A study of the near wake deformation of the X-Rotor vertical-axis wind
turbine with pitched blades
Abstract
Recent studies have revealed the large potential of
vertical-axis wind turbines (VAWTs) for high-energy-density wind farms
due to their favorable wake recovery characteristics. The present study
provides an experimental demonstration and proof-of-concept for the wake
recovery mechanism of the novel X-Rotor VAWT. The phase-locked flowfield
is measured at several streamwise locations along the X-Rotor’s wake
using stereoscopic particle image velocimetry (PIV) with fixed-pitch
offsets applied to the blades. The streamwise vortex system of the upper
half of the X-Rotor is first hypothesized and then experimentally
verified. The induced wake deformations of the vortex systems are
discussed in comparison with previous studies concerning traditional
H-type VAWTs. The results suggest that positive blade pitch is more
favorable for accelerated wake recovery due to the dominant tip-vortex
generated on the upwind windward quadrant of the cycle. Utilizing
theoretical blade load variations along the span explains distinct
unsteady flow features in the near wake generated at select quadrants of
the rotor rotation, shedding light on the potential of the two pitch
schemes.
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