final cpy-(exp study of rotor with wing lets)

8/3/2019 Final Cpy-(Exp Study of Rotor With Wing Lets)

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EXPERIMENTAL STUDY OF WIND TURBINE ROTOR

BLADES WITH WINGLETS

A PROJECT REPORT

Submitted by

RAMAKRISHNA DHARMENTHIRA S (42006101034)

SUKUMAR D (42006101041)

YOGESWARAN S (42006101050)

in partial fulfillment for the award of the degree

of

BACHELOR OF ENGINEERING

in

AERONAUTICAL ENGINEERING

TAGORE ENGINEERING COLLEGE, VANDALOOR (POST)

ANNA UNIVERSITY:: CHENNAI 600 025

MAY 2010


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BONAFIDE CERTIFICATE

Certified that this project reportEXPERIMENTAL STUDY OF WIND TURBINE

ROTOR BLADES WITH WINGLET is the bonafide work of

RAMAKRISHNA DHARMENTHIRA S (42006101034), SUKUMAR D

(42006101041) AND YOGESWARAN S (42006101050) who carried out the

project work under my supervision.

SIGNATURE SIGNATURE

Dr. P. Baskaran Mr. P. Saravanan

PROFESSOR AND HEAD OF DEPARTMENT SUPERVISOR AND LECTURERDepartment of Aeronautical Engineering Department of Aeronautical Engineering

Tagore Engineering College Tagore Engineering CollegeRathinamangalam Rathinamangalam

Chennai600048 Chennai600048


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ACKNOWLEDGEMENT

We would like to express our sincere thanks and gratitude to Dr. P.Baskaran,

Prof and Head of the Department, Aeronautical engineering for offering all the

support and encouragement that was instrumental in the successful completion of the

project.

We also thank Mr.P.Saravanan, M.E., Our Supervisor for having given us

valuable suggestions and support to make this project successful.

We would also like to thank all our department staffs for providing the

necessary facilities and helping us in every point during the completion of our project.

We acknowledge the support given by all the faculty members, lab technicians,

friends and family members for the completion of the project.


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TABLE OF CONTENTS

CHAPTER NO. TITLE PAGE

ABSTRACT iii

LIST OF TABLES v

LIST OF FIGURES vi

NOMENCLATURE vii

1. INTRODUCTION

1.1 Wind turbine 1

1.2 Importance of rotor 2

1.3 Winglets 3

1.4 Composite materials 6

1.5 Objective 6

1.6 Methodology 7

1.7 Importance of work 7

2. EXPERIMENTAL PROCEDURE

2.1 Model selection 8

2.2 Model fabrication 12

2.2.1 Wind turbine tower 12

2.2.2 Wind turbine rotor 14


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2.3 Experiment instruments 17

2.4 Experimental methodology for models efficiency study 21

2.5 Experimental methodology for noise comparison 31

2.6 Experimental methodology for rotor wake study 35

3. RESULTS AND DISCUSSION

3.1 Result 39

4. CONCLUSION 39


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ABSTRACT

For thousands of years mankind is utilizing wind energy. Increasing

world population and increasingly reducing the oil reserves and resulting

requirement for clean, reliable, renewable energy system intensifies the

requirements of wind energy in long term. Nowadays wind turbines are mostly

used for transforming that energy into electrical energy. In order to gain from a

wind turbine economically the efficient wind turbine rotor must be designed

and studied experimentally.

This paper is about experimentally studying the change of efficiency and

performance of wind turbine rotor blades by introducing winglets. The flow

distribution behind the rotor was studied. The wake study helps in planning the

location of the wind turbine in wind farms allowing for the effective utilization

of the available area. During the introduction of winglets in the rotor blades, the

vortices is reduced which in turn reduce the vibration and increase the

efficiency. The reduction of vortices decreases the vibration noise allowing the

wind turbine to work even in populated regions in a reliable manner.


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LIST OF TABLES

Table 1: Technical specifications of Nordtank NTL 550

Table 2: Specification of MN-00

Table 3: Specifications of Winglets

Table 4: Specification of Wind turbine Rotors

Table 5: Wind tunnel specifications

Table 6: RMN-01 power coefficient calculation





Table 11: velocity distribution at 1D distance behind rotor

Table 12: velocity distribution at 1.5D distance behind rotor

Table 13: velocity distribution at 2D distance behind rotor



Table 16: comparison of Cp and rpm of RMD-00, 01,02,03,04


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LIST OF FIGURES

Figure 1: Typical wind turbine

Figure 2: Schematic diagram wind turbine rotor

Figure 3: Definition of key parameters describing the winglet

Figure 4: Welded projection and sensor in tower

Figure 5: Completely fabricated tower

Figure 6: Wooden pattern of turbine blade

Figure 7: Wax dye

Figure 8: Winglets in rotor

Figure 9: Wind turbine rotor

Figure 10: Image of subsonic wind tunnel

Figure 11: Tip speed ratio vs Cpshmitz

Figure 12: Wind speed vs Slide number

Figure 13: RMD-01 CP vs rpm





Figure 18: Noise level in 32bit vs time a) test section b) RMD-03 c) RMD-00


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Figure 19: Velocity distribution at 1D distance behind rotor

Figure 20: Velocity distribution at 1.5D distance behind rotor

Figure 21: Velocity distribution at 2D distance behind rotor



Figure 24: Cp comparison of RMD-00, 01, 02, 03 and 04

Figure 25: rpm comparison of RMD-00, 01, 02, 03 and 04


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NOMENCLATURE

V Wind speed (m/s)

Vc tip speed (m/s)

tip speed ratio

slide number

B Blade number

Cp coefficient of power

CpSchmitz Schmitz number

A Area of the rotor (m2)

p density of air (Kg/m3)

n rotation per minute

r radius of the rotor (m)

D diameter of the rotor (m)

profile profile loss (%)

uc tip loss (%)

Ck lift coefficient

Cd drag coefficient

Pmax maximum theoretical power (watt)

Re Reynolds number


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1.INTRODUCTION

Wind one of the most renewable resources available in our Earth. The

fossil fuels are being slowly degrading due to over-exploitation. This leading us to

start depend more on the renewable resources like wind energy, solar energy and

etc. Wind energy is one most available resource were we can convert them into

electrical energy which can likely satisfy our upgrading needs. This conversion is

done with an ever known machine called as the WIND TURBINE.

1.1Wind TurbineA wind turbine converts the energy of wind into kinetic energy. If the

mechanical energy is used directly by machinery, such as pumping water, cutting

lumber or grinding stones, the machine is called a windmill. If the mechanical

energy is instead converted to electricity, the machine is called wind turbine. A

typical wind turbine is shown in figure 1.

Fig 1. Typical wind turbine


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Wind turbines have the main rotor shaft and electrical generator at the top of a

tower, and must be pointed towards the wind. Small turbines are pointed by a

simple wind vane, while large turbines generally use a wind sensor coupled with a

servo motor. Most have a gearbox, which turns the slow rotation of the blades into

a quicker rotation that is more suitable to drive an electrical generator.

Turbines[Wikipedia]

used in wind farms for commercial production of electric power

are usually three-bladed and pointed into the wind by computer-controlled motors.

A gear box is commonly used to step up the speed of the generator, although

designs may also use direct drive of an annular generator. Some models operate at

constant speed, but more energy can be collected by variable-speed turbines which

use a solid-state power converter to interface to the transmission system

1.2 Importance of RotorRotor

is the device that transforms the available kinetic energy of

wind into mechanic energy. For this reason it is very important for wind turbines.

It is important for blade and blade profiles for to have optimum features, because

these have a direct effect on the efficiency of wind turbine. The rotor commonly

consists of three blades, which are aerodynamically designed airfoils. These airfoil

blades produce lift and drag due to air flows from leading edge. This lift together

with drag force generates the thrust force and the difference of them gives the

driving force which is required to rotate the rotor in an efficient manner. The

blades are designed at certain blade angle in order to face the apparent wind.


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)

Fig 2. Schematic diagrams of wind turbine rotor

1.3 WingletsWinglets are usually intended to improve the efficiency of fixed wing aircrafts.

There are several types and the main purpose is to reduce the drag at the wingtips.

It effectively increases the aspect ratio without increasing the span. The winglets

increase the lift near the wingtip by smoothing the airflow across the upper surface

of blade near the tip and reduce the lift induced drag caused by wingtip vortices.

Adding a winglet to an existing wind turbine rotor will increase power produced

and there is also an additional increase in thrust. The art is then to design a winglet,

which optimizes drag reduction, maximizes power production and minimizes

thrust increase.

The main purpose of adding a winglet to a wind turbine rotor is to decrease the

total drag from the blades which could decrease the vibration and noises due to

them and thereby increase the aerodynamic efficiency of the turbine. Reduction of

total drag is obtained if the additional drag from the winglet is less than the

reduction of the induced drag on the remaining blade.


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During operation of wind turbine blade the resulting pressure difference on the

blades causes inward span wise flow on the suction side and outward span wise

flow on the pressure side near the tip. At the trailing edge, vortices are generated,

which is the origin of induced drag. The resulting pressure difference on an

operating wind turbine blade causes inward span wise flow on the suction side and

outward span wise flow on the pressure side near the tip. At the trailing edge,

vorticity is generated, which is the origin of induced drag.

A winglet is a load carrying device that reduces the span wise flow, diffuses and

moves the tip vortex away from the rotor plane reducing the downwash and

thereby the induced drag on the blade

The key parameters describing the winglets are:

1. Radius of curvature.2. Height3. Cant angle4. Sweep5. Toe6. Twist

Fig 3. Definition of key parameters describing the winglet.


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In this experiment the winglet parameter like height, radius of curvature, cant

angle were considered for designing our winglets. Since based on previous study

[1.pdf]the variation of the other parameters like sweep and twist dint effectively

change the efficiency of the wind turbine rotor. Due the vortices produced at the

wingtips creates large decimals of noise when the wind turbine reaches higher rpm

which would allows to settle the wind turbine away from populated region were

higher power is required. The introduction of winglets can reduce the wingtip

vortices and therefore decreasing the vibrations. This reduction of vibration could

reduce the noise and allow the wind turbine to reach higher rpm increasing its

efficiency.

1.4 Composite MaterialThe result of developing a material to have properties like high strength and

stiffness without gaining weight is the composite material. These composites

overcome the conventional materials like metals and alloy by providing low weight

and cost. Rapid advancement in this material technology[wtbp.pdf]

has created some

variations in the structure of wind turbines. That variation primarily provided

positive impact for lowering the prices of wind turbines and increasing the

strength.

Due to many factors such as mechanical equipment, fatigue, resistance,

corrosion resistance, breaking toughness, rigidity, weight and appearance have

impacts on wind turbine materials. That fact has caused composite materials to be

used widely in wind turbine structure.


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1.5 ObjectiveIn the present work, an attempt is made on comparing the efficiency

of scaled down and redesigned wind turbine rotor blades by introducing four sets

of various winglets to the same wind turbine rotor blades without winglets. A

study in rotor wake of the most efficient wind turbine rotor blades with winglets

was also conducted.

1.6 Methodology

An operational Wind Turbine (Nordtank NTK 550) in scaled down to

the ratio of 1:120. Four winglets of various dimensions which were designed from

the reference of previous studies of winglets were attached to the wind turbine

rotor blades. The total five sets of rotor blade were fabricated four rotors with

winglet and one without winglet. These models were been tested in wind tunnel at

various wind speed and there respective rpm was recorded. Wind turbine rotor with

winglets showed higher rpm and power coefficient than the rotor without wingletallowing possible increase in overall efficiency. The efficient wind turbine rotors

flow distribution after the rotor (rotor wake) is studied by reading the pressure

variation in the area behind the rotor.

1.7 Importance of work

In the development of renewable energy generation the wind turbine plays a

major role. Increase of efficiency with reduction of vibration and noise by using of

winglet increases the reliability and dependence of wind turbine. The design of

wind turbine blades with winglets can be done which could help in increasing the

efficiency and reduction of noise can allowing the wind turbine to locate in


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populated region were the power is required highly, such that the transmission loss

can be reduced in large scale. The study of the rotor wake allows getting

information of the air flow behind the rotor of wind turbine. This information

could help in construction and planning of wind farms, where the air flow of one

wind turbine rotor must not affect the other turbine. This could help in reducing the

area of dependence for required power that gives us high watt per area ratio for

wind farms.

This experimental study could help in designing wind turbine rotor to achieve

higher efficiency by introducing winglets.


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2. EXPERIMENTAL PROCEDURE2.1 Model selection

A wind turbine design was initially required, which allowed us to survey the

commercial wind turbine being operated. This allowed us to come across a

Nordtank wind turbine systems. The Nordtank NTK 550 was selected as our

primary design. Technical specifications of the models are detailed in table 1.

Table 1. Technical specifications of Nordtank NTL 550

Company & Country

originated

Nordtank (U.K)

Model name NORDTANK NTK 550Rated power 550 kilo-watt

Rotor Diameter 41m

Number of blades 3

Swept area 1320.25m

Blade settling angle 20

Length of blade 19.04m

Hub height 35m

Maximum chord 1.65m

Rotational direction Clockwise

Optimum wind speed 13.887m/s

Cut-in wind speed 4m/s

Cut-off wind speed 25m/s

Rotational speed 27.1rpm


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We scaled down the Nordtank NTK 550 wind turbine to a ratio of 1:120. The

respective ratio was selected because of available test section in wind tunnel. This

scaled down model MN-00 was fabricated to specific dimensions in table 2.

Table 2. Specification of MN-00

Rotor Diameter 340mm

Number of blades 3

Swept area 90792.02mm2

Length of blade 141m

Hub height 300m

Maximum chord(root

chord)

32mm

Minimum chord (tip

chord)

13.7mm

Rotational direction Clockwise

Blade settling angle 20

The rotor of MN-00 was taken as basic design for the rotor with winglets. The

winglets were designed from the reference of previous studies. The parameters

considered in designing the winglet was height, can angle and radius of curvature.

Winglet height was taken as 2% and 4% of rotor radius. The cant angle was

selected as 75o

constant since from previous studies this angle was given good

results and radius of curvature were 12.5% and 25% of their respective heights.

The dimensions of these winglets are detailed in table 3.


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Table 3. Specifications of Winglets

Winglet model

nameWMN-01 WMN-02 WMN-03 WMN-04

Height 6.8mm 3.4mm 6.8mm 3.4mm

Cant angle 75o

75o

75o

75o

Root chord 13.7mm 13.7mm 13.7mm 13.7mm

Tip chord 7.46mm 10.58mm 7.46mm 10.58mm

Radius curvature 1.7mm 0.85mm 0.85mm 0.425mm

The total of five sets of wind turbine rotor blades was designed and their

respective dimensions are detailed in table 4.

Table 4. Specification of Wind turbine Rotors

Rotor model

nameRMN-00 RMN-01 RMN-02 RM-03 RMN-04

Rotor

diameter170mm 174mm 172mm 174mm 172mm

Hub

diameter25mm 25mm 25mm 25mm 25mm

Blade span 141mm 145mm 143mm 145mm 143mm

Blade root

chord32mm 32mm 32mm 32mm 32mm

Blade tip

chord13.7mm 7.46mm 10.58mm 7.46mm 10.58mm


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Swept area90792.02

mm2

95114.85

mm2

924940.87

mm2

95114.85

mm2

924940.87

mm2

Rotor weight 45gm 49gm 47gm 48gm 46gm

The above mentioned rotors were designed and selected for experimental

study. Since the tower and hub height is common to all the scale downed models a

common tower was deigned to hub height of 300mm.

2.2 Model fabrication

The fabrication for the project was done using various innovative

methods. The commercially available materials were used to make it economical

and composite materials were also used. Initially the wind turbine was taken into

two parts they were:

a. Wind turbine towerb. Wind turbine rotors

2.2.1 Wind turbine tower

The wind turbine tower was fabricated using mild steel. The tower was

designed using a hollow steel pipe of diameter 36mmwith length of 320mm and

flat steel plate of length 22mm and width 30mm with thickness of 3mm is used as

bottom stand. These two pieces are welded using Shielded metal arc welding.

Shielded metal arc welding (SMAW), also known as manual metal arc

(MMA) welding or informally as stick welding, is a manual arc welding process

that uses a consumable electrode coated in flux to lay the weld. An electric current,

in the form of either alternating current or direct current from a welding power

supply, is used to form an electric arc between the electrode and the metals to be

joined. As the weld is laid, the flux coating of the electrode disintegrates, giving


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off vapors that serve as a shielding gas and providing a layer of slag, both of which

protect the weld area from atmospheric contamination.

A horizontal shaft for the wind turbine rotor is fixed to frictional free ball

bearing in a 24mm hollow steel pipe of length 85mm. This hollow pipe is

horizontally fixed to the tower using nuts and bolts. The rpm sensor for reading the

number of rotation in the rotor is fixed above the horizontal pipe such that it faces

the small welded projection in the rotor shaft as shown in figure 4.

Fig 4. Welded projection & sensor Fig 5. completely fabricated tower

This tower is completely fabricated as shown in figure 5. The tower was

painted with primer and oil paint over the surface to reduce the drag produced by

them during the experiment which could possibly reduce the rotor wake in small

percent. The tower is fitted to the wind tunnel such that there is no vibration is in

the model during the running of the tunnel.


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2.2.2 Wind turbine rotors

The wind turbine rotors were fabricated using an innovative method Resin

Casting using wax dye. This method allowed us to produce the required number of

rotor blades in an economical manner without losing the quality equivalent to iron

dye casting method. The usage of composite materials allowed easing the

fabrication of the rotor and providing the required material properties like strength

and stiffness for the blades.

Initially one blade pattern was prepared using teak wood, since it meets the

surface finish requirement. While preparing the blade pattern, geometrical

requirements that are common to all five sets of rotor were taken into

consideration. The wooden pattern has been coated with olive oil due to the reason,

it provides enough. But we can use any oil which can act as good releasing agent

for the wax not to get stuck with the wooden pattern shown in Fig 6. Commercially

available candle wax is taken and melted by heating it around 450

C to550C. This

molten wax was poured in perfectly designed container which allows the wooden

pattern to accommodate in required orientation. The container was provided with

sufficient shrinkage allowances.

The container was kept on a bed of water which provides sufficient cooling in

all directions of the container walls. The water maintains the temperature limit

between 200C to 30

0C, which takes approximately 2 hours of curing time for the

wax. Finally the wax dye is removed from the container with great precautions.

The wax mould was cleaned using dry cotton which allows us to remove the

excessive oil (releasing agent). Then dimensions of the wax dye were measured in

order to match the required dimensions of the turbine blade shown in Fig 7.


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Fig 6. Wooden pattern of turbine blade Fig 7. Wax dye

. Since the small wind turbine blades require less strength when compared to

the large ones, we use resin and hardner which combined together alone provides

enough engineering property as required.

The composition taken to prepare the blade was resin LY566 and hardner HY

951[4]

, which was mixed in ratio of 10:1. This composite was mixed with small

quantity of chopped glass rowing. The glass fibers provide sufficient strength to

the composition.

The wax dye was coated with a small layer of releasing agent (oil) and the

excess was removed using dry cotton. The resin hardener composition is poured

into the wax dye and allowed to settle. Since we have designed a flat bottomed

airfoil small wind turbine blade, open mould technique [6] was followed. It was

even possible to cast in closed mould method, which could allow us to design

complicated pattern. The blade was allowed to settle in the dye for the respective

settling period at normal room temperature. After some duration the mould was

removed carefully using the additional projection provided in the dye without

affecting the main surface of the mould and wax dye.

Finally the composite blade has been taken out and the excessive composite

was removed. These blades fixed in 3 numbers in acrylic hub forming 5 sets of

wind turbine rotors.


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This fabrication method saved us lots of money when compared to the regular

iron casting method for this small quantity of blades. This fabrication can be

replaced by Plaster of Paris instead of wax, but the surface finish of wax is very

high, when compared to Plaster of Paris. The voids and cracks can affect the

surface of the mould, which is reduced in large scale for the wax dye. Thus making

it more reliable and good in quality.

Fig 8. Winglets in rotors Fig 9. Wind turbine rotors

These five sets rotors were drilled with hole in centre that allows us to fix in the

horizontal shaft in the tower. These composite small wind turbine rotors are shown

in figure 9.

2.3Experiment instruments

In our study we tested the models in subsonic suction type wind tunnel.

These wind tunnels are used for operations at very low mach number, with speeds

in the test section up to 400 km/h (~ 100 m/s, M = 0.3). The air is moved with a

propulsion system made of a large axial fan that increases the dynamic pressure to

overcome the viscous losses. In a real case the model is made moving and the

atmosphere is stable. But in the case of a wind tunnel the model is scaled and made

static in the wind tunnel and the air is in motion. Therefore the pressure and other

features of the model are calculated as per our requirements. The technical

specifications of the wind tunnel is shown in table 5.


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Figure 10. Image of a subsonic wind tunnel

Wind tunnel type Subsonic

Flow type Suction type

Test section area 0.37m2

Exit area 1.81m

2

Motor type 3 Phase, induction motor

Current 230 V, AC

Maximum motor rpm 1450rpm

Maximum wind speed

Table 5. Wind tunnel specifications

The non-contact type optical tachometer was used. It has a distance

difference indicating sensor. This sensor gets active when any metal surface gets

near its head and de-active when no metal is near. The signal from the sensor is

sent to the tachometer that measures the rate of change status. This rate of change

is converted to revolution per minute and indicated.


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Anemometer consisted simply of a glass U tube containing liquid, a

manometer, with one end bent in a horizontal direction to face the wind and the

other vertical end remains parallel to the wind flow If the wind blows into the

mouth of a tube it causes an increase of pressure on one side of the manometer.

The wind over the open end of a vertical tube causes little change in pressure on

the other side of the manometer. The resulting liquid change in the U tube is used

to calculate the wind speed.

2.4 Calculation of power coefficient:

The fabricated wind turbine tower was mounted inside the test section of

the wind tunnel. The wires of the sensor on the tower were passed through the

holes available in the test section and connected to the tachometer. The two ends

anemometer U- tube is connected to the respective pressure ports available in

wind tunnel. First the rotor RMN-00was fixed in the wind turbine tower inside

the wind tunnel and rpm and pressure difference were identified.

The rpm of the model was noted and the variation of the anemometer

reading in the wind tunnel is also noted respectively. Wind velocity in the wind

tunnel is calculated by applying the formulae

Tunnels wind velocity, V = 2*sqrt [(total pressure static pressure) / Air

density at room condition]

Where,

(Total pressurestatic pressure) is the difference in Anemometer multiplied with

value of 98.373.

The tip speed of the wind turbine rotors were calculated using formulae,

Tip speed, Vc = ( *rotor radius* models rpm) / 30


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The tip speed ratio was derived from ratio of tip speed to wind speed at rotor which

are,

Tip speed ratio, = ( tip speed, Vc / wind speed , V )

The wind turbine rotor coefficient of power is given by

Cp= Cpshmitzprofile lossuc.

Calculations of Cpshmitz for the rotor were obtained from the table, which has a

specific value for each tip speed ratio. The corresponding values are plotted in a

graph and extrapolated to get the required values.

Tip speed ratio Vs Cpshmitz

0.545

0.55

0.555

0.56

0.565

0.57

0 2 4 6 8 10 12

Tip speed ratio

Cpshmitz

Series1

Figure 11. Tip speed ratio vs Cpshmitz

The profile loss is given by,

profile loss = 1- /.

The tip loss is given by,

uc= 1-1.84/B.


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Where,

is the tip speed ratio and B is the blade number which denotes the number of

blades.

is the slide number for the rotor blade profile

The slide number is the ratio between the lift and the drag coefficient of the

particular aerofoil. The aerofoil selected for the turbine blade is NACA 4412

symmetrical aerofoil. The slide number for the airfoil at different wind speed is

obtained from the table and the values are extrapolated to get the slide number for

the different wind speeds.

Wind speed vs Slide number

0

5

10

15

20

25

30

35

40

0 2 4 6 8

Wind speed

Slidenumber

Series1

Figure 12. Wind speed vs Slide number

The maximum theoretical power of the wind turbine is given by,

Pmax

= 0.5**swept area*wind velocity3*0.59( Betz limit)

The actual power available in the wind turbine model is given by,

P = 0.5**swept area*wind velocity3*Cp


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Thus, the available power, power coefficient, tip speed ratio and rotor rpm were

tabulated for RMN-00. The same procedure is applied to the remaining RMN-01,

RMN-02, RMN-03 and RMN-04.

Model (RMN-01).

Rotor radius : 174mm,

Winglet height : 6.8mm,

Winglet curvature : 25% of winglet height.

Model

rpm

Vc=

nr/30

Wind

velocity,

V m/s

=Vc/V Power ,

watt

Coefficient

of power

200 3.644 2.82 1.290 1.3062 0.227

710 12.936 4.00 3.24 3.7273 0.336

960 17.491 6.32 2.76 14.729 0.319

1210 22.042 6.92 3.18 19.366 0.419

1470 26.783 7.48 3.58 24.373 0.418

1750 31.885 8.95 3.56 41.672 0.421

2010 36.622 9.79 3.73 54.779 0.425

2310 42.088 11.31 3.71 84.324 0.426

2650 48.283 12.64 3.81 117.86 0.428

3010 54.842 13.26 4.13 135.78 0.433

3230 58.850 13.85 4.24 154.92 0.435

3460 63.040 14.60 4.31 181.25 0.437

3860 70.329 15.49 4.54 216.45 0.439


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Cp vs rpm

0

0.05

0.1

0.15

0.2

0.25

0.30.35

0.4

0.45

0.5

0 1000 2000 3000 4000 5000

Coefficient of power

Figure 13. RMD-01 CP vs rpm

Model (RMN-02).

Rotor radius : 174mm

Winglet height : 3.4mm

Winglet curvature : 25% of winglet height.

Model

rpm

Vc=

nr/30

Wind

velocity,

V m/s

=Vc/V Power ,

watt

Coefficient

of power

410 7.47 4.00 1.86 3.64 0.316

690 12.57 4.89 2.56 6.68 0.371

750 13.66 6.92 1.97 18.92 0.364

1200 21.86 7.48 2.92 23.82 0.407

1450 26.41 8.00 3.30 29.14 0.416

1730 31.52 8.94 3.52 40.72 0.422

2030 36.98 9.79 3.77 53.53 0.425

2360 42.99 11.31 3.80 82.41 0.427

Table 7. RMN-02 power coefficient calculation


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Cp vs rpm

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 500 1000 1500 2000 2500

Cp vs rpm


Model (RMN-03)



Winglet curvature : 12.5% of winglet height

Model

rpm

Vc=

nr/30

Wind

velocity,

V m/s

=Vc/V Power ,

watt

Coefficient

of power

510 9.18 4.00 2.295 3.727 0.339

750 13.5 4.89 2.755 6.843 0.376

1000 18.0 5.65 3.182 10.53 0.403

1250 22.5 6.92 3.247 19.36 0.412

1520 27.4 7.48 3.656 24.37 0.419

1780 32.1 8.00 4.005 29.81 0.424

2070 37.3 8.94 4.169 41.67 0.427

2390 43.1 11.3 3.802 84.32 0.427

2720 48.9 12.6 3.870 117.8 0.429

3080 55.4 13.5 4.088 145.2 0.437


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3280 59.0 14.1 4.175 164.7 0.436

3480 62.6 14.9 4.187 194.9 0.437

3890 70.0 16.0 4.376 238.5 0.439


Cp vs rpm

0

0.05

0.1

0.15

0.20.25

0.3

0.35

0.4

0.45

0.5

0 1000 2000 3000 4000 5000

Cp vs rpm


Model (RMN-04).



Winglet curvature : 12.5% of winglet height

Model

rpm

Vc=

nr/30

Wind

velocity,

V m/s

=Vc/V Power ,

watt

Coefficient

of power

500 9.00 2.82 3.182 1.287 0.3276

700 12.6 4.00 3.150 3.643 0.3625

970 17.5 4.89 3.564 6.688 0.3899

1230 22.1 5.65 3.914 10.29 0.4127

1480 26.6 6.92 3.845 18.92 0.4191


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1780 32.0 8.00 4.005 29.14 0.4237

2070 37.3 8.94 4.165 40.72 0.4252

2380 42.8 10.5 4.049 67.40 0.4279


Cp vs rpm

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 500 1000 1500 2000 2500

Cp vs rpm


Model (RMN-00)


Without winglet

Model

rpm

Vc=

nr/30

Wind

velocity,

V m/s

=Vc/V Power ,

watt

Coefficient

of power

400 7.12 2.82 2.51 1.256 0.3158

530 9.43 4.00 2.35 3.552 0.3420

770 13.7 4.89 2.78 6.521 0.3732

1020 18.2 5.65 3.21 10.04 0.4043

1280 22.7 6.92 3.28 18.45 0.4119

1550 27.6 7.48 3.68 23.25 0.4285


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1840 32.7 8.00 4.09 28.41 0.4231

2140 38.1 8.94 4.25 39.71 0.4264

2440 43.4 11.3 3.83 80.35 0.4271


Cp vs rpm

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 500 1000 1500 2000 2500 3000

Cp vs rpm


The model RMD-03 was found to be the efficient rotor among other models.

Thus, the RMD-03 was selected for further investigation in noise comparison and

rotor wake study.

2.5 Experimental methodology for noise comparison

An high sound recognizing microphone were installed over the surface of test

section. The wind tunnel was run to a specific wind velocity and noise produced

was plotted in decibels (dB) in 32bit with respective to time. The rotor RMD-03

was mounted and noise level was plotted same specific wind velocity. Now the

rotor without winglet RMD-00 was replaced with RMD-03 and the noise level was

plotted. The graphs were compared and studied.


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Figure 18. of noise level in 32bit vs time a) test section b) RMD-03 c) RMD-00


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2.6 Experiment methodology for Rotor wake study

A wake is the region of disturbed flow downstream of a solid body moving

through a fluid, caused by the flow of the fluid around the body. In wind turbine

this flow is found behind the rotor.

The model RMN-003 was mounted inside the wind tunnels test section.

The grid formed with single row of 14 pitot tubes and 2 static tubes as shown in

figure was placed inside the test section. The grid was moved to various length of

rotor diameter like 1D, 1.5D, 2D etc horizontally behind the wind turbine rotor.

The row in the grid was moved vertically to 7 positions giving us the wind speed at

various positions behind the rotor. Thus the wake distribution behind the rotor was

identified. The flow structure in the wake region has been investigated with the

wind tunnel experiment at constant wind speed especially paying attention to the

scale effects of the wind turbine model.

The wind velocity of 5.86m/s was created inside the test section ignoring

the losses due to boundary layer effect. The virtual test section of 1.87ft X 1.87ft

was taken into consideration from 2ft X 2ft test section to avoid the disturbance in

the wind flow caused by the walls of test section.

The wake is identified by the variation of pressure at the locations the

respective locations. This variation is shown in the pressure distribution scale

connected to the pitot and static tubes in the grid.

This pressure variation is converted to wind velocity using the formulae (1)

and tabulated to their respective positions as shown in tables 11,12,13,14 and 15.


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The tabulated wind velocities are represented in 3Dgraphs with vertical and

horizontal location with respective wind speed.

Figure 19. Velocity distribution at 1D distance behind rotor

Figure 20. Velocity distribution at 1.5D distance behind rotor


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Figure 21. Velocity distribution at 2D distance behind rotor



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The wake study showed that wind flow variation becomes steamline behind the

rotor after the distance 2.75D of the wind turbine rotor at wind speed of5.86m/s. thevariation of the velocity flow due to rotor and tower was alone considered during this

study.


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3. RESULTS AND DISCUSSION

3.1ResultThe comparison of the models RMD-01, RMD-02, RMD-03, RMD-04 and

RMD-00 with respective to their rpm and coefficient of power is tabulated in

table 16.

RMD-01 RMD-02 RMD-03 RMD-04 RMD-00

Rpm Cp rpm Cp Rpm Cp rpm Cp rpm Cp200 0.227 410 0.316 510 0.339 500 0.3276 400 0.3158

710 0.336 690 0.371 750 0.376 700 0.3625 530 0.342

960 0.319 750 0.364 1000 0.403 970 0.3899 770 0.3732

1210 0.419 1200 0.407 1250 0.412 1230 0.4127 1020 0.4043

1470 0.418 1450 0.416 1520 0.419 1480 0.4191 1280 0.4119

1750 0.421 1730 0.422 1780 0.424 1780 0.4237 1550 0.4285

2010 0.425 2030 0.425 2070 0.427 2070 0.4252 1840 0.4231

2310 0.426 2360 0.427 2390 0.427 2380 0.4279 2140 0.4264

2650 0.428 2720 0.429 2440 0.4271

3010 0.433 3080 0.437

3230 0.435 3280 0.436

3460 0.437 3480 0.437

3860 0.439 3890 0.439

Table 16. comparison of Cp and rpm of RMD-00,01,02,03,04

The graphical representation of the comparison of rpm and coefficient of power

of the various models RMD-00, RMD-01, RMD-02 ,RMD-03 and RMD-04 are

shown in figure 24 and 25 respectively.


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Figure 24. Cp comparison of RMD-00, 01, 02, 03 and 04

Figure 25. rpm comparison of RMD-00, 01, 02, 03 and 04


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The results of the experiment indicated in the table 16 and figures 24,25 shows that

the model RMD-01 and RMD-03 with 6% winglet height in common and with a

curvature of 12.5% and 25% of radius were the efficient models. In which the RMD-

03 indicated higher rpm, lower staring wind speed and coefficient of power than

RMD-01.

The noise produce by the rotor RMD-03 with winglets of 6% height and 12.5%

radius of curvature was lower than the rotor RMD-00 without winglets.

The wake created by the rotor RMD-03 with winglet settled at an distance of

2.75D of the rotor.

4. CONCLUSION

The present study indicates a strong relation between winglet height, rotation

rate (rpm), curvature radius and power co-efficient. Winglet added rotor models gives

increase in power coefficient. An increase in winglet height and optimum radius of

curvature shows lower starting wind velocity and increase in rotational speed even in

low wind speeds allowing overall increase in power coefficient and reduction in noise

due to vibration. The wake study of the wind flow behind the rotor allowed us to find

the location were the wind get stream lined again. This could positively increase the

effective utilization of area in an wind farm in which large number of wind turbines

are installed together to satisfy higher energy needs. It is also possible that winglet

added wind turbine is best suited for remote areas, where wind power available is less.


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REFERENCES

1. Shane.M, Jason G; 2009; Wind tunnel analysis of a counter-rotating windturbine; proceeding ASEE annual conference; Baylor University.

2. Martin O. L. Hansen; 2008; Aerodynamics of wind turbines; second edition.3. J.F.Manwell, J.G.mcGowan, A.L.Rogers; 2002; Wind Energy Explained; John

Willey & Sons Ltd; England.

4. F.Wang, L.Bai; 2008; The methodology for aerodynamic study on a smalldomestic wind turbine with scoop; Journal of wind Engg and industrial

Aerodynamics; p 1-24.

5. Betz.A; 1926; Wind energy and their utilization by wind mills; GermanyBandenhoeck & Ruprect.

6. J Johansen, N.Sorensen; 2006; Numerical analysis of winglets on wind turbineblades using CFD, Riso-R-1543(EN); Riso National laboratory,

Roskilde;Denmark.

7. Dreese J; 2000; Aero basics and design foil; user guide; USA, Capitola.8. Ali vardar, Bulent Eker; 2006; Principle of rotor design for horizontal axis wind

turbines; Journal of applied sciences 6(7); p 1572-1533.

9. Ozdamar A, Kavas MG; 1999; A research about wind turbine propeller design.Sun day symposium presentation book; p 151160.

10.Ali Vardar, Halil Unal; 2006; A research towards meeting the electricitydemand of a plant via wind turbine; Journal of applied sciences 6(5); p 1176-

1181.

final cpy-(exp study of rotor with wing lets)

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