Analysis And Optimization Of A Subway Train Air Supply Duct And Passenger Room Flow Field

With the rapid development of subway construction and the improvement of people’s living standards,people have put forward higher requirements for the comfort and air quality of the indoor environment.The subway air-conditioning and ventilation system is a necessary hardware device to provide passengers with a comfortable riding environment.A reasonable ventilation scheme and air supply structure can effectively improve the air quality and thermal comfort in the car.Therefore,optimizing the air supply structure of the existing subway airconditioning system is of great significance to improve the uniformity of air supply and the comfort of the passenger room environment.This paper takes the air supply structure of a subway air-conditioning system as the research object,establishes a three-dimensional air supply air duct model,and uses the CFD simulation software FLUENT to simulate the internal airflow distribution characteristics and the average flow velocity of each air outlet under the original air duct structure.The influence of the air duct inlet air volume ratio and the internal structure of the air duct on the air outlet uniformity of the air duct,and based on the simulation results,a reasonable optimization scheme is given.The research results show that: under the original air duct structure,the average flow velocity of the air outlet of the high and short air ducts increases gradually from the inlet end to the end of the air supply,and there is an obvious vortex phenomenon inside the inlet end.There is also a big difference in wind speed,which needs to be further optimized.In order to characterize the improvement of the uniformity of the flow velocity at the outlet,the concept of uneven reduction rate is introduced.By adjusting the air intake volume ratio of the tall and short air ducts,the flow velocity difference between the two can be effectively reduced.Under the condition of the optimal air intake volume ratio,the uneven reduction rate between the two can be reduced by 72%;,such as distributors,static pressure chambers and main air ducts are optimized,and the uneven reduction rate is further reduced to 97%.The air ducts before and after the optimization are assembled with the passenger compartment of the car,and the real air supply wind speed is used as the input condition of the car to simulate the cooling and peak passenger flow in summer,and the human body as a constant temperature heat source and the coupling of air flow and heat transfer in the passenger compartment are also considered.Under the action conditions,the velocity field and temperature field distribution in the passenger compartment.Comparing the flow field characteristics of the air in the cabin before and after optimization,it is found that the average non-uniform reduction rate of wind speed in the Y-axis section of the cabin is 95%,and the average non-uniform reduction rate of temperature is 87%,which meets the relevant national standards.The research in this paper shows that it is feasible to use the numerical simulation method to analyze the air supply structure of the subway air-conditioning system and the distribution characteristics of the air distribution in the passenger compartment.