Flow Field Analysis And Structure Optimization Of Air Supply Duct And Carriage Of A Metro Bus

With the development of social economy,the construction of urbanization and the release of carbon neutral policy,subway,as one of the public transportation modes of a city,is being vigorously developed by government departments.Because of its high operation efficiency and large passenger capacity,subway travel has become the preferred way for people to travel in the city.With the improvement of living standards,people have higher requirements for the comfort of subway travel,and the comfort of passengers’ riding environment is closely related to the wind speed and temperature in the car.Therefore,it is of theoretical research value and practical significance to study the air outlet uniformity of air conditioning system and the rationality of flow field distribution in the car.In this paper,a car in the middle of a certain type of subway is taken as the research object to establish a three-dimensional model.The CFD numerical simulation method is used to simulate and analyze the air duct ventilation and the flow field in the car through the FLUENT software,and the relevant structure is optimized,so as to improve the air outlet performance and uniformity of the air duct,and improve the distribution of the flow field in the car.The main contents are as follows:Through the simulation analysis of the air supply duct of the air conditioning system under the condition of the initial air intake ratio,it is concluded that the average air outlet velocity of the high and low air ducts is very different,which seriously reduces the uniformity of the overall air outlet of the air duct.By optimizing the air intake ratio of the high and low air ducts of the distributor,the average air outlet velocity difference of the main air ducts of the high and low air ducts is reduced.In order to improve the ventilation in the high air duct,a deflector is added at the inlet of the high air duct,and the position parameters of the deflector are optimized.The improvement effect of the ventilation in the high air duct with different deflector angles and different lengths is compared and analyzed,and the deflector angle is 20 °,When the length is 130 mm,the ventilation performance of the high air duct is obviously improved.In order to reduce the fluctuation of the air outlet velocity,a wind shield is added in the main air duct,and the improvement effect of the wind shield with different forms and different position parameters on the air outlet uniformity of the main air duct is compared and analyzed.In this paper,the air duct optimization is different from other literature.It not only optimizes the main air duct,but also optimizes the outlet air volume of the side branch air duct for high and low air ducts.On the premise of not affecting the ventilation performance and outlet uniformity of the main air duct,it compares and analyzes the outlet air speed of the side branch air duct under different position parameters.Taking the air supply duct and the carriage of the air conditioning system as the whole calculation domain,the flow field in the carriage under full load condition in summer is simulated.After analysis,it is found that the distribution of the flow field in the carriage is not uniform.The flow field in the carriage is improved by optimizing the number and layout of the air outlets on the side of the air branch duct and the layout of the air return and exhaust outlets in the carriage.Finally,by analyzing the flow field in the car,it is found that the temperature field and velocity field are consistent with the riding environment.The research of this paper can provide a reference for the optimization of the main air duct structure,the design of the branch air duct and the optimization of the air distribution in the carriage.