| The Heat and Pressure Recycle Ducts(HPRD)are proposed to add in the Vacuum Tube Transportation System(VTT)in this paper.This paper tacks three parameters of the blocking ratio,the interval length and opening width of HPRD.The finite volume method and the dynamic grid method in Fluent software is adopted in this paper.According to the mechanism of the train running in the vacuum tube,physical model and mathematical model of the running train under the thermal-pressure coupling effect are established.When the system pressure is 10 kPa,aerodynamic and the aerodynamic properties in the general VTT and VTT with HPRD are analyzed in detail under the different blocking ratios,train speeds and different interval length of HPRD(25m,50 m,75m,100m)and the opening width(2m,4m,6m,8m,10m),the results show that:(1)The aerodynamic and thermodynamic properties of the general VTT and VTT with HPRD are as follows: The differential pressure and differential temperature between the train head and tail increase with the increasing of train velocity when the system pressure and blocking ratio are fixed.The VTT with HPRD can reduce the differential pressure and differential temperature between the train head and tail effectively compared with the general VTT.The differential pressure and differential temperature between the train head and tail increase with the increase of the intervallength of HPRD and the differential pressure and differential temperature decrease with the increase of the interval opening width of HPRD when the system pressure,blocking ratio,train running speed and the opening width of HPRD are fixed.(2)The aerodynamic and thermodynamic properties of the two trains intersection in VTT with HPRD are as follows: The existence of HPRD can reduce the differential pressure and differential temperature between the train head and tail effectively during the intersection of the two trains in VTT with HPRD.The differential pressure and differential temperature between the train head and tail increase with the increase of the blocking ratio during the intersection of the two trains in VTT with HPRD when the opening width and interval length of HPRD and the train running speed and the system pressure are fixed.The pressure distribution and temperature condition are analyzed and the important function of reducing the differential pressure and differential temperature is explained by HPRD during the intersection of the two trains in VTT with HPRD.A triangular model of 3E(Engineering-Energy-Efficiency)for evaluating the VTT is proposed in this paper.The comprehensive evaluation of the VTT with HPRD is carried out from the three aspects of the operation efficiency and energy consumption and engineering construction cost of VTT and the optimum range of parameters suitable for the operation of the VTT is also determined. |
