Introduction to gas turbines
Gas turbines can be used for electricity generation, it is very ideal for this operation because it can be started and stopped quickly there are two basic types of gas turbines they are
- Aero derivative
- Industrial
A gas turbine consists of three sections they are compressor, combustor and a power turbine
Working principle
Air can be compressed to high pressure by a fan like a device called the compressor then the compressed air and the fuel are mixed together in a combustion chamber and ignited, and hot gases are produced by this and these gases are used to spin the turbine wheels. Gas turbine burns fuels such as oil natural gas and pulverized coal, but they won’t use the heat to produce steam instead of that it uses hot gases directly to turn the turbine blades
The compressor and the turbine are mounted at the common end on a combustion chamber with a common horizontal axle with the combustion chamber between them
This turbine is not a self-starter a starting motor is used for that which initially drives the compressor till the first combustion of the fuel takes place and after that, the turbines power runs the compressor
- The burning gas which is created by fuel and air in the combustion chamber is rushed into the turbines where it will rotate the turbine
- These hot gases move through a multistage gas turbine
- It has fixed and moving blades, the stationary blades guides the moving gas to the rotor and adjust its velocity
Which fuel is used in gas turbines
- It can operate on any gaseous or liquid fuels such as crude oil, natural gas, methane, distillate, and jet fuel
- Gas produced by biomass can be used too
- Gas produced by gasification process is used, example coal and municipal waste
- Gas produced by the industrial process is used such as oil refining
- But while using natural gases the output and thermal efficiency of the gas turbine is higher than using most of the liquid fuels
Inlet air
The air which enters the combustion chamber must be cleaned of impurities such as dust and smoke which may erode or stick to the blades of the compressor or turbine and it will reduce the power efficiency of the gas turbine. Water baths and dry filters are used to do the cleaning
What are the advantages that gas power plant have over diesel power plant
- Vibration is less due to perfect balancing
- Less space required
- Less capital cost
- Mechanical efficiency is high
- Speed of the turbine is high
- Maintenance and installation cost is less
- Ignition and lubrication system are simple
- Fuel consumption does not increase in time
- Low-quality fuels can be used
What are the advantages does gas power plant have over steam power plants
- There is no ash handling problem
- Capital cost is low
- Required space for installation is less
- Requires less space and water supply
- Only fewer auxiliaries are required
- Handling and storage of fuel is easy and economical
- Efficiency is higher above 550 degree
- It can be bought to load quickly so it can be used as peak load plant
- Exhaust to inlet ratio can be less
How to improve the performance and power input of gas turbine
Intercooling
Intercooling in multistage compression reduces compressor work, it increases work ratio and specific work ratio
Regeneration
Heat energy is transferred from exhaust to the compressed air before it enters the combustion chamber It saves fuel. heat waste is reduced and thus thermal efficiency is increased
Reheat
It increases the work output of the plant
Advantages of gas turbine power plant
- Storage space of fuel is less
- Less maintenance
- Construction is simply no need for boiler and condenser
- Cheaper fuels can be used
- Gas turbine plants can be used in water scarcity area
- Less pollution and less water is required