A machine that transforms
energy from thermal, electrical
or pressure form to mechanical
gradual change of momentum
Heat energy of the high pressure
steam is converted into kinetic energy
Change direction of steam issuing
from the nozzle
Single cylinder turbines are the one which have all the stages enclosed in one
cylinder while in multi cylinder turbines the stages are accommodated in more
than one cylinders, say two or three. Flow in these can be single flow, double
flow, cross flow or reversed flow.
Radial flow turbine incorporates two shafts end to end and can be
of suitably small sizes.
Radial flow turbines can be started quickly and so well suited for
peak load and used as stand by turbine or peak load turbines.
These are also termed as
In radial flow turbines the steam is
injected in middle near shaft and
steam flows radially outwards
through the successive moving
blades placed concentrically.
In radial flow turbines there are no
stationary blades so pressure drop
occurs in moving blade passage.
Concentric moving blades rings are
designed to move in opposite
The steam is the nozzle directs steam
tangentially into buckets at the
periphery of single wheel and steam
reverses back and re-enters other
bucket at its’ periphery.
This is repeated several times as steam
follows the helical path.
Tangential flow turbines are very robust
but less efficient.
Steam flows along the axis of turbine
These axial flow turbines are well suited
for large turbo generators and very
commonly used presently.
The force because of change in
tangential component of velocity
of fluid which may be due to
change in direction or magnitude.
The steam is first made to flow through nozzle.
Then the steam impinges on the turbine blades.
After impinging, steam glides over the concave
surface of the blades and finally, leave the turbine.
It is a circular guide mechanism.
It regulates the flow of steam.
It is kept close to the blades, in
order to minimize the losses due
These consist of a circular disc fixed
to a horizontal shaft.
The steam jet impinges on the buckets,
which move in the direction of the jet.
This movement of the blades makes the
runner to rotate.
It is air-tight metallic case, which
contains the turbine runner and blades.
It controls the movement of steam
from the blades to the condenser.
It is essential to safegaurd the runner
against any accident.
The pressure of steam jet is reduced in the nozzle and
remain constant while passing through the moving
The velocity of steam is increased in the nozzle, and is
reduced while passing through the moving blades.
The steam enters through a section
of curved blades in a fixed position.
The steam then enters the set of
moving blades and creates enough
reactive force to rotate them.
The steam exits the section of
The direction of rotation.
The water enters the guide case of the turbine with high
potential energy and relatively low kinetic energy.
The potential energy, which is a function of the pressure
difference between the runner inlet and exit, causes the fluid
to flow through the runner buckets.
As the fluid flows over the curved surface of the runner
buckets, the fluid velocity on one side of the bucket is higher
than on the opposite side.
This difference in velocity on the surfaces of the bucket causes a
pressure differential across the bucket which exerts a force on
This force at its respective radius in the runner, the revolving
part, then causes the runner to restore and impart mechanical
energy to the turbine shaft.
It is an air-tight metallic case, in which
the steam from the boiler, under high
pressure & temperature.
This casing is designed in such a way
that steam enters the fixed blades
with a uniform velocity.
It is mechanism, made up with the
help of guide blades, in the form of a
This wheel is, generally fixed to casing;
that is why these guide blades are
Allow the steam to enter the runner
Allow the required quantity of steam
to enter the turbine.
The turbine runners consists of runner
blades fixed to a shaft or rings.
The surface of the turbine runner is
made smooth to minimize the
The steam, after passing through
runner, flow into the condenser
through a tube called
In case of its absence, steam eddies
The pressure in a reaction turbine is reduced in fixed
blades as well as in moving blades.
The velocity of steam is increased in the fixed blades
and is reduced while passing through the moving
Rankine cycle is a thermodynamic cycle derived from
Carnot vapour power cycle for overcoming its
High pressure water supplied by feed pump is heated and
transformed into steam with or without superheat as per
requirement. This high pressure and temperature steam is sent
for expansion in steam turbine. Heat added in boiler, for unit
mass of steam.
(h2 – h1)
Steam available from boiler is sent to steam turbine, where it's
adiabatic expansion takes place and positive work is available.
Expanded steam is generally found to lie in wet region.
(h2 – h3)
Heat rejection process occurs in condenser at constant pressure
causing expanded steam to get condensed into saturated liquid
at state 4.
(h3 – h4)
Condensate available as saturated liquid at state 4 is sent to feed
pump for being pumped back to boiler at state 1.
(h1 – h4)
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