摘要
为了深入分析含水乙醇对汽油直喷(Gasoline Direct Injection,GDI)发动机性能的影响,利用CONVERGE软件,结合耦合含水乙醇汽油燃烧机理和碳烟模型,进行了三维模拟,从微观角度研究了GDI发动机结合废气再循环(Exhaust Gas Recirculation,EGR)技术燃用含水乙醇汽油时的燃烧及碳烟生成与排放特性。结果表明:含水乙醇掺混比的增大有助于加快火焰传播速度,进一步缩短燃烧持续期。碳烟前驱物(PAHs)控制碳烟的成核和生长,含水乙醇汽油的含氧特性及高活性的OH可以抑制碳烟生成,与E0(含水乙醇体积分数为0)相比,E20W(含水乙醇体积分数为20%)的碳烟前驱物苯、萘、菲、芘的质量峰值分别降低了60.0%、54.5%、73.3%、52.4%,碳烟质量峰值降低了63.6%,碳烟数量密度峰值下降了40.0%。EGR的引入使燃烧效率降低,PAHs和碳烟生成质量升高,碳烟数量密度降低,含水乙醇的添加能改善EGR环境中的燃烧效率,降低未燃HC和碳烟生成量。相比纯汽油,含水乙醇汽油结合EGR技术,弱化了EGR对燃烧和碳烟排放的负面影响。因此,EGR结合含水乙醇汽油能够改善发动机燃烧特性,降低发动机的碳烟等污染物排放,对提升GDI发动机性能和改善颗粒物排放有较好的作用。
In recent years,the gradual increase in automobile production has accelerated the consumption of petroleum resources,and a large amount of harmful exhaust gas has also brought great threats to the climate and human health.It is the general trend to seek low-carbon,clean and renewable alternative fuels and realize energy diversification.Gasoline direct injection(GDI)engines have been widely used due to the advantages of high efficiency and cleanliness,but the problem of higher particulate emissions has not yet been resolved.As an alternative fuel for engines,ethanol has the advantages of highoctane number,low pollution,strong renewability,safety and non-toxicity,and good compatibility with gasoline.Compared with absolute ethanol,hydrous ethanol is less sensitive to moisture in the air,and it is more stable when mixed with gasoline.Exhaust gas recirculation(EGR)technology can effectively reduce pumping losses,reduce fuel consumption,and reduce NOx emissions.The introduction of EGR in gasoline direct injection engines can lower the combustion temperature,and the dilution effect of exhaust gas can reduce the local concentration of the mixture,which is beneficial to inhibit the soot generated by the fuel cracking and dehydrogenation reactions.In this study,the three-dimensional simulation was carried out by using CONVERGE software coupled with the combustion mechanism of hydrous ethanol gasoline and the soot model,to explore the effects of the combination of hydrous ethanol and EGR on the combustion and soot generation characteristics of GDI engine.The results showed that the increase of the volume fraction of the hydrous ethanol accelerated the flame propagation speed,shortened the combustion duration.The soot precursors(PAHs)control the nucleation and growth of soot.The formation of soot can be inhibited by the oxygen-content characteristics of hydrous ethanol gasoline and the high activity OH.Compared with E0(hydrous ethanol volume fraction is 0%),the peak mass of soot precursors of E20W(hydrous ethanol volume frac
作者
石秀勇
段毅菲
康杨
廖延苏
倪计民
Shi Xiuyong;Duan Yifei;Kang Yang;Liao Yansu;Ni Jimin(School of Automotive Studies,Tongji University,Shanghai 201804,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2020年第17期64-72,共9页
Transactions of the Chinese Society of Agricultural Engineering
基金
上海市自然科学基金项目(16ZR1438500)
内燃机燃烧学国家重点实验室开放课题(K2016-04)。
关键词
汽油直喷发动机
燃烧
CFD
含水乙醇汽油
碳烟
gasoline direct injection(GDI)engine
combustion
CFD
hydrous ethanol gasoline
soot
