Development of the Gaseous Fuel Direct Injection System for Small Two-Stroke Transports

It is well known that conventional carbureted two-stroke engines have high exhaust emission and poor fuel efficiency. To solve these problems direct gaseous fuel injection (DI) was introduced as a lower cost alternative to the gasoline direct injection (GDI) System. In this paper we investigate the use of liquefied petroleum gas (LPG) as a fuel in terms of lean combustion operation, and focus on analysis of in cylinder combustion pressure, fuel mass fraction burned, engine performance and exhaust emissions. Results are compared for various injection timings from premixed (early injection) to fully direct injection mode (late injection). Results show that late start of injection timing causes the torque to drop off significantly and poorer exhaust emission, mainly due to poor mixing of gaseous fuel and air. The DI of gaseous fuel effectively reduces exhaust emission and can substantially improve the fuel economy of two-stroke engines.