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A Twin Unidirectional Impulse Turbine for Wave Energy Conversion

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Journal of Thermal Science 2011年第5期20卷 394-397页

作者： Manabu Takao Akiyasu Takami shinya okuhara Toshiaki Setoguchi Matsue College of Technology 14-4 NishiikumaMatsueShimane 690-8518Japan Saga University 1 HonjoSagaSaga 840-8502Japan

A twin unidirectional impulse turbine has been proposed in order to enhance the performance of wave energy *** turbine system uses two unidirectional impulse turbines and their flow direction is different from each ***,the turbine characteristics have not been clarified to *** performances of a unidirectional impulse turbine under steady flow conditions were investigated experimentally by using a wind tunnel with large piston/cylinder in this ***,efficiency of the twin impulse turbine have been estimated by a quasi-steady analysis using experimental results.

关键词：冲击式水轮机单向波能转换涡轮机流动方向轮机系统准稳态活塞

Wells Turbine for Wave Energy Conversion —Improvement of the Performance by Means of Impulse Turbine for Bi-Directional Flow

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Open Journal of Fluid Dynamics 2013年第2期3卷 36-41页

作者： shinya okuhara Manabu Takao Akiyasu Takami Toshiaki Setoguchi Department of Mechanical Engineering Matsue College of Technology Matsue Japan Institute of Ocean Energy Saga University Saga Japan Techno Center Matsue College of Technology Matsue Japan

Wells turbine has inherent disadvantages in comparison with conventional turbines: relative low efficiency at high flow coefficient and poor starting characteristics. To solve these problems, the authors propose Wells turbine with booster turbine for wave energy conversion, in order to improve the performance in this study. This turbine consists of three parts: a large Wells turbine, a small impulse turbine with fixed guide vanes for oscillating airflow, and a generator. It was conjectured that, by coupling the two axial flow turbines together, pneumatic energy from oscillating airflow is captured by Wells turbine at low flow coefficient and that the impulse turbine gets the energy at high flow coefficient. As the first step of this study on the proposed turbine topology, the performance of turbines under steady flow conditions has been investigated experimentally by model testings. Furthermore, we estimate mean efficiency of the turbine by quasi-steady analysis.

关键词： Fluid Machinery Wells Turbine Impulse Turbine Wave Energy Conversion Ocean Engineering

A Twin Unidirectional Impulse Turbine for Wave Energy Conversion

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Open Journal of Fluid Dynamics 2012年第4期2卷 343-347页

A twin unidirectional impulse turbine has been proposed in order to enhance the performance of wave energy plant. This turbine system uses two unidirectional impulse turbines and their flow direction is different each other. However, the effect of guide vane solidity on the turbine characteristics has not been clarified to date. The performances of a uni- directional impulse turbine under steady flow conditions were investigated experimentally by using a wind tunnel with large piston/cylinder in this study. Then, mean efficiency of the twin impulse turbine in bidirectional airflow has been estimated by a quasi-steady analysis using experimental results in order to investigate the effect of guide vane solidity on the performance.

关键词： Fluid Machinery Impulse Turbine Wave Energy Conversion Ocean Energy

A Twin Unidirectional Impulse Turbine for Wave Energy Conversion—Effect of Fluidic Diode on the Performance

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Open Journal of Fluid Dynamics 2014年第5期4卷 433-439页

作者： shinya okuhara Manabu Takao Hideki Sato Akiyasu Takami Toshiaki Setoguchi Support Center for Practical Education National Institute of Technology Matsue College Matsue Japan Department of Mechanical Engineering National Institute of Technology Matsue College Matsue Japan Advanced Engineering Faculty National Institute of Technology Matsue College Matsue Japan Institute of Ocean Energy Saga University Saga Japan

As a system using a conventional unidirectional air turbine in oscillating water column (OWC) based on a wave energy plant, a twin unidirectional impulse turbine topology has been suggested in previous studies. However, the average efficiency of the suggested twin turbine is considerably lower than that of a conventional unidirectional turbine in this topology because reciprocating air flow can’t be rectified adequately by a unidirectional turbine. In order to improve the efficiency, using fluidic diode is discussed. In this study, two different fluidic diodes were discussed by computational fluid dynamics (CFD) and a wind tunnel test. Further, its usefulness is discussed from a view point of the turbine efficiency. The fluidic diode was shown to improve rectification of the topology. However, it needs more improvement in regards to its energy loss in order to enhance the turbine efficiency.

关键词： Fluidic Diode Twin Unidirectional Turbine Wave Energy Conversion Oscillating Water Column

A Study on Fluidic Diode for Wave Energy Conversion-Effect of Bypass Geometry on the Turbine Performance

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Open Journal of Fluid Dynamics 2020年第3期10卷 270-278页

作者： Keito Matsumoto Manabu Takao shinya okuhara Miah Md. Ashraful Alam Yoichi Kinoue National Institute of Technology Matsue College Matsue Japan Institute of Ocean Energy Saga University Saga Japan

A twin-impulse turbine for bi-directional flow has been developed for wave energy converter. However, the previous studies elucidated that the mean efficiency of the twin turbine is much lower than that of the impulse turbine for a unidirectional flow because a portion of airflow passes through the reverse flow turbine whose efficiency is very low. Therefore, a fluidic diode was adopted in the twin-impulse turbine in order to reduce the air flow through the reverse flow turbine. In this study, the rectification effect of the fluidic diode was investigated where a bypass is introduced into a blunt body. A computational fluid dynamics (CFD) analysis was conducted to investigate the effect of fluidic diodes on the turbine performance. In this analysis, RANS equations were used as the governing equations and the standard k-ε model was used as the turbulence model. The computational domain is composed of a circular tube and fluidic diode, and the domain meshed with an approximately 1.5 million mesh elements. As a result, it was found that the rectification effect of the fluidic diode is enhanced by installing a blunt body with a bypass hole of 5° taper angle.

关键词： Fluidic Diode Wave Energy Conversion Twin-Impulse Turbine CFD Analysis

A Counter-Rotating Impulse Turbine for Wave Energy Conversion

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Open Journal of Fluid Dynamics 2018年第4期8卷 435-442页

作者： Manabu Takao Kohei Yamada shinya okuhara M. M. Ashraful Alam Yoichi Kinoue Toshiaki Setoguchi Department of Mechanical Engineering National Institute of Technology Matsue College Matsue Japan Advanced Course of Production and Construction Systems National Institute of Technology Matsue College Matsue Japan Support Center for Practical Education National Institute of Technology Matsue College Matsue Japan Department of Mechanical Engineering Saga University Saga Japan Institute of Ocean Energy Saga University Saga Japan

Wave energy can be converted to the electrical energy by using a wave energy converter. The wave energy converter with oscillating water column (OWC) is one of the most promising devices because of its simple structure and easy maintenance. In this device, an oscillating water column due to the wave motion is used to drive an air column. An air turbine is used to convert the pneumatic energy of this bi-directional airflow into the mechanical energy. The counter-rotating impulse turbine for wave energy conversion has been proposed and tested so far, and the average efficiency has been shown to about 0.3. On the contrary, in another offshore experiment, it has been reported that the power generation efficiency of this turbine is larger than Wells turbine in case of small waves. However, there is a scarcity of the detailed characteristics data of counter-rotating impulse turbine. In a previous study, the authors investigated the effect of rotor blade solidity and setting angle of guide vane on the performance of this turbine, and they clarified that the efficiency of this turbine is higher than impulse turbine with single rotor in the range of high flow coefficients. The present study aimed to investigate the effect of rotor blade profile on the turbine performance by using the computation fluid dynamic (CFD) analysis. The inner and outer angles of turbine rotor blade are changed in the range of 50° to 70°. The commercial CFD software of SCRYU/Tetra of Cradle Co. Ltd. was used in the present work. The Reynolds averaged Navier-Stokes (RANS) equations were used as the governing equations and the low Reynold’s number SST k-ω model was used to predict the turbulent stresses. As a result, it was found that the inner angle of γ = 70° and the outer angle of γ = 60° of the turbine rotor blades can give the best turbine efficiency and it shows the efficiency close to the impulse turbine with single rotor, even in the range of low flow coefficients.

关键词： Air Turbine CFD Fluid Machinery Oscillating Water Column (OWC) Wave Energy Conversion