利用含PAH的正庚烷简化机理对柴油机富氧燃烧的数值模拟  

Numerical Simulation of a Diesel Engine Oxygen Enriched Combustion with N-Heptane Reduced Mechanism Containing PAH Formation

作　　者：张韦[1,2] 舒歌群[1] 沈颖刚[2] 赵伟[1] 徐彪[1] 

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 [2]昆明理工大学交通工程学院,云南昆明650500

出　　处：《内燃机学报》2012年第4期296-304,共9页Transactions of Csice

基　　金：国家自然科学基金资助项目(50976077)

摘　　要：在直喷柴油机上采用氧体积分数为21%～24%的进气增氧技术,进行燃烧及排放试验.建立适用于柴油机燃烧的含PAH的正庚烷简化机理,并将其与CFD模型耦合,进行富氧燃烧的数值模拟.试验及模拟工况为发动机的最大转矩点.结果表明,随发动机进气氧体积分数的增加,燃烧始点提前,瞬时放热及最大压力出现时刻均随之提前.NO的排放随氧体积分数的增加而快速增长.碳烟的排放随氧体积分数增加而大幅下降.模拟计算结果显示,CFD与化学动力学模型的耦合比较准确地预测富氧燃烧的缸内着火时刻及燃烧状况.分析上止点后6°CA、20°CA时刻燃烧室内苯环的质量分布切片可知,与21%进气氧体积分数的空气助燃相比,24%氧体积分数的富氧燃烧对苯环的形成有明显的抑制作用.模拟计算结果与试验测量值随进气氧体积分数的变化趋势基本一致.The oxygen-enriched intake air technology was applied in a DI diesel engine （the volume frac- tions of oxygen are from 21% to 24%）. The effect of atmospheric air and oxygen-enriched combustion on combustion and emission was investigated. Engine operating condition was simulated by coupling multi- dimensional computational fluid dynamic （CFD）code with an updated reduced chemical reaction kinetics model for the n-heptane combustion containing the polycyclic aromatic hydrocarbon （PAH） formation. The experiment and simulation were both carried out under the maximum torque point, Experimental results show that, with the increase of oxygen concentration, the ignition delay is decreased, the heat release rate and peak cylinder pressure are advanced. NO emission increases and smoke decreases with the in- crease of oxygen content. Simulation results show that, the ignition timing, various physical quantities and combustion products can be predicted accurately by the coupling method. Analysis on the benzene mass distribution field in chamber impress-cuts at 6° CA ATDC and 20°CA ATDC showed that 24% oxy- gen-enriched combustion could significant inhibit the benzene ring＇s formation comparing to normal air. Simulation shows the similar trend to that of experiment to the variation of inlet oxygen concentration.

关 键 词：直喷柴油机 富氧燃烧 多环芳香烃 

分 类 号：TK421.2[动力工程及工程热物理—动力机械及工程]