米勒循环和废气再循环对涡轮增压汽油机燃烧性能的影响和优化  

Influence and Optimization of Miller Cycle and Exhaust Gas Recirculation on Combustion Performance of a Turbocharged Gasoline Engine

作　　者：张振东[1] 屈卓燊 王博[1] 陈泓 尹丛勃[1] ZHANG Zhendong;QU Zhuoshen;WANG Bo;CHEN Hong;Yin Congbo(School of Mechanical Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China;Guangzhou Automobile Group Co.,Ltd.,Guangzhou 510640,China)

机构地区：[1]上海理工大学机械工程学院,上海200093 [2]广州汽车集团股份有限公司,广州510640

出　　处：《内燃机工程》2020年第5期48-53,61,共7页Chinese Internal Combustion Engine Engineering

摘　　要：为了研究米勒循环和废气再循环对高负荷和最佳油耗点燃烧性能的影响,通过修改进气凸轮型线,将一台1.5 L采用废气再循环的涡轮增压直喷汽油机由奥托循环改为米勒循环运行。试验结果显示,在对米勒循环和奥托循环两种不同运行方式进行的对比试验中,在低负荷下,米勒循环的泵气损失比奥托循环小。随着负荷的增加,米勒循环的影响开始减小,与奥托循环泵气损失的差异逐渐变小,阻碍米勒循环热效率的改进。此外,米勒循环还降低了压缩终了温度,从而增加了燃烧持续期和排气温度,使其难以提高最佳油耗点的燃油经济性。就废气再循环对米勒循环和奥托循环的影响也进行了对比试验。随着废气再循环率的增加,两种循环的热效率均呈现先升后降的趋势。但采用米勒循环减少了进气时间和气门升程,大大降低了缸内滚流比和湍动能,从而延迟了已燃50%质量分数对应的曲轴转角(MBF50)并延长了燃烧持续期,这使其在高负荷下的热效率和燃油经济性均低于奥托循环。In order to study the influence of Miller cycle and exhaust gas recirculation(EGR)on combustion performance at the best fuel consumption point and high load,a 1.5 L turbocharged direct injection gasoline engine with EGR system was changed from Otto cycle operation to Miller cycle operation by modifying its intake cam profile.Results show that in a comparative test of two different operating modes of Miller cycle and Otto cycle,the pumping loss from the Miller cycle operation is smaller than from the Otto cycle operation.However,as the load increases,the influence of the Miller cycle begins to decrease,causing the difference in pumping loss between the two cycles to gradually become smaller,which hinders the improvement of the Miller cycle thermal efficiency.In addition,the Miller cycle also reduces the end-of-compression temperature,increasing the combustion duration and exhaust temperature,which makes it difficult to improve the fuel economy at the best fuel consumption point.Moreover,this study also compares the effect of EGR on Miller cycle and Otto cycle.With the increase of EGR rate,the thermal efficiency of both cycles increases first and then decreases.However,the use of Miller cycle reduces the intake time and valve lift,and then greatly decrease the in-cylinder tumble ratio and turbulent kinetic energy,thus retarding the angle of 50%mass fraction burned(MBF50)and extending the combustion duration,which makes its thermal efficiency and fuel economy lower than the Otto cycle operation at high load.

关 键 词：米勒循环 外部废气再循环 涡轮增压直喷汽油机 燃烧 湍动能 

分 类 号：TK41[动力工程及工程热物理—动力机械及工程]