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 distri-
bution 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. The intermediate gear wheels are fixed together by means of a hydraulically
tightened central bolt.
4.2.11
Fuel system
The Wärtsilä 34DF 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 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
single 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).
The venting valve of the gas common rail pipe is used to release the gas from the common rail pipe when
the engine is transferred from gas operating mode to diesel operating mode. The valve is pneumatically
actuated and controlled by the engine control system.
Main fuel oil injection system
The main fuel oil injection system is in use when the engine is operating in diesel mode. When the engine
is operating in gas mode, fuel flows through the main fuel oil injection system at all times enabling an instant
transfer to diesel mode.
The engine internal main fuel oil injection system comprises the following main equipment for each cylinder:
•
Fuel injection pump
•
High pressure pipe
•
Twin fuel injection valve (for main and pilot injection)
The fuel injection pump design is of the mono-element type designed for injection pressures up to 150
MPa. The injection pumps have built-in roller tappets, and are also equipped with pneumatic stop cylinders,
which are connected to overspeed protection system.
The high-pressure injection pipe runs between the injection pump and the injection valve. The pipe is of
double wall shielded type and well protected inside the engine hot box.
Product Guide Wärtsilä 34DF - 3/2012
23
Product Guide
4. Description of the Engine
