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Design of a novel spillway turbine and optimisation of its intake hydrodynamics

Adzic, Filipa 2020. Design of a novel spillway turbine and optimisation of its intake hydrodynamics. PhD Thesis, Cardiff University.
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Abstract

The motivation to expand electricity production from renewable energy sources exists worldwide. A novel, horizontal axis, spillway turbine that attempts to convert high-speed, supercritical flow in steeply sloped channels into electricity is presented in this thesis. The spillway turbine is intended for use in lowhead, low-flow, man-made, concrete-linedchannelssuchaschutes, spillwaysand other similar steeply sloped open-channels. The design of the spillway turbine is inspired by the impulse turbine runner but without a pipe or a nozzle. Thespillwayturbinepresentedinthisthesisconsistsoftherunnerandtheaccelerator channel/wedge that is used to direct the water towards and through the channel blades. The runner design process shows that once the runner is fitted with Pelton-inspired inserts, performance improves both in terms of efficiency and specific speeds. The specific speed and the speed factors calculated confirm that this novel spillway turbine can be categorised as an impulse turbine. The maximum performance efficiency obtained is 43.3 %. The observations made during laboratory testing indicate that the accelerator channel in the final design version could be improved in terms of energy losses inside it if the insight into the hydrodynamics of the flow can be gained. This is the motivation for computational fluid dynamics research into the hydrodynamics of the flow through a contraction. The in-house large-eddy simulation (LES) code Hydro-3D is employed to simulate supercritical flow in a straight-wall, open-channel contraction. The initial channel contraction angle simulated is 6◦, and the ratio of contraction is 2:1, which is the same ratio used in the final accelerator channel design. The LES code solves the filtered Navier-Stokes equations for two-phase flows and uses the level-set method to track the interface between water and air. Overall, a satisfactory agreement of simulated results with experimental data is obtained. Contours of the time-averaged velocities indicate that the flow loses energy and momentum in the contracting channel. The effect of different contraction angles is analysed, and recommendations from numerical simulation research are implemented in the field application prototype of the spillway turbine.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Spillway Turbine; Hydro-Turbine; Low-Head turbine; Large-Eddy simulation; Free-Surface; Open-channel contraction.
Date of First Compliant Deposit: 17 November 2020
Last Modified: 17 Nov 2020 16:33
URI: http://orca.cardiff.ac.uk/id/eprint/136422

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