Woodyard D. (ed.) Pounders Marine diesel engines and Gas Turbines

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556 MaK (Caterpillar Marine Power Systems)

Fuel injection can be adjusted for commencement, duration and pressure.

Specially shaped control edges on the injection pump plunger secure correct com-

mencement of injection as a function of output and speed. The M32 engine can

also be provided with eccentric control of the cam follower between the camshaft

and the injection pump. This arrangement facilitates simple adjustment of the ﬁr-

ing pressure to suit the particular fuel grade or the climatic conditions and achieve

optimum economy and operation on heavy fuel. Control of injection pressure is

effected by an MaK-patented system which is said to foster part-load running

with particularly low emissions and to enhance the ignition of heavy fuels.

Conventional injection pump systems deliver fuel in pulses which can

cause vibrations in the associated piping and damage to upstream systems.

The M32 engine features a system based on larger volumes with intermediate

throttles for damping the delivery process without restraining it. The remain-

ing vibrations in the fuel admission and return pipes are reportedly so low that

elastic transition elements can be ﬁtted between the pumps.

Adjustable valve timing is also required for special operating modes or to

inﬂuence emission behaviour. The pushrods for the inlet and exhaust valves

are therefore arranged on cam followers which can be adjusted by an optional

eccentric adjustment. This arrangement reportedly allows valve overlap and

the turbocharging group characteristic to be adapted to secure good part-load

performance.

Like its predecessors, the M32 design is served by a pulse charging system

allowing permanent operation on the propeller curve. As an option for particu-

larly difﬁcult applications, the in-line engine can be speciﬁed with control of

the turbocharger turbine surface by MaK’s Variable Multi-Pulse (VMP) sys-

tem. Faster acceleration, lower temperatures and higher part-load torques are

possible. The designer has also developed systems for air bypass, exhaust gas

blow-off and air blow-off.

Figure 21.7 M32 cylinder head

M32 Engine Data

Bore

320 mm

Stroke, in-line models 480 mm

Stroke, vee-models 420 mm

Cylinders 6, 8, 9L/12, 16V

Speed, in-line models

600 rev/min

Piston speed 9.6 m/s

Speed, vee-models 750 rev/min

Piston speed 10.5 m/s

Output/cyl 480 kW

Mean eective pressure 22.8 bar

Output range 2400–7700 kW

M32C engine

A C-version of the M32 engine was introduced in 2000 with design reﬁne-

ments promising cuts in operating costs, easier maintenance and installation,

and performance and fuel economy boosted by a higher efﬁciency turbocharger

(Figure 21.8). Among the numerous modiﬁcations are simple plug-in connec-

tions for the cooling water system, improved access to each cylinder unit in

the camshaft region, single-pipe exhaust ducting and a newly designed exhaust

pipe casing with a smaller installation volume, and a nodular cast iron crank-

case with integrated ducts.

The entire exhaust system was simpliﬁed in such a way that only one

exhaust pipe (instead of two) is now required for the six-cylinder engine; the

number of pipes for the eight- and nine-cylinder models was reduced from

three or four to one. Improvements were also made to the cooling water pipe-

work at the supercharge air cooler. The cooler was modiﬁed by providing cast

elbows as interfaces and simplifying accessibility to the cooler for cleaning.

The application of stainless steel components on the ‘cold side’ also fosters an

extended lifetime for these elements. The V12- and V16-cylinder versions of

the M32C were introduced with two power ratings: 480 kW/cylinder at 720 rev/

min and 500 kW/cylinder at 750 rev/min.

The C-versions were progressively introduced across the MaK engine pro-

gramme to replace the original designs, the process completed with the 2007

launch of the M25C (see Section on C-versions).

M43 engine

A fourth series of new generation long-stroke engines, the M43, was intro-

duced by MaK in 1998, effectively replacing the 450 mm bore M552C model

and exploiting the same design philosophy as that of the M20, 25 and 32

M43 engine 557

558 MaK (Caterpillar Marine Power Systems)

series. With a speciﬁc rating of 900 kW/cylinder at 500/514 rev/min, the initial

in-line six-, seven-, eight- and nine-cylinder models covered an output range

up to 8100 kW. The power band was extended in 2002 with the launch of V12-,

16- and 18-cylinder (VM43) models taking the upper output of the series to

16 200 kW (Figure 21.9).

Eighty per cent component commonality is shared by the in-line and vee-

cylinder designs, and simplicity of assembly was sought by combining as many

functions as possible into single structural elements, thus reducing the over-

all number of components in the engine. Common components and component

groups are: the complete cylinder head; valve drive; cylinder liner with ﬂame

ring; exhaust gas system (without compensator); camshaft bearings; fuel-injection

pump; high-pressure connection; injection nozzles; cooling water distributor

housing and line (without insertion tube); connecting rod and bearings; and

vibration damper.

Cylinder head: A proven double-ended nodular cast iron design ensuring a

high level of shape retention, the four-valve head is held on the cylinder liner

by six hydraulically tightened studs (all the bolts are tightened simultaneously).

Simple dismantling and assembly is fostered by insertion tube connections for

Figure 21.8 MaK’s 320 mm bore M453C engine was replaced by the M32 design

all the media. The two exhaust valves are arranged to rotate, and the valve seat-

ing rings and ducts are aerodynamically optimized.

Piston: The two-part component comprises a steel crown and steel skirt.

The crown is equipped with two compression rings and an oil stripper ring; the

ﬁrst ring is chromium-plated on the ﬂanks. The oil-cooled shaker space of the

piston ensures effective cooling at a high mean effective pressure and contrib-

utes to a long piston life.

Connecting rod: The split-shaft design allows low piston installation/

withdrawal heights. The rod bolts and shaft bolts are tightened hydraulically.

(The size and weight of the hydraulic tools used for tightening bolts on the

engine are minimized by operating with 2500 bar pressure technology.)

Special Features of VM43 engine

Crankcase is a nodular cast iron design speciﬁed for resilient or rigid mount-

ing. Stiffness in bending and in torsion is achieved by strong base strips and

by integration of the boost air and camshaft casings; the transverse bolting

of the basic cover also contributes. The multi-functionality of the crankcase

is increased by its integration of the gearing space and damper space, which

avoids numerous bolted connections and contributes to noise and vibration

damping. Integrating the oil pipes in the crankcase also contributes here and

facilitates maintenance work. Good accessibility to the main bearings and con-

necting rod bearings is provided via large space openings. The crankcase is

naturally free from cooling water and hence protected against corrosion. The

ﬁrst main bearing is of tandem design, reducing the engine length.

M43 engine 559

Figure 21.9 A V12-cylinder version of the 430 mm bore M43 design (The VM43)

560 MaK (Caterpillar Marine Power Systems)

Crankshaft is manufactured from heat-treated alloy steel, with unhardened

bearing trunnions and concave ﬁllets. A ﬂange is provided for the vibration

damper at the end, opposite to the coupling; a gearwheel for the gear drive is

ﬂanged on the coupling end.

Exhaust gas installation is designed as a single-pipe system with gas out-

lets and pipe cross-sections optimized for efﬁciency. The elements are the same

as those used in the in-line cylinder engines. The different distance between

cylinders is made possible by compensators of varying lengths.

Turbochargers are conﬁgured as a sub-assembly and equipped with a block

aftercooler; the turbocharger group can be arranged at either end of the engine,

facilitating electric power generation or propulsion drives. A 10 000 kW power

take-off drive can be speciﬁed optionally at the front end of the engine. The

turbocharger arrangement contributes to a minimized centre distance in twin-

engine installations, a low vibration level, reduced engine height, a main-

tenance-friendly block cooler and optimized exhaust gas ﬂow. ABB Turbo

Systems TPL73 turbochargers serve the V12 engine, and TPL77 models serve

the V16 and V18 models.

Contributing to even lower emissions, the optional ﬂexible camshaft tech-

nology (FCT) system (detailed from p. 563) was applied to an MaK engine for

the ﬁrst time, promising NOx emissions of less than 8 g/kW h and soot emis-

sions below the visibility limit in any operational mode. This is accomplished

by adjusting fuel injection and inlet valve timing relative to the given load.

M43 Engine Data

Bore

430 mm

Stroke 610 mm

Output 900 kW/cyl

Speed 500/514 rev/min

Cylinders 6, 7, 8, 9L/V12, 16, 18

Power range

5400–16 200 kW

Mean piston speed 10.2/10.5 m/s

Mean eective pressure 24.4/23.7 bar

Maximum combustion pressure 190 bar

Specic fuel consumption

175 g/kW h

Specic lube oil consumption 0.6 g/kW h

100 per cent mcr

M43C engine

The ﬁrst two M43 engines were commissioned in April 2000 and by end of

September 2004 more than 200 examples in service had accumulated an

aggregate running time of over 1.4 million hours. Of these, some 90 per cent

were operating on heavy fuel oil (HFO). By September 2008, the M43 and

M43C reference list totalled more than 800 engines with a popular base in

feeder container ship, roro vessel and ropax ferry propulsion.

In late 2003, Caterpillar Motoren strengthened the competitiveness of the

M43 engine by raising the output from 900 kW/cylinder to 1000 kW/cylinder

at 500/514 rev/min. Uprating to C-status initially beneﬁted the in-line cylinder

models but was later applied to the V12- and V16-cylinder models, taking the

upper power limit of the M43C programme to 16 000 kW. Apart from seeking

a higher power output, the design and development work sought increased reli-

ability, simpliﬁed maintenance, reduced noise levels and lower emissions.

A redesigned cylinder block incorporated features from the established

VM43 and M32C engines, such as the modular design lower valve and injec-

tion pump drive, the new governor drive and the removal of the mounting plate

for the lube oil and cooling water pumps. The changes aimed to improve the

maintenance friendliness of these functional groups. New covers for the cam-

shaft drive area also improved noise levels, matching those achieved on the

VM43 engines.

The new lower valve and injection pump drive design yielded greater sim-

plicity and eliminated the need for adjustments. It also facilitated installation

of FCT (p. 563), as original equipment or by retroﬁt, to achieve lower NOx and

particulate emissions. NOx levels below 8 g/kW h (30 per cent less than IMO

Tier I requirements) and the elimination of visible smoke under part-load and

transient conditions could thus be met by primary in-engine measures alone.

Access to the camshaft area was also improved signiﬁcantly.

A new vibration damper for the crankshaft was dictated by the higher

power output, a component which can now be removed radially. Easier and

safer maintenance was also fostered by removing the plate that formerly

mounted the lube oil and cooling water pumps and integrating these assemblies

into the cylinder block.

A higher efﬁciency turbocharger was necessary to maintain the favourable

performance data of the original engine, resulting in a redesign of the com-

plete turbocharger assembly group. ABB’s TPL71C and TPL76C turbocharg-

ers were respectively speciﬁed for the six-cylinder model and for the seven-,

eight- and nine-cylinder models. A number of associated improvements were

also made, including a new vibration-free charge air cooler, which can now be

removed laterally in either direction.

Two other key elements—the aftercooler support and air box of the turbo-

charger compressor outlet—were combined into a single housing. One inter-

face was thus removed and potential leakages prevented. The turbine washing

device was also improved to make its function more precise and safer; washing

is carried out at part load to enhance the efﬁciency of the process.

Feedback from M43 engines in service was translated into design changes,

an example being a new engine turning device designed to be vibration free,

positioned closer to the engine and incorporating a new turning gear and motor.

M43C engine 561

562 MaK (Caterpillar Marine Power Systems)

A higher power rating was also addressed by modifying the exhaust mani-

fold covers for increased durability. Making the whole design more vibration

free was achieved by combining the cast iron blocks for the cooling water

brackets with the supports for the manifold covers and detaching the covers

from the exhaust pipes themselves. It was also decided to relocate the control

cabinet for improved access and adopt the standard cabinet used with all other

MaK engines.

Experience with the 900 kW/cylinder M43 engine suggested that improve-

ments to the fuel-injection equipment were necessary. For heavy fuel opera-

tion, therefore, the injector was changed to a cooled type, as already used on

the VM43 engine. The modiﬁcation enhanced durability and reliability as well

as reducing particulates emissions, especially at part load. Modiﬁcations were

also made to the cylinder head to accommodate the cooled nozzle.

A feature of modern MaK engines is the minimal use of external pipework;

and where a pipe is unavoidable it is ﬁtted with a plug-in connection whenever

possible. This principle is applied to the media guides supplying the cylinder

heads with injection cooling and rocker arm lubrication and handling the fuel

return from the injectors. These connections were unchanged for the M43C but

at the far end of the engine, where the media return to the ship’s system, plug-

in connections were adopted. Overall, efforts were made to reduce the engine’s

component count by exploiting as many multi-functional parts as possible to

promote simplicity and maintenance friendliness.

M43C Engine Data

Bore

430 mm

Stroke 610 mm

Cylinders 6, 7, 8, 9L/V12, 16

Output

1000 kW/cyl

Power range 5400–16 000 kW

Speed 500/514 rev/min

Mean piston speed 10.2/10.5 m/s

Mean eective pressure 27.1/26.4 bar

Firing pressure 205 bar

Specic fuel consumption 177 g/kW h

C-VerSiOnS

The full MaK engine programme is now offered in C-versions, the last model

to beneﬁt from upgrading (in 2007) being the 255 mm bore M25. A slightly

increased rating was introduced for the M25C derivative (up to 334 kW/cyl-

inder), resulting in a power band extending from 1800 kW to 3000 kW with

unchanged fuel economy from six-, eight- and nine-cylinder models.

A number of minor changes in the crankcase area fostered smoother engine

operation and easier maintenance, the modiﬁcations including a modular lower

valve drive, improved crankcase covers and a new speed-governor drive. Well

proven in the larger M32C and M43C engines, the governor drive is a pre-

assembled module with fewer parts and a lower part wear rate than before; its

straight-teeth gearwheel drive requires no further adjustment.

An improved casting process for manufacturing the M25C crankcase yields

better dimensional precision, and the optional deep oil pan beneﬁts from a

strengthened design which is approved for heavy fuel operations. An unchanged

engine footprint for rigid installation and gearbox connection addresses existing

engine room designs. Improved damping for resiliently mounted installations

further reduces engine vibrations and their transmission to the hull. Resilient

mounting is also available for M25C engines with deep oil pans.

Manufacturing quality was raised by pre-assembling the complete turbo-

charger group, comprising the turbocharger, charge air cooler and turbocharger

bracket. The turbocharger itself is completely covered to meet the latest Solas

requirements, the new cladding preventing hot spots while facilitating mainte-

nance of the turbocharger and piping. Like other C-engines throughout the pro-

gramme, the M25C was designed to incorporate advanced emission reduction

technologies developed for MaK engines.

LOW eMiSSiOnS TeChnOLOgieS

Three emission levels for MaK engines were envisaged by Caterpillar Motoren

in 2000 to address short- to medium-term regulations: a baseline IMO engine

fulﬁlling Marpol 73/78 Annex VI requirements; an IMO-compliant engine

with invisible smoke emissions; and a low emission engine (LEE) meeting the

expected NOx emission range of IMO II and also having invisible smoke.

Such a strategy favoured the adoption of in-engine measures offering

advantages in cost, complexity and maintenance, with an increased compres-

sion ratio for the base engine a key factor for low NOx emissions. A previously

typical standard compression ratio of 11–12:1 was raised to 14–15:1 for IMO

I, with IMO II calling for ratios of around 17:1.

Another cornerstone of the MaK LEE concept is the Miller cycle, whereby

the engine’s inlet valve timing is modiﬁed to achieve cooler combustion. For

IMO I requirements only a small Miller effect of 5 per cent was exploited but

IMO II requires a Miller effect of 20 per cent: a challenge for the turbocharger

which has to provide boost ratios of around 5 to maintain today’s mean effec-

tive pressure values.

By combining an increased compression ratio and the Miller effect, NOx

emissions can be reduced by around 30 per cent without sacriﬁcing engine efﬁ-

ciency (brake-speciﬁc fuel consumption). Such a simple LEE, however, would

suffer from poor load pick-up at idling and visible smoke emissions at part

load. The MaK LEE concept therefore exploits Flexible Camshaft Technology

(FCT) to secure low NOx emissions, excellent load pick-up and invisible soot

at all loads (Figures 21.10 and 21.11).

Low emissions technologies 563

564 MaK (Caterpillar Marine Power Systems)

Described as a robust mechanical solution, FCT facilitates variation of

the fuel and air systems in part-load operations. By advancing the start of fuel

injection and increasing the injection pressure, combustion is improved and

soot emissions reportedly reduced by 50 per cent. Shifted inlet valve timing

switches off the Miller cycle and contributes another 25 per cent reduction

in soot. Overall, FCT is said to reduce soot emissions by 75 per cent while

improving engine performance during transient operation.

FCT essentially comprises a modiﬁed lower valve train, a pneumatic

adjusting unit and a programmable logic controller. An eccentric lifter lever

Figure 21.10 Mounting a exible camshaft technology (FCT) unit on an MaK low

emission engine

shaft automatically inﬂuences fuel injection timing as well as pressure and

valve timing. The engine load required to activate the lever can be ﬂexibly set

according to the operator’s requirements. Either way, visible smoke is said to

be eliminated while IMO NOx emission standards are satisﬁed at all loads. By

the end of February 2008, around 80 MaK M32C and M43C engines had been

speciﬁed with FCT. All existing MaK M20C, M25C, M32C and M43C engines

at sea can also be converted to LEE standards, reportedly at around 15–25 per

cent of the cost of a new IMO II-compliant engine.

COMMOn rAiL FueL SySTeM

Over a decade of R&D and comprehensive pre-ﬁeld testing resulted in

the Caterpillar Common Rail (CCR) system, ofﬁcially launched in 2006.

(Although a common rail solution for MaK engines was tested as early as 1988

and unit fuel pumps featuring electronically controlled solenoid valves were

developed in 1995.) The CCR system was initially offered for the M32C series

but progressively extended to the smaller and larger bore members of the MaK

portfolio. The complete system was also designed for retroﬁt to all C-series

engines already in service (Figures 21.12 and 13).

Common rail fuel system 565

Figure 21.11 The pneumatic adjusting unit of the FCT system