A steam turbine is a machine that turns thermal energy into mechanical energy by turning it. Turbines are used to drive the rotor shafts of generators; they are at the core of all power plants, and they are in charge of providing a rotating movement that produces an electromotive force (emf) in the generator coil to generate electricity. The dynamic action of the high-pressure steam expelled via the nozzle is fully dependent on the performance of the steam turbine.
Turbines are divided into four categories: water turbines, steam turbines, gas turbines, and wind turbines. Varied scientists and engineers have contributed to the development of these various designs. Steam turbines are used in power plants, industries, and cogeneration plants.
STEAM TURBINE’S WORKING PRINCIPLE
The rotor blades are dynamic and the nozzles are stationary. When high-pressure steam passes through the nozzle and strikes the blades’ surface, it causes the blades to rotate owing to a change in momentum. The resulting force on the blade causes a change in the momentum of the blades as they enter and exit. The blades are linked to the rotor shaft and transfer rotational force into momentum change.
The working principle is theoretically understood by comparing it to the rate of change in momentum of a high-velocity jet of steam striking a curved blade, that is, F=m(c1+c2)/t, using Newton’s second law of motion.
The Steam Turbine Control System monitors and protects the power plant from unsafe situations. In the case of a malfunction, the system is designed to operate automatically and minimize harm. Steam turbine power facilities are often substantially larger than power plants with other types of engines. Even if a problem occurs, the steam turbine control system ensures that the power plant remains functional. Control systems for gas and steam turbines are provided by brands like GE and Woodward. The GE series includes items like the DS200DTBBG1A and DS200GDPAG1A.
MAIN COMPONENTS OF STEAM TURBINE
The design of steam turbine components is a difficult process since it necessitates the creation of three-dimensional models of the components. Heat, pressure, impulsive force, sensitivity, stress, strain, vibrations, the number of revolutions, efficiency, and other elements must all be addressed when designing. There are different components of steam turbines, such as the rotor, shaft, blades, casing, bearings, valves, nozzle, seals, trip system, governor system, casing, and so on.
1. Rotor
Steam turbines have a casing and a rotor with rotating blades attached. The rotor is housed within the casing, which is made up of rows of moving blades that pass through rows of fixed blades. The high-pressure steam that flows through the turbine alternates between fixed and moving blades. The mechanism is designed such that the steam is directed at a straight angle into the moving blades by the fixed blade. The rotor and its case must be carefully designed to endure heat stress, and the rotor’s rotating blades must firmly withstand tremendous centrifugal forces.
2. The Casing
The casing is necessary to prevent steam from leaking into the steam turbine. A seal is required at the ends of the casing where the rotor shaft passes to avoid steam leakages. Leakages are not completely eradicated, but they can be kept to a minimum.
3. Speed controller
The entire turbine speed is controlled by the speed regulator. The speed turbines are designed to run at a rated speed known as synchronous speed, and exceeding this speed might cause harm to the machine. The turbine’s efficiency is highest at synchronous speed.
4. Back-up system
The rotor is supported by the support system, which includes a bearing lubrication system that absorbs the thrust force generated within the turbine.
5. Speed of the Governor
A speed-sensitive control system linked with a steam turbine is known as a governor or governor. It aids in the speed regulator’s synchronization. Both are intertwined and rely on one another for feedback. The governor valve detects how much steam is flowing through the turbine. The servo motor system is coupled to the steam valve, and the turbine speed is constantly compared to the synchronous speed or reference speed that is set to the servo motor’s output signal. The amount of incoming steam and exhaust steam in the turbine influence the speed.
