Research On Thermal-pressure Coupling Effect Aerodynamic Characteristics In The Evacuated Tube Transport System

With the rapid development of social economy, the evacuated tube transportsystem will be an important tool for life in the future. The achievement by this time isonly limited to the study about aerodynamic drag field under the low Mach number.Due to the evacuated tube transport system is running by supersonic speed in a limitedspace, generating intense friction between the train and the air, at the same time,producing a lot of aerodynamic heating, and mutual coupling between aerodynamicheating and aerodynamic drag. The aerodynamic heating is no only relates to its safeworking, but also effecting the high speed and high efficiency working of the ETTsystem.In this paper, three important parameters including the blocking ratio, the trainspeed and the system pressure are taken into account. With combining the theoreticalanalysis, numerical simulation is used as main research method. Physical andmathematical models of objects with high speed linear motion are built under thethermal-pressure coupling effect. For safe operation, comfortable, operating efficiency,economic construction and operating cost, the problems of thermal-pressure couplingeffect aerodynamic characteristics are studied in the evacuated tube transport system,and the thermodynamic economy of the system has carried on the preliminarydiscussion. It could provide proof for the efficient economic safe operation inevacuated tube transport system.In this paper, based on hydromechanics and heat transfer theory, the unsteadymodel of three-dimensional compressible and viscidity is built. Based on finite volumemethod and used fluent software to numerical simulation of the model. It laborsthree-dimensional pressure field and temperature field in the system under differenttrain speed（400m/s、450m/s、500m/s）, different system pressure （1atm、0.1atm、0.5atm）and different blocking ratios （0.18、0.23、0.32）. The simulation results showthat: when the speed of the train and the pressure of the system are constants, thedifferential pressure between the head and the end of the train is linear increment with the blocking ratios increase, also the aerodynamic heating is growing as ascendingparabolic; when the speed of the train and the blocking ratios are constants, thedifferential pressure between the head and the end of the train is linear increment withthe system pressure increase, and it is significantly low as the system pressure is small,means the traction of the train to maintain a certain speed is significantly small, and theoperation is more economic, the highest temperature of the system appears a certainamplitude increases with the decreasing of pressure; when the pressure of the systemand the blocking ratios are constants, the differential pressure between the head and theend of the train is growing as ascending parabolic with the speed increase, and they aredirect ratio relationship between square of train speed, also the aerodynamic heating islinear increment. The economy of tube construction and energy consumption of thesystem should be taken into account when choosing the best blocking ratio; combiningrelations between the pressure with the temperature to choose the suitable pressurewhen we establish the ETT system, do not blindly reduce the pressure.Based on the thermal economics theory, the thermodynamic economy of thesystem has carried on the preliminary discussion. Two aspects of consumption aretaken into account: air resistance consumption and maintain pressure consumption.The simulation results show that: the energy consumption of the train which running inthe open air environment is equal2times to the ETT system. Means the speed of theETT system is greater than it in the open air environment with the same energyconsumption.