Numerical Simulation Of Vehicle Traveling Distance Effect On Exhaust Dispersion Characteristics Of The Vehicle

With the rapid development of the economic growth and the automobile industry, moreand more cars have been the members of the family and provide convenience for people’slife and work. But at the same time, the increasing number of cars has also led to manyproblems, such as traffic congestion and exhaust emissions. Automobile exhaust pollutionhas seriously affected people’s normal life and health, but also has brought a great threat tothe environment. So the research of vehicle exhaust emission has become one of the hotissues.Dilution tunnel is commonly used to measure automobile exhaust in the lab. But thismethod can not reflect the actual conditions of the diffusion characteristics of automobileexhaust. Now some scholars began to study the diffusion characteristics of track drivingmethod of exhaust gas. Therefore, the purpose of this study is to determine the necessity andimportance of tracking measurement method. This paper is to simulate vehicle travelingdistance effect on exhaust dispersion characteristics of the vehicle through the method ofcombining CFD simulation and automotive wind tunnel test. The specific contents are asfollows:First, with four different density grid method, research on flow field characteristics ofpickup. In the premise of ensuring the wake field is correct, compared with the CFDnumerical simulation data and the experimental data in the literature, to choose a proper gridscheme. After comparing the model of velocity, pressure and other characteristics, selectscheme (b) as the target grid strategy. Second, study on the wake flow field using the tracergas on gas diffusion properties, and prove that the correctness of the numerical simulation.The main purpose of this part of the work is to validate the correctness of the model wakefield pickup with the tracer gas. By comparison, obtained four sets of grid scheme results arebasically the same, so the grid strategy (b) is correct. Third, the design and fabrication of busmodel and van model, application of grid method (b), study on the wake characteristics of the two car models under different driving distanc（e0.6m、1.2m and1.8m）. At the same time,the surface pressure measurement and using PIV technology to model the tail of the carspeed test are completed. The numerical simulation solution compared with the wind tunneltest value, high degree of agreement was found in two patients, which proves the correctnessof the simulation results. Fourth, using propane as a tracer gas, research on effect of wakeflow field of exhaust with different pacing. Simulation results show that, when the spacing is0.6m, van changed the bus wake structure, and the propane gas has a higher concentrationthan the other two spacing in the same range. As the distance increasing, the bus tail vortexalso slowly fall off naturally, and propane gas diffuse with natural diffusion.