5510-0145-00ppr_WEB

Propulsion of 2,200-2,800 teuContainer Vessel

Content

Introduction .................................................................................................5

EEDI and Major Ship and Main Engine Parameters........................................6

Energy Efficiency Design Index (EEDI) ......................................................6

Major propeller and engine parameters ....................................................7

2,500 teu container vessel ......................................................................8

Main Engine Operating Costs – 20.0 knots ...................................................9

Fuel consumption and EEDI .................................................................. 10

Operating costs .................................................................................... 12

Main Engine Operating Costs – 19.0 knots ................................................. 13

Fuel consumption and EEDI .................................................................. 13

Operating costs .................................................................................... 15

Retrofit of Existing 7L70ME-C8.2 with EGB-LL for Reduced Ship Speeds ... 16

Exhaust gas bypass – Low Load (EGB-LL) ............................................ 17

Saving in operating costs and payback time .......................................... 17

Summary ................................................................................................... 18

3Propulsion of 2,200-2,800 teu Container Vessel

Propulsion of 2,200-2,800 teu Container Vessel

Introduction

The main ship particulars of 2,200-

2,800 teu container vessels are nor-

mally approximately as follows: the

overall ship length is 210 m, breadth 30

m and scantling draught 11.4-12.0 m,

see Fig. 1.

Recent development steps have made

it possible to offer solutions which will

enable significantly lower transporta-

tion costs for larger feeder container

vessels as outlined in the following.

One of the goals in the marine industry

today is to reduce the impact of CO2

emissions from ships and, therefore,

to reduce the fuel consumption for the

propulsion of ships to the widest pos-

sible extent at any load.

This also means that the inherent de-

sign CO2 index of a new ship, the so-

called Energy Efficiency Design Index

(EEDI), will be reduced. Based on an

average reference of the CO2 emission

from existing earlier built container ves-

sels, the CO2 emission from new con-

tainer vessels in gram per dwt per nau-

tical mile must be equal to or lower than

the reference emission figures valid for

the specific container vessel.

This drive may often result in opera-

tion at lower than normal service ship

speeds compared to earlier, resulting

in reduced propulsion power utilisation.

The design ship speed at Normal Con-

tinuous Rating (NCR), including 15%

sea margin, used to be as high as 22-

23 knots. Today, the ship speed may

be expected to be lower, possibly 19-

20 knots, or even lower.

A more technically advanced develop-

ment drive is to optimise the aftbody

and hull lines of the ship – including bul-

bous bow, also considering operation in

ballast condition. This makes it possible

to install propellers with a larger pro-

peller diameter and, thereby, obtaining

higher propeller efficiency, but at a re-

duced optimum propeller speed, i.e. us-

ing less power for the same ship speed.

Fig. 1: Large feeder container ship


Furthermore, the wish to reduce fuel

costs and thereby to reduce the design

ship speed from 22-23 knots to about

19-20 or even lower, may involve lower

main engine power, but also a demand

to have lower engine speeds.

As the two-stroke main engine is di-

rectly coupled with the propeller, the

introduction of the ultra long stroke

G60ME-C9.2 engine with even lower

than usual shaft speed than the exist-

ing S60ME-C8.2 will meet this goal.

The main dimensions for these engine

types, and for the existing L70ME-C8

engine, normally used in the past, are

shown in Fig. 2. Also K80 engine types

were often used.

On the basis of a case study of a 2,500

teu feeder container vessel in compli-

ance with IMO Tier II emission rules,

this paper shows the influence on fuel

consumption when choosing the new

G60ME-C9.2 engine compared with

the existing S60ME-C8.2 and the ear-

lier and normally used larger L70ME-

C8.2 engine. The layout ranges of 6

and 7G60ME-C9.3 engines compared

with 6 and 7S60ME-C8.2 together with

the existing 7L70ME-C8.2 are shown

later in Fig. 4.

L70ME-C8.2 G60ME-C9.2S60ME-C8.2

3,770

1,26

2

1,50

0

1,30

0

1,99

0

2,33

0

2,06

7

10,4

18

11,5

88

10,7

38

4,2203,980

Fig. 2: Main dimensions for the new G60ME-C9.2 and existing S60ME-C8.2 engines and the L70ME-C8 applied earlier

EEDI and Major Ship and Main Engine Parameters

Energy Efficiency Design Index

(EEDI)

The IMO (International Maritime Organi-

sation) based Energy Efficiency Design

Index (EEDI) is a mandatory index re-

quired on all new ships contracted after

1 January 2013. The index is used as

an instrument to fulfil international re-

quirements regarding CO2 emissions

on ships. EEDI represents the amount

of CO2 emitted by a ship in relation to

the transported cargo and is measured

in gram CO2 per dwt per nautical mile.

6 Propulsion of 2,200-2,800 teu Container Vessel

Fig. 3: Influence of propeller diameter and pitch/diameter ratio on SMCR for a 2,500 teu feeder container

vessel operating at 19.0 knots

The EEDI value for container ships is

calculated on the basis of 70% of the

maximum cargo capacity, propulsion

power, ship speed, SFOC (Specific

Fuel Oil Consumption) and fuel type.

Depending on the date of contract,

the EEDI is required to be a certain

percentage lower than an IMO defined

reference value depending on the type

and capacity of the ship.

The main engine’s 75% SMCR (Speci-

fied Maximum Continuous Rating) fig-

ure is as standard applied in the cal-

culation of the EEDI figure, in which

also the CO2 emission from the auxiliary

engines of the ship is included. How-

ever, certain correction factors are ap-

plicable, e.g. for installed waste heat

recovery systems.

According to the rules finally decided

on 15 July 2011, the EEDI of a new ship

is reduced to a certain factor compared

to a reference value. Thus, a ship built

after 2025 is required to have a 30%

lower EEDI than the 2013 reference fig-

ure, see later in Figs. 8 and 14.

Major propeller and engine param-

eters

In general, the highest possible pro-

pulsive efficiency required to provide a

given ship speed is obtained with the

largest possible propeller diameter d,

in combination with the corresponding,

optimum pitch/diameter ratio p/d.

A lower number of propeller blades, for

example when going from 5 to 4 blades

if possible, means approximately 10%

higher optimum propeller speed, and

the propeller efficiency will be slightly

increased, and vice versa when going

from 5 to 6 blades, see later in Fig. 4.

As an example, this is illustrated for a

2,500 teu feeder container ship with

a 5-bladed FP propeller and with a

service ship speed of 19 knots, see

the black curve in Fig. 3. The needed

propulsion SMCR (Specified Maximum

Continuous Rating) power and speed

is shown for a given optimum propeller

diameter d and p/d ratio.

According to the black curve, the ex-

isting propeller diameter of 6.8 m may

have the optimum pitch/diameter ratio

of 0.95, and the lowest possible SMCR

shaft power of about 12,540 kW at

about 97 r/min.

The black curve shows that if a bigger

propeller diameter of 7.2 m is possible,

the necessary SMCR shaft power will be

reduced to about 12,280 kW at about

87 r/min, i.e. the bigger the propeller,

the lower the optimum propeller speed.

If the pitch for this diameter is changed,

the propulsive efficiency will be re-

duced, i.e. the necessary SMCR shaft

power will increase, see the red curve.

The red curve also shows that propul-

sion-wise it will always be an advantage

to choose the largest possible propel-

ler diameter, even though the optimum

pitch/diameter ratio would involve a

too low propeller speed (in relation to

the required main engine speed). Thus,

when using a somewhat lower pitch/

diameter ratio, compared with the op-

timum ratio, the propeller/engine speed

may be increased and will only cause a

minor extra power increase.

The efficiency of a two-stroke main en-

gine particularly depends on the ratio of

the maximum (firing) pressure and the

mean effective pressure. The higher the

ratio, the higher the engine efficiency,

i.e. the lower the Specific Fuel Oil Con-

sumption (SFOC).

Furthermore, the higher the stroke/bore

ratio of a two-stroke engine, the higher

11,000

12,500

13,000

11,500

12,000

13,500

60 70 80 90 100 110 r/minEngine/propeller speed at SMCR

PropulsionSMCR power

kW

Power and speed curve for the given propeller diameterd = 7.2 m with different p/d ratios

Power and speed curve for various propeller diameters (d) with optimum p/d ratio

SMCR power and speed are inclusive of:15% sea margin10% engine margin 5% propeller light running

5-bladed FP-propellersd = Propeller diameterp/d = Pitch/diameter ratio Design Ship Speed = 19.0 knDesign Draught = 10.0 m

S60ME-C8.2

G60ME-C9.2

1.201.10 0.900.98

0.950.80

7.6 m

1.01

7.2 m

6.8 m

dp/d

p/d


0

5,000

10,000

15,000

20,000

25,000

30,000

60 70 80 90 100 110 120 130 140 r/minEngine and propeller speed at SMCR

PropulsionSMCR powerkW

M1

M

M2’

M3’

M1’M4’

M6

M5’

M5

M4 M2M37G60ME-C9.2

6G60ME-C9.2

6L70ME-C8.2

7S60ME-C8.2

6S60ME-C8.2

7L70ME-C8.28L70ME-C8.2

Future7.6 m × 5

7.6 m × 4 7.2 m × 4 6.8 m × 4

Existing7.2 m × 5

Existing7.0 m × 6

Existing6.8 m × 5

23.0 kn

22.0 kn

21.0 kn

20.0 kn

19.0 kn

18.0 kn

∝

∝

∝

∝

∝

∝

Dprop × = Nblade:

23.0 kn (for EEDI calculations)23.0 kn, 7.0 m × 6MM = 26,160 kW × 108 r/min (8L70ME-C8.2)

22.0 kn22.0 kn, 7.1 m × 5M = 21,780 kW × 108 r/min (7L70ME-C8.2)

20.0 kn20.0 kn, 6.7 m × 5M1 = 15,200 kW × 105 r/min (7S60ME-C8.2)

20.0 kn, 7.0 m × 5M2 = 14,970 kW × 97 r/min (7S60ME-C8.2)

20.0 kn, 7.0 m × 5M3 = 14,970 kW × 97 r/min (6G60ME-C9.2)

20.0 kn, 7.4 m × 5M4 = 14,730 kW × 89 r/min (6G60ME-C9.2)

20.0 kn, 7.4 m × 5M5 = 14,730 kW × 89 r/min (7G60ME-C9.2)

20.0 kn, 7.6 m × 5M6 = 14,570 kW × 84 r/min (7G60ME-C9.2)

19.0 kn19.0 kn, 6.7 m × 5M1’ = 12,570 kW × 98 r/min (6S60ME-C8.2)

19.0 kn, 7.0 m × 5M2’ = 12,420 kW × 92 r/min (6S60ME-C8.2)

19.0 kn, 7.0 m × 5M3’ = 12,420 kW × 92 r/min (6G60ME-C9.2)

19.0 kn, 7.4 m × 5M4’ = 12,180 kW × 83 r/min (6G60ME-C9.2)

19.0 kn, 7.6 m × 5M5’ = 12,070 kW × 79 r/min (6G60ME-C9.2)

4, 5 and 6-bladed FP-propellersconstant ship speed coefficient ∝ = 0.19

SMCR power and speed are inclusive of:15% sea margin10% engine margin5% light running

Tdes = 10.0 m

108 r/min97 r/min

105 r/min

MM

Fig. 4: Different main engine and propeller layouts and SMCR possibilities (M1, M2, M3, etc. for 20.0 knots and M1’, M2’, M3’, etc. for 19.0 knots) for a 2,500

teu container ship operating at 20.0 knots and 19.0 knots, respectively

the engine efficiency. This means, for

example, that an ultra long stroke en-

gine type, as the G60ME-C9.2, may

have a higher efficiency compared with

a shorter stroke engine type, like a

super long stroke S60ME-C8.2 and a

long stroke L70ME-C8.2.

The application of new propeller design

technologies may also motivate use of

main engines with lower rpm. Thus, for

the same propeller diameter, these pro-

peller types can demonstrate an up to

4% improved overall efficiency gain at

the same or a slightly lower propeller

speed.

This is valid for propellers with Kappel

technology available at MAN Diesel &

Turbo, Frederikshavn, Denmark.

Furthermore, due to lower emitted

pressure impulses, the kappel propel-

ler requires less tip clearance that can

be utilised for installing an even larger

propeller diameter, resulting in a further

increase of the propeller efficiency.

Hence, with such a propeller type,

the advantage of the new low speed

G60ME-C9.2 engine can be utilised

also in case a correspondingly larger

propeller cannot be accommodated.

2,500 teu container vessel

For a new 2,500 teu feeder container

ship, the following case study illus-

trates the potential for reducing fuel

consumption by reduced ship speed

and by increasing the propeller diam-

eter and introducing the G60ME-C9.2

as main engine.


The ship particulars assumed are as

follows:

Deadweight, scantling dwt 34,800

Scantling draught m 11.4

Deadweight, design dwt 27,700

Design draught m 10.0

Length overall m 203.0

Length between pp m 197.0

Breadth m 30.0

Sea margin % 15

Engine margin % 10

Design ship speed kn (22) 20.0 and 19.0

Type of propeller FPP

No. of propeller blades 5

Propeller diameter m target

Based on the above-stated average

ship particulars assumed, we have

made a power prediction calculation

(Holtrop & Mennen’s Method) for dif-

ferent design ship speeds and propel-

ler diameters, and the corresponding

SMCR power and speed, point M,

for propulsion of the container ship is

found, see Fig. 4. The propeller diame-

ter change corresponds approximately

to the constant ship speed factor α =

0.19 [ref. PM2 = PM1 × (n2/n1)α.

Referring to the two reduced ship

speeds of 20.0 knots and 19.0 knots,

respectively, three potential main engine

types, pertaining layout diagrams and

SMCR points have been drawn-in in Fig.

4, and the main engine operating costs

have been calculated and described.

For the reduced ship speeds, but with-

out increasing the propeller diameter,

the old S60ME-C8.2 may be relevant.

The existing L70ME-C engine type (108

r/min) has often been used in the past as

prime movers in the existing 2,200-2,800

teu large feeder container ships with a

relatively high ship speed of 22.0 kn. This

engine type is also included in the main

engine comparisons when operating at

20.0 and 19.0 knots, respectively.

A comparison between the new

G60ME-C9.2 and the existing S60ME-

C8.2 and L70ME-C8.2 therefore is of

major interest in this paper.

It should be noted that for the S60ME-

C8.2 and the G60ME-C9.2, the ship

speed stated refers to normal continu-

ous rating NCR = 90% SMCR includ-

ing 15% sea margin. If based on calm

weather, i.e. without sea margin, the

obtainable ship speed at NCR = 90%

SMCR will be about 0.8 knots higher

than the design ship speed.

If based on 75% SMCR and 70% of

maximum dwt., as applied for calcula-

tion of the EEDI, the ship speed will be

about 0.2 knots higher than the design

ship speed, still based on calm weather

conditions, i.e. without any sea margin.

As the existing L70ME-C8.2 has a rela-

tively high SMCR power, where NCR

= 90% refers to the high design ship

speed of 22.0 knots, the corresponding

NCR at 20.0 and 19.0 knots is lower

than 90% SMCR, namely 61.7% and

51.0% SMCR, respectively.

Referring to an existing 2,500 teu

container ship earlier designed for

22.0 knots and with the main engine

7L70ME-C8.2 installed, a retrofit solu-

tion of the main engine is also described

later for operation at 19.0 knots.

Main Engine Operating Costs – 20.0 knots

The calculated main engine examples

are as follows:

20.0 kn

1 Dprop = 6.7 m × 5

M1 = 15,200 kW × 105 r/min

7S60ME-C8.2

2 Dprop = 7.0 m × 5

M2 = 14,970 kW × 97 r/min

7S60ME-C8.2

3 Dprop = 7.0 m × 5

M3 = 14,970 kW × 97 r/min

6G60ME-C9.2

4 Dprop = 7.4 m × 5

M4 = 14,730 kW × 89 r/min

6G60ME-C9.2

5 Dprop = 7.4 m × 5

M5 = 14,730 kW × 89 r/min

7G60ME-C9.2

6 Dprop = 7.6 m × 5

M6 = 14,570 kW × 84 r/min

7G60ME-C9.2

22.0 kn

1 Dprop = 7.1 m × 5

M = 21,780 kW × 108 r/min

7L70ME-C8.2

The selected main engine examples,

among others, make it possible to see

the influence of the propeller diameter,

installation of one extra cylinder and en-

gine type.

The main engine fuel consumption and

operating costs at N = NCR = 90%

SMCR, but N = 61.7% SMCR for the

existing 7L70ME-C8.2, have been cal-

culated for the above seven main en-

gine/propeller cases operating on the

reduced ship speed of 20.0 knots, as

often used today. Furthermore, the cor-

responding EEDI has been calculated


1

6,000

8,000

10,000

2

3

12,000

16,000

14,000

4

5

6

7

8

Relative powerreduction

%

Propulsion power demand at N = NCR

kW

0

2,000

4,000

0

Dprop:

13,680 kW

7S60ME-C8.2N1

6.7 m × 5

13,473 kW

7S60ME-C8.2N2

7.0 m × 5

13,473 kW

6G60ME-C9.2N3

7.0 m × 5

13,257 kW

6G60ME-C9.2N4

7.4 m × 5

13,257 kW

7G60ME-C9.2N5

7.4 m × 5

13,113 kW

7G60ME-C9.2N6

7.6 m × 5

13,428 kW

7L70ME-C8.2N

7.1 m × 5

Including a 15% sea margin

0%

1.5% 1.5%

3.1% 3.1%

4.1%

1.8%

Fig. 5: Expected propulsion power demand at N=NCR = 90% SMCR for 20.0 knots (N = 61.7% SMCR for 7L70ME-C8.2)

on the basis of the 75% SMCR-related

figures for 70% of max. dwt. (without

sea margin).

Fuel consumption and EEDI

Fig. 5 shows the influence of the pro-

peller diameter with five propeller

blades when going from about 6.7 m to

7.6 m. Thus, N6 for the 7G60ME-C8.2

with a 7.6 m propeller diameter has a

propulsion power demand that is about

4.1% lower compared with N1 used as

basis valid for the 7S60ME-C8.2. with a

propeller diameter of about 6.7 m.

Fig. 6 shows the influence on the main

engine efficiency, indicated by the Spe-

cific Fuel Oil Consumption, SFOC, for

the seven cases. For N1 = 90% M1

used as basis with the 7S60ME-C8.2

SFOC is 164.2 g/kWh, for N5 = 90%

M5 with 7G60ME-C8.2 SFOC is 160.5

g/kWh and for N = 61.7% M with

7L70ME-C8.2 SFOC is 165.4 g/kWh.

In N5, the SFOC is about 2.3% lower

compared with N1.

When multiplying the propulsion power

demand at N (Fig. 5) with the SFOC (Fig.

6), the daily fuel consumption is found

and is shown in Fig. 7. Compared with

N1 for the existing 7S60ME-C8.2, the

total reduction of fuel consumption of

the new 7G60ME-C9.2 at N6 is about

5.6% (see also the above-mentioned

savings of 4.1% and 1.5% stated in

Figs. 5 and 6).

Engine shaft power

174

175

176

25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100% SMCR156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

SFOCg/kWh

171

172

173

IMO Tier llISO ambient conditionsLCV = 42,700 kJ/kg

Standard high-loadoptimised engines

For 7L70ME-C8.2 61.7% 68.6%M = SMCRN = NCR

N4

N5

N6

N2

N

N3

N1

Savings in SFOC

0.0%Basis

-0.7%-1.1%

-0.4%

0.9%

1.5%

2.3%

DpropM2 7S60ME-C8.2 7.0 m x 5

M1 7S60ME-C8.2 6.7 m x 5 BasisM4 6G60ME-C9.2 7.4 m x 5

(M) 7L70ME-C8.2 7.1 m x 5M3 6G60ME-C9.2 7.0 m x 5

M5 7G60ME-C9.2 7.4 m x 5

M6 7G60ME-C9.2 7.6 m x 5

Fig. 6: Expected SFOC for 20.0 knots


The reference and the actual EEDI

figures have been calculated and are

shown in Fig. 8 (EEDIref = 174.22 x max.

dwt -0.201, 15 July 2011). As can be seen

for all six cases with S60ME-C8.2 and

G60ME-C9.2 and layouted for 20.0

2013Year

Contract datebefore 1 January

2015

2020

2025

Dprop:

0

5

10

15

20

25

0

10

20

30

40

50

60

70

80

90

100

110

Reference and actual EEDICO2 emissionsgram per dwt/n mile Actual/Reference EEDI %

6G60ME-C9.2N4

7.4 m × 5

62%

7L70ME-C8.2N

7.1 m × 5(22.0 kn)

83%

8L70ME-C8.2NN

7.0 m × 5(23.0 kn)

96%

7G60ME-C9.2N5

7.4 m × 5

60%

7G60ME-C9.2N6

7.6 m × 5

60%

EEDI reference (21.29/100%) EEDI actual

7S60ME-C8.2N1

6.7 m × 5

63%

7S60ME-C8.2N2

7.0 m × 5

63%

6G60ME-C9.2N3

7.0 m × 5

62%

75% SMCR and 70% of max dwt: 20.2 kn without sea margin

13.13

20.44

12.81 12.7613.49 13.43 13.19

17.69

Fig. 8: Reference and actual Energy Efficiency Design Index (EEDI) for 20.0 knots

2

30

40

50

4

6

60

70

8

10

12

14

Relative saving of fuel consumption

%

Fuel consumptionof main engine

t/24h

IMO Tier llISO ambient conditions

LCV = 42,700 kJ/kg

0

10

20

0

Dprop:

53.91t/24h

7S60ME-C8.2N1

6.7 m × 5

0%

53.68t/24h

7S60ME-C8.2N2

7.0 m × 5

0.4%

52.63t/24h

6G60ME-C9.2N3

7.0 m × 5

2.4%

52.42t/24h

6G60ME-C9.2N4

7.4 m × 5

2.8%

51.06t/24h

7G60ME-C9.2N5

7.4 m × 5

5.3%

50.90t/24h

7G60ME-C9.2N6

7.6 m × 5

5.6%

53.30t/24h

7L70ME-C8.2N

7.1 m × 5

1.1%

Fig. 7: Expected fuel consumption at N = NCR = 90% SMCR for 20.0 knots (N = 61.7% SMCR for 7L70ME-C8.2)

knots, the actual EEDI figures are rela-

tively low with the lowest EEDI (60%)

for cases 5 and 6 with 7G60ME-C9.2.

All these cases may also meet the

stricter EEDI reference figure valid after

2025.

For information, the calculated EEDI

valid for the old cases 7L70ME-C8.2 (22

kn.) and 8L70ME-C8.2 (23 kn.) is also

shown in Fig. 8. The old 8L70ME-C8.2

(23 kn.) is more or less the reason for the

100% EEDI reference figure used today.


Fig. 9: Total annual main engine operating costs for 20.0 knots

0.0

2.0

4.0

6.0

1.0

3.0

5.0

Annual operating costsMillion USD/Year

Relative saving in operating costs

%

Dprop:

7.0

8.0

9.0

10.0

0

2

4

6

1

3

5

7

8

9

10

7S60ME-C8.2N1

6.7 m × 5

0%

7S60ME-C8.2N2

7.0 m × 5

0.4%

6G60ME-C9.2N3

7.0 m × 5

2.5%

6G60ME-C9.2N4

7.4 m × 5

2.9%

7G60ME-C9.2N5

7.4 m × 5

5.1%

7G60ME-C9.2N6

7.6 m × 5

5.4%

7L70ME-C8.2N

7.1 m × 5

0.8%

MaintenanceLubricating oil

Fuel oil


250 days/yearNCR = 90% SMCR (61.7% for 7L70ME-C8.2)

Fuel price: 700 USD/t

YearsLifetime

0

2

1

3

0 5 10 15 20 25 30

4

5

6

7

8

9

Saving in operating costs (Net Present Value)Million USD

10

11

IMO Tier llISO ambient conditionsN = NCR = 90% SMCR (61.7% for 7L70ME-C8.2)250 days/yearFuel price: 700 USD/tRate of interest and discount: 6% p.a.Rate of inflation: 3% p.a.

N2: 7.0 m × 57S60ME-C8.2

N3: 7.0 m × 56G60ME-C9.2

N4: 7.4 m × 56G60ME-C9.2

N5: 7.4 m × 57G60ME-C9.2

N6: 7.6 m × 57G60ME-C9.2

N1: 6.7 m × 57S60ME-C8.2

N:7.1 m × 57L70ME-C8.2

Fig. 10: Relative saving in main engine operating costs (NPV) for 20.0 knots

Operating costs

The total main engine operating costs

per year, 250 days/year, and fuel price

of 700 USD/t, are shown in Fig. 9. The

lube oil and maintenance costs are

shown too. As can be seen, the major

operating costs originate from the fuel

costs – about 96%.

After some years in service, the rela-

tive savings in operating costs in Net

Present Value (NPV), see Fig. 10, with

the existing 7S60ME-C8.2 used as

basis N1 with the propeller diameter

of about 6.7 m, indicates an NPV sav-

ing for the new 7G60ME-C9.2 engine.

After 25 years in operation, the saving

is about 8.7 million USD for N5 with

7G60ME-C9.2 with the SMCR speed

of 89.0 r/min and propeller diameter of

about 7.4 m.


Main Engine Operating Costs – 19.0 knots

The calculated main engine examples

are as follows:

19.0 kn

1 Dprop = 6.7 m × 5

M1’ = 12,570 kW × 98 r/min

6S60ME-C8.2

2 Dprop = 7.0 m × 5

M2’ = 12,420 kW × 92 r/min

6S60ME-C8.2

3 Dprop = 7.0 m × 5

M3’ = 12,420 kW × 92 r/min

6G60ME-C9.2

4 Dprop = 7.4 m × 5

M4’ = 12,180 kW × 83 r/min

6G60ME-C9.2

5 Dprop = 7.6 m × 5

M5’ = 12,070 kW × 79 r/min

6G60ME-C9.2

22.0 kn

1 Dprop = 7.1 m × 5

M’ = 21,780 kW × 108 r/min

7L70ME-C8.2

The main engine fuel consumption and

operating costs at N’ = NCR = 90%

SMCR, but N’ = 51% SMCR for the ex-

isting 7L70ME-C8.2, have been calcu-

lated for the above six main engine/pro-

peller cases operating on the reduced

ship speed of 19.0 knots, which is prob-

ably going to be a more normal choice

in the future. Furthermore, the EEDI has

been calculated on the basis of the 75%

SMCR-related figures for 70% of max.

dwt. (without sea margin).

Fuel consumption and EEDI

Fig. 11 shows the influence of the pro-

peller diameter with five propeller blades

when going from about 6.7 m to 7.6 m.

Thus, N5’ for the 6G60ME-C9.2 with

an about 7.6 m propeller diameter has

1

6,000

8,000

10,000

2

3

12,000

14,000

4

5

6

7

Relative powerreduction

%Including a 15% sea margin

Propulsion power demand at N’ = NCR

kW

0

2,000

4,000

0

Dprop:

11,178 kW

6S60ME-C8.2N2’

7.0 m × 5

11,313 kW

6S60ME-C8.2N1’

6.7 m × 5

11,178 kW

6G60ME-C9.2N3’

7.0 m × 5

10,962 kW

6G60ME-C9.2N4’

7.4 m × 5

10,863 kW

6G60ME-C9.2N5’

7.6 m × 5

11,117 kW

7L70ME-C8.2N’

7.1 m × 5

0%

1.2% 1.2%

3.1%

4.0%

1.7%

Fig. 11: Expected propulsion power demand at N = NCR = 90% SMCR for 19.0 knots (N’ = 51% SMCR

for 7L70ME-C8.2)

a propulsion power demand that is

about 4.0% lower compared with the

N1’ used as basis for the 6S60ME-C8.2

with an about 6.7 m propeller diameter.

Fig. 12 shows the influence on the main

engine efficiency, indicated by the Spe-

cific Fuel Oil Consumption, SFOC, for

the six cases. For N1’ = 90% M1’ with

the 6S60ME-C8.2 used as basis SFOC

is 165.1 g/kWh compared with the

159.2 g/kWh for N3’ = 90% M3’ for the

6G60ME-C9.2, i.e. an SFOC reduction

for N3’ of about 3.6%. For N’ = 51.0%

M’ with 7L70ME-C8.2 SFOC is 167.3

g/kWh, i.e. an SFOC increase of about

1.3%.

The daily fuel consumption is found by

multiplying the propulsion power de-

mand at N’ (Fig. 11) with the SFOC (Fig.

12), see Fig. 13. The total reduction of

fuel consumption of the new 6G60ME-

C9.2, N5’ with propeller diameter 7.6

m, is about 5.5% compared with N1’

for the existing 6S60ME-C8.2.

Engine shaft power

174

175

176

25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100% SMCR156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

SFOCg/kWh

171

172

173


Standard high-loadoptimised engines

For 7L70ME-C8.2 51.0% 56.7%M’ = SMCRN’ = NCR

N1’

N3’

N2’N’

N4’

N5’

Savings in SFOC

0.0%Basis

-1.3%-0.9%

1.6%

2.2%

3.6%

Dprop

M2’ 6S60ME-C8.2 7.0 m x 5

M1’ 6S60ME-C8.2 6.7 m x 5 Basis(M’) 7L70ME-C8.2 7.1 m x 5

M5’ 6G60ME-C9.2 7.6 m x 5

M4’ 6G60ME-C9.2 7.4 m x 5

M3’ 6G60ME-C9.2 7.0 m x 5

Fig. 12: Expected SFOC for 19.0 knots


The reference and the actual EEDI

figures have been calculated and are

shown in Fig. 14 (EEDIref = 174.22 ×

max. dwt -0.201, 15 July 2011). As can

be seen for all five cases with 6S60ME-

C8.2 and 6G60ME-C9.2 and layouted

for 19.0 knots, the actual EEDI figures

are much lower than the reference fig-

ure because of the relatively low ship

speed of 19.0 knots.

All these cases may also meet the

stricter EEDI reference figure valid after

2025.

As for the earlier stated cases based

on 20 knots, the EEDI for the old cases

7L70ME-C8.2 (22 kn.) and 8L70ME-

C8.2 (23 kn.) is also shown in Fig. 14

for information.

2

30

40

50

4

6

60

70

8

10

12

14


%


t/24h


LCV = 42,700 kJ/kg

0

10

20

0

44.69t/24h

6S60ME-C8.2N2’

7.0 m × 5

44.83t/24h

6S60ME-C8.2N1’

6.7 m × 5

42.72t/24h

6G60ME-C9.2N3’

7.0 m × 5

42.46t/24h

6G60ME-C9.2N4’

7.4 m × 5

42.36t/24h

6G60ME-C9.2N5’

7.6 m × 5

44.64t/24h

7L70ME-C8.2N’

7.1 m × 5

0%0.3%

4.7%5.3% 5.5%

0.4%

Dprop:

6S60ME-C8.2N1’

6.7 m × 5

6S60ME-C8.2N2’

7.0 m × 5

6G60ME-C9.2N3’

7.0 m × 5

6G60ME-C9.2N4’

7.4 m × 5

6G60ME-C9.2N5’

7.6 m × 5

7L70ME-C8.2N’

7.1 m × 5(22.0 kn)

Dprop:

0

5

10

15

20

25

0

10

20

30

40

50

60

70

80

90

100

110

Reference and actual EEDICO2 emissionsgram per dwt/n mile

Actual/ReferenceEEDI %

2013Year

Contract datebefore 1 January

2015

2020

2025

56% 53% 53%

83%

53%

EEDI actualEEDI reference (21.29/100%)

56%

8L70ME-C8.2NN’

7.0 m × 5(23.0 kn)

96%

75% SMCR and 70% of max dwt: 19.2 kn without sea margin

11.82 11.33 11.26

17.69

11.2311.86

20.44

Fig. 14: Reference and actual Energy Efficiency Design Index (EEDI) for 19.0 knots

Fig. 13: Expected fuel consumption at N’ = NCR = 90% SMCR for 19.0 knots (N’ = 51% SMCR for

7L70ME-C8.2)


0.0

2.0

4.0

6.0

1.0

-1.0

3.0

5.0



%

Dprop:

7.0

8.0

9.0

0

2

4

6

1

-1

3

5

7

8

9

6S60ME-C8.2N1’

6.7 m × 5

6S60ME-C8.2N2’

7.0 m × 5

6G60ME-C9.2N3’

7.0 m × 5

6G60ME-C9.2N4’

7.4 m × 5

6G60ME-C9.2N5’

7.6 m × 5

7L70ME-C8.2N’

7.1 m × 5

0%

0.3%

4.5%5.1%

5.4%

-0.3%


Fuel oil


250 days/yearNCR = 90% SMCR (51.0% for 7L70ME-C8.2)


Fig. 15: Total annual main engine operating costs for 19.0 knots

YearsLifetime

0

–1

2

1

3

0 5 10 15 20 25 30

4

5

6

7

8

9

Saving in operating costs (Net Present Value)Million USD

IMO Tier llISO ambient conditionsN’ = NCR = 90% SMCR (51.0% for 7L70ME-C8.2)250 days/yearFuel price: 700 USD/tRate of interest and discount: 6% p.a.Rate of inflation: 3% p.a.

N2’: 7.0 m × 56S60ME-C8.2

N3’: 7.0 m × 56G60ME-C9.2

N4’: 7.4 m × 56G60ME-C9.2

N5’: 7.6 m × 56G60ME-C9.2

N1’: 6.7 m × 5 Basis6S60ME-C8.2N’:7.1 m × 57L70ME-C8.2

Fig. 16: Relative saving in main engine operating costs (NPV) for 19.0 knots

Operating costs

The total main engine operating costs

per year, 250 days/year, and fuel price

of 700 USD/t, are shown in Fig. 15.

Lube oil and maintenance costs are

also shown at the top of each column.

As can be seen, the major operating

costs originate from the fuel costs –

about 96%.

After some years in service, the relative

savings in operating costs in Net Pre-

sent Value, NPV, see Fig. 16, with the

existing 6S60ME-C8.2 with the propel-

ler diameter of about 6.7 m used as ba-

sis, indicates an NPV saving after some

years in service for the new 6G60ME-

C9.2 engine. After 25 years in opera-

tion, the saving is about 7.3 million USD

for N4’ with the 6G60ME-C9.2 with the

SMCR speed of 83.0 r/min and propel-

ler diameter of about 7.4 m.


Retrofit of Existing 7L70ME-C8.2 with LL-EGB for Reduced Ship Speeds

As mentioned earlier in this paper, the

container ships built a few years ago

were designed for sailing in service at

relatively high ship speeds, which at

that time was beneficial due to the high

freight rates and low fuel prices.

Today, the high fuel prices, low freight

rates, and stricter EEDI demands have

forced the shipowners to sail with a

relatively low ship speed compared to

what was originally intended, i.e. to op-

erate the main engine continuously at

reduced main engine loads.

60

Low-Load (LL)

70

Closed Partly open Open

80 90 100% SMCREngine load

Exhaust Gas Bypass, EGB – open and closed EGB (for guidance only) – ME/ME-C

EGB-Valve

Expansion Joint(Compensator)

Expansion Joint(Compensator)

Orifice

YardSupply

MAN B&WSupply

Exhaust Receiver

Main Engine

Exhaust Gas

Manifold

Fig. 17: Exhaust gas bypass for Low Load tuning (LL-EGB)

Fig. 18: SFOC reduction for 7L70ME-C8.2 with LL-EGB operating at 45% SMCR at reduced ship speed

174

175

176

25 30 35 40 45 50 55 60

168.7

163.7

65 70 75 80 85 90 95 100% SMCR156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

SFOCg/kWh

171

172

173


New averageservice

AA

B

LL-EGB

HL-Standard

Case A: 7L70ME-C8.2 HL-standard tuned (Existing)Case B: 7L70ME-C8.2 with LL-EGB (Retrofit)

Retrofit7L70ME-C8.2 with LL-EGB

SMCR = 21,780 kW × 108 r/min

B


Exhaust Gas Bypass – Low Load

(LL-EGB)

A reduction of SFOC when operating at

low loads is possible but is limited by

NOx regulations on two-stroke engines.

Thus, NOx emission will increase if the

SFOC is reduced and vice versa.

Compared to a standard high load op-

timised ME-C engine, an SFOC reduc-

tion of 5g/kWh at low load is possible,

but at the expense of a higher SFOC in

the high-load range without exceeding

the IMO NOx limit.

This is possible by means of an exhaust

gas bypass, low load optimised, see Fig.

17. The corresponding SFOC curve for

a 7L70ME-C8.2 with SMCR = 21,780

kW x 108 r/min is shown in Fig. 18.

Saving in operating costs and pay-

back time

The existing standard high load op-

timised 7L70ME-C8.2 with SMCR =

21,780 kW x 108 r/min and design ship

speed of 22.0 knots has been used as

basis.

The SFOC and fuel consumptions have

been calculated valid for the new aver-

age engine service load of 45% SMCR

which more or less corresponds to

the reduced average ship speed of 19

knots, case A, see Figs. 18 and 19.

The corresponding SFOC and fuel

consumptions valid for LL-EGB, case

B, is also shown in Figs. 18 and 19.

The LL-EGB case B has an about 3%

lower fuel consumption than for the HL-

standard tuned engine, case A.

The annual operating costs are shown

in Fig. 20, and the saving in operating

Fig. 20: Total annual main engine operating costs in average service on 45% SMCR

0.0

2.0

4.0

6.0

1.0

3.0

5.0



%

7.0

8.0

9.0

10.0

0

1

2

3

4

5

0%

7L70ME-C8.2LL-EGB

B

7L70ME-C8.2HL-Standard

A

2.9%


Fuel oil


SMCR = 21,780 kW × 108 r/min250 days/year


1

30

40

50

2

3

60

70

4

5

6

7


%


t/24h


LCV = 42,700 kJ/kg

0

10

20

0


SMCR = 21,780 kW × 108 r/min

39.67t/24h

0%


A

38.50t/24h

7L70ME-C8.2LL-EGB

B

3.0%

Fig. 19: Expected fuel consumption in average service on 45% SMCR


and investment costs (net present value)

is shown in Fig. 21. However, the total

extra investment costs needed for ret-

rofit with LL-EGB and indicated in Fig.

21, depend very much on the existing

turbochargers as some turbocharger

layouts may need more comprehensive

modifications than others. Each retrofit

project, therefore, has to be checked

individually from case to case.

In general, the payback time of the LL-

EGB modification may be about 2 years.

Summary

Traditionally, short and long stroke K80

and L70 engines, with relatively high en-

gine speeds, have been applied as prime

movers in large feeder container vessels.

Following the efficiency optimisation

trends in the market, including reduced

ship speeds, the possibility of using

even larger propellers has been thor-

oughly evaluated with a view to using

engines with even lower speeds for

propulsion.

Container ships with lower ship speeds

are indeed compatible with propellers

with larger propeller diameters than the

current designs, and thus high propel-

ler efficiencies following an adaptation

of the aft hull design to accommodate

the larger propeller, together with opti-

mised hull lines and bulbous bow, con-

sidering operation in ballast conditions.

Even in cases where an increased size

of the propeller is limited, the use of

propellers based on the new propeller

technology will be an advantage.

The new and ultra long stroke G60ME-

C9.2 engine type meets this trend in

the large feeder container market. This

paper indicates, depending on the pro-

peller diameter used, an overall efficien-

cy increase of up to 5-6% when using

G60ME-C9.2, compared with the exist-

ing main engine type S60ME-C8.2.

The Energy Efficiency Design Index

(EEDI) will also be reduced when us-

ing the G60ME-C9.2. However, the use

of lower design ship speed may by it-

self reduce the EEDI involving that the

stricter EEDI demands in the future may

always be met.

For existing container ships designed

for high ship speeds, the retrofit of the

main engine with a LL-EGB may reduce

the operating costs with about 3%

when sailing at reduced ship speeds.

The payback time may be about 2

years, but depends on the existing tur-

bocharger configuration.

Fig. 21: Relative saving in Net Pressent Value costs in average service on 45% SMCR

YearsLifetime

–0.5

–1.0

0.5

0

1.0

0 5 10 15 20 25 30

1.5

2.0

2.5

3.0

3.5

4.0

Saving in operating and investment costs (Net Present Value)Million USD

IMO Tier llISO ambient conditions250 days/yearFuel price: 700 USD/tRate of interest and discount: 6% p.a.Rate of inflation: 3% p.a.


7L70ME-C8.2LL-EGB


MAN Diesel & TurboTeglholmsgade 412450 Copenhagen SV, DenmarkPhone +45 33 85 11 00Fax +45 33 85 10 [email protected]

MAN Diesel & Turbo – a member of the MAN Group

All data provided in this document is non-binding. This data serves informational purposes only and is especially not guaranteed in any way. Depending on the subsequent specific individual projects, the relevant data may be subject to changes and will be assessed and determined individually for each project. This will depend on the particular characteristics of each individual project, especially specific site and operational conditions. Copyright © MAN Diesel & Turbo. 5510-0145-00ppr Oct 2013 Printed in Denmark

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