M15甲醇柴油的燃烧过程及循环变动分析

通过增压中冷柴油机燃用M15甲醇柴油混合燃料的台架试验,研究了外部EGR对柴油机燃烧过程及循环变动的影响。结果表明:与燃用0号柴油比,原机燃用M15甲醇柴油工作柔和,循环波动小。低转速低负荷时宜采用小EGR率,滞燃期短,放热重心基本不变,循环波动小;中等负荷时可采用大EGR率,随着EGR率的增大,滞燃期延长,放热重心推后,最大燃烧压力循环变动率稍有上升,平均指示压力和最大压力升高率波动大幅降低。经相关性分析,低转速中低负荷下,滞燃期对循环波动影响较小,放热重心与最大压力升高率有着很好的线性关系。

Analysis of Combustion Process and Cycle-to-cycle Variation of M15 Methanol-diesel Blended Fuel

Through the bench test of a turbocharged and intercooled diesel engine fueled with M15 methanol-diesel blended fuel,the influences of external EGR on combustion process and cycle-to-cycle variation were studied.The results show that,compared with zero diesel,M15 methanol-diesel can make diesel engine operate smoothly and have little cycle-to-cycle variation.At low speed and low load,the small EGR rate should be adopted,which can make the ignition delay short,keep the center of heat release curve unchanged and have little cycle-to-cycle variation.At medium load,the large EGR rate may be adopted.With the increase of EGR rate,the ignition delay extends,the center of heat release curve moves backward,the cycle-to-cycle variation rate of maximum combustion pressure slightly increases and the fluctuation of mean indicated pressure and maximum pressure rise rate greatly decreases.According to the correlation analysis,the ignition delay has little influence on cycle-to-cycle variation and a good linear relation exists between center of heat release curve and maximum pressure rise rate at low speed with medium and low loads.