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

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receives its control input from a cylinder control unit. The fuel injection pump

features well proven technology, and the fuel valves are of a standard design.

Second- and third-generation fuel injection pumps are much simpler than

the ﬁrst-generation design, and their components are smaller and easier to

manufacture (Figure 10.38). A major feature of the third-generation pump is

its ability to operate on heavy fuel oil; the pump plunger is equipped with a

modiﬁed umbrella design to prevent heavy fuel from entering the lube oil sys-

tem. The driving piston and injection plunger are simple and kept in contact

by the fuel pressure acting on the plunger and the hydraulic oil pressure acting

on the driving piston. Both the beginning and the end of the plunger stroke are

controlled solely by the fast-acting NC valve, which is computer controlled.

Optimum combustion (and thus optimum thermal efﬁciency) calls for an

optimized fuel injection pattern, which in a conventional engine is generated

by the fuel injection cam shape. Large two-stroke engines are designed for a

speciﬁed maximum ﬁring pressure and the fuel injection timing is controlled

so as to reach that pressure with the given fuel injection system (cams, pumps,

injection nozzles).

For modern engines, the optimum injection duration is around 18–20° crank

angle at full load, and the maximum ﬁring pressure is reached in the second

half of that period. To secure the best thermal efﬁciency, fuel injected after the

maximum ﬁring pressure is reached must be injected (and burned) as quickly as

possible in order to obtain the highest expansion ratio for that part of the heat

released. From this, it can be deduced that the optimum ‘rate shaping’ of the fuel

injection is one showing an increasing injection rate towards the end of injection,

thus supplying the remaining fuel as quickly as possible. The camshaft of the

conventional engine is designed accordingly, as is the fuel injection system of

the ME engine. In contrast to the camshaft-based injection system, however, the

ME system can be optimized at a large number of load conditions.

Electronically controlled ME engines 341

Circulation

Fuel

valve

Circulation

Fuel

valve

Inlet

Drain

Inlet

Fuel

valve

First-generation pump

Second-generation pump Third-generation pump

FigurE 10.38 Development of fuel injection pump for ME engine

342 MAN B&W Low-Speed Engines

MAN Diesel claims that the fuel injection system for the ME engines can

execute any sensible injection pattern needed to operate the engine. It can per-

form as a single-injection system as well as a pre-injection system with a high

degree of freedom to modulate the injection in terms of injection rate, timing,

duration, pressure or single/double injection. In practice, a number of injec-

tion patterns are stored in the computer and selected by the control system for

operating the engine with optimum injection characteristics from dead slow to

overload, as well as during astern running and crash stop. Changeover from

one to another of the stored injection characteristics may be executed from one

injection cycle to the next.

ExHAuST VALVE ACTuATioN SYSTEM

The exhaust valve is driven by the same servo oil system as that for the fuel

injection system, using cool pressurized lube oil as the working medium. The

necessary functionality of the exhaust valve is less complex than fuel injection,

however, calling only for the control of the timing of its opening and closing.

This is arranged by a simple fast-acting on/off control valve.

Well-proven technology from the established MC engine series was retained.

The actuator for the exhaust valve system is of a simple, two-stage design. The

ﬁrst-stage actuator piston is equipped with a collar for damping in both direc-

tions of movement. The second-stage actuator piston has no damper of its own

and is in direct contact with a gear oil piston transforming the hydraulic system

oil pressure into oil pressure in the oil push rod. The gear oil piston includes a

damper collar that becomes active at the end of the opening sequence, when the

exhaust valve movement will be stopped by the standard air spring.

CoNTroL SYSTEM

Redundant computers connected in a network provide the control functions

of the camshaft (timing and rate shaping). The engine control system—an

integrated element of the IE—comprises two engine control units (ECU),

a cylinder control unit (CCU) for each cylinder, a local control terminal and

an interface for an external application control system. Both the ECU and the

CCU were developed as dedicated controllers, optimized for the speciﬁc needs

of the IE (Figure 10.39).

The ECU controls functions related to the overall condition of the engine.

It is connected to the plant control system, the safety system and the super-

vision and alarm system, and is directly connected to sensors and actuators.

The ECU’s function is to control the action of the following components and

systems:

l The engine speed in accordance with a reference value from the applica-

tion control system (an integrated governor control)

l Engine protection (overload protection as well as faults)

l Optimization of combustion to suit the running condition

l Start, stop and reversing sequencing of the engine

l Hydraulic (servo) oil supply (lube oil)

l Auxiliary blowers and turbocharging.

The cylinder control unit is connected to all of the functional components

to be controlled on each cylinder, its purpose to control the activation of fuel

injection, the exhaust valve, the starting valve, and the cylinder lubricator for

a speciﬁc cylinder. Since each cylinder is equipped with its own controller (the

CCU), the worst consequence of a CCU failure is a temporary loss of power

from that particular cylinder (e.g., similar to a sticking fuel pump on a con-

ventional engine). The engine controller (ECU) has a second ECU as a hot

standby, which, in the event of a failure, immediately takes over and continues

the operation without any change in performance (except for the decreased tol-

erance for further faults until repair has been completed).

In the event of a failure in a controller, the system will identify the faulty

unit, which can be simply replaced with a spare. As soon as the spare is con-

nected, it will automatically be conﬁgured to the functions it is to replace, and

resume operation. As both the ECU and the CCU are implemented in the same

type of hardware, only a few identical spares are needed. If failures occur in

connected equipment—sensors, actuators, wires—the system will locate the

area of the failure and, through built-in guidance and test facilities, assist the

engine operating staff in the ﬁnal identiﬁcation of the failed component.

Electronically controlled ME engines 343

Local

operation

panel

ECU BECU A

CCUACU

Auxiliaries control

unit 1, 2 and 3

Cylinders control

unit 1 per cylinder

Engine Control Unit A and B

Control

Network

Engine interface control unit A and B

EICU BEICU A

Back-up

for MOP

Bridge

panel

Control

room

panel

Main

operating

panel

FigurE 10.39 Control system conguration for ME engines

344 MAN B&W Low-Speed Engines

CYLiNDEr PrESSurE MEASuriNg SYSTEM

Reliable measurement of the cylinder pressure is essential for ensuring sus-

tained ‘as new’ engine performance. A conventional mechanical indicator in the

hands of skilled engineroom staff can provide reasonable data on this parameter,

but the process is quite time-consuming, and the cylinder pressure data derived

are not available for analysis in a computer. Some valuable information is there-

fore less likely to be used in a further analysis of the engine condition.

A computerized measuring system with a high quality pressure pick-up

connected to the indicator bore—pressure measuring system (PMI) off-line—

was developed by MAN Diesel for application to its MC engines. For the ME,

however, on-line measurements of the cylinder pressure are necessary, or at

least highly desirable. In this case, the indicator cock cannot be used because

the indicator bore would clog up after a few days of normal operation.

The strain-pin type of pressure sensor was applied instead. Here, the pres-

sure sensing element is a rod located in a bottom hole in the cylinder cover, in

close contact with the bottom of the hole and close to the combustion chamber

surface of the cylinder cover. The sensor thus measures the deformation of the

cover caused by the cylinder pressure without being in contact with the aggres-

sive combustion products. The position of the sensor also makes it easier to

prevent electrical noise from interfering with the cylinder pressure signal.

The pressure transducer of the above-mentioned off-line system is used for

taking simultaneous measurements for calibrating the online system. A calibration

curve is determined for each cylinder by feeding the two signals into the computer

in the calibration mode. The fact that the same high-quality pressure transducer is

used to calibrate all cylinders means that the cylinder-to-cylinder balance is not at

all inﬂuenced by differences between the individual pressure sensors.

Both on-line and off-line systems provide the user with valuable assistance

in keeping the engine performance at ‘as new’ standard, extending the TBOs

and reducing the workload of the crew. The systems automatically identify the

cylinder being measured without any interaction from the person carrying out

the measurement (because the system contains data for the engine’s ﬁring order).

Furthermore, compensation for the crankshaft twisting is automatic, exploiting

proprietary data for the engine design. If there is no such compensation, the mean

indicated pressure will be measured wrongly, and when the ﬁgure is applied to

adjust the fuel pumps, the cylinders will not have the same true uniform load

after the adjustment, although it may seem so. (Crankshaft twisting may lead to

errors in mean indicated pressure of some 5 per cent, if not compensated for.)

The computer executes the tedious task of evaluating the ‘indicator card’

data, which are now in computer ﬁles; and the cylinder pressure data can be

transferred directly to MAN Diesel’s CoCoS-EDS engine diagnostic system for

inclusion in the general engine performance monitoring. The result presented

to engineroom staff is far more comprehensive, comprising a list of necessary

adjustments. These recommendations take into account that the condition of

the non-adjusted cylinders changes when the adjustments are carried out; it is

not necessary therefore to check the cylinder pressure after the adjustment.

STArTiNg Air SYSTEM

The starting air valves on the ME engine are opened pneumatically by elec-

tronically controlled on/off solenoid valves, which replace the mechanically

activated starting air distributor of the MC engine. Greater freedom and more

precise control are yielded, while the ‘slow turning’ function is maintained.

ME ENgiNES iN SErViCE

Seeking to conﬁrm the efﬁciency and reliability of the ME systems in regu-

lar commercial service, the Hitachi-MAN B&W 6L60MC main engine of the

chemical/product carrier Bow Cecil—delivered in October 1998—was pre-

pared for the systems during its production. The mechanical–hydraulic system

components were installed on the upper platform of the engine in parallel with

the conventional camshaft. The camshaft system was used during the sea trial

and the early operating period of the tanker until the electronic components

were installed in September 2000. The engine was subsequently commissioned

as the ﬁrst ME engine in service in November 2000.

System ﬂexibility is accessed by different running modes, selected either

automatically to suit speciﬁc operating conditions or manually by the operator

to meet speciﬁc goals such as ‘low fuel consumption’ or ‘limited exhaust gas

emissions’ (Figure 10.40). The mode selection screen of the human machine

interface in the control room allows the operator to switch from fuel economy

ME engines in service 345

Change

in %

g/kw h

100

110

120

130

140

30 50 70 90

Engine load in%

SFOC

MC-C

ME-C

110 130

−1

−2

−3

−4

−5

FigurE 10.40 Flexibility of the electronically controlled ME concept compared with

a traditional camshaft-controlled MC-C engine in terms of Nox emissions and sfc

346 MAN B&W Low-Speed Engines

and emission control modes, as well as to switch between governor control

modes such as constant speed and constant torque.

The ﬁrst engine built from the start as an electronically controlled ME design—

a 7S50ME-C model—was completed by MAN B&W Alpha Diesel in Denmark

in early 2003 and entered service in November that year. Subsequent delivery

references have expanded to embrace 500-mm, 600-mm, 650-mm, 700-mm,

800-mm, 900-mm and 980-mm-bore ME or ME-C models for diverse ship types.

A 650-mm-bore design with a stroke–bore ratio of 4.2 was added to the

ME programme in 2004 to meet the propulsion requirements of Cape-size bulk

carriers, Suezmax tankers and 2000–3000 TEU container ships. A power band

from 14 350 kW to 22 960 kW at 95 rev/min is covered by ﬁve- to eight-cylinder

models in this S65ME-C range. The ﬁrst example, a seven-cylinder model, was

completed in 2006 for powering an ice-class Suezmax tanker.

MArK 9 LArgE BorE ENgiNES

Introduced in the 1980s, MAN B&W 900-mm-bore K90MC and MC-C

engines targeted the largest container ships of the time, which had capacities

of up to 4000 TEU and service speeds of up to 24 knots. The 800-mm-bore

K80MC-C model addressed propulsion projects for ships up to 3000 TEU with

similar speeds. Numerous references were gained for the K80 and K90 engines

in medium-to-large container ships over many years, but the largest vessels are

now typically speciﬁed with the 980-mm-bore K98 engines in either mechani-

cal MC or electronic ME versions. In VLCC propulsion, as well as the very

large bulk carrier market, the S80MC was commonly selected for tonnage

with limited speed requirements, while faster and larger ships were typically

speciﬁed with S80MC-C or S90MC-C engines (both are now available in

ME form).

With full orderbooks at major yards for some time ahead in 2005/2006,

MAN Diesel took the opportunity to sharpen the competitiveness of the

S/K80ME-C and K90ME/ME-C engines through a comprehensive updating

and uprating to Mark 9 status (Table 10.4 and Figure 10.47).

Options for owners specifying propulsion plant for large tanker, bulk car-

rier and container-ship tonnage were extended by the modiﬁed 800-mm-bore

engine designs. The new K80ME-C and S80ME-C Mark 9 models were higher

output variants of the established shorter stroke engines of this bore size, which

remained in the production programme. Both K80 and S80 series could be

speciﬁed in ME-C or MC-C versions.

VLCCs and large bulk carriers with a limited need for speed were targeted

by the S80ME-C engine, available in six- to nine-cylinder models covering a

power range from around 27 000 kW to just over 40 000 kW at 78 rev/min. With

an output band from 27 000 kW to 54 400 kW at 104 rev/min covered by six- to

twelve-cylinder models, the K80ME-C series was tailored to the requirements of

medium and large container-ship propulsion. Improved power-to-weight ratios

were achieved, reportedly without compromising reliability from a combination

of new and proven developments and design features (Figures 10.41 and 10.42)

as follows:

l An Oros combustion chamber: reduced surface temperatures, elimina-

tion of piston top coating, less piston top stress

l Slide fuel valve: less deposits, improved combustion process, less visible

smoke, reduced emissions

l Piston ring pack conﬁguration: CPR piston rings, PC rings, high topland

piston crown, increased height of ﬁrst piston ring, copper band on piston

skirt

l W-seat: increased TBOs for the exhaust valve seat, reduced number of

grindings, fewer dent marks

l An Alpha Lubricator.

A higher mean effective pressure of 20 bar, maximum ﬁring pressure of

160 bar and a mean piston speed of 9 m/s contributed to power increases of

up to 25 per cent for the 800 mm and 900-mm-bore S and K designs, without

undermining sfc. A lower production cost and weight per kilowatt were also

reported, along with enhanced reliability and extended service intervals fos-

tered by design features adopted from the new S65ME-C engine, which also

support the higher ratings and enhanced compactness.

The combination of mep and P

max

ensured an unchanged sfc despite a rise

in power output of up to 25 per cent from the modiﬁed K-type engines (albeit

compared with the engines originally designed in the late 1980s). The power

increase was such that the modiﬁed models were able to replace contemporary

Mark 9 large bore engines 347

FigurE 10.41 Design features of MAN B&W MC and ME engines with increased

ratings

348 MAN B&W Low-Speed Engines

engines of a different design having a larger cylinder bore as well as new

engines of a different design with a slightly larger bore.

It was decided to launch the updated engines only in relevant cylinder num-

bers: the K80/90 designs in six to twelve-cylinder versions and the S80ME-

C design in six to nine-cylinder versions. A higher speciﬁc output enables

engines with fewer cylinders to be speciﬁed for a given power requirement,

thereby reducing maintenance costs.

A number of well-proven design features were adopted from other engines,

one of which—differentiated cylinder distances—yields a large weight saving

and reduces the engine length. Typically, it is possible to exploit a shorter cyl-

inder distance in the forward cylinder units because the torque to be transferred

through the crank throws is smaller compared with the aft end of the engine. For

a 12-cylinder K90ME/ME-C Mark 9 engine, this means that the six foremost

cylinder units can have a cylinder distance of 1492 mm compared with 1602 mm

for the six aftmost units. The resulting weight saving on such an engine is more

than 25 tonnes and the reduction in overall length more than 0.5 m.

MAN Diesel reports that the beneﬁts for an eight-cylinder version of this

engine are even more impressive, because the shorter cylinder distance can be

applied on all cylinders: the weight saving is more than 34 tonnes and the overall

FigurE 10.42 Modied 80-bore engines feature an oros combustion chamber,

W-seat for the exhaust valve, an improved piston ring pack conguration and a slide

fuel valve

engine length is reduced by almost 1 m. A similar result is gained for the

K80ME-C engine.

In order to reduce production costs, no machining of the bearing side girder

walls is applied in the bedplate. The main bearings are of the proven thin shell

design using white metal as the material. Further reducing production costs,

the building-in of the bearing housing is modiﬁed in that the 25°/65° mating

face between cap and bearing support in the existing design is changed to a

horizontal assembly. This simpliﬁcation dictates a pair of high friction plates

between cap and bearing support to enable the assembly to handle the shear

forces.

For the updated engines with nine to twelve-cylinders, the designers speci-

ﬁed a 360° thrust bearing yielding a weight saving over the traditional 240°

bearing while achieving a stronger bedplate structure in the aft end. The dia-

meter of the thrust cam was also reduced, as was the thrust bearing length.

The thrust bearing housing forms a vessel and contains an oil bath provid-

ing additional lubrication for the bearing segments. Other beneﬁts cited include

only one type of segment and optimized use of the segments according to the

magnitude of the thrust at the fore and aft ends by using 12 segments fore

(360°) and eight segments aft (240°). A further advantage of this design is that

the thrust acts on the centreline of the crankshaft whereas with the traditional

design the force is somewhat offset from the centreline. For engines with fewer

than nine to twelve-cylinders, the 240° thrust bearing is retained to meet the

lower thrust force to be transferred.

A ﬂexible thrust cam—introduced in the S65ME-C engine—features

machined grooves that optimize the load in the thrust bearing, yielding reduced

oil ﬁlm pressure, hence lowering the maximum bearing pressure, increased

ﬁlm thickness and improved load distribution on the thrust segments, thereby

reducing the area and thus the thrust cam dimensions. Efforts were also made

to reduce production costs and weight in the structure of the thrust bearing sec-

tion. Calculations showed that the vertical stiffeners could be removed without

reducing the strength of the structure.

Like other newer engines among the ME/ME-C/MC-C types, the updated

designs feature a triangular plate framebox (Figure 10.43) with twin staybolts.

Essentially, the design is like the S-MC-C framebox with ribs. The main differ-

ence is the substitution of ribs with vertical plates, forming a continuing trian-

gular proﬁle from top to bottom. In this way an even stiffness is derived along

the guide bar, which improves conditions for the sliding surface of the guide

shoes. Contact simulations veriﬁed this improvement and service experience

has reportedly shown an excellent bearing condition.

In general, production costs (especially welding costs) are reduced. With

the lower stress level in the structure, weld joints with lower quality require-

ments could be used, ideally suited to robot welding techniques. After labo-

ratory and service testing, it was decided to omit the speciﬁcation of post

weld-heat treatment (PW-HT) for the frameboxes of triangular plate guide bar

design, allowing enginebuilders to beneﬁt from the cost saving.

Mark 9 large bore engines 349

350 MAN B&W Low-Speed Engines

The cylinder frames of the updated engines are of cast design as standard,

with a welded structure as an option. The decision reﬂected the preferences of

MAN B&W engine licensees in recent years, whose foundry capacity had gen-

erally increased after earlier shortages. Another factor is that machining of the

top plate of the welded cylinder frame demands substantial plano-miller time.

A number of inherent advantages are nevertheless acknowledged for the

welded cylinder frame, such as increased rigidity and reduced weight. In addi-

tion, the welded design makes it possible to integrate the scavenge air receiver

in the frame; the chain case is integrated as well, securing a total weight saving

of 30 per cent. Furthermore, dimensions are smaller, thereby lowering the total

engine height.

Large bore MAN B&W engines have exploited the Oros combustion

chamber since the late 1990s (and it is now also speciﬁed for medium-bore

designs). In terms of cylinder condition the design has reportedly proven very

successful, enabling overhauling intervals for the combustion chamber compo-

nents to be extended. The Oros chamber is formed by the piston and cylinder

cover geometry, which concentrates the hot combustion gases around the fuel

nozzles, and the high topland piston, which allows a low position of the mating

surface between cylinder liner and cover (thereby reducing liner wall tempera-

tures and giving controlled cold corrosion, which is favourable for refreshing

the liner surface) (Figures 10.44 and 10.45).

Piston ring packs of the latest design also beneﬁt the updated engines

(Figure 10.46), the change in design introduced to increase resistance against

scufﬁng. Hard coating on the ﬁrst and fourth rings has been introduced to

K90 and K98 engines, and the position of the CL grooves was also changed to

secure a more even heat distribution. The CL groove depth was reduced by 20

per cent. The hard coating is a Cermet (ceramic metal) material with a 0.1-mm

running-in layer (e.g., Ni-graphite or Al-coat). The Cermet coating comprises

50 per cent chrome carbides in a matrix of NiCr with some molybdenum.

Since the hard coating takes longer to adapt to the cylinder liner surface, there

is higher risk of a poor gas seal during running-in. To minimize this risk, the

FigurE 10.43 A triangular plate framebox provides increased strength