Finite-Rate Chemistry Effects in Subsonic and Supersonic Combustion

Finite-rate chemistry effects are revealed in subsonic and supersonic lifted hydrogen flames using narrowband KrF excimer laser (248 nm) induced Raman scattering and fluorescence to measure simultaneously species concentrations (H 2, H 2 O, N 2, O 2, OH) and temperature. The fluorescence measurement of OH concentration is quantitative since it is predissociative and insensitive to collisional quenching. Using these simultaneous measurements, the chemistry of turbulent reaction zones is compared to the limits of fast chemistry (equilibrium), slow chemistry (mixing without reaction), and 1D stretched laminar flamelets. The reaction zone chemistry in turbulent subsonic flames is found to be inconsistent with 1D stretched laminar diffusion flames.