乙醇/生物柴油/柴油混合燃油的燃烧与排放特性

Combustion and Emission Characteristics of Ethanol/Biodiesel/Diesel Blends

通过建立柴油机燃烧室模型,仿真对比研究5种燃油的索特平均直径、油束生长过程、缸内压力、缸内温度、NO x和碳烟的排放量。结果表明:大比例掺混生物柴油使得混合燃油黏度、密度、表面张力等理化特性参数值增大,导致燃油在缸内雾化质量变差,但添加乙醇后不仅改善了雾化质量,而且改善了燃油缸内燃烧过程,燃油燃烧更加充分彻底。与0#柴油BD100(100%的柴油)相比,添加生物柴油和乙醇后,缸内最高压力上升,混合燃油BD75(25%生物柴油+75%柴油)、BD72E3(25%生物柴油+72%柴油+3%乙醇)、BD70E5(25%生物柴油+70%柴油+5%乙醇)、BD65E10(25%生物柴油+65%柴油+10%乙醇)的最高缸内压力由13.6624 MPa分别升高到13.7735,13.8846,13.9728,14.2924 MPa;燃烧始点对应的曲轴转角前移,由355.0°分别前移为353.0°,353.5°,354.0°,燃油BD65E10燃烧始点对应的曲轴转角后移为356.5°;NO x排放量整体平均值均升高,转速n=2200 r/min时分别升高3.947%、4.578%、6.540%、6.812%,转速n=3600 r/min时分别升高2.678%、1.246%、3.584%、4.770%;soot排放量均降低,转速n=2200 r/min时,降低平均降幅分别为2.019%、7.168%、19.202%、39.666%;转速n=3600 r/min时,平均降幅分别为1.190%、7.446%、15.362%、31.810%。

A diesel engine combustion chamber model was established to simulate and compare the Sauter Mean diameter,fuel spray growth process,in-cylinder pressure,in-cylinder temperature,NO x and soot emissions of five fuels.The results show that a large proportion of biodiesel mixed increases the viscosity,density,surface tension and other physical and chemical property parameters of the mixed fuel,resulting in the poor atomization quality of the fuel in the cylinder.However,the addition of ethanol not only improves the atomization quality,but also improves the combustion process in the fuel cylinder,making the fuel combustion more fully and thoroughly.Compared to the 0#diesel BD100(100%diesel),the maximum pressure in the cylinder rises after the addition of biodiesel and ethanol.The maximum in-cylinder pressures of the mixed fuels BD75(25%biodiesel+75%diesel),BD72E3(25%biodiesel+72%diesel+3%ethanol),BD70E5(25%biodiesel+70%diesel+5%ethanol),and BD65E10(25%biodiesel+65%diesel+10%ethanol)increase from 13.6624 MPa to 13.7735 MPa,13.8846 MPa,13.9728 MPa and 14.2924 MPa respectively;The crankshaft angle corresponding to the combustion starting point moves forward from 355.0°to 353.0°,353.5°and 354.0°respectively,and the crankshaft angle corresponding to the combustion starting point of fuel BD65E10 moves backward to 356.5°;the overall average value of NO x emission are all increased,and the increase is 3.947%,4.578%,6.540%and 6.812%respectively when rotation speed is 2200 r/min,and the increase is 2.678%,1.246%,3.584%and 4.770%respectively when the rotation speed is 3600 r/min;soot emissions are all decreased,and the average decreases is 2.019%,7.168%,19.202%and 39.666%when rotation speed n=2200 r/min,respectively.When the rotation speed n=3600 r/min,the average reduction is 1.190%,7.446%,15.362%and 31.810%,respectively.