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Publication Title | Unidirectional Radial-Air-Turbine OWC Wave Energy Converters

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energies
Article
Design Optimisation of a Unidirectional Centrifugal Radial-Air-Turbine for Application in OWC Wave Energy Converters
Nazanin Ansarifard 1,*, Alan Fleming 1, Alan Henderson 2, S.S. Kianejad 1 and Shuhong Chai 1
1 2
Received: 13 June 2019; Accepted: 17 July 2019; Published: 19 July 2019
Australian Maritime College, University of Tasmania, Maritime way, Newnham, TAS 7248, Australia
School of Engineering, University of Tasmania, Sandy Bay, TAS 7001, Australia * Correspondence: nazanin.ansarifard@utas.edu.au
Abstract: Research on employing unidirectional air turbines for oscillating water columns (OWC) has received much attention in the last few years. Most unidirectional turbine topologies considered to date use axial flow unidirectional turbines. The radial turbine offers an alternative with increased resistance to backflow. However, in general, the efficiency of radial turbines is lower than axial turbines. This study describes a computational fluid dynamics (CFD)-based design optimisation of an outflow radial turbine for the intended application in an OWC system configured to enable primarily unidirectional flow through the turbine. The rotor blade geometry is parametrically described in addition to other turbine components. The central composite design (CCD) and genetic algorithm were used to explore an optimum design of a centrifugal radial turbine for a maximum total-to-static efficiency. Seven computer aided design (CAD) parameters were investigated as the design variables, and the optimum turbine design was identified in a population of 79 design points. The optimum outflow turbine was found to have a peak steady-state efficiency of 72%, and the leading-edge angle, guide vane angle, trailing edge angle, and the chord length were found to have the highest sensitivity. Compared to an inflow radial turbine, the geometrical features of the outflow turbine permit higher absolute velocities of the flow at the rotor entrance and increase the dynamic pressure changes across the rotor. Therefore, the optimised outflow radial turbine can obtain acceptable rotor energy transfer despite having a negative centrifugal energy transfer term.
Keywords: outflow radial air turbine; optimisation; efficiency maximization; computational fluid dynamics (CFD); wave energy conversion; OWC; twin-turbine; vented
1. Introduction
An oscillating water column (OWC) is a well-known type of wave energy converter (WEC). The incident waves cause the water level inside the OWC chamber to oscillate. The oscillations of the water column cause a pressure differential between the atmosphere and the settling chamber. This pressure differential drives a turbine, mounted on top of the chamber, and mechanical power is produced. This mechanical power is then converted to electricity by a directly coupled electric generator.
In the current WEC industry, initiatives are required to reduce the cost of harnessing renewable energy and drive down the levelized cost of energy (LCOE) [1]. Efficient wave to wire performance of the OWC converter requires design optimisation of different parts of the conversion chain [2]. Research on the OWC, Power Take-Off (PTO), and generator units has been expanded in recent years to identify efficient designs of these elements and maximize the energy conversion of the whole system [3].
To date, self-rectifying turbines have been almost extensively used in OWC plants, due to the capability to operating in bidirectional flows which eliminated the requirement for air valves.
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Energies 2019, 12, 2791; doi:10.3390/en12142791 www.mdpi.com/journal/energies

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MicroAD: This research and pdf compilation was sponsored Infinity Turbine Turn your waste heat into energy to save on grid based power or sell back to the grid Organic Rankine Cycle utilizes waste heat to make power. Infinity Turbine Waste Heat to Power Solutions

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