Degenerate four-wave mixing measurements of methyl radical distributions in hydrocarbon flames: Comparison with model predictions

摘要: We report an investigation of the use degenerate four-wave mixing (DFWM) to measure CH3 radical distributions in premixed hydrocarbon flames. Experimental results are compared with flame model calculations. By exciting Herzberg β1 band near 217 nm, we monitored DFWM signals from as a function height above laboratory flat-flame burner at atmospheric pressure. Coherent anti-Stokes-Raman spectroscopy (CARS) N2 was performed obtain temperature profiles. The dependence signal on shown theoretically be reduced by short predissociative lifetimes upper states. A two-color FWM experiment indicated that CH4 flames predominately result population gratings. Using population-grating theory, profile corrected for varying temperature, beam absorption, and lower-state lifetimes. were reasonable agreement calculations demoustrate can provide useful relative concentration profiles polyatomic rich However, found weak background limited detection sensitivity ≈70 ppm comparable C3H8 flames, it obscured C2H2 C2H4 Strategies alleviate discussed.