Hydraulic Turbine & its Types

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3. Fluid Mechanics Lab
MED, HITEC University Taxila Cantt
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4. Hydraulic Turbines
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5. What Are Hydraulic Machines?
 Machine which convert hydraulic energy( energy possessed
by water) into mechanical energy (which is further converted
into electrical energy)---turbine
 Machine which convert mechanical energy into hydraulic
energy---pump
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6. Hydraulic Turbines
 Hydraulic Turbines have a row of blades fitted to the rotating shaft or a
rotating plate. Flowing liquid, mostly water, when pass through the Hydraulic
Turbine it strikes the blades of the turbine and makes the shaft rotate. While
flowing through the Hydraulic Turbine the velocity and pressure of the liquid
reduce, these result in the development of torque and rotation of the turbine
shaft.
 Classification of Hydraulic Turbines:
Based on flow path
 Based on pressure change
Based on head
Based on specific speed
Based on disposition of turbine main shaft
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7. Based On Flow Path
 Axial Flow Hydraulic Turbines: This category of Hydraulic Turbines has
the flow path of the liquid mainly parallel to the axis of rotation. Kaplan
Turbines has liquid flow mainly in axial direction.
 Radial Flow Hydraulic Turbines: Such Hydraulic Turbines has the
liquid flowing mainly in a plane perpendicular to the axis of rotation.
 Mixed Flow Hydraulic Turbines: For most of the Hydraulic Turbines
used there is a significant component of both axial and radial flows.
Such types of Hydraulic Turbines are called as Mixed Flow Turbines.
Francis Turbine is an example of mixed flow type, in Francis Turbine
water enters in radial direction and exits in axial direction.
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8. Based On Pressure Change
 Impulse Turbine: The pressure of liquid does not change while flowing
through the rotor of the machine. In Impulse Turbines pressure change
occur only in the nozzles of the machine.
 Example of impulse turbine: Pelton Wheel.
 Reaction Turbine: The pressure of liquid changes while it flows
through the rotor of the machine. The change in fluid velocity and
reduction in its pressure causes a reaction on the turbine blades; this is
where from the name Reaction Turbine may have been derived.
 Examples: Francis and Kaplan Turbines fall in the category of Reaction
Turbines.
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9. Based On Head
 High head turbine (Above 250 m) Pelton Turbine
 Medium head turbine (60 – 250 m) Francis Turbine
 Low head turbine (Below 60 m) Kaplan Turbine
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10. Based On Specific Speed
 Specific speed Ns = N √P / H5/4
 Low specific speed (8.5 – 30) - Pelton Turbine
 Medium specific speed (50 – 340) - Francis Turbine
 High specific speed (255 – 860) - Kaplan Turbine
Based On Disposition Of Turbine Main Shaft
 Horizontal shaft
 Vertical shaft
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11. Layout Of A Hydro Electric Power Plant11

12. Parts Of A Hydroelectric Plant
 Dam. Raises the water level of the river to create falling water. Also controls the flow
of water. The reservoir that is formed is, in effect, stored energy.
 Turbine. The force of falling water pushing against the turbine's blades causes the
turbine to spin. A water turbine is much like a windmill, except the energy is provided
by falling water instead of wind. The turbine converts the kinetic energy of falling
water into mechanical energy.
 Generator. Connected to the turbine by shafts and possibly gears so when the
turbine spins it causes the generator to spin also. Converts the mechanical energy
from the turbine into electric energy. Generators in hydropower plants work just like
the generators in other types of power plants.
 Transmission lines. Conduct electricity from the hydropower plant to homes and
business.
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13. Pelton Turbine/ Wheels
 Water strikes the vanes along tangent of the runner and the
energy available at the inlet of turbine is only kinetic
energy, there fore is is a tangential flow impulse turbine
 In a Pelton Turbine or Pelton Wheel water jets impact on
the blades of the turbine making the wheel rotate,
producing torque and power.
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14. Main Parts Of A Pelton Wheel
 Nozzle: it control the amount of water striking the vanes of the
runner
 Casing: it is used to prevent splashing of water and plays no part in
power generation
 Runner with bucket: runner is a circular disc on the periphery of
which a number of evenly spaced bucket are fixed
 Breaking jet: to stop the runner in short time breaking jet is used
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15. Diagrammatic View of Pelton Turbine15

16. Working Principle of Pelton Turbine
Water jets emerging strike the buckets at splitter and split into two.
Stream flow along the inner curve of the bucket and leave it in the direction
opposite to that of incoming jet.
The high pressure water can be obtained from any water body situated at some
height or streams of water flowing down the hills.
The change in momentum (direction as well as speed) of water stream produces
an impulse on the blades of the wheel of Pelton Turbine. This impulse
generates the torque and rotation in the shaft of Pelton Turbine.
Horizontal shaft - Not more than 2 jets are used and
Vertical shaft - Larger no. of jets (up to 6) are used.
Iron/Steel casing to prevent splashing of water and to lead water to the tail race.
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17. Pelton Turbine Review (video)17

18. Francis Turbine
 1st hydraulic turbine with radial inflow
 Water flow from outward to inward, k/a inward radial flow turbine
 Francis turbine is a reaction turbine as the energy available at the
inlet of the turbine is a combination of kinetic and pressure energy.
 Water pressure decreases as it passes through the turbine
imparting reaction on the turbine blades making the turbine rotate
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19. Main Parts Of A Francis Turbine
 Casing: the runner is completely enclosed in an air-tight spiral
casing. The casing and runner are always full of water
 Guide mechanism: it consists of stationary circular wheel on which
stationary guide vanes are fixed. The guide vanes allow the water to
strike the vanes of the runner without shock at inlet
 Runner: is a circular wheel on which a series of curved radial guide
vanes are fixed
 Draft tube: it is used for discharging water from the outlet of the
runner to the tail race.
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20. Parts of Francis Turbine20

21. Schematic View of Francis Turbine21

22. Applications of Francis Turbine
 Francis turbines may be designed for a wide range of heads and flows.
 This, along with their high efficiency, has made them the most widely used
turbine in the world.
 Francis type units cover a head range from 40 to 600 m (130 to 2,000 ft), and
their connected generator output power varies from just a few kilowatts up to
800 MW.
 Large Francis turbines are individually designed for each site to operate with the
given water supply and water head at the highest possible efficiency, typically
over 90%.
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23. Working Principle Of Francis Turbine
 Francis Turbines are generally installed with their axis vertical.
 Water with high head (pressure) enters the turbine through the spiral casing
surrounding the guide vanes.
 The water looses a part of its pressure in the volute (spiral casing) to maintain its
speed.
 Then water passes through guide vanes where it is directed to strike the blades on
the runner at optimum angles. As the water flows through the runner its pressure and
angular momentum reduces.
 This reduction imparts reaction on the runner and power is transferred to the turbine
shaft.
 If the turbine is operating at the design conditions the water leaves the runner in axial
direction.
 Water exits the turbine through the draft tube, which acts as a diffuser and reduces
the exit velocity of the flow to recover maximum energy from the flowing water.
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24. Francis Turbine Review24

25. Kaplan Turbine
 Kalpan turbine is an axial flow reaction turbine
 The water flows through the runner of the turbine in an axial direction and the energy
at the inlet of the turbine is the sum of kinetic and pressure energy.
 In an axial flow reaction turbine the shaft is vertical.
 Lower end of shaft is k/a hub or boss.
 On the hub vanes are attached. If the vanes are adjustable then it is k/a kalpan turbine,
if vanes are not adjustable then is k/a propeller turbine
 Best suited where large quantity of low head water is available.
 Kaplan Turbine has propeller like blades but works just reverse. Instead of displacing
the water axially using shaft power and creating axial thrust, the axial force of water
acts on the blades of Kaplan Turbine and generating shaft power.
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26. Main Parts Of A Kaplan Turbine
 Scroll casing
 Guide vane mechanism
 Hub with vanes
 Draft tube
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27. Schematic View of Kaplan Turbine27

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29. Working Principle Of Kaplan Turbine
 The working head of water is low so large flow rates are allowed in the Kaplan
Turbine.
 The water enters the turbine through the guide vanes which are aligned such as
to give the flow a suitable degree of swirl determined according to the rotor of
the turbine.
 The flow from guide vanes pass through the curved passage which forces the
radial flow to axial direction with the initial swirl imparted by the inlet guide
vanes which is now in the form of free vortex.
 The axial flow of water with a component of swirl applies force on the blades of
the rotor and looses its momentum, both linear and angular, producing torque
and rotation (their product is power) in the shaft.
 The scheme for production of hydroelectricity by Kaplan Turbine is same as that
for Francis Turbine.
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30. Kaplan Turbine Review (video)30

31. Comparison Between Pelton, Francis &
Kaplan Turbine (video)
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32. Draft Tube
 It is a pipe of gradually increasing area which connects the
outlet of the runner with the tailrace.
 One end of the draft tube is connected to the outlet of the
runner while the other end is submerged below the level of
water in the tailrace
 It creates a negative head at the outlet of the runner
thereby increasing the net head on the turbine
 It converts a large proportion of rejected kinetic energy into
useful pressure energy
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33. Governing of Turbines
 It is the operation by which the speed of the turbine is kept
constant under all conditions of the working load. This is done
automatically by a governor which regulate the rate flow
through the turbine according to the changing load condition
on the turbine
 It is absolutely necessary if the turbine is coupled to an
electric generator which is required to run at constant speed
under all fluctuating load conditions
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