双模态消声器低频消声特性分析及应用

Analysis and Application of Low Frequency Noise Reduction Characteristics of Dual Mode Mufflers

低频阶次噪声占居排气噪声的主要成分,且对排气噪声声品质有着重要影响,双模态消声器对于排气低频噪声具有良好的控制效果,但目前还缺乏深入的消声特性分析及快捷的实际应用设计方法。建立最简双模态消声器结构,通过三维数值仿真,发现双模态消声器具有低频消声峰值,且随着阀体开度的增加,峰值频率向高频方向移动,并通过声压云图分析确定发挥低频消声作用的腔室。针对双模态消声器中的共振腔部分,通过一维/三维混合仿真方法,提取阀体结构的声学参量,建立基于集总参数的声学特性预测模型。仿真分析发现随阀体结构开度变化的阀体部分声质量抗,是影响消声峰值频率移动的关键。通过集总参数预测模型设计了匹配某款汽车的双模态消声器,并通过数值仿真及传递损失实验验证了设计参数的正确性。进行实车测试,结果表明匹配设计的双模态消声器降低了排气四阶噪声,验证了提出的正向匹配设计方法的有效性。

The low-order frequency noise dominates the exhaust noise, which has a significant influence on the exhaust noise quality. The dual mode muffler has a good control effect on the low-frequency exhaust noise, but there is still lack of in-detail analysis of the acoustic characteristics and fast design method for practical application. In this paper, a simplest model of a dual mode muffler structure was established. Through three-dimensional numerical simulation, it is found that the muffler owns an important low-frequency noise reduction peak, and the peak frequency shifts to high frequency direction when the valve opening increases. The chamber with the function of low-frequency noise reduction was determined through the analysis of sound pressure nephogram. The acoustic parameters of the valve in the dual mode muffler were extracted through the one-dimensional/three-dimensional hybrid simulation method. And the prediction model for acoustic characteristics based on lumped parameters was established for the resonant cavity part of the dual mode muffler. The simulation analysis shows that the sound inertial impedance of the valve body, which varies with the valve opening, is the key factor influencing the shifting direction of the resonance frequency. A dual mode muffler matching a vehicle was designed by the lumped parameter prediction model, and the correctness of the design parameters was verified by numerical simulation and transmission loss experiments. At last, a real vehicle road test was carried out. The test results show that the dual mode muffler of the matching design can greatly reduce the fourth-order exhaust noise, which validates the effectiveness of the proposed forward matching design method.