TURBINES
A turbine is a rotary engine that extracts energy from a fluid flow
and converts it into useful work.It converts the energy of rushing
water, steam or wind into mechanical energy to drive a generator.Then
generator produce electricity with mechanical energy given by turbine.
Turbine type according to available head
Propeller up to 15 metres
Kaplan up to 30 metres
Francis 10 to 300 metres
Pelton 300 metres and over
Propeller turbine
propeler shaft
Since they can reach very high rotation
speeds, propeller turbines are effective for low heads. Consequently,
this type of turbine is suitable for run-of-river power stations.
PELTON TURBINE
The Pelton turbine is an impulse
turbine.It requires tangential water flow on one side of the wheel and
must therefore operate when only partly submerged. It is best suited to
applications with a high head but a low volume flow rate such as fast
flowing shallow water courses though it is used in a wide range of
situations with heads from as low as 15 metres up to almost 2000 metres.
High pressure heads give rise to very fast water jets impinging in the
blades resulting in very high rotational speeds of the turbine.Pelton
wheels are ideal for low power installations with outputs of 10kW or
less but they have also been used in installations with power outputs of
up to 200 MW. Efficiencies up to 95% are possible.Named after its
American inventor, Lester Pelton (1829-1908), this turbine uses
spoon-shaped buckets to harness the energy of falling water.
FRANCIS TURBINE
Francis turbine is mainly used in hydro electric power plants.It was named after James Bicheno Francis
(1815-1892), the American engineer who invented the apparatus in
1849.The Francis turbine is a reaction turbine designed to operate fully
submerged. Water flow enters in a radial direction towards the axis and
exits in the direction of the axis. Its is suitable for lower heads of
water of 500 metres or less and is the most commonly used high power
turbines. Large scale turbines used in dams are capable of delivering
over 500 MW of power from a head of water of around 100 metres with
efficiencies of up to 95%.
KAPLAN TURBINE
The propeller turbine, is an example of
a reaction turbine. Designed to work fully submerged, it is similar in
form to a ship’s propeller and is the most suitable design for low head
water sources with a high flow rate such as those in slow running
rivers. Designs are optimised for a particular flow rate and
efficiencies drop of rapidly if the flow rate falls below the design
rating. The Kaplan version has variable pitch vanes to enable it to work
efficiently over a range of flow rates.Austrian engineer Viktor Kaplan
(1876-1934) invented this turbine. It’s similar to the propeller
turbine, except that its blades are adjustable; their position can be
set according to the available flow.
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