1. Propulsion Introduction
Force, Energy & Power
Thermodynamics

2. What makes ships go?
Force
Energy
Power

3. FORCE Units: Pounds (lbs) Tons (1 Ton = 2000 lbs)
Newtons (1 N = lbs, 1 lb = 4.45 N)
Examples:
Thrust Force: produced by propeller to drive ship)
Resistance Force: determined by hull shape & vessel speed—opposes thrust

4. FORCE THRUST = RESIST (equilibrium) Ship proceeds at a constant speed
Velocity = distance / time
1 knot = 1 nautical mile / hour
1 naut mi. = 6076 ft
1 statute mi. = 5280 ft

5. FORCE THRUST > RESIST Ship accelerates
Resistance increases with speed
Until Resistance = Thrust
Ship at new, faster speed

6. FORCE RESIST > THRUST Ship decelerates
Resistance decreases with speed
Until Resistance = Thrust
Ship at new, slower speed

7. What makes ships go?
Force
Energy
Power

8. Gal (231 cu.in.) x lbs = force x distance
Propeller as a Pump
Moves a quantity of water (GPM)
And raises pressure (psi)
Propeller Horsepower = GPM x PSI
1714
Gal (231 cu.in.) x lbs = force x distance
min (60 sec) sq.in time
Press Difference (DP) x Propeller Area = THRUST

9. Efficiency Nothing is 100% efficient! PWR in PWR out Losses
Process or System
Efficiency
Nothing is 100% efficient!

10. Efficiency
Delivered Horsepower (DHP)= energy per unit time delivered to the propeller
DHP
EHP
Losses
(30% or more)
Stern Tube
Propulsive Efficiency = EHP
DHP

11. Efficiency
Shaft Horsepower (SHP)= energy per unit time delivered to the tailshaft
DHP
SHP
EHP
Losses
SHP - Shaft Horsepower
DHP - Delivered Horsepower
(30% or more)
Line shaft
Stern Tube
Tailshaft Losses (< 1%)

12. Efficiency DHP BHP EHP SHP FUEL
Heat for Auxiliaries & Losses
BTU/min to engine
DHP
BHP
SHP
EHP
BTU’s Released:
HHV x Fuel Rate
Engine
Transmission & Shafting
FUEL
Brake Horsepower (BHP)= engine output delivered to drive train (line shaft losses: 2-5%)
ENGINE converts Thermal Energy to Mechanical Energy (efficiencies < 50%)
Thermal Energy produced by the combustion of fuel

13. Propulsion Plants
BTU/min to engine
BHP
Engine
Transmission & Shafting
FUEL
Many Energy Conversion (thermal  Mechanical) Alternatives including …
STEAM (conventional or nuclear), DIESEL (slow speed or medium speed), and GAS TURBINE

14. Steam Propulsion BOILER REDUCTION GEAR or REACTOR TURBINES STEAM WATER
Advantages:
Conventional plants can burn very low grade fuel
Nuclear plants can go years without refueling
Good efficiency over a wide range of speeds
Disadvantages
Large Space requirements
Long start-up time
Difficult to completely automate (large crew sizes)
High initial (capital) costs

15. (Slow Speed) Diesel Propulsion
Advantages:
Simple to automate (“unmanned” engine room & Bridge Control)
Can burn low grade fuel
Relatively short start-up time
Disadvantages
Low efficiency at low speed
Restricted maneuverability
Many parts—failure of one causes downtime

16. (Medium Speed) Diesel PropulsionG M
Advantages:
Flexible engine arrangements
Suitable for electric drive
Short start-up time
Disadvantages
Burns higher grade fuel
Multiple engines required for high hp ships
Significant maintenance burden

17. Gas Turbine Propulsion
Gas Generator (jet engine)
Power Turbine
Reduction/ reversing Gear
Advantages:
Short start-up time
Engines (Gas Generators) changed out for regular maintenance

18. Gas Turbine PropulsionM M
Advantages:
Short start-up time
Engines (Gas Generators) changed out for regular maintenance
Suitable for electric drive
Disadvantages
High grade (jet) fuel
Non-reversing—requires auxiliary gear for astern operation