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

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for better distribution. A new exhaust valve cage (Figure 28.5) with a thin-

ner seat wall and more efﬁcient cooling from improved water circulation was

speciﬁed to reduce the valve seat temperature and extend valve life when the

engine burns fuels with high sodium and vanadium contents. Better cooling of

the cage seat and effective pulse turbocharging lowered the temperature of the

grandi Motori trieste 721

FigurE 28.3 gMt’s Bl550 design in in-line and V-cylinder form

Original version Bore-cooled version

A B

FigurE 28.4 Sections through gMt B550 cylinder head (left) and the redesigned

Bl550 component

722 Other Medium-Speed Engines

continuously rotated composite exhaust valves which comprise a Nimonic 80A

alloy head and anti-corrosion coated steel stem.

A much stiffer cylinder liner unit (Figure 28.6) was designed, without a

heat shield and bore cooled at the top near the gas-side wall. The cooling bores

are of the blind type in which the inlet and outlet water ﬂows are separated

by diaphragms, allowing the radial outlet holes to be positioned in the lower

part of the liner and thus eliminate a concentration of stresses in those areas

most affected by dynamic load ﬂuctuations below the cylinder head gasket.

Tests showed that the bore-cooling arrangement secures a lower peak tempera-

ture and a more uniform distribution on the piston ring rubbing surface. Load-

dependent cooling was speciﬁed as standard.

The composite pistons (steel crown and aluminium alloy skirt) carry three

compression and one oil scraper ring in chromed grooves. The upper two com-

pression rings were increased in thickness to withstand the higher combustion

pressure and reduce torsional deformation.

A subsequent development programme in 1992/93 resulted in the A55

design (Figure 28.7) which retained the 550 mm bore of its precursors but

1—Original valve cage

Exhaust gas

Flywheel side

200° 300°

400°

2—Valve cage with improved cooling

FigurE 28.5 temperature distributions of the gMt B550 valve cage and the

improved design for the Bl550 engine (21 bar mep and 450 rev/min)

featured an extended stroke (680 mm). An eight per cent power increase over

the BL550 series was derived—taking the speciﬁc output to 1250 kW/cylinder

at 425 rev/min—along with enhanced fuel economy. The redesign also sought sim-

pliﬁed maintenance procedures and higher reliability from a range comprising six,

eight and nine in-line and V12-, 14-, 16- and 18-cylinder models covering a power

band up to 22 500 kW. Special propulsion market targets included cruise ships and

high-powered ferries, GMT citing the low height of the A55 engine for its power

output: 5.765 m for the in-line version and 5.67 m for the V-cylinder model.

grandi Motori trieste 723

Composite version Bore-cooled version Cooling hole detail

with internal

diaphragm

FigurE 28.6 improved cooling arrangement for gMt Bl550 cylinder liner (B) over

original conguration (A)

FigurE 28.7 gMt’s A55 design

724 Other Medium-Speed Engines

The A55 beneﬁted from GMT’s technical collaboration with New Sulzer

Diesel, permitting elements of the Swiss designer’s successful ZA40S medium-

speed engine to be exploited. The longer stroke took the stroke/bore ratio from

1.15 to 1.24:1, giving a better thermal efﬁciency. This was achieved without

raising the cylinder head; a more compact piston allowed the same head cast-

ing to be used. A reduction in engine speed compared with the BL550 limited

the mean piston speed and yielded the increased output with virtually the same

brake mean effective pressure as the earlier model.

Fuel injection system improvements were also made. Fuel enters the valve

laterally rather than vertically, underwriting a reduced fuel pipe length and a

shorter fuel valve. The injection itself takes place over a shorter period, cover-

ing around 30° of the cycle, and at a higher pressure (around 1200 bar).

The crank mechanism and other components were also redesigned, mainly

to simplify maintenance. The connecting rod, for example, is in three parts (a

shank and two caps) connected by hydraulically tightened studs. Despite the

longer stroke, it was possible to house the crank mechanism in the same crank-

case as the BL550 by redesigning the crankshafts and connecting rods. The

bedplate and cylinder block remained virtually unchanged.

Most notable of the A55 reﬁnements was the adoption of Sulzer’s unique

rotating piston concept, previously unique to the ZA40S engine and its pred-

ecessors (Chapter 26). A bore-cooled steel crown is mated with a cast iron

skirt. Cast iron rather than aluminium alloy was speciﬁed to allow the operat-

ing clearance of the skirt to be reduced; this, together with the inertia from

the rotating piston, reduces impact velocities with the liner resulting from pis-

ton slap. The rotating piston (Figure 28.8) underwrites reliability and a lower

FigurE 28.8 gMt’s A55 design beneted from a Sulzer-derived rotating piston

lubricating oil consumption. Simpler and more efﬁcient turbocharging was

introduced. In-line and V-cylinder propulsion engines are served by a single-

pipe exhaust system associated with high efﬁciency and compact conﬁgura-

tion; an air/gas bypass is also provided.

GMT was also active in the popular 320 mm bore class, its A32 design

having emerged in the 1990s as a longer stroke derivative of the A320 engine

introduced in 1986. The 320 mm bore/390 mm stroke A32 series (Figure 28.9)

had a maximum continuous rating of 440 kW/cylinder at 750 rev/min and was

produced in six, eight and nine in-line and V12-, 14- and 16-cylinder versions

to cover a power range up to 7040 kW.

A monobloc casting of high-strength iron arranged for an underslung

crankshaft forms the structure of both in-line and V-cylinder engines. The

high-strength lamellar iron cylinder head (Figure 28.10) is secured by four stud

bolts for ease of dismantling and has a thick bore-cooled bottom plate for low

thermal loading and high stiffness. The inserted thin-walled exhaust valve seat

rings are directly cooled by water circulation to achieve a low seat temperature

and extended time-between-overhauls on heavy fuel.

High-strength cast iron cylinder liners have a thick bore-cooled collar for

low mechanical and thermal stresses. The composite pistons feature thin-forged

grandi Motori trieste 725

FigurE 28.9 gMt A32 design

726 Other Medium-Speed Engines

steel crowns and aluminium alloy skirts. The connecting rods are drop forged

in two pieces and withdrawable from the top along with the piston.

Reliable operation on residual fuels was addressed by basic design para-

meters (mean piston speed, compression ratio, combustion pressure and air–

fuel ratio) and attention to key component and system design, GMT citing:

l A facility to provide automatic load-dependent control of jacket cooling

water and charge air temperatures, gradually raising them with dimin-

ishing load to improve combustion, reduce fouling and maintain the

combustion chamber walls above the acidic condensation temperature to

prevent cold corrosion.

l Exhaust valves of Nimonic 80A material with corrosion-resistant coated

stems and rotating devices to prevent hot spots.

l Forged steel piston crown carrying corrosion- and wear-resistant

plasma-coated rings.

l High-pressure fuel injection system ensuring ﬁne atomization for better

ignition; and availability of a remote-controlled facility for recirculation

of fuel through the injectors at engine standstill for starting on fuels of

the highest viscosities.

l Bore cooling of the hot components of the combustion chamber (cyl-

inder liner, head and exhaust valve seats) through machined passages,

allowing precise temperature control in inhibiting both hot and cold

corrosion.

FigurE 28.10 Section and plan of gMt A32 cylinder head

GMT also developed 420 mm bore engines for a number of years. The

A420 had a stroke of 500 mm and ran at 500 rev/min to deliver 515 kW/cylin-

der, while the shorter-stroke (480 mm) A420H ran at 600 rev/min for an output

of 588 kW/cylinder.

Higher speed 230 mm bore GMT engines are covered in Chapter 30.

hiMSEn (hyunDAi hEAVy inDuStriES)

A proliﬁc South Korean builder of two-stroke and four-stroke diesel engines

under licence, Hyundai Heavy Industries developed its ﬁrst own-design

medium-speed engine, the 210 mm bore HiMSEN H21/32 series, for launch-

ing in 2001. Since then the HiMSEN brand has expanded to embrace 170 mm,

250 mm and 320 mm bore models based on common design principles and cov-

ering power demands up to 10 000 kW for genset and propulsion plant applica-

tions. Home and export market penetration was swiftly achieved, supported by

installations for the HHI group’s substantial newbuilding commitments.

Initially targeting marine genset drives, the H21/32 engine was also

intended for propulsion markets (Figure 28.11). A heavy fuel-burning 210 mm

bore/320 mm stroke design was selected for development; the high stroke/

bore ratio (1.52) and high compression ratio (17) were considered appropriate

hiMSEn (hyundai heavy industries) 727

FigurE 28.11 Cross-section of hiMSEn h21/32 engine, whose design principles

were extended to 170 mm, 250 mm and 320 mm models

728 Other Medium-Speed Engines

for fuel economy and low NOx emissions. A simpliﬁed conﬁguration with a

minimal number of components was pursued to enhance reliability and to ease

production and maintenance. Two sets of prototypes were built and tested to

conﬁrm engine performance and reliability. The current programme covers a

power band from 1200 kW to 1800 kW at 900 rev/min with in-line six-, eight-

and nine-cylinder models; speciﬁc ratings from 150 kW to 200 kW per cylinder

at 720/750/900 and 1000 rev/min are delivered.

Key structural and running elements of the design were optimized for

Hyundai’s production facilities, with generous dimensions underwriting mod-

erate fatigue safety factors. Ease of maintenance was addressed by adopting

a cylinder unit concept, allowing the cylinder head, valve train, fuel injection

equipment, cylinder liner, piston and connecting rod to be withdrawn as an

assembly for servicing onboard or ashore (Figure 28.12).

The engine block is a simple and robust structure of nodular cast iron. A

large volume of combustion air chamber and lubricating oil channel is incorpo-

rated but water spaces are excluded to avoid any risk of corrosion and ﬂooding

into the oil chamber. The nodular cast iron cylinder head features a V-type ﬁre

deck support to combat the high maximum ﬁring pressure (200 bar); the inlet

and exhaust ports were evolved in-house by Hyundai using its own ﬂow test

rig and computational ﬂuid dynamics (CFD) analysis. The structural design of

the head and the cylinder liner was optimized based on the CFD analysis of

coolant ﬂow as well as ﬁnite element analysis.

The two-piece piston comprises a steel crown and box-type steel skirt,

delivering lower deformation under high cylinder pressure. Two compression

rings and one oil scraper ring are ﬁtted, the top ring coated with chromium-

ceramic material on its running surface to curb wear. The connecting rod is a

three-piece marine head-type component, shot peened to prevent any fretting

FigurE 28.12 h21/32 engine cylinder unit

from relative movement of the mating surfaces of rod and big end. The crank-

pin bearing is an aluminium tri-metal Rillenlager type, and the main bearing an

aluminium bimetal component.

A special chromium–molybdenum steel camshaft incorporates a fuel cam

and intake and exhaust cams arranged as a one-piece element serving each

cylinder. The cam proﬁles were optimized using the Hermite Spline Curve

method developed by Hyundai. The robust fuel injection system is designed

for pressures up to 2000 bar. The injection pump has a roller tappet with gener-

ous dimensions, the injection pipe is of the short block type and the injection

valve has a high opening pressure capability with an oil-cooled nozzle body for

heavy fuel operation.

An innovative design of air cooler cover controls the cooling water ﬂow

and hence the combustion air temperature at low load; the air cooler is arranged

to function as a heater at low loads. ABB Turbo Systems’ compact TPS turbo-

charger is speciﬁed to boost engine efﬁciency, power density and durability,

offering the potential to support future rating rises.

The 250 mm bore HiMSEN H25/33 design emerged from a joint develop-

ment project with the Rolls-Royce group’s Bergen Diesel and was independ-

ently updated to suit Hyundai’s speciﬁc requirements. (Rolls-Royce offers the

engine as its C-series, Chapter 23.) The H25/33 programme embraces six-,

eight- and nine-cylinder models covering an output band from 1740 kW to

2610 kW at 900 rev/min.

A smaller bore (170 mm) version, the H17/28 series, was subsequently

introduced for genset drive duties in ﬁve- to eight-cylinder versions with rat-

ings from 575 kW to 960 kW at 900/1000 rev/min.

Hyundai stepped up its challenge to established medium-speed engine-

builders in 2007 with the launch of a contender in the popular 320 mm bore

propulsion and genset drive arena. With a speciﬁc rating of 500 kW/cylinder

at 720/750 rev/min, the H32/40 series covers power demands up to 4500 kW

from in-line six- to nine-cylinder propulsion models (see the following table).

hiMSEn (hyundai heavy industries) 729

HiMSEN H32/40P data

Bore, mm 320

Stroke, mm 400

Cylinders

6–9l

Output/cylinder, kW 500

Speed, rev/min 720/750

piston speed, m/s 9.6/10

Mean eective pressure, bar 25.9/24.9

max

, bar 190

power range 3000–4500

730 Other Medium-Speed Engines

The ﬁrst prototype, an eight-cylinder model, was type approved by the major

classiﬁcation societies in December 2006 for commercial availability in the

following year. The upper power limit will be raised to 10 000 kW by V-cylin-

der models. Tests on an H32/40V engine for type approval started in summer

2008, with market launching expected early in 2009.

Hyundai has also pursued development of an electronically controlled com-

mon rail fuel injection system (1600 bar pressure) for the H32/40 engine as a

measure for meeting Tier II emission requirements.

MirrlEES BlACKStOnE

An impressive medium-speed engine-building tradition was established by

Mirrlees Blackstone of the UK which traced its roots back to the ﬁrst British

licence arranged with Dr Diesel at the end of the 19th century. The Stockport-

based company was acquired by the MAN B&W Diesel (now MAN Diesel)

group from Alstom Engines in June 2000, along with Paxman and Ruston.

Mirrlees Blackstone’s ﬁnal programme—now phased out—was headed by

the 800 kW/cylinder MB430L engine, a 430 mm bore/560 mm stroke in-line

cylinder derivative of the MB430 design which was launched in V45° cylinder

form in 1985 with a shorter stroke of 480 mm. The two types were respectively

produced in six, eight and nine in-line and V12-, V16- and V18-cylinder ver-

sions to cover power demands up to 13 144 kW, the in-line engines running at

514 rev/min and the V-engines at 600 rev/min.

The MB430 (Figure 28.13) was introduced with a rating of 665 kW/

cylinder (later increased to 730 kW) and the following key component

speciﬁcation.

Crankshaft: underslung, thin web and high overlap.

Cylinder liners: centri-cast grey iron of heavy section with intensively

cooled ﬂanges.

Cylinder heads: individual, with six holding-down bolts, housing caged

exhaust valves and air inlet valves seated on pressed-in seat inserts; valve oper-

ation is by Y lever-type gear.

Connecting rods: three-piece construction with a palm-ended shank

secured to the large end block with four alloy steel studs, and the halves of the

large end block secured together by alloy steel bolts. Large end bearing shells

are of steel-backed lead–bronze design. Oilways are provided in the connect-

ing rod to facilitate lubrication of the piston pin bearings and deliver a copious

ﬂow of cooling oil to the piston.

Pistons: two-piece construction with heat-resistant alloy steel crown and

aluminium alloy skirt.

Camshafts: driven by a crankshaft gearwheel via compound intermediate

gears; all meshing points are lubricated and cooled by oil sprays; separate cyl-

inder casings house the camshafts and high-level fuel pumps.

Engine-driven lubricating oil and water pumps are mounted at the free end

of the engine; air manifolds are mounted on the outside of the vee; and turbo-

chargers and intercoolers can be located at either end of the engine.