Fuel Injection Parameters Effect On Combustion Of Diesel Engine On The Steady-state And Transient Conditions

Most of the time, diesel engine works, due to the delay of the turbine, resulting inparticulate emissions surge. In particular, in recent years, haze problem is serious inchina, the government and the community are seeking methods to solve the problem,so the purification of diesel engine exhaust gas on transient conditions is particularlyimportant. By optimizing the combustion is a fundamental means of reducingemissions. The conventional diesel engine uses open-loop control based on thecalibration method, in recent years, the feedback control of combustion shows someadvantages in terms of optimization of transient engine performance. To optimizecombustion of diesel on transient conditions, this paper focuses on that the boundaryconditions effect on combustion on transient conditions, on this basis, to explore thetransient combustion optimization strategy.Specific research is divided into two parts in this study.The first part, in steady state conditions, this paper studies injection timing andrail pressure effect on CA50and combustion duration, and establishes the map ofdiesel emissions and economy which CA50and combustion duration are independentvariable; BP neural network prediction model which about CA50and IMEP isestablished. The specific conditions are selected at50%load of1650r/min speed,injection timing selected seven levels, the rail pressure select five levels. The resultsshow that:1. With the advance of injection timing and elevating rail pressure, CA50is inadvance, but combustion duration is almost unchanging; with the exaltation of railpressure, combustion duration shortens, the influence of fuel injection timing and railpressure on combustion duration of CA50did not produce significant interference.2. With the advance of CA50, specific fuel consumption reduces and combustionduration shortens; NOx emissions increased significantly with the advance of CA50; shortening the combustion duration can help reduce smoke.3. BP neural network prediction model of CA50and IMEP is establishes, for thismodel, CA50prediction error is less than2%and IMEP prediction error is less than1%.The second part, on transient conditions, we study the influence of injectiontiming, rail pressure and EGR on combustion and emissions of diesel engine. To solvesmoke explosion problems on transient conditions, we adjust the fuel injectionparameters. At1650r/min speed, the load increases from10%to90%, the transitiontime5s,10s and15s. The results showed that:1. Compared with the steady conditions, diesel engine under transient operatingconditions, smoke surges, NOx emissions decrease, CA50lags, the maximumexplosion pressure decreases.2. On transient conditions, with the fuel injection advancing, CA50is in advance,the maximum explosion pressure increases, NOx emissions increase; with theincreasing of the rail pressure, CA50is in advance, the maximum explosion pressurerises, smoke decreases significantly, NOx emissions increase.3. Optimizing engine transient performance based on the characteristicparameters of combustion, specific measure is increasing rail pressure20Mpa, inthat situation，CA50on transient conditions is closed to steady-state conditions, thismethod improves the smoke surge problems on transient conditions, making smokeand NOx emissions on transient conditions are closed to steady state conditions.4. After leading into EGR, diesel smoke rise sharply; we solve this problem byadjusting injection parameters. The results show that if the injection timing areadvanced6°CA, the peak of smoke will decrease from90%to55%; and throughimproving rail pressure, the peak of smoke drops from90%to70%.