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Dual Fuel EnginesSelection & Operational issues
Gerasimos TheotokatosNAOME, University of Strathclyde
Classification of Reciprocating ICE • Ignition type
• Spark ignition
• Compression ignition
• Engine cycle (2-s, 4-s)Fuel
• Fuel• Petrol / Gas (Natural Gas, LPG)
• Diesel (MGO, MDO, HFO)
• Methanol, Ethanol
• Dual fuel
• Petrol/Ethanol mixture (90-10)
• Bio-diesel
Classification of Marine Engines
• Slow speed engines
• Medium/High speed engines
Classification of Marine EnginesSlow speed engines (2-s)
1100-80000 kW (1480-110000 HP), 55-250 rpm, BMEP up to 20 bar, efficiency up to 53%, BSFC 165g/kWh
Cylinder diameter from 260 to1080 mm, Cylinder No.: 4-12
Crosshead piston rod: Isolation of crankcase from combustion chambers
Large value of ratio piston stroke/diameter
Uniflow scavenging using ports and 1 exhaust valve located in cylinder head
Directly connected to the ship propeller
Constant pressure turbocharging system (1 or more turbochargers connected in parallel)
Air cooler instaled downstream of each turbocharger compressor
Electric driven blowers (activated for engine loads lower than 40%)
Versions with large s/D (3.8 or more) for operation around 55 rpm – usage of large diameter propeller (high efficiency) in bulk carriers & tankers
Engine with s/D=2.8 operating around 100 rpm in containerships
Engine with lower s/D in ships of smaller draft or engine room height
Can burn Low quality (cheap) fuels
Classification of Marine EnginesMedium/High speed engines (4-s)
Medium speed: 400-1000 rpm – High speeed: above1000 rpm
Up to23500 kW (32000 HP), BMEP up to 25 bar, Efficiency up to 50%, BSFC 185 g/kWh, Cylinder diameter:160-640 mm
In line 5-9 cylinders, V 8-20 cylimders
Lighter and smaller volume compared to same power 2-s engines (10-15 kg/kW instead of 35-40kg/kW for 2-s engines) in the range of 10000 kW
20-30% lower weight even when taking into account the required clutch and gearbox
Connected to the ship propellers via gearbox and clutch (clutch is not required for CPPs)
Constant or Pulse pressure turbocharging system and air cooling
Utilization in Ferry type vessels and in cases where low engine room height is required/ Generator sets
Usage of 2 or more engines (maintenance easiness)
Good quality fuels although HFO is also used
Marine Engines
Large 2-s marine Diesel engine, 6 cylinders in-line
Power: 13530 kW, length: 7.7 m, weight: 360 t
Large 4-s marine Diesel engine, 16 cylinders V
Power: 11520 kW, length: 9.4 m, weight: 132 t 4-s marine Diesel engine, V configuration
Ship engine room layout/ 2-s engine
Ship engine room layout/ 2-s engine
Ship engine room layout / 4-s engine
Ship engine room layout / 4-s engine
Ship engine room layout / 4-s engine
ICE operating parameters
Mean effective pressure
3( )2( ) ( / )
mDD
W JW pV p N mV
/Db
W Vb
p
/i i D
p W V
brake mean effective pressure (BMEP)
indicated mean effective pressure (IMEP)
f i bif b
D D
W W Wp p p
V V
Friction mean effective pressure (FMEP)
ICE operating parameters
Typical BMEP values in bar
SI engines: 8.5÷10.5
Small Diesel engine s (natural aspirated): 7.5÷9.5
Large 4-s engines: ÷25
Large 2-s engines: ÷20
b b bm
ii i
W p PpW P
Engine mechanical efficiency
ICE operating parameters
Torque
Ability of the engine to produce work
Ability of the engine to overcome load
Brake Power
produced work per time
W Fr T
1 / 22
2 / 4
k rotation cycle for senginesk
k rotations cycle for sengines
2 2Db b
W p VT
k k
60 60Db b b
bcycle
W W N p V NP
t k k
60cycle
ktN
30bT NP T
ICE operating parameters
Indicated Power
produced indicated work per time
60 60ii D
i
p V NW NP
k k
Friction Power
if bP P P
1HP=0.7457 kW 1kW=1.341 HP
1 PS=0.736 kW 1kW=1.36 PS
Specific power
Displacement power
Specific volume
Specific weight
/ pistonbSP P A
/Db
PD P V
/D b
SV V P
/b
SW w P
ICE operating parameters
Air-Fuel Ratioa a
f f
m mAF
m m 1f f
a a
m mFA
m m AF
Air-Fuel Equivalence Ratio Fuel-Air Equivalence Ratio
st
AFAF
1
st
FAFA
Fuel-Air Ratio
AFst 15:1
Combustion can be done for 6≤AF≤25
Otto engines: 12<AF<18 (0.83<λ<1.25)
Diesel engines: 18<AF<70 (1.25<λ<4.8)
ICE operating parameters
Brake specific fuel consumption f
b
mbsfc
P
Indicated specific fuel consumptionf
i
misfc
P
, ,g g gkWh HPh PSh
ICE operating parameters
Engine efficiencies
Brake efficiency
out
in
PP
bb
f f
P
m LHV
Indicated efficiency ii
f f
P
m LHV
mib
61( ) 3.6 10( / ) ( / )b
f
gsbsfc g kWh LHV kJ kg h kg
Combustion efficiency,
,
f burnedc
f injected
m
m
ICE operating parameters
Volumetric efficiency
60a aV
a ad d
m kmV NV
5 2
R 287J/kgK
1.01 1.0110 /
298 25o
oo
p bar N m
T K C
31.181 /oa
o
pkg m
RT
ICE Energy Balance
Conservation of energy
engineEnergy in Energy out
Fuel,
Air,
Coolant
Brake power,
Coolant,
Heat transfer to environment (convection,
radiation)
Exhaust gas
f f a a b c misc e em h m h P Q Q m h
ICE Energy Balance
f f a a b c misc e em h m h P Q Q m h
f b c e miscQ P Q Q Q
Note: LHV uses when the H2O contained in the exhaust gas is in vapor form HHV=LHV+ hev
, ,( )f f a a e e o b c misc e e e om h m h m h P Q Q m h h
,f f f a a e e om LHV m h m h m h
ICE Energy Balance
1b e c misc
f f f f
P Q Q Q
Q Q Q Q
bb
f
P
Q Engine brake efficiency:
Exhaust gas loss percentage: /e fQ Q
Cooling power percentage: /c fQ Q
Miscellaneous thermal power percentage:
(radiation, incomplete combustion)/misc fQ Q
Exhaust Gas Emissions
2
2
( / ) 21 (% ) 2
( / ) 21.9 (% ) 2.1 4
SO kg ton s wt s slow speed marine Diesel engines
SO kg ton s wt s medium speed marine Diesel engines
Exhaust Gas Emissions
Selective catalytic reduction
(SCR)
use of LNG
Exhaust Gas Emissions
Typical fuel constituents
carbon (C),
hydrogen (H),
sulphur (S),
nitrogen (N),
oxygen (O),
water (H2O)
non-combustible components (e.g. ash)
1c h s n o w a kg fuel 12 1 32 14 16
c h s n oC H S N O
Gasoline Kerosene Diesel
(MGO)
Diesel
(MDO)
Diesel
(HFO)
c (%wt) 85.5 86.3 86.7 86.7 86.6
h (%wt) 14.4 13.6 13.2 12.3 11.3
s (%wt) 0.1 0.1 0.1 1.0 2.1
LNG composition
2
2 2 2 2 2
3 2
c h 2 2
12 1 32 14
2 2 2 2 2
3 2
C H ( 3.762 )Os n st
CO CO H O SO N H
SO HC NO NO
S N n O N
n CO n CO n H O n SO n N n H
n SO n HC n NO n NO PM
Pollutant Anthropogenic Source Environmental Effect
Nitrogen oxides (NO + NO2) High temperature fuel combustion—motor vehicles,
industrial, and utility
Primary pollutants that produce photochemical smog, acid rain,
and nitrate particulates. Destruction of stratospheric ozone.
Human health impact.
Particulates Combustion of biofuels such as wood, and fossil fuels such
as coal or diesel
Reduced atmospheric visibility. Human health impact. Black
carbon particulates contribute to global warming.
Sulphur dioxide Coal combustion, ore smelters, petroleum refineries, diesel
engines burning high-sulphur fuels
Acid rain. Human health impact.
Ozone Secondary pollutant produced in photochemical smog Damage to plants, crops, and man-made products. Human health
impact.
Carbon monoxide Rich & stoichiometric combustion, mainly from motor
vehicles
Human health impact
Carbon dioxide Fossil fuel and wood combustion Most common greenhouse gas
Non-methane hydrocarbons (VOC) Incomplete combustion, solvent utilization Primary pollutants that produce photochemical smog
Methane Natural gas leak and combustion Greenhouse gas
Chlorofluorocarbons (CFC) Solvents, aerosol propellants, refrigerants Destruction of stratospheric ozone
Exhaust Gas Emissions
Exhaust Gas Emissions
Molecular amount and volumetric composition of the exhaust gas produced by the combustion of 1
kg of fuel
2
2 22( / ) 3.6645CO
CO CO e
c
c MWC kg CO kg fuel y m c
AW
2
2 22( / ) 2SO
SO SO e
s
c MWC kg SO kg fuel y m s
AW
ii i e i e
e
MWm y m x m
MW
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Dual Fuel Engines – 4-s
Dual Fuel Engines – 2-s
LNG storage and feeding system
LNG carrier propulsion
LNG storage & feeding system
LNG storage & feeding system
Engine conversion (from Wärtsilä)
Questions?
