Numerical study on hydraulic verticallift gate during shutdown process

University essay from KTH/Mekanik; KTH/Mekanik

Abstract: China is undergoing a rapid increase in their development of hydropower.Due to this rapid increase, China has become one of theleading countries in technological solutions regarding the constructionof the hydropower plant. The hydro resources in China are extensivebut building a new power plant is laborious and costly. Upgrading anexisting power plant is therefore of interest. Increasing the volume flowis one way, but this can bring problems to the hydraulic structures.The design of hydraulic gates is crucial for operating a hydropowerplant safely. An emergency gate is especially important as it protectsthe turbine situated downstream of the gate. In this study, a numericalsimulation of the shutdown process of a hydraulic vertical lift gatewas conducted. The simulation was done in two dimensions using theReynolds Navier Stokes Equations (RANS), together with the RNGk ≠ ‘ turbulence model and the Volume of Fluid method (VOF). Thegoal was to extract the pressure distribution around the gate, subsequently,attaining the hydrodynamic forces and also to observe andanalyze the flow surrounding the gate. The simulation was comparedwith existing experimental data, from a 1/18 scale model, for validation.Once the model was validated, eight different cases were tested toimprove the operating conditions. The closing speed of the gate andthe gate bottom angle was altered in order to reduce the down-pullforce and undesirable flow phenomena. It was found that lowering thegate speed to 8.1 m/min would have positive effect. As the gate closesrelatively fast with reduced forces compared to a faster speed, and withless induced vibrations than with a slower speed. Changing the gatebottom angle from 9¶ to 30¶, would also have a considerable positiveinfluence of the lowered gate vibrations. However changing the bottomangle needs to be more thoroughly studied concerning structuraleffects.

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