Abstract:
Evacuated tubes can realize the ultra-high-speed and energy-saving operation of trains by providing a closed low-pressure environment. This paper proposes a multi-section evacuated tube to obtain a smoother transition between the train's open-line and vacuum-running modes. The initial vacuum pressure in each section are different. When a train passes through the tube, the air in adjacent sections is mixed to fulfill the proper transition between regular- and low-pressure environments. Referring to work and energy theory of ideal gas, aerodynamic energy consumption is analyzed by numerical calculation method, with particular attention paid to tube parameters' influence on aerodynamic energy consumption. Results show that by selecting reasonable parameters, the reduction of the energy consumption induced by the aerodynamic drag surpasses the vacuum potential energy loss, indicating that the system can indeed reach an aerodynamic energy-saving state. In particular, the system achieves an impressive energy-saving performance when the tube is equipped with transition sections and a long large-blockage-ratio middle section. The multi-section evacuated tube system design method based on aerodynamic energy-saving criteria can hopefully provide new insights for developing ultra-high-speed trains as well as designing and operating evacuated tubes in the future.