飞机短舱声衬作为飞机降噪的关键手段，其设计的成功与否强烈依赖于声学性能验证实验技术的发展。短舱声衬的声学设计一般分为两个层面，各自关注不同的研究目的与验证对象。在初步设计层面，一般借助声衬声阻抗提取技术对阻抗设计进行验证；在详细设计层面，一般使用缩比尺度和全尺寸短舱样件、借助声模态测控技术对整体声学效果进行验证。本文对比了基于双传声器法和直接提取方法发展而来的声衬阻抗提取技术，和基于相位控制阵列方法发展而来的声模态测控技术，以及这两种技术在发动机进排气道声衬设计中的应用。研究结果表明，双传声器法在低频下具有更高的精度，高频范围内双传声器法和直接提取方法的精度均降低，中频范围内双传声器法和直接提取方法的无量纲声阻和无量纲声抗差别小于0.2，均展示了较好的适用性。基于相位精细控制的旋转声模态发生技术研制的发生器能够产生超过10 dB以上的模态分辨率，能够用于测试声衬对多个目标模态的调控效果。为了进一步研究无缝声衬降噪量提升的主要机制，实验中使用模态发生器依次发出单独纯净的声模态，对两型声衬实验件开展对比测试。采用新一代技术研制的无缝声衬相比上一代成型工艺制成的带拼缝声衬在多声模态调控和关键频率处降噪效果提升明显，无缝声衬的整体降噪效果提升5.2 dB以上。
Aircraft nacelle acoustic liner is a key mean of aircraft noise reduction. The success of its design depends strongly on the development of experimental technology of acoustic performance verification. The acoustic design of nacelle acoustic liner is generally divided into two stages, each focusing on different research purposes and verification objects. At the preliminary design stage, the acoustic impedance design is generally verified by the impedance eduction technology with proper designed experimental installation; at the detailed design stage, the overall acoustic performance is verified by the use of acoustic mode decomposition technology. The comparative study in this paper summarizes the acoustic liner impedance eduction technology based on the in-situ method and the direct extraction method, and the acoustic modal measurement and control technology based on the phase control array, as well as the application of the two in the design of the acoustic liner of the engine intake and exhaust ducts. The research results show that the in-situ method has higher accuracy at low frequencies, and the accuracy of the both methods are decreased in the high frequency range. The difference in the non-dimensional acoustic resistance and the non-dimensional acoustic reactance measured from the two methods in the mid-frequency range is less than 0.2, both showing an acceptable accuracy and good applicability. The rotating acoustic mode generation technology based on designated phase control and the developed generator can produce a modal resolution of more than 10 dB, which can be used to test the noise reduction effect of the acoustic liner on multiple target modes. To further study the main mechanism of increasing the noise reduction of seamless acoustic liners, a modal generator was built and used in the experiment to emit separate and pure acoustic modes in sequence, and a comparative test was carried out on the two types of acoustic liner test pieces. Compared with the seamed acoustic liner made by the previous generation of molding technology, the seamless acoustic liner developed by the new generation technology has significantly improved the noise reduction effect at the multi-acoustic mode control and target frequencies, which improves the overall noise reduction effect of the seamless acoustic liner about 5.2 dB. Through research, the article has established the key and validated the technology of acoustic performance test for nacelle acoustic liner.
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