Hydraulic Turbines
Lecture slides by
Sachin Kansal
NATIONAL INSTITUTE OF TECHNOLOGY
KURUKSHETRA
2
Objectives
• To have an understanding of working of Hydro-Power
Plant and Hydraulic Turbines
• To have an understanding of classification of various
types of turbines
• To know about the various types of heads associated
with a hydro-power plant
• To understand the different types of efficiencies arising
due to losses at various instances
3
Sardar Sarovar Dam
(Narmada River , Gujarat)
1450 MW
Nathpa Jhakri Hydroelectric power
project (Satluj, Himachal Pradesh)
1530 MW
Koyna Dam
(Koyna River,Maharashtra)
1960 MW
Giant Hydro Power Plants of India
4
Introduction
Hydraulic Turbines are defined as the hydraulic 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.
Thus the mechanical energy is converted into electric
energy.
The electric power, which is obtained from the hydraulic
energy is known as Hydro-electric power.
At present, the generation of hydro-electric power is the
cheapest as compared to the power generation by other
sources such as oil, coal, etc.
6
Components of Hydropower Plant
Reservoier• Natural (Lakes on Mountains) or Artificial (Dams)
Head Works
• Equipment used to control water into waterways
• e.g. Gates, Valves, Fish-traps etc.
Water Ways
• Passage to take water from reservoir to power house
• e.g. Penstock, Tunnels, Channels etc.
Forbays or Surge Tank
• To meet the load fluctuations for small period as for a day
• Situated at the end of a tunnel or open channel
Powerhouse and Tail Race
• Consist of turbine, generator etc.
• Tailrace is waterways takes the water from the turbine outlet into channel or river.
7
Fig. – Layout of Hydroelectric Power Plant using an Impulse Turbine
Turbines
(a) According to the type of
energy at the inlet
(i)
Imp
uls
e T
urb
ine
(ii) R
ea
ctio
n T
urb
ine
(b) According to the direction of
flow through runner
(i)
Ta
ng
en
tia
l F
low
Tu
rbin
e
(ii) R
ad
ial F
low
Tu
rbin
e
(iii)
Axia
l F
low
Turb
ine
(iv)
Mix
ed
Flo
w T
urb
ine
(c) According to the head at the
inlet of the turbine
(i)
Hig
h H
ea
d T
urb
ine
(ii) M
ed
ium
He
ad
Tu
rbin
e
(iii)
Lo
w H
ea
d T
urb
ine
(d) According to the specific speed of the
turbine
(i)
Lo
w S
pe
cific
Sp
ee
d
Tu
rbin
e
(ii) M
ed
ium
Sp
ecific
S
pe
ed
T
urb
ine
(iii)
Hig
h S
pe
cific
Sp
ee
d
Tu
rbin
e
8
Classification of Hydraulic Turbines
9
(a) According to the type of energy at
the inlet (i) Impulse Turbine
All the available energy of the water is converted into
kinetic energy or velocity head by passing it through a
convergent nozzle provided at the end of the penstock.
So, at the inlet of the turbine, only kinetic energy is
available
Pressure of water flowing over the turbine blades
remains constant (i.e. atmospheric pressure)
Examples: Pelton wheel, Turgo-impulse turbine, Girard
turbine, Banki turbine, Jonval turbine, etc
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(ii) Reaction Turbine
At the entrance to the runner, only a part of the available
energy of water is converted into kinetic energy and a part
remains in the form of pressure energy.
So at the inlet of the turbine, water possesses kinetic
energy as well as pressure energy.
As the water flows through the turbine blades, the change
from pressure energy to kinetic energy takes place
gradually.
For this gradual change of pressure, the runner must be
completely enclosed in an air-tight casing and the passage
should be full of water.
The difference of pressure between the inlet and outlet of
the runner is called reaction pressure ,and hence these
turbines are known as reaction turbines.
Examples: Francis turbine, Kaplan turbine, Propeller
turbine, Thomson turbine, Fourneyron turbine etc
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Aspect Impulse Reaction
Fluid energy conversion K.E. in the nozzle K.E. in the fixed blade
Flow path Nozzle-runner Fixed blade – runner
Energy inlet to moving
blades
Only K.E. K.E. + P.E.
Changes in pressure &
velocity
Pressure =Constant P & V both changes
Entering of water Water may be admitted
over apart or whole
circumference of runner
wheel
Must admitted over whole
circumference of runner
wheel
Water fills the turbine Not required wheel run full Run full and kept full of
water
Flow regulation Possible Not
Casing Prevent splashing & guide
water to tail race
Water tight casing is
required & has to sealed
from atm.
Governing Needle valve Guide blade
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(b) According to the direction of flow
through runner(i) Tangential flow turbine
In tangential flow, the water strikes the runner in the direction
of the tangent to the path of rotation of the runner. OR
The water strikes the vane/bucket along the tangent of the
runner.
Example: Pelton wheel
(ii) Radial flow turbine
In radial flow, water flows through the turbine along the
direction normal to the axis of rotation (i.e. radial direction).
A radial flow turbine is further classified as inward or outward
flow depending upon whether the flow is inward from the
periphery to the center or outward from the center to
periphery.
Example: Old Francis turbine
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(iii) Axial flow turbine
In an axial flow turbine, water flows along the direction
parallel to the axis of rotation of the runner.
Here the water flows parallel to the turbine shaft.
Examples: Kaplan turbine, Propeller turbine
(iv) Mixed flow turbine
In mixed flow, water enters the runner in the radial direction
and leaves in the direction parallel to the axis of rotation
(i.e. axial direction)
Example: Modern Francis turbine
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(c) According to the head at the inlet of
the turbine(i) High head turbine
High head turbines which operate under high head (above
250m) and require relatively less quantity of water
Example: Pelton wheel turbine
(ii) Medium head turbine
Medium head turbines which operate under medium head
(60m to 250m) and require medium flow rate.
Example: Modern Francis turbine
(iii) Low head turbine
Low head turbines that operate under head up to 30m and
require a very large quantity of water.
Example: Kaplan and Propeller turbine
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(d) According to the specific speed of
the turbine(i) Low specific speed turbine
For Pelton wheel turbine with a single jet,
𝑁𝑠 = 8.5 𝑡𝑜 30
For Pelton wheel turbine with the double jet,
𝑁𝑠 = 40
Medium specific speed turbine
For Francis turbine,
𝑁𝑠 = 50 𝑡𝑜 340
High specific speed turbine
Kaplan and other Propeller turbines,
𝑁𝑠 = 255 𝑡𝑜 860
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Efficiencies & Head of Hydraulic
TurbinesGross Head (𝑯𝒈)
It is the difference between the headrace level and tail race
level when no water is flowing
It is also known as the total head of the
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Effective Head or Net Head (H)
A net head or effective head is the actual head available at
the inlet of the turbine
When water is flowing from the headrace to the turbine, a
loss of head due to friction between water and penstock
occurs.
Though there are other losses also such as loss due to
bend, pipe fittings, loss at the entrance of the penstock, etc.
These all having small magnitude as compared to head
loss due to friction.
So,𝐻 = 𝐻𝑔 − ℎ𝑓, where 𝐻 = Net head or Effective head
𝐻𝑔 = Gross head
ℎ𝑓 = Head loss due to friction between penstock and water = 4𝑓𝐿𝑉2 / 2𝑔𝐷
𝑓 = Coefficient of friction of depending on the type of material of penstock
𝐿 = Total length of penstock
𝑉 = Mean velocity of water through the penstock
𝐷 = Diameter of penstock and
𝑔 = Acceleration due to gravity
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Hydraulic Efficiency (𝜼𝒉 )
It is the ratio of the power developed by the runner of a
turbine to the power supplied by the water at the inlet of a
turbine.
Since the power supplied is hydraulic, and the probable
loss is between the striking jet and vane it is rightly called
hydraulic efficiency
Mechanical Efficiency (𝜼𝒎 )
The power delivered by water to the runner of a turbine
is transmitted to the shaft of the turbine.
It is the ratio of the power available at the shaft of the
turbine to the power developed by the runner of a turbine
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This depends on the slips and other mechanical problems
that will create a loss of energy i.e. friction
Overall Efficiency (𝜼O)
It is the ratio of the power available at the shaft to the
power supplied by the water at the inlet of a turbine
Euler’s Equation and Degree of
ReactionWork done or energy transfer in case of radial curved
vanes = E/unit mass-sec= 𝑉𝑤1 𝑢1 ± 𝑉𝑤2 𝑢2
This fundamental equation of hydraulic machines are
known as Euler’s Equation, applicable to both turbines and
pump
If E= +ve, then Energy is transferred from the water to
wheel , which gives motion to that and is principle of motion
of turbines
If E= -ve, then Energy is transferred from wheel to water ,
which can raise its velocity or pressure, which is principle of
motion of centrifugal pump
Transformation of equation in another form
21
2
2
2)(
2
)(
TriangleVelocity Inlet From
21
21
2
11
21
21
211
112
12
12
122
1
112
12
12
12
1
112
1
1
1
1
2
rw
rw
wwwr
wwfr
wrw
VuVuV
VuVuV
uVuVVVV
uVuVVV
uVV
2
2
2)(
2
)(
TriangleVelocity Outlet fromSimilarly
22
222
22
22
22222
222
22
22
222
2
222
22
22
22
2
222
2
2
2
2
2
uVVuV
uVVuV
uVuVVVV
uVuVVV
uVV
rw
rw
wwwr
wwfr
wrw
22
222
22
,
21
22
22
21
22
22
222
21
21
2
21
21
21
21
rr
rr
ww
VVuuVVE
uVVVuVE
uVuVENow
Dynamic
Energy
Change:Difference in
square of
absolute
velocities or
change in K.E
of the liquid
Centrifugal
Energy
Change::Difference in
square of
tangential
velocities or
change in
centrifugal
head and
pressure
change due to
that
Pressure
Energy
Change::Difference in
square of
liquid velocity
or pressure
change due to
change in
relative
velocity
23
∴
Degree of Reaction : Ratio of Energy conversion inside therunner to the total energy conversion
ChangeEnergy Total
ChangeEnergy Pressure ChangeEnergy lCentrifugaReaction of Degree
For Impulse Turbine, flow is tangential (u1=u2), pressure is atmospheric and
vane is smooth (Vr1=Vr2)
Energy Change is only due to change in K.E. of the liquid
In reaction turbine, if flow is axial then u1=u2
Energy change is due to change in K.E and Pressure Energy
In reaction turbine, if flow is radial or mixed, all the three terms are effective
2
2221 VV
E
22
21
22
2221 rr VVVV
E
24
Reference Links
• Types of Fluid Machines: https://youtu.be/TiJZp-KB6h8
https://youtu.be/Lu4oKZXSAyQ
• Euler’s Equation https://youtu.be/6Opq1_RfsOo
https://youtu.be/pzKWoMPh4Xg