Design of an Effective Cycloidal Blade System and its Applications

Abstract

A cycloidal blade system resembles cylindrical wheel, with several blades. Its pitch angle is varied collectively with mechanical linkage. This system is able to change the direction and the magnitude of thrust by locating control point eccentrically. As a conventional rotor system used in aircraft and wind turbine, the cycloidal blade system is able to use in VTOL (Vertical Take-Off and Landing) aircraft and vertical axis wind turbine. In this work, a cycloidal blade system is investigated in its theoretical aerodynamic model. An aim of cycloidal blade system for aircraft is to maximize the lift force and thrust. But that of wind turbine is to maximize tangential force. Hence, there are significant differences of theoretical and numerical manner and this work describes how the cycloidal blade system is applied to aircraft or wind turbine effectively. To verify the performance, a twin rotor cyclocopter and cycloidal vertical axis wind turbine are designed and developed. In research of a 110kg class twin rotor cyclocopter is propelled by two cycloidal rotors and one conventional propeller. To obtain numerical data needed in this procedure, computational fluid dynamics was applied. Power transmission using 4-stroke rotary petrol engine was designed, and the whole vehicle by composite blade, etc. was manufactured. The novel cam pitch-control mechanism is installed and the end plate is attached on the tips of the blades for reduction of drag. The twin rotor cyclocopter (weight is 110kg) conducts ground test and the test results compare with theoretical and CFD analysis results. Finally, the twin rotor cyclocopter demonstrates the hovering flight at tethered condition. The cycloidal vertical axis wind turbine actively controls pitch angles of rotor blades to improve turbine efficiency according to wind conditions. It is capable of self-starting through changing the pitch angle pattern and is able to achieve the best operating efficiency. An optimization scheme with Response Surface Method (RSM) was used to find the most efficient design variables while performing CFD analysis with variables of number of blades, chord length, tip speed ratio and maximum pitch angle. For the experiments, a 400W (at 10m/s of wind speed) class cycloidal VAWT was designed and developed. The two kinds of experiments are carried out and compared with the CFD analysis result. The result of the constant wind speed test verified the CFD analysis and the field test in Jeju Island demonstrated its reliability. Furthermore, another cycloidal vertical axis wind turbine which a flap control device is added in the tip of blades is also studied and designed for the highest efficiency. Transforming the blade airfoil into positive or negative cambered, the flap control device operated with simple mechanical linkages.