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Page Title:
Section Ill. TECHNICAL PRINCIPLES OF OPERATION |
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 TM 3-1040-279-12&P
Section Ill. TECHNICAL PRINCIPLES OF OPERATION
1-12 FUEL AND AIR SYSTEMS.
1-11 PULSE JET ENGINE.
The fuel pump assemblies pump fuel from
Initially a mixture of fuel and air is forced
the 5-gallon (18.2-litre) fuel tanks to the nozzle
into the combustion chamber of the pulse jet
assemblies mounted on the pulse jet engines head
engine by holding the ENGINE switch at the
of each smoke generator assembly. At the same
control panel assembly in the START position.
time, the air compressor assembly provides the
A spark at the igniter causes the fuel/air mixture
start air to the same nozzle assemblies. The mix-
to explode. The positive pressure developed as
ture of fuel and air pass through the nozzle
this explosion occurs closes the engine valve and
assemblies and is injected into the pulse jet
forces the burning gases through the engine tube.
engines where the mixture is exploded.
Reflection of the shock wave off the engine valve
develops a negative pressure on the combustion
1-13 FOG OIL SYSTEM.
chamber side of the engine valve. The negative
pressure permits external air under atmospheric
The fog oil pump assembly draws fog oil from
pressure to enter the combustion chamber. As
a storage tank and pumps it into the pulse jet
the air passes over the nozzle assembly, fuel is
engines once they are in operation. Vaporization
forced into the air stream. Once again, the fuel/
occurs as the fog oil is mixed with the engine
air mixture is forced through the engine valve
exhaust gases produced when the fuel/air mixture
and into the combustion chamber, where the
is exploded. The vaporized fog oil is forced out
mixture is exploded by the heat of the pulse
into the atmosphere where it cools and condenses
jet engine.
into very small liquid droplets which make up the
smoke.
The FOG OIL FLOW control knob, on the
The igniter is required for only the first
control panel, varies the flow of fog oil and oper-
explosion. After the ENGINE indicator lights,
ating temperature of the smoke generator. As the
the ENGINE switch on the control panel assem-
fog oil flow is increased, the operating tempera-
bly can be released to RUN and successive charges
ture decreases. The nominal operating range is
of fuel/air mixture will be exploded by contact
between 650 -950F (343-510C), and can be
with the hot gases and metal in the combustion
read from the SMOKE TEMP indicator on the
chamber. The frequency of explosion in the pulse
control panel.
jet engine is approximately 60 times per second.
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