1 / 18

Propulsion Introduction

Propulsion Introduction. Force, Energy & Power Thermodynamics. What makes ships go?. Force. Energy. Power. FORCE. Units : Pounds (lbs) Tons (1 Ton = 2000 lbs) Newtons (1 N = 0.225 lbs, 1 lb = 4.45 N) Examples: Thrust Force: produced by propeller to drive ship)

ron
Télécharger la présentation

Propulsion Introduction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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 = 0.225 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. THR RES 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. 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. Losses PWR in PWR out Efficiency Process or System Efficiency Nothing is 100% efficient!

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

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

  12. DHP SHP BHP Engine Transmission & Shafting EHP Efficiency Heat for Auxiliaries & Losses • 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 BTU/min to engine BTU’s Released: HHV x Fuel Rate FUEL

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

  14. Steam Propulsion STEAM Advantages: • Conventional plants can burn very low grade fuel • Nuclear plants can go years without refueling • Good efficiency over a wide range of speeds REDUCTION GEAR BOILER or REACTOR TURBINES WATER 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. G G G G G M (Medium Speed) Diesel Propulsion 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 Advantages: • Short start-up time • Engines (Gas Generators) changed out for regular maintenance Gas Generator (jet engine) Reduction/ reversing Gear Power Turbine

  18. G G M M G Gas Turbine Propulsion 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

More Related