Influence Of Cross-pass Piping On The Aerodynamic Characteristics Of Subsonic Vacuum Tube Trains

The vacuum tube transportation is a high-speed,high-capacity transportation system of the future,where economy and safety are key factors in its early implementation.The flow resistance inside the system is directly related to its operating costs and safety.The addition of cross-pass piping can effectively change the air flow inside the tube and significantly optimize the flow resistance characteristics.This paper focuses on the effect of cross-pass piping on the flow resistance characteristics of vacuum tube transportation systems,using theoretical analysis plus numerical simulation to investigate the influence of train running resistance,tube pressure and pipe blockage ratio on single-tube vacuum tube transportation systems and vacuum tube transportation systems with cross-pass piping,including train head and tail pressure difference,running resistance and resistance coefficient.The effect of cross-pass piping on vacuum tube transportation systems is also investigated by comparing the aerodynamic characteristics of trains in single-pipe vacuum tube transportation systems and vacuum tube traffic systems with cross-pass piping.In addition,by varying the cross-pass pipe parameters（length of cross-pass pipe,cross-pass pipe spacing,cross-pass pipe cross-sectional area）,the influence of cross-pass pipe parameters on the train running resistance is investigated.The main conclusions of this paper are as follows:（1）A comparison of the aerodynamic characteristics of trains in single-pipe vacuum tube transportation systems and those in vacuum tube transportation systems with cross-pipe shows that the cross-pipe can reduce the average differential pressure between the first and last train,the train running resistance,the train drag coefficient and the total energy consumption of the vacuum tube transportation system.In the range of 160m/s～280m/s,100Pa～10000Pa,and with a blockage ratio of 0.5,the presence of cross-pass piping can reduce the average differential pressure between the first and last train by 29%～33%,the train running resistance by 27%～31%,and the train drag coefficient by 30%,resulting in a significant energy saving effect.（2）In the vacuum tube transportation system with cross-pass pipe,when the cross-pass pipe interval and cross-sectional area are fixed and the length of the cross-pass pipe increases from 2m to 6m,the train running resistance decreases continuously,and when the length of the cross-pass pipe increases from 6m to 8m,the running resistance does not change significantly;when the cross-pass pipe length and cross-sectional area are fixed and the cross-pass pipe interval increases from 0.5 times the body length to 1.5 times the body length,the train running When the length of the cross-pass pipe and the cross-sectional area of the cross-pass pipe are fixed,the cross-pipe cross-sectional diameter increases from 1.0m to 2.0m,i.e.the area increases from 0.79m~2to 3.14m~2,the train running resistance decreases continuously.In other words,when the cross-pass pipe cross-sectional area is fixed,the cross-pass pipe length is 6m,and the cross-pass pipe interval is taken to be 2 times the body length and above,the vacuum pipe traffic system operates in the most ideal condition.