Propulsion Train & Shaft Line Components by FfB43W

VIEWS: 0 PAGES: 20

									  Propulsion Train &
Shaft Line Components
               Introduction
•   Reduction Gears - fast to slow
•   Lubrication System - overcome friction
•   Shaft components - turbines to the working
    medium (ocean)
•   Propeller - transform rotational energy into
    thrust
                 Reduction Gears
•   Purposes
    –   Allow turbine and
        propeller to operate
        at most efficient
        speeds
    –   Combine two
        turbines to common
        shaft
                       Reduction Gears
•   Gear Types
    –   Straight
         •   excessive vibration
         •   low power-transfer
             ability
    –   Helical
         •   Reduces vibration,
             quieter
         •   Higher power transfer
             ability
         •   Excessive axial thrust
    –   Double Helical
         •   Two sets of teeth cut at
             opposite angles
         •   Eliminates axial thrust
                    Reduction Gears
•   Reduction Process
    –   Pinion (small) gear
        drives reduction (large)
        gear
    –   Reduction ratio = turns
        of pinion : turns of
        reduction gear
    –   Double-reduction:
        reduction in 2 steps
        (more compact design)
    –   For naval reduction
        gears, normally 30:1
                   Reduction Gears
•   Locked Train
    –   Two sets of gears and
        shafts
    –   Torque transmitted
        equally
    –   Increases ability to
        transmit torque using
        smaller components
•   Turbine shafts
    connected to reduction
    gears by flexible
    couplings to allow for
    thermal expansion
          Shaft Turning/Jacking Gear
•   Electric motor that
    rotates reduction gears,
    turbines, and shaft w/o
    using steam
    –   Cool down turbines after
        operation
    –   Prior to startup for even
        heating
    –   Position for maintenance
•   Can be used to lock shaft
    in place
    –   In event of casualty (i.e.,
        loss of lube oil)
                   Shaft Bearings
•   Designed to support the
    moving parts of:
    –   Shaft
    –   Turbines
•   Thrust bearings
    –   Absorb axial forces
    –   Ex: Kingsbury Thrust
        bearing
•   Radial (Journal) bearings
    –   Absorb radial forces
                   Lube Oil System
•   Provide lubrication and remove heat generated by
    bearings in overcoming friction
•   Major components:
    –   Sump
    –   Pump                                 Cooler
                                                       SW
    –   Strainer
                    Moving Parts
    –   Cooler
    –   Bearings                          Strainer
                                   Pump

                        Sump
                Lube Oil System
•   Lube oil can be kept in service for a long
    time if kept pure (two methods)
•   Batch Purification
    –   In-port only
    –   Uses heated settling tank
•   Continuous Purification
    –   At-sea method
    –   Centrifugal purifier separates oil &
        contaminants
                Propulsion Shaft
•   Shaft is hollow: reduces weight & increases
    resiliency
•   Consists of four sections
    –   Thrust shaft - from thrust bearing in reduction
        gears to end of engineroom
    –   Line shaft - located in shaft alley (supported by
        line shaft bearings)
    –   Stern shaft - part of shaft which penetrates hull
        (supported by Stern Tube bearings)
    –   Propeller shaft - shaft connected to propeller
        (supported by Strut Bearings)
           Propulsion Shaft
•   Different sections needed for easy
    installation, removal, & maintenance
                           Propeller
•   Made of hub and blades & creates the thrust
    necessary to propel the ship through the water
•   Terms:
     –Pitch: axial
     distance advanced
     during one
     complete
     revolution of screw
     –Face: the pressure
     side
     –Back: the suction
     side
                       Propeller Types
•   Constant vs. Variable Pitch
    –   Variable has the twisted look
    –   Adv: more efficient over wide
        range of speeds
•   Fixed vs. Controllable Pitch
    –   In controllable, blades can
        rotate on hub to change pitch
        (change direction)
•   Right vs. Left Hand Screw
    –   Viewed from aft of ship
    –   Twin-screw ships have one of
        each
CRP System
                     Propeller
•   Cavitation
    –   Formation and subsequent collapse of bubbles
        as propeller turns
    –   Occurs at critical speed
•   Effects
    –   Excessive noise
    –   Erosion of blades
    –   Decreased efficiency
Propeller Power vs. Shaft RPM
•   Flow a RPM; Thrust (head) a RPM2;
    Power a RPM3
•   So, if 10% power yields 100 RPM, how
    much power will produce 200 RPM?

      10%    x%         x = 10 * (200/100)3
      1003   2003         = 80% power
               Sample Problems
•   Shaft hP
       •   shp=2πNT/33,000
•   Effective hP
•   Propulsive efficiency
•   Slip ratio
Questions?

								
To top