An Experimental Study And Numerical Modeling Of A Electronic High Pressure Common Rail Diesel Engine With Multiple-Injection And EGR

Diesel must reduce NOx and soot emissions simultaneously to meet with the loweremissions regulations. Recent research has shown that EGR combined withmultiple-injection is a useful way to meet the more stringent emission regulations byreducing the emissions of NOx and soot simultaneously. Therefore, the study of EGR andmultiple-injection technology to reduce diesel emissions is significant.Based on the electronically controlled common rail and high pressure injection dieselengine, this paper researched the influence of multiple-injection on diesel engineperformance and emissions. The results showed that: the smaller amount of pilot injectionand appropriate pilot-main injection interval appropriate to can reduce engine noise levelsand improve the NOx emissions because of that pilot injection could early release heat toincrease the in-cylinder temperature and pressure, reduce the main injection fuel ignitiondelay period, reduce the rate of pressure rise and the rate of heat release and the maximumcombustion temperature. The appropriate main-post injection interval and fuel amount ofpost injection can reduce soot emissions and improve fuel consumption.This paper built the diesel engine in-cylinder combustion three-dimensionalnumerical simulation model. Then, the model has been validated by the test data. Thispaper studied the influence of different EGR fraction and different multiple injections onthe in-cylinder combustion and emissions. The results show that: the higher EGR rate, thelower exothermic reaction rate, the lower the combustion temperature, the longercombustion duration. NOx emissions could be significantly reduced, but soot formationwill increase by a certain amount. Fortunately, soot formation can be further reduced in thecase of the appropriate main-post injection interval and the right post injection quantity.Thereby, the trade-off relationship of the NOx and soot emissions could be improved.The advantage of this paper is that the key point and the change law ofmultiple-injection strategies has been point out and the law of EGR fraction couple withmultiple-injection to improve combustion and emissions has been given out. It is veryuseful and important for the engine design and development of calibration.