What is a Turbine ?

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What is a Turbine ?

• A Turbine is a device which converts the heat
  energy of steam into the kinetic energy then
  to rotational energy.
• The Motive 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 basic cycle for the steam turbine power plant
  is the Rankine cycle. The modern Power plant uses
  the rankine cycle modified to include
  superheating, regenerative feed water heating
  reheating.

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RANKINE CYCLE
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Impulse Reaction Turbine

• 1. Based on Blading Design
• a) Impulse turbine
• There is no pressure drop across moving blades.
  Steam energy is transferred to the rotor entirely
  by the steam jets striking the moving blades.
  Since there is no pressure drop, negligible
  thrust is produced.
• Reaction turbine
• Steam expands in both the stationary moving
  blades. Moving blades also act as nozzles. High
  axial thrust is produced.
• c) Combination of Impulse Reaction turbine

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IMPULSE TURBINE
a
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IMPULSE REACTION TURBINE
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DIFFERENCES
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Impulse Reaction Turbine

• On the Principle of working
• Impulse Turbine
• Reaction Turbine

• Impulse
  Reaction
• -Pressure drops in nozzles and not in moving
  blade -Pressure drops in fixed blade as
  well as in moving blades
• Constant blade channel area -Varying
  blade channel area
• Profile type blades -Aerofoil type blades
• Restricted round or incomplete admission of
  steam -All round or complete admission
• Diaphragm contains nozzles -Fixed blades
  similar to moving blades attached to casing
  serve as nozzles and guide the steam
• Occupies less space for same power -Occupies
  more space for same power
• Higher efficiency in initial stage - higher
  efficiency in final stages.
• Suitable for small power requirements -Suitable
  for medium or high power requirements.
• Blade manufacturing is not difficult -Blade
  manufacturing process is difficult.
• Velocity of steam is high -Velocity of steam is
  less.

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Turbines Classification

• Based on Inlet Outlet Steam Condition
• Back pressure turbines The Exhaust steam from
  the turbine flows out of the steam piping at
  medium or low pressure. Basically, the exhaust
  steam can be used effectively in any other
  machines or equipment in the plant.
• Condensing turbines Full steam quantities
  entering into the turbine are exhausted, and
  converted to condensate in a condenser. The
  exhaust steam pressure is lower than the
  atmospheric pressure.
• Extraction turbines Medium or low pressure
  steam required by the process plant is extracted
  from the intermediate stage of a condensing or
  back pressure turbine.

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CONSTRUCTIONAL FEATURES

• CASING MADE OF CAST STEEL EXCEPT CONDENSING
  STAGE WHICH IS MADE OF CAST IRON. IT IS MOUNTED
  ON THE FRONT-END BEARING PEDESTAL. EXPANSION OF
  CASING IS TOWARDS FRONT END.
• ROTOR MACHINED FROM A FORGED BLANK OF ALLOY
  STEEL. ROTOR IS A SINGLE FORGING INCORPORATING
  THE THRUST BEARING COLLARS. IT IS SUPPORTED ON
  TWO PRESSURE LUBRICATED JOURNAL BEARINGS.
  EXPANSION OF ROTOR IS TOWARDS REAR END.
• CONTROL STAGE CONSISTS OF MOVING BLADES
  NOZZLES. NOZZLES ARE MACHINED FROM SOLID BLANKS.
  THE MOVING BLADES ARE MACHINED FROM SOLID BAR
  STOCK HAVE INVERTED TEE ROOTS. TEE ROOTS ARE
  INSERTED INTO GROVES IN THE TURBINE ROTOR
  CAULKED WITH BRASS STRIP.

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LOSSES

• External Losses
• - ESV strainer losses
• - Governing losses (throttling losses)
• - Leaving Energy Losses (Latent heat of exhaust
  steam in condenser)
• - Radiation Loss to the surroundings
• Internal Losses
• Blade losses
• i) Primary Losses
• Friction loss due to profile surface finish
• ii) Secondary Losses
• - Impingement loss

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• Losses in Turbine (contd.)
• Inter stage Tip Leakages
• Steam throttles in the inter stage seals
  without doing work
• Residual velocity Losses
• Kinetic energy of the leaving steam of one
  stage will be carried over to the next stage. As
  the axial clearances increase between the stages
  (or stage groups) part of the kinetic energy will
  be lost.

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CROSS-SECTIONAL DRAWING OF BLADED ROTOR
COUPLING
THRUST
COLLAR
HAND BARRING
DISCONNECT
FOR OIL TURBINE
COUPLING
MOVING WHEEL
H.P.BLADES
WHEEL
L.P BLADES
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• Blade Profiles
• Impulse
• Reaction
• Twisted Blade

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DEFINITION OF GOVERNING SYSTEM
A SYSTEM WHOSE PURPOSE IS TO CONTROL A PRIME
MOVER The function of governor is to control
the speed of the turbine.It does this by
controlling the flow of steam to the nozzles.When
the governor reacts to speed, it controls the
steam flow and steam flow by defination is power.
Therefore, through speed governing shaft output
speed is governed with variable power output.
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Types of Governor

1. Mechanical Governor
2. Hydraulic Governor
3. Combination of mechanical Hydraulic
4. Pneumatic Governor
5. Electronic Governor

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• Protection Requirements
• Over speed
• Low Lube oil pressure
• Low vacuum
• Axial shift
• High Vibration
• Bearing temperature
• High/low extraction pressure
• Exhaust temperature
• Generator / Compressor protections
• Manual / Remote trip

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STOP VALVE
CYLINDER WITH TEST PISTON
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HP GOVERNING VALVE ASSEMBLY
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YOKE ASSEMBLY
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SERVOMOTOR
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PILOT VALVE
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MECHANICAL OVER SPEED GOVERNOR
MECHANICAL TRIPPING DEVICE (VERTICAL MOUNTING)