Based on Shear Stress Transport (SST) turbulence model for unsteady simulation of an axial-flow fan, this paper studies the time-frequency information in the hump region, and investigates the disturbance information of spike and modal wave under different flow coefficients based on continuous wavelet transform (CWT). The results show that before the hump point, the low-frequency modal wave occupies the main disturbance form and circularly propagates at 1/10 of the rotor speed, and the axial-flow fan does not enter the stall stage; while after the flow coefficient reduces to the hump point, the spike wave with higher frequency replaces the modal wave as the main disturbance mode while the axial-flow fan enters the stall stage. Through in-depth investigation of unsteady flow characteristics under the hump point, it is found that after experiencing the emerging spike, with the sharp increase of incidence angle, some flow distortions appear on the intake surface, and further induce some flow paths to form stall vortices. When a path goes into stall stage, the airflow state is greatly affected, the inverse flow and air separation phenomenon in the rim region increase significantly, and the flow capacity decreases significantly, so the flow capacity in the hub region increases correspondingly. The flow path distortion of tip leakage flow (TLF) and leading edge (LE) spillage caused by the stall vortices are the main inducements of rotating stall.

中文翻译：

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失速条件下轴流风机的非定常流动特性研究

基于剪切应力传递湍流模型，对轴流风扇进行非稳态仿真，研究了驼峰区域的时频信息，并基于连续性研究了不同流量系数下尖峰和模态波的扰动信息。小波变换（CWT）。结果表明，在驼峰点之前，低频模态波占主要干扰形式，以转子速度的1/10循环传播，轴流风机不进入失速阶段。当流量系数降低到驼峰点后，当轴流风机进入失速阶段时，频率较高的尖峰波取代了模态波成为主要的扰动模式。通过深入研究驼峰点下的非定常流动特性，结果发现，在经历了出现的尖峰之后，随着入射角的急剧增加，在进气表面上出现了一些流动畸变，并进一步诱发了一些流动路径以形成失速涡流。当路径进入失速阶段时，气流状态受到很大影响，轮缘区域的逆流和空气分离现象显着增加，流量显着降低，因此轮毂区域的流量相应增加。失速旋涡引起的尖端泄漏流（TLF）和前沿（LE）溢出的流路畸变是旋转失速的主要诱因。气流状态受到很大影响，边缘区域的逆流和空气分离现象显着增加，流量显着下降，因此轮毂区域的流量相应增加。失速旋涡引起的尖端泄漏流（TLF）和前沿（LE）溢出的流路畸变是旋转失速的主要诱因。气流状态受到很大影响，边缘区域的逆流和空气分离现象显着增加，流量显着下降，因此轮毂区域的流量相应增加。失速旋涡引起的尖端泄漏流（TLF）和前沿（LE）溢出的流路变形是旋转失速的主要诱因。