某汽车排气管结构优化与验证

孙颖¹，李武^2*，秦臻¹

1.柳州工学院机械工程学院，广西 柳州  545000；2.广西柳工元象科技有限公司，广西 柳州  545000

摘要：为防止某汽车排气管固有频率与发动机主要阶次振动频率、驾驶室声腔固有频率共振，采用Abaqus软件建立排气管有限元模型，进行模态仿真分析并提出优化方案，通过模态分析测试试验进行对比验证。结果表明：排气管第1阶次固有频率为24.23 Hz，而发动机怠速振动频率为25.00 Hz，两者频率相近，共振风险较大；采用改变吊钩位置和直管段加弯管2种优化方案，并进行仿真分析，其中改变吊钩位置方案的第11阶固有频率与驾驶室的固有频率相近，也存在共振风险，而排气管直管段加弯管方案的第1阶次固有频率为19.40 Hz，有效避开发动机怠速振动频率，解决了排气管固有频率与发动机怠速振动频率共振问题；对比排气管模态分析测试试验与有限元仿真结果，两者振型基本一致，第1阶、第2阶振动频率偏差均小于8%，仿真模型有效。

关键词：排气管；模态分析；结构优化；共振

Structural optimization and verification of an automobile exhaust pipe

SUN Ying¹, LI Wu^2*, QIN Zhen¹

1.School of Mechanical Engineering, Liuzhou Institute of Technology, Liuzhou 545000, China;

2.Guangxi Liugong Yuanxiang Technology Co., Ltd., Liuzhou 545000, China

Abstract: To prevent resonance between the natural frequency of an automobile exhaust pipe, the main order vibration frequency of the engine, and the natural frequency of the cab acoustic cavity, the finite element model of the exhaust pipe is established by using Abaqus software, modal simulation analysis is carried out, optimizationschemes are proposed, and comparative verification is conducted through modal analysis tests. The results show that the first-order natural frequency of the exhaust pipe is 24.23 Hz, while the engine idle vibration frequency is 25.00 Hz. The two frequencies are close to each other, indicating a high resonance risk. By adopting the two optimization schemes of changing the hanger position and adding an elbow to the straight pipe section of the exhaust pipe and conducting simulation analysis, the 11th-order natural frequency of the scheme that only changes the hanger position is close to the natural frequency of the cab acoustic cavity, which also has resonance risk. It is found that the first-order natural frequency of the exhaust pipe with an elbow added to the straight pipe section reaches 19.40 Hz, which effectively avoids the engine idle vibration frequency and solves the resonance problem between the natural frequency of the exhaust pipe and the engine idle vibration frequency. A comparison between the exhaust pipe modal analysis test and the finite element simulation shows that their vibration modes are basically consistent, and the deviations of the first-order and second-order vibration frequencies are both less than 8%, which verifies the effectiveness of the simulation model.

Keywords: exhaust pipe; modal analysis; structural optimization; resonance