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Propulsion Train & Shaft Line Components

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Presentation on theme: "Propulsion Train & Shaft Line Components"— Presentation transcript:

1 Propulsion Train & Shaft Line Components

2 Introduction Reduction Gears - fast to slow
Lubrication System - overcome friction Shaft components - turbines to the working medium (ocean) Propeller - transform rotational energy into thrust

3 Reduction Gears Purposes
Allow turbine and propeller to operate at most efficient speeds Combine two turbines to common shaft

4 Reduction Gears Gear Types Straight Helical Double Helical
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

5 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

6 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

7 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)

8 Shaft Bearings Designed to support the moving parts of:
Turbines Thrust bearings Absorb axial forces Ex: Kingsbury Thrust bearing Radial (Journal) bearings Absorb radial forces

9 Lube Oil System Provide lubrication and remove heat generated by bearings in overcoming friction Major components: Sump Pump Strainer Cooler Bearings Cooler SW Moving Parts Strainer Pump Sump

10 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

11 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)

12 Propulsion Shaft Different sections needed for easy installation, removal, & maintenance

13 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

14 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

15 CRP System

16 Propeller Cavitation Effects
Formation and subsequent collapse of bubbles as propeller turns Occurs at critical speed Effects Excessive noise Erosion of blades Decreased efficiency


18 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 = 80% power

19 Sample Problems Shaft hP Effective hP Propulsive efficiency Slip ratio
shp=2πNT/33,000 Effective hP Propulsive efficiency Slip ratio

20 Questions?

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