Theories of Turbulent Combustion in High Speed Flows

Since Damkohler and Reynolds numbers over the range of conditions relevant to supersonic hydrogen-air combustion were found to be consistent with the combustion occurring in the reaction-sheet regime, detailed numerical integrations were performed on the structures of counterflow hydrogen-air diffusion flames, for pressure from 0.5 to 10 atm and air temperatures from 300 K to 1200 K, at a hydrogen temperature of 300 K. The results showed extinction to occur at high enough rates of strain in most cases, but no extinction for air temperatures above 1000 K. Nitrogen chemistry was shown to have a negligible effect, and reduced chemical-kinetic mechanisms were developed for simplifying the computations. The compound extinction strain rates were found to be in excellent agreement with newly performed experiments. Compressibility effects are being taken into account, and the results are being worked into methods for describing turbulent combustion in high-speed flows.