Gravo‐aeroelastic scaling of a 13‐MW downwind rotor for 20% scale blades

Abstract

A 105‐m, 13‐MW two‐bladed downwind Segmented Ultralight Morphing Rotor (SUMR‐13) blade was gravo‐aeroelastically scaled by 20% to a 20.87‐m‐long demonstrator blade and confirmed through structural ground testing. The subscale model was achieved through geometric scaling and by aeroelastic scaling principles based on operational flapwise deflections combined with rotational and structural frequencies while retaining the turbine tip‐speed ratio. In particular, the subscale demonstrator was designed to replicate, as closely as possible, the nondimensional geometry, the ratio of centrifugal to gravitational moments, the tip‐speed ratio, and the nondimensional rotation rate. The intent for this demonstrator was to achieve the same nondimensional flapwise blade deflections and dynamics of the full‐scale 13‐MW rotor. The manufactured SUMR‐D blade resulted in less than half of the mass of the conventional two‐bladed Controls Advanced Research Turbine (CART2) rotor blade based on scaling and a lower power rating, though with some differences in mass and stiffness from the ideal scaled‐down design to meet safety requirements at the test site. To achieve proper scaling, operational pitch control set points were altered to account for the differences by evaluating simulated operation of both the SUMR‐13 and SUMR‐D rotors. Structural testing of the SUMR‐D blade investigated the response to well‐defined flapwise loads and indicated that the subscale blade had the appropriate elastic properties needed for both scaling and for safe operational field testing.

Multi‐fidelity digital twin structural model for a sub‐scale downwind wind turbine rotor blade

“…blade was an edge-wise mode, thus resulting in the GAS targets reflecting the same. 19 This trend of the first natural frequency being an edge-wise mode is not observed in the SUMR-D blades owing to relatively higher edge-wise stiffness in SUMR-D versus SUMR13i.…”

“…Based on GAS, targets for blade distributed properties like linear mass density, sectional flap-wise, and edge-wise stiffness are defined. 19 The full-scale SUMR13i turbine 12 was designed to be a two bladed downwind highly coned turbine with an expected 25% reduction in mass in comparison to its three-bladed upwind baseline. 13 The resulting blades are unique, in having a lower first edge-wise frequency than first flap.…”

“…Kaminski et al 19 have used the DTv1.3 model to evaluate the GAS targets for flap-wise deflections and first flap-wise frequency. Additionally, this study examined the performance of the DTv1.3 to the original SUMR13i blade and found that the scaled performance match well in above rated conditions in aeroelastic simulations.…”

Design and analysis of a segmented blade for a 50 MW wind turbine rotor

“…First, the total bolt area required to withstand the shear and axial forces at the joint are determined with equation (1) (shear force on the bolt) and equation ( 2) (von Mises stress on the bolt) which were used to analyze and size the root bolts for SUMR-D (Bay et al, 2019;Chetan et al, 2021;Kaminski et al, 2021;Yao et al, 2019Yao et al, , 2020. We chose to use DLC 1.2 loads in this step because the bolts are made of metal that has a much lower fatigue Wo¨hler exponent (m) than fiberglass and carbon fiber.…”

Influence of tower shadow on downwind flexible rotors: Field tests and simulations

“…The SUMR-D rotor was flown on the CART-2 test turbine over fall 2019 and spring 2020 at the NREL Flatirons Campus. The rotor, shown in Table 1, and further details on the design and testing can be found in Yao et al, 14 Bay et al, 15 Kaminski et al, 16 and Simpson and Loth. 25 The blade chord and the blade clearance from the tower to the rotor are provided in Table 1 at 70% blade span.…”