Upload
amit4u1984
View
240
Download
0
Embed Size (px)
Citation preview
8/12/2019 fluid machinery lab manual
1/20
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) (%)
8/12/2019 fluid machinery lab manual
2/20
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:
8/12/2019 fluid machinery lab manual
3/20
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
8/12/2019 fluid machinery lab manual
4/20
8/12/2019 fluid machinery lab manual
5/20
CONDUCTING EXPERIMENTS AND DRAWING THE
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 (%)
8/12/2019 fluid machinery lab manual
6/20
8/12/2019 fluid machinery lab manual
7/20
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.
8/12/2019 fluid machinery lab manual
8/20
8/12/2019 fluid machinery lab manual
9/20
8/12/2019 fluid machinery lab manual
10/20
CONDUCTING EXPERIMENTS AND DRAWING THE
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)
8/12/2019 fluid machinery lab manual
11/20
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:
8/12/2019 fluid machinery lab manual
12/20
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
8/12/2019 fluid machinery lab manual
13/20
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.
8/12/2019 fluid machinery lab manual
14/20
8/12/2019 fluid machinery lab manual
15/20
8/12/2019 fluid machinery lab manual
16/20
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.
8/12/2019 fluid machinery lab manual
17/20
8/12/2019 fluid machinery lab manual
18/20
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
8/12/2019 fluid machinery lab manual
19/20
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:
8/12/2019 fluid machinery lab manual
20/20
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.