Effect of taper modification on the performance of NREL VI wind turbine blade for low and mid wind speeds

2019 ◽  
Vol 43 (4) ◽  
pp. 392-403 ◽  
Author(s):  
Mustafa Kaya ◽  
Munir Elfarra
Keyword(s):  
Wind Turbine ◽  
Turbulence Model ◽  
Rotor Blade ◽  
Eddy Viscosity ◽  
Chord Length ◽  
Navier Stokes ◽  
Spanwise Direction ◽  
New Approach ◽  
Wind Speeds ◽  
Nrel Phase Vi

The taper distribution along the span of the NREL phase VI rotor blade is modified using a new approach. The taper distribution in this approach is expressed as a cubic spline defined by three chord lengths values in the spanwise direction: root, mid-span and tip. Then, the effect of the modified taper distribution on the thrust and the torque is studied. Various blade geometries are generated using different chord length values on the root, mid-span and tip locations while the planform area is kept fixed as the original blade, NREL VI. The flowfields are calculated using a commercial Reynolds averaged Navier–Stokes solver. The k-epsilon turbulence model is used to calculate the eddy viscosity. The computations are carried out for three different wind speeds: 5, 7 and 9 m/s. Increasing torque and decreasing thrust cases are observed. It is noticed that torque increases when the tip chord length is about one-fifth of the root and mid-span chord lengths. The thrust is decreased, as the root chord is much longer than the mid-span and the tip chord.

Performance Enhancement Analysis of a Horizontal Axis Wind Turbine by Vortex Trapping Cavity

2021 ◽  
pp. 1-13
Author(s):  
Khaoula Qaissi ◽  
Omer A Elsayed ◽  
Mustapha Faqir ◽  
Elhachmi Essadiqi
Keyword(s):  
Wind Turbine ◽  
Performance Enhancement ◽  
Lift Coefficient ◽  
Separated Flow ◽  
National Renewable Energy Laboratory ◽  
Wake Region ◽  
High Twist ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Nrel Phase Vi

Abstract A wind turbine blade has the particularity of containing twisted and tapered thick airfoils. The challenge with this configuration is the highly separated flow in the region of high twist. This research presents a numerical investigation of the effectiveness of a Vortex Trapping Cavity (VTC) on the aerodynamics of the National renewable Energy laboratory (NREL) Phase VI wind turbine. First, simulations are conducted on the S809 profile to study the fluid flow compared to the airfoil with the redesigned VTC. Secondly, the blade is simulated with and without VTC to assess its effect on the torque and the flow patterns. The results show that for high angles of incidence at Rec=106, the lift coefficient increases by 10% and the wake region appears smaller for the case with VTC. For wind speeds larger than 10 m/s, the VTC improves the torque by 3.9%. This is due to the separation that takes place in the vicinity of the VTC and leads to trapping early separation eddies inside the cell. These eddies roll up forming a coherent laminar vortex structure, which in turn sheds periodically out of the cell. This phenomenon favourably reshapes excessive flow separation, reenergizes the boundary layer and globally improves blade torque.

Navier-Stokes and Comprehensive Analysis Performance Predictions of the NREL Phase VI Experiment

2003 ◽  
Author(s):  
Earl P. N. Duque ◽  
Michael D. Burklund ◽  
Wayne Johnson
Keyword(s):  
Experimental Data ◽  
Wind Turbine ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Horizontal Axis Wind Turbine ◽  
Performance Predictions ◽  
Nasa Ames Research ◽  
Nrel Phase Vi ◽  
Wind Turbine Rotor

A vortex lattice code, CAMRAD II, and a Reynolds-Averaged Navier-Stoke code, OVERFLOW-D2, were used to predict the aerodynamic performance of a two-bladed horizontal axis wind turbine. All computations were compared with experimental data that was collected at the NASA Ames Research Center 80-by 120-Foot Wind Tunnel. Computations were performed for both axial as well as yawed operating conditions. Various stall delay models and dynamics stall models were used by the CAMRAD II code. Comparisons between the experimental data and computed aerodynamic loads show that the OVERFLOW-D2 code can accurately predict the power and spanwise loading of a wind turbine rotor.

scholarly journals Aerodynamic Investigation of a Horizontal Axis Wind Turbine with Split Winglet Using Computational Fluid Dynamics

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4983 ◽  
Author(s):  
Miguel Sumait Sy ◽  
Binoe Eugenio Abuan ◽  
Louis Angelo Macapili Danao
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Renewable Energy ◽  
Wind Turbine ◽  
Renewable Energy Sources ◽  
Horizontal Axis ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Blade Tip ◽  
Nrel Phase Vi

Wind energy is one of the fastest growing renewable energy sources, and the most developed energy extraction device that harnesses this energy is the Horizontal Axis Wind Turbine (HAWT). Increasing the efficiency of HAWTs is one important topic in current research with multiple aspects to look at such as blade design and rotor array optimization. This study looked at the effect of wingtip devices, a split winglet, in particular, to reduce the drag induced by the wind vortices at the blade tip, hence increasing performance. Split winglet implementation was done using computational fluid dynamics (CFD) on the National Renewable Energy Lab (NREL) Phase VI sequence H. In total, there are four (4) blade configurations that are simulated, the base NREL Phase VI sequence H blade, an extended version of the previous blade to equalize length of the blades, the base blade with a winglet and the base blade with split winglet. Results at wind speeds of 7 m/s to 15 m/s show that adding a winglet increased the power generation, on an average, by 1.23%, whereas adding a split winglet increased it by 2.53% in comparison to the extended blade. The study also shows that the increase is achieved by reducing the drag at the blade tip and because of the fact that the winglet and split winglet generating lift themselves. This, however, comes at a cost, i.e., an increase in thrust of 0.83% and 2.05% for the blades with winglet and split winglet, respectively, in comparison to the extended blade.

scholarly journals Numerical Study of Effect of Blade Twist Modifications on the Aerodynamic Performance of Wind Turbine

2019 ◽  
Vol 8 (3) ◽  
pp. 285-292 ◽  
Author(s):  
Wiroj Beabpimai ◽  
Tawit Chitsomboon
Keyword(s):  
Wind Turbine ◽  
Numerical Study ◽  
Twist Angle ◽  
Turbine Rotor ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Computational Results ◽  
Baseline Phase ◽  
Wind Speeds ◽  
Modification Technique

This paper aims to investigate aerodynamic performance of a wind turbine blade with twist modifications using computational fluid dynamics (CFD). The phenomenon of 3D stall-delay effect in relation to blade twist is the key feature to be investigated in order to improve efficiency of a wind turbine. The NREL (National Renewable Energy Laboratory) Phase VI wind turbine rotor was used for validation and as the baseline rotor. The baseline blade geometry was modified by increasing/decreasing the twist angles in the inboard, mid-board and outboard regions of the blade in the form of a symmetrical curve with maximum twist angle of 3°. The steady incompressible Reynolds-averaged Navier-Stokes (RANS) equations with the k-ω Shear Stress Transport (SST) turbulence closure model were used for the calculations at wind speeds ranging from 5-20 m/s. The computational results for the baseline Phase VI rotor were validated against experimental data and a good agreement was found. The computational results for the modified blades were compared against those of the baseline blade. It was found that increase of annual energy production of up to 5.1% could be achieved by this modification technique.  ©2019. CBIORE-IJRED. All rights reserved

Power Generation From Wind Turbines in a Solar Chimney

2011 ◽  
Author(s):  
Tudor Foote ◽  
Ramesh Agarwal
Keyword(s):  
Power Generation ◽  
Wind Turbine ◽  
Wind Power ◽  
Wind Turbines ◽  
Stokes Equations ◽  
Computational Study ◽  
Boussinesq Approximation ◽  
Navier Stokes ◽  
Solar Chimney ◽  
Wind Speeds

In past several years, several studies have shown that the shrouded wind turbines can generate greater power compared to bare turbines. A solar chimney not only generates an upward draft of the wind inside the solar tower but also creates a shroud around the wind turbine. There is large number of empty silos on farms, especially in mid-western U.S. They can be used as a solar chimney with minor modifications at very modest cost. The objective of this study is to determine the potential of these silos/chimneys in generating wind-power by installing a wind turbine inside the silo. An analytical/computational study is performed to evaluate this potential by employing the well known commercial Computational Fluid Dynamics (CFD) software FLUENT. An actuator disc model is used to model the turbine. Calculations are performed for three cases using the dimensions of a typical silo and assuming Class 3 wind velocity: (a) bare turbine (without enclosing silo), (b) turbine enclosed by a cylindrical silo, and (c) the turbine enclosed by the cylindrical silo with a diffuser at the top of the silo. The incompressible Navier-Stokes equations with Boussinesq approximation and a two equation realizable k–ε model are employed in the calculations. Cp and generated power are calculated for the three cases. It was found that the silo increases the Cp beyond the Betz’s limit significantly and as a result the generated power; this effect is consistent with that found in the recent literature that the shrouded wind-turbines can generate greater power than the bare turbines. The inclusion of a diffuser on top of the silo further increases the generated power and Cp. The results reported here are for typical silo dimensions and wind speeds; the results for silos with different dimensions and wind speeds can be easily generated. This study shows the potential of using abandoned silos in mid-west for wind power generation.

A New Method for Horizontal Axis Wind Turbine Angle of Attack Determination

2013 ◽  
Vol 291-294 ◽  
pp. 425-428 ◽  
Author(s):  
Mohammad Moshfeghi ◽  
Kun Lu ◽  
Yong Hui Xie
Keyword(s):  
Wind Turbine ◽  
High Velocity ◽  
Normal Force ◽  
Data Extraction ◽  
Angle Of Attack ◽  
Horizontal Axis ◽  
New Method ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Nrel Phase Vi

This paper proposes a new method for horizontal axis wind turbine (HAWT) angle of attack (AOA) determination. Despite common circular planes for data extraction, here, data is extracted on rectangular planes. NREL Phase VI is used for validation of the method. Results show that even in a high velocity wind the proposed plane can be an appropriate choice. Furthermore, the average radial distributions of axial and tangential induction factors are calculated based on the velocity values at the planes. Moreover, local normal force coefficients are calculated and then, the local AOA are compared with 2D results and other 3D values for different wind speeds.

Evaluation of Turbulence Models for the Prediction of Wind Turbine Aerodynamics

2003 ◽  
Author(s):  
Sarun Benjanirat ◽  
Lakshmi N. Sankar ◽  
Guanpeng Xu
Keyword(s):  
Wind Turbine ◽  
Model Development ◽  
Turbulence Models ◽  
Separated Flow ◽  
Equation Model ◽  
Navier Stokes ◽  
Implicit Time ◽  
Horizontal Axis Wind Turbine ◽  
Attached Flow ◽  
Nrel Phase Vi

The performance of the NREL Phase VI horizontal axis wind turbine has been studied with a 3-D unsteady Navier-Stokes solver. This solver is third order accurate in space and second order accurate in time, and uses an implicit time marching scheme. Calculations were done for a range of wind conditions from 7 m/s to 25 m/s where the flow conditions ranged from attached flow to massively separated flow. A variety of turbulence models were studied: Baldwin-Lomax Model, Spalart-Allmaras one-equation model, and k-ε two equations model with and without wall corrections. It was found all the models predicted the normal forces and associated bending moments well, but most of them had difficulties in modeling the chord wise forces, power generation, and pitching moments. It was found that the k-ε model with near wall corrections did the best job of predicting most the quantities with acceptable levels of accuracy. Additional studies aimed at transition model development, and grid sensitivity studies in the tip region are deemed necessary to improve the correlation with experiments.

Unsteady Heat Transfer in Stator–Rotor Interaction by Two-Equation Turbulence Model

1999 ◽  
Vol 121 (3) ◽  
pp. 436-447 ◽  
Author(s):  
V. Michelassi ◽  
F. Martelli ◽  
R. De´nos ◽  
T. Arts ◽  
C. H. Sieverding
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Rotor Blade ◽  
Two Dimensions ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Turbine Stage ◽  
Pressure Losses ◽  
Transonic Turbine ◽  
Variable Operating Conditions

A transonic turbine stage is computed by means of an unsteady Navier–Stokes solver. A two-equation turbulence model is coupled to a transition model based on integral parameters and an extra transport equation. The transonic stage is modeled in two dimensions with a variable span height for the rotor row. The analysis of the transonic turbine stage with stator trailing edge coolant ejection is carried out to compute the unsteady pressure and heat transfer distribution on the rotor blade under variable operating conditions. The stator coolant ejection allows the total pressure losses to be reduced, although no significant effects on the rotor heat transfer are found both in the computer simulation and the measurements. The results compare favorably with experiments in terms of both pressure distribution and heat transfer around the rotor blade.

Numerical Simulations of the Aerodynamics of Circulation Control Wind Turbines Under Yawed Flow Conditions

2010 ◽  
Author(s):  
Lakshmi N. Sankar ◽  
Chanin Tongchitpakdee ◽  
Mina Zaki ◽  
Robert Englar
Keyword(s):  
Wind Turbine ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Circulation Control ◽  
Horizontal Axis Wind Turbine ◽  
Flow Solver ◽  
Wind Speeds ◽  
Low Wind Speeds ◽  
Nrel Phase Vi

The aerodynamic performance of a wind turbine rotor equipped with circulation control technology is investigated using a three-dimensional unsteady viscous flow analysis. The National Renewable Energy Laboratory (NREL) Phase VI horizontal axis wind turbine (HAWT) is chosen as the baseline configuration. Experimental data for the baseline case is used to validate the flow solver, prior to its use in exploring these concepts. Steady and pulsed Coanda jet calculations have been performed for axial and yawed flows at several wind conditions. Results presented include radial distribution of the normal and tangential forces at selected radial locations, shaft torque, and root flap bending moments. At low wind speeds where the flow is fully attached, it is found that steady and pulsed Coanda jets at the trailing edge are both effective at increasing circulation resulting in an increase of lift and the chordwise thrust force. This leads to an increased amount of net power compared to the baseline configuration for moderate blowing coefficients. Preliminary calculations are also shown to demonstrate how Coanda jets may be used as jet spoilers to alleviate structural loads under extreme wind conditions.

Numerical Simulation of the Aerodynamics of Horizontal Axis Wind Turbines under Yawed Flow Conditions

2005 ◽  
Vol 127 (4) ◽  
pp. 464-474 ◽  
Author(s):  
Chanin Tongchitpakdee ◽  
Sarun Benjanirat ◽  
Lakshmi N. Sankar
Keyword(s):  
Wind Speed ◽  
Turbulence Model ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Transition Model ◽  
Flow Conditions ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Nrel Phase Vi

The aerodynamic performance of the National Renewable Energy Laboratory (NREL) Phase VI horizontal axis wind turbine (HAWT) under yawed flow conditions is studied using a three-dimensional unsteady viscous flow analysis. Simulations have been performed for upwind cases at several wind speeds and yaw angles. Results presented include radial distribution of the normal and tangential forces, shaft torque, root flap moment, and surface pressure distributions at selected radial locations. The results are compared with the experimental data for the NREL Phase VI rotor. At low wind speeds (∼7m∕s) where the flow is fully attached, even an algebraic turbulence model based simulation gives good agreement with measurements. When the flow is massively separated (wind speed of 20m∕s or above), many of the computed quantities become insensitive to turbulence and transition model effects, and the calculations show overall agreement with experiments. When the flow is partially separated at wind speed above 15m∕s, encouraging results were obtained with a combination of the Spalart-Allmaras turbulence model and Eppler’s transition model only at high enough wind speeds.

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