Marine Installation Manual
2021-08
4-34
4 Ancillary Systems
4.4 Fuel gas system
X72DF
4.4.2
Operating principles
The WinGD X-DF engines are normally installed for dual-fuel operation, where
the engine can operate in either gas or diesel mode. The operating mode can be
changed while the engine is running, within certain limits, without interruption
of power generation. If the fuel gas supply fails, then the engine will automati
-
cally trip to diesel mode operation.
The lean-burn concept
In gas operating mode, the X-DF engine runs as a lean-burn engine utilising nat
-
ural gas as the main source of fuel. The fuel gas is supplied to the engine at low
pressure. Gas ignition is initiated by injecting a small amount of pilot fuel
(MDO /MGO), providing a high-energy ignition source for the main fuel charge
(gas-air mixture) in the cylinder (see
). Fuel gas admission is
hydraulically actuated and electronically controlled.
With the lean fuel gas mixture it is possible to achieve good engine characteris
-
tics regarding output, efficiency and emissions. A lean air to fuel gas mixture is
also utilised to avoid knocking. However, at high loads the misfiring limit gets
closer to the knocking limit, which means that the available operating window is
decreasing (see
). Thanks to continuous combustion moni
-
toring, the engine operation will remain in the correct operating window.
Combustion control
for each cylinder
One of the key measures is to control the combustion process separately in each
cylinder to remain within the operating window and have optimal performance
under all conditions for each cylinder regarding safety, efficiency and emissions.
The X-DF engine facilitates individual cylinder combustion control, which
makes it possible to obtain optimal operating performance at conditions where
gas quality, ambient temperature, etc. may vary.
