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 phase relationship between a reference propeller or fan and some or all of the other propellers or fans is adjusted dynamically during flight to minimize propeller noise in the cabin over a range of flying conditions.
Abstract: In propeller of fan driven aircraft, cabin noise levels may be reduced by adjustment of the phase relationship between a reference propeller or fan and some or all of the other propellers or fans. An aircraft cabin (1) contains four microphones and two loudspeakers which form the active elements of a noise control system. The microphone outputs are fed via amplifiers to a digital signal processor (11) having an adaptation algorithm in a memory store. The processor generates an error signal which is used to adjust the synchrophase angle between the reference propeller and a synchrophased propeller, controlled by a synchrophaser. Thus the synchrophase angle is varied dynamically during flight to minimize propeller noise in the cabin over a range of flying conditions.
53 citations
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TL;DR: In this article, a parallel path modification is proposed to avoid instability without increasing the generator speed variation, and the results of comprehensive simulations and load calculations carried out on a benchmark wind turbine are presented.
Abstract: Applying a land-based designed pitch controller on a floating wind turbine may cause severe instability. A common strategy to overcome this problem is to reduce the closed-loop bandwidth of the pitch control system. In doing so, the generator speed variation increases possibly leading to shutdowns because of overspeed. This study uses a parallel path modification to avoid instability without increasing the generator speed variation. The results of comprehensive simulations and load calculations carried out on a benchmark wind turbine are presented. These demonstrate that by using the proposed method it is possible to apply the land-based designed pitch controller on its floater-based equivalent.
53 citations
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13 May 1991TL;DR: In this paper, an actuator that is responsive to the relative rotation of two input members is used to change the blade pitch in one direction when a braking torque is applied to one member and in another direction when applied to the other member.
Abstract: Blade pitch is changed by an actuator that is responsive to the relative rotation of two input members. Blade pitch is not changed when the members are rotated at the same speed. However, blade pitch is changed in one direction when a braking torque is applied to one member, and blade pitch is changed in an opposite direction when a braking torque is applied to the other member.
53 citations
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04 Jan 2011TL;DR: In this paper, combined feedback/feedforward blade pitch control is compared to industry standard feedback control when simulated in realistic turbulent winds, and three feedforward designs are studied: Non-Causal Series Expansion, Preview Control, and Optimized FIR Filter.
Abstract: Combined feedback/feedforward blade pitch control is compared to industry standard feedback control when simulated in realistic turbulent winds. The feedforward controllers are designed to reduce fatigue loads, increasing turbine lifetime and therefore reducing the cost of energy. Three feedforward designs are studied: Non-Causal Series Expansion, Preview Control, and Optimized FIR Filter. The input to the feedforward controller is a measurement of incoming wind speed, which could potentially be provided by lidar. Noncausal series expansion and Preview Control methods reduce blade root loads but increase tower bending in simulation results. The optimized FIR filter reduces loads overall, keeps pitch rates low, and maintains rotor speed regulation and power capture, while using imperfect wind measurements provided by a lidar model.
53 citations
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01 Jan 2002
Abstract: A computationaluid dynamics model of a hovering helicopter main rotor is developed to examine airow in the presence of ship structures and side winds. An illustratio n of the problem is given. The rotor is modelled by modifying the governing N avier±Stokes equations in the region of the disc. The extra terms added to the governing equations apply a downward force to theuid; these forces are independent of theow around the rotor and are equal to the helicopter weight. The helicopter rotor model and the ship model are combined to yield oneow solution, which, due to the severe non-linearities of the problem, cannot be achieved by superpositio n. The resultantow yields valuable data about the induced velocities at the rotor, which ultima tely determine the control pitch and power required to maintain the hover in a given location. Indeed, the interactions between the rotor downwash and ship airow are known to produce unexpected and adverseight dynamic behaviour of the aircraft.
53 citations