高流速高声强下两维多阻抗周期微孔发动机声衬的宽频吸声研究

Referring to the scientific problem of improving the acoustic absorption performance of engine liner to meet the strategic demand for airworthiness of domestic aircraft，two-dimensional periodic multi-impedance micro-perforated(MPP) arrays is presented to obtain broad absorption band applying sound scatter effect between units of arrays. Nonlinear effect of orifice at high sound pressure, theoretical impedance model of perforation at high speed grazing flow, sound scatter theory, sound propagation theory in duct with varying impedance, and finite element method are adopted jointly in the research to: (1)establish theoretical acoustic absorption model of two-dimensional periodic arrays of MPP with multi-impedance at high sound pressure and high grazing flow, (2)establish theoretical sound transmission model propagating at high sound pressure and high grazing flow in duct with two-dimensional periodic multi-impedance arrays of MPP. (3)study intensively the effect of pore parameters, degree-of-freedom, cavity parameters and array distribution mode to the sound absorption performance of the two-dimensional periodic structure with multi-impedance at high sound pressure and high speed flow, by theoretical models verified by measurement results, and analyze the influential factors. Characteristics and rules of sound absorption performance of two-dimensional periodic multi-impedance MPP arrays at high sound pressure and high grazing flow are to be reveled and investigated in detail. Optimization design method to get extraordinary wideband absorption for aircraft engine liner is to be put forward. Study results of the research will supplement the acoustic theory of micro-perforated structures and expand the application of two-dimensional periodic micro-perforated absorbers. Research results also help to solve the difficulties of wideband sound absorption of aircraft engine liner. The research work has significant scientific importance and is of great value in aircraft engine liner application to reduce fan noise.

为满足国产客机适航噪声的战略需求，针对航空发动机声衬吸声频带拓展的科学问题，提出两维多阻抗周期微穿孔宽频声衬结构，利用单元间阻抗变化引起的散射拓宽吸声频带。根据微孔的高声强非线性效应、切向流微孔声阻抗理论、声散射理论、变阻抗壁面管道声传播理论和有限元法，(1)建立高声强和高流速共同作用下两维多阻抗周期微穿孔声衬的吸声理论模型；(2)建立高声强和高流速共同作用下两维多阻抗周期微穿孔声衬在管道中的声传播理论模型；(3)深入研究高声强和高流速时单元穿孔参量、单元自由度、空腔参量、单元排列等对两维多阻抗周期微穿孔声衬的吸声性能和管道内声传播特性的影响，分析重要参量。研究结果将揭示高声强高流速下两维多阻抗周期微穿孔板结构的声学特性和规律，形成航空发动机宽频声衬的优化方法。研究成果对完善微穿孔结构的吸声理论、拓展两维周期吸声结构的应用有重要科学意义，对解决发动机声衬宽频吸声的难点问题有重要应用价值。

涡轮风扇发动机噪声是商用飞机在各飞行阶段中的主要噪声源，其中风扇噪声是主要贡献源。高效的消声短舱声衬是降低发动机风扇噪声的主要措施，其优化声学设计成为航空声学的重要问题之一。阻抗耦合周期结构因单元间阻抗和结构的突变引起的声散射，在阻抗匹配的情况下可以耗散声能从而显著拓宽吸声频带。本项目对高速气流和高声强下的多阻抗穿孔结构的声学理论和优化设计进行研究，主要内容包括：高速切向流和高声强条件下穿孔声阻抗计算模型的研究；高速切向流和高声强条件下多阻抗周期穿孔声衬的声学性能研究及参数影响分析；高速气流和高声强综合作用下多阻抗周期穿孔结构的声学特性研究及在管道中的声传播理论模型；优化算法的提出和优化结构的设计。根据研究，项目提出了适用于不超过0.2马赫数高速切向流条件下基于Lee&Ih模型和Cummings模型的穿孔阻抗计算模型；提出了适用不同高声强声压级的穿孔非线性模型，并分别对双层及多层穿孔板提出了基于传递矩阵考虑不同层流场和声场强度的吸声理论模型；提出高流速及高声强综合作用的穿孔声阻抗模型。所提出的高速切向流及高声强模型均与试验结果吻合良好。在此基础上，对高流速和高声强下不同类型及不同自由度组合的多阻抗周期穿孔结构基于散射理论提出吸声计算模型，确定主要影响因素，及基于传递单元法的声衬传递损失模型；对不同多阻抗周期吸声结构提出适用不同频谱特性目标要求的优化遗传算法，针对发动机主要频谱在中高频段和低频段提出吸声系数0.9以上的优化超宽频吸声结构。研究过程中建立了150dB以上的高声强系统。项目成果对完善高速气流和高声强下的穿孔吸声理论和周期结构吸声理论具有重要的科学意义，对拓宽周期吸声结构的应用有积极的指导意义，成果在发动机风扇噪声的降低等具有高声强、高流速、降噪要求高、空间及重量限制条件苛刻特点的应用场景中具有巨大的潜力和广阔的前景。