WÄRTSILÄ WARTSILA 50DF, Руководство по эксплуатации продукта

Страница: 43 / 240

together with the upper deck and the side walls form a box section in the four corners of which
the hydraulically tightened cylinder head bolts are situated.
The cylinder head features two inlet and two exhaust valves per cylinder. All valves are equipped
with valve rotators. No valve cages are used, which results in very good flow dynamics. The
basic criterion for the exhaust valve design is correct temperature by carefully controlled water
cooling of the exhaust valve seat. The thermally loaded flame plate is cooled efficiently by
cooling water led from the periphery radially towards the centre of the head. The bridges
between the valves cooling channels are drilled to provide the best possible heat transfer.
4.2.9 Camshaft and valve mechanism
There is one campiece for each cylinder with separate bearing pieces in between. The cam
and bearing pieces are held together with flange connections. This solution allows removing
of the camshaft pieces sideways. The drop forged completely hardened camshaft pieces have
fixed cams. The camshaft bearing housings are integrated in the engine block casting and are
thus completely closed. The bearings are installed and removed by means of a hydraulic tool.
The camshaft covers, one for each cylinder, seal against the engine block with a closed O-ring
profile. The valve mechanism guide block is integrated into the cylinder block. The valve
tappets are of piston type with self-adjustment of roller against cam to give an even distribution
of the contact pressure. Double valve springs make the valve mechanism dynamically stable.
4.2.10 Camshaft drive
The camshafts are driven by the crankshaft through a gear train.
The driving gear is fixed to the crankshaft by means of flange connection.
4.2.11 Fuel system
The Wärtsilä 50DF engine is designed for continuous operation on fuel gas (natural gas) or
Marine Diesel Fuel (MDF). It is also possible to operate the engine on Heavy Fuel Oil (HFO).
Dual fuel operation requires external gas feed system and fuel oil feed system. For more details
about the fuel system see chapter Fuel System.
Fuel gas system
The fuel gas system on the engine comprises the following built-on equipment:
●
Low-pressure fuel gas common rail pipe
●
Gas admission valve for each cylinder
●
Safety filters at each gas admission valve
●
Common rail pipe venting valve
●
Double wall gas piping
The gas common rail pipe delivers fuel gas to each admission valve. The common rail pipe is
a fully welded double wall pipe, with a large diameter, also acting as a pressure accumulator.
Feed pipes distribute the fuel gas from the common rail pipe to the gas admission valves
located at each cylinder.
The gas admission valves (one per cylinder) are electronically controlled and actuated to feed
each individual cylinder with the correct amount of gas. The gas admission valves are controlled
by the engine control system to regulate engine speed and power. The valves are located on
the cylinder head (for V-engines) or on the intake duct of the cylinder head (for in-line engines).
The gas admission valve is a direct actuated solenoid valve. The valve is closed by a spring
(positive sealing) when there is no electrical signal. With the engine control system it is possible
to adjust the amount of gas fed to each individual cylinder for load balancing of the engine,
while the engine is running. The gas admission valves also include safety filters (90 µm).
Wärtsilä 50DF Product Guide - a16 - 9 September 2016 4-3
4. Description of the Engine Wärtsilä 50DF Product Guide