PODE掺混比对电控共轨柴油机排放特性的影响

Effect of PODE blending ratio on emission characteristics of an electronically controlled common-rail diesel engine

为了降低柴油机排放、提高热效率,将体积分数为10%、20%、30%和70%的聚甲氧基二甲醚(PODE)掺混于柴油中制得PODE/柴油混合燃料,标记为P10、P20、P30和P70,在一台四缸增压中冷电控共轨柴油机上开展了PODE掺混比对混合燃料燃油经济性与排放特性的试验,并采用热重分析仪研究了混合燃料的蒸发性能。结果表明:随PODE掺混比增加混合燃料的初始失重温度、终止失重温度和峰值失重温度均向低温区域偏移,峰值失重率增大;随PODE掺混比增加,柴油机的排气温度降低,有效热效率显著提升,混合燃料的HC、CO和烟度排放逐渐降低,而NOx排放有所增加;在ESC试验循环下P30的HC、CO和PM排放量较柴油分别降低了25%、16%和51%,均低于国V排放限值,且CO2排放量也明显减小。

This paper is to introduce an experimental exploration of the effects of polyoxymethylene dimethyl ethers（ PODE）/diesel blends on the exhaust emission features so as to reduce the diesel emissions and improve the thermal efficiency. For the above purpose,the PODE has to be mixed with the diesel fuel at the mixed volume rates of 10%,20% and 30% labeled as P10,P20 and P30,respectively. The effects of PODE blending ratio on the fuel economy and emission features can be carried out on a4-cylinder turbo-charged intercooling common-rail diesel engine with the PODE/diesel blends,whereas the evaporation performance of the blends can also be tested with the thermo-gravimetric analysis method. Furthermore,the HC,CO,NOx,particulate matters（ PM） and CO2 emissions of the four different blends can also be measured and worked out under the guide of the European stationary cycle（ ESC）. Thus,the experimental results prove that,with the increase of PODE blending ratio in the blends,the initial weight loss temperature,the final combustion temperature,and the peak weight loss rate temperature would gradually move to the lower temperature areas,however,the peak weight losing rate increases. When the common-rail diesel engine is fueled with PODE/diesel blends,the exhaust temperature may tend to decrease,while the brake specific fuel consumption（ BSFC） would rise,thus,it would be possible to raise the brake thermal efficiency（ BTE） with the increase of PODE blending ratio. Thus,at full load of 1 750 r/min,the brake thermal efficiencies of P10,P20 and P30 can reach 41. 7%,42. 4% and 43. 7%,respectively. Even at the medium and high loads,it is also possible to reduce the HC,CO and smoke emissions of the blend fuel due to the increase of PODE blending ratio,in addition to increasing NOxemission. At low load,the HC and CO emissions can be made to decrease first and then increase with the increase of the PODE blend ratio,with NOxemissions remaining unchanged.For,as is known,under the ESC test cycle,it is possible for the HC,CO,PM and CO2 emissions to get gradually reduced with the increase of PODE blending ratio,in spite of the NOxemissions tending to rise somehow. Thus,as compared with the diesel fuel,it is also possible to reduce the HC,CO and PM emissions of P30 by about 25%,16% and 51%,respectively,so as for their emissions to meet the restriction of the country＇s V emission.Therefore,the application of PODE fuel in the diesel engine can be expected to lead to the thermal efficiency improvement by reducing their exhaust emissions and loosening the contradiction between the supply and demand of the fuel.