For the NH3 uniformity of SCR mixer for China Ⅵ light-duty diesel engine, the NH3 distribution inside SCR system was simulated with CFD and the simulation model was verified by the test of NH3 distribution. The mixer structure was optimized and designed, and the influences of different static mixers on the structure of flow field, the uniformity of NH3 distribution before SCR and the pressure drop of aftertreatment system were investigated. The results show that the simulated results of NH3 distribution are consistent with the experimental results. Compared with the original mixer, the NH3 uniformity of B2 mixer increases to 0.97 from 0.88 and the back pressure decreases to 19.2 kPa from 22.3 kPa. Therefore, the porous plate at the rear of the mixer can improve the NH3 uniformity due to the enhancing air flow disturbance and increasing small urea droplet impact on the wall. B3 mixer shows that the porous plate that is not suitable for mixer will result in the decrease of NH3 uniformity.
