Marine Installation Manual 2021-08 1-7
1 Engine Summary
1.3 Fuel operating modes
X72DF
1.3.1 Operation in gas mode
The engine operates in gas mode according to the Otto cycle with a pre-mixed
lean air-gas mixture, which is ignited by a small amount of pilot fuel. The
amount of injected pilot fuel used is approximately the same across the entire en-
gine power range. This is equivalent to approximately 1-2 % of the total energy
consumption at 100 % engine power (for the energy distribution during gas mode
see Figure 1-4).
Figure 1-4 Gas mode operation
Dynamic combustion control
Dynamic Combustion Control (DCC) allows full power output for gas mixtures
with a methane number of 65 and higher (see subsection Methane number de-
pendent engine output, 4-37), independent of ambient condition and engine
rating. While DCC is active in combustion stabilising mode, a small amount of
liquid fuel is injected by the main fuel injectors, boosting the turbocharger to pro-
vide sufficient combustion air, maintaining the intended air-gas mixture
(lambda).
NOTE
At any time, the gas operation can be stopped immediately by initiating
a gas trip.
NOTE
While DCC is active the engine remains Tier III compliant.
Total fuel
[power %]
Gas
10050
0
0
50
100
Pilot fuel (enlarged for visibility reasons, not scaled)
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