CFD-aided design of mixers for the urea injection

The performance of a Selective Catalytic Reduction SCR systems in a modern Diesel engines is strongly related to the urea-water solution injection system, to vaporization of liquid droplets, decomposition of urea vapor to ammonia (NH3) and mixing of the NH3 vapor from the urea injector to the SCR catalyst inlet. To improve the evaporation and the mixing of urea vapor with the exhaust gas, passive flow mixing devices (mixers) are commonly adopted in SCR systems. Notwithstanding, the mixer device introduces a high pressure drop in the SCR system that could affect negatively the overall engine performances. An optimal design of the mixer that provides a uniform flow of exhaust gas and the NH3 vapors at front face of the catalyst and, at same time, produces a low pressure drop is desired to maximize the NOx conversion efficiency of the SCR system without losing engine performances.

In this work, a CFD-based, multi-objective optimization loop is presented and applied to the study of the performances of an SCR system. Different optimization algorithms are compared in terms of design results quality and computational efficiency, to find the most promising algorithm for industrial application in an aftertreatment systems design environment.

Session Time Slot(s): 
06/03/2017 - 4:15pm-06/03/2017 - 4:40pm
Convention Hall 1C
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First Name: 
Sumithra Raju
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Company / Institution: 
GM Global Propulsion Systems