On diffusive supersonic combustion (chemical kinetic effects in diffusive supersonic combustion)

Abstract

Simple analytical methods are presented for the analysis of chemical kinetic effects in supersonic combustion. Three different regions are shown to occur in supersonic diffusive combustion. The first region is close to the injector exit, where the flow may be considered frozen for the main reacting species and where the radical concentration is being built up. This is the ignition delay region. A simplified kinetic scheme of the H2-air reaction is deduced for this region. The linear differential equation giving the H concentration has been discussed and integrated in a representative case. In terms of this solution the limits of the ignition region may be determined. Far from the injector exit the flow is close to chemical equilibrium. The reaction region is very thin, so that convection effects may be neglected. Then the governing equations reduce to ordinary differential equations, that may be integrated by using an integral method. In this way, deviations from equilibrium may be determined in terms of the reaction kinetics. An extension of the integral method, developed for the analysis of the near-equilibrium region is proposed for the study of the transition region.