Influence of the wall temperature on the mixture preparation in DI gasoline engines

Spray-wall interaction and liquid film models are developed, validated and used to provide better understanding of fuel distribution in a DI gasoline engine with a "wide" concept. Numerical calculations including combustion w ere performed to study the influence of piston temperature on mixture prepa ration under stratified charge operating conditions. During cold operation or cold start, up to 25% of injected mass forms a liquid film on the piston bowl bottom. This largely affects the combustion efficiency. Increasing pi ston temperature decreases the gasoline unburned film amount. No significan t liquid film remains on the piston when its temperature exceeds the mean o f the boiling and Leidenfrost temperatures. This result agrees well with th e available experimental observations which confirm the absence of liquid f ilm when piston temperature exceeds 460 K.