What is that gas turbine?
A gas turbine, also called a combustion turbine, is a type of continuous and internal combustion engine.
The main elements common to all gas turbine engines are an upstream rotating gas compressor a combustor a downstream turbine on the same shaft as the compressor.
The first gas powered turbine was developed in the year 1950 for application on automobile by Rovers.
Soon after this General Motors Ford and Chrysler started developing the gas turbine for Automotive application.
Inspite of the fact use amount has been spent on research and development the gas turbine has not found its place in regular production and is only used for racing cars.
Classification of gas turbine.
The gas turbines are classified into two main types these are: (A) open cycle turbines,(B) closed cycle turbines.
OPEN CYCLE TURBINES.
It also comes under internal combustion engine where heat is applied to incoming air.
Due to application of heat the gases expand and proper the turbine.
Exhaust gases are let out from the exhaust end.
*Open type turbines are again Sub-classified into two category such as –
(1) simple cycle:-
In simple cycle turbine on a common shaft compressor is mounted at one end which to the air to the turbine unit and on the other end turbine is fixed.
The compressed air is made to pass through a combustion area where fuel is injected and ignited.
Due to burning of fuel the gases expand and this expand gases with high velocity make the turbine to rotate.
(2) Regenerative cycle:-
In regenerative cycle hot gases after driving the turbine are made to pass through re generated chamber.
Here, we pre-heat the air going to the combustion chamber.
This save the amount of fuel used for rising inlet air temperature.
Apart from the to arrangement there is another another arrangement also by which the drive from the turbine is taken to the transmission which is called a two shaft or free turbine unit.
Hear, you will see that unlike single shaft arrangement air compressor and turbine are mounted on a single shaft and drive is transmitted by the same shaft to the transmission.
But in two Shaft drive the total expansion is provided in two turbines.
The first turbine is known as gas filler and is coupled to the compressor just like open cycle turbine.
Power thus developed by this turbine is utilise only for driving compressor.
The hot expanded gases after driving this turbine drive the power turbine which in turn in coupled to the transmission of the vehicle.
CLOSE CYCLE TURBINES.
In this closed cycle turbine the combustion takes place externally and the fluid does not come in contact with product of combustion.
The heat is added to heat exchanger and fuel used is is hydrogen or helium.
As the fuel used is costly, such turbines are not used for automobile application.
Working of the gas turbine.
To understand the subject Let us study the simplest turbine single shaft turbine which consists of the following major components:
(B) Combustion chamber.
(D) Starting system.
When the compressor is made to revolve with the help of starting motor it pump the air into to the combustion chamber.
In the combustion chamber fuel is spray and ignited by an electric Spark.
Due to burning of fuel gases expand and its velocity increases.
This gases strike against the Venice of the turbine making them to revolve.
As the turbine is mounted on a shaft the chapter revolves.
Since the turbine works on constant pressure and continuous combustion process.
There are no vibrations and any fuel diesel or petrol, can be used in the combustion chamber.
Advantage of gas turbine.
(1) It can operate on wide variety of fuel.
(2) It does not produce vibration.
(3) The exhaust gases are cool.
(4) It is a simple machine with less moving parts.
(5) No starting problem because of low temperature.
(6) It does not require cooling system as it have self cooling action.
(7) It is light in weight.
(8) Being compact it does not require much space.
Disadvantage of gas turbine.
(1) Due to high quality of material used in turbines cost of production is more
(2) At part load the efficiency is much less
(3) The turbine does not respond to quick acceleration
NOTE:- From the advantages, you must have noticed that turbine is capable of operating on wide variety of fuel.
It is quite in operation and is vibration free.
Once the cost factor is over come for which lot of research is going on.
The gas turbine has a bright future for being fitted on automobiles.