Gas Turbine

Gas Turbine

Gas turbines have been used for electricity generation.

Gas turbine are ideal for this application as they can be started and stopped quickly.

Over the last ten years there have been major improvements to the sizes and efficiencies of these gas turbines.

Introduction:-Gas turbine functions in the same way as the Compressed Ignition Engine. It sucks in air from the atmosphere, compresses it.

The fuel is injected and ignited. The gases expand doing work and finally exhausts outside.

The only difference is instead of the reciprocating motion, gas turbine uses a rotary motion throughout.

How does Gas Turbine works?

Working of Gas TurbineActual view of gas turbine

Compressor

Combustor

Turbine

The three main sections of the Gas Turbine

1. CompressorThe compressor sucks the air from the atmosphere and compresses it and guides it to the combustion chamber.This is an annular chamber where the fuel burns and is similar to the furnace in a boiler. The air from the compressor is the Combustion air.

2. Combustor

Stationary guide vanes of turbine direct the gases to the next set of blades. The kinetic energy of the hot gases impacting on the blades rotates the blades and the shaft.

3. TurbineA. On basis of combustion process: 1. Continuous combustion or Constant pressure type 2. The explosion or constant volume typeB. On basis of path of working substance: 1. Open cycle gas turbine 2. Closed cycle gas turbineC. On basis of action of expanding gases: 1. Impluse turbine 2. Impulse- Reaction turbineD. On the basis of direction of flow: 1. Axial flow 2. Radial flow

Classification of Gas TurbinesOpen Cycle Gas turbine Fresh air is drawn into the compressor from atmosphere.

Heat is added by combustion of fuel.

Exhaust from turbine is released in atmosphere.

Arrangement of continuous replacement of working medium is required.

Closed Cycle Gas turbine In this , cycle is closed and exhaust is not open to atmosphere.

In this there is continuously supply of same working gas.

Higher density gases like hydrogen or carbon dioxide is used.

So we get higher efficiency then open cycle GT.

Brayton cycle Comparison b/w Gas & Steam Turbine Application of GTs Advantages & Disadvantages of GT

Brayton Cycle (Ideal)Process 1-2: Isentropic compression in the compressor Process 2-3: Addition of heat at constant pressure Process 3-4: Isentropic expansion of air Process 4-1: Rejection of heat at constant pressure

Brayton cycleActual Brayton cycle

1-2 (adiabatic process ) Compression.2-3 (isobaric process ) Heat addition.3-4 (adiabatic process ) Expansion.4-1 (isobaric process )Heat rejection.

Comparison of gas & steam turbineGAS TURBINE

Use high energy fuel directly for combustionSimple in useThe gases leaving gas turbine are so hot they can be used in waste heat recovery boilerGas turbine are more expensive More flexibility

Steam turbineSteam turbine doesnt use the fuel directly

Little complex in use and takes time to start

Less flexible in startup

Less expensiveWhy gas turbine preferred over steam turbine

The Gas Turbine Plant is simple in Design and Construction. It has few Reciprocating Parts and is lighter in weight.

In Steam Turbine Plant, water is used for cooling purpose, hence there are chances of Freezing in winter nights. There are no likelihood of Freezing in Gas Turbine Plant.

The Gas Turbine is quite useful in the regions where due to scarcity it is not possible to supply water in abundance for raising steam.Applications Turbojet engines

Marine field

Railway engines

Generation of electrical power Applications

Application in AircraftNearly all the military aircrafts are powered by gas turbine.

These are used for the higher generation of power in plane.

As there is cut off the auxiliary engine gas turbine gets started

As the speed of the plane increases the compressor gets rotated and compresses the air that gets combusted in combustion chamber Then the exhaust gases are thrown out

High power-to-weight ratio, compared to reciprocating enginesSmaller than most reciprocating engines of the same power ratingFewer moving parts than reciprocating enginesLow operating pressures High operation speedsLow lubricating oil cost and consumption

Advantages Higher Cost

Less efficient than reciprocating engines

Longer startup than reciprocating engines

Less responsive to changes in power demand compared to reciprocating engines

Disadvantages THANK YOU