Novel Controlled-Velocity Wind Turbine Testing Apparatus to Simulate Turbulent, Non-Return Flow

2014 ◽  
Author(s):  
Corey P. Ressler ◽  
James Hilbish ◽  
Jesse J. French
Keyword(s):  
Wind Tunnel ◽  
Vertical Axis ◽  
Test Method ◽  
Return Flow ◽  
Test Apparatus ◽  
Number Range ◽  
Wind Speeds ◽  
Valid Test ◽  
Flow Interference ◽  
Work Done

This paper presents the work done by the authors to analyze the method of performance characterization of a 100W scale vertical axis wind turbines using a controlled-velocity test apparatus. The design of the power transfer system containing a gearbox and generator requires test data to determine the peak and operating range of wind speed, corresponding to RPM and torque. Multiple methods of turbine testing were considered, including in situ, wind tunnel, and control-velocity. Controlled-velocity, a method where the turbine is moved through a fluid, was selected based on lack of test location wind speeds or access to a wind tunnel of sufficient size. The test apparatus is designed to be effective for VAWT turbines of a diameter range from 1.45 to 4.2 meters in a wind velocity range of 1 to 17 m/s. This covers a Reynolds number range between (2.5 × 10^5 < Re < 4.2 × 10^6). A change from previous control-velocity test apparatus is the use of a separate truck and trailer compared to a flatbed truck, which allows greater distance between the truck cab and the turbine, to decrease any flow interference of the cab. This previous work and testing has shown to be a valid test method in that the turbine is in similar turbulent conditions as near the ground and buildings which the turbine is designed for. The main advantage of this test apparatus is the ability to test turbines in a region with low average wind speeds and minimum infrastructure.

Wind-Tunnel Tests of Vertical-Axis Wind Turbine Blades

2011 ◽  
Author(s):  
B. D. Plourde ◽  
J. P. Abraham ◽  
G. S. Mowry ◽  
W. J. Minkowycz
Keyword(s):  
Power Generation ◽  
Wind Tunnel ◽  
Turbine Blade ◽  
Vertical Axis ◽  
Cellular Communication ◽  
Wing Design ◽  
Ongoing Research ◽  
Wind Speeds ◽  
Wide Range ◽  
Communication Towers

An ongoing research project is investigating the potential of locating vertical-axis wind turbines (WT) on remote, off-grid cellular communication towers. The goal of the WT is to provide local power generation to meet the electrical needs of the tower. While vertical-axis devices are less efficient than their more traditional horizontal-axis counterparts, they provide a number of practical advantages which make them a suitable choice for the present situation. First, the direction of their axis is aligned with the existing tower and its rotation does not interfere with the tower structure. Second, vertical-axis devices are much less susceptible to the direction of wind and they do not require control-systems to ensure they are oriented correctly. Third, vertical-axis turbines have very low start-up wind speeds so that they generate power over a wide range of speeds. Fourth, since vertical-axis turbines rotate at a slower speed compared with horizontal counterparts, they impart a lessened vibration load to the tower. These facts, collectively, make the vertical-axis turbine suitable for the proposed application. The design process involved a detailed initial design of the turbine blade using computational methods. Next, a trio of designs was evaluated experimentally in a large, low-speed wind tunnel. The wind tunnel is operated by the University of Minnesota’s St. Anthony Falls Fluid Laboratory. The tunnel possesses two testing sections. The larger section was sufficient to test a full-size turbine blade. Accounting was taken of the blockage effect following the tests. The experiments were completed on (1) a solid-wing design (unvented), (2) a slotted-wing design (vented), and (3) a capped-and-slotted design (capped). Conditions spanned a wide range of wind speeds (4.5–11.5 m/s). The turbines were connected to electronics which simulated a range of electrical loads. The tested range was selected to span the expected range of resistances which will be found in practice. It was discovered that over a range of these wind speeds and electrical resistances, slots located on the wings result in a slight improvement in power generation. On the other hand, the slotted-and-capped design provided very large increases in performance (approximately 200–300% compared with the unvented version). This large improvement has justified commercialization of the product for use in powering remote, off-grid cellular communication towers.

Experimental Study and Optimization of a 2.44 Meter Vertical Axis Wind Turbine

2011 ◽  
Author(s):  
Brad Nichols ◽  
Timothy Dimond ◽  
Josh Storer ◽  
Paul Allaire
Keyword(s):  
Wind Tunnel ◽  
Power Output ◽  
Vertical Axis ◽  
Chord Length ◽  
Small Scale ◽  
Physical Parameters ◽  
Wind Tunnel Testing ◽  
Wind Speeds ◽  
The Given ◽  
Tunnel Testing

Vertical axis wind turbines (VAWTs) have long been considered a viable source for alternative energy; however, limited published research has contributed to limited technological advancement in these machines. Slower advancements are due, in part, to their complex aerodynamic models which include wake effects, vortex shedding, and cyclical blade angles of attack and Reynolds numbers. VAWTs are believed to hold several advantages over their more popular and better studied horizontal axis counterparts, including a simpler design and better efficiencies in lower wind speeds. They may have a unique niche in standalone applications at moderate wind speeds such as on an island, a remote military installation, or an inland farm. Currently, no published design standards or criteria exist for optimizing the physical properties of these turbines to maximize power output. A 2.44 m tall VAWT prototype with variable physical parameters was constructed for wind tunnel testing. The purpose of the experiment was to maximize the turbine’s power output by optimizing its physical configuration within the given parameters. These parameters included rotor radius, blade chord length, and pitch offset angle. The prototype was designed as a scaled-down model of a potential future VAWT unit that may be used to sustain a small farm or 2–4 houses. The wind tunnel consisted of a 2.74 m by 1.52 m cross section and could produce maximum wind speeds of 3.56 m/s. The turbine prototype consisted of three sets of interchangeable blades featuring two airfoils of varying chord length. Spokes of varying length allowed for rotor radii of 190.5, 317.5, and 444.5 mm. The pitch offset of the blades was varied from 0°–20° with a focus on the 10°–16° range as preliminary results suggested that this was the optimal range for this turbine. Ramp-up and steady-state rotational speeds were recorded as the blades were interchanged and the turbine radius was varied. A disk brake provided braking torque so that power coefficients could be estimated. This study successfully optimized the turbine’s power output within the given set of test parameters. The importance of finding an appropriate aspect ratio and pitch offset angle are clearly demonstrated in the results. A systematic approach to small scale wind tunnel testing prior to implementation is presented in this paper.

The Influence of the Number of Semi-Cycindrical Cups on the Behavior of an Experimental Model of Vertical Axis Wind Turbine at Low Wind Speed and no Load

2020 ◽  
Vol 43 (3) ◽  
pp. 43-53
Author(s):  
Nelu CAZACU ◽  
◽  
◽  
Keyword(s):  
Wind Tunnel ◽  
Experimental Model ◽  
Vertical Axis ◽  
Experimental Models ◽  
Vertical Axis Wind Turbine ◽  
Cross Sectional ◽  
Wind Speeds ◽  
Low Wind Speed ◽  
Cylindrical Cup ◽  
Electrical Loads

The work is based on experiments made in the wind tunnel on experimental models of Savonius type wind turbines with blades in the shape of a semicylindrical cup. The number of blades changes: 2, 3, 4, 5 and 6. The experimental model allows the addition / removal of blades in the form of a semi-cylindrical cup followed by static balancing. The wind tunnel used has the measuring area 0.5 mx0.5 m and the length of 1.25 m and the experimental models have the interception surface at a maximum value of 10% of the cross-sectional area of the wind tunnel (diameter 158 mm and height 158 mm). The experiments were performed at wind speeds between 0...9.7 m/s between peaks and no (mechanical and / or electrical) loads. The results confirm the influence of the number of semi-cylindrical cups on the rotational speed and other factors over experimental model of Savonius type turbines in no load conditions.

Investigation of Aerodynamic Performance of Helical Shape Vertical-Axis Wind Turbine Models With Various Number of Blades Using Wind Tunnel Testing and Computational Fluid Dynamics

2016 ◽  
Author(s):  
Mosfequr Rahman ◽  
Travis Salyers ◽  
Mahbub Ahmed ◽  
Adel ElShahat ◽  
Valentin Soloiu ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Twist Angle ◽  
Average Power ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Power Coefficient ◽  
Wind Tunnel Testing ◽  
Vertical Axis Wind Turbine ◽  
Wind Speeds ◽  
Tunnel Testing

The demand for wind energy as a renewable source is rising substantially. A growing interest exists in utilizing potential energy conversion applications in areas with less powerful and less consistent wind conditions. In these areas, vertical-axis wind turbines (VAWTs) possess several advantages over the conventional horizontal-axis type. Savonius turbines are drag-based rotors which operate due to a pressure difference between the advancing and retreating blades. These turbines are simpler in design, less expensive to install, independent of wind direction, and more efficient at low wind speeds. In the present study, rotors were designed with semi-circle blades consisting of a helical shape with twist angle of 90 degrees. Helical designs spread the torque applied to the rotor over a complete revolution with the purpose of increasing efficiency. Three models were analyzed with different number of blades including 2, 3, and 4 blade models. Models for testing were designed using the CAD software SolidWorks. The blades were then 3D printed with PLA plastic. A consistent swept area was maintained for each model, and only blade number was varied. Subsonic, open-type wind tunnel testing was used for measuring RPM and reactional torque over a range of wind speeds. For the numerical approach, ANSYS Fluent simulations were used for analyzing aerodynamic performance by utilizing moving reference frame and sliding mesh model techniques. Due to the helical twist, the cross-section of the blades varied in the Y-direction. Because of this, a 3-dimensional and transient method was used for accurately solving torque and power coefficients. It has been found that the highest average power coefficient observed in the study is achieved by the Helical2 model (2-bladed helical design VAWT model), both numerically and experimentally.

Aerodynamic Performance Evaluation of a Novel Savonius-Style Wind Turbine Under an Oriented Jet

2014 ◽  
Author(s):  
Sukanta Roy ◽  
Prasenjit Mukherjee ◽  
Ujjwal K. Saha
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Power Coefficient ◽  
Small Scale ◽  
Practical Applications ◽  
Wind Speeds ◽  
Energy Applications

The Savonius-style wind turbine, a class of vertical axis wind turbines, can be a viable option for small scale off-grid electricity generation in the context of renewable energy applications. A better self-starting capability at low wind speeds is one of the major advantages of this turbine. However, as reported in open literature, the power coefficient of the conventional design is found to be inferior as compared to its counterparts. In this regard, a new blade design has been developed. In the present investigation, the aerodynamic performance of this newly designed turbine is assessed under an oriented jet. This is affected by installing deflectors upstream of the turbine blades. The intention of this study is to maximize the utilization of wind energy at the exhaust systems of several practical applications. Experiments are carried out in a low speed wind tunnel at a wind speed of 6.2 m/s. The gradual loads applied to the turbine, and the corresponding rotational speeds are recorded. Power and torque coefficients are calculated at various mechanical loads. Further, all the estimated data are corrected by a suitable correction factor to account for the wind tunnel blockage effects. The results obtained are compared with the experimental data of modified Bach and conventional designs. The results have shown a significant improvement in the performance of newly designed Savonius-style wind turbine under the concentrated and oriented jet.

A Method for Evaluating the Thermal Performance of Passenger Seats

2003 ◽  
Vol 217 (6) ◽  
pp. 449-459 ◽  
Author(s):  
E B Ratts ◽  
J W McElroy ◽  
W G Reed
Keyword(s):  
Thermal Performance ◽  
Thermal Energy ◽  
Water Source ◽  
Fixed Time ◽  
Test Method ◽  
Test Apparatus ◽  
Passenger Seat ◽  
Time Period ◽  
Seat Cushion ◽  
Heat And Moisture

In this paper, an experimental method to quantify the capability of an automotive seat to move heat and moisture away from the heat and water source is presented. To test the method, a test apparatus was constructed that generates heat and water vapour. The apparatus was placed on a seat cushion for a fixed time period. At the end of the period, heat and water transported were measured. These integrated values were used to quantify the seat's capability to move heat and moisture and ultimately to compare seats. By the impulse test method, the passenger seat had an effusivity of 94.7 W s1/2/m2 K. A non-ventilated seat transferred 5 W of thermal energy and an average of 0.36 g/min of water in 1800 s. A ventilated seat transferred 13.9 W of thermal energy and 0.70 g/min of water in 1800 s.

Gliding Flight of the Dog-Faced Bat Rousettus Aegyptiacus Observed in a Wind Tunnel

1971 ◽  
Vol 55 (3) ◽  
pp. 833-845 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
Wind Tunnel ◽  
Lift Coefficient ◽  
Trailing Edge ◽  
Number Range ◽  
High Speeds ◽  
Gliding Flight ◽  
Speed Range ◽  
Simple Regression Analysis ◽  
Drag Analysis ◽  
Very High

1. A bat was trained to fly in a tilting wind tunnel. Stereoscopic photographs were taken, both by reflected and by transmitted light, and measurements of best gliding angle were made. 2. Variation of wing span and area at different speeds was much less than in birds. This is attributed to the construction of the wing, which prevents the bat from folding back the manus in flight, because this would lead to collapse of the plagiopatagium. 3. The trailing edge of the wing is normally deflected upwards in flight, at least in the distal parts. This is interpreted as providing longitudinal stability. The plagiopatagialis proprii muscles appear to act as an elevator, by deflecting the trailing edge of the plagiopatagium upwards. 4. The speed range over which the bat could glide was 5·3-11·0 m/s. Its maximum lift coefficient was 1·5, and its best glide ratio 6·8:1. The Reynolds number range, based on mean chord, was 3·26 x 104 to 6·79 x 104. 5. A simple regression analysis of the glide polar indicated a very high span efficiency factor (k) and low wing profile drag coefficient (Cdp). On the other hand, a drag analysis on the assumption that k = 1 leads to an improbably large increase in the estimated Cdp at low speeds. It is suggested that the correct interpretation probably lies between these extremes, with k ≊ 1·5; Cdp would then be about 0·02 at high speeds, rising to somewhat over 0·1 at the minimum speed. 6. It would appear that the bat is not so good as a pigeon at fast gliding, but better at low-speed manoeuvring. On most points of performance, however, the two are remarkably similar.

Study on the Relation Between Side Ratios of Rectangular Cross Sections and Secondary Vortices at Trailing Edge in Motion-Induced Vortex Excitation

2017 ◽  
Author(s):  
Kazutoshi Matsuda ◽  
Kusuo Kato ◽  
Kouki Arise ◽  
Hajime Ishii
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Cross Sections ◽  
Leading Edge ◽  
Trailing Edge ◽  
Wind Speeds ◽  
Smoke Flow ◽  
Flow Visualizations ◽  
Institute Of Technology ◽  
Secondary Vortices

According to the results of conventional wind tunnel tests on rectangular cross sections with side ratios of B/D = 2–8 (B: along-wind length (m), D: cross-wind length (m)), motion-induced vortex excitation was confirmed. The generation of motion-induced vortex excitation is considered to be caused by the unification of separated vortices from the leading edge and secondary vortices at the trailing edge [1]. Spring-supported test for B/D = 1.18 was conducted in a closed circuit wind tunnel (cross section: 1.8 m high×0.9 m wide) at Kyushu Institute of Technology. Vibrations were confirmed in the neighborhoods of reduced wind speeds Vr = V/fD = 2 and Vr = 8 (V: wind speed (m/s), f: natural frequency (Hz)). Because the reduced wind speed in motion-induced vortex excitation is calculated as Vr = 1.67×B/D = 1.67×1.18 = 2.0 [1], vibrations around Vr = 2 were considered to be motion-induced vortex excitation. According to the smoke flow visualization result for B/D = 1.18 which was carried out by the authors, no secondary vortices at the trailing edge were formed, although separated vortices from the leading edge were formed at the time of oscillation at the onset wind speed of motion-induced vortex excitation, where aerodynamic vibrations considered to be motion-induced vortex excitation were confirmed. It was suggested that motion-induced vortex excitation might possibly occur in the range of low wind speeds, even in the case of side ratios where secondary vortices at trailing edge were not confirmed. In this study, smoke flow visualizations were performed for ratios of B/D = 0.5–2.0 in order to find out the relation between side ratios of rectangular cross sections and secondary vortices at trailing edge in motion-induced vortex excitation. The smoke flow visualizations around the model during oscillating condition were conducted in a small-sized wind tunnel at Kyushu Institute of Technology. Experimental Reynolds number was Re = VD/v = 1.6×103. For the forced-oscillating amplitude η, the non-dimensional double amplitudes were set as 2η/D = 0.02–0.15. Spring-supported tests were also carried out in order to obtain the response characteristics of the models.

scholarly journals Wind Tunnel testing of small Vertical-Axis Wind Turbines in Turbulent Flows

2017 ◽  
Vol 199 ◽  
pp. 3176-3181 ◽  
Author(s):  
Andreu Carbó Molina ◽  
Gianni Bartoli ◽  
Tim de Troyer
Keyword(s):  
Wind Tunnel ◽  
Turbulent Flows ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Wind Tunnel Testing ◽  
Vertical Axis Wind Turbines ◽  
Tunnel Testing
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