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MAN B&W 2.04
Engine Layout and Load Diagram
Engine Layout Diagram
An engine’s layout diagram <strong>is</strong> limited by two constant
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 <strong>is</strong> full freedom to select
the engine’s specified MCR point M which
suits the demand for propeller power and speed
for the ship.
On the horizontal ax<strong>is</strong> the engine speed and on
the vertical ax<strong>is</strong> the engine power are shown on
percentage scales. The scales are logarithmic
which means that, in th<strong>is</strong> 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.
Specified 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 drawn�in. The
specified MCR point (M) must be inside the limitation
lines of the layout diagram; if it <strong>is</strong> not, the propeller
speed will have to be changed or another
main engine type must be chosen.
Continuous service rating (S)
The continuous service rating <strong>is</strong> the power at
which the engine <strong>is</strong> normally assumed to operate,
and point S <strong>is</strong> identical to the service propulsion
point (SP) unless a main engine driven shaft generator
<strong>is</strong> installed.
Matching point (O)
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For practical reasons we have chosen to use the
designation ‘O’ for the matching point.
The engine matching point (O) <strong>is</strong> 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 optim<strong>is</strong>ed over a
wide operating range of the engine, the selection
of matching point only has a meaning in connection
with the turbocharger matching and the compression
ratio.
The lowest specific fuel oil consumption for ME
engines <strong>is</strong> obtained at 70% of the matching point
(O).
Power
Fig. 2.04.01: Engine layout diagram
178 51 39�4.0
MAN B&W ME/ME-C/ME-GI engines 198 38 97-3.6
MAN Diesel
L 3
L 4
L
L 2
Speed