steam engine - system
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Steam Engine
SYSTEM
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General Learning Objective: Describe thebasic cycle and design features of amodern Steam propulsion system
Specific Learning Objectives:
• Define the theory of steam turbine
propulsion• Sketch and describe a steam propulsion
plant, parts and layout arrangement• Describe functions of major components• Describe the type and arrangement of
steam turbine engine
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Major Components (Pleaser efer
to page 61(ME) Boiler
Turbine
Condenser Extraction Pump
Feed Pump
Economiser Superheaters
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Steam propulsion plant layout arrangement
Condenser
Condensate pump
Deaerator
Main feed pump
Heater stages
Economizer
BoilerSuperheater
Saturated steam
Superheated steam
HP turbine
LP turbineAstern
turbine
Gearing &
propeller shaft
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Ranking Cycle
T
2’
3’4
s
3
2
1
6 5
1-2 –> Water is heated in boiler
2`-2->wet steam heated in superheated boiler
2-3->HP dry steam expand in turbine to obtainmuch work
3-4->LP steam coming out of turbine is
condensed into water in condenser 4-1-> water from the condenser heated return
back to boiler drum- this complete the cycle
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Components function
Boiler To produce steam from water
Superheater To dry the wet steam produced in the boiler
Turbine Converts heat energy of steam into
mechanical work
Condenser
To condense exhaust steam from turbine forre-use in boiler
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Components function
Feed Pump
To transfer high pressure feed water
De-aerator economizer
To raise the temperature of feed water before
entry into the boiler drum so that less heat will be
required to transform water into steam
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Steam Plant Auxiliary System
However, these system require auxiliary system. i.e
the turbine require LO System
The condenser require cooling circulating system which use
pumping system
The condensate or feed pump require power source
The boiler require fuel oil pump and forced draft fans
The pumps and the blower can be motor driven with electric
power supply from generator driven off the shaft of turbine The turbine driven generator can also have its own auxiliary
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Other Auxiliaries
Additional equipment like air ejector is also
required to remove the air and non
condensate vapors that leaks into the part
of the system – this to prevent creation of
partial pressure that impair the condenservacuum
The turbine also require sealing and gland
leadoff steam The system also require storage (surge
tank) for unneeded working fluid
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Power Equation
E
Q p Heat Power
vf
778
144)(
The power input is the heat equivalent of feed pump work
Where Pvf is the total pump head in feet water Q is the quantity of heat pumped per hour
E- Mechanical efficiency
The weight of fuel require = Net heat added/ fuel heating x boiler efficiency
Net heat added = Total heat – heat entering the boiler/
Heat rate = net heat added / horsepower produced
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Boilers Main propulsion boilers are water tube types
Steam rate of main boilers is 40-60 bar,
5000C and 60-90 tons/hr
Auxiliary steam boilers are Fire tube boilers
of low steaming capacity
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ESD I Boiler
•Super Htr located
in low temp region
exhaust gas path
•
Both Primary andSecondary have
contra flow
heating
•
Metal temp ofsecondary high
•Air attemperator
less efficient
•Burner frontfired
•Flame
impingement
reduced not
eliminated
•Response to
sudden load is
slow
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Water Tube Boiler
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Typical Fire Tube Boiler
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Fire tube and Waterside Boiler
B il S l ti id ti
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Boiler Selection consideration To design boiler to produce required quantity of steam at
required temperature and pressure the following design
consideration are necessary: Efficient operation when burning various fuel
Fit easily and conveniently in engine room space and be
accessible for operation , inspection and maintenance
Rugged enough to with stand adverse sea condition Redundant control and automation system
Reliability of thermal and structural design
Compliance to regulation
Cycle requirement
Heat balance
Fuel and firing method
Boiler for marine vehicles- space, weight , and regulation
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Fuel combustion systemBoiler Design
- fuel analysis, combustion air, efficiency
Furnace – exit gas temperature, radiant heat absorbing surface,heat absorption rate, tube metal temperature
Boiler tube bank- from type boiler, header type, boiler delivery
superheating steam
Superheater-Types and characteristics,, arrangement of steampasses, tube temperature material and attachment of headers,
supports, location of headers, slagging ad high temperature
corrosion, reheater
Air heater and economizer- air heater, economizer Desuperheater and atemperature
Circulation and steam baffle-circulation, heated down comers,
steam drum baffle
Burner
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Boiler Design Consideration Page 94) Combustion
Heat absorption rate
Circulation
Pressure drop
Duty cycle
Design limitation-Construction and physical requirement: according to Lloyd,
ABS…etc- Drums, headers, casing
-Boiler mounting:stop valve, fed check valves, feed water
regulator, safety valve, sentinel valve, high and low water levelalarm,
Pressure guage, vent and drain valve, lowdown valves, water
level indicator, water sampling connections, soot blowers
burner flame scanner and ignitors, instrumentation and control
o er pera on an
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o er pera on anMaintainaceConsideration (Page129)
Water treatment Feed water
Boiler water
Initial preparation Normal operation
Boiler cleaning
Boiler storage
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STEAM
TURBINE
INTRODUCTION
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INTRODUCTION
The Steam turbine is a device for obtainingmechanical work from the energy stored in steam.
Steam enters the turbine with high energy contentand leaves after giving up most of it.
The high pressure steam from the boiler isexpanded in nozzles to create a high velocity jet of
steam. In any type of steam engine, it is the VELOCITY of
the liberated steam, and NOT the pressure, whichproduces the force which causes rotation of the
shaft.
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The nozzle acts to convert heat energy in the
steam into kinetic energy.
Commencing with a high pressure, a high
velocity can be produced, and it is the kinetic
energy which provides the motive force of the
turbine engine. The amount of energy or force available from
steam is directly proportional to the amount of
heat available from the steam.
Heat available is proportional to the massflow of steam times change in velocity…….
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Force (kgm/s2) = Mass flow (kg/s) X
Velocity (m/s)
This is the operating principle of all steam
turbines, although the arrangements may
be vary considerably.
The heat is available only when the steam
remains in gaseous state
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If condensation takes place during passage
through the turbine, then the part which
changes state to water will not be capable ofproducing further motive power.
So the steam should therefore enter DRY and
theoretically remain dry until it is exhausted. When dry saturated steam passes through the
normal working cycle of a turbine, condensation
will take place throughout many stages, but ifSUPERHEATED steam is used this
condensation is reduced considerably.
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Types of Turbines
Impulse Turbine
Reaction turbine
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IMPULSE TURBINE
The impulse arrangement is made up of a ring ofnozzles followed by a ring of blades.
In the pure impulse turbine, the high energy
steam is expanded only through fixed nozzles,
with a decrease in pressure and an increase invelocity.
Energy in the steam is converted to kinetic energy
when the jet of steam impinges / directed onto the
moving blades and leaves in a different direction.
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The changing direction and therefore velocity
produces an impulsive force which mainly
acts in the direction of rotation of the moving
turbine blades causing rotation and
mechanical work.
The passage between the blades is ofparallel section, no expansion or change of
pressure takes place between the inlet and
outlet sides of the blade.
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Impulse Turbine Blades
•Flow area between two blades is constant
• No pressure drop when steam flows over blade
•Flow velocity constant
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Two stage impulse
turbine with diaphragm blades to change
direction of steam flow
to enter next stage of
turbine
Impulse turbines were classified
as below:
Single Stage
Velocity compounded
Pressure compounded
Pressure-velocity compounded
Velocity-pressure compounded
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Reactive turbine
They are turbines develop torque by reacting
to the gas or fluid's pressure or mass.
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Efficiency calculation
Efficiency of turbine bade = work in blade /
energy in steam
E
Q p Heat Power vf
778
144)(
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Summary
• Steam propulsion plant, parts and layout
•
Major components• arrangement of steam turbine propulsion