Reduced Kinetic Mechanisms for Acetylene Diffusion Flames

Abstract

Previous studies of acetylene combustion have predominantly focussed on premixed flames, e.g. Frenklach and Warnatz [14.1] and Miller and Melius [14.2], while little attention has been given to non-premixed combustion or a systematic reduction of the chemical kinetics for either case. For premixed flames the latter is the topic of Chap. 7 of the current book while the present study is using the planar counterflow geometry to investigate the structure of acetylene-air diffusion flames. The counterflow geometry forms an ideal and computationally efficient configuration for theoretical investigations of chemical kinetics in diffusion flames and many past studies have been performed for alkane fuels. Among these are the numerical studies of the structure of counterflow methane-air and propane-air diffusion flames with detailed [14.3,14.4] and simplified [14.3] – [14.5] chemistry. However, previous studies have not analysed diffusion flames with alkene or alkyne fuels. This is in part a reflection of the uncertainties surrounding the chemistry of such flames. Among the additional problems encountered is the formation of soot and cyclic compounds such as benzene. The former is particularly important at low rates of strain and as a consequence experimental flames are under such conditions strongly non-adiabatic due to radiation from soot particles. Recently soot models have been proposed [14.6] which in principle can be applied to obtain a first approximation of such effects in studies of the kind present here. However, the scope of the present study is limited to an investigation of the primary reaction channels including the formation of C₃ species but excluding the formation of aromatics or soot.