Engine downsizing has become a leading trend for fuel consumption reduction while maintaining the high specific power and torque output. Because of this, Turbo-charged Gasoline Direct Injection (TGDI) technology has been widely applied in passenger vehicles even though a number of technical challenges are presented during the engine development.
This paper presents the investigation results of three key issues in the combustion development of a 2.0L TGDI engine at SAIC motor: fuel dilution, smoke emission and low speed stochastic pre-ignition(LSPI). The effect of the injection timing and injection strategy on fuel dilution and smoke emission, and LSPI are the focus of the experimental study.
Dyno test results show that early fuel injection induces severe piston wetting and results in high smoke emission, reversely, retarding injection too far produces higher fuel dilution and increases smoke emission too due to the fuel spray impinging on the liner..There is a short time for evaporation and mixing of the fuel based on the constrained injection timing window, particularly in the higher load operation.
Test results on this engine show that using the double injection can effectively reduce LSPI occurrence, by reducing the liner impingement. This indicates that the higher fuel dilution on cylinder wall is likely one of the key mechanism for the occurrence of LSPI events in this engine.