A computational analysis of the transient internal flow of a three-hole Urea-SCR injector was carried out in this study. The injector seat angle, which affects the sac volume, and the nozzle-hole area, which determines the minimum cross-sectional area, were selected as design parameters. The results of the computational analysis showed that injector seat angle did not affect the flow rate characteristics at the inlet/outlet or the total amount of a single injection. The total amount of a single injection increased with increasing nozzle-hole area; however, the amount of injection was less than the conduit area. The reduced amount of injection was likely attributable to the reduction in effective flow area caused by vena contracta, which was introduced by the increased nozzle-hole area. An increase in the nozzle-hole area would increase the total amount of a single injection under the conditions used in this study. However, an increase in the average flow coefficient by reducing the nozzle-hole area would enable precise control of injection and improve the responsiveness thereof. The results of this study can be used as basic data for design of injectors.

Urea-SCR injector, mass flow rate, seat angle, nozzle hole area, flow coefficient, vena contracta, sac volume, CFD.