不同米勒循环方式对柴油机工作过程影响的一维模拟分析

1-Dimensional simulation analysis about the influence of different Miller cycle strategies on diesel engine operating process

基于柴油机的工作模型,运用-维模拟分析了进气门早关和晚关两种米勒循环形式对柴油机燃烧和排放的影响,通过改变气门正时、增压压力和喷油正时,在两种米勒循环方式下对该型柴油机在额定转速下的工作状态进行了优化。实验结果表明,推迟或者提前进气门关闭时刻可以减小压缩阶段的压力和温度,从而使滞燃期增长,但是由于缸内工质的减少,缸内平均温度和碳烟排放升高;增压压力的提高可以弥补进气损失,进气门晚关或者早关并结合提高增压压力及推迟喷油,可同时降低NOx和碳烟的排放;在保持爆发压力与原机相同时,M-50配合定爆发压力与上止点前10°CA喷油的方案相对于原机其油耗下降1.21%,NOx排放下降22%,碳烟下降58.1%,M100配合定爆发压力与上止点前12°CA喷油的方案相对于原机其油耗下降1.56%,NOx下降12.96%,碳烟下降54.75%。

Based on the working model of a diesel engine,the influences of two Miller cycle strategies,Early Intake Valve Closure（EIVC）and Late Intake Valve Closure（LIVC）on the combustion and emissions of diesel engine were analyzed by 1-Dimensional simulation.Then,the working condition of each Miller cycle strategy on the engine under the rated speed was optimized through the adjust of the valve timing,the boost pressure and the injection timing.It was found that both delaying and advancing the closure timing of the intake valve can decrease the pressure and temperature during compression stroke,prolonging the ignition delay.However,due to the decrease of the workingmedia inside the cylinder,the average in-cylinder temperature and soot emission increase,which can be alleviated by raising the boost pressure and the resulting compensation of the intake air loss.The study also found that together with increasing boost pressure and delaying injection timing,both EIVC and LIVC can reduce NOxand soot emission simultaneously.The simulation results show that while keeping the peak firing pressure the same as the original engine,M-50 together with constant peak firing pressure boosting and a 6°CA injection delay can decrease the Fuel Consumption（FC）by 1.21%,and NOxemission by 22%,and soot emission by 58.1%,while M100 together with constant peak firing pressure boosting and a 4°CA injection delay can reduce the FC by 1.56%,and NOxemission by 12.96%,and soot emission by 54.75%.