Aero-Structural Performance of Multiplane Wind Turbine Blades

TitleAero-Structural Performance of Multiplane Wind Turbine Blades
Publication TypePresentation
Year of Publication2011
AuthorsJohnson, Perry M., and Richard E. Wirz
Keywordsbiplane, blade design, computational fluid dynamics, finite element analysis, inboard region, parametric analysis
AbstractIn current wind turbine blade designs, the inboard region suffers performance losses from competing structural and aerodynamic requirements. The objective of this effort is to develop multiplane inboard configurations that provide attractive aero-structural performance for wind turbine blades. A biplane approach may be sufficient to realize the full benefits of this approach. To compare the performance of a conventional inboard section with a biplane inboard section, cross-sectional properties of a thick monoplane and a biplane were measured to obtain their approximate structural and aerodynamic characteristics. Numerical simulations were used to explicitly compare the aerodynamic performance of a thick monoplane to a biplane. Then, several model beams were designed to be simple approximations of a conventional wind turbine blade ("monoplane beam") and the biplane blade approach ("biplane beam"). Three canonical bending loads were applied to each of these model beams and the deflection of each beam was compared. Numerical simulations show that the lift-to-drag ratio of the biplane is significantly greater than the lift-to-drag ratio of the thick monoplane for the angles of attack investigated (0-15.5 degrees). A parametric analysis of different biplane beam configurations shows that tip deflections of the biplane beam configurations are smaller than those of monoplane beams of the same length. For example, a nominal 50 m biplane blade has less than 30% of the deflection of a 50 m monoplane blade. Thus, for a monoplane beam of fixed length, it is possible to construct a longer biplane beam with an equal tip deflection. These combined aerodynamic and structural benefits can lead directly to greater turbine power by three important advantages: (1) improved aerodynamic performance, (2) improved spacing due to the potential for decreased vortex shedding, and, most importantly, (3) potential increases in blade length due to improved inboard blade strength. Therefore, these results suggest that the biplane blade approach is an attractive design for the next-generation of large wind turbine blades.

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