hydraulic turbines

2. CONTENTS
• Introduction
• Principle
• History
• Parts of hydraulic turbine
• Types of turbines
• Classification of turbines
• Working principle of Pelton turbine
• Design aspects of Pelton turbine

3. INTRODUCTION
Definition of hydraulic turbine:
It is machine which uses the raw energy of a substances and converts
into mechanical energy . This mechanical energy is used in running an electrical
energy which is directly coupled to the shaft of the hydraulic turbine.
In hydraulic turbine
hydraulic means water
turbines means power
totally called as water power.
Principle for turbine
Hydraulic energy Mechanical energy Electrical energy
Hydro electric power is the most cheapest source of power generation.
Mechanical energy developed by turbines is used to run electric
generators coupled to the shaft of turbines

4. History
J.V. Poncelet first introduced the idea of the development of mechanical energy through
hydraulic energy
Modern hydraulic turbines have been developed by L.A. Pelton (impulse), G. Coriolis
and J.B. Francis (reaction) and V Kaplan (propeller)
 First hydraulic turbine is started to construct in America in 1882.
 Thereafter development took place very rapidly.
 In India, the first major hydroelectric development of 4.5 MW capacity name as
Sivasamudram in Mysore was commissioned in 1902.

6. It consists of the following:
1. A Dam constructed across a river or a channel to store water. The reservoir is also known
as Headrace.
2. Pipes of large diameter called Penstocks which carry water under pressure from storage
reservoir to the turbines. These pipes are usually made of steel or reinforced concrete.
3. Turbines having different types of vanes or buckets or blades mounted on a wheel called
runner.
4. Tailrace which is a channel carrying water away from the turbine after the water has
worked on the turbines. The water surface in the tailrace is also referred to as tailrace.
PARTS OF TURBINE

7. Types of Turbines :
 Impulse Turbine:-
Potential energy of water is converted to kinetic energy.
Works under atmospheric pressure
E.g: Pelton wheel
 Reaction Turbine
Pressure & velocity energies of water are converted to mechanical energy.
Works under pressure more than atmospheric
E.g: Francis & Kaplan turbines

8. Classification of Hydraulic Turbine
1. According to head and quantity of water available
2. According to name of originator.
3. According to action of water on moving blades.
4. According to direction of flow of water in the
runner.
5. According to disposition of turbine shaft.
6. According to specific speed.

9. 1. According to head and quantity of water available
a) High head turbines
b) Medium head turbines
c) Low head turbines
a) High head turbines
High head turbines are the turbines which work under heads more than 250m. The
quantity of water needed in case of high head turbines is usually small. The Pelton
turbines are the usual choice for high heads.
b) Medium head turbines
The turbines that work under a head of 45m to 250m are called medium head
turbines. It requires medium flow of water. Francis turbines are used for medium
heads.
c) Low head turbines
Turbines which work under a head of less than 45m are called low head turbines.
Owing to low head, large quantity of water is required. Kaplan turbines are used
for low heads.

10. 2. According to name of originator
Impluse turbine
Pelton turbine-----Lester Allen Pelton
-----high head & low discharge
 Reaction turbine
Francis turbine -----James Bichess Francis
– medium high head& medium low head
for medium high head---- low discharge
for medium low head ---- high discharge
Kaplan Turbine--- Dr.Victor Kaplan
---- low head & high discharge

11. 3. Based on hydraulic action of water
According to hydraulic action of water, turbines can be
classified into
a) Impulse turbines
b) Reaction turbines
a) Impulse turbines
If the runner of a turbine rotates by the impact or impulse
action of water, it is an impulse turbine.
b) Reaction turbines
These turbines work due to reaction of the pressure
difference between the inlet and the outlet of the runner.

12. Impulse turbine Reaction turbine
Only kinetic energy is available Kinetic energy and pressure is available
Tangential direction of flow Radial or mixed flow
Pressure is atmospheric Pressure is not atmospheric
Runner is not running with full of water Runner is running with full of water.
Regulation of flow is easy Regulation of flow is difficult
It is suited for high heads It is for medium or low heads
For same operating heads turbine size is
large
For same operating heads turbine size is
small
Repairs are very easy Repairs are very difficult
Air tight casing is not essential Air tight casing is essential
Draft tube is not necessary Draft tube is necessary
Efficiency is less Efficiency is high
Governing is easy Governing is difficult

13. 4. Based on direction of flow of water in the runner
Depending upon the direction of flow through the runner,
following types of turbines are there
a) Tangential flow turbines
b) Radial flow turbines
c) Axial flow turbines
d) Mixed flow turbines

14. a) Tangential flow turbines
When the flow is tangential to the wheel circle, it is a tangential
flow turbine. A Pelton turbine is a Tangential flow turbine.
b) Radial flow turbines
In a radial flow, the path of the flow of water remains in the
radial direction and in a plane normal to the runner shaft. No
pure radial flow turbine is in use these days.
c) Axial flow turbines
When the path of flow water remains parallel to the axis of the
shaft, it is an axial flow turbine. The Kaplan turbine is axial
flow turbine
d) Mixed flow turbines
When there is gradual change of flow from radial to axial in the
runner, the flow is called mixed flow. The Francis turbine is a
mixed flow turbine.

15. 5.Based on specific speed of turbines
Specific speed of a turbine is defined as the speed of a geometrically
similar turbine which produces a unit power when working under a unit
head.
The specific speed of Pelton turbine ranges between 8-30, Francis turbines
have specific speed between 50-250, Specific speed of Kaplan lies
between 250-850.
NS = N√P/H5/4
N=Normal working speed.
P=power output of the turbine.
H=net or effective head in m.
Turbines with low specific speed work under high head & low
discharge conditions.
High specific speed turbines work under low head & high discharge
conditions.
6.Based on disposition of shaft of runner
Usually, Pelton turbines are setup with horizontal shafts, where as other
types have vertical shafts.

16. Working principle of Pelton turbine

18. WORKING PRINCIPLE OF PELTON WHEEL
PRINCIPLE:-
All the available energy of water is converted into kinetic energy or velocity head
by passing it through a contracting nozzle provided at the end of the penstock.
Working:-
 The water from the reservoir flows through the penstocks at the outlet of which a nozzle
is fitted.
 The nozzle increases the kinetic energy of the water flowing through the penstocks.
 At the outlet of the nozzle, the water comes out in the form of a jet and strikes the
buckets of the runner.
 The water strikes the bucket along the tangent of the runner
 The energy available at the inlet of the turbine is only kinetic energy.
 The pressure at the turbine is used for high heads
 The pressure at the inlet and outlet of the turbine is atmosphere.

19. The main components of a Pelton wheel are
1)Runners and buckets
2) Nozzle and flow regulating arrangement.
3) Casing.
4) Breaking jet.
1) Runners with buckets
The runner consists of a circular disc with a number of buckets evenly spaced round its
periphery.
The shape of the buckets is of a double hemispherical cup or bowl.
Each bucket is divided into two symmetrical parts of a sharp edged ridge known a 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 get deflected through 1600 to 1700.
At the lower tip of the bucket ,a notch is cut .it avoids the deflection of water towards the
centre of the wheel.

21. 2 Nozzle and flow regulating arrangement
 To control the quantity of water striking the runner ,the nozzle fitted
at the end of the penstock is provided with a spear.
 The spear may be operated either by a wheel or automatically.
 When the spear is pushed forward into the nozzle ,the amount of
water striking the runner is reduced.
 On the other hand ,if the spear is pushed back ,the amount of water
striking the runner increases.

22. 3. CASING
• The function of casing is to prevent splashing of water and to lead the tail race.
• It also acts as a safe guard against accidents.
• It does not perform any hydraulic function.
• It is made of cast iron or fabricated steel plates.
4) Breaking jet
Large pelton wheel are usually equipped with
small break nozzle.
The small nozzle directs a jet of water on the
back of the buckets thereby the wheel quickly to
rest after it is shut down.
Otherwise the runner goes on revolving due to
inertia for a long time.

23. Design aspects of pelton wheel
1. Velocity of jet V1=Cv√(2gH) Cv =0.98 to 0.99
2. Velocity of wheel u= Ku√(2gH) Ku = 0.43 to 0.48
3. Angle of deflection of jet 165
4. Mean diameter of wheel u=∏DN/60 ; D= 60u/ ∏N
5. Jet ratio m= D/d
6. Buckets dimensions B = 3 to 4d ; L= 2 to 3d; T= 0.8 to 1.2d
7. Number of jets 6 nozzles 2 –jets in vertical runner ,
4 jets in horizontal runner
8. Number of buckets Z=15+(D/2d)
Where H= net head on turbine
D=wheel diameter
d= diameter of jet
Ku =speed ratio

24. Definitions of heads in the turbines:-
Gross Head (Hg):
It is the vertical difference between headrace and tail race.
Net Head :(H ):
N et head or effective head is the actual head available at the inlet of
the t o work on t he turbine.
H = Hg-hL
Where
hL = the total head loss during the transit of water from the head race t o tailrace
which is mainly head loss due to friction, and is given by
hf= 4flv2/2gd
Where
F= the co efficient of friction of penstock depending on the type o f material o
f penstock
L = the total length of penstock
V = the mean flow velocity o f water through the penstock
D= the diameter o f penstock and
g = the acceleration due to gravity

25. TYPES OF EFFICIENCIES
Depending on the considerations of input and output, the
efficiencies can be classified as
(i) Hydraulic Efficiency.
(ii) Mechanical Efficiency
(iii) Overall efficiency

26. (i) Hydraulic Efficiency(ŋh):-
It is the ratio o f the power developed by the runner o f a turbine to the
power supplied 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.
If R.P. is the Runner Power and W.P. is the Water Power
ŋh= Runner power/ water power
(ii) Mechanical Efficiency: (ŋm):-
It is the ratio of the power available at the shaft to the power
developed by the runner of a turbine. This depends on the slips and other
mechanical problems that will create a loss of energy between the runner in the
annular area between the nozzle and spear, the amount o f water reduces as the
spear is pushed forward and vice- versa and shaft which is purely mechanical
and hence mechanical efficiency.
If S.P. is t he Shaft Power
ŋm= shaft power/ runner power

27. iii )Overall Efficiency (ŋo):-
It is t h e ratio o f t he power available at t he shaft to the
power supplied at the inlet of a turbine. As this covers overall
problem s of losses in energy, it is know n as overall efficiency.
This depends on both the hydraulic losses an d the slips and
other mechanical problems
ŋo = ŋhX ŋm