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

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The MB430 retained many basic features of Mirrlees Blackstone’s long-

established 400 mm bore/457 mm stroke K Major series which remained in

the programme in Mark 3 form, delivering an output of 545 kW/cylinder at

600 rev/min. The design matured from the K-engine of the 1950s, one of the

ﬁrst large medium-speed engines in the world, which in its previous Mark 2

form featured a 381 mm bore (Figure 28.14). The connecting rod assembly of a

Mark 3 engine is shown in Figure 28.15.

The MB430 design also exploited some concepts introduced for the

MB275 series in 1979. This 275 mm bore/305 mm stroke engine was available

in six and eight in-line and V12- and 16-cylinder versions covering a power

range up to 5070 kW at 1000 rev/min.

Mirrlees Blackstone 731

FigurE 28.13 Mirrlees Blackstone MB430 design

732 Other Medium-Speed Engines

Lower power requirements were served by Mirrlees Blackstone’s 222 mm

bore/292 mm stroke ESL series (Figure 28.16) whose upper output limit was

doubled in 1986 by V12- and V16-cylinder models, the latter developing

2985 kW at 1000 rev/min. The programme also embraced ﬁve, six, eight and

nine in-line cylinder models.

The V-versions tapped the pedigree of the former E range but incorporated

several interesting features, including an underslung crankshaft and a belt drive

for the lubricating oil and water pumps. The V-models have a 45° cylinder con-

ﬁguration, deep main bearing caps, side bolts for added structural stiffness and

a central air intake. A simpliﬁed rocker arrangement operates four valves (two

inlet and two exhaust) through two levers and bridge pieces enclosed within

an aluminium cover. The valve gear is actuated by side-loaded camshafts

driven from the ﬂywheel end through nitride-hardened gears. The three-piece

FigurE 28.14 Cross-section of Mirrlees Blackstone KV Major Mk 2 engine

construction of the connecting rod allows piston withdrawal without disturbing

the large end bearing.

A pulley and ﬂat belt arrangement for the service pumps, mounted on the

engine front, represented a departure from the traditional gear drive used by

most enginebuilders. Its adoption was considered beneﬁcial in lower produc-

tion costs, pump speed ﬂexibility, easier installation and maintenance, and

weight and power savings. The belt comprises a core of endless polyester cords

helically wound with a chrome leather friction face covering. A minimum belt

life of 10 000 h was anticipated.

MitSui

A major licensee of MAN Diesel in the production of MC/ME low-speed

engines, Mitsui also once offered its own 420 mm bore/450 mm stroke

medium-speed design whose last version was designated the L/V42MA series.

Mitsui 733

Large end

block

Connecting rod

foot valve

Large end bearing

half shell

Connecting rod shank

Small end bush

Palm end stud

Lock nut

Locking plate

Dowel

Palm end shim

Large end nut, lock

nut & locking plate

Large end

bolt

Palm end nut

FigurE 28.15 Mirrlees Blackstone K Major Mk 3 connecting rod assembly

734 Other Medium-Speed Engines

The launch of the Japanese group’s earlier venture in the four-stroke sector,

the 600 mm bore 60M design with a rating of 1120 kW/cylinder, unfortunately

coincided with the 1973 oil crisis which undermined its market.

The smaller bore L/V42M design, however, beneﬁted from that ill-fated

project and became available in in-line and V-cylinder form with an output

per cylinder of 558 kW at 530 rev/min. The frame is in two parts, comprising a

welded steel crankcase structure made from cast sections and plate and a cast

iron cylinder housing held together with tie-bolts. The underslung crankshaft

bearings are secured by vertical and lateral bolts, all hydraulically tightened.

The designers sought a stress-free structure, controlling the lateral ﬁt between

bearing keep and frame, for example, by tapered adjusting liners before tight-

ening to avoid stressing the frame unduly.

For the crankshaft bearings, Mitsui was able to keep within the stress

capacity of thin white metal (on a lead–bronze backing in the case of the

crankpins) with an overlay. While this is a function of the control of maximum

bearing pressures, it also means that damage to a bearing does not necessarily

lead to shaft damage.

The combustion area and cylinder head conﬁguration can be appreciated

from Figure 28.17. Note the composite piston, bore-cooled cylinder liner,

three-deck head, caged exhaust valves and rigid high-pressure fuel line, as well

FigurE 28.16 Mirrlees Blackstone ESl Mk 2 design

as the camshaft bearing arrangement. In addition to the four compression rings

in the piston crown (the second is Ferrox-ﬁlled to improve running-in) there

are two conformable SOC rings at the top of the cast iron piston skirt and two

broad lead–bronze bands above the gudgeon and one below; these also assist

during the running-in phase.

A three-part marine-type connecting rod was selected with serrations at the

big end joint. The exhaust valve cage can be removed easily by taking out the

pushrod and lifting clear the rocker. Rotators are applied on the exhaust valves,

and guide vanes are formed in the inlet passages of the head to foster swirl in

the charge air. A mist catcher is installed after the intercooler to reduce the

water loading of the charge air in humid ambient conditions.

The fuel injector sleeve is provided with small water passages at the seat.

These passages communicate with the cylinder head water passages and foster

a convection ﬂow which gives adequate cooling to the nozzle for operation on

all fuels without the complication of water cooling the nozzles.

Subsequent reﬁnements led to the Mitsui L/V42MA design with an output

raised to 625 kW/cylinder at 600 rev/min, allowing 6L- to V18-cylinder models

to cover a power band up to 11 250 kW.

Mitsui 735

FigurE 28.17 Cross-section through cylinder head and piston of Mitsui 42M engine

736 Other Medium-Speed Engines

niigAtA

A wide range of own-design high- and medium-speed engines from Niigata

Engineering of Japan was supplemented by licences to build SEMT-Pielstick

PA and PC series and MAN B&W Holeby 23/30 and 28/32 series engines.

Niigata’s own MG (Marine Geared) medium-speed programme embraces

designs with 190 mm, 220 mm, 250 mm, 260 mm, 280 mm, 320 mm, 340 mm,

400 mm, 410 mm and 460 mm bore sizes; the high-performance FX series

includes 165 mm and 260 mm bore versions. (See Chapter 30 for Niigata high-

speed engines.)

Its largest medium-speed engine, the MG46HX, is a 460 mm bore/600 mm

stroke design with an output per cylinder of 823 kW at 450 rev/min and the

capability to operate on 700 cSt fuel. Power demands up to 13 180 kW are met

by 6/8L and V12/16-cylinder models, the targeted propulsion plant applica-

tions including medium-to-large ferries, container ships and RoRo freight ves-

sels. The crankcase is built as a box structure to secure rigidity in handling a

maximum combustion pressure of 180 bar; engine noise and vibration levels

are also claimed to be low. Easier maintenance was addressed by simpliﬁed

component designs and hydraulic tools.

Niigata also developed the HLX series, which embraces 220 mm, 280 mm

and 340 mm bore sizes covering a power band from 1392 kW to just under

10 000 kW from in-line and V-cylinder models.

nOhAB

The Nohab engine business was acquired by Wärtsilä, which focused on the

Swedish designer’s Nohab 25 series before phasing out the programme.

This 250 mm bore/300 mm stroke design was offered in six in-line and

V12- and 16-cylinder versions covering output demands up to 3680 kW at

720/750/825/900 rev/min and 1000 rev/min for auxiliary and propulsion plant

markets. The engine proved particularly popular in the offshore power arena.

A cross-section of the 6R25 model is shown in Figure 28.18.

SKl

Four-stroke engines in a number of bore sizes—160 mm, 200 mm, 240 mm and

320 mm—were produced by SKL whose pedigree dates back to 1905 when the

Magdeburg, German-based company’s forerunner (Lokomobilenfabrik R. Wolf),

took out a licence to build diesel engines. SKL Motor was taken over in 2008

by MTU Friedrichshafen, which has invested in a remanufacturing centre for

its own high-speed engines.

SKL Motor’s medium-speed engine programme remains in production,

including the VDS 29/24 AL series for propulsion and genset duties which is

offered in six, eight and nine in-line cylinder versions to cover an output range

up to 2350 kW at 750/900 rev/min and 1000 rev/min. Its brake mean effective

pressure rating is 23.9 bar.

The 240 mm bore/290 mm stroke design (Figure 28.19) is based on a rigid

nodular cast iron cylinder block housing a suspended crankshaft. The block is

free of cooling water thanks to a special cylinder liner design which incorpo-

rates a raised, rigid and separately cooled collar; this feature protects against

corrosion and deposits, and reduces maintenance costs. The alloyed ﬂake-

graphite cast iron liner beneﬁts from all-round nitration to enhance its wear

resistance. Four cylinder head screws with long anti-fatigue shafts transmit

forces via intermediate walls and ribs in the block and via the main bearing

screws to the main bearing covers.

SKl 737

FigurE 28.18 Wärtsilä nohab r25 design

738 Other Medium-Speed Engines

A deformation-resistant bedplate forms the bottom of the housing and can,

in appropriately extended form, also serve as the mounting for an alternator.

The camshaft is carried by bearings in the cylinder block and driven by gear-

ing at the opposite end to the coupling. A hardened and tempered crankshaft,

upset forged from C-steel, is supported by interchangeable thin-walled multi-

layer slide bearings. A viscosity-type torsional vibration damper is arranged

at the free end of the crankshaft. The control gear and vibration damper ﬂange

are attached to the crankshaft by a cone interference ﬁtting and hydraulically

mounted. Up to 60 per cent of the rated output can be taken off at the opposite

FigurE 28.19 SKl’s VDS 29/24 Al design

end to the coupling. Also hardened and tempered and forged from alloyed C-

steel, the connecting rod is divided horizontally at its large end and supported

by interchangeable thin-walled multi-layer slide bearings.

The composite piston consists of a steel crown and aluminium alloy skirt,

bolted from the top and supplied with cooling oil through a longitudinal bore

in the connecting rod. The ring pack comprises three compression and one oil

scraper rings with chromium-plated surfaces.

Four necked-down bolts secure the cylinder head to the block, the head

incorporating two inlet and two exhaust valves. Engines destined for heavy

fuel burning are equipped with turning devices for the exhaust valves. The hard

facing of the valve seat surfaces in combination with the cooling of the exhaust

valve seat rings, mounted in the cylinder head, fosters extended operational

lifetimes for the components. The fuel injection valve is located in the centre

of the cylinder head. The valve drive (lubricated by pressure oil and arranged

in an oil-tight enclosure) is effected from the camshaft via roller tappets, push-

rods and forked rockers.

Turbocharging is based on a three-pulse system with a claimed maximum

efﬁciency of at least 64 per cent. A compressor washing device and, for heavy

fuel service, a turbine washing device are speciﬁed to reduce maintenance

demands.

Fuel is injected by individual top-mounted pumps at maximum injection

pressures of 1400 bar-plus which, in conjunction with an optimized cam geom-

etry, ensures a short combustion time. Ideal combustion with minimal noxious

emissions is further pursued by short injection pipes (incorporating double

walls for safety) and optimized nozzle spray angles and injection hole diam-

eters. In heavy fuel engines the injection nozzle is continuously cooled with

lubricating oil from the engine circuit, and fuel pipings sheathed with heating

piping are isolated. The quantity of fuel injected is controlled by a mechani-

cal–hydraulic speed governor via a compound control rod arrangement.

Engine cooling is effected by two circuits. The cylinder liner, head and

turbocharger are cooled via a high-temperature circuit while a low-tempera-

ture circuit serves the oil and charge air cooler as well as the heat exchanger

(water). Both circuits are designed for the direct ﬁtting of centrifugal pumps.

Engine lubrication is carried out by a pressure circulation system served by a

lubricating oil pump, ﬁlter and cooler mounted on the engine. The system also

supplies the piston with cooling oil.

StOrK-WErKSpOOr DiESEl

Formed in 1954 by the merger of Stork and Werkspoor, along with other inter-

ests in the Dutch enginebuilding industry, Stork-Werkspoor Diesel (SWD) was

acquired in 1989 by the Finland-based multinational Wärtsilä Diesel group,

now the Wärtsilä Corporation. SWD’s own-design medium-speed engines

were gradually phased out of the production programme and replaced by the

Wärtsilä 26 and 38 series (Chapter 27), largely designed by SWD staff and

Stork-Werkspoor Diesel 739

740 Other Medium-Speed Engines

subsequently manufactured in Zwolle, The Netherlands. These models were

later assigned for production by Wärtsilä Italia in Trieste.

Not long after its formation, SWD decided to develop a high-powered

medium-speed engine to contest diverse coastal and deep-sea propulsion are-

nas, the resulting TM410 series appearing on the market in the later 1960s.

The 410 mm bore/470 mm stroke design (Figure 28.20) was uprated a number

of times in its career to a level of 564 kW/cylinder at 600 rev/min, the series

embracing six, eight and nine in-line and V12-, 16-, 18- and 20-cylinder

versions.

A scaled-up version—the TM620 series—was introduced in the mid-1970s

to complement the TM410, the 620 mm bore/660 mm stroke design enjoying a

status for many years as the world’s largest and most powerful medium-speed

engine (Figure 28.21). Examples of both types—in in-line and V-cylinder

form—remain at sea (Figure 28.22).

FigurE 28.20 Cross-section of in-line SWD tM410 engine