fluid machinery lab manual

8/12/2019 fluid machinery lab manual

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CONDUCTING EXPERIMENTS AND DRAWING THE

CHARACTERISTICS CURVES OF PELTON WHEEL TEST RIG

AIM:

To conduct load test on pelton wheel turbine and to study the characteristics of pelton wheel turbine.

APPARATUS REQUIRED:

1. Venturimeter

2. Stopwatch

3. Tachometer

4. Dead weight

FORMULAE:

1. VENTURIMETER READING:

h = (P1 ~ P2)x 10 (m of water)

Where,

P1, P2 - Venturimeter reading in Kg /cm2

2. DISCHARGE:

Q = 0.0055 x h (m3 / s)

3. BRAKE HORSE POWER:

BHP = (x D x N x T) / (60x 75) (hp)

Where,

N = Speed of the turbine in (rpm)

D = Effective diameter of brake drum = 0.315 mT = Torsion in To + T1T2 (Kg)

4. INDICATED HORSE POWER:

IHP = (1000x Q xH) / 75 (hp)

Where,

H = Total head (m)

5. PERCENTAGE EFFICIENCY:

% = (B.H.P / I.H.P x 100) (%)


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DESCRIPTION:

Pelton wheel turbine is an impulse turbine, which is used to act on high loads and for generating electricity. All

the available heads are classified in to velocity energy by means of spear and nozzle arrangement. Position of the

jet strikes the knife-edge of the buckets with least relative resistances and shocks. While passing along the

buckets the velocity of the water is reduced and hence an impulse force is supplied to the cups which in turn are

moved and hence shaft is rotated.

Theory:

Hydraulic turbines are defined as those machines which convert hydraulic energy into mechanical energy. This

mechanical energy is used in running an electric generator which is directly coupled to the shaft of the turbine.

Pelton wheel is a tangential flow impulse turbine. This turbine is used for higher heads. Figure shows schematic

layout of a Pelton wheel. A Pelton wheel consists of four major components:

Nozzle and flow regulating arrangement (spear)

Runner and buckets

Casing and

Breaking jet

Nozzle and flow regulating arrangement (spear):

The amount of water striking the buckets of the runner is controlled by providing a spear in the nozzle as shown

in the fig. A spear is a conical needle which is operated either by a hand wheel or automatically in an axial

direction. When the spear is pushed forward the amount of water is reduced and vice versa.

Runner with buckets:

It consists of a circular disc on the periphery of which a number of buckets evenly spaced are fixed. The shape of

the buckets is of a double hemispherical cup or bowl. Each bucket is divided into two symmetrical parts by a

dividing wall which is known as splitter. The splitter divides the jet into two equal parts and the jet comes out at

the outer edge of the bucket. The buckets are shaped in such a way that the jet gets deflected through 1600or

1700.

Casing:

Casing prevents splashing of the water and discharges it to tail race.

Breaking jet:


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When the nozzle is completely closed there would not be any discharge from the nozzle. However, the runner

continues to rotate because of inertia. In order to stop the runner in a shorter period, a small nozzle is provided to

direct the jet of water on the back of vanes. This jet is called the breaking jet.

PROCEDURE:

1. The Pelton wheel turbine is started.

2. All the weight in the hanger is removed.

3. The pressure gauge reading is noted down and it is to be maintained constant for different loads.

4. The Venturimeter readings are noted down.

5. The spring balance reading and speed of the turbine are also noted down.

6. A 5Kg load is put on the hanger, similarly all the corresponding readings are noted down.

7. The experiment is repeated for different loads and the readings are tabulated


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CHARACTERISTICS CURVES OF FRANCIS TURBINE TEST RIG

AIM:

To conduct load test on Francis turbine and to study the characteristics of Francis turbine.

APPARATUS REQUIRED:

1. Stop watch

2. Tachometer

FORMULAE:

1. VENTURIMETER READING:

h = (p1 - p2) x 10 (m)

Where

P1, P2- Venturimeter readings in kg /cm2

2. DISCHARGE:

Q = 0.011 x h (m3 / s)

3. BRAKE HORSEPOWER:

BHP = x D x N x T / 60 x 75 (hp)

Where

N = Speed of turbine in (rpm)

D = Effective diameter of brake drum = 0.315 m

T = torsion in [kg]

4. INDICATED HORSEPOWER:

HP = 1000 x Q x H / 75 (hp)

Where

H = Total head in (m)

5. PERCENTAGE EFFICIENCY:

% = B.H.P x 100 / I.H.P (%)


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2.Guide mechanism: There are two main functions of the guide mechanism (a)To regulate the quantity of water

supplied to the runner and (b)To adjust the direction of flow so that there is minimum shock at the entrance to

runner blades. It consists of series of guide vanes of aerofoil section fixed between two rings, in the form of

wheel known as guide wheel, Each guide vane can be rotated about the pivot centre ,which is connected to a

regulating ring by means of a link and lever. By operating the regulating ring the vane can be rotated, varying the

width of the flow passage between adjacent vanes, thus altering both the flow angle as well as quantity of flow.

3.Runner. The runner consists of series of curved vanes arranged evenly around the circumferences, in the

angular space between two plates. it may be cast in one piece or made of separate steel plates welded together.

The runner vanes are so shaped that the water enters the runner radially at the outer periphery. This change in thedirection of flow from radial to axial as it passes over the curved vanes changes the angular momentum of the

fluid thereby producing a torque, which rotates the runner. The runner is keyed to the shaft of turbine.

4.Draft tube. It is a gradually expanding closed passage connecting the runner to the tail race. The lower end of

the draft tube is always kept submerged in water. The function of draft tube is to convert the high kinetic energy

of at runner exit into pressure energy, thus increasing the efficiency of the turbine. It also enables the turbine to

be installed above the tailrace level without any loss of head.

PROCEDURE:

1. Note the inlet and outlet diameters and measure the brake drum diameter and i.e., the distance

of inlet and outlet pressure guage tapping from the centre line of turbine.

2. Keeping the guide vanes completely closed, start the supply pump.

3. Open the guide vane partially (e.g.

of total opening) simultaneously adjusting the load on the

brake drum so that the speed of turbine is within limits.

4. Measure the discharge(Q)

5. Note the readings of the pressure gauge at inlet () and outlet().

6. Note the spring balance readings and the shaft speed(N).

7. Vary the speed of the turbine by varying the load (i.e., ) on the brake drum and take six to

seven readings in the allowable range of speed.

8. Change the guide vane opening and repeat steps 4 to 7.


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CHARACTERISTICS CURVES OF CENTRIFUGAL PUMP

AIM:

To study the performance characteristics of a centrifugal pump and to determine the characteristic with maximum

efficiency.

APPARATUS REQUIRED:

1. Centrifugal pump setup

2. Meter scale

3. Stop watch

FORMULAE:1. ACTUAL DISCHARGE:

Q act = A x y / t (m3 / s)

Where:

A = Area of the collecting tank (m2)

y = 10 cm rise of water level in the collecting tank

t = Time taken for 10 cm rise of water level in collecting tank.

2. TOTAL HEAD:

H = Hd + Hs + Z

Where:

Hd = Discharge head, meter

Hs = Suction head, meter

Z = Datum head, meter

3. INPUT POWER:

I/P = (3600 x N x 1000) / (Ex T) (watts)

Where:

N = Number of revolutions of energy meter disc

E = Energy meter constant (rev / Kw hr)

T = time taken for Nr revolutions (seconds)


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4. OUTPUT POWER:

Po = x g x Q x H / 1000 (watts)

Where,

= Density of water (kg / m)

g = Acceleration due to gravity (m / s2)

H = Total head of water (m)

5. EFFICIENCY:

o = (Output power o/p / input power I/p) x100 %

Where,

O/p = Output power kW

I/ p = Input power kW

DESCRIPTION:

PRIMING:

The operation of filling water in the suction pipe casing and a portion delivery pipe for the removal of air before

starting is called priming.

After priming the impeller is rotated by a prime mover. The rotating vane gives a centrifugal head to the pump.

When the pump attains a constant speed, the delivery valve is gradually opened. The water flows in a radially

outward direction. Then, it leaves the vanes at the outer circumference with a high velocity and pressure. Now

kinetic energy is gradually converted in to pressure energy. The high-pressure water is through the delivery pipe

to the required height.

Theory:

The fluid machine which converts the mechanical energy into fluid energy is called a pump. The fluid energy is

in the form of pressure energy.

If the mechanical energy is converted into pressure energy by means of centrifugal force acting on the fluid, the

machine is called centrifugal pump.

The flow in centrifugal pumps is in the radial outward direction. The centrifugal pump works on the principle of

forced vortex flow which means that when a certain mass of liquid is rotated by an external torque, there is a rise

in the pressure head. The rise in the pressure head is proportional to the square of tangential velocity of the liquid.

Higher the radius of the impeller, higher will be the pressure head. Due to this high pressure head, the liquid can

be lifter to a higher level.

The centrifugal pumps can handle higher discharge rates with very little variations in efficiency, but are not

suitable where higher head is required.

Main parts of a centrifugal pump are given below:

Impeller:


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This is the rotating part of the pump. It consists of a series of backward curved vanes. The impeller is mounted on

a shaft which receives drive from an electric motor.

Casing:

The casing of a centrifugal pump is a airtight passage surrounding the impeller and is designed in such a way that

the kinetic energy of the water discharged at the outlet of the impeller is converted into pressure energy beforewater leaves the casing. Following types of casings are commonly adopted.

Volute casingThis is of a spiral type in which the flow area increases gradually. The increase in area reduces

the velocity of the flow thereby increasing the pressure.

Vortex casingIf a circular member is introduced between the casing and the impeller then the casing would be

known as a vortex type of casing. This is used to avoid the formation of eddies observed in volute type of casing.

Casing with guide blades:Here the impeller is surrounded by a series of stationary guide blades whose flow area

increases and acts like a diffuser.

Suction pipe:

Suction pipe connects the inlet of the pump with the water in the sump. This also has a foot valve which opens

only in the upward direction.

Delivery pipe:

This pipe connects the pump outlet to the required height where the water is required.

Suction pipe

Impeller

Delivery pipe

Casing

Sump


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PROCEDURE:

1. Prime the pump close the delivery valve and switch on the unit

2. Open the delivery valve and maintain the required delivery head

3. Note down the reading and note the corresponding suction head reading

4. Close the drain valve and note down the time taken for 10 cm rise of water level in collecting tank

5. Measure the area of collecting tank

6. For different delivery tubes, repeat the experiment

7. For every set reading note down the time taken for 5 revolutions of energy meter disc.


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4. OUTPUT POWER:

Po = x g x Q x H / 1000 (Kw)

Where,

= Density of water (kg / m)

g = Acceleration due to gravity (m / s2)

H = Total head of water (m)

Q = Discharge (m3 / sec)

5. EFFICIENCY:

o = (Output power po / input power pi) x 100 %

Where,

Po = Output power KW

Pi = Input power KW

PROCEDURE:

1. Close the delivery valve and switch on the unit

2. Open the delivery valve and maintain the required delivery head

3. Note down the reading and note the corresponding suction head reading

4. Close the drain valve and note down the time taken for 10 cm rise of water level in collecting tank

5. Measure the area of collecting tank

6. For different delivery tubes, repeat the experiment

7. For every set reading note down the time taken for 5 revolutions of energy meter disc.


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Study of performance characteristics of a Hydraulic ram

Aim:

To determine the efficiency of the hydraulic ram

Apparatus reqd.:

1) Water supply tank with pipes

2) Hydraulic ram apparatus

3) Two collecting tanks

4) Pressure gauges

5) Stop watch

Theory:

Hydraulic ram is pump which raises water without any external power for its operation. It requires a large

quantity of water at a small height for discharging a small quantity of water to a greater height.

A schematic diagram of a hydraulic ram with major components is shown in the figure. When the inlet valve

fitted to the supply pipe is opened, water starts flowing from the supply tank to the chamber, which has two

valves, a waste valve and the delivery valve. The delivery valve is fitted to an air vessel. As water is coming into

the chamber from supply tank, the waste valve starts closing. At a certain stage the waste valve suddenly closes

and this creates a high pressure inside the chamber. This high pressure opens the delivery valve and the water

enters the air vessel compressing the air. This compressed air exerts force on the water and a small quantity of

water is raised to a greater height.The efficiency of the ram is given by,

Supply

pipe

Inlet

valve

Air Vessel

Delivery

pipe

Waste valve

chamber

Supply

tank


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Procedure:

1) Note down the relevant dimensions, viz, diameter of supply pipe & delivery pipe, area of collecting tank,

supply head, etc.,

2) Start the pump and fill the supply tank and ensure overflow in the running condition. Open the inlet valve

connected to supply pipe near the ram and at the same time adjust the waste valve nut so that ram starts

working.

3) After a few strokes the water is discharged through delivery pipe and gets collected in the collecting tank.

4) Note down the discharge of water flowing through the delivery pipe. Also note down the water dischagred

from waste valve.

5) Note down the reading of pressure gauge for the particular setting of the lift of the waste valve.

6) Count the number of beats of waste valve per minute.

7) Change the position of waste valve and repeat the above procedure for different readings.

8) Repeat the steps from 4 to 7 for different readings of pressure head while opening the regulation valve

connected in the delivery pipe.

9) Tabulate the above readings and calculate the efficiency using the formulae given.

10)Plot graphs of useful water discharge, waste water discharge and efficiency versus number beats perminute.

Observations / measurements:

Diameter of supply pipe m

Diameter of delivery pipe m

Supply head, hs m

Area of collecting tank for delivered water, Ad m2

Area of collecting tank for waste water, Aw m2

Delivery head, hd m

Calculations:

Net height of waste water tank, ha= h1h2

Waste water discharge,W1 =

Net height of delivered water tank, hb= h3h4

Delivered water discharge,W2 =

Efficiency, =

()

Conclusion:


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Efficiency,

(%)

D

eliveredwaterdischarge

Discharge

W2(m

3/s)

Time

td(s)

Netheight

ofwater,

hb(m)

Fin

al

lev

el,

h4(m)

Initial

level,

h3(m)

Wastewaterdischa

rge

Discharge

W1(m3/s)

Time

tw(s)

Netheight

ofwater,

ha

(m)

Final

level,

h2(m)

Initial

level,

h

1(m)

Strokes/

minute

Sl.No.

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fluid machinery lab manual