摘要:

The nonlinear problem of a curved flame interaction with a weak shock is considered. Collisions of curved flames propagating in open tubes with weak shocks of controlled intensity are studied numerically by means of two-dimensional simulations of the complete set of equations of flame dynamics including chemical kinetics, thermal conduction and fuel diffusion. It is shown that the result of a flame-shock collision depends on the shock intensity and on the expansion coefficient of the burning matter. The critical intensity of a shock needed to invert the shape of a curved flame is calculated. The obtained critical intensity is in a good agreement with the analytical scalings found for the linear problem of flame-shock interaction. It is obtained that for sufficiently large intensities of the shock the flame-shock interaction leads to considerable increase of the flame curvature and velocity. Special attention is paid to the flame-shock collisions for the case of shock intensities close to the intensities of shocks generated by a flame in a closed burning chamber. It is shown that most of the laboratory flames are destabilized by weak shocks in closed burning chambers.

ISSN:0010-2202    

DOI:10.1080/00102209908924186

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A theoretical model of exergy analysis, based on availability transfer and flow availability, in the process of spray combustion has been developed to evaluate the total thermodynamic irreversibility and second law efficiency of the process at various operating conditions. The velocity, temperature and concentration fields in the combustor, required for the evaluation of the availabilities and irreversibilities, have been computed numerically from a two phase separated flow model of the spray along with a suitable reaction kinetics for the gas phase reaction. The thermodynamic irreversibilities associated with the gas phase processes in the combustor have been obtained from the entropy transport equation, while that due to the interphase transport processes have been obtained as a difference of gas phase irreversibilities from the total irreversibility. The thermodynamic irreversibilities associated with different processes and a comparative picture of the variation of second law efficiency at various operating conditions have been made to throw light on the trade-off between the effectiveness of combustion and the lost work in a spray combustion process.

ISSN:0010-2202    

DOI:10.1080/00102209908924187

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Single droplet combustion processes including heating, evaporation, burning, soot formation and flame radiation were theoretically investigated by adopting nongray gas radiation model for the radiative transfer equation (RTE).n-Heptane was chosen as a fuel in the numerical calculation and the results were compared with the experimental data available in the literature. The discrete ordinate method (DOM) was employed to solve the radiative transfer equation and the weighted sum of gray gases model (WSGGM) was applied to account for nongray gas radiation effect by CO2and H2O while soot was assumed gray. Therefore, very detailed effects by nongray gases could be figured out in the results. The results have shown that the total burning time increases due to a decrease in total heat flux with the nongrey gas model. It is also found that for the nongray case the radiative loss to external environment is higher, thereby reducing the maximum gas temperature and the flame thickness. Consequently, a better agreement with experimental data could be obtained by using nongray gas model.

ISSN:0010-2202    

DOI:10.1080/00102209908924188

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Studying of ignition, combustion and detonation processes in dusty gases is presented. The dusty gas is considered as a two-continuum medium with taking into account transport effects in the phases and non-equilibrium chemical reactions. Two-dimensional problems of ignition and detonation developing in a plane gallery caused by a supersonic inflow stream and heating of the closed end of the gallery are studied with the analytical mediod of catastrophe and two finite-difTerence numerical methods.

ISSN:0010-2202    

DOI:10.1080/00102209908924189

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper reports experiments on initially quasi-conical premixed flames subjected to acoustic forcing of the cold gases with high amplitude and high frequency (≈ 1000 Hz). The resulting hemispherical-shaped flame, induced by a restabilization effect described previously by Duroxel al., shows a parametric instability when stronger acoustic forcing is applied (the oscillating acceleration is typically about l000g). In this case, the front exhibits unsteady cusp-shaped cells. These patterns oscillate with a period which is twice the acoustic period. This state is identified as the parametric response of a harmonic oscillator.

ISSN:0010-2202    

DOI:10.1080/00102209908924190

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor