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Fuel intake, start and propagation of combustion were studied in a Z-liter in-line four-cylinder SI engine. Two-dimensional laser induced fluorescence was used to characterize the performance of the engine. A tunable excimer laser at 248 nm and a broadband excimer laser at 308 nm were used to measure simultaneously distributions of hydroxyl radicals and fuel. LIF measurements of fuel (iso-octane) were performed by adding diethyl-ketone as fluorescence tracer to the iso-octane. The complementary information obtained from fuel and hydroxyl radical distributions is shown and differences are pointed out. Cycle to cycle variations and averaged results are discussed as function of equivalence ratio.

This paper presents results from a quantitative characterization of the NO distribution in a SI engine fueled with a stoichiometric iso-octane/air mixture. Different engine operating conditions were investigated and accurate results on NO concentrations were obtained from essentially the whole cylinder for crank angle ranges from ignition to the mid expansion stroke. The technique used to measure the two-dimensional NO concentration distributions was laser induced fluorescence utilizing a KrF excimer laser to excite the NO A-X (0,2) bandhead. Results were achieved with high temporal and spatial resolution. The accuracy of the measurements was estimated to be 30% for absolute concentration values and 20% for relative values. Images of NO distributions could also be used to evaluate the flame development. Both the mean and the variance of a combustion progress variable could be deduced.