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Blade pitch

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


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Patent
14 Jun 1976
TL;DR: In this article, an overspeed control arrangement for vertical axis wind turbines employing normally vertically positioned rotor blades is presented, which allows the rotor blades to tilt either forward or backwards to form a swept wing configuration, at wind turbine speeds beyond the design rpm.
Abstract: This invention is an overspeed control arrangement for vertical axis wind turbines employing normally vertically positioned rotor blades, said control arrangement allows the rotor blades to tilt either forward or backwards to form a swept wing configuration, at wind turbine speeds beyond the design rpm. When the rotor blade is in a highly swept wing configuration its high drag and low lift reduces the turbine rotor torque to zero and eliminates excessive overspeeding and structural damage. The rotor blade can tilt about a radial or nearly so, tilt-support arm, mounted on a concentric bearing, the tilting starts at the feathering design rpm which is controlled by the geometric position of the combined center of gravity of both rotor blade and tilt-support arm. The control arrangement is automatic and passive and does not require the use of springs, pulleys or levers.

39 citations

Patent
04 Dec 2009
TL;DR: In this paper, a wind turbine includes a plurality of wind turbine blades attached to a rotor positioned atop a tower affixed to a tower foundation, and a rotor/generator speed sensor is configured to measure the rotational speed of the wind turbine rotor, a corresponding wind turbine generator or both.
Abstract: A wind turbine includes a plurality of wind turbine blades attached to a rotor positioned atop a tower affixed to a tower foundation. At least one blade pitch sensor is configured to measure blade pitch angles for one or more of the wind turbine blades. A rotor/generator speed sensor is configured to measure the rotational speed of the wind turbine rotor, a corresponding wind turbine generator, or both. A wind turbine nacelle yaw sensor is configured to measure the nacelle yaw, while at least two tower-base bending sensors are configured without use of adhesives, cements or bonding agents to provide large-area measurement of tower deflection. A controller is configured to adjust the pitch angle of one or more of the wind turbine blades in response to the measured one or more blade pitch angles, the measured rotational speed, the measured nacelle yaw and measured tower longitudinal deflection.

39 citations

Journal ArticleDOI
TL;DR: Hong et al. as discussed by the authors presented a follow-up study using the data collected during multiple deployments from 2014 to 2016 around the 2.5MW turbine at the EOLOS field station.
Abstract: Super-large-scale particle image velocimetry (SLPIV) and the associated flow visualization technique using natural snowfall have been shown to be effective tools to probe the turbulent velocity field and coherent structures around utility-scale wind turbines (Hong et al.Nat. Commun., vol. 5, 2014, article 4216). Here, we present a follow-up study using the data collected during multiple deployments from 2014 to 2016 around the 2.5 MW turbine at the EOLOS field station. These data include SLPIV measurements in the near wake of the turbine in a field of view of 115 m (vertical) 66 m (streamwise), and the visualization of tip vortex behaviour near the elevation corresponding to the bottom blade tip over a broad range of turbine operational conditions. The SLPIV measurements provide velocity deficit and turbulent kinetic energy assessments over the entire rotor span. The instantaneous velocity fields from SLPIV indicate the presence of intermittent wake contraction states which are in clear contrast with the expansion states typically associated with wind turbine wakes. These contraction states feature a pronounced upsurge of velocity in the central portion of the wake. The wake velocity ratio , defined as the ratio of the spatially averaged velocity of the inner wake to that of the outer wake, is introduced to categorize the instantaneous near wake into expansion ( ) and contraction states ( ). Based on the criterion, the wake contraction occurs 25 % of the time during a 30 min time duration of SLPIV measurements. The contraction states are found to be correlated with the rate of change of blade pitch by examining the distribution and samples of time sequences of wake states with different turbine operation parameters. Moreover, blade pitch change is shown to be strongly correlated to the tower and blade strains measured on the turbine, and the result suggests that the flexing of the turbine tower and the blades could indeed lead to the interaction of the rotor with the turbine wake, causing wake contraction. The visualization of tip vortex behaviour demonstrates the presence of a state of consistent vortex formation as well as various types of disturbed vortex states. The histograms corresponding to the consistent and disturbed states are examined over a number of turbine operation/response parameters, including turbine power and tower strain as well as the fluctuation of these quantities, with different conditional sampling restrictions. This analysis establishes a clear statistical correspondence between these turbine parameters and tip vortex behaviours under different turbine operation conditions, which is further substantiated by examining samples of time series of these turbine parameters and tip vortex patterns. This study not only offers benchmark datasets for comparison with the-state-of-the-art numerical simulation, laboratory and field measurements, but also sheds light on understanding wake characteristics and the downstream development of the wake, turbine performance and regulation, as well as developing novel turbine or wind farm control strategies.

39 citations

Patent
13 Nov 1972
TL;DR: In this paper, an axial-flow variable-pitch fan, a diffuser, an enlarged duct immediately contiguous to the diffuser and sets of controllable variablegeometry, series-related, articulatable vanes mounted in a boattail configuration at the rear or egress end of the aft fuselage.
Abstract: A helicopter devoid of a conventional exteriorly mounted antitorque rotor and having at the rear end of its aft fuselage a system utilized for auxiliary propulsion and anti-torque and directional control. This combination includes an axial-flow variable-pitch fan, a diffuser, an enlarged duct immediately contiguous to the diffuser, and sets of controllable variablegeometry, series-related, articulatable vanes mounted in a boattail configuration at the rear or egress end of the aft fuselage. The fan is located immediately forward of the diffuser, with the duct extending from the diffuser to the vanes, and an air inlet through which the flow of air is induced by the fan is disposed immediately forward of the fan. The vanes operate to dually provide auxiliary thrust and anti-torque control. In operating as an anti-torque control, the flowing air in the enlarged duct is made to converge and accelerate as such air is turned by positioned articulated vanes to achieve maximum efficiency in the production of the required anti-torque force. A pair of spaced elongated slots, with automatically closing lips, extend longitudinally of the fuselage skin, along the enlarged duct and below the sweep of the main rotor, to augment the performance of the basic anti-torque system by inducing a circulation of air around the fuselage which, with the downwash from the main rotor, produces an additional anti-torque force. By varying the pitch of the fan, a large power drain from the main rotor system during critical power-off auto-rotation descents is prevented. The blade pitch also controls auxiliary propulsion thrust, independently of yaw control, while skin friction losses of air flowing in the enlarged duct are minimized.

39 citations

Journal ArticleDOI
TL;DR: In this paper, an optimum seeking-based robust non-linear controller is proposed to maximize wind energy captured by variable speed wind turbines at low-to-medium wind speeds by simultaneously controlling the blade pitch angle and tip-speed ratio, through the turbine rotor angular speed, to an optimal point at which the power coefficient, and hence the wind turbine efficiency, is maximum.
Abstract: In this study, an optimum seeking-based robust non-linear controller is proposed to maximise wind energy captured by variable speed wind turbines at low-to-medium wind speeds The proposed strategy simultaneously controls the blade pitch angle and tip-speed ratio, through the turbine rotor angular speed, to an optimal point at which the power coefficient, and hence the wind turbine efficiency, is maximum The optimal points are given to the controller by an optimisation algorithm that seeks the unknown optimal blade pitch angle and rotor speed The control method allows for aerodynamic rotor power maximisation without exact knowledge of the wind turbine model A representative numerical simulation is presented to show that the wind turbine can be accurately controlled to achieve maximum energy capture

39 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202377
2022163
202184
2020110
2019105
2018109