【作者】 税永波；

【导师】 丁渭平；

【作者基本信息】 西南交通大学 ， 车辆工程， 2013， 硕士

【摘要】 薄壳排气消声器实际工作时,会存在高温高速气流,精确分析弹性壁、气流和温度对消声器声学性能、压力损失和模态参数的影响具有重要意义。本文结合数值仿真和相关试验手段,从气固声热耦合的角度做了如下研究工作：(1)设计搭建了测量消声器声学性能和压力损失的气动-声学试验台。将简单膨胀腔消声器传递损失的测量值、仿真结果与一维平面波理论值进行比较,在无精确理论值的条件下实现了对试验台上消声器传递损失测量的间接标定。通过对压力损失测量和仿真进行对比,发现它们之间差异较小。应用所搭台架对某型消声器GT-POWER仿真模型进行了置信度检验,对另外两只复杂结构消声器进行了声学试验和压力损失测量,通过对测量结果的综合评价,实现了对消声器的相对择优。(2)在Workbench中从气固耦合和热固耦合方面,分析了气流和温度对简单膨胀腔消声器结构模态参数的影响,发现气流对模态参数的影响较小,而温度因素则不能忽略。(3)基于Virtual.Lab软件,应用声固耦合有限元法研究了弹性壁对消声器传递损失的影响,将只约束进气端和进出气端都约束时的结构模态参数分别参与声固耦合计算,都发现传递损失降低且在某些结构模态频率处发生了跳变。并且改变壳体厚度,发现壳体越薄,跳变现象越明显。(4)基于CFD分析所提供的温度场边界条件,实现了热声单向耦合,研究得出内部气体温度较高且非均匀分布时消声器传递损失在高频段增大,在声固耦合和热声耦合的基础上,分析了热声固耦合作用下的传递损失。(5)仿真分析了常温和高温状态下消声器的声学模态频率和声压分布。发现相对常温而言,高温下的声学模态频率有所增大,声压分布基本不变。(6)考虑气流速度对消声器传递损失的影响,通过仿真发现相对无流情况,气流速度的方向决定了传递损失是增大还是减小,气流速度的绝对值越大,对传递损失的改变越大。本课题的研究工作具有如下的创新性：考虑弹性壁和非均匀分布的高温的共同作用时,所得到的消声器传递损失将更加精确,热声固的耦合在消声器的研究中尚不多见。更多还原

【Abstract】 When thin shell exhaust muffler actually works, there will be high temperature and high speed airflow. Analyzing the influence of the elastic wall, airflow and temperature to the acoustic performance, pressure loss and the modal parameters of the muffler accurately is of great significance. Based on the numerical simulation and related experiments, some research done in this paper by coupling the gas-solid-acoustics-thermal is as follows.(1) Aero-dynamic&acoustic test rig which can measure the acoustics performance and pressure loss of the muffler has been set up. By comparing the measuring result and the simulation result with the theoretical value in the one-dimensional plane wave of the simple expansion chamber muffler transmission loss, the indirect calibration of transmission loss measurement is realized on the test rig on condition that there is no precise theoretical value. By comparing measuring result and simulation result of pressure loss, only little difference between them is found. The confidence of the muffler’s GT-POWER simulation model is verified by the test rig and by conducting the acoustic experiments and measuring the pressure loss of two other structure-complicated mufflers, the test results are evaluated comprehensively to choose the relatively better muffler.(2) From the sides of gas-solid coupling and thermal-solid coupling, the airflow and temperature on the influence of the simple expansion chamber muffler structure modal parameters is analyzed on the Workbench software and the conclusion is made that airflow has less effect on the modal parameters, while the temperature factor can not be ignored.(3) Based on the Virtual. Lab software, the influence of elastic wall to transmission loss of muffler has been studied using acoustics-solid coupling finite element method.Whether only the inlet side is constrained or both the inlet and outlet sides are constrained in the acoustics-solid coupling analysis, the transmission loss always decreases and jumps in some structure modal frequency. And the conclusion is made that changing the shell thickness, the thinner the shell, the more obvious the jump phenomenon.(4) The boundary condition of temperature field based on the CFD analysis is used in the one-way thermal acoustic coupling analysis and it is found that the transmission loss of muffler increases in high frequency when it is full of non-uniform distribution high temperature gas, and on this bases of acoutics-solid coupling and thermal-acoustic coupling, the transmission loss curve is analyzed under the thermo-fluid-structure coupling condition.(5) The acoustic modal frequency and sound pressure distribution are analyzed under normal temperature and high temperature condition. Compared with the normal temperature, the acoustic modal frequency increased and the sound pressure distribution basically remained unchanged on high temperature condition.(6) Considering the influence of airflow velocity to transmission loss of the muffler, the simulation result shows that compared with no flow case, the velocity direction of airflow determines whether the transmission loss increases or decreases, the greater the absolute value of the airflow velocity, the greater the change of transmission loss.The research work of this paper has certain innovations as follows.The transmission loss will be more accurate under the combined action of the elastic wall and non-uniform distribution high temperature, coupling thermal acoustics with solid in the study of muffler is rarely seen.更多还原