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排放测试法规定,柴油机颗粒物PM的测定需要采用稀释系统。而稀释系统中混合气的均匀度直接影响尾气检测的准确性、重复性等。论文以某汽车尾气微粒检测系统中的稀释单元为研究对象,构建了稀释器的三维几何模型。在给定条件下,应用FLUENT软件对稀释器内部流场进行了仿真计算。通过计算发现,稀释气体在进入稀释器混合腔时出现堵塞现象。改进样气喷嘴参数后,气体堵塞现象消失。这表明样气和稀释空气在稀释器混合腔内混合均匀,有利于尾气检测系统检测精度的提高,也为尾气检测系统稀释器结构参数优化提出了新途径。
Emission test method, the determination of diesel particulate matter PM need to use dilution system. The uniformity of the mixed gas in the dilution system directly affects the accuracy, repeatability and the like of the exhaust gas detection. In this paper, a dilution unit in an automobile exhaust particulate detection system is taken as the research object, and a three-dimensional geometric model of a diluter is constructed. Under given conditions, FLUENT software was used to simulate the flow field in the diluter. It was found by calculation that the dilution gas clogged when it entered the diluter mixing chamber. Improve gas nozzle parameters, the phenomenon of gas clogging disappear. This shows that the sample gas and dilution air mixed in the dilute mixing chamber is conducive to improve the detection accuracy of exhaust gas detection system, but also for the tail gas detection system diluter structural parameters proposed a new way.