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2618484 
Book/Book Chapter 
Effect of swirl ratio on performance of semi-direct injection SI engine 
Wu, Y; Manh-Cuong Nguyen; Anh-Trung Tran 
2010 
WSEAS Mechanical Engineering Series 
172-177 
WOS:000291666900032 
The targeted developments for future vehicles are how to reduce fuel consumption, pollutant emission while maintaining high level of engine performance. To deal with those issues, fuel system has been taken great concerns by scientists for a long period of time. As we know, Port Fuel Injection system (PFI) and Gasoline Direct Injection system (GDI) are popular techniques which are being used on commercial vehicles. This paper presents the possible improvement of engine performance by applying effect of swirl motion on lean-limit of semi-direct injection SI engine. The fuel goes into cylinder directly through intake valve near the middle intake stroke to make richer mixture around the spark plug, which is called semi-direct injection (SDI). Thus, this system includes high swirl charge, injection during intake valve opening, and air-assisted fuel injection. The modifications of intake port by using baffle plate and the other by closing one intake valve for the 125 cc, 4-valve, port-fuel-injection (PFI) engine to increase swirl ratio of in-cylinder air motions which helped to form rich mixture around spark plug, and lean mixture at other location. The effects of swirl motion were measured and verified on steady flow bench. Therefore, a new idea known as investigated effect of swirl ratio on performance of lean burn SDI comparing to original PFI engine. Additionally, in-cylinder swirl motion which was made by swirl generator in the intake port was used to reach stratified charge. The SDI engine then was tested under lean conditions at 4500 rpm and 5300 rpm. Engine torque, fuel consumption, exhaust emissions, and engine combustion characteristics were investigated. Experimental results indicated that lean-limit was extended to maximum air-fuel ratio 26.28 (lambda = 1.8) at swirl ratio 3.5 while brake specific fuel consumption and coefficient of cycle variation were very low. In addition, analysis on engine exhausted gas showed the decrease of CO and HC emissions. 
Semi-direct Injection System; Swirl ratio; Lean burn