Abstract: To analyze the fan noise of an aviation engine, spectrum characteristic and circular modal characteristic for forward noise of the scaled fan at different rotational speeds were investigated experimentally. And noise reduction performance of the acoustic liner was also verified. Results indicate that the frequency spectrum and circular mode decomposition results of the measured data meet the theory of rotor-stator interference. The tonal noise becomes larger with the rotational speed increasing, which amounts about 85% of forward fan noise energy at the high rotational speed. For the cases studied in this paper, the acoustic liner has significant effect for the target blade passing frequency and mode, and its optimal transmission loss of 59dB for the dominant mode can be achieved at 85% rotational speed. Also, the acoustic liner has certain broadband noise reduction characteristic, average transmission loss of broadband noise obtained by the acoustic liner is about 3dB at 85% rotational speed.

Key words: Forward fan noise;Acoustic liner;Duct mode decomposition;Transmission loss

摘要： 为了探究航空发动机的风扇噪声，通过试验研究了缩尺风扇前传噪声在不同转速工况下的频谱特性和周向模态特性，并对所设计的环形声衬降噪效果进行了验证。研究结果表明，基于试验测量数据分析得到的频谱特性和周向模态特性满足转静干涉噪声理论。随着转速的提高，风扇纯音噪声越显著，高转速工况下纯音噪声的能量约占风扇前传噪声的85%。在所研究的工况范围内，该声衬对目标频率及模态均有显著的降噪效果，且在85%转速工况时的纯音降噪效果最优，其主模态的传声损失约为59dB。该声衬对于设计频率附近的宽频噪声也有一定降噪效果，在85%转速时的宽频噪声平均传递损失约为3dB。

关键词: 风扇前传噪声;声衬;管道模态分解;传递损失