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Steam turbine

  1. STEAM TURBINES Muhammad Yahya 2015-Uet-CCET-Mech-18
  2. What is Turbine?  A turbine is a rotary mechanical device that extracts energy from a fast moving flow of water, steam, gas, air, or other fluid and converts it into useful work..
  3. WORKING PRINCIPLE: The working principle is very much simple.  When the fluid strikes the blades of the turbine, the blades are displaced, which produces rotational energy.  When the turbine shaft is directly coupled to an electric gene- -rator mechanical energy is converted into electrical energy.  This electrical power is known as hydroelectric power.
  4. Basic types of turbines  Water Turbine  Steam Turbine  Gas Turbine  Wind Turbine Although the same principles apply to all turbines,
  5. Steam Turbines “Steam Turbine is a prime-mover in which heat and pressure energy of steam is transformed into Kinetic energy, and later in its turn is transformed into the mechanical energy of rotation of turbine shaft”
  6. Construction oF Steam Turbines
  7. Working Principle of Steam Turbine  The power in a steam turbine is obtained by the rate of change in momentum of a high velocity jet of steam impinging on a curved blade which is free to rotate.  The steam from the boiler is expanded in a nozzle, resulting in the emission of a high velocity jet. This jet of steam impinges on the moving vanes or blades, mounted on a shaft. Here it undergoes a change of direction of motion which gives rise to a change in momentum and therefore a force.  Steam turbines are mostly 'axial flow' types; the steam flows over the blades in a direction Parallel to the axis of the wheel. 'Radial flow' types are rarely used.
  8. Steam Turbine
  9. Classification Based on Principle oF Action 1.Impulse Turbine  Pressure energy of Steam is converted into Kinetic Energy.  Impulse action of high velocity jet of steam, due to change in its direction is used to rotate the turbine shaft. 2.Reaction Turbine  Reaction force due to expansion of high pressure steam when it passes through a set of moving and fixed blades is used to rotate the turbine shaft.  Due to expansion of steam, pressure drop occurs continuously over both fixed and moving blades.  This pressure difference exerts a thrust on the blades.  The resulting reaction force imparts rotary motion.
  10. Impulse Turbine 1. Casing 2. Nozzle – Pressure energy of Steam is converted into Kinetic Energy 3. Turbine Blade – Convert kinetic energy into mechanical work. 4. Rotor 5. Shaft
  11. Impulse turbine - Working  High pressure steam from boiler is supplied to fixed nozzles.  Nozzle – Pressure falls from boiler pressure to condenser pressure  Reduction in pressure increases velocity.  High velocity steam impinges on moving curved vanes  Causes change in momentum Impulsive force on blades.  Pressure remains constant when steam flows through blades.
  12. Reaction Turbine  Casing  Fixed Blades  Performs the function of Nozzle in Impulse turbine.  It directs steam to adjacent moving blade.  Moving Blades  Shaft  Rotor
  13. Working Principle  High pressure steam directly supplied to turbine blades with out nozzles.  Steam expands(diameter increases) as it flows through fixed and moving blades Continuous drop of pressure.  Velocity of steam is increased when it passes through the fixed blades.  Produces reaction on blades  Reaction causes rotor to rotate.  Propulsive force causing rotation of turbine is the reaction force. Hence called reaction turbine.
  14. Working Principle of IMPULSE And REACTION TURBINE
  15. Difference b/w Impulse and Reaction Turbine  The main difference between impulse and reaction turbine lies in the way in which steam is expanded while it moves throw them In the former type steam expands in the nozzle and its pressure doesn’t change as it moves over the blades while in the later types the steam expands continuously as it passes over the blades and thus there is a gradual fall in pressure during expansion
  16. Efficiency  To maximize the efficiency of steam turbine the steam is expanded, generating work in a number of stages.  Multiple stages turbines are highly efficient.  Most steam turbines use a mixture of both impulse and reaction design.
  17. Advantages oF Steam Turbines  Thermal Efficiency of a Steam Turbine is much higher than that of a steam engine.  The Steam Turbine develops power at a uniform rate and hence does not required Flywheel.  If the Steam Turbine is properly designed and constructed then it is the most durable Prime Mover.  In a steam turbine there is no loss due to initial condensation of steam.  In Steam Turbine no friction losses are there.
  18. Disadvantages oF Steam Turbines  High efficiency is ordinarily obtained only at high speed.  Gas turbine locomotives had similar problems, together with a range of other difficulties.  These devices are heavy and cumbersome.  Turbines can rotate in only one direction.
  19. CONCLUSION  The steam turbine is a prime mover in which the potential energy of steam is transformed into kinetic energy, and then transferred into mechanical energy by the turbine shaft. so it is concluded that the steam turbine is very useful for mechanical work.