PULSE JET WITH “CYCLONIC VALVE”
PROOF-OF-CONCEPT MODEL
by
John Tindall
During research on a recent project I began to tinker with pulse jet
engines. This type of jet engine uses valves that open and close to
allow air to enter after each explosion. The Germans had a complex
array of spring reed valves that are beyond the capability of most garage
inventors to recreate. I came up with a novel design that is simple to
make that creates a uniform cyclonic airflow within the combustion
chamber. To test my design I made a clear acrylic model. I hoped that
the model would hold together long enough for me to see the interior
airflow.
PULSEJETS were used on the famous German V-1 “buzz bombs”
during WW II. But as far as jets go, they were destined to lose out to the
efficient, dependable, and powerful turbofan jets that power modern
airliners, fighters, and even helicopters. Maybe that’s their charm. It
could be the knowledge that you are part of a battle lost long ago and
forgotten by mainstream developers that draws in so many amateur
science buffs to these dead branches of the jet engine tree of
development.
Whatever the case, pulsejet engines fit the ideal model for development
in anyone’s garage because of a winning combination of attributes.
They are not complex to build, you only need a knowledge
of welding and some metal working.
There is vast online support.
If you actually get one to work it is inefficient, red hot and
louder than a boat horn.
It may explode like a cannon and take out a wall of your
house!
It’s easy to see why pulsejets have endeared themselves to so many
hobbyists.
PULSE JET VS. TURBOFAN JETS
Turbofan jet engines use a series of turbines to pull air in, pressurize mix
with fuel and create thrust. It is a continuous process with air flowing
through the engine in a non-interrupted flow.
TURBOFAN JET ENGINE
image courtesy of aerospaceweb.org
The pulse jet engine by contrast creates thrust through a series of
explosions that are tuned by the length and diameter of the engine.
VALVES OPEN
air flows into
combustion
chamber.
VALVES SHUT
Exploding Gases
create pressure wave
and thrust
CYCLONIC VALVE DESIGN
Most people settle on a
“flower petal” design that
allows air to enter around the
edge of the combustion
chamber. This creates a lot
of turbulence and makes for
inefficient fuel mixing and
airflow.
My theory: by making the
valves follow a radial
design a smoother
(cyclonic) airflow would
be achieved.
The proof of concept
model was constructed
of clear acrylic plastic
and aluminum valves
arranged to direct the
airflow in a clockwise
direction.
Clockwise:
The valves create cyclonic action. It
definitely works.
The valve and combustion chamber
are attached to exhaust/thrust tube.
Zoz Brooks PhD witnesses the pulse
jet in action. The thrust blew lab
coats off of their hooks.
It is clear why steel is the preferred
material for pulse jet engines – after
running successfully for 20 seconds
the jet backfired and blew itself
apart.
`
The remains of the pulse jet proof of
concept model. The model did last
long enough to see the cyclonic
airflow. A Success!
Now it’s on to the steel version!
PULSE JET PROOF OF CONCEPT
ASSEMBLY INSTRUCTIONS
Cut out aluminum valves 1 ¼” x 1 ½“.
Mark a 6” circle on the ¼” x 12” x 18”
acrylic sheet.
Drill four 1” holes at 12, 3, 6, 9 o’clock
position on the marked circle. Mark and
drill holes for mounting valves as seen in
picture.
Use undersized bit and tape holes and
thread acrylic with #8 tap. This will allow
the adjustment of the valves so that they
will seat properly.
Use backing nuts to lock screw at proper
adjustment.
Rig up propane tank to certified
pressure hose. Attach ½ “ copper
pipe to hose via pressure fittings.
Put ½ “ pipe (fuel injector) into hole
drilled in center of circle.
Heat pipe with short burn of
propane.
While hot form 6” pipe around 2”
pipe. Add electrodes.
Glue in place.
Complete!
Keep in mind that this proof of
concept model by design was only
expected to last a few seconds.
The goal was to see the internal air
flow to see if a radial valve design
would create a smoother airflow.
And it did! Now, on to the steel
version.