Optical Studies of Spray Development in a Quiescent Chamber and in a Direct-Injection Spark-Ignition Engine

The effects of fuel type and in-cylinder flow on spray formation from a multi-hole injector were studied by high-speed imaging techniques in a quiescent injection chamber and in a single-cylinder Direct-Injection Spark-Ignition (DISI) engine. To examine the effect of fuel volatility on spray formation, the injector was heated from 20 °C to 120 °C in the chamber for iso-octane and gasoline. The injection chamber was operated at 0.5 and 1.0 bar to mimic in-cylinder pressures for early injection strategies. Droplet sizing was also employed in the chamber using Phase Doppler Anemometry (PDA). Fuel-type and temperature effects were studied in-cylinder by operating the engine at 20 °C and 90 °C head temperature at 1500 RPM. For both sets of experiments, the study was carried out for two orthogonal views, relating to the tumble and swirl planes of in-cylinder flow motion. Spray formation was observed to be different for the two fuels, especially at high injector temperatures. Wetted footprint spray areas were calculated for both experimental setups. © IMechE 2007