进气压力和喷油对二冲程汽油机稀燃特性的影响  

Effects of Intake Pressure and Injection on the Combustion Characteristics of a Poppet-Valve Two-Stroke Direct Injection Gasoline Engine in Lean Conditions

作　　者：何邦全[1] 李晓 He Bangquan;Li Xiao(State Key Laboratory of Engines,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学内燃机燃烧学国家重点实验室,天津300072

出　　处：《燃烧科学与技术》2018年第2期111-119,共9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)

摘　　要：利用三维数值模拟软件CONVERGE研究了在循环喷油量和点火时刻固定的大负荷条件下,进气压力对二冲程直喷汽油机缸内燃油分布和稀燃特性的影响.结果表明,在相同的第2次喷油比例下,随着进气压力的升高,气缸内燃油浓度降低.在相同的进气压力下,随着第2次喷油比例的增加,火花塞附近的燃油浓度先减小后增加.在第2次喷油比例为70%,时燃油分层形式最有利于燃烧.在相同的第2次喷油比例下,随着进气压力的升高,着火时刻逐渐提前,燃烧持续期先略有缩短后又增长,最大压力升高率先增加后减小.在相同的进气压力下,随着2次喷油比例的增加,着火时刻先略有推迟后提前,燃烧持续期先增长后缩短,最大压力升高率先减小后增加.气缸内燃油浓度和温度分层形式影响火焰传播过程中气缸周围混合气的自燃特性.提高进气压力能降低气缸周围混合气的浓度,抑制自燃的发生.The effect of intake pressure on fuel distribution and combustion characteristics in a poppet-valve twostroke direct injection gasoline engine with lean mixture at high loads was simulated with a 3-dimentional computational fluid dynamic CONVERGE software.Simulation results show that with the increase of intake pressure,the average fuel-air equivalent ratio in the cylinder decreases at a fixed ratio of the second injection to the total.With the increase of the second injection ratio at fixed intake pressure,the fuel-air equivalent ratio around spark plug first slightly decreases and then rises.At the second injection ratio of 70%,the fuel distribution is prone to combustion.With the increase of intake pressure at a given second injection ratio,ignition timing advances,combustion duration slightly decreases first and then increases while the maximum pressure rise rate first rises and then drops.With the increase of the second injection ratio at given intake pressure,ignition timing slightly delays first and then advances,combustion duration first increases and then decreases while the maximum pressure rise rate drops first and then decreases.The fuel concentration and temperature stratification in the cylinder affect autoignition in the cylinder.High intake pressure can prevent the occurrence of auto-ignition through decreased fuel-air equivalent ratio around the cylinder.

关 键 词：二冲程 汽油机 稀混合气 燃烧 数值模拟 

分 类 号：TK411.2[动力工程及工程热物理—动力机械及工程]