Nonequilibrium model for hydrogen combustion in supersonic flow

Abstract

A model for nonequilibrium combustion of hydrogen in air is presented and demonstrated for one-dimensional supersonic combustion in a duct. The computational tractability makes the model appropriate for multidimensional Navier-Stokes calculations. This model contains eight chemical species and associated reactions but can be described by only two variables in addition to the gasdynamic set. These variables are a reaction progress variable for the radical pool and the mixture fraction for the local composition. The latter is not needed in premixed flows. The model makes the realistic assumption that ignition is rapid compared with burnout, the latter being governed by decay of the radical pool via relatively slow three-body recombination reactions. Such models have been successfully tested against laser-based spectroscopic data for major and minor species, temperature, velocity, and NO* in subsonic turbulent flames. The model shows that the length of a constant-area supersonic combustor increases rapidly with decreasing static pressure and that an asymptotic maximum progress toward equilibrium is attained in diverging combustors.