1. Unit 2 -Gas And Diesel Power Plants
Gas turbine types
Open and closed cycle gas turbine
Advantage and disadvantages
Diesel engine power plant
Component and layout
Components

2. Gas turbine power plant

3. A Gas Turbine consists of three main segments
   Compressor
   Combustor
   Turbine.

4. Principle Of Operation
Ambient air is compressed to bar pressure and as a consequence its temperature rises.
Most of this warm air is used in the combustor to burn the fuel (natural gas or a liquid e.g. oil etc.).
The resulting hot gas expands through the turbine, doing work, and exits at nearly atmospheric pressure but a temperature of up to °C.

5. Principle Of Operation
Work extracted during the expansion is used to turn the turbine which drives the generator that produces electricity.
The hot exit gas from the turbine still has significant amounts of energy which is used to raise steam to drive a steam-turbine and another generator. This combination of gas and steam cycle gives rise to the term ‘combined cycle gas turbine’ (CCGT) plant

6. Open cycle-gas turbine

7. combined cycle – gas turbine

8. Advantages Of Gas Turbine Plants
They are more compact, since fuel is burnt directly in the small combustion Chamber in the gas turbine rather than in a bulky boiler
Gas Turbine has no condenser
They can be started and take more load quickly (i.e.30 seconds to 30 min)
They are simpler in design and easy to maintain
They consume less metal and other materials for the same capacity
They cost less
Unlike steam turbines , they require very less water for cooling
Gas Turbine is more suitable for power generation, where water scarcity exists or the water is more precious

9. Disadvantages Of Gas Turbine Plants
They have a lower specific power
They have lower efficiency at the modern
state of progress
They have a shorter service life
They are more sensitive to fuel quality

10. Diesel Engine Power Plant
A Diesel power station(also known as Stand-by power station) uses a diesel engine as prime mover for the generation of electrical energy.
This power sattion is generally compact and thus can be located where it is actually required. This kind of power station can be used to produce limited amounts of electrical energy. In most countries these power stations are used as emergency supply stations

11. Operation
The diesel burns inside the engine and the combustion process causes rotational mechanical energy that turns the engine shaft and drives the alternator. The alternator inturn, converts mechanical energy into electrical energy.
This type of electricity generating power station will probably be used a long time into the future, due to a need for reliable stand-by electrical source for emergency situations.

12. Essential components of diesel power plant
Diesel engine
Air intake system
Exhaust system
Fuel supply system
Engine starting system
Lubricating system
Engine cooling system
Governing system

13. Advantages Higher thermal efficiency than thermal plant
Wide range of fuels can be used
Easy fuel handling
Simple layout, easy to install
Quick to respond to load variations
Initial investment is less than other plants

14. Disadvantages Diesel cost is high
Does not work satisfactorily under continuous overload conditions
Noise pollution
Maintenance cost is high
Capacity limited to 50 MW
Life less than steam power plant