Study on the Impact of Arrangement of Urea Injector and Mixer in Diesel Engine Selective Catalytic Reduction System on Ammonia Uniformity

<div>With the continuous upgrading of emission regulations for internal combustion engines, the nitrogen oxide treatment capacity of selective catalytic reduction (SCR) aftertreatment needs to be continuously improved. In this study, based on a prototype of SCR aftertreatment, the impact of the arrangement of key components in the SCR system (urea injector, mixer, and catalyst unit) on ammonia uniformity was investigated. First, parameterized designs of the urea injector, mixer, and SCR unit were conducted. Then, using computational fluid dynamics (CFD), numerical simulations of the established aftertreatment system models with different parameter factors were performed under a high-exhaust temperature and a low-exhaust temperature conditions to study the impact of each individual parameter on ammonia uniformity. Finally, an optimized solution was designed based on the observed patterns, and the optimized samples were tested on an engine performance and emission test bench to compare their ammonia uniformity. The test results showed that the ammonia uniformity of the optimized solution was improved by 2%–3% compared to the original design, reaching 0.952 and 0.967, respectively.</div>