《Airfoil characteristics for wind turbines》

liuyangtao

丹麦Risoe的研究报告
Abstract
Airfoil characteristics for use in the Blade Element Momentum (BEM) method
are derived by use of systematic methods. The characteristics are derived from
data on Horizontal Axis Wind Turbines (HAWT). The investigation and derivation
of the airfoil characteristics are based on four different methods: 1) Inverse
momentum theory, 2) Actuator disc theory, 3) Numerical optimisation
and 4) Quasi-3D CFD computations.
The two former methods use as input 3D CFD computations and wind tunnel
measurements on a 41-m full-scale rotor with LM 19.1 blades. The derived airfoil
characteristics show that the maximum lift coefficient at the tip is low and
that the maximum lift coefficient is high at the root compared to 2D airfoil
characteristics. The use of the derived characteristics in aeroelastic calculations
shows good agreement with measurements for power and flap moments. Furthermore,
a fatigue analysis shows a reduction in the loads of up to 15 % from
load calculations with the derived airfoil characteristics compared with a commonly
used set of airfoil characteristics.
The numerical optimisation is based on both the 3D CFD computations and
measurements on a 41-m rotor with LM 19.1 and LM 19.0 blades, respectively.
The method requires measurements or CFD calculations of power and loads
from a turbine and is promising since a set of lift and drag curves is derived that
can be used to calculate mean values of power and loads. The maximum lift at
the tip is low and at the root it is high compared to 2D airfoil characteristics. In
particular the power curves were well calculated by use of the optimised airfoil
characteristics.
In the quasi-3D CFD computations, the airfoil characteristics are derived directly.
This Navier-Stokes model takes into account rotational and 3D effects.
The model enables the study of the rotational effect of a rotor blade at computing
costs similar to what is typical for 2D airfoil calculations. The depicted results
show that the model is capable of determining the correct qualitative behaviour
for airfoils subject to rotation. The method shows that lift is high at the
root compared to 2D airfoil characteristics.
The different systematic methods show the importance of rotational and 3D effects
on rotors. Furthermore, the methods show high maximum lift coefficients
at the inboard part of the blade and low maximum lift coefficients at the outboard
part of the blade compared to 2D wind tunnel measurements.
ISBN 87-550-2415-7
ISBN 87-550-2568-4 (internet)
ISSN 0106-2840
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