Investigation of the unsteady flow mechanism in a centrifugal compressor adopted in the compressed carbon dioxide energy storage system

• Published in: Journal of energy storage 2024-12, Vol.104, p.114488, Article 114488
• Main Authors: Zhang, Lei, An, Guangyao, Lang, Jinhua, Yang, Fan, Yuan, Wei, Zhang, Qian
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Centrifugal compressor; Energy storage technology; Flow unsteadiness; vortex breakdown
• ISSN: 2352-152X
• DOI: 10.1016/j.est.2024.114488

The efficiency and stability of centrifugal compressors, which serve as a crucial element in the compressed carbon dioxide (CO2) energy storage technology, are influenced by the complex unsteady flow within the flow field. The evolution mechanism of flow unsteadiness from design condition to near-stall condition in the compressor were investigated in this study. The results indicated that during the process from the design condition to near-stall condition, the tip leakage vortex (TLV) underwent a transition from a stable state to an unstable state, which was manifested as the breakdown of TLV and subsequently gave rise to a new vortex structure named the leading edge vortex (LEV). Similarly, a separation vortex (SV) formed by flow separation on the suction side of the blade experienced a transition from stable to unstable and then back to stable. The aforementioned process contributed dominant flow fluctuation with frequencies of 0.21 times blade passing frequency (BPF), 1.04 BPF and 1.08 BPF. Specifically, the unsteady fluctuation of 0.21 BPF was a result of the periodic motion of the LEV which was formed after the TLV breakdown. The periodic oscillation of the SV breakdown regions caused an unsteady fluctuation of 1.04 BPF. The periodic motion of the low-speed regions in the diffuser accounted for the unsteady fluctuations of 1.08 BPF. This work is supposed to shed lights on a better understanding of the internal flow field of S-CO2 compressors which is beneficial for the safety operation and performance improvement of the compressed CO2 energy storage system. •The evolution mechanism of flow unsteadiness in a centrifugal compressor adopted•To the compressed CO2 energy storage technology is investigated.•Time–frequency analysis was introduced to resolve the characteristics of the unsteady flow.•The evolution mechanism of flow structures corresponding to different unsteady flow perturbations was revealed.