kaplan turbine

1. FLUID MACHINES
Chapter 3: Water Turbines
Kaplan Turbine
Presented by
Keshav Kumar Acharya
Teaching Assistant
TU, IOE
Purwanchal Campus

2. Kaplan turbine
Spiral Casing
Runner
Guide Vanes
Stay Vanes
Draft Tube Cone

3. When to use a Kaplan Turbine

4. Kaplan Turbines
• Operates under low head and
high discharge
• Axial flow reaction turbine
• The runner vanes can be
governed i.e. the pitch of the
blades are automatically
adjusted by the governor,
while the turbine is in motion
at constant speed to suit the
particular load, thus
maintaining the optimum
efficiency over wide range of
loading
• Space between guide vanes
and the leading edge of runner
is called swirl chamber

5. Kaplan Turbines
• The direction of flow changes
from radial to axial in this
chamber
• Flow pattern changes
approximately to free spiral
vortex (i.e Vu. r = constant)
• The guide vanes impart whirl
component to the flow and the
runner blades remove the
whirl making discharge purely
axial
• The number of blades in
Kaplan turbine is 3 to 6 or
utmost 8 in exceptional cases

6. Kaplan Turbines
• All the parts such as spiral
casing, guide mechanism and
draft tube are similar to those of
Francis turbine except the runner
• The runner has two major
differences:
– Water enters axially while it
enters radially in case of
Francis turbine
– The no. of blades in case of
Francis turbine is 16 to 24
while it is only 3 to 6 or atmost
8 in exceptional cases in case
of Kaplan or Propeller turbine
(this reduces the contact
surface and thus frictional
resistance)

7. Kaplan Turbines

8. Kaplan Turbines
• The runaway speed of a Kaplan
turbine is 2.5 to 3 times its normal
working speed whereas the
Francis that of Francis turbine is
2 to 2.2 times
• So, the revolving parts of the
turbo set are designed to
withstand runaway speed of 2.5
to 3.5 times the working speed.
• Emergency oil pressure system
and runner braking vanes have
been devised to prevent the
maximum runaway speed being
attained particularly where intake
gates are omitted

9. Kaplan Turbines
Adjustment of Kaplan Blades
• Blades can be adjusted to vary
passage area between the two
blades
• Done by means of servomotor
mechanism operating inside the
hollow coupling of turbine and
generator shaft
• The mechanism consists of a
cylinder with a piston working
under oil pressure on either side

10. Kaplan Turbines
Adjustment of Kaplan Blades
• The piston is connected to upper
end of a regulating rod or blade
operating rod, the up and down
movement of which turns the
blades
• The regulating rod passes
through the turbine main shaft
which is made hollow for this
propose
• Movement of rod is controlled by
governor

11. Application of Aerofoil Theory to
Axial flow turbo-machinery

12. Application of Aerofoil Theory to
Axial flow turbo-machinery contd..

13. Pressure distribution and torque

14. Energy Conversion in a Kaplan
Turbine
Outlet
draft tube
Outlet
runner
Inlet
runner
Outlet
guide vane
Inlet
guide vane

15. Hydraulic Efficiency
Flow rate Q
Runner blade angle
f = constant

16. Velocity triangles for an axial turbine
contd..
Outlines of runners
Inlet & Outlet velocity triangles at
Edge
Inlet & Outlet velocity triangles at
Hub
Inlet velocity triangles at both at
Edge & Hub