Research On Optimization Design Of Air Duct Structure Of A Vehicle-mounted Shelter

The design of air duct mainly focuses on the uniformity of air supply,and the noise in the shelter affects the ride comfort.Reasonable design of the duct structure is of great significance to improve the uniformity of air supply and reduce noise.In this paper,based on the theory of computational fluid dynamics and computational aeroacoustics,multi-objective optimization was used to optimize the structure of the air duct in the shelter.The main contents are as follows.Firstly,the CFD model of the air duct and the shelter was built.The air uniformity and aerodynamic noise of the air duct under refrigeration,defrosting and ventilation conditions of the air-conditioning were analyzed.The refrigeration condition was found to be the worst one.Considering the vortex at the left side of the duct in the flow field analysis under the refrigeration condition,the influence of the filleted corner and guide plates at the bend on it was studied.It was found that the combination of the two is the best solution.In addition,a monitoring point was set in the passenger area,and the total noise pressure level was calculated to be 54.47 d B.The simulation results of the flow field and sound field are essentially based on the air velocity,so the velocity at the outlets under the refrigeration condition was measured by QDF-6 anemometer.The experimental results are in good agreement with the simulation results,which verifies the accuracy of the model.Then,the design variables and optimization objectives were selected.The optimal Latin hypercube design was used to select 20 groups of sample points for simulation.A fourth-order polynomial response surface model was built.The accuracy of it was verified by variance analysis.The optimization scheme was obtained using NSGA-II algorithm,which improves the uniformity of air supply at the straight duct on both sides by 47% and 42%,and reduces the total sound pressure level of noise at the monitoring point of the passenger area by 2.65 d B.Finally,the duct was placed in the shelter to simulate the flow field and sound field.The error of the simulation results between single duct and the whole shelter is small.Through the analysis of the flow field,sound field and temperature field of the whole shelter before and after optimization,it was found that the optimization scheme increases the total air supply volume,improves the cooling effect and the uniformity of air supply.The temperature distribution in the shelter,especially in the front part,is more uniform.The intensity of the noise source in the shelter is also weakened.