摘要
UWS （optimized Urea-Water Solution） injection system is required to increase the NH3 conversion efficiency of urea-based SCR （Selective Catalytic Reduction） system of modem automobiles. The focus of the current study is to do parametric studies by simulation in a three-dimensional model using CFD （Computational Fluid Dynamics） code AVL FIRE. Simulations were carried out to study the characteristics of evaporation and thermolysis UWS considering the effect of injection velocity, duration of injection, injection angle and for different types of injection. In the case of the injection velocities up to 20-50 m/sec, the ammonia concentration continues to increase. It is found that as the duration injection decreases, the concentration of ammonia increases. In case of continuous injection, the flow rate is less which results in lower velocity of injection, lesser atomization and slower evaporation resulting lesser conversion of UWS into NH3. Shorter duration of injection leads better atomization with increased velocity of injection which results in faster evaporation and thermolysis.
