This document provides a comparison of different types of hydraulic turbines and considerations for selecting the appropriate turbine for a hydroelectric power plant. It compares Pelton, Francis, and Kaplan turbines based on criteria such as head, discharge required, efficiency, and more. The key points for selection include considering the specific speed to match the generator speed, choosing the turbine with the highest efficiency, ability to operate at part loads, available head and fluctuations, and shaft orientation. The turbines are recommended for different head ranges, with Pelton used for very high heads and Kaplan for heads below 30 meters.

1. 11
Prepared by:
Satish G. Taji
Assistant Professor
Civil Engineering Department
SRES’s Sanjivani College of Engineering, Kopargaon
Topic Covered:
• Comparison of Turbines
• Selection of Turbine
Fluid Mechanics:
Hydraulic Turbines

2. Turbine – Comparison
Prepared By Prof. S. G. Taji
Sr.
No
Criteria Pelton Turbine Francis Turbine
Kaplan
Turbine
1 Type
Pelton turbine is
an impulse type
water turbine
Francis Turbine
is an inward flow
reaction turbine.
Kaplan turbine
is a propeller
type reaction
turbine.
2 Head
It is used for high
heads ranging
from 250 to
1000m
The operating
water head of a
Francis turbine
ranges from 40
to 400m.
It is used for
low heads
ranging from
10 to 70
metres

3. Turbine – Comparison
Sr.
No
Criteria Pelton Turbine
Francis
Turbine
Kaplan Turbine
3
Direction
of Flow of
Water
Through
the
Blades
The flow of water
is tangential to
the runner.
Hence it is also
called as
tangential flow
impulse turbines
The flow of
water through
the blades
combines
both radial
and axial flow.
Mixed Flow
Turbine
The flow of
water is axial
through the
blades. Axial
Flow Turbine
4
Discharge
Required
The required
discharge is low.
Medium
discharge is
required
requires high
discharge
Prepared By Prof. S. G. Taji

4. Turbine – Comparison
Sr.
No
Criteria Pelton Turbine
Francis
Turbine
Kaplan Turbine
5
Type of
Energy
The Pelton
turbines uses
kinetic energy
and converts
into
mechanical
energy
The Francis
turbine
converts
potential and
KE energy
into
mechanical
energy
The Kaplan
Turbine uses both
kinetic and
potential energy,
which then is
converted into
mechanical
energy.
6 Efficiency
The efficiency
of a Pelton
turbine is
about 85%
The efficiency
of a Francis
turbine is
about 90%.
The Kaplan turbine
gives higher
efficiency about
90%
Prepared By Prof. S. G. Taji

5. Turbine – Comparison
Sr.
No
Criteria Pelton Turbine
Francis
Turbine
Kaplan Turbine
7
Runner
Speed
rpm
750 - 1000 94 - 1000 72 - 600
8 Blades
Double
Hemispherical
Fixed on
Wheel
Radial Vane
fixed on
runner
Adjustable
9
Specific
Speed
8.5 to 43 50 to 340 255 to 860
Prepared By Prof. S. G. Taji

6.  The following points should be considered while
selecting right type of hydraulic turbines for
hydroelectric power plant.
1) Specific speed:
 High specific speed is essential where the head is low and
output is large, because otherwise the rotational speed
will be low which means cost of turbo-generator and
powerhouse will be high.
 On the other hand there is practically no need of
choosing a high value of specific speed for high
installations, because even with low specific speed high
rotational speed can be attained with medium capacity
plants.
Selection of Turbine
Prepared By Prof. S. G. Taji

7. Selection of Turbine
Prepared By Prof. S. G. Taji
Turbine Specific Speed Remark
Pelton Wheel
With single jet
8.5 to 30
Upto 43 with
double jet
Francis
Turbine
50 to 340 --
Kaplan
Turbine
255 to 860 --

8. 2) Rotational speed:
 Rotational speed depends upon specific speed. Also the
rotational speed of an electrical generator with which the
turbine is to be directly coupled depends on the frequency
and number of pair of poles.
 The value of specific speed adopted should be such that it
will give the synchronous speed of the generator.
3) Efficiency:
 The efficiency selected should be such that it gives the
highest overall efficiency of various conditions.
Selection of Turbine
Prepared By Prof. S. G. Taji

9. 4) Part Load Operation:
 In general the efficiency at part loads and overloads is less
than that with rated (design) parameters. For the sake of
economy the turbine should always run with maximum
possible efficiency to get more revenue.
 Pelton wheel is preferable for part load
operation in comparison to
Francis turbine, though the
former involves higher initial
cost.
 For heads below 30 m,
Kaplan turbine is
preferable for part load
operation in comparison to
Propeller turbine.
Selection of Turbine
Image Source: Fluid Mechanics by P N Modi

10. 5) Available head and its fluctuation:
 Very high (350m and above): for heads greater than 350m,
Pelton Turbine is generally employed and practically there is no
any choice except in very special cases.
 High heads (150 m to 350 m): in this range either Pelton or
Francis turbine may employ. For higher specific needs Francis
turbine is more compact and economical than the Pelton turbine
that for the same working conditions would have to be much
bigger and rather cumbersome.
 Medium heads (60 m to 150 m): a Francis turbine is usually
employed in this range. Whether a high or low specific speed
would be used depends on the selection of the speed.
Prepared By Prof. S. G. Taji
Selection of Turbine

11. 5) Available head and its fluctuation:
 Low heads (below 60m): between 30m to 60m both Kaplan and
Francis turbines may be used.
 Kaplan turbine is generally employed less than 30m. Propeller
turbines are however, commonly used for heads up to 15m.
They are adopted only when there is practically no load
variation.
6) Deposition of turbine shaft:
 Experience has shown that the vertical shaft arrangement is
better for large-sized reaction turbines, therefore, it is almost
universally adopted, whereas, in case of large size impulse
turbines, horizontal shaft arrangement is preferable.
Prepared By Prof. S. G. Taji
Selection of Turbine