某混合动力轿车外流场气动噪声特性研究

发布时间：2018-03-24 00:21

本文选题：气动噪声　切入点：脉动压力　出处：《江苏大学》2016年硕士论文

【摘要】：随着汽车技术的不断发展,人们对于乘坐舒适性的要求也越来越高。本文以某混合动力轿车为研究对象,通过数值仿真方法结合实车道路试验研究了其外流场气动噪声特性,以及气动噪声对车内声场的影响。具体研究方法和创新点如下。利用CATIA软件的逆向建模功能建立了该车的车身模型和Qg声腔模型,利用GAMBIT软件和HYPERMESH软件对模型进行了几何清理、网格划分和流场边界条件设置。在CFD软件FLUENT中求解了三种不同车速下的流场结果,得到了车身表面的动压云图、湍流动能等值线图。在求解瞬态流场时综合对比了几种常用湍流模型的优缺点,采用了一种新型的湍流模型——分离涡模拟,得到了车身表面的脉动压力分布情况,为进行声场仿真奠定了基础。本文的最大创新点在于在求解声场时采用了虚拟激励法。首先求解车身结构模态和内声腔声学模态,将车身表面的脉动压力视为随机载荷,并将其分解为虚功率谱密度,采用VIRTUAL.LAB软件中的随机声学模块进行求解,将流场数据映射到车身结构网格上,利用声振耦合原理结合有限元方法得到了驾驶员双耳及后排乘客双耳处的声压响应。为验证仿真方法的正确性,参考国标GB/T 18697-2002《声学汽车车内噪声测量方法》对汽车气动噪声进行了实车道路试验。试验得到的声压级曲线与仿真结果大致吻合,讨论了可能导致二者误差的原因。最后在车内添加了多孔吸声材料考察其吸声降噪效果。最终得到相关结论如下:(1)分离涡模拟非常适合求解分离流动现象,较好地捕捉到了后视镜以及汽车尾部的湍流情况;(2)脉动压力频谱是宽频谱,能量主要集中在中低频,是产生气动噪声的根本原因。(3)气动噪声频谱在某特征频率处达到峰值,随后开始下降,峰值频率随着车速的提高向高频移动。(4)驾驶员左右耳的声压级有所差别,由于左耳靠近车窗,受湍流影响较大,故声压级也较大;后排乘客靠近车尾部的复杂湍流场,且车尾部的辐射面积较大,故声压级大于前排驾驶员人耳处。(5)由于多孔吸声材料属于阻性材料,可以使车内声压级平均降低5dB左右,其在高频段的吸声效果明显好于低频段。
[Abstract]:With the development of automobile technology, the requirement of ride comfort is becoming higher and higher. In this paper, the aerodynamic noise characteristics of a hybrid car are studied by numerical simulation and road test. The specific research methods and innovations are as follows. The body model and QG cavity model of the vehicle are established by using the reverse modeling function of CATIA software. The geometric cleaning of the model is carried out by using GAMBIT software and HYPERMESH software. The flow field results of three different vehicle speeds are solved in the CFD software FLUENT, and the hydrodynamic pressure cloud diagram of the body surface is obtained. Turbulent kinetic energy isoline diagram. In solving transient flow field, the advantages and disadvantages of several common turbulence models are compared synthetically. A new turbulence model-separated vortex simulation is used to obtain the distribution of fluctuating pressure on the surface of the body. The most innovative point of this paper is that the virtual excitation method is used to solve the sound field. Firstly, the body structure mode and the acoustic mode of the inner acoustic cavity are solved, and the fluctuating pressure on the surface of the body is regarded as a random load. It is decomposed into virtual power spectral density and solved by random acoustic module in VIRTUAL.LAB software. The flow field data is mapped to the body structure grid. The acoustic pressure response between the driver's ears and the rear passengers' ears is obtained by using the principle of acoustic and vibration coupling and the finite element method. Referring to the national standard GB/T 18697-2002, the actual road test of vehicle aerodynamic noise is carried out. The sound pressure level curve obtained from the test is in good agreement with the simulation results. The possible causes of the errors are discussed. Finally, a porous sound absorption material is added to the vehicle to investigate the effect of sound absorption and noise reduction. Finally, the related conclusions are as follows: 1) the separation vortex simulation is very suitable for solving the separation flow phenomenon. The spectrum of pulsating pressure is a wide frequency spectrum, and the energy is mainly concentrated in the middle and low frequency, which is the root cause of the aerodynamic noise. The spectrum of aerodynamic noise reaches its peak at a certain characteristic frequency. Then it began to decrease, the peak frequency moved to high frequency with the increase of speed.) the sound pressure level of the driver's left ear and left ear was different, because the left ear was close to the window, so the sound pressure level was larger because of the influence of turbulence. The complex turbulence field of rear passenger near the rear end of the vehicle, and the radiation area of the rear end of the vehicle is large, so the sound pressure level is larger than that in the front row driver's ear. (5) because the porous sound absorption material belongs to the resistive material, the sound pressure level in the vehicle can be reduced about 5dB on average. The sound absorption effect in high frequency band is better than that in low frequency band.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U461.1

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