Influence Of EGR And Injection Parameters On Diesel Engine Performance

Automotive diesel engine running in transient conditions most of time, the frequent change of engine speed and torque will cause the intake air lag behind the fuel injection. So the diesel engine combustion instability, the economic performance and emission performance will deterioration. The research in this study adapting a heavy vehicle turbocharged diesel engine electronic control as the research object, and setting up INCA control system. The EGR valve in this study is a electric control EGR valve, the EGR valve opening in the transient process controlled by Freescale microcontroller. The study mainly improve the smoke deterioration in the transient of diesel engine and the smoke value as the important evaluation index, the transient condition of diesel is that the torque of diesel from 0% to 100% in the 5 seconds at a constant loading rate, the speed of diesel is 1650r/min.The first part mainly studies the injection parameters on the influence of the transient process of diesel engine. Adjust the injection pressure to study the influence on combustion performance and emission performance under different strategies. The conclusions is that:Increasing the injection pressure can make burning center of gravity in advance, the smoke emissions peak declined. But increasing the injection pressure at little load will increase the smoke value. We studied the different transient conditions, the smoke of 20-100% transient condition is lower than 10-100% transient condition, and increasing the pressure could effectively reduce the smoke value in the transient conditions.Subsection rail pressure strategies could effectively reduce the smoke peak value at different transient conditions. Different transient conditions and subsection rail pressure can effect the combustion performance and emission performance of diesel transient condition. Increase the injection pressure could shorten the combustion duration, CA50 in advance, NOx emission increasing, smoke peak value decreasing. The conclusion showed that after 35% load began to increase injection pressure as the optimal strategy.Under the same load, compare steady and transient conditions, the maximum pressure of steady condition is higher than transient condition. At little load of diesel, the start of heat release in transient lag to the steady condition. The longer ignition delay period could make the air and fuel mix well, so heat release and maximum pressure are higher. With the load increasing, the premix combustion decrease, the combustion performance deteriorate.The second part mainly studies the three different transient condition, adjust the EGR valve closed and open time and subsection to improve smoke emission. And so through these strategies we could get the optimal control strategy.Closed the EGR valve in the transient condition, so the air will increase, the different time closed the valve will cause the diesel different emission performance. In the whole transient condition, before 40% closing the EGR valve could effective reduce the smoke peak. Before 10% and 20% in in the transient condition closed the EGR vavle could most efficient reduce the smoke. The smoke from 25% to 8%.In the transient condition, adapting the subsection rail pressure could reduce the smoke. Combine EGR strategies with subsection rail pressure could reduce the smoke. In the 20-100%transient condition, at 20% time and 35% load increase the rail pressure could make the smoke from 25% to 7%.In the transient condition, delay EGR valve open time can reduce the smoke peak value. With the EGR valve open time delay, NOx emission peak delay.