利用特征时间燃烧模型研究燃料分层对柴油PCCI燃烧过程的影响  

Study of Fuel Distribution on Diesel PCCI Combustion Using New Characteristic-Time Combustion Model

作　　者：于洋[1] 苏万华[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

出　　处：《内燃机学报》2009年第1期1-10,共10页Transactions of Csice

基　　金：国家重点基础研究发展规划项目(2007CB210000);国家自然科学基金重点项目(50636040)

摘　　要：针对柴油可控的预混燃烧方式,提出了一种基于化学动力学反应和湍流混合特征时间尺度的改进燃烧模型。介绍了一个燃料混合不均匀性程度函数H(),由此导出了模型中的湍流混合时间尺度系数f,用来表征燃料混合不均匀性程度与湍流混合时间尺度的关系。利用该模型对调制多脉冲喷油模式下柴油可控预混充量压燃PCC I燃烧进行了数值模拟,计算结果与试验数据符合良好。调制多脉冲喷油模式下柴油可控预混充量压燃PCC I燃烧的着火过程是分步容积式的,并受燃料分层的强烈影响。由于缸内存在浓度与温度的分层,降低了高浓度区域的温度,有助于减少NOx,此外"V"型当量比分布有利于推迟高温反应。To understand the premixed charge compression ignition （PCCI） combustion, a new combustion model of kinetic-and-turbulent characteristic-time is developed. A ununiformity function H （Ф） is presented by analyzing the effect of fuel/air distributions on turbulent timescale in the combustion model, and then an analytical turbulent timescale coefficientfwas deduced, which was proved to be able to correlate the fuel ununiformity with the turbulent timescale in the combustion model. The new model was employed in the simulation of the PCCI combustion under various multi-pulse injection strategies in a heavy duty diesel engine. The simulation results agreed well with the experimental data. The ignition process of the PCCI combustion was a separated volume autoignition process, which was strongly influenced by the condition of fuel stratification. Due to the existence of concentration and temperature stratifications, the decreasing in combustion temperature and lower formation rate of NOx were achieved in the richer area. Meanwhile, a＂ V＂ type distribution of equivalence ratio was found to be beneficial to retarding of high temperature reaction.

关 键 词：PCCI 燃烧模型 燃料分布 多脉冲喷射 

分 类 号：TK402[动力工程及工程热物理—动力机械及工程]