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Numerical analysis of a unidirectional axial turbine for twin turbine configuration

2014; Elsevier BV; Volume: 47; Linguagem: Inglês

10.1016/j.apor.2014.03.003

1879-1549

Bruno Pereiras, Pablo Valdez, Francisco Castro,

Cavitation Phenomena in Pumps

One of the most developed technologies in ocean energy is the OWC concept. It is well-known that the efficiency of the device is closely related to the efficiency of the Power-Take-Off (PTO) which is usually a turbine. Traditionally, self-rectifying turbines are the most widely considered for working in an OWC because unidirectional turbines require a system of valves to rectify the flow. However, another option has been recently proposed: "twin turbine" configuration. This paper is focused on the performance of the turbines used in this configuration. A CFD model has been created in Fluent® software and validated with data from the bibliography. This model has been used to analyze the flow field of the turbine when working in both operation modes: direct and reverse. Flow angles and loss distribution have been analyzed and interesting conclusions can be extracted. The efficiency of the twin turbine configuration has been calculated from the results of the numerical model. The calculations have been made paying attention to the effect of the torque and the flow rate of the turbine which is working in reverse mode. The results obtained are the core of this work. Once the flow field has been analyzed, changes in the turbine geometry are proposed in order to improve the efficiency of the whole system by increasing the blockage made by the turbine in reverse mode. These changes were focused on the solidity of the rotor and guide vanes.