X-Jet

[Bruno Ogorelec]

everyone though the valves would have to travel too far but didnt seem to pick up on the fact that if they were made V shaped the internal resistance and travel distance is greatly reduced.

Eric, I still like this design and regret the fact that (to the best of my knowledge) no one has tried it.

What I find very interesting is that this thing will not move the flaps in quite the same way as, say, a Dynajet. The V-shaped valve flap will be both pushed by the hot gas pressure and pulled by the vacuum. Normal reeds are pulled by the vacuum to open and pushed by the hot gas to close. (This is not quite true, but good enough for the purpose of explanation.)

So, the dynamics will be different. Its surface area will be greater than in a conventional engine for a given engine section. Aerodynamic drag of the flap will be massively lower than in the reed valve assembly. The inevitably lower working frequency will be more than offset by the fact that the useful frequency will be double, because of two combustors working out of phase.

Practically the only thing that bothers me is the symmetrical working cycle.

Warning! Warning! A major boast follows!

Let me say here that I think I have discovered why paired identical combustors develop less than double the thrust of a single combustor. (That much was established by the Kentfield team in Calgary – the only people I know of who have done extensive work on pairing combustors.) Conventional theory said that they should aid each other and thus develop more than double -- but in practice, the combined thrust was a bit lower than double. The reason has been a complete mystery to everyone – including Kentfield, who expected a gain in performance.

I’ve been chewing on that for years without becoming any wiser -- and then it finally dawned on me.

As always, the answer is amazingly simple. The secret is that with synchronized work, the working cycle is symmetrical. The intake must last exactly as long as the exhaust or the combustors will not be in sync. This is not good! In single operation, you try to time the intake phase to last quite a bit longer than the exhaust. If you restrict the intake to just a half of the cycle, performance will suffer.

[Eric]

Well thats true, and the same reason why you can only get about 20% noise cancelation, but the power loss only applies to dual engines working out of phase.

I have a design that would be somewhere in between 1.5 and dual.

It definately has improved performance from in phase operation, more along the lines of 3x instead of 2x, though sound is also higher :(

Im thinking of releasing some of the more experimental projects I have done, especially since I have already gone as far as given plans to several people.

Eric

[gundamnitpete]

Here is a quick 5 minute unskewed diagram of the 180 degree out of phase valved engine.

When I posted the first diagram of the engine I had the valve plates flat, and both in line with eachother, everyone though the valves would have to travel too far but didnt seem to pick up on the fact that if they were made V shaped the internal resistance and travel distance is greatly reduced.

This engine layout seems to fit most of the xjet claims and definately the appearance.

Eric

hmm....that's very interesting.

one question tho, if this is the setup he's using, how does he manage such a short tail pipe? perhaps he uses a nozzle to increase the resist of the expanding exhaust gases, slow them down quicker, but still manage to have just enough vaccum in the combustion chamber to reignite the new mixture.


since it's design has one combustion closing the valve as the vaccum sucks in air, maybe the vaccum effect doesn't need to be as strong as a normal pulsejet??

[Eric]

The reason it is so short is because it has 4 tailpipes, nicely hidden away in a shroud.

Eric

[Najm]

So the x-jet is an engine running on forced frequency, not the natural frequency of the tailpipe.The frequency is being provided by the combustion process in the other tailpipe.
Am I right there?

Also what's with the extended runtime of the valves on the x-jet.

[HattoriHanzo]

Interesting reading!

Bruno,

Are the valveless pulsejet papers of yours available on the net?

(some grammar help please. In the sentence above, is it correct to begin with "are" or should it be "is"?) :oops:

[Bruno Ogorelec]

Bruno,

Are the valveless pulsejet papers of yours available on the net?

I am not certain what papers you mean. Those I have published or those other people have written and I have collected?

I have a collection of at least 50 research papers and a few books published over the past 60 years by various researchers. Some of those are availble on the Internet if you search hard enough. Others are available for purchase from some scientific institutions. NASA has a lot of stuff on sale, for instance.

Personally, I have only published a historical review of valveless pulsejets -- which is available for download on this website -- and (many years ago) a paper describing a novel twin-combustor blast compression pulsejet engine. The latter is of dubious value; most people think the engine I ahve coinceived cannot be made to work successfully.

[gundamnitpete]

The reason it is so short is because it has 4 tailpipes, nicely hidden away in a shroud.

Eric

so it's more like 4 15lbs thrust pulse jets running with that force frquency system, all wrpped together in a shroud?

[tufty]

a paper describing a novel twin-combustor blast compression pulsejet engine. The latter is of dubious value; most people think the engine I ahve coinceived cannot be made to work successfully.

Most people thought Fermat was talking through his hat, too.

Simon

[Bruno Ogorelec]

Most people thought Fermat was talking through his hat, too.

Bwahahahaha... nice to be likened to Fermat, whatever the circumstances. The problem here is that Fermat had background that indicated he knew what he was saying. You look at my background and a picture of an ingenious inventor just doesn't come up, even with the help of a PR agency. But thanks, anyway.

[Mike Everman]

just ran an engine with Nick and Graham. SFC of .1, thrust of 1,000 lb, CC diameter of 2". Amazing proof hinted at in the margins of this post. ha

[Mark]

What kind of engine? Is it cheaper than a small lead acid battery?
Mark

[Eric]

The speculation about the x jet was based off of some construction / pre-run pictures I saw of it before Bruce thought it was anything worthy of hiding.

It may not have multiple combustors but the pictures I saw definatley had 4 tailpipes.

The square intake / combustion chamber shroud, and the view down the intake also seemed to be very similar to the diagram I posted.

I would post the pics but I lost them many hard drives ago.

Eric

[leo]

here is a picture off the first one.

http://aardvark.co.nz/pjet/images/xjet01.jpg

[Bruno Ogorelec]

Bruce's valved X-Jet engine does look as if it contained Eric's double combustor layout. But, it's a single combustor engine. It just has a very unusual and original valve head, which offers little aerodynamic resistance to the incoming charge, protects the valves against heat and generates excellent mixing. It also has a peculiar but effective shape of the combustion chamber. I find the whole thing very original and I'm prepared to believe Bruce's claims about it. (Claims I have frankly forgotten -- it was a long time ago and my interest in valved engine has never been very high).

BTW -- given that the video is available on Bruce's website, has anyone made an acoustical analysis of the sound? I'd really like to know the operating frequency of such a short duct.

As for the valveless version of the X-Jet, we have to stray into mysticism and conspiracy theory in search for answers, I guess. As Mike suggests, maybe the data can be found somewhere on the margins. I have looked but only found indications that Bruce has remarried to Mary Magdalene and lives in exile on the French Riviera, soaking his papyrus in vinegar.