ESSOM COMPANY LIMITED
Section 2: Theory
4
3
3
2
2
2
3
2
2
2
2
T
p
V
p
V
Z
Z
H
g
g
(
2.5
)
Since,
Z
2
=
Z
3
=
0
(
datum line
)
V
2
=
0
(
Normally p
2
is very high and V
2
is low because of large penstock diameter and hence negligible
)
p
3
=
0
(
atmospheric pressure
)
V
3
=
0
(
normally large turbine outlet tailrace velocity is low, and hence negligible
)
H
T
=
0 Energy generated by turbine
▪
Water Turbine Test Set
For the turbine test set, the energy of the water is not from static or elevation head but from the pressure head
created by the pump
.
P
T
f
H
H
h
(
2.6
)
Where
H
T
=
Energy generated by turbine
2
.
3 Type of Hydro Turbines
Generally, water turbines may be classified into 2 main types according to the method of converting water power to
useful mechanical power as follows
:
2
.
3
.
1 Impulse type turbine
In this type of turbine, pressure head is completely transformed into velocity head by a nozzle at an atmospheric pressure
.
The water jet is directed towards the turbine runner buckets
.
With proper design, the velocity of water leaving the buckets
should drop to nearly zero
.
Notable turbines under this type are Pelton and Cross Flow Turbines
.
▪
Pelton Turbine
This impulse type of turbine, as shown in
Error! Reference source not found.
is suitable for medium size
hydroelectric power station operating at a rather high head of water with a rather small quantity of water flow
.
The function of a Pelton turbine is to transform the fluid energy, first in the potential form of pressure head, into
the kinetic form of velocity head by means of a free water jet in one or more nozzles
.
The impact of the jet on the runner
bucket produces kinetic energy, which can be measured by a mechanical or hydraulic dynamometer
.
Figure 2- 3
:
Typical Impulse
(
Pelton
)
turbine installation
.
