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

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reﬁnements—including a turbocharger optimized for lower loads, charge air

preheating and a new cooled part-load fuel nozzle—can be applied to new

engines and retroﬁtted to engines in service (see Chapter 3 for details). MAN

favoured the fuel–water emulsion route to reduced smoke over direct water

injection (Figure 22.28).

48/60B engine 597

25 50 75 100

Load [%]

25 50 75 100

Load [%]

charge air

exh. gas before TC

Firing pressure

Fuel consumption be ISO

Cyl. output = 1 200 kW n = 514 rev/min = constant NO

acc. IMO

Smoke index Bosch

Cyl. output = 1 200 kW n = 514 rev/min = constant NO

acc. IMO

[bar] 4

[C] 520

480

440

400

[bar] 200

150

100

[g/kW h] 210

200

190

180

170

] 1.0

0.8

0.6

0.4

0.2

Figure 22.27 Operating data from the 12V48/60B test engine

DWI – water injection

FWE – fuel–water emulsion + partial load characteristic

Engine with DWI

Visible limit

48/60

48/60 FWE

0 25 50 75 100

Load %

Smoke

]

0.8

0.6

0.4

0.2

Figure 22.28 Smoke reduction from a 48/60 engine equipped with fuel–water

emulsion (FWe) system

598 Man Diesel

See Chapter 16 for details of 48/60B engine development procedure.

L27/38 anD L21/31 engineS

A new generation of smaller medium-speed designs for propulsion and genset

drives—the L27/38 and L21/31 series—extrapolated the principles of the suc-

cessful L16/24 auxiliary engine (see section MAN B&W Holeby in Chapter 30),

including the twin camshaft conﬁguration pioneered by the L32/40 series.

The L27/38 series (Figure 22.29) was introduced in 1997 and the L21/31 series

in 2000.

The monobloc cast iron engine frame is designed for a maximum combus-

tion pressure of 200 bar and direct resilient mounting. A static preloading of the

casting is maintained by through-going main bearing tie-rods and deeply posi-

tioned cylinder head tie-rods, thus absorbing the dynamic loads from gas and

mass forces with a high safety margin. All the rods are tightened hydraulically.

Well-supported main bearings carry the crankshaft with generously dimen-

sioned journals. The combination of a stiff box design and carefully balanced

crankshaft promotes smooth and vibration-free running. Large noise-dampen-

ing covers on the frame sides offer good access for inspection and overhaul.

A ‘pipeless engine’ philosophy resulted in integrated oil ducts, with no water

ﬂowing through the frame; risk of corrosion or cavitation is thereby eliminated.

An innovation inherited from the L16/24 design, the front-end box, is

arranged at the free end of the engine. It contains connecting ducts for cool-

ing water and lube oil systems as well as pumps (plug-in units), thermostatic

valve elements, the lube oil cooler and automatic back-ﬂushing lube oil ﬁlter.

External pipe connections are arranged on the sides of the front-end box to

reduce engine length. A small optional power take-off is located on the for-

ward side.

Man B&W 48/60B engine data

Bore 480 mm

Stroke 600 mm

Speed 500/514 rev/min

Output 1200 kW/cyl

Cylinders 6, 7, 8, 9L/12, 14, 16, 18V

Power range

7200–21 600 kW

Mean piston speed 10/10.3 m/s

Mean eective pressure 25.8/26.5 bar

Maximum ring pressure 200 bar

Specic fuel consumption* 173 g/kW h

Specic lube oil consumption 0.6–0.8 g/kW h

*at 85 per cent mcr

Less advanced but pursuing the same philosophy as the front-end box, an

aft-end box is arranged at the ﬂywheel end. This carries the turbocharger and

incorporates a two-stage charge air cooler and integrated ducts for high- and

low-temperature cooling systems. A regulating valve controls the water ﬂow to

the second stage of the cooler, adjusting to the operating conditions to secure

an optimum charge air temperature.

High performance from the piston and ring pack depends on the cylinder

liner geometry over the entire load range, the temperature in the TDC position

of the top piston ring, and measures to avoid bore polishing. The liner is of the

thick-walled high collar design, which protects the sealing between cylinder

L27/38 and L21/31 engines 599

Figure 22.29 Cross-section of L27/38 engine, a larger version of the L21/31 design

600 Man Diesel

head and liner from the inﬂuence of engine frame distortions. Only the collar

is water cooled, ensuring a stable geometry under variable load conditions. The

temperature in the TDC position of the top piston ring is optimized to prevent

cold corrosion, which is especially important in HFO operation.

Years of experience with the ﬂame ring concept successfully applied to the

28/32A and 23/30A engine series (see Chapter 18) was adopted for the L27/38

engine. The ﬂame ring, inserted directly in the top of the cylinder, has a smaller

inside diameter than the cylinder bore. The piston has a similar reduction in its

top land diameter, allowing the ﬂame ring to scrape away coke deposits and

avoid bore polishing of the liner; optimum ring performance and low lube oil

consumption over a long period are fostered.

Monobloc pistons in nodular cast iron had been state of the art for a number

of years for applications imposing a maximum combustion pressure of around

160 bar. With pressures up to 200 bar, however, a monobloc piston was not suit-

able for the new engine generation. A composite piston, with bore-cooled steel

crown and nodular cast iron body, was therefore speciﬁed. The different barrel-

shaped proﬁle of the piston rings and the chromium-ceramic layer on the top

ring target low wear rates and extended maintenance intervals.

The connecting rod is of the marine head-type, with the joint above the

head ﬁtted with hydraulically tightened nuts; the head remains on the crank-

shaft when the nuts are loosened for removal. A low overhaul height is secured.

If engineroom space allows, the complete cylinder unit (cylinder head, water

collar, liner, piston and connecting rod) can be withdrawn as a single assem-

bly. A complete unit can thus be sent ashore for overhaul and replaced with a

new or overhauled unit. The thin-walled main bearing shells are dimensioned

for moderate bearing loads and a thick oil ﬁlm. The crankshaft is a one-piece

forged component provided with counterweights on all crank webs (attached

by hydraulically tightened nuts) to yield suitable bearing loads and vibration-

free running.

A combustion pressure of 200 bar and a mean effective pressure of 23.5 bar

inﬂuenced the choice of nodular cast iron as the material for the four-stud

cylinder head. The rocker arms for the two inlet and two exhaust valves are

mounted on a single shaft supported in the casting. The cylinder segment

charge air receiver is integrated in the casting, with the exhaust gas outlet arranged

on the opposite side. This cross-ﬂow design, together with ﬂow-optimized

inlet and outlet ducts, creates a swirl effect beneﬁting charge air renewal and

combustion.

Inlet and exhaust valve spindles are armoured with heat-resistant hard

metal on the seats. The exhaust valve spindles feature integrated propellers for

rotation by the gas ﬂow in order to equalize and lower the seat temperature,

and to prevent deposits forming on the seat and on the water-cooled valve seat

ring. The inlet valve spindles have valve rotators to minimize seat wear.

Two independent camshafts separate the functions of fuel injection and

charge air renewal, one operating the injection pumps and one actuating the

valve gear. Optimum adjustment of the gas exchange without inﬂuencing

the injection timing is thus secured. Cam followers on the valve camshaft each

actuate two valves via pushrods, rocker arms and a yoke.

A dedicated camshaft for fuel injection makes it possible to alter the tim-

ing, when required, for a low NOx emission mode while the engine is in oper-

ation; the engine can also be easily adapted for running on different fuel oil

qualities. The injection pump has an integrated roller guide directly activated

by the fuel cam (Figure 22.30). Pipe systems are virtually eliminated, thanks

to slide connections between the pumps, promoting easy assembly/disassem-

bly and safety against vibration and leakage. An uncooled injection valve con-

tributes to simplicity of the injection system, which is designed for a pressure

of 1600 bar; effective atomization is thus fostered even at part-load operation

with small injection volumes, contributing to a low exhaust smoke value. The

L27/38 and L21/31 engines 601

Figure 22.30 Fuel pump and injector of L27/38 engine

602 Man Diesel

complete injection equipment is enclosed behind easily removed covers. A fuel

feed pump and ﬁlter are standard on propulsion engines.

The constant pressure turbocharging system incorporates a bypass connec-

tion from the turbocharger air outlet to the gas inlet side in order to increase

the charge air pressure at part load. For certain operating conditions requiring

high engine torque at reduced engine speed, a waste gate arrangement is incor-

porated in the exhaust system.

An entirely closed lube oil system eases installation and avoids the risk of

dirt entering the lube oil circuit. A helical gear-type lube oil pump is mounted

in the front-end box and draws oil from the wet sump. The oil ﬂows via a pres-

sure regulator through the lube oil plate cooler and the automatic back-ﬂushing

ﬁlter; this solution eliminates the exchange of ﬁlter cartridges as well as the

waste disposal problem. The back-ﬂushing ﬁlter is drained to the sump and a

puriﬁer connected to maintain the lube oil in a proper condition. An integrated

thermostatic valve ensures a constant lube oil temperature to the engine.

A cooling water system based on separate low-temperature (LT) and high-

temperature (HT) systems is standard, both circuits cooled by freshwater

(Figure 22.31).

Regulating

valve

Orifice

Gear oil

cooler

Lub. oil

cooler

LT pump

standby

LT pump

HT pump

Charge air cooler

Central

cooler

Seawater

LT systemHT system

HT cooler

HT pump

stand–by

Circulating

pump

Preheater

Heat

recovery

Figure 22.31 Cooling water system of the L27/38 engine, with the high-temperature

(HT) circuit on the left and low-temperature (LT) circuit on the right

Engine speed is controlled by a mechanical or electronic governor with

hydraulic actuator. All media systems are equipped with temperature and

pressure sensors for local and remote reading. The number and type of param-

eters to be monitored are speciﬁed in accordance with (but not limited to) the

classiﬁcation society requirements. Shutdown functions for lube oil pressure,

overspeed and emergency stop are provided as standard. The monitoring,

control and safety system is arranged for compatibility with MAN Diesel’s

CoCoS system for engine diagnosis, maintenance and planning, and spare

parts handling.

V28/33D engine

Developed by the British designer Ruston, the RK280 engine was inherited

by MAN Diesel when the German group acquired the UK portfolio of Alstom

Engines and transplanted to Augsburg as the MAN V28/33D series. The ﬁrst

production engines (V20-cylinder models) were delivered at end-2005 for

powering a monohull fast ferry; others in V12, V16 and V20 conﬁgurations

have since been supplied for high-speed catamaran ferries, a mega yacht and a

naval offshore patrol vessel.

A completely new medium-speed engine, the RK280 design had joined

the Ruston programme in 2001, offering a considerably higher output than

the long-established RK270 series (see Chapter 24) for commercial and naval

propulsion and genset drive applications (Figures 22.32–22.34). The 280 mm

bore engine was introduced as the world’s most powerful 1000 rev/min design,

released with an initial rating of 450 kW/cylinder. The programme of V12-,

16- and 20-cylinder models thus covers a power range from 5400 kW to

9000 kW. An output of 500 kW/cylinder was speciﬁed for the design, however,

equating to a future rating of 10 000 kW for the 20RK280 engine.

V28/33D engine 603

L21/31 and L27/38 propulsion engine data

L21/31 L27/38

Bore

210 mm 270 mm

Stroke 310 mm 380 mm

Cylinders 6–9L 6–9L

Speed (rev/min) 1000 800

Output (kW/cyl) 215 340

Power range (kW) 1290–1935 2040–3060

Mean eective pressure (bar) 24.1 23.5

Mean piston speed (m/s) 10.3 10.1

Combustion pressure (bar) 200 200

Five-cylinder versions are also oered for genset applications

604 Man Diesel

An STC (sequentially turbocharged) version of the V28/33D engine features

a digitally controlled system programmed to automatically switch off one of the

two turbochargers at low revolutions per minute, improving the amount of air

reaching the combustion chambers. STC, applied in installations requiring an

extended torque envelope, is controlled by the SaCoS electronic control unit.

The engine is designed to operate on middle distillate fuels, such as DMA or

DMB and equivalent speciﬁcations. A competitive speciﬁc fuel consumption of

less than 190 g/kW h is reported, with NOx emission levels of less than 10 g/kW h

from primary reduction measures alone. Compactness and lightness are reﬂected

Figure 22.32 V16-cylinder version of the 28/33D engine

V28/33D design data

Bore 280 mm

Stroke 330 mm

Cylinders V12, 16, 20

Output*

450 kW/cyl

rated speed 1000 rev/min

Mean eective pressure 26.6 bar

Mean piston speed 11 m/s

Power range 5400–9000 kW

Power density 5.1 kg/kW

Fuel consumption 190 g/kW h

*Continuous rating

V28/33D engine 605

A B

Key to main components

A Turbocharger

B Air filters

C Freshwater pumps

D Seawater outlet

E LT water outlet

F Fuel inlet

G Lubricating oil filter & dipstic

H Fuel lift pump

I Lubricating oil pump

J Fuel filters

K HT water outlet

L Duplex lubricating oil filter

M Lubricating oil cooler

N Heat shields

O Intercoolers

Figure 22.33 Cutaway of V28/33D engine showing the gear train for the camshaft and service pump drives

606 Man Diesel

in a dry weight of 46 tonnes and a power density of 5.1 kg/kW for the V20-

cylinder version, which measures 7.33 m long  2.1 m wide  3.18 m high. A

detailed analysis of all parts was carried out to achieve the high power-to-weight

and size ratios, and aluminium alloy materials were used where possible.

The V28/33D (RK280) design beneﬁted from experience with RK270 engines

powering fast ferries, as well as feedback from RK215 engine installations.

Advantage was also taken of advanced software packages, new development

methodologies and project management techniques. Areas of the RK270 design

that had proved particularly successful—such as the integrity of the bottom end

Figure 22.34 Cross-section of V28/33D engine