Results 141 to 150 of about 1,904 (180)

Surface Morphology and Self-Acceleration of Expanding Spherical Flames

47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, 2009
This paper reports results on the cellular and pulsating instabilities developed over the surface of expanding spherical premixed flames. Regarding the cellular instabilities, experimental data from time-resolved images of hydrogen–air flames exhibiting hydrodynamic and diffusional-thermal cells were used to determine the flame acceleration exponent α,
Grunde Jomaas, C.K. Law
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Modeling of Turbulent Scalar Transport in Expanding Spherical Flames

SAE Technical Paper Series, 2005
<div class="htmlview paragraph">In the first part of the paper, a generalization of the turbulent diffusivity concept is considered and a generalized diffusion coefficient is introduced to account for the development of turbulent diffusivity, pressure-driven countergradient transport, and effects of chemical reactions on turbulent scalar flux ...
Andrei N. Lipatnikov, Jerzy Chomiak
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An experimental study of laminar ammonia/methane/air premixed flames using expanding spherical flames

Fuel, 2021
Abstract The fundamental flame properties of ammonia/methane/air mixtures were experimentally investigated using expending spherical flames in a constant pressure chamber. The laminar flame speeds, Markstein lengths and flammability limits were reported for ammonia/methane fuel blends with the equivalence ratios varying from 0.6 to 1.4, at room ...
Tao Shu, Yuan Xue, Zijun Zhou, Zhuyin Ren   +3 more
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The Turbulent Flame Speed of Premixed Spherically Expanding Flames

2017
Premixed syngas/air flames expanding in turbulent flow fields are investigated using large scale direct numerical simulations. A parametric analysis is performed in circular and spherical geometries for the detailed investigation of the interaction between the flame front and the turbulent flow field.
G. K. Giannakopoulos, C. E. Frouzakis, M. Matalon, A. G. Tomboulides   +3 more
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Hydrodynamic and diffusion effects on the stability of spherically expanding flames

Combustion and Flame, 1987
We examine the stability of an outwardly propagating spherical flame accounting for both hydrodynamic and thermodiffusive effects. For Lewis numbers less than a critical value Le∗ Le∗, the flame, which is stable to thermodiffusive effects, becomes unstable only after a critical size is reached. This instability is hydrodynamic in nature and is caused
J.K. Bechtold, M. Matalon
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Radiation effects in confined spherically expanding flames: Application to C5C10 flames at engine-relevant conditions

Proceedings of the Combustion Institute, 2021
Abstract Radiation heat loss introduces one of the main uncertainties associated with the determination of laminar flame speeds from experiments using the spherically expanding flame constant volume method. In this study, a radiation model was developed to solve for the volumetric radiative power in spherical geometry using discrete transfer method ...
Ashkan Movaghar, Robert Lawson, Fokion N. Egolfopoulos   +2 more
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Markstein lengths of CO/H2/air flames, using expanding spherical flames

Symposium (International) on Combustion, 1996
Markstein lengths (defined as the reduction in burning velocity per unit stretch) have been measured for a series of CO/H2/air flames at atmospheric pressure. Values as a function of stoichiometry are reported for three fuels (95%/5% CO/H2, 50%/50% CO/H2, and 100% H2).
Martin J. Brown, Ian C. McLean, David B. Smith, Simon C. Taylor   +3 more
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Nonlinear effects in the extraction of laminar flame speeds from expanding spherical flames

Combustion and Flame, 2009
Abstract Various factors affecting the determination of laminar flames speeds from outwardly propagating spherical flames in a constant-pressure combustion chamber were considered, with emphasis on the nonlinear variation of the stretched flame speed to the flame stretch rate, and the associated need to nonlinearly extrapolate the stretched flame ...
A.P. Kelley, C.K. Law
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Observation and regime classification of pulsation patterns in expanding spherical flames

Physics of Fluids, 2010
The development of pulsating instability in expanding spherical premixed flames was experimentally studied, leading to the observation and quantification of spiral waves and target patterns over the flame surfaces in rich hydrogen-air, rich hydrogen-oxygen, and lean butane-oxygen-helium mixtures at elevated pressures.
G. Jomaas, C. K. Law
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Schlieren and Shadowgraph Images of Transient Expanding Spherical Thin Flames

Energy Conversion, 2002
Experimental facilities have been built to visualize transient expanding spherical flames. Facilities include a cylindrical chamber with two end glasses for optical observation. Shadowgraph and Schlieren pictures of flame propagation have been taken using a high speed Charged Coupled Device (CCD) camera.
Matyas Matlo, Farzan Parsinejad, Hameed Metghalchi   +2 more
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