Acoustic Experimental Technology for Aircraft Nacelle Liner

An 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, which is generally divided into two stages: impedance eduction and the modal verification of acoustic performance. The comparative study summarizes the impedance eduction technology based on the in-situ method and the straight forward method, and the acoustic modal measurement and control technology, as well as their applications in the design of the acoustic liner of an engine intake and exhaust ducts. The results show that the in-situ method has higher accuracy at low frequencies, and the accuracies of both methods are decreased in the high frequency range. Both methods show an acceptable accuracy and good applicability in the mid-frequency range. A modal generator was designed and used to emit separate and pure acoustic modes in sequence, and a comparative test was carried out on the two types of acoustic liner. Compared with the seamed acoustic liner, the seamless acoustic liner significantly improved its noise reduction effect at the multi-acoustic modes and target frequencies, which further increases the overall reduction up to 5.2 dB. Through research, reliable and validated technologies of acoustic performance tests for a nacelle acoustic liner were established.

Automated summary

An aircraft nacelle acoustic liner plays a crucial role in reducing aircraft noise, and its design success relies heavily on the development of experimental technology. This study summarizes the impedance reduction technology and acoustic modal measurement and control technology for the design of an engine intake and exhaust ducts acoustic liner. The in-situ method shows higher accuracy at low frequencies while both methods have acceptable accuracy and applicability in the mid-frequency range. Comparatively, the seamless acoustic liner significantly improves noise reduction effect at multi-acoustic modes and target frequencies, achieving an overall reduction of up to 5.2 dB. Reliable and validated technologies of acoustic performance tests for a nacelle acoustic liner were established through this research.