Vijay Marcel D
I year M.Tech(R.E)
• Invented by Prof. Viktor Kaplan of Austria during 1913 – 1922.
• The Kaplan is of the propeller type, similar to an airplane
• The difference between the Propeller and Kaplan turbines is that
the Propeller turbine has fixed runner blades while the Kaplan
turbine has adjustable runner blades.
• The kaplan's blades are adjustable for pitch and will handle a great
variation of flow very efficiently.
• The kaplan turbine, unlike all other turbines, the runner's blades
• The application of Kaplan turbines are from a head of 2m to 30m.
Comparison with other turbines
• Pelton turbines are tangential flow impulse turbines
operate above a head of 200m and low discharge. low
specific speed of 8.5 to 30 for single jet and 30 to 51
for two or more jets.
• Francis turbine is a mixed flow reaction turbine
operate under a head of 30 to 200m and medium
discharge specific speed of 51 to 255.and has
minimum slow rate
• Kaplan turbine is axial flow reaction turbine operate
under a head of 2 to 30m and large discharge. a high
specific speed of 255 to 860.
Parts of kaplan turbine
The main part of kaplan turbine are
Guide vanes mechanism
Runner of turbine
• Scroll casing:The water from penstock enters scroll
casing and surrounds the runner.It provides an even
distribution of water around the circumference of the
turbine runner maintaining the constant velocity for the
• Stay ring:The function of stay ring is to direct the water
from scroll casing to guide vanes.
• Guide vanes:The guide vanes direct the water at an
appropriate angle and regulates the quantity of water
supplied to the runner
• Runner blades:The blades are attached to the hub and
so shaped that water flows axially through the runner
• A Draft tube connects the runner exit to tail race.
• It is a pipe of gradually increasing area used for
discharging water from exit of turbine to tail race.
• By using draft tube, the kinetic energy rejected at the
outlet of turbine is converted to useful pressure
• The turbine may be placed above the tail race and
hence it can be inspected properly.
Types of Draft tubes:
The following are the important type of draft
tube which is used are
a. Conical draft tubes
b.Single elbow tubes
c. Moody spreading tubes and
d.Elbow draft tube with circular inlet and
• The conical draft tubes and moody spreading
draft tubes is more efficient.
Operation of kaplan turbine
• The water from the penstocks enters the scroll casing and
then moves to the guide vanes.
• From the guide vanes, the water turns through 90° and
flows axially through the runner.
• For Kaplan Turbine, the shaft of the turbine is vertical.
The lower end of the shaft is made larger and is called
‘Hub’ or ‘Boss’.
• The vanes are fixed on the hub and hence Hub acts as
runner for axial flow turbine.
Important parameters for kaplan turbine
• The peripheral velocity at inlet and outlet are equal
u1=u2= ∏DoN/60 were Do is outer dia of runner
• Velocity of flow at inlet and outlet are equal
• Area of flow at inlet = area of flow at outlet
A = (∏/4)(Do2-Db2) ,Db is diameter of hub
• Specific speed of kaplan turbine is given by
Ns = N√P/H5/4 were P is shaft power in KW
• Discharge Q=A*Vf1
Overall efficiency is given by ηo=P/