Development of an Aerodynamic Analysis Methodology for Segmented Ultralight Morphing Rotors

Abstract

The Segmented Ultralight Morphing Rotor (SUMR) concept for a 50 MW wind turbine will help alleviate the technical challenges presented by a conventional upwind rotor design for such extreme-scale wind turbines. Such segmented rotor blades can be morphed to achieve load alignment which will significantly reduce the cantilever moments, thus allowing for a lighter blade design. Depending on the wind speed, these rotors may be morphed into highly coned configurations. Consequently, a computational tool was developed in this study for the analysis of the SUMR rotors in different morphing configurations. The analysis tool was developed by modifying the Blade Element Momentum method for the morphing rotor geometry. The model was implemented in a MATLAB code, BladeMorph, and will be subsequently combined with PROPID for the purpose of rapid design and analysis of the large-scale SUMR rotors. An example 13 MW SUMR rotor, referred to as the E-13 rotor in this paper, was designed in PROPID and analyzed in BladeMorph for various cone angles to obtain the C P and C T vs tip speed ratio curves and radial distributions of pertinent aerodynamic parameters. The predictions from BladeMorph were then compared with AeroDyn v14, and it was found that the predictions from both codes were in fairly good agreement. A large reduction in both rotor power and rotor thrust coefficients with an increase in coning angles was found. The angles of attack α, lift coefficient C l , and drag cofficient C d along the blade length were reduced at higher coning, while the variation in the net relative velocity, Reynolds number, and dynamic pressure along the blade was found to be minimal. Finally, with increasing coning, the axial induction distribution was found to increase toward the outboard region of the blade compared with the zero coning case, while decreasing near the inboard region of the blade.

Subscale Testing of Horizontal-Axis Wind Turbines

“…The results obtained will be used for validation of BEMT codes developed for analysis of highly coned rotors. 3…”

“…However, coning the wind turbine blades at high angles and the possible use of segmented multiconing is something that has not been explored before. Therefore, a new BEMT code, BladeMorph, 3 is being developed as a part of the ARPA-E SUMR program for the purpose of rapid design and analysis of highly-coned rotors. To validate BladeMorph along with other computational analysis codes for wind turbines, such as AeroDyn 4,5 and PROPID 6,7 and to address the dearth in wind tunnel testing data for high coning angles in literature, a wind tunnel rig was designed and manufactured for subscale testing of horizontal axis wind turbines.…”

“…Due to many practical limitations, a perfect scaling of the extreme-scale SUMR wind turbine rotors for testing in the UIUC wind tunnel was not achievable. However, since the aim of these experiments was to validate the codes at high coning angles, 3 an entirely new rotor was designed to be tested at low Reynolds number for various coning and pitch angles. Both the freestream velocity and turbine rotation speed (RPM) were also varied, and the measured outputs were power (C P ) and thrust (C T ) coefficients.…”