Equivalence Ratio Measurement in Fuel Rich Combustion by Laser-Induced Breakdown Spectroscopy

- Fundamental Study Using Luminous Flame in a Counterflow Burner -

Abstract

Laser-induced breakdown spectroscopy (LIBS) has been applied to measure local air-fuel ratio (equivalence ratio) in combustion. However, the research about luminous flame has not been reported. In this study, using a counterflow diffusion luminous flame (Propane-Air), LIBS spectra were observed at various measurement points with various equivalence ratios in the luminous flame (Φ<8). The equivalence ratios of those measurement points are estimated with corresponding CHEMKIN calculations. The relationship between the calculated equivalence ratios and the measured emission intensity ratios (CN_385nm/H_656nm, CN_385nm/O_777nm, H_656nm/O_777nm) are investigated. The results demonstrate that LIBS measurements of local equivalence ratio may be feasible even in the luminous flame.