Wind turbine trailing-edge aerodynamic brake design

Abstract

The Wind Technology Division of the National Renewable Energy Laboratory (NREL) is conducting exploratory research on aerodynamic d vices that are intended to enhance wind-turbine rotor performance and attenuate structural loads. Desired properties of these devices include simplicity, reliability, maintainability, low cost, and fail-safe design. Initial efforts have focused on the use of trailing-edge aerodynamic brakes for overspeed protection. Long-term efforts will address more aggressive and innovative strategies that have the potential to significantly advance the state of the art. • This report touches on the work performed in two projects: Subcontract No. TAD-3-13400 entitled "Wind Turbine Trailing-Edge Aerodynamic Brake Design" performed by Gene A. Quandt, and Subcontract No. XAD-3-133365 entitled "Aerodynamic Devices for Wind Turbine Performance Enhancement" performed by Wichita State University (WSU). These two projects progressed in parallel, with considerable interaction between the principal investigators. The WSU Phase 1 Report discussed the configurations studied and the attempts to identify promising alternatives through the analysis of the wind tunnel test data. The Phase 2 Report presented wind tunnel results for "spoiler-flaps" of 30%, 40% and 50% chord; for various leading-edge lip extensions; for different venting arrangements; and for different device hinge locations. Gene Quandt's subcontract report, the document you are presently reading, focuses on aerodynamic and structural design, and includes preliminary design calculations for a centrifugally actuated aerodynamic brake. As is often the case with exploratory research, these projects have spawned additional follow-on studies. Wind-tunnel tests are planned at Ohio State University in which a pressure-tapped S809 airfoil model will be tested with three trailing-edge devices: the spoiler-flap, a plain flap ("unvented aileron") and a vented plain flap ("vented aileron"). Rotating-blade tests of these same configurations will be conducted at the National Wind Technology Center (NWTC), with the goal of quantifying the effects of unsteadiness, blade rotation, and aspect ratio, so that corrections can be applied to wind tunnel test data for use by wind-turbine designers in the future. iii wind turbine design 1 7. SECURITY CLASSIFICATION

Atmospheric tests of trailing-edge aerodynamic devices

“…Investigators haved focused on identifying device configurations that produce reasonable braking capabilities, subject to simplicity of construction, ease of actuation, and operational reliability considerations. Indeed, a number of different configurations have been evaluated in wind tunnel tests (Quandt 1994, Miller 1995, Griffin 1996, Ramsay, Janiszewska, and Gregorek 1996.…”

Investigation of aerodynamic braking devices for wind turbine applications

“…The publication of these recent tests results is pending. Quandt is currently working on the testing of prototype spoiler-flaps f7], and has published the preliminary design of spoiler-flaps for a Micon 65/1 3 [8]. …”

Experimental Investigation of Aerodynamic Devices for Wind Turbine Rotational Speed Control: Phase I

“…Final choices were based primarily on their assumed potential for aerodynamic braking applications. Additional details on the various trailing-edge controls are provided by Quandt (1994), who conceived and developed with WSU the various test configurations.…”