an introduction to marine steam propulsion plant [source: us navy]
TRANSCRIPT
An Introduction
To
Marine Steam Propulsion Plant
[Source: US Navy]
Four Phases of Steam Cycle
GenerationExpansionCondensationFeed
SG/Boiler
Superheater
Economizer
GENERATION (Boilers)
GENERATIONBoiler
– fuel is converted to heat– largest and heaviest part of steam plant– heat is transferred via conduction to water in the
metal tubes– some of this water becomes steam
Steam drum– as steam is generated it collects in the upper
portion of the boiler– steam collecting in the steam drum is called
saturated steam
GENERATION
Super heater– saturated steam does not contain enough
thermal energy to make the turbines operate efficiently
– uses heat from the burner section of the boiler to increase the temperature of the steam
– superheated steam is also dryer which helps prevent erosion of the turbine blades and main feed pumps
GENERATIONGENERATION
Economizer– improves efficiency in the steam plant– uses thermal energy that would go up the
stack to preheat feedwater before the steam drum
– nest of tubes located between the generating tubes of the boiler and the stack
MainShaft
ReductionGears HP
Turbine
LPTurbine
EXPANSION (Turbines)
EXPANSION
TurbinesHigh pressure/high temperature steam
goes from the superheater outlet to the high pressure turbine of the main engine – this is where expansion begins– superheated steam expands in the turbine
and is converted to mechanical energy to turn the rotor
EXPANSION
– energy conversion takes place in two steps in each stage of turbine blades
– first the steam passes through the nozzles which increase the steam’s velocity
– this kinetic energy is then converted into work by the turbine blades
– after steam leaves the HP turbine it still has thermal energy
– steam undergoes the same process in the LP turbine
Condenser MU FeedTank
CondensatePump
Air EjectorCondenser
CONDENSATION (Condenser, MCP, AEC)
CONDENSATIONMain Condenser
– large sealed container that serves as an indirect-type shell and tube heat exchanger
– cool seawater flows through thousands of internal tubes
– steam from the exhaust of the LP turbine flows over these tubes and heat is removed from the steam, condensing the steam in to a liquid (Condensate)
– The condensing action of the steam creates and maintains a vacuum in the condensers
CONDENSATION
Main condensate pump– one or two stage centrifugal pump,
electrically driven– moves condensate from the hotwell through
the main air ejector condenser to the deaerating feed tank
– pump is drawing a suction on the water in the hotwell
– lowest pressure in the system occurs here
CONDENSATION
Air ejector condenser– shell and tube heat exchanger – two functions
removes latent heat from the auxiliary steam being discharged by the air ejector
transfers heat from the steam to the condensate to preheat it before it enters the deaerating feed tank
DFT
BoosterPump
FeedPump
FEED (DFT, MFBP, MFP)
FEED PHASEFEED PHASEThe Deaerating feed tank is the
beginning of the feed phaseDirect type heat exchanger - three
functions– feed is heated by auxiliary steam and then
falls to the lower section - causing the oxygen held in solution to be removed
– heats feed and maintains proper temperature of water
– storage tank for heated oxygen free feedwater
FEED PHASEFEED PHASE
Feedwater goes from deaerating tank to main feed boost pump(MFBP)
MFBP– one or two stage double suction centrifugal
pump– installed below the DFT– discharges into the suction side of the main
feed pump (MFP)
FEED PHASEFEED PHASE
MFP– Large Multistage Centrifugal pumps (steam or
electrically driven)– delivers feedwater in sufficient amounts and
develops enough pressure to force the water into the boiler against the pressure of the steam drum
MACHINERY PLANT LAYOUT
MACHINERY PLANT LAYOUT
No two ships are exactly alikeMachinery is arranged in various ways as
space and weight permitGenerally speaking
– Propulsion machinery is usually on two levels condensers and main reduction gear on lower
level propulsion turbines and pinion gears are on
upper level
MACHINERY PLANT LAYOUT
MACHINERY PLANT LAYOUT
– Low pressure turbine exhaust is directly above the condenser
– Boilers are on the lower and upper levels along the centerline of the ship
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