The spray from a multi-hole injector applied to direct injection spark ignition (DISI) engine was investigated. In order to understand the detailed structure of the transient spray near the nozzle a combined LDA/PDA system was used. PDA system was optimized in order to detect relative smaller droplets. Size-classified technique was used to get deep information about the spray characterizations near nozzle. The experiments were performed at 7 MPa of injection pressure. At early stage of spray the droplet velocity distribution in the centre of the spray showed high value. Smaller droplets under 15 µm showing followability to air flow, while larger droplets over 20 µm will have drag due to momentum decay. Droplets of 15 <D≤20 µm in diameter is criteria for follow/penetration near the nozzle. Near the nozzle, the atomization predominantly occurs at the centre region of the spray.
2010 by The Japan Society of Mechanical Engineers and The Heat Transfer Society of Japan