Experimental study and numerical simulation of impact factors on spray impingement of urea water solution

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.