Active control of noise generated from axial-flow turbomachinery

我们的实验分为两部分。一种是关于阶段压力波动的基本特征，这对处理噪声很重要。另一种是通过扩音器增加声压来主动控制噪音。前两种实验的主要结果总结如下：1。随着流量的变化，压力波动幅度、跨谱强度和声压级也有相似的变化。这意味着波动与产生的噪声密切相关。转子叶片上的压力呈相位波动，并且在叶片上具有几乎相同的大小。这种显著的特征是现有的理论无法解释的。作为其原因，假定压缩性由于高不稳定性而起作用。后一个实验是为了了解主动控制的有效性，并获得基本数据。结果表明，本文提出的主动控制方法是有效的。主要研究结果如下：1。总体噪声降低约11 dB，对应叶片通过频率的噪声降低约23 dB.2。扩音器增加的声压相位和振幅与理论预测一致。

Our experiments are divided into two parts. One is concerned with the fundamental features of pressure fluctuations in the stage which is important in handling the noise. The other is the active control of the noise by adding sound pressure with loud speakers.The main results of the former experiment are summarized as follows :1. The magnitude of the pressure fluctuation, the intensity of the cross-spectrum and the sound pressure level vary similarly for the change of flow rates. This means that the fluctuation is closely related to the generated noise.2. The pressures on a rotor blade fluctuate in phase and have almost the same magnitude over a blade. Such a remarkable feature cannot be explained by the existing theories.3. As a reason for this, it is assumed that compressibility plays a part due to high unsteadiness.The latter experiment was done to know the usefulness of active control and also to obtain the fundamental data. The result shows that our approach to the active control is much effective. The main results are as follows :1. The reduction of overall noise was obtained by about 11 dB and that corresponding to the blade passing frequency by about 23 dB.2. The phase and the amplitude of sound pressure added by loud speakers coincide with those predicted by the theory.