Study on drag reduction of the bottom fairing of high-speed train bogies
The complex mechanical structure and non-streamlined shape of bogies have adverse effects on the aerodynamic performance of high-speed trains.Optimizing the flow field structure at the bottom of the train bogie and reducing the aerodynamic drag ratio of bogies are important to reduce the aerodynamic drag of high-speed trains.Two types of bottom fairings designed were proposed based on the existing structure of high-speed train bogies,and three bogie covering schemes were established.Scheme 1 is an inclined bottom fairing combined with a full side fairing,scheme 2 involves a straight bottom fairing paired with a full side fairing,while scheme 3 serves as a control group without the installation of bottom fairings.The k-ω turbulence model was employed to investigate the alternations in the aerodynamic drag of high-speed trains with various covering schemes.The effects of three distinct covering schemes on the aerodynamic drag of both the bogie and the entire train,as well as the pressure distribution within the bogie cavity and the underbody flow characteristics,were systematically compared and analyzed.The reliability of numerical simulation was verified through full-scale wind tunnel tests on bogies.The results show that the bottom fairing effectively mitigates the impact of airflow on the bogie components and the rear end plate of the bogie cavity,resulting in a more uniform pressure distribution inside the bogie cavity and a consequent reduction in the aerodynamic drag of the bogie.Scheme 1 and scheme 2 result in a reduction of the drag coefficient for the head car by 17.3%and 22.2%,respectively,and for the entire train,it reduces by 11.6%and 12.9%,respectively.In comparison with scheme 2,the inclination angle at both ends of the bottom fairing in scheme 1 guides airflow into the interior of the bogie cavity,this,in turn,accelerates flow circulation within the cavity and facilitates heat exchange between the traction motor,shaft,and other bogie components with the external air.These results serve as a valuable reference for optimizing the design of bogie fairings and reducing the aerodynamic drag of high-speed trains.
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