Abstract
Pantographs are important devices on high-speed trains. When a train runs at a high speed, concave and convex parts of the train cause serious airflow disturbances and result in flow separation, eddy shedding, and breakdown. A strong fluctuation pressure field will be caused and transformed into aerodynamic noises. When high-speed trains reach 300 km/h, aerodynamic noises become the main noise source. Aerodynamic noises of pantographs occupy a large proportion in far-field aerodynamic noises of the whole train. Therefore, the problem of aerodynamic noises for pantographs is outstanding among many aerodynamics problems. This paper applies Detached Eddy Simulation (DES) to conducting numerical simulations of flow fields around pantographs of high-speed trains which run in the open air. Time-domain characteristics, frequency-domain characteristics, and unsteady flow fields of aerodynamic noises for pantographs are obtained. The acoustic boundary element method is used to study noise radiation characteristics of pantographs. Results indicate that eddies with different rotation directions and different scales are in regions such as pantograph heads, hinge joints, bottom frames, and insulators, while larger eddies are on pantograph heads and bottom frames. These eddies affect fluctuation pressures of pantographs to form aerodynamic noise sources. Slide plates, pantograph heads, balance rods, insulators, bottom frames, and push rods are the main aerodynamic noise source of pantographs. Radiated energies of pantographs are mainly in mid-frequency and high-frequency bands. In high-frequency bands, the far-field aerodynamic noise of pantographs is mainly contributed by the pantograph head. Single-frequency noises are in the far-field aerodynamic noise of pantographs, where main frequencies are 293 Hz, 586 Hz, 880 Hz, and 1173 Hz. The farther the observed point is from the noise source, the faster the sound pressure attenuation will be. When the distance of two adjacent observed points is increased by double, the attenuation amplitude of sound pressure levels for pantographs is around 6.6 dB.
Highlights
With the rapid development of high-speed trains, the running speed of trains is increased continuously, and train bodies are developed towards a lighter weight
Most surfaces on the windward side are located at positions with large positive pressures, mainly including pantograph heads, sector plates, bottom frames, and insulators
Pressure distributions on the pantograph surface are symmetric mainly because the pantograph structure is symmetric and impacts of train bodies on the pantograph are not considered in this computation
Summary
With the rapid development of high-speed trains, the running speed of trains is increased continuously, and train bodies are developed towards a lighter weight. Studied results indicate that main energies of the single-arm pantograph were concentrated within 100∼700 Hz. When the running speed was stable, with the increased frequency, the amplitude of dipole noise source on the surface of pantographs would be decreased. Yu et al [16] designed three kinds of pantograph guide guards and conducted a noise reduction analysis based on opened running mode of pantographs, finding that noise reduction effects were obvious and sound pressure levels were decreased by 3 dB adopting this pantograph guide guard similar to air barriers In those published papers, just using wind tunnel or real-train tests has a high cost and low efficiency, while the repeatability of experimental results is poor. Single-frequency noises are in the far-field aerodynamic noise of pantographs, where main frequencies are 293 Hz, 586 Hz, 880 Hz, and 1173 Hz
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