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Beskrivelse
Modern optical measurement techniques play an essential role in the evolution of gasoline engines. Especially the visualization of in-engine processes and the measurement of species concentrations are important tools to optimize mixture formation and combustion. The goal is to reduce fuel consumption at minimum emissions. Subject of this work is the qualitative and quantitative investigation of the mixture formation process within the combustion chamber to optimize the injection parameters regarding hydrocarbon emissions. For the measurements the two-dimensional laserinduced tracer-fluorescence technique was used to visualize fuel vapor and droplets and to quantify the air-fuel ratio. A fluorescence measurement system was applied to a four-cylinder transparent engine and the necessary calibration- and evaluation methods have been developed in order to achieve interpretable quantities. The verification and application of the measurement technique was performed in two operation modes of the engine. Under steady state operation in part load the air-fuel ratio was determined. Under cold start conditions the measurement technique was used to distinguish between the liquid fuel and the gaseous phase. This was the first time this method was used under instationary cold start conditions. By correlating the results of the measurements with the global hydrocarbon emissions in the exhaust gas a basic under- standing of the mechanisms between injection, mixture formation and combustion could be acquired. Furthermore the results of these investigations ended up in specific recommendations for the configura- tion of injection parameters.