patent describes a gaseous fueled engine having at least a cylinder with an fuel\\/air intake and combustion product exhaust to be used in a cylinder head having a flat lower surface enclosing one end of the cylinder, and a piston with a flat top piston head slidably received in the cylinder. The improvement consists of: a. an ignition device

Joyce

1988-01-01

271

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

NASA Technical Reports Server (NTRS)

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

Wadel, Mary F.

1998-01-01

272

The influence of some synfuels on the performance and thermal loading of a pre-combustion chamber diesel engine  

SciTech Connect

Blends of different proportions of straight run naphtha/gas oil and BTX/Gas oil were used in a four-stroke pre-combustion chamber diesel engine in order to illustrate the aspects of performance and thermal loading likely to arise when using syncrudes, multifuel or coal derived fuel. The engine was instrumented for performance monitoring as well as for heat flux and metal temperature measurement and the results were compared with those obtained with gas oil. Correlations were found for the heat flux level in the cylinder head, piston and cylinder liner with the various blends employed. It was concluded that engines running on syncrudes, multifuel or coal derived fuel shall require greater attention in design and/or development since the higher heat flux prevailing in certain conditions will encourage fatigue induced cracking or liner scuffing. Also the larger heat flux differential across the component will exacerbate the thermal stress problem.

Radwan, M.S.

1985-01-01

273

Principle of soft x-ray Moire deflectometry for flow-field visualization in a diesel combustion chamber  

NASA Astrophysics Data System (ADS)

The technique based on Moire deflectometry with soft x-ray laser beam has been demonstrated by the research group of D. Ress in the research of plasma produced by laser. We apply this method to visualize the flow field in diesel combustion chamber, and it is also a new application in the world. When a beam of collimated light passes through the flow field, the index-of-refraction gradient in the plasma bends the rays through an angle. A Moire pattern is created when a probe beam is passed through a pair of rotationally offset (angle (theta) ) 1D rulings consisting of evenly spaced opaque and transmissive stripes. By measuring the fringe shift we can get the information of flow field.

You, Haihang; Yan, Dapeng; Wang, Zhengdong; He, Anzhi

1997-10-01

274

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

275

Spectral modeling of radiation in combustion systems  

NASA Astrophysics Data System (ADS)

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 the overall heat transfer in turbulent combustion systems due to nonlinear interactions between turbulent fluctuations and radiation. The present work is aimed at the development of finite volume-based high-accuracy thermal radiation modeling, including spectral radiation properties in order to accurately capture turbulence-radiation interactions (TRI) and predict heat transfer in turbulent combustion systems correctly and efficiently. The turbulent fluctuations of temperature and chemical species concentrations have strong effects on spectral radiative intensities, and TRI create a closure problem when the governing partial differential equations are averaged. Recently, several approaches have been proposed to take TRI into account. Among these attempts the most promising approaches are the probability density function (PDF) methods, which can treat nonlinear coupling between turbulence and radiative emission exactly, i.e., "emission TRI". The basic idea of the PDF method is to treat physical variables as random variables and to solve the PDF transport equation stochastically. The actual reacting flow field is represented by a large number of discrete stochastic particles each carrying their own random variable values and evolving with time. The mean value of any function of those random variables, such as the chemical source term, can be evaluated exactly by taking the ensemble average of particles. The local emission term belongs to this class and thus, can be evaluated directly and exactly from particle ensembles. However, the local absorption term involves interactions between the local particle and energy emitted by all other particles and, hence, cannot be obtained from particle ensembles directly. To close the nonlinear coupling between turbulence and absorption, i.e., "absorption TRI", an optically thin fluctuation approximation can be applied to virtually all combustion problems and obtain acceptable accuracy. In the present study a composition-PDF method is applied, in which only the temperature and the species concentrations are treated as random variables. A closely coupled hybrid finite-volume/Monte Carlo scheme is adopted, in which the Monte Carlo method is used to solve the composition-PDF for chemical reactions and the finite volume method is used to solve for the flow field and radiation. Spherical harmonics method-based finite volume solvers (P-1 and P-3) are developed using the data structures of the high fidelity open-source code flow software OpenFOAM. Spectral radiative properties of the participating medium are modeled using full-spectrum k-distribution methods. Advancements of basic k-distribution methods are performed for nongray nonhomogeneous gas- and particulate-phase (soot, fuel droplets, ash, etc.) participating media using multi-scale and multi-group based approaches. These methods achieve close-to benchmark line-by-line (LBL) accuracy in strongly inhomogeneous media at a tiny fraction of LBL's computational cost. A portable spectral module is developed, which includes all the basic to advanced k-distribution methods along with the precompiled accurate and compact k-distribution databases. The P-1 /P-3 RTE solver coupled with the spectral module is used in conjunction with the combined Reynolds-averaged Navier-Stokes (RANS) and composition-PDF-based turbulence-chemistry solver to investigate TRI in multiphase turbulent combustion systems. The combustion solvers developed in this study is employed to simulate several turbulent jet flames, such as Sandia Flame D, and artificial nonsooting and sooting flames derived from Flame D. The effects of combustion chemi

Pal, Gopalendu

276

Effect of combustion-chamber shape on the performance of a prechamber compression-ignition engine  

NASA Technical Reports Server (NTRS)

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

Moore, C S; Collins, J H , Jr

1934-01-01

277

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

278

An ignition and combustion model based on the level-set method for spark ignition engine multidimensional modeling  

SciTech Connect

To improve the prediction accuracy of the spark ignition and combustion processes in spark ignition engines, improved ignition and flame propagation models have been developed and implemented in the CFD code, KIVA-3V. An equation to calculate the spark ignition kernel growth rate is derived that considers the effects of the spark ignition discharge energy and flow turbulence on the ignition kernel growth. In addition, a flamelet combustion model based on the G equation combustion model was developed and implemented. To test the ignition and combustion models, they were applied to a homogeneous charge pancake-shaped-combustion-chamber engine, in which experimental heat flux data from probes in the engine head and cylinder liner were available. By comparing the flame arrival timings with the simulation predictions, the ignition and combustion models were validated. In addition, the models were also applied to a homogeneous charge propane-fueled SI engine. Good agreement with experimental cylinder pressures and NO{sub x} data was obtained as a function of ignition timing, engine speed, and EGR levels. (author)

Tan, Zhichao; Reitz, Rolf D. [Engine Research Center, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706 (United States)

2006-04-15

279

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

280

PDF Modeling of Turbulent Lean Premixed Combustion  

SciTech Connect

The joint velocity-scalar-frequency probability density function (PDF) methodology is employed for prediction of a bluff-body stabilized lean premixed methane-air flame. A reduced mechanism with CO and NO chemistry is used to describe fuel oxidation. The predicted mean and rms values of the velocity, temperature and concentrations of major and minor species are compared with laboratory measurements. This technical effort was performed in support of the National Energy Technology Laboratory’s on-going research in “Assessment of Turbo-Chemistry Models for Gas Turbine Combustion Emissions” under the RDS contract DE-AC26-04NT41817.

Yilmaz, S.L.; •Givi, P.; Strakey, P.A.

2007-10-01

281

Mathematical modeling of MILD combustion of pulverized coal  

Microsoft Academic Search

MILD (flameless) combustion is a new rapidly developing technology. The IFRF trials have demonstrated high potential of this technology also for N-containing fuels. In this work the IFRF experiments are analyzed using the CFD-based mathematical model. Both the Chemical Percolation Devolatilization (CPD) model and the char combustion intrinsic reactivity model have been adapted to Guasare coal combusted. The flow-field as

N. Schaffel; M. Mancini; R. Weber

2009-01-01

282

Carbon Deposition Model for Oxygen-Hydrocarbon Combustion, Volume 2  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

283

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

284

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

NASA Technical Reports Server (NTRS)

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

Schoenman, Leonard

1987-01-01

285

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

286

Modelling and PIP control design for open-top chambers  

Microsoft Academic Search

The paper first describes the identification of a control model for carbon dioxide concentration in an open-top chamber (OTC) used in plant physiology atmospheric change experiments. This model is then employed in the design of a gain-scheduled controller utilising the Proportional-Integral-Plus (PIP) control design methodology developed by Young et al. (1987). The system has been evaluated in a number of

M. J. Lees; C. J. Taylor; P. C. Young; A. Chotai

1998-01-01

287

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

DOEpatents

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

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

2013-12-17

288

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

SciTech Connect

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

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

2004-12-13

289

A pure Eulerian model for simulating dilute spray combustion  

Microsoft Academic Search

A pure Eulerian model is developed to simulate steady-state dilute spray combustion. This model is based on a fundamental description of various interacting processes which occur during spray combustion including gas-phase and spray droplet-phase turbulent flow, gas-phase turbulent combustion, radiation heat transfer and spray droplet evaporation. Both gas-phase and spray droplet-phase conservation equations are described using Eulerian coordinates. A comprehensive

Y. C. Guo; C. K. Chan; K. S. Lau

2002-01-01

290

Numerical approaches to combustion modeling. Progress in Astronautics and Aeronautics. Vol. 135  

Microsoft Academic Search

Various papers on numerical approaches to combustion modeling are presented. The topics addressed include; ab initio quantum chemistry for combustion; rate coefficient calculations for combustion modeling; numerical modeling of combustion of complex hydrocarbons; combustion kinetics and sensitivity analysis computations; reduction of chemical reaction models; length scales in laminar and turbulent flames; numerical modeling of laminar diffusion flames; laminar flames in

E. S. Oran; J. P. Boris

1991-01-01

291

Sub-grid scale combustion models for large eddy simulation of unsteady premixed flame propagation around obstacles.  

PubMed

In this work, an assessment of different sub-grid scale (sgs) combustion models proposed for large eddy simulation (LES) of steady turbulent premixed combustion (Colin et al., Phys. Fluids 12 (2000) 1843-1863; Flohr and Pitsch, Proc. CTR Summer Program, 2000, pp. 61-82; Kim and Menon, Combust. Sci. Technol. 160 (2000) 119-150; Charlette et al., Combust. Flame 131 (2002) 159-180; Pitsch and Duchamp de Lageneste, Proc. Combust. Inst. 29 (2002) 2001-2008) was performed to identify the model that best predicts unsteady flame propagation in gas explosions. Numerical results were compared to the experimental data by Patel et al. (Proc. Combust. Inst. 29 (2002) 1849-1854) for premixed deflagrating flame in a vented chamber in the presence of three sequential obstacles. It is found that all sgs combustion models are able to reproduce qualitatively the experiment in terms of step of flame acceleration and deceleration around each obstacle, and shape of the propagating flame. Without adjusting any constants and parameters, the sgs model by Charlette et al. also provides satisfactory quantitative predictions for flame speed and pressure peak. Conversely, the sgs combustion models other than Charlette et al. give correct predictions only after an ad hoc tuning of constants and parameters. PMID:20471163

Di Sarli, Valeria; Di Benedetto, Almerinda; Russo, Gennaro

2010-08-15

292

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

293

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

294

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

295

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

296

Modeling complex chemical effects in turbulent nonpremixed combustion  

NASA Technical Reports Server (NTRS)

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

Smith, Nigel S. A.

1995-01-01

297

Realistic modeling of chamber transport for heavy-ion fusion  

SciTech Connect

Transport of intense heavy-ion beams to an inertial-fusion target after final focus is simulated here using a realistic computer model. It is found that passing the beam through a rarefied plasma layer before it enters the fusion chamber can largely neutralize the beam space charge and lead to a usable focal spot for a range of ion species and input conditions.

Sharp, W.M.; Grote, D.P.; Callahan, D.A.; Tabak, M.; Henestroza, E.; Yu, S.S.; Peterson, P.F.; Welch, D.R.; Rose, D.V.

2003-05-01

298

Control Oriented Modeling of Combustion Phasing for an HCCI Engine  

Microsoft Academic Search

A promising method for reducing emissions and fuel consumption of internal combustion engines is the Homogeneous charge compression ignition (HCCI) engine. Control of ignition timing must be realized before the potential benefits of HCCI combustion can be implemented in production engines. A model suitable for real time implementation is developed and this model is able to predict ignition timing with

Mahdi Shahbakhti; Charles Robert Koch

2007-01-01

299

Combustion in a Divided Chamber, Stratified Charge, Reciprocating Engine: Inititial Comparisons of Calculated and Measured Flame Propagation  

Microsoft Academic Search

A divided-chamber, stratified-charge engine was operated at different speeds and loads, and with two prechamber nozzle sizes. Pressure was recorded and flame propagation was filmed through a transparent head. For each condition, several sets of data were taken and the experimental scatter identified. Pressure and flame propagation were then computed with a two-dimensional model and compared with the measured ones.

H. C. GUPTA; R. L STEINBERGER; F. V. BRACCO

1980-01-01

300

Incorporating advanced combustion models to study power density in diesel engines  

Microsoft Academic Search

A new combustion model is presented that can be used to simulate the diesel combustion process. This combustion process is broken into three phases: low temperature ignition kinetics, premixed burn and high temperature diffusion burn. The low temperature ignition kinetics are modeled using the Shell model. For combustion limited by diffusion, a probability density function (PDF) combustion model is utilized.

Daniel Michael Lee

1999-01-01

301

Combustion system CFD modeling at GE Aircraft Engines  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

302

MACRO-MODELLING OF NONLINEAR EFFECTS IN THE REVERBERATION CHAMBER UNDER HIGH-FREQUENCY EXCITATION  

Microsoft Academic Search

The method of construction of nonlinear model of stirred chamber with nonlinear object is con- sidered. The nonlinear model is a polynomial of split signals. This model can be used for compensation of distortions of characteristics of an electromagnetic field in the chamber. A source of these distortions is nonlinear processes. The example of modeling of the stirred chamber with

303

A combustion model for incompressible flows  

SciTech Connect

Flow of a pre-mixed, reactive, incompressible, viscous fluid was studied using a combination of vortex methods and a flame propagation algorithm based on Huygens principle. The random vortex methods are lagrangian methods used to resolve the motion of incompressible fluids regulated by the Navier-Stokes equations. They are best suited for flows at high Reynolds numbers. Detailed description of the vortex blobs, and vortex sheets methods is given together with the presentation of a hybrid vortex method that relates the two. The combustion part of the problem is modeled by a variation of the SLIC (Simple Line Interface Calculation) algorithm, that involves the use of a flame dictionary which contains flame speeds and preheat thicknesses. The combined algorithms are tested on a cold flat plate with different free stream velocities. The numerical results show the effects of cold boundaries, turbulence, and exothermicity on the burning process.

Calzada, M.E.

1991-01-01

304

a Combustion Model for Incompressible Flows  

NASA Astrophysics Data System (ADS)

We study the flow of a pre-mixed, reactive, incompressible, viscous fluid, using a combination of vortex methods and a flame propagation algorithm based on Huyghens' principle. The random vortex methods are lagrangian methods used to resolve the motion of incompressible fluids regulated by the Navier -Stokes equations. They are best suited for flows at high Reynolds numbers. Detailed description of the vortex blobs, and vortex sheets methods is given together with the presentation of a hybrid vortex method that relates the two. The combustion part of the problem is modeled by a variation of the SLIC (Simple Line Interface Calculation) algorithm, that involves the use of a flame dictionary which contains flame speeds and preheat thicknesses. The combined algorithms are tested on a cold flat late with different free stream velocities. The numerical results show the effects of cold boundaries, turbulence, and exothermicity on the burning process.

Calzada, Maria Eugenia

305

Lattice Boltzmann model for combustion and detonation  

NASA Astrophysics Data System (ADS)

In this paper we present a lattice Boltzmann model for combustion and detonation. In this model the fluid behavior is described by a finite-difference lattice Boltzmann model by Gan et al. [Physica A, 2008, 387: 1721]. The chemical reaction is described by the Lee-Tarver model [Phys. Fluids, 1980, 23: 2362]. The reaction heat is naturally coupled with the flow behavior. Due to the separation of time scales in the chemical and thermodynamic processes, a key technique for a successful simulation is to use the operator-splitting scheme. The new model is verified and validated by well-known benchmark tests. As a specific application of the new model, we studied the simple steady detonation phenomenon. To show the merit of LB model over the traditional ones, we focus on the reaction zone to study the non-equilibrium effects. It is interesting to find that, at the von Neumann peak, the system is nearly in its thermodynamic equilibrium. At the two sides of the von Neumann peak, the system deviates from its equilibrium in opposite directions. In the front of von Neumann peak, due to the strong compression from the reaction product behind the von Neumann peak, the system experiences a sudden deviation from thermodynamic equilibrium. Behind the von Neumann peak, the release of chemical energy results in thermal expansion of the matter within the reaction zone, which drives the system to deviate the thermodynamic equilibrium in the opposite direction. From the deviation from thermodynamic equilibrium, ? m *, defined in this paper, one can understand more on the macroscopic effects of the system due to the deviation from its thermodynamic equilibrium.

Yan, Bo; Xu, Ai-Guo; Zhang, Guang-Cai; Ying, Yang-Jun; Li, Hua

2013-02-01

306

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...

307

Mathematical modelling of particle mixing effect on the combustion of municipal solid wastes in a packed-bed furnace.  

PubMed

Packed bed combustion is still the most common way to burn municipal solid wastes. In this paper, a dispersion model for particle mixing, mainly caused by the movement of the grate in a moving-burning bed, has been proposed and transport equations for the continuity, momentum, species, and energy conservation are described. Particle-mixing coefficients obtained from model tests range from 2.0x10(-6) to 3.0x10(-5)m2/s. A numerical solution is sought to simulate the combustion behaviour of a full-scale 12-tonne-per-h waste incineration furnace at different levels of bed mixing. It is found that an increase in mixing causes a slight delay in the bed ignition but greatly enhances the combustion processes during the main combustion period in the bed. A medium-level mixing produces a combustion profile that is positioned more at the central part of the combustion chamber, and any leftover combustible gases (mainly CO) enter directly into the most intensive turbulence area created by the opposing secondary-air jets and thus are consumed quickly. Generally, the specific arrangement of the impinging secondary-air jets dumps most of the non-uniformity in temperature and CO into the gas flow coming from the bed-top, while medium-level mixing results in the lowest CO emission at the furnace exit and the highest combustion efficiency in the bed. PMID:17697769

Yang, Yao Bin; Swithenbank, Jim

2008-01-01

308

Mathematical modeling of MILD combustion of pulverized coal  

SciTech Connect

MILD (flameless) combustion is a new rapidly developing technology. The IFRF trials have demonstrated high potential of this technology also for N-containing fuels. In this work the IFRF experiments are analyzed using the CFD-based mathematical model. Both the Chemical Percolation Devolatilization (CPD) model and the char combustion intrinsic reactivity model have been adapted to Guasare coal combusted. The flow-field as well as the temperature and the oxygen fields have been accurately predicted by the CFD-based model. The predicted temperature and gas composition fields have been uniform demonstrating that slow combustion occurs in the entire furnace volume. The CFD-based predictions have highlighted the NO{sub x} reduction potential of MILD combustion through the following mechanism. Before the coal devolatilization proceeds, the coal jet entrains a substantial amount of flue gas so that its oxygen content is typically not higher than 3-5%. The volatiles are given off in a highly sub-stoichiometric environment and their N-containing species are preferentially converted to molecular nitrogen rather than to NO. Furthermore, there exists a strong NO-reburning mechanism within the fuel jet and in the air jet downstream of the position where these two jets merge. In other words, less NO is formed from combustion of volatiles and stronger NO-reburning mechanisms exist in the MILD combustion if compared to conventional coal combustion technology. (author)

Schaffel, N. [Silesian University of Technology, Institute of Thermal Technology, Konarskiego 22, 44-101 Gliwice (Poland); Clausthal University of Technology, Institute of Energy Process Engineering and Fuel Technology, Agricolastrasse 4, 38678 Clausthal-Zellerfeld (Germany); Mancini, M.; Weber, R. [Clausthal University of Technology, Institute of Energy Process Engineering and Fuel Technology, Agricolastrasse 4, 38678 Clausthal-Zellerfeld (Germany); Szlek, A. [Silesian University of Technology, Institute of Thermal Technology, Konarskiego 22, 44-101 Gliwice (Poland)

2009-09-15

309

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

310

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

311

Modeling of Nonacoustic Combustion Instability in Simulations of Hybrid Motor Tests  

NASA Technical Reports Server (NTRS)

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

Rocker, M.

2000-01-01

312

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

313

Combustion Chamber Fluid Dynamics and Hypergolic Gel Propellant Chemistry Simulations for Selectable Thrust Rocket Engines.  

National Technical Information Service (NTIS)

This paper describes the application of high performance computing to accelerate the development of hypergolic propulsion systems for tactical missiles. Computational fluid dynamics is employed to model the chemically reacting flow within a system's combu...

C. Chen M. J. McQuaid M. J. Nusca

2007-01-01

314

Theory and modeling in combustion chemistry.  

National Technical Information Service (NTIS)

This paper discusses four important problems in combustion chemistry. In each case, resolution of the problem focuses on a single elementary reaction. Theoretical analysis of this reaction is discussed in some depth, with emphasis on its unusual features....

J. A. Miller

1996-01-01

315

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

316

Towards a Stochastic Cellular Automata Model of Log Wood Combustion  

NASA Astrophysics Data System (ADS)

Describing the combustion of log wood and others solid fuels with complex geometry, considerable water content and often heterogenous struture is a nontrivial task. Stochastic Cellular Automata models offer a promising approach for modelling such processes. Combustion models of this type exhibit several similarities to the well-known forest fire models, but there are also significant differences between those two types of models. These differences call for a detailed analysis and the development of supplementary modeling approaches. In this article we define a qualitative two-dimensional model of burning log wood, discuss the most important differences to classical forest fire models and present some preliminary results.

Lichtenegger, Klaus; Schappacher, Wilhelm; Hebenstreit, Babette; Schmidl, Christoph; Höftberger, Ernst

2014-03-01

317

Premixed Combustion Models for Gas Turbine with Stratified Fueling Systems  

NASA Astrophysics Data System (ADS)

The most popular conventional combustion models are the “Eddy-Break-Up Model” by Spalding and “Eddy Dissipation Model” by Magnussen, both of which are accepted as applicable to premixed flames. However, these models have not simulated all the premixed combustion phenomena. In this paper we assess four combustion models; (1) “Eddy Dissipation Model”: “Magnussen Model” (2) premixed combustion model of the “Katsuki Model” which controls the reaction rate by the Damköhler number; (3) the “Kido Model”, which predicts turbulent burning velocity by laminar burning velocity and turbulent characteristics and (4) the “Modified Katsuki Model”, in which the fluctuations of concentrations and temperature are solved by the transport equation. In present work, the Kido model is newly presented as computational code based on the flame cell concept and the modified Katsuki model is also developed for application to multi-fuel systems. Our study showed that the “Modified Katsuki Model” could predict the premixed combustion phenomena sufficiently and could trace the changes of the frame front.

Mandai, Shigemi; Uda, Nobuki; Nishida, Hiroyuki

318

Oxy-combustion of pulverized coal : modeling of char combustion kinetics.  

SciTech Connect

In this study, char combustion of pulverized coal under oxy-fuel combustion conditions was investigated on the basis of experimentally observed temperature-size characteristics and corresponding predictions of numerical simulations. Using a combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometer, combustion characteristics (particle temperatures and apparent size) of pulverized coal char particles was determined for combustion in both reduced oxygen and oxygen-enriched atmospheres with either a N{sub 2} or CO{sub 2} bath gas. The two coals investigated were a low-sulfur, high-volatile bituminous coal (Utah Skyline) and a low-sulfur subbituminous coal (North Antelope), both size-classified to 75-106 {micro}m. A particular focus of this study lies in the analysis of the predictive modeling capabilities of simplified models that capture char combustion characteristics but exhibit the lowest possible complexity and thus facilitate incorporation in existing computational fluid dynamics (CFD) simulation codes. For this purpose, char consumption characteristics were calculated for char particles in the size range 10-200 {micro}m using (1) single-film, apparent kinetic models with a chemically 'frozen' boundary layer, and (2) a reacting porous particle model with detailed gas-phase kinetics and three separate heterogeneous reaction mechanisms of char-oxidation and gasification. A comparison of model results with experimental data suggests that single-film models with reaction orders between 0.5 and 1 with respect to the surface oxygen partial pressure may be capable of adequately predicting the temperature-size characteristics of char consumption, provided heterogeneous (steam and CO{sub 2}) gasification reactions are accounted for.

Shaddix, Christopher R.; Haynes, Brian S. (University of Sydney, Sydney, Australia); Geier, Manfred

2010-09-01

319

Oxy-combustion of pulverized coal : modeling of char-combustion kinetics.  

SciTech Connect

In this study, char combustion of pulverized coal under oxy-fuel combustion conditions was investigated on the basis of experimentally observed temperature-size characteristics and corresponding predictions of numerical simulations. Using a combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometer, combustion characteristics (particle temperatures and apparent size) of pulverized coal char particles was determined for combustion in both reduced oxygen and oxygen-enriched atmospheres with either a N{sub 2} or CO{sub 2} bath gas. The two coals investigated were a low-sulfur, high-volatile bituminous coal (Utah Skyline) and a low-sulfur subbituminous coal (North Antelope), both size-classified to 75-106 {micro}m. A particular focus of this study lies in the analysis of the predictive modeling capabilities of simplified models that capture char combustion characteristics but exhibit the lowest possible complexity and thus facilitate incorporation in existing computational fluid dynamics (CFD) simulation codes. For this purpose, char consumption characteristics were calculated for char particles in the size range 10-200 {micro}m using (1) single-film, apparent kinetic models with a chemically 'frozen' boundary layer, and (2) a reacting porous particle model with detailed gas-phase kinetics and three separate heterogeneous reaction mechanisms of char-oxidation and gasification. A comparison of model results with experimental data suggests that single-film models with reaction orders between 0.5 and 1 with respect to the surface oxygen partial pressure may be capable of adequately predicting the temperature-size characteristics of char consumption, provided heterogeneous (steam and CO{sub 2}) gasification reactions are accounted for.

Shaddix, Christopher R.; Haynes, Brian S. (University of Sydney, Sydney, Australia); Geier, Manfred

2010-09-01

320

Detailed Chemical Kinetic Modeling of Diesel Combustion with Oxygenated Fuels  

SciTech Connect

Emission standards for diesel engines in vehicles have been steadily reduced in recent years, and a great deal of research and development effort has been focused on reducing particulate and nitrogen oxide emissions. One promising approach to reducing emissions involves the addition of oxygen to the fuel, generally by adding an oxygenated compound to the normal diesel fuel. Miyamoto et al. [1] showed experimentally that particulate levels can be significantly reduced by adding oxygenated species to the fuel. They found the Bosch smoke number (a measure of the particulate or soot levels in diesel exhaust) falls from about 55% for conventional diesel fuel to less than 1% when the oxygen content of the fuel is above about 25% by mass, as shown in Figure 1. It has been well established that addition of oxygenates to automotive fuel, including both diesel fuel as well as gasoline, reduces NOx and CO emissions by reducing flame temperatures. This is the basis for addition of oxygenates to produce reformulated gasoline in selected portions of the country. Of course, this is also accompanied by a slight reduction in fuel economy. A new overall picture of diesel combustion has been developed by Dec [2], in which laser diagnostic studies identified stages in diesel combustion that had not previously been recognized. These stages are summarized in Figure 2. The evolution of the diesel spray is shown, starting as a liquid jet that vaporizes and entrains hot air from the combustion chamber. This relatively steady process continues as long as fuel is being injected. In particular, Dec showed that the fuel spray vaporizes and mixes with air and products of earlier combustion to provide a region in which a gas phase, premixed fuel-rich ignition and burn occurs. The products of this ignition are then observed experimentally to lead rapidly to formation of soot particles, which subsequently are consumed in a diffusion flame. Recently, Flynn et al. [3] used a chemical kinetic and mixing model to study the premixed, rich ignition process. Using n-heptane as a representative diesel fuel, they showed that addition of an oxygenated additive, methanol, to the fuel reduced the concentrations of a number of hydrocarbon species in the products of the rich ignition. Specifically, methanol addition reduced the total concentrations of acetylene, ethylene and 1,3-butadiene, as well as propargyl and vinyl radicals, in the ignition products. These are the same species shown in a number of studies [4-6] to be responsible for formation of aromatic and polycyclic aromatic species in flames, species which lead eventually to production of soot. Flynn et al. did not, however, examine the kinetic processes responsible for the computed reduction in production of soot precursor species. At least two hypotheses have been advanced to explain the role that oxygenated species play in diesel ignition and the reduction in the concentrations of these species. The first is that the additive, methanol in the case of Flynn et al., does not contain any C-C bonds and cannot then produce significant levels of the species such as acetylene, ethylene or the unsaturated radicals which are known to lead to aromatic species. The second hypothesis is that the product distribution changes very naturally as oxygen is added and the overall equivalence ratio is reduced. In the present study, we repeat the ignition calculations of Flynn et al. and include a number of other oxygenated species to determine which of these theories is more applicable to this model.

Curran, H J; Fisher, E M; Glaude, P-A; Marinov, N M; Pitz, W J; Westbrook, C K; Flynn, P F; Durrett, R P; zur Loye, A O; Akinyemi, O C; Dryer, F L

2000-01-11

321

Tetra-ol Glycidyl Azide Polymer Combustion Modeling  

NASA Astrophysics Data System (ADS)

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

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

322

Numerical modelling of one-dimensional laminar pulverized coal combustion.  

National Technical Information Service (NTIS)

A model for laminar, premixed pulverized-coal flame propagation has been developed which includes particle radiation, conduction between gas and particles, and combustion of volatiles and char. Radiative heat transfer between particles is described by the...

Chinh Minh Trinh

1995-01-01

323

Tetra-ol Glycidyl Azide Polymer Combustion Modeling  

Microsoft Academic Search

Tetra-ol glycidyl azide polymer (GAP) is one of the best candidates for the solid fuel of gas hybrid rocket system because of self-combustibility and high heat of formation. Combustion model of GAP was developed by Beckstead et al. and they applied it to tri-ol GAP successfully. We have applied this model to tetra-ol GAP as an initial attempt, and numerical

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

2009-01-01

324

A numerical model of combustion in gasless pyrotechnic systems  

SciTech Connect

A simple numerical model has been developed for the propagation of a combustion wave through a gasless pyrotechnic mixture. A pseudo one-dimensional approach has been adopted in which an allowance for heat loss has been made by the inclusion of a simple Newtonian heat transfer term. Implementation requires a knowledge of the thermal and kinetic properties of the pyrotechnic mixture. The model reproduces the observed trends in burning velocity and predicts conditions leading to combustion failure.

Boddington, T.; Cottrell, A.; Laye, P.G.

1989-04-01

325

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

326

Experimental Investigation of Film Cooling with Tangential Slot Injection in a LOX/CH4 Subscale Rocket Combustion Chamber  

NASA Astrophysics Data System (ADS)

Within the frame of a broader activity towards research into the application of methane in cryogenic liquid rocket engines, the efficiency of film cooling was studied in a LOX/CH4 fired subscale sized model combustor. Aiming at booster as well as upper stage applications, the combustion pressure levels have been varied between 4 MPa and 7 MPa. The effectiveness of the ambient temperature film was determined in axial and circumferential directions by measuring temperature gradients in the copper liner material. The experiments revealed remarkable circumferential differences of the film cooling efficiency which remain existent far downstream. However, circumferential film cooling varieties are more pronounced at close proximity of the point of film coolant injection.

Arnold, Richard; Suslov, Dmitry I.; Haidn, Oskar J.

327

Stochastic combustion modeling of direct injection diesel engines  

Microsoft Academic Search

A comprehensive diesel engine combustion model has been developed. The model is an extension of similar thermodynamic multi-zone models for gasoline engines. In this model, the charge is divided into many distinct zones to express geometric information and to provide spatial resolution. Within each zone structure, mass, momentum and energy conservations are expressed as lumped formulations. This basic structure is

Xiao; Yun

1991-01-01

328

Results of a model for premixed combustion oscillation  

SciTech Connect

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

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

1996-12-31

329

Partial modeling for plasma assisted combustion -- Turbine combustor application  

NASA Astrophysics Data System (ADS)

Modern gas turbine combustors have to meet increasingly stringent emissions requirements at enlarged operability at conditions of lean-premixed natural gas combustors. This work is dedicated to analysis of possible plasma effect on natural gas combustion gas turbine operation via partial modeling approach. It was shown that plasma effect has potential to enhance the stability of premixed natural gas combustion by widening the lean-blowout limit and enabling operation at lower flame temperatures thus achieving lower emissions and higher turndown capability.

Potapkin, Boris; Deminsky, Maxim; Strelkova, Marina; Chernysheva, Irina; Kochetov, Igor; Saddoughi, Seyed; Herbon, John T.; Sommerer, Timothy

2009-10-01

330

Results of a model for premixed combustion oscillations  

SciTech Connect

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

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

1996-09-01

331

Combustion  

NASA Astrophysics Data System (ADS)

The process whereby a substance is combined with oxygen with the production of heat. Burning is a familiar example of this process. The energy required to propel chemical rockets is provided by the combustion of fuel with an oxidant at very high temperatures. A common oxidant is liquid oxygen (often denoted by LOX). Others include hydrogen peroxide and nitrogen tetroxide....

Murdin, P.

2000-11-01

332

'Bubble chamber model' of fast atom bombardment induced processes.  

PubMed

A hypothesis concerning FAB mechanisms, referred to as a 'bubble chamber FAB model', is proposed. This model can provide an answer to the long-standing question as to how fragile biomolecules and weakly bound clusters can survive under high-energy particle impact on liquids. The basis of this model is a simple estimation of saturated vapour pressure over the surface of liquids, which shows that all liquids ever tested by fast atom bombardment (FAB) and liquid secondary ion mass spectrometry (SIMS) were in the superheated state under the experimental conditions applied. The result of the interaction of the energetic particles with superheated liquids is known to be qualitatively different from that with equilibrium liquids. It consists of initiation of local boiling, i.e., in formation of vapour bubbles along the track of the energetic particle. This phenomenon has been extensively studied in the framework of nuclear physics and provides the basis for construction of the well-known bubble chamber detectors. The possibility of occurrence of similar processes under FAB of superheated liquids substantiates a conceptual model of emission of secondary ions suggested by Vestal in 1983, which assumes formation of bubbles beneath the liquid surface, followed by their bursting accompanied by release of microdroplets and clusters as a necessary intermediate step for the creation of molecular ions. The main distinctive feature of the bubble chamber FAB model, proposed here, is that the bubbles are formed not in the space and time-restricted impact-excited zone, but in the nearby liquid as a 'normal' boiling event, which implies that the temperature both within the bubble and in the droplets emerging on its burst is practically the same as that of the bulk liquid sample. This concept can resolve the paradox of survival of intact biomolecules under FAB, since the part of the sample participating in the liquid-gas transition via the bubble mechanism has an ambient temperature which is not destructive for biomolecules. Another important feature of the model is that the timescale of bubble growth is no longer limited by the relaxation time of the excited zone ( approximately 10(-12) s), but rather resembles the timescale characteristic of common boiling, sufficient for multiple interactions of gas molecules and formation of clusters. Further, when the bubbles burst, microdroplets are released, which implies that FAB processes are similar to those in spraying techniques. Thus, two processes contribute to the ion production, namely, release of volatile solvent clusters from bubbles and of non-volatile solute from sputtered droplets. This view reconciles contradictory views on the dominance of either gas-phase or liquid-phase effects in FAB. Some other effects, such as suppression of all other ions by surface-active compounds, are consistent with the suggested model. PMID:12872284

Kosevich, Marina V; Shelkovsky, Vadim S; Boryak, Oleg A; Orlov, Vadim V

2003-01-01

333

Theory and modeling in combustion chemistry  

SciTech Connect

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

Miller, J.A.

1996-10-01

334

Large eddy simulation modelling of combustion for propulsion applications.  

PubMed

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

Fureby, C

2009-07-28

335

Nonlinear Analysis and Modelling of Combustion Instabilities in a Laboratory Combustor  

Microsoft Academic Search

The spectra of pressure oscillations in combustion chambers often contain large peaks at frequencies corresponding to chamber acoustic modes. Pulsed combustors are designed to operate with fixed amplitude oscillations but in many systems the oscillations have undesirable consequences. An understanding of the nonlinear mechanisms responsible for the limiting-amplitude behavior is therefore desired. This paper is divided into two parts. First,

JAMES D. STERLING

1993-01-01

336

Velocity and turbulence measurements in a combustion chamber of S. I. engine under motored and firing operations by L. D. A. with fiber-optic pick-up  

SciTech Connect

In order to improve adaptability of the laser Doppler anemometer (LDA) to measurement of gas flow velocities in an internal combustion engine, an optical fiber system composed of a couple of single mode, polarization-preserving optical fibers has been developed to transmit the incident beams. The overall light transmission efficiency of the system is 24% and not so high, but the system enables real-time measurements of gas flow velocity in the combustion chamber of a small two-cycle engine during firing operation. The velocity data measured are processed with cycle by cycle analysis by stationary time-averaged method to obtain bulk velocity, turbulence intensity and integral time scale of turbulence.

Obokata, T.; Hanada, N.; Kurabayashi, T.

1987-01-01

337

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

Microsoft Academic Search

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

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

1990-01-01

338

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

339

Computing combustion noise by combining large eddy simulations with analytical models for the propagation of waves through turbine blades  

NASA Astrophysics Data System (ADS)

Two mechanisms control combustion noise generation as shown by Marble and Candel (1977) [1]: direct noise, in which acoustic waves propagate through the turbine stages and indirect noise, in which vorticity and/or entropy waves generate noise as they are convected through turbine stages. A method to calculate combustion-generated noise has been implemented in a tool called CHORUS. The method uses the large eddy simulations of the combustion chamber obtained with the unstructured solver AVBP developed at CERFACS (Schønfeld and Rudgyard, 1999 [2]) and analytical models for the propagation through turbine stages. The propagation models (Cumpsty and Marble, 1977 [3]) use the compact row hypothesis to write matching conditions between the inlet and the outlet of a turbine stage. Using numerical simulations, the validity of the analytical methods is studied and the errors made quantified.

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

2013-01-01

340

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

Microsoft Academic Search

Effect of kinds of one-component n-alkane liquid fuels on combustion characteristics was investigated experimentally using a model combustor of scramjet engine. The inlet condition of a model combustor is 2.0 of Mach number, up to 2400K of total temperature, and 0.38MPa of total pressure. Five kinds of n-alkane are tested, of which carbon numbers are 7, 8, 10, 13, and

2010-01-01

341

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

342

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

343

Combustor nozzle for a fuel-flexible combustion system  

DOEpatents

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

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

2011-03-22

344

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

345

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

346

Thermophysics Characterization of Kerosene Combustion  

NASA Technical Reports Server (NTRS)

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

Wang, Ten-See

2001-01-01

347

A mathematical model of ash formation during pulverized coal combustion  

Microsoft Academic Search

A mathematical model of ash formation during high-rank pulverized coal combustion is reported in this paper. The model is based on the computer-controlled scanning electron microscope (CCSEM) characterization of minerals in pulverized coals. From the viewpoint of the association with coal carbon matrix, individual mineral grains present in coal particles can be classified as included or excluded minerals. Included minerals

L. Yan; R. P. Gupta; T. F. Wall

2002-01-01

348

A Nonlinear Model for Ducted Flame Combustion Instabilities  

Microsoft Academic Search

This paper presents a direct simulation of low frequency combustion instabilities in premixed turbulent combustors. The simulation is based on the thin flame sheet (TFS) model proposed by Marble and Candel in their investigation of ramjet and afterburner instabilities. This model is solved numerically to allow the prediction of the flame response to any excitation. The numerical calculations are performed

THIERRY POINSOT; SEBASTIEN M. CANDEL

1988-01-01

349

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

350

Kinetic models of combustion of kerosene and its components  

Microsoft Academic Search

Modern investigations on creation of kinetic models of combustion of hydrocarbons entering into the composition of kerosene\\u000a and kerosene as a whole have been analyzed. Certain recommendations on application of these models to calculation of actual\\u000a gasdynamic flows have been given.

G. Ya. Gerasimov; S. A. Losev

2005-01-01

351

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

National Technical Information Service (NTIS)

An analytical investigation on the effect of high aspect ratio (height/width) cooling channels, considering different coolant channel designs, on hot-gas-side wall temperature and coolant pressure drop for a liquid hydrogen cooled rocket combustion chambe...

M. F. Wadel

1998-01-01

352

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

353

Modelacao de Combustao, Transferencia de Calor e Emissao de Poluentes em Sistemas de Queima de Combustiveis Liquidos (Modelling of Combustion, Heat Transfer and Release of Pollutants in Chemical Systems for Combustible Liquids).  

National Technical Information Service (NTIS)

The study is concerned with the prediction of the fluid flow, combustion, heat transfer and pollutant emissions in liquid fueled systems. First, a three dimensional numerical solution technique is used to calculate the combustion chamber, the glass tank a...

V. S. de Almeida Semiao

1989-01-01

354

On-line analysis of gas-phase composition in the combustion chamber and particle emission characteristics during combustion of wood and waste in a small batch reactor.  

PubMed

The emission of particulate matter and gaseous compounds during combustion of wood and refuse-derived fuel in a small batch reactor is investigated by laser mass-spectrometric on-line measurement techniques for gas-phase analysis and simultaneous registration of physical aerosol properties (number size distribution). The gas-phase composition is addressed by a laser-based mass spectrometric method, namely, vacuum-UV single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). Particle-size distributions are measured with a scanning mobility particle sizer. Furthermore, a photoelectric aerosol sensor is applied for detection of particle-bound polycyclic aromatic hydrocarbons. The different phases of wood combustion are distinguishable by both the chemical profiles of gas-phase components (e.g., polycyclic aromatic hydrocarbons, PAH) and the particle-size distribution. Furthermore, short disturbances of the combustion process due to air supply shortages are investigated regarding their effect on particle-size distribution and gas-phase composition, respectively. It is shown that the combustion conditions strongly influence the particle-size distribution as well as on the emission of particle-bound polycyclic aromatic hydrocarbons. PMID:15819190

Ferge, T; Maguhn, J; Hafner, K; Mühlberger, F; Davidovic, M; Warnecke, R; Zimmermann, R

2005-03-15

355

Large-eddy simulation of turbulent flow inside a sudden-expansion cylindrical chamber  

Microsoft Academic Search

A large-eddy simulation (LES) is performed for turbulent flow inside a combustion device. The combustion device is simplified as a cylinder with sudden expansion. To promote turbulent mixing and to accommodate flame stability, a flame holder is attached inside the combustion chamber. Emphasis is placed on the flow details with different geometries of the flame holder. The Smagorinsky model and

Sang Cheol Ko; Hyung Jin Sung

2002-01-01

356

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

357

Supercomputer modeling of hydrogen combustion in rocket engines  

NASA Astrophysics Data System (ADS)

Hydrogen being an ecological fuel is very attractive now for rocket engines designers. However, peculiarities of hydrogen combustion kinetics, the presence of zones of inverse dependence of reaction rate on pressure, etc. prevents from using hydrogen engines in all stages not being supported by other types of engines, which often brings the ecological gains back to zero from using hydrogen. Computer aided design of new effective and clean hydrogen engines needs mathematical tools for supercomputer modeling of hydrogen-oxygen components mixing and combustion in rocket engines. The paper presents the results of developing verification and validation of mathematical model making it possible to simulate unsteady processes of ignition and combustion in rocket engines.

Betelin, V. B.; Nikitin, V. F.; Altukhov, D. I.; Dushin, V. R.; Koo, Jaye

2013-08-01

358

The study of chamber rockburst by the CUSP model of catastrophe theory  

Microsoft Academic Search

By means of CUSP model of catastrophe theory, this paper has studied the physics process of rockburst occurred on circular\\u000a chamber. The present paper has not only described the instability process of rockburst more deeply, but also got the critical\\u000a depth of plastic softening area of chamber that is valuable in the controlling engineering of rockburst. The chamber displacement\\u000a jump

Pan Yi-shan; Zhang Meng-tao; Li Guo-zheng

1994-01-01

359

A mixing controlled direct chemistry (MCDC) model for diesel engine combustion modelling using large eddy simulation  

Microsoft Academic Search

A mixing controlled direct chemistry (MCDC) combustion model with sub-grid scale (SGS) mixing effects and chemical kinetics has been evaluated for Large Eddy Simulation (LES) of diesel engine combustion. The mixing effect is modelled by a mixing timescale based on mixture fraction variance and sub-grid scalar dissipation rate. The SGS scalar dissipation rate is modelled using a similarity term and

Yuxin Zhang; Christopher J. Rutland

2011-01-01

360

A mixing controlled direct chemistry (MCDC) model for diesel engine combustion modelling using large eddy simulation  

Microsoft Academic Search

A mixing controlled direct chemistry (MCDC) combustion model with sub-grid scale (SGS) mixing effects and chemical kinetics has been evaluated for Large Eddy Simulation (LES) of diesel engine combustion. The mixing effect is modelled by a mixing timescale based on mixture fraction variance and sub-grid scalar dissipation rate. The SGS scalar dissipation rate is modelled using a similarity term and

Yuxin Zhang; Christopher J. Rutland

2012-01-01

361

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

362

A combustion kinetic model for estimating diesel engine NOx emissions  

Microsoft Academic Search

A phenomenological combustion model, which considers the space and time evolutions of a reacting diesel fuel jet, has been developed in order to estimate the instantaneous NOx concentration in a diesel engine cylinder from the start of the injection until the exhaust valve opening. The total injected fuel mass has been divided into different fuel packages, through the fuel injection

J. J. Hernandez; M. Lapuerta; J. Perez-Collado

2006-01-01

363

A Nonlinear Model for Fuel Atomization in Spray Combustion  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

364

Detailed chemical kinetic models for the combustion of hydrocarbon fuels  

Microsoft Academic Search

The status of detailed chemical kinetic models for the intermediate to high-temperature oxidation, ignition, combustion of hydrocarbons is reviewed in conjunction with the experiments that validate them.All classes of hydrocarbons are covered including linear and cyclic alkanes, alkenes, alkynes as well as aromatics.

John M. Simmie

2003-01-01

365

A numerical model of combustion in gasless pyrotechnic systems  

Microsoft Academic Search

A simple numerical model has been developed for the propagation of a combustion wave through a gasless pyrotechnic mixture. A pseudo one-dimensional approach has been adopted in which an allowance for heat loss has been made by the inclusion of a simple Newtonian heat transfer term. Implementation requires a knowledge of the thermal and kinetic properties of the pyrotechnic mixture.

T. Boddington; A. Cottrell; P. G. Laye

1989-01-01

366

Modeling a Rogowski coil in an EMC chamber taking into account the displacement current  

Microsoft Academic Search

A Rogowski coil in an EMC chamber is modeled by a magnetodynamic vector potential formulation. The model is taking into account the effect of the displacement current on the electromotive force induced in the coil and measured for different frequencies.

M. V. Ferreira da Luz; A. Kost; R. T. Jacobs; N. Sadowski; D. Weinzierl; M. Rigoni; N. J. Batistela; J. P. A. Bastos

2010-01-01

367

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...

368

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...

369

Total scattering cross section improvements from electromagnetic reverberation chambers modeling and stochastic formalism  

Microsoft Academic Search

This article is dedicated to deterministic and stochastic improvements for TSCS computations. Firstly, the To- tal Scattering Cross Section (TSCS) measurements are achieved in a numerical Reverberation Chamber (RC) for different targets. From a theoretical point of view, a free-space environment (for instance an anechoic chamber modeled numerically by absorbing boundary conditions) jointly with plane waves stimulations are needed to

Sebastien Lallechere; Ibrahim El Baba; Pierre Bonnet; Francoise Paladian

2011-01-01

370

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...

371

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

372

Low-Frequency Model for Rectangular Semi-Anechoic Chambers  

Microsoft Academic Search

An efficient and accurate method to compute the electromagnetic field inside a rectangular semi-anechoic chamber from 30 to 100 MHz is provided. A modal analysis method is used to develop the homogeneous and inhomogeneous solution. They are then combined with a generalized circuital analysis to take into account the effect of the several layers of ferrite and dielectrics on the

I. M. Perez; L. Nuno; Fernando Daniel Quesada Pereira; Juan V. Balbastre Tejedor

2006-01-01

373

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

374

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.

375

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

376

Turbulent entrainment model for spark-ignition engine combustion  

Microsoft Academic Search

A turbulent entrainment model for the turbulent combustion process in spark-ignition engines is described. The model uses the basic quantities of turbulent flow, i.e., the integral length scale, micro length scale, and turbulent intensity. The characteristic reaction time for a large eddy tau was calculated using the characteristic reaction time tau\\/sub c\\/ for the microscale, lambda\\/S\\/sub l\\/, where S\\/sub l\\/

R. J. Tabaczynski; C. R. Ferguson; K. Radhakrishnan

1977-01-01

377

Numerical modeling of LOX/methane impingement, evaporation, and combustion  

NASA Astrophysics Data System (ADS)

A computational fluid dynamics approach is used to model the impingement and subsequent combustion of LOX/LCH4 "green" propellants. The objective of this investigation is to assess the capabilities of current state-of-the-art CFD codes, here STAR-CCM+ v5.2, to model the associated multi-phase, multi-component, reacting flow field. The two multiphase methods, Volume of Fluid and Lagrangian Discrete Droplet, are evaluated to model the like-on-like and unlike doublet impingement configurations. Subsequently, droplet combustion simulation is performed in Lagrangian-Eulerian coupled framework using integrated models including Standard Eddy Break-Up combustion, quasi-steady evaporation, and RANS k-epsilon turbulence models. For an oxidizer-to-fuel ratio of3.4, flame temperatures of2880 K and 2670 K are predicted for two different kinds of Lagrangian injectors, point and cone, respectively, which, as expected, is less than the Chemical Equilibrium Analysis prediction of 3000 K. Besides recommendations in current methodology, an outline of modeling multi-species reaction in immiscible multiphase domain is presented.

Harpal, Naimishkumar

378

MODELING OF SITE ATTENUATION IN A SEMI-ANECHOIC CHAMBER FOR EMC MEASUREMENTS  

Microsoft Academic Search

In this paper, a site attenuation model for semi-anechoic chambers using ray-tracing technique is developed. The proposed model considers multi-re?ection rays, and allows the true radiation pattern of difierent antennas to be included. Thus, this model can be used in the site attenuation measurement prediction performed for all types of electromagnetic compatibility (EMC) antennas in various chambers. The efiect of

KAZI M. AHMED; XU LIN

379

Time-domain modeling, characterization, and measurements of anechoic and semi-anechoic electromagnetic test chambers  

Microsoft Academic Search

We present time-domain techniques for modeling, characterizing, and measuring anechoic and semi-anechoic chambers used for emission and immunity testing of digital devices. The finite difference time-domain (FDTD) approach is used to model and characterize these chambers. In the FDTD model presented here, we discuss methods used to eliminate the need to spatially resolve the fine detail of the absorbing structures;

Christopher L. Holloway; Paul M. McKenna; Roger A. Dalke; Rodney A. Perala; Charles L. Devor

2002-01-01

380

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

381

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

SciTech Connect

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

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

1984-01-01

382

Rotary internal combustion engine  

Microsoft Academic Search

This patent describes an internal combustion rotary engine. It comprises: a housing; a casing mounted in the housing and defining, at least in part, an annular circular piston chamber, a continuous chamber slot formed in the casing and extending the full interior circumference thereof, and a combustion chamber; a shaft mounted in the housing for rotation about its axis and

Bayless

1990-01-01

383

A filtered tabulated chemistry model for LES of premixed combustion  

SciTech Connect

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

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

2010-03-15

384

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

385

Combustion turbine dynamic model validation from tests  

Microsoft Academic Search

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

L. N. Hannett; Afzal Khan

1993-01-01

386

NUMERICAL MODELING OF TURBULENT FLOW IN A COMBUSTION TUNNEL  

SciTech Connect

A numerical technique for the analysis of turbulent flow associated with combustion is presented, The technique utilizes Chorin's RVM (Random Vortex Method), an algorithm capable of tracing the action of elementary turbulent eddies and their cumulative effects without imposing any restriction upon their motion. In the past RVM has been used with success to treat non-reacting turbulent flows, revealing, in particular, the mechanics of large scale flow patterns, the so-called coherent structures. Introduced here is a flame propagation algorithm, also developed by Chorin, in conjunction with volume sources modeling the mechanical effects of the exothermic process of combustion. As an illustration of its use, the technique is applied to flow in a combustion tunnel where the flame is stabilized by a back-facing step. Solutions for both non-reacting and reacting flow fields are obtained, under the restriction of a set of most stringent idealizations, mimicking nonetheless quite satisfactorily the essential features of turbulent combustion in a lean propane-air mixture that were observed in the laboratory by means of high speed schlieren cinematography.

Ghoniem, A. F.; Chorin, A. J.; Oppenheim, A. K.

1980-09-01

387

Numerical modelling of turbulent flow in a combustion tunnel  

NASA Technical Reports Server (NTRS)

A numerical technique is presented for the analysis of turbulent flow associated with combustion. The technique uses Chorin's random vortex method (rvm), an algorithm capable of tracing the action of elementary turbulent eddies and their cumulative effects without imposing any restriction upon their motion. In the past, the rvm has been used with success to treat nonreacting turbulent flows, revealing in particular the mechanics of large-scale flow patterns, the so-called coherent structures. Introduced here is a flame propagation algorithm, also developed by Chorin, in conjunction with volume sources modelling the mechanical effects of the exothermic process of combustion. As an illustration of its use, the technique is applied to flow in a combustion tunnel where the flame is stabilized by a back-facing step. Solutions for both nonreacting and reacting flow fields are obtained which satisfactorily describe the essential features of turbulent combustion in a lean propane-air mixture that were observed in the laboratory by means of high speed Schlieren photography.

Ghoniem, A. F.; Chorin, A. J.; Oppenheim, A. K.

1982-01-01

388

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

389

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

390

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

NASA Astrophysics Data System (ADS)

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

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

391

Modelling NOx emissions of single droplet combustion  

Microsoft Academic Search

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

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

2012-01-01

392

Modelling NOx emissions of single droplet combustion  

Microsoft Academic Search

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

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

2011-01-01

393

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

394

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

395

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

396

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

397

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

398

Annual progress report for the fiscal year 1991 and CUSP catastrophe in advanced two chamber model  

SciTech Connect

This year the research efforts were concentrated on the Advanced Two Chamber Model for DIII-D. We have written two codes ADVTCM1 and ADVTCM2 to solve the equations of this advanced model. Both codes have been tested and debugged. At present, we are studying this model in detail using these two codes. This report discusses this model.

Punjabi, A. [Hampton Univ., VA (United States)

1991-06-01

399

Heterogeneous ice nucleation in the AIDA chamber: a microphysical modelling study  

NASA Astrophysics Data System (ADS)

In July 2002 a heterogeneous ice nucleation campaign was carried out in the highly instrumented AIDA cloud chamber facility at Forschungszentrum Karlsruhe. A variety of temperatures and pumping speeds (cooling rates) were investigated using two types of aerosol: spark generated soot and mineral dust. Detailed measurements of temperature, pressure, humidity, aerosol and hydrometeor characteristics (concentration and size) were made. The detailed observations of the chamber environment conditions allow us to critically test published heterogeneous ice nucleation parametrizations. We will present the results of a detailed microphysical model of the AIDA chamber runs.

Cotton, R.; Field, P.; Moehler, O.; Stetzer, O.; Connolly, P.; Mangold, A.; Kramer, M.; Schurath, U.

2003-04-01

400

Macrokinetics of Combustion of Monodisperse Agglomerates in the Flame of a Model Solid Propellant  

Microsoft Academic Search

The paper describes a procedure for studying the macrokinetics of combustion of agglomerates in a solid propellant flame using special samples of a model propellant generating monodisperse agglomerates. Empirical dependences of the incompleteness of aluminum combustion in the combustion products of a propellant based on ammonium perchlorate and HMX on time and pressure were established. The mass fraction of oxide

O. G. Glotov; V. E. Zarko; V. V. Karasev; T. D. Fedotova; A. D. Rychkov

2003-01-01

401

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

402

The modeling of the combustion of high-ash coal–char particles suitable for pressurised fluidized bed combustion: shrinking reacted core model  

Microsoft Academic Search

An investigation was undertaken involving the combustion of high-ash coal\\/char particles under conditions suitable for pressurised fluidised bed combustion, in order to evaluate an overall combustion model. The use of very poor quality feedstocks (greater than 40% ash, low calorific value and high sulphur content) in conventional pulverised fuel combustors (PFC) could be technically difficult and un-economical, and has the

Raymond Everson; Hein Neomagus; Rufaro Kaitano

2005-01-01

403

Modeling and chemical reactions. Detailed modeling of NOx emissions from staged combustion in full scale units.  

National Technical Information Service (NTIS)

The report presents a modelling approach aimed at predicting the NOx emissions from combustion furnaces. In the approach detailed chemistry is used for calculation of NOx emissions. The approach consists of three stages. Firstly, a 3-D flow pattern consid...

P. Ernola M. Hupa L. Kjaeldman P. Oksanen

1989-01-01

404

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

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

405

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

406

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

NASA Astrophysics Data System (ADS)

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

407

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

408

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

409

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

NASA Technical Reports Server (NTRS)

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

Hung, R. J.

1991-01-01

410

Reverberation Chamber Modeling Based on Image Theory: Investigation in the Pulse Regime  

Microsoft Academic Search

In this paper, we propose a straightforward 3-D time-domain model of a reverberation chamber (RC) based on image theory. This model allows one to describe the earliest moments of an arbitrary waveform in an RC. Time domain and frequency domain results from this model are analyzed and compared with measurements conducted in a RC.

Emmanuel Amador; Christophe Lemoine; Philippe Besnier; A. Laisne?

2010-01-01

411

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

412

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

2011-01-01

413

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

414

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

415

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

416

Partial equilibrium model for predicting concentration of CO in combustion  

NASA Technical Reports Server (NTRS)

A simple kinetic model, based upon the concept of partial equilibrium, is developed for predicting carbon monoxide concentrations in such steady-flow hydrocarbon-air combustion systems as gas-turbine combustors. The only two kinetic constraints used in the model are on the rate of change of the total number of gaseous particles in the system, and on the rate of change of the CO concentration. The accuracy of the model is verified by comparison with experimental results obtained by burning kerosene with air in a 130,000 Btu/hr atmospheric-pressure steady-flow burner. Burnt-gas cooling rates of 1,000,000 K/sec, about the magnitude encountered in the dilution zone of gas-turbine combustors, were obtained with a compact water-cooled heat exchanger. Good agreement between measured CO concentrations and the values predicted by the partial-equilibrium model was obtained.

Morr, A. R.; Heywood, J. B.

1974-01-01

417

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

418

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) [Lacon, IL

2007-10-09

419

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...

420

Numerical modeling of a stripline antenna in a large semi-anechoic chamber  

Microsoft Academic Search

Stripline antennas are used for automotive immunity testing in semi-anechoic chambers at low frequencies (<30 MHz). In order to investigate the behavior of such devices, a numerical model of the radiating elements of such a system has been developed using a 3D field modeling technique (TLM). The field distribution beneath this structure has also been measured for comparison with the

Alastair R. Ruddle; David D. Ward; Simon C. Pomeroy

2001-01-01

421

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

SciTech Connect

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

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

1995-01-27

422

Leading Studies of the Staged Combustion Hybrid Rocket  

Microsoft Academic Search

The staged combustion hybrid rocket is under development by our research group since 1999. This hybrid rocket engine consists of two combustion chambers. The primary combustion chamber is the fuel tank itself filled with granular solid fuels. The fuel rich gas generated by the first stage combustion flows into the secondary combustion chamber, which is located in the bottom of

Ryojiro Akiba; Yoshinori Aoki; Seiyu Kayuta; Atushi Fujii; Harunori Nagata; Shin Satori

2003-01-01

423

A simplified model of high pressure spray combustion  

NASA Technical Reports Server (NTRS)

A simplified model of high-pressure spray combustion is examined. The analysis relies on a kappa-epsilon-g turbulence model in conjunction with the locally homogeneous flow (LHF) approximation of two-phase flow, which implies infinitely fast transport rates between the phases. High-pressure phenomena near the thermodynamic critical point are treated using the Redlich-Kwong equation of state. Predictions are compared with existing measurements of spray boundaries in a pressure-atomized n-pentane spray (Sauter mean diameter, approximately 30 microns) burning in stagnant air at 3, 6, and 9 MPa. The LHF model overestimates the rate of development of the flow, yielding spray lengths roughly 20% shorter than measured. Calibrated drop-life-history calculations suggest that finite interphase transport rates are the primary cause of the discrepancy.

Mao, C.-P.; Wakamatsu, Y.; Faeth, G. M.

1981-01-01

424

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

425

Equipment, technology, perspectives and modeling of pulse combustion drying  

Microsoft Academic Search

The paper presents the analysis of potential and real benefits of pulse combustion process applied in drying. The phenomenon of pulse combustion, its mechanism, pulse combustors designs, advantages and disadvantages of this technology were described and reviewed. Pulse combustion applications in industry were analyzed and evaluated. Experimental investigations carried out at the Faculty of Process and Environmental Engineering, Technical University

Ireneusz Zbicinski

2002-01-01

426

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, Russi