基于详细蒸发和热解的SCR系统尿素添加过程模拟

Simulation of Urea Addition Based on Detailed Evaporation and Thermolysis for Urea-SCR

为研究柴油机尿素-SCR系统还原剂的分布,在研究尿素水溶液具体分解过程的基础上,基于OpenFOAM平台利用两步蒸发方法和热解过程的副反应模型,建立还原剂添加过程的气/液两相流三维模型.同时,设计多通道组分探测系统对出口截面的还原剂进行浓度采集,利用全局遗传算法对蒸发、热解过程中的化学反应进行参数辨识,并进行流动试验以验证流动模型参数的准确性,将模拟的出口截面还原剂体积分数与试验对比,结果表明:考虑两步蒸发及热解副反应的气/液两相流模型能够以较高的精度描述还原剂分布情况,为柴油机尿素-SCR系统的还原剂分布均匀性的研究提供参考.

In order to study the distribution of reducing agent in urea-SCR system of diesel engines,after analyzing the specific decomposition process of urea water solution,a three-dimensional model of gas-liquid two phase flow for reducing agent generation based on OpenFOAM platform was established,in which two-step evaporation method and kinetic reaction were used for thermolysis of urea.Meanwhile,a multi-channel component detection system was designed to collect the concentration of reducing agent at the exit section.The global genetic algorithm was carried out to identify parameters of kinetic reaction for thermolysis,and the data of flow test was used to verify the accuracy of the flow model.The results show that the gas-liquid two phase flow model can describe the distribution of reducing agent with high accuracy,providing a reference to study the NH3 uniformity of urea-SCR system.