Experiment on the instability process in a one-stage transonic axial compressor

To fully understand the instability process and reveal the occurrence, development and essence of the unstable flow phenomena of one-stage transonic axial compressor with high loading, test investigation was carried out with both steady and dynamic measurements. The analysis was performed by the original signal, the low pass filtering and the FFT (fast Fourier transform) method. The results show that the large amplitude, low frequency axisymmetric axial disturbance appears firstly at the stator hub during the instability process. At that time, there is a decrease in the performance below 50% span of the compressor. But the compressor can still be operated. Meanwhile, considering the features of this disturbance such as low frequency, axisymmetricity, large amplitude, this kind of unstable flow phenomena, named as partial surge, is identified. Then, this disturbance spreads axially and radially with the further decrease of the mass flow. Next, this disturbance extend to the full span. Finally, it leads to the rotating stall cells at the rotor tip region, and the indicating the compressor reached the instability boundary.