浓度分层下正庚烷自点火过程的直接数值模拟  

Direct Numerical Simulation of n-Heptane Autoignition Process with Charge Stratification

作　　者：吴煜杨 叶桃红[1] 朱旻明[1] Wu Yuyang;Ye Taohong;Zhu Minming(Department of Thermal Science and Energy Engineering,University of Science and Technology of China,Hefei 230027,China)

机构地区：[1]中国科学技术大学热科学和能源工程系

出　　处：《燃烧科学与技术》2019年第4期353-358,共6页Journal of Combustion Science and Technology

基　　金：国家自然科学基金资助项目(51576182;91441117)

摘　　要：针对实际内燃机内存在浓度分层的情况,采用直接数值模拟,研究了浓度分层对正庚烷在空气中的自点火过程的影响.结果表明:在压力2.4MPa,初始温度860K(位于负温度系数区域)下,随着浓度分层的增加,整体着火时间提前,但是第1阶段点火延迟时间几乎没有变化.第2阶段着火位置的混合物分数随着浓度分层的增加而变大,说明两阶段着火不存在统一的最易着火的混合分数.通过budget分析,揭示低温反应和高温反应阶段存在不同的火焰传播模式.Considering the existence of charge stratification in real engines,direct numerical simulation is used to study the effect of charge stratification on the n-heptane/air autoignition process.Results show that under the initial pressure of 2.4MPa and initial temperature of 860 K(within the negative temperature coefficient regime),the overall ignition delay time decreases with the increasing charge stratification;however,the first-stage ignition delay time barely changes.The mixture fraction in the second-stage ignition area increases with the increasing charge stratification,indicating that there is no uniform most reactive mixture fraction for the two-stage ignition process. Through budget analysis,different flame propagation modes are revealed to exist in the low- and hightemperature reaction stages.

关 键 词：自点火过程 点火延迟时间 浓度分层 直接数值模拟 负温度系数 

分 类 号：TK11[动力工程及工程热物理—热能工程]