hi, I am sujon I just completed graduate at International University of Business Agriculture and Technology in Bangladesh Department of Mechanical Engineering

1. Welcome
1
Md Sujon Babu
15207019

2. Performance of Turbines

3.  What is turbine
 Basic Types of turbines
 Performance of Turbines
 Characteristics of Turbines
 Significance of unit power, unit speed and unit discharge
 Specific speed of Turbine
 Significance of Specific Speed
 Selection of Turbines
 Characteristics Curves of Turbines
 Cavitation
 Conclusion
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4. What is turbine?
.
A turbine (from the Latin turbo)
is a rotary mechanical device
that extracts energy from a
fluid flow and converts it into
useful work. For example: The
work produced by a turbine
can be used for generating
electrical power when
combined with a generator.
4

5. Basic Types of turbines
Hydraulic turbines
 Wind turbines
Gas turbines
Steam turbines
5

6. Hydraulic Turbines
Impulse Turbine:
(Pelton Wheel)
Reaction Turbine:
(Kaplan, Francis)
6

7. Performance of Turbines
Turbines are often required to work under varying conditions of head,
speed, output and gate opening. As such, in order to predict their
behavior, it is essential to study the performance of the turbine under
varying conditions.
The head and output of the turbine may change. In this case, keeping
the discharge constant, the speed is adjusted so that the efficiency
remains constant.
Keeping the head and the speed constant, the output may vary by
adjusting the discharge. These are the normal operating conditions, and
the curves drawn for these conditions are called operating
characteristics curves.
7

8.  Working under low heads, the head of water and speed may vary.
Although the speed is allowed to fluctuate within narrow
permissible limits , yet the head may vary up to 50%.
 Keeping the head and discharge constant, the speed may vary by
adjusting the load on the turbine. These conditions are possible
only in the laboratories. The curves so obtained for such conditions
are known as main characteristics curves.
8

9. Characteristics of Turbines
We always study the following three characteristics of a
turbine under a unit head while comparing the
performances of turbines.
a) Unit Power
b) Unit Speed
c) Unit discharge
9

10. 10

11. Example : A Pelton wheel develops 1750 kw under a head of 100 metres, while
running at 200 r.p.m and discharging 2500 litres of water per second .Find the
unit power,unit speed and unit discharge of the wheel?
Solution:
Given Data:
P=1750 kW;
H=100 m
N=200 r.p.m
Q=2500 litres/s=2.5 𝑚3
/s .
Required :
𝑈𝑛𝑖𝑡 𝑜𝑓 𝑃𝑜𝑤𝑒𝑟 𝑜𝑓 𝑡ℎ𝑒 𝑊ℎ𝑒𝑒𝑙 𝑃𝑢 =?
𝑈𝑛𝑖𝑡 𝑜𝑓 𝑆𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑊ℎ𝑒𝑒𝑙 𝑁 𝑢=?
11

12. 𝑈𝑛𝑖𝑡 𝑜𝑓 𝐷𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑊ℎ𝑒𝑒𝑙 𝑄 𝑢 =?
 Solution:
𝑈𝑛𝑖𝑡 𝑜𝑓 𝑃𝑜𝑤𝑒𝑟 𝑜𝑓 𝑡ℎ𝑒 𝑊ℎ𝑒𝑒𝑙 𝑃𝑢 =
𝑃
𝐻
3
2
=
1750
100
3
2
= 1.75 kW.( Ans)
And
𝑈𝑛𝑖𝑡 𝑜𝑓 𝑆𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑊ℎ𝑒𝑒𝑙 𝑁𝑢 =
𝑁
𝐻
1
2
=
200
100
1
2
= 20 r.p.m. (Ans)
12

13.  𝑈𝑛𝑖𝑡 𝑜𝑓 𝐷𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑊ℎ𝑒𝑒𝑙 𝑄 𝑢 =
𝑄
𝐻
1
2
=
2.5
100
1
2
=
2.5
10
= 0.25 𝑚3
/s (Ans)
13

14. Significance of unit power, unit speed and
unit discharge
As a matter of fact, the significance of the unit power, unit speed and
unit discharge is of much important in the field of Hydraulic Machines.
Its help us in finding out the behavior of a turbine, when it is put to
work under different heads of water as discussed as follows:
Significance of unit power:
𝑃1 = 𝑃 ×
𝐻1
𝐻
3/2
Here,
H= Head of water under which turbine is working
P= Power under head of H
𝑃1=Power under head of 𝐻1
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15. Signification of unit speed:
𝑁1 = 𝑁 ×
𝐻1
𝐻
1/2
Here,
H= Head of water under which turbine is working
N= Speed of under head of H
𝑁1=Speed of under head of 𝐻1
Signification of unit discharge:
𝑄1 = 𝑄 ×
𝐻1
𝐻
1/2
Here,
H= Head of water under which turbine is working
Q= Discharge under head of H
𝑄1=Discharge under head of 𝐻1
15

16. Example : An impulse turbine develops 4500 kW under a head of 200
metres. The turbine runner has a speed of 200 r.p.m and discharges
0.8 cubic metre of water per second.If the head on the same turbine
falls during summer season to 184.3 metres.Find the new
discharge,power and speed of the turbine.
 Given Data:
P=4500kW
H=200 m
N=200 r.p.m
Q= 0.8 𝑚3/s
𝐻1= 184.3 m
16

17. Required :
New Discharge of the turbine 𝑄1=?
New Power of the turbine 𝑃1=?
New Speed of the turbine 𝑁1=?
Solution:
𝑁𝑒𝑤 𝐷𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑡𝑢𝑟𝑏𝑖𝑛𝑒 𝑄1= 𝑄 ×
𝐻1
1
2
𝐻
= 0.8 ×
184.3
1
2
200
= 0.8× 0.96
= 0.768 𝑚3/s (Ans)
17

18.  𝑁𝑒𝑤 𝑝𝑜𝑤𝑒𝑟 𝑜𝑓 𝑡ℎ𝑒 𝑡𝑢𝑟𝑏𝑖𝑛𝑒 𝑃1= 𝑃 ×
𝐻1
3
2
𝐻
= 4500 ×
184.3
3
2
200
= 4500× 0.88
= 3960 kW (ans)
 𝑁𝑒𝑤 𝑆𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑡𝑢𝑟𝑏𝑖𝑛𝑒 𝑁1= 𝑁 ×
𝐻1
1
2
𝐻
= 200 ×
184.3
1
2
200
= 200× 0.96
= 192 r.p.m (ans)
18

19. Specific speed of Turbine
The specific speed value for a turbine is the speed of a
geometrically similar turbine which would produce unit power
under unit head. The specific speed of a turbine is given by the
manufacturer and will always refer to the point of maximum
efficiency. This allows accurate calculations to be made of the
turbine's performance for a range of heads.
Well-designed efficient machines typically use the following
values: Impulse turbines have the lowest ns values, typically
ranging from 1 to 10, a Pelton wheel is typically around
4, Francis turbines fall in the range of 10 to 100, while Kaplan
turbines are at least 100 or more, all in imperial units
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20. The specific speed of turbine,
𝑁𝑠 = 𝑁 ×
𝑃
𝐻5/4
Here,
N= Wheel speed (rpm)
P= Power (kw)
H= Water head (m)
20

21. Significance of Specific Speed
The significant feature of the specific speed of a
turbine, is that it is independent of the dimensions or
size of both actual and specific turbines. So it is
obvious, that all the turbines geometrically similar,
working under the same head and having the same
values of speed ratio and flow ratio will have the same
specific speed.
The mere value of specific speed helps us in predicting
the performance of a turbine.
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22. Selection of Turbines
The selection of turbine is generally based upon the following
two factors:
a) Selection based on the specific speed
b) Selection based on the head of water
Selection based on the specific speed is a scientific method that
gives a precise information.
Selection based on the head of water is based on experience
and observational factors only.
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23. Selection Based on Specific Speed
Sl No Specific Speed Type of Turbine
1 8 to 30 Pelton wheel with one nozzle
2 30 to 50 Pelton wheel with two or more nozzles
3 50 to 250 Francis turbine
4 250 to 1000 Kaplan Turbine
23

24. Selection Based on The Head of Water
Sl
No
Head of Water ( in meters) Type of Turbine
1 0 to 25 Kaplan / Francis (preferably Kaplan)
2 25 to 50 Kaplan / Francis (preferably Francis)
3 50 to 150 Francis
4 150 to 250 Francis / Pelton (preferably Francis)
5 250 to 300 Francis / Pelton (preferably Pelton)
6 Above 300 Pelton
24

25. Characteristics Curves of Turbines
These are curves which are characteristic of a particular turbine which helps
in studying the performance of the turbine under various conditions.
These curves pertaining to any turbine are supplied by its manufacturers
based on actual tests.
The data that must be obtained in testing a turbine are the following:
1. The speed of the turbine N
2. The discharge Q
3. The net head H
4. The power developed P
5. The overall efficiency n
6. Gate opening (this refers to the percentage of the inlet passages provided
for water to enter the turbine)
25

26. Characteristics Curves for Pelton Wheels
1. Characteristics Curves for Constant Head:
26

27. Characteristics Curves for Pelton Wheels
1. Characteristics Curves for Constant Head:
27

28. Characteristics Curves for Pelton Wheels
2. Characteristics Curves for varying gate opening:
28

29. Characteristics Curves for Pelton Wheels
2. Characteristics Curves for varying gate opening:
29

30. Characteristics Curves of Francis’ Turbines
1. Characteristics Curves for unit speed:
30

31. Characteristics Curves of Francis’Turbines
1. Characteristics Curves for unit speed:
31

32. Characteristics Curves of Francis’Turbines
1. Characteristics Curves for unit speed:
32

33. Characteristics Curves of Francis’Turbines
2. Characteristics Curves for speed with varying heads:
33

34. Characteristics Curves of Francis’Turbines
2. Characteristics Curves for speed with varying heads:
34

35. Characteristics Curves of Francis’Turbines
2. Characteristics Curves for speed with varying heads:
35

36. Characteristics Curves of Francis’ Turbines
3. Characteristics Curves for varying gate opening:
36

37. Characteristics Curves of Francis’ Turbines
3. Characteristics Curves for varying gate opening:
37

38. Cavitation
Cavitation is formation of vapor bubbles in the liquid flowing through any
Hydraulic Turbine. Cavitation occurs when the static pressure of the liquid
falls below its vapor pressure. Cavitation is most likely to occur near the fast
moving blades of the turbines and in the exit region of the turbines
It usually occurs when a liquid is subjected to rapid changes of pressure that
cause the formation of cavities in the liquid where the pressure is relatively
low. When subjected to higher pressure, the voids implode and can
generate an intense shock wave.
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39. Conclusion
It assume assumptions that a turbine will work under a
constant head, speed and output. But in actual practice, these
assumptions rarely prevail. It is thus essential to review the
nature of such variations, which generally take place.
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40. Thank You
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