INVESTIGATION INTO LEAN BURN ABILITY INTO FOUR-STROKE SPARK- IGNITION ENGINEs FOR SEMI-DIRECT INJECTION SYSTEM USING AIR- ASSISTED INJECTORs

Tóm tắt

This paper presents the possible combinations of advantage factors from PFI and GDI system by applying an air-assisted injector on Semi-direct Injection System (SDI).Firstly, an adaptor that uses compressed air to improve the atomization of conventional injector and reduce droplet size is made. Secondly, the modifications of intake port by using vortex plate and the other by closing one intake valve increase swirl ratio of in-cylinder air motions which help to form rich mixture around spark plug and lean mixture at other locations. This combination transforms traditional PFI system into SDI one. The engine then is tested on test bench at 3000 rpm engine speed and 2 Nm torque. Experiment results indicate that lean limit increases from air-fuel ratio (AFR) 17.1 to 23.7 while brake specific fuel consumption and coefficient of variation are reduced significantly.