Influence of Urea Uneven Injection on the Performances of a Diesel Engine

Abstract

The influence of heterogeneous flow injection of urea at different velocities and temperatures on NO x conversion efficiency, ammonia storage and ammonia leakage is investigated experimentally. A diesel engine employing a selective catalytic reduction (SCR) technology is considered. It is found that for a fixed injection velocity, the degree of ammonia leakage changes depending on the temperature. The higher the temperature, the faster the catalytic reduction reaction and the smaller the degree of ammonia leakage. The temperature has a great influence on the catalytic reduction reaction rate. At an injection velocity of 10000/h, the average reaction rate at 420 C is 12 times higher than that at 180 C. The injection velocity has a weak influence on the reaction rate. When the injection velocity changes from 10000/h to 40000/h at the same temperature, the average reaction rate does not change appreciably. However, increasing the space velocity can accelerate the leakage of ammonia, thereby mitigating the benefits associated with the NO x conversion.