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<p>The complex three-dimensional flow within the last turbine stage under low-load condition intensifies internal flow instabilities, decreasing turbine efficiency and operational reliability. In this paper, to investigate the flow instability characteristic of air turbine used in Compressed Air Energy Storage (CAES) systems, three-dimensional unsteady numerical simulations are conducted on two-stage axial flow turbines, namely a small-scale turbine (AT-S) and a large-scale turbine (AT-L). Two low-load conditions of AT-S with a radial inlet chamber (RIC) were firstly analyzed. At the lowest relative mass flow (<i>m</i><sub>rel</sub>) of 0.18, no rotating instability (RI) and rotating stall (RS) phenomena were observed in AT-S, which features an aspect ratio of 2.4 for the last-stage rotor blades (R2). However, vortex instability was observed in the RIC, and it was not related to the occurrence of RI or RS. Thus, analysis on four low-load conditions of AT-L without RIC was conducted, where the R2 aspect ratio is 5.4. When <i>m</i><sub>rel</sub> was reduced to 0.28, RI occurred. As <i>m</i><sub>rel</sub> furtherly decreased to 0.18, RS occurred. The RI and RS phenomena were accompanied by disturbance clusters appearing at the blades top. Different flow modes were observed in RI and RS, which features with different combinations of Through-flow mode (TM), Choke mode (CM), and Separation mode (SM). This study not only considers the influence of the RIC, but also the factors of blade length on flow instabilities of CAES turbine.</p>

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Flow Instabilities in Axial Turbines of Compressed Air Energy Storage System under Low-Load Conditions

  • 期刊论文

  • 发表日期：

    2025年6月26日

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  • Gongrui Huang,
  • Jun Xiong,
  • Yangli Zhu,
  • Xing Wang,
  • Junfeng Wang,
  • Haisheng Chen

摘要

The complex three-dimensional flow within the last turbine stage under low-load condition intensifies internal flow instabilities, decreasing turbine efficiency and operational reliability. In this paper, to investigate the flow instability characteristic of air turbine used in Compressed Air Energy Storage (CAES) systems, three-dimensional unsteady numerical simulations are conducted on two-stage axial flow turbines, namely a small-scale turbine (AT-S) and a large-scale turbine (AT-L). Two low-load conditions of AT-S with a radial inlet chamber (RIC) were firstly analyzed. At the lowest relative mass flow (mrel) of 0.18, no rotating instability (RI) and rotating stall (RS) phenomena were observed in AT-S, which features an aspect ratio of 2.4 for the last-stage rotor blades (R2). However, vortex instability was observed in the RIC, and it was not related to the occurrence of RI or RS. Thus, analysis on four low-load conditions of AT-L without RIC was conducted, where the R2 aspect ratio is 5.4. When mrel was reduced to 0.28, RI occurred. As mrel furtherly decreased to 0.18, RS occurred. The RI and RS phenomena were accompanied by disturbance clusters appearing at the blades top. Different flow modes were observed in RI and RS, which features with different combinations of Through-flow mode (TM), Choke mode (CM), and Separation mode (SM). This study not only considers the influence of the RIC, but also the factors of blade length on flow instabilities of CAES turbine.