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Main Steam Cycle

Main Steam Cycle. Let the fun begin…. Introduction. Parts of the Main Steam Cycle Four Phases of the cycle Definitions of each phase Components involved with phases Press-temp relationships. Parts of Main Steam Cycle. Steam Generator (nuclear) or Boiler (conventional) Turbines Condenser

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Main Steam Cycle

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  1. Main Steam Cycle Let the fun begin…

  2. Introduction • Parts of the Main Steam Cycle • Four Phases of the cycle • Definitions of each phase • Components involved with phases • Press-temp relationships

  3. Parts of Main Steam Cycle • Steam Generator (nuclear) or Boiler (conventional) • Turbines • Condenser • Main Condensate Pumps • Deaerating Feed Tank / Reserve Feed Tanks • Main Feed Pumps

  4. Main Steam Cycle

  5. Background • Cycle used is a Rankine cycle • P-v and T-s Diagrams • Trace the points of cycle • Provide graphical understanding of cycle • Four phases of cycle • Conventional vs. Nuclear

  6. Rankine Cycle T-s Diagram P-v Diagram 1-2: Feed Phase (DQ=0, DS=0), Win 2-3: Generation Phase (DP=0), Qin 3-4: Expansion Phase (DQ=0, DS=0), Wout 4-1: Condensation Phase (DP=0), Qout

  7. Generation Phase - Conventional • Boiler (1200 # steam) • Fuel burned to produce heat -> transferred to water which boils to steam • Steam collects in steam drum (saturated) • Superheater • Increase temp of steam and dries steam • Three reasons for superheating? • Minimize erosion (dry steam better for blading) • Minimize corrosion (less chemicals entrained) • Maximize DT (Carnot efficiency)

  8. Boiler and Superheater

  9. Generation Phase - Nuclear • Reactor (Rx) Plant • Fission in Rx core transforms nuclear energy to thermal energy • Steam Generator • Water Space • U-tubes • Steam Space • Moisture Separators

  10. Reactor Plant

  11. Expansion Phase • Steam travels down main steam piping • Turbines convert thermal energy -> mechanical energy (nozzles) and then work (blading) -> turn rotor/shaft • Pressure drops as steam goes through • Work performed on turbine blading • Main Engines (ME) -> propulsion • Ship’s Service Turbine Generators (SSTG) -> electricity

  12. Condensation • Vacuum 26-29” Hg • Air Ejectors - use 150# steam to establish initial vacuum and remove air • Maintained by condensation • volume of water << volume of steam -> contraction • Why vacuum? • Ease of steam recovery (“pulls” steam into MC) • More work out of turbines (larger DP and DT) • Ease of conversion to water

  13. Condensation • Main Condenser • Large, indirect, cross-flow, shell-and-tube HX • Seawater used to condense steam • Hotwell - holding area for condensate water at 80-100 F (lowest temp in cycle) • Main Condensate Pumps - send condensate to the DFT at 20-30 psi (suction side is lowest pressure in cycle)

  14. Main Condenser

  15. Feed Phase • Deaerating Feed Tank (DFT) • Direct-type HX (Aux Steam used) • Purposes • preheats feed • storage/surge volume • removes dissolved oxygen to minimize corrosion • FYI: RFT’s often used instead • Main Feed Pump • Supplies feed water to Steam Generator (must be high pressure to overcome pressure)

  16. Deaerating Feed Tank

  17. Putting It All Together

  18. Your Drawing • Boiler/Steam Generator • Superheater • Turbine • Condenser • Main Condensate Pumps • Main Feed Pumps • DFT/RFT • Economizer

  19. Questions?

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