This thesis comprises two main original contributions. The first concerns the
aeroelastic modelling of a large-scale prototype wind turbine undertaken specifically
to explain experimentally observed mechanical instabilities. The second
explores the aerodynamic aspect of turbine modelling in greater detail since this
is the main identified technical challenge, this process makes use of detailed largescale
wind tunnel test data from NREL for model validation purposes.
The MS4 prototype wind turbine was modelled using ADAMS/WT software, the
aerodynamic model was provided by the NREL AERODYN subroutines. The
drivetrain instability of the machine of 0.75Hz was reproduced by the computer
simulation. The causes of the instability were found to be negative aerodynamic
damping, complex blade bending modes caused by the blade design and rapid
yawing and tilting inducing Coriolis forces in the rotor structure.
Accurate analysis of the aerodynamic forces acting on the MS4 was not possible
because of the lack of detailed data available and the complicated aeroelastic
response of its flexible structure.
Theoretical comparisons with the results from the NREL wind tunnel tests were
made using several different engineering aerodynamic models (including those used
with AERODYN). It was found that blade element aerofoil data had a controlling
influence on the blade forces predicted through theory. The effect of inflow models
was found to be marginal at lower tip speed ratios and to decrease with decreasing tip speed ratio.
Experimental blade forces at low tip speed ratios were found to be defined by gross
3 dimensional effects and the use of 2 dimensional aerofoil data led to inaccurate
prediction of blade forces. The use of a stall delay model improved results but
was not convincing.
Yawed flow predictions were again controlled by the blade element aerofoil data
used, use of a stall delay model again improved results in a steady state fashion.
A dynamic stall model also improved results but the phasing of results towards
the blade root was questionable and may be caused by unsuitable time constants
or the influence of the delayed stall effect.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.