The Study of GDI Engine Performance Under Two Stage Various Fuel Injection Ratio and Timing

• Main Authors: Zhe-Cheng Kuo, 郭哲成
• Other Authors: Kuo-Liang Shih
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/04129481811821995410

碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 100 === This research applies a modified GDI engine (re-assemble from a 500C.C. gasoline EFI engine). A common-rail 100 bar injection system is equipped with a injector placed on the top of the cylinder head (perpendicular to the piston surface). The engine runs at 3000, 4000, and 5000 rpm, the throttle opens at 20%, 30%, and 40% TPS. The fuel is injected at two stage with the injection mass ratio 4：6, 5：5, and 6：4 respectively. The engine performance and exhaust emissions are studied. The GDI engine has two stage injection, by increasing the first injection amount, the cylinder charge has better homogeneous charge mixing before the second inject onset. Results show the increased first injection ratio can promote the engine torque by 5%~20%. The CO emission is reduced by 5%~15% and the HC emission is reduced by 15%~40%. When the comparison is made between the optimized two stage injections and the single stage injection (semi-port fuel injection), the volumetric efficiency is slightly increased by 1%~2%. The engine torque under high engine load and engine speed case is not able to be increased by running the GDI mode since the spray plug is placed on the side of the combustion chamber. The CO emission is increased by 10%~40%, the HC emission is increased by 5%~20%, and the NO emission is reduced by 10~30% due to instantaneous charge temperature. However when this two-stage injection mode is compared to the singe stage (quasi-EFI injection) mode, the side placed spark plug causes the un-effective flame propagation inside the combustion chamber, thus, the engine performance is deteriorated, and the emissions are increased.