Study Of Optimized Air Duct Structure On The Distribution Of Uniform Air Flow Organization In Subway

As the application of air-conditioning Metro Trains rapid developing, Metro Trains has become a very important means of modern urban transport, the basic requirements and important indexs for Metro Trains are supply the comfortable environment to travelling passengers. The Ventilation System is the important subsystems in current Metro Trains, the thermal comfort of passengers indoor depend on supplying Air uniformity. Since the traditional method of temperature and velocity distribution depending on experimental equations to determine the distribution of temperature and speed on each section indoor, Since using the experimental equations obtain the rough results, the traditional airflow design can not be accurately forecast the indoor air distribution organizations.This article research on a medium carriage of a Metro Train, use computational fluid dynamics software-Fluent to simulate the airflow and heat transfer conditions for the three-dimensional regional carriage which added the porous baffle in Ventilation System before and after,and comparative analysis and evaluation the calculation results.It indicated that the air uniformity indoor and the flow condition of the outlet can be improved by adding the porous baffle in the specified location in the Ventilation System.Numerically simulates the temperature and velocity distribution of the Ventilation System with or without the porous baffle. This article do the appropriate vehicle model simplification,use the k ?εthree-dimensional turbulent model in the Ventilation System and workstation, The density of air in the passenger compartment conformed to Boussinesq assumption,used the various wall surface heat dissipation conditions and give a comprehensive consideration to the car body heat transfer ,radiation heat transfer ,human body heat loss and so on and consider the impact of uplift which caused by the temperature difference, wall function method is adopted for the viscous-layer near the wall The model used Tet tetrahedral grid,and refined grids in the outlet,the border and the heat source which temperature and velocity field variables gradients a large regional.Compared the simulation results of the Ventilation System with or without the porous baffle,obtained distributing character of the temperature and velocity distribution of the two cases,found that the effect of the initial optimization is obvious by summing up the distribution and main affecting factors of the flow.This study indicated that the air uniformity indoor and the flow condition of the outlet can be improved by adding the porous baffle in the specified location in the Ventilation System. In the case of without the porous baffle, the temperature gradient indoor is larger, the air flow rate below the outlet is smaller. In the middle of the carriage, the air flow rate is larger with a high air velocity, the draught rating(DR) can be more obviously,the distribution of the indoor air is not very satisfactory. In the case of with the porous baffle, the inside temperature gradient is within 3℃, the air velocity is also consistent with the design requirements.In order to verified the accuracy of the numerical simulation results.The article measured the joint delivery outlet of the optimization test vehicle ventilation systems.Compared results of numerical simulation with the experimental measurements, the results showed that: results of numerical simulation with the experimental measurements become nearly after added the porous baffles,and the distribution trend is basically consistent.Verified the numerical simulation results have higher accuracy,supply air uniformity and air flow organization indoor is better after added the porous baffles.Through the study of the subject found that the use of numerical simulation methods to analysis and study the ventilation system supply air uniformity and feasible air flow organization indoor is reasonable.The reasonable suggestions which are for improving internal structure of the ventilation systems were beneficial to supply air more uniformity and increase indoor comfort. The results will provide reference for the design of air conditioning system of the urban railcar.