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Investigation of vortex generators for augmentation of wind turbine power performance

Description: This study focuses on the use of vortex generators (VGs) for performance augmentation of the stall-regulated AWT-26 wind turbine. The goal was to design a VG array which would increase annual energy production (AEP) by increasing power output at moderate wind speeds, without adversely affecting the loads or stall-regulation performance of the turbine. Wind tunnel experiments were conducted at the University of Washington to evaluate the effect of VGs on the AWT-26 blade, which is lofted from National Renewable Energy Laboratory (NREL) S-series airfoils. Based on wind-tunnel results and analysis, a VG array was designed and then tested on the AWT-26 prototype, designated P1. Performance and loads data were measured for P1, both with and without VGs installed. the turbine performance with VGs met most of the design requirements; power output was increased at moderate wind speeds with a negligible effect on peak power. However, VG drag penalties caused a loss in power output for low wind speeds, such that performance with VGs resulted in a net decrease in AEP for sites having annual average wind speeds up to 8.5 m/s. While the present work did not lead to improved AEP for the AWT-2 turbine, it does provide insight into performance augmentation of wind turbines with VGs. The safe design of a VG array for a stall-regulated turbine has been demonstrated, and several issues involving optimal performance with VGs have been identified and addressed. 15 refs., 34 figs., 10 tabs.
Date: December 1, 1996
Creator: Griffin, D.A.
Partner: UNT Libraries Government Documents Department

Effects of surface roughness and vortex generators on the NACA 4415 airfoil

Description: Wind turbines in the field can be subjected to many and varying wind conditions, including high winds with rotor locked or with yaw excursions. In some cases the rotor blades may be subjected to unusually large angles of attack that possibly result in unexpected loads and deflections. To better understand loadings at unusual angles of attack, a wind tunnel test was performed. An 18-inch constant chord model of the NACA 4415 airfoil section was tested under two dimensional steady state conditions in the Ohio State University Aeronautical and Astronautical Research Laboratory (OSU/AARL) 7 x 10 Subsonic Wind Tunnel (7 x 10). The objective of these tests was to document section lift and moment characteristics under various model and air flow conditions. These included a normal angle of attack range of {minus}20{degree} to +40{degree}, an extended angle of attack range of {minus}60{degree} to +230{degree}, applications of leading edge grit roughness (LEGR), and use of vortex generators (VGs), all at chord Reynolds numbers as high as possible for the particular model configuration. To realistically satisfy these conditions the 7 x 10 offered a tunnel-height-to-model-chord ratio of 6.7, suggesting low interference effects even at the relatively high lift and drag conditions expected during the test. Significantly, it also provided chord Reynolds numbers up to 2.0 million. 167 figs., 13 tabs.
Date: December 1, 1995
Creator: Reuss, R.L.; Hoffman, M.J. & Gregorek, G.M.
Partner: UNT Libraries Government Documents Department

Preliminary technical and economic evaluation of vortex extraction devices. Summary report

Description: The rotor subsystem represents one of the major cost drivers in conventional wind energy systems. Despite the fact that the two vortex extraction systems evaluated have the potential for substantially reducing rotor costs, these cost savings are more than offset by the additional costs required for the augmentation devices. Based on a preliminary analysis of the presently envisioned conceptual designs of the Tornado Wind Energy System and the Vortex Augmentor System, it does not appear that either system could achieve economic parity with conventional horizontal axis wind systems even if all of the technical uncertainties surrounding these innovative concepts are favorably resolved.
Date: April 1, 1980
Creator: Kornreich, T. R.; Kottler, Jr., R. J. & Jennings, D. M.
Partner: UNT Libraries Government Documents Department

Preliminary technical and economic evaluation of vortex extraction devices

Description: Two innovative vortex extraction devices - the Tornado Wind Energy System (TWES) and the Vortex Augmentor Concept (VAC) - are critically evaluated to provide a preliminary assessment of their technical and economic viability as compared to conventional horizontal axis wind energy systems. This assessment was carried out over a wide range of power output levels and augmentation ratios appropriate to each of the concepts.
Date: April 1, 1980
Creator: Kornreich, T. R.; Kottler, Jr., R. J. & Jennings, D. M.
Partner: UNT Libraries Government Documents Department