PCCI柴油机燃用DMC和生物柴油的燃烧活性调节模拟研究

Combustion Activity Adjusting of PCCI Diesel Engine Fueled with DMC and Biodiesel

应用CHEMKIN-PRO化学反应动力学和Converge三维模拟仿真相结合的手段,研究了DMC(碳酸二甲酯)和大豆生物柴油两种酯类燃料对低负荷下采用“预喷+预喷+主喷”喷油策略的PCCI(premixed charge compressed ignition)柴油机燃烧与排放的影响。建立并验证了DMC-柴油混合燃料机理模型,分析了DMC-柴油和生物柴油-柴油两种混合燃料体系中低温下关于OH的反应流。结果表明:添加含氧燃料后OH生成量及反应系统活性增加,B10燃料(在柴油中添加10%质量分数的大豆生物柴油)的OH生成量比D10燃料(在柴油中添加10%质量分数的DMC)高,且随生物柴油掺混量增加而增加。D10燃料对反应系统活性的增加作用体现在整个反应系统中,燃空当量比浓区减少,油气扩散情况较好,而B10燃料反应系统活性的增加作用则仅体现在局部区域中,燃空当量比浓区及局部高温区域增加,但可燃混合气区域缩小。相比于柴油,D10,B10和B48(在柴油中添加48%质量分数的大豆生物柴油)燃料的NO x排放分别升高了6.2%,5.3%和8.1%,soot排放分别降低了58.1%,23.5%和68.4%。

Based on CHEMKIN-PRO chemical reaction kinetics and Converge three-dimensional simulation software,the effects of diesel mixed with dimethyl carbonate(DMC)and soybean biodiesel respectively on combustion and emission were investigated on a premixed charge compression ignition(PCCI)diesel engine which operated in a pilot-pilot-main injection strategy under low load.The mechanism model of DMC-diesel blended fuel was built and validated,and then the reaction paths of OH in DMC-diesel and biodiesel-diesel dual fuel system were investigated respectively.The results showed that the amount of OH and the reaction activity of combustion system increased after adding the oxygenated fuel.B10 fuel that was blended fuel of diesel with 10%of soybean biodiesel generated more OH than D10 fuel that was blended fuel of diesel with 10%of DMC,and the difference became more pronounced with the increase of biodiesel blending ratio.D10 fuel could improve the diffusion of fuel and air mixture,reduce the zones of rich mixtures,and hence increase the reaction activity of the whole system.However,B10 fuel boosted the combustion temperature and formed rich mixtures in some local zones,reduceed the combustible mixture zones,and hence increased the reaction activity only in some local zones.Compared with diesel,NO x emissions of D10,B10 and B48 fuel increased by 6.2%,5.3%and 8.1%respectively and soot emission decreased by 58.1%,23.5%and 68.4%respectively.