ENGINEERING LESSON GUIDE 11

1
INTRODUCTION TO NAVAL ENGINEERING
POWER TRAIN COMPONENTS
2
SHAFT LINE COMPONENTS

• REDUCTION GEAR
• SHAFT
• JACKING GEAR
• FLEXIBLE COUPLING
• THRUST BEARINGS
• JOURNAL BEARINGS
• PROPELLER

3
MAIN REDUCTION GEARS

• Used for 2 Reasons
• Allow both the prime mover (turbine) and the
  propeller to operate at their most efficient
  speeds
• Combining the output of 2 turbine shafts to power
  a common shaft

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MRG CLASSIFICATION

• Double Helical
• two sets of gear teeth cut at opposite but
  complementary angles across the face of the gear
• Stronger
• Quieter
• Eliminate side thrusts

6
MRG CLASSIFICATION (cont.)

• Double Reduction
• Speed reduction takes place in two separate steps
• High speed pinion to first reduction gear to
  Second Reduction pinion then to Bull gear

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MRG CLASSIFICATION (cont.)

• Locked Train
• Power is distributed equally by two sets of gears
  and shafts from the high speed pinions to the
  bull gear
• Eliminates side thrusts

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REVIEW OF REDUCTION GEAR CLASSIFICATION

• Double Helical
• Double Reduction
• Locked Train

11
FLEXIBLE COUPLING

• OVERCOMES MISALIGNMENTS
• ALLOWS THERMAL EXPANSION

12
TURNING (JACKING) GEAR

• Turns shaft at a slow speed (1/4 of a turn a
  minute or even slower)
• Reasons to use
• Allow turbine rotor cooldown following use
• Startup for even heatup
• Daily when in port for lubrication purposes
• Maintenance

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BEARINGS

• THRUST BEARINGS
• Delivers axial thrust to the ship from the shaft
• RADIAL (JOURNAL) BEARINGS
• Support and position the shaft
• Absorb radial (perpendicular) load

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CONTROLLABLE PITCH PROPELLER (CPP)

• Can change the position of the blades relative to
  the HUB
• More flexible because you do not have to change
  shaft direction to change ship direction
• Used mainly in gas turbine ships

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CAVITATION

• Formation of a partial vacuum around a propeller
  and then subsequently collapse
• Bad for several reasons
• High level of underwater noise
• Erosion of blades
• Vibration with subsequent blade failure from
  metallic fatigue
• Overall loss of propeller efficiency

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Horse Power to Speed
110
H O R S E P O W E R
100
50
20
20
80
100
SPEED