experiment no - wordpress.com · 2019. 7. 10. · thus impact of jet means the force exerted by the...

1 Prepared By: Prof. Shyam S. Darewar

EXPERIMENT NO.1

AIM: VERIFICATION OF IMPULSE MOMENTUM PRINCIPLE

Introduction:

Impact of jets apparatus enables experiments to be carried out on the reaction force produced

on Vanes when a jet of water impacts on to the vane. The study of these reaction forces is an essential

step in the subject of mechanics of fluids which can be applied to hydraulic machinery such as the

Pelton wheel and the impulse turbine. The jet is directed on to the vanes of a turbine wheel, which is

rotated by the force generated on the vanes due to the momentum change or impulse that taken

position as the jet hit the vane. Water turbines working on this impulse principle have been

constructed with outputs of the order of 100000 kW and with efficiencies greater than 90%.

Apparatus Required: Impact of jet apparatus, weights and stop watch.

Theory:

The liquid comes out in the form of a jet from the outlet of a nozzle, which is fitted to a pipe

through which the liquid if flowing under pressure. If some plate, which may be fixed or moving, is

placed in the path of the jet, a force is exerted by the jet on the plate. This force is obtained from

Newton’s second law of motion or from impulse-moment equation. Thus impact of jet means the

force exerted by the jet on a plate which may be stationary or moving. The following cases of the

impact jet i.e., the force exerted by the jet on a plate, will be considered:

1. Force exerted by a jet on a stationary plate when

a. Plate is vertical to the jet,

b. Plate is inclined to the jet, and

c. Plate is curved.

2. Force is exerted by the jet on the moving plate, when

a. Plate is vertical to the jet,

b. Plate is inclined to the jet, and

c. Plate is curved

Force exerted by a jet on a stationary vertical plate:

Consider a jet of water coming out of the nozzle, strikes a flat vertical plate as shown in the

figure. 1


Let,

The jet after striking the plate will move along the plate. But the plate is right angles to the jet.

Hence the jet after striking will get deflected by 90°. Hence the component of the velocity of the jet,

in the direction of the jet, after striking will be zero. The force exerted by the jet on the plate in the

direction of the jet.

Force exerted by a jet on a stationary inclined flat plate:

Let a jet of water, coming out from the nozzle; strike an inclined flat plate as shown in the

figure.2.

Figure Error! No text of specified style in document..1 Force

exerted by a jet on a stationary vertical plate


Figure Error! No text of specified style in document..2. Force exerted by a jet on a stationary inclined flat

plate

Let

v = velocity of the jet in the direction of X

If the plate is assumed smooth and if it is assumed that there is no loss of energy due to the

impact of the jet, then the jet will move over the plate after striking with a velocity equal to initial

velocity i.e., with a velocity V.

Let find the force exerted by the jet on the plate In the direction normal to the plate. Let this

force is represented by Fn

then, Fn = Mass of the jet striking per second × [initial velocity of the jet before striking in the

direction of n - final velocity of the jet after striking in the direction of n.

This force can be resolved into two components, one in the direction of the jet and the other

perpendicular to the direction of the flow. Then we have,

(Along the direction of the flow) and

(Perpendicular to flow)


Force exerted by a jet on a stationary cover plate:

Jet strikes the curved plate at the centre. Let a jet of water strike a fixed curved plate at the

centre as shown in figure.3. The jet after striking the plate comes out with the same velocity if the

plate is smooth and there is no loss of energy due to impact of the jet, in the tangential direction of the

curved plate. The velocity at the outlet of the plate can be resolved in to two components, one in the

direction of the jet and the other perpendicular to the direction of the jet.

Figure Error! No text of specified style in document..3. Force exerted by a jet on a stationary cover plate

(-ve sign is taken as the velocity at the outlet is in the opposite direction of the jet of water coming out

from nozzle).

Force exerted by the jet in the direction of the jet,

Where,


Similarly,

Where,

-ve sign means the force is acting in the downward direction. In this case the angle of deflection of the

jet =

Experimental Setup:

The set up primarily consists of a nozzle through which jet emerges vertically in such a way

that it may be conveniently observed through the transparent cylinder. It strikes the target plate or disc

positioned above it. An arrangement is made for the movement of the plate under the action of the jet

and also because of the weight placed on the loading pan. A scale is provided to carry the plate to its

original position i.e. as before the jet strikes the plate. A collecting tank is utilized to find the actual

discharge and velocity through nozzle.

Precaution:

1. Ensure sufficient quantity of water (90 Litre) is available in sump tank

2. Before starting the pump bypass valve must be in open position so that after starting the pump

water flows from sump tank to pump and pump to sump tank.

3. Apparatus should be in levelled condition.

4. Make stepwise loading.

5. Reading must be taken in steady conditions.

6. Discharge must be varied very gradually from a higher to smaller value.

Procedure:

i. Note down the relevant dimensions as area of collecting tank and diameter of nozzle.

ii. When jet is not running, note down the position of upper disc or plate.

iii. Admit water supply to the nozzle.

iv. As the jet strikes the disc, the disc moves upward, now place the weights to bring back

the upper disc to its original position.

v. At this position find out the discharge and note down the weights placed above the disc.


vi. The procedure is repeated for different values of flow rate by reducing the water supply in

steps.

Figure Error! No text of specified style in document..4 Impact of jet apparatus

Observation:

1. Pipe diameter D = 1” or 25.4mm Material: PVC

2. Bypass valve = Gate valve 1” dia. Material: Brass.

3. Acrylic Cylinder = ID Φ250 x 300mm

4. Centrifugal Pump Power = 0.5HP

Head Range = 6-25m

Speed = 2780 rpm

Discharge Range: 2000-4000 lph

5. Sump Tank Capacity = 100 ltr.

6. Area of Measuring Tank = 0.260 x 0.360 m2

7. Diameter of nozzle (d) = 8 mm

8. Area of the nozzle (A) = πd2/4


9. Distance between the nozzle and target deflector at rest = 30 mm

10. Mass density of water = 1000 Kg/m3

11. Distance from hinge to the weight attached position X1 = 0.308 m

12. Distance from hinge to line of impact force X2 = 0.124 m

13. Inclined plate angle Ɵ = 0

14. Curved plate angle Ɵ= 0

Observation Table:

1. For Flat Plate

Sr. No. Time to rise 100mm of water

in measuring tank in ‘sec’

Weight attached

to lever in ‘gm’

1.

2.

3.

4.

5.

2. For Inclined Plate



Weight attached


1.

2.

3.

4.

5.

3. For Curved Plate



Weight attached


1

2

3

4

5

Calculation Procedure:


1. For Flat Plate

i. Discharge ‘Q’

ii. Jet Velocity ‘V’

iii. Theoretical Force (Fth):

For Flat Plate:

For Inclined Plate:

For Curved Plate:

iv. Actual Force (Fact):

For Flat Plate:

X1 = Distance from hinge to the weight attached position

X2 = Distance from hinge to line of impact force


For Inclined Plate:



For Curved Plate:



Result Tables:

1. For Flat Plate

Sr. No.

Discharge Q in ‘m

3/sec’

Velocity V in ‘m/sec’

Theoretical Force Fth in ‘N’

Actual Force Fact in ‘N’

1

2

3

4

5

2. For Inclined Plate

Sr. No.

Discharge Q in ‘m

3/sec’




1

2

3

4

5

3. For Curved Plate


Sr. No.

Discharge Q in ‘m

3/sec’




1

2

3

4

5

Conclusions:

__________________________________________________________________________________

__________________________________________________________________________________

______________________________________________________________________________

Graphs:

1. Fth V/S Fact (For Flat Plate)

2. Fth V/S Fact (For Inclined Plate)

3. Fth V/S Fact (For Curved Plate)


EXPERIMENT NO.2

AIM: STUDY AND TRIAL ON IMPULSE WATER TURBINE (PELTON WHEEL) AND PLOTTING OF

MAIN AND OPERATING CHARACTERISTICS.

APPARATUS

a) Centrifugal pump set, sump tank, turbine, piping to operate the turbine on closed circuit

water circulating system.

b) Digital RPM indicator, pressure gauge, flow control valve, mechanical loading with

spring balance.

PART-I THEORY

INTRODUCTION:

Energy may exist in various forms. Hydraulic energy is that which may be possessed by a

fluid. It may be in the form of kinetic, pressure, potential, strain or thermal energy. Fluid machinery is

used to convert hydraulic energy into mechanical energy or mechanical energy into hydraulic energy.

This distinction is based on the direction of energy transfer and forms the basis of grouping fluid

machinery into two different categories. One is power producing machines which convert hydraulic

energy into mechanical energy like turbines and motors; the other is power consuming machines

doing the reverse like pumps, fans and compressors. Another classification for fluid machinery can

also be done based on the motion of moving parts. These are rotodynamics machines and positive

displacement machines. A detailed chart is given below explaining the classifications

The turbines, a sub group of rotodynamic machines, are used to produce power by

means of converting hydraulic energy into mechanical energy. They are of different types according

to their specification. Turbines can be subdivided into two groups, impulse and reaction turbines.

Moreover due to working fluid used, turbines can be named as steam turbines, gas turbines, wind

turbines and water turbines. The water turbine converts the energy possessed by the water to

mechanical energy. Pelton turbine (or Pelton wheel), an impulse turbine, is one of the well-known

type of water turbines.

DISCRIPTION:

In the impulse turbines, the total head available is first converted into the kinetic

energy. This is usually accomplished in one or more nozzles. The jets issuing from the nozzles strike

vanes attached to the periphery of a rotating wheel. Because of the rate of change of angular

momentum and the motion of the vanes, work is done on the runner (impeller) by the fluid and, thus,

energy is transferred. Since the fluid energy which is reduced on passing through the runner is

entirely kinetic, it follows that the absolute velocity at outlet is smaller than the absolute velocity at

inlet (jet velocity). Furthermore, the fluid pressure is atmospheric throughout and the relative

velocity is constant except for a slight reduction due to friction. The Pelton wheel is an impulse


turbine in which vanes, sometimes called buckets, of elliptical shape are attached to the

periphery of a rotating wheel, as shown in Fig. 2.1 One or two nozzles project a jet of water

tangentially to the vane pitch circle. The vanes are of double-outlet section, as shown in Fig. 2.2, so

that the jet is split and leaves symmetrically on both sides of the vane. This type of turbine is used for

high head and low flow rates. It is named after the American engineer Lester Pelton

Figure 2.1: Schematic diagram of a Pelton Turbine

Components of the Pelton turbine:

Runner with bucket: Runner (also named impeller) of Pelton turbine consists of a circular disc on

the periphery of which a number of buckets are fixed.

Nozzle: The water coming from the reservoir through penstock is accelerated to a certain velocity by

means of a nozzle.

Spear: The spear is a conical needle which is operated either by a hand wheel or automatically in an

axial direction depending upon the size of the unit. The amount of water striking the buckets of the

runner is controlled the spear in the nozzle.


Figure 2.2: Configuration of water flow in buckets

Casing: Casing is used to prevent the splashing of the water and to discharge water to tail race. It is

made up of cast iron or steel plate.

Breaking jet: When the nozzle is completely closed by moving the spear in the forward direction the

amount of water striking the runner reduce to zero. However, the runner due to inertia goes on

revolving for a long time. To stop the runner in a short time, a small nozzle is used which directs the

jet of water on the back of buckets. This jet of water is called breaking jet.

Governing mechanism: The speed of turbine runner is required to be maintained constant so that

electric generator can be coupled directly to turbine. Therefore, a device called governor is used to

measure and regulate the speed of turbine runner.

Velocity Triangle and Work Done For Pelton Wheel:

The jet of the water from the nozzle strikes the bucket at the splitter, which splits up the jet into two

parts. These parts of jet, glides over the inner surfaces and comes out at the outer edge. The splitter is

the inlet tip while outer edge of the tip is outlet tip of the bucket. The inlet velocity triangle is drawn

at the splitter and outlet velocity triangle is drawn at the outer edge of the bucket.

Let,


Where

Where,

Then,

The velocity triangle at inlet will be a straight line where;

From the velocity triangle at outlet, we have,

The force exerted by the jet of water in the direction of motion is given by,

As the angle β is an acute angle, +ve sign should be taken. also this is the case of series of vanes, the

mass of water striking is and not .

Now work done by the jet on the runner per second

Power to the runner by jet,

Work done/sec per unit weight of water striking/sec

The energy supplied to the jet at inlet is in the form of kinetic energy and is equal to

Now,


Substituting the value of and in above equation,

The efficiency will be maximum for a given value of when,

Or

Above equation states that hydraulic efficiency of a Pelton wheel will be maximum when the velocity

of the wheel is half the velocity of the jet of water at inlet. The expression for maximum efficiency

will be obtained by substituting the value of

in equation.

Points to be remember for Pelton wheel

i. The velocity of the jet at inlet is given by

Where

ii. The velocity of wheel (u) is given by

iii. The angle of deflection of the jet through bucket is taken at 165o

if no angle of deflection is

given.

iv. The mean diameter or the pitch diameter D of the Pelton Wheel is given by,


v. Jet Ratio: it is defined as the ratio of the pitch diameter (D) of the Pelton wheel to the

diameter of the jet (d). it is denoted by ‘m’ and is given as

vi. Number of bucket on a runner is given by

Where m = Jet ratio

vii. Number of Jets. It is obtained by dividing the total rate of flow through the turbine by the rate

of flow of water through a single jet.

Power, Efficiency and Specific Speed Expressions:

From Newton’s second law applied to angular motion,

Angular momentum = (Mass) (Tangential velocity) (Radius)

Torque = Rate of change of angular momentum

Power = (Torque) (Angular velocity)

Considering the water jet striking the runner generates a torque of ‘T’ and rotates the runner with ‘N’

(rev/m), then power obtained from the runner can be expressed as:

The total head available at the nozzle is equal to gross head less losses in the pipeline leading to the

nozzle (in the penstock) and denoted by ‘H’. Then available power input to the turbine becomes:

Where,

During conversion of energy (hydraulic energy to mechanic energy or vice versa) there occur some

losses. They can be in many form and main causes of them are friction, separation and leakage.

For a turbine:

Fluid Input Power = (Mechanical loss) + (Hydraulic losses) + (Useful shaft power output)

Where,

Hydraulic Losses = (Impeller loss) + (Casing loss) + (Leakage loss)

Considering all losses as one term:


Then, overall efficiency of turbine becomes:

Pelton wheel is directly coupled to a generator to produce electricity. Therefore, another efficiency

term, namely generator efficiency is used to show how efficiently the mechanical energy is converted

to electricity.

Where:

The performance or operating conditions for a turbine handling a particular fluid are usually

expressed by the values of N, P and H. It is important to know the range of these operating parameters

covered by a machine of a particular shape at high efficiency. Such information enables us to select

the type of machine best suited to a particular application, and thus serves as a starting point in its

design. Therefore, a parameter independent of the size of the machine (D-rotor or impeller diameter)

is required which will be the characteristic of all the machines of a homologous series. A parameter

involving N, P and H but not D is obtained and this parameter is called as specific speed. It is

expressed by the equation:

Sometimes it is also expressed with a dimensional form of the above equation:


PART-II EXPERIMENTATION

A Trial on Pelton Wheel Turbine:

Description:

The experimental setup consists of Centrifugal pump set, Turbine unit, sump tank arranged in

such a way that the whole unit works as recirculation water system. The centrifugal pump set supplies

the water from the sump tank to turbine through control valve situated on the pump and a sphere valve

before entering the turbine. The water after passing through the Turbine unit flows back to sump tank.

The loading of the turbine is achieved by a brake drum with rope & spring balance, provision for

measurement of turbine speed (digital RPM indicator), Head on turbine (pressure gauge) are built in

on the control panel.

Specification:

1. Pump Head: 25-30m

2. Pump Discharge Q: 680 lpm

3. Motor: 5HP/3000rpm/420V/3-Phase induction.

4. Inside Diameter of pipe (d1): 50.8mm

5. Orifice Diameter: (d2): 30.5mm

6. Coefficient of Discharge of orifice meter (Cd): 0.84

7. Brake Drum

a) Brake Drum Diameter: 250mm

b) Rope Diameter: 16mm

8. Pelton Wheel

a) No. of buckets:

b) Pitch Diameter of Bucket (D): 216mm

c) Outlet angle of Bucket (ϕ): 250

d) Tank Size: 1200x1000x600m3

e) Jet Diameter (d): 16mm

f) Head at nozzle: 3 kg/cm2

Procedure:

1) Connect the panel to the electrical source & ascertain the direction of the pump is in order (clock

wise direction from shaft end) by momentarily starting the pump.

2) Fill filtered clear water into the sump tank up to ¾th its full capacity

3) Keep the control valve situated above the pump in fully closed position, and the sphere valve in

half open position.

4) Start the pump; gradually open the control valve slowly so that the turbine achieves sufficient

speed.

5) Wait till the speed of the turbine maintained constant.

6) Load the turbine by turning the hand wheel situated on the load frame clock wise observing the

dial spring balance to any desired minimum load.


7) Allow the turbine speed to stabilize.

8) Record the readings indicated on pressure gauge, dial balance RPM indicator.

9) Continue loading the turbine in steps up to its full load and record the corresponding readings at

each steps

10) After the experiment is over bring the turbine to no load condition by rotating the hand wheel on

the load frame in anti clock wise direction and stop the pump.

11) Repeat the procedure from step 3 to step 10 for half open valve postion.

12) Tabulate all the recorded readings and calculate the input power, output power & efficiency of the

Turbine.

Observation Table:

1. for Constant Head:

Sr. No.

Speed ‘N’ In RPM

Spring Balance

‘S1’ in Kg

Spring Balance

‘S2’ in Kg

Net Load ‘S1-S2’ in

Kg

Orifice meter Pressure Gauge Reading

P1 in kg/cm

2

P2 in kg/cm

2

dh= P2-P1 in ‘m’

a)

b)

c)

d)

e)

2. for Constant Speed

Sr. No.

Speed ‘N’ In RPM

Spring Balance

‘S1’ in Kg

Spring Balance

‘S2’ in Kg

Net Load ‘S1-S2’ in

Kg

Orifice meter Pressure Gauge Reading

P1 in kg/cm

2

P2 in kg/cm

2


Sample Calculation:

Brake Power (BP) or (Shaft Power)(Ps):


Where,

a) Power Supplied to the turbine (Water Power) (Pin):

Where,

Discharge through pipe ‘Q’:

Where,

b) Power developed by the turbine runner (Runner Power) (P):

c) Various efficiencies of turbine:

i.

ii.

iii.

d) Unit Quantities ( , , and )


Result Tables:

1. for constant Head

Sr. No.

Brake Power Ps ‘Kw’

Water Power

Pin ‘Kw’

Runner Power

P

Hydraulic Efficiency ηh in %

Mechanical Efficiency ηm in %

Overall Efficiency η0 in %

Unit Speed

Nu

Unit Discharge

Qu

Unit Power

Pu

a)

b)

c)

d)

e)

2. for constant Speed

Sr. No.

Brake Power Ps ‘Kw’

Water Power

Pin ‘Kw’

Runner Power

P

Hydraulic Efficiency ηh in %

Mechanical Efficiency ηm in %

Overall Efficiency η0 in %

Unit Speed

Nu

Unit Discharge

Qu

Unit Power

Pu

a)

b)

c)

d)

e)

Conclusions:

__________________________________________________________________________________

__________________________________________________________________________________

______________________________________________________________________________


Graphs:

I) Plotting of Main Characteristics

1. Plot V/S (

2. Plot V/S

3. Plot V/S

II) Plotting of Operating Characteristics

1. Plot (Q) V/S

2. Plot (Q) V/S


EXPERIMENT NO.3

AIM: STUDY AND TRIAL ON ANY ONE HYDRAULIC REACTION TURBINE (FRANCIS/KAPLAN)

AND PLOTTING OF MAIN AND OPERATING CHARACTERISTICS.

Objective: The purpose of this experiment is to study the constructional details and performance

parameters of Francis Turbine.

APPARATUS

a) Centrifugal pump set, sump tank, turbine, piping to operate the turbine on closed circuit

water circulating system.

b) Digital RPM indicator, pressure gauge, flow control valve, mechanical loading with

spring balance.

PART-I THEORY

INTRODUCTION:

Hydraulic (water) Turbines are the machines, which use the energy of water (Hydro –power)

and convert it into Mechanical energy, which is further converted into electrical energy. Thus the

turbine becomes the prime mover to run the electrical generators to produce electricity (Hydroelectric

power).

The Turbines are classified as impulse & reaction types. In impulse turbine, the head of water

is completely converted into a jet, which exerts the force on the turbine; it is the pressure of the

flowing water, which rotates the Impeller of the turbine. Of many types of turbine, the Pelton wheel,

most commonly used, falls into the category of impulse turbine, while the Francis & Kaplan falls into

the category of reaction turbines.

Normally, Pelton wheel (impulse turbine) requires high heads and low discharge, while the

Francis & Kaplan (reaction turbines) require relatively low heads and high discharge. These

corresponding heads and discharges are difficult to create in laboratory because of the limitation of

required head & discharges. Nevertheless, an attempt has been made to study the performance

characteristics within the limited facility available in the laboratories. Further, understanding various

elements associated with any particular turbine is possible with this kind of facility.

THEORY:

The reaction turbine consists of fixed guide vanes called stay vanes, adjustable guide vanes

called wicket gates, and rotating blades called runner blades. Flow enters tangentially at high pressure,

is turned toward the runner by the stay vanes as it moves along the spiral casing or volute, and then

passes through the wicket gates with a large tangential velocity component. Momentum is exchanged

between the fluid and the runner as the runner rotates, and there is a large pressure drop. Unlike the

impulse turbine, the water completely fills the casing of a reaction turbine. For this reason, a reaction


turbine generally produces more power than an impulse turbine of the same diameter, net head, and

volume flow rate. The angle of the wicket gates is adjustable so as to control the volume flow rate

through the runner. In most designs the wicket gates can close on each other, cutting off the flow of

water into the runner. At design conditions the flow leaving the wicket gates impinges parallel to the

runner blade leading edge to avoid shock losses. In Francis turbine, a reaction turbine, there is a drop

in static pressure and a drop in velocity head during energy transfer in the runner. Only part of the

total head presented to the machine is converted to velocity head before entering the runner. This is

achieved in the adjustable guide vanes.

Similarly to Pelton wheel, Francis turbine usually drives an alternator and, hence, its speed

must be constant. Since the total head available is constant and dissipation of energy by throttling is

undesirable, the regulation at part load is achieved by varying the guide vane angle. This is possible

because there is no requirement for the speed ratio to remain constant. In Francis turbines, sudden

load changes are catered for either by a bypass valve or by a surge tank.

Components of the Francis Turbine:

Spiral Casing: Most of these machines have vertical shafts although some smaller machines of this

type have horizontal shaft. The fluid enters from the penstock (pipeline leading to the turbine from the

reservoir at high altitude) to a spiral casing which completely surrounds the runner. This casing is

known as scroll casing or volute. The cross-sectional area of this casing decreases uniformly along the

circumference to keep the fluid velocity constant in magnitude along its path towards the stay vane.

This is so because the rate of flow along the fluid path in the volute decreases due to continuous entry

of the fluid to the runner through the openings of the stay vanes.

Stay Vanes and Wicket Gates: Water flow is directed toward the runner by the stay vanes as it

moves along the spiral casing, and then it passes through the wicket gates. The basic purpose of the

wicket gate is to convert a part of pressure energy of the fluid to the kinetic energy and then to direct

the fluid on to the runner blades at the angle appropriate to the design. Moreover, they are pivoted and

can be turned by a suitable governing mechanism to regulate the flow while the load changes. The

wicket gates impart a tangential velocity and hence an angular momentum to the water before its entry

to the runner.

Runner: It is the main part of the turbine that has blades on its periphery. During operation, runner

rotates and produces power. For a mixed flow type Francis Turbine, the flow in the runner is not

purely radial but a combination of radial and axial. The flow is inward, i.e. from the periphery towards

the centre. The main direction of flow changes as water passes through the runner and is finally turned

into the axial direction while entering the draft tube.

Draft Tube: After passing through the turbine runner, the exiting fluid still has appreciable kinetic

energy. To recover some of this kinetic energy the flow enters an expanding area (diffuser) called


draft tube, which slows down the flow speed, while increasing the pressure prior to discharge into the

downstream water. Therefore, the primary function of the draft tube is to reduce the velocity of the

discharged water to minimize the loss of kinetic energy at the outlet. This permits the turbine to be set

above the tail water without any appreciable drop of available head. Moreover careful design of draft

tube is vital, otherwise cavitation can occur inside the tube.

Francis turbine (reaction type) which is of present concern consists of main components such

as Impeller (runner), scroll casing and draft tube. Between the scroll casing and the Impeller there are

guide vanes, which guides the water on to the impeller thus rotating the Impeller shaft. There are eight

guide vanes, which can be turned about their own axis so that the angle of inclination may be adjusted

while the turbine is in motion. When guide vane angles are varied, high efficiency can be obtained

over wide range of operating conditions.

Figure 1. Construction of Francis Turbine

Work done, power and efficiency of an inward radial flow reaction turbine:


Figure 2. Velocity diagram for an inward flow reaction turbine

Let,

Tangential velocities of wheel at inlet and outlet

Outer and inner diameter of runner

And

N= speed of the turbine in RPM

The meanings of the other terms are same as that of Pelton turbine

The work done per second by the water on the runner is called as runner power. It s given by,

The work done per second per unit weight of water striking per second is,

The above equation is called Euler’s equation of hydrodynamic machines.

Efficiency of Reaction turbine:

1. Hydraulic Efficiency:


If β=900 and =0, then

2. Mechanical Efficiency:

3. Overall Efficiency:

Working Proportions of Francis Turbine:

1 Ratio of width to the diameter (n):

Let B1= width of the blade at inlet

D1= diameter of runner blade then

2 Flow Ratio :

It is defined as the ratio of flow velocity at inlet to the theoretical jet velocity.

It varies in between 0.15 to 0.30.

3 Speed ratio (ψ):

It is the ratio of peripheral speed at inlet to theoretical jet velocity.

It varies in between 0.6 to 0.9.

4 Discharge of turbine (Q):

If thickness of the vane is considered then,

Where; Z = Number of Vanes

t = thickness of each vane

6 Head available at the inlet of turbine (Q) :


If there is no loss energy when water flows through the vanes then

7 Specific speed for reaction turbine (Ns):

8 Degree of Reaction :

Degree of reaction is defined as the ratio of change in pressure energy inside a runner to the

total energy change inside the runner.



A Trial on Francis Turbine:

Description:

The actual experiment facility supplied consists of a sump tank, centrifugal pump set, turbine

unit and Venturimeter arranged in such a way that the whole unit works on re-circulating water

system. The centrifugal pump set supplies the water from the sump tank to the turbine through control

valve (Gate valve). The water from the pump passes through a Venturimeter (for measurement of

discharge) to the turbine unit enters the sump tank through the draft tube.

The loading of the turbine is achieved by a brake drum with rope & spring balance, provision

for measurement of turbine speed (Mechanical tachometer), Head on turbine (pressure gauge) are

built in on the control panel.

Specifications:

1. Francis Turbine: 1 KW (1.34 HP)

2. Pump Discharge Q: 680 lpm

3. Motor: 5HP/3000rpm/420V/3-Phase induction.

4. Inside diameter of pipe: 65mm

5. Venturimeter coefficient: 0.98

6. Throat diameter ratio: 0.6

7. Hanger Weight: 1kg

8. Brake drum diameter: 0.2m

9. Brake drum rope diameter: 15mm

Procedure:

1. Keep the guide vanes at required opening.

3. Prime the pump if necessary.

4. Start the pump to circulate water to the turbine.

5. Open the gate valve for required discharge.

6. Load the turbine by adding weights in the weight hanger. Open the brake drum cooling water

gate valve for cooling the brake drum.

7. Measure the turbine rpm with tachometer.

8. Note the pressure gauge and vacuum gauge readings:

9. Note the venturimeter pressure gauge readings.

10. Repeat the experiments for other loads.

11. For constant speed tests, the main sluice valve has to be adjusted to vary the inlet head and

discharge for varying loads (at a given guide vane opening position).

12. The experiment can be repeated for other guide vane positions.

Observation Tables:



Sr. No.

Inlet Pressure

(P) in kg/cm

2

Outlet Pressure

(V) in mm of

Hg

Speed ‘N’ In

RPM

Spring Balance ‘S1’ in

Kg


Kg

Net Load

‘S1-S2’ in Kg

Venturimeter meter Pressure Gauge Reading

P1 in kg/cm

2

P2 in kg/cm

2


a)

b)

c)

d)

e)


Sr. No.

Inlet Pressure

(P) in kg/cm

2

Outlet Pressure

(V) in mm of

Hg

Speed ‘N’ In

RPM


Kg


Kg

Net Load

‘S1-S2’ in Kg

Venturimeter meter Pressure Gauge Reading

P1 in kg/cm

2

P2 in kg/cm

2


a)

b)

c)

d)

e)


Sample Calculations:

1. Inlet Head of Water:

Where P = turbine pressure gauge reading

V = vacuum gauge reading

2. Discharge through pipe (Q):

Inlet pressure gauge reading P1 kg/cm2 = ……………………

Throat pressure gauge reading P2 kg/cm2 = ……………………

Pressure difference dh =

Where

B= throat diameter ratio

3. Water power input (Pin):

4. Power developed by turbine/shaft Power (Ps):

Where

5. Overall Efficiency :


6. Unit Quantities ( , , and )

Result Tables:


Sr. No.

Total Head in ‘m’

Discharge Q in m

3/sec

Power Input

Pin in KW

Power Output Ps in KW

Overall Efficiency

η0 in %

f)

g)

h)

i)

j)


Sr. No.

Total Head in ‘m’

Discharge Q in m

3/sec

Power Input

Pin in KW

Power Output Ps in KW

Overall Efficiency

η0 in %

a)

b)

c)

d)

e)


Conclusions:

__________________________________________________________________________________

__________________________________________________________________________________

______________________________________________________________________________

Graphs:

I) Plotting of Main Characteristics

1. Plot V/S (

2. Plot V/S

3. Plot V/S

II) Plotting of Operating Characteristics

1. Plot (Q) V/S

2. Plot (Q) V/S


EXPERIMENT NO.4

AIM: STUDY AND TRIAL ON CENTRIFUGAL PUMP AND PLOTTING OF OPERATING

CHARACTERISTICS.

Objective: The purpose of this experiment is to study the constructional details and performance

parameters of Centrifugal pump.

APPARATUS

a) Centrifugal pump set, sump tank, measuring tank, piping to operate the pump on closed

circuit water circulating system.

b) Digital RPM indicator, pressure gauge, flow control valve.

Introduction:

Pump is a machine or mechanical equipment which is required to lift liquid from low level to

high level or to flow liquid from low pressure area to high pressure area or as a booster in a piping

network system.

Principally, pump converts mechanical energy of motor into fluid flow energy.

Pump also can be used in process operations that require a high hydraulic pressure. This can

be seen in heavy duty equipment’s. Often heavy duty equipment’s requires a high discharge pressure

and a low suction pressure. Due to low pressure at suction side of pump, fluid will lift from certain

depth, whereas due to high pressure at discharge side of pump, it will push fluid to lift until reach

desired height.

Classification of Pumps

Pumps are divided into 2 major categories: Dynamic and Positive Displacement

Positive displacement pumps: A Positive Displacement Pump has an expanding cavity on

the suction side and a decreasing cavity on the discharge side. Liquid flows into the pumps as

the cavity on the suction side expands and the liquid flows out of the discharge as the cavity

collapses. The volume is a constant given each cycle of operation. A Positive Displacement

Pump, unlike a Centrifugal or Roto-dynamic Pump, will produce the same flow at a given

speed (RPM) no matter the discharge pressure. A Positive Displacement Pumps is a "constant

flow machine". Positive Displacement Pump must never operate against closed valves on the

discharge side of the pump - it has no shut-off head like Centrifugal Pumps. A Positive

Displacement Pump operating against closed discharge valves continues to produce flow

until the pressure in the discharge line is increased until the line bursts or the pump is

severely damaged - or both.

http://www.engineeringtoolbox.com/centrifugal-pumps-d_54.html




A relief or safety valve on the discharge side of the Positive Displacement Pump is absolute

necessary. The relief valve can be internal or external the pump. An internal valve should in

general only be used as a safety precaution. An external relief valve installed in the discharge

line with a return line back to the suction line or supply tank is highly recommended.

Figure 1 Types of pumps

Dynamic Pumps:

In dynamic pumps the water is always in contact with the rotor while working and has a

relative motion with the impeller. This action of the water is called as dynamic action of water. Casing

of the pumps are in such a way that the rotor and casing has a clearance, this would be result in

leakage losses in dynamic pumps. These types of the pumps are more suitable in the application

where high discharge is required. The rotodynamics pumps are those pumps in which energy level is

increased due to combination of centrifugal energy, pressure energy and kinetic energy.


Centrifugal Pump:

The centrifugal pump is the type of rotodynamics pump. Centrifugal pump is one of the basic

and a superb piece of equipment possessing numerous benefits over its contemporaries. The main

advantages of a centrifugal pump includes its higher discharging capacity, higher operating speeds ,

lifting highly viscous liquids such as oils, muddy and sewage water, paper pulp, sugar molasses,

chemicals etc. against the reciprocating pumps which can handle relatively small quantity of liquid

operating at comparative slower range of speeds that is limited to pure water or less viscous liquids

free from impurities limited from the considerations of separation ,Cavitation and frequent choking

troubles. The overall maintenance cost of a centrifugal pump is also comparatively lesser due to less

wear and tear. While major disadvantage includes vulnerability to a complexities of eddies

formations, noise and vibrations and inability to generate higher pressures as executed by the

reciprocating pumps.

Components of Centrifugal pump:

The main parts of the centrifugal pumps are as follows;

1. Impeller

2. Casing

3. Suction Pipe

4. Delivery pipe

1. Impeller: it is a wheel or rotor which is provided with a series of backward curved blades or

vanes, . It is mounted on a shaft which is coupled to an external source of energy (usually an

electric motor) which imparts the required energy to the impeller of the system thereby making it

to rotate as desired. The impellers may be classified as closed, semi-open and open types. Closed

or shrouded impeller has vanes provided with metal cover plates or shrouds on both sides. These

plates or shrouds are known as crown plate and lower or base plate the closed impeller provides

better guidance for the liquid and is more efficient. However, this type of impeller is most suited

when the liquid to be pumped is pure and comparatively free from debris. Semi-Open impeller

has vanes provided only with the base plate and no crown plate. Such impeller is suitable for the

liquids charged with some debris. An Open impeller is that whose vanes have neither the crown

plate nor the base plate. Such impellers are useful in the pumping of liquids containing suspended

solid matter, such as paper pulp, sewage and water containing sand or grit. These impellers are

less liable to clog when handing liquids charged with a large quantity of debris.

2. Casing: It is an airtight chamber which surrounds the impeller. It is similar to the casing of a

reaction turbine. The two different types of casings commonly adopted are volute and diffuse

types. Volute casinghas impeller surrounded by a spiral shaped casing which is known as volute

chamber. The shape of the casing is such that the sectional area of flow around the periphery of

the impeller gradually increases towards the delivery pipe. This increase in the cross-sectional

area results in developing a uniform velocity throughout the casing, because as the flow

progresses towards the delivery pipe, more and more liquid is added to the stream from the


periphery of the impeller. Diffuser casing has impeller surrounded by a series of guide vanes

mounted on a ring called diffuser ring. the diffuser ring and the guide vanes are fixed in position.

The adjacent guide vanes provide gradually enlarged passages for the flow of liquid. The liquid

after leaving the impeller passes through these passages of increasing area, wherein the velocity

of flow, decreases and the pressure increases. The guide vanes are so designed that the liquid

emerging from the impeller enters these passages without shock. After passing through the guide

vanes the liquid flows into the surrounding casing.

3. Suction Pipe: t is a pipe which is connected at its upper end to the inlet of the pump or to the

centre of the impeller which is commonly known as eye. The lower end of the suction pipe dips

into liquid in a suction tank or a sump from which the liquid is to be pumped or lifted up. The

lower end of the suction pipe is fitted with a foot valve and strainer. The liquid first enters the

strainer which is provided in order to keep the debris away from the pump. It then passes through

the foot valve to enter the suction pipe. A 'foot valve' is a non-return or one-way type of valve

which opens only in the upward direction. As such the liquid will pass through the foot valve only

upwards and it will not allow the liquid to move downwards back to the sump.

4. Delivery Pipe: It is a pipe which is connected at its lower end to the outlet of .the pump and it

delivers the liquid to the required height. Just near the outlet of the pump on the delivery pipe a

valve is invariably provided. A delivery valve is a regulating valve which is of sluice type and is

required to be provided in order to control the flow from the pump into delivery pipe.

Working of centrifugal pump:

The basic principle on which a centrifugal pump works is that when a certain mass of liquid is

made to rotate by an external force, it is thrown away from the central axis of rotation and a

centrifugal head is impressed which enables it to rise to a higher level. The centrifugal action converts

energy of an electric motor or engine via the associated shaft into velocity or kinetic energy and then

into pressure of a fluid that is being pumped. The energy changes occur into two main parts of the

pump, the impeller and the volute. The impeller is the rotating part that converts driver energy into the

kinetic energy. The volute is the stationary part that converts the kinetic energy into pressure. Liquid

enters the pump suction and then the eye of the impeller. Whirling motion is imparted to the liquid by

the means of backward curved blades mounted on a wheel known as impeller. When the impeller

rotates, it spins the liquid sitting in the cavities between the vanes outward and imparts centrifugal

acceleration. As the liquid leaves the eye of the impeller a low pressure area is created at the eye

allowing more liquid to enter the pump inlet. The pressure head developed by centrifugal action is

entirely due to velocity imparted to the liquid by the rotating impeller and not due to any displacement

or impact.


Fig. 2 Centrifugal Pump

Fig. 3 Types of impeller

Fig 4. Types of Casings [Note: Fig. 2 shows a) volute casing]

Work done by Centrifugal Pump or by Impeller on Liquids:


Fig 5. Velocity Triangle for an Impeller

In case of centrifugal pump the liquid enters the impeller radially at inlet which means the absolute

velocity of water at inlet makes an angle of 900 (α = 90

0) with the direction of motion of an impeller at

inlet. Therefore the whirl component is zero and the flow component is equal to absolute

velocity . There is no loss of energy in the impeller due to friction and formation of eddies. There is

no loss of energy due to shock at entry. There is uniform velocity distribution in the space between

two adjacent vanes. The fig. shows a portion of the impeller of a centrifugal pump with one vane and

the velocity triangle at the inlet and outlet tips of the vane.

Let,

D1 = Impeller diameter at inlet in m = 2R1

D2 = Impeller diameter at outlet in m = 2R2

R1 & R2 = Impeller radius at inlet and outlet respectively

N = Speed of impeller in RPM

u1 = Tangential velocity of impeller at inlet in m/sec

u2 = Tangential velocity of impeller at outlet in m/sec

V1 & V2 = Absolute velocity at inlet and outlet respectively.

Vf1 & Vf2 = velocity of flow at inlet and outlet respectively.

Vw1 & Vw2 = velocity of whirl at inlet and outlet respectively.

Vr1 & Vr2 = Relative velocity at inlet and outlet respectively.

α = Angle made by absolute (V1) at inlet with the direction of rotation of vane.

θ = Angle made by relative velocity (Vr1) at inlet with the direction of motion of vane.

β = Angle made by absolute (V2) at outlet with the direction of rotation of vane.


ϕ = Angle made by relative velocity (Vr2) at outlet with the direction of motion of vane.

The centrifugal pump is the reverse of radially inward flow reaction turbine. But for radially inwards

flow reaction turbine the work done by the liquid on the runner per second per unit weight of liquid

striking per second is given by,

Now work done by the pump impeller on the water per second per unit weight of water striking per

second is;

This head developed by the pump is called as Eulers’s head.

Similarly, work done by the pump impeller on water per second is,

Discharge or volume flow rate of the water is given by,

= width of an impeller at inlet and outlet in ‘m’

Various Heads of Centrifugal Pump:

1. Suction Head (hs): it is the vertical between level of sump and eye of an impeller. It is also called

as suction lift.

2. Delivery Head (hd): it is the vertical distance between the eye of an impeller and the level at

which water is delivered.

3. Static Head (Hs): it is the sum of suction head and delivery head. It is given by,

4. Manometric head (Hm): the head against which the centrifugal pump has to work is called as

Manometric head. It is given by;

If the losses are neglected then,

Various Efficiencies of a Centrifugal Pump:


1. Manometric efficiency ( : it is the ratio of Manometric head developed by the pump to the

head imparted to the liquid. Mathematically,

2. Volumetric efficiency ( : it is defined as the ratio of quantity of liquid discharged per second

from the pump to quantity passing per second through the impeller. Mathematically,

Where Q = Actual liquid discharged at the pump outlet per second

q = Leakage of liquid per second from impeller

3. Mechanical Efficiency ( : it is defined as the ratio of the power delivered by the impeller to

the power input to the pump shaft. Mathematically,

4. Overall Efficiency ( : it is defined as the ratio of the output power of the pump to the input

power of the pump. Mathematically,

It is also given by,



A Trial on Centrifugal Pump:

Description:

A Centrifugal Pump consists of an impeller rotating 'inside a casing. The impeller has a

number of curved vanes. Due to the centrifugal force developed by the rotation of the impeller, water

entering at the centre flows outwards to the periphery. Here it is collected in a gradually increasing

passage in the casing known as a volute chamber. This chamber converts a part of the velocity head

(kinetic energy) of the water into pressure head (potential energy). For higher heads, multistage

centrifugal pumps having two or more impellers in series will have to be used.

The test pump is a single stage centrifugal pump of size (50mmx50mm). It is coupled to a 5

HP capacity three phase AC motor by means of a cone pulley belt drive system.

An energy meter and a stop watch are provided to measure the input to the motor and a

collecting tank to measure the actual discharge. A pressure gauge and a vacuum gauge are fitted in the

delivery and suction pipe lines to measure the pressure at respective locations.

NOTE: Since the centrifugal pump is not self priming, the pump must be filled with water (priming)

before starting. For this reason, water should not be allowed to drain and a foot valve is provided.

Specifications:

1. Area of measuring tank: 500x500 mm2

2. Level difference between vacuum and delivery gauge (x) : 320mm

3. Energy meter constant (K):

4. Centrifugal pump size: 50mmx50mm

5. Motor: 5 HP/Squirrel cage/Three Phase induction

6. Suction side pipe diameter: 2” inch

7. Delivery side pipe diameter: 2” inch

Procedure:

1. Loosen the V-belt by rotating the hand wheel of the motor bed and position the V-belt in the

required groove of the pulley.

2. Prime the pump with water if required.

3. Close the delivery gate valve completely.

4. Start the motor and adjust the gate valve to required pressure and delivery.

5. Note the observations

6. Note down the energy meter reading.

7. Note down suction and delivery side pressure.

8. Take 5 or 6 sets of readings by varying the held from a maximum at shut off to a minimum

where gate valve is fully open. The experiment is repeated for other pump speeds.


Precautions:

1) Priming is necessary if pump doesn’t give discharge.

2) Leakage should be avoided at joints.

3) Foot valve should be checked periodically.

4) Lubricate the swivelled joints & moving parts periodically.

Observation Table:

Sr.

No.

Pressure gauge

reading (Delivery)

Kg/cm2

Vacuum gauge

reading (mm of

Hg)

Time for 10

revolution of

energy meter (sec)

Time for

100mm rise of

water (sec)

Speed (N)

RPM

1 0.4

2 0.6

3 0.8

4 1.

5 1.2


1. Determination of Total Head (H):

2. Determination of Discharge (Q):

3. Power output of pump (Pout):


4. Power input to the pump (Pin):

Pin can be calculated from the energy meter reading.

5. Overall efficiency ( :

Result Table:

Sr. No.

Total Head (H) in m

Flow rate (Q) in m

3/sec

Power output (Pout) in KW

Power input (Pin) in KW

Overall Efficiency (ηo)

in %

1

2

3

4

5

6

Graphs:

1. Plot (Q) V/s (H)

2. Plot (Q) V/s (

3. Plot (Q) V/s (


EXPERIMENT NO.5

AIM: INDUSTRIAL VISIT REPORT ON BHIRA HYDROPOWER STATION.

- POINTS TO BE CONSIDERED FOR REPORT WRITING

1. Power plant profile

i. Name of the power plant

ii. Year of Establishment

iii. Owned by

iv. Address

v. Name of the dam

vi. Name of the river

vii. Power generation Capacity of the plant

viii. Name of the instructor, his/her position in power plant

2. Power plant layout (Explain with Diagram)

3. Specifications of the Turbine

4. Specifications of the Generator

5. Specifications of Tail race

6. Working of the power plant

7. Information regarding actual power generation at turbine at step up transformation.

8. Write a note on Synchronization with the grid.

9. No. of the villages or city’s under power circulation.

10. Few words about your experience with the power plant


EXPERIMENT NO.6

AIM: STUDY OF MULTISTAGING OF STEAM TURBINE.

Introduction:

To improve the thermal efficiency of any power plant, generally high pressure (near about

120 to 140 bar), high temperature and high-velocity steam is used. Steam expands from boiler

pressure to the condenser in one stage. So, steam's pressure drop and it will increase its velocity. This

high-velocity strikes the turbines rotor and the speed of the rotor becomes high. Compounding of

steam turbine is used to reduce the rotor speed. It is the process by which rotor speed come to its

desired value. A multiple system of rotors are connected in series keyed to a common shaft and the

steam pressure or velocity is absorbed in stages as it flows over the blades. Generally, three different

types of compounding are used to reduce the rotor speed of steam turbine

Need of Compounding:

If high velocity of steam is allowed to flow through one row of moving blades, it produces a

rotor speed of about 30000 rpm which is too high for practical use. It is therefore essential to

incorporate some improvements for practical use and also to achieve high performance. This is

possible by making use of more than one set of nozzles, and rotors, in a series, keyed to the shaft so

that either the steam pressure or the jet velocity is absorbed by the turbine in stages. This is called

compounding. Two types of compounding can be accomplished: (a) velocity compounding and (b)

pressure compounding

Either of the above methods or both in combination are used to reduce the high rotational

speed of the single stage turbine.

The following are the methods used for compounding of steam turbine;

a) Velocity Compounding

b) Pressure Compounding

c) Pressure-Velocity Compounding

1. Velocity Compounding:

The velocity-compounded impulse turbine was first proposed by C.G.

Curtis to solve the problems of a single-stage impulse turbine for use with high pressure and

temperature steam. In velocity compound impulse turbine, moving and fixed blades are placed

alternately. Moving blades are fitted with the wheel while the fixed blades are fitted with the casing.

The steam is expanded in the nozzle from the boiler pressure to condenser pressure, to a high velocity.

It is then passed over the first ring of moving blades. Only a portion of the high velocity of steam jet

is absorbed by this blade ring, the remainder being exhausted on to the next ring of fixed or guide

blades. These fixed blades change the direction of steam jet.

http://www.mechanicaltutorial.com/thermal-and-overall-efficiency-of-thermal-power-plant

http://www.mechanicaltutorial.com/working-principle-of-steam-turbine-classification-or-types-of-steam-turbine


Fig 1. Velocity Compounding

The jet is then passed on to the next ring of moving blades. A further portion of the steam

velocity is now absorbed by this second moving blade ring. The process is then repeated as the steam

flows over the remaining pairs of blades until practically all the velocity of the jet has been absorbed

and the kinetic energy is converted into mechanical work.

It should be noted that the entire pressure drop takes place in the nozzle itself, the pressure

remaining constant, as the steam flows over the blades. Hence the turbine is an impulse turbine. The

Curtis turbine is an example of velocity compound impulse turbine.

Advantages:

1. This arrangement needs small space.

2. This is very reliable and easy to operate.

3. Initial cost is low for this arrangement.

4. Since nozzle's steam is considerable, the turbine does not need to work in high pressure and

turbines structure need not be very strong.

Disadvantages:

1. Friction loss is high due to high velocity of steam of nozzle.

2. Its efficiency is low. Because the ratio of blade velocity and steam velocity is not optimum.

http://www.mechanicaltutorial.com/losses-in-steam-turbine

http://www.mechanicaltutorial.com/calculate-different-types-of-steam-turbine-efficiency-improvement-of-steam-turbine-efficiency


3. First, row is developed maximum power in this system. Later rows are developed very small

power rather than first row. But fabrication and cost of materials will be same in all rows.

Fig. Curtis Turbine

2. Pressure Compounding:

To alleviate the problem of high blade velocity in the single-stage impulse turbine, the total

enthalpy drop through the nozzles of that turbine are simply divided up, essentially in an equal

manner, among many single-stage impulse turbines in series (Figure 2). Such a turbine is called a

Rateau turbine, after its inventor. Thus the inlet steam velocities to each stage are essentially equal

and due to a reduced Δh.

The arrangement consists of a number of simple impulse turbines in series mounted on a

common shaft. The exit steam from one turbine is made to enter the nozzle of the succeeding turbine.

Each of the simple impulse turbines would then be termed a "stage" of the turbine. Each stage

comprises its ring of nozzle and blades. The steam from the boiler passes through the first nozzle ring

where its pressure drops and velocity increases. The high velocity jet steam is directed onto the first

moving blades wherein nearly all of its velocity is absorbed. The steam pressure remains unaltered.

The steam from the first ring of moving blades enters the second ring of nozzles where its pressure is

further reduced and velocity increased again. The next ring of moving blades absorbs the velocity

obtained from this second ring nozzle. The process is repeated in the remaining rings until the whole

of the pressure has been absorbed.


Fig. 2 Pressure Compounding

So, the total pressure drop of the steam does not take place in the first nozzle, but is split

equally between all the nozzle rings in the arrangement. The effect of absorbing the pressure drop in

stages is to reduce the velocity of the steam entering the moving blades.

Fig Rateau Turbine


Advantages:

1. Speed ratio remain constant in turbine

Disadvantages:

1. Large number of stages required

2. Expensive method of compounding

3. Pressure and Velocity Compounded Impulse Turbine:

This type of turbine is a mixture of pressure and velocity compounding. There are two wheels

or rotors and on each, only two rows of moving blades are attached since two-row wheel are efficient

than three-row wheel. In each wheel or rotor, velocity falls i.e. drop in velocity is achieved by more

rows of moving blades hence it is velocity compounded. There are two sets of nozzles in which whole

pressure drop takes place i.e. whole pressure drop has been divided in little drops, hence it comes

under pressure-compounded.


In the first set of nozzles, there is some drop in pressure, which provides some kinetic energy

to the steam and there is no fall in pressure in the two rows of moving blades of the primary wheel

and in the first row of fixed blades. Only, there is a velocity drop in moving blades while there is also

a slight fall in velocity due to friction in the fixed blades. In second set of nozzles, the remaining

pressure fall takes place but the velocity here raises and the drop in velocity takes place in the moving

blades of the second wheel or rotor.

Fig. Pressure Velocity Compounded Turbine (Curtis Turbine)

Compared to the pressure-compounded impulse turbine this arrangement was quite popular

because of its simple construction. It is, however, not often used now due to its low efficiency

reasons.

Conclusions:

1.

2.


EXPERIMENT NO. 7

AIM: STUDY AND TRIAL ON CENTRIFUGAL BLOWER AND PLOTTING OF PERFORMANCE

CHARACTERISTICS

Introduction:

Fans and blowers provide air for ventilation and industrial process requirements. Fans

generate a pressure to move air (or gases) against a resistance caused by ducts, dampers, or other

components in a fan system. The fan rotor receives energy from a rotating shaft and transmits it to the

air.

Blowers are turbo machines which deliver air at a desired high velocity (and accordingly at a

high mass flow rate) but at a relatively low static pressure.

The rise in static pressure across a blower is relatively higher and is more than 1000 mm of

water gauge that is required to overcome the pressure losses of the gas during its flow through various

passages. A blower may be constructed in multi stages for still higher discharge pressure

Difference between Fans, Blowers and Compressors:

Fans, blowers and compressors are differentiated by the method used to move the air, and by

the system pressure they must operate against. As per American Society of Mechanical Engineers

(ASME) the specific ratio – the ratio of the discharge pressure over the suction pressure – is used for

defining the fans, blowers and compressors (see Table 7.1)

DIFFERENCES BETWEEN FANS, BLOWERAND COMPRESSOR

Equipment Specific Ratio Pressure rise (mmWg)

Fans Up to 1.11 1136

Blowers 1.11 to 1.20 1136 – 2066

Compressors more than 1.20 -

Type of Fans:

Fan and blower selection depends on the volume flow rate, pressure, type of material handled,

space limitations, and efficiency. Fan efficiencies differ from design to design and also by types.

Typical ranges of fan efficiencies are given in Table 7.2. Fans fall into two general categories:

centrifugal flow and axial flow. In centrifugal flow, airflow changes direction twice - once when


Entering and second when leaving (forward curved, backward curved or inclined, radial) in axial

flow, air enters and leaves the fan with no change in direction (propeller, tube axial, vane axial).

FAN EFFICIENCIES

Type of Fans Peak Efficiency Range

Centrifugal Fans

Aerofoil, backward curved/inclined 79-83

Modified Radial 72-79

Radial 69-75

Pressure Blower 58-68

Forward Curved 60-65

Axial Fans

Vane Axial 78-85

Tube Axial 67-72

Propeller 45-50

Centrifugal Blower:

Blowers can achieve much higher pressures than fans, as high as 1.20 kg/cm2. They are also

used to produce negative pressures for industrial vacuum systems. Major types are: centrifugal blower

and positive-displacement blower. Centrifugal blowers look more like centrifugal pumps than fans.

The impeller is typically gear-driven and rotates as fast as 15,000 rpm. In multi-stage blowers, air is

accelerated as it passes through each impeller. In single-stage blower, air does not take many turns,

and hence it is more efficient. Centrifugal blowers typically operate against pressures of 0.35 to 0.70

kg/cm2, but can achieve higher pressures. One characteristic is that airflow tends to drop drastically as

system pressure increases, which can be a disadvantage in material conveying systems that depend on

a steady air volume. Because of this, they are most often used in applications that are not prone to

clogging.

The centrifugal (or radial) blowers are generally characterized by high static pressure and

high efficiency at the working point. The air is sucked in the same direction as the wheel’s shaft and

pushed in a radial direction.

The centrifugal blowers are classified according to the direction of the blade curvature with

respect to the rotation of the wheel. So they are classified as forward curved blade, backward curved

blade or radial blade blowers.


Fig 7.1 Type of Impellers

The set-up of the blade curvature gives significant differences in the blower performance. The

forward curved blade centrifugal blowers are to be always used with the wheel placed in a housing,

contrary to the backward curved blade blowers. The latter in fact increases the air pressure within the

blades. According to the aeraulic or geometric requirements, the suction side of the forward curved

blade blowers can be single or dual.

Forward curved centrifugal Blower

Fig 7.2 Forward curved centrifugal Blower

Amongst the primary features of the centrifugal blowers with forward curved blades there is

the high power density, which means a high pressure of air flow produced within a confined space.

These blowers are suited to applications where a large air volume is to be moved within a small space.

The noise generated by these units is relatively low. They can be used both as exhaust fans or as

blowers. The efficiency in the working point can be maximized, but when the working point

approaches the free air point, the input power can increase considerably. The housing of the single


suction blowers is open only on one side. The main features of this range of products by Trial are high

efficiency, low noise, high static pressure, rugged design and reduced size. The motor types applied

on this blower include: shaded pole, external rotor PSC or brushless.

Applications

Fans

Boilers and burners

Printing and offset machines

Industrial machinery

Fume or vapour extractors

Backward centrifugal Blower

Fig 7.3 Backward centrifugal Blower

The backward curved blade blowers stand out for the number of blades (6 to 14) which are

much larger than the forward curved ones and for the reverse rotation sense. The backward curved or

negative blade blowers normally run at a high rotational speed and result in a high pressure air flow.

They are normally used as exhaust units. These blowers match a good aeraulic efficiency to a low

noise level. A significant feature of this type of blower is that the blades will not gather dirt particles

thanks to the shape.

Applications:

Extractor hoods

Pellet stoves and fireplaces

Central units for air conditioning

Ventilation systems for buildings


Dual inlet Centrifugal Blower

Fig 7.4 Dual inlet blower

The scroll of the dual suction centrifugal blower is open on both sides. The wheel length to

axial size ratio is thus maximized. The main features of this range of Trial products are: high

efficiency, low noise, rugged design and small size. It is designed to produce low noise when the

supply comes from an electronic speed regulator (Triac) belongs to this family. The motors foreseen

for this blower are: shaded pole, external rotor PSC or brushless. The wheel diameters range from 76

to 133mm with 87 to 196 mm length.

Applications:

Pellet stoves

Fireplaces

Ventilation units



A Trial on Centrifugal Blower:

To find out the inlet and outlet velocity, the Pitot tube is provided. A differential manometer

is provided to find out the difference of pressure of pilot tube and Static tube. Energy meter is

provided to find out the input H.P. to blower so that to find out the overall efficiency of blower. For

changing the discharge and head, a valve is provided at outlet.

Fig 7.5 Centrifugal Blower Test Rig

Observations:

1. Delivery pipe diameter : 0.02m

2. Energy meter constant : 900rev/Kw-hr

3. Room temperature :___________0C

4. Barometer Reading : _____________mm of Hg

5. Blower capacity : 750watt

Observation Table:

Sr. No.

Valve Opening

Delivery Head (Section-I)

(mm of water)

Deliver Temp. (section-I)

(0C)

Head at Section-II

(mm of water)

Time for 2revolution of energy meter

(sec)

1 Full Open

2 ¾ open

3 ½ open

4 ¼ open


Precautions:

1. To operate the blower test rig, close the delivery valve and start the blower.

2. Take the readings of static tube, Pitot tube and differential pressure by operating the suitable

valves provided on differential Manometer.

3. Take the reading of Pitot tube at all the positions and find out the mean reading. By this

procedure, inlet and outlet readings can he found.

4. Record the energy meter Rev/Time to find out the H.P. input.

5. Now open the outlet valve at desired position and repeat the procedure of readings.

6. From the above observed readings, inlet velocity, outlet velocity, discharge, head, Output,

efficiency can be found by applying given formulae.

7. Repeat this procedure at different openings of valves provided at outlet.


1. Determination of Density of air at inlet of the blower (ρ1):

Where, R

2. Determination of Density of air at outlet of the blower (ρ2):

3. Determination of Discharge (Q):


4. Power output of blower (Pout):

5. Input Power to the Blower (Pin):

6. Overall Efficiency (ηo):

Result Table:

Sr. No.

Valve Opening

Discharge Q in m

3/sec

Head (H) in m of air

Pin in KW Pout in KW Overall

Efficiency (ηo)

1 Full Open

2 ¾ open

3 ½ open

4 ¼ open

Conclusions:

1. ___________________________________________________________________________

2. _________________________________________________________________________

Graphs:

1. H V/S Q

2. Pin V/S Q

3. ηo V/S Q


EXPERIMENT NO. 8

AIM: DESIGN OF PUMPING SYSTEM INSTALLATION USING MANUFACTURES CATALOGUE FOR

HOUSING SOCIETY (THE REGENT PARK)

Address of Housing Society:

‘THE REGENT PARK’,

Gat No. 435/3, Kaljewadi, Charholi Bk.

Pune- 412105

Fig 8.1 Actual Photograph of site (The Regent Park)

Introduction:

Water pumping is required in situations where site conditions do not favour the use of gravity

supply. This may occur in irrigation or water supply projects. In either case, gravity systems tend to

involve high capital costs but low operating costs. On the other hand, pumping systems tend to require

lower capital costs but high operating costs. The choice between gravity supply, and pump fed supply

is therefore, an economic one. When the economic case is not obvious, then the economic viability of

each alternative must be established, and the economically superior alternative chosen.


Design specifications for pumping systems:

The requirements to be met by any pumping system are specified as:

1. A discharge flow rate for transfer of liquid from suction to discharge reservoir

2. A total pressure head to be overcome by pumping system.

Specification of the discharge flow rate required:

The discharge flow rate required is stated in litres per second (l/s), or cubic metres per

second (m3/sec). It is determined by a study of water demand.

Water demand is determined by segregating the total demand into categories such as;

1 Total water consumption per day of individual

2 Total water consumption per day of each flat

Total no of flats in the society – 60

No. of inhabitants living in society – 183

1. Total water consumption per individual

1. Brushing – 3 litres/day

2. Bathing – 25 litres/day

3. Flushing – 20 litres/day

4. Drinking – 8 litres/day

So, Total water consumption for everyday of every individual is;

2. Total water consumption per each Flat

1. Washing (Cloths) - 30 litres/day

2. Washing (Utensils) - 20 litres/day

3. Cooking - 10 litres/day

4. Cleaning (Floor) - 30 litres/day

5. Cleaning (Furniture) - 5 litres/day

6. Cleaning (Bathrooms and toilets) - 15 litres/day

7. Miscellaneous – 15 litres/day

So, Total water consumption for everyday of every flat is;


Now, Total daily water consumption of the housing society is given by;

Now, assume that the working hours of the pump is 2 hours/day

Now,

From water consumption and working time of pump, the required discharge can be calculated as;

So, total daily discharge requirement of the pump is 2.5 litres/sec or

So, from above calculation it is found that the discharge requirement of the pump is

Preliminary design procedure for pumping system

The design of a pumping system therefore proceeds in three steps;

(a) Survey of site conditions;

(b) Selection of a pipeline;

(c) Selection of a pump.

(a) Survey of Site conditions:


This step determines the opportunities and constraints of the environment at which the

pumping system is to be located. The essential data to be determined in this physical survey of the site

is pipeline length and static head to be overcome by pumping.

i. Pipeline route and length: The specification of pipeline length is determined through a survey of

the intended pipeline route.

ii. Determination of Static Head: This is the level difference between suction reservoir and

delivery reservoir.

(b) Pipeline selection:

A preliminary selection of the pipeline is therefore made using a recommended flow velocity

for water pipelines. This flow velocity recommended for preliminary design of water pipelines is

chosen such that pressure losses due to fluid friction in pipeline are kept within acceptable limits. This

ensures that pumping equipment size and costs are also kept within certain limits. The recommended

range of flow velocities for water pipelines, to be applied during preliminary design, is between 1 and

3 m/s. After this preliminary stage, the design specifications should guide further decisions

i. Selection of Pipe size

The selection of pipe size is the first step in system design. The pipe size is selected such that

the flow velocity, when the pipeline delivers the design flow rate, remains within a specified

range. The flow velocity recommendation is an empirical guide, aimed at the compromise of

ensuring that the pressure loss due to fluid friction in the pipeline is not too high, while the

discharge flow rate through the pipeline is also not too low. The trade-off is therefore between the

size of pump, and the size of pipe. The total head to be overcome dictates the size of pump. The

size of pump therefore depends on the friction loss in pipe; and this in turn varies inversely with

the size of pipe. The size of pump therefore varies inversely with the size of pipe. For a given set

of design specifications therefore, the smaller the pipe selected, the larger the pump required, and

vice versa, all else being equal.

ii. Selection of Pipe material

The pressure loss due to fluid friction in pipeline depends on the pipe size, material, length,

fittings, and flow velocity. The second step in the selection of pipeline is therefore to select the

pipe material. The available pipe materials for water pipelines are: UPVC (plastic), steel, cast

iron, and ductile iron.

After studying different types of the pipes from catalogue of the different manufactures, it is

decided to select PVC-U plumbing pipe of diameter 2 inch =50mm, from FINOLEX

CATALOGUE.


PVC-U plumbing pipe: it is hard and rigid with an ultimate tensile

stress of approximately 52Mpa at 200C and is resistant to most

chemicals. Generally PVC-U can be used at temperature upto 600C,

although the actual temperature limit is depends on stress and

environmental conditions. This type of the pipe is generally used for the

water distribution to the housing society.

Fig. Finolex PVC-U Pipe

(c) Pump selection:

(i) Head loss due to friction in pipeline;

Once the selection of pipe size and material is made, the pressure head loss due to fluid

friction in pipeline can be determined.

Specification of the total Pressure head to be overcome by pumping system:

Now, as per the continuity equation,

i.e Velocity of water flowing through the selected pipe will be

Now, from the value of velocity of water flowing through the pipe Reynolds number,

On the basis of the above Reynolds number and the property of PVC-U Pipe the friction factor is f =

0.4. So, head loss due to friction is given as;


And total minor loss due to pipe fittings is approximately given as;

The Vertical Height of the pipe is (Static Head) = 25m

Total Manometric head required by the pump is,

The required power output of the pump is;


So, required capacity of the pump for the given application to meet daily requirement of the water is

2.5 HP.

As water is being supplied from the bore well, it is required to use bore well pump for the this

application. On the basis of the calculated results and Kirloskar Pumps catalogue it is advisable to use

submersible pump of 2.5 HP to meet daily water requirement of the Regent Park Society. So, selected

pump is a kirloskars submersible pump of 2.5HP.

Product Specifications:

SKU – PU.AG.BO.289051

Type of Product: Bore well submersible pump

Sub-type- oil filled type

Bore well size- 4 inch

Head – 23-251 m

Discharge range – 5 to 35 lpm

Outlet (mm) – 50

Stages – 7

Phase – Single Phase

Del. Size – 50mm

Material – Stainless Steel

Power – 1.9 KW

Power (HP) – 2.5 HP

Model No – KU4-25075-CP A

Conclusion:

Currently 5HP of submersible pump is installed in the society which runs for the 2hrs a day.

But after this detail study and calculations it is recommended to use 2HP of motor which will save

power consumption of the society.

Fig. Kirloskar Submersible

Pump of 2.5 HP

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