Abstract

The impingement behavior is inevitable during the injection process of urea water solution in selective catalytic reduction aftertreatment system of diesel engine. The impingement contributes to the formation of liquid film on the pipe wall and mixer, and it will block the pipe and reduce the urea water solution decomposition efficiency. In this work, the morphological changes of the spray during the impingement process were captured by the CCD camera. The liquid film development under different injection flow rates, compressed air pressures, injection heights, injection angles and metal wall temperatures were simulated and analyzed by AVL_FIRE. A good agreement with the experiment results is achieved. The results indicate that the liquid film area increases with higher injection flow rate, compressed air pressure, injection height and lower injection angle. According to Kuhnke model, the behaviors of impingement droplets are dominated by the sub-velocity of droplets which is affected by the injection flow rate and injection angle. Higher metal wall temperature can promote the evaporation of the liquid film and droplets, which reduces the liquid film area. It is an effective way to prevent the liquid film formation through rising the metal wall temperature.

中文翻译：

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尿素水溶液喷雾撞击影响因素的实验研究与数值模拟

摘要

在柴油机选择性催化还原后处理系统中，在尿素水溶液的注入过程中，碰撞行为是不可避免的。撞击有助于在管壁和混合器上形成液膜，并会阻塞管子并降低尿素水溶液的分解效率。在这项工作中，在撞击过程中喷雾的形态变化是由CCD相机捕获的。通过AVL_FIRE模拟和分析了在不同注入流量，压缩空气压力，注入高度，注入角度和金属壁温度下的液膜发展。与实验结果吻合良好。结果表明，液膜面积随着注入流速，压缩空气压力的增加而增加，注射高度和较低的注射角度。根据库恩克模型，冲击液滴的行为主要受液滴的子速度影响，子速度受注入流速和注入角度的影响。较高的金属壁温度可促进液膜和液滴的蒸发，从而减小液膜面积。这是通过提高金属壁温度来防止液膜形成的有效方法。