The investigation of a coaxial twin-counter-rotating turbine with variable-pitch adaptive blades

Tidal current turbine need to utilize the tidal kinetic energy of the two flow directions of high tide and low tide. Most of the previous power flow energy units used electric motors or hydraulic systems to pitch. This thesis proposes a new design in which the turbine employs swept-back flat blades with a NACA0012 airfoil cross-section, allowing the blades to easily change pitch and adapt to changes in flow direction through the use of hydrodynamic forces. The installation angle of the blades can be adjusted within 15°, and the pitch angle varies according to the flow velocity, with a range of plus or minus 15°. Magnetic coupling is also used to transmit torque in the prototype, rather than the traditional shaft seal or dynamic seal and the static seal greatly improves the equipment's reliability. The article also thoroughly investigates the effects of a self-pitching double turbine's front and rear turbines, as well as the performance comparison with a single turbine. Theory, simulation, and experiment are used to validate the design's innovation and feasibility. •The pitch angle of swept-back flat blades with NACA0012 airfoil changes with flow direction and velocity.•The magnetic coupling disc modifies the torque transmission in the tidal current turbine.•The performance of self-pitching twin turbines outperforms that of a single turbine.