Gas Turbine : Introduction, working, types and its applications.

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Gas Turbine

A gas turbine is a combustion engine that can convert natural gasses or other liquid fuels on mechanical energies. And then this energy is converted into electrical energy with the help of generator.
The gas turbine is a prime mover which develops the power by burning of fuels. The gas turbine are the axial flow machine which converted the heat from combusted fuel into the thrust power or shaft power. The hot gasses undergo momentum changes when the flow through the passages from by the stationery and rotating blades.

Gas turbine are used to electricity generation. the gas turbine is a one of the most widely used for power generating technologies. Gas turbine are a type of internal combustion engine in which burning of air and fuel mixture produces the hot gasses that spin a turbine to produce power. It is the production of hot gasses during fuel combustion, not the fuel itself that the gives that the gas turbine name. Gas turbine can utilized a variety of fuels, including natural gas, fuel oil,and synthetic fuels. combustion occurs continuously in gas turbine ,as opposite to reciprocation internal combustion engine, in which combustion occurs intermittently.

Fuel used in Gas turbine :
The gas turbine can use fuel in the combustion chamber of three different varieties.
Liquid fuel
Gaseous fuel
Solid fuel.

Working of the Gas Turbine

Gas turbine are contain of three primary sections mounted on the same shaft : the compressor, combustion chamber and the turbine. The compressor can be either axial flow or centrifugal flow. Axial flow compressor are more common in in power generation because the are the high flow rate and efficiencies. Axial flow compressor are compressed of multiple stages of rotating and stationary blades through air is drown is parallel to the axis of rotation inn incrementally compressed at is passes through each stages. The acceleration of the air through the rotating blades and the diffusion by the stators increase the pressure and reduce the volume of the air. Although no heat is added, the compression of the air also causes the temperature to increase.


The compressor air is mixed with the fuel injected through nozzles. The fuel and compressed air can be premix or the compressed air can we introduced directly into the combustor. The fuel air mixed ignited under constant pressure condition and the hot produce gasses are directly through the turbine where it expended rapidly and impart to rotation the shaft. Thus the turbine is also compressed of the stages ,each row with a stationary blades or nozzle to direct the expending the direct the expanding the gasses followed by a row of moving blades.
The rotation of the shaft drive the compressor to draw in a compress more air to sustain continuous combustion. The remaining shaft power used to drive a generator which produce the electricity.
Approximately 55 to 65 % of the power produce by turbine is use to drive the compressor. To optimize the transfer of kinetic energy from the combustion gasses to shaft rotation, gas turbine can have multiple compressor and turbine stages.

Types of Gas turbine

Basically the gas turbine can be divide into two types- 
1. Constant volume type
2. Constant pressure type.

1. Constant Volume type Gas Turbine

It is also known as explosion combustion type. The combustion of fuel in this case take place at constant volume.The air drown from the atmosphere is compressed in the compressor to the pressure of 15 to 35 N/cm squire. and forced in tho the combustion chamber through the valves. the oil which is stored in the fuel tank is pumped into the combustion chamber through the injector by mean of the fuel injection pump.
Afterwords the injection is stopped and the oil is ignite in pressure of air by the help of spark plug. the ignition takes place or constant volume resulting in an explosion and during this the pressure suddenly rise to about 10 to 145 N/cm squire.

2. Constant Pressure type Gas Turbine

It is also called as continuous combustion type. It works on the braytron cycle or jule cycle. Atmospheric air is drown and compressed by the compressor which is usually driven by the turbine rotor shaft to a pressure of 15 to 40 N/cm squire. The high temperature and pressure air flows through the annular space between the wall of combustion and mixing chamber. This hot air then meets and mixes with the hot gasses from the burner. thus it seems that  a quantity of air quite in axes of the required for the combustion of oil in the combustion chamber is supplied by the compressor.
The mixture of the hot gasses and the excess air passes over the various rings of moving blades of the turbine it expends continuously and inn the process of pressure drops giving rise to an equivalent increase in kinetic energy.
The turbine drive the compressor and the generator . The part of the turbine output which is used to drive the compressor is called the back work. The net power available out of a gas turbine is equal to total power developed by the turbine minus power required to drive the compressor.
The compressor consume about 75% of the power developed by the turbine only the remaining 255 being made available to the plant for driving the generator.

Advantages and Disadvantages of Gas Turbines

Advantages:
  • There are the some following advantages of gas turbine -
  • The fuel and the lubrication cast are low.
  • The vibrations are very less.
  • These are less fluctuations of energies.
  • It has high speed operations.
  • It has low power to weight ratio.
  • There is smooth operations.

Disadvantages:
  • The significant part of the work developed by the turbine is used to derive the compressor. therefore, network output of the plant is low.
  • The temperature of the product of combustion becomes too high, so the service conditions become complicated even at moderate.

Applications : 

There are the following applications of Gas turbine -

  • Gas Turbine is used for supercharging.
  • It is used in turbojets and turbo propeller engines..
  • It is also used in marine fields and in railways.
  • The gas turbines are used for heavy duty armoured vehicle to cruise at high speed.
  • The gas turbine are very popular for electricity generation, because of the ability of starting and brought up to fill load quickly and less cost in installation and maintenance.
  • Gas turbine are also used for industrial purpose. 




























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