Research on Optimization Design of SCR Nozzle for National VI Heavy Duty Diesel Engine

• Main Authors: Feng Qian, Dong Ma, Neng Zhu, Peng Li, Xiaowei Xu
• Format: Article
• Language: English
• Published: MDPI AG 2019-05-01
• Series: Catalysts
• Subjects: SCR system; nozzle optimization; Sauter mean diameter; NO_x conversion efficiency; deposit
• Online Access: https://www.mdpi.com/2073-4344/9/5/452

For the National VI heavy-duty diesel vehicles, NO_x emission regulations are becoming more and more stringent, and the selective catalytic reduction (SCR) system has become a necessary device. The design of the adblue nozzle in the SCR system is especially critical, directly affecting the NO_x conversion efficiency and deposit formation. According to the structure of a National VI diesel engine exhaust pipe and SCR system, the nozzle is optimized by computational fluid dynamics (CFD) method to avoid the collision between the urea droplets and the exhaust pipe wall, to ensure that the exhaust gas and the urea droplets are as much as possible in full contact to ensure a sufficient urea pyrolysis. With the optimized nozzle, the NH₃ distribution uniformity of the inlet face of the SCR catalyst can increase from 0.58 to 0.92. Additionally, test verifications are implemented based on the spray particle size test and the engine bench tests; the results show that the Sauter mean diameter of the optimized nozzle is more decreased than the initial nozzle and that the NO_x conversion efficiency of the World Harmonized Transient Cycle (WHTC) and World Harmonized Stationary Cycle (WHSC) cycle improves by nearly 3%; additionally, it can also avoid deposit formation.