M Specified MCR of engine
S Continous service rating of engine
O Optimising point of engine
A Reference point of load diagram
178 39 31-4.4
Fig. 2.04.08: Engine with Controllable Pitch Propeller
(CPP), with or without a shaft generator
Layout diagram without shaft generator
If a controllable pitch propeller (CPP) is applied,
the combinator curve (of the propeller) will nor-
mally be selected for loaded ship, including a sea
margin.
For a given propeller speed the combinator curve
may have a given propeller pitch, and this may
be heavy running in heavy weather like for a fixed
pitch propeller.
Therefore, it is recommended to use a light run-
ning combinator curve (the dotted curve which
includes the sea power margin) as shown in the
figure to obtain an increased operation margin of
the diesel engine in heavy weather to the limit, indi-
cated by lines 4 and 5.
Layout diagram with shaft generator
The hatched area shows the recommended speed
range between 100% and 96.7% of the specified
MCR speed for an engine with a shaft generator
running at constant speed.
The service point S can be located at any point
within the hatched area.
The procedure shown in examples 3 and 4 for
engines with FPP can also be applied here for en-
gines with CPP running with a combinator curve.
The optimising point O
O may, as earlier discribed, be chosen equal to
point M, see below.
Load diagram
Therefore, when the engine’s specified MCR point
(M) has been chosen, including engine margin,
sea margin and the power for a shaft generator,
if installed, point M can be used as point A of the
load diagram, which can then be drawn.
The position of the combinator curve ensures the
maximum load range within the permitted speed
range for engine operation, and it still leaves a
reasonable margin to the limit indicated by curves
4 and 5.
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