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The Science of Making Torque from Wind (TORQUE 2018)

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Room: BL.27.0.1
Chaired by: Martin Kühn | ForWind – University Oldenburg
Topic: MET. Measurement and Experimental Techniques
Form of presentation: Oral
Duration: 110 minutes

Authors:
Christopher L Kelley, Thomas G Herges, Paula Doubrawa, Luis A Martinez, Torben Mikkelsen

Abstract:
A method for measuring wake and aerodynamic properties of a wind turbine with reduced error based on simulated lidar measurements is proposed. A scanning lidar measures air velocity scalar projected onto its line of sight. However, line of sight is rarely parallel to the velocities of interest. The line of sight projection correction technique showed reduced axial velocity error for a simple wake model. Next, an analysis based on large-eddy simulations of a 27 m diameter wind turbine was used to more accurately assess the projection correction technique in a turbulent wake. During the simulation, flow behind the turbine is sampled with a nacelle mounted virtual lidar matching the scanning trajectory and sampling frequency of the DTU SpinnerLidar. The axial velocity, axial induction, freestream wind speed, thrust coefficient, and power coefficient are calculated from virtual lidar measurements using two different estimates of the flow: line of sight velocity without correction, and line of sight with projection correction. The flow field is assumed to be constant during one complete scan of the lidar field of view, and the average wind direction is assumed to be equal to the instantaneous wind direction at the lidar measurement location for the projection correction. Despite these assumptions, results indicate that all wake and aerodynamic quantity error is reduced significantly by using the projection correction technique; axial velocity error is reduced on average from 7.4% to 2.8%.

Authors:
Mark A Miller

Abstract:
Vertical Axis Wind Turbines have yet to see wide-spread use as a means of harvesting the kinetic energy of the wind. This may be due in part to the difficulty in modeling the relatively complex flow field and hence performance of these units. Additionally, similar to Horizontal Axis Wind Turbines, VAWTs are quite difficult to properly test in a conventional wind tunnel. Typically Reynolds numbers cannot be matched or the turbine geometry must be altered, limiting the applicability of the results. In full-scale field experiments, steady and unsteady effects are difficult to separate due to the lack of inflow control. The proposed paper utilizes a set of laboratory experiments performed using highly compressed air in a specialized wind tunnel coupled with a geometrically scaled model of a VAWT. This method has allowed for a range of Reynolds numbers that match and more than double that of the full-scale unit. The proposed paper will provide more in-depth analysis of the unsteady turbine loads with Reynolds number changes by performing phase-averaging of the torque signal. The objective of this research is to gain additional insight into the mechanism by which Reynolds number invariance is achieved and to increase the utility of the data set as a reference case for modeling and simulation efforts.

Authors:
Emmanouil Marios Nanos

Abstract:
This paper describes the methodology that was followed for designing a scaled wind turbine model. This model is intended to be used in complex terrain studies as well as deep array wind farm control tests. Therefore, emphasis was given on making it as compact as possible while keeping a high level of instrumentation. The result is a three blade wind turbine with rotor diameter of 0.6m equipped with active pitch, yaw and torque control. After a discussion on the design procedure, we present the performance characteristics of the model obtained both numerically and experimentally.

Authors:
Frederik Berger

Abstract:
Investigations of dynamic inflow phenomena obtained in wind tunnel measurements with a 1.8 m scaled model wind turbine are presented. The focus is on a pitching step experiment at design and rated tip speed ratio with different pitch steps as well as sudden rotor speed changes. Further turbine operation in a free field based, turbulent fluctuating wind flow is shown.

Authors:
Oscar Pires, Xabier Munduate, Ozlem Ceyhan, Koen Boorsma, Helge Aagaard Madsen, Nando Timmer

Abstract:
Aerodynamic experimental tests on wind turbine blade surface roughness and laminar to turbulent transition have been performed on a wind tunnel model and a wind turbine rotor. The wind tunnel tests have been performed at the LSLT facility of TU-Delft and the wind turbine tests at ECN’s Wind turbine Test Site (EWTW). Roughness simulation material has been installed on the airfoil leading edge to measure the impact on the airfoil performance. Microphones have been mounted on the airfoil surface to detect the boundary layer laminar to turbulent transition position. The objectives of the tests are to measure the impact of roughness on airfoil aerodynamic characteristics and the associated effect on the rotor power performance, and to detect the flow transition position on a rotating blade using surface microphones.

20 June  |  21 June  |  22 June  |  Events View
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