ESSOM HB023P, Инструкция по эксплуатации

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ESSOM COMPANY LIMITED Section 2: Theory
3
▪
Friction Head
When a liquid flows from one point to another, part of energy or head of liquid flow is lost due to friction between
the liquid and the pipe wall or the flow channel wall as well as the interaction of the liquid molecules
.
The resulting head
loss is called Friction Head
.
Friction Head between point 1 and 2 is
:
 
1 2 1 2
1 2
2 2
2 2
f
p p V V
h Z Z
g g
 
  

 
     
 
 
  

 
(
2.2
)
Where
:
f
h

Difference in pressure head due to friction, m
2
.
2 Hydro Turbine at a Power Station
.
A reservoir above the hydropower dam stores water at high elevation, hence creating static head or potential energy
due to elevation
.
If the water is allowed to flow to a lower elevation through a pipe, normally a large diameter steel pipe
that is known as “penstock”, going into a water turbine .
In the turbine, part of the energy of the fluid flow or hydraulic
energy is transferred to mechanical energy at the rotating shaft of the turbine to drive the generator for producing electrical
power
.
Water then flows out of the turbine through the trail gate at the atmospheric pressure
The schematic diagram of a typical hydro power station is as shown in Error! Reference source not found. below
:
Figure 2- 2
:
Schematic flow diagram of hydro power station
.
The ideal theoretical consideration of the fluid flow system of the hydro
-
power plant with a turbine per general energy
passing from point
(
1
)
to point
(
2
)
through the penstock is as follows
:
1 1 2 2
1 2
2 2
2 2
p V p V
Z Z
g g
 
     (
2.3
)
Since,
1
Z
=
Elevation of the dam reservoir above turbine outlet as datum line
.
1
V
=
0
1
p
=
0
(
atmospheric pressure
)
2
Z
=
0
(
turbine outlet as datum line
)
Water at point
(
2
)
is under very high pressure and the velocity of fluid passing through a normally large diameter penstock
is rather low and may be negligible
(
V
2
=
0
)
Hence,
2
1
p
Z


(
2.4
)
And from sections
(
2
)
and
(
3
)
passing through the turbine the equation is as follows
.
1
2
3
Surge tank
Pen
stoc
k
Turbine
Tail water
Headwater
Pressure pipe
Energy grade line
Y