TECHNOLOGY REVIEW

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SETTING NEW STANDARDS FOR ECONOMICAL POWER PRODUCTION ............................. 5

DESIGN PHILOSOPHY ................................................... 5

NOX COMPLIANCE ....................................................... 5

WÄRTSILÄ WETPAC HUMIDIFICATION ............................ 6

PISTON ....................................................................... 6

PISTON RING SET ........................................................ 6

CONNECTING ROD AND BIG END BEARINGS .................. 6

CYLINDER LINER AND ANTI-POLISHING RING ................. 7

CYLINDER HEAD .......................................................... 8

MULTIDUCT ................................................................. 8

CRANKSHAFT AND MAIN BEARINGS ............................. 8

ENGINE BLOCK AND FOUNDATION ................................ 8

FUEL SYSTEM ............................................................ 10

TURBOCHARGING SYSTEM ......................................... 10

COOLING SYSTEMS ................................................... 10

LUBRICATING OIL SYSTEM ......................................... 11

AUTOMATION SYSTEM ............................................... 12

APPLICATION FLEXIBILITY ........................................... 14

EASY MAINTENANCE.................................................. 14

MAIN TECHNICAL DATA .............................................. 15

This is a summary of the technical features and performance

of the Wärtsilä 20 engine.

TECHNOLOGY REVIEW

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The tug Thetis is equipped with two Wärtsilä 9L�0 engines. The FPSO Berge Hugin is equipped with four Wärtsilä 6L46 main engines and one Wärtsilä 9L�0 auxialiary engine.

The anchorhandling tug supply vessel Bourbon Orca is equipped with two Wärtsilä 9L�0 and four Wärtsilä 6L�� engines, two Wärtsilä steerable thrusters with CP propellers in HR-nozzles, one LIPS transverse tunnel thruster, one LIPS steerable thruster of retractable design with a CP propeller, two Lipstronic 7000 Advance control systems and four JMT MKII Unnet seal protection systems.

4

The 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 the Wärtsilä 20 the

ultimate in reliable performance using Light Diesel

Oils. Overhaul intervals up to 24,000 hours and

maintenance-friendly design 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.

DESIGN PHILOSOPHYThe design of the Wärtsilä 20 engine is based

on Wärtsilä’s heavy fuel know-how and is fully

optimized for today’s fl exible 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.

••••••

Generally 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 certifi ed according

to the NOX Technical Code, and delivered with

an EIAPP (Engine International Air Pollution

Prevention) certifi cate. The certifi cation

process includes NOX measurements,

marking of components that are affecting

NOX formation and a Technical File that is

delivered with the engine.

All major classifi cation societies are on

behalf of the fl ag state granting the EIAPP

certifi cate for the Wärtsilä 20 engine family.

If lower NOX levels are required, the

engine can be equipped with a SCR catalyst,

which can reduce NOX by up to 95%, down

to a level < 1 g/kWh.

The Wärtsilä 20 is suitable for power plant

applications with the NOX emission limits of

710-970 ppm (dry,15vol-% O2).

SETTING NEW STANDARDS FOR ECONOMICAL POWER PRODUCTION

NOX COMPLIANCE

20

18

16

14

12

10

8

60 500 1000 1500 2000

Rated engine speed (rpm)

IMO GLOBAL MARINE NO LEGISLATIONX

Wärtsilä 20 Fuel: Marine diesel oil

NOem

issi

ons,

wei

ghte

d (g

/kW

h)X

A Wärtsilä 9L�0 Powerskid for power plants.

5

Principle of Wetpac humidifi cation.

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.

PISTON RING SETThe two compression rings and the oil control

ring are located in the crown. In a three-ring

pack every ring is dimensioned and profi led

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 effi ciency. For maximum wear

resistance the top ring features a special wear-

resistant coating.

CONNECTING ROD AND BIG END BEARINGSThe “stepped split line” design used in the

Wärtsilä Vasa 22 and 32 for many years now

Compressor

Heat

Waterinjection

Saturated air70...90°C

Water mist catcher

The new NOX reduction technology developed by Wärtsilä

is named Wetpac humidifi cation. The principle of Wetpac

humidifi cation is to introduce water with the intake air

to reduce the combustion temperature and thereby the

formation of NOX. Pressurized water is injected directly

after the compressor of the turbocharger. The high

temperature of the compressed air evaporates the water,

which enters the cylinders as steam. A water mist catcher

prevents water in liquid state from entering the cylinders.

The anticipated NOX reduction is up to 50%, and the

water consumption is expected to be about two times the

fuel oil consumption. Wetpac humidifi cation is available

as an option.

WÄRTSILÄ WETPAC HUMIDIFICATION

6

offers the maximum pin diameter while still

making it possible to pull the connecting rod

through the cylinder liner. 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 fi lm thickness and low oil fi lm 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 fi lm thickness.

CYLINDER LINER AND ANTI-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 fl ow 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.

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Exhaust gas Cooling water Charge air

CYLINDER HEADFour-screw cylinder head technology was

introduced by Wärtsilä more than 30 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 effi cient channel confi guration.

A distributed water fl ow pattern is used for

proper cooling of the exhaust valves and

cylinder head fl ame plate.This minimizes

the thermal stress levels and guarantees a

suffi cient low exhaust valve temperature.

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

for optimal part load combustion

Exhaust transfer to exhaust system

Cooling water transfer from cylinder head to

return channel in the engine block

Insulation/cooling of the exhaust transfer

duct

Support for exhaust system including

insulation

•

•

••

•

•

CRANKSHAFT AND MAIN BEARINGS

With 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 specifi c 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 fi lm

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.

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

8

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 fl ywheel end of the

engine. Thanks to its overall stiffness, easy-

to-install, four point support is standard for

the engine. To allow the most fl exible common

base plate arrangement independent of the

alternator make, the alternator is fi tted with

an adjustable mounting pad arrangement.

For resilient mounting simple structure and

effective isolation is provided by separate

engine feet.

9

3-pulse

Pulse converter

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

confi gurations of the engine are equipped with

an optimized pulse system.

COOLING SYSTEMSHigh temperature (HT) cooling systemThe system is totally integrated with the

various engine components; virtually no pipes

are used. Supply and return channels are cast

The 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 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.

FUEL SYSTEM

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3-pulse

Pulse converter

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 effi ciency. An engine-driven

pump of the cassette type is standard.

Low temperature (LT) cooling systemThis 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.

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 fl ow fi lter and centrifugal

fi lter. Pressure regulation and safety valves

are integrated into engine driven pump fi tted

at the free end of the engine where also

prelubricating pump with electric motor is

fi tted. Filter, cooler and thermostatic valves

are built up in a module located at the engine

rearside.

The lube oil fi ltration is based on an

automatic back-fl ushing fi lter requiring a

minimum of maintenance. The fi lter 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 fi lter, connected to

the back-fl ushing line of the automatic fi lter.

This provides the means for extraction wear

particles from the system.

FilterCooler Pump

Primingpump

Lube oil system

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UNIC C1

UNIC C�

AUTOMATION SYSTEMThe Wärtsilä 20 engine is equipped with

the Wärtsilä unified controls (UNIC) engine

automation system. The different systems

available for Wärtsilä 20 engine are UNIC

C1 and C2, described as follows.

UNIC 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

UNIC C1In the UNIC C1 engine automation system,

the fundamental aspects of the engine

control and safety are handled by the

embedded control and management

system. This includes engine speed

and load control as well as overspeed

protection, lube oil pressure and cooling

water temperature protection. For the other

parts, the design requires the majority of

the sensors to be hardwired to a plant or

ship control and monitoring system.

The UNIC C1 system provides the following

functionality:

Fundamental safety (overspeed, LO

pressure, cooling water temp.)

Basic local monitoring

Hardwired interface to plant or ship

control system.

Speed and load control (electronic speed

control by MCM if engine equipped

with actuator, otherwise by mechanical

governor)

Start/stop management

The engine control system is designed to:

Achieve the highest possible reliability,

with components, e.g. sensors,

designed specifically for the on-engine

environment,

Reduce cabling on and around

the engine, with a clear point of

interconnection and a standardized

interface, and

Provide high performance with optimized

and pre-tested controls.

•

••

•

•

•

•

•

UNIC C�The UNIC C2 engine automation system

provides a complete embedded engine

control and monitoring system. UNIC C2 is a

distributed and bus-based system in which

the monitoring and control function is placed

close to the point of measurement and control.

This significantly simplifies both the on- and

off-engine wiring. Additionally, the advanced

functions in the system, e.g. for diagnostics

and control, provide outstanding performance

and reliability, and the need for off-engine

systems is significantly reduced.

The UNIC C2 system provides the following

functionality:

Complete engine safety system

Complete local monitoring, including all

readings, events and diagnostics

••

Speed and load control (electronic speed

control by MCM if engine equipped with

actuator, otherwise by mechanical governor)

Complete engine control, including start/

stop, load reduction request, etc.

Alarm signal provision

Full system diagnostics

Fieldbus interface

The engine control system is designed to:

Provide a compact embedded engine

control and management system for space-

saving applications,

Reduce installation and commissioning time

by providing a very simple fieldbus-based

interface that is delivered pre-tested and

fully operational from the factory,

Achieve the highest possible reliability

with components, e.g. sensors, designed

•

•

•••

•

•

•

1�

specifically for the on-engine environment,

Considerably reduce cabling on and

around the engine through a bus-

based architecture, with a clear point of

interconnection and with a standardized

hardwire and fieldbus interface, and

Provide high performance with optimized

and pre-tested controls.

UNIC C2 shares the same mechanical

design as the UNIC C1, and can therefore

easily be retrofitted when needed. Common

components and functionality also simplifies

operator training and spare parts logistics,

since all UNIC options use the same basic

design and components.

•

•

1�

APPLICATION FLEXIBILITY

Wärtsilä 20 is suitable for wide range of

applications in various respects. Different fuels

from lowest viscosity of 1,8 cSt up to 730 cSt

HFO (at 50 °C) 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.

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 DATACylinder bore 200 mmPiston stroke 280 mmCylinder output 130 - 200 kW/cylSpeed 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 55 SFOC 188-196 g/kWh at ISO condition ± 5% tolerance

Rated power: Propulsion engines

Engine type

Output in kW/bhp at 1 000 rpmC2 -output C3 -output

kW bhp kW bhp

4L20 6L20 8L20 9L20

720 1080 1440 1620

980 1470 1960 2200

800 1200 1600 1800

1085 1630 2175 2450

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

Engine type

A* A B* B C* C D

4L20 6L20 8L20 9L20

– 3292 4011 4299

2510 3108 3783 4076

– 1528 1614 1614

1348 1348 1465 1449

– 1580 1756 1756

1483 1579 1713 1713

1800 1800 1800 1800

E F H K N* Weight*

4L20 6L20 8L20 9L20

325 325 325 325

725 624 624 624

155 155 155 155

980 980 980 980

– 589 708 696

7.2 9.3 11.0 11.6

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

Engine type

C2 -output C3 -output900 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

4L20 6L20 8L20 9L20

680 1020 1360 1530

645 970 1290 1455

720 1080 1440 1620

685 1025 1370 1540

740 1110

–1665

700 1055

– 1580

800 1200

– 1800

760 1140

– 1710

Principal genset dimensions (mm) and weights (tonnes)Engine A* H* I L* M Weight*

4L20 6L20 8L20 9L20

4910 5325 6030 6535

1770/1920 1770/1920 1920/2070 2070/2300

1800 1800 1800 1800

2338 2243/2323 2474/2524 2524/2574

1168 1299 1390 1390

14.0 16.8 20.7 23.8

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

Fuel Quality LimitsRange DMX min RML55 max

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

1.8 – – – – – –

730 1010 870 22 30 5 600

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Wärtsilä enhances the business of its customers by providing them with

complete lifecycle power solutions. When creating better and environmentally

compatible technologies, Wärtsilä focuses on the marine and energy markets

with products and solutions as well as services. Through innovative products

and services, Wärtsilä sets out to be the most valued business partner of

all its customers. This is achieved by the dedication of more than 14,000

professionals manning 130 Wärtsilä locations in close to 70 countries around

the world.

WÄRTSILÄ® is a registered trademark. Copyright © 2007 Wärtsilä Corporation.

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