QUANTITATIVE-DETERMINATION OF FUEL AIR MIXTURE DISTRIBUTIONS IN AN INTERNAL-COMBUSTION ENGINE USING PLIF OF ACETONE

Quantitative determination of planar fuel/air mixture distribution in an internal SI engine are obtained using planar laser induced fluoresc ence of acetone. In order to get quantitative informations different f uel tracer substances have been investigated. Special requirements hav e to be fulfilled by the tracer molecule with regard to the applicatio n under the unstationary and hostile conditions of internal combustion . The most important is that the fluorescence intensity has to be dire ctly proportional to the fuel density. It must be unaffected by surrou nding gas composition, temperature- and pressure-fluctuations. As it t urned out during the experiments acetone meets this unusual requiremen ts almost perfectly. The experiments were carried out in one cylinder of a modified production line four cylinder SI engine from Volkswagen AG. Time resolved planar fuel distributions were obtained for the whol e mixture formation process during the intake, the compression and at the beginning of the combustion stroke. Single shot and cyclic average d measurements revealed a) cycle-to-cycle variations as well as recurr ing structures of the fuel distribution, b) mixture uniformity and c) flow field structures. The direct relationship between the acetone flu orescence intensity and the fuel density allows the quantitative deter mination of 2-D fuel/air ratio maps for a multitude of different crank angles.