摘要
为在保持柴油机动力性和经济性能的同时有效改善其排放性能,在一台4缸柴油机上针对6、12、24mg循环喷油量的负荷工况(记作低、中、高负荷)对比研究了冷、热废气再循环(EGR)对性能、燃烧及排放特性的影响。结果表明:EGR的引入减少了新鲜进气量,整体上延长了滞燃期,减缓了燃烧放热速率,降低了压力升高率;热EGR提高了进气温度,使低负荷时的碳氢化合物(HC)排放显著降低,热效率提高,而高负荷高EGR率时由于过量空气系数偏低引起了热效率的明显降低,对最大压力升高率的降低作用也弱于冷EGR;随着EGR率的提高,三种负荷下的氮氧化物(NO_x)排放均大幅度降低,碳烟排放在低、中负荷时较低,而在高负荷时则明显升高,NO_x与碳烟排放之间出现此消彼长的矛盾趋势。冷的高EGR率下的碳烟排放升高幅度减小,有效地缓解了这种矛盾。综合分析低、中、高负荷下的热效率及排放,低负荷时为提高热效率宜采用热EGR,高负荷时为降低过高的压力升高率并兼顾热效率则更适合采用冷EGR。
To effectively improve the emissions of a diesel engine without reducing its performance in power and fuel economy, the effects of cold and hot EGR on engine performance, combustion and emissions characteristics were experimentally studied. The experiment was conducted on a four-cylinder diesel engine at three different loads of 6,12 and 24 mg of fuel injected a cycle. The three loads hereinafter are temporarily referred to as low, medium and high loads. The experimental results show that the introduction of EGR can reduce the fresh air inflow, extend the ignition delay and slow down the heat release rate, thus reducing the cylinder pressure rise rate. The hot EGR, on the one hand, decreases HC emission effectively and increases the thermal efficiency at the low load due to its heating intake air; on the other hand, it obviously reduces the thermal efficiency at the high load with high EGR rate because of lower excess air coefficient. The effect of the hot EGR on reducing the maximum pressure rise rate is smaller than that of the cold EGR. With the increase of EGR rate, NOx emission decreases Significantly at the three different loads, and soot emission keeps small at the low and medium loads, but increases quickly at the high load with high EGR rate, requiring a trade-off between NOx and soot. The cold EGR, however, can effectively ease this requirement due to its slow increase in soot emission. The thermal efficiency and emissions at the three loads being considered, the hot EGR is appropriate at the low load to improve thermal efficiency, and the cold EGR is more suitable at the high load to maintain high thermal efficiency and reduce the excessive pressure rise rate.
作者
马帅营
刘方杰
王鑫
杜慧勇
徐斌
MA Shuaiying LIU Fangjie WANG Xin DU Huiyong XU Bin(Vehicel ＆ Transportation Engineering Institute, Henan University of Science and Technology, Luoyang 471003,China)
出处
《内燃机工程》
EI
CAS
CSCD
北大核心
2017年第4期33-40,共8页
Chinese Internal Combustion Engine Engineering
基金
国家自然科学基金项目(51506047)
河南科技大学博士科研启动资金项目(13480039)
河南省高等学校重点科研项目(16A470006)~~
关键词
柴油机
冷EGR
热EGR
燃烧
排放
diesel engine
cold EGR
hot EGR
combustion
emissions
