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

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566 MaK (Caterpillar Marine Power Systems)

Figure 21.12 The Caterpillar common rail (CCr) fuel injection system made its

debut on a six-cylinder MaK M32C propulsion engine

Figure 21.13 A CCr system rail segment and injectors

Caterpillar highlights these merits of CCR technology: high fuel-injection

pressure over the entire engine operating range; fully ﬂexible fuel injection fos-

tering optimized emissions and engine performance; and suitability for engines

operating on HFO or marine diesel oil. A CCR system incorporates the follow-

ing main elements:

High-pressure pumps: Two sets deliver the required amount of fuel to the

rail and provide the desired rail pressure in closed-loop control. The pumps are

based on a proven design but with modiﬁcations for heavy fuel operation. A

two-pump conﬁguration for all in-line cylinder engines signiﬁcantly reduces

the amount of high-pressure connections and components while securing

redundancy; and suction control ensures high pump efﬁciency (Figure 21.14).

Rail: The double-walled rails are pressurized and serve as an accumula-

tor. One rail segment feeds fuel to several injectors; for example, a nine-cyl-

inder engine has three rail segments, each feeding three injectors, while an

eight-cylinder engine has two rail segments, each feeding four injectors. Such

an arrangement reduces the overall number of parts and high-pressure con-

tacts required. Flow limiters prevent the cylinder from over-fuelling; and a

safety valve acts as pressure relief in the event of an over-pressurized rail. A

scavenging circuit enables the complete fuel system (high and low pressure)

to be maintained in a preheated condition, which is essential for safe HFO

operation.

Injectors: A simple, robust and compact approach was pursued by using

the fuel itself to control the injector, thereby eliminating the need for a sep-

arate control ﬂuid. The injector nozzle is cooled with lube oil, a typical fea-

ture for HFO operation. For the CCR system, however, the lube oil circuit was

extended to provide cooling as well to the electrical components within the

injector, thus increasing their lifetime. The injection process is electronically

controlled, facilitating ﬂexible injection timing and duration, including the

capability for multi-shots. Injection pattern and shaping was optimized using

the combustion modelling offered by Caterpillar’s own 3D software as well as

by comprehensive engine testing.

Injection mapping enables injection characteristics to be ﬁne-tuned for

every single engine operating point, reportedly guaranteeing optimum injec-

tion pressure and timing at a given load even in transient operation. Both soot

and NOx emissions are thereby signiﬁcantly reduced. There is also the poten-

tial through injection mapping to balance the overall wear of an ageing engine

using modiﬁed control parameters implemented during regular servicing.

Electronics: Caterpillar’s proprietary ADEM Electronic Control Module

(ECM) manages fuel delivery, air supply and other fundamental engine proc-

esses to achieve an optimum balance of performance and emissions. The soft-

ware was tailor-made for CCR-equipped MaK engines, addressing the speciﬁc

demands of HFO operation. The ECM functions can be divided into a core

system and a performance system, the former comprising: an A4E4 control

device; a crankshaft speed pick-up; two camshaft speed pick-ups; two high-

pressure sensors; two suction throttles; and injectors.

Common rail fuel system 567

568 MaK (Caterpillar Marine Power Systems)

Optimum engine settings under all operating conditions are sought by

the performance system, using such information as exhaust gas temperature,

charge air pressure, ambient conditions and lube oil temperature. The engine

protection system works independently of the engine control system and has

its own sensor equipment, ensuring that engine operation is monitored inde-

pendently of other control systems.

Figure 21.14 Two high-pressure pumps deliver fuel to the common rail of the CCr

system

expert System Support

MaK offers intelligent expert systems to lower operational costs, minimize

downtime and increase availability. DICARE is a Windows-based expert sys-

tem providing real-time engine diagnosis. It describes and diagnoses the actual

engine condition and provides references for condition-based maintenance.

Remote data transfer to a ship owner’s shore base is facilitated by a commu-

nication module; additionally, MaK offers a link to its service department for

evaluating and interpreting the data.

DICARE was launched in 1987 on an MS DOS platform. A 16-bit MS

Windows version in 1997 eventually led to the latest 32-bit variant. Data was

initially received from the alarm system but today the engine’s existing control

bus system is leveraged. Measured values are displayed on engine schematics

and gauges, with automatic data recording facilitating black box functions.

DIMOS is a computer-based maintenance and service system covering

MaK engines. It delivers service interval supervision and immediate access to

maintenance and component information via an electronic operations hand-

book. Bus technology underwrites safe digital signal transmission and repre-

sents a clearly deﬁned connecting point for all ship management systems.

eArLier MAK MOdeLS

Numerous examples of earlier MaK medium-speed designs are in service in

propulsion and auxiliary power installations based on 240 mm bore M282C/

M332C, 320 mm bore M453C, 450 mm bore M552C and 580 mm bore M601C

engines. The ‘C’ designation models were introduced in the 1980s with reﬁne-

ments enhancing the capability to operate on heavy fuel (Figure 21.8).

The robust engines feature housings of high-duty cast iron which, in the

case of the 320 mm bore and larger models, take the form of multi-sectional

blocks connected by steel tension rods. The high pre-stressing of the rods,

which keep the cast components under compression stress, prevents any tensile

stress in the cast material, even under ignition loads. The 240 mm bore series

features an underslung crankshaft.

The cylinder liners of all the engines are salt bath nitrated for high wear

resistance and anti-corrosion properties; crankshafts are forged in one piece

from wear-resistant, quenched and tempered alloy steel. Single fuel injection

pumps are used throughout the series, the injection system and inlet/exhaust

valves being controlled by a one-part camshaft.

earlier MaK models 569

571

C h a p t e r | t w e n t y t w o

Man Diesel

A long tradition in medium-speed engine design was exploited by MAN Diesel

to create a new generation of 400 mm, 480 mm and 580 mm bore models sharing

common principles. The 40/54, 48/60 and 58/64 series (Figures 22.1 and 22.2),

progressively launched during the 1980s, were joined in 1992 by the 32/40 design

which inherited similar features but modiﬁed to suit its smaller bore. The four

engines have since formed the core of the Augsburg, Germany-based group’s

programme offering outputs from 2880 kW to 21 600 kW (see Table 22.1), with

progressive reﬁnements enhancing power ratings, fuel economy and emissions

performance. Common rail (CR) fuel injection beneﬁts the latest CR versions.

L58/64 engine

The ‘new generation’ programme was headed in 1984 by the 580 mm bore/

640 mm stroke L58/64 series, whose designers sought a high overall operating

Figure 22.1 an eight-cylinder version of Man Diesel’s largest medium-speed

engine design, the L58/64

572 Man Diesel

economy, reliability, ease of maintenance, component durability and unre-

stricted heavy fuel compatibility. The rugged (Figure 22.3) result can be

contrasted with MAN Diesel’s previous large bore engine, the 520 mm bore

52/55B (Figure 22.4).

Among the main features of the L58/64 and its 400 mm and 480 mm bore

derivatives is a stiff monobloc frame casting with continuous tie-rods from

the underslung main bearings to the top edge of the engine frame, and tie-

rods from the cylinder head to the frame diaphragm plate (Figures 22.5 and

22.6). This arrangement was associated with the following: an optimum ﬂow

of forces from the cylinder head down to the crankshaft; minimal deformation

of the cylinder liner; more reliable piston performance; all parts of the frame

under pre-stress; cross-braced crankshaft bearings; an amply dimensioned out-

board bearing for absorbing high radial forces at the power take-off end of the

Figure 22.2 Cross-sections of original ‘new generation’ family (left to right L58/64,

L48/60, L40/54)

Table 22.1 Man’s original ‘new generation’ medium-speed engine line-up

Parameter Model

32/40 40/54 48/60B 58/64

Bore (mm) 320 400 480 580

Stroke (mm) 400 540 600 640

Cylinders 5–9L/12–18V 6–9L 6–9L/12–18V 6–9L

Output (kW/cyl) 480 720 1200 1390

Speed (rev/min) 720/750 550 514 428

crankshaft; no cooling water passage in the casing (eliminating the potential

for corrosion); sturdy landings to prevent plant deformation; and camshaft

drive gear and vibration damper integrated in the engine casing.

Minimal deformation of the liner, reliable piston performance, no deforma-

tion of the neighbouring cylinder and reduced deformation over the full length

of the engine are further underwritten by individual cylinder jackets.

Cavitation of the cylinder liner (Figure 22.7) is prevented by thick walls

giving a high resistance to deformation, while virtually uniform temperatures

over the entire liner surface result from intensive cooling of just the upper part

of the liner (cooling is not considered necessary elsewhere), thanks to a special

arrangement of the cooling water spaces. Good lubricating conditions result

and low-temperature corrosion is inhibited.

L58/64 engine 573

Figure 22.3 Man L58/64 design

574 Man Diesel

A thin ﬂame plate for the cylinder head promotes good heat conductivity

while high stiffness is imparted by a strong deck plate absorbing the vertically

acting gas forces (Figures 22.8–22.10). A long valve life and clean, gas-tight

seats are promoted by: water-cooled exhaust valve cages which are withdraw-

able without removing the rocker arms; armoured exhaust valves with gas-

driven propeller rotators; and caged inlet valves rotated by a Rotocap device.

Pollution of operating media is avoided in the cylinder head by separate spaces

for lubricating oil, fuel and cooling water. A simple connection attaches the

exhaust manifold to the head.

A composite piston (Figure 22.11) is formed from a forged aluminium

skirt and a forged thin-walled crown of high-grade steel (the smaller bore

Figure 22.4 The L52/55B design preceded the ‘new generation’ range headed by

the L58/64 engine

engines in the MAN programme feature a nodular cast iron skirt). Effective

cooling of the crown is sought from the cocktail shaker method (splash effect)

which nevertheless maintains temperatures in way of the ring grooves high

enough to prevent wet corrosion. Cooling oil ﬂow arrangements are optimized

from inside to outside. A piston pin without cross-bore enhances component

reliability. A reduction of mechanical loads on the piston rings was addressed

by a narrow piston clearance, keeping out abrasive particles and protecting

the lubricating ﬁlm. A long piston groove life was sought from induction

hardening, with the depth of hardening sufﬁcient to allow re-machining sev-

eral times.

L58/64 engine 575

Figure 22.5 L58/64 engine frame

576 Man Diesel

All three compression rings are mounted in the crown, their durability

enhanced by plasma coating of the ﬁrst ring and chrome plating of the sec-

ond and third rings. A consistently low lubricating oil consumption is reported

from the optimized ring set conﬁguration.

The L58/64 engine was reportedly the ﬁrst to feature a connecting rod with

a joint in the upper part of its shaft (Figure 22.12). A compact and very stiff

ﬂange is permitted, and motion of the joint under mass forces (observed in tra-

ditional connecting rods) is not encountered. A merit is the very low overhead

space required for piston removal, with no need to open the crankpin bearing

when pulling the piston (Figure 22.13).

A fuel-optimized injection system with economy plunger is installed

(Figures 22.14–22.16). A modiﬁed control edge on the pump plunger keeps the

ﬁring pressure virtually constant between 85 per cent and 100 per cent of max-

imum continuous rating, fostering favourable consumption rates throughout the

part-load range. A pressure-equalizing valve prevents the formation of partial

vacuums (and thus cavitation) as well as pressure ﬂuctuations in the system

(and thus fuel dribbling). A high injection pressure yields efﬁcient atomization

of the fuel, while an advantageous ﬁring pressure/mean effective pressure ratio

Figure 22.6 Monobloc frame of L58/64 engine