Fuel Distillation Effects on the Outgassing from a Simulated Crevice in a SI Engine Measured by Planar Laser-lnduced Fluorescence

We present a planar laser-induced fluorescence (PLIF) study of the effect of fuel volatility on the unburned hydrocarbons (UHC) outgassing from a simulated crevice in a single cylinder 1992 GM quad-4 engine. The crevice consists of a small volume in the cylinder wall which is connected to the cylinder by a small orifice. The crevice volume and orifice are intended to simulate the piston ring-pack region and the top ring gap. A fuel that consists of 90% by volume iso-octane and 10% of a ketone is used in these experiments. The ketone serves both to represent a particular fuel distillation fraction and as the fluorescent marker. A range of ketones are used to represent fuel distillation fractions between 56°C and 173°C. For each fuel, in-cylinder single-shot and multi-cycle averaged two-dimensional fluorescence images are obtained from a region near the simulated crevice. The relative concentration of the UHC outgassing from this crevice is determined semi-quantitatively as a function of distillation fraction.