Abstract
Hydraulic turbine runners experience high excitation forces in their daily operations, and these excitations may cause resonances to runners, which may induce high vibrations and shorten the runner's lifetimes. Increasing the added damping of runners in water can be helpful to reduce the vibration level during resonances. Some studies have shown that the modification of the trailing edge shape can be helpful to increase added damping of hydrofoils in water. However, the influence of blade trailing edge shape on the added damping of hydraulic turbine runners has been studied in a limited way before. Due to the difficulties to study this problem experimentally, the influence of blade trailing edge shape on a Kaplan turbine runner has been studied numerically in this paper and the one-way FSI method was implemented. The performances of three different turbulence models, including the k − ϵ , k − ω SST , and transition SST models, in the added damping simulation of the NACA 0009 hydrofoil were evaluated by comparing with the available results of the two-way FSI simulation in the references. Results show that, unlike the significantly different performances in the two-way FSI method, the performances of all the turbulence models are very close in the one-way FSI method. Then, the k − ϵ turbulence model was applied to the added damping simulation of a Kaplan turbine runner, and results show that the modification of the blade trailing edge shape can be helpful to increase the added damping to some extent.
Highlights
Nowadays, hydropower plays an important role in world electricity generation, and over 21% percent of world electricity is produced by hydropower every year [1]
Compared with the influence of the trailing edge shape on the added damping, its influence on the Kaplan turbine runner is less significant, and for each inlet velocity, the difference between two tailing edge shapes is less than 10%. e reason for this may be because the Kaplan turbine blade is wider than the narrow hydrofoil, and the modal displacement concentrates more on other areas of the blade than the hydrofoil, which determines that the trailing edge shape modification produces less significant influence on the modal force than the hydrofoil, less significant influence on the added damping
Unlike the turbulence model which affects the results of the two-way fluid-structure interaction (FSI) method a lot, the performances of different turbulence models in the on-way FSI method are very close
Summary
Hydropower plays an important role in world electricity generation, and over 21% percent of world electricity is produced by hydropower every year [1]. Gauthier et al developed an improved one-way fluid-structure method with the consideration of the added stiffness and added mass change due to the water flowing and applied this method to investigate the added damping of a hydrofoil and a Kaplan turbine runner [28]. Due to the too high computation cost of the two-way FSI method, in this study, the one-way FSI method in [28] will be used to investigate the influence of the blade trailing edge shape on the added damping of a Kaplan turbine runner. From equations (11) and (12), CF can be obtained for the added damping ratio calculation in equation (4)
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