PERFORMANCE OF LARGE WIND-TURBINES IN A FULL-SCALE ENVIRONMENT
Dr. (Peter)
H.-T. Liu
StereoVision Engineering
Fig. 1 Boeing 2.5MW MOD 2 wind turbine at Goodnoe Hill
Test Site.
Fig. 2 Three stages of vortex instability (looking
downwind): forward, reversing, and reversed spouts.
Fig. 3 Time lapsed photographs of reversed spout.
A full-scale wind turbine test site at Goodnoe
Hill near Goldendale, Washington was
established in 1979 by the Department of Energy to understand the
performance of large wind turbines in a full-scale environment. The site
consisted of a cluster of 3 2.5 MW Boeing MOD-2 wind turbines with a 94-m rotor
diameter and a 61-m tall tower (Fig. 1). Flow-visualization experiments
were conducted to investigate
several wake phenomena [1, 2]. In one of the experiments, smoke was released downstream
of the rotating blade tips from a tethered generator to visualize the
evolution of the rotor-tip vortices. The smoke generator released a large
volume of smoke continuously for several minutes. When the rotor
blades cut in front of the smoke trail, a section of the
helical vortex generated locally became visible as smoke was entrained and
trapped in the low-pressure core. The vortex became unstable when it
passed through the wake of the turbine tower. The vortex reversed its
course forming a long "spout" shooting at high
speeds away from the turbine wake (Figs. 2 and 3). As the vortex
swept across the relatively narrow tower wake,it experienced a sudden
increase and then decreased in the ambient pressure. It is believed that
the vortex reversal, a form of instability, is triggered by the above
vortex-wake interaction.
[1] Liu, H.-T., Hiester, T. R., Waite, J. W.,
Tacheron, P. H., and Srnsky, R. A. (1983) "Flow Visualization Study of a
MOD-2 Turbine Wake," Pacific Northwest Laboratory Technical Report
PNL-4535, UC-60, June.
[2] Hiester, T. R., Liu, H.-T., and Waite, J. W. (1983) "Results of
MOD-2 Wake Flow Visualization," presented at 1983 American Solar Energy
Society Meeting, June 1-3.