Numerical Simulation Study On Airtightness Index And Interior Pressure Comfort Of High-Speed Train

With the continuous increase in the mileage of high-speed railways in the central and western regions of China,coupled with the relentless demand for high-speed train operation speed,the pressure environment inside high-speed trains is deteriorating day by day.It is necessary to conduct systematic and in-depth research on the air tightness indicators of highspeed trains and the ear comfort of drivers and passengers.At present,it can be seen that when using numerical simulation methods to study the static airtightness experiment of high-speed trains,there is no in-depth study on the shape,type,and length of equivalent leakage holes.And the commonly used airtightness index method for calculating pressure fluctuations inside the train is not closely related to actual train body leakage.This article is based on the threedimensional compressible N-S equation and SST k-ω The turbulent flow model,using the Finite volume method,reproduces the positive pressure and negative pressure conditions of the simplified vehicle body ground static air tightness experiment,and based on this,studies on the relationship between air tightness indexes and pressure comfort of high-speed trains are carried out.This study can provide reference and reference for subsequent experimental research on the airtightness of high-speed trains.The main research content and conclusions of this article include:1.Referring to the research method for high-pressure pipeline leakage,the influence of equivalent leakage hole shape,type,and length on the airtightness index(static time constant)was studied.It was found that the shape of the leakage hole has almost no effect on the static time constant,while the leakage hole type(external extension,internal extension,thin wall,etc.)has a significant impact on the static time constant.In addition,except for thin-walled leakage holes,the extension or extension length of leakage holes has a significant impact on the static time constant.The fitting found that the static time constant is directly proportional to the-1st power of the external extension length of the leakage hole,the 2nd power of the internal extension length,and the-2nd power of the thin-walled thickness,respectively.2.Based on the flow characteristics of the external expansion leak hole,a unified 7 °external expansion leak hole was used for the first time,and numerical simulation methods were used to reproduce the static air tightness experiments on the ground with positive pressure and negative pressure inside the vehicle.Research has shown that the pressure relief curve calculated using a 7° external expansion leak hole is in good agreement with the experimental curve.The numerical simulation results show that the external expansion angle of the leakage hole has a significant impact on the static time constant.Within the range of 5° to 8° external expansion angle of the leakage hole,the static time constant obtained by filling positive pressure and extracting negative pressure inside the vehicle gradually decreases and then increases.In addition,it was found that the seats in the carriage only affect local flow characteristics and have almost no effect on pressure changes inside the car.3.Based on the external expansion of the 7° leakage hole and the measured external pressure fluctuation data in literature,numerical simulation methods were used to calculate the internal pressure fluctuation of the vehicle.Research has shown that the pressure fluctuation in the vehicle obtained by taking 4.8 times the static equivalent leakage area is in good agreement with the actual vehicle experimental results.The relative errors of the maximum positive pressure and maximum negative pressure in the vehicle are only 0.34% and 7.4%,respectively.Based on this,the pressure comfort of high-speed trains passing through the 1067 m,1249 m,1710 m,and 3087 m tunnels on the Beijing Guangzhou Line was evaluated.It was found that the pressure changes at different time intervals of high-speed trains passing through the above tunnels at 300 km/h meet the regulatory requirements of countries and organizations such as China,Germany,Japan,the United Kingdom,ERRI,and UIC.