摘要
针对均质SI-CAI混合燃烧存在循环波动大、较高负荷下最大压力升高率过高等问题,提出一种基于分层火焰引燃(stratified flame ignition,SFI)的SI-CAI混合燃烧技术.并在一台直喷(DI)四缸汽油机上,采用内部废气重压缩策略配合进气道喷射(PFI)方式实现了SFI燃烧.探索了PFI/DI喷射对SFI燃烧特性的影响规律.研究结果表明,随着直喷时刻在压缩冲程初期的推迟,直喷燃油的物理冷却作用使得燃烧始点推迟,同时分层的稀释混合气使得最大压力升高率大幅下降,但指示平均有效压力IMEP略微恶化;过晚的直喷时刻将导致自燃燃烧提前,放热变快,最大压力升高率迅速增大,IMEP恶化显著,循环变动变大.直喷比例的增大能大大降低最大压力升高率,同时能够保持稳定的燃烧.点火时刻在不同的喷油策略下都能有效控制SFI燃烧过程.相比均质混合燃烧,SFI燃烧可以较好地缓和混合燃烧中最大压升率与燃烧稳定性的矛盾,能同时保证较低循环波动和较小压升率.
Stratified flame ignition（SFI）hybrid combustion was proposed to solve the problems of high cycle-tocyclevariation（CCV）and unacceptable pressure rise rate（PRR）of homogeneous SI-CAI hybrid combustion at higherload.SFI combustion was achieved by internal exhaust gas recompression strategy combined with inlet port fuel injection（PFI）in a direct injection（DI）four-cylinder gasoline engine,and then the effects of different PFI/DI injectionstrategies on SFI hybrid combustion were further studied.The results indicate that with the delay of the start of directinjection timing（SOI） in the early compression stroke period,the combustion start points delayed by the physicalcooling effects from direct injection fuel,while the auto-ignition combustion process is moderated by the stratifiedlean mixture in the peripheral region,greatly lowering the PRRmax but with a slight deterioration of IMEP.Too lateSOI timings will advance auto-ignition combustion and accelerate heat release process,which increases the PRRmaxrapidly,deteriorates IMEP significantly,and increases the CCV of IMEP.The increase of the ratio of direct injectionwill greatly reduce the PRRmax,but have no influence on combustion stability.Spark timing is effective in controllingthe SFI combustion process regardless of different injection strategies.Compared with homogeneous hybridcombustion,SFI can better moderate the contradiction between PRRmax and combustion stability,meanwhile maintainingrelatively small CCV and low PRRmax level.
作者
江维海
谢辉
宋康
陈权
赵华
Jiang Weihai Xie Hui Song Kang Chen Quan Zhao Hua(State Key Laboratory of Engines,Tianjin University,Tianjin 300072,Chin)
出处
《燃烧科学与技术》
EI
CAS
CSCD
北大核心
2016年第5期433-440,共8页
Journal of Combustion Science and Technology
基金
国家重点基础研究发展计划(973计划)资助项目(2013CB228403)
国家自然科学基金资助项目(51376135)
关键词
混合燃烧
分层火焰引燃
PFI/DI
最大压升率
循环变动
hybrid combustion
stratified flame ignition（SFI）
port fuel injection/direct injection（PFI/DI）
maximum pressure rise rate
cycle-to-cycle variation
