Laser-induced breakdown spectroscopy in reactive flows of hydrocarbon-air mixtures

Laser-induced breakdown spectroscopy is used for the determination of the local equivalence ratio (i.e., the ratio of the actual fuel-to-oxidizer mass over the ratio of the fuel-to-oxidizer mass at stoichiometry) in different methane-, ethylene-, and propane-air mixtures. In particular, it is shown that the ratio of the intensities of the atomic spectral lines of H, C, and O, emitted from a laser-induced spark in the gaseous mixture, can be used for the rapid and accurate determination of the local equivalence ratio.