Numerical analysis of a Kaplan turbine model during transient operation

Hydropower plants are currently being intensively employed for electrical grid regulation. As a consequence, the frequency of start/stops and load variations is considerably increasing, leading to the operation of hydraulic turbines under improper conditions. During the last years, studies have focu...

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Bibliographic Details
Published in:IOP conference series. Earth and environmental science 2019-01, Vol.240 (2), p.22046
Main Authors: Iovănel, R G, Bucur, D M, Dunca, G, Cervantes, M J
Format: Article
Language:English
Subjects:
Boundary conditions
Finite element method
Flow rates
Flow velocity
Hydraulic loading
Hydraulic turbines
Hydroelectric plants
Hydroelectric power
Load fluctuation
Mathematical models
Numerical analysis
Sensitivity analysis
Simulation
Transient operation
Turbines
Velocity distribution
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Summary:Hydropower plants are currently being intensively employed for electrical grid regulation. As a consequence, the frequency of start/stops and load variations is considerably increasing, leading to the operation of hydraulic turbines under improper conditions. During the last years, studies have focused on Francis turbines. The present paper aims to investigate a Kaplan turbine model. The flow through the turbine is modelled during transient operation, from the best efficiency point to a part load operating point, using a moving mesh for the guide vane displacement. The simulations are validated against experimental velocity profiles. A time step sensitivity analysis is performed in order to determine the optimum discretization time. The possibility of using large time steps is explored. The numerically simulated unsteady pressure pulsations on the runner blades are analysed. The influence of the inlet boundary conditions on the accuracy of numerical simulations is studied. The results show that a linear flow rate variation defined during the guide vane closure leads to an overestimation of the turbine head compared to the experimental value due to an overestimation of losses. The second type of boundary conditions, a constant total pressure, results in an underestimation of the flow rate compared to the experimental value due again to an overestimation of the losses.
ISSN:1755-1307
1755-1315
1755-1315
DOI:10.1088/1755-1315/240/2/022046