Blade pitch

About: Blade pitch is a research topic. Over the lifetime, 5321 publications have been published within this topic receiving 63134 citations.

Optimization of a counter-rotating wind turbine using the blade element and momentum theory

Abstract: A counter-rotating wind turbine has a front rotor and a rear rotor which rotate in opposite directions on the same axis. Compared to a single rotor, the flow field of the counter-rotating wind turbine is complicated due to the interactions between the front rotor and the rear rotor. The wake induced by the front rotor works on the inflow of the rear rotor and is essentially an unsteady flow state. In order to estimate the performance of a counter-rotating wind turbine, it is necessary to consider more variables than the case of a single-rotor wind turbine and to prepare an estimation system capable of performing delicate predictions. For the optimization of a counter-rotating wind turbine, the pitch angles, radius ratios, and rotation speeds of two rotors are chosen as the design values and variations of the power coefficients and thrust coefficients can be observed in this study. The torque balance of the two rotors due to the kinematic coupling of the generator is considered. Modeling by means of the blade element and momentum theory for the optimization of a counter-rotating wind turbine is developed to predict the front rotor flow and the wake flow generated by the front rotor. The wake flow is then applied for the inflow of the rear rotor. A vehicle test is carried out to validate the prediction. The optimized solution is found using a multi-island genetic algorithm.

Control algorithm of a floating wind turbine for reduction of tower loads and power fluctuation

Abstract: A new control algorithm for a MW class spar-type floating offshore wind turbine has been developed to improve its performance and to reduce its mechanical load. The new blade pitch control having two PI control loops applied for different wind speed regions were designed. The bandwidth of the controller at near above-rated wind speed region was made lower to keep the vibration mode of the floating platform from being driven, and the bandwidth of the controller at far above-rated wind speed region was made higher to improve the wind turbine performance. Also, a feedback control loop using the angular acceleration information of the nacelle in the fore-aft direction was designed additionally to reduce the tower vibration. To perform modeling and simulation, a commercial multidynamics simulation program widely used for wind turbine design and certification, DNV-GL Bladed was used. The DNV-GL Bladed simulation results for the proposed new control algorithm showed that the output performance is improved and the tower load is reduced in various wind speeds above the rated wind speed.

Vortex shedding cyclical propeller

Abstract: A propeller having one or more blades eccentrically mounted to a shaft dynamically changes the blade pitch to produce free vortices in a fluid. For extracting energy from a moving fluid, the fluid flow acting on the blades rotates the propeller, while the pitch changes create a fluid flow pattern known as a von Karman vortex street. The resulting time averaged flow field distant from the propeller is a wake flow, and the energy of the fluid flow can be efficiently converted to rotation of a shaft driven device. For propulsion, applied shaft rotation and the dynamic pitch change in a fluid together create a flow pattern that is the inverse of the von Karman vortex street. For either energy extraction or propulsion, the propeller is particularly suited for low flow speeds, where the effects of low Reynolds number induced flow separation on blades may make other propellers inefficient.

Aircraft propeller construction

Abstract: This invention relates to propellers adapted for use with aircraft and more particularly to a novel composite propeller construction. Air screws as used nowadays are designed for -the increasing engine power and the increasing blade speed of modern aircraft. However, the customary propeller...

Wind turbine generator and blade pitch angle control method thereof

Abstract: The present invention provides a wind turbine generator and a blade pitch angle control method thereof in which an aerodynamic imbalance of a wind turbine rotor at the time of shutdown is further reduced, the maximum load of a wind turbine is further reduced, and the wind turbine generator can be reduced in weight and cost. The wind turbine generator includes a collective pitch angle controller 11 that produces a collective pitch angle demand that is common to blade pitch angles of wind turbine blades, an individual pitch angle producing unit 13 that produces an individual pitch angle demand inherent in each wind turbine blade, multipliers 21 to 23 that multiply the individual pitch angle demand by the individual pitch angle gain, an individual pitch angle gain producing unit 14, and adder 24 to 26 that add collective pitch angle demands to the output of the multipliers 21 to 23 and supply the same to pitch actuators 31 to 33 inherent in the wind turbine blades. When shutdown is performed, the individual pitch angle gain is adjusted such that a individual pitch angle gain is reduced gradually and reaches to zero by the individual pitch angle gain producing unit 14 after first set time.