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Non-intrusive temperature measurements based on single-line laser-induced fluorescence of molecular oxygen in the transparent IDEA Diesel engine were investigated. Oxygen molecules were excited to fluorescence with a narrowband, tunable ArF excimer laser at 193 nm. The resulting fluorescence signals were recorded with an image-intensified CCD camera. The temperature increase during the compression phase of the four-cylinder direct injection Diesel engine could be evaluated from the LIF signals. In the crank angle range of the measurements, good agreement between measured and calculated temperatures (polytropic compression) was observed.

Absolute two-dimensional concentration distributions of nitric oxide have been measured in a fully transparent square piston engine with planar laser induced fluorescence. A calibration procedure was used to obtain absolute NO concentrations. The NO formation was studied in the propane/air fueled engine as a function of air/fuel ratio, crank angle and load. Simultaneous measurements of NO distributions by LIF and temperature fields via Rayleigh scattering allowed to study the correlation of NO formation and temperature. It was found that the measured NO was mainly formed via the Zeldovich mechanism.

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.