Study On Air Tightness And Thermal Comfort Of Train

The rapid development of the high-speed railway has not only brought great convenience to people's travel,but also put forward higher requirements for the air tightness and thermal comfort of the narrow train coach.Once the changes of the interior pressure reach a certain level,the passengers will be uncomfortable.And the car thermal comfort is also related to the passenger's ride environment,so the air tightness and thermal comfort of a car need to meet certain requirements.In this paper,the airtightness and thermal comfort of the vehicle were studied by numerical method.Firstly,the relationship between the decompression time and the leakage area was deduced by the basic principle of fluid mechanics.Based on the three-dimensional unsteady and compressible N-S equation,and the k-co SST two-equation turbulence model,the static leakage model was simulated by using the finite volume method with the help of commercial software FLUENT.The result shows that the theoretical formula and simulation results are consistent with the experimental results.The decompression time decreases with the increase of the number of leaks,and the pressure variation is almost same when the number of leaks is 3 and 4.In addition,the decompression time decreases as slenderness ratio decreases,and the decompression time basically unchanged when slenderness ratio is decreased to 0.001 and 0.0008.The grille on the door has a significant effect on the pressure change in the vehicle.For the changes of interior pressure in the train passing through a tunnel,the recursion formula was used to calculate the internal pressure.The result shows that the changes of pressure in the coach meet the requirements of human comfort.In the extreme conditions,the maximum ratio between leakage area and train carriage volume is 0.1.For the problem of thermal comfort of the car,the numerical simulation method was used to simulate the thermal comfort of the sleeping EMU and the standard EMU.And according to the results,the unreasonable structure and the design parameters were optimized.The main work of this part is as follows:1.For the problem of low air flow in the No.10 compartment in all the working conditions and lower temperature in summer night condition of the sleeping EMU,the structure of air supply outlet of No.10 compartment in the air supply duct was optimized,and the air supply temperature in summer night was increased.As a result,the temperature distribution in the coach was improved and met the requirements.2.For the problem of uneven temperature distribution of standard EMU in summer and winter conditions,several improvement measures were put forward to improve the situation,such as adjusting the arrangement of the fins and distribution of air flow in summer and winter,increasing the branch area of the air supply duct to 1.25 times of the original,and suggesting that the heat transfer coefficient should be reduced to less than 0.2W/m2·K.The result shows a good temperature distribution inside the coach.