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CHAPTER 3

FABRICATION OF MULTIPLE NOZZLE SYSTEM AND

EXPERIMENTAL SETUP

3.0 INTRODUCTION

The main objective of the present study is to increase the efficiency

of laboratory model wind turbine using multiple nozzle system. The

steps involved in the manufacture of multiple nozzle system and

parameters of research are discussed in this chapter. The method of

conducting an investigation in various stages using nozzle system is

also discussed in this chapter. Experimental setup consisting wind

tunnel and lab model wind turbine are demonstrated. This chapter

also includes the specifications of instruments like Anemometer, Non-

contacting tachometer, Thermocouple, Wattmeter, Voltmeter and

Ammeter. The method used in finding the theoretical and

experimental power coefficients of wind turbine in each module of the

experiment, heat gain by air, etc, are also presented.

3.1 PROBLEM FORMULATION

The investigation is focused on enhancing the power coefficient.

The effect of various nozzle systems on power coefficient of wind

turbine is discussed in the thesis. The internal nozzle set is fabricated

and inserted inside the outer convergent nozzle. The outer convergent

nozzle is fabricated as per recommendations. If the length of the

nozzle is too short, the velocity increases in a short period along with

turbulence. Due to increase in turbulence, back flow may occur. It

39

reduces the coefficient of discharge. In the other case, when length of

the nozzle is large, inner wall surface increases resistance to the fluid

flow in the form of friction. Coefficient of discharge then, decreases.

Hence, proper care is to be taken in selecting the length of the nozzle.

After fabrication of the multiple nozzle system, importance is given

to vary the angle of attack. The facility of blade swivel is provided to

the wind turbine. The distance of wind turbine from wind tunnel is

found through an experiment.

Theoretically and experimentally the power coefficient is

determined under various stages of the experiment using nozzle

system. Only, by knowing the air velocity at the inlet and outlet of the

wind turbine the theoretical power coefficient can be determined. But,

another experimental setup is made ready to determine experimental

power coefficient using dynamo and inverter.

The theoretical and experimental power coefficient of the turbine is

compared in various stages of investigation at different angles of

attack. The amount of energy absorbed by air while heating is also

determined as a part of the investigation. Both driver and driven

shafts rotate at different speeds. Hence, variation in speed ratio is also

studied in various stages of the experiment.

Computational fluid dynamics is used for the validation of air

velocities from nozzle system. Computationally and experimentally air

velocities from nozzle systems are determined and compared. Variations

in fluid properties like pressure, turbulent kinetic energy, etc, along the

length of nozzle system are also studied using CFD. The drop in air

40

temperature for the flow through multiple nozzle system is analyzed as

part of the research.

3.2 EXPERIMENTAL SETUP AND ITS DESCRIPTION

Investigation requires a wind tunnel since it produces air at

constant velocity. Complete description of wind tunnel, wind turbine,

etc, are furnished in this section.

3.2.1 Wind Tunnel

Wind tunnel is used to supply air continuously at constant

velocity. It is driven by a blower mounted at one end. It is illustrated

in Figure 3.1. Air is sucked at the other end called inlet duct. The

equipment consists of convergent and divergent portions and, with a

test section at throat. Wind tunnel is used to analyze the lift and drag

forces on airfoil - shaped blades of aero planes, wind turbine, rotary

compressor, etc. The pressure developed on blades at different

positions can be determined using manometers. Wind tunnel is driven

by D.C blower.

Blower Specifications:

Make : Kirloskar Electrical Company Limited

Phase : Three phase induction motor

Speed : 1400 RPM

Voltage : 415 volts

Current : 4.9 A

Power : 2.2 kW

Connection : Delta

41

Size of the inlet duct:

Length : 0.91 m;

Width : 0.91 m

Size of the test section:

Length : 0.48 m

Height : 0.29 m

Width : 0.30 m

Size of the outlet circular duct:

Diameter : 0.6 m

Total length of wind tunnel : 5.05 m

Various portions of wind tunnel and their details are stated below.

Inlet duct:

It is aerodynamically contoured section with contraction area

ratio 9:1. The square shaped duct has dimensions of 900 mm X 900

mm. For effective flow of air, the ratio of length to cell size of the

honeycomb is taken as 6, as per the recommendations of the vendor

of wind tunnel. Further, the wire mesh smoothens the air flow.

Provision is made to remove the screen for cleaning of wind tunnel.

Also, higher velocities can be obtained if the screen is removed, but it

is not of laminar. The duct is secured to the test section by

flange/bolts. The provision is made to separate test section and inlet

duct. Inlet duct is shown in Figure 3.2.

Test section:

It is the center portion of the tunnel cram between the inlet duct

and the diffuser. It has a transparent window, which facilitates

42

visualization easy. It is illustrated in Figure 3.3. The traversing

mechanism is fixed on its top for the movement of pressure probe.

There is a provision to calibrate strain gauge for determining lift and

drag force. A few holes on all sides test section are made to keep airfoil

model tight in the test section and pressure probes. Test section is

shown in Figure 3.3.

Diffuser:

The diffuser starts with 300 mm x 300 mm square section at the test

section end and, enlarges to diameter of 600 mm at the outlet. The length

is 2000 mm with the taper of 5 degrees. It is flanged and bolted to the test

section along with driving unit. For the smooth flow of air, the outlet of

wind tunnel is changed to round shape from square shape. The end of the

diffuser is assembled with an axial flow fan unit driven by a DC motor.

Control console:

The velocity of air, lift, drag and the pressure distribution on airfoil

can be controlled using control console. Thirstier speed controller is

connected to DC motor. The digital strain indicators are connected to

the strain gauge. Twelve numbers of manometers are provided to

record pressure developed on the surface of component in the test

section. External power supply is given to smoke generator and its

accessories. The control console is energized through 3 phase, 440V,

15A, A.C supply with neutral and earth connections. All safety

precautions to take care of excessive electrical loading are provided.

The arrangement of the control console is illustrated in Figure 3.4.

(Instruction manual of Ind- lab Equipments82)

43

3.2.2 Laboratory Model Wind Turbine

Out of the vertical axis and horizontal axis wind turbines, a

horizontal axis wind turbine is preferred to generate electricity. In the

present investigation, a three bladed horizontal axis wind turbine is

used. Laboratory model wind turbine is shown in Figure 3.5.

Specification of wind turbine:

Weight of each blade : 500 gm

Length of each blade : 0.24 m

Height of tower : 1.45 m

Diameter of hub : 0.04 m

Type of Airfoil : Flat and symmetrical (NACA0012)

3.2.3 Fabrication Of Outer Convergent Nozzle

As a part of manufacture of multiple nozzle system, the outer

convergent nozzle is fabricated first. It is fabricated with its outlet

diameter equal to the rotor diameter and inlet diameter is made equal to

the outlet diameter of wind tunnel. The side view of outer convergent

nozzle is shown in Figure 3.6.

Specification of outer convergent Nozzle

Material : Galvanized Iron

Inlet diameter : 0.6 m

Outlet diameter : 0.45 m

Length of the nozzle : 0.6 m

3.2.3.1 Theory of Cd for a Nozzle

The flow rate of fluid from a nozzle can be determined using the

relation 3.1.

44

Where, Q is the rate of discharge of fluid, Cd is the coefficient of

discharge, A is the area of cross section, β is the diameter ratio

(D1/D2) and hL is the loss of head. Instead of the coefficient of

discharge, it is more convenient to use the velocity coefficient Cv. It is

represented by the equation 3.2.

From equations 3.1 and 3.2 the coefficient of discharge becomes

Where, is the pressure drop and is density of flowing fluid. Cd

can be calculated based on applicable standards like ISO 5167 or

similar ASME standards. It is represented in the equation 3.4 and is

suited for small size nozzles. (ISI 1932 Code and Similar ASME

standards)

But, if the diameter of the nozzle is large i.e, the inlet diameter lies

in the range of 50 mm to 630 mm the equation 3.5 is suitable. For

in the range of 104 to 107 and β in the range of 0.2 and 0.8, the

relation shown in equation 3.5 is best suited.

45

3.2.3.2 Reason for Choosing L=D1 for Outer Nozzle

According to law of continuity, air velocity is independent of the

length of the nozzle. According to Karasawa83 et al. (1992) whenever

the ratio of the length to the inlet diameter of the rounded nozzle is

50, the coefficient of discharge becomes 0.67. But, when the length of

the nozzle is made equal to the inlet diameter, the coefficient of

discharge is found to be 0.98. The rise in the coefficient of discharge is

particularly significant in the nozzle flow. The outer nozzle in the

present study is circular in shape. Hence, the length of the outer

nozzle in the present study chosen is equal to its inlet diameter.

3.2.4 Set of Internal Convergent Nozzle

In the next stage of fabrication, a set of internal convergent nozzles

is made. The fabrication of a set of internal convergent nozzles is

shown in Figure 3.7. Two circular flanges are made using galvanized

iron. Six circular holes are drilled in both circular flanges, to fit

internal nozzles. The opposite ends of holes of round flanges are joined

using circular, conical pipes. The group is named ‘Set of Internal

Convergent Nozzles’. Arc welding is used in the fabrication.

Specification of Internal Convergent Nozzle:

Material : Galvanized Iron

Number of nozzles : 6

Inlet diameter of each nozzle : 0.15 m

Outlet diameter of each nozzle : 0.10 m

Length of each nozzle : 0.60 m

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3.2.4.1 Reason for Using Six Internal Nozzles

Ghassemieh84 et al. (2006) studied the effect of the coefficient of

discharge of fluid flow on geometry of nozzles. The effect of cone angle

in the range of 100 to 1200 is studied in the article. In the study,

Ghassemeih used the following relations.

Equation 3.6 and 3.7 are used to determine the coefficient of

discharge and Coefficient of velocity. Equation 3.8 is used to

determine the coefficient of contraction. Ghassemieh conducted

experiments by varying the pressure with the possible fluctuation of

temperature + 20C. The author concluded that nozzles with cone angle

less than 450 have a coefficient of discharge 0.89 to 0.95 and is

independent of cone angle. For, the cone angle in the range of 350 to

450, the Cd is substantially independent of supply pressure. But in

the case of low cone angles the coefficient of discharge increases

slightly as the supply pressure increases. In the analysis, m is the

mass flow rate of fluid, d1 is the inlet diameter of nozzle, P is the

supply pressure and V2 is the velocity of fluid from nozzle system.

Gassemieh also conducted experiments to identify the effect of the

coefficient of discharge on various ratios of inlet to outlet diameters. In

the study, diameter ratios are varied namely, 1.31, 1.33, 2.0, etc, up to

4.0. The author concluded that the coefficient of discharge increases

slightly as diameter ratio increases. Also, the author of the article states

47

that multi-hole nozzle facilitates the increase in the coefficient of

discharge through an experiment on 3, 4 and 5 number of multi-hole

nozzles.

The nozzle cone angle is determined from the equation 3.9.

(Rajput85, 2008)

For outer nozzle system with inlet diameter 0.6 m, outlet diameter

0.45 m and length 0.6 m the cone angle becomes 14.030. While

selecting the internal nozzle set, the diameter ratio taken is 1.5, which

is slightly more than 1.33. The geometry of single outer nozzle

provides the facility to have six number of nozzles with inlet diameter

0.15 m and outlet diameter 0.10 m. The cone angle in case of internal

nozzle thus becomes 4.760. According to Gassemieh, The decrease in

the cone angle increases the coefficient of discharge. Hence, the

multiple nozzle system is fabricated with six internal nozzles with the

cone angle 4.760.

3.2.5 Multiple Nozzle System

The assembly of outer nozzle and internal nozzle set is titled

“Multiple Nozzle System”. Perspective views of multiple nozzle system

are shown in Figure 3.8 and 3.9. Care is taken to avoid leakage loss

through joints. At the end, length of internal nozzles is projected

slightly outwards to keep air in the proper direction. The addition of

outer convergent nozzle to internal convergent nozzle set is made with

the help of bolts and nuts.

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3.2.6 Electric Air Heaters

Countries like India and China are exceptionally warm, especially

in summer and temperatures range from 400C to 450C in different

zones. Electric air heaters are used to heat flowing air through

multiple nozzle system. These electric heaters heat air by 100C more

than the atmospheric conditions. But, in the open-wind farms electric

heaters are not required. Air is heated up using solar radiation. Air

heaters are available with different configurations and designs. Finned

tubular type air heaters are used in the investigation. These heaters

are shown in Figure 3.10. These are made of aluminium tube with

corrugated aluminium fins. Fins are wrapped around the tube and

then brazed.

Specification of Air Heaters:

Capacity : 750 W

Length : 0.43 m

Outer diameter with fins : 0.076 m

3.3 INSTRUMENTS USED IN THE INVESTIGATION

Rotating disc type anemometer is used to determine air velocity. A

Non-contacting type tachometer is used to measure speed of driver

and driven pulleys during power measurement. The temperature of air

is measured using K-type thermocouple. The instruments used in the

study are calibrated and, the error analysis of instruments is

furnished in Appendix-B.

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3.3.1 Rotating Disc Type Anemometer

Rotating disc type anemometer is placed in the direction normal to

the direction of air flow. Anemometer is shown in Figure 3.11. The

circular disc of anemometer rotates when it is placed in the direction

of air flow. The number of rotations made by the disc is calibrated into

air velocity in m/s. Air velocity can also be measured in knots or

Kilometers per hour using such anemometer. It works safely even in

the range of 25-30 m/s. A digital monitor is provided to indicate wind

speed. Anemometer is calibrated in the range of 6 m/s to 29.5 m/s.

3.3.2 Non - Contact Tachometer

A Non-contacting tachometer is shown in Figure 3.12. It is a device

used to measure speed of the rotating shaft of turbine in revolutions

per minute. It does not have any physical contact with rotating shaft.

Such tachometer is best suited in wind farms since turbine is

mounted at great heights.

A light beam from source is focused on to a target marked on the

rotating shaft. A photo receiver receives the re-reflected light beam

with the help of photo probe. Both light source and photo receiver are

housed at front side of tachometer. The time interval between the two

consecutive sensations is calibrated into R.P.M. A digital screen is

provided to indicate speed of the rotating shaft. The instrument is

calibrated in the range of 500 R.P.M to 14000 R.P.M.

3.3.3 Temperature Measurement

In the study, K – Thermocouple is used to measure temperature of

the air. A thermocouple works on See beck effect. When two dissimilar

50

metals are at two different temperatures and if joined together, at

junction net e.m.f is induced. (Sachdeva86, 2005)

K-type thermocouple has been made of two different materials

Nickel and Chromium. It works in the range of -2000C to 13500C. Its

sensitivity is 41µV/°C. Totally, three different thermocouples are used.

One is placed at the inlet of multiple nozzle system and, another is

placed at the outlet of multiple nozzle system. To measure

temperature of air at the inlet of turbine one more thermocouple is

used. Method of temperature sensing is shown in Figure 3.13.

Thermocouples are calibrated in the range of 00 -100 0C.

3.3.4 Wattmeter, Voltmeter and Ammeter

Wattmeter is used to determine the amount of power given to heat

air. Voltmeter and ammeter are used to determine the power produced

by wind turbine. All instruments are calibrated before use. A

voltmeter of capacity 300 V, ammeter of 1A-2A capacity and wattmeter

of capacity 1A-2A and 300 V are used in the study. Another wattmeter

of capacity 3000 W is used in the analysis of energy gain by air. The

experimental set up with these instruments is shown in Figure 3.14.

3.4 EXPERIMENTAL SETUP FOR POWER MEASUREMENT

The rotor wind turbine is coupled to power producing device

dynamo. The rotational mechanical energy of the rotor is converted

into electric energy. The ratio of power produced to the power available

in the wind is the experimental power coefficient. Details of setup

needed for determining experimental power coefficient are furnished

below.

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3.4.1 Dynamo

The dynamo uses rotating coils of wire and magnetic field to

convert mechanical rotation into a pulsing direct electric current

through Faraday’s law of induction. A dynamo machine consists a

stationary structure, called stator. It facilitates the rotation of

armature against magnetic field. The motion of armature within the

magnetic field causes the field to push on the electrons, creating an

electric current in it. In small machines, the constant magnetic field is

provided using one or two permanent magnets; larger machines have

the constant magnetic field provided by one or more electromagnets.

When an armature rotates in a magnetic field, the e.m.f is induced in

it generating direct current. The commutator is essentially a

rotary switch. It consists of a number of contacts mounted on the

machine's shaft, combined with graphite-block stationary contacts,

called "brushes". The commutator reverses the connection of the

windings to the external circuit. When the potential reverses, instead

of alternating current, a pulsing direct current is produced. (Wikipedia

of Dynamo) A dynamo of capacity 12 Volts has been used in the

investigation. The column element of wind turbine is welded with two

V type thin rods. It provides support to Dynamo. The produced D.C

power is converted into A.C power using inverter.

3.4.2 Pulley and Belt Arrangement

The rotational mechanical energy of rotor of the turbine is

transmitted to dynamo using belt and pulley arrangement. The

arrangement of belt and pulley is shown in Figure 3.15. Dynamo

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produces large power when its shaft rotates at high speed. The shaft

of dynamo can be rotated at high speed by increasing the speed ratio.

Pulleys and belts have two uses; to increase or decrease speed of

driven pulleys. They are used to transmit power from one shaft to

another shaft. The dynamo may not generate power if the driver and

driven pulleys are made of the same diameter. The speed of dynamo

pulley is increased by using pulleys of different sizes. Driver pulley is

made of larger diameter than driven pulley to increase speed ratio. In

the investigation, synthetic nylon pulleys have been used. They are

machined using lathe machine to correct diameter. Nylon material

offers low resistance when compared to cast iron. Dynamo shaft

rotates at almost double the speed of rotor shaft. Hence, the speed

ratio becomes 2.0. The belt used in the transmission is of V-type.

Between grooves of two pulleys the belt slides.

3.4.3 Dynamo Testing

The working of dynamo is tested with 6 V and 12 V D.C bulbs. The

bulbs glow bright as shown in Figure 3.16. Wind turbine rotates at

more speed when it is not connected with belt and pulley. Figure 3.17

shows the operation of wind turbine without dynamo. It runs at high

speed in the absence of dynamo. The arrangement of turbine with

dynamo using belt and pulley arrangement is shown in Figure 3.18.

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Figure 3.1 Wind Tunnel

Figure 3.2 Inlet Duct of Wind Tunnel

Figure 3.3 Test Section

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Figure 3.4 Control Console

Figure 3.5 Laboratory Model Horizontal Axis Wind Turbine

Figure 3.6 Side View of Outer Convergent Nozzle

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Figure 3.7 Set of Internal Convergent Nozzles

Figure 3.8 Rear Front View of Multiple Nozzle System

Figure 3.9 Perspective View of Multiple Nozzle System

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Figure 3.10 Corrugated Aluminium Fin Electric Air Heaters

Figure 3.11 Rotating Disc Type Anemometer

Figure 3.12 Non – contacting Tachometer

57

Figure 3.13 Temperature Detection Using Thermocouple

Figure 3.14 Use of Wattmeter, Voltmeter and Ammeter

Figure 3.15 Belt and Pulley Arrangement

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Figure 3.16 Test of Dynamo

Figure 3.17 Wind Turbine without Pulley Arrangement

Figure 3.18 Wind Turbine with Pulley Arrangement

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3.5 RESEARCH METHODOLOGY

In this section, the method of carrying research has been

discussed.

3.5.1 Practical Difficulties of Multiple Nozzle System

Figure 3.19 Thematic Representation of Wind turbine with Multiple Nozzle System

The addition of multiple nozzle system to rotor of wind turbine is

shown in Figure 3.19. The rotor of turbine and tower may suffer due

to excessive stress produced by multiple nozzle system. Yaw

mechanism helps to keep the rotor of wind turbine in the direction of

the wind. Multiple nozzle system if, is mounted on rotor, also follow

the path of the rotor. This causes additional stresses. These practical

60

difficulties can be overcome using innovative design of “High Wind

Power Generator” as shown in Appendix.

3.5.2 Experiment Modules of Investigation

The research is aimed at high power coefficient of the wind turbine.

Nozzle system is assembled to wind tunnel instead of wind turbine to

overcome the practical difficulties. It releases tension on wind turbine.

Enhancement in power coefficient of wind turbine is estimated in the

following modules of the experiment. Totally experiment is conducted

in four stages namely,

Module Mo : Study of laboratory model wind turbine without any

nozzle system. It is shown in Figure 3.20.

Module M1 : Study using outer Convergent nozzle. It is shown in

Figure 3.21.

Module M2 : Study with multiple nozzle system without electric

heaters. It is shown in Figure 3.22.

Module M3 : Study with multiple nozzle system with electric

heaters. It is shown in Figure 3.23.

Figure 3.20 Module Mo (Without Nozzle System)

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Figure 3.21 Module M1 (With Outer Convergent Nozzle)

Figure 3.22 Module M2

(Multiple Nozzle System without Electric Heaters)

Figure 3.23 Indicating Position of Heaters in Module M3

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3.5.3 Heat Gain by Air

Electric power is supplied to heaters to heat air. Hundred percent

of heat may not be transferred to air. A part of energy has been wasted

in the form of heat losses. The power given to electric heaters (Qi) is

measured using wattmeter. Heat is supplied to air which is flowing

through multiple nozzle system. Heat absorbed by air is estimated

using the following relation.

Where,

is the mass flow rate of air at the inlet of multiple nozzle

system, is total inlet area of multiple nozzle system, Cp is the

specific heat at constant pressure of air, and dT is the rise in

temperature due to heating. The total heat absorbed by air is

determined in the presence of one, two and all three heaters.

3.5.4 Blade Orientation

Figure 3.24 Blade Swivel in the Quarter Segment of a Circle

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The angle at which the wind faces the chord of an airfoil is the

angle of attack. Wind tunnel produces wind in the fixed direction. But,

a facility has been provided to change the location of blade of wind

turbine by varying the orientation of airfoil. The blades can be

swiveled at 00, 300, 450, 600 and 900 in quarter segment of a circle. All

three blades of wind turbine are swiveled to the same inclination

during the experiment. The blade orientation in a quarter segments of

a circle is illustrated in Figure 3.24.

3.6 EXPERIMENTAL PROCEDURE

In various modules of experiments stated above, the power

coefficient of wind turbine is determined at various blade orientations.

The distance of the wind turbine is determined by changing its

position at different distances from wind tunnel. Power coefficient is

determined theoretically and experimentally. In every module of

investigation the chord of all blades, is oriented at angles of 00, 300,

450, 600 and 900. The air at high speed from wind tunnel is focused on

to rotor of the turbine. In these modules, the efficiency of the lab

model wind turbine is determined with and without using the nozzle

system at different positions of blade. The horizontal shaft of the wind

turbine rotates freely in bearings. Initially, the rotor is allowed to

rotate without connecting dynamo. Power coefficient is determined

theoretically by knowing wind speed at the inlet and outlet of wind

turbine. Later, experimental power coefficient is determined when the

shaft of the turbine is coupled with shaft of dynamo, using belt and

pulley arrangement.

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3.6.1 Determining Theoretical Power Coefficient

Rotating disc anemometer is placed in a direction normal to the

flow of air to determine air velocity at the inlet and outlet of the wind

turbine. The equation 3.12 is used to determine the power in the

wind. For a wind turbine rotor with swept area ‘A’ and, air density ‘ρ’

the power available in wind becomes

The theoretical power of wind turbine can be determined using the

equation 3.13. Thus, theoretical power coefficient, which is the ratio of

theoretical power to power in the wind, is determined in various

modules.

In module M1, under the first change in the experiment, the

fabricated outer/single nozzle is assembled to wind tunnel. The high

velocity of air rotates the rotor of turbine at high speeds. Theoretical

power coefficient is determined at different positions of blade.

As part of the next evolution in conducting the investigation i.e,

under module M2, multiple nozzles system is joined to wind tunnel.

The multiple nozzle system produces air at a high speed and kinetic

energy due to increased coefficient of discharge. The theoretical power

coefficient is then, determined.

To study the effect of conversion of heat energy into kinetic energy

electric heaters are used. These heaters are placed at the inlet of

multiple nozzle system. The air is heated almost 100C more than

65

ambient conditions. Three heaters each of 750 W is used to heat air.

Energy gain from heaters is also determined using the equation 3.1.

The hot air is allowed to pass through multiple nozzle system. The

change in revision is named as module M3, and the theoretical power

coefficient is determined.

No rotating parts are used in raising kinetic energy in all modules.

In all the modules of experiments, wind turbine is placed at same

distance from wind tunnel.

3.6.2 Determining Experimental Power Coefficient

The dynamo is connected to inverter to convert produced D.C

current into A.C current. Then experimental power coefficient of wind

turbine becomes the ratio of power produced to the power available in

the wind. It is determined in all stages of the experiment as discussed

above. All instruments are calibrated in recording the data. The

equivalence of kW and kVA is shown below. (Mukharjee87, 2001)

3.6.3 Comparing Air Velocities from Nozzle System

The blower fan produces air at 8.5 m/s of velocity. Air at this

velocity enters into nozzle system (V1). At the outlet of nozzle system,

velocity of air (V2) is recorded using rotating disc type anemometer.

Anemometer is placed at three defined positions, horizontally and

then vertically. The average of all these velocities is considered to

determine the experimental velocity of air from nozzle system. The

rise in velocity of air at the outlet of multiple nozzle system is verified

computationally, using computational fluid dynamics (CFD). The

66

temperature of air at the inlet of nozzle system (T1), outlet of the nozzle

system (T2), and at the inlet of wind turbine (Ti) is recorded using

thermocouple.

3.6.4 Speed Ratio

The ratio of speed of driver pulley to driven pulley is speed ratio.

Driver pulley is made twice the diameter of the driven pulley.

Theoretically, driven pulley should rotate twice the speed of driver

pulley. But, practically it would not happen. Belt between grooves of

pulley may offer some resistance. Hence, actual speed ratio may be

reduced. The speeds of both the pulley of rotor (Nrp) and pulley of

dynamo (Ndp) are measured using non-contacting tachometer.

3.7 SUMMARY AND CONCLUSIONS

The problem is formulated based on determining experimental and

theoretical power coefficients of the wind turbine. Under research

methodology, various modules of experiment are discussed. Various

instruments like rotating disc type anemometer, non-contacting

tachometer etc, are demonstrated. The research methodology in

carrying out the investigation is also discussed. After the conduct of

the experiment, the results are discussed in chapter 4.