Diffusion flames structure

Hewson, J. C., and F.A. Williams. 1998. Rate-ratio asymptotic analysis of methane-air diffusion-flame structure for predicting production of oxides of nitrogen. Combustion Flame 117 441-76. 

In full-scale Are modeling, a diffusion flame structure is usually assumed. However, in many fire situations, such as underventilated fires, premixed or partially premixed flame theory may be more appropriate. The Burke-Schumann description of the diffusion flames can be used to conveniently represent the transport of gaseous species by a single scalar quantity called mixture fraction. For a simple one-step reaction ... 

Among the earliest works employing simplified kinetics and obtaining analytical approximations are those of Y. B. ZeVdovich, Zhur. Tekhn. fiz. 19,1199 (1949) [English translation, NACA Tech. Memo. No. 1296 (1950)] and of D. B. Spalding, Fuel 33,255 (1954). Chapter 7 of The Mathematical Theory of Combustion and Explosion by Y. B. Zel dovich,G. I. Barenblatt, V. B. Librovich, and G. M. Makhviladze, Moscow Nauka, 1980, treats the question of diffusion-flame structure for a one-step, second-order, Arrhenius reaction in a clear fashion. 

A frequent cause of a complicated diffusion flame structure is the cracking of the fuel in the preheating zone resulting in the formation of soot particles (e.g. the flame of a candle). In the dark preheating zone at 600—1000 °C cracking of the combustible, evaporating from the wick and forming the soot, occurs. The soot particles burn on the luminescent flame zone at 1200°C (see [230]). 

Fig. 11.1 Diffusion flame structure determined on basis of one-step kinetics in an asymptotic approximation to the kinetic activation I - reaction zone II - convection-diffusion zone Fp - fuel concentration Fq - oxidizer concentration Daoc - the Damkohler number corresponds to an infinitely fast reaction Daext - the Damkohler number when flame extinction takes place...

Miesse C, Masel RI, Short M, Shannon M (2(X)5) Experimental observations of methane-oxygen diffusion flame structure in a sub-millimeter microbumer. Combust Theory Model 9 77-92... 

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