Fm Hm Lab Manual July 2011

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8106464676 [email protected] 2

Vanjari Seethaiah Memorial Engineering College Patancheru, Medak

FLUID MECHANICS &

HYDRAULIC MACHINERY - R Srikanth

(M.Tech), B.E Asst Professor

Mechanical Department

LABORATORY MANUAL

Department of Mechanical Engineering

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PREFACE

The problems, man encountered in the fields of water supply, irrigation, navigation and water

power resulted in the development of Fluid Mechanics. Some two hundred years ago man kind’s

centuries of experience with the flow of water began to crystallize in scientific form. Two distinct

schools of thought gradually evolved in the treatment of fluid mechanics. One, commonly known as

Classical Hydrodynamics, which deals with theoretical aspect of the fluid flow assuming that shearing

stresses are non-existent in the fluids (i.e. ideal fluid concept). The other is known as Hydraulics. It deals

with the practical aspects of fluid flow which has been developed from experimental findings and is

therefore, more of Empirical Nature.

These lab sessions are intended to make the students understand the different methods of flow

rates in pipe flow and open channel flows, conversion of hydraulic energy possessed by the water in

running turbines and how pumps are used to increase the hydraulic energy of the water etc.

The Laboratory for Engineering Fluid Mechanics/Hydraulics and Hydraulic Machineries

complements the learning experience of the lecture. Laboratory exercises provide opportunities for

direct study of fluid behavior. All of the laboratory experiments reinforce material presented during

lecture. Some of the experiments will also expose material that is not presented during lecture. You

are responsible for the union of the laboratory and lecture experience, not their intersection.

Use the laboratory as a chance to enhance your understanding of fluid statics and dynamics. The

following Learning Objectives for the laboratory will guide you in taking an active role in your

education.

1. Gain familiarity with physical manifestations of fluid mechanics.

You will perform experiments dealing with the basic fluid properties: Viscosity and Pressure.

a. Static Fluid Forces.

b. Dynamic Fluid Forces.

c. The relation between pressure and velocity in a flowing fluid.

These experiments will give you first hand experience with fluid behavior. As a result of

performing these experiments you should be able to recognize the effects of fluid pressure and

to relate measurements of pressure to velocity in a moving fluid.

In addition to learning about fluid behavior, you should be able to recognize the physical

Equipment in the laboratory and explain the basic operating principles of the equipment.

You should learn how to operate the equipment properly and safely.

2. Develop and reinforce measurements skills.

You should know how to read gauges, manometers, flow meters, spring scales, and balance

scales. You should be able to time events with a stopwatch. You should strive to measure

quantities with the maximum precision of the instruments provided in the laboratory.

3. Develop and reinforce skills in documenting observations.

You should develop goo habits in the organization and recording of raw data in a notebook,

and take care to document the data such that it can be analyzed at a later time. You should

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sketch the physical apparatus used in the experiment. In doing so, pay special attention to the

specific mechanical and operational details that enable the apparatus to achieve the

purpose for which it was designed. You should be able to list and describe the steps used to

obtain the desired measurements. You should be able to identify whether any actions were

taken to improve the outcome of the experiment. Likewise, you should e able to identify any

actions that may have contributed to undesirable outcomes.

4. Develop skills at writing laboratory reports.

You will create reports to document your measurements in the laboratory. You will use a writing

style and format that is common to technical documentation used in Civil and Mechanical

Engineering. Your reports should be complete, yet concise. By writing the report, you should

develop a clear understanding of the laboratory exercise, and communicate that

understanding in your written words.

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CCCCONTENTSONTENTSONTENTSONTENTS

S. No Name of the Experiment Page No

1. Impact of Jets on Vanes 6

2. Determination of Friction factor in Flow Through Pipes 10

3. Determination of Coefficient of contraction 15

4. Calibration of Venturi meter 18

5. Calibration of Orifice Meter 22

6. Performance Test on Single Stage Centrifugal Pump 26

7. Performance Test on Multi Stage Centrifugal Pump 30

8. Performance Test on Reciprocating Pump 34

9. Performance Test on Pelton Wheel 38

10 Performance Test on Kaplan Turbine

��

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Experiment No. 1

IMPACT OF JET ON VANES

Aim:

To determine the actual force and compare it with the theoretical force for stationary vanes

of different shapes viz. Hemi-spherical, Flat plate and inclined plate.

Apparatus:

1. Sump Tank for storing water for constant supply.

2. Measuring Tank with Piezometer to measure water level.

3. Mono block motor with a valve in the discharge pipe for controlling flow.

4. Nozzle of suitable diameter.

5. Leak proof Nozzle housing with transparent watch glass.

6. Flat and Hemispherical Vanes mounted on rod connected with a Weight Balance.

7. Stop Watch to measure time.

Theory:

When the jet of water is directed to hit the vane of any particular shape, the force is exerted

on it by the fluid. This force is large in magnitude, acts for a short duration and is termed as Impact

Force. The magnitude of the force exerted on the Plate/Vane depends on the velocity of jet, shape

of Vane, Fluid Density and Area of cross section of the jet. More importantly, it also depends on

whether the vane is moving or stationary. In our present case, we are concerned about the force

exerted on the Stationary Plates/Vanes. The following are the theoretical formulae for different shapes

of vane, based on flow rate.

1) Flat Plate : Ft = ρ A V2

2) Flat Plate inclined at θ angle from horizontal:

Ft = ρ A V2 cosθ

3) Hemi – Spherical: Ft = 2 ρ A V2

4) Curved Plate with angle of deflection 180-θ:

Ft = ρ A V2 (1 + cosθ)

Where

‘A’ – Area of jet in m2 ‘ρ’ – Density of water = 1000 kg/m3

‘V’ – Velocity of jet in m/sec

‘Ft’ – The theoretical force acting in the direction of jet.

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Observation Table:

Type of Vane S No Time for x=___ cm of

water, t (Seconds)

Reading in Weight

balance, W (grams)

a

Flat

1a.1 1a.2 1a.3

b

Curved Plate

1b.1 1b.2 1b.3

Formulae:

t

xAQ

tank=

A = 4

2d×π

For Flat Vane

Ft = ρ A V2 ()

For Curved Vane

Ft = ρ A V2 (1 + cosθ)

9.811000

WWFa ×

+= P

Where,

Atank – Area of Measuring Tank (0.3 X 0.3 m2)

x – Height of water considered in meter (from the table above)

d - Nozzle Diameter (8 mm or 0.008 m)

Ft – Theoretical Force

Fa – Actual Force (from the spring balance) ρ – Density of water = 1000 Kg/m3

A – Area of nozzle

V – Velocity of jet

W – Spring balance reading in grams

WP – Mass of the plates (For Flat Vane: 225 and for Curved Vane: 175)

Calculation Table:

S No Q V = Q/A Ft Fa

1a.1 1a.2 1a.3 1b.1 1b.2 1b.3

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Procedure:

1. Fix the suitable Vane and Nozzle in the nozzle housing.

2. Make sure the low end of suction pipe is submerged in the Sump Tank.

3. Open the control valve fully and start the pump.

4. Note down the reading in Weight balance.

5. Measure the time taken for ‘x cm’ height of water collection in measuring tank.

6. Repeat the procedure by changing the control valve position for different spring balance

readings.

7. Repeat the procedure for another Vane or Nozzle.

Precautions:

1. Do not start the pump if the voltage is less than 180 V.

2. Ensure the electrical neutral & earth connections are given correctly.

3. Frequently (at least once in three months) grease / oil the rotating parts.

4. Ensure that the moving parts are oiled regularly and that they are operated at least some time

every week to avoid clogging.

5. Ensure there are no leakages in the piping and nozzle housing.

Conclusion:

The actual Force is observed to be slightly differed than theoretical because of frictional losses

and reduction of velocity due to gravity.

Applications:

The force of impact calculated in this experiment is useful in determining the work done and

torque exerted by the jet of water on moving vanes in turbines.

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Experiment No. 2

DETERMINATION OF FRICTION FACTOR IN FLOW THROUGH PIPES

Aim:

To determine the coefficient of friction for different type of pipes.

The Apparatus

1. Sump Tank storing water for constant supply.

2. Measuring Tank with Piezometer to check water level.

3. A mono block pump with a valve in discharge pipe to control flow rate.

4. Two pipes with Diameters 15 mm (GI pipe) and 20 mm (GI pipe) for friction loss calculation.

5. A differential manometer to measure pressure difference at two points in the pipes.

6. Stop Watch to measure time for rise of water.

Theory:

Any Fluid flowing through a pipe experiences resistance from the walls of the pipe due to shear

forces or in simple terms - Viscosity. The amount of loss depends on the Velocity of flow and area of

contact between the pipe and fluid particles. It also depends upon the type of flow, i.e. Laminar or

Turbulent. This frictional resistance causes loss of pressure in the direction of flow.

The Drop of head can be calculated by using the Darcy-Weisbach Formula:

d.g.2

4.f.L.Vh

2

f =

From the above formula coefficient of friction of friction will be

2

f

.V.4

.2.d.gh

Lf =

Where,

‘hf‘ – Drop of head (got from the manometer difference).

‘f‘ – Coefficient of Friction

‘L‘ – Length of pipe (1 meter)

‘V‘ – Velocity of flow,

‘g‘ – Acceleration due to gravity, 9.8m/s2

‘d‘ – Diameter of the pipe

The value of coefficient of friction is not constant and depends upon roughness of pipe inside

surface and Reynold’s number. Any oil content in water also affects its value.

Repeat the same procedure for other pipes.

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Observation Table:

Type of Pipe S No Manometric Reading Time for x = ____ cm

of water h1 h2 h = h1 – h2

A (GI)

d=_____

a.1 a.2 a.3

B (GI)

d=_____

b.1 b.2 b.3

Formulae:

t

xAQ tank=

h1-S

Sh

w

Hg

f ×=

A

QV=

2f

.V.4

.2.d.gh

Lf =

Where,

Atank – Area of Measuring Tank (0.3 X 0.3 m2) x – Height of water considered in m(from the table above)

t – Time taken for x cm of water collection.

hf – head loss due to friction in pipe

d – Pipe Diameter

g – acceleration due to gravity (9.81 m/s2)

L – Length of the pipe in meters

V– Velocity of water flow

Result Table:

A S No Q V = Q/A f faverage

For D=20mm

A=_________

a.1 a.2

a.3

For D=15mm

A=_________

b.1 b.2

b.3

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Experimental Procedure:

1. Make sure the water in sump Tank is free of any oil content.

2. Open all the outlet valves and start the pump.

3. Except the outlet valve of the pipe to be tested, close all other valves.

4. Remove all the air bubbles from manometer and connecting pipes.

5. Adjust the flow at suitable rate.

6. Note down the manometric readings.

7. Note down the time ‘t’ for height ‘x cm’ of water collection in Measuring Tank.

8. Change the flow rate and take similar readings.

9. Repeat the procedure for other pipes.

Note: While measuring the heads, slight variation may occur due to voltage changes, valves etc. in

such cases, average readings may by taken.)

Precautions:




4. Ensure that the apparatus is operated at least some time every week to avoid clogging.

5. Ensure there are no leakages in the piping and Measuring Tank.

Conclusions:

1. Loss of head due to friction is proportional to length of pipe and square of velocity.

2. Loss of head is inversely proportional to inside diameter of pipe.

3. Average value of coefficient of friction, ‘f’ for

a. 15 mm GI pipe : _________

b. 20 mm GI pipe: _________

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Experiment No. 3

DETERMINATION OF COEFFICIENT OF CONTRACTION

Aim:

To determine the coefficient of contraction for a sudden enlargement of given pipes.

The Apparatus


2. Measuring Tank with Piezometer to check water level.

3. A mono block pump with a valve in discharge pipe to control flow rate.

4. A pipe with Sudden Contraction from 25 mm to 15mm diameter. It is provided with valve to

allow or stop water flow.

5. A differential manometer to measure pressure difference between two points.


Theory:

Whenever there is a sudden contraction in a pipe there is a loss of pressure head. This Drop of

head can be calculated by using the following formula:

−= 1

C

1

2.g

Vh

C

2

2c

It is possible to measure the head loss directly using manometer. However it is difficult to attach

orifice meters wherever this loss needs to be calculated. But we can calculate it with the above

formula in case we know the Coefficient of contraction which is constant for a given fluid. The formula

for Cc becomes

1V

2.g.h

1C

2

2

cC

+

= OR )V(2.g.h

VC

2c

2C 2

2

+=

Where,

‘hc‘ – Drop of head (got from the manometer difference).

‘V2‘ – Velocity of flow after contraction,

‘g‘ – Acceleration due to gravity, 9.8m/s2

‘Cc‘ – Coefficient of contraction

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Observation Table:

S No Manometric Reading Time for

x=___cm of water h1 h2 h = h1 – h2

1 2 3

Formulae:

t

xAQ tank

a =

( )21

w

Hg

c h-h1-S

Sh ×

=

( )222 d4

Aπ

=

2

a2

A

QV =

Where,

Atank – Area of Measuring Tank (0.3 X 0.3 m2) x – Rise of water level for which time is measured(from the table above)

t – Time taken for x cm of water collection.

hc – head loss due to sudden contraction in pipe

d2 – Pipe Diameter after contraction (15mm or 0.015m)

g – acceleration due to gravity (9.81 m/s2)

V2– Velocity of water flow after contraction

A2– Area of smaller pipe

Result Table:

S No hc Q V2 Cc

1 2 3

Average of CC = _________

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Experimental Procedure:



3. Except the outlet valve of the pipe to be tested, close all other valves.



6. Note down the manometric readings. 7. Note down the time ‘t’ for height ‘x cm’ of water collection in measuring tank.



Note: While measuring the heads, slight variation may occur due to voltage changes, valves etc. in

such cases, average readings may by taken.)

Precautions:




4. Ensure that the apparatus is operated at least some time every week to avoid clogging.

5. Ensure there are no leakages in the piping and Measuring Tank.

Conclusions:

1. The coefficient of contraction is found to be ________.

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Experiment No. 4

CALIBRATION OF VENTURIMETER

Aim:

To find the Coefficient of Discharge for the given Venturimeter and hence to calibrate it.

Apparatus Required:



3. A mono block pump with a valve in discharge pipe to control discharge.

4. The discharge pipe from pump gets divided into two pipes one holding a Venturimeter and

another holding an Orifice meter. Valves are provided at the ends to stop or allow discharge.



Theory:

A Venturimeter is a device which is used for measuring the rate of flow of fluid through pipe

line. The pressure difference due to reduced cross-sectional area is proportional to Water Discharge.

So, if we know the coefficient of Discharge we can determine the Water Discharge just by measuring

the pressure difference in the throat and inlet.

A Venturimeter consists of,

1. An inlet section followed by a Convergent Cone,

2. A Cylindrical Throat and

3. A gradually Divergent Cone.

Theoretical Discharge can be calculated using the following formula:

( )

/Secmaa

2gHaaQ 3

2

2

2

1

21

th =

where,

a1 – area of pipe or inlet section of Venturimeter

a2 – area of throat of Venturimeter

g – acceleration due to gravity, (9.81 m/s2)

H – the head difference between inlet and throat of Venturimeter.

Co - efficient of Discharge is the ratio of Actual discharge to the theoretical discharge as given

by the equation:

th

a

d Q

Q

dischargelTheoretica

dischargeActualC ==

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Observation Table:

S No Manometer Reading Time for x=__ cm water

discharge t (Sec) h1 h2 h = h1 – h2

1 2 3 4 5 6

Formulae:

1) Theoretical Discharge:

( )

/Secmaa

2gHaaQ 3

2

2

2

1

21

th =

where,

a1 – area of inlet section of Venturimeter =________(πD2 / 4) m2

D – Diameter of pipe a2 – area of throat of Venturimeter =_______(πd2 / 4) m2

d – Diameter of the throat



Substituting the values of a1, a2 & g, the formula reduces to:

Qth = 662.84 x 10-6 x H

2) Actual Discharge:

t

xAQ tank

a =

where, x – Height of water considered

t – Time taken for the x height of water discharge

3) Co - efficient of Discharge:

th

a

d Q

Q


dischargeActualC ==

Calculation Table:

S No Qa Qth Cd (Qa/Qth)

1 2 3 4 5 6

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Procedure:

All the necessary instrumentations along with its accessories are readily connected. It is just

enough to follow the instructions below:



3. Open the outlet valve of the Venturimeter and close the valve of orifice meter.




7. Close the gate valve of measuring tank & determine the time‘t’ for height ‘x cm’ of

water collection in measuring tank.


Precautions:


2. Do not forget to give electrical neutral & earth connections correctly.


4. Initially, put clean water free from foreign material, and change once in three months.

5. At least every week, operate the unit for five minutes to prevent clogging of the moving parts.

Result /Conclusion:

The average co-efficient of discharge was calculated and found out to be _______.

Applications:

They are found in many applications where the discharge and velocity of the fluid are

important, and form the basis of devices like a carburetor.

Venturimeter is also used to measure the velocity of a fluid, by measuring pressure changes

from one point to another along the Venturimeter. Placing a liquid in a U-shaped tube and

connecting the ends of the tubes to both ends of a Venturimeter is all that is needed. When the fluid

flows though the Venturimeter the pressure in the two ends of the tube will differ, forcing the liquid to

the "low pressure" side. The amount of that move can be calibrated to the speed of the fluid flow.

Questions:

1. What is the main aim of the experiment?

2. What is the working principle of a Venturimeter?

3. What are the sections of a Venturimeter?

4. What are the losses on account of flow through a Venturimeter?

5. What is the normal co-efficient of discharge in a Venturimeter?

6. What are the precautions to be taken while performing the experiment?

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Experiment No: 5

CALIBRATION OF ORIFICEMETER Aim:

To find coefficient of Discharge and hence Calibrate Orifice meter.

Apparatus Required:



3. A mono block pump with a valve in discharge pipe to control discharge.

4. The discharge pipe from pump gets divided into two pipes one holding a Venturimeter and

another holding an Orifice meter. Valves are provided at the ends to stop or allow discharge.



Theory:

An ORIFICE METER is another simple device used for measuring the discharge through pipes.

Orifice meter also works on the same principle as that of Venturimeter i.e., by reducing the cross-

sectional area of the flow passage, a pressure difference between the two sections before and after

orifice is obtained and the measurement of the pressure difference enables the determination of the

discharge through the pipe. However, an orifice meter is a cheaper arrangement for discharge

measurement through pipes and its installation requires a smaller length as compared with

Venturimeter. As such where the space is limited, the orifice meter may be used for the measurement

of discharge through pipes.

A Orifice meter consists of,

1. An inlet section followed by a

Sudden Contraction,

2. A sudden enlargement to the

same diameter as inlet.

Theoretical Discharge can be

calculated using the following formula:

( )

/Secmaa

2gHaaQ 3

2

2

2

1

21

th =

where,

a1 – area of inlet section of Venturimeter

a2 – area of throat of Venturimeter


H – the head difference between the point just before orifice and at Vena Contracta.

Co - efficient of Discharge is the ratio of Actual discharge to the theoretical discharge as given

by the equation:

th

a

d Q

Q


dischargeActualC ==

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Observation Table:

S No Manometer Reading Time for x=____ cm water

discharge t (Sec) h1 h2 h = h1 – h2

1 2 3 4 5 6

Formulae:

1) Theoretical Discharge:

( )/Secm

aa

2gHaaQ 3

22

21

21th

−=

where, a1 – area of inlet section of Venturimeter =________(πD2 / 4) m2

D – Diameter of pipe a2 – area of throat of Venturimeter =_______(πd2 / 4) m2

d – Diameter of the throat



Substituting the values of a1, a2 & g, the formula reduces to:

Qth = 610.67 x 10-6 x H

2) Actual Discharge:

t

xAQ tanka =

where, x – Height of water considered

t – Time taken for the x height of water discharge

3) Co - efficient of Discharge:

th

a

d Q

Q


dischargeActualC ==

s

Result Table:

S No Qa Qth Cd (Qa/Qth)

1 2 3 4 5 6

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Procedure:


enough to follow the instructions below:



3. Open the outlet valve of the orifice meter and close the valve of Venturimeter.




7. Close the gate valve of measuring tank & determine the time‘t’ for height ‘x cm’ of water

collection in measuring tank.



Precautions:


2. Do not forget to give electrical neutral & earth connections correctly.

3. There is no danger of water being not there in the sump tank, since the measuring tank is fitted

with overflow pipe.


5. Initially, put clean water free from foreign material, and change once in three months.

6. At least every week, operate the unit for five minutes to prevent clogging of the moving parts.

Result /Conclusion:

The average co-efficient of discharge was calculated and found out to be _______.

Applications:

They are found in many applications where the discharge and velocity of the fluid are

important.

Orificemeter is also used to measure the velocity of a fluid, by measuring pressure changes

from one point to another along the orificemeter. Placing a liquid in a U-shaped tube and connecting

the ends of the tubes to both ends of an orificemeter is all that is needed. When the fluid flows though

the orificemeter the pressure in the two ends of the tube will differ, forcing the liquid to the "low

pressure" side. The amount of that move can be calibrated to the speed of the fluid flow.

Questions:


2. What is the working principle of an orificemeter?

3. What are the sections of an orificemeter?

4. What are the losses on account of flow through an orificemeter?

5. What is the normal co-efficient of discharge in an orificemeter?

6. What are the precautions to be taken while performing the experiment?

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Experiment No. 6

CENTRIFUGAL PUMP

Aim:

To find the overall efficiency of a Centrifugal Pump and plot the following characteristics.

a. Hydraulic Efficiency (ηh) Vs Discharge

b. Overall Efficiency (ηo) Vs Discharge

Apparatus Required:

Centrifugal pump test rig, Stop Watch.

The present Pump Test Rig is a self – contained unit operated on Closed Circuit (Recirculation)

Basis. The Centrifugal Pump, AC Motor, Sump Tank, Collecting Tank, Control Panel are mounted on

rigid frame work with anti-vibration mounts and arranged with the following provisions:

1. For conducting the experiments at three speeds using AC Motor.

2. To measure overall input power to the AC motor using Energy Meter.

3. For recording the Pressure & vacuum.

4. For recording the speed using Digital RPM Indicator.

5. For changing the pressure (Delivery Head) and Vacuum (Suction Head) by operating the

valves.

6. For measuring the discharge by Collecting Tank-Level Gauge provision.

7. For recirculation of water back to the sump tank by overflow provision.

Theory:

In general, a pump may be defined as a mechanical device which, when interposed in a

pipe line, converts the mechanical energy supplied to it from some external source into hydraulic

energy, thus resulting in the flow of liquid from lower potential to higher potential.

The pumps are of major concern to most Engineers and Technicians. The types of pump vary

in principle and design. The selection of the pump for any particular application is to be done by

understanding their characteristics. The most commonly used pumps for domestic, agricultural and

industrial purposes are; Centrifugal, Piston, Axial Flow (Stage pumps), Air Jet, Diaphragm and Turbine

pumps. Most of these pumps fall into the main class, namely, Rotodynamic, Reciprocating (Positive

Displacement), Fluid (Air) operated pumps.

In centrifugal pump the liquid is made to rotate in a closed chamber (Volute Casing), thus

resulting in the continuous flow. These pumps compared to Reciprocating Pumps are simple in

construction, more suitable for handling viscous, turbid (muddy) liquids. But, their hydraulic heads per

stage at low flow rates is limited, and hence not suitable for very high heads compared to

Reciprocating Pumps of same capacity. But, still in most cases, this is the only type of pump which is

being widely used for agricultural purposes.

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Observation Table:

S

No

Discharge Pressure

Head ‘Pd’ (kg/cm2)

Suction Vacuum

‘Ps’

(in mm of Hg)

Time taken for 50 lit

(10cm of tank)

water Discharge, t

(sec)

Time taken for 1

rev. of Energy

meter te (sec).

Calculations:

1. Discharge head

10Phdd×= m of water

2. Suction Head:

1000

×=

13.6Ph

s

s m of water

3. Total Head:

ht = hd + hs + 2m of water

4. Discharge:

t

xAQ tank

a = m3/s

5. Water power (or Output Power)

1000

.Q.hWP

tω= kW

Where,

ω – Specific Weight of water = 9810 N/m3.

Q – Discharge (m3/sec).

ht – Total head (m)

6. Electrical Input

Let time required for 10 rev. of energy meter disc be te-Sec.

Electrical Input Power, IP

eC t

3600

E

nIP ×= kW

Taking motor efficiency as 75% we have Input Shaft Power,

SP = IP x 0.75

7. Hydraulic Efficiency

100SP

WPh ×=η %

8. Overall efficiency

100IP

WPo ×=η %

Result Table

S

No ht Q WP IP oη SP hη

1. 2. 3. 4. 5.

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Procedure:


enough to follow the instructions below

1. Fill in the Sump Tank with clean water.

2. Open the priming nipple plug (at the top of pump) and pour water into it filling it up to the

nipple

3. Close the discharge valve.

4. Start the pump. As discharge valve is closed, no discharge will be observed, but discharge

pressure will be indicated. This is called Shut off head of the pump.

5. Slowly open the discharge valve, so that small discharge is observed.

6. Note down discharge head, suction vacuum, time required for 10 lit water discharge and 10

revolutions of energy meter disc.

7. Note down the observations at different valve openings.

8. Repeat the steps 3 to 7 for different speeds. Different speeds can be obtained by changing

the position of motor and belt for different pulley configurations.

Graphs:

1. Main characteristics – Plot the graphs of discharge vs total head and overall efficiency at

different speeds.

Precautions:

1. Priming is must before starting the pump. Pump should never be run empty.

2. Use clean water in the sump tank.

3. Use all the controls and switches carefully.

4. Do not disturb the pressure gauge connections.

Result /Conclusion:

The overall efficiency for different speeds were calculated and graphs plotted.

Applications:

The most commonly used pumps for domestic, agricultural and industrial purposes are;

Centrifugal pumps. These pumps fall into the main class, namely, Rotodynamic pumps.

Questions:

1. What is meant by a Roto-dynamic machine?

2. What is meant by priming of a pump?

3. What energy is converted in a pump?

4. What types of fluids are pumped by centrifugal pumps?

5. What are the pumping characteristics of a centrifugal pump?

6. What is meant by efficiency of a pump?

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Experiment No: 7

Performance Test on Multi Stage Centrifugal Pump

Aim:

To find the overall efficiency of a Centrifugal Pump and plot the following characteristics.

c. Hydraulic Efficiency (ηh) Vs Discharge

d. Overall Efficiency (ηo) Vs Discharge

Apparatus Required:

Multi-Stage Centrifugal pump test rig, Stop Watch.

Introduction:

Centrifugal pumps are basically Roto-Dynamic Pumps, which develop Dynamic Pressures for

Liquids. In Centrifugal pumps, liquid in Impeller is made to rotate by external force, so that it is thrown

away from the Center of Rotation. As constant supply of fluid is needed at the center of rotation, its

supply can be taken from higher level.

Normally, head produced by a single impeller depends upon the peripheral speed of the

impeller. In order to produce higher heads, either rotational speed or diameter of the impeller has to

be increased, which increases stresses in the material of impellers. Hence, two pumps in series can be

used to produce higher heads. Now, this method is replaced by multistage pumps. In multistage

pumps, two or more impellers are arranged on a single shaft so that liquid discharged by first stage

impeller at certain head passes to the next stage impeller, where the head is increased till the liquid

finally enters into delivery pipe.

The unit consists of a two stage centrifugal pump driven by a 3-phase induction motor. An

energy meter provided measures electrical input to the motor and a measuring tank provided

enables to measure the discharge of the pump. A gate performance of the pump can be estimated

at various heads.

A 5 Stage Centrifugal Pump

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Observation Table:

S

No

Discharge

Pressure, Pd (kg/cm2)

Suction Vacuum,

Ps (mm of Hg)

Time for ___ lit

water (___cm of

tank) discharge,

tm (sec)

Time for n=___rev

of Energy meter, te (sec)

1. 2. 3. 4. 5.

Formulae:

1. Discharge head

10Ph dd ×= m of water

2. Suction Head:

1000

13.6Ph ss

×= m of water

3. Total Head:

ht = hd + hs + 2m of water

4. Discharge:

t

xAQ tank

a = m3/s

5. Water power (or Output Power)

1000

W.Q.hWP t

= kW

6. Electrical Input

Let time required for 10 rev. of energy meter disc be te-Sec.

Electrical Input Power, IP

eC t

3600

E

nIP ×= kW

Taking motor efficiency as 75% we have Input Shaft Power,

SP = IP x 0.75

7. Hydraulic Efficiency

100SP

WPh ×=η %

8. Overall efficiency

100IP

WPo ×=η %

Result Table

S

No ht Q WP IP o

η SP hη

1. 2. 3. 4. 5.

Where,

W – Specific Weight of water = 9810 N/m3.



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Procedure:

1. Make sure the Sump tank is filled with water.

2. If the pump doesn’t start discharging water, open the Priming Nipple and pour water till the

casing is fully filled.

3. Open the discharge valve fully.

4. Start the pump. As the discharge valve is closed, no discharge will be observed, but the

pressure gauge shows some reading. This is called “shut off head” of the pump.

5. Now slowly open the discharge valve, so the small discharge is observed.

6. Note down the discharge head (by pressure gauge on discharge pipe) and suction vacuum.

7. Note down time required for 25 ltr water collection in measuring tank.

8. Note down the time required for 10 revolutions of energy meter.

9. Repeat the procedure by varying the discharge valve opening, and fill up the observation

table.

Graphs:

Operating characteristics – Plot the graph of discharge vs total head, overall efficiency

From the operating characteristics, it is noted that

a. Shut off head of pump ( head at zero discharge) is ….m

b. Maximum efficiency occurs at the discharge of ….. m3/sec & is ……

c. Maximum power input to pump is … kW

d. Maximum discharge of pump is ….. m3/sec.

Precautions:

1. Priming is must before starting the pump. Pump should never be run empty.

2. Observe the direction of rotation of pump. If it is reverse, interchange any two of the 3

connections of motor.

3. Use clean water in the sump tank.

4. Use all the controls and switches carefully.

5. Do not disturb the pressure gauge connections.

6. Drain all the water after completion of experiment.

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Observation Table:

S No

Speed of

Pump, Np (in

rpm)

Discharge

Pressure Head

‘Pd’ (kg/cm2)

Suction

Vacuum ‘Ps’

(in mm of Hg)

Time for ___ lit water

(___cm of tank)

discharge, tm (sec)

Time for

n=___rev of

Energy meter,

te (sec)

1. 2. 3. 4. 5.

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Experiment No: 8

RECIPROCATING PUMP

Aim:

To find the overall efficiency of a Reciprocating Pump and plot the following characteristics.

a. Hydraulic Efficiency (ηh) Vs Discharge

b. Overall Efficiency (ηo) Vs Discharge

Apparatus Required:

Reciprocating pump test rig, stop watch.

The present Reciprocating Pump Test Rig is a self-contained unit operated on Closed Circuit

(Recirculation) Basis. The main components are singe acting Single Cylinder Reciprocating Pump, AC

Motor, Sump Tank, Collecting Tank, control Panel are mounted on rigid frame work with anti-vibration

mounts and arranged with the following provisions:

1. Stepped Cone Pulley arrangement to run pump at 3 different speeds and AC Motor.

2. To measure the input horse power to the pump using energy meter reading.

3. To measure the speed in rpm of the motor and the pump, separately.

4. To measure the delivery and suction heads using pressure and vacuum gauges separately.

(The delivery head pressure tapping is connected, upstream of delivery valve, and that of the

suction tapping downstream of suction valve).

5. To change the head and flow rate using control valves.

6. To measure the discharge using collecting tank fitted with tank level indicator.

Specifications:

Reciprocating Pump : 30 cm core, stroke length 20mm, double acting with air vessel on

discharge side suction Ф 19mm, discharge Ф 12.7mm.

AC Motor : AC Motor, 1 HP, speed variations controlled by a stepped cone

pulley.

Measuring (Metering) Tank : 400mm x 400mm x 450mm height provided with gauge tbe and

swiveling joint in piping for diverting the flow into measuring tank r

sump tank.

Sump tank : 600mm x 900mm x 600mm height.

Measurements

Pressure gauge : 0-7 Kg/cm2 for discharge pressure.

Vacuum gauge : 0-760 mm Hg suction vacuum

3 Ph Energy meter for motor input measurements.

Theory:

In general, a pump may be defined as a mechanical

device which, when interposed in a pipe line, converts the

mechanical energy supplied to it from some external source

into hydraulic energy, thus resulting in the flow of liquid from

lower potential to higher potential.

The pumps are of major concern to most Engineers and

Technicians. The types of pump vary in principle and design.

The selection of the pump for any particular application is to

be done by understanding their characteristics. The most

commonly used pumps for domestic, agricultural and

industrial purposes are: Centrifugal, Piston, Axial Flow (Stage

pumps), Air Jet, Diaphragm and Turbine pumps. Most of these

pumps fall into the main class, namely, Rotodynamic,

Reciprocating (Positive Displacement), Fluid (Air) operated

pumps.

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Calculations:

1. Volume per stroke: =π/4 x D2 x L x 2

= 28.27 cc/stroke

= 2.827x10-5 m3/stroke

2. Theoretical discharge,

60

xN2.82x10Q

p-5

t = m3/sec

3. Suction head

hs = Ps x 13.6

4. Delivery head

hd= Pd x 10

5. Total head assuming loss of head as 3 m.

ht = hs + hd + 3 m.

6. Actual discharge

t

xAQ tank

a =

7. Output power of pump

1000

W.Q.hP t

w =

8. Input power to pump

ce E

3600

t

nIP ×=

9. Coefficient of discharge of pump

t

ad

Q

Q=C

10. Slip

x100Q

Q-QSlip

t

at=

11. Graphs – Plot the graph of head vs Discharge, Efficiency of the pump.

Result Table

S

No ht Q WP IP o

η SP hη

Where,




Where,

n – No of revolutions considered.

te – Time taken by energy meter.

Ec – Energy meter constant

Where,

hd – Discharge head in m of water.

Pd – Discharge pressure in Kg/cm2.

hs – Suction head in m of water.

Ps – Suction pressure in m of Hg

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Procedure:

All the necessary instrumentation along with its accessories are readily connected. It is just enough to

follow the instructions below:

1. Fill in the sump tank with clean water.

2. Full up the air vessel for about 2/3rd capacity.

3. Open the gate valve in the discharge pipe of the pump fully.

4. Close the gate valve and drain valve of the measuring tank.

5. Check nut bolts & the driving belt or proper tightening.

6. Divert the outlet pipe into funnel and slowly increase the pump speed, slightly close the

discharge valve. Note down the various readings in the observations table. Repeat the

procedure for different gate valve openings. Take care that discharge pressure does not rise

above 4 Kg/cm2.

7. Change the speed and take readings for different gate valve openings. Repeat the

procedure for different speeds and complete the observation table.

Precautions:

1. Operate all the controls gently.

2. Never allow to rise the discharge pressure above 4kg/cm2

3. Always use clean water for experiment.

4. Before starting the pump ensure that discharge valve is opened fully.

Result /Conclusion:

The overall efficiency for different speeds were calculated and graphs plotted.

1. For default belt position, the overall efficiency was found out to be _________.

Applications:

1. To drill oil from deep wells.

2. To pump any liquid which is free from debris.

Questions:


2. What is meant by a positive displacement pump?

3. What types of fluids are pumped by Reciprocating pumps?

4. What are the pumping characteristics of a Reciprocating pump?

5. What is the normal efficiency of a Reciprocating pump?

6. What are the normal precautions to be taken when operating a pump?

7. What is the function of air vessel?

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Experiment No: 9

PELTON WHEEL TURBINE

Aim:

To determine the performance characteristics of Pelton wheel turbine under constant head

and constant speed.

Apparatus Required:

Pelton wheel turbine test rig.

Construction:

The actual experimental set-up consists of a Sump Tank, Centrifugal pump, Delivery pipe and

Turbine unit arranged in such a way that the whole unit works as re-circulating water system. The

centrifugal pump set supplies water from the sump tank to the turbine through a Venturimeter. The

flow rate can be changed by control valve. The water after impinging on the turbine unit falls back

into the Sump Tank.

The loading of the turbine is achieved by rope brake drum connected to spring balances. The

turbine speed is measured with a Tachometer, head on the turbine is measured with pressure gauge

and the discharge rate is calculated with the help of Pressure readings at Venturimeter.

Supply Pump / Motor Capacity : 15 hp, 3 ph, 440V, 50 Hz AC.

Mean Dia. of runner : 280 mm

No. of buckets : 20

Dia. Of Nozzle : 30 mm

Runaway Speed : ________

Max Head : ________

Loading : Brake Drum (radius : 30 cm)

Provision : Venturimeter with gauges for Flow Rate

Theory:

Hydro-Power is one of major cheap source of power available on earth, and hence it is widely

used for generation of electric power world wide. Water stored in the Dam contains potential energy.

This is utilized to run turbine, which then drives a generator. The output from the generator can be

transmitted to the areas of electric power requirement.

Turbines are basically of two types, viz. Impulse turbines

and Reaction turbines. In impulse turbines, water coming from

high head acquires high velocity. The high velocity water jet

strikes the buckets of the turbine runner and makes it to rotate by

impact force. In reaction turbine, total head of water is partly

converted into velocity head as it approaches turbine runner

and it fills the runner and pressure of water gradually changes as

it flows through runner. In impulse turbine, the only turbine used

now-a-days is Pelton Wheel Turbine. In reaction turbines, Francis

Turbine and Kaplan Turbine are the examples.

The Pelton wheel turbine consists of a runner mounted

over the main shaft. Runner consists of buckets fitted to the disc.

The buckets have a shape of double ellipsoidal cups. The runner

is encased in a casing provided with a Perspex window for

viewing the turbine. A nozzle fitted in the side of casing directs

the water jet over the 'Splitter' or center ridge of the buckets. A

spear operates inside the nozzle to control the water flow. On the other side of the shaft, a rope brake

is mounted for loading the turbine.

Impulse turbines convert all the energy of Water into Kinetic Energy at the nozzle. The jet

impinges on the turbine's curved blades and gets diverted (by about 160o). The resulting change in

momentum (impulse) causes a force on the turbine blades.

All the Pressure/Potential Energy is converted to kinetic energy by the nozzle and focused on

the turbine. No pressure change occurs at the turbine blades, and the turbine doesn't require a

housing for operation. Newton's second law lets us calculate transfer of energy for impulse turbines.

Impulse turbines are most often used in very high head applications, but the discharge used is less.

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Observation Table:

Table I

Constant Speed Characteristics

Method : By keeping Butterfly Valve position fully open and changing the spear valve position to

get constant speed.

‘N’ in

rpm

Spear

valve

position

Pressure ‘P’

in kg/cm2

Head over

the notch ‘h’

in meters

‘F1’

kgf

‘F2’

kgf Remarks

Table II

Constant Head Characteristics

Method: 1) Spear rod at fixed position

2) Butterfly Valve fully open &

3) Change Brake Drum load

Turbine speed ‘N’ in

rpm

Pressure

“P” in kg /

cm2

Head over

notch (flow

rate), “h” in

m

‘F1’

kgf

‘F2’

kgf

Remarks

CALCULATIONS:

Table I

Constant Speed Characteristics

Turbine

Speed

‘N’ rpm

Net head

on Turbine

‘H’ m.

Discharge

(flow rate)

‘Q’ m3/sec

HPhyd BHP % ηtur % of Full

Load Remarks

Table - II

Constant Head Characteristics

Turbine

Speed ‘N’

in rpm

Net head

on Turbine

‘H’ m.

Discharge

(flow rate) ‘Q’

in m3/Sec

HPhyd BHP % ηtur Remarks

Unit quantities under unit head

(Calculations based on Table of Calculations – II)

Net head on

turbine “h” m.

unit speed

“nu”

unit power

“pu”

unit discharge

“qu”

specific

speed “ns” % ηtur remarks

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Procedure:

1. Make sure the connections are properly done: Motor unit connected to 3 ph, 440V, 30A, electrical

supply, with neutral and earth connections and ensure the correct direction of pump-motor unit.

2. Keep the Butterfly valve and spear valve closed.

3. Keep the Brake Drum loading at minimum.

4. Press the green button of the supply pump starter. Now the pump picks-up the full speed and

becomes operational.

5. Slowly, open the spear valve so that the turbine rotor picks up the speed and attains maximum at

full opening of the valve.

a) To obtain constant speed characteristics:

1. Keep the Butterfly valve opening at maximum

2. For different Brake Drum loads on the turbine, change the spear rod setting, between

maximum and minimum so that the speed is held constant.

3. Tabulate the results as per Table - I .

4. The above readings are utilized for drawing constant speed characteristics Viz.,

b. Percentage of full load V/s efficiency.

c. Efficiency and BHP V/s discharge characteristics.

b) To obtain constant head characteristics:

1. Keep the spear rod setting and Butterfly Valve setting at maximum.,

2. For different Brake load, note down the speed, Head over notch

and tabulate the results as given in Table – II.

c) To obtain run-away speed characteristics:

1. Keep the load on the brake , zero.

2. Keep spear rod and Butterfly Valve at maximum .

Note:

Run – away speed is also influenced by the tightening in gland packing of the turbine shaft. More

the tightness, less the run – away speed.

d) Performance under unit head – Unit quantities:

In order to predict the behavior of a turbine working under varying conditions and to facilitate

comparison between the performances of the turbines of the same type but having different outputs

and speeds and working under different heads, it is often convenient to express the test results in terms

of certain unit quantities.

From the output of a turbine corresponding to different working heads (Table of Calculations –

II) it is possible to compute the output which would be developed if the head was reduced to unit

(say 1 m..); the speed being adjustable so that the efficiency remains unaffected.

a. Unit Speed, H

NNu =

b. Unit power, 3/2u

H

PP =

c. Unit Discharge, H

QQu =

d. Specific Speed,

The specific speed of any turbine is the speed in rpm of a turbine geometrically similar to the actual

turbine but of such a size that under corresponding conditions it will develop 1 metric horse power

when working under unit head (i.e., 1 meter.).

The specific speed is usually computed for the operating conditions corresponding to the maximum

efficiency.

5/4u

H

PNN =

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Calculations:

1. Net/Working head on the Turbine:

H=10 x P

Where,

P – Pressure gauge reading (Kg/cm2)

2. Discharge (Flow rate)of water through the Turbine,

2

2

2

1-

=

AA

2xgxHxAxACQ

21d

t m3/sec

Where,

dC -Coefficient of Discharge for Venturimerter = 0.9

1A - Area of Cross Section of Pipe

2A - Area of Cross Section of Venturimeter Throat

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

H – Pressure head (Calculated above)

3. Hydraulic Power (Input to the Turbine):

1000

W.Q.HHP =

Where,



H – Total head (m)

4. Brake Power (Output from the turbine),

)FF(60

gNDBP 21

××××

=π

Where,

F1 and F2 are the spring balance readings in kgf

D – Diameter of the Brake Drum (30 cm)

5. Turbine Efficiency (Output from the turbine),

100HP

BP×=η

6. Unit quantities – under unit head,

a. Unit Speed, HN/Nu =

b. Unit power, 3/2

u BHP/HP =

c. Unit Discharge, HQ/Qu =

7. Specific speed,

5/4u H

BPNN =

Obtained at maximum efficiency.

8. Percentage Full load = 100.

×BPloadMax

BPloadPart (at any particular speed.)

Graph:

Constant head characteristics

1. Unit discharge (Qu) vs. Unit speed (Nu).

2. Unit power (Pu) vs. Unit speed (Nu).

3. Percentage efficiency (%η) vs. Unit speed (Nu).

Constant speed characteristics

1.Percentage efficiency (%η) vs. percentage full load.

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Precautions:

1. Do not start pump set if the supply voltage is less than 300 V (phase to phase voltage).

2. Do not forget to give electrical earth and neutral connections correctly. Otherwise, the

RPM indicator gets burnt if connections are wrong.

3. Frequently, at least once in three months, grease all visual moving parts.

4. Initially, fill-in the tank with clean water free from foreign material. Change the water

every six months.

5. At least every week, operate the unit for five minutes to prevent any clogging of the

moving parts.

6. To start and stop the supply pump, always keep gate valve closed.

7. It is recommended to keep spear rod setting at close position before starting the turbine.

This is to prevent racing of the propeller shaft without load.

8. In case of any major faults, please write to manufacturer, and do not attempt to repair.

Result /Conclusion:

The unit head and other quantities were calculated from the knowledge of constant head

characteristics and the curves were drawn. Similarly the constant speed characteristics were

calculated and the percentage efficiency vs. percentage full load was drawn.

Questions:

1. On what principle the Pelton wheel turbine works?

2. What is the shape of buckets in Pelton wheel turbine?

3. What is the clearance angle of the buckets? State why it is not 1800?

4. Define unit quantities and specific speed.

5. Why multiple jets are used in Pelton wheel turbine?

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Documents

Fm Hm Lab Manual July 2011