Influence of covers for the bogies with external axle boxes on the aerodynamic drag of a high-speed train
The bogie,as a large exposed complex-shaped operational component of the high-speed trains,was directly affected by the airflow at the bottom of the train.Its aerodynamic shape had an important effect on the aerodynamic drag of the high-speed train.Based on the three-dimensional steady SST k-ω two-equation turbulence model,the influence of different covering methods for the bogies with external axle boxes on the aerodynamic performance of the high-speed trains were studied by numerical simulations.Five schemes,including the small,half and full bogie fairings,and the full bogie fairing with small bottom plates,the full bogie fairing with large bottom plates,were set up to investigate the variations of aerodynamic drag forces.The effect of covering methods for the bogies on the total drag,underneath flow characteristics and train surface pressure distributions were discussed.The results show that with the increase of covered area of the bogie fairing,the impact of airflow on the rear end plate of the bogie cavity is gradually weakened.The positive pressure distribution on the back plate is decreased and the difference of the pressure distribution in the bogie area tends to be smaller,thus achieving the reduction of the aerodynamic drag of the whole train.In addition,the thickness of the boundary layer around the bogie area is gradually reduced.Compared with the small fairing model,the aerodynamic drag coefficients of the half fairing model,full fairing model,full fairing model with small bottom plates and full fairing model with large bottom plates are reduced by 5.2%,8.65%,10.3%and 11.1%,respectively.For the bogies with external axle boxes,the full fairing scheme with big bottom plates can effectively improve the flow field in the bogie area and reduce the aerodynamic drag of the train.Thus,the bogie covering method proposed in this paper will provide a favorable support for the aerodynamic drag reduction design of a new generation of high-speed trains and realize aerodynamic energy saving.
bogies with external axle boxeshigh-speed traincovering methoddrag reductionflow structure
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