Mystery Valveless PJ Sighted

[hinote]

Hi all:

Please see the attached photo.

This valveless pulsejet was spotted in my driveway, starting and operating as easily as any PJ I've ever experienced.

I'll provide further details in the near future; for now, this photo is just a teaser.

Several of you Forum members know what's going on; Hagen (and Mike E.) please don't give the secret away (yet).

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[larry cottrill]

Nice, graceful looking design - almost like like a slimmed-down Lockwood with a misplaced bend. Are you getting augmentation out of the tail-end gimmick, or is it more or less just a slider for tuning?

L Cottrill

[hinote]

Are you getting augmentation out of the tail-end gimmick, or is it more or less just a slider for tuning?
L Cottrill

The photo is misleading, I'm afraid. There's a ring of exhaust pipe material, left in place during construction (and due for removal). I use pieces of exhaust pipe to maintain a circular cross-section; when it's slid along the meg and forced down as far as it will go it prevents deformation during the weld-up process.

The ring in the photo is the same size as the final section--so it's easily confused.

As always, the final tailpipe section shown is responsible for a lot of the total thrust figure, due to re-ingestion of cold air.

Please see the attached image. It shows the mass outflow from the engine. Cycle time is about 1.5X of a full cycle; the lighter green is outflow from the exhaust end (above the line); darker green is outflow from the intake end.

You can see the secondary outflow from the exhaust, after the end of the cycle (red arrow).

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[hinote]

It cycles slow enough for the indicated area to be included in a cycle?

Sorry--I wasn't quite clear about it. As usual (with pulsejets) there's a complex relationship of output activity overlaying the resonant cycle.

I doctored the graph above, to try and refine the observations. See below.

The dark green (below the line) is still mass outflow from the intake end of the engine.

Primary outflow is labelled #4. #5 is a second primary outflow, occurring during the cycle. it follows an reingestion event, so it too ejects cold air.

Now, the end of the event is indicated by the blue line at #1. Cycle length is .0062 sec.

If we restart the event at #1, we add the primary outflow (again) to the next cycle. This outflow (#4) began at approx .0015 sec--so if we add that to the beginning of the 2nd cycle we get .0087 sec (labelled as #2 in the graph) I duplicated the #4 event and placed it at the correct timeline on the graph--you can see that it complements the secondary outflow event (#3) quite well.

EDIT: The obvious result of this overlap is that the waveform depicted in the 2nd cycle is completely inaccurate! The actual output would probably be a combined waveform instead. It would still appear to be an advantageous overlap to this humble PJ designer.

This simulation is subject to considerable inaccuracies, because of the presumptions used to create it (in Uflow). OTOH the information used to create the graph is also creating some pretty nice engines!!

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[Eric]

Your creations are starting to make me a little nervous here Bill :)

Is this drifting towards what I think it is with the U-bend front being even with the front of the combustion chamber?

If it is the length can be greatly reduced once it is finished :). If not then just ignore me... ok I will shut up now since no one else probably has a clue to what I am talking about....

Eric

[hinote]

I will shut up now since no one else probably has a clue to what I am talking about....

I do.

Bill Hinote
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[hinote]

Is this drifting towards what I think it is with the U-bend front being even with the front of the combustion chamber?

Not yet--but soon.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[Eric]

Well of course YOU do :D lol

So later on how are you going to do the other things, on the exterior of the axis or the interior?

Eric

[hinote]

So later on how are you going to do the other things, on the exterior of the axis or the interior?

Exterior, to start. Gotta be able to change things. Then, I'll decide.

Bill H.

Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[Mike Everman]

Sweet motor, Bill! And I have no idea what Eric's talking about, so your inferences are sufficiently obtuse! Your secret appears to be safe. ;-P

[hagent]

Nice Bill !

Can't wait to hear and see it run.

Any preliminary thrust measurements?

Good Job.

[Eric]

LoL. I thought you two were the ones that were supposed to have an idea of what was going on.

Its really not too hard to imagine...

Eric

[Viv]

Increased surface area will be the issue along with boundry layer problems due to the local velocity, not unsolvable but it will throw your initial dimensions out more than you would at first think.

Best of luck

Viv;-)

[Mike Everman]

LoL. I thought you two were the ones that were supposed to have an idea of what was going on.

Its really not too hard to imagine...

Eric

"It" what? I can imagine a lot of things. Let's just say that I'll do mine a little to the left, with a twist!
In the politest possible way I can say this, perhaps you two should talk off-line if you're compelled to speak in code...

[Viv]

LoL. I thought you two were the ones that were supposed to have an idea of what was going on.

Its really not too hard to imagine...

Eric

"It" what? I can imagine a lot of things. Let's just say that I'll do mine a little to the left, with a twist!
In the politest possible way I can say this, perhaps you two should talk off-line if you're compelled to speak in code...

Oh come on Mike its not that hard to work out;-)

Viv