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Diffusion flame

About: Diffusion flame is a research topic. Over the lifetime, 9266 publications have been published within this topic receiving 233522 citations.


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Journal ArticleDOI
TL;DR: In this article, the stretch rate of flamelets in premixed turbulent combustion is computed using detailed numerical simulations of vortex-flame interactions and a model for intermittent turbulence taking into account all possible turbulence scales acting on the flame front.

416 citations

Journal ArticleDOI
TL;DR: In this article, a new mixing model is proposed, which is local in composition space and which seeks to address problems encountered in flows with simultaneous mixing and reaction, where the change in particle composition is determined by particle interactions along the edges of a Euclidean minimum spanning tree (EMST).

407 citations

Journal ArticleDOI
TL;DR: In this article, the effects of heat release and mixture fraction gradients on flame propagation in partially premixed flows are studied. But the effects are not independent, however; heat release modifies the effective mixture fraction gradient in front of the flame.
Abstract: Heat release effects on laminar flame propagation in partially premixed flows are studied. Data for analysis are obtained from direct numerical simulations of a laminar mixing layer with a uniformly approaching velocity field. The structure that evolves under such conditions is a triple flame, which consists of two premixed wings and a trailing diffusion flame. Heat release increases the flame speed over that of the corresponding planar premixed flame. In agreement with previous analytical work, reductions in the mixture fraction gradient also increase the flame speed. The effects of heat release and mixture fraction gradients on flame speed are not independent, however; heat release modifies the effective mixture fraction gradient in front of the flame. For very small mixture fraction gradients, scaling laws that determine the flame speed in terms of the density change are presented.

400 citations

Journal ArticleDOI
TL;DR: In this paper, a model describing the combustion of ammonium perchlorate (AP) composite propellants has been developed based on a flame structure surrounding individual oxidizer crystals; the relationship between crystals and the binder matrix was evaluated statistically.
Abstract: A model describing the combustion of AP composite propellants has been developed. The model is based on a flame structure surrounding individual oxidizer crystals; the relationship between crystals and the binder matrix being evaluated statistically. Three separate flame zones are considered: 1) a primary flame between the decomposition products of the binder and the oxidizer, 2) a premixed oxidizer flame, and 3) a final diffusion flame between the products of the other two flames. Simple global kinetics are assumed for gas-phase reactions, and the surface decomposition of the propellant ingredients is assumed to be adequately described by simple Arrhenius expressions. The oxidizer decomposition is taken as being the over-all controlling factor in the combustion process. The results obtained show that the calculated surface temperature and the effect of oxidizer concentration predicted by the model are in agreement with observed experimental trends. The predicted effect of particle size is somewhat greater than observed experimentally while the temperature sensitivity is in excellent agreement with experimental data. The results of the calculations indicate a relatively strong exothermic reaction taking place at the propellant surface. Apparently the ammonium perchlorate (AP) partially decomposes exothermically in the thin surface melt previously reported in AP deflagration studies.

382 citations

Journal ArticleDOI
01 Jan 1996
TL;DR: In this paper, the authors studied the stability of a fuel jet diffusion flame by using finite-rate chemistry and showed that it is actually an ensemble of instantaneous local premixed, diffusion., and partially premixed flames.
Abstract: Flame stability of a fuel jet diffusion flame was studied numerically by using finite rate chemistry. The flow is time dependent and plane two-dimensional, and the chemical reaction is described by simplified, overall one-step kinetics. The variable parameters are the jet Reynolds number, P Rc o and Damkohler number, Da o : and three types of flame stability behavior were observed depending on values of these parameters. The first one is the local and occasional extinction at the transition point from a laminar to a turbulent flame. When Re 0 is kept at a rather high value and Da 0 is decreased, local extinction at the transition point begins to occur at a certain critical value. The occasional extinction is caused at the instant when the local scalar dissipation rate in the reaction zone becomes too large, producing a rupture in the reaction zone layer. The rupture is quickly connected again to recover the continuous reaction zone layer. As Da 0 is decreased further, however, the frequency of rupture increases, and at another critical value, complete extinction is produced at the transition point, leaving a short, residual rim flame immediately downtream of the injector. This is the second type of flame stability. As Da 0 is decreased further, the third and final stability characteristic is observed: the blow-off of the whole flame from the injector rim. When the flme is extinguished completely at the transition point, most of the injected fuel flows downstream as a fuel jet entraining the surounding air to produce a lifted, turbulent diffusion flame in the downstream flow. This study of the structure of the flame has shown that it is actually an ensemble of instantaneous local premixed, diffusion., and partially premixed flames.

382 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023183
2022331
2021194
2020133
2019141
2018157