Some raman/rayleigh/lif measurements in turbulent propane flames

Simultaneous Raman/Rayleigh/LIF measurements have been made, for the first time, in piloted turbulent jet diffusion flames of diluted propane, in which high mixing rates well downstream of the nozzle are found to induce, finite chemistry effects which lead to extinction when the jet velocity is sufficiently increased. Raman measurements are shown to be feasible in these flames only when they are substantially diluted, either with nitrogen or air, to reduce the soot precursor interference which would otherwise completely mask the Raman signals. The Raman signature of propane, both as regards signal strength and interference with other species, is quite similar to that reported elsewhere for methane, and correction factors for soot precursors are also found to be close to those for methane. Conditional probability density functions show that increasing dilution reduces the bimodal burnt-unburnt characteristics around stoichiometric composition. The extent of departure from partial equilibrium of the water-gas shift reaction and reactions in the H₂-O₂ system is established by direct species measurements. It seems likely that other hydrocarbon flames, hitherto inaccessible by the spontaneous Raman technique due to soot interference, could also become tractable with sufficient dilution.