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MAN B&W 2.04
Example 6:
Engines running at constant speed with controllable
pitch propeller (CPP)
Fig. A Constant speed curve through M, normal
and correct location of the matching point O
Irrespective of whether the engine <strong>is</strong> operating on
a propeller curve or on a constant speed curve
through M, the matching point O must be located
on the propeller curve through the specified MCR
point M or, in special cases, to the left of point M.
The reason <strong>is</strong> that the propeller curve through
the matching point O <strong>is</strong> the layout curve of the
engine, and the inter<strong>section</strong> between curve and
the maximum power line 7 through point M <strong>is</strong>
equal to 00% power and 00% speed, point A of
the load diagram � in th<strong>is</strong> case A=M.
In Fig. A the matching point O has been placed
correctly, and the step�up gear and the shaft generator,
if installed, may be synchron<strong>is</strong>ed on the
constant speed curve through M.
Fig. B: Constant speed curve through M, wrong
position of matching point O
If the engine has been service�matched at point O
on a constant speed curve through point M, then
the specified MCR point M would be placed outside
the load diagram, and th<strong>is</strong> <strong>is</strong> not perm<strong>is</strong>sible.
Fig. C: Recommended constant speed running
curve, lower than speed M
In th<strong>is</strong> case it <strong>is</strong> assumed that a shaft generator,
if installed, <strong>is</strong> synchron<strong>is</strong>ed at a lower constant
main engine speed (for example with speed equal
to O or lower) at which improved CP propeller efficiency
<strong>is</strong> obtained for part load running.
In th<strong>is</strong> layout example where an improved CP propeller
efficiency <strong>is</strong> obtained during extended periods
of part load running, the step�up gear and the
shaft generator have to be designed for the lower
constant engine speed that <strong>is</strong> applied.
Engine speed
Page of
MAN B&W ME/ME-C/ME-GI engines 198 38 97-3.6
MAN Diesel
Power
4
Constant speed service
curve through M
Fig. A: Normal procedure
Constant speed service
curve through M
Fig. B: Wrong procedure
Constant speed service
curve with a speed lower
than M
Fig. C: Recommended procedure
Logarithmic scales
4
4
1
1
5
5
1
5
A=M
O
A=M
M A
M: Specified MCR
O: Matching point
A: 00% power and speed of load diagram (normally A=M)
178 19 69�9.0
Example 6:
Position of matching point O for engines running
at constant speed.
O
O
7
7
3
3
7
3