Research Papers

Updating and Optimization of a Coning Rotor Concept

[+] Author and Article Information
Curran Crawford

Department of Mechanical Engineering, University of Victoria, PO Box 3055 STN CSC, Victoria, BC, V8W 3P6, Canadacurranc@uvic.ca

Jim Platts

Institute for Manufacturing, Department of Engineering, Cambridge University, Mill Lane, Cambridge, CB2 1RX, UKmjp@eng.cam.ac.uk

1.5MW was chosen as generic machine data were available for this size and are around the average capacity actually sold, notwithstanding the industry drive to capacities exceeding 4MW for offshore sites where economies of size are still unclear.

Pitch flap coupling can be achieved by inclining the hinge axis at an angle of δ3 in a plane normal to the rotor’s main rotation axis. For δ3=0, the hinge axis is normal to the blade axis when the blade is vertical and unconed. For any δ30, rotation about the hinge axis results in two component rotations, one coning and the other pitching.

The τ-Ω map can be easily constructed once the operating profile over wind speed is known.

Modified to have an external rotor (magnets) and internal stator (windings)

Without any modification to the root for pitch bearing

J. Sol. Energy Eng 130(3), 031002 (Jun 13, 2008) (8 pages) doi:10.1115/1.2931497 History: Received March 09, 2006; Revised September 05, 2006; Published June 13, 2008

The work detailed in this paper is focused on updating and refining a coning rotor wind turbine concept. The coning rotor combines the load shedding properties of flapping hinges with gross change in rotor area, via large coning angles, to affect increased energy capture at nominally constant system cost. Previous studies have indicated that the large cost of energy reductions is possible, compared to the state-of-the-art machines then, particularly for abundant but presently uneconomic low-wind sites. Almost ten years later, the fundamentals of the design remain sound, but bear reevaluation relative to current machines, both exploiting modern power electronics and control technology. The coning rotor was never optimized in its own right, so an integrated design tool suitable for human and computer refinement of the design has been developed. Incorporated into the tool is a corrected blade element momentum method that more properly accounts for coned rotor aerodynamics. A discussion of the development of coning rotors is presented, along with a comparison to present operational strategies. Results obtained for nondimensionalized rotors and specific machine optimization studies are presented, followed by a discussion of further issues to be addressed.

Copyright © 2008 by American Society of Mechanical Engineers
Topics: Rotors , Blades , Optimization
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Figure 1

Torque-speed (τ-Ω) control map

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Figure 2

Operational rotor thrust curves

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Figure 3

Nondimensional steady curves for actual tip radius as a function of coning angle β

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Figure 4

Power curves for reference radius as a function of control parameter

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Figure 5

Nondimensional optimized planforms for a range of cone angles

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Figure 6

Chord and twist definition

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Figure 7

Operating profiles for variable-speed stall control

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Figure 8

CP curves at β=0 for various blades with differing airfoils, optimized for λ=8

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Figure 9

Operating profiles for variable speed and pitch-to-stall control




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