Blade pitch

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

Horizontal axis wind generator having adaptive cyclic pitch control

Abstract: Cyclic pitch variation of the rotor blades of a horizontal axis wind energy conversion machine permit its operation at substantially design rotor speed and rotor torque over a range of wind speeds, by heading the rotor progressively out of the wind through a range from approximately 20° for light winds to a near 90° setting for gales, at which the power output is interrupted to permit the rotor to idle. Changes in wind direction will cause the rotor to follow the wind even though so headed out of it. By allowing the blades substantial freedom to adapt their pitch to side winds, the present construction allows rapid rates of yaw into a shifting wind, such as may destroy conventional rotors by the attendant gyroscopic forces. Further, by actively controlling their pitch, aerodynamic forces exerted by the cyclic pitch change blades substantially balance out the gyroscopic forces attendant to yaw. The preferred rotor uses only two blades mounted on a common shaft which oscillates cyclically in the hub. Since cyclic variation of blade pitch establishes a cyclic pitch center of rotation offset from the rotor axis; by moving this offset the rotor is caused to yaw at a controlled rate in a desired sense.

Improvements in or relating to blading arrangement for turbomachines

Abstract: 1,235,006. Turbines; axial flow compressors; jet propulsion plant. SOC NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. Dec. 5, 1968 [Dec. 12, 1967], No. 57836/68. Headings F1C, F1J and F1T. A two-tier blade ring for a turbomachine such as a compressor ducted fan or the like comprises angularly spaced blades each formed by an inner section 2 having a tip portion 5 and a radially aligned outer section 3 having a base portion 6a mounted in a groove 6 in the tip 5. The blade sections 2, 3 are exposed to different working fluid flows, such as two air-flows or flows of air and combustion gases, and are separated by an annular member 1 having circumferentially spaced apertures engaging the tips 5 to strengthen the assembly. Insertion of each base 6a in its groove 6 is facilitated by a groove 7 in the member 1 in alignment with each aperture. As shown, the blades may be variable pitch having a spigot 4 secured in taper-roller bearings 8 in an annular member 9 fixed to the shaft r of a gas turbine engine compressor. Each spigot 4 carries Fig. 1, a gear 10 meshing with a rack 11 on an arm 12 secured to an axially slidable sleeve 13 mounted on shaft r. A hydraulic jack or other pneumatic, mechanical or electrical device can actuate the sleeve 13 to vary the blade pitch. In a modification, Fig. 6, the pitch varying mechanism comprises a toothed sector 21 secured to each spigot 4 and meshing with a gear 22 mounted on shaft r. Normally gear 22 rotates at the same speed as shaft r but can be rotated relative thereto to effect variation of the blade pitch. Fig. 5 (not shown) illustrates an arrangement in which two succesive two-tier compressor rotor stages have pitch varying mechanism as shown in Fig. 1, the respective control sleeves 13 being slidable in mutually opposite directions by a common hydraulic actuator (16) fixed to stator structure between the rotor stages. The two-tier stator blade rings (15) of the compressor may also be constructed similar to Fig. 1 with fixed or variable pitch blades.

Method and system for noise controlled operation of a wind turbine

Abstract: A method for controlling noise generated from a wind turbine. The method including providing a blade attached to a hub having a rotor shaft, and a generator in communication with the rotor shaft. The at least one blade includes an adjustable pitch angle. The method further includes providing a wind turbine acoustical profile and a wind turbine power profile. The wind turbine acoustical profile and the wind turbine power profile are compared to determine a noise reduced operational condition. The wind turbine is controlled to provide a rotor speed and the pitch angle of the blade corresponding to the noise reduced operational condition.

Wind energy conversion system

Abstract: The wind energy conversion system includes a wind machine having a propeller connected to a generator of electric power, the propeller rotating the generator in response to force of an incident wind. The generator converts the power of the wind to electric power for use by an electric load. Circuitry for varying the duty factor of the generator output power is connected between the generator and the load to thereby alter a loading of the generator and the propeller by the electric load. Wind speed is sensed electro-optically to provide data of wind speed upwind of the propeller, to thereby permit tip speed ratio circuitry to operate the power control circuitry and thereby optimize the tip speed ratio by varying the loading of the propeller. Accordingly, the efficiency of the wind energy conversion system is maximized.

Wind Tunnel Testing of Subspace Predictive Repetitive Control for Variable Pitch Wind Turbines

Abstract: An increasing number of wind turbines implement individual blade pitch control (IPC) to reduce turbine dynamic loading, and thereby, to reduce the capital and operational costs associated with energy production. The aim of this paper is to demonstrate IPC on a wind turbine prototype, in a model-free data-driven manner and with reduced pitch activity. For this, subspace predictive repetitive control (RC) is used, which combines online system identification with the continuous implementation of RC to form a fully adaptive control law. The controller is tested on a scaled two-bladed wind turbine with active pitchable blades, placed in an open-jet wind tunnel. Substantial load reductions to an extent of 68% are observed, and strict control over actuator signal frequency content is achieved. The control law also demonstrates the ability to adjust to changes in system dynamics while maintaining a high degree of load alleviation.