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

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710 Wärtsilä

it to control the injection timing during engine operation. New possibilities thus

opened up for controlling different load modes and fuel qualities, even allowing

injection retardation when lower NOx emission values are demanded.

A contribution to reliability by the fuel pump design comes from splitting

the plunger loading between two cams and rollers, thus lowering the loading

on these components and underwriting safe operation at injection pressures up

to 2000 bar. The associated tappets for these components are both integrated in

the same housing as the tappets for the inlet and exhaust valves.

The high-pressure fuel system was designed and endurance tested at

2000 bar; an actual injection pressure of around 1400 bar thus represents

a substantial safety margin. No lubricating oil is required for the pump ele-

ment because the plunger has a wear-resistant low-friction coating. A proﬁled

plunger geometry keeps the clearance between the plunger and barrel small,

allowing only minimal oil to pass down the plunger; the small leakage is col-

lected and returned to the fuel system. Any chance of fuel mixing with the lube

oil is eliminated. Both the nozzle and nozzle holders are made of high-grade

hardened steel to withstand the high injection pressures and, combined with oil

cooling of the nozzles, to foster extensive nozzle lifetimes.

Low-pressure fuel system safety is underwritten by the Wärtsilä-patented

multi-housing concept. The fuel line consists of channels drilled in cast parts

which are clamped ﬁrmly on the engine block and connected to each other by

simple slide-in connections for ease of assembly and disassembly. The pumps

are connected together to form the complete low-pressure fuel line with both

feed and return channels; any need for welded pipes is eliminated. Safety is

further enhanced by housing the entire low-pressure and high-pressure systems

in a fully covered compartment.

Turbocharging system: based on non-cooled turbochargers with inboard

plain bearings lubricated from the engine’s lube oil system. The Spex turbo-

charging system is standard, with the option of exhaust waste gate or air bypass

321

Injector

Delivery valve

Timing

plunger

Quantity

plunger

– tappets on cam base

circle

– filling of injection pump

– quantity plunger shuts

off spill port

– excessive fuel out to

low pressure side

through filling port

– both ports are shut off

– delivery valve lifts

– start of injection

– spill port opens

– excessive fuel out to

low-pressure side

through spill port

– end of injection

Figure 27.33 Functions of twin plungers of fuel pump for the Wärtsilä 64 engine

according to the application. Spex, which exploits the pressure pulses without

disturbing the cylinder scavenging, is described in the section Wärtsilä 46. The

interface between the engine and turbocharger is streamlined, eliminating all

the adaptation pieces and piping formerly used.

Cooling system: split into separate HT and LT circuits (Figure 27.34). The

cylinder liner and cylinder head temperatures are controlled through the HT cir-

cuit; the system temperature is kept at a high level (around 95°C) for safe igni-

tion/ combustion of low-quality heavy fuels, including operation at low loads. An

additional advantage is maximum heat recovery. To further increase the recov-

erable heat from this circuit, it is connected to the HT part of the double-stage

charge air cooler. The HT water pump is integrated in the pump cover module at

the free end of the engine; the complete HT circuit is thus virtually free of pipes.

The LT circuit serves the LT part of the charge air cooler and the built-on

lube oil cooler. It is fully integrated with engine parts such as the LT water

pump with pump cover module, the LT thermostatic valve with the lube oil

module and transfer channels in the engine block. In addition, the LT circuit

provides separate cooling of the exhaust valve seats and a lower seat/valve tem-

perature, thus promoting long lifetimes for these components. Directly driven

pumps ensure safe operation even during a short power cut.

Lubricating oil system: all W64 engines are equipped with a complete

built-on lube oil system comprising:

l Pump cover module: engine-driven main screw pump with built-in

safety valve; pre-lubricating module; electrically driven pre-lubricating

screw pump; pressure regulating valve; and centrifugal ﬁlter for lube oil

quality indication.

Air separator

Heat

recovery

Central

cooler

Exp.

0.7–1.5

bar

75°C

Valve

seats

95°C

55°C

Luboil

cooler

Charge

air cooler

Charge

air cooler

Pre-

heating

38°C

Cylinder

jacket

Figure 27.34 Cooling water system of Wärtsilä 64 engine

Wärtsilä 64 711

712 Wärtsilä

l Lubricating oil module: lube oil cooler; oil thermostatic valves; full ﬂow

automatic ﬁlter; and special running-in ﬁlters before each main bearing,

camshaft line and turbocharger.

On in-line cylinder engines the lubricating oil module is always located at

the back side of the engine, while on V-engines it can be built on the engine at

the ﬂywheel or free end, depending on the turbocharger position. The lube oil

ﬁltration is based on an automatic back-ﬂushing ﬁlter requiring minimal main-

tenance and no disposable ﬁlter cartridges.

Automation system: an engine-integrated system, WECS, is standard and

has these main elements:

l The main control unit (MCU) cabinet, which comprises the MCU itself,

a relay module with back-up functions, a local display unit (LDU), con-

trol buttons and back-up instruments. The MCU handles all communica-

tion with the external system.

l The distributed control unit (DCU) handling signal transfer over a CAN

bus to the MCU.

l The sensor multiplexing units (SMU) transferring sensor information to

the MCU.

Software loaded into the system is easily conﬁgured to match the instru-

mentation and the safety and control functions required for each installation.

The MCU cabinet is well protected and built into the engine; most of the

remaining hardware is housed in a special electrical compartment alongside

the engine.

W64 in-service experience

Observations made at the 12 000-h overhaul of the ﬁrst Wärtsilä 64 engine in

marine service (a seven-cylinder model) revealed no evidence of heavy carbon

deposits on the cylinder head ﬂame deck. Excellent behaviour was indicated by

the exhaust valves, with no failure or burn marks on the contact surface with the

seat ring and no sign of wear or corrosion on the valve stem. The wear on the

ring grooves fell within the permitted limit, promising an expected lifetime of at

least 86 000 h; only minor carbon deposits were noted on the ring grooves (aver-

aging 60 microns on the ﬁrst groove, and no deposits on the other two grooves).

Lube oil consumption and its quality, especially in an engine running on

heavy fuel oil, is a useful indicator of wear. The anti-polishing ring used on

all Wärtsilä engines ensured that consumption and wear of the piston top and

liner upper part remained low. Good lube oil quality also results in less carbon

deposits on the piston crown-cooling gallery, and consequently the absence of

hot corrosion problems on top of the piston crown.

The connecting rods inspected showed no fretting marks on the mating sur-

face and no cavitation marks on the oil feeding channels. The big end bearings

(tri-metal type) proved to work very well without cavitation or fretting; some

scratches were found on the running surface but the overlay had worked well.

The extensive use of integrated channels adopted in the W64 design contrib-

uted to a lack of oil leakage anywhere around the installation; similarly, the

absence of piping reduces problems during overhauls.

A few failures were reported, however, some resulting from a combination

of second-order causes:

Fuel injection equipment: some problems emerged in the sealing and minor

components on the injection valve and were addressed in cooperation with the

supplier, allowing the nozzle lifetime to be extended up to 7000 h.

Cylinder head stud: failures on two installations were caused by poor qual-

ity in the material and the production process (rolling of the large M110 

6 size thread) combined with high ﬂexural vibration. It is unlikely that any

of these factors alone would have caused the failure. A new damping device

tested on the prototype engine yielded lower vibration levels and was adopted.

Intermediate gear stud: three cases of failure were logged, the prob-

lem solved by reducing the free length of the stud stem. A stem support was

integrated on the structure and helped to achieve the targeted reduction in

stud stress.

COMMON rAiL eNgiNeS

Wärtsilä claims to have pioneered the application of computer-controlled CR

fuel injection systems operating on heavy fuel, its developments for medium-

speed engines starting in 1997 and the ﬁrst deliveries following in 2000.

Numerous installations are now in service and CR fuel injection can be speci-

ﬁed throughout the programme for all models except the W64 engine. The sys-

tem is described earlier under the W46F section and more fully in Chapter 8.

See Chapter 2 for Wärtsilä 32 and 50 dual-fuel engines; Chapter 3 for

Enviroengine versions of the W32 and W46 designs; and Chapter 8 for

Wärtsilä’s common rail fuel injection system.

Common rail engines 713

715

C h a p t e r | t w e n t y e i g h t

Other Medium-Speed

Engines

AnglO BElgiAn COrpOrAtiOn

Two medium-speed engine series are ﬁelded by the Anglo Belgian Corporation

(ABC) for propulsion and auxiliary power applications. The 242 mm bore/

320 mm stroke DX type is produced in three, six and eight in-line cylinder ver-

sions to cover an output band up to 883 kW at 720 or 750 rev/min. DX models

are naturally aspirated; DXS models are turbocharged; and DXC models are

turbocharged and intercooled.

The DZ type is a 256 mm bore/310 mm stroke design offered in six and

eight in-line and V12- and V16-cylinder form to serve power demands up to

3536 kW at 720/750/800/900 and 1000 rev/min. The turbocharged/intercooled

engine is designed for burning heavy fuel with suitable adaptation. Its nodu-

lar cast iron piston features a Hesselman-type head which is oil cooled by the

shaker effect, and four rings: a chrome ﬁre ring, two compression rings and an

oil scraper ring located above the ﬂoating piston pin.

The cylinder liner is produced from a wear-resistant centrifugal cast iron

slightly alloyed with chromium. The slightly alloyed cast iron cylinder head

is ﬁtted with two inlet and two Stellited exhaust valves. An intermediate deck

assures a forced water circulation around the valve seats and the centrally

mounted fuel nozzle. The one-piece crankshaft, forged from 42CrMo4 steel

and with induction-hardened running surfaces, is arranged in a box-type crank-

case of nodular cast iron. An additional bearing on the ﬂywheel side limits

crankshaft deﬂection and bearing wear.

ABC effectively doubled the power threshold of its programme in 2000

with V-cylinder variants of the in-line DZ design, the new V12 and V16 mod-

els offering outputs of 2650 kW and 3536 kW at 720–1000 rev/min (Figure

28.1). A 45° V-bank was selected, fostering an overall width of 1.65 m; an

engine height of 2.5 m is quoted, with lengths of 4.18 m and 4.94 m respec-

tively for the V12 and V16 models. As much commonality of parts as possible

with the in-line cylinder models was sought in the development, but new com-

ponents were designed to permit a 20 per cent rating rise in the future and to

716 Other Medium-Speed Engines

support a peak cylinder pressure of 150 bar. Easy accessibility to parts needing

frequent control or regular preventative maintenance was also pursued.

DAihAtSu

A Japanese contender in the domestic and international small-bore medium-

speed engine arenas, Daihatsu evolved its current programme from the PS

series which was developed in 1950 and helped establish the company as a

major supplier of auxiliary diesel engines. Some 10 000 examples of the PS-26

model, for example, were sold worldwide.

The PS was succeeded in 1967 by a second-generation engine, the DS

series, whose development goals focused on high output, low speciﬁc fuel con-

sumption and compactness for genset and main engine roles. Market demands

Cover charge

air manifold

Integrated

charge air

manifold

Stiff

intermediate

deck

Integrated

water inlet

manifold

Cross

Bolting main

bearing cap

Hydraulic

tightened

main bearing

cap studs

and conrod

studs

Camshaft

tunnel

Main oil

gallery

FigurE 28.1 V-version of Anglo Belgian Corporation’s DZ engine

for higher fuel economy with the capability to burn lower-grade bunkers led

to the introduction of a third generation engine, the longer stroke DL series,

which includes eight medium-speed models with bore sizes ranging from

190 mm to 400 mm and covering an output band up to 4415 kW. The DL series

remained in the production programme alongside the fourth generation DK

series, designed to address requirements in the 1990s for high reliability, dura-

bility and extended service intervals.

The DK series (Figure 28.2) embraces 200 mm, 260 mm, 280 mm, 320 mm

and 360 mm bore medium-speed models covering power demands up to

6325 kW at 600/720/750/900 rev/min from in-line and V-cylinder models.

The engine is based on a one-piece cast iron frame designed and manu-

factured for high rigidity to minimize noise and vibration. Large crankcase

windows are arranged on both sides to ease access for maintenance. The

thick bore-cooled ﬂame plate of the cylinder head seeks improved mechani-

cal and heat resistance, and an extended service life. The head is secured by

four hydraulically tightened studs. The crankshaft incorporates hardened large

diameter pins and journals forged in one piece and supported by heavy-duty

bearings for durability. The connecting rod is formed from three pieces with

horizontal joints to reduce piston overhauling height and yield high rigidity.

A gap between the DK-20 and DK-28 models was ﬁlled by the 260 mm

bore/380 mm stroke DK-26, intended as a genset drive or propulsion plant for

small ferries, cargo vessels and tugs. Produced as in-line ﬁve- and six-cylinder

models, the design develops up to 1710 kW at 720/750 rev/min.

Daihatsu 717

FigurE 28.2 Daihatsu DK-28 engine in six-cylinder form

718 Other Medium-Speed Engines

Similar design principles to the previous DK models are exploited by

the DK-26, notably a high stroke/bore ratio of 1.46:1, but the engine fea-

tures an improved combustion chamber proﬁle and higher compression ratio.

Combustion is claimed to be stable over the entire load range when operating

on heavy fuel, without compromising NOx emission and fuel consumption per-

formance. The engine frame is ﬁtted with deep mounting feet with I-contour

sections so that rubber elements for resilient supports can be attached directly

to the feet. The charge air manifold, lubricating oil gallery and cooling water

passages are all integrated in the frame, creating a double-wall conﬁguration to

help reduce noise and vibration.

A simple yet efﬁcient exhaust layout designated Daihatsu single-pipe

(DSP) exhaust system recovers gas energy effectively by allowing a good

match to the turbocharger. An NOx emission level of 9.4 g/kW h and a speciﬁc

fuel consumption of 185 g/kW h at full load are claimed, with temperatures of

key combustion chamber components well within the optimum range.

Supplied with matching gearboxes, the DKM series is produced in 200 mm,

250 mm, 260 mm, 280 mm and 360 mm bore sizes in six- and eight-cylinder

models covering an output band from 880 kW to 4413 kW at speeds from

900 rev/min to 600 rev/min.

A new auxiliary engine, the DC-17, was introduced in 2001 in ﬁve- and

six-cylinder versions offering generator outputs of 440 kW and 560 kW at

900/1000 rev/min. The 170 mm bore/270 mm stroke design is released for

heavy fuel-burning applications.

Blending experience from the DK-series and the DC-17 engine, Daihatsu

subsequently developed a 320 mm bore version of the latter. Six- and eight-cyl-

inder variants of this DC-32 design deliver outputs of 2905 kW and 3884 kW

at 720/750 rev/min. A signiﬁcant reduction in the number of overall parts con-

tributed to the designers’ goals of compactness, simplicity and light weight,

Daihatsu DC-32 data

Bore, mm 320

Stroke, mm 400

Stroke/bore ratio 1.25:1

Cylinders

6/8l

Output, kW 2905/3844

Speed, rev/min 720/750

piston speed, m/s 9.6/10

Mean eective pressure, bar 23.9/25.1

max

, bar 177

Weight (dry), kg

35 000/40 000

ease of installation and maintenance, high reliability and durability, low oper-

ating costs and environmental friendliness. Swift withdrawal of a complete

unit assembly (cylinder head, piston, connecting rod and liner) is facilitated,

although conventional dismantling of the individual elements is possible.

Engine frame: a cast iron high-tensile monobloc structure incorporating

inlet air, oil and coolant passages, and arranged for underslung main bearings

with hydraulically tightened main and side bolts. The gearcase is attached to

the front of the frame, along with the turbocharger, air cooler, oil cooler, cool-

ing water pump, oil pump and ﬁlter.

Crankshaft and bearings: the continuous grain ﬂow forged crankshaft fea-

tures increased crankpin and journal diameters for optimized surface pressure

and oil ﬁlm thickness. Large-capacity weights are applied for better rotational

balance adjustment and reduced vibration. The ﬂywheel is attached to the rear of

the shaft, and the gears for the camshaft and pumps are mounted at the other end.

The main and crankpin bearings are of a special corrosion- and wear-resistant

aluminium alloy with a thrust metal attached to the ﬂywheel side No.1 bearing.

Camshaft and timing gears: air inlet valve, exhaust valve and fuel injec-

tion cams are arranged on a large diameter unit camshaft built in two-cylinder

sections. The camshaft timing gear is attached to the front end of the engine,

positioned between the crank gear and cam gear. Each gear is surface hardened

for durability.

Cylinder liner: the thick-walled liner of high-wear resistance cast iron is

bore cooled, the water-cooling only its upper part and the passages optimized

for even water distribution. An anti-polishing ring (termed a ‘liner protect ring’

by Daihatsu) is incorporated at the top of the liner to reduce lube oil consump-

tion and liner wear, extending maintenance intervals and liner life.

Piston and connecting rod: the composite piston features a steel crown

and a nodular cast iron skirt, with the grooves for the top and second rings

induction surface hardened for durability. Effective forced piston cooling is

performed by oil passing through the connecting rod and piston pin. The hori-

zontally cut three-piece rod design allows the piston to be overhauled without

removing the crankpin bearing section; it also reduces the height necessary for

piston withdrawal.

Cylinder head and valves: a special high-strength cast iron improves the

durability of the head which is fastened to the engine frame by four hydrau-

lically tightened bolts. The twin inlet and twin exhaust valves are ﬁtted with

rotators. The water-cooled exhaust valve seats are attached directly to the cyl-

inder head. The fuel injection valve and the surrounding area at the centre of

the head are cooled by the tornado cooling method (Daihatsu patent), allow-

ing non-cooled valves to be used even for heavy fuel operation. Piping on and

around the head is eliminated to ease maintenance.

Fuel injection: Bosch-type high-pressure injection pumps with built-in

tappets and a closed-type plunger barrel are used, with a pressure valve incor-

porated in the fuel outlet valve. The non-cooled heat-treated injectors are con-

nected to the pumps by a forged high-pressure pipe.

Daihatsu 719

720 Other Medium-Speed Engines

Turbocharging and exhaust system: the DSP exhaust system, promoting

a higher turbocharging efﬁciency and simplicity, is located on the same side

as the inlet air duct for easier maintenance of the manifold and bellows. The

number of components is reportedly 40 per cent fewer than in a conventional

system. A two-stage air cooler facilitates charge air heating at low engine loads.

Freshwater cooling system: split into separate high-temperature and low-

temperature circuits; a two-stage intercooler system beneﬁts combustion when

burning heavy fuel at low loads. The main cooling water outlet pipes for the

engine cylinders are connected by sliding ﬂanges for ease of dismantling.

Lube oil ﬁlter: an automatic, continuous back-ﬂushing ﬁlter serves both

engine and turbocharger, eliminating the need for an extra ﬁlter for the latter.

Daihatsu has developed a common rail fuel injection system for the DK-

series and has investigated two-stage turbocharging systems in conjunction

with the Miller cycle for applications calling for very low NOx emissions.

grAnDi MOtOri triEStE

A wide range of medium-speed engines were designed and produced over

many years by Grandi Motori Trieste (GMT), which was founded in the late

1960s to pool the diesel engine expertise and resources of Fiat, Ansaldo and

CRDA, and rationalize the Italian engine-building industry. GMT later became

part of the state-owned Fincantieri shipbuilding group’s diesel engine division

and in 1997 entered a new era as a member of the Wärtsilä Corporation (see

Chapter 27), after which its own design portfolio was phased out.

GMT’s last large engine, the A55 series, was the ﬁnal evolution of a

550 mm bore model ﬁrst designed and produced in Torino by Fiat Grandi

Motori in the early 1970s. The original A550 design with a 590 mm stroke and

a rating of 880 kW/cylinder was developed into a B550 version with an out-

put of 1080 kW/cylinder at 450 rev/min. The BL550 derivative (Figure 28.3),

launched in 1986, retained the same bore size and running speed but exploited

a longer stroke (630 mm) to yield a 10 per cent higher output and a reduc-

tion in speciﬁc fuel consumption on low-grade fuel. The power uprating—to

1213 kW/cylinder—was achieved with a modest increase in mean effective

pressure (from 20.6 bar to 21.6 bar) and a rise in mean piston speed from

8.85 m/s to 9.45 m/s.

Higher mechanical and thermal loads dictated some changes in the design

of combustion chamber elements and running gear but the engine frame and

bedplate remained separate units of nodular cast iron for the in-line cylinder

engines. Unlike the original design, the eight- and nine-cylinder bedplates and

frames are monobloc castings secured by tie-rods; however, the V-type engines

feature a welded steel bedplate and a special cast iron frame for which tie-rods

are unnecessary and replaced by stud bolts.

The cylinder head for the BL550 engine (Figure 28.4) was redesigned to

assure a more even distribution of temperatures between the exhaust valves and

the fuel nozzle, and additional bore cooling introduced in the gas-side walls