柴油轿车车内低频噪声特性研究

【作者】 李晓宁；

【导师】 沈颖刚；

【作者基本信息】 昆明理工大学 ， 动力机械及工程， 2009， 硕士

【摘要】 随着汽车工业的飞速发展以及人们对节能和环保的要求,车辆朝着高速化、轻量化方向发展,使得汽车噪声、振动与舒适性(NVH)问题凸现出来,质量轻量化是增大汽车车身结构低频振动和车辆内部噪声,特别是低频低沉轰鸣噪声的原因。作为轿车的一个重要发展趋势,柴油轿车的NVH问题更加突出。本文以某国产柴油轿车为研究对象,并应用数值模拟与实验相结合的方法来研究该轿车的车内低频噪声特性,在数值模拟过程中充分考虑了车身结构与车内空气的相互作用,使模拟结果更加接近实际情况。首先在对轿车白车身模型进行实验模态分析的基础上,建立了轿车车身结构有限元模型,对该轿车的乘坐室由建立了空腔声学三维有限元模型与该车的车身板件-乘坐室空腔三维声耦合模型,并分别对以上各模型进行模态分析,通过白车身有限元模型模态与实验模态结果对比分析,验证了模型的正确性。然后利用多体动力学软件ADAMS建立该轿车多体动力学模型,提取发动机和路面对车身的激励力,应用结构及声场动态分析技术,对该车车身结构-乘坐室空腔声固耦合系统的动态特性给于了细致研究,并在此基础上分析了耦合系统的乘坐室声学响应,并与实车路面测试结果进行了对比,结果显示：随发动机转速升高时测试车辆乘坐室内的噪声值也有所增大,低速时车内噪声峰值较多,但幅值变化较小,高速时车内噪声水平明显升高,噪声峰值主要集中在几个频率点处。通过车内噪声测量值与计算值的对比可以看出,在较低频段两者符合较好,在较高频段两者相差较大。对车身板件振动声学贡献分析获得如下结果：后围板、地板中部、衣帽架板为主要正贡献板件,是该车车内噪声的主要声学贡献来源；最后针对板件贡献分析中对车内噪声较大的衣帽架板、后围板和中地板,对其中振动较剧烈的部位通过优化加强筋来增加局部刚度,优化后的分析结果表明：衣帽架板、后围板和中地板的优化效果较好,加强肋布置合理,能够较好的降低板件的振动幅度,达到降低车内噪声的目的。更多还原

【Abstract】 With the rapid development of the automobile industry as well as people’s energy-saving and environmental protection requirements, high-speed moving vehicles, light direction, making vehicle noise, vibration and comfort (NVH) problems emerged, the quality of light is increased Motor vehicle body structure of the low-frequency vibration and noise within the vehicle, in particular the resonance of low-frequency noise. Diesel cars which NVH issues become more prominent is an important development trend of the car. This paper made a diesel car for the study and application of numerical simulation and experimental combination of methods to study the low-frequency noise inside the car’s characteristics, In the process of numerical simulation takes full account of the interaction of the air inside the vehicle and body structure so that the results closer to reality.In the first, on the basis of the experimental modal analysis of the body in white, a car body structure of the finite element model, the cavity of cabin acoustic sound field of the finite element model and the structure-acoustic coupled model of the car structure and the cavity of cabin were established. And modal analysis was performed respectively for the models that were established above all. The correctness of the model was verified by the results of the comparison of the modal analysis by finite element model of the body in white and experimental modal analysis. Then the use of multi-body dynamics software ADAMS to build multi-body dynamic model of the car, the driving forces which derived from the engine and road were extracted respectively and the dynamic analysis techniques of the structure and sound field were applied. A detailed study of the dynamic characteristics of the coupled acoustic-structure system of the car was performed. The acoustic response of the coupled system by the driving forces which derived from the engine and road was analyzed and the road test results as well as calculated values were compared. The results show that: the magnitude of the car’s interior noise increased as engine speed increase. The noise peak inside the vehicle was more at low-speed, but smaller changes in the amplitude. The level of the noise inside the car increased obviously and the noise peak was concentrated mainly in a few frequency points. Through the contrast of the measured value and calculated value of the cabin noise can be seen that the tendency was good to correspond with them in lower frequency bands and the gap was large in the higher frequency bands. The results of the further studies for acoustic contribution analysis of the vibration of the body panels showed that clothes tree panel, squab panel and the middle part of the floor panel which were the main noise source inside the car of contributions to the acoustics were the main panel for contribution; finally to direct at clothes tree panel, squab panel and the middle part of the floor panel which had larger contributions cabin noise in the analysis of panel contribution. And local stiffness was increased through the optimization of rebar of the more violent parts of vibration. The results for optimization analysis showed that there were good effects for clothes tree panel, squab panel and the middle part of the floor panel and the arrange of the strengthening rib were reasonable, which can reduce the amplitude of vibration apparently. The goal to reduce car noise had been to achieve.更多还原