Propulsion Introduction

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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) - PowerPoint PPT Presentation

Transcript of Propulsion Introduction

Propulsion Propulsion IntroductionIntroduction

Force, Energy & PowerForce, Energy & Power

ThermodynamicsThermodynamics

What makes ships go?What makes ships go?

Energy

Force

Power

FORCEUnits:: Pounds (lbs) Tons (1 Ton = 2000 lbs) Newtons (1 N = 0.225 lbs, 1 lb = 4.45 0.225 lbs, 1 lb = 4.45

N)N)

Examples: Thrust Force: produced by propeller to

drive ship) Resistance Force: determined by hull

shape & vessel speed—opposes thrust

FORCE

THRUST = RESIST (equilibrium) Ship proceeds at a constant speedShip proceeds at a constant speed VelocityVelocity = distance / time = distance / time

o 1 1 knot = 1 nautical mile / hour = 1 nautical mile / houro 1 naut mi. = 6090 ft = 1.15 statute mi.1 naut mi. = 6090 ft = 1.15 statute mi.

RES THR

FORCE

THRUST > RESIST Ship Ship acceleratesaccelerates Resistance Resistance increasesincreases with speed with speed

o Until Until Resistance = Thrusto Ship at new, Ship at new, fasterfaster speed speed

FORCE

RESIST > THRUST Ship Ship deceleratesdecelerates Resistance Resistance decreasesdecreases with speed with speed

o Until Until Resistance = Thrusto Ship at new, Ship at new, slowerslower speed speed

050

100150200250300350400450

0 5 10 15 20 25

Knots

Thrust (multiple of "K")

RESISTANCE = K x VRESISTANCE = K x V22

KK is a function of hull is a function of hull shape & conditionshape & condition

DoublingDoubling velocity velocity requires requires 4 times4 times the the thrustthrusto at 5 kt at 5 kt T = 25K T = 25Ko at 10kt at 10kt T = 100K T = 100K

at 20 kt at 20 kt T = 400K T = 400Ko ((16 times16 times the thrust at the thrust at

5 kt)5 kt)

RESISTANCE = K x VRESISTANCE = K x V22

Each increasing knot Each increasing knot requires requires more thrust more thrust than the previousthan the previous 1- 1-knot increaseknot increase

o From 5 to 10 kt required From 5 to 10 kt required an increase of an increase of 75K75K

o From 15 (225K) to 20 From 15 (225K) to 20 (400K) is an increase of (400K) is an increase of 175K175K tons of thrust tons of thrust

050

100150200250300350400450

0 5 10 15 20 25

Knots

Thrust (multiple of "K")

What makes ships go?What makes ships go?

Energy

Force

Power

ENERGY (mechanical)Force x DistanceUnits:: Pounds x Feet (lb-ft) Newtons x meters (1 N-m = 1 joule) Other: Tons-miles; oz-inches; etc.

Examples: Thrust x Distance (port A to port B) Since Thrust = K x V2, ship speed

significant in energy (fuel) costs

ENERGY in many formsMechanical Energy (“work”): Force x Distance (lb-ft; Ton-mi; N-m; etc.)

Thermal Energy (“heat”): 1 BTU will raise 1 lb of H2O 1oF 1 BTU equivalent to 778 lb-ft of mechanical “work” The amount of heat released in the combustion of

1 lb of fuel (BTU/lb) is the Higher Heating Value (HHV) of the fuel

Electrical Energy (“kW-Hrs”): One 60-watt (0.06 kW) bulb burning for 24 hrs

consumes 1.44 Kw-Hrs of energy (at 15 cents per Kw-Hr, a 60 watt bulb burning for a month costs 0.06 x 24 x 30 x $0.11 = $4.75)

What makes ships go?What makes ships go?

Energy

Force

Power

POWERRate of Energy Production or consumptionForce x Distance / Time: lb-ft/min; Ton-mi/hr; N-m/sec (=joule/sec = watt) 550 lb-ft/sec = 33,000 lb-ft/min = 1 horsepower 1 horsepower = 746 watts = 0.746 kW

= 0.707 BTU/sec = 2545 BTU / Hr

Force x Distance / Time = Force x Velocity Thrust x Velocity = K x V2 x V = K x V3

=Ship’s Effective Horsepower (EHP) EHP proportional to speed cubed!

0100020003000400050006000700080009000

0 5 10 15 20 25

Knots

EHP (multiple of "K")

EHP = THRUST x VELOCITYEHP = THRUST x VELOCITY

At any At any constantconstant speed speed

Thrust = Resistance = Thrust = Resistance = K x VK x V22

So Thrust x Velocity = So Thrust x Velocity =

K x VK x V22 x V = x V = K x VK x V33

(Doubling V requires 8 x HP!)(Doubling V requires 8 x HP!)

EHP(10) = K x 1000 EHP(10) = K x 1000 EHP(20) = K x 8000EHP(20) = K x 8000 ““K” for TSES VI is ≈ 2K” for TSES VI is ≈ 2

X 8

X 2

0100020003000400050006000700080009000

0 5 10 15 20 25

Knots

EHP (multiple of "K")

EHP = THRUST x VELOCITYEHP = THRUST x VELOCITY

So EHP = So EHP = K x VK x V33 & Doubling V requires 8 x HP& Doubling V requires 8 x HP EHP(10) = K x 1000 EHP(10) = K x 1000 EHP(20) = K x 8000EHP(20) = K x 8000

101011 kt: 11 kt:

331xK increase in HP331xK increase in HP 191920 kt: 20 kt:

1141xK increase HP1141xK increase HP

Propeller as a ScrewPropeller as a Screw

PITCHPITCH x Total Revs in 1 day = x Total Revs in 1 day = ENGINE MILAGEENGINE MILAGE SlipSlip = = Eng mi – Obs miEng mi – Obs mi

Eng miEng mi PitchPitch x RPM x x RPM x 60 min/hr = ship speed (knots) = ship speed (knots)

6077 ft/n.mi6077 ft/n.mi

PITCH (ft or m)

PITCHPITCH = = theoretical theoretical advance of advance of propeller in 1 propeller in 1 revolutionrevolution

Propeller as a PumpPropeller as a Pump

Propeller Horsepower = Propeller Horsepower = GPM GPM xx PSI PSI 17141714

Gal (231 cu.in.)Gal (231 cu.in.) x x lbslbs = = force x distanceforce x distance min (60 sec) sq.in timemin (60 sec) sq.in time

Press Difference (Press Difference (P) x Propeller Area = P) x Propeller Area = THRUSTTHRUST

Moves a Moves a quantity of quantity of water (water (GPMGPM))

And raises And raises pressure (pressure (psipsi))

EfficiencyEfficiency

Eff = Pout Pin

= Pout Pout + Losses

= Pin - Losses Pin

Process or

System

PWR in

PWR out

Losses

Nothing is 100% efficient!

EfficiencyEfficiency

EfficiencyEfficiency Delivered Horsepower (Delivered Horsepower (DHPDHP)= energy )= energy

per unit time delivered to the propellerper unit time delivered to the propeller

DHP EHP

Losses(30% or more)Stern

Tube

Propulsive Efficiency = Propulsive Efficiency = EHPEHPDHP

EfficiencyEfficiency Shaft Horsepower (Shaft Horsepower (SHPSHP)= energy per )= energy per

unit time delivered to the tailshaftunit time delivered to the tailshaft

DHP EHP

Losses(30% or more)Stern

Tube

SHP

Line shaft

Tailshaft Losses (< 1%)

EfficiencyEfficiency

FUEL

BTU’s Released:HHV x Fuel Rate

BTU/min to engine

Engine Transmission &

Shafting

SHP

DHP EH

P

Brake Horsepower (Brake Horsepower (BHPBHP)= engine output )= engine output delivered to drive train (line shaft losses: 2-5%)delivered to drive train (line shaft losses: 2-5%)

ENGINEENGINE converts converts Thermal EnergyThermal Energy to to Mechanical Mechanical EnergyEnergy (efficiencies < 50%) (efficiencies < 50%)

Thermal EnergyThermal Energy produced by the combustion of produced by the combustion of fuelfuel

Heat for Auxiliaries & Losses

BHP

Propulsion PlantsPropulsion Plants

FUEL

BTU/min to engine

Engine Transmission &

Shafting

Many Energy Conversion (thermal Many Energy Conversion (thermal Mechanical) Alternatives including …Mechanical) Alternatives including …

STEAMSTEAM (conventional or nuclear),(conventional or nuclear), DIESELDIESEL (slow speed or medium speed), and (slow speed or medium speed), and GAS GAS TURBINETURBINE

BHP

Steam PropulsionSteam Propulsion

Advantages:Advantages: Conventional plants can burn very low grade Conventional plants can burn very low grade

fuelfuel Nuclear plants can go years without Nuclear plants can go years without

refuelingrefueling Good efficiency over a wide range of speedsGood efficiency over a wide range of speeds

BOILER

or

REACTOR

TURBINES

REDUCTION GEAR

STEAM

WATER

DisadvantagesDisadvantages Large Space requirementsLarge Space requirements Long start-up timeLong start-up time Difficult to completely Difficult to completely

automate (large crew sizes)automate (large crew sizes) High initial (capital) costsHigh initial (capital) costs

(Slow Speed) Diesel (Slow Speed) Diesel PropulsionPropulsion

Advantages:Advantages: Simple to automate (“unmanned” Simple to automate (“unmanned”

engine room & Bridge Control)engine room & Bridge Control) Can burn low grade fuelCan burn low grade fuel Relatively short start-up timeRelatively short start-up time

DisadvantagesDisadvantages Low efficiency at low speedLow efficiency at low speed Restricted maneuverabilityRestricted maneuverability Many parts—failure of one Many parts—failure of one

causes downtimecauses downtime

(Medium Speed) Diesel (Medium Speed) Diesel PropulsionPropulsion

Advantages:Advantages: Flexible engine arrangementsFlexible engine arrangements Suitable for electric driveSuitable for electric drive Short start-up timeShort start-up time

DisadvantagesDisadvantages Burns higher grade fuelBurns higher grade fuel Multiple engines required for Multiple engines required for

high hp shipshigh hp ships Significant maintenance Significant maintenance

burdenburden

G

G

G

G

G

M

Gas Turbine PropulsionGas Turbine Propulsion

Advantages:Advantages: Short start-up timeShort start-up time Engines (Gas Generators) changed out Engines (Gas Generators) changed out

for regular maintenancefor regular maintenance

Gas Generator (jet engine) Power

TurbineReduction/

reversing Gear

Gas Turbine PropulsionGas Turbine Propulsion

Advantages:Advantages: Short start-up timeShort start-up time Engines (Gas Generators) changed out Engines (Gas Generators) changed out

for regular maintenancefor regular maintenance Suitable for electric driveSuitable for electric drive

DisadvantagesDisadvantages High grade (jet) fuelHigh grade (jet) fuel Non-reversing—requires Non-reversing—requires

auxiliary gear for astern auxiliary gear for astern operationoperation

M

MG

G

G