The fundamental of “working of
steam turbines” is can be broken into 5 steps:
- Generation of steam in a boiler
- Pressurization of steam
- Propulsion of rotors/blades by pressurized steam
- Condensation of steam after exhaust
- Continuation of the circle
In practice turbines is not that
5-step simple process. It requires utmost precision in making and
placing blades, positioning of shaft, minimization of heat loss and
proper streamlining of steam for propulsion of turbine blades.
After generation of steam by boiler it passes through a streamlined
nozzle and gains very high velocity which pushes against the blades and
causes the wheel to turn. Which drives the connected machinery. Though
turbines can be driven by water, steam, gas or wind, steam is prevalent.
The expansive force of steam is the greater than any common gas used for
power. Steam turbines are operating with an inlet pressure as high as
3500 psi, and/or with a temperature as high as 1200° F (649°C).
The heat energy contained in steam at this pressure and temperature is
extremely high. If the steam is extracted mid-way in a multistage
turbine it is called extracting type turbine.
In multistage system the speed of through successive levels goes on
increasing, therefore, there has been several control measures to
regulate speed. Also the turbine must not run in critical speed (below
operating speed). It can wear down the turbine. The control systems of
steam turbines are: Governor system, Overspeed Trip System and
Lubrication System.
