Evaluation of Changes in Soot Formation with Variation of Start Angle of Fuel Injection in Diesel Engine

Controlling of the fuel injection، including the spray structure and injection timing has a significant impact on the engine performance، especially the formation of pollutants. In this study، a computational fluid dynamics software (AVL Fire) has been used to simulate the start time of the fuel injection in diesel engines and its effect on the soot formation rate. Results show that if the start angle of the fuel injection approaches the TDC، the maximum soot formed will be increased. Also، the amount of the remained soot is increased. Mixing of the fuel and the air cannot be completed as the start angle of the fuel injection gets closer to the TDC، because of increasing the combustion chamber pressure and so decreasing the ignition delay، as a consequent، the rich mixture volume increases and leads to more soot formations. Although that is better to the inject fuel earlier (far from the TDC)، but considering other effective parameters on the engine performance، like the ignition delay، produced power، it has been concluded that lower soot formation can not be an advantage by itself.