Research On Numerical Simulation Of Airtightness And Pressure Comfort For High-Speed Trains In Tunnel Conditions

China is a mountainous country.In order to ensure the safety of trains,high-speed railways use straight lines as much as possible to maintain high speed,thus building a large number of tunnels or groups of tunnels.When trains pass through a tunnel at high speed or meet in a tunnel,complex compression waves and expansion waves are formed in the tunnel due to the"piston effect",resulting in the aerodynamic effect of the train tunnel.Among them,the problem of train pressure comfort is more prominent,which is the most obvious influence on passengers’subjective feelings of train performance.Because the train is not completely sealed,the intense pressure change outside the train is transmitted to the train interior through the cracks of the car body,resulting in the following changes in the pressure inside the train.Due to the physiological reasons of human ear,train passengers need a certain amount of time to adjust the change of pressure.If cannot meet the requirements,people will feel uncomfortable,which will bring great influence on passengers’ride comfort.Therefore,it is of great scientific significance and engineering application value to carry out the research on the analysis method of pressure wave transmission inside and outside the train under tunnel conditions,and to evaluate and improve the air tightness and pressure comfort of the train.Firstly,in this thesis,the pressure waves of trains crossing tunnels of different lengths are studied based on computational fluid dynamics.Secondly,on this basis,the equivalent leakage hole is used as the interface of pressure transfer inside and outside the car body to study the change law of pressure inside the car body,and the calculation method of dynamic air tightness index of high-speed train is proposed.Then,based on the domestic pressure comfort standard,the equivalent leakage area threshold under different tunnel lengths is calculated and analyzed.Finally,the influencing factors of pressure comfort and measures to improve pressure comfort are discussed.The results show that:(1)The pressure wave of short tunnel is more intense than that of long tunnel.Under tunnel of different lengths,the pressure wave of head vehicle is the most intense,and the maximum positive pressure decreases with the increase of tunnel length.(2)The dynamic air tightness analysis model proposed in this paper can better simulate the pressure fluctuation inside the vehicle.The simulation results of dynamic air tightness index during train crossing under the condition of 7.05cm~2 equivalent leakage area and 1000 m long tunnel are 66.3,which is approximately consistent with the literature results.Comparing the fluctuation range of pressure in different tunnel lengths,it is found that the fluctuation range of pressure in long tunnel is larger than that in short tunnel.(3)By comparing the leakage area threshold,it is found that the pressure change rate determines the leakage area threshold under short tunnel conditions.Under the condition of long tunnel,the factor determining the leakage area threshold is the pressure variation amplitude.(4)The shaft has the best effect on reducing the pressure wave of tunnel crossing,and the pressure reduction amplitude of the head vehicle is the largest.The inclined entrance can reduce the pressure wave of tunnel intersection to some extent,but the effect is not as great as that of the shaft,and the pressure reduction amplitude of the head car is also the largest.The pressure reduction effect of nose optimization is not obvious,but it can reduce the drag.The air tightness of the train directly affects the pressure comfort of the passengers inside the train.Tunnel operation is one of the worst operating conditions of high-speed train.In this thesis,by studying the numerical simulation method of air tightness and pressure comfort of high-speed train under tunnel conditions,the numerical calculation method of air tightness of high-speed train,the threshold value of equivalent leakage area and the measures to improve pressure comfort are discussed,which can provide reference for the sealing design of car body and the improvement of pressure comfort of train.