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Large stall regulated wood epoxy blades: dynamics and aerodynamics

Objective



1. Objectives
1. To improve the understanding of the stall mechanisms involved on a large stall regulated wind turbine rotor by a novel technique for visualising boundary layer separation with and without vortex generators.
2. To improve the understanding of the dynamic and structural behaviour of large wood epoxy blades by comparing monitored loads with predictions.
3. To improve the performance of the blades through systematic flow enhancement (from 1 and 2)
4. To investigate in-plane vibrations which can be design-drivers on large stall-regulated blades and to design and test means for reducing them
5. To reduce the mass and therefore the cost of these blades (from 2 and 4)
2. Technical Approach
A NEG-Micon 1.5MW wind turbine with a 64m diameter rotor with wood-epoxy fixed pitch stall regulated blades will be used for the research and trial of performance enhancing devices. The turbine is on a test site which is already well instrumented and characterised for wind conditions.
The project relies on three research techniques:
- Direct structural measurements on the instrumented rotor
- Flow visualisation on a full scale rotor using novel stall flags developed by one of the partners to allow a much more detailed map of instantaneous flows to be built up
- Computer simulations on aerodynamic software developed by another partner for simulation of blade dynamics.
The results will enable particular flow conditions and aerodynamic features to be linked with global rotor performance namely power and loads.
Performance enhancement will include:
- Vortex generators are usually in the form of a row of small upstanding barriers applied to the leeward side of the blade near the leading edge. These delay stall and produce greater lift which improves the medium wind energy capture.
- Add on damping devices to reduce edgewise vibrations particularly at higher wind speeds.
3. Expected achievements
- Detailed predictions and measurements will be made of the behaviour of a 64m 1.5 MW machine equipped with wood epoxy blades.
- The energy capture of the 1.5 MW machine will be increased by between 3 and 4% at a 7.5 m/s site as a result of a better understanding of the flow behaviour, and in particular, the stall.
- Devices will be designed, manufactured and tested which will reduce the lead-lag vibrations
experienced by some large scale stall regulated machines by up to 20%. - The cost of the 31 m blades used on the 1.5 MW machine will be reduced by up to 5% through an improvement in the load specification, the use of the vibration reducers and the resultant reduction in material.
- Based on the combination of these two results, a new blade will be designed using a better
understanding of stall behaviour which should result in the reduction of energy costs by about 4%.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Aerolaminates Ltd.
Address
The Phoenix Centre
SO40 3SA Totton
United Kingdom

Participants (3)

ENERGY RESEARCH CENTRE OF THE NETHERLANDS
Netherlands
Address
3,Westerduinweg 3
1755 LE Petten
GARRAD HASSAN AND PARTNERS LTD
United Kingdom
Address
Saint Vincent Works, Silverthorne Lane
BS2 0QD Bristol
NEG MICON A/S
Denmark
Address
21,Alsvej 21
8900 Randers