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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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Journal ArticleDOI
TL;DR: In this article, a five-year historical data set has been assembled for constructing the reference curves of wind power, rotor speed, and blade pitch angle, with wind speed as an input variable.
Abstract: Three different operational curves-the power curve, rotor curve, and blade pitch curve-are presented for monitoring a wind farm's performance. A five-year historical data set has been assembled for constructing the reference curves of wind power, rotor speed, and blade pitch angle, with wind speed as an input variable. A multivariate outlier detection approach based on k-means clustering and Mahalanobis distance is applied to this data to produce a data set for modeling turbines. Kurtosis and skewness of bivariate data are used as metrics to assess the performance of the wind turbines. Performance monitoring of wind turbines is accomplished with the Hotelling T2 control chart.

152 citations

Journal ArticleDOI
01 Apr 2013-Wear
TL;DR: In this article, the authors examined contact failures of bearings from wind turbine gearboxes and observed the localized microstructural change, known as white etching area (WEA), in order to guide the development of lasting solutions to a pressing problem.

151 citations

Patent
16 Dec 2003
TL;DR: A wind turbine has a generator with a connected rotor having a hub (4) and blades (5) rotatably connected to the hub for adjusting the pitch angle as mentioned in this paper, where the generator is used as a motor for driving the rotor and pitch angle of the blades is adjusted to ensure that the resulting wind substantially hits the leading edge of the turbine blades.
Abstract: A wind turbine has a generator (7) with a connected rotor (3) having a hub (4) and blades (5) rotatably connected to the hub for adjusting the pitch angle. In a method of operating such a wind turbine under climatic conditions, where there is a risk of icing on the blades and no or weak wind, the generator is used as a motor for driving the rotor and the pitch angle of the blades is adjusted to ensure that the resulting wind substantially hits the leading edge of the blades. Any ice formed may be removed by means of de-icing in a known manner.

151 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of curvilinear flow on Darrieus turbine blade aerodynamics are described and a simple kinematic analysis demonstrates that the turbine blade relative inflow velocity and angle of attack are unique everywhere on the chord.
Abstract: The effects of curvilinear flow on Darrieus turbine blade aerodynamics are described. Analysis shows that these effects can have a sizeable impact on performance for blades of large chord. Experimental data are presented which verify this forecast. Unusually large boundary-layer radial pressure gradients and virtually altered camber and incidence are identified as causal phenomena. Conformaf mapping techniques are used to transform geometric airfoils in curved flow to their virtual equivalents in rectilinear flow. It is argued that flow curvature is an important determinant of Darrieus turbine blade aerodynamic efficiency and that its proper consideration will yield performance improvements, even for blades of small chord. uncovered blade aerodynamic complexities which were beyond initial expectations. Most noteworthy are the peculiar aerodynamic phenomena associated with the orbital motion of the blades. In essence, these blades are subjected to a curvilinear flow and behave very differently than if they were immersed in a rectilinear flow. Furthermore, centrifugal forces alter the boundary layer of the airfoils rotating in this fashion. This situation presents problems in the design and analysis of all cross-flow wind turbines, because virtually all published airfoil data are derived from tests in rectilinear flow. Recent studiesl show that modest improvements in Cp yield desirable reductions in the cost of energy. Since these Cp improvements can be achieved by increasing blade aerodynamic efficiency, there exists ample incentive for considering the aerodynamic idiosyncrasies of rotating blades. In the material which follows, boundary-layer centrifugal effects will be discussed first. Treatment of this subject is brief; its significance has only recently been appreciated and extensive studies of the phenomenon have not been con- ducted. Flow curvature effects are treated next. A simple kinematic analysis demonstrates that the turbine blade relative inflow velocity and angle of attack are unique everywhere on the chord. It is then shown how conformal mapping techniques, which transform airfoils in the curved flow field to their virtual equivalents in rectilinear flow, may be used in the aerodynamic analysis of the turbine blades. The method indicates that flow curvature effects are strongly dependent upon the blade chord to turbine radius C/R. Experimental data are introduced for two sets of blades, both of NACA 0015 airfoil section. The first set of blades had C/R = 0.114 and the second set had C/R = 0.260.

150 citations

Journal ArticleDOI
TL;DR: In this article, numerical simulations of granular flow in a cylindrical vessel agitated by a four-blade impeller were performed using the discrete element method, and the system's frictional characteristics are shown to strongly influence the granular behavior within the mixer.
Abstract: Numerical simulations of granular flow in a cylindrical vessel agitated by a four-blade impeller were performed using the discrete element method. Velocity, density, and stress profiles within the mixer displayed a periodic behavior with a fluctuation frequency equal to that of the blade rotation. Blade orientation was found to affect flow patterns and mixing kinetics. For an obtuse blade pitch orientation, a three-dimensional recirculation zone develops in-front of the blade due to formation of heaps where the blades are present. This flow pattern promotes vertical and radial mixing. No recirculation zone was observed when the blade orientation was changed to an acute blade pitch. The system's frictional characteristics are shown to strongly influence the granular behavior within the mixer. At low friction coefficients, the 3-D recirculation in front of the obtuse blade is not present reducing convective mixing. Higher friction coefficients lead to an increase in granular temperature which is associated with an increase in diffusive mixing. Normal and shear stresses were found to vary with mixer height with maximum values near the bottom plate. Additionally, a strong dependence between the magnitude of the shear stresses and the friction coefficient of the particles was found. The stress tensor characteristics indicate that the granular flow in our simulations occurs in the quasi-static regime. At the same time, the averaged pressure was found to vary linearly with bed height and could be predicted by a simple hydrostatic approximation. © 2009 American Institute of Chemical Engineers AIChE J, 2009

149 citations


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