Abstract
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.
Highlights
Japan is surrounded by the ocean, and abundant wave energy exists around the country
The oscillating water column (OWC)-based power generator converts the wave energy into the electrical energy driving an air turbine coupled with an electrical generator by means of the reciprocating air flow generated in the air chamber [1]
The rectification effect of the fluidic diode has been investigated by using a computational fluid dynamics (CFD) analysis
Summary
Japan is surrounded by the ocean, and abundant wave energy exists around the country. The oscillating water column (OWC) type wave energy converter was used because of its simple structure and the characteristic feature of the use in abnormal sea conditions. The OWC-based power generator converts the wave energy into the electrical energy driving an air turbine coupled with an electrical generator by means of the reciprocating air flow generated in the air chamber [1]. A twin-impulse turbine as shown in Figure 1 has been developed for the OWC-based wave energy converter. In this study, the flow rectification performance of fluidic diode was investigated by a computational fluid dynamics (CFD) analysis. In order to achieve a further improvement in the rectification characteristics, the rectification effect of the fluidic diode was investigated when a bypass, aimed at increasing the flow rate in the forward flow turbine, was provided into a blunt body
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