In this detailed post we are going to see what is turbine and what are the different types of turbines and how they work & their applications in various power plants.
What is turbine ?
A turbine is a rotating device which converts kinetic energy of a fluid into mechanical energy and/or electrical energy. The fluid can be either water or gas or steam according to the availability. It is mainly used in power plant to generate useful electric energy.
But you know how turbine work ?
Lets see in simple language
Turbines have set of blades which are mounted on rotor which helps in extracting energy from the moving fluid. The efficiency of turbines depend on the design of the blades.
Different applications need different designs and size of blades.
Turbines are categorized into Four types. The first is hydraulic turbine, second one is gas turbine , third one is steam turbine and last one is wind turbine.
Hydraulic turbine use water as their working fluid and converts hydraulic energy of water into mechanical energy. It installed at dam or near any large water reservoir.
Gas turbine in other word is internal combustion engine which produce compressed air or other gases which used to rotate the turbine and convert kinetic energy of gases into mechanical energy.
steam turbine is used in nuclear and thermal power plant in which first water is converted into high pressure super heated steam, which is further used to drive turbine.
Wind turbine rotor has 3 blades & is designed in such a way that when wind flows straight through them, they start rotating.
Turbines used in hydro power plants :-
The hydraulic turbines used in hydroelectric power plants are water turbines which have water as their working fluid. It installed at dam or near any large water reservoir which contain millions of liters of water.
More the height of dam, more the pressure it contain. The highly pressurized water is then made to flow via large pipe called as pen stock.
And the main part turbine is located at the end of pen stock from where the pressurized water strike the blades of turbine at high velocity and high speed making it to rotate. This turbine is connected to a generator which generates electricity.
The shape of turbine blades depend upon the pressure & velocity of water. Water turbines are classified into 2 types-
- Impulse type
- Reaction type
- Impulse turbine:
If a turbine uses only impulse energy of fluid, it is known as impulse turbine and Impulse turbines basically work on Newton’s 2nd law. The impulse energy means it uses only kinetic energy of fluid. In this type of turbine, first whole pressure energy or head converted into kinetic energy and this kinetic energy used to rotate turbine. The water uses only its kinetic energy and the pressure of water remains constant at inlet and exit of it.
In impulse turbines, number of elliptical half sized buckets are fitted on the rotor hub. When water with high velocity strike the buckets the rotor starts rotating. In short, the kinetic energy of water gets converted into rotational mechanical energy .
Example – Pelton turbine
- Reaction turbine:
Reaction turbines are a type of turbine that develops torque by reacting to the gas or fluid’s pressure or mass. Reaction turbine work on Newton’s third law of motion (action and reaction are equal and opposite).
In a reaction turbine, the water enters the wheel under pressure and flows over the vanes, As the water, water use its kinetic energy as well as pressure energy to rotate the turbine. Water in reaction turbine flow over the vane under high pressure, therefore wheel of the turbine runs full and may be submerged below the tail race or may discharge into the atmosphere.
Example – Kaplan turbine
Turbines used in thermal power plants :-
Thermal power plant also called as steam turbines, this type of turbine are used in nuclear & thermal powerplants where water is heated at high temperature and converted into steam & then flowed through turbines to produce electricity. Steam turbines are classified into impulse & reaction types turbine but the arrangement & design is different. Today all the modern steam turbines are a combination of impulse & reaction type.
Steam turbines have rotating blades called as rotor but also static blades called as stator. This Rotors & stators are placed alternately in order to extract most of the energy out from steam. This method is called as compounding.
Also, if you observe, the moving buckets in impulse turbine are designed to get pushed by the steam. While the rotor blades in reaction turbine are aerofoiled shape, which lets itself generate reaction & also let steam maintain its velocity !
Gas turbines :-
The gas turbine is an internal combustion engine with sets of rotating blades which suck huge amount of air & compress it which also increases the temperature. This air is then supplied to the combustion chamber .that air is uses as the working fluid. In gas turbine there are. Fuel is added into the combustion chamber & igniter ignites the fuel. Thus large amount of exhaust gases are produced which are made to flow through turbines
The different types of gas turbines/jet engines are –
- Turbo shaft
This above mention turbine are open cycle gas turbine and this turbine release exhaust gas directly to atmosphere. The other type i.e closed cycle gas turbines where the exhausted are reused again for reheating are used in power plants
Wind turbines :-
Wind turbines are most famous and affordable, clean & sustainable ! Some wind turbines are so big that they could produce 50MW or more power.
Wind turbine have rotor. This rotor has 3 blades & are designed in such a way that when wind flows straight through them, they start rotating.