基于碳氢喷射的柴油机尾气热管理模型

Model Based Investigation on Thermal Management of Diesel Engine Exhaust System with HC-Dosing

针对尾气热管理系统进行了一维柴油催化氧化器(DOC)化学反应动力学与流动的耦合模型研究.基于已有的柴油机原排碳氢反应机理研究,对碳氢喷射尾气热管理系统进行了整合修正.模型主要考虑了系统在DOC上游安装的碳氢喷嘴喷入的柴油液滴,在DOC内部形成气态碳氢化合物的蒸发热解和催化反应过程.同时将柴油液滴蒸发热解过程进行改进优化,设计了一种"两步蒸发热解法"简化复杂的柴油蒸发热解过程,并给出了相应的阿伦尼乌斯型蒸发热解速率经验公式.模型基于GT-Power软件搭建,同时在柴油机上进行了稳态工况碳氢喷射升温试验,并利用试验数据针对模型进行了标定.结果表明:标定后的模型与试验动态结果误差较小,这一理论与工程标定相结合的模型研究方法可以用于国Ⅵ尾气热管理控制策略开发.

One-dimensional diesel oxidation catalyst(DOC)model coupled with chemical reaction kinetics was investigated on this system. Based on the previous research of the hydrocarbon reaction in engine original exhaust,the model was integrated and modified considering the diesel thermal management system with hydrocarbon dosing. The model mainly considered the evaporation and thermolysis process that diesel droplet injected by DOC upstream injector was transformed into gaseous hydrocarbon inside DOC. Simultaneously,the evaporation and thermolysis process of diesel droplet was optimized by a "two-step E-T method" to simplify the complex process of diesel evaporation and thermolysis. The rate formula of evaporation and thermolysis was given by Arrhenius form. The model was simulated on GT-Power and experimented on an engine displacement under steady-state conditions,with hydrocarbon dosing inducing temperature rising. Model was calibrated by experimental data. The result showed that the dynamic error between calibrated model and experiment was relatively small. This model research method which was combined by theory and engineering calibration could provide reference for control strategy development for China Ⅵ diesel exhaust thermal management.