Deposit Formation from Urea Injection: a Comprehensive Modeling Approach
Deposit Formation from Urea Injection: a Comprehensive Modeling Approach
复制标题
尿素注射形成沉积物：综合建模方法
DOI：
--
复制
发表时间：
2020
影响因子：
1.6
通讯作者：
T. Lauer
中科院分区：
文献类型：
--
作者：
U. Budziankou;M. Börnhorst;C. Kuntz;O. Deutschmann;T. Lauer
长期可靠性是以尿素水溶液（UWS）为载氨液的选择性催化还原（SCR）汽车尾气后处理系统的主要要求之一。UWS的高注入速率或不利的操作条件可能导致固体沉积物的形成，这通过增加背压和损害氨均匀性来降低系统效率。尿素SCR系统中存款形成的可靠数值预测对于系统设计的优化是期望的。然而，在排气管以及不同的时间尺度的现象的物理和化学过程的综合建模是一项具有挑战性的任务。本研究提出了一种基于CFD模拟的UWS喷射、液滴撞击、液膜和存款形成的综合建模方法。现有的尿素分解动力学模型被集成到CFD代码中，以预测壁膜形成的固体副产物。物理模拟时间被广泛地增加了替代拉格朗日粒子与源项的质量，动量和能量减少模拟时间的20倍。实测和模拟结果的比较表明，所提出的建模方法预测固体沉积物的位置和化学成分的能力。
Long-term reliability is one of the major requirements for automotive exhaust aftertreatment systems with selective catalytic reduction (SCR) using urea water solution (UWS) as NH 3 carrier fluid. A high injection rate of UWS or unfavorable operating conditions may lead to formation of solid deposits, which decrease system efficiency by increasing backpressure and impairing ammonia uniformity. A reliable numerical prediction of deposit formation in urea SCR systems is desired for optimization of system design. However, comprehensive modeling of physical and chemical processes in the tailpipe as well as different time scale phenomena represents a challenging task. This study presents a comprehensive approach for modeling UWS injection, droplet impingement, liquid film and deposit formation based on CFD-simulation. An existing kinetic model for urea decomposition is integrated into the CFD code to predict solid by-product formation from wall films. Physical simulation time is extensively increased by substituting the Lagrange-particles with source terms of mass, momentum and energy reducing simulation time by a factor of 20. The comparison of measured and simulated results shows the capability of the presented modeling approach to predict position and chemical composition of solid deposits.