Blade pitch

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

Cyclic pitch control having torsion spring system

Abstract: A pitch control system for a vertically launchable and recoverable winged aircraft includes a collective and cyclic pitch control system, a drive yoke and a rotor hub. The collective and cyclic pitch control system is operably connected to two proprotor blades to cyclically control the pitch of each proprotor blade, so that the aircraft is capable of controlled helicopter mode flight when the aircraft body is pointed in a generally upward direction. Proprotor blade flapping caused by applying cyclic pitch control results in teetering of the rotor hub with respect to the drive yoke. Torsion bar springs are used with suitable mechanical linkages to resist this teetering motion and generate the hub moment which is transmitted to the airframe and used to maneuver the aircraft.

Simulation of Offshore Wind Turbine Response for Extreme Limit States

Abstract: When interest is in estimating long-term design loads for an offshore wind turbine using simulation, statistical extrapolation is the method of choice. While the method itself is rather well-established, simulation effort can be intractable if uncertainty in predicted extreme loads and efficiency in the selected extrapolation procedure are not specifically addressed. Our aim in this study is to address these questions in predicting blade and tower extreme loads based on stochastic response simulations of a 5 MW offshore turbine. We illustrate the use of the peak-over-threshold method to predict long-term extreme loads. To derive these long-term loads, we employ an efficient inverse reliability approach which is shown to predict reasonably accurate long-term loads when compared to the more expensive direct integration of conditional load distributions for different environmental (wind and wave) conditions. Fundamental to the inverse reliability approach is the issue of whether turbine response variability conditional on environmental conditions is modeled in detail or whether only gross conditional statistics of this conditional response are included. We derive design loads for both these cases, and demonstrate that careful inclusion of response variability not only greatly influences long-term design load predictions but it also identifies different design environmental conditions that bring about these long-term loads compared to when response variability is only approximately modeled. As we shall see, for this turbine, a major source of response variability for both the blade and tower arises from blade pitch control actions due to which a large number of simulations is required to obtain stable distribution tails for the turbine loads studied.

Rotor blade for a wind energy installation

Abstract: A rotor blade is provided for a wind energy installation, and has at least one first and one second component. The first component has the rotor blade tip, and the second component has the rotor blade root. The first and the second component are formed as separate parts in order to jointly form the rotor blade. The first component is composed of a first material, and the second component is composed of a second material.

Air driven turbine having a blade pitch changing mechanism including overspeed protection

Abstract: An air driven turbine having variable pitched blades is provided that includes a pitch change mechanism for adjusting the pitch of the blades during either rotating or non-rotating operational modes of the air driven turbine. The pitch control mechanism includes a resettable overspeed protection device which is directly actuated by an overspeed condition of the turbine and operates independently from the pitch change mechanism to move the blades to a failsafe, feathered, or coarse pitch, low speed position. The pitch control mechanism utilizes a linear actuator in the form of an acme screw drive. The air driven turbine includes a ball ramp thrust bearing for attaching the blades to a hub of the turbine in such a manner that during rotation of the turbine actuation loads on the pitch change mechanism are reduced.

Morphing Segmented Wind Turbine Concept

Abstract: A morphing segmented concept is proposed herein for future extreme-scale wind turbine systems. The morphing may be accomplished by using segmented blades connected by screw sockets and a tension cable system. At low wind and rotor speeds, the segmented blades are fully tensioned and set at high pitch to ensure start-up and maximum power at low speeds. At high rotor rpm, the cable tension can be designed such that centrifugal forces drive the blade segments outward so as to unwind/feather the rotor and prevent over-speed. This effectively acts like a passive pitch control for rotor speeds. Perhaps more importantly, the airfoils of the blade segments can be designed with a center of pressure downstream of the socket axis. This will cause an aerodynamic moment at high wind speeds which will serve to unwind the blade segments to prevent torque spikes and blade stall. For a given rotor diameter and torque, such stall prevention can permit operation at higher average lift coefficient with a reduced blade chord length which can reduce blade and overall system weight. In addition, the segmented blade concept can alleviate manufacturing and shipping constraints for extreme-scale systems. In the proposed concepts, the bending loads will be carried by the segmented rotor spar and not the blade skin. This will result in much larger downstream deflections of the blades at high wind speeds as compared to that of a conventional rigid single-piece turbine blade. Therefore, a downstream design would be needed to avoid potential strike of the blades with the tower. This will require a more aerodynamic tower to reduce wake interactions but a downstream system may eliminate yaw-control and substantially relax blade rigidity constraints, thus further reducing blade weight. However, this morphing concept faces several technical challenges including substantially increased susceptibility to flutter instability and dynamic stall which is expected to require active control systems.