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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LNG storage and feeding system

LNG carrier propulsion

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LNG storage & feeding system

Engine conversion (from Wärtsilä)

Questions?