高速铁路轮轨噪声理论计算与控制研究

Theoretical Calculation and Control Study on the Wheel/Rail Noises of High Speed Railway

轮轨噪声是铁路主要的噪声源。针对高速铁路轮轨噪声辐射问题，综合运用车辆一轨道耦合动力学理论与噪声辐射理论，建立高速铁路轮轨噪声预测模型，应用数值仿真的方法研究高速铁路轮轨噪声产生机理、辐射特性、传播规律以及控制技术。主要研究内容和结论如下。

Wheel/rail noise is the main noise source of railway. The work in this dissertation focuses on wheel/rail noise radiation in high-speed railway. Based on the vehicle-track coupling dynamics theory and the acoustics radiation theory, a model is proposed to predict wheel/rail noise in high speed railway. Numerical simulation method is used to investigate the wheel/rail noise generation mechanism, radiation characteristics, propagation law and control technology in high-speed railway. The main research contents are as follows. (1) Structure admittance and sound radiation efficiency of wheel-rail system are two important basic problems to predict wheel/rail noise. Structure admittances of wheel-rail system are calculated and analyzed by the FEM (Finite Element Method) in the present paper. Then on this basis, using the BEM (Boundary Element Method), sound radiation efficiencies of the wheel-rail system structure are investigated. (2) Using computer program language FORTRAN95, WRNOISE (Wheel/Rail Noise) system is developed to predict and analyze wheel/rail noise. WRNOISE system is compared with the existing wheel/rail noise prediction model TWINS (Track and Wheel Interaction Noise Simulation), STTIN (Simulation of Train and Track Interaction Noise) and test data. The result shows that the prediction result of WRNOISE system basically agrees with that of TWINS. Compared with STTIN model, WRNOISE model in predicting wheel/rail noise is more accurate. There are some differences between the noise prediction values of the WRNOISE model and the noise test values of high-speed train running in some frequency range, but both trends are consistent in the range of 500~4 000 Hz. (3) Using WRNOISE prediction system, the wheel/rail impact noise and rolling noise generated by high speed train running on ballastless track sections are analyzed theoretically. The mechanism of wheel/rail impact noise generated by wheel flats and rail welded joints, are proved. And the spectrum characteristics, time characteristics and sound propagation law of wheel/rail rolling noise excited by the surface roughness of wheel and rail are investigated. The results show that the energies of wheel/rail impact noise excited by wheel flats and rail welded joints are concentrated in the middle and high frequency. With the increase of train speed, the structural defects of wheel-rail system will stimulate more serious noise radiation. It is shown that the rail radiates chiefly middle and high frequency noises, and that the wheel radiates chiefly high frequency noises, and that the slab radiates middle and low frequency noises. It makes clear that wheel/rail rolling noise spectrums show broadband characteristics and the noise energy is mainly concentrated in the range of 400~4 000 Hz. In the distances of 5~50 m from the track center, wheel/rail noise pressure level will decay 3~6 dB (A) with doubling distance, which basically meet the finite line source attenuation law with the distance. (4) Using WRNOISE prediction system, the structural parameters of wheel-rail system are investigated in low-noise idea. It can be concluded that, without affecting the train running safety, if the web thickness of the wheel is appropriately increased, the wheel noises above 500 Hz will be decreased. The wheel of straight-type web can more effectively reduce wheel/rail noises at 300~1 000 Hz than the one of S-type web. If the rail mass is appropriately increased, the vibration and noise of the rail and slab at high frequency will be decreased. The stiffness of rail pad has no influence on wheel/rail noise reduction. The greater the damping of the rail pad, the more the loss of vibration energy transferring to the rail infrastructure, and the more favorable to vibration and noise reduction of wheel-rail system. For the ballasted track, the parameters of the sleeper and ballast have more influence on the noise radiations of the sub-rail structure, while have little influence on the noise radiations of the wheel and rail. If the sleeper mass is appropriately increased, the ballast stiffness is decreased and the ballast damping is increased, the noise and vibration of wheel-rail system will be effectively reduced. For the slab track, the greater weight of the slab, the less noise emissions of the slab, so the more favorable on wheel/rail noise reduction on the whole. The greater the elastic modulus of CA mortar under the slab, the less the noise emissions of the slab. For the higher environment requirement sections of high-speed railway, the rubber pads installed under the slab is beneficial to wheel/rail noise reduction. (5) Using WRNOISE prediction system, the influences of the porosity, thickness and micro-porous diameters of the porous sound absorption panels on the wheel/rail noise reduction effect are analyzed. The result shows that, the greater porosity of the porous sound absorption panels, the better the wheel/rail noise absorption, but too much of porosity can reduce the absorption of wheel/rail noise of middle and high frequency. The greater the thickness of the porous sound absorption panels, the better the wheel/rail noise absorption. In the range of 0.2~0.4 mm, the greater micro-porous diameters of the sound absorption panels, the worse the wheel/rail noise absorption. (6) The BEM is used to analyze in detail the influence of the source frequencies, the installation location of the sound barrier, the sound barrier structure itself and the sound barrier surface laying sound-absorption materials on noise reduction. The results show that the noise reduction of the sound barrier for high frequency noise is better than the one for low frequency noise. The sound pressure insert loss will increase with the increasing of the height of sound barrier. For different structure type of sound barrier on the effect of noise reduction, the arc-type, inverse L-type and incline-type are better than the straight-type. A-type, T-type and V-type are the best. To lay the sound-absorbing material with low impedance on the inner surface of the sound barrier has a good noise reduction effect.