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An Introduction To Marine Steam Propulsion Plant [Source: US Navy]

An Introduction To Marine Steam Propulsion Plant [Source: US Navy]. Four Phases of Steam Cycle. Generation Expansion Condensation Feed. GENERATION (Boilers). GENERATION. Boiler fuel is converted to heat largest and heaviest part of steam plant

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An Introduction To Marine Steam Propulsion Plant [Source: US Navy]

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  1. An Introduction To Marine Steam Propulsion Plant [Source: US Navy]

  2. Four Phases of Steam Cycle • Generation • Expansion • Condensation • Feed

  3. GENERATION (Boilers)

  4. GENERATION • Boiler • 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

  5. 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

  6. GENERATION • 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

  7. EXPANSION (Turbines)

  8. EXPANSION • Turbines • High 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

  9. 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

  10. CONDENSATION (Condenser, MCP, AEC)

  11. CONDENSATION • Main 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

  12. 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

  13. 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

  14. FEED (DFT, MFBP, MFP)

  15. FEED PHASE • The Deaerating feed tank is the beginning of the feed phase • Direct 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

  16. FEED 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)

  17. FEED 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

  18. MACHINERY PLANT LAYOUT • No two ships are exactly alike • Machinery is arranged in various ways as space and weight permit • Generally 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

  19. 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 === END ===

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