Numerical Study on the Internal Flow Field of a Reversible Turbine during Continuous Guide Vane Closing

Abstract

The unsteady flow field in a reversible pump-turbine is investigated during the continuous load rejection using a 3D computational fluid dynamic analysis. Numerical calculations are carried out using the detached eddy simulation (DES) turbulence model and a new approach involving automatic mesh motion. In this way, the instability of the flow field is analyzed by continuously changing the guide vane openings from the best efficiency point (BEP). Unsteady flow characteristics are described by post-processing signals for several monitoring points including mass flow, torque, head and pressure in the frequency and time-frequency domains. The formation of vortices of different scales is observed from the origin to further enlargement and stabilization; the effect of the rotating structures on the flow passage is analyzed, and the influence of unsteady flow development on the performance of the turbine is investigated. Finally, the evolution during the period of load rejection is characterized in order to determine the hydrodynamic conditions causing the vibrations in the machine.

Numerical Study of the Axial Gap and Hot Streak Effects on Thermal and Flow Characteristics in Two-Stage High Pressure Gas Turbine

“…The unsteady RANS model used in this study has a low computational cost; however, it has the drawback of being unable to precisely predict vortices and flow separation phenomena that occur around the tips and walls. DES is more accurate; however, it has a high computational cost and previous studies using DES have mostly focused on the local flow phenomena rather than full blade simulations [25][26][27]. With significant advances in computational resources, it is expected that DES or LES will soon be used to accurately predict the complex unsteady flow physics near the tips and walls within full blade simulations.…”

Numerical Modeling of the Hydrodynamic Performance of Slanted Axial-Flow Urban Drainage Pumps at Shut-Off Condition

“…Energies 2022, 15, 1905 3 of 17 In most transient processes, the water flow switches, such as the SGs of axial-flow pumps and the wicket gates of mixed-flow pumps, are the core components to implement the regulation order [30][31][32]. If the switch is not properly handled, a large reverse flow rate may contribute to positive axial force [33,34].…”

Investigation of Pumped Storage Hydropower Power-Off Transient Process Using 3D Numerical Simulation Based on SP-VOF Hybrid Model

“…Li [27] used dynamic mesh to simulate the 3D dynamic turbulent flow of whole flow channels in start transition process and runaway process of bulb hydraulic turbine. Mao [28] investigated unsteady flow field in a reversible pump-turbine during the continuous load rejection by a 3D CFD analysis. Luo [29] carried out a 3D transient numerical simulation method to simulate the runaway process of tubular turbine through secondary development of CFX software and Fortran.…”