Research on Optimization and Verification of Selective Catalytic Reduction Mixer for Off-Road Diesel Engines
In order to solve the problem that the loader space is small and the cylindrical post-processing cannot be arranged,a hybrid optimization and crystallization performance verification scheme of non-road diesel selective catalytic reduction(SCR)system with U-type structure was proposed.Through computational fluid dynamics(CFD),the turbulent motion,velocity field and ammonia(NH3)distribution uniformity of the typical mixer structure model of 3 U-type SCR systems for diesel engines under 3 typical working conditions were simulated and analyzed.The influences of different mixing structures on NH3 distribution and NOx conversion efficiency were studied.Based on the analysis of simulation results,some structural design schemes can accelerate the process of droplet breaking,hydrolysis and atomization,improve the distribution uniformity of NH3 and the NOx conversion efficiency of SCR system in the fresh state.But these schemes are more likely to generate and accumulate crystals,resulting in a decline in the NOx conversion performance of SCR system.Therefore,a new method was proposed to optimize the mixer scheme of U-type SCR system of diesel engine,which was designed with a combination of guide device,spoiler and vent plate,etc.A concentric internal and external cylinder static mixer structure was obtained.The duration of crystallization test failure of engine carrying loader was more than 28.0 h.
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