Flow Deflection between Guide Vanes in a Pump Turbine Operating in Pump Mode with a Slight Opening

Abstract

During the startup and shutdown processes of a reversible-pump turbine (RPT) working in pump mode, abnormal sounds and vibrations usually occur in the distributor when the guide vanes (GVs) are at a slight opening (max opening of about 6%). The objective of this paper is to apply a three-dimensional numerical CFD method to study the unsteady flow behavior in the guide vane region of a pump turbine operating in pump mode. The dynamic meshing technique is introduced to simulate the startup and shutdown processes, and it is shown to be critical in accurately capturing the details of the flow pattern variations. In addition, the RNG k-epsilon two-equation turbulence model is applied and the governing equations are discretized with the finite volume method. Moreover, the boundary conditions are set through the calculation of the transient process of the power station. The results show that the main flow between the GVs is deflected during the startup and shutdown processes. In the shutdown process, the deflection occurs when the guide vane opening (GVO) is between 1.99 and 5.32 degrees, on average. In the startup process, the deflection occurs when the GVO is between 2.83 and 4.11 degrees, on average. In these processes, the velocity field and pressure field change dramatically. Simultaneously, the hydraulic torque (HT) on the GVs has a sharp change. The abrupt change in the HT leads to vibrations and abnormal sounds.

Study on the Hydraulic and Energy Loss Characteristics of the Agricultural Pumping Station Caused by Hydraulic Structures

“…This paper uses the continuity equation based on incompressible fluid and the time-averaged Reynolds equation (RANS equation), and the RNG k-ε model was used for the turbulence model. Several studies [23,24] have revealed that the RNG k-ε model can predict the swirling flow and vortex flow very well, and has good applicability in the flow field of the axial flow pump.…”

Redesign of Adjustable Guide Vane Cascades of Pump Turbine and Its Effect on Self-Excited Vibrations at Slight Opening During Pump Mode’s Starting Up Process

“…They found that the length of the lap between guide blades is closely related to the self-excited oscillation of guide vanes, and the vibration problem can be improved by modifying the profile [4]. The dynamic meshing technique was adopted to simulate the starting up and shutting down processes by Q F Ji and H G Fan, to capture the flow details between the guide vanes [7,8,9]. They found that there is bistable flow between guide vanes in pump condition, which was believed to be the cause of abnormal vibration.…”

Numerical Investigation of Guide Vane Hydraulic Torque Characteristics of a Pump Turbine in Pump Mode

“…By introducing the torque variation rate of a single guide vane and CFD flow simulation, they found that the repeating reversal of fluid in the guide vane region is the cause of vibration during load rejection. Ji et al [7] investigated abnormal sounds and vibrations occurring in the distributor of a reversible pump-turbine when guide vanes were slightly opened (maximum opening of about 6%) during the pump mode. They applied a three-dimensional numerical CFD method to study the unsteady flow behaviour in the guide vane region of a pump-turbine operating in pump mode.…”