Laser-induced fluorescence thermometry and concentration measurements on NOA–X (0-0) transitions in the exhaust gas of high pressure CH4/air flames

Laser-Induced Fluorescence (LIF) excitation spectra in the NOA–X (0-0) band were used for temperature measurements in the postflame region of high-pressure CH₄/air flames. To improve the quality of the measured spectra and to perform reliable line-shape measurements, the initial mixture was doped with approximately 400 ppm NO. At pressures up to 18 bar, excellent agreement was obtained between NO LIF temperatures and NARS/rotational Raman temperatures. Effective broadening coefficients were also determined in these flames. Problems with quantitative concentration measurements of NO and single-pulse temperature measurements at high pressures are discussed.