A contra-rotating fan offers several aerodynamic advantages that make it a potential candidate for future aircraft engine configurations. Stall in a contra-rotating axial fan is interesting since instabilities could arise from either or both of the rotors. In this experimental study, a contra-rotating axial fan is analysed under clean or distorted inflow conditions to understand its performance and stall inception characteristics. The steady and unsteady measurements identified the relative contribution of each rotor towards the performance of the stage. The tip of rotor-1 is identified to be the most critical region of the contra-rotating fan. The contribution of rotor-2 to the overall loading of the stage is observed to be relatively less than rotor-1. The penalty due to distortion in the stage pressure rise is mostly felt by rotor-1, while rotor-2 also shows a reduction in performance for distorted inflows. Rotor-2 stalls at a high flow coefficient marking the initiation of partial stall of the stage, and the stall of the whole stage occurs once rotor-1 stalls. A fluid phenomenon that is attached to the blade surface marks the stall of rotor-1, and this fluid phenomenon initially rotates at a speed close to the speed of rotation of the blade. As the stage moves towards the fully developed stall, this fluid phenomenon sheds from the blade surface. The fluid phenomenon thus propagates at a speed much lower than the rotational speed of the blade during fully developed stall.

中文翻译：

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扭曲进流对对转风机性能的影响

对转风扇具有多种空气动力学优势，使其成为未来飞机发动机配置的潜在候选者。对转轴流风扇中的失速是有趣的，因为不稳定可能来自一个或两个转子。在这项实验研究中，对旋转轴流风机在清洁或扭曲流入条件下进行分析，以了解其性能和失速初始特性。稳态和非稳态测量确定了每个转子对舞台性能的相对贡献。转子 1 的尖端被确定为对转风扇最关键的区域。观察到转子 2 对级的整体负载的贡献相对小于转子 1。一级压力上升失真造成的损失主要由转子 1 感受到，而转子 2 也显示出扭曲流入的性能下降。转子 2 以高流量系数失速标志着该级部分失速的开始，一旦转子 1 失速，整个级就会发生失速。附着在叶片表面的流体现象标志着转子 1 的失速，并且这种流体现象最初以接近叶片旋转速度的速度旋转。随着平台向完全发展的失速移动，这种流体现象从叶片表面脱落。因此，流体现象以远低于完全发展失速期间叶片旋转速度的速度传播。并且一旦转子1失速，就会发生整个阶段的失速。附着在叶片表面的流体现象标志着转子 1 的失速，并且这种流体现象最初以接近叶片旋转速度的速度旋转。随着平台向完全发展的失速移动，这种流体现象从叶片表面脱落。因此，流体现象以远低于完全发展失速期间叶片旋转速度的速度传播。并且一旦转子1失速，就会发生整个阶段的失速。附着在叶片表面的流体现象标志着转子 1 的失速，并且这种流体现象最初以接近叶片旋转速度的速度旋转。随着平台向完全发展的失速移动，这种流体现象从叶片表面脱落。因此，流体现象以远低于完全发展失速期间叶片旋转速度的速度传播。