6.3.1.1 Injection Equipment
For gas operation:
When running in gas mode the main components are the gas admission valves and the smaller
needle in the dual fuel injection valve.
Gas admission valve
The gas admission valves are working as the engine speed regulator and are controlling the
amount of gas fed to each cylinder of the engine. The valve is located on the cylinder head
and the gas is fed into the inlet channel of the cylinder head. The main gas valve is a direct
actuated solenoid valve. The engine automation system (UNIC) adjusts the amount of gas fed
to individual cylinders.
On-engine MCC de-gassing valve (formerly called “venting valve”)
The Main Combustion Chamber line de-gassing valve (MCC) is one of the venting valves of
gas system. Other venting valves are placed in the external gas system. MCC de-gassing
valve is on-engine, at end of gas manifold. Line engines have internally one MCC de-gassing
valve. Vee engines have internally two of them, one per bank. An MCC de-gassing valve
releases the gas pressure when changing from gas mode to diesel mode, or backup mode,
or at engine stopping in gas mode. It acts shortly also at gas mode initiation. It acts also at
automation purging.
When operating the engine in gas mode, the gas is injected through gas admission valves into
the inlet channel of each cylinder. The gas is mixed with the combustion air immediately
upstream of the inlet valve in the cylinder head. Since the gas valve is timed independently of
the inlet valve, scavenging of the cylinder is possible without risk that unburned gas is escaping
directly from the inlet to the exhaust.
6-14 DBAD209883
Wärtsilä 46DF Product Guide6. Fuel System
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