Investigating The Vibroacoustic Characteristics And Noisereduction Measures Of Pantograph Flat Roof Of High-speed Train

The operating speed of high-speed trains in China is currently up to 350 km/h,and the problem of vehicle noise is becoming more and more prominent with the increase of the train speed.Due to the complex geometrical structure of the pantograph,the airflow will be disturbed during the high-speed train operation and aerodynamic noise will be radiated.At the same time,the shed vortices hit the wall of the car body to produce turbulent pulsating pressure on the car body surface.In addition,the pantograph also generates force excitation on the car body under the combined action of pantograph-catenary contact force and aerodynamic lifting force.The above multiple excitations contribute to the interior noise through the complex roof structure and air.Therefore,compared with the middle of the passenger compartment and the upper compartment of the ordinary bogie,the compartment under the pantograph has more prominent noise problems.Clarifying the sound transmission characteristics of pantograph flat roof under various excitation conditions is of guiding significance for the design of effective noise control scheme.The thesis is mainly composed of the following parts :First of all,through literature research,the reasons for the prominent interior noise problem in the pantograph area of high-speed trains are clarified : various excitation sources and high excitation intensity;The transmission path is complex.The current research progress is discussed from three aspects : acoustic and vibration characteristics of pantograph and flat roof,aerodynamic excitation characteristics of pantograph region and noise control of pantograph and flat roof.Finally,the research content of this paper is determined.Secondly,based on the FE-SEA theory,considering the detail characteristics of the pantograph flat-top sound transmission link,the sound transmission characteristics analysis model of the combined roof structure is established.Firstly,the white noise is used as the excitation to preliminarily grasp the sound transmission characteristics of the pantograph flattop,and the contribution of each component in the path to the acoustic energy of the vehicle cavity is quantitatively analyzed.Thirdly,the flow field of pantograph region is simulated based on CFD method,and the aerodynamic excitation of pantograph is obtained.It includes the aerodynamic noise above the flat roof and the fluctuating pressure on the roof wall extracted by the wave numberfrequency method.Then,based on DAF acoustic excitation model and Corcos turbulence excitation model,the acoustic-vibration response and transmission characteristics of roof structure under aerodynamic acoustic excitation,turbulent boundary layer excitation and pantograph force excitation are analyzed.The flat-top aluminum profile of pantograph flattop structure is the main component of radiated noise,and its vibration acoustic radiation contributes about 67%～77% to the acoustic energy of the acoustic cavity in the vehicle.’Installation base-body profile-hoisting structure-interior roof ’ is the main structural sound transmission path,which contributes about 15%～21% to the acoustic energy of the interior acoustic cavity.In addition,the acoustic-vibration response spectrum of the pantograph flat roof structure peaked at the natural frequency of the profile itself,indicating that the acoustic contribution of the body profile to the vehicle is mainly controlled by its own modal.Finally,the noise control scheme of pantograph flat roof structure is designed,and the optimization scheme is applied to the verified vehicle interior noise model.The noise in the carriage below the pantograph is reduced by 2.4 d BA,and the vibration velocity level of each component of the flat roof structure is reduced by 4～5 d B.The vibration and noise reduction effect is obvious.