Intracavity laser absorption spectroscopy of sooting acetylene/air flames

Intracavity laser absorption spectroscopy (ICLAS) is used to measure the absolute concentration profiles of HCO and C-2 in low-pressure acetylene/oxygen/nitrogen flames with equivalence ratios phi = 0.8, 1.0, 1.5, 2.0 and 2.5. The flames with phi = 2.0 and 2.5 are soot-producing, with light extinction reaching 0.1% per pass in the flame with. = 2.5. This strong broadband extinction does not affect the sensitivity of ICLAS, however. The temperature profiles of the flames were measured using laser-induced fluorescence of the OH radicals. For C-2 concentration measurements, the (0-2) vibronic transition of the d(3)Pi(g)<- a(3)Pi(u) Swan band is used. The lines of this transition are located close to the HCO lines, making it possible to measure the two radical concentrations simultaneously. The C-2 concentration is highest in the phi = 1.5 flame, and lower in the lean and heavily sooted phi=2.5 flames.