Technology review

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Technology review

Setting new standards for

economical power production . . . . . . . . . . 4

Design philosophy . . . . . . . . . . . . . . . . 4

IMO NOX compliance . . . . . . . . . . . . . . 6

Piston. . . . . . . . . . . . . . . . . . . . . . . 6

Piston ring set . . . . . . . . . . . . . . . . . . 7

Connecting rod and big end bearings . . . . . . 7

Cylinder liner and anti-polishing ring . . . . . . . 8

Cylinder head. . . . . . . . . . . . . . . . . . . 8

Multiduct . . . . . . . . . . . . . . . . . . . . . 9

Crankshaft and main bearings . . . . . . . . . . 9

Engine block and foundation . . . . . . . . . . 10

Fuel system . . . . . . . . . . . . . . . . . . . 10

Turbocharging system . . . . . . . . . . . . . 11

Cooling systems . . . . . . . . . . . . . . . . 11

Lubricating oil system. . . . . . . . . . . . . . 12

Automation system . . . . . . . . . . . . . . . 12

Application flexibility . . . . . . . . . . . . . . 13

Easy maintenance. . . . . . . . . . . . . . . . 14

Main technical data . . . . . . . . . . . . . . . 15

20

Setting new standards for economical power productionThe WÄRTSILÄ® 20 medium-speed engine offers a

remarkable combination of state-of-the-art design and top

performance in a compact, space-saving package. With its

virtually pipeless, operator-friendly "heavy duty" design,

the engine has started a new era in the development of

medium-speed engines. Where power-to-weight and

power-to-space rations are concerned, the engine is

unmatched in its power range.

The fact that the Wärtsilä 20 has originally been

designed to operate reliably with the poorest quality heavy

fuel, makes Wärtsilä 20 the ultimate in reliable

performance using Light Diesel Oils. Overhaul intervals

up to 24,000 hours and maintenance-friendly desing are

some of the main valuable features that have earned the

Wärtsilä 20 an installed base of more than two thousand

engines since the launch in 1992.

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Design philosophyThe design of the Wärtsilä 20 engine is based on

Wärtsilä’s heavy fuel know-how and is fully optimized for

today’s flexible manufacturing methods.

The Wärtsilä 20 engine offers customers the following

core values:

� Proven and reliable heavy fuel technology� Cost-effective design� Easy and cost-effective installation� Low operating costs� Low NOX emission� Minimal consumables

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FPSO Berge Hugin. MST Berge Hugin, Navion Munin and West Navionare all equipped with four Wärtsilä 6L46 main engines and one Wärtsilä9L20 auxiliary engine. Total output per vessel 22,890 kW.

Seismic vessel Geco Bluefin.Auxiliary engines: four Wärtsilä9L20 generating sets.Total output of 6120 kW/rpm.

Tug, Sanergy JayaMain engines:two Wärtsilä 6L20

Container "Contship Italy"Auxiliary engines: three Wärtsilä 6L20 enginesEmergency engine: one Wärtsilä 4L20 engine

Research vessel Scotia. Main engines: three Wärtsilä 9L20, totaloutput 4,455 kW/1000 rpm. Shipyard: Ferguson ShipbuildersLtd. Shipowner: Fisheries Research Services

IMO NOX complianceGenerally diesel engines have less harmful emissions

(CO2, CO etc.) than many other power sources. The

standard engine can easily meet the NOX level set by IMO

(International Maritime Organisation), in Annex VI to

MARPOL 73/78. To show compliance, the engine is

certified according to the NOX Technical Code, and

delivered with an EIAPP (Engine International Air

Pollution Prevention) Statement of Compliance. The

certification process includes NOX measurements,

marking of components that are affecting NOX formation

and a Technical File that is delivered with the engine.

All major classification societies are on behalf of the flag

state granting the EIAPP Statement of Compliance for the

Wärtsilä 20 engine family.

If lower NOX levels are required, the engine can be

equipped with a Compact SCR catalyst, which can reduce

NOX by up to 95%, down to a level < 1 g/kWh.

PistonPistons are of the low-friction, composite type with steel

top and nodular cast iron skirt. Based on a track record of

more than twenty years, this is the superior concept for

highly rated heavy fuel engines. The design itself is of

course tailored for an engine of this size and includes a

number of innovative solutions. Experience has shown

that nodular cast iron is the best piston material for

modern diesel engines which operate with high pressures

and temperatures in the combustion chamber. Low

friction is obtained by Wärtsilä’s patented skirt lubrication

system.

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20

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16

14

12

10

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60 500 1000 1500 2000N

OX

emis

sio

ns,w

eig

hted

(g/k

Wh)

Rated engine speed (rpm)

IMO global marine NO legislationX

Low NO combustionX

Low NOx design

Engine maximum firing pressure

Pressure riseinduced fromcombustion

Conventional design

Engine maximum firing pressure

Pressure riseinduced fromcombustion

Pressure riseinduced fromcompression

Pressure riseinduced fromcompression

TDC TDC

Cyl

ind

erp

ress

ure

Cyl

ind

erp

ress

ure

-90 -90-60 -60-30 -300 030 3060 6090 90120 120

Wärtsilä 20 Fuel: Marine diesel oil

Piston ring setThe two compression rings and the oil control ring are

located in the crown. This three-ring concept has proved

its efficiency in the Wärtsilä 46 engine. In a three-ring

pack every ring is dimensioned and profiled for the task it

has to perform. It is also well-known that most of the

frictional loss in a reciprocating combustion engine

originates from the piston rings. Thus a three-ring pack is

considered optimal with respect to both function and

efficiency. For maximum wear resistance the top ring

features a special wear-resistant coating.

Connecting rod and big endbearingsThe “stepped split line” design used in the Wärtsilä Vasa

22 and 32 for many years now offers the maximum pin

diameter while still making it possible to pull the

connecting rod through the cylinder liner. The advantage

over the conventional straight, oblique split line is an

increase in pin diameter of at least 15%. This is of vital

importance in a modern engine designed for high

combustion pressures.

When an engine type is designed for both in-line and

V-version the big end bearing width is often a

compromise between the bearing load and overall length

of the V-version. As the Wärtsilä 20 is designed as an

in-line engine only, no compromises are necessary. A

direct consequence is superior oil film thickness and low

oil film pressure. The bearing material used in this engine

can withstand cylinder pressures of well over 200 bar.

The non-grooved upper half of the big end bearing in the

Wärtsilä 20 also helps to maximize the oil film thickness.

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Spec. Cr

Cr

Cr

Cylinder liner andanti-polishing ringThe cylinder liner is designed for minimum deformation

thanks to its own stiffness and support from the engine

block. It is equally important to adjust the inner wall

temperature to a level just above the sulphuric acid dew

point. This is done by creating an increased tangential

cooling water flow velocity just below the liner collar.

The liner is made of wear-resistant material developed

through a dedicated R&D programme lasting several

years. To eliminate the risk of bore polishing, the liner is

provided with an anti-polishing ring at 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 at any position of the piston. This

mechanism is the source of the “bore- polishing” which

causes local liner wear and increased lube oil

consumption.

Cylinder headFour-screw cylinder head technology was introduced by

Wärtsilä more than 20 years ago. Especially at cylinder

pressures of 200 bar it has proved its superiority when it

comes to liner roundness and dynamic behaviour. In

addition to easier maintenance and reliability it provides a

lot of freedom in employing the most efficient channel

configuration.

A distributed water flow pattern is used for proper cooling

of the exhaust valves and cylinder head flame plate.

This minimizes the thermal stress levels and guarantees a

sufficient low exhaust valve temperature.

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MultiductA multifunctional duct is connected to the cylinder head.

The functions of this multiduct are as follows:

� Air transfer from air receiver to cylinder head

� Introduction of an initial swirl to the inlet air foroptimal part load combustion

� Exhaust transfer to exhaust system

� Cooling water transfer from cylinder head to returnchannel in the engine block

� Insulation/cooling of the exhaust transfer duct� Support for exhaust system including insulation

Crankshaft and main bearingsWith increasing cylinder pressures and engine output the

crankshaft dimensions will necessarily increase. This goes

hand in hand with the larger bearing surfaces required to

keep the specific bearing loads at an acceptable level.

Thanks to careful optimization of the crankshaft design, the

Wärtsilä 20 has actually reduced bearing loads. In other

words, the material is used in the most favourable way in

terms of both bearing load and crankshaft stress. Low

bearing load and optimized balancing of the rotating masses

ensure ample oil film thicknesses at all loads and speeds. In

the past, corrosion took a heavy toll on bearings in trunk

engines operating on heavy fuel. This is now history, as

corrosive resistant bearing materials are available.

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Exhaust gas Cooling water Charge air

Engine block and foundationThe engine block has been designed for maximum overall

stiffness and local stiffness around the upper part of the

cylinder liner. As a consequence of the general design

philosophy of component integration, it contains a

number of cast-in or machined water and oil channels.

Furthermore, the camshaft bearings are housed directly in

the engine block as is the camshaft gear train at the

flywheel end of the engine. Thanks to its overall stiffness,

easy-to-install, four point support is standard for the

engine. To allow the most flexible common base plate

arrangement independent of the alternator make, the

alternator is fitted with an adjustable mounting pad

arrangement. For resilient mounting simple structure and

effective isolation is provided by separate engine feet.

Fuel systemThe low pressure fuel system is an integrated part of the

injection pump. This is realized with a multihousing,

which contains the following:

� the single cylinder injection pump

� a fuel supply line along the whole engine

� the fuel return lines from each pump

� the pneumatic overspeed trip device� guiding for the valve tappets

This arrangement represents the ultimate in safe fuel

systems. Moreover, the high pressure fuel line is also fully

enclosed with an alarm for possible leakages and all fuel

carrying parts are housed in a fully covered compartment,

i.e. a hotbox. The high pressure side is designed for a 2000

bar injection pressure while the pressure utilized is around

10

1500 bar. The pump element itself features a method to

eliminate cavitation erosion. The fuel injection valve is

designed for uncooled nozzles and the nozzles are

heat-treated for low wear and high heat resistance. All this

ensures easy maintenance and long lifetimes. The Wärtsilä

20 can of course start, stop and operate over the whole

load range using heavy fuel.

Turbocharging systemThe Wärtsilä 20 engine is designed for applications where

the most demanding load pick-up and prolonged

operation on low loads are required. This means that all

cylinder configurations of the engine are equipped with an

optimized pulse system.

Cooling systems

High temperature (HT) cooling system

The system is totally integrated with the various engine

components; virtually no pipes are used. Supply and

return channels are cast into the engine block while the

pump cover and turbocharger support hold the

connections between the pump and engine block.

The system temperature is kept at a high level, about

95°C, for safe ignition/combustion of low quality heavy

fuels at low loads. An additional advantage is maximum

heat recovery and total efficiency. An engine-driven pump

of the cassette type is standard.

Low temperature (LT) cooling system

This system is also fully integrated with the engine

components, i.e. engine block, pump cover, air and lube

oil cooler housings. An engine-driven pump of the same

type as for the HT-system is standard.

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3-pulse

Pulse converter

Lubricating oil systemAll Wärtsilä 20 engines are equipped with a complete lube

oil system, i.e. an engine-driven main pump, electrically

driven prelubricating pump, cooler, full flow filter and

centrifugal filter. Pressure regulation and safety valves are

integrated into engine driven pump fitted at the free end

of the engine where also prelubricating pump with electric

motor is fitted. Filter, cooler and thermostatic valves are

built up in a module located at the engine rearside.

The lube oil filtration is based on an automatic

back-flushing filter requiring a minimum of maintenance.

The filter elements are made of seamless sleeve fabric with

high temperature resistance. An overhaul interval of one

year is recommended. The expected lifetime is four years.

A special feature is the centrifugal filter, connected to the

back-flushing line of the automatic filter. This provides

the means for extraction wear particles from the system.

Automation systemMaking the electronic connections to the external system

usually involves a lot of work. The Wärtsilä 20 is made for

easy plug-in connection of sensors to prefabricated cabling

modules.

The following functions are incorporated in the

automation system:

� Instrumentation for local reading of engine andturbocharger speed, exhaust temperature after eachcylinder and after the turbocharger and an operatinghour counter

� Electronic boards for speed measuring and charge airtemperature control

� Plug-in connectors for connection to the externalcontrol system

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FilterCooler Pump

Primingpump

Lube oil system

The main cabinet is firmly mounted on the engine to

isolate it from engine vibrations. There is a battery of

pressure switches and a manometer panel near the cabinet

for operating convenience.

A more advanced electronic control unit with capability

for direct bus-connection will be provided for shipyards

that want to make use of the latest ship automation

technology.

Application flexibilityWärtsilä 20 is suitable for wide range of applications in

various respects. Different fuels from lowest viscosity of

1,8cSt up to 730cSt HFO (at 50ºC) can be used and

optimised engine performance is provided by standard

engine specifications for constant and variable speed

applications.

Flexibility in engine support arrangements allows

optimised rigid or flexible foundation for wide range of

application types in marine and land based power

solutions. Easy and cost effective installation is provided

by minimised application work due to on-built auxiliary

equipment with low positioned interface connections.

Suitability for small engine rooms is supported by low

installation height and by standard options with

turbocharger at free end and also at driving end for 6-, 8-

and 9-cylinder engines.

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Easy maintenanceEfficient maintenance is incorporated in the engine

design. Hydraulics are used for pretensioning the

cylinder head screws, connecting rod screws and main

bearing screws. Access to the injection pumps is

excellent thanks to limited piping in the hotbox, where

the pumps are housed. An injection pump element is

easy to replace without removing the multihousing.

Neither is it necessary to remove fuel feed/return pipes

for the simple reason that there are not any. The

multiduct remains on the engine block holding the

exhaust system when the cylinder head is removed.

Neither is it necessary to remove water pipes because

they are integrated with the multiduct. Only two screws

have to be loosened to remove the rocker arms and

bracket. The water pump is easy to replace thanks to

the cassette design. It is even easier to remove the end

cover alone if the impeller has to be changed.

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Main technical data

Cylinder bore . . . . . . . . . . . . . . . . . . . . . . . . 200 mmPiston stroke. . . . . . . . . . . . . . . . . . . . . . . . . 280 mmCylinder output . . . . . . . . . . . . . . . . . . . 130 - 200 kW/cylSpeed . . . . . . . . . . . . . . . . . . . . . . . . 720 - 1000 rpmMean effective pressure . . . . . . . . . . . . . . . 22.5 - 28.0 barPiston speed . . . . . . . . . . . . . . . . . . . . . . 6.7 - 9.3 m/sVoltage . . . . . . . . . . . . . . . . . . . . . . . . . 0.4 – 13.8 kVAlternator efficiency . . . . . . . . . . . . . . . . . . . 0.94 – 0.96Fuel specification:Fuel oil . . . . . . . . . . . . . . . . . . . . . . . . . 730 cSt/50°C

. . . . . . . . . . . . . . . . . . . . . . . . . . . 7200 sR1/100°F

. . . . . . . . . . . . . . . . . ISO 8217, category ISO-F-RMK 55SFOC 188-196 g/kWh at ISO condition ± 5% tolerance

Rated power: Propulsion engines

Enginetype

Output in kW/bhp at 1 000 rpm

C2 -output C3 -output

kW bhp kW bhp

4L205L206L208L209L20

720825

108014401620

9801120147019602200

1200

1800

1630

2450

Principal engine dimensions (mm) and wet weights (tonnes)

Enginetype A* A B* B C* C D

4L205L206L208L209L20

––

325439734261

25102833310837834076

––

152816141614

13481423134814651449

––

158017561756

14831567157917131713

18001800180018001800

E F H K N* Weight*4L205L206L208L209L20

325325325325325

725725624624624

155155155155155

980980980980980

––

589708696

7.27.89.3

11.011.6

For this engine type the dimension B refers to the highest point of the engine.Weight with liquids (wet sump) but without flywheel.*Turbocharger at flywheel end.

Rated power: Generating sets

Enginetype

C2 -output C3 -output

720 rpm/60 Hz

750 rpm/50 Hz

900 rpm/60 Hz

1000 rpm/50 Hz

900 rpm/60 Hz

1000 rpm/50 Hz

Eng.kW

Gen.kW

Eng.kW

Gen.kW

Eng.kW

Gen.kW

Eng.kW

Gen.kW

Eng.kW

Gen.kW

Eng.kW

Gen.kW

4L205L206L208L209L20

520–

78010401170

495–

740990

1110

540–

81010801215

515–

77010251155

680775

102013601530

645735970

12901455

720825

108014401620

685785

102513701540

––

1110–

1665

––

1055–

1580

––

1200–

1800

––

1140–

1710

Principal genset dimensions (mm) and weights (tonnes)

Engine A* H* I L* M Weight*

4L205L206L208L209L20

49105220532560306535

17701920

1770/19201920/20702070/2300

18001800180018001800

23382458

2243/23232474

2524/2574

11681329129913901390

14.015.116.820.723.8

* Values are based on standard alternator, whose type (water or air cooled) and sizeaffects width, length, height and weight. Weight is based on wet sump engine with engineliquids. Gen. output based on generator efficiency of 95%.

Fuel Quality Limits

Range DMX min RML55 max

Viscosity (cSt)Density (kg/m3)CCAICCR (%)Pour point (°C)S (%)V (ppm)

1.8––––––

730101087022305

600

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Wärtsilä Finland OyP.O.Box 252,FIN-65101 Vaasa,Finland

Tel. +358 10 709 0000Fax (Ship Power) +358 6 356 7188Fax (Power Plants) +358 6 356 9133

Wärtsilä is The Ship Power Supplier for builders, owners and operators

of vessels and offshore installations. We are the only company with a

global service network to take complete care of customers’ ship

machinery at every lifecycle stage.

Wärtsilä is a leading provider of power plants, operation and lifetime

care services in decentralized power generation.

The Wärtsilä Group includes Imatra Steel, which specializes in special

engineering steels.

For more information visit www.wartsila.com

WÄRTSILÄ ® is a registered trademark. Copyright © 2004 Wärtsilä Corporation.