| In recent years,with the continuous development of diesel fuel injection technology,the performance of diesel engine has been further improved,leading to higher efficiency and lower emissions.However,with the increasingly stringent emission regulations,the demand for advanced fuel injection strategy is becoming urgent.In order to explore the effect of advanced injection strategy on engine performance,a combination of experiments and simulations were employed to study the different fuel injection strategies.At first,the effects of main injection timing,pilot fuel quality,rail pressure,and intake air flow mass rate on diesel engine torque,HC,CO and soot emissions was the investigated in an engine test rig.The experimental results showed that under the two-injection condition,when the main injection timing was located after the top dead center,the emissions would have maintained at a low level,and the torque was generally constant.When the fuel injection pressure changes,with the increase of injection pressure,the content of HC changes little,while the content of CO and NOx increases gradually.Only soot decreases slightly.。.Then,based on the KIVA-3V code,a three-dimensional simulation model was established to study the advanced fuel injection strategy(pilot injection timing swing,spray angles)and the effect of injection rate shapes such as rectangle,triangle,slope up,slope down,and step down on the engine performance on engine performance.It is found that When the pilot injection timing was between 5 degrees and 7 degrees before the TDC,the CO,NOx and HC generation capacity would remain at a low level,and it would not affect the indicated fuel consumption rate.The final generation of HC and CO was mainly located near the pits of combustion chambers.The reason was that some of the fuel was injected on the wall of the combustion chamber,and the temperature near the wall is lower than the temperature in the middle part of the combustion chamber,which further affected the atomization and evaporation process of the fuel.Furthermore,the shapes of fuel injection rate,played a significant role on ignition delay time,combustion duration and emissions.The concentration of nitrogen oxides can be reduced by using the rectangle injection rate shape.When using the step down shape,HC and CO can be reduced,and the indicated fuel consumption rate was minimum,but the amount of NOx would increase.In addition,the slope up injection rate results in the highest combustion efficiency. |
