Open Access

ARTICLE

Optimal Design and Experimental Study of Tightly Coupled SCR Mixers for Diesel Engines

Jianhua Zhang^1,2, Wen Sun³, Zhijun Li^1,*
1 State Key Laboratory of Engines, Tianjin Univesity, Tianjin, 300072, China
2 Weichai Power Emission Solutions Technology Co., Ltd., Weifang, 261061, China
3 School of Energy and Power Engineering, Shandong University, Jinan, 250061, China
* Corresponding Author: Zhijun Li. Email:

Energy Engineering https://doi.org/10.32604/ee.2024.051093

Received 27 February 2024; Accepted 13 May 2024; Published online 08 July 2024

Abstract

Two types of tightly coupled Selective Catalytic Reduction (SCR) mixers were designed in this study, namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately. Computational Fluid Dynamics (CFD) software was utilized to model the gas flow, spraying, and pyrolysis reaction of the aqueous urea solution in the tightly coupled SCR system. The parameters of gas flow velocity uniformity and ammonia distribution uniformity were simulated and calculated for both Mixer 1 and Mixer 2 in the tightly coupled SCR system to compare their advantages and disadvantages. The simulation results indicated that Mixer 1 exhibited a gas velocity uniformity of 0.972 and an ammonia distribution uniformity of 0.817, whereas Mixer 2 demonstrated a gas velocity uniformity of 0.988 and an ammonia distribution uniformity of 0.964. Mixer 2 performed better in the simulation analysis. Furthermore, a 3D-printed prototype of Mixer 2 was manufactured and installed on an engine test bench to investigate ammonia distribution uniformity and NO conversion efficiency. The experimental investigations yielded the following findings: 1) The ammonia distribution uniformity of Mixer 2 was measured as 0.976, which closely aligned with the simulation result of 0.964, with a deviation of 1.2% from the model calculations; 2) As exhaust temperature increased, the ammonia distribution uniformity gradually improved, while an increase in exhaust flow rate resulted in a decrease in ammonia distribution uniformity; 3) When utilizing Mixer 2, the NO conversion efficiency reached 84.7% at an exhaust temperature of 200°C and 97.4% at 250°C. Within the exhaust temperature range of 300°C to 450°C, the NO conversion efficiency remained above 98%. This study proposed two innovative mixer structures, conducted simulation analysis, and performed performance testing. The research outcomes indicated that the separately arranged Mixer 2 exhibited superior performance. The tightly coupled SCR system equipped with Mixer 2 achieved excellent levels of gas velocity uniformity, ammonia distribution uniformity, and NO conversion efficiency. These findings can serve as valuable references for the design and development of ultra-low emission after-treatment systems for diesel engines in the field of diesel engine aftertreatment.

---

Keywords

Tightly coupled SCR; mixer; ammonia distribution uniformity

---