Formation of fuel mixture in a SI two-stroke engine with direct fuel injection

Decreasing of fuel consumption and high hydrocarbon emission in a SI two-stroke engine applied in motorcycles, scooters and small power units is possible by change of fuelling system on direct fuel injection. The main problem of mixture formation is short time for fuel evaporation after injection which should begin after closing of the exhaust port. However well interaction between the scavenge air and fuel jet from the injector located in the cylinder head can induce the small size of fuel droplets and fast evaporation. The paper presents the computational results of fuel mixture formation and combustion process in direct fuel injection two-stroke engine Robin EC-12 with capacity 115 cm3. The simulation was carried out by use KIVA code with assumption of initial parameters from the experiment of the carbureted engine. Earlier fuel injection influences on better evaporation and mixture formation with small stratification, which enables full mixture combustion. The paper shows phases of mixture formation, combustion and concentration of the combustion product in the cylinder. Spray guided high pressure direct injection system in SI two-stroke engine enables fulfill the restrictions of gas emission of one-wheeler vehicles and small power units. New modern two-stroke engines and environmental protection require new fuelling systems and one of the most promising methods is direct spray guided fuel injection. Many work were done in this subject, however still there is no better option for small power two-stroke engines.