Numeric investigation of mixture formation at partial load conditions in direct injection gasoline engines

In the context of this master thesis, numerical calibration of a hollow cone type injector, which is used in spray-guided gasoline direct injection engines nowadays, has been provided by using experimental studies in the literature. Spray analysis was performed using this injector and the effect of ambient conditions on fuel bundle characteristics was investigated. In-cylinder flow analyses were then performed for a gasoline direct injection engine equipped with this injector. Three different multiple injection strategies were used in the in-cylinder flow analysis and an appropriate spraying strategy was determined from the multiple injection strategies given for the formation of a good mixture around the spark plug. The increase of ambient pressure in the effect of the ambient conditions on the fuel spray characteristics decreases the penetration depth of the fuel cluster and the Sauter mean diameter, while the evaporation increases. In addition, it has been determined that the ambient pressure is more effective than the temperature in the evaporation of the fuel. In the in-cylinder flow analyzes, it was observed that the fuel to be sent towards the end of the compression has a positive effect on the intake of flammable fuel-air mixture in the vicinity of the spark plug, while very early sprayings made it difficult to hold the flammable fuel-air mixture around the spark plug. Due to the low in-cylinder pressure in early spraying, the penetration depth of the fuel has increased. Finally, for the most suitable multiple injection strategy, the amount of vaporized fuel is changed according to the crankshaft angle.