Wind Energy

42
Performance of the Risø-B1 Airfoil Family
for Wind Turbines
Christian Bak, Mac Gaunaa and Ioannis Antoniou
Summary. This paper presents the measurements on the Risø-B1 airfoil family
with relative thicknesses of 15%, 18%, 24% and 27% tested in the Velux wind tunnel.
The measurements carried out at a Reynolds number of 1.6 × 10 6 showed that the
airfoils have a high maximum lift and that they are very insensitive to leading edge
roughness. This makes the airfoils suitable for design of less solid rotors and still
obtain reliable energy production.
42.1 Introduction
The Risø-B1 airfoil family was developed with a relative thickness range from
15% to 53% and with high maximum lift [1]. They were designed for megawatt
size wind turbines with pitch control and variable rotor speed (PRVS). For
PRVS wind turbines a high maximum lift (cl,max) with a corresponding high
design lift means that less solid rotors can be obtained. The reduced solidity
potentially ensures savings in manufacturing the blades and reduced loads
on the remaining components of the turbine. Furthermore, the airfoils were
designed for high driving force in the chordwise direction, to be insensitive
to leading edge roughness and to have a smooth trailing edge stall despite
of the high lift. The design Reynolds number was Re =6× 10 6 and was
based on a design tool for multi-point airfoil design [2] coupled to XFOIL.
For evaluation the CFD solver, EllipSys2D, [3,4] was used. The design of the
series and measurements of the 18% and 24% airfoil were reported in [1] and
since then measurements on the 15% and 27% airfoil have been carried out.
Therefore, this paper presents the verification of the performance of the 15%,
18%, 24% and 27% Risø-B1 airfoils.
42.2 The Wind Tunnel
The Risø-B1 airfoils were tested in the Velux wind tunnel in Denmark. This
tunnel and the measuring techniques are described and verified in detail in [5].