消声器设计.doc

基于传递矩阵的消声器吸声降噪的理论研究 摘要 内燃机和柴油机的排气噪声是工业噪声的主要声源之一，而使用排气消声系统是降低其排气噪声的主要途径之一。消声器作为降低空气动力性噪声的主要装置，其研究一直受到关注，其在工业噪声的控制中起着重要的作用。 对于一个复杂的消声系统，通常可以将其分解为若干个消声单元，每一个消声单元的两侧状态可以用声压和体积速度两个状态参数来描述，对于给定的单元来讲，有一侧的状态参数可以决定另一侧的状态参数，其声学单元相当于四端子网络，在数值上用传递矩阵来表示。 本文在声学运动方程、连续性方程和四端子网络法的基础上，推导常见消声单元串并联线路，建立了并联共振式消声结构元件模型，得出其声场传递矩阵；针对6135柴油发电机组的噪声频谱设计了三种类型的消声器。通过对所设计的消声器进行现场试验，得到实际消声单元的插入损失，将理论计算与实验结果对比并考虑到误差的影响，验证了本文所建立数学模型具有较高的预测精度。 关键词：消声器，传递矩阵，四端子网络，传递损失，插入损失 The Theoretic Research of Sound Absorption and Noise Reduction by Muffler with Transmission Matrix Abstract Exhaust noise elimination system is the most effective component to reduce the internal combution engine and diesel engine’s noise,which is one of the primary pars of the industrial noise.Much attention has been paid to the study of muffler,which is the main device to eliminate aerodynamic noise,so the mufflers are playing more and more important In general, a complicated muffler is disassembled into some anechoic units and every unit can been depicted by two parts:sound pressure and volume velocity. An anechoic unit is equivalent to a four-pole network and represented by a transmission matrix in the calculation. In this part,the total transmission matrix of common anechoic units is deduced in accordance with acoustical theory and four-pole networks.Then the incision of equivalent circuitry model is advanced,which is applied to simplify parallel reactive anechoic units,then the anechoic unit model of parallel resonance is established,the transmission matrix of its sound field is obtained.Three types of mufflers are designed in accordance with the noise spectrum of 6135 diesel engine.Then insertion loss of the anechoic units studied in this paper is attained by the spot experiment.Considering the effect of the error,the accuracy of these methods is validated by contrasting with the experiment data. Key Words:Muffler,Transmission matrix,Four-pole network,Transmission loss,Insertion loss