WÄRTSILÄ MEDIUM-SPEED ENGINES

WÄRTSILÄ MEDIUM-SPEED ENGINES
The Oasis of the Seas, equipped with six Wärtsilä 46 engines.
MEDIUM-SPEED ENGINES
Medium-speed diesel and dual-fuel
engines for reliability
and total economy .................................3
Compliance with environmental
regulations and other standards............4
Main features.........................................4
Engine performance ..............................5
Engine design ........................................6
Engine block......................................6
The Thetis, equipped with a Wärtsilä 20 engine.
Crankshaft and bearings.....................6
The submersible heavy load ship Blue Marlin is
equipped with three Wärtsilä 8L32 engines.
Connecting rod ..................................7
Cylinder liner and antipolishing ring.....7
Piston & piston rings ..........................8
Cylinder head.....................................8
Multiduct ...........................................9
Camshaft and valve gear ....................9
Operational systems
POWER RANGE FOR WÄRTSILÄ MEDIUM­SPEED ENGINES
DIESEL ENGINES
Wärtsilä 20
Wärtsilä 26
Wärtsilä 32
Fuel injection system........................10
Wärtsilä 38
Turbocharging system ......................11
Wärtsilä 46
Cooling system ................................12
Wärtsilä 46F
Lubricating oil system.......................12
Wärtsilä 64
Automation system ..........................12
DUAL­FUEL ENGINES
Dual-fuel technology ...........................14
Wärtsilä 20DF
Maintenance features..........................18
Wärtsilä 34DF
Services ..............................................18
Wärtsilä 50DF
kW
2
5000
10,000
15,000
20,000
25,000
The LNG Tanker, GDF-Suez Global Energy is equipped with four Wärtsilä 50DF engines.
The Naval vessel De Zeven Provincien is equipped with
two Wärtsilä 16V26 engines.
The tanker Bitflower is equipped with a
Wärtsilä 6L38 engine.
MEDIUM-SPEED DIESEL AND DUAL-FUEL ENGINES
FOR RELIABILITY AND TOTAL ECONOMY
The design of the Wärtsilä medium-speed
engine range is based on the vast amount
of knowledge accumulated over years of
successful operation.
Robust engines and generating sets,
developed from pioneering heavy fuel
technology, have been engineered to provide
unquestionable benefits for the owners and
operators of marine vessels.
These benefits include:
„„
Proven reliability
„„
Low emissions
„„
Low operating costs
„„
Fuel flexibility
„„
Integrated system solutions
„„
All services from spare parts to
reconditioning available from Wärtsilä’s
global network
In shipyard applications, the installation
friendliness, embedded automation system,
and built-on modularized auxiliary systems are
amongst the many added advantages.
Wärtsilä is continuously developing its
portfolio of gas and multi-fuel engines to suit
different marine applications, offshore oil
and gas installations where gaseous fuel is
available from the process, and merchant
vessels operating in environmentally
sensitive areas. Wärtsilä engines offer high
efficiency, low exhaust gas emissions, and
safe operation. The innovative multi-fuel
technology allows the flexibility to choose
between gas or liquid fuel. When necessary,
the engines are capable of switching from
one fuel to the other without any interruption
in power generation.
3
COMPLIANCE WITH ENVIRONMENTAL REGULATIONS AND OTHER STANDARDS
Environmental issues, especially emissions
reduction and fuel consumption, have
become increasingly important in the
shipping sector where enforcement of
environmental regulations, at both global
and local levels, has notably increased. This
puts pressure on the marine industry to
constantly explore new ways of reducing the
environmental impact of ships.
Wärtsilä creates added value for its
customers by providing products, solutions
and services that fulfill their needs and
expectations. The development of highquality, reliable, and environmentally
sound solutions and services has come
as a result of long-term collaboration and
continuous interaction with our customers.
We provide service support to ensure
optimal performance throughout the product
lifecycle. The upgrading of installed products
can also extend their service life.
WÄRTSILÄ MEETS THE NEW
REQUIREMENTS ON SHIP EMISSIONS
The International Maritime Organization (IMO)
has approved amendments to the MARPOL
Annex VI regulations on ship emissions. These
regulations set stricter limits on emissions
of Nitrogen Oxides (NOX) from the engines,
as well as on the sulphur content of the fuel.
The new requirements will enter into force in
various phases during the years 2010–2020.
As regards NOX emissions, Wärtsilä has
already introduced solutions that comply with
these requirements. Wärtsilä engines are
designed for operation on any fuel sulphur
content. As a response to the tightening
Sulfur Oxides (SOX) emissions, Wärtsilä has
developed scrubber technology that allows
exhaust gases to be cleaned to meet the tight
regulations.
GAS ENGINES HIGHLIGHTED
Wärtsilä has a multifaceted gas engine
strategy, and can provide gas engines
for vessels. Being at the forefront of
technological developments gives Wärtsilä
many opportunities arising from the tightening
environmental regulations. Shipping can
reduce its carbon footprint through ship
design, efficient engines, and optimal
propulsion solutions.
4
NOx emissions, g/kWh
20
18
16
IMO Tier I, 2000
14
12
10
IMO Tier II, 2011
8
6
IMO Tier III, 2016 in emission control areas
4
2
0
0
200
400
600
800
1000
1200
1400
1600
Engine speed, rpm
MAIN FEATURES
Wärtsilä engines offer outstanding powerto-weight and power-to-space ratios in their
power range. They have bore sizes from 200 to
640 mm and different cylinder configurations
to cover a power range from 0.5 MW to
20 MW and are capable of using various fuels.
Wärtsilä 4-stroke engines comply with both
IMO Tier I and IMO Tier II emission legislation
without secondary purification systems.
Full advantage is taken of the proven
solutions developed in earlier Wärtsilä engines,
while new features and customer benefits
have been added. Reliability and total economy
are the guiding principles, although emission
control options and installation friendliness are
strongly emphasized.
„„
Cylinder power from 185 kW to 2150 kW
„„
Nominal speed from 500 to 1000 rpm
„„
Multi-fuel operation capability
„„
High thermal efficiency and low emissions
„„
High reliability and low maintenance costs
„„
Low exhaust gas emissions
„„
Fuel economy throughout the entire engine
operational range
„„
Embedded automation system including
speed control
ENGINE PERFORMANCE
Wärtsilä 4-stroke engines utilize the latest
developments in turbo-charging technology, which
enables Miller valve timing and the Variable Inlet
Valve Closing (VIC) system to be employed.
At full-load operation, early closure of the
inlet valves enables a low effective compression
ratio, and as a result, comparatively low
temperatures at the end of the compression
stroke. The charge air, being both somewhat
expanded and cooled on its way through the
receiver into the cylinders, has a low global
temperature that is still high enough to
guarantee reliable and stable ignition of the
fuel/air mixture in the combustion chamber.
This contributes to the creation of favourable
conditions for an environmentally friendly
combustion process.
In Wärtsilä engines, these advantageous
initial conditions are combined with a higher
engine speed and a high expansion ratio,
i.e. with design parameters that make the
combustion chamber expand quickly when
the combustion process has started. Due to
the quick expansion of the combustion gases,
high temperatures that are most critical to the
formation of intensive NOX within the combustion
chamber are rapidly abated. This combination
creates a combustion process that is not only
environmentally friendly, but also extremely
efficient as the high expansion ratio produces
the conditions needed for efficient utilization of
the heat energy released by combustion at the
beginning of the power stroke.
However, it is not only the choice of the
compression/expansion ratio that makes
Wärtsilä engines highly efficient. All versions
of the engine are equipped with fuel injection
systems that allow adjustment of the injection
characteristics to the prevailing load conditions.
The advanced common-rail fuel injection
system offers the freedom to control and finetune the injection process. This enables full use
of the engine’s loading potential over a wide
power range in order to achieve optimum fuel
economy. Similarly, this freedom offered by the
flexible fuel injection equipment can be utilized
to adjust the engine to the existing limitations
of exhaust gas emissions, to minimize smoke
formation. Thermal load and mechanical stress
levels are kept within the safety margins
established by Wärtsilä over decades of engine
development.
5
ENGINE DESIGN
ENGINE BLOCK
Nodular cast iron is the natural choice for
engine blocks today because of its strength
and stiffness properties. Wärtsilä engine monoblock designs are based on modern foundry
technology to integrate most oil and water
channels, as well as the charge air receiver.
The result is a virtually pipe-free engine with a
clean outer exterior.
Resilient mounting, available as an option,
is required in many application types. The
engine block has been designed especially for
this purpose. Integrated channels designed
with this in mind serve a double purpose.
CRANKSHAFT AND BEARINGS
The latest advances in combustion
development require a crank gear that can
operate reliably at high cylinder pressures.
The crankshaft must be robust and the
specific bearing loads kept at a safe level.
6
This is achieved by careful optimization of the
crankshaft’s throw dimensions and fillets. The
specific bearing loads are conservative and
the cylinder spacing, which is important to
the overall length of the engine, is minimized.
Besides low bearing loads, the other crucial
factor for safe bearing operation is oil film
thickness. Ample oil film thickness in the main
bearings is ensured by optimal balancing of the
rotational masses and, in the big end bearing,
by ungrooved bearing surfaces in the critical
areas. All the factors needed for a free choice
of the most appropriate bearing material are
present..
The main features of the crankshaft and
bearings design are:
„„
Clean steel technology to minimize the
amount of slag forming elements, and to
guarantee superior material properties
„„
A crankshaft line assembled from three
elements: the crankshaft, gear and end
piece. The crankshaft itself is forged in one
piece
„„
Each throw is fully balanced individually for
safe bearing function
„„
Main bearing temperature monitoring
„„
Patented crankpin bearing temperature
monitoring
„„
Modest bearing loads thanks to generous
bearing dimensions.
CONNECTING ROD
The three-piece connecting rod is of the
marine type used in Wärtsilä engines having
a cylinder power of more than 400 kW, where
the combustion forces are distributed over
a maximum bearing area, and the relative
movements between mating surfaces are
minimized. The connecting rod is optimized for
both strength and weight. The shank is fully
machined. The three-piece design simplifies
piston overhauling, as this can be carried out
without touching the big end bearing. The big
end bearing can also be inspected without
removing the piston.
The two-piece design is used for smaller
engines having a cylinder power of less than
400 kW. The design offers the maximum pin
diameter while still making it possible to pull
the connecting rod through the cylinder liner.
The main features of the connecting rod
design are:
„„
Two/three-piece type design depending on
engine size
„„
Hydraulically tightened bolts
„„
Both strength and weight are optimized
„„
Easy maintenance
CYLINDER LINER AND ANTIPOLISHING RING
The cylinder liner is designed to have the
stiffness needed to withstand both pretension
forces and combustion pressures with virtually
no deformation. This gives the best cylinder
function and ensures good basics for the
tightness of the cylinder head gasket. The
temperature is controlled by optimizing the
cooling water flow in the upper part of the
collar to achieve a low thermal load, and to
avoid sulphuric acid corrosion.
The liner is made of wear-resistant material
developed from a dedicated and long-term
R&D programme. To eliminate the risk of bore
polishing, the liner is provided with an antipolishing ring on the upper part. The purpose
of this ring is to limit the carbon deposits
built up on the piston top land to a thickness
small enough to prevent contact between
the inner liner wall and the deposits on any
position of the piston. The absence of contact
between the liner and piston top land deposits
eliminates the risk of bore polishing. Nor can
oil be scraped upwards by the piston. This
significantly reduces liner wear and keeps the
lube oil consumption stable for long periods of
time.
The main features of the cylinder liner
design are:
„„
Centrifugal casting with high strength and
good wear resistance
„„
Cooling of the bore for optimum wall
temperatures
„„
High-collar technology to ensure good
cylinder head gasket tightness
„„
Anti-polishing ring removes deposits from
the piston top land, ensuring proper cylinder
function, no bore polishing, stable lube oil
consumption, and low wear to the liner.
7
PISTON & PISTON RINGS
For years, the outstanding piston concept
for highly rated heavy fuel engines has been
a rigid composite piston with a steel crown
and nodular cast-iron skirt. More than twenty
years of experience has fine-tuned this
concept. When it comes to reliability, there is
no real alternative today for modern engines
with high cylinder pressures and combustion
temperatures.
Wärtsilä’s patented skirt lubrication
minimizes frictional losses, and ensures the
appropriate lubrication of both piston rings and
the piston skirt. In Wärtsilä’s three-ring concept
each ring has a specific task. The rings are
dimensioned and profiled for consistent
performance throughout their operating lives.
To avoid carbon deposits in the ring
grooves of a heavy fuel engine, the pressure
balance above and below each ring is crucial.
Experience has shown that this effect is most
likely achieved with a three-ring pack. Finally,
it is well known that most frictional losses in
a reciprocating combustion engine originate
from the rings. Thus a three-ring pack is the
obvious choice in this respect, too. The piston
8
ring package and ring grooves are optimized
for long life by a special wear-resistant coating
and groove treatment.
The main features of the piston design are:
„„
A two-piece composite structure
„„
A steel crown and nodular cast-iron skirt
„„
Two compression rings and one oil scraper
ring, which in combination with a pressure
lubricated piston skirt, achieve low friction
and high seizure resistance
„„
Optimized piston ring groove temperature to
prevent cold corrosion.
CYLINDER HEAD
The cylinder head design features high
reliability and easy maintenance. A stiff cone- /
box-like design can cope with high combustion
pressures, and is essential for obtaining both
liner roundness and even contact between the
exhaust valves and their seats. Wärtsilä’s vast
global experience of heavy fuel operation has
contributed greatly to the efficient design and
development of exhaust valves.
The basic criterion in exhaust valve design
is having the correct temperature. This is
achieved through optimized cooling and closed
seat ring technology, which extend the life of
the valves and seats.
The cylinder head design is based on the
four-screw concept developed and used by
Wärtsilä for many years. A four-screw cylinder
head design also provides the possibility
for having inlet and exhaust ports with a
minimum of flow losses. The port design
has been optimized using a combination of
computational fluid dynamics analysis and fullscale flow measurements.
The main features of the cylinder head design
are:
„„
Four cylinder head screws only, giving
space for flow-efficient ports
„„
Inlet and exhaust gas ports that are on the
same side
„„
The height and rigid design, which ensure
even and sufficient surface pressure on the
cylinder head gasket
„„
A bore-cooled flame plate for optimum
temperature distribution
„„
Two inlet valves and two exhaust gas
valves, all with valve rotators.
MULTI-DUCT
A multifunctional duct is connected to the
cylinder head. The functions of this multi-duct
are as follows:
„„
Air transfer from air receiver to cylinder head
„„
Introduction of an initial swirl to the inlet air
for optimal part load combustion
„„
Exhaust transfer to the exhaust system
„„
Cooling water transfer from the cylinder
head to the return channel in the engine
block
„„
Insulation/cooling of the exhaust transfer
duct
„„
Support for the exhaust system, including
insulation
CAMSHAFT AND VALVE GEAR
The engine is available with either traditional
mechanical valve actuation, or variable inlet
valve closing actuation.
The camshaft is built of single cylinder
sections with integrated cams. The camshaft
sections are connected through separate
bearing journals, which make it possible to
remove the shaft sections sideways from the
camshaft compartment.
The valve follower is of the roller tappet
type, where the roller profile is slightly
convex for good load distribution. The valve
mechanism includes rocker arms working on
yokes guided by pins.
Both exhaust and inlet valves are equipped
with valve rotators to ensure a safe valve and
seat function. The rotation means that the
temperature distribution and wear to the valves
is even, and that the sealing surface is kept
free of deposits.
The main features of the camshaft and valve
design are:
„„
Each cylinder section of the camshaft is
forged in one piece with integrated cams
„„
Separate bearing journals
„„
The valve follower is of the roller tappet type
„„
Traditional valve actuation
„„
Variable Inlet Valve Closing (VIC) for
IMO Tier II compliance.
The VIC system is designed to improve the
engine’s partial load performance by enabling
alternative inlet valve closing timings. The
major advantages are a reduction in visible
smoke, load application improvement, and
thermal load reduction. The variation of inlet
valve closing timing is achieved through the
addition of a hydraulic chamber between
the inlet valve tappet and the push rod.
Adjustability of the inlet valve movement is
achieved by controlling the oil flow into and out
the hydraulic chamber.
The main features of the VIC system are:
„„
Inlet valve closing timing that can be
adjusted
„„
With VIC employed, the inlet valve is open
longer
As compared to the standard valve train, the
VIC system comprises the following additional
parts:
„„
Pressure accumulator
„„
Piston and oil supply
„„
Non-return valve
9
OPERATIONAL SYSTEMS
FUEL INJECTION SYSTEM
The patented Wärtsilä multi-housing principle
ensures outstanding safety of the low-pressure
fuel system. The fuel line consists of channels
drilled in cast parts, which are clamped firmly
to the engine block. For easy assembly and
disassembly, these parts are connected to
each other using slide connections.
Wärtsilä 4-stroke engines are available
with three alternative fuel injection systems
depending on configuration: a conventional
fuel injection system, with either single- or
twin plunger injection pumps, and commonrail fuel injection. High injection pressures
giving low smoke emissions characterize all
three systems. The common-rail technology
in particular, enables operation at any load
without visible smoke.
10
An unmatched level of safety is achieved
through housing both the entire low-pressure
and high-pressure systems in a fully covered
compartment.
Common-rail technology offers almost
unlimited possibilities to adjust the fuel
injection process to the prevailing engine
operating conditions, fuel characteristics,
and to achieve emission levels. The main
components of the common-rail injection
system that are designed especially for
Wärtsilä engines are the high-pressure pumps,
the balance accumulators, the fuel injection
valves, and the built-on control oil pump. The
control oil is engine oil with additional filtration.
The system’s high-pressure pumps are
camshaft-driven and amply dimensioned for
supplying fuel to two cylinders. Each pump is
connected to a fuel accumulator that evens
out the pressure and feeds the two cylinders.
The accumulators are connected to each other
through double-walled pipes, a detail that
both guarantees continuously even pressure
in all accumulators, and that allows the engine
to operate with one or two disconnected
high-pressure pumps, should this ever be
necessary.
From the accumulators, fuel is supplied
at the required pressure into the cylinders
through injection valves controlled by electrohydraulic actuators. The individual, and
therefore cylinder-specific, control of injection
timing and duration is an important feature that
is made possible by this injection equipment.
One significant safety detail is that the
injection valves are designed to ensure that the
injection nozzles are totally unloaded between
injection periods. This feature eliminates the
risk of unintended fuel supply into the cylinders
caused, for example, by incomplete closure of
the nozzle needle at the end of injection.
The twin-pump system, likewise, offers the
possibility to optimize the prevailing engine
operating conditions, fuel characteristics and
emission levels, thanks to twin plunger pump
elements. One plunger controls the quantity
of fuel while the other controls the injection
timing.
TURBOCHARGING SYSTEM
Turbocharger technology has undergone
intense design and performance development
in recent years, resulting in higher performance
and greater reliability. Only the best available
charger technology is used on Wärtsilä
engines.
The main features of the turbocharging
system are:
„„
One-stage turbocharging
„„
An oil-cooled turbocharger with plain
bearings lubricated by engine oil
„„
A two-stage charge air cooler depending on
engine configuration
„„
An LT water bypass valve for charge air
temperature control
„„
The charge air receiver is integrated into
the engine block
„„
A water mist catcher as a standard option
„„
Air and exhaust waste gate functions for
best engine performance, depending on
engine configuration
„„
A single-pipe exhaust gas system (SPEX)
or pulse charging, depending on engine
configuration
The SPEX system is designed for minimum
flow losses on both the exhaust and air sides.
The charging systems are designed to give
high efficiency and good load acceptance.
SPEX is designed for best possible full-load
performance. SPEX, combined with the
exhaust waste gate and air bypass, meets
the established low load performance of
pulse charging. With its unique design, the
load acceptance is close to that of pulse
charging. Non-cooled chargers, with inboard
plain bearings lubricated by the engine’s lube
oil system, are used. The end result is that
intervals between overhauls are reduced, as is
maintenance.
11
Lubricating
oil
cooler
Charge
air cooler
HT
Charge
air cooler
LT
LT
stand­by
pump
Heat recovery
Cyl.
Central
cooler
HT
pump
LT
pump
Pre­
heater
HT
stand­by
pump
PRINCIPLE LAYOUT OF THE COOLING SYSTEM.
Oil cooler
Automatic filter
Centrifugal filter
Oil pump
Electric
stand­by
oil pump
Electric
pre­lube
oil pump
Suction
strainer
Dry oil sump
System oil tank
PRINCIPLE LAYOUT OF THE LUBRICATING SYSTEM.
�
COOLING SYSTEM
The cooling system on the engine is split
into two separate circuits: high-temperature
(HT) and low-temperature (LT). The cylinder
liner, the cylinder head, and the first stage
in the charge air cooler are all connected to
the HT circuit. The lubricating oil cooler and
the second stage in the charge air cooler are
connected to the LT circuit.
The amount of water passing through the
LT stage in the charge air cooler is controlled
by a thermostatic valve. This maintains the
desired intake air temperature, regardless of
load level or variations in the cooling water
temperature. Engine-driven pumps and builton thermostatic valves are standard. As an
option, the engine is also available without
built-on pumps and thermostatic valves.
12
LUBRICATING OIL SYSTEM
The engine is available with a complete builton lube oil system that offers the following
features:
„„
An engine-driven main lube oil pump (screw
type) with built-in safety valve
„„
A pressure regulating valve that keeps the
pressure before the main bearings at a
constant level
„„
A lubricating oil module, including lube oil
cooler, filter and thermostatic valves
„„
The lube oil filtration is based on a full flow
automatic back-flushing filter. This requires
a minimum of maintenance and needs no
disposable filter cartridges
„„
A centrifugal filter connected to the backflushing line of the automatic filter. This
enables wear particles from the system to
be extracted
„„
An electric motor driven pre-lubricating
pump, depending on engine configuration
„„
The oil sump is either a wet or dry type,
depending on engine configuration. A
separate system oil tank is needed for the
dry sump
„„
Connections for stand-by auxiliaries.
AUTOMATION SYSTEM
Wärtsilä engines can be equipped with a
modular embedded automation system, the
Wärtsilä Unified Controls – UNIC, which is
available in three different versions. The basic
functionality is the same in all versions, but
the functionality can be easily expanded to
cover different applications. UNIC C1 and
UNIC C2 are versions applicable for engines
with conventional fuel injection, whereas UNIC
C3 additionally includes fuel injection control
Hardwired
connections
Loadsh.
CAN
Ethernet
LDU
CCM
CCM
LCP
IOM
ESM
MCM
PDM
UNIC
for engines with common-rail fuel injection.
UNIC C3 automation is also used in gas
engines.
The Wärtsilä UNIC is a flexible and fully
scalable control system for large reciprocating
diesel and gas engines.
The UNIC system is designed to fulfill the
long lifetime expectations for large marine
diesel and gas engines operating in the
toughest of conditions. The system is based
on a high degree of commonalities and
standard interfaces, covering different engine
sizes and fuel systems in a modular way.
A modular, standardized interface provides
an easily reusable design for off-engine
automation systems. It allows, for example,
diesel engines to be converted to dual fuel or
common rail with a minimum of modifications.
Thanks to the pre-tested configuration,
minimal commissioning or installation work
is needed before the engine or generating
set is operational. The critical parts of the
UNIC system are either redundant or very
fault-tolerant to guarantee high safety and
availability in all circumstances. In particular,
parts like the communication and power supply
are fully redundant to allow single failures
without interruptions in engine operation.
The electronic control enables the engine to
be adapted to different operating conditions.
The main features of the UNIC system are:
„„
A complete engine safety system
„„
Local monitoring
„„
Speed control with load sharing
„„
Fuel injection
„„
Timing control and knock detection
„„
Alarm signal acquisition
AUTOMATION SYSTEM COMPONENTS
ESM
Engine Safety Module
MCM
Main Control Module
TCM
Thermocouple Module
IOM
Input Output Module
PDM
Power Distribution Module
LCP
Local Control Panel
LDU
Local Display Unit
CCM
Cylinder Control Module
„„
Start/stop sequencing and load reduction
request
„„
System diagnostics and a fieldbus interface
applicable to each engine’s configuration.
13
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
NOX (g/kWh)
2 g/kWh
Thermal efficiency (%)
BMEP (bar)
45%
Misfiring
Operating
window
Knocking
2.6
Air/fuel ratio
DUAL-FUEL TECHNOLOGY
THE LEAN-BURN CONCEPT
The Wärtsilä dual-fuel technology operates
on the lean-burn principle: the mixture of air
and gas in the cylinder has more air than
is needed for complete combustion. Lean
combustion reduces peak temperatures
and therefore NOX emissions. Efficiency
is increased and higher output is reached
while avoiding knocking.
Combustion of the lean air-fuel mixture
is initiated by injecting a small amount of
LFO (pilot fuel) into the cylinder. The pilot
fuel is ignited in a conventional diesel
process, providing a high-energy ignition
source for the main charge. To obtain the
best efficiency and lowest emissions, every
cylinder is individually controlled to ensure
operation at the correct air-fuel ratio and
with the correct amount and timing of pilot
fuel injection.
Wärtsilä has developed a special
electronic control system to cope with
the demanding task of controlling the
combustion in each cylinder, and to ensure
optimal performance in terms of efficiency
and emissions under all conditions by
keeping each cylinder within the operating
window. Stable and well-controlled
combustion also contributes to less
mechanical and thermal load on the engine
components.
14
FUEL SYSTEM
The fuel system of the Wärtsilä dual-fuel engine
has been divided into three: for gas, for liquid fuel,
and for a separate pilot fuel system. The Wärtsilä
dual-fuel engine is started in diesel mode using
both main diesel and pilot fuel. Gas admission
is activated when combustion is stable in all
cylinders. When running the engine in gas mode,
the pilot fuel amounts to less than 1% of full-load
fuel consumption. The amount of pilot fuel is
controlled by the engine control system. When
running the engine in liquid fuel mode the pilot is
also in use to ensure nozzle cooling.
GAS SUPPLY
The natural gas is supplied to the engine
through a gas valve unit. The gas is first filtered
to ensure a clean supply. The gas pressure
is controlled by a valve located in the valve
station. The gas pressure is dependent on
engine load. At full load the pressure before
the engine is 3.5 bar (g) for LHV 36 MJ/m3.
For lower LHV the pressure has to be
increased. The system includes the necessary
shut-off and venting valves to ensure a safe
and trouble-free gas supply.
On the engine, the gas is supplied through
large common-rail pipes running along the
engine. Each cylinder then has an individual
feed pipe to the gas admission valve on the
cylinder head.
Gas piping in marine installations is of
double wall design as standard.
LIQUID FUEL OIL SUPPLY
The fuel oil supply on the engine is divided into
two separate systems: pilot fuel and back-up
fuel oil system.
The pilot fuel is elevated to the required
pressure by a pump unit. This includes
duplex filters, pressure regulator and an
engine-driven radial piston-type pump. The
high-pressure pilot fuel is then distributed
through a common-rail pipe to the injection
valves at each cylinder. Pilot fuel is injected at
approximately 900 bar pressure and the timing
and duration are electronically controlled. The
pilot fuel system is separated from the back-up
fuel system with separate connections on the
engine. The back-up fuel system is fed to a
normal camshaft-driven injection pump. From
the injection pump, the high-pressure fuel goes
to a spring-loaded injection valve of standard
design for a diesel engine.
INJECTION VALVE
The Wärtsilä dual-fuel has a twin-needle
injection valve. The larger needle is used in
back-up mode for LFO or HFO operation and
the smaller for pilot fuel oil when the engine
is running in gas mode and also in back-up
fuel operation to ensure nozzle cooling. Pilot
FUEL INJECTION PUMPS FOR
LIQUID FUEL OPERATION
INJECTION VALVES
BOOSTER
PUMP
UNIT
M
PRESSURE
BOOSTER
PUMP
UNIT
PRESSURE
PRESSURE
RETURN FUEL
Control
system
COMMON RAIL FOR HIGH
PRESSURE PILOT FUEL
RETURN FUEL
PILOT FUEL PUMP UNIT
MAIN FUEL TANK
LFO or HFO
PILOT FUEL TANK
LFO
injection is electronically controlled and the
main diesel injection is hydromechanically
controlled. The individually controlled solenoid
valve allows optimum timing and duration of
pilot fuel injection into every cylinder when
the engine is running in gas mode. Since NOX
formation depends greatly on the amount of
pilot fuel, this design ensures very low NOX
formation while still employing a stable and
reliable ignition source for the lean air-gas
mixture in the combustion chamber.
15
GAS ADMISSION VALVE
Gas is admitted to the cylinders just before
the air inlet valve. The gas admission valves
are electronically actuated and controlled by
the engine control system to give exactly the
correct amount of gas to each cylinder. In this
way, the combustion in each cylinder can be
fully and individually controlled. Since the valve
can be timed independently of the inlet valves,
the cylinder can be scavenged without risk of
gas being fed directly to the exhaust system.
Independent gas admission ensures the
correct air-fuel ratio and optimal operating
point with respect to efficiency and emissions.
It also enables reliable performance without
shutdowns, knocking or misfiring. The gas
admission valves have a short stroke and
16
at all times and will switch over from gas to
fuel oil if necessary. The plunger is equipped
with a wear-resistant coating.
specially selected materials, thus providing low
wear and long maintenance intervals.
INJECTION PUMP
The Wärtsilä dual-fuel engine utilizes the wellproven monoblock injection pump developed
by Wärtsilä. This pump withstands the high
pressures involved in fuel injection and has
a constant-pressure relief valve to avoid
cavitation. The fuel pump is ready for operation
PILOT PUMP
The pilot fuel pump is engine-driven. It receives
the signal for correct outgoing fuel pressure
from the engine control unit and independently
sets and maintains the pressure at the required
level. It transmits the prevailing fuel pressure to
the engine control system.
High-pressure fuel is delivered to each
injection valve through a common-rail pipe,
which acts as a pressure accumulator and
damper against pressure pulses in the system.
The fuel system has a double wall design with
alarm for leakage.
“INSTANT” CHANGE OVER FROM GAS TO LIQUID FUEL MODE
WITH THE DUAL-FUEL SOLUTION
gas to liquid fuel
liquid fuel to gas
100 %
*
~80%
Instant
Gas
~0,5 h
LFO
~0,5 h
~0,1 h
HFO
Gas
LFO
HFO
In the dual-fuel solution the twin injection nozzles are used also for HFO operation.
The LFO pilot is in use also during the HFO operation.
* The time needed to reach full load on gas depends on the duration of HFO-mode operation.
Load
Speed
Engine control
system
Exhaust waste­gate
P
I
T
Exhaust
TC
Air
P
OPERATION MODE TRANSFER
The engine can be switched automatically
from liquid fuel oil to gas operation at loads
below 80% of the full load. Transfer takes place
automatically after the operator’s command
without load changes. During switchover, which
lasts about one minute, the fuel oil is gradually
substituted by gas.
In the event of for instance a gas supply
interruption, the engine converts from gas to
liquid fuel operation at any load instantaneously
and automatically. Futhermore, the separate
liquid fuel system makes it possible to switch
over from LFO to HFO without power reduction.
The pilot fuel is in operation at liquid fuel mode to
ensure nozzle cooling. The pilot fuel consumption
is less than 1% of full load fuel consumption.
Switching over to LFO from HFO operation can
also be done without load reduction. From LFO
to gas operation, the switch can be made as
described above. This operation flexibility is the
real advantage of the dual-fuel system.
AIR-FUEL RATIO CONTROL
The correct air-fuel ratio under any operating
conditions is essential to optimum performance
and emissions. For this function, Wärtsilä dualfuel engines are equipped with an exhaust gas
waste-gate valve.
Part of the exhaust gases bypasses the
turbocharger through the waste-gate valve. The
valve adjusts the air-fuel ratio to the correct value
independent of the varying site conditions under
high engine loads.
17
MAINTENANCE FEATURES
SERVICES
During design and development, engine
manufacturers typically emphasize ease of
maintenance by including tooling and easy
access in the basic design, and by providing
easy-to-understand instructions.
Wärtsilä´s maintenance principle is
substantiated by the following:
„„
A cylinder head with four fixing studs and
simultaneous hydraulic tightening of all four
studs
„„
Uniform one-cylinder camshaft pieces
„„
Slip-on fittings wherever possible
„„
Exhaust gas system insulation using easyto remove panels on an engine mounted
frame
„„
A hydraulic jack for the overhaul of the main
bearing where applicable
„„
A three-piece connecting rod in bigger
engines, allowing inspection of the big end
bearing without removal of the piston, and
piston overhaul without dismantling the big
end bearing
„„
Weight-optimized and user-friendly
maintenance tools
Several customers have recognized us as
their preferred service supplier to ensure the
availability and cost-efficient operation of their
installations. They benefit from having their
entire power system fully serviced by one
global supplier. Wärtsilä Services provides full
service throughout the product lifecycle for
both marine and power plant customers, and is
constantly developing its network worldwide.
Additionally we are continually broadening
our range of services by adding valuable
products and specialist services to our
portfolio. In this way we also support
equipment onboard your vessel or at your
installation and in our numerous workshops
around the globe and in key ports, regardless
of equipment make.
We offer lifecycle efficiency solutions in the
following services product lines:
„„
Engine Services
„„
Propulsion Services
„„
Electrical & Automation Services
„„
Boiler Services
„„
Operations & Management Services
„„
Training Services
„„
Environmental Services
18
These services cover everything from basic
support with parts, field service and technical
support to service agreements and condition
based maintenance; from installation and
commissioning, performance optimization,
including upgrades and conversions, to
environmental solutions, technical information
and online support.
The choice available to you extends from
parts and maintenance services to a variety
of comprehensive, customized long-term
service agreements, including performance
and operations & management agreements.
Our Services organization currently features
more than 11,000 dedicated professionals in
70 countries.
Wärtsilä adds value to your business at
every stage in the lifecycle of your installations.
With us as your service partner, you receive
many measurable benefits such as availability
and performance, productivity gains and
cost benefits. Above all, peace of mind in
the knowledge that your installation is being
serviced by the most experienced partner you
could have – Wärtsilä.
and energy markets. By emphasising technological innovation and total
efficiency, Wärtsilä maximises the environmental and economic performance
of the vessels and power plants of its customers. Wärtsilä is listed on the
NASDAQ OMX Helsinki, Finland.
WÄRTSILÄ® is a registered trademark. Copyright © 2010 Wärtsilä Corporation.
06.2010 / Bock´s Office / Waasa Graphics
Wärtsilä is a global leader in complete lifecycle power solutions for the marine
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