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
1
– L
3
and L
2
– L
4
, and by two constant engine speed
lines L
1
– L
2
and L
3
– L
4
. The L
1
point refers to the
engine’s nominal maximum continuous rating, see
Fig. 2.04.01.
Within the layout area there is full freedom to se-
lect the engine’s specified SMCR 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 (1st power) and
constant ship speed curves (0.15 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 drawnin. The
SMCR point (M) must be inside the limitation lines
of the layout diagram; if it is not, the propeller
speed will have to be changed or another main
engine type must be chosen. The selected SMCR
has an influence on the turbocharger and its
matching and the compression ratio.
For ME and ME-C/-GI engines, the timing of the
fuel injection and the exhaust valve activation are
electronically optimised over a wide operating
range of the engine.
For ME-B engines, only the fuel injection (and not
the exhaust valve activation) is electronically con-
trolled over a wide operating range of the engine.
178 60 85-8.1
Fig. 2.04.01: Engine layout diagram
For a standard high-load optimised engine,
the lowest specific fuel oil consumption for
the ME and ME-C engines is optained at 70%
and for MC/MC-C/ME-B engines at 80% of the
SMCR point (M).
For ME-C-GI engines operating on LNG, a further
SFOC reduction can be obtained.
Continuous service rating (S)
The continuous service rating is the power need-
ed in service – including the specified sea margin
and heavy/light running factor of the propeller
– at which the engine is to operate, and point S
is identical to the service propulsion point (SP)
unless a main engine driven shaft generator is in-
stalled.
To Next Page
Loading...
Need help?
General
