Phase VI Blade Research Articles

Improvement of wind turbine performance using a novel tip plate structure

In this study, the improvement of a horizontal-axis wind turbine performance is numerically studied using different configurations of tip plates. To do so, we independently develop a 3-D numerical code based on the finite volume method to solve the governing equations including the continuity and Reynolds Averaged Navier-Stokes equations using SST k-ω turbulence model. The NREL Phase VI blade is used as a target blade to suppress the induced drag of the blade tip vortices by the plates attached to the blade tips. The numerical results obtained indicate sixteen percent of power improvement in the two-blade horizontal axis wind turbine for the best tip plate configuration.

Prediction of Aerodynamic Loads for NREL Phase VI Wind Turbine Blade in Yawed Condition

Aerodynamic loads for a horizontal axis wind turbine of the National Renewable Energy Laboratory (NREL) Phase VI rotor in yawed condition were predicted by using the blade element momentum theorem. The classical blade element momentum theorem was complemented by several aerodynamic corrections and models including the Pitt and Peters' yaw correction, Buhl's wake correction, Prandtl's tip loss model, Du and Selig's three-dimensional (3-D) stall delay model, etc. Changes of the aerodynamic loads according to the azimuth angle acting on the span-wise location of the NREL Phase VI blade were compared with the experimental data with various yaw angles and inflow speeds. The computational flow chart for the classical blade element momentum theorem was adequately modified to accurately calculate the combined functions of additional corrections and models stated above. A successive under-relaxation technique was developed and applied to prevent possible failure during the iteration process. Changes of the angle of attack according to the azimuth angle at the specified radial location of the blade were also obtained. The proposed numerical procedure was verified, and the predicted data of aerodynamic loads for the NREL Phase VI rotor bears an extremely close resemblance to those of the experimental data.

A site-specific design of a fixed-pitch fixed-speed wind turbine blade for energy optimization using surrogate models

This work seeks to add a new approach to optimize a wind turbine blade's performance by implementing a surrogate model using the Kriging function with the chord, twist and the use of 3 different airfoils as design variables for the maximization of the Annual Energy Production. A combination of Genetic Algorithms and the SQP method for Local Search are used to exploit the model. A baseline design of the blade starts with a replica of the Phase VI blade utilized in a NASA-Ames experiment and a MatLab script utilizes the Blade Element Momentum Theory (BEM) for the aerodynamic analysis. Results show a 23% improvement in energy production by using this method.

Aeroelastic analysis of wind turbines using a tightly coupled CFD–CSD method

This paper presents aeroelastic analyses of wind turbines, using the compressible flow Helicopter Multi-Block (HMB2) solver of Liverpool University, coupled with a Computational Structural Dynamics method. For this study, the MEXICO and NREL Phase VI wind turbines were employed. A static aeroelastic method was first employed for the analysis of the MEXICO blade and the effect of the torsional stiffness was studied at 10, 15 and 24m/s axial wind speeds. The torsional deformations showed strong dependency on this parameter and the blade region from mid-span to the tip was the most susceptible to aeroelastic effects. The work progressed by studying both the static and dynamic response on the NREL wind turbine, where the nacelle and the tower were considered. Mean deflections between the static and dynamic methods showed consistency and, due to the structural properties of this blade, flapping modes were dominant. The dynamic aeroelastic method enabled an assessment of the effect of flapping on the blade loads, in conjunction with the effect of tower. Aeroelastic effects were found to be secondary for the MEXICO blade, but had a stronger effect on the larger NREL Phase VI blade.

Inverse design of horizontal axis wind turbine blades using a vortex line method

AbstractA new inverse design process for horizontal axis wind turbine blades is developed to account for three‐dimensional blade features such as non‐planar wing tip. The multidimensional Newton iteration method combined with a vortex line method is used to provide blade geometry parameters given desired aerodynamic behaviors such as lift coefficient and axial induction. The Jacobian matrix is visualized to show the effect of the change of the blade twist and chord on the change of the aerodynamic behaviors. The method is validated for a canonical straight blade with uniform lift coefficient and axial induction distributions. The results show an excellent agreement with those obtained by PROPID, which is a blade element momentum theory‐based inverse design code. The National Renewable Energy Laboratory Phase VI blade is used to validate the method for a straight blade with non‐uniform distributions of the lift coefficient and axial induction. The method is also applied successfully to a non‐straight blade design with a non‐planar wing tip. A noticeable change in the twist and chord for this non‐straight blade is seen compared with a straight blade. Finally, the inverse design code is used to make a large rotor blade, and the power output generated by this blade is computed. Copyright © 2014 John Wiley & Sons, Ltd.

Performance prediction of NREL (National Renewable Energy Laboratory) Phase VI blade adopting blunt trailing edge airfoil

This study uses Computational Fluid Dynamics (CFD) to evaluate the performance of a blade with blunt airfoil which is adapted at the root. FLUENT software is used of numerical analysis, and ICEM-CFD is used for generating mesh representations. The experimental conditions of the blade used for this study were based on experimental data presented by the National Renewable Energy Laboratory. The models for numerical analysis are blades in which the blunt trailing-edge thickness was 1%, 5% and 10% of the chord. These blades are modifications of the NREL (National Renewable Energy Laboratory) Phase VI blade. For detailed data, the numerical analysis has been performed for wind speeds of 7, 10, 15, 20, and 25 m/s. Also, the comparison analysis of results of a baseline and modified blades has been performed.

Analysis of the Flow Characteristics of Two Nonrotating Rotor Blades

The investigation focuses on the analysis of the airfoil segment performances along rotor blades in the parked configuration. In this research, wind tunnel experiments on two twisted blade geometries with different airfoils played a dominant role. These measurements were carried out by the Swedish Aeronautical Research Institute, former FFA, and by the American National Renewable Energy Laboratories (NREL) during the Unsteady Aerodynamic Experiment. The spans of the blades were 2.375m and 5m, the STORK 5 WPX and the NREL Phase VI blade, respectively. Five span locations (inboard, midspan, outboard, and tip regions) were considered and compared with the 2D airfoil characteristics. Wing model experiments with similar blade aspect ratio were included in the research. Furthermore, the commercial computational fluid dynamics code FLUENT was used for the validation and analysis of the spanwise lift and drag coefficients at four different pitch settings, 20deg, 30deg, 45deg, and 60deg. The computed pressure distributions compared reasonably well, but the derived lift and drag showed quite some differences with the blade measurements. The lift coefficients for the sections beyond the leading-edge stall angle of the STORK blade were larger than for the NREL blade and were close to that of a wing model with similar airfoil and aspect ratio. Lift and drag coefficients for the sections of the two blades were always much smaller than the 2D results. The drag values for both blades showed quite some agreement, and airfoil and blade dependency seemed to be small.

Detached‐eddy simulation of flow around the NREL Phase VI blade

AbstractThe detached‐eddy simulation model implemented in the computational fluid dynamics code EllipSys3D is used to calculate the flow around the non‐rotating NREL Phase VI wind turbine blade. Results are presented for flow around a parked blade at fixed angle of attack and a blade pitching along the blade axis. Computed blade characteristics are compared with experimental data from the NREL/NASA Ames Phase VI unsteady experiment. The detached‐eddy simulation model is a method for predicting turbulence in computational fluid dynamics computations, which combines a Reynolds‐averaged Navier–Stokes method in the boundary layer with a large‐eddy simulation in the free shear flow. The present study focuses on static and dynamic stall regions highly relevant for stall‐regulated wind turbines. Computations do predict force coefficients and pressure distributions fairly well. Results using detached‐eddy simulation show considerably more three‐dimensional flow structures compared to conventional two‐equation Reynolds‐averaged Navier–Stokes turbulence models, but no particular improvements are seen in the global blade characteristics. Copyright © 2002 John Wiley & Sons, Ltd.