Numerical Study on the Effects of Fuel Injection Characteristics on the Performance of a Lean Burn SG-GDI Engine towards High Efficiency and Emissions Reduction

The effects of spark and injection characteristics as well as split injection on the performance and emissions of a spray-guided gasoline direct injection (SG-GDI) engine operating close to stoichiometric conditions are assessed. To accomplish this, a 6-holes injector is simulated and the results are validated against available experimental data for spray penetration length. In addition, an open-cycle multi-dimensional model is developed for a port fuel injection (PFI) engine and the model outcomes are verified against in-cylinder pressure profile and normalized heat release rate. The GDI engine model is yielded under the light of embedment of the above-mentioned models. The model is then employed for investigation of the effects of injector angle, injection pressure, start of first and second injections and two-stage fuel injection with different fuel mass ratios at first and second injections, i.e., split injection, on mixture formation, combustion and engine emissions. The results show the pivotal role of the injector angle on formation of the mixture and output power. On the other hand, it is indicated that while practicing the split injection strategy, the flammability of the relatively stratified lean mixture with fuel to air equivalence ratio of 1.15 around the spark plug, surpasses that of stratified mixture.