Experimental study on ammonia storage characteristics and factors affecting the ammonia slip of diesel engine urea SCR

The study on the factors affecting the ammonia slip and ammonia storage characteristics of urea SCR system was conducted on a diesel engine bench. The research focused on the effects of the temperature, space velocity and the ammonia storage on the ammonia slip. The results show that at the space velocity of 20 000 h^-1, the time from the injection start to the maximum NO_x conversion efficiency and the time from zero to the saturated amount of storage ammonia tend to decrease with increased temperature. The saturated amounts of storage ammonia are 1.23 g~8.56 g under various engine modes which tend to decrease with increased temperature. At the catalyst inlet temperature of 250℃, the saturated amounts of storage ammonia are 2.68 g~12.10 g under various engine modes. The time from the injection start to the maximum NO_x conversion efficiency and the time from zero to the saturated amount of storage ammonia decrease with increased space velocity. At the fixed space velocity, the NO_x conversion efficiency increases with increased NSR, but does not increase obviously at lower than 250℃. The amount of ammonia slip with various NSR shows a trend of rise first then fall.At the fixed inlet temperature, the amount of ammonia slip will increase with the increase of space velocity.