COMBINED CYCLE POWERPLANTSTEAM TURBINE TRAININGCOMBINED CYCLE POWERPLANTSTEAM TURBINE TRAINING
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LEARNING OBJECTIVES
When you complete this lesson, you will:
Have a basic understanding of theprinciples and theories behind the steamturbine
Be familiar with different types of turbinesand their applications
Know the importance of temperaturedistribution and monitoring.
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Hero's Aeolipile
(Reaction Turbine)
Principles and Structural Charateristics
A steam turbine is a device that convertsthermal energy of steam into mechanical energyby using it to turn the blades of a rotor.
High-temperature, high-pressure steam passesthrough a nozzle or fixed blades and shoots outand expands, or has its direction altered into ahigh-speed jet that is directed against rotorblades which spin the shaft to which they areattached, creating rotational energy.
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Typical Steam Turbine System
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Impulse Turbine
Vs
Reaction Turbine
Main feature of impulseturbines is that heat drop perstage can be quite large,allowing for large blades anda smaller number of stages.
The main feature of reactionturbines is that the heat dropper stage is lessened, soblades become smaller andnumber of stages increases.
Impulse Turbine vs ReactionTurbineImpulse Turbine vs ReactionTurbine
Classifications of Turbines
Impulse or reaction
Type and arrangement of staging
Direction of steam flow
Repetition of steam flow
Division of steam flow
Condensing or Non-Condensing
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Steam Turbine Construction
Foundations
◦Elongated bolt holes or grooved sliding seats
◦Flexible I-beam
Casings
◦Cast carbon steel for non-superheated steamapplications
◦Carbon molybdenum steel for non-superheatedsteam applications
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Steam Turbine Construction
Nozzles
◦Converts thermal energy of steam into kineticenergy
◦Directs steam against blades
Rotors
◦Manufactured from steel alloys
◦Carries moving blades that convert steam’skinetic energy to rotating mechanical energythereby transferring that rotation to thegenerator.
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Steam Turbine Construction
Bearings
◦Journal Bearings – support the weight ofthe rotor and maintain correct radialclearance between the rotor and casing.
◦Thrust Bearings - limit the fore-and-aft travelof the rotor. Absorb axial thrust, which maydevelop on a turbine rotor and hold the turbinerotor within definite axial positions.
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Steam Turbine Construction
Shaft Packing Glands
◦Prevent leaking of steam, out of, or air, intothe turbine casing where the turbine rotorshaft extends through the turbine casing.
◦Labyrinth and carbon rings are two types ofpacking used either separately or incombination.
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Labyrinth Seal
Labyrinth packing consists ofrows of metallic strips or fins.
The strips fasten to the glandliner so there is a small spacebetween the strips and the shaft.
As the steam from the turbinecasing leaks through the smallspace between the packing stripsand the shaft, steam pressuregradually reduces.
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Carbon Packing Rings
Restrict the passage of steam alongthe shaft. Carbon packing ringsmount around the shaft and are heldin place by springs.
Three or four carbon rings areusually used in each gland. Each ringfits into a separate compartment ofthe gland housing and consists of two,three, or four segments that are butt-jointed to each other. A garterspring is used to hold these segmentstogether. The use of keepers (lugs orstop pins) prevent the rotation of thecarbon rings when the shaft rotates.The outer carbon ring compartmentconnects to a drain line.
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ReviewReview
Q&AQ&A