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The Wärtsilälow-speed low-pressure
dual-fuel enginedevelopment
LNG IN PRACTICE
SEMINAR ON BOARD
MS VIKING GRACE
SEPT. 18, 2013 Rudolf Wettstein
Wärtsilä Switzerland Ltd
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RTX-5 test engine on GAS
• Engine commissioned for full scale gas
operation during August
• All systems up and running:
– Gas admission system
– Pilot injection
– Engine control system
– etc…
• Performance optimization started
– 75% power output achieved
– Fuel change over from gas to diesel and vice
versa
– NOx level on gas far lower than Tier lll limit
– Low load operation on gas seems feasiblewith sufficient stability
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Transfer Diesel – Gas – Diesel
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Transfer from Diesel to Gas
NOx emissions
in gas mode!
Trip back to Diesel
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Engine performance
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Gas mode Diesel mode
Output BMEPtarget 18.8 bar
currently 17.3 bar
Energy
consumption *
target +/- 0% * +2% *
currently
NOx emissions IMO Tier III IMO Tier II
Gas pressure (bar g) < 10 ---
* Reference = Standard diesel R1 Tier II tuning
Current focus on installations running mostly on gas
(ECA vessels, LNGC, …)
Efficiency to be confirmed on full scale test engine
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Emission values – medium-speed dual-fuel engine
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CO2
NOx
SOx
Particulates
Dual-Fuel engine
in gas mode
Diesel
engine0
10
20
30
40
50
60
70
80
90
100
Emission
values [%]
-25%
-85%
-99%
-99%
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Methane slip
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• THC emissions (‘methane slip’) is not limited by IMO
• CO2 equivalent emissions in any case lower than on diesel/HFO operation
0
0,2
0,4
0,6
0,8
1
1,2
Diesel/HFO Gas/DF Gas/GD (ME-GI)
Contribution from methane slip;Contribution from Carbon in fuel;
Relative CO2 equivalent
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Basic concept (2 stroke – low pressure)
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Principles:
Engine operating accordingly
to Otto process
Injection of gas at mid-stroke.
Low pressure gas injection
(<10 bar) sufficient High impact on NOX reduction
Meets IMO Tier III without
after treatment
‘Pr e-mixed l ean-bur n’ c o mbust ion
ScavengingCompression/
gas admission
Ignition
expansion
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Other concept (2 stroke – high pressure)
Principles:
Engine operating accordingly
to Diesel process
Injection of gas close to TDC.
Air is completely compressed
and, therefore, high pressuregas injection (300 bar) is
required.
No significant NOX reduction
Requires SCR or EGR (not
proven) in order to meet IMOTier III levels
Scavenging/
compression
Pilot & HP gas
injection Expansion
Dir ect inj ect ion, dif f usion co mbust io n
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Otto or Diesel cycles: effects on NOX
Big temperature
difference
NOx formation!
Otto, max flame temp.
Diesel, max flame temp.
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1858-1913
1831-1891
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Technical features – Gas admission
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Gas admission system
2 x GAV (gas admission valve) per cylinder
GAV actuated by hydraulically ‘fast-switching’
solenoid valves
Hydraulic power supply from exhaust valve
servo oil system
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Technical features – Pilot fuel system
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Pilot fuel system
Pilot fuel utilized for ignition(as in four-strokes DF engines)
Pilot fuel consumption ~1% of BSFC at 100% load
Pre-chamber technology for best ignition and
combustion stability
Fuel supply based on common-rail technology
Pre-chamber
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Technical features – Pilot fuel system
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Pilot fuel system
Single fuel oil pump serving all cylinders(common-rail technology)
Filters and pressure regulation included
Pilot fuel pump electrically driven
UNIC
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Technical features – Automation
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Engine automation and control system
UNIC based control system Individual control of combustion related
parameters (cyl.pressure, combustion process,
….)
Safety functions related to gas operation
included
Pilot fuel injector Pilot fuel injector
Gas admission valvesGas admission valves
Test
cylinder
running on
gas
Control
system
2x Gas admission valves2x Gas admission valves
Pilot fuel injectorsPilot fuel injectors
Engine speed/CA-signalEngine speed/CA-signal
Engine stop signalEngine stop signal
Gas durationGas duration
Gas pressureGas pressure
(Pilot fuel pressure)(Pilot fuel pressure)
Exhaust valve driveExhaust valve drive
Exhaust valveExhaust valve
Pilot fuel injector
Gas admission valves
Test
cylinder
running on
gas
Control
system
2x Gas admission valves
Pilot fuel injectors
Engine speed/CA-signal
Engine stop signal
Gas duration
Gas pressure
(Pilot fuel pressure)
Exhaust valve drive
Exhaust valve
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Designing by CFD simulations
• CFD = computational fluid dynamics
• Used to evaluate and validate designs before engine tests, like: – number and location of gas admission points
– gas injection nozzle design
– gas pressure and injection timing influence
– pre-chamber optimization and combustion simulations
• Target
– screening/evaluation of design alternatives before testing
– optimize the engine already during the design phase
• Purpose
– shorten development time
– improved engine performance
Gas velocity distribution during
the initial phase of gas injection
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2-stroke gas engine – potential applications
1. Ships operating on gas when going into a ECA
(Emission Controlled Area)• operating temporarily on gas in ECA zones and
on HFO outside ECA
2. Ships operating ‘continuously’ on gas• majority of the time running on gas
• LNG Carriers, any other ship types using gas on
long-haul trips
Driver: emissions
Driver: operating costs
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Dual-fuel engine machinery for Merchant Vessels
DF auxil iary enginesGas
valve
unit G
G
G
Gas
valve
unit
Gas
valve
unit
Gasvalve
unit
LNG PacCyl.tank IMO C-type
Wärtsilä Package…..
a complete andmodularized solution for
LNG fuelled ships
Low-speed DF
main engine
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• Single wall piping on open deck
• Ventilated double wall piping for class
rules for ‚inherently safe engine room‘• Purging system for piping, GVU, tank,….
Cold box with LNG low-pressure pumps
evaporator, heater, valves, etc Very low electrical energy
consumption for gas feed
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175’000 m3 LNG Carrier with twin-shaft machinery
Gas
valve
unit
Gas
valve
unit
Gas
valve
unit
Gas
valve
unit
5X72DF or 6/7X62DFCMCR = 12500 kW
Fuel Gas
Handling
System
(FGHS)
Gas
valve
unit
5X72DF or 6/7X62DFCMCR = 12500 kW
175‘000 m3
LNG, - 163 °C
2610 kW / 720 rpm
6L34DF
G
G
G
3915 kW / 720 rpm
9L34DF
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Boil-off gas rate and engine gas demand
Qh
Qv
Low pressure
compressor set
Heater
Evaporator
Boil-off gas rate = 0,1% per day
175 m3 per day = 80 ton/day
Main engines daily gas consumption
at Service Speed
2 x 37.5 ton/day = 75 ton/day
Aux engine daily gas consumption
6L34DF (at 50% of load)6 ton/day
Total gas demand: 81 t/day
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Low pressure feed pumps
Fuel Gas
Handling System
Wärtsilä Hamworthy
Nitrogen Generator
Wärtsilä Hamworthy
Reliquefactionplant
Wärtsilä Hamworthy
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Gas engine history within SULZER
• 1965-’72: low pressure loop scavenged 6RD76 tested in Winterthur
• 7RNMD90 installed in 29’400m3 LNG-carrier “MV Venator ” in 1972
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High pressure engine was developed
in co-operation with IHI (Diesel
United).
It was demonstrated in 1986 on onecylinder of a 6RTA84 engine.
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Conclusions
Why to choose a Wärtsilä low-pressure dual-fuel engine:
1) Meet IMO Tier III requirements without exhaust gas after-treatment due to
lean burn Otto combustion process
2) Low CAPEX due to low pressure gas supply system (<10bar)
• No large gas compression equipment
• No exhaust gas after treatment
3) Low OPEX due to high overall efficiency (low parasitic load)
4) Full Wärtsilä Package Complete and modularized
solutions for LNG fuelled ships
5) Availabil ity
• RT-flex50DF mid 2014 4775 - 11520 kW• X62DF 2015 6160 - 19080 kW
• X72DF 2015 8320 - 25800 kW
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THANK YOU!
Wär ts il äWär ts il äLeading gas applications in the marine marketLeading gas applications in the marine market
22 © Wärtsilä 2sDF Engine / May 2013