【作者】 冯真真；

【导师】 张兆合；

【作者基本信息】 哈尔滨工业大学 ， 车辆工程， 2010， 硕士

【摘要】 汽车车内噪声特性是汽车乘坐舒适性的重要评价指标之一。日益激烈的市场竞争迫使汽车厂商都在努力缩短新车型设计与开始生产之间的周期,通过计算机仿真分析可以对噪声控制措施效果进行评估和预测。本文利用统计能量法对某国产轿车进行了室内噪声的分析。本文阐述了基于统计能量分析的车辆噪声分析中子系统划分的工程依据,以某国产轿车为研究对象,在其三维CAD数据的基础上,使用统计能量分析法划分此车型的结构子系统及声腔子系统,确定各子系统间的能量传递关系,建立起该轿车的统计能量分析模型。确定了轿车SEA模型中各结构子系统的材料及物理属性并计算了每个子系统的模态密度、内损耗因子、互相连接的子系统间的耦合损耗因子,将所得结果作为统计能量的模型输入参数。利用Fluent软件完成了轿车高速行驶时车身表面空气压力波动激励的CFD仿真计算,将所得激励值施加到每个子系统,利用统计能量分析软件Autosea对轿车的车内噪声进行了仿真分析。通过9次正交试验仿真得出轿车车身主要参数变化对车内噪声的影响。研究结果表明:前风挡角对汽车气动阻力影响最大,其次为前端盖角,最后是前上翘角及后风窗角。根据试验所得结果取最优组合,取后风窗角的值为35°,前风挡角的值为42°,前端盖角为20°,前上翘角为10°;A立柱附近存有强大的空气脉动压力,是产生车内气流噪声的主要来源。A立柱附近的空气脉动压力会通过风窗、前侧窗及固体传声的方法向车内传播;轿车在高速行驶时(车速为120km/h)车内噪声的主要来源是车身空气波动激励产生的噪声。将车身悬置处振动激励、动力总成悬置处振动激励、动力总成辐射声压激励及车身表面空气压力波动激励共同施加到轿车SEA模型中,分析预测了驾驶员和乘客耳旁噪声声压级。根据计算结果得出子系统主要的能量流,在此基础上提出有针对性的减振降噪措施,分析讨论了采用不同吸、隔声材料和阻尼材料对车内噪声响应特性的影响。主要研究成果有:对前围板施加隔音吸音材料可使前后上声腔声压级平均下降0.9~1.2dB,此降噪措施值得推广使用;对前后车门、侧围板处施加车身增强垫,可使车内前后上声腔噪声声压级在整个频段上都有所下降,大约下降0.5~1.5dB;轿车侧窗玻璃厚度的增加可降低车内噪声;对隔热墙施加阻尼材料降噪效果明显,在500~4000Hz内可使噪声级下降2~4dB;将隔热墙板厚增加为原来的2.5倍对4000Hz以下噪声控制很有效,使前后声腔声压级可降低1~3dB,对4000Hz以上噪声控制效果不好,不适于对高频段噪声降噪;对前后顶棚施加夹板后可使5000Hz以下频段噪声降低1.75dB,在5000~10000Hz频段内下降0.4dB;对衣帽架、后座隔板增加吸声材料和阻尼层可明显降低车内噪声,尤其对高频部分降噪效果显著;对发动机舱内壁添加阻尼材料可有效降低轿车室内噪声,使前后上声腔平均降低2dB;轿车车身材料的中层噪声材料及内层噪声控制材料厚度的选择并不是越厚越好,应该视具体情况而定;阻尼层的厚度及阻尼材料的选择对车内噪声的声压级水平影响很大,应该注意车身阻尼层的使用。本文的研究对如何应用统计能量法以及Autosea软件进行声振研究、如何有效地对轿车内室进行减振降噪有一定的指导意义及参考价值。更多还原

【Abstract】 The property of Automotive interior noise is one of the evaluation indexes which is involved in the comfort of the automotive. The manufactures of auto are contriving to curtail the period between model design and manufacture under the increasingly fierce competition. We can assess and calculate the noise level through computer simulation. In this thesis, we predict and analyze the level of inner noise in a domestic car by statistical energy analysis method.This thesis explains the engineering rule how to establish a vehicle noise analysis system based on the Statistical Energy Analysis theory. Based on the three-dimensional CAD data of the domestic car , the car are divided into structure subsystems and Acoustic cavity subsystems. The energy transfer relationship between subsystems is established. The SEA model of the car can be got. The material and physical properties of subsystems are determined. At the same time, the modal density, internal loss factor, coupling loss factor between connected subsystems are also calculated. These results are input into the SEA model.Secondly, the CFD simulation which is about the air pressure fluctuations incentives on the Automotive body surface at high speed are completed. Incentive value is applied to each subsystem. Then the level of inner noise of Automotive can be simulated by software Autosea which is based on the theory of Statistical energy analysis. Through nine time orthogonal test, we can know which body parameter of car has most important impact on the interior noise. The studying results show that: The front windshield angle have the greatest effect on aerodynamic drag for car, which followed by the angle of the front cover, and the least is upturned angle and back windshield angle .Based on the test results, the best combination of value obtained is taken, Specifically, the back windscreen angle of 35°, the front windshield angle value of 42°, the front cover angle of 20°and the upturned angle of 10°. In the vicinity of A column there is strong pressure of air pulse, which is the main source of air noise generated inside. the air pulsating pressure near A column will spread to the car through the windscreen, front side windows and solid way; the major source of noise inside the body when car travel at high speed (speed is 120km/h) is produced by the air wave excitation noise.Then, the body mounting vibration excitation, the vibration excitation of powertrain mounting, the radiation pressure incentive of powertrain and the air pressure fluctuations of car body surface are applied to the SEA model. The noise level of acoustic cavity which near the ears of driver and passenger can be analyzed and forecasted.According to the calculation results, the major subsystem energy flow is obtained, on this basis the vibration noise reduction is put forward, which have been analyzed the influence on the different absorption, sound insulation materials and damping materials for car noise response characteristics. Main achievements are: imposing noise-reducing materials on front panel can dropped the before the tune sound pressure level by an average 0.9 ~ 1.2dB, the noise reduction measures worth to be widely used; the front door and side body panels which was imposed to enhanced pad can be decreased in the interior sound pressure level in the whole band, a drop of about 0.5 ~ 1.5dB; Increasing the thickness of the side windows can reduce interior noise; the effect is obvious when putting damping material on the wall of noise insulation, the noise level which inside the 500 ~ 4000Hz can down 2 ~ 4dB; it is very effective that increasing the insulation wall thickness of 2.5 for the original times under the 4000Hz for noise control, that sound pressure level before and after the tune can be reduced 1 ~ 3dB, but the effect on more than 4000Hz for noise control is poor, not suitable for high-frequency noise reduction; put plywood on the ceiling after the band can 5000Hz noise reduce 1.75dB, in 5000 ~ 10000Hz down 0.4dB; On the coat rack, rear partition and the damping layer increasing absorption material can reduce noise, especially for high-frequency part of the noise reduction, the effect is remarkable; on the engine compartment wall to add damping materials can reduce the car interior noise, it makes the Tune average dropped 2dB; the middle-noise noise control materials of car body material and material thickness of the inner layer is not thicker which is the better, it should be, as the case may be; the thickness of damping and choice of damping material have a great influence on interior acoustic noise of pressure class, it should be noted that how to use the damping layer body.The work above provides some guidance and reference on how to use SEA and Autosea to carry through noise-vibration study, how to effectively reduce the noise level of passenger car.更多还原