The evacuated tube transportation has great potential in the future because of its advantages of energy saving and environmental protection. The train runs in the closed tube at ultra-high speed. The heat quantity generated by aerodynamic heating is not easy to spread to external environment and then accumulates in the tube, inducing the ambient temperature in the tube to rise gradually. In this paper, a three-dimensional geometric model and the Shear Stress Transport (SST) κ-ω turbulence model are used to study the influence of initial ambient temperature on the structure of the flow field in the tube. Simulation results show that when the train runs at transonic speed, the supersonic flow region with low temperature and low-pressure is produced in the wake. The structure of the flow field of the wake will change with the initial ambient temperature. And the higher the initial ambient temperature is, the shorter the low temperature region in the wake will be. The larger temperature difference caused by the low temperature region may increase the temperature stress of the tube and affect the equipment inside the tube. Consequently, the temperature inside the tube can be maintained at a reasonable value to reduce the influence of the low temperature region in the wake on the system.
In the high temperature superconducting maglev-evacuated tube transport (HTS Maglev-ETT) system, the air drag is the most principal resistance to the speed improvement and energy conservation. Considering the aerodynamic performance of the HTS Maglev-ETT system has great significance in practical application. As the first step, we experimentally explored the influence of velocity, blockage ratio and airshaft on the air drag of a running maglev vehicle at atmospheric pressure (95.6 kPa in Chengdu), coupled with the simulation by using the ANSYS-FLUENT software. The results preliminarily confirmed the feasibility of the aerodynamic experiments on the HTS maglev-ETT test system, as the drag is proportional to the blockage ratio and the square of velocity respectively. Moreover, airshafts are suggested to be added in the future design of the HTS Maglev-ETT system, aimed at its good relief on the air drag displayed in the experiment and simulation.
To improve the productivity and efficient of modern large-scale open-cut mines, a number of technologies are developed and trialed, including new blasting equipment, larger blasting holes, high benches, air spacing, and short-delay blasting within holes. However, the relative blasting parameters need field calibration and further investigation of theories on these techniques are required. This paper studied the open-cut bench blasting at Barun Eboxi Mine of Baotou Iron and Steel Group via theoretical analysis on shock wave, numerical simulation, and field test. According to the technical conditions of the site, three sets of vertical boreholes at 310 mm diameter were drilled on 24 m high batter; and three sets of air-spaced charges were set up. The digital electronic detonator was used to initiate at millisecond intervals. The study found that under the condition of 24 m high bench, the use of intermediate air interval is beneficial to the rock fragmentation. The delay time within the hole is 3-8 ms. The bottom of the lower explosives and the top of the upper explosives were devised for initiation to optimize the initiation location. The peak effective stress points are 63.6%, 52.2%, and 8.9% higher, respectively. The field test of high-bench intrahole millisecond blasting in Barun Eboxi mine shows that the intrahole millisecond blasting parameters proposed in this study are feasible.
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