Numerical investigation of the flow regime and cavitation in the vanes of reversible pump-turbine during pump mode's starting up

摘要

In reversible pump-turbines, cavitation mainly occurs on runner blade especially in pump mode. However, cavitation erosion can be found in the guide and stay vanes. When pump-turbine started up in pump mode, the guide vane kept small opening angle with runner pumping for a relatively long-time. In this study, the submerged jet flow inter-guide-vane was studied during pump mode's starting up to evaluate the easily-ignored vane cavitation. Twenty-six combinations of guide vane opening angle (7 degrees) and flow rate (40% maximum flow rate) were numerically tested in total. Submerged jet flow existed inter-guide-vane induced sudden pressure drop especially when flow rate proportion (against the maximum flowrate) was bigger than the guide vane opening angle proportion (against the maximum opening angle). Pressure can drop to the minimum in the entire domain and induce cavitation under actual conditions. Cavitation mainly generated on the guide vane leading-edge and trailing-edge and probably occurred on the stay vane leading-edge and in the vaneless region. The jet-vortex cavitation in vanes was found possible by interpolating the guide vane opening law. This paper would help researchers to focus and prevent the inter-vane cavitation and summarize a more reasonable law for pump mode's starting up. (C) 2019 Elsevier Ltd. All rights reserved.