SECTION 2.
05
FUEL SYSTEM DESCRIPTION
FUEL SYSTEM COMPONENTS
The engine fuel system consists of the following
engine mounted components:
Carburetors
Throttle valves
Fuel pressure regulator and balance line(s)
Fuel shutoff valve
CARBURETOR
The carburetor uses an air valve to meter the fuel gas
proportionally to the air flow. A regulator controls the
fuel gas supply pressure to the carburetor.
The IMPCO carburetors consist of a main body with a
venturi and a diaphragm operated gas metering valve
(see Figure 2.05-1, Figure 2.05-2, Figure 2.05-3 and
Figure 2.05-4). The amount of air passing into the
engine is measured by an air-flow measuring valve
which rises proportionally to the air volume passing
through the carburetor. The gas metering valve is
attached to the air measuring valve which opens the
gas valve proportionally to the air volume. This controls
the air/fuel ratio throughout the engine speed and load
range.
CARBURETOR
Figure 2.05-2 H24G IMPCO 600 Carburetor
CARBURETOR
CARBURETOR
POWER
ADJUSTMENT
SCREW
Figure 2.05-3 F18/H24GSID IMPCO 600 Carburetor
Figure 2.05-1 F18/H24GL IMPCO 400 Carburetor
FORM 6284 Third Edition
2.05-1
FUEL SYSTEM DESCRIPTION
CARBURETOR
Figure 2.05-4 F18/H24GLD IMPCO 600D Carburetor
Deltec carburetors have low inlet restriction for
improved performance. The carburetor's flat tracking
provides desirable performance and low emissions
and allows lean operation with low octane fuels (see
Figure 2.05-5).
WARNING
The Deltec carburetion system must have a positive gas shutoff valve that opens upon cranking
and closes whenever engine rotation stops. Failure to provide the valve will cause an explosive
environment resulting in severe personal injury or
death.
Deltec carburetors contain no moving parts. The main
adjustment screw (MAS) controls the fuel gas to the
carburetor (see Figure 2.05-5 and Figure 2.05-6). The
carburetor consists of a main body with a perforated
venturi insert that allows fuel gas to be drawn into the
air stream. The size and number of the holes controls
the air/fuel mixture.
DELTEC
CARBURETOR
MAIN ADJUSTING
SCREW
CARBURETOR
Figure 2.05-6 F18/H24GLD Deltec Carburetor
CARBURETOR GL
The IMPCO carburetor used on the GL engine uses
an air valve to meter the fuel gas proportionally to the
air flow (see Figure 2.05-7). A regulator controls the
fuel gas supply pressure to the carburetor. A carburetor inlet pressure range of 154.2 12 mm (6 0.5 in.)
water column is typical for the L36/P48GL operating
on 900 Btu LHV natural gas.
CARBURETORS
Figure 2.05-7 IMPCO GL Carburetors
The carburetors consist of a main body with a venturi
and a diaphragm-operated gas metering valve. The
amount of air passing into the engine is measured by
two air-flow measuring valves which rise proportionally
to the air volume passing through the carburetor. The
gas metering valves are attached to the air measuring
valves which open the gas valves proportionally to the
air volume. This controls the air/fuel ratio throughout
the engine speed and load range.
Figure 2.05-5 F18/H24GLD Deltec Carburetor
2.05-2
FORM 6284 Third Edition
FUEL SYSTEM DESCRIPTION
FUEL PRESSURE REGULATOR GL
BALANCE LINE
The GL engines typically use a Y692 cast iron regulator which reduces the supply line pressure (25 50 psi) to a carburetor inlet pressure above turbocharger boost pressure (see Figure 2.05-8). From this
regulator, the fuel gas is directed to the carburetor.
BALANCE
TUBE
SPRING
OUTLET
VALVE
DISC
Figure 2.05-10 L36/P48GL Fuel Regulator
CARBURETOR GLD/GSID
PUSHER
POST
ORIFICE
INLET
Some GLD/GSID engines use Deltec carburetors (see
Figure 2.05-11). The Deltec carburetor has low inlet
restriction for improved performance. A gas over air
pressure range of 0 12 mm (0 0.5 in.) water column is typical for the L36/P48GLD/GSID operating on
900 Btu LHV natural gas.
Figure 2.05-8 Fuel Pressure Regulator
BALANCE LINE
A balance line is required to connect the pressurized air
in the intercooler to the spring side of the fuel regulator
diaphragm (see Figure 2.05-9 and Figure 2.05-10). This
balance line will cause the regulator to change the carburetor gas pressure as the intake air pressure
changes.
BALANCE LINE
CARBURETOR
Figure 2.05-11 GLD/GSID Deltec Carburetor
WARNING
The Deltec carburetion system must have a positive gas shutoff valve that opens upon cranking
and closes whenever engine rotation stops. Failure to provide the valve will cause an explosive
environment resulting in severe personal injury or
death.
Figure 2.05-9 H24G IMPCO 600 Carburetor
Balance Line
FORM 6284 Third Edition
Deltec carburetors contain no moving parts. The main
adjustment screw (MAS) controls the fuel gas to the
carburetor (see Figure 2.05-12). The carburetor consists of a main body with a perforated venturi insert
that allows fuel gas to be drawn into the air stream.
The size and number of the holes controls the air/fuel
mixture.
2.05-3
FUEL SYSTEM DESCRIPTION
THROTTLE VALVES
MAIN ADJUSTMENT
SCREW
Figure 2.05-14 L36/P48GL Throttle Valves
Figure 2.05-12 GLD/GSID Deltec Fuel Adjustment
FUEL PRESSURE REGULATOR ZERO
PRESSURE (IF EQUIPPED)
On Deltec fuel systems the fuel regulator is often
called a zero pressure regulator (ZPR). This term is
used to refer to the fuel pressure at the regulator outlet
/carburetor inlet (-25 51 mm (-1 to 2 in.) H2O), which
is very close to the value of the air pressure going into
the carburetor. The basic principle is that the Deltec
will draw in the amount of fuel it needs (through the
venturi), but that fuel should not be under pressure nor
should it be under a vacuum (in reference to the air).
THROTTLE VALVES
The flow of air into the engine is controlled by the governor operated throttle valves located downstream from
the carburetor (see Figure 2.05-13 and Figure 2.05-14).
THROTTLE
VALVE
MANUAL FUEL SHUTOFF VALVE (IF EQUIPPED)
All
VGF
engines
include hand throttle
controls for emergency shutdown procedures.
Make sure that the hand throttle is maintained in
the open position during startup and normal running conditions. Disregarding this information
could result in product damage and/or personal
injury.
CAUTION
The fuel solenoid shutoff valve is located at the gas
fuel inlet to the regulator valve (see Figure 2.05-15).
This valve is electrically actuated by a safety switch
powered by the magneto. An electrical signal causes
the gas valve to close off the fuel supply for normal
and emergency shutdowns. The latching valve should
be turned 1/4 turn clockwise to latch the valve open for
starting. The manual lever can be rotated clockwise to
manually close the valve for shutdown.
TRIP ARM
COIL
VALVE
SEAT
Figure 2.05-13 F18/H24 Throttle Valve
INLET
OUTLET
VENT PLUG
LATCH VALVE
Figure 2.05-15 Shutoff Valve
2.05-4
FORM 6284 Third Edition
FUEL SYSTEM DESCRIPTION
LEFT BANK CARBURETOR AFFECTS
RIGHT BANK CYLINDERS
LEFT BANK
INTAKE MANIFOLD
FRONT
FLOW FROM LB CARBURETOR
RIGHT BANK CARBURETOR AFFECTS
LEFT BANK CYLINDERS
FLOW FROM RB CARBURETOR
RIGHT BANK
INTAKE MANIFOLD
Figure 2.05-16 L36/P48 GLD/GSID Air/Fuel Flow As Viewed From The Top
At rated speed, the L36/P48GLD/GSID carburetors
feed the opposite cylinder bank. Any leaks in one bank
of air filters, air ducting systems or carburetor will affect
the opposite bank cylinders (see Figure 2.05-16).
OPERATION
Rotate the manual lever counterclockwise to open the
latch valve for starting, this causes the plunger to lift
away from the valve seat and latches the trip arm.
When the safety switch actuates, a circuit is completed
through the coil, causing a magnetic action that
releases the trip arm. Spring tension forces the
plunger down on the valve seat, sealing off fuel gas
flow. Gas pressure on top of the plunger helps to
assure a positive seal. Once the valve has operated, it
must be manually reset before restarting the engine.
CUSTOM ENGINE CONTROL AIR/FUEL
MODULE SYSTEM
SYSTEM DESCRIPTION
This section gives a brief introduction to Waukesha's
Custom Engine Control (CEC) Air/Fuel Module (AFM)
FORM 6284 Third Edition
system. For complete information on the system, see
Form 6263 (Software Version 2.8a) or Form 6286
(Software Version 4 Series), AFM Custom Engine
Control Air/Fuel Module, Installation, Operation And
Maintenance.
The CEC AFM system is designed to control the
air/fuel ratio of Waukesha's gaseous fueled VGF
engines including stoichiometric and lean burn, naturally aspirated and turbocharged. Basic information
about the engine model and application is programmed to the AFM using a personal computer (PC).
An engine's air/fuel ratio defines the amount of air in
either weight or mass in relation to a single amount of
fuel supplied for combustion. Air/fuel ratio influences
engine power, emissions, and fuel economy. By controlling an engine's air/fuel ratio with the AFM system,
you will benefit in fuel savings, emissions control,
and/or peak engine performance. The AFM system
regulates and maintains the engine's air/fuel ratio even
with changes in engine load, speed, fuel pressure, and
fuel quality.
2.05-5
FUEL SYSTEM DESCRIPTION
The AFM system is programmed at the engine site
with a PC and is customized for the engine based on
site specific information to run in one of four control
modes: catalyst, best power, best economy, or lean
burn. Catalyst and best power/economy modes apply
to stoichiometric or rich burn engines. Lean burn mode
only applies to lean burn engines.
OPERATOR INTERFACE
The AFM module is equipped with several features to
inform site personnel of system status. These features
include:
Power and Alarm lights (LED display) on the
front panel of the AFM module (see Figure 2.05-17)
The green Power LED is lit any time power is
applied to the AFM module
The yellow Alarm LED is lit any time the AFM
system's diagnostic functions are activated or
when AFM execution has been stopped by the
operator (such as during the saving of a dataset)
an alpha-numeric liquid crystal display (LCD display) visible from the front of the AFM module
allows the operator to monitor important system
parameters
a sealed membrane keypad located on the front of
the AFM module
LED DISPLAY
THEORY OF OPERATION
The AFM system controls engine air/fuel ratio and
consists of three basic components: an oxygen sensor, stepper motor, and AFM module. The AFM system is a closed-loop process that looks at system
outputs and adjusts system inputs according to preprogrammed instructions.
The AFM system functions by monitoring oxygen levels in the exhaust gases with an oxygen sensor
located in the engines exhaust stream (see
Figure 2.05-18). The oxygen level, detected by the
sensor, is then fed to the AFM module through an
electrical signal. If the oxygen level detected by the
sensor is different than the programmed oxygen setpoint, the AFM module directs the actuator to adjust
the gas over air pressure of the fuel regulator.
The actuator adjusts the fuel regulator setting, within
programmed limits, by increasing or decreasing the
spring pressure acting on the regulator diaphragm.
The design gives very accurate positioning capability.
This assembly essentially automates the manual
adjusters that are sold with many Waukesha engines.
The regulator adjustment riches or leans the air/fuel
ratio.
A thermocouple is used to assure that temperatures
are high enough for correct operation of the sensor. A
programmed minimum temperature must be achieved
before closed-loop control is enabled. A programmed
maximum temperature is also incorporated as a safety
to shut down operation on high exhaust temperature
conditions.
The oxygen sensor provides continuous feedback of
oxygen levels to the AFM module. The AFM module
makes the necessary actuator adjustments to correctly
control the engine's air/fuel ratio.
LCD DISPLAY
KEYPAD
Figure 2.05-17 CEC Air/Fuel Module
2.05-6
FORM 6284 Third Edition
FUEL SYSTEM DESCRIPTION
OXYGEN
SENSOR
ELECTRICAL
SIGNAL
AFM
MODULE
REGULATOR WITH
ACTUATOR
Figure 2.05-18 AFM Systems Closed-Loop Process
FORM 6284 Third Edition
2.05-7
