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. Howeve...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.展开更多
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 structur...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.展开更多
文摘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.
文摘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.
