STEAM TURBINES TO GENERATE POWER
A steam turbine is a specially designed mechanical device that converts high-pressure steam into mechanical energy that can be used to rotate blades to produce electricity using the generator. Steam turbines are widely used in industries and power plants due to their high-efficiency energy conversion. Modern industries and power plants utilize high-efficiency steam turbines that are used in multi-stage and can touch efficiency of up to 70 percent (and even up to 90 percent in industries).
Most steam turbines are integrated with a boiler in which fossil fuels are burned to produce high-pressure steam. Steam turbines utilize heat from the high-pressure steam to rotate at a very high speed. They are more compact and energy-efficient than steam engines and that is why they replace conventional steam engines in various applications.
HOW STEAM TURBINE GENERATES POWER?
The operation of a steam turbine requires a thermal energy source. Thermal energy by burning fossil fuels and nuclear energy are common energy sources. Here the concept of maximum heat transfer needs to be understood.
Latent heat of vaporization
The amount of energy to be supplied to move water molecules far apart to turn the boiling water into a steam or hot gas.
The latent heat of water is 2.2 KJ that is 2.2 KJ of energy is required to turn 1 kg of water into 1 kg of steam at 100’C.
Have ever experience that burning skin with steam is more painful than burning with hot water? Why does steam hurt more to the skin? The reason is steam contains extra heat than hot water.
When high-pressure steam flows through the inlet, it hits the turbine’s spinning blades, it further expands and cools transferring most of its energy. This makes turbine blades rotate continuously extracting most of the steam’s potential energy into kinetic energy. The kinetic energy is used to continuously rotate the generator.
The steam expands and gives all its heat in the form of kinetic energy to the turbine blade in an ideal case but in practice, it’s not possible due to various losses. A set of turbine blades is known as a stage.
A steam turbine blades are designed in such a way that it controls speed, direction, and pressure of the steam while it passes through the turbine. Depending upon the size and application, different sets of blades are attached to the rotor. Each set of blades are responsible to extract energy to a great extent by keeping the pressure at an optimal level. In multistage the turbine blades reduce the steam pressure by a very small value at each stage. Thus making the steam turbine a high-efficiency turbine.
STEAM TURBINE TYPES:
There are two basic types of turbines
1. Impulse turbine
The rotating blades are cup-shaped. When high-pressure jet steam hits the blade, it creates torque through a series of impulses making the turbine rotate.
2. Reaction turbine
There is a second set of stationary blades fixed in between the rotating blades to the rotor shaft within the turbine case. This design configuration help to improve speed and direct steam onto the rotating blades at the right angle for maximum impact. The steam leaves with reduced temperature and pressure but with almost the same speed it entered.
STEAM TURBINE TYPES:
1. Rotor
A rotor is an axle that runs through the central axis, it translates the thermal power into rotation.
2. Blades
Blades are the crucial parts of the turbine that are responsible to capture heat from the steam.
3. Inlet nozzle
The inlet nozzle is responsible to spray a jet of high-pressure steam into the turbine casing.
4. Governer
Steam turbines also need some control mechanism in order to control their speed and output power.
WHY STEAM IS PREFERRED RATHER THAN AIR OR OTHER FLUIDS?
The turbine blade spins when it gets kinetic energy from a fluid passing through it. The law of conservation of energy suggests that a gas, liquid, and most of the fluids slows down or changes their direction when they hit turbine blades losing much of their energy. This is the reason why steam turbines are more efficient than wind turbines and water turbines.
STEAM TURBINE IN MULTIPLE STAGES:
Actually, the design and working of steam turbines are complex. There is a number of different sets of blades. Each set of blades is called the stage. Each stage helps to extract energy from the steam before it gets exhausted and this design is called a compound steam turbine. Each set works either by impulse or reaction force.
STREAM TURBINES IN POWER PLANTS:
Most of the world’s electricity generated in electric power generation plants is with the use of turbines. In industries, steam turbines are used in co-generation plants. Different types of turbines used in modern power plants include steam turbines, combustion turbines or gas turbines, hydroelectric turbines, and wind turbines.