Assessment of two-phase unsteady leakage flow induced blade vibration in subsea counter-rotating axial flow compressor

As a novel lift method for subsea oilfield development, the subsea counter-rotating axial compressor can achieve a higher pressure ratio with a smaller size through a row of counter-rotating blades. However, unsteady tip leakage flow inevitably exists due to the clearance between blade tips, which may cause blade vibration and lead to fatigue failure eventually. Here, a numerical study based on fluid-structure interaction analysis is conducted on a laboratory subsea counter-rotating compressor to investigate its tip leakage flow-induced vibration characteristics. Firstly, the unsteady two-phase flow field is simulated using computational fluid dynamics. Flow characteristics and aerodynamic force are obtained. Then, the aerodynamic force is loaded on the blade surface to achieve the one-way fluid-structure interaction analysis. Finally, finite element analysis simulations are performed to obtain the blade vibration characteristics. Simulation results show that rotating speed has a dominant influence on high-cycle fatigue failure. A potential fatigue risk is identified at 4250 rpm, where the maximum stress (680–713 MPa) exceeds the yield strength (580 MPa) of the blade material. A two-phase turbulence unsteady flow model is established here to simulate the state of the working fluid more accurately. A simplified unsteady flow simulation method for counter-rotating compressors is applied to save computational cost. Besides, the fluid-structure interaction analysis technique presented here helps understand blade vibration mechanisms, facilitating anti-vibration design with reduced reliance on physical experiments. It also serves to identify potential fatigue failures caused by unsteady tip leakage flow, ensuring the secure operation of subsea counter-rotating axial compressors.