Spontaneous Raman measurements of acetylene in atmospheric-pressure methane/air flames

Spontaneous Raman spectra of native acetylene in a premixed CH4/air flat flame are reported. Spectra were obtained using a kHz-pulsed Nd:YLF laser, and absolute concentrations of acetylene are determined from the frequency-integrated Raman intensity of the ν2 band and associated hot bands. The detection limit of the spontaneous Raman technique for C2H2 in the current setup is estimated at ∼500 ppm at 1750 K. Axial profiles of acetylene measured by the Raman method are found to be in good agreement with those obtained by an extractive probe technique, and in substantial disagreement with the predictions of numerical flame calculations.