Abstract
Based on the airflow rotation concept, a new packaging structure was designed to meet the performance requirements of China-VI stage emission regulations. The new structure is a hybrid structure of spiral space with small blades and conical plates. The Computational Fluid Dynamics (CFD) simulation was used to analyze the velocity uniformity and ammonia uniformity of the flow field, and the results showed that velocity uniformity and ammonia uniformity were higher than 0.95, and the possibility of crystallization risk was very low. The actual performance of the new structural prototype was verified by means of engine bench testing. The test results were excellent and the conversion efficiency reached 0.96. The new selective catalytic reduction (SCR) urea mixed structure design greatly improved the conversion efficiency of the after-treatment system and has excellent anti-crystallization performance.
Highlights
From July 2021, China VI emission regulation will be implemented national wide throughout the country
After the secondary rectification of the orifice plate, the airflow is concentrated and diffused from the center to the entire cross-sectional distribution, which improves the uniformity of the speed of the diesel oxidation catalyst (DOC) carrier
The vortex mixer at the front end of the Selective Catalytic Reduction (SCR) increases the flow distance10ofofthe airflow by extending the airflow, extends the contact time between the two, promotes the mixing of the airflow and the urea aqueous solution, and provides more space for the hydrolysis and pyrolysis consisting of a time
Summary
From July 2021, China VI emission regulation will be implemented national wide throughout the country. The existing traditional canning and mixer structure under China V will be difficult to meet the updated emission regulation. Selective Catalytic Reduction (SCR) is regarded as the most promising technical solution for reducing nitrogen oxides (NOx) in exhaust gas in most countries, and it is widely used all over the world [1]. The structure of the SCR mixing chamber in the after-treatment system has a great impact on the conversion efficiency of the catalytic unit [2]. Choi et al applied a numerical analysis of NOx reduction for compact design in marine urea-SCR system and found that the compact structure can reduce 55% of the chamber and connecting pipe without decreases of NOx reduction efficiency [4]
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