WÄRTSILÄ PAAE051728, Инструкция по эксплуатации

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16.1.2 Function
The injection pump pressurises fuel to the injection nozzle. It has
a regulating mechanism for increasing or decreasing the fuel feed
quantity according to the engine load and speed. The pumps are
governed by the governor.
The plunger, pushed up by the camshaft via the roller tappet
and pulled back by the spring acting on the plunger, reciprocate
in the element on a predetermined stroke to feed fuel under
pressure.
The plunger also controls the injected amount by adjusting the
helix edge position relative to the discharge port. The plunger has
an obliquely cut groove (lead) on its side. When the plunger is at
the lowest position or bottom dead centre, fuel flows through the
inlet port into the element bore. Rotation of the camshaft moves
the plunger up. When the top edge of the plunger step is lined up
with the ports, application of pressure to fuel begins. As the
plunger moves up further, and the helix of the plunger meets with
the ports, the high pressure fuel flows through the lead to the
ports and the pressure feed of fuel is completed.
The plunger stroke during which the fuel is fed under pressure
is called the effective stroke.
According to the engine load, the amount of fuel injected is
increased or reduced by turning the plunger a certain angle to
change the helix position where the ports are closed on the up
stroke and hence increasing or reducing the effective stroke. The
fuel rack is connected to the regulating mechanism of the gover-
nor. If the fuel rack is moved, the control sleeve in mesh with the
rack is turned. Since the control sleeve acts on the plunger, the
plunger turns with the control sleeve, thus the effective stroke
changes and the injected fuel amount increases or decreases.
The fuel delivery valve and constant pressure valve are located
in the head piece. The ports are of a special design to prevent
cavitation.
The delivery valve, provided into the head piece, performs the
function of discharging the pressurized fuel to the injection pipe.
The fuel compressed to a high pressure by the plunger forces the
delivery valve to pop up. Once the effective stroke of the plunger
ends, the delivery valve is brought back to its original position by
the spring and blocks the fuel path, thereby preventing counter
flow of the fuel.
After the effective stroke, the fuel is drawn back through the
constant pressure valve from the high pressure injection pipe to
instantly lower the residual pressure between the delivery valve
and the nozzle. This termination maintain consistent injection
“shot to shot” by maintaining a constant pressure in the pipe line
between injections.
The multihousing is provided with two erosion plugs, which can
easily be replaced when necessary.
16 Injection System 32-200627-01
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