Analysis on the influence of air strike angle To Aerodynamic performance of vertical axis wind turbi

IJIRST –International Journal for Innovative Research in Science & Technology| Volume 1 | Issue 6 | November 2014 ISSN (online): 2349-6010

All rights reserved by www.ijirst.org 170

Analysis on the Influence of Air Strike Angleto

Aerodynamic Performance of Vertical Axis Wind

Turbine

Mayank D. Patel Mr Tushar P. Gundarneeya

M.E. Student Assistant Professor

Department of Mechanical Engineering Department of Mechanical Engineering

Government Engineering College, Dahod-391351 Government Engineering College, Dahod-391351

Abstract

The small wind turbine industry has recently seen a significant amount of growth due to the need for energy storage and a

reduced dependence on fossil fuels in rural environments. A novel vertical axis wind turbine (VAWT) has been developed that

consists of several vertically-stacked segments. Compu¬tational fluid dynamics (CFD) simulations were performed in the

present study using ANSYS CFX, a commercially-available CFD package, to characterize the behaviour of the new VAWT.

Static three-dimensional CFD simulations were conducted. The static torque characteristics of the turbine and the simplicity of

design highlight its suitability for the small wind turbine market. The major factor for generating the power through the VAWT

is the velocity of air and the position of the blade angle in the VAWT blade assembly. The study presents the effect of the

position of the blade angle from 0 degree to the 30 degree on the power developed by the VAWT. Literature revealed that some

parameter like wind speed, tip-speed ratio, air-strike angle, solidity, surface roughness, pitch angle has significant sensitivity for

the efficiency change to the performance of the vertical axis wind turbine. So the parameter like wind speed, tip-speed ratio, air

strike angle are likely to use in the research for these dissertation work. CFD workbench of ANSYS is used to carry out the

virtue simulation and testing. The software generated test results are validated through the experimental readings. Through this

obtainable result will be in the means of maximum constant power generation from VAWT.

Keywords: vertical axis wind turbine, Aerodynamic, ANSYS CFX software

_______________________________________________________________________________________________________

I. INTRODUCTION

The focus on Renewable Energy Resources has increased significantly in the recent years in the wake of growing environmental

pollution, rising energy demand and depleting fossil fuel resources. Different sources of renewable energy include biomass,

solar, geothermal, hydroelectric, and wind. Among these resources wind has proved to be a cheaper alternative energy resource

and hence extensive research efforts have been put to improve the technology of electricity generation through wind. The world

has enormous potential of wind energy that can be utilized for electricity generation.

Fig 1.1 Average wind velocity in different regions of the world

Analysis on the Influence of Air Strike Angleto Aerodynamic Performance of Vertical Axis Wind Turbine (IJIRST/ Volume 1 / Issue 6 / 029)


Fig. 1 shows the wind velocities at various locations around the world. In areas where favourable sites exist, it has already

been preferred over conventional fossil fuels for electricity generation. Wind power is now the world’s fastest growing energy

resource.

Currently, large scale VAWTs are not economically attractive; however, they offer energy solutions for remote places away

from the main distribution lines and places where large wind farms cannot be installed due to environmental concerns and small

scale dispersed generation units are preferred. That is why mass production of VAWTs has recently been started as small scale

wind power generating units.

II. CONFIGURATIONS

A great degree of design versatility exists in the vertical axis wind turbines as shown in Table. There are a few problems inherent

to the currently available designs including low starting torque, blade lift forces, low efficiency, poor building integration, etc. In

the past few decades, the engineers came up with many new and innovative design approaches to resolve these issues associated

with VAWTs. A detailed review of VAWT configurations available till now and the work done on each configuration has been

discussed in the following sections.

Fig. 1.3 Darrieus rotor – straight bladed wind turbine

A. Darrieus type wind turbine

Darrieus wind turbine designs were first patented in 1931. These types of turbines have highest values of efficiency among

VAWTs but generally suffer from problems of low starting torque and poor building integration. Darrieus type wind turbines

have many variants, as discussed in the following lines, all of which are Lift-type wind turbines, i.e. lift forces acting on the

blades of turbine cause the rotor to rotate and hence generate electricity.

III. LITERATURE SURVEY

(1) Robert Howell, Ning Qin, Jonathan Edwards, Naveed Durrani, “wind tunnel Numerical study of a small vertical axis

and wind turbine”, Renewable energy, 20 July 2009.

In this thesis they had done computational predictions of the performance coefficient of this turbine and the 3D simulation which

were shown to be in reasonably good agreement with the experimental measurements, considering errors and uncertainties in

both the CFD simulations and the wind tunnel measurements. The 2D simulations showed a significantly increased performance

compared to the 3D simulations and this was shown to be mainly due to the presence of the large tip vortices present in the real

turbine and the 3D simulations. Simulations illustrated the periodic pulsing nature of the tip vortices caused by the changing lift

generated by the rotor blades as they travel through each rotor revolution. At phases where higher amounts of lift are generated,

stronger tip vortices are present, whereas at phases where little lift is generated, the vortices are significantly reduced.

(2) S. McTavish, D. Feszty, T. Sankar, “Study and rotating computational fluid dynamics simulation of a novel vertical axis

wind turbine for small-scale power generation” energy, 13 October 2011

In this paper an assessment of the performance of a novel vertical axis wind turbine using CFD simulations. Steady and rotating

validation studies were conducted using experimental data for a Savonius rotor. The static and dynamic torque curves for the

Savonius rotor were well characterised. Steady two-dimensional CFD simulations were conducted and it was determined that the

Aeolun Harvester_ produces a comparable amount of static torque to existing Savonius rotors. And concluded that rotating three-

dimensional CFD simulations demonstrated that the average dynamic torque generated by this new rotor decays more rapidly

with increasing tip speed ratio than the torque output of existing Savonius rotors. Pressure coefficient contours and the local

torque coefficient indicate that this rapid decay in torque with increasing tip speed ratio occurs due to stagnation effects acting on

the convex side of the outer wall as the blade is retreating. These stagnation effects increase with increasing tip speed ratio and

have similar characteristics to the torque production mechanisms observed on Savonius rotors. The results of the study, however,

have shown that the shape of the inner and outer rotor walls should be the focus of future work as a means to increase the torque

generated by the rotor to render it more competitive with existing designs.



(3) Marco Raciti Castelli, Alessandro Englaro, Ernesto Benini, “The Darrieus wind turbine: Proposal for a new

performance prediction model based on CFD”, energy, 20 May 2011.

In this paper I have seen that the average rotor power coefficient is rather lower, the instantaneous power coefficient locally

exceeds the Betz’s limit three times per rotor revolution. This phenomenon, probably caused by a sudden pressure coefficient

drop concerning the whole rotor disc and the surrounding flow region (thus violating the assumptions of Rankine-Froude

actuator disc theory) should be further investigated. After describing and validating the computational model against

experimental data, a full campaign of simulation is proposed for a classical NACA 0021 three-bladed rotor. Flow field

characteristics are investigated for several values of tip speed ratio, allowing a comparison among rotor operation at optimum

and lower Cp values, so that a better understanding of vertical-axis wind turbines basic physics is obtained.

IV. OBJECTIVES

A. OBJECTIVE OF WORK:

A survey of the previous research work has shown that various authors have carried out investigations under completely different

conditions. I have selected the Darrieus type wind turbine. I have collects experimental reading from the company and analysis

Blade profile of VAWT is done in software. First, I have completed modeling and meshing of Blade and I have been completed

CFD analysis of it. Then experimental readings from company and analysis results from ANSYS CFX software compared. The

parameter like air strike angle and Blade profile is changed for analysis so that I can get different results for different parameters

The objective of this work is to calculate the design parameter of the vertical axis wind turbine (VAWT).

Create the 3-D model of the blade profile and blade for the simulation in SOLID-WORK.

Create the mesh model of the blade.

Create the cavity model for the cavity analysis for the CFD analysis and simulation.

Manufacture the prototype blade with calculated profile parameter for the experimental analysis.

Experimental analysis will be done in the wind tunnel.

Comparison of the software simulation data and experimental analysis Result will be done.

Validation of the result will be done by comparing the Experimental result with ANSYS result.

V. MODELLING OF VERTICAL AXIS WIND TURBINE

A. Modelling of Vertical Axis Wind Turbine

First Find the Co-ordinate for NACA 2415 from NACA Standard. 1)

X y z

0.0125 0.0134 0

0.025 0.019 0

0.05 0.0267 0

0.075 0.032 0

0.1 0.0362 0

0.15 0.0424 0

0.2 0.046 0

0.3 0.0488 0

0.4 0.0478 0

0.5 0.0437 0

0.6 0.0377 0

0.7 0.0296 0

0.8 0.0208 0

0.9 0.0112 0

1 0 0

0.95 -0.0061 0

0.9 -0.0112 0



0.8 -0.0208 0

0.7 -0.0296 0

0.6 -0.0377 0

0.5 -0.0437 0

0.4 -0.0478 0

0.3 -0.0488 0

0.2 -0.046 0

0.15 -0.0424 0

0.1 -0.0362 0

0.075 -0.032 0

0.05 -0.0267 0

0.025 -0.019 0

0.0125 -0.0134 0

0 0 0

NACA 2415

Multiply all above co-ordinate point with chord length which is found from above calculation to find actual co-ordinate 2)

point

X Y Z

0.0125 0.0134 0

0.025 0.019 0

0.05 0.0267 0

0.075 0.032 0

0.1 0.0362 0

0.15 0.0424 0

0.2 0.046 0

0.3 0.0488 0

0.4 0.0478 0

0.5 0.0437 0

0.6 0.0377 0

0.7 0.0296 0

0.8 0.0208 0

0.9 0.0112 0

1 0 0

0.95 -0.0061 0

0.9 -0.0112 0

0.8 -0.0208 0

0.7 -0.0296 0

0.6 -0.0377 0

0.5 -0.0437 0

0.4 -0.0478 0

0.3 -0.0488 0

0.2 -0.046 0

0.15 -0.0424 0

0.1 -0.0362 0



0.075 -0.032 0

0.05 -0.0267 0

0.025 -0.019 0

0.0125 -0.0134 0

0 0 0

Import above coordinate to Solid works for Curve generation. 3)

FIG 12 NACA 2415 Curve Generation

In above fig the curve is shown, which is generated after using the above parameter for the blade generation. The blade model

is generated in the SOLID WORK software.

Create Blade Profile 4)

Fig 13 NACA 2415 Blade for VAWT

After Creating Blade set the Blade at different air strike angle 5)

Fig 14 Blade at certain air strike angle

After creating the blade of vertical axis wind turbine it is set to different air strike angle for the simulation.

Create Cavity model of VAWT Blade 6)

Our Analysis method: - Cavity Pattern Analysis

In Cavity pattern analysis, we have to create cavity of air domain.



Fig 15 Cavity Domain for air

The cavity model for the vertical axis wind turbine is constructed in SOLID WORK for the analysis. We will going to done

the analysis called the cavity pattern analysis for the simulation of vertical axis wind turbine.

VI. CFD ANALYSIS OF VERTICAL AXIS WIND TURBINE BLADE

A. First Create Cavity of the VAWT in Solid works

CFX Analysis is performed by Cavity Pattern Analysis method. So we have to Create Cavity of the VAWT in which Air flows.

Fig 5.1:- Cavity of VAWT

B. Import IGES model of Air Cavity in ANSYS Workbench for Meshing

Fig 5.2: - Cavity of VAWT in ANSYS Workbench

Import IGES File in the ANSYS Workbench environment for meshing. Before meshing. We have to Verify Geometry for Clean

up

C. Create Volume Mesh.

Fig 5.3:- Meshed Model of VAWT

After Verifying Geometry, We have to Create Volume mesh.



Elements Statics for this Meshing is as under:

Type of Element:- 10 node Tetrahedral

Total Number of Nodes = 277225

Total Number of Elements = 1566437

Mesh Preferences is CFX Mesh

Save file as VAWT. cmdb.

D. Import Mesh File into ANSYS CFX Pre

In general, a finite-element solution may be broken into the following three stages.

(1) Preprocessing: defining the problem

The major steps in preprocessing are (i) define key points/lines/areas/volumes, (ii) define element type and

material/geometric properties, and (iii) mesh lines/areas/ volumes as required.

(2) Solution: assigning loads, constraints, and solving Here, it is necessary to specify the loads (point or pressure),

constraints (translational and rotational), and finally solve the resulting set of equations.

(3) Post processing: further processing and viewing of the results

In this stage one may wish to see (i) lists of nodal displacements, (ii) element forces and moments, (iii) deflection plots,

and (iv) Pressure contour diagrams or temperature maps.

Figure 5.4 Model in the ANSYS environment

After Creating Meshing file. Import meshing file into CFX pre for preprocessing step.

E. Define Domain

Figure 5.5 Meshed model of the wind cavity



Domain defines type of fluid, Co-ordinate System, Reference Pressure, its Buoyancy Condition, Domain Motion, Heat

Transfer Model, etc.

Here,

Domain Type: - Fluid Domain

Fluid: - Air Ideal Gas

Co-ordinate Frame:- Defaults

Reference Pressure: - 1 Atmosphere

Buoyancy Condition: - Non Buoyant

Domain Motion: - Stationary

Mesh Deformation: - None

Heat Transfer Model: - ISOTHERMAL

Turbulence: - K-epsilon

Where k is the turbulence kinetic energy and is defined as the variance of the fluctuations in velocity. It has dimensions of (L2

T-2); for example, m2/s2.

ε is the turbulence eddy dissipation (the rate at which the velocity fluctuations dissipate), as well as dimensions of k per unit time

(L2 T-3) (e.g., m2/s3).

The k-ε model introduces two new variables into the system of equations. The continuity

Equation is then:

( )

and the momentum equation becomes

( ) ( ) ( )

Wall Function: - Automatic

F. Define Inlet and Outlet Condition as Below

Fig 5.6 Input conditions applied on the wind cavity

Inlet Condition is as under:

Fluid Regime: - Subsonic

Mass and Momentum:-

Normal Speed: - 8 m/s

Turbulence: - Medium

Figure 5.7 Input and Output condition of the wind cavity



Outlet Condition is as under:-

Fluid Regime: - Subsonic

G. Go on Solver Option

Set Iteration to 100

H. Run Analysis

I. ANSYS CFX will Create Supersonic Nozzle.res file

J. Open CFX Post

K. Load .res file

VII. RESULTS OF ANALYSIS

A. NACA 0013

20.1 Degree

B. NACA 2415

20.1 Degree



Result Table ANSYS

Blade Angle Velocity(Original NACA) m/s Velocity (NACA 0013) m/s Power (Original)KW Power (NACA 0013)KW

15 14.21 10.64 24.230892 13.585152

20 17.89 13.39 38.406252 21.515052

20.1 18.04 13.5 39.052992 21.87

20.3 17.76 13.31 37.850112 21.258732

VIII. CONCLUSION

CFD is capable of designing the VAWT with higher degree of accuracy. It can also be used for the optimization of blade design.

Moreover, flow field around various configurations’ blades can also be visualized with the help of CFD. It has not only

accelerated the design process of VAWT but also has brought down the overall cost of designing.

Various vertical axis wind turbines can offer solution to the energy requirements ranging from 2 kW to 4 MW with a

reasonable payback period. Coefficient of power can be maximized by selecting a suitable TSR range for various configurations.

The parameter like air strike angle and aerofoil of the blade, wind speed, tip speed ratio, chord length are one of most effecting

parameter for the vertical axis wind turbine. By the analysis using this parameter can become useful in the performance

optimization of the vertical axis wind turbine.

Through the CFD analysis software ANSYS the Cavity Model of the Blade profile is generated which is used for analysis.

And their results were useful for the validation.

From the above analysis we have concluded that the optimum air strike angle for VAWT will be 20.1 degree. And the blade

profile of NACA 2415 is giving much more satisfying data than the NACA 0013 for the VAWT. From above we can discover

that CFD analysis in a ANSYS is giving solutions for VAWT are close to perfection and it can be used for the optimum design

for the VEWT.

REFERENCE

[1] Huimin Wang, Jianliang Wang, Ji yao, Weibin Yuan, Liang Cao “analysis on the aerodynamic performance of vertical axis wind turbine subjected to

Change of wind velocity”, Renewable energy, January 2012. [2] Ji Yao, Jianliang Wang, Weibin Yuhan, Huimin Wang, Liang Cao, “analysis on the influence of turbulence model Changes to aerodynamics performance

of vertical axis wind turbine” Energy, January 2012.

[3] Liang Cao , Huimin wang, Yao ji, Zhiliang wang, Weibin Yuhan, “analysis on the influence of Rotational speed to aerodynamic performance of vertical

axis wind turbine”, Renewable energy, January 2012.

[4] K. McLaren, S.Tullis, S.Ziada, “Measurement of high solidity vertical axis wind turbine aerodynamic loads under High vibration response conditions”,

Renewable energy, 6 January 2012. [5] Yuwei Li, Kwang-jun Paik, Tao Xing, Pablo M. Carrica, “Dynamic overset CFD simulation of wind turbine aerodynamics”, Renewable energy, 18 June

2011.

[6] Ivan Dobrev, Fawaz Massouh, “CFD and PIV investigation of Unsteady flow through Savonius wind turbine”,energy, May 2011. [7] Shwan Armstrong, Andrzej Fiedler, Stephen Tullis “Flow separation on a high Reynolds number, high solidity vertical axis wind turbine with Straight,

canted blades, Canted blades with fences” , Renewable energy, 3 September 2011.

[8] Nasir Hayat, Ahmad Uzair Farooq, Zain Ali, Sh. Rehan Jamil, Zahid Hussain, “Vertical axis wind turbine - A review of various configuration and design techniques”, Renewable energy, 18 December 2011.

[9] S. McTavish, D. Feszty, T. Sankar, “Study and rotating computational fluid dynamics simulation of a novel vertical axis wind turbine for small-scale power

generation” energy, 13 October 2011. [10] Marco Raciti Castelli, Alessandro Englaro, Ernesto Benini, “The Darrieus wind turbine: Proposal for a new performance prediction model based on CFD”,

energy, 20 May 2011.

Analysis on the influence of air strike angle To Aerodynamic performance of vertical axis wind turbi

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