Study of unsteady aerodynamic loads and structural response of axial flow compressor in compressed air energy storage system

Axial compressors are the core component of large-scale advanced compressed air energy storage (CAES) systems, and their aerodynamic performance and flow loss characteristics directly determine the energy conversion efficiency and operational stability of the whole system. To reveal the unsteady flow mechanism and energy loss characteristics induced by the rotor‒stator interaction, a full-channel three-dimensional unsteady numerical method is adopted to investigate the time-domain and frequency-domain features of the rotor blade aerodynamic load, as well as the entropy generation and flow loss distribution under the combined effect of the upstream inlet guide vane (IGV) wake and downstream stator potential flow. The results indicate that the unsteady aerodynamic characteristics are dominated by the IGV wake, while the potential flow shows a more significant influence on the pressure surface. The main excitation frequencies include the IGV wake passing frequency, its second harmonic, the potential-flow sweeping frequency, and twice the rotational frequency. The entropy production and aerodynamic fluctuation energy are higher at the blade tip region and on the pressure surface, and the energy caused by wake excitation is evidently higher than that caused by potential flow disturbance. Quantitatively, the time-averaged unsteady aerodynamic load under rotor‒stator interaction is larger than the steady aerodynamic load; compared with the steady flow field, the maximum equivalent stress and total deformation of the rotor blades increase by 2.9 and 3.2%, respectively. The transient dynamic stress response at the critical position of the rotor blade has no obvious periodicity, and the maximum transient dynamic stress reaches 13.594 MPa. The rotor‒stator interaction enhances the unsteady flow loss and local pressure pulsation, thereby slightly affecting the compressor efficiency and stable operating range. This study clarifies the unsteady flow loss mechanism and aerodynamic excitation law in axial compressors for CAES systems, which can provide important theoretical support for the high-efficiency aerodynamic design and energy-saving optimization of large-scale compressed air energy storage systems.