Multi-Component Fuel Imaging in a Spray-Guided Spark-Ignition Direct-Injection Engine

A two-tracer planar laser-induced fluorescence (PLIF) diagnostic technique was developed and applied to visualize the in-cylinder evaporation and distribution of different volatility fuel components in an optical spray-guided spark-ignition direct-injection (SIDI) engine. An image doubling and filtering system was designed so that LIF signals from the two tracers could be effectively separated and recorded simultaneously with one intensified charge coupled device (ICCD) camera. Cycle-resolved measurements were performed in the optical engine operated under late injection mode at different intake temperatures and pressures to assess the significance of sequential evaporation. The results demonstrate that the evaporation process under current experimental conditions is diffusion-controlled and the effects of sequential evaporation are insignificant on fuel distribution stratification. An order-of-magnitude estimate based on a Peclet number analysis supports this finding.