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 NOx. In this study, a series of tests was conducted to investigate the effects of temperature and exhaust gas mass flow on the NOx 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 NH3 desorption rate gradually decreased. An uneven distribution of ammonia storage similar to the shape of ɛ 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.