Temperature Measurements by Radar REMPI in methane/air flames at atmospheric pressure

摘要

Here we present non-intrusive local rotational temperature measurement of molecular oxygen, based on coherent microwave scattering (Radar) from Resonance Enhanced Multi-Photon Ionization (REMPI) in methane/air flame at atmospheric pressure. The hyperfine rotational state distribution of the ground state X~3∑(v'=0) of molecular oxygen was determined by the rotational line strengths of the two-photon molecular oxygen C~3∏(v=2)←X~3∑(v'=0) transition. 2+1 REMPI spectra of the molecular oxygen transition in the methane/air flame with two different equivalence ratios were obtained in the experiments. Rotational temperatures of molecular oxygen have been inferred from the results of Boltzmann plots. The error of the temperature measurements was less than ～6.0% in the methane/air flames. Fairly good agreement was obtained between experimental results and theoretical temperatures.