Abstract
It is shown in the literature that wind turbine designs with different load distributions have different wake features. To systematically study how different load distributions affect turbine wakes, a method for designing variants of blades with different radial load distributions, but with approximately the same power (CP) or thrust coefficient (CT), is needed. In this work, an inverse design method based on the blade element momentum method and the multi-dimensional Newton’s method, with the normal and tangential force coefficients as the design objective and iterations for satisfying the CP or CT constraint, is developed. The proposed method is validated using the two-bladed small-scale NREL phase VI S809 wind turbine blade design and the three-bladed utility-scale NREL 5 MW wind turbine blade design. Four variants of the NREL 5 MW wind turbine, i.e., the Root-CP, Tip-CP, Root-CT, and Tip-CT designs, which represent the variants of the original design (NREL-Ori) with a higher load near the blade root and tip regions with approximately the same power coefficient (CP) or thrust coefficient (CT) as that of the NREL-Ori design, respectively, are then designed using the proposed method. At last, the flapwise blade bending moment and the power coefficients from different variants of the NREL 5 MW turbine are compared for different tip speed ratios, showing that the “Root” designs are featured by a wider chord near the root, lower blade bending moment, and higher power coefficients for tip-speed ratios greater than nine.
Highlights
Driven by the increasing demand for energy systems with low or net-zero carbon emission to slow climate change, wind energy is becoming one of the fastest growing renewable energies [1–4]
The methods for designing wind turbine blades can be classified into two categories: (i) the direct approach which is called the design-by-analysis approach, and (ii) the inverse design approach
Since the direct approach is time consuming with no guarantee of achieving the desired optimum values, an inverse design approach was developed by Selig and Tangler [24]
Summary
Driven by the increasing demand for energy systems with low or net-zero carbon emission to slow climate change, wind energy is becoming one of the fastest growing renewable energies [1–4]. Since the direct approach is time consuming with no guarantee of achieving the desired optimum values, an inverse design approach was developed by Selig and Tangler [24] They combined the multi-dimensional Newton’s iteration method with the BEM method to design the blade twist and chord distributions with the desired distributions of the lift coefficient and the axial induction factor along the blade radial directions. It will be convenient if one can obtain such blade designs from the existing wind turbine blade design To achieve this objective, in this paper, we develop an inverse method based on the multi-dimensional. One drawback of the method developed in this work is the low fidelity of the employed blade element momentum method for modeling the aerodynamics of wind turbines, which depends on the quality of the lift and drag coefficients as well as the corrections for the three-dimensional effect and the tip loss correction [9].
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