Characteristics of the axial compressor with different stator gaps in compressed air energy storage system

Abstract

The axial compressor in compressed air energy storage (CAES) system needs to operate stably and efficiently within a wide working range. The stator gap plays a critical role in suppressing corner separation and enhancing blade throughflow. The primary objective of this study is to determine the optimal combination of stator gaps to further expand the stable working range of the compressor while ensuring high efficiency. In this study, the flow characteristics of different stator gaps of the five-stage axial compressor in a specific CAES system are researched numerically. Firstly, the impact of different stator gaps on the aerodynamic performance is analyzed. The stator gap effectively broadens the stable working range of the compressor, with the hub gap exhibiting greater potential for expansion compared to the shroud gap. Subsequently, a comparative analysis is conducted on the internal flow of the third stage stator under near-stall conditions. Different gap leakage forms different vortex structures, and the gap leakage can effectively eliminate the accumulation of low-energy fluid in the corner area, optimize the limit streamlines on the blade suction surface and the temperature distribution. The low-velocity area caused by different stator gaps is also different. Finally, energy loss and energy dissipation with different stator gaps are explored. The gap leakage flow results in high energy loss, and different stator gaps exhibit notable differences in distribution of the high energy loss regions. Different types of stator gaps exhibit consistent high energy dissipation areas, which include the leading-edge stagnation area, boundary layer area on blade surface, and wake area. It is important to note that the high energy loss area does not necessarily coincide with the high energy dissipation area. The combined application of two loss evaluation methods contributes to a more comprehensive investigation of the loss distribution characteristics of the compressor.