航空发动机风扇机匣声衬与进气道声衬联合设计方法

对于现代的大涵道比涡扇发动机,风扇噪声是主要的噪声源。风扇机匣声衬(风扇前)与进气道声衬能显著降低风扇前传噪声。该两段声衬距离接近,所处的声场互相影响,有必要研究风扇机匣声衬(风扇前)与进气道声衬的联合设计方法。本研究首先结合国内外进展,对声衬优化设计方法、声传播计算模型、声源模型、声阻抗模型、代价函数等声衬设计的关键环节进行讨论,并选择合适的方法形成一套完备的声衬设计体系与设计工具。同时,对航空发动机风扇机匣声衬(风扇前)与进气道声衬进行联合设计,得到单自由度与双自由度声衬两套方案,证明该工具的工程可行性与有效性。最后,对两种声衬方案进行了不同方面的评估,包括BPF噪声降噪效果、宽频降噪效果等。评估表明,在该设计思路下,两方案在飞越、边线、进场前两阶BPF噪声都能得到很好的降噪效果,并且双自由度声衬能够在更宽的频率范围内显示出降噪优势。但是,如果代价函数能够进一步囊括声衬的宽频吸声效果,双自由度声衬能够更优的宽频降噪效果。

Joint design method of aero-engine fan casing acoustic liner and nacelle inlet acoustic liner

Fan noise is the main noise source of modern high bypass ratio turbofan engines. Fan casing acoustic liner (in front of the fan) and nacelle inlet acoustic liner can significantly reduce fan forward noise. The two liners are close, and the sound fields influence each other. Therefore, it is necessary to study the joint design method of fan casing acoustic liner(in front of the fan) and nacelle inlet liner. In this study, the key aspects of acoustic liner design such as optimal design method, acoustic propagation calculation model, acoustic source model, acoustic impedance model and cost function are discussed, and a complete set of acoustic liner design system and design tools are formed. At the same time, the aero-engine fan casing acoustic liner (in front of the fan) and the inlet liner were designed, and both single-degree-of-freedom and double-degree-of-freedom acoustic liner methods were obtained. Finally, acoustic liners are evaluated, including the effect of BPF noise reduction, broadband noise reduction, etc. The evaluation shows that, the two type of liners can obtain good noise reduction effect in the two orders of BPF noise in flyover, sideline and approach condition, and the two-degree-of-freedom liners can show the noise reduction advantage in a wider frequency range. However, if the cost function can further include the broadband sound absorption effect of the acoustic liner, the two-degree-of-freedom sound liner can achieve better broadband noise reduction effect.