In the past few decades, “buzz-saw” noise was mostly measured and predicted along the shroud wall. Uniform or nonuniform axial flows were applied to the predictions. Besides, the strength of the “buzz-saw” noise was widely assumed to be identical along the radius. However, nonuniform background flows and distinct radial distributions of shock strength are observed in almost all transonic fans. A possible way to solve these problems is to couple the shock trajectory with the evolution of the shock wavefront. In case the state of background flow field varies slowly, the shock trajectory is depicted by geometric acoustics. Meanwhile, the evolution of the wavefront can be solved by the governing equation of the weak-shock. Under this framework, a method is proposed to tackle the prediction of the “buzz-saw” noise under nonuniform axial and radial flows. This method is first validated by the test data from the literature. Then, it is applied to predict the near-field noise generated by the ideal and four modified versions of NASA rotor 67. The results indicate that the nonuniform radial and axial flows introduced by the wall boundary have strong effects on the distribution of the “buzz-saw” noise. Additionally, the eccentric-force problem is revealed as a side effect of blade sorting, which is an efficient method to suppress the “buzz-saw” noise. A bi-pyramid blade sorting strategy is proposed to suppress the eccentric force introduced by other blade sorting strategies.

中文翻译：

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轴流和径向流不均匀时“蜂鸣”噪声传播的预测

在过去的几十年中，“嗡嗡声”噪声主要是沿着围墙测量和预测的。将均匀或不均匀的轴向流应用于预测。此外，广泛认为“蜂鸣”噪声的强度沿半径方向是相同的。但是，几乎在所有跨音速风扇中都观察到不均匀的背景流和明显的径向抗冲击强度分布。解决这些问题的一种可能方法是将冲击轨迹与冲击波前的发展耦合起来。如果背景流场的状态变化缓慢，则通过几何声学来描绘冲击轨迹。同时，波前的演化可以通过弱震的控制方程来求解。在这个框架下 提出了一种方法来解决轴向和径向流不均匀情况下“蜂鸣”噪声的预测问题。首先通过文献中的测试数据验证此方法。然后，它被用于预测理想和四个改进版本的NASA转子67产生的近场噪声。结果表明，壁边界引入的不均匀的径向和轴向流动对“嗡嗡声”的分布有很大影响-锯”的声音。此外，偏心力问题是由于叶片分选的副作用而暴露出来的，这是抑制“蜂鸣”噪声的有效方法。提出了一种双金字塔叶片分类策略，以抑制其他叶片分类策略引入的偏心力。它被用于预测理想和四个改进版本的NASA转子67产生的近场噪声。结果表明，壁边界引入的不均匀的径向和轴向流动对“蜂鸣锯”的分布有很大影响”噪音。此外，偏心力问题是由于叶片分选的副作用而暴露出来的，这是抑制“蜂鸣”噪声的有效方法。提出了一种双锥体叶片分类策略，以抑制其他叶片分类策略引入的偏心力。它被用于预测理想和四个改进版本的NASA转子67产生的近场噪声。结果表明，壁边界引入的不均匀的径向和轴向流动对“蜂鸣锯”的分布有很大影响”噪音。此外，偏心力问题是由于叶片分选的副作用而暴露出来的，这是抑制“蜂鸣”噪声的有效方法。提出了一种双金字塔叶片分类策略，以抑制其他叶片分类策略引入的偏心力。偏心力问题显示为叶片分类的副作用，这是抑制“蜂鸣”噪声的有效方法。提出了一种双金字塔叶片分类策略，以抑制其他叶片分类策略引入的偏心力。偏心力问题显示为叶片分类的副作用，这是抑制“蜂鸣”噪声的有效方法。提出了一种双金字塔叶片分类策略，以抑制其他叶片分类策略引入的偏心力。