Estimation of Ammonia Storage Nonuniformity for Urea-Based Selective Catalytic Reduction Systems Available to Purchase

Ammonia storage nonuniformity has a significant impact on the emission reduction performance of urea-based selective catalytic reduction (SCR) systems. In this paper, a unique SCR platform with two catalysts in a parallel configuration was created for investigating the impact of ammonia storage nonuniformity on the emission reduction performance in a simulation environment. The established two-cell SCR platform allows users to independently control the ammonia-to-NO_x ratio (ANR) for each catalyst using two independent urea solution injectors. Simulation results over US06 cycle demonstrate that, compared to the case without ammonia storage nonuniformity, the tailpipe NO_x and ammonia emissions can be increased by 6.73% and 22.0%, respectively, due to the nonuniform ammonia storage in the case of an ANR nonuniformity index (NUI) at 0.2. Furthermore, an innovative model-based method was proposed for estimating the ammonia coverage ratio nonuniformity (i.e., ammonia storage nonuniformity if storage capacity is known) by utilizing a control-oriented SCR model and the tailpipe NO_x and ammonia measurements at the confluence point. Simulation results proved the effectiveness of the proposed method in estimating the ammonia coverage ratio nonuniformity.