scholarly journals Experimental investigation of Mini Gurney Flaps in combination with vortex generators for improved wind turbine blade performance

2021 ◽  
Author(s):  
Jörg Alber ◽  
Marinos Manolesos ◽  
Guido Weinzierl-Dlugosch ◽  
Johannes Fischer ◽  
Alexander Schönmeier ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Leading Edge ◽  
Suction Side ◽  
Rotor Blades ◽  
Force Balance ◽  
Vortex Generators ◽  
Gurney Flaps ◽  
First Case ◽  
The Impact

Abstract. This wind tunnel study investigates the aerodynamic effects of Mini Gurney flaps (MGFs) and their combination with vortex generators (VGs) on the performance of airfoils and wind turbine rotor blades. VGs are installed on the suction side aiming at stall delay and increased maximum lift. MGFs are thin angle profiles that are attached at the trailing edge in order to increase lift at pre-stall operation. The implementation of both these passive flow control devices is accompanied by a certain drag penalty. The wind tunnel tests are conducted at the Hermann- Föttinger Institut of the Technische Universität Berlin. Lift is determined with a force balance and drag with a wake rake for static angles of attack from −5° to 17° at a constant Reynolds number of 1.5 million. The impact of different MGF heights including 0.25 %, 0.5 % and 1.0 % and an uniform VG height of 1.1 % of the chord length are tested on three airfoils that are characteristic for different sections of large rotor blades. Furthermore, the clean and the tripped baseline cases are considered. In the latter, leading edge transition is forced by means of Zig Zag (ZZ) turbulator tape. The preferred configurations are the smallest MGF on the NACA63(3)618 and the AH93W174 (mid to tip blade region) and the medium sized MGF combined with VGs on the DU97W300 (root to mid region). Next, the experimental lift and drag polar data is imported into the software QBlade in order to design a generic rotor blade. The blade performance is simulated with and without the add-ons based on two case studies. In the first case, the retrofit application on an existing blade mitigates the adverse effects of the ZZ tape. Stall is delayed and the aerodynamic efficiency is partly recovered leading to an improvement of the power curve. In the second case, the new design application allows for the design of a more slender blade while maintaining the power output. Moreover, the alternative blade appears to be more resistant against forced leading edge transition.

scholarly journals Aerodynamic Effects of Gurney Flaps on the Rotor Blades of a Research Wind Turbine

2020 ◽  
Author(s):  
Jörg Alber ◽  
Rodrigo Soto-Valle ◽  
Marinos Manolesos ◽  
Sirko Bartholomay ◽  
Christian Navid Nayeri ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Leading Edge ◽  
Control Device ◽  
Rotor Blades ◽  
Passive Flow Control ◽  
Performance Improvements ◽  
Gurney Flaps ◽  
Passive Flow ◽  
Gurney Flap ◽  
Horizontal Axis Wind Turbines

Abstract. This paper investigates the aerodynamic impact of Gurney flaps on a research wind turbine of the Hermann-Föttinger Institute at the Technische Universität Berlin. The rotor radius is 1.5 meters and the blade configurations consist of the clean and the tripped baseline cases emulating the effects of forced leading edge transition. The wind tunnel experiments include three operation points based on tip speed ratios of 3.0, 4.3 and 5.6, reaching Reynold numbers of approximately 250,000. The measurements are taken by means of three different methods; Ultrasonic Anemometry in the wake, surface pressure taps in the mid-span blade region and strain gauges at the blade root. The retrofit application consists of two Gurney flap heights of 0.5 % and 1.0 % in relation to the chord length, which are implemented perpendicular to the pressure side at the trailing edge. As a result, the Gurney flap configurations evoke performance improvements in terms of the axial wake velocities, the angles-of-attack and the lift coefficients. The enhancement of the root bending moments imply an increase of both the rotor torque and the thrust. Furthermore, the aerodynamic impact appears to be more pronounced in the tripped case compared to the clean case. Gurney flaps are considered a worthwhile passive flow-control device in order to alleviate the adverse effects of early separation and leading edge erosion of horizontal axis wind turbines.

scholarly journals Aerodynamic effects of Gurney flaps on the rotor blades of a research wind turbine

2020 ◽  
Vol 5 (4) ◽  
pp. 1645-1662
Author(s):  
Jörg Alber ◽  
Rodrigo Soto-Valle ◽  
Marinos Manolesos ◽  
Sirko Bartholomay ◽  
Christian Navid Nayeri ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Leading Edge ◽  
Control Device ◽  
Rotor Blades ◽  
Passive Flow Control ◽  
Performance Improvements ◽  
Gurney Flaps ◽  
Passive Flow ◽  
Gurney Flap ◽  
Horizontal Axis Wind Turbines

Abstract. This paper investigates the aerodynamic impact of Gurney flaps on a research wind turbine of the Hermann-Föttinger Institute at the Technische Universität Berlin. The rotor radius is 1.5 m, and the blade configurations consist of the clean and the tripped baseline cases, emulating the effects of forced leading-edge transition. The wind tunnel experiments include three operation points based on tip speed ratios of 3.0, 4.3, and 5.6, reaching Reynolds numbers of approximately 2.5×105. The measurements are taken by means of three different methods: ultrasonic anemometry in the wake, surface pressure taps in the midspan blade region, and strain gauges at the blade root. The retrofit applications consist of two Gurney flap heights of 0.5 % and 1.0 % in relation to the chord length, which are implemented perpendicular to the pressure side at the trailing edge. As a result, the Gurney flap configurations lead to performance improvements in terms of the axial wake velocities, the angles of attack and the lift coefficients. The enhancement of the root bending moments implies an increase in both the rotor torque and the thrust. Furthermore, the aerodynamic impact appears to be more pronounced in the tripped case compared to the clean case. Gurney flaps are considered a passive flow-control device worth investigating for the use on horizontal-axis wind turbines.

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.

Comparison of Wind Tunnel Airfoil Performance Data With Wind Turbine Blade Data

1992 ◽  
Vol 114 (2) ◽  
pp. 119-124 ◽  
Author(s):  
C. P. Butterfield ◽  
George Scott ◽  
Walt Musial
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Peak Power ◽  
Unsteady Aerodynamics ◽  
Leading Edge ◽  
Operating Conditions ◽  
Performance Data ◽  
Horizontal Axis Wind Turbine ◽  
Force Coefficients ◽  
Basic Fluid

Horizontal axis wind turbine (HAWT) performance is usually predicted by using wind tunnel airfoil performance data in a blade element momentum theory analysis. This analysis assumes that the rotating blade airfoils will perform as they do in the wind tunnel. However, when stall-regulated HAWT performance is measured in full-scale operation, it is common to find that peak power levels are significantly greater than those predicted. Pitch-controlled rotors experience predictable peak power levels because they do not rely on stall to regulate peak power. This has led to empirical corrections to the stall predictions. Viterna and Corrigan (1981) proposed the most popular version of this correction. But very little insight has been gained into the basic cause of this discrepancy. The National Renewable Energy Laboratory (NREL), funded by the DOE, has conducted the first phase of an experiment which is focused on understanding the basic fluid mechanics of HAWT aerodynamics. Results to date have shown that unsteady aerodynamics exist during all operating conditions and dynamic stall can exist for high yaw angle operation. Stall hysteresis occurs for even small yaw angles and delayed stall is a very persistent reality in all operating conditions. Delayed stall is indicated by a leading edge suction peak which remains attached through angles of attack (AOA) up to 30 degrees. Wind tunnel results show this peak separating from the leading edge at 18 deg AOA. The effect of this anomaly is to raise normal force coefficients and tangent force coefficients for high AOA. Increased tangent forces will directly affect HAWT performance in high wind speed operation. This report describes pressure distribution data resulting from both wind tunnel and HAWT tests. A method of bins is used to average the HAWT data which is compared to the wind tunnel data. The analysis technique and the test set-up for each test are described.

scholarly journals Brief communication: Nowcasting of precipitation for leading-edge-erosion-safe mode

2020 ◽  
Vol 5 (3) ◽  
pp. 977-981 ◽  
Author(s):  
Anna-Maria Tilg ◽  
Charlotte Bay Hasager ◽  
Hans-Jürgen Kirtzel ◽  
Poul Hummelshøj
Keyword(s):  
Liquid Phase ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Leading Edge ◽  
Wind Turbine Blades ◽  
Spatio Temporal ◽  
The Impact ◽  
Theoretical Considerations ◽  
Mode A ◽  
Precipitation Events

Abstract. Leading-edge erosion (LEE) of wind turbine blades is caused by the impact of hydrometeors, which appear in a solid or liquid phase. A reduction in the wind turbine blades' tip speed during defined precipitation events can mitigate LEE. To apply such an erosion-safe mode, a precipitation nowcast is required. Theoretical considerations indicate that the time a raindrop needs to fall to the ground is sufficient to reduce the tip speed. Furthermore, it is described that a compact, vertically pointing radar that measures rain at different heights with a sufficiently high spatio-temporal resolution can nowcast rain for an erosion-safe mode.

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.

Development and Application of a Simulation Tool for Vertical and Horizontal Axis Wind Turbines

2013 ◽  
Author(s):  
David Marten ◽  
Juliane Wendler ◽  
Georgios Pechlivanoglou ◽  
Christian Navid Nayeri ◽  
Christian Oliver Paschereit
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Horizontal Axis ◽  
Vertical Axis Wind Turbine ◽  
First Case ◽  
Horizontal Axis Wind Turbines ◽  
Lift And Drag ◽  
The Impact

A double-multiple-streamtube vertical axis wind turbine simulation and design module has been integrated within the open-source wind turbine simulator QBlade. QBlade also contains the XFOIL airfoil analysis functionalities, which makes the software a single tool that comprises all functionality needed for the design and simulation of vertical or horizontal axis wind turbines. The functionality includes two dimensional airfoil design and analysis, lift and drag polar extrapolation, rotor blade design and wind turbine performance simulation. The QBlade software also inherits a generator module, pitch and rotational speed controllers, geometry export functionality and the simulation of rotor characteristics maps. Besides that, QBlade serves as a tool to compare different blade designs and their performance and to thoroughly investigate the distribution of all relevant variables along the rotor in an included post processor. The benefits of this code will be illustrated with two different case studies. The first case deals with the effect of stall delaying vortex generators on a vertical axis wind turbine rotor. The second case outlines the impact of helical blades and blade number on the time varying loads of a vertical axis wind turbine.

scholarly journals Wind Tunnel Test of the S814 Thick Root Airfoil

1996 ◽  
Vol 118 (4) ◽  
pp. 217-221 ◽  
Author(s):  
D. M. Somers ◽  
J. L. Tangler
Keyword(s):  
Wind Tunnel ◽  
Lift Coefficient ◽  
Wind Tunnel Test ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Rotor Blades ◽  
Roughness Effects ◽  
Root Region ◽  
University Of Technology ◽  
Thick Airfoil

The objective of this wind-tunnel test was to verify the predictions of the Eppler Airfoil Design and Analysis Code for a very thick airfoil having a high maximum lift coefficient designed to be largely insensitive to leading-edge roughness effects. The 24 percent thick S814 airfoil was designed with these characteristics to accommodate aerodynamic and structural considerations for the root region of a wind-turbine blade. In addition, the airfoil’s maximum lift-to-drag ratio was designed to occur at a high lift coefficient. To accomplish the objective, a two-dimensional wind tunnel test of the S814 thick root airfoil was conducted in January 1994 in the low-turbulence wind tunnel of the Delft University of Technology Low Speed Laboratory, The Netherlands. Data were obtained with transition free and transition fixed for Reynolds numbers of 0.7, 1.0, 1.5, 2.0, and 3.0 × 106. For the design Reynolds number of 1.5 × 106, the maximum lift coefficient with transition free is 1.32, which satisfies the design specification. However, this value is significantly lower than the predicted maximum lift coefficient of almost 1.6. With transition fixed at the leading edge, the maximum lift coefficient is 1.22. The small difference in maximum lift coefficient between the transition-free and transition-fixed conditions demonstrates the airfoil’s minimal sensitivity to roughness effects. The S814 root airfoil was designed to complement existing NREL low maximum-lift-coefficient tip-region airfoils for rotor blades 10 to 15 meters in length.

scholarly journals Numerical Analysis of Wind Turbine Airfoil Aerodynamic Performance with Leading Edge Bump

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Majid Asli ◽  
Behnam Mashhadi Gholamali ◽  
Abolghasem Mesgarpour Tousi
Keyword(s):  
Wind Turbine ◽  
Control Method ◽  
Flow Behavior ◽  
Renewable Energy Sources ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Vortex Generator ◽  
Leading Edge ◽  
Suction Side ◽  
Aerodynamic Performance

Aerodynamic performance improvement of wind turbine blade is the key process to improve wind turbine performance in electricity generated and energy conversion in renewable energy sources concept. The flow behavior on wind turbine blades profile and the relevant phenomena like stall can be improved by some modifications. In the present paper, Humpback Whales flippers leading edge protuberances model as a novel passive stall control method was investigated on S809 as a thick airfoil. The airfoil was numerically analyzed by CFD method in Reynolds number of 106and aerodynamic coefficients in static angle of attacks were validated with the experimental data reported by Somers in NREL. Therefore, computational results for modified airfoil with sinusoidal wavy leading edge were presented. The results revealed that, at low angles of attacks before the stall region, lift coefficient decreases slightly rather than baseline model. However, the modified airfoil has a smooth stall trend while baseline airfoil lift coefficient decreases sharply due to the separation which occurred on suction side. According to the flow physics over the airfoils, leading edge bumps act as vortex generator so vortices containing high level of momentum make the flow remain attached to the surface of the airfoil at high angle of attack and prevent it from having a deep stall.

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