Simulation Study of Ammonia Storage Characteristics of Selective Catalytic Reduction for Diesel Engines

Abstract

Non-road machinery is very important, but non-road machinery has problems such as working under complex operating conditions. Agricultural machinery is an important type of non-road machinery, which mainly relies on diesel engines due to their high fuel efficiencies. The exhaust temperature of agricultural machinery changes drastically under different working conditions. This article aims to research on pollution control of non-road machinery. Among the exhaust after treatment technologies, selective catalytic reduction (SCR) technology is a very important method to reduce NO x. In this study, a series of tests was conducted to investigate the effects of temperature and exhaust gas mass flow on the NO x conversion and dynamic ammonia storage space distribution characteristics in simulation models. The genetic algorithm, a kind of global optimization algorithm that can avoid local optimization, was used in the parameter identification process. The simulation results showed that the ammonia storage capacity of SCR catalyst decreases as the temperature of SCR increases. With the decrease in temperature, the NH 3 desorption rate gradually decreased. An uneven distribution of ammonia storage similar to the shape of e was observed in the simulation and this kind of uneven distribution is obvious at low temperature. The effective area of the catalyst is near the inlet of the catalyst. This work presents an approach to help figure out the details in the ammonia storage process. This work provides information about the dynamic ammonia storage characteristics and guide for better SCR design.

Study on Diesel Engine Selective Catalytic Reduction Performance at Different Atmospheric Pressures Using the Response Surface Method

“…Nie et al 7 studied the influence of intake and exhaust throttling on SCR performance at different altitudes through bench tests, and the results showed that intake and exhaust throttling could effectively improve exhaust temperature, thus improving NO x conversion efficiency. Tan et al 8 investigated the effects of temperature on ammonia storage in SCR using genetic algorithms and found that the ammonia storage capacity in SCR increased first and then decreased with the increase in temperature and that in ammonia storage there was an uneven distribution in a ε pattern, which was more pronounced at low temperatures. Raza et al 9 studied the effects of exhaust temperature and ammonia-to-nitrogen ratio on the formation of N 2 O in SCR through bench tests, and the results showed that a higher ammonia-to-nitrogen ratio would lead to an increase in N 2 O, and the concentration of N 2 O was also higher at 200–250 °C.…”