Effects Of Injection Strategies And EGR Of Diesel Engine On Combustion Characteristics And Particulate Matter Emissions

In recent years, the concentration of particulate matter in many cities in Chinahas always exceeded, leading to the haze appears frequently. It will make respiratorysystem diseases that living in the ash haze in the ambient air for a long time. As theresult, events of abnormal death are more common. Therefore the ash haze pollutionbecome the top priority of environmental problem facing our country. Car, as one ofthe main sources of atmospheric particulates, has received more and more attention.Due to its combustion characteristic, diesel particulate matter (DPM) emissions areoften far more than gasoline vehicles. Thus become hotspot in research of automobileto control and reduce the diesel particulate matter emissions. Systematically effortsare made on combustion, emissions and especially particulate matter distribution withdifferent injection and EGR strategies of diesel engine in this paper, and the particlenumber concentration and diameter distribution of particles emitted in the carboncomponents. are mainly studied.Experimental study has been done on main injection timing, rail pressure, EGRrate, and pilot injection timing contributing to combustion, the conventional emissionsas well as the distribution of PM and carbonaceous component. Main injection timingexperiment results show that, in the same rotate speed with the main injection timedelaying, maximum heat release rate first decreases and then increases under low load,while not obvious under high load. CO, HC increase, and NO_xdecreases gradually,the smoke is almost zero at low load, and decrease first and then increase under highload. Particles number goes up. Under low load, the particulate matter is developingsmaller, and the quality of the accumulation is reduced, while nucleation modeparticles becoming more. Under high load, the mass of PM gradually increases. GMDincreases firstly and then decreases, but there is no obvious relationship betweenGMD and main injection timing. Furthermore, injection strategies have little effect onthe OC/EC. Char-EC/Soot-EC gradually goes up under low load, but decreasesgradually under high load. Rail pressure experiments were conducted secondly. Results show that, with thein rail pressure increasing, the combustion heat release rate and maximum pressurerise rate increase, but the fuel consumption rate decreases. CO and HC reduces, NO_xis getting more. Accumulation mode particulate matter and total particulate mattermass decreases, on the contrary in the quality of nucleation mode particles. Thenumber of nucleation mode particles and total particles gradually increases, while acorresponding decrease in the accumulation mode particles. PM is directed to besmaller, leading to the reducing GMD. TC is becoming less, but Char-EC/Soot-EC isgoing up.Introduction of EGR changes the traditional pre-mixed combustion and diffusioncombustion mode, leading to a single peak of the heat release. With the EGRincreasing, there is different variation of heat release rate in different conditions. Itshows that fuel consumption is gradually increasing, as well as HC, CO and smoke.On the other hand, NO_xis significantly reduced. When EGR rate is added to30%,NO_xalmost does not exist in the tailpipe. EGR increases the quality and quantity ofthe accumulation mode and the total particulate matter concentration. But at the sametime reduces the nucleation mode. GMD is getting bigger along with the direction ofparticle size being to larger. The EGR increases TC while Char-EC/Soot-EC decreasesdue to the reduction of the oxygen content.Pilot injection timing test results show that the smaller pilot intervals of the maininjection, the higher peak of heat release. With the pilot injection timing advancing,pilot combustion is getting lower and longer. The peak heat release rate becomeslower, and fuel consumption grows up. HC and CO gradually getting more under lowload, but did not change under high load. NO_xand smoke are gradually reduced. PMdeclines in the quality, and develops toward be smaller at the same time. The qualityand quantity of the nucleation mode particles increases but accumulation mode goingdown. Therefore GMD is slightly reduced. But when pilot-main injection interval istoo small, the heat release rate, and PM emission significantly increases.