Today we will learn about types, advantages and disadvantages, application and working of gas turbine. There are different gas turbines which used in different conditions. Gas turbine is mainly used air as the working fluid. The air is taken from atmosphere and compressed into a compressor. The compressed air is passed through combustion chamber where it is heated. Due to continuously heating in combustion chamber, pressure and temperature of air increases. This high pressure hot air allow to flow over the moving blades of turbine, which rotate the turbine. Finally the air is exhausted into the atmosphere. This is the main process of gas turbine. The power developed by the gas turbine is used for rotate the compressor and for doing some external work.
The gas turbine may be classified as follow.
According to the path of the working substance:
1. Closed cycle gas turbine
It is the simplest form of gas turbine, which consist a compressor, combustion chamber, gas turbine and a cooling chamber. This turbine is worked on Brayton cycle. First the air is compressed into a compressor. This compressed air is send into the combustion chamber where the fuel is burn where air is heated at constant pressure. Than this heated air is passed over the turbine, which rotate it. This expansion of air takes place issentropically. Now the air is cooled into the condenser at constant pressure and again sends to compressor. This process is run continuously which generate power. The air is again used into this system and does not exhaust into atmosphere, so it is known as the closed cycle gas turbine.
2. Open Cycle Gas Turbine:
An open cycle gas turbine consist same parts as closed cycle gas turbine except cooling chamber. It consist a compressor, a combustion chamber and a gas turbine. The compressor sucked the fresh air from atmosphere and compresses it. This compress air sends to combustion chamber where heat is added into it. Finally this high temperature air sends to gas turbine where it expands issentropically and rotates the turbine. At the end after air is fully expanded into combustion chamber it is exhausted into the atmosphere and new air sucked by the compressor. This process runs continuously to develop the power. The air does not complete the full cycle and every time new air drawn from atmosphere, so it is known as open cycle gas turbine.
According to the process of heat absorption:
According to heat absorption the gas turbine can be divided into two types.
1. Constant pressure heat absorption
This is an ideal cycle of gas turbine. The air is compressed issentropically and heat is added at constant pressure. This turbine works on Brayton cycle.
2. Constant volume heat absorption
In this turbine the gas is heated at constant volume in combustion chamber while heat is rejected into the condenser at constant pressure. This turbine works on Atkinson cycle.
Advantages and Disadvantages:
1. It requires less space for installation.
2. The installation and running cost of gas turbines are less compare to others.
3. It has very high power to weight ratio.
4. It generates less vibration compare to reciprocating engine.
5. It starts easily and quickly.
6. It can work in changing load condition easily.
7. Its efficiency is higher than IC engines.
8. It can develop uniform torque, which is not possible in IC engines.
1. Starting problem. It cannot start easily because compressor is driven by the turning itself. So an external unit is required to rotate the compressor to start the turbine.
2. Most of power is used to drive the compressor so it gives less output.
3. Overall efficiency of turbine is low because exhaust gases contain most of heat.
The gas turbine is used where high power and speed are main consideration. Gas turbine is used in jet population unit in air craft, in ships as population unit, in supercharging system in automobile and also in electric generating station and in locomotives. The open cycle turbine is mainly used in airplanes.
Today we have discussed about gas turbine types, advantages and disadvantages, working and application. If you have doubt regarding gas turbine, ask by commenting.