Numerical Analysis on Enhancing Spray Performance of SCR Mixer Device and Heat Transfer Performance Based on Field Synergy Principle

Jiedong Ye,Junshuai Lv,Dongli Tan,Zhiqiang Ai,Zhiqiang Feng

doi:10.3390/pr9050786

Jiedong Ye, Junshuai Lv + Show 3 more

Open Access

https://doi.org/10.3390/pr9050786

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Abstract

The NH3 uniformity and conversion rate produced by the urea–water solution spray system is an essential factor affecting de-NOx efficiency. In this work, a three-dimensional simulation model was developed with the CFD software and was employed to investigate the effects of two typical injection methods (wall injection and center injection) and three distribution strategies (pre-mixer, post-mixer, pre-mixer, and post-mixer) of two typical mixers on the urea conversion rate and uniformity. The field synergy principle was employed to analyze the heat transfer of different mixer flow fields. The results show that the single mixer has instability in optimizing different injection positions due to different injection methods and injection positions. The dual-mixer is stable in the optimization of the flow field under different conditions. The conclusion of the field synergy theory of the single mixer accords with the simulation result. The Fc of the dual-mixer cases is low, but the NH3 conversion and uniformity index rate are also improved due to the increase in the residence time of UWS.

Highlights

Because the post-mixer generates theQvortex the same direction tothan maintain the vortex generated by the pre-mixer, the of thein dual-mixer is similarto the vortex generated by the pre-mixer, the Q of the dual-mixer is similar to the that tomaintain that of the pre-mixer
The pre-mixer can act on longer pipelines, so the Q of the pre-mixer is higher than the post-mixer
Many scholars have found that ammonia is critical for improving catalytic efficiency

Summary

Introduction

Diesel engines have obtained widespread application in vessels and vehicles due to the superior efficiency, performance, and emission characteristics [1]. People have noticed that the particulate matter (PM) and nitrogen oxides (NOx ) emitted by diesel engines can cause irreversible health hazards [2]. In order to meet the emission regulations of all countries in the world [3], the emissions of diesel engines should be limited. It has been challenging to achieve the current emission regulations by a purification technology or exhaust gas after-treatment technology in-machine purification technology alone to meet the currently prescribed limits [4]. In-machine purification technology and exhaust gas after-treatment technology were proposed by scholars [5]

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