Man B&W L35MC6-TII, Project Manual

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MAN B&W 2.04
Page 9 of 10
MAN Diesel
198 69 94-7.1 MAN B&W MC/MC-C-TII engines
Example 4: Special running conditions.
Engine coupled to a fixed pitch propeller (FPP) and with a shaft generator
M Specified MCR of engine
S Continuous service rating of engine
O Optimising point of engine
A Reference point of load diagram
MP Specified MCR for propulsion
SP Continuous service rating of propulsion
SG Shaft generator
Point A and M of the load diagram are found:
Line 1 Propeller curve through point S
Point A Intersection between line 1 and line L
1
– L
3
Point M Located on constant power line 7
through point A and with MP’s speed
Point O Equal to point A
Fig. 2.04.07: Special running conditions. Engine coupled to a fixed pitch propeller (FPP) and with a shaft generator
178 39 28-0.0
Also in this special case, a shaft generator is installed but,
compared to Example 3, this case has a specified MCR for
propulsion, MP, placed at the top of the layout diagram.
This involves that the intended specified MCR of the engine
M’ will be placed outside the top of the layout diagram.
One solution could be to choose a larger diesel engine with
an extra cylinder, but another and cheaper solution is to re-
duce the electrical power production of the shaft generator
when running in the upper propulsion power range.
In choosing the latter solution, the required specified MCR
power can be reduced from point M’ to point M as shown in
the Layout diagram. Therefore, when running in the upper
propulsion power range, a diesel generator has to take over
all or part of the electrical power production.
However, such a situation will seldom occur, as ships are
rather infrequently running in the upper propulsion power
range.
Point A, having the highest possible power, is then found at
the intersection of line L
1
– L
3
with line 1. see the Layout dia-
gram, and the corresponding load diagram is drawn. Point M
is found on line 7 at MP’s speed, and point O= A.
Propulsion curve
for fouled hull
and heavy weather
Power, % of L
1
100%
Engine speed, % of L
1
100%
7
5
4
1 2 6
1
2 6
7
SP
SG
MP
S
O=A
M
M
Propulsion curve
for fouled hull
and heavy weather
Power, % of L
1
100%
Engine speed, % of L
1
100%
1
2
6
7
SP
SG
MP
S
O=A
M
5% L
1
3.3%A 5%A
M
Engine service curve for fouled
hull and heavy weather
incl. shaft generator
4
3
3
Engine
service
curve
L
1
L
2
L
3
L
4
L
1
L
2
L
3
L
4
Layout diagram Load diagram