SFOC Optimization Methods - For MAN B&W Two-Stroke IMO Tier II Engines

SFOC Optimisation Methods For MAN B&W Two-stroke IMO Tier II Engines

Content

Introduction .................................................................................................5 Influence of NO x Regulations on Reduced SFOC ........................................... 6 Engine Tuning Methods Available.................................................................. 6 Exhaust Gas Bypass (EGB) .....................................................................6 Variable Turbine Area or Turbine Geometry (VT) ........................................ 8 Engine Control Tuning (ECT) .................................................................... 9 Potential Fuel Savings on Low-Load Operation ........................................... 10 Summary ................................................................................................... 13

MAN B&W Diesel SFOC Optimisation Methods – For MAN B&W Two-stroke IMO Tier II Engines

3

SFOC Optimisation Methods For MAN B&W Two-stroke IMO Tier II Engines

Introduction

mum Continuous Rating) ranges shown

will only be introduced for engines in

One of the goals in the marine industry

in Table 1a.

compliance with the IMO NO x Tier II re-

today is to reduce the impact of CO 2

quirements.

emissions from ships and thereby to re-

The high-load range corresponds to a

duce the fuel consumption for the pro-

normal, standard-tuned engine of today.

pulsion of ships to the widest possible estimate at any load. This drive may often result in operation

As an example, Figs. 1a and 1b show the impact on the SFOC curves valid

For part-load and low-load optimisa-

for ME/ME-C and MC/MC-C/ME-B en-

tion, the following engine tuning meth-

gines in general, based on a standard-

ods are available, see Table 1b.

tuned engine (high load), VT part load

of the ship at reduced ship speed and,

and VT low load, respectively. They are

consequently, at reduced engine load.

The above-described engine tuning

available for both nominally rated and

This has placed more emphasis on op-

methods are only available for engines

derated engines.

erational flexibility in terms of demand

with high-efficient turbochargers, and

for reduced SFOC (Specific Fuel Oil Consumption) at part/low-load opera-

SFOC-optimised load ranges

tion of the main engine. However, on

High load

85-100% SMCR (standard-tuned engine)

two-stroke engines, reduction of the

P ar t l oa d

5 0- 85% S MC R

SFOC is affected by NO x regulations in

L ow l oa d

25 -70% S MC R

order to maintain compliance with the

Table 1a

IMO NOx Tier II demands. Engine tuning methods available Depending on the intended operation

EGB

Exhaust Gas Bypass

range of the main engine, the engine

VT

Varia ble Turb ine A rea o r Turbin e Geo metr y

may be SFOC-optimised in the follow-

ECT

Engine Control Tuning (only for ME/ME-C)

ing percentage SMCR (Specified Maxi-

Table 1b

SFOC

SFOC

High-load optimised Part-load optimised (VT tuning) Low-load optimised (VT tuning)

High-load optimised Part-load optimised (VT tuning) Low-load optimised (VT tuning)

−1 g/kWh

−2 g/k Wh −1 g/kWh

−3 g/kWh −3 g/kWh −5 g/kWh 35

65

70

80

100 % SMCR Engine load

Fig.1a: Example of SFOC reductions for ME/ME-C engines with VT

MAN B&W Diesel

35

65

70

80

100 % SMCR Engine load

Fig.1b: Example of SFOC reductions for MC/MC-C/ME-B engines with VT

SFOC Optimisation Methods – For MAN B&W Two-stroke IMO Tier II Engines

5

An SFOC reduction of 5 g/kWh makes

The IMO NO x limit is given as a weight-

Engine Tuning Methods Available

it possible to obtain a fuel cost reduc-

ed average of the NO x emission cycle

The engine tuning methods available

tion of up to approx. 3% of the specific

values at 25, 50, 75 and 100% load,

are described in more detail below.

will of course be reduced further due to

5% x NOx (25) + 11% x NO x (50) + 55%

Exhaust Gas Bypass (EGB)

the low load.

x NO x (75) + 29% x NOx (100).

This method requires installation of an

consumption. The daily consumption

EGB, individually tailored at approx 6% The influence of NO x regulations and

This relationship can be utilised to shape

EGB. The EGB technology is available

the engine tuning methods available

or tailor the SFOC profile over the load

for both the ME/ME-C and MC/MC-C/

for ME/ME-C and MC/MC-C/ME-B en-

range, i.e. the SFOC can be reduced at

ME-B type engines. The SFOC poten-

gines are described below.

low load at the expense of higher SFOC

tial is better on the ME type engine,

in the high-load range without exceed-

where EGB is combined with variable

ing the IMO NO x limit.

exhaust valve timing.

As mentioned, the SFOC is limited by

Compared with MC/MC-C/ME-B en-

The turbochargers on the ME/ME-C

NO x regulations on two-stroke engines.

gine types, the SFOC reduction po-

engines for part load and low load are

In general, the NO x emission will in-

tential is better for the ME/ME-C type

matched at 100% load with fully open

crease if the SFOC is reduced and vice

engines because variable exhaust valve

EGB. At approximately 90% load, the

versa. In the standard configuration, our

timing is available.

EGB starts to close and is fully closed

Influence of NOx Regulations on Reduced SFOC

engines are optimised close to the IMO

below about 80% load. For MC/MC-C/

NO x limit, which is why the NO x emis-

ME-B engines, the similar engine load

sion cannot be increased.

figures are about 90%/70% for part load and 85%/65% for low load. For MC6/MC-C6, it is about 85%/70% for part load and 85%/65% for low load.

Exhaust Gas Bypass, EGB – open and closed EGB

The above description of open/closed

ME/ME-C : Part load

EGB is shown in graphical form in Fig. 2.

: Low load

With this technology, the SFOC is de-

Engine load 60

70

80

creased at low load at the expense of

100% SMCR

90

MC/MC-C/ME-B : Part load : Low load Engine load 60

70

80

100% SMCR

90

MC6/MC-C6 : Part load : Low load Engine load 60

70

Closed

Partly open

80

90

Open

Based on ISO ambient conditions and for guidance only.

Fig. 2: Exhaust Gas Bypass (EGB) – open and closed EGB

6


100% SMCR

higher SFOC at high load.

SFOC g/kWh

SFOC g/kWh 180

176 Standard EGB, part load EGB, low load

175 174

179 178

SMCR: 25,080 kW x 78 r/min

173

Standard EGB, part load EGB, low load


177

172

176

171

175

170 174 169 173 168 172

167

171

166

170

165

169

164 163

168

162

167

161

166 165

160 159

ISO ambient conditions 25

30

35

40

45

50

55

60

65

70

75

80

85

90

ISO ambient conditions 164 25

95 100

30

35

40

Engine shaft power % SMCR

Fig. 2a: Example of SFOC reductions for 6S80ME-C8.2 with EGB

45

50

55

60

65

70

75

80

85

90

95 100


Fig. 2b: Example of SFOC reductions for 6S80MC-C8.2 with EGB

With part-load optimisation and com-

The most optimal method depends on

pared with a standard engine, the

the operating pattern.

SFOC is reduced at all loads below about 85%.

As an example, Fig. 2a shows the SFOC curves valid for a nominally rated

With low-load optimisation, and com-

6S80ME-C8.2 engine based on stand-

pared with part-load optimisation, the

ard high load, EGB part load and EGB

SFOC is further reduced at loads below

low load, respectively. Fig. 2b shows

about 70%, at the expense of higher

the similar SFOC curves valid for the

SFOC in the high-load range.

nominally rated 6S80MC-C8.2.


7

Variable Turbine Area or Turbine Geometry (VT)

Variable Turbine Area or Turbine Geometry (VT) – Nozzle Ring Area ME/ME-C

This method requires special turbo: Part load

charger parts allowing the turbocharger(s)

: Low load

on the engine to vary the area of the

Engine load 60

70

80

nozzle ring. The VT method is available

100% SMCR

90

for both the ME/ME-C and MC/MC-C/ ME-B type engines. The SFOC potential

MC/MC-C/ME-B

is better on the ME/ME-C t ype engines, : Part load

where VT is combined with variable ex-

: Low load

haust valve timing.

Engine load 60

70

80

100% SMCR

90

The nozzle ring area has a maximum at the higher engine load range. When the

MC6/MC-C6

engine load for ME/ME-C engines for : Part load

part load and low load is reduced below

: Low load

approx. 90%, the area gradually starts

Engine load 60

70

Minimum area

80

Intermediate area

90

to decrease and reaches its minimum at

100% SMCR

about 80% engine load. For MC/MC-C/

Maximum area

ME-B engines, the similar engine load

Based on ISO ambient conditions and for guidance only.

figures are about 90%/70% for part load and about 85%/65% for low load.

Fig. 3: Variable Turbine area or turbine geometry (VT) – nozzle ring area

SFOC g/kWh

SFOC g/kWh 176

180

Standard VT, part load VT, low load

175 174 173

179

Standard VT, part load VT, low load

178 177

172


176


171

175

170

174

169

173

168 172

167 171

166 170

165

169

164

168

163 162

167

161

166 165

160 ISO ambient conditions 159

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95 100


Fig. 3a: Example of SFOC reductions for 6S80ME-C8.2 with VT

8


ISO ambient conditions

164 25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100


Fig. 3b: Example of SFOC reductions for 6S80MC-C8.2 with VT

For MC6/MC-C6, it is about 85%/70% for part load and 85%/65% for low load. The above description of t he VT nozzle ring area is shown in graphical form in Fig. 3. With this technology, the SFOC is reduced at low load at the expense of higher SFOC at high load.

SFOC g/kWh 176 Standard ECT, part load ECT, low load

175 174 173


172 171 170 169

With part-load optimisation and compared with a standard engine, the SFOC is reduced at all loads below about 85%.

168 167 166 165 164

With low-load optimisation and com-

163


162

SFOC is further reduced at all loads

161

below about 70%, at the expense of

160

higher SFOC in the high-load range.

ISO ambient conditions

159 25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

1 00


The most optimal method on a specific engine depends on the operating pattern.

Fig. 4: Example of SFOC reductions for 6S80ME-C8.2 with ECT

As an example, Fig. 3a shows the SFOC curves valid for a nominally rated 6S80ME-C8.2 engine based on stand-

With part-load optimisation and com-

a change in trade pattern is permitted if

ard high load, VT part load and VT low

pared with a standard-tuned engine,

reported and approved by the flag state

load, respectively.

the SFOC is reduced at all loads below

representative, usually a classification

about 85%.

society. Hence, on a longer term basis,

Fig. 3b shows the similar SFOC curves

the owner can select one or the other of

valid for the nominally rated 6S80MC-

With low-load optimisation and com-

the modes for the engine, provided the

C8.2.


authorities are informed.

SFOC is further reduced at all loads Engine Control Tuning (ECT)

below about 70%, at the expense of

Both modes will need to be verified on

This method can be implemented with-

higher SFOC in the high-load range.

test bed if decided in time. Otherwise, a

out change of engine components, and

special, approved process is called for.

can be implemented as an engine run-

The most optimal method on a specific

ning mode. Only p max and engine con-

engine depends on the operating pat-

As an example, Fig. 4 shows the SFOC

trol parameters are changed.

tern.

curves valid for a nominally rated 6S80ME-C8.2 engine based on stand-

The met hod uses the possibility of vari-

Random shifting between the part-load

ard high load, ECT part load and ECT

able exhaust valve timing and injection

and low-load modes is not allowed by

low load, respectively.

profiling, and is only available for ME/

the authorities. A mode shift in case of

ME-C engine types. Two different service optimisation possibilities are available.


9

Potential Fuel Savings on Low-Load

However, shipowners will still mostly

Under such conditions, the application

Operation

require the possibility of operating the

of one of the previously described en-

Today, a reduction of CO 2 emissions,

ship at the earlier higher ship speed,

gine tuning methods, e.g. the Variable

and thereby a reduction of the fuel con-

if occasionally needed. This means

Turbine area, V T, optimised for low-load

sumption of a ship, is an increasing de-

that the SMCR power of the main en-

operation, will add to reduce the fuel

mand that will be even stronger in the

gines may still be maintained, while the

consumption.

future. This may result in lower service

changed trading pattern of the ship may

ship speeds compared with earlier ship

result in operation with a relatively lower

Table 2a shows, as an example, the cal-

speeds. Thus, the lower the ship speed,

load of the main engine, with only few

culations of the potential fuel consump-

the lower the required propulsion power

days of operation on high engine loads.

tion savings for a 6S80ME-C8.2 by us-

and, thereby, the lower the fuel con-

ing the VT low-load optimised method,

sumption is.

compared with a similar engine with the standard high-load optimised version.

Main engine 6S80ME-C8.2 IMO Tier ll SMCR = 25,080kW x 78r/min Standard engine, high load optimised Engine load

% SMCR

35%

50%

65%

85%

100%

kW

8,778

12,540

16,302

21,318

25,080

SFOC g/kWh Re LCV = 42,700 kJ/kg

171.4

167.0

164.3

165.0

168

t/day

36.1

50.3

64.3

84.4

101.1

day/year

40

100

90

15

5

t/year

1,444

5,030

5,787

1,266

506

14,033 t/year

% SMCR

35%

50%

65%

85%

100%

Total fuel consumption

kW

8,778

12,540

16,302

21,318

25,080


166.4

162.0

159.3

165.3

168.5

t/day

35.0

48.8

62.3

84.6

101.4

day/year

40

100

90

15

5

Fuel consumption

t/year

1,400

4,880

5,607

1,269

507

13,663 t/year

Fuel savings

t/year

44

150

180

-3

-1

370 t/year

Fuel savings

%/year

3.0

3.0

3.0

-0.2

-0.3

Engine power

Fuel consumption Days in service Fuel consumption


VT, low load optimised Engine load Engine power

Fuel consumption Days in service

Table 2a: Savings in fuel consumption for 6S80ME-C8.2 with “VT, low load” compared with a standard engine

10 SFOC Optimisation Methods – For MAN B&W Two-stroke IMO Tier II Engines

2.6%/year

For the given trading pattern, the po-

The corresponding potential relative

tential specific fuel saving found for the

fuel saving for other engine types are

6S80ME-C8.2 engine type is approx.

of the same magnitude, with the higher

2.6%.

savings valid for the ME/ME-C engine types and the lower savings valid for the

Table 2b shows the corresponding cal-

MC/MC-C/ME-B types.

culations, but now valid for a 6S80MCC8.2 engine.

Of course, in all cases, the daily fuel consumption will be lowered mostly

For the given trading pattern, the po-

due to the lower ship speed, i.e. lower

tential specific fuel savings found for the

power needed.

6S80MC-C8.2 engine type is approx. 1.5%.

Main engine 6S80MC-C8.2 IMO Tier ll SMCR = 25,080kW x 78r/min Standard engine, high load optimised Engine load

% SMCR

35%

50%

65%

85%

100%

kW

8,778

12,540

16,302

21,318

25,080


175.2

171.0

168.7

168.3

171.0

t/day

36.9

51.5

66.0

86.1

102.9

day/year

40

100

90

15

5

t/year

1,476

5,150

5,940

1,292

515

14,373 t/year

% SMCR

35%

50%

65%

85%

100%


kW

8,778

12,540

16,302

21,318

25,080


172.2

168.0

165.7

168.8

172.0

t/day

36.3

50.6

64.8

86.4

103.5

day/year

40

100

90

15

5

Fuel consumption

t/year

1,452

5,060

5,832

1,296

518

14,158 t/year

Fuel savings

t/year

24

90

108

-4

-3

215 t/year

Fuel savings

%/year

1.6

1.7

1.8

-0.3

-0.6

Engine power

Fuel consumption Days in service Fuel consumption


VT, low load optimised Engine load Engine power

Fuel consumption Days in service

1.5%/year

Table 2b: Savings in fuel consumption for 6S80MC-C8.2 with “VT, low load” compared with a standard engine


11

Please note that the reduced SFOC on low-load operation, when using one of the engine tuning methods available, involves a correspondingly lower exhaust gas temperature at low-load operation, which has to be considered at the de-

6S80ME-C8.2 SMCR: 25,080 kW x 78 r/min C 280 Standard

VT, low load

260 240

sign state of the exhaust boiler of the ship. As an example, the influence on the

220 ISO ambient conditions

200 25

30

35

40

45

50

55

60

65

70

75

exhaust gas temperature of the engine

80 85 90 95 100 Engine shaft power % SMCR

tuning methods valid for 6S80ME-C8.2

Fig. 5a: Exhaust gas temperature after t/c for 6S80ME-C8.2 with “VT, low load” compared with a stand-

with “VT, low load” compared with a

ard engine

standard engine is shown in Fig. 5a. The similar exhaust gas temperature influence for 6S80MC-C8.2 is shown in Fig. 5b, and the same tendency is also applied to the EGB and ECT tuning methods.

6S80MC-C8.2 SMCR: 25,080 kW x 78 r/min C 280 Standard

VT, low load

260 240 220 ISO ambient conditions

200 25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Engine shaft power % SMCR Fig. 5b: Exhaust gas temperature after t/c for 6S80MC-C8.2 with “VT, low load” compared with a stand ard engine

12 SFOC Optimisation Methods – For MAN B&W Two-stroke IMO Tier II Engines

Summary The introduction of the described main engine tuning methods EGB, VT and ECT makes it possible to optimise the fuel consumption when normally operating at low loads, while maintaining the possibility of operating at high load when needed, for example when the time schedule is tight. In this way, the MAN B&W two-stroke engine is meeting the more stringent demand of the future for reduction of CO 2 emissions and thereby the fuel costs. A reduction of up to 3% of the specific fuel consumption is possible.


13

P C r o i n p t e y r d g i i h n t D © e M n m A a N r k D i e s e l & T u r b o · S u b j e c t t o m o d i f i c a t i o n i n t h e i n t e r e s t o f t e c h n i c a l p r o g r e s s . · 5 5 1 0 0 0 9 9 0 0 p p r S e p 2 0 1 0

MAN Diesel & Turbo Teglholmsg ade 41 2450 Copenhagen SV, Denmark Phone +45 33 85 11 00 Fax

+45 33 85 10 30

[email protected] www.mandieselturbo.com

SFOC Optimization Methods - For MAN B&W Two-Stroke IMO Tier II Engines

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