柴油机Urea-SCR系统沉积物生成临界状态模型研究

大量研究表明,Urea-SCR系统沉积物相关研究模型无法有效预测沉积物开始生成的临界状态,该临界状态常伴随着"莱登弗罗斯特"现象的消失。本研究基于"莱登弗罗斯特"点建立沉积物生成临界状态模型,由此仿真计算表征临界状态的临界添蓝流量,并与试验测得的临界添蓝流量值对比,发现喷雾体积通量q>7×10^-4m^3s^-1m^-2时,基于致密喷雾"莱登弗罗斯特"点的临界状态模型有较好的仿真精度;喷雾体积通量q>7×10^-4m^3s^-1m^-2时,基于单液滴"莱登弗罗斯特"点的临界状态模型仿真误差大。究其原因,由于喷雾体积通量q>7×10^-4 m^3s^-1m^-2时,单液滴沉积并未引起沉积物生成,沉积液滴易被壁面快速蒸发热解,则在该体积通量范围内考虑尿素在壁面的蒸发热解,最终提高了模型的仿真精度,实现了各喷雾体积通量下临界状态的有效预测。

Research on Modeling of Diesel Engine Urea-SCR System Deposits Formation Critical State

A large number of studies have shown that the critical state of the beginning of Urea-SCR system deposits formation can' t be effectively estimated by deposit-related research models, which is often accompanied by the disappearance of Leidonfrost phenomenon. Therefore, in this work, the model based on Leidonfrost point is built to estimate deposits formation critical state, which calculates critical adbule flux representing the deposits formation critical state. And then the comparison of critical adbule flux simulation data with that of test data shows: When spray volumetric flux is q〉7×10^-4m^3s^-1m^-2,the model based on dense spray Leidonfrost point has high precision;when spray volumetric flux is q〉7×10^-4m^3s^-1m^-2,the model based on signal droplet Leidonfrost point has large error, which is because when spray volumetric flux is q〉7×10^-4m^3s^-1m^-2,deposited droplets don not cause deposits formation and can be easily evaporated and thermal decomposed. Accordingly, the model is advanced through considering urea evaporation and thermal decomposition when spray volumetric flux is q〉7×10^-4m^3s^-1m^-2.