engineeringlab4 fluid mechanics manual

5/26/2018 EngineeringLab4 Fluid Mechanics MANUAL

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UNIVERSITI MALAYSIA SARAWAK

FACULTY OF ENGINEERING

MECHANICAL AND MANUFACTURING

ENGINEERING DEPARTMENT

KNJ2261 Laboratory IV

MECHANICAL AND MANUFACTURING

ENGINEERING LABORATORY IV

LABORATORY MANUAL

Revised: December 2010


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TABLE OF CONTENT

Lab Code Title PageF1

F2

F3

F4

F5

F6

F7

F8

F9

F10

Venturi Meter

Flowmeter Measurement Apparatus

Flow Through Orifice

Orifice and Free Jet Flow

Bernoullis Theorem Demonstration

Osborne Reynolds Demonstration

Energy Losses in Bends and Fittings

Pelton Turbine

Wind Tunnel

Pump Performance Test

1

8

20

30

38

49

54

58

65

71

Appendix

A

B

C

D

Safety First

Guidelines for Laboratory Report

Example of Front Page Cover

Example

76

77

78

79


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KNJ2261 Mechanical and Manufacturing Engineering Laboratory IVFaculty of Engineering

Universiti Malaysia Sarawak

1. TOPIC 1: VENTURI METER.1.1 THEORY:

Introduction

In engineering and industrial practice, fluid measurement of many of the variables and properties,

such as density, viscosity, pressure, velocity, flow rate, etc, is one of the problems most frequently

encountered by engineers. It is therefore an essential for engineers to be well equipped with

knowledge of the fundamentals and existing methods of measuring various fluid properties and

phenomena. This apparatus is specially designed to obtain the flow rate measurement by utilizing

venturi meter.

Venturi Meter

The venturi meter consists of a venturi tube and differential pressure gauge. The venturi tube has a

converging portion, a throat and a diverging portion as shown in the figure below. The function of the

converging portion is to increase the velocity of the fluid and lower its static pressure. A pressure

difference between inlet and throat is thus developed, which pressure difference is correlated with the

rate of discharge. The diverging cone serves to change the area of the stream back to the entrance area

and convert velocity head into pressure head.

Figure 1.1: The Venturi Tube

Assume incompressible flow and no frictional losses, from Bernoullis Equation

2

2

221

2

11

22Z

g

vpZ

g

vp++=++

(1)

Use of the continuity Equation Q = A1V1= A2V2, equation (1) becomes

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=+

2

1

2

2

221 1

2

21

A

A

gZZ

pp

(2)

Ideally,

2/1

21

2/12

1

2222

2121

+

==

ZZpp

gA

AAVAQi

(3)

However, in the case of real fluid flow, the flow rate will be expected to be less than that given by

equation (3) because of frictional effects and consequent head loss between inlet and throat. Therefore,

21

21

212

1

22

2121

+

=

ZZppgAAACQ da

(4)

In metering practice, this non-ideality is accounted by insertion of an experimentally determined

discharge coefficient, Cdthat is termed as the coefficient of discharge. With Z1= Z2in this apparatus,

the discharge coefficient is determined as follow:

i

a

dQ

QC =

(5)

Discharge coefficient, Cd usually lies in the range between 0.9 and 0.99.

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1.2 APPARATUS:

`

Figure 1.2: Parts Identification and Equipment Set-up of Venturi Meter

1. Staddle Valve 6. Baseboard

2. Manometer Tubes 7. Unions

3. Manometer Board 8. Venturi Inlet Connection

4. Discharge Valve 9. Venturi Meter

5. Venturi Outlet Connection 10. Adjustable Feet

The Venturi Meter has been designed to be operated together with a basic hydraulic bench or any

water supply to study the characteristics of flow through both converging and diverging sections.

During the operation, water is fed through a hose connector. A discharge valve is installed at the

1

2

3

4

5

7

8

106

9

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Venturi outlet for flow rate control. The venturi can be demonstrated as a means of flow measurement

and the discharge coefficient can be determined.

1.3 MAINTENANCE AND SAFETY PRECAUTIONS:

1. It is important to drain all water from the apparatus when not in use. The apparatusshould be stored properly to prevent damage.

2. Any manometer tube, which does not fill with water or slow fill, indicates that tapping orconnection of the manometer is blocked. To remove the obstacle, disconnect the flexible

connection tube and blow through.

3. The apparatus should not be exposed to any shock and stresses.4. Always wear protective clothing, shoes, helmet and goggles throughout the laboratory

session.

5. Always run the experiment after fully understand the unit and procedures.

General Shut-Down Procedures

1. Close water supply valve and venturi discharge valve.2. Turn off the water supply pump.3. Drain off water from the unit when not in use.

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1.4 EXPERIMENTAL PROCEDURES:

1.4.1 Experiment 1: Discharge Coefficient

Objective

To determine the discharge coefficient of the venturi meter.

Procedures

1. Adjust the discharge valve to the maximum measurable flow rate of the venturi.2. After the level stabilizes, measure the water flow rate using volumetric method

and record the necessary readings.

3. Repeat the steps for few data collection by regulating the venturi discharge valve.4. Obtain the actual flow rate, Qa5. Calculate the ideal flow rate, Q i6. Finally obtain the discharge coefficient, Cd7. Discuss your result.

Experimental Data Sheet

Qa

(LPM)

Water Head (mm)

hA hB hC hD hE hF

Data Analysis :

Throat Diameter, D3(mm) = 16.0

Inlet Diameter, D1(mm) = 26.0

Throat Area, At(m2) = 2.011E-04

Inlet Area, A (m2) = 5.309E-04g (m/s2) = 9.81(kg/m3) = 1000

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1.4.2 Experiment 2: Flow Meter Measurement

Objective

To measure the flow rate with venturi meter

Procedures

1. Adjust the discharge valve to a high measurable flow rate.2. After the level stabilizes, measure the water flow rate using volumetric method

and record the manometers reading.

3. Repeat the steps with other few data collection.4. Calculate the venturi meter flow rate of each data.5. Compare the volumetric flow rate with venturi meter flow rate.6. Discuss your result.


Qa

(LPM)

Water Head (mm)

hA hB hC hD hE hF

Data Analysis :

Cd = _____

Throat Dia, D3(mm) = 16.0

Inlet Dia, D1(mm) = 26.0

Throat Area, At(m2) = 2.011E-04

Inlet Area, A (m2) = 5.309E-04

g (m/s2) = 9.81

r (kg/m3) = 1000

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Qa(LPM) hA-h C(m) Calculated Flow Rate (LPM) Error (%)

1.5 OPEN ENDED QUESTIONS:

1. Briefly explain any two common devices that are used to measure velocity and flow rate.2. In your own words, explain how flow rate is measured with obstruction-type flowmeter. 3. If the flow rate of fluid increase, explain what happen to the pressure inside a venturi meter.

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2. TOPIC 2: FLOWMETER MEASUREMENT APPARATUS2.1 THEORY:

RotameterThe rotameter is a flow meter in which a rotating free float is the indicating element.

Figure 2.1:The Rotameter

Venturi MeterThe venturi meter consists of a venturi tube and a suitable differential pressure gauge.

Figure 2.2: Venturi Meter

Assume incompressible flow and no frictional losses, from Bernoullis Equation

2

2

221

2

11

22Z

g

vpZ

g

vp++=++

....(1)Use of the continuity Equation Q = A1V1= A2V2, equation (1) becomes

=+

2

1

2

2

221 1

2

21

A

A

g

VZZ

pp

....(2)

Ideal

Tapered tube

Flow

Scale

1 2

Inlet

Throat

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21

21

212

1

2222

2121

//

+

==

ZZpp

gA

AAVAQ

.....(3)

However, in the case of real fluid flow, the flow rate will be expected to be less than that given byequation (2) because of frictional effects and consequent head loss between inlet and throat. Inmetering practice, this non-ideality is accounted by insertion of an experimentally determinedcoefficient, Cd that is termed as the coefficient of discharge. With Z 1= Z2in this apparatus, equation(3) becomes

Actual

21212

1

22

2121

=

ppg

A

AACdQ

...... (4)

Hence,

( )[ ] 2121

212

/21 PPgA

AtAtCdq

=

....... (5)

Where,Cd = Coefficient of discharge (0.98)D2 = Throat diameter = 16 mmD1 = Inlet diameter = 26 mmAt = Throat area = 2.011 x 10-4m2A = Inlet area = 5.309 x 10-4m2g = 9.81 m/s2

= Density of water = 1000 kg/m3

P1 = Inlet pressure (Pa)P2 = Throat pressure (Pa)

Orifice MeterThe orifice for use as a metering device in a pipeline consists of a concentric square-edged circularhole in a thin plate, which is clamped between the flanges of the pipe as shown in the figure below.

Figure 2.3:Orifice Meter

Equation (4) for the venturi meter can also be applied to the orifice meter where

A1

A2

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Actual

21

21

212

1

22 21

=

ppg

A

AACdQ

..(6)

The coefficient of discharge, Cd in the case of the orifice meter will be different from that for the caseof a venturi meter.

( )[ ] 2187

212

21 hhgA

AtAtCdQ

=

.(7)

Where,Cd = Coefficient of discharge (0.63)D7 = Orifice diameter = 16 mm

D8 = Orifice upstream diameter = 26 mmAt = Orifice area = 2.011 x 10-4m2A = Orifice upstream area = 5.309 x 10-4m2(h7 h8) = Pressure difference across orifice (m)

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90oelbowFigure below shows fluid flowing in a pipeline where there is some pipe fitting such as bend or valve,and change in pipe diameter. Included in the figure is the variation of piezometric head along the piperun, as would be shown by numerous pressure tappings at the pipe wall.

Figure 2.4:Piezometric head along a pipeline

If the upstream and downstream lines of linear friction gradient are extrapolated to the plane of fitting,

a loss of piezometric head, h, due to the fitting is found. By introducing the velocity heads in theupstream and downstream runs of pipe, total head loss, H can be determined in which

g

V

g

VhH

22

2

2

2

1 += (8)

Energy losses are proportional to the velocity head of the fluid as it flows around an elbow, through anenlargement or contraction of the flow section, or through a valve. Experimental values for energylosses are usually expressed in terms of a dimensionless loss coefficient K, where

gV

Hor

gV

HK

22 2

2

2

1 //

=

..(9)

depending on the context.For results of better accuracy, long sections of straight pipe are required to establish with certainty therelative positions of the linear sections of the piezometric lines. However, in a compact apparatus as

described in this manual, only two piezometers are used, one placed upstream and the otherdownstream of the fitting, at sufficient distances as to avoid severe disturbances. These piezometers

measure the piezometric head loss, h between the tapping. Thus

fhhh = ' ..(10)

Where

V22 / 2g

V12 / 2g

H

h

V 2V 1

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=

g

V

D

Lfhf

24

2

hf = friction head loss which would be incurred in fully developed flow

along the run of pipe between the piezometer tappingsf = friction factorL = distance between the piezometer, measured along the pipe center lineD = pipe diameterV = average velocity of fluid flow in pipe

The friction head loss is estimated by choosing a suitable value of friction factor, f for fully developedflow along a smooth pipe. The method used in this manual to determine the friction factor is thePrandtl equation

( ) 4041 .Relog = ff (11)

Typical values derived from this equation are tabulated in the table below:

Re, x104 0.5 1.0 1.5 2.0 2.5 3.0 3.5

f, x 10-3 9.27 7.73 6.96 6.48 6.14 5.88 5.67

In determination of the fraction factor, f, it is sufficient to establish the value of f at just one typicalflow rate, as about the middle of the range of measurement due to the fact that f varies only slowly

with Re, and the friction loss is generally fairly small in relation to the measured value of h.

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2.2 APPARATUS:

Figure 2:Flowmeter Measurement Apparatus

1. Manometer Tubes 6. Rotameter

2. Discharge Valve 7. 90 Elbow

3. Water Outlet 8. Orifice

4. Water Supply 9. Venturi

5. Staddle Valve

4

3

2

1

5

6

7

8

9

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Specification of dimensions

i) Venturi meter

Figure 3:Specification of the Venturi Meter

Tapping A = 26 mmTapping B = 21.6 mm

Tapping C = 16 mmTapping D = 20 mmTapping E = 22 mmTapping F = 26 mm

ii) Orifice

Figure 4:Specification of the Orifice Plate

Orifice upstream diameter (G) = 26 mm

Orifice diameter (H) = 16 mm





3. The apparatus should not be exposed to any shock and stresses.

CA D E FB

G H

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4. Always wear protective clothing, shoes, helmet and goggles throughout the laboratorysession.



1. Close water supply valve and venturi discharge valve.2. Turn off the water supply pump.3. Drain off water from the unit when not in use.

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2.4.1 Experiment 1: Characteristics of Flowmeter Measurement Devices

Objective

To obtain the flow rate measurement by utilizing three basic types of flow measuring

techniques, which are rotameter, venturi meter and orifice meter.

Procedures

1. With the bench valve fully closed and the discharge valve fully opened, start upthe pump supply from hydraulic bench.

2. Slowly open the bench valve until it is fully opened.3. When the flow in the pipe is steady and there is no trapped bubble, start to close

the bench valve to reduce the flow to the maximum measurable flow rate.

4. Adjust water level in the manometer board. Retain maximum readings onmanometers with the maximum measurable flow rate.

5. Note readings on flowmeter devices.6. Repeat the steps for few data collection.7. To demonstrate similar flow rates at different system static pressures, adjust

bench and flow control valve together. Adjusting manometer levels as required.

8. Discuss the result

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Manometer reading (mm) Rotameter(l/min)

Vol(l)

Time(min)

Flowrate,Q

(l/min)

Flowrate calculated using theBernoulli's Equation (l/min)

A B C D E F G H I J Ventur i Orif ice

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2.4.2 Experiment 2: Loss Coefficient

Objective

To investigate losses at one typical fitting, which is a 90 elbow

Procedures

1. With the bench valve fully closed and the discharge valve fully opened, start upthe pump supply from hydraulic bench.

2. Slowly open the bench valve until it is fully opened.3. When the flow in the pipe is steady and there is no trapped bubble, start to close

the bench valve to reduce the flow to the maximum measurable flow rate.

4. Adjust the water level in the manometer board. Retain maximum readings onmanometers with the maximum measurable flow rate.

5. Note readings on manometers.6. Repeat the steps for few data collection.7. Determine the coefficient of losses.8. Discuss the result.

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1. Explain what are the primary considerations when selecting a flowmeter to measure the flowrate of a fluid.

2. In your own words, explain the mechanism of rotameter.3. Compare rotameter, venture meter and orifice meter with respect to cost, size, head loss and

accuracy.

Volume

(L)

Time

(sec)

Flowrate,Q

(l/min)Differential Piezometer Head, h' (mm)

V

(m/s)

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3. TOPIC 3: FLOW THROUGH ORIFICE3.1 THEORY:

A fluid passing though an orifice constriction will experience a drop in pressure across the orifice.

This change can be used to measure the flowrate of the fluid.

To calculate the flowrate of a fluid passing through an orifice plate, enter the parameters below. (The

default calculation involves air passing through a medium-sized orifice in a 4" pipe, with answers

rounded to 3 significant figures.)

As long as the fluid speed is sufficiently subsonic (V < mach 0.3), the incompressible Bernoullis

equation describes the flow reasonably well. Applying this equation to a streamline traveling down the

axis of the horizontal tube gives,

2

1

2

2212

1

2

1VVppp ==

where location 1 is upstream of the orifice, and location 2 is slightly behind the orifice. It isrecommended that location 1 be positioned one pipe diameter upstream of the orifice, and location 2

be positioned one-half pipe diameter downstream of the orifice. Since the pressure at 1 will be higher

than the pressure at 2 (for flow moving from 1 to 2), the pressure difference as defined will be a

positive quantity.

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Fromcontinuity,the velocities can be replaced by cross-sectional areas of the flow and the volumetric

flowrate Q,

=

2

1

2

2

2

2

1

1

2

1

A

A

AQp

Solving for the volumetric flowrate Qgives,

2

1

2

2

1

2

=

A

A

ApQ

The above equation applies only to perfectlylaminar,inviscid flows. For real flows (such as water or

air), viscosity and turbulence are present and act to convert kinetic flow energy into heat. To account

for this effect, a discharge coefficient Cdis introduced into the above equation to marginally reduce

the flowrate Q,

2

1

2

2

1

2

=

A

A

ApCQ D

Since the actual flow profile at location 2 downstream of the orifice is quite complex, thereby making

the effective value of A2 uncertain, the following substitution introducing a flow coefficient Cf is

made,

2

1

2

2

1

=

A

A

ACAC DOf

whereAois the area of the orifice. As a result, the volumetric flowrate Qfor real flows is given by the

equation,

pACQ Of = 2

The flow coefficient Cfis found from experiments and is tabulated in reference books; it ranges from

0.6 to 0.9 for most orifices. Since it depends on the orifice and pipe diameters (as well as theReynolds

Number), one will often find Cf tabulated versus the ratio of orifice diameter to inlet diameter,

sometimes defined as b,

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inlet

O

D

D=

The mass flowrate can be found by multiplying Qwith the fluid density,

QQmass =

This experiment allows us to detect the effect of friction on water flow. There are three coefficients

that are useful in determining the performance of water through a jet and the effect of friction on that

performance. Cd, Cv, and Cc as defined earlier give us insite into the effects of friction on water flow.

Each of these coefficients is ratio of the actual performance to ideal performance as related to

discharge, velocity, and contraction. Without friction, each of these coefficients would be 1. With the

presence of friction, the actual performance is less than the ideal performance and therefore, each

coefficient is less than 1.

The coefficient of discharge is heavily related to the volumetric flow rate of the fluid flow and the

cross sectional area of the orifice. It is also related to the gravitational constant and the head pressure.

The coefficient of discharge is a ratio of the actual discharge divided by the ideal discharge. The

actual discharge is the discharge that occurs and which is affected by friction as the jet passes through

the orifice. The ideal discharge would be the discharge achieved without friction. Thus,

OO

CD

gHAQC2

= = O

C

DQQC =

(1)

Where,

=cQ Actual Volumetric Flow Rate

=oQ Ideal Volumetric Flow Rate

oo

cDVA

QC

thusVAQ

=

= ,

Actual Velocity, VC ;

CC gHV 2=

(2)

Ideal Velocity, VO ;

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OO gHV 2=

(3)

Cross Section, A;

( )4

2

OO

DA = (4)

( )4

2

C

C

DA

= (5)

Theoretical Discharge, Q

Ideal Velocity x Orifice Area

Actual Discharge, QC

t

VQC

=

1000 (7)

Coefficient of Velocity, CV

O

CV

V

VC =

(8)

Coefficient of Contracta

V

DC

C

CC =1

(9)

o

c

CD

DC =2 (10)

where,

DO= Orifice Diameter

DC= Vena Diameter

All three of these coefficients are a measure of energy loss. From this particular relationship it is

evident that energy loss in the system can be directly related to the difference in head levels between

ideal and actual conditions.

The Coefficient of Contraction is a ratio of the actual diameter of the jet divided by the ideal diameter

of the jet. The actual diameter is the diameter that occurs and which is affected by friction as the jet

passes through the orifice. The ideal diameter would be the diameter of the orifice. The narrowing of

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the water jet is the direct result of friction on the jet as it passes through the sharp edge orifice. The

place at which the majority of narrowing has occurred is known as the Vena Contracta

The Vena Contracta is generally considered to occur at a distance downstream from the orifice equal

to one half the diameter of the orifice. The Coefficient of Contraction can be derived from a

relationship with the Coefficients of Discharge and Velocity.

v

Dc

C

CC =

The Coefficient of Contraction can also be derived from direct measurement if adequately precise

tools are available. This can be done using the blade attachment as described in the experimentalprocedures section.

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3.2 APPARATUS:

Figure 3.1: Parts of Identification

1. Manometer2. Water Inlet3. Overflow4. Traverse Total Head Tube5. Orifice6. Adjustable Feet

6

3

5

4

1

2

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Correction Factor

Figure 3.2 : Correction factor for Ho and Hc

Figure 3.2 shows the correction factor for Ho and Hc which is 10mm. Due to the placement of the

manometer scale is below the designated point of measurement of these two parameter, the readings

should be deducted with 10mm to acquire the desired readings.

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1. It is important to drain all water from the apparatus when not in use. The apparatus shouldbe stored properly to prevent damage.

2. Any manometer tube, which does not fill with or slow fill, indicates that tapping or connectionof the manometer is blocked. To remove the obstacle, disconnect the flexible connection tube

and blow through.

3. The apparatus should not be exposed to any shock and stresses.4. Always wear protective clothing, shoes, helmet, and goggles throughout the laboratory session.5. Always run the experiment after fully understand the unit and procedures.


1.

Close water supply valve and venturi discharge valve.2. Turn off the water supply pump.3. Drain off water from the unit when not in use.

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Characteristics of Vena ContractaObjective

To determine the coefficient of contracta, coefficient of velocity and coefficient of discharge

for a flow through an orifice

Procedures

1. Turn on the hydraulic bench on and allow water flow to enter the cylindrical tank.Adjust the flow until the water level in the tank is just above the overflow.

2. Using the adjustable inlet pipe, raise the level of the diffuser till it is just below waterlevel. For the best results, the level of the diffuser should always be adjusted to meet

this condition.

3. Record the water level in the tube connected to the bottom of the cylindrical tank.Make sure there are no bubbles in the tube.

4. Move the Pitot tube onto position directly underneath the exiting water jet. Onceequilibrium is reached, record the water level in the tube connected to the Pitot tube.

5. Record the diameter of the exiting water jet using the wire.6. Record the distance traversed by the wire to determine the diameter of the vena

contracta.

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Orifice Diameter,mm

Volume(mL)

Time(s)

Orifice Manometer,(mm)

Pitot Manometer,(mm)

Vena Diameter,(mm)


1. Explain what are is vena contracta2. In your own words, discuss the relation between vena contracta and cavitation developed in

orifice

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KNJ2261 Mechanical and Manufacturing Engineering Laboratory IV

Faculty of EngineeringUniversiti Malaysia Sarawak

4. TOPIC 4: ORIFICE AND FREE JET FLOW4.1 THEORY:

Theory of Small Orifices

An orifice is an opening, usually circular, in the side or base of a tank or reservoir through which fluid

is discharged in the form of jet, usually into the atmosphere. The volume rate of flow discharged

through an orifice will depend upon the head of the fluid above the level of the orifice, and it can,

therefore be used as a mean of flow measurement. The term small orifice is applied to an orifice

which has a diameter or vertical dimension, which is small compared with the head producing flow.

Jet Flow

Figure 4.1 shows an orifice with a free discharge. Energy losses as fluid moves down a stream tube is

very small, so the application of Bernoulli should be appropriate. Applying the equation between

sections 1 & 2 for the flow gives:

2

2

221

2

11

22z

g

v

y

pz

g

v

y

p++=++

(1)

1

2

h doVena

Contracta

Figure 4.1Orifice with free discharge

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If the free surface and jet at section 2 each were open to the atmosphere, then p 1 would equal to p2. If

the area A1 were large in comparison with A2, the continuity equation shows that v1would be small in

comparison with v2. Thus, if v1can be neglected,

ghv 22 = (2)

Because of the friction, the actual jet velocity at the exit of orifice, vo is less than ideal. A coefficient

can be introduced so that this expression gives an accurate result.

ghCv vo 2= (3)

The coefficient Cvis called the coefficient of velocity of the orifice. For a sharp-edged small orifice

(that is d0


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=ghACd 20 (7)

The coefficient Cdis called the coefficient of discharge and is equal to the product C vand Cc.

Thus the three coefficient can be summarized as below

o

vcc

A

A

orificetheofArea

contractavenatheatareaActualC ==

(8)

yhx

ghvelocitylTheoreticaygxcontractavenatheatvelocityActualCv

222

2

== , (9)

cvd CCedischlTheoretica

contractavenatheatedischActualC ==

arg

arg

(10)

This coefficient can be determined independent of each other. The diameter at the vena contracta is

measured to calculate C c, the coordinates of the jet trajectory to obtain the actual velocity for finding

Cvand the actual discharge to determine C d.

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4.2APPARATUS:Description and Assembly

Figure 4.4:Orifice and Free Jet Flow

Specifications:i) Quadrant-edged Orifice (No. 1)

Diameter : 4 mm and 8 mm

ii) Square-edged Orifice (No. 2)Diameter : 4 mm and 8 mm

iii) Jet Trajectory ProbesNo. of Tracing Probes : 8

iv) Constant Head TankMax. Constant Head : 450 mmTank Diameter : 200 mm

1. Adjustable Overflow Baffle 4. Adjustable Feet

2. Adjustable Head Tank 5. Level Scale Board3. Interchangeable Orifice 6. Jet Trajectory Probes

2

1

3

4

5

6

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session.

4. Always run the experiment after fully understand the unit and procedures.5. Clean and wipe the bench with damp cloth after every laboratory session.

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4.4.1 Experiment 1: Jet Trajectories

Objective

To compare the predicted and measured jet trajectories.

Procedures

1. Insert an orifice into orifice fitting.2. Connect the apparatus to the water supply of the hydraulic bench and start the pump.3. Adjust the water head to readable reading by means of the adjustable overflow.4. Read the measured of the jet and note them down in tabular form.5. Plot the Trajectory Graph for both measured and calculated position.6. Discuss the differences between the trajectories.


Measured and calculated jet trajectory (water head 0.4 m)

x position in my position in m(measured)

y position in m(calculated)

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4.4.2 Experiment 2: Flow Meter Measurement

Objective

Visual appreciation of the change of jet shape by varying the water head and the orifice

diameter

Procedures

1. Insert an orifice into the Orifice fitting device.2. Connect the apparatus to the water supply of the hydraulic bench and start the pump.3. Adjust the water head supply of the adjustable overflow to readable water head

reading.

4. Read the measurement y-position of the jet and note them down in a tabular form.5. Repeat the experiment with different water head.6. Repeat the steps with different orifice size.7. Discuss the effect of diameter and water head to the trajectories.


Orifice no. 1

x position (m)y position (m)

Water head,

h = . mm

Water head,

h = mm

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Orifice no. 2

x position (m)

y position (m)

Water head,h = mm

Water head,h = .. mm


1. In your own words, describe the working principle of an orifice meter.2. Give at least two (2) examples of engineering applications which are using orifice meter.3. If the water head is higher, explain what will happen to the trajectories distance. Justify your

answer.

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5 TOPIC 5: BERNOULLIS THEOREM DEMONSTRATION5.1 THEORY:

Bernoullis Law

Bernoulli's law states that if a non-viscous fluid is flowing along a pipe of varying cross section, then

the pressure is lower at constrictions where the velocity is higher, and the pressure is higher where the

pipe opens out and the fluid stagnate. Many people find this situation paradoxical when they first

encounter it (higher velocity, lower pressure). This is expressed with the following equation:

Constant==++ *hz

g

v

g

p

2

2

(3.8)

Where,

p = Fluid static pressure at the cross section

= Density of the flowing fluid

g = Acceleration due to gravity

v = Mean velocity of fluid flow at the cross section

z = Elevation head of the center at the cross section with respect to a datum

h* = Total (stagnation) head

The terms on the left-hand-side of the above equation represent the pressure head ( h), velocity head

(hv ), and elevation head (z), respectively. The sum of these terms is known as the total head (h*).

According to the Bernoullis theorem of fluid flow through a pipe, the total head h* at any cross

section is constant. In a real flow due to friction and other imperfections, as well as measurement

uncertainties, the results will deviate from the theoretical ones.

In our experimental setup, the centerline of all the cross sections we are considering lie on the same

horizontal plane (which we may choose as the datum, z = 0, and thus, all the z values are zeros so

that the above equation reduces to:

Constant==+ *hg

v

g

p

2

2

(3.9)

This represents the total head at a cross section.

For the experiments, the pressure head is denoted as h iand the total head as h*i, where irepresents the

cross sections at different tapping points.

Static, Stagnation and Dynamic Pressures

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The pressure, p, which we have used in deriving the Bernoullis equation, Equation 3.7, is the

thermodynamic pressure; it is commonly called the static pressure. The static pressure is that pressure

which would be measured by an instrument moving with the flow. However, such a measurement is

rather difficult to make in a practical situation.

As we know, there was no pressure variation normal to straight streamlines. This fact makes it

possible to measure the static pressure in a flowing fluid using a wall pressure tapping, placed in a

region where the flow streamlines are straight, as shown in Figure 4 (a). The pressure tap is a small

hole, drilled carefully in the wall, with its axis perpendicular to the surface. If the hole is perpendicular

to the duct wall and free from burrs, accurate measurements of static pressure can be made by

connecting the tap to a suitable pressure measuring instrument.

Flowstreamlines

Pressure

tap

(a) Wall Pressure Tapping

Flow

Small holes

Stem

To manometer orpressure gage

(b) Wall Pressure TappingFigure 5.1:Measurement of Static Pressure

In a fluid stream far from a wall, or where streamlines are curved, accurate static pressure

measurements can be made by careful use of a static pressure probe, shown in Figure 4 (b). Such

probes must be designed so that the measuring holes are place correctly with respect to the probe tip

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and stem to avoid erroneous results. In use, the measuring section must be aligned with the local flow

direction.

Static pressure probes or any variety of forms are available commercially in sizes as small as 1.5 mm

(1/16 in.) in diameter. The stagnation pressure is obtained when a flowing fluid is decelerated to zero

speed by a frictionless process. In incompressible flow, the Bernoulli Equation can be used to relate

changes in speed and pressure along a streamline for such a process. Neglecting elevation differences,

Equation 3.7 becomes

constant=+2

2vp

(3.10)

If the static pressure ispat a point in the flow where the speed is v, then the stagnation pressure, Po,where the stagnation speed, Vo, is zero, therefore,

2

2

1Vppo +=

(3.11)

Equation 3.11 is a mathematical statement of stagnation pressure, valid for incompressible flow. The

term V generally is the dynamic pressure. Solving the dynamic pressure gives:

ppV o =2

2

1

(3.12)

Or

( )

ppV o

=

2

(3.13)

Thus, if the stagnation pressure and the static pressure could be measured at a point, Equation 3.13

would give the local flow speed.

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Small hole

Flow

To manometer orpressure gage

Figure 5.2:Measurement of Stagnation Pressure

Flow

p po

A

Total

head

tube

(a) Total Head Tube Used with Wall Static Tap

Flow

Small holes

Stem

p

B

C

po

(a) Pitot-Static Tube

Figure 5.3:Simultaneous Measurement of Stagnation and Static Pressures

Stagnation pressure is measured in the laboratory using a probe with a hole that faces directly

upstream as shown in Figure 5. Such a probe is called a stagnation pressure probe (hypodermic probe)

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or Pitot (pronouncedpea-toe) tube. Again, the measuring section must be aligned with the local flow

direction.

We have seen that static pressure at a point can be measured with a static pressure tap or probe (Figure

4). If we know the stagnation pressure at the same point, then the flow speed could be computed from

Equation 3.14. Two possible experimental setups are shown in Figure 6.

In Figure 6(a), the static pressure corresponding to point Ais read from the wall static pressure tap.

The stagnation pressure is measured directly atAby the total head tube, as shown. (The stem of the

total head tube is placed downstream from the measurement location to minimize disturbance of the

local flow)

Two probes often are combined, as in the Pitot-static tube shown in Figure 6(b). The inner tube is used

to measure the stagnation pressure at pointB, while the static pressure at Cis sensed using the tapping

on the wall. In flow fields where the static pressure variation in the streamwise direction is small, the

Pitot-static tube may be used to infer the speed at point B in the flow by assuming pB =pCand using

Equation 3.14. (Note that whenpB pC, this procedure will give erroneous results)

Remember that the Bernoulli equation applies only for incompressible flow (Mach number,M 0.3).

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5.2 APPARATUS:

Figure 5.4:Parts Identification Diagram

1. Manometer Tubes 6. Flow Control Valve

2. Test Section 7. Gland Nut

3. Water Inlet 8. Hypodermic Probe

4. Unions 9.Adjustable Feet

5.Air Bleed Screw

The unit consists of the followings:

a) Venturi: The venturi meter is made of transparent acrylic with the followingspecifications:

Throat diameter : 16 mm

Upstream Diameter : 26 mm

Designed Flow Rate : 20 LPM

b) Manometer: There are eight manometer tubes; each length 320 mm, for static pressureand total head measuring along the venturi meter. The manometer tubes are connected to

an air bleed screw for air release as well as tubes pressurization.

5

1

2

3

4

6

7

8

9

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c) Baseboard: The baseboard is epoxy coated and designed with 4 height adjustable standsto level the venturi meter.

d) Discharge valve: One discharge valve is installed at the venturi discharge section forflow rate control.

e) Connections: Hose Connections are installed at both inlet and outlet.

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5.3MAINTENANCE AND SAFETY PRECAUTIONS:1. It is important to drain all water from the apparatus when not in use. The apparatus

should be stored properly to prevent damage.




session.


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5.4.1 Experiment 1: Discharge Coefficient Determination

Objective

To determine the discharge coefficient of the venturi meter

Procedures

1. Withdraw the hypodermic tube from the test section.2. Adjust the discharge valve to the maximum measurable flow rate of the venturi.3. Measure the water flow rate using volumetric method and record the manometers reading.4. Repeat the steps for few data collection.5. From results, determine the discharge coefficient, Cd.6. Compare the results of actual flow rate and ideal flow rate.

5.4.2 Experiment 2: Bernoullis Theorem Demonstration

Objective

To demonstrate Bernoullis Theorem

Procedures

1. Adjust the discharge valve to a high measurable flow rate.2. After the level stabilizes, measure the water flow rate using volumetric method.3. Gently slide the hypodermic tube (total head measuring) connected to manometer #G, so

that its end reaches the cross section of the Venturi tube at #A. Wait for some time and

note down the readings from the manometers

4. Repeat step 1 to 3 with different flow rates.5. Determine the difference between two calculated velocities, using Bernoullis equation

and using continuity equation.

6. Discuss on the comparison between the two velocities.

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*

P

l

e

a

s

e

*Refer to Schematic of Diagram for Cross Section Diameter


1. In your own words, explain what are the differences between stagnation pressure anddynamic pressure.

2. You are an engineer in a company and your company is setting up an experiment thatinvolves the measurement of airflow rate in a duct. You are assigned to come up with proper

instrumentation. Research the available techniques and devices for airflow rate measurement,

and discuss the advantages and disadvantages of each technique. Also, make

recommendations.

Cross

Section

Using Bernoulli equationUsing Continuity

equation

Difference

ih*=hG(mm)

h i(mm)

ViB

(m/s)Ai

(m2)ViC

(m/s)V (m/s)

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6 TOPIC 6:OSBORNE REYNOLDS DEMONSTRATION6.1 THEORY:

The theory is named in honor of Osborne Reynolds, a British engineer who discovers the variables that

can be used as a criterion to distinguish between laminar and turbulent flow.

The Reynolds number is widely used dimensionless parameters in fluid mechanics.

Reynolds number formula:

v

VLR=

Where; R = Reynolds number

V = Fluid velocity, (m/s)

L = characteristic length or diameter (m)

V = Kinematic viscosity (m2/s)

Reynolds number R is independent of pressure.

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6.2APPARATUS:The Osborne Reynolds Demonstration apparatus is equipped with a visualization tube for students

to observe the flow condition. The rocks inside the stilling tank are to calm the inflow water so

that there will not be any turbulence to interfere with the experiment. The water inlet / outlet valve

and dye injector are utilized to generate the required flow.

Figure 6.1: Unit Assembly of Osborne Reynolds Demonstration

1. Dye reservoir 2. Dye injector3. Stilling tank 4. Observation tube5. Water inlet valve 6. Bell mouth7. Water outlet valve 8. Overflow tube

1

2

4

3

5

6

7

8

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1. Place the unit on a level ground2. Beware with the observation tube


6.4.1 Experiment 1: Observation of Flow Regimes

Objective

To compute Reynolds number and to observe the laminar, transitional and turbulent flow.

Procedures

1. Lower the dye injector until it is seen in the glass tube.2. Open the inlet valve and allow water to enter stilling tank.3. Ensure a small overflow spillage through the over flow tube to maintain a constant

level.

4. Open the flow control valve fractionally to let water flow through the visualizing tube.5. Slowly adjust the dye control needle valve until a slow flow with dye injection is

achieved.

6. Regulate the water inlet and outlet valve until an identifiable dye line is achieved.Identify the type of the flow and take the picture of the flow.

7. Measure the flow rate.8. Repeat the experiment to produce few different types of flow.9. Discuss on the development of different flow in pipe.

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Laminar flow

Volume T1 T2 T3 Tavg Q

Take diameter of the observation tube to be 15.6 mm, and the water temperature is

27 C

6.4.2 Experiment 2: Loss Coefficient

Objective

To determine the Reynolds number and to determine the upper and lower critical velocities at

transitional flow.

Procedures

1. Lower the dye injector until it is seen in the glass tube.2. Open the inlet valve and allow water to enter stilling tank.3. Ensure a small overflow spillage through the over flow tube to maintain a constant

level.

4. Allow water to settle for a few minutes.5. Open the flow control valve fractionally to let water flow through the visualizing

tube.

6. Slowly adjust the dye control needle valve until flow with dye injection is achieved.7.

Produce small disturbance or eddies to determine the lower critical velocity.

8. Determine the flow rate.9. Repeat the experiment by first introducing a turbulent flow and produce the laminar

flow to determine the upper critical velocity.

10. Summarize findings from your results


1 Explain the reasons why liquid is usually transferred in circular pipe.2 In fully developed straight-duct flow, the velocity profiles do not change, but the pressure

drops along the pipe axis. Thus there is pressure work done on the fluid. If, say, the pipe is

insulated from heat loss, where does this energy go? Make a thermodynamic analysis of the

pipe flow.

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7 TOPIC 7: ENERGY LOSSES IN BENDS AND FITTINGS7.1 THEORY:

When fluid flow through typical pipe fittings such as an elbow or a bend, an enlargement or

contraction in cross-section, or through a valve, energy losses occur. These energy losses, which are

termed as minor losses, are primarily due to the change in the direction of flow and the change in the

cross-section of the flow path typically occurs in valves and fittings. Experimental techniques are used

to determine minor losses. Tests have shown that the head loss in valves and fittings is proportional to

the square of the average velocity of the fluid in the pipe in which the valve or fitting is mounted.

Thus the head loss is also proportional to the velocity head of the fluid. Experimental values for

energy losses are usually reported in terms of a loss coefficient, K, as follows:

g

vKhL

2

2

= (1)

in which

K = Loss coefficient

v = Average velocity of flow in the smaller pipe (m/s)

g = Acceleration due to gravity (9.81 m/s2)

Gate valve

Gate valve is one of several types of valves that is used to control the amount of flow. The value of

loss coefficient Kof a gate valve is dependent on the position of the valve. Fluids flow through fully

open gate valves in straight line paths, thus there is little resistance to flow and the resulting pressure

loss is small. For fluid flow through partially opened gate valve, resistance to flow will be greater and

thus produces a larger value of K. Below are the theoretical values of loss coefficient for gate valve at

several positions.

Valve position Loss coefficient,K

Fully open

open

open

open

0.19

0.90

4.50

24.00

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7.2 APPARATUS:

Figure 7.1:Unit Construction for Energy Losses in Bends and Fittings

Note: Pipe and fittings sizes are as follows:Pipe : OD = 20 mm

ID = 17 mmEnlarged Section : OD = 50 mm

ID = 32 mmFittings : ID = 17 mm

1. 45 Elbow 7. Manometers Bank

2. Contraction 8. Gate Valve3. Enlargement 9. Differential Pressure Gauge

4. 90 Elbow 10. 90 Elbow

5. Water Inlet Connection 11. Water Drain Connection

6. 90 Short Bend

1

2

3

4

6

7

8

9

10

5 11

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1. It is important to drain all water from the apparatus when not in use. The apparatus should bestored properly to prevent damage.




session.

5. Always run the experiment after fully understand the unit and procedures.6. Clean and wipe the bench with damp cloth after every laboratory session.


7.4.1 Experiment 1: Energy Losses in Bends and Pipe Fittings

Objective

To measure the losses in the fittings related to flow rate and calculate the loss coefficients

related to velocity head.

Procedures

1. With the bench valve fully closed and the discharge valve fully opened, start up the pumpsupply from hydraulic bench.

2. Slowly open the bench valve until it is fully opened.3. When the flow in the pipe is steady and there is no trapped bubble, start to close the

bench valve to reduce the flow to the maximum measurable flow rate.

4. Adjust water level in the manometer board.5. Note necessary readings.6. Repeat the experiment for few data collection.7. Determine the loss coefficients for each of the fittings and devices

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Volume,V

(liter)

Time,T(s)

Flowrate, Q(m3/s)

Manometer readings (mmH2O)

1 2 3 4 5 6 7 8 9 10 11 12

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7.4.2 Experiment 2: Energy Losses through Gate Valve

Objective

To determine the loss coefficients related to velocity head through gate valve

Procedures

1. With the bench valve fully closed and the discharge valve fully opened, start up the pumpsupply from hydraulic bench.

2. Slowly open the bench valve until it is fully opened.3. When the flow in the pipe is steady and there is no trapped bubble, start to close the

bench valve to reduce the flow to the maximum measurable flow rate.

4. Slowly close the gate valve and measure and record necessary readings.5. Repeat the differential pressure measurement for few data readings.6. Determine the loss coefficient.

7.5OPEN ENDED QUESTIONS:1. Explain what is minor loss and major loss in pipe flow.2. How does surface roughness affect the pressure drop in a pipe if the flow is turbulent?

What would your responses be if the flow were laminar?

3. Propose two ways to reduce the head loss in pipe.

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8 TOPIC 8: PELTON TURBINE8.1 THEORY:

Turbines are classified into two general category impulse and reaction. In both types the fluid passes

through a runner having blades. The momentum of the fluid in the tangential direction is changed and

so a tangential force on the runner is produced the runner therefore rotates and performs useful work,

while the fluid leaves with reduced energy. The important feature of the impulse machine is that there

is no change in static pressure across the runner. In the reaction machine the static pressure decreases

as the fluid passer through the runner.

For any turbine the energy held by the fluid is initially in the form of pressure. i.e. a high level

reservoir in a hydroelectric scheme. The Impulse turbine has one or more fixed nozzles, in each of

which this pressure is converted to the kinetic energy of an unconfined jet. The jets of fluid then

impinge on the moving blades of the runner where they lose practically all their kinetic energy.

In a reaction machine the changes from pressure to kinetic energy takes place gradually as the fluid

moves through the runner, and for this gradual change of pressure to be possible the runner must be

completely enclosed and the passages in it entirely full of the working fluid.

The basic terms used to define, and therefore measure, turbine performance in relation to rotational

speed includes:

i) Volume flow rateii) Headiii) Torque, power output and efficiencies

Volume Flow Rate, Q

The volume flow rate of fluid through the turbine is the volume passing through the system per unit

time. In SI units, this is expressed in cubic meters per second (m3/s).

Head, H

The term head refers to the elevation of a free surface of water above or below a reference datum. In

the case of a turbine we are interested in the head of the water entering the rotor, which of course has a

direct effect on the characteristics of the unit.

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Power Output and Efficiencies

The brake power Pbproduced by the turbine in creating torque, T on the brake at rotor speed N is

given by Equation 4:

( )WattsNmTNPb == /2 (4)

The torque itself is given by the equation:

rFT b= (5)

Where Fb is the brake force reading on the balance and r is the pulley radius.

However, the fluid friction losses in the turbine itself, represented as F requires a hydraulic efficiency

Eh to be defined as:-

( )( )

%''

100=h

rh

PSuppliedPowerUseful

ProtorbyabsorbedPowerE

(6)

Further, the mechanical losses in the bearing, etc require a mechanical efficiency Em to be defined as:

( )( )

%sup

100=r

mm

ProtorbyabsorbedPower

ProtorbypliedPowerE

(7)

The Pelton turbine units do not include the direct measurement of mechanical power Pm, but indeed

measures brake force applied to the rotor via pulleys. A further efficiency is therefore required

expressing the friction losses in the pulley assembly Eb:

( )( )

%sup

100=m

bb

ProtorbypliedPower

PbrakethebyabsorbedPowerE

(8)

The overall turbine efficiency E t is thus:

( )( )

%''

100=h

bb

PPowerFluidUseful

PbrakethebyabsorbedPowerE

%1002

=

WiW QHg

TN

(9)

Thus,

bmht EEEE = (10)

In general the efficiency of the turbine is provided as isoefficiency curves. They show the

interrelationship among Q, w, and h. A typical isoefficiency plot is provided in Figure 8.1.

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Figure 8.1Isoefficiency curve for a laboratory-scale Pelton turbine

Figure 8.2 shows the form taken by the curve relating hydraulic efficiency and the ratio of rotor

bucket to jet speed.

Bucket Speed/ Jet Speed

Figure 8.2 Hydraulic efficiency versus bucket/jet speed ratio

The graph shows how the curve rises to a relatively sharp peak, and hence for a high hydraulic

efficiency it is essential for the ratio of bucket to jet speed to remain close to the theoretical value of

one half (the velocity of the jet being twice that of the bucket).

hydraulicfficiency (%)

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1.0

Maximum efficiency

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The rotational speed (and hence the bucket speed) of the rotor is required to remain constant in a

generating installation in order to produce power at the correct frequency. It then follows that for the

hydraulic efficiency to remain high, the jet speed must also remain the same. This is so even when the

power demand falls off and the flow rate passing through the turbine is therefore reduced (or vice-

versa).

With a standard throttle valve, the area of the outlet jet remains the same as the volume flow rate

changes. This causes a change in the jet velocity (Qv/A).

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8.2 APPARATUS:

a) Turbine

Material : Bronze

Impeller External Diameter : 5 inch

Width of Vane : 35 mm (17 Vanes)

Pulley Radius : 40 mm

b) Force BalanceRange : 0 2 kg x 10g

c) Pressure GaugeRange : 0 2 kgf/cm2

d) TachometerMeasurement Range : 5 to 99999 rpm (optical)

Resolution : 0.1 rpm

Accuracy : 0.05%

Sensing Range : 50 to 150 mm


1. It is important to drain all water from the apparatus when not in use. The apparatus should bestored properly to prevent damage.


session.

4. Always run the experiment after fully understands the unit and procedures.

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8.4.1 Experiment 1: Turbine characteristics

Objective

To study the characteristic curves of a Pelton turbine operating at a different fluid flow rates

with high head.

Procedures

1. Open and adjust the spear valve until 1.5 kgf/cm2of inlet water head is obtained.2. Tighten up the tensioning screw on the pulley wheel until the turbine is almost stalled

(rotor just turning).

3. Note the value of the pulley brake. Decide on suitable increments in force to giveadequate sample points (typically 8 points between zero and maximum brake force).

4. Slacken off the tensioning screw so no force is being applied to the turbine, i.e. Fb atalmost 0. Obtain the volumetric flowrate (Q), force reading (Fb), water head (P1) and

turbine rotational speed (N), then record into the experimental data sheet. This represents

the first point on the characteristic curve.

5. Tighten the screw to give the first increment in force for the brake. When readings aresteady enough, record all the readings again.

6. Repeat the steps above for a gradually increasing set of Fbvalues.7. Now decrease the volume flow rate to a new setting by changing the throttle valve

position (half round) and at the same time also change the spear valve position to

maintain the pressure at 1.5 kgf/cm2. Repeat the taking of samples for gradually

increasing values of torque, as above. Repeating this step will produce a series of result

sets for comparison.

8. Plot the turbine performances curve; torque, power output and efficiency versus theturbine rotational speed.

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V1 T T Q Q

(L) (S) (MIN) (LPM) (m3/s)

m1 m2 Fb1 Fb2 Fb N1 N2 N N

(g) (g) (N) (N) (N) (rpm) (rpm) (rpm) (Hz)

Q Fb N P1 Hi Ph T Pb Et

(m3/s) (N) (Hz) (kgf /cm2) (m) (W) (Nm) (W) (%)


1. In your own words, explain the differences between impulses, dynamic and reaction turbine.2. We know that an enclosed rotating bladed impeller will impart energy to a fluid, usually in

the form of a pressure rise, but how does it actually happen? Discuss with sketches the

physical mechanisms through which an impeller actually transfers energy to a fluid.

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9 TOPIC 9: WIND TUNNEL9.1 THEORY:

Introduction to Wind Tunnel

When studying aerodynamics, few engineers have access to full scale wind tunnel or actual airborne

laboratories. The majority rely on what is probably the most common tool for aerodynamics study, the

laboratory based wind tunnel. This tool saves both money and time, while producing very accurate

results, as long as the scale effect and reduced Reynolds numbers are taken into consideration.

The wind tunnel used in the experiment is of the closed working-section, open return suction type. Air

enters the tunnel through an aerodynamically designed effuser (cone) that accelerates the air in a linear

manner. It then enters the working section and passess through a grille before moving through a

diffuser and then to the variable speed axial fan. The grille protects the fan from damage by loose

objects. Then, the air leaves the fan, passes through a silencer unit and then back out to the atmosphere.

The speed of the axial fan which is also becoming the speed the air velocity in the working section is

controlled by an electronic drive control in the separate Control and Instrumentation unit. Figure 9.1

shows the general layout of the wind tunnel.

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Figure 9.1 General Layout of Wind Tunnel

Control and Instrumentation Frame

The control and instrumentation frame contains:

1. main electrical isolator for apparatus2. motor drive control3. switchgear and circuit protection for the motor drive4. two sets of electrical sockets for additional equipment5. support frame for additional equipment/ instruments

Figure 9.2 shows the main section of the Control and Instrumentation Frame. This section has all

controllers for the variable speed motor (fan). Technical data of the equipments is shown in Table

9.1.

Figure 9.2 Main Section of Control Panel frame

Table 9.1 Technical Data of Wind Tunnel

ITEM SPECIFICATION

Total length of Apparatus 3700 mm

Total Depth (front to back) 850 mm

Total Height 1900

Working Section Mm

Air Velocity 305 x 305 x 600 mm

Fan Motor 0 to 36 m/s

Electrical Supply

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Type Three-phase AC

Total Current with all optional instruments

connected

21A (415 V) / 26 A (220V)

Fuses

Drive Unit (415 V) Three 16 A MCB (Miniature Circuit

Breaker)

IEC Outlets 10 A MCB

Low Voltage Instrumentation Supply 2A MCB

Flat Boundary Layer

Using the wind tunnel, phenomena of boundary layer development and separation can be studied. Thephenomena are studied using a Flat Boundary Layer Model. This model is made of 2 hinged stainless

steel plates as shown in Figure 9.3. When the model is fitted inside the working section of a wind

tunnel, the angle of the plates can be adjusted to set the maximum conditions for the experiment.

Figure 9.3 Flat Boundary layer Model

On the upper surface of the model are 5 small aerofoil set at right angle to the surface. Each aerofoil is

drilled with 5 tiny pitot holes on the leading edge. Each hole is connected to a separate tube. All the

tubes are routed together and emerge at the side of the model. The aerofoils are staggered so that their

wakes do not interfere with each other. When the model is fitted in the wind tunnel, the tubes may be

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connected to a multi-tube manometer for pressure measurements. Figure 9.4 shows the schematic

diagram of the model.

Figure 9.4 Schematic diagram of Flat Boundary Layer Model

9.2 APPARATUS:

Wind tunnel testing unit


1. Do not walk in front the diffuser when the tunnel is operating.2. Always clean the manometer tubes to avoid clogging

b) Distance of pitot holes from baseplate

a) Distance from leading edge of each aerofoil with the numbers of each pitot hole

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Experiment 1: Characteristics of Flowmeter Measurement Devices

Objective

The objective of the experiment is to illustrate the phenomena of boundary layer development and

separation of an external flow.

Procedures

1. Adjust the angle of attack down.2. Adjust the trailing edge down.

Figure 9.5 Adjusting angle of attack and trailing edge

3. Draw the new shape form by the model4. Ensure all fixings are tight.5. Experiment shall start at a lower velocity.6. Record the wall pressures upstream and downstream of the wind tunnel. Calculate the h0

in [mm] and find the approximate figure for the working section static pressure P0.

7. The local velocity, Vis a function of the difference between the total pressure measuredat each tapping PTand the local static pressure,P0.

8. Record all pressure readings and calculate the local velocities.9. Plot a graph of local velocity to give the curves for boundary layer growth around each

aerofoil.

10. Repeat the test at different wind tunnel velocities for few data collection.

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1. In your own words, explain what is boundary layer and how does it developed.2. Some colleges such as Colorade State University have environmental wind tunnels that can

be used to study phenomena like wind flow over city buildings. What details of scaling might

be important in such studies?

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10TOPIC 10: PUMP PERFORMANCE TEST10.1 THEORY:

The pump to be tested is of a centrifugal type which generates a pressure rise in the fluid by virtue of

centrifugal action on the fluid contained within and rotating with the blades. The rotor, which is

usually called the impeller, rotates inside a spiral casing. Fluid is pushed into the centre of the impeller

and is expelled under centrifugal action at the outer periphery where it is collected in a spiral casing

(volute) leading the delivery pipe.

The pump is driven by an electric motor which is mounted on trunnion bearings with a balance

mechanism and pointer for torque measurement. Combined with the measured speed of rotation, this

allows the power delivered to the pump to be determined. The trunnion pointer must be aligned with

the frame pointer using the hand-wheel before the spring balance is read.

The volumetric flow rate, Q, of water delivered by the pump is determined by direct measurement of

the time needed to fill a known volume.

Summary of important parameters

Pump Efficiency,

a. Pump speed in rad/s : = 2N/60b.

Power required to drive the pump (shaft power):

TorqueSW =

0( )

SW g S S R =

[Watt]

where;

g: gravitational acceleration [m/s2]

S: spring balance reading [kg]

S0: spring balance zero reading [kg]

R: torque radius of trunnion balance [m]: pump speed [rad/s]

c. Energy per unit mass,w, delivered by the pump to the water is obtained from themechanical energy equation;

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2 2

1 1 2 21 2

2 2

P V P V z w z

+ + + = + +

where, suffixes 1 and 2 denote the conditions in the suction and the delivery pipes

respectively.

Before starting the calculations, consider the positions of the pressure gauge in

relation to the points in the pipe where the energy balance is to be applied, and adjust

the pressure readings accordingly.

The total head increase across the pump isH = w/g

The velocities, V1and V2can be determined from the continuity equation;

Q = AV ;where Qis the measured volumetric flow rate andAis the area of the pipe

d. Power delivered by the pump :wW m w Qw= =

; where m

: mass flow rate

e. Overall efficiency of the pump is given by the ratio of the useful power transferred to thefluid to the input power

w

S

W

W

=

w

S

W

W

=

10.2 APPARATUS:

Centrifugal pump unit


1. Always wear protective clothing, shoes, helmet and goggles throughout the laboratorysession.

2. Always run the experiment after fully understands the unit and procedures.

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10.4.1 Experiment 1: Characteristics of Flowmeter Measurement Devices

Objective

The objectives of the experiment are to operate a centrifugal pump at a fixed speed and to

determine the performance characteristics of the pump.

Procedures

1. Measure from the same datum heightsz1andz2at the pressure tapping points as well asheights of pressure gaugeszpg1andzpg2to measure P1and P2.

2. Adjust the spring balance such that the spring balance zero reading S0is 03.

Set he pump at a fixed speed and vary the volumetric flow rate, Q, by adjusting theoutlet valve. Start the test by taking readings at the shut-off, i.e. no flow, condition,

which corresponds to the maximum increase in pressure drop, .p, across the pump. Then

conduct a test for the maximum flow rate through the pump. Adjust the flow to give 7

approximately equal steps in .p until the maximum flow rate is reached.

4. Record the necessary readings.5. Use all the pump tests (to get the largest flow rate) and for one test only direct the flow

through the middle pipe only and measure the pressure drop across the orifice plate flow

meter by recording the difference in levels .ho on a mercury/water manometer the water

manometer into the circuit by directing the lever on the tap towards the relevant

connecting pipe.

6. Plot , W , andH as function of Q on a single graph paper and determine the flow ratecorresponding to maximum efficiency.

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i) Relevant data

a. Maximum power of the electric motor driving the pump ____ kWb. Torque radius of trunnion balance R= ____ mc. Inside diameter of the pipes where the inlet & outlet pressures are

measured

D1= ____m

D2= ____m

d. Pump impeller diameter _______ mme. Orifice meter diameter d =_______ mmf. Inside diameter of the pipe containing the orifice plate D =_______ mmii) Experimental data

Height : z1 = _____________ m z2 = _____________ m

Pressure gauge height : zg1 = _____________ m zg2 = _____________ m

Spring balance zero reading : S0= _____________

TakeD1= 49 mm, andD2= 39 mm

Table of Observations

Test Shaft speed,N

[rpm]

Spring balance, S

[kg]

Inlet pressure,

P1[kPa]

Outlet pressure,

P2[kPa]

Volume of water

collected, V0 [L]

Time,t[s]

1.2.3.4.5.6.7.8.9.10.11.12.13.14.15.

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For the orifice plate measurement:

V0= ________________ [L]

Time Interval = ________________ [S]

h0= ________________ [mmHg]

Analysis

Test Shaft speed,

[rad/s]

Water flow rate, Q

[m3/s]

Head across the

pump, H[m]

Shaft power,

SW

[W]

Power delivered to

water, WW

[W]

Efficiency, [%]

1.2.3.4.5.6.7.8.9.10.11.12.13.14.15.


1. Performance data for centrifugal pumps, even if well scaled geometrically, show a decrease inefficiency with decreasing impeller size. Discuss some physical reasons why this is so.

2. One of the parameter that affects the pump performance is number of blades on an impeller.Do some reading on this subject and explain how the number of blades affects the

performance.

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APPENDIX A

SAFETY FIRST

Follow all instructions carefully. Appropriate clothing must be worn in the lab. No loose clothing or jewelry around operating

equipment. Do not wear open toe shoes or sandal in operating laboratories.

Do not operate equipment or carry on experiments unless the instructor/technician is present inthe laboratory.

Assure that necessary safety equipment is readily available and in usable condition. Become familiar with safety precautions and emergency procedures before undertaking any

laborator

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