Numerical Investigation on Mixture Formation of Two-Stroke LPG Direct Injection Engine Used as Range Extender for Electric Car

The two-stroke DI engine has distinct advantages such as high speed, high power density, and simple structure . LPG has a low boiling point and high saturation vapor pressure, which is very helpful in accelerating the fuel-air mixing. Owing to these characteristics and advantages, the two-stroke LPG engine is generally regarded as the preferred power source of the generator unit for extended-range electrical vehicles. The process of mixture formation is numerically simulated after the calculation model is validated by results from optical experiments. The results show that, under conditions of avoidance of fuel short-circuiting, an injection timing of 50° CA ABDC for engine start and warming (2000 rpm), and an 40° CA ABDC for running as the power source of the generator (4800 rpm) are appropriate. Further analysis of the velocity and concentration fields shows that the fresh mixture is locked in the cylinder when the exhaust port is closed (73° CA ABDC) and the homogeneous mixture can be formed at spark timing.