propulsion introduction
DESCRIPTION
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 PresentationTRANSCRIPT
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