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

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280 Low-Speed Engines—Introduction

risk of after-dripping. Signiﬁcantly lower NOx emissions are reported, as well

as reduced smoke and even carbon monoxide, but at the expense of a slightly

higher fuel consumption. This type of fuel valve is included in the options for

special low NOx applications of MC engines (Figure 9.8).

The 4T50MX engine was used to test a triple fuel valve-per-cylinder con-

ﬁguration, the measurements mirroring Wärtsilä’s results in yielding reduced

temperature levels and a more even temperature distribution than with a

two-valve arrangement. The K80MC-C, K90MC/MC-C, S90MC-T and

K98MC-C engines were subsequently speciﬁed with triple fuel valves to

enhance reliability.

INTELLIgENT ENgINES

Both MAN Diesel and Sulzer (before being acquired by Wärtsilä) demon-

strated ‘camshaftless’ operation with their research engines, applying elec-

tronically controlled fuel injection and exhaust valve actuation systems.

Continuing R&D will pave the way for a future generation of highly reliable

‘intelligent engines’: those which monitor their own condition and adjust

Atomizer sac

volume 1990 mm

Atomizer sac

volume 520 mm

Mini sac

Standard 90MC

FIgurE 9.8 reduced emissions result from a fuel valve with a smaller sac volume

(MAN Diesel)

parameters for optimum performance in all operating regimes, including

fuel-optimized and emissions-optimized modes. An ‘intelligent engine-

management system’ will effectively close the feedback loop by built-in

expert knowledge.

Engine performance data will be constantly monitored and compared with

deﬁned values in the expert system; if deviations are detected, corrective action

is automatically taken to restore the situation to normal. A further step would

incorporate not only engine optimizing functions but management responsibili-

ties such as maintenance planning and spare parts control.

MAN Diesel explains that to meet the operational ﬂexibility target, it is

necessary to be able to change the timing of the fuel injection and exhaust

valve systems while the engine is running. To achieve this objective with cam-

driven units would involve a substantial mechanical complexity, which would

undermine engine reliability. An engine without a traditional camshaft is there-

fore dictated.

The concept is illustrated in Figure 9.9 whose upper part shows the operat-

ing modes, which may be selected from the bridge control system or by the

intelligent engine’s own control system. The centre part shows the brain of the

system: the electronic control system which analyses the general engine condi-

tion and controls the operation of the engine systems shown in the lower part

Intelligent engines 281

Engine

protection

mode

Emission

controlled

mode

Optimal

reversing/

crash stop

Fuel

economy

mode

Cylinder

condition

monitoring

Fuel

pump

control

Exhaust

valve

control

Cylinder

lubricating oil

dosage

Turbocharging

system

control

Load

control

Integrated

governor

Electronic

control with

full redundancy

The Intelligent Engine

Cylinder pressure

monitoring

system

Injection/exhaust

valve control

programs

FIgurE 9.9 Schematic diagram of the intelligent engine (MAN Diesel)

282 Low-Speed Engines—Introduction

of the diagram (the fuel injection, exhaust valve, cylinder lube oil and turbo-

charging systems).

To meet the reliability target, it is necessary to have a system which can

actively protect the engine from damage due to overload, lack of maintenance

and maladjustments. A condition monitoring system must be used to evalu-

ate the general condition of the engine, thus maintaining its performance and

keeping its operating parameters within prescribed limits. The condition monitor-

ing and evaluation system is an on-line system with automatic sampling of all

‘normal’ engine performance data, supplemented by cylinder pressure measure-

ments. The system will report and actively intervene when performance param-

eters show unsatisfactory deviations. The cylinder pressure data delivered by the

measuring system are used for various calculations:

l The mean indicated pressure is determined as a check on cylinder load

distribution as well as total engine output.

l The compression pressure is determined as an indicator of excessive

leakage caused by, for example, a burnt exhaust valve or collapsed pis-

ton rings (the former condition is usually accompanied by an increased

exhaust gas temperature in the cylinder in question).

l The cylinder wall temperature is monitored as an additional indicator of

the piston ring condition.

l The ﬁring pressure is determined for control of injection timing and

mechanical loads.

l The rates of pressure rise (dp/dt) and heat release are determined for com-

bustion quality evaluation as a warning in the event of ‘bad fuels’ and to

indicate any risk of piston ring problems in the event of high dp/dt values.

The cylinder condition monitoring system is intended to detect faults such

as blow-by past the piston rings, cylinder liner scufﬁng and abnormal combus-

tion. The detection of severe anomalies by the integrated systems triggers a

changeover to a special operating mode for the engine—the ‘engine protec-

tion mode’. The control system will contain data for optimum operation in a

number of different modes such as ‘fuel economy mode’, ‘emission control-

led mode’, ‘reversing/crash stop mode’ and various engine protection modes.

The load limiter system (load diagram compliance system) aims to prevent any

overloading of the engine in conditions such as heavy weather, fouled hull,

shallow water, too heavy propeller layout or excessive shaft alternator output.

This function will appear as a natural part of future governor speciﬁcations.

The fuel injection system is operated without a conventional camshaft using

high-pressure hydraulic oil from an engine-driven pump as a power source and

an electronically controlled servo system to drive the injection pump plunger.

The general concept of the intelligent fuel injection (InFI) system and the intel-

ligent valve actuation (InVA) system for operating the exhaust valves is shown

in Figures 9.10 and 9.11. Both systems, when operated in the electronic mode,

receive the electronic signals to the control units. In the event of failure of the

electronic control system, the engine is controlled by a mechanical input sup-

plied by a diminutive camshaft giving full redundancy.

Unlike a conventional, cam-driven pump, the InFI pump has a variable

stroke and will pressurize only the amount of fuel to be injected at the relevant

load. In the electronic mode (i.e., operating without a camshaft), the system

can perform as a single injection system as well as a pre-injection system with

a high degree of freedom to modulate the process in terms of injection rate,

timing, duration, pressure, single/double injection, cam proﬁle and so on.

Several optimized injection patterns can be stored in the computer and cho-

sen by the control system in order to operate the engine with optimum injec-

tion characteristics at several loads: from dead slow to overload as well as for

starting, astern running and crash stop. Changeover from one to another of the

stored injection characteristics is affected from one injection to the next. The sys-

tem is able to adjust the injection amount and injection timing for each cylin-

der individually in order to achieve the same load (mean indicated pressure)

and the same ﬁring pressure (P

max

) in all cylinders, or, in protection mode, to

reduce the load and P

max

on a given single cylinder if the need arises.

The exhaust valve system (InVA) is driven on the same principles as the

fuel injection system, exploiting the same high-pressure hydraulic oil supply

Intelligent engines 283

Electronic

control

input

Exhaust valve

piston with

damper

Injection pipes

Accumulator

Input for

mechanical

redundancy

Valve pump with

servo piston

Exhaust

valve

Fuel valves

Mechanical

redundancy

drive unit

Accumulator

Index shaft

Stroke limiter

Fuel injection

pump with

servo piston

FIgurE 9.10 Electronically controlled hydraulic systems for fuel injection and

exhaust valve operation on MAN Diesel’s 4T50MX research engine

284 Low-Speed Engines—Introduction

and a similar facility for mechanical redundancy. The need for controlling

exhaust valve operation is basically limited to timing the opening and closing

of the valve. The control system is thus simpler than that for fuel injection.

Cylinder lubrication is controllable from the condition evaluation system

so that the lubricating oil amount can be adjusted to match the engine load.

Dosage is increased in line with load changes and if the need is indicated by

the cylinder condition monitoring system (e.g., in the event of liner scufﬁng

and ring blow-by). Such systems are already available for existing engines.

The turbocharging system control will incorporate control of the scavenge

air pressure if a turbocharger with variable turbine nozzle geometry is used, and

FIgurE 9.11 MAN Diesel’s 4T50ME-X research engine equipped with electronically

controlled fuel injection and exhaust valve systems

control of bypass valves, turbocompound system valves and turbocharger cut-off

valves if such valves are incorporated in the system. Valves for any SCR

exhaust gas cleaning system installed will also be controlled.

Operating modes may be selected from the bridge control system or by

the system’s own control system. The former case applies to the fuel economy

modes and the emission-controlled modes (some of which may incorporate the

use of an SCR system). The optimum reversing/crash stop modes are selected

by the system itself when the bridge control system requests the engine to carry

out the corresponding operation. Engine protection mode, in contrast, will be

selected by the condition monitoring and evaluation system independently of

actual operating modes (when this is not considered to threaten ship safety).

The fruit of MAN Diesel’s and Wärtsilä’s R&D is now established com-

mercially, their respective electronically controlled ME and RT-ﬂex engines

being offered alongside the conventional models and increasingly speciﬁed for

diverse tonnage (Figure 9.12). The designs are detailed in Chapters 10 and 12,

the Wärtsilä RT-ﬂex engines being distinguished by common rail fuel injection

technology.

ability to run stably at very low speeds (down to 7 rev/min) was among

the merits demonstrated during test-bed trials of the ﬁrst 12-cylinder RT-ﬂex96C

engine. Very slow running (lower than engines with mechanically controlled

fuel injection) is facilitated by precise control of injection, higher injection

pressures achieved at low speed, and shutting off injectors.

Research and development by Mitsubishi, the third contender in low-speed

engines, has successfully sought weight reduction and enhanced compact-

ness while retaining the performance and reliability demanded by the market.

The Japanese designer’s current UEC-LS type engines yield a speciﬁc power

output of around three times that of the original UE series of the mid-1950s.

The speciﬁc engine weight has been reduced by around 30 per cent over that

period, and the engine length in relation to power output has been shortened by

one-third.

An electronically controlled system for fuel injection and exhaust valve

operation was developed by Mitsubishi and applied to a 600-mm-bore LSII

engine, which entered service as the ﬁrst production Eco-Engine in mid-2005.

Mitsubishi’s market share remains minor and heavily dependent on its

domestic business, but the Japanese group seems destined to be the only low-

speed engine designer directly engaged in engine production at its own facili-

ties. The last Sulzer low-speed engine was delivered from the Winterthur plant

in 1988 and MAN Diesel is winding down production of such engines at its

Frederikshavn factory in Denmark, leaving licensees in Europe and Asia as the

sole producers of MAN B&W models.

Wärtsilä and Mitsubishi Heavy Industries (a Sulzer licensee since 1925)

signed an agreement in November 2002 to design and develop a 500-mm-bore

engine, resulting in an RTA50 series from which the RT-ﬂex50 common rail

version and an MHI 50LSE engine were subsequently created. In addition to a

strengthening development alliance between the groups, Mitsubishi’s smaller

Intelligent engines 285

286 Low-Speed Engines—Introduction

bore UEC engines (370 mm, 430 mm and 450 mm) have been marketed in the

Wärtsilä programme. Another agreement resulted in the joint development of a

new range of 350-mm and 400 mm-bore designs for powering small bulk car-

riers, product and chemical tankers, feeder container ships and reefer vessels.

Announced in 2008, these engines—offered in mechanical and electronic

versions—will be jointly branded and produced by the partners as rivals to

MAN Diesel’s ME-B series.

A range of technologies are available or under development to enable low-

speed engines to meet future IMO exhaust emission limits, particularly NOx

controls. The measures include engine combustion reﬁnements, water–fuel

emulsions, direct water injection, EGR and appropriate combinations of these.

FIgurE 9.12 Cross-section of MAN B&W S70ME-C electronically controlled engine

Scope for securing lower NOx emission levels through tuning measures alone

is enhanced in electronically controlled engines, whose fuel injection and

exhaust valve operating systems provide greater ﬂexibility and accuracy in set-

tings than is possible with the ﬁxed timings of camshaft-based systems. Such

engines can be more easily adapted in service to economy- or emissions-optimized

modes. SCR systems offer effective exhaust gas after-treatment, cutting NOx

emissions by over 90 per cent.

A future focus on curbing carbon dioxide emissions from shipping can be

addressed by advances in engine thermal efﬁciency (although scope is lim-

ited) and waste heat recovery (WHR) systems. MAN Diesel and Wärtsilä have

developed and applied WHR systems in conjunction with specialist suppliers

to boost the overall plant efﬁciency of large container ship propulsion installa-

tions, hence reducing fuel consumption and thus carbon dioxide emissions.

Intelligent engines 287

289

C h a p t e r | t e n

MAN B&W Low-Speed

Engines

MAN Diesel’s roots are closely entwined with the early days of the diesel

engine through both its German and Danish branches, respectively, MAN

and Burmeister & Wain (B&W). Both groups evolved distinctive low-speed

two-stroke crosshead engine designs before MAN acquired control of B&W

in 1980. MAN subsequently discontinued the development of its own loop-

scavenged engines at Augsburg and centred all low-speed design and R&D

operations in Copenhagen, pursuing the reﬁnement of the MAN B&W uniﬂow-

scavenged programme in the shape of the MC series.

The prototype, an L35MC model, entered service in 1982 and the ﬁrst large

bore example, a six-cylinder L60MC engine, was started on the Christianshavn

testbed in September 1983. The full L-MC programme was introduced in 1982

with bore sizes of 350 mm, 500 mm, 600 mm, 700 mm, 800 mm and 900 mm.

Reﬁnement of the MC design and the introduction of new bore sizes (260 mm,

420 mm, 460 mm and 980 mm) and stroke options continued through the

1980s/1990s in line with service experience and market trends. The portfolio

eventually embraced 11 bore sizes from 260 mm to 1080 mm and K (short stroke),

L (long stroke) and S (super-long stroke) variations, with stroke–bore ratios rang-

ing from 2.44 to 4.2:1 and rated speeds from 56 rev/min to 250 rev/min.

Output demands from around 1100 kW to 97 300 kW were covered by four-

to 14-cylinder in-line models in the MC programme, whose individual rating

envelopes are shown in Figure 10.1. Additions to the portfolio and key para-

meter reﬁnements over the years—progressing to Mark 7 versions with mean

effective pressures of 19 bar or higher—are shown in Table 10.1. Performance

curves are typiﬁed by those for an S60MC engine (Figure 10.2).

Higher rated Mark 9 versions of 800-mm and 900-mm-bore S and K

engines were released in 2006, an mep of 20 bar, a maximum ﬁring pressure of

160 bar and a mean piston speed of 9 m/s underwriting power increases of up

to 25 per cent. Smaller bore MC-C models had already beneﬁted from an mep

rise to 20 bar introduced in 2004, delivering 5 per cent power increases.

Electronically controlled ME versions of the 500–1080-mm bore models

(detailed below) were progressively introduced from 2001, offering the same

290 MAN B&W Low-Speed Engines

outputs as their MC engine equivalents. ME-B models with bore sizes from

350 mm to 600 mm extended the electronic engine programme from 2006, with

stroke–bore ratios up to 4.42:1 and mean effective pressures of 21 bar.

The layout diagram in Figure 10.3 (in this case for an S60MC engine)

shows the area within which there is full freedom to select the combination of

engine power (kW) and speed (rev/min) that is the optimum for the projected

ship and the expected operating proﬁle. The engine speed (horizontal axis) and

engine power (vertical axis) are shown in percentage scales. The scales are log-

arithmic, which means that, in this diagram, exponential curves such as propel-

ler curves (third power), constant mean effective pressure curves (ﬁrst power)

and constant ship speed curves (0.15–0.30 power) are straight lines. The con-

stant ship speed lines, shown at the uppermost part of the diagram, indicate

the power required at various propeller speeds in order to keep the same ship

speed, provided that, for each ship speed, the optimum propeller diameter is

used, taking into consideration the total propulsion efﬁciency.

An engine’s layout diagram is limited by two constant mean effective pres-

sure lines L1–L3 and L2–L4, and two constant engine speed lines L1–L2 and

L3–L4. The L1 point refers to the engine’s nominal maximum continuous

50 60 70 80 100 120 140 160 200 250

Speed (rev/min)

S26

S35

S42

S50

S60

S70

S80

S90

S70-C

S60-C

L80

K90

L90

K98

K98-C

L35

L42

L50

S50-C

L60

L70

K90-C

K80-C

Power

BHP kW

x 1000

100

S46-C

FigurE 10.1 MAN Diesel’s MAN B&W MC engine programme