Numerical Simulation Of Pressure Waves Produced By Fast Trains Passing Through Subway Tunnel

With the developing of urban rail transit,there have been cases of rapid subway and rapid urban railway projects with speed levels ranging from 100 km/h to 160 km/h in China.The domestic subway operation history accounts for more than 73%of the entire urban rail transit.In addition,the tunnel pressure waves generated under complex conditions such as large blocking ratio,complex tunnel structure,high traffic density and the existence of multi-trains tracking and running in the tunnel at the same time requires attention and research.Aiming at the special problem while the trains passing through subway tunnel,the one-dimensional,compressible,non-homentropic and unsteady flow model and the method of characteristics of generalized are used,and select a domestic subway line as the background to study the pressure wave of subway tunnel.The main contents and results are as follows:1.Based on the characteristic line method of the one-dimensional compressible unsteady unequal entropy flow model,combined with the complexity of the subway tunnel structure and the particularity of train operation in subway tunnel.The calculation model and calculation method of the pressure waves of multi-trains tracking through the tunnel are established and developed,on this basis,the first pressure waves code program for numerical simulation of trains tracking running in tunnels was developed in China.Combined with the results of full-scale experiments,model tests and numerical simulations,the indirect verification of the program has been preliminarily achieved.Besides,considering the initial atmospheric pressure in the tunnel,the pressure wave code program for a single train passing through a simple structure tunnel with different slope types and gradients is improved,and combined with the results of full-scale experiments and numerical simulations,the accuracy of the program is verified.2.In view of the situation of a single train passing through a tunnel with a simple structure,the results show that the pressure waves fluctuation outside the vehicle when the train passes through the tunnel directly at a constant speed from the tunnel port is more severe than when it is first started in the tunnel and then passed through at a constant speed.The propagation direction of the compression wave is the same as the wind speed when(reverse),it promotes(inhibits)the wind speed;when the propagation direction of the expansion wave is in the same direction as the wind speed(reverse),it inhibits(promotes)the wind speed.The effect of tunnel slope type and gradient on pressure waves and wind speed is essentially the initial atmospheric pressure in the tunnel.The maximum vehicle body pressure load,the maximum wind speed and pressure in the tunnel have a linear relationship with the gradients when the train passes through tunnels with different slopes.3.Aiming at situation while a single train and multi-trains passing through tunnel with ventilation shafts at constant speed,the effects of different factors on the external pressure waves are investigated and analyzed.The results show that the external pressure fluctuations of multi-trains are higher than that of a single train passing through.The maximum pressure load of the vehicle body increases with the increase of train speed,blocking ratio and air shaft area.When the train passes through shafts,the pressure waves rises and drops sharply,and it has the greatest impact on the pressure.In terms of alleviating the pressure wave and reducing the angle of the pressure load of the vehicle body,the area of the shaft is not as large as possible.Since the maximum pressure vehicle body appears when the train passes through the shaft,the tunnel length has no effect on the maximum pressure load.When multi-trains are tracking and running in the tunnel,except for the last train,the outside pressure fluctuation trend of the rest of the trains is basically the same,and it is more severe than the last train,therefore,it is necessary to focus on the first train and the last train.Different number of multi-trains are tracking through the tunnel,the maximum pressure positive load value of the first train remains unchanged,and the maximum pressure load value of the first train appears when 15 trains are tracking.The maximum pressure positive load value of the first coache of the last train gradually decreases with the increase of the number of multi-trains.Comprehensive analysis from the perspective of the maximum vehicle body pressure load,the departure time interval is best to be 150 s.4.Aiming at situation while a single train and multi-trains passing through the tunnel with shafts at unconstant speed,the influence of different factors on the pressure waves outside the coachess are studied and analyzed.The results show that the pressure fluctuation trend outside the coache when a single train starts and stops passing through the tunnel inside the tunnel is the same as when starting and stopping outside the tunnel,but the vehicle body pressure load value is slightly larger than when starting and stopping outside the tunnel.The influence of train speed on the maximum load of the vehicle body pressure is greater than that of the positive load,the stop time at the station has no effect on the trend of pressure fluctuations outside the vehicle,and the maximum value of the vehicle body pressure load is basically the same.In the case of multi-trains tracking in the tunnel,the longer time of the train stop at the station the greater the maximum positive load value of the vehicle vehicle pressure,and the smaller the negative maximum load value.From the analysis of the maximum value of the vehicle body pressure load,the best departure time interval is 180 s.5.Based on the interior pressure comfort criterias of American subways and China s high-speed railway,the recommended value of train dynamic air tightness threshold is proposed.When a single train passes through the tunnel,the airtight time constants of the first/last car and the middle car shall not be less than 0.7 s and 0.5 s,respectively,the airtight equivalent leakage area of the first/last car and the middle car shall not be greater than 229 cm~2and 260 cm~2,respectively.When the multi-trains tracking through the tunnel,the airtight time constants of the first/last car and the middle car cannot be less than 3.5 s and 3.0 s,respectively,the airtight equivalent leakage area of the multi-trains car and the middle car cannot be greater than 106 cm~2 and 109 cm~2,respectively.When meeting the same comfort standard,the air-tightness requirements for trains when multi-trains is higher than when a single train passes.From the perspective of the final recommended value of the dynamic air-tightness threshold,meeting the 800 Pa/3s standard has the highest air-tightness requirement for train,and meeting the 700 Pa/1.7s standard has the lowest air-tightness requirement for train.In view of the characteristics of subway tunnel structure and the complexity of train operation scenarios,this thesis developed the first pressure waves code program for simulating the operation of multi-trains tracking in tunnels in China.The tunnel pressure wave issues such as the train numbers,departure time interval,parking time,shafts location and tunnel length,so as to provide reasonable parameter suggestions for the selection of tunnel clearance area and the design of car body air tightness.The improved pressure waves code program for numerical simulation of train passing through tunnels with different slope types and gradients can not only be used to study the pressure wave problem of subway tunnels,but also can be used to simulate the pressure waves problems of high-speed trains passing through high altitude,large gradients,and extra-long and extra-long tunnels.