Basic Mechanical Engineering- Hydraulic Turbines 4 November 2010.
Steam Turbines Expansion Phase References Required – Introduction to Naval Engineering (Ch. 8)...
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Transcript of Steam Turbines Expansion Phase References Required – Introduction to Naval Engineering (Ch. 8)...
![Page 1: Steam Turbines Expansion Phase References Required – Introduction to Naval Engineering (Ch. 8) Recommended – Principles of Naval Engineering (pp. 144-145)](https://reader035.fdocuments.in/reader035/viewer/2022062715/56649d815503460f94a66503/html5/thumbnails/1.jpg)
Steam TurbinesExpansion Phase
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References
• Required– Introduction to Naval Engineering (Ch. 8)
• Recommended– Principles of Naval Engineering (pp. 144-145)
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Objectives
A. Comprehend the basic design of steam turbines.
B. Comprehend the energy conversions present in steam turbines and represent those conversions on a pressure velocity diagram.
C. Know the various uses of steam turbines used onboard ships.
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Introduction
• Turbines are energy conversion devices• Turbines used for:– Propulsion– Electricity generation– Prime mover for various pumps• MSW Pumps• MFP• Fire pumps• Lube Oil Pumps
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Turbine Components
• Casing - containment vessel• Nozzle(s)- energy conversion devices that
converts the thermal energy of the steam to kinetic energy
• Blades- energy conversion devices that convert kinetic energy to rotational mechanical energy
• Rotor- supports the blades and transfers rotational mechanical energy out of the turbine
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Nozzles
• Definition: mechanical device which:– uses a reduction in surface area to
convert thermal energy to kinetic energy (enthalpy to kinetic energy)
– directs fluid flow onto turbine blading
• Components: inlet, throat (smallest diameter), and mouth (outlet)
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Nozzles
• As Pressure drops velocity KE(=mv2/2)• Types:
ConvergingConverging-Diverging
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Blades
• Steam exiting nozzles hits blades on rotor and pushes them through a distance
• KE Work• Two types of blades:– Impulse– Reaction
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Blades
• Impulse– Steam hits blade @ high
velocity, moves blade by a “direct push” and exits at low velocity
• Reaction– “Fixed vane” nozzles increase
velocity, and “moving vane” blades move by a reaction force or “kickback”
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Blades
• Reaction Turbines are moved by three main forces:– Reactive force produced on the
moving blades as the steam expands between the blades.
– Reactive force produced on the moving blades when the steam changes direction.
– Push or impulse of the steam impinging on the blading.
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Classification of Turbines
• Staging (groups of blades)• Compounding (groups of stages)• Direction of Steam Flow • Division of Steam Flow
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Staging
• Rateau Stage One set of nozzles and moving impulse blades– Only one pressure drop
P
V
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Staging
• Curtis Stage • 1 nozzle, 2 sets of moving blades, one set
of fixed blades– Two velocity drops
P
V
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Staging
• Reaction Stage (called Parsons stage)– One set of fixed vane nozzles and moving
nozzle-shaped blades– Two pressure drops
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Compounding
• Building turbine with multiple stages to extract maximum energy
• Velocity Compounding– Only one pressure drop with multiple
velocity drops using multiple stages• Pressure Compounding– Multiple pressure drops using
multiple stages
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Compounding - Impulse Turbines• Velocity-Compounded
Impulse Turbine– One nozzle, row of
moving blades, row of fixed blades, & second row of moving blades (called Curtis stage)
– Adv: Good if initial high pressure
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Compounding - Impulse Turbines
• Pressure-Compounded Impulse Turbine– Two or more
impulse/Rateau stages– Adv: increases
efficiency by using lower pressures
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Compounding - Impulse Turbines
• Velocity-Pressure Compounded Impulse Turbine– One Curtis stage followed
by single or series of Rateau stages
– Common for many propulsion turbines (allows for lower blade speed)
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Compounding - Reaction Turbines• Pressure-Compounded
Reaction Turbine– Called Parsons turbine
because uses Parsons stages
– Adv: efficient at low pressure/low velocity
– Disadv: long stage and impractical
– Used in some auxiliary applications
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USS Narwhal (SSN-671)
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Direction of Steam Flow
• Axial Flow– Steam flow parallel to
turbine shaft axis (used a lot, particularly for propulsion)
• Radial Flow– Steam flow
perpendicular to turbine shaft axis (used some for auxiliary turbines)
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Division of Steam Flow
• Single Flow– Steam enters at inlet and flows in
one direction to the exhaust
• Double Flow– Steam flow split & flows in two
directions– Allows turbine size to be reduced– Axial thrust on shaft avoided
(axial flows cancel)
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Turbine Components
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Questions?