基于分流电路的压电复合板用于管道噪声控制研究

Low frequency duct noise control remains a technical challenge. Existing technology of sound absorption (duct lining) is passive and preferred in engineering practice. However, it is not effective in the low frequency regime mainly due to the natural air properties beyond our control. Active noise control is still too costly and not robust enough as a practical solution in most cases. This study explores a new technique that allows the passive control to achieve breakthrough enhancement with a shunt circuit, but without complications of active control. The proposed method is to transform the normal plate in our recent invention of plate silencer into a smart plate with bonded piezoelectric elements and shunt circuit...Plate silencer was introduced in our group immediately following the invention of drumlike silencer (US patent 6988057). The mechanism of the plate silencer lies in the intricate acoustic interference between sound reflections by various modes of the plate vibration induced by the incident sound. At a few frequency points the plate silencer experiences coupled modal resonance giving complete sound reflection. Between these discrete frequencies, careful choice of material property allows a reasonable sound attenuation performance to be maintained. In this project, we attach piezoelectric elements on the plate so that the deformation of plate by incident sound would either stiffen or soften the plate through electro-mechanical coupling. Such coupling is frequency dependent and is determined by a shunt circuit attached to the piezoelectric layer. The result is expected to be a composite plate with frequency-dependent structural property. It is hoped that resonance-like performance is achieved over a broadband instead of at a few discrete frequencies in the original silencer. The main task of the project is to investigate the circuitry required. The proposed work benefits from experience by others in the vibration control field and our own work on related control of broadband acoustic reactance which is experimentally proved. If successful the new device is expected to significantly enhance industrial silencing performance and reduce energy cost associated with the traditional silencing designs.

现有的降噪方法在低频、宽带范围对管道噪声进行有效控制仍然具有挑战性。最近的研究发现，管道内适当参数的板结构在声波激励下的振动能够在低、中频引发强烈的声波反射，从而实现管道消声的目的。基于上述声致振动消声机理，本课题探索将带有负电容分流电路的压电复合板应用于管道噪声控制，通过机电耦合改变板的参数使其能够在更宽的频带产生更强的消声效果。为了研究上述压电复合板消声器的声学特性，首先建立声场、压电复合板结构振动和分流电路之间的耦合理论模型；通过理论与实验研究，揭示分流电路参数与消声器声学特性之间的关系，优化分流电路设计使其与板型消声器所需要的刚度频率依赖性相匹配；实验验证压电复合板型消声器的理论预测模型和理论分析结果；阐明气流对压电复合板型消声器声学特性的影响。期望通过该研究，为压电复合板型消声器建立较为完善的理论基础，也为低频、宽带管道噪声控制提供一个新的途径和方法。

项目主要对分流电路控制的压电复合结构和磁场线圈鼓膜用于管道声控制进行了理论与实验探索。.首先构建了声场-振动-分流电路的耦合模型用于仿真分流电路对结构振动与声学耦合的影响。用经过实验验证的理论模型对分流电路设计参数进行优化，并进行实验测量。研究表明吸声系数曲线的峰值频率取决于复合板结构的动力学特性；分流电路可以改变复合结构动力学特性。实验结果表明，通过改变分流电路的电阻抗可以有效控制复合结构的动力学特性，进而调节以及改善其声学性能。仿真结果和实验测量结果吻合。.对电路参数与电路设计方法的研究发现使用 LC 并联与 LC 串联滤波方式会产生不同的频率依赖特性，从而导致不同的控制带宽。为了制造多个电共振以扩展吸声带宽，我们对两种滤波电路的电声控制效果分别进行了探索，通过数值模拟分析了电路设计方法与电路参数对于频响特性及控制带宽的影响，发现LC并联滤波方式可以在更加宽频的范围内实现较好的降噪效果。.利用经过验证的声场-振动-分流电路耦合方法，分析了分流电路对安装在管道侧壁的压电复合板型消声器的消声性能的影响。通过改变电路参数，对降噪谱线进行优化，以达到更好的消声效果。研究发现，更轻的复合板可以实现更好的反射效果，借助复合板上的多个接有分流电路的压电片，可以进一步扩宽消声器的消声效果。同时，压电复合板消声器能够通过改变分流电路参数来改变其消声频谱，从而可以优化消声频带宽度。.在磁场中鼓膜线圈两极连接了合适的电路阻抗以扩展吸声频宽，实验中使用一个带分流电路的扬声器进行吸声测试，得到更宽的吸声频谱。为了研究管道声波传播，并且借助管道声衬进一步提升消声效果，我们研究了基于波动有限元法的建模方法，以分析管道中声波在声衬中的传播特性,以及在带流动的管道中的传播特性，并据此分析了风扇流噪声频谱及传播模态特性。