Evolution and impingement of an automotive fuel spray investigated with simultaneous Mie/LIF techniques

The spatial and temporal evolution of an automotive hollow-cone-type spray was investigated with laser-based imaging diagnostics. Optical conditions o f an IC engine were emulated with a test cell that was built from an engine cylinder head to hold a high-pressure gasoline-fuel injector. The use of i so-octane fuel that was doped with 3-pentanone allowed measurements of lase r-induced fluorescence (LIF) after excitation with a KrF excimer-laser beam . A versatile optical filter system was designed and built that permits sim ultaneous measurements of Mie-scattering and laser-induced-fluorescence ima ges using a single laser-light sheet and a single intensified CCD camera. T he influence of background signals, caused by reflection of signal light fr om surfaces, laser-sheet intensity attenuation and signal decrease by scatt ering, was characterized. Mass distributions showed a distinct pre-spray ph ase, more so than the Sauter mean diameter (SMD) that was determined from t he ratio of LIF to Mie signals using single pulse as well as averaged image pairs. Significant changes in SMD distributions were found after the spray had impinged on a flat surface. The impingement also led to the buildup of a liquid film whose thickness was quantitatively determined from LIF image s.