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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Patent•
07 Oct 1988
TL;DR: An essentially composite propeller or fan blade is provided which is rotatably mounted to a blade retention pitch member by a pin radially outside of a propeller spinner or hub as mentioned in this paper.
Abstract: An essentially composite propeller or fan blade is provided which is rotatably mounted to a blade retention pitch member by a pin radially outside of a propeller spinner or hub. The blade has a plurality of composite layers wrapped directly around a root fairing which engages the pin. The propeller blade has a motion limiter provided at the base thereof which cooperates with the blade retention pitch member to damp rotational movement of the blade about the pin to minimize blade angular excursions when centrifugal loads are low, to moderate blade vibratory motion, to help tune out undesirable blade resonant frequencies and to transmit force created by impact with foreign objects to the pitch member. By cooperating with the pitch retention member, the root of the blade may be more aerodynamically shaped than other composite blades which must absorb the force of impact in their root portions.
30 citations
Patent•
30 Sep 2009TL;DR: In this article, the authors present a control system for a wind turbine having a tower, a generator, and at least one rotor blade, which includes a sensor configured to measure an angle of inclination of the tower with respect to a surface.
Abstract: A control system for a wind turbine having a tower, a generator, and at least one rotor blade. The control system includes a sensor configured to measure an angle of inclination of the tower with respect to a surface, at least one pitch assembly configured to adjust a pitch angle of the rotor blade, and a controller configured to control at least one of the pitch assembly and the generator based on the measured angle of inclination.
30 citations
Patent•
31 Dec 1986
TL;DR: In this article, the pitch control motors individually vary the pitch of the rotor blades to control the feathering angle as a function of the angular position so that lift is obtained from the advancing and laterally moving blades only.
Abstract: A high speed helicopter, ideally suited for use with rotors which are tip propelled, has an offset flapping hub mounted on a tiltable mast which is located a substantial distance off to the retreading blade side of the fuselage of the helicopter. This causes the fuselage to be located completely under the advancing blades. Individual pitch control motors individually vary the pitch of the rotor blades to control the feathering angle as a function of the angular position so that lift is obtained from the advancing and laterally moving blades only.
30 citations
TL;DR: In this paper, an experimental study is performed on a three-bladed rotor model in two water tanks, showing the development of both short-wave and long-wave instabilities on the helical vortices in the wake.
Abstract: : An experimental study is performed on a three-bladed rotor model in two water tanks. The blade pitch, rotational velocity, descent angle, and descent speed are all varied in order to simulate a wide range of rotorcraft operating states, focusing on descent cases where the rotor is operating in or near vortex ring state--an area in which there is currently very little available data. Flow visualization is done by injecting air bubbles and fluorescent dye tangentially from the blade tips to mark the vortex core, showing the development of both short-wave ("sinuous") and long-wave ("leapfrogging") instabilities on the helical vortices in the wake. Strain gages are used to record transient loads, allowing a correlation between the rotor thrust performance and the development of the vortex wake. Reynolds numbers are of order 105 and test runs are performed for extended periods--up to 500 rotor revolutions-- demonstrating the repeatability of the patterns of thrust variation. The data indicate that as the instabilities develop, adjacent vortices merge and form thick vortex rings, particularly during descent. Periodic shedding of these rings from the wake associated with vortex ring state is observed, resulting in peak-to-peak thrust fluctuations of up to 95% of the mean and occurring at regular intervals of 20-50 rotor revolutions, depending on flow parameters.
30 citations
Patent•
20 Jul 1998
TL;DR: In this article, a rigid trowel frame mounts separate spaced-apart, downwardly-projecting, bladed rotor assemblies that frictionally engage the concrete surface, and a joystick system enables operator hand control with minimal physical exertion.
Abstract: High performance, multiple rotor riding trowels for finishing concrete comprise hydraulic circuitry enabling complete joystick control to the operator. The rigid trowel frame mounts separate spaced-apart, downwardly-projecting, bladed rotor assemblies that frictionally engage the concrete surface. The rotor assembly blades finish the surface while supporting the trowel. The rotor assemblies are tilted with double acting, hydraulic cylinders to effectuate steering and control. Double acting hydraulic cylinders also control blade pitch. Separate gimbaled, hydraulic motors revolve each rotor assembly. A joystick system enables operator hand control with minimal physical exertion. The joystick system activates electrical circuitry that fires solenoid control valves to energize various hydraulic cylinders that tilt the rotors and alter blade pitch. The hydraulic steering control circuit driven by a motor driven pump pressures a flow divider circuit to control the solenoid tilt control valves. A bypass-valve in line before the flow divider enables an operator to customize the trowel steering speed. A motor drive control circuit responsive to a hydraulic pump controls each hydraulic drive motor, and provides for speed control and heat dissipation.
30 citations