基于温度场的排气消声器声学性能仿真优化

发布时间：2018-04-08 17:14

本文选题：消声器　切入点：有限元　出处：《武汉理工大学》2014年硕士论文

【摘要】：汽车的排气噪声水平直接关系到车内乘客的舒适程度，在竞争激烈的现代市场中越来越受到厂商的重视，安装排气消声器是降低汽车排气噪声的最有效方法。采用计算机对消声器性能进行模拟计算可以有效降低开发成本，确保模拟计算的准确性是消声器模拟研究中的重要课题。传统的一维模拟计算速度快，在工程中得到了广泛地应用，但是此方法在声波频率升高时准确性得不到保证。此外在实际工作过程中，气体的温度对消声器的性能有很大的影响，目前的研究中一般将内部温度假设为线性或均匀分布，影响预测结果的精确度。本文以Virtual-Lab为工具，利用有限元法首先对最基本的消声结构的声学特性做了预测计算，分析了不同的结构参数和温度对其消声能力的影响。利用CATIA建立了某车型排气系统的流体域模型，以FLUENT为平台计算得到了不同转速下消声器内部温度场数据。将声学网格耦合不同工况下的温度场后，计算了其相应的传递损失，以计算结果为依据，针对怠速噪声存在的问题提出了相应的改进方案。对比两方案的传递损失后发现，在怠速工况下，改进后的消声器的低频消声能力得到了较好地改善，传递损失在20-500Hz的低频段内有了很大提高。有限元法仅可得到消声器传递损失，为了模拟消声器在实际工作中的性能，利用GT-POWER软件建立了发动机和消声器的耦合模型，分别计算了两套方案的尾管噪声。结果显示，采用改进方案后，在整个转速范围内发动机的尾管噪声声压级都有所降低，转速为2800r/min时，采用新方案后尾管噪声从93.5dB降低到了89.6dB，降幅为3.9dB。对消声器进行了装车实验，结果显示优化的方案有效的降低了汽车的噪声，解决了该车型在尾管和后座中间处声压级超标的问题。且整个三档全油门加速过程中的噪声都有所降低。
[Abstract]:The level of exhaust noise is directly related to the comfort degree of the passengers in the vehicle. In the competitive modern market, more and more attention has been paid to the installation of exhaust muffler, which is the most effective method to reduce the exhaust noise.Using computer to simulate the muffler performance can effectively reduce the development cost and ensure the accuracy of the simulation calculation is an important subject in the muffler simulation research.The traditional one-dimensional simulation method has been widely used in engineering because of its high speed, but the accuracy of this method can not be guaranteed when the frequency of acoustic wave is increased.In addition, the temperature of the gas has a great influence on the performance of the muffler in the actual working process. In the present research, the internal temperature is generally assumed to be linear or uniform distribution, which affects the accuracy of the prediction results.In this paper, using Virtual-Lab as a tool, the acoustic characteristics of the most basic silencing structure are forecasted and calculated by using finite element method, and the influence of different structural parameters and temperature on the silencing ability is analyzed.The fluid domain model of a vehicle exhaust system is established by using CATIA, and the internal temperature field data of muffler at different speeds are calculated by using FLUENT as the platform.After coupling the temperature field of the acoustic mesh under different working conditions, the corresponding transfer loss is calculated. Based on the calculation results, the corresponding improvement scheme is proposed to solve the problem of idle noise.Compared with the transmission loss of the two schemes, it is found that the low frequency silencing ability of the improved muffler has been improved well under idle condition, and the transmission loss has been greatly improved in the low frequency band of 20-500Hz.In order to simulate the performance of muffler in practice, the coupling model of engine and muffler is established by using GT-POWER software, and the tail tube noise of two sets of schemes is calculated respectively.The results show that the sound pressure level of engine tailpipe noise decreases in the whole speed range after adopting the improved scheme. When the speed is 2800r/min, the rear tail tube noise of the new scheme is reduced from 93.5dB to 89.6dB, with a decrease of 3.9 dB.The results show that the optimized scheme can effectively reduce the noise of the vehicle and solve the problem that the sound pressure level of the vehicle exceeds the standard at the middle of the tail tube and the rear seat.And the noise of the whole third speed accelerator is reduced.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U464.134.4;TB535.2

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