Experimental Study on N2O Emission Characteristics of a Two-Stage SCR System
A two-stage SCR aftertreatment system was built for a heavy-duty diesel engine of China 6.The N2O emission charac-teristics of cold and hot WHTC cycles were studied.The results show that a large amount of N2O emission is produced in both cold and hot WHTC cycles with an obvious peak value of N2O emission.The mean volume fraction of N2O in cold cycle is 22.3×10-6.The mean volume fraction of N2O in hot cycle is 24.4×10-6.When the front SCR works alone,the N2O emission is lower at the exit.Because of the excessive urea injection,the peak N2O emission is larger at the tail end,and the average volume fraction of N2O in the hot cycle reaches 13.5×10-6.The peak value of N2O emission is small when the main SCR works alone.The mean volume fraction of N2O in cold and hot cycles are 5.5×10-6 and 11.2×10-6,respectively.N2O emissions can be effectively reduced by reducing the amount of urea in-jection of the front SCR to control NH3 leakage and optimizing urea injection strategy of the main SCR.
diesel engineN2O emissionSCREuro-Ⅶ emission standardaftertreatment system
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