Wave energy power take-off typically consists of a Wells turbine. This self-rectifying axial air turbine has shown to be constrained by severe stall at high angle of attack or in the supercritical range. This paper presents an experimental and numerical investigation of the CA9 aerofoil, which was optimised for stall resistance. Analysis was done for a 0.6m rotor and tests were carried out at Re × 5 × l05and Ma × 0.2. Results showed that the CA9 profile was more resistant to stall and had a higher average efficiency than NACA0015; thus being more suitable for wave energy conversion systems. Numerical data was benchmarked using experimental ones and provided ~n insight in the separation mechanism of the flow. Guide vanes improved both starting and running characteristics of rotor.
The ozone depletion and global warming have alerted the international community and urged the need for more focus on alternative "green" sources of energy. Wave energy is showing its potential as a green energy source throughout Europe. Energy conversion plants have been installed in various countries such as U.K., Portugal and Denmark. The prototype plant in the island of Islay, Scotland has been recently connected to the grids and provided the breakthrough required to attract more investment in this area. The Wells self-rectifying air turbine, though being proposed frequently for use in wave energy conversion systems, has still to be further improved and optimised. Probably, improving its range of operation is the key issue to its popularisation. An improvement in range of operation would imply improved average efficiency and require a stall insensitive rotor. It was optimised in terms of the leading edge radius, maximum thickness position and trailing edge slope, so as to enhance the pressure distribution around the aerofoil shape blade and improve resistance to stalling.
