ESSOM COMPANY LIMITED
Section 2: Theory
9
A
Outlet
A
Cm
1
C
1
1
2
Cm
1
Direction of Rotation
W
2
C
1
u
1
W
1
1
2
a
.
Typical Francis Turbine runner
b
.
Front View of Guide Vanes and Runner
Diagram of velocities at inlet point
(
1
) :
The water at inlet has a radial inward component
of velocity Cm
1
.
The outlet velocity is substantially
axial at C
1
at and near optimum efficiency
.
u
1
=
peripheral wheel velocity
C
1
=
absolute water velocity
W
1
=
relative water velocity
Cm
1
=
radial component of velocity C
1
Because the channel between adjacent vanes is
tapered, the velocity W
1
is increased to W
2
at
exit point
(
2
).
Figure 2- 12
:
a
.
Typical Francis turbine runner, and
b
.
Front view of guide vanes and runner diagram of velocities at inlet point
(
1
)
and exit point
(
2
).
