燃料分层对乙醇/柴油双燃料发动机循环波动的影响  

Effects of Fuel Stratification on Cyclic Variability of an Ethanol/Diesel Dual-Fuel Engine

作　　者：董世军[1] 杨灿[1] 欧彪[1] 卢宏广 徐浩成 成晓北[1] Dong Shijun;Yang Can;Ou Biao;Lu Hongguang;Xu Haocheng;Cheng Xiaobei(School of Energy and Power Engineering,Huazhong University of Science and Technology,Wuhan 430074,China)

机构地区：[1]华中科技大学能源与动力工程学院

出　　处：《内燃机学报》2019年第4期297-304,共8页Transactions of Csice

基　　金：国家自然科学基金资助项目(51576083)

摘　　要：基于一台单缸柴油机,采用进气道喷射乙醇同时缸内直喷柴油的方式实现双燃料预混压缩着火(PCI)燃烧模式.固定发动机转速和负荷,通过调整预混乙醇比例以及柴油直喷策略,实现了不同程度的混合气燃料分层,并测量了相应的发动机循环波动特性,试验中NOx排放和COVIMEP分别控制在0.4 g/(kW·h)和7%以下.结合数值模拟研究了混合气燃料分层对双燃料发动机循环波动的影响,结果表明:燃料分层直接影响双燃料发动机循环波动.首先,着火正时在上止点附近时有助于降低双燃料发动机循环波动,乙醇预混当量比、柴油直喷中主喷油量以及主喷正时直接影响混合气初始着火区域燃料活性以及当量比,进而影响混合气着火正时.其次,混合气着火正时稳定性对于保证双燃料发动机燃烧稳定性较为关键.此外,燃烧相位以及缸内爆压不变,采用较高的乙醇预混比例结合推迟的主喷正时可以实现更加稳定的着火,进而降低双燃料发动机循环波动率.The effects of in-cylinder fuel stratification on the combustion stability of ethanol/diesel dual-fuel premixed compression ignition(PCI)operation were investigated based on a single-cylinder diesel engine. During the experiments,ethanol was delivered with port injection and diesel was directly injected into the cylinder,and various in-cylinder fuel stratifications were achieved by adjusting ethanol proportion and direct injection strategy.Also,the corresponding cyclic variations were studied. Meanwhile,NOx emissions and COVIMEP were maintained below 0.4 g/(kW·h)and 7%,respectively. The results show that in-cylinder fuel stratification can greatly affect the cyclic variability of dual-fuel operation. It is found that ignition occurring near the top dead center is conducive to decreasing the cyclic variations of dual-fuel operation. The equivalence ratio of premixed ethanol as well as diesel injection timing can directly affect the local equivalence ratio and fuel reactivity of regions where ignition pockets first occur,which consequently determines the ignition delay. Meanwhile,stable auto-ignition is essential to maintain the combustion stability of dual-fuel operation. Under the test conditions,with same combustion phasing and peak pressure,it is found that higher ethanol proportion coupled with retarded main injection could contribute to stable auto-ignition,which consequently results in lower cyclic variations.

关 键 词：柴油机 双燃料 预混压缩着火 乙醇/柴油 燃料分层 循环波动 着火正时稳定性 

分 类 号：TK421[动力工程及工程热物理—动力机械及工程]