Analysis of direct fuel injection in a small power two-stroke engine

Small power two-stroke engines can be competitive in regard of work parameters and pollutants emission in relation to four-stroke engines at some modifications, particularly changing of fuelling system. The paper presents a modifted air-assisted direct fuel injection in a two-stroke engine, which changes propagation of fuel jet in the combustion chamber. The main problem of mixture formation is short time for fuel evaporation after injection which should begin after closing of the exhaust port. The paper shows interaction between the scavenge air, additional air stream and fuel jet from the injector located in the cylinder head, which can induce the small size of fuel droplets and fast evaporation. The computational results of fuel mixture formation and combustion process in direct fuel injection two-stroke engine Robin EC-12 with capacity 115 cm3 are presented. The simulation was carried out by use KIVA code with assumption of initial parameters from the experimental tests on the carburetted engine. Setting of the injector in a regard of the cylinder head decides of fuel motion and evaporation in the combustion chamber. Air-assisted fuel injection influences on higher mixing of fuel and better combustion than by using DFI system. The paper shows phases of mixture formation, combustion and concentration of the combustion product in the cylinder with additional air stream. Spray guided high pressure direct injection system in SI two-stroke engine enables fulfil the restrictions of gas emission of one-wheeler vehicles and small power units.