MAN B&W 2.04
Page of
MAN Diesel
MAN B&W ME/ME-C/ME-GI engines
198 38 97-3.6
Engine Layout and Load Diagram
Engine Layout Diagram
An engine’s layout diagram is limited by two con-
stant mean effective pressure (mep) lines L
– L
3
and L
2
– L
4
, and by two constant engine speed
lines L
– L
2
and L
3
– L
4
. The L
point refers to the
engine’s nominal maximum continuous rating.
Within the layout area there is full freedom to se-
lect the engine’s specied MCR point M which
suits the demand for propeller power and speed
for the ship.
On the horizontal axis the engine speed and on
the vertical axis the engine power are shown on
percentage scales. The scales are logarithmic
which means that, in this diagram, power function
curves like propeller curves (3rd power), constant
mean effective pressure curves (st power) and
constant ship speed curves (0.5 to 0.30 power)
are straight lines.
Specied maximum continuous rating (M)
Based on the propulsion and engine running
points, as previously found, the layout diagram
of a relevant main engine may be drawnin. The
specied MCR point (M) must be inside the limita-
tion lines of the layout diagram; if it is not, the pro-
peller speed will have to be changed or another
main engine type must be chosen.
Continuous service rating (S)
The continuous service rating is the power at
which the engine is normally assumed to operate,
and point S is identical to the service propulsion
point (SP) unless a main engine driven shaft gen-
erator is installed.
Matching point (O)
For practical reasons we have chosen to use the
designation ‘O’ for the matching point.
The engine matching point (O) is placed on line
in the load diagram, Fig. 2.04.02, and can be from
85 to 00% of point M’s power, however it has to
be placed inside the layout diagram.
Overload running (0% of M) will still be possible.
As the timing of the fuel injection and the exhaust
valve activation are electronically optimised over a
wide operating range of the engine, the selection
of matching point only has a meaning in connec-
tion with the turbocharger matching and the com-
pression ratio.
The lowest specic fuel oil consumption for ME
engines is obtained at 70% of the matching point
(O).
178 51 394.0
Fig. 2.04.01: Engine layout diagram
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