Woodyard D. (ed.) Pounders Marine diesel engines and Gas Turbines
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618 Bergen (Rolls-Royce)
system for the eight-cylinder model. Operation at low loads is fostered by ele-
vated charge air temperatures through two-stage charge air cooling, high fuel
injection pressures and optimized valve timing.
BV engine
The first BV engines—twin V12-cylinder models, each developing 5294 kW
at 750 rev/min—were delivered in 1998 for powering a large anchor handling/
tug/supply vessel (Figure 23.1). The BV design is based on a single-piece
engine block cast in GGG500 nodular iron carrying two banks of cylinders in a
55° V-configuration (Figure 23.2), an underslung crankshaft (Figure 23.3) and
two camshafts; it also incorporates the charge air receiver between the cylin-
der banks. The camshafts are located outside each bank and housed in open-
sided recesses in the block, allowing the complete camshafts to be removed
sideways. At the front of the block is an opening for the charge air cooler and
another for the auxiliary gear drive; the timing gears are arranged at the rear
of the engine. The whole structure is designed for firing pressures in excess of
200 bar. An advantage of the block material is that it can be repaired by weld-
ing in the event of accidental damage.
A new cylinder liner design specified for the BV engines features a thicker
upper wall section than the in-line cylinder BR models and a revised bore-
cooling layout (Figure 23.4). The liner, rated for mean effective pressures up to
FiguRe 23.1 A Bergen B32:40 engine in V12-cylinder form
32 bar and peak pressures in excess of 220 bar, was subsequently standardized
for all B-series engines. Small changes were made to the BV cylinder heads,
mainly a new head gasket matching the redesigned liner. The two-piece pis-
ton is essentially the same as that used in the BR engines, with a nodular iron
skirt and bore-cooled steel crown. The connecting rods were lengthened but
the same bearings were used as before.
Shorter fuel injection periods dictated strengthened camshafts to meet the
increased loads, with a larger diameter both for the shaft and for the cam base circles.
The fuel pumps are the same as those for BR engines but the fuel supply system was
modified, chiefly by increasing pipe volumes and changing the layout to avoid cavi-
tation and smooth out vibration caused by pressure pulses from the pumps.
Twin turbochargers mounted above the two insert-type charge air cool-
ers operate on the impulse system, the pipework enclosed in an insulated box
between the cylinder banks. A choice of electronic governors is offered, oper-
ating in conjunction with a standardized hydro-mechanical actuator. All elec-
trical transducers on the BV engine are linked to a common electrical rail, one
on each side of the engine, in a neat layout enabling faulty transducers to be
quickly changed.
B32:40 engine
The B-series benefited from another rejuvenation in the shape of the longer
stroke (400 mm) B32:40 design, offering an output of 500 kW/cylinder at
750 rev/min with a mean effective pressure of 24.9 bar.
Production engines became available in the year 2000, supplementing
the standard B-series in the programme. The B32:40 was initially offered in
B32:40 engine 619
FiguRe 23.2 The BV engine block is a nodular iron casting
620 Bergen (Rolls-Royce)
six-, eight- and nine-in-line and V12-cylinder configurations to span a power
band from 3000 kW to 6000 kW; outputs up to 9000 kW were planned by
extending the V-cylinder programme.
A new crankshaft design was incorporated to achieve the longer stroke and
provide increased bearing areas, with new bearing technology addressing the
larger bearing loads. Modified cylinder liners sought good control over tempera-
tures at all points, and the piston/ring designs were also changed to minimize
lube oil consumption and cylinder wear. The cylinder head design and mate-
rial specification were refined to allow a small rise in the maximum combustion
pressure and to handle the greater combustion air throughput from the upgraded
turbocharging system. A new fuel injection system provided both an increase in
capacity and a higher injection pressure. These changes contributed to a specific
fuel consumption of 183 g/kW h at the rated speed of 750 rev/min and NOx emis-
sions under the IMO limit. Improved reliability and maintainability were prom-
ised by a new pump-end module and turbocharger support structure.
FiguRe 23.3 Crankshaft of the BV engine
B32:40 Details
Cylinder block: one-piece nodular cast iron design of rigid structure with
underslung crankshaft, cast-in charge air manifold and large crankcase doors.
The main bearing bolts are hydraulically tightened.
Cylinder liner: centrifugally cast, bore-cooled design with a running sur-
face treated to improve wear resistance; a carbon-cutting ring is incorporated
at the top of the liner.
Cylinder head: bore-cooled flame plate; six hydraulically tightened secur-
ing bolts to ensure even distribution; new cooled exhaust valve seat.
Crankshaft: continuous grain flow forged; large diameter journals and pins;
hydraulically tightened counterweight bolts.
Connecting rod: forged of alloy steel and fully machined; obliquely split
and serrated big end; hydraulically tightened big end bolts.
Bearings: steel backed with Sn/Al bearing material.
Piston: improved oil-cooled two-piece design; two compression rings and
one oil scraper ring, all chromium plated.
Fuel injection system: pumps designed for 2000 bar injection pressure;
totally enclosed in heat-insulated compartment; constant pressure unloading
for cavitation-free operation at all loads and speeds.
Turbocharging system: multi-pulse converter system based on ABB TPL
series turbochargers; easily removable insulation panels for inspection and
maintenance.
B32:40 engine 621
FiguRe 23.4 BV engine cylinder liner with bore-cooled upper part, also applied to
the in-line cylinder BR models
622 Bergen (Rolls-Royce)
Clean Design versions of the B32:40 engine were introduced for opera-
tors keen to minimize the environmental impact of their tonnage, the first
B32:40V12P models to this specification being delivered in mid-2006 for off-
shore vessel projects. The challenge of reducing NOx emissions to 80 per cent
below IMO Tier I requirements was met by Rolls-Royce without undermin-
ing power output or significantly increasing specific fuel consumption levels.
Among the many refinements adopted were a revised piston bowl shape, along
with modifications to the injector nozzles and other fuel system components,
and turbocharger matching. Such changes reportedly avoided an increase in
smoke output during part-load operation, which is a potential side effect of
NOx reduction measures.
A 10 per cent uprating announced in 2008 raised the maximum output to
550 kW/cylinder, the B32:40 series then spanning a power band from 3300 kW
to 8800 kW.
C-engine (C25:33L)
A completely new design, the C25:33L, was launched in mid-2001 after a joint
development project between Bergen and Hyundai Heavy Industries of South
Korea, which markets and builds the engine as the HiMSEN H25/33. Flexibility
in terms of power and speed ranges was a key development criterion to allow
the 250 mm bore engine to target heavy fuel-burning gensets and smaller pro-
pulsion plants. Outputs from 1200 kW to 2700 kW at speeds from 720 rev/min
to 1000 rev/min were initially covered by five- to nine-cylinder in-line models,
with V-engines planned to double the power threshold. The C25:33L was
expected eventually to replace the popular but ageing K-series, particularly in
the genset market. The first four production engines (nine-cylinder models)
were due for delivery in spring 2002 as the core of a diesel–electric propulsion
plant for an offshore service vessel.
In drawing up the design parameters, the stroke (330 mm) was determined by
the piston speed which, in turn, was set by the desired time-between-overhauls
of 15 000 h for the top end and 30 000 h for the bottom end, running on heavy
fuel oil. The running speed was determined by the frequencies in genset
applications, focusing on 900 rev/min to 1000 rev/min for 60 Hz and 50 Hz
requirements. These ratings sought the best compromise between an indus-
try preference for a moderate speed in heavy-duty gensets and the potentially
lower price per kilowatt from a faster running set. The engines can also be sup-
plied, however, for 720/750 rev/min operation.
The C25:33L engine, Figure 23.5, is based on a compact and stiff nodular
cast iron frame, with the charge air receiver, lube oil channel and coolant transfer
channel incorporated in the casting to eliminate pipework. A continuous grain
flow forged steel crankshaft with steel plate balance weights allowed the cylinder
centre distance to be kept the same as the K-series engine in the interests of com-
pactness and rigidity. Full power can be taken off at either end of the crankshaft,
and an additional main bearing allows single-bearing alternators to be driven.
A key feature is the cylinder unit system, allowing a complete liner, piston,
upper connecting rod, water jacket and cylinder head to be drawn as an assem-
bly for servicing or exchange. The components are clamped together by the
cylinder jacket and held down by four cylinder head bolts. A duct transfers air,
exhaust and cooling water to and from the head, each cylinder unit being con-
nected to its neighbour by quick-acting couplings to speed assembly and dis-
mantling. The cylinder liner and water jacket combination is of the ‘open deck’
type, designed for intensive cooling and high strength without stress raisers in
the critical top-end zone.
The piston comprises a steel crown with three rings and a nodular cast iron
skirt. An extended life and low controlled lube oil consumption are fostered by
a chrome-ceramic piston ring coating, an anti-polishing ring at the top of the
cylinder liner and special honing of the liner surface. A three-part connecting
rod enables its upper part to be detached when drawing pistons without dis-
turbing the big end bearing.
One mechanical fuel pump is provided for each cylinder, with a sim-
ple two-step electronic timing feature controlled by the engine management
system. (A common rail fuel system was not selected by Bergen because it
was not seen as essential for the genset applications envisaged, nor as dura-
ble enough for unrestricted heavy fuel operation.) An impulse turbocharging
system is based on an uncooled radial turbocharger which can be mounted at
either end of the engine to suit the particular installation. A swift response to
load changes, with minimal smoke emissions under rapidly changing load and
C-engine (C25:33L) 623
FiguRe 23.5 Primary modules of Bergen C25:33L engine
624 Bergen (Rolls-Royce)
speed conditions, is fostered by the high-efficiency turbocharging, two-stage
charge air cooling with electronic temperature control and a high-speed elec-
tronic governor.
Ease of maintenance was addressed by providing good access to key com-
ponents and a small number of hydraulic tools able to handle all the main bolts.
Ancillaries are grouped in a front-end module accommodating pumps, charge
air cooler, lube oil cooler and filters. The components are designed for plug-
ging-in, with a minimum of joints avoiding leakages.
Bergen C25:33 engine data
Bore
250 mm
Stroke 330 mm
Speed 720–1000 rev/min
Output 220–300 kW/cyl
Cylinders 5, 6, 7, 8, 9L
Power range
1200–2700 kW
Mean eective pressure 22.6–24.7 bar
Mean piston speed 7.9–11 m/s
Firing pressure 190 bar
Specic fuel consumption 182–186 g/kW h
Output of the C25:33 design was raised by 10 per cent to 330 kW/cylinder
in 2008, taking the upper rating to just under 3000 kW from the nine-cylinder
model, and a Clean Design version introduced with emissions reduced to a mini-
mum of 20 per cent less than IMO limits. The environmental improvement
resulted from applying the Miller cycle in combination with an increase in
compression ratio. To avoid smoke at low load and poor transient load behav-
iour in the low load range, which are negative consequences of the Miller
cycle, the CD engines are equipped with variable valve timing (VVT) mecha-
nisms. This enables the Miller cycle inlet valve timing to be turned off for low
load running, with control of the VVT system exercised by the engine’s control
logic. Advances in turbocharging technology, delivering higher pressure ratios,
contributed to the power uprating in association with some changes in engine
parameters.
gAS engineS
Growing availability of LNG for gas-fuelled vessels, particularly in Scandinavian
and Baltic regions, stimulated Bergen to invest further in spark-ignited
engines. The KV-G4 gas engine, now in Norwegian ferry service, was derived
from the long-established 250 mm bore K-series medium-speed diesel design.
Introduced as a marine genset drive in 2002, it was released in 2004 as a vari-
able speed engine for direct-mechanical propulsion.
Design work on the spark-ignited 350 mm bore B-gas engine (B35:40) began
in spring 2002, tapping experience with the successful 320 mm bore B-series
diesel engine. A V12-cylinder prototype engine developing 5100 kW made its
commercial debut in a Danish combined heat and power station in 2003 after
a comprehensive test programme in Bergen. Orders booked in 2008 call for
B35:40V12PG engines developing 5250 kW to power small roro/container ves-
sels, the world’s first LNG-fuelled cargo tonnage. The B-gas engine series also
offers V16- and V20-cylinder versions, taking the power band up to 9000 kW.
Adding to the K-series and B-series gas engine portfolio, Rolls-Royce is
developing a gas variant of the 250 mm bore C-series diesel design in six-,
eight- and nine-cylinder versions.
See also Chapter 2 for Bergen gas engines.
gas engines 625
627
C h a p t e r | t w e n t y f o u r
Ruston (MAN Diesel)
A programme embracing three medium-speed designs—the RK215, RK270
and RK280 series—was developed and produced by Ruston Diesels, a pioneer-
ing British enginebuilder which was a member of the Alstom Engines group
until acquired by MAN B&W Diesel AG (now MAN Diesel) of Germany in
June 2000. The RK215 and RK270 engines are no longer manufactured but
the RK280 continues to be in production as MAN Diesel’s 28/33D series (see
Chapter 22).
The RK270 engine entered service in 1982, the 270 mm bore/305 mm
stroke design inheriting the pedigree of the 254 mm bore RK series which
originated in the 1930s and continued in the programme as an upgraded RKC
series also with a 305 mm stroke. The RK270 retained well-proven features of
its predecessor but exploited new components to underwrite a higher perform-
ance and achieve enhanced lightness and compactness. A fast ferry version of
the engine was progressively refined after entering service in 1990, with alu-
minium alloy specified in non-stressed areas and fabrications replacing cast-
ings where feasible. Attention was also paid to the weight of the ancillary
equipment serving the engine. Later design refinements included revised cylin-
der heads with larger valves and upgraded fuel injection systems.
Early fast ferry propulsion installations were based on 16RK270 engines
with individual ratings of 3650 kW at 750 rev/min (Figure 24.1). The output
was raised in succeeding ferry generations to 4050 kW at 760 rev/min, 4440 kW
at 782 rev/min and 5500 kW at 1000 rev/min. Demand for higher powers stim-
ulated Ruston in early 1995 to introduce a V20-cylinder model to the pro-
gramme, supplementing the established six and eight in-line and V12 and V16
engines. An output of 6875 kW at 1000 rev/min on a mean effective pressure of
23.6 bar was quoted for the 20RK270 design; some fast ferries featured engines
specified with continuous ratings of 7080 kW at 1030 rev/min; and a naval rat-
ing of 7550 kW at 1032 rev/min was sanctioned (maximum power required for
no more than 5 per cent of the operating profile). The V-engines are arranged
with 45° cylinder banks (Figures 24.2 and 24.3).
628 Ruston (MAN Diesel)
FiguRe 24.1 Two 16RK270 engines are arranged in each hull of the fast catamaran
ferry Hoverspeed Great Britain
FiguRe 24.2 One of four V20-cylinder RK270 engines installed in a fast ferry, each
rated at 7080 kW