Improvements in the Power Output of a Horizontal Axis Wind Turbine Due to the Introduction of a Curved Blade

2002 ◽  
Author(s):  
Erin K. Clarke ◽  
Sylvester Abanteriba
Keyword(s):  
Wind Tunnel ◽  
Flow Visualization ◽  
Wind Turbine ◽  
Power Output ◽  
Turbine Blades ◽  
Horizontal Axis Wind Turbine ◽  
Modified Model ◽  
Curved Blade ◽  
Generation Capacity ◽  
The Impact

This paper examines the impact on the power generation capacity of a wind turbine as a result of the modification of the shape of the blades of an existing wind turbine. The modification involves curving the blades in the direction of rotation resulting in an increase in generated lift and therefore an increase in the power output of the wind turbine. Two three-bladed models were tested in a wind tunnel, one original straight-bladed model and one modified model both of which were 0.84 m in diameter. A study of the methods of flow visualization for a wind turbine in a wind tunnel was investigated. The corresponding results are presented. It was discovered that the china clay method of flow visualization in conjunction with a strobe light gave a good indication of the direction of the airflow over the turbine blades as did condensed oil droplets from a smoke wand which presented a very clear indication of the span-wise flow. It was concluded from the investigation that curving the blade into the direction of rotation on a wind turbine produced a greater power output at the same wind speed as an unmodified wind turbine.

Modeling of Rain Drop Erosion in a Multi-MW Wind Turbine

2015 ◽  
Author(s):  
Alessandro Corsini ◽  
Alessio Castorrini ◽  
Enrico Morei ◽  
Franco Rispoli ◽  
Fabrizio Sciulli ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Design Stage ◽  
Base Line ◽  
Horizontal Axis Wind Turbine ◽  
Relevant Effect ◽  
The Impact ◽  
Rain Erosion

The actual strategy in offshore wind energy development is oriented to the progressive increase of the turbine diameter as well as the per unit power. Among many pioneering technological and aerodynamic issues linked to this design trend, the wind velocity at the blade tip region reaches very high values in normal operating conditions (typically between 90 to 110 m/s). In this range of velocity, the rain erosion phenomenon can have a relevant effect on the overall turbine performance in terms of power and energy production (up to 20% loss in case of deeply eroded leading edge). Therefore, as a customary approach erosion related issues are accounted for in the scheduling of the wind turbine maintenance. When offshore, on the other hand, the criticalities inherent to the cost of maintenance and operation monitoring suggest the rain erosion concerns to be tackled at the turbine design stage. In so doing, the use of computational tools to study the erosion phenomenon of wind turbines under severe meteorological conditions could define the base-line approach in the wind turbine blades design and verification. In this work, the authors present a report on numerical prediction of erosion on a 6 MW HAWT (horizontal axis wind turbine). Two different blade geometries of different aerodynamic loading, have been studied in a view to explore their sensitivity to rain erosion. The fully 3D simulations are carried out using an Euler-Lagrangian approach. Flow field simulations are carried out with the open-source code OpenFOAM, based on a finite volume approach, using Multiple Reference Frame methodology. Reynolds Averaged Navier-Stokes equations for incompressible steady flow were solved with a k-ε turbulence. An in-house code (P-Track) is used to compute the rain drops transport and dispersion, adopting the Particle Cloud Tracking approach (PCT), already validated on large industrial turbomachinery. At the impact on blade, erosion is modelled accounting for the main quantities affecting the phenomenon, which are impact velocity and material properties of the target surface. Results provide the regions of the two blades more sensitive to erosion, and the effect of the blade geometry on erosion attitude.

Investigation of Wind Turbine Blades with Tubercles

2014 ◽  
Vol 1051 ◽  
pp. 832-839 ◽  
Author(s):  
Kelvin Leung
Keyword(s):  
Flow Visualization ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Flow Separation ◽  
Power Output ◽  
Turbine Blades ◽  
Length Ratio ◽  
Wind Turbine Blades

This paper describes the testing of wind turbine blades with tubercles in two different ways: outdoor testing and flow visualization. In the outdoor testing, the tubercle pitch was varied for turbine blade lengths of 30 cm, 40 cm, and 50 cm. The pitch-to-length ratio of approximately 1/10 to 1/16 produced the most power output. In flow visualization, both tubercle pitch and amplitude were varied. Vortices created behind the tubercles were shown to increase lift by minimizing flow separation.

Assessment of a Modified Blade Element Momentum Methodology for Diffuser Augmented Wind Turbines

2017 ◽  
Author(s):  
Stavros N. Leloudas ◽  
Georgios N. Lygidakis ◽  
Ioannis K. Nikolos
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Power Output ◽  
Horizontal Axis Wind Turbine ◽  
Correction Model ◽  
Short Period ◽  
Turbine Design ◽  
The Impact ◽  
Bem Theory ◽  
Blade Element

The Blade Element Momentum (BEM) theory is nowadays the cornerstone of the horizontal axis wind turbine design, as its application allows for the accurate aerodynamic simulation and power output prediction of wind turbine rotors in a remarkably short period of time. Therefore, efforts have been made for the extension of the classic BEM theory to the performance analysis of Diffuser Augmented Wind Turbines (DAWTs) as well. In this study, the development and assessment of such an in-house BEM code are presented. The proposed computational model is based on the modification of the momentum part of the classical BEM theory; thus, it is capable to account for the diffuser’s effect on the calculation of the axial and tangential induction factors, through the utilization of the velocity speed-up distribution over the rotor plane of the unloaded diffuser. Furthermore, a detailed Glauert’s correction model, which employs Buhl’s modification, specially tailored for the DAWT case is included, to deal with the high values of the axial induction factor. The accuracy of the model is assessed against numerical and experimental results available in the literature, while the impact of the Prandtl’s tip loss correction model on the rotor’s predicted power output is also examined.

PERFORMANCE EVALUATION AND WAKE STUDY OF A MICRO WIND TURBINE

2011 ◽  
Vol 35 (1) ◽  
pp. 101-117 ◽  
Author(s):  
Graeme I. Comyn ◽  
David S. Nobes ◽  
Brian A. Fleck
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Power Output ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Published Data ◽  
Wind Turbine Blades ◽  
Axial Thrust ◽  
Cross Sectional ◽  
Output Performance

In preparation for a study on icing of wind turbine blades, we tested a horizontal axis micro wind turbine in a low speed wind tunnel. The ratio of wind turbine rotor area to wind tunnel cross-sectional area resulted in highly blocked experimental configuration. The turbine was instrumented to measure rotational speed of the rotor, axial thrust and power output. Performance characteristics were calculated and compared with the manufacturer’s published data. In addition, the near wake of the turbine was measured with a Kiel probe. One dimensional axial momentum theory, including a modification that includes channel walls, was applied to determine power extracted from the wind by the rotor. The results were compared to actual power output and show that though the assumptions of the model over-predict power by 50 % the basic trend is followed.

Blade Dynamic Stall Vortex Kinematics for a Horizontal Axis Wind Turbine in Yawed Conditions*

2001 ◽  
Vol 123 (4) ◽  
pp. 272-281 ◽  
Author(s):  
Scott J. Schreck ◽  
Michael C. Robinson ◽  
M. Maureen Hand ◽  
David A. Simms
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Turbine Blades ◽  
Unsteady Aerodynamics ◽  
Horizontal Axis ◽  
Dynamic Stall ◽  
Deformation Analysis ◽  
Horizontal Axis Wind Turbine ◽  
The Impact ◽  
Vortex Kinematics

Horizontal axis wind turbines routinely suffer significant time varying aerodynamic loads that adversely impact structures, mechanical components, and power production. As lighter and more flexible wind turbines are designed to reduce overall cost of energy, greater accuracy and reliability will become even more crucial in future aerodynamics models. However, to render calculations tractable, current modeling approaches admit various approximations that can degrade model predictive accuracy. To help understand the impact of these modeling approximations and improve future models, the current effort seeks to document and comprehend the vortex kinematics for three-dimensional, unsteady, vortex dominated flows occurring on horizontal axis wind turbine blades during non-zero yaw conditions. To experimentally characterize these flows, the National Renewable Energy Laboratory Unsteady Aerodynamics Experiment turbine was erected in the NASA Ames 80 ft×120 ft wind tunnel. Then, under strictly-controlled inflow conditions, turbine blade surface pressures and local inflow velocities were acquired at multiple radial locations. Surface pressure histories and normal force records were used to characterize dynamic stall vortex kinematics and normal forces. Stall vortices occupied approximately two-thirds of the aerodynamically active blade span and persisted for nearly one-fourth of the blade rotation cycle. Stall vortex convection varied dramatically along the blade radius, yielding pronounced dynamic stall vortex deformation. Analysis of these data revealed systematic alterations to vortex kinematics due to changes in test section speed, yaw error, and blade span location.

Experimental investigations and aerodynamic shape optimization of small horizontal axis wind turbine blades

2021 ◽  
Author(s):  
Manoj Kumar Chaudhary ◽  
S Prakash
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Research Work ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Wind Turbine Blades ◽  
Horizontal Axis Wind Turbine ◽  
The Impact ◽  
Blade Geometry

This paper aims to optimize and investigate the small horizontal axis wind turbine blades at low wind speed. The objective of this research work is to explain the design method based on BEM theory for 0.2 m blade rotors with constant, variable and linear chord with twisted blade geometry. MATLAB and Xfoil programs were used for BEM principles and wind turbines with SG6043 airfoil. A numerical and experimental study was carried out to examine the impact of rotor solidity from 0.057 to 0.207 and the number of blades from 3 to 7 in this research work. The experimental blades were developed by using the 3D printing additive manufacturing technique. The investigation of the rotors has been done in an open wind tunnel, at wind speed from 2 to 8 m/s. The initial investigation range included tip speed ratios from 2 to 8, and angle of attacks from 2 to 20°. Later on these parameters were varied in Matlab and Xfoil software optimization and investigation of the power coefficient, blade geometry, number of blades and blade pitch angle. It was found that the rotor solidity 0.055 to 0.085 displayed better performances.

Experimental investigations of flow over NACA airfoils 0021 and 4412 of wind turbine blades with and without Tubercles

2021 ◽  
pp. 0309524X2110071
Author(s):  
Usman Butt ◽  
Shafqat Hussain ◽  
Stephan Schacht ◽  
Uwe Ritschel
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Wind Turbine ◽  
Critical Region ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Wind Turbine Blades

Experimental investigations of wind turbine blades having NACA airfoils 0021 and 4412 with and without tubercles on the leading edge have been performed in a wind tunnel. It was found that the lift coefficient of the airfoil 0021 with tubercles was higher at Re = 1.2×105 and 1.69×105 in post critical region (at higher angle of attach) than airfoils without tubercles but this difference relatively diminished at higher Reynolds numbers and beyond indicating that there is no effect on the lift coefficients of airfoils with tubercles at higher Reynolds numbers whereas drag coefficient remains unchanged. It is noted that at Re = 1.69×105, the lift coefficient of airfoil without tubercles drops from 0.96 to 0.42 as the angle of attack increases from 15° to 20° which is about 56% and the corresponding values of lift coefficient for airfoil with tubercles are 0.86 and 0.7 at respective angles with18% drop.

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