Joint Design Method of Aero-engine Fan Casing Acoustic Liner and Nacelle Inlet Acousitc 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.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 were discussed,and a complete set of acoustic liner design system and design tools were 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 were 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 blade passing frequency(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.
fan casing acoustic linernacelle inlet acoustic linerjoint designturbofan engine
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