Simulating PM2.5 Diffusion Characteristics Of Exhaust Flow In Wake

PM2.5 is one of the important causes of China regional hazy weather.Because of its small size,light quality,small gravity,large specific surface area and strong activity, PM2.5 have a great effect on human health,urban air qualitya and bisibility.The reseatches of PM2.5 source in different areas agree that motor vehicle emissions is one of important PM2.5 sources.So it is particularly important to study automobile exhaust flow diffusion characteristics.The study combines experiment and CFD simulation model to understand the single vehicle exhaust flow diffusion characteristics of PM2.5.KIA k2 automobile is added 95# gasoline as the experiment object.SEMTECH-EFM3 vehicle tail gas flowmeter,TSI8530 dust monitor,drying tube and the computer are the experiment tools.And the experiment adopts direct sampling method.Experiment respectively collected flow,density of exhaust and PM2.5 concentration under different tap positions and velocities. Calculate the exhaust velocity according to the experiment data.Establish and mesh the corresponding geometric model with GAMBIT and then calculate it with FLUENT solver.Finally,post process and analyze the experiment results.The study can get the conclusions as follows: PM2.5 concentration increases with the increase of velocity under the same gear.The exhaust emission rate is lowest under idle,but the concentration of PM2.5 is not.The speed and direction of emission can influence the exhaust flow diffusion characteristics.The range of diffusion is larger with higher speed of emission under the same gear.The higher gear will lead to accumulation of PM2.5 under the same speed.The upword and downword direction of emission will result in suspension and accumulation of PM2.5 respectively.