航空发动机宽频噪声预测及控制方法研究

One of the crucial problems in aviation industry is how to effectively reduce the aircraft noise. After significant techniques, such as higher by-pass ratio of a turbofan engine, optimization of counts of rotor blades and stator vanes, acoustic liner were applied, the technology of noise attenuation is developed slowly in recent years. One of the main factors is that the broadband noise has become one of the important contributions with the reduction of discrete tone noise. Therefore, a new investigation on the reduction of broadband noise in aero-engine is suggested in the present application. Unlike the existing researches, this investigation will focus on the interaction between rotor/stator cascades as sound source and acoustic liner to find further gains on the noise abatement. Three parts are included in this attempt: 1) Setting up a three-dimensional calculation model for broadband noise generated by rotor-turbulence wake and stator interaction or intake turbulence and rotor cascade interaction to investigate the effect of rotor/stator swept and lean on the decrease of broadband noise; 2) Developing a fast and reliable model to investigate the effect of multi-resonance non-locally reacting liner on broadband and multi-modal noise; 3) Building a novel mathematical model for interaction between sound source and acoustic liner with broadband and multi-modal noise in finite domain, finding further noise reduction gains basing on the interaction investigation.

随着涡轮风扇发动机涵道比不断增高，宽频噪声已经成为主要噪声源之一，同时相对于离散噪声，它的降低极其困难，可以说它正在成为制约民用航空发动机气动噪声进一步降低的瓶颈因素之一。为此，以美国NASA，欧洲AIRBUS为首支持的各种研究项目一直在尝试解决宽频噪声的预测、降噪问题，但尚未取得期望的进展。本项申请与业已存在的国际上降低宽频噪声的方案不同，首先致力于发展能够有效包括叶片造型影响的宽频噪声模型，使其对叶片弯掠组合的降噪效果能够更准确的刻画，从而把降低声源本身噪声发挥到更好的水平。其次，在我们独立发展的多腔共振非局域反应声衬基础上，寻求降噪频带更宽的声衬来抑制噪声的传播。其三，建立非局域声衬与宽频声源的传递单元模型，研究声源与声衬相互作用对上述降噪方法的影响，寻求降噪收益的最大化。本项申请期望通过这三个理论、技术方案的实施丰富对宽频噪声形成机理的认识，并显著拓宽的宽频噪声的降噪频带。

航空发动机声学适航标准在不断提高，如何有效控制航空推进器旋转机械的噪声是航空工业发展的关键技术之一。本项目正是围绕这一关键问题，开展了三个方面的研究工作。其一是从声源方面入手，建立三维叶片响应函数，并考虑不同径向位置的非定常载荷干涉作用后，研究静子叶片的弯/掠及其组合效应对宽频噪声降噪的影响；在此基础上建立多排叶片的相互作用，探索通过转子屏蔽效应降低转/静干涉噪声的有效方法。其二是从传播途径入手，建立有效的包含非局域反应声衬及非均匀声衬的管道内部多模态宽频噪声传播的计算模型，并在此基础上深入研究了这类声衬的降噪特性，直接指导工程应用中宽频声衬的设计。其三是建立有效模型考虑声源与声衬相互作用带来的降噪收益，其中包括建立转子与声衬相互作用的计算模型，讨论声衬存在下对转子叶片上非定常载荷分布的影响，实现了进一步降低噪声的有效措施；建立弯掠组合静子叶片与声衬相互作用的计算模型，验证两种降噪措施的综合效果并不是简单叠加，需要精心设计实现更好降噪效果；建立热声源壁面阻抗边界控制方法，为控制燃烧室内压力震荡提供有效措施。