Topic
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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TL;DR: In this article, the first four harmonics of rotation from a full-scale two-bladed propeller were measured and compared with values calculated from theory, and a relation for rotation noise from an element of radius developed by Gutin was given showing the effect of number of blades on the rotation noise.
Abstract: Sound pressure of the first four harmonics of rotation from a full-scale two-blade propeller were measured and are compared with values calculated from theory. The comparison is made (1) for the space distribution with constant tip speed and (2) for fixed space angles with variable tip speed. A relation for rotation noise from an element of radius developed by Gutin is given showing the effect of number of blades on the rotation noise.
30 citations
Patent•
17 Oct 1989
TL;DR: In this paper, the pitch change signal is transmitted across a rotating gap between the two hub assemblies and a synchronizer is used to coordinate the signals of the first and second motors so that a pitch lock moves simultaneously with the actuator.
Abstract: A propeller system has a pair of hub assemblies (12,14) driven in counter-rotation, each hub assembly having a mechanical pitch change actuator (18,20), each actuator being provided with a pitch lock (60) that rotates simultaneously with the motion of the actuator to allow the actuator to set propeller blade pitch, but locks the propeller blade positionally when not rotating simultaneously with the actuator, and a differential for transmitting a pitch change signal across a rotating gap between the two hub assemblies and for providing power to a means for providing the pitch change signals. A pair of motors (112,114) provide the rotative signal to set the pitch of the blades in each hub assembly. One of the pair of motors drives the actuator towards high pitch and the other motor drives the actuator towards low pitch. A synchronizer (76) coordinates the signals of the first and second motors so that a pitch lock moves simultaneously with the actuator.
30 citations
TL;DR: In this paper, the authors compared three kinds of flexible propellers and compared their performance characteristics and found that the flexibility of the flexible propeller is strongly dependent on the thrust produced at the blade and the variation in the advance ratio.
30 citations
Patent•
09 Nov 2007TL;DR: In this paper, an improvement for use in a wind turbine having a plurality of variable-pitch blades mounted on a hub for rotation relative to a nacelle is presented.
Abstract: The present invention provides an improvement for use in a wind turbine (20) having a plurality of variable-pitch blades (24) mounted on a hub (23) for rotation relative to a nacelle (22). The improvement broadly includes: a electro-hydraulic actuator (25) for controlling the pitch of one of the blades, the actuator including: a motor (26) adapted to be supplied with a current; a pump (27) driven by the motor and arranged to provide a hydraulic output as a function of the current supplied to the motor; and a hydraulic actuator (28) operatively arranged to selectively vary the pitch of the associated blade as a function of the hydraulic output of the pump; and wherein the motor, pump and actuator are physically arranged within the hub of the wind turbine.
30 citations
Patent•
10 Feb 2005
TL;DR: A rotor blade of a wind power installation in which the rotor blade, in particular in the central region of the rotor, the so-called main board, has a lift-drag ratio which in the region of about ± 2° from the optimum pitch angle has a value of more than 80%, preferably 90% and more of the maximum value of the lift-rate.
Abstract: A rotor blade of a wind power installation in which the rotor blade, in particular in the central region of the rotor, the so-called main board, has a lift-drag ratio which in the region of about ±2° from the optimum pitch angle has a lift-drag ratio value of more than 80%, preferably 90% and more of the maximum value of the lift-drag ratio.
30 citations