A numerical and asymptotic investigation of structures of hydrogen-air diffusion flames at pressures and temperatures of high-speed combustion

Abstract

The structure and extinction of counterflow diffusion flames of hydrogen and air are investigated for pressures from 0.5 to 10 atmospheres and for initial temperatures from 300 K to 1200 K. Numerical integrations are performed for air-side strain rates from 60 s⁻¹ to extinction. The numerical results are compared with predictions of an asymptotic analysis that involves reduction to one-step chemistry through introduction of steady-state and partial-equilibrium approximations. Reasonable agreement is found for concentrations in the main reaction zone at low strain rates. Predicted extinction strain rates appear to be less than found in earlier numerical integrations but greater than experiment, for reasons identified herein.