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
16 - 2
WÄRTSILÄ 32
Summary of Contents for PAAE051728
Page 4: ......
Page 18: ...Appendix B Welding Precautions 200640 00 6...
Page 26: ...01 Main Data Operating Data and General Design 32 200634 01 01 8 W RTSIL 32...
Page 60: ...Appendix A Environmental Hazards 200507 02A 10...
Page 68: ...Page 7 7 Document No 4V92A0645 Rev j...
Page 84: ...03 Start Stop and Operation 32 200402 04 03 12 W RTSIL 32...
Page 98: ...04 Maintenance Schedule 32 200623 01 04 14 W RTSIL 32...
Page 154: ...07 Tightening Torques and Use of Hydraulic Tools 32 200643 01 07 30 W RTSIL 32...
Page 162: ...08 Operating Troubles Emergency Operation 32 200402 01 08 8 W RTSIL 32...
Page 164: ...Specific Installation Data 2005 01 09 2...
Page 178: ...10 Engine Block with Bearings Oil Sump and Cylinder Liner 32 200150 10 14 W RTSIL 32 34SG...
Page 216: ...Appendix A Testing of cylinder tightness 32 200142 A 4 W rtsil 20 32 34...
Page 226: ...13 Camshaft Driving Gear 32 200546 02 13 10 W RTSIL 32...
Page 254: ...15 Turbocharging and Air Cooling 32 200549 10 15 20 W RTSIL 32...
Page 274: ...16 Injection System 32 200627 01 16 20 W RTSIL 32...
Page 280: ...Fuel System 32 200508 07 17 6 W RTSIL 32...
Page 314: ...19 Cooling Water System 32 200050 19 14 W RTSIL 32...
Page 394: ...23 Instrumentation and Automation 32 200115 II 23 60 W RTSIL 32...