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

Shinya Okuhara,Manabu Takao,Toshiaki Setoguchi,Akiyasu Takami

doi:10.4236/ojfd.2013.32a006

Abstract

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.

Highlights

Several of the wave energy devices being studied under many wave energy programs in the United Kingdom, Japan, Portugal, India and other countries make use of the principle of an oscillating water column (OWC) [1]
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
The turbine performance under steady flow conditions evaluated by turbine efficiency, torque coefficient CT and input coefficient CA against flow coefficient

Summary

Introduction

Several of the wave energy devices being studied under many wave energy programs in the United Kingdom, Japan, Portugal, India and other countries make use of the principle of an oscillating water column (OWC) [1]. This turbine rotates in a single direction in oscillating airflow and does not require a system of non-return valves. This turbine is one of the simplest and probably the most economical turbines for wave energy conversion. Wells turbine has high noise level and maintenance problem because of high rotational speed

Methods

Results

Conclusion