Straight tailpipe length with new(?) valve arrangement...

[Hank]

Hello- I'm sure Bruno has the document I am about to mention so I will quote it to the forum as we seem to have so many new faces about.
NACA TM 1131 is a reprint of a technical document that was written at the Aachen Technical High School in 1941. I have piles of tech stuff related to this subject (literally, it's getting tough to move around in here without creating a landside) but TM 1131 remains at the top of the heap. This document should still be available through the NACA Technical Report Server, I haven't checked there lately. I have fears that the government may want this stuff reclassified,grab it while you may, Patriot.
Wave forms are discussed in this document and equations provided that should help the tyro in his quest for understanding these gizmos. It's worth it for the wave propogation graphs alone.
I hold with the last statement of my previous post. A better tuned duct is worth your while to consider than a straight tube. Hank

[Bruno Ogorelec]

Hello- I'm sure Bruno has the document I am about to mention so I will quote it to the forum as we seem to have so many new faces about.

Of course I do. Here it is. make a copy, whoever thinks it worthwhile.

NOTE: Server says 'upload error'. Couldn't upload the file. Maybe later.

I hold with the last statement of my previous post. A better tuned duct is worth your while to consider than a straight tube.

Hank, I agree with you. I never said a straight duct was for an amateur enthusiast. I just said it can be done with good results with valves and may just be possible without valves. Indeed, in some respects it may well outperform the duct with bulges and constrictions.

But, it is certainly a job for a very experienced builder with a lot of patience. Even with the best man doing it, it is likely to be a demanding and temperamental machine. Without access to superior computer modelling, it will be more of a laboratory curiosity than a practical engine.

[Bruno Ogorelec]

Hank, look at Bruce Simpson's website, at the very first X-jet he showed to the public eye. There's a video of its run. It has a valve head, albeit a rather unconventional one.

See the shape of its duct. Note how short it is. An amazing machine. I am sorry he did not develop it further. (The most probable reason is that having 'no moving parts' is a major selling point if you are looking for investors.)

By the way -- it wasn't even temperamental. But, as I said, doing it with valves is much easier than going valveless.

[jmhdx]

Hank, I agree with you. I never said a straight duct was for an amateur enthusiast. I just said it can be done with good results with valves and may just be possible without valves. Indeed, in some respects it may well outperform the duct with bulges and constrictions.

But, it is certainly a job for a very experienced builder with a lot of patience. Even with the best man doing it, it is likely to be a demanding and temperamental machine. Without access to superior computer modelling, it will be more of a laboratory curiosity than a practical engine.

I've achieved very weak pulses in a straight tube and believe it to be a valved option only at present. In my mind achieving usefull pressure would require a very long combustion zone, the reaction time of which would be far slower than say a sphere of combustable mixture, which in turn would require a very long exhaust. A low frequency of operation is thus ensured. But I look forward to testing a rotary valved gatling gun of long tubes when facilities become available. Sure would scare the wildlife.
Mike.

[Mark]

What was the claimed thrust on the ~4 inch diameter X-Jet pulsejet? The area for a 4 inch exhaust is ~12.56 square inches.
Mark

[Viv]

Hank, I agree with you. I never said a straight duct was for an amateur enthusiast. I just said it can be done with good results with valves and may just be possible without valves. Indeed, in some respects it may well outperform the duct with bulges and constrictions.

But, it is certainly a job for a very experienced builder with a lot of patience. Even with the best man doing it, it is likely to be a demanding and temperamental machine. Without access to superior computer modelling, it will be more of a laboratory curiosity than a practical engine.

I've achieved very weak pulses in a straight tube and believe it to be a valved option only at present. In my mind achieving usefull pressure would require a very long combustion zone, the reaction time of which would be far slower than say a sphere of combustable mixture, which in turn would require a very long exhaust. A low frequency of operation is thus ensured. But I look forward to testing a rotary valved gatling gun of long tubes when facilities become available. Sure would scare the wildlife.
Mike.

There was a nice paper floating around on the old forum for the pipeline explosion handbook,

It had a very nice set of experiments and results for gas pipleine explosions and the mechanism for transition from conflaguration to detonation.

I have it somewere but basically yes you need the valves or something to act as a wall to build up pressure against to accelerate the flame front and get some ummph in to it.

Viv

[Bruno Ogorelec]

What was the claimed thrust on the ~4 inch diameter X-Jet pulsejet? The area for a 4 inch exhaust is ~12.56 square inches.
Mark

Damned if I can remember. It was long ago and I don't seem to have noted anything permanently. Isn't there anything on it on Bruce's website? I do remember that the claimed figures were very impressive, though.

[evildrome]

Bruno,

I have pics of the 510 on my site:

http://www.wilsonlogan.com/Jets02.htm

Cheers,

Wilson.

[Bruno Ogorelec]

I have pics of the 510 on my site

Thanks, Wilson! Great pictures. I wish I could see and hear that giant tube roar and spit flame. Must have been impressive.

[Mike Kirney]

Pulseduuuuuuuuuuuuuuuuuuuuuuuude, from cross-referencing your posts, it seems that your tube is the same diameter of the the Tiger Jet combustion chamber. Assuming that you will have to cut this tube to length anyway, you might as well make the valveplate (cause it will be the right size regardless what you do) and just stick it right onto the tube and if it doesn't work, oh well, you just built the Tiger Jet like you were planning to anyway. What are the dimensions of the tube in its present form?

[Mark]

Bruno,

I have pics of the 510 on my site:

http://www.wilsonlogan.com/Jets02.htm

Cheers,

Wilson.

Is the yellow perforated section with all the various holes a kind of flame holder or to protect the valves or what. I just can't be sure how far the internal shell extends?
Mark

[evildrome]

Its actually from a British Jet.

Start here: http://www.wilsonlogan.com/SJets01.htm

This may explain things better.

Cheers,

Wilson.

[Mark]

Thanks Wilson, I was beginning to wonder if I had missed something, as if pulsejets would have flame holders.
Mark

[PulseDuuude]

Pulseduuuuuuuuuuuuuuuuuuuuuuuude, from cross-referencing your posts, it seems that your tube is the same diameter of the the Tiger Jet combustion chamber. Assuming that you will have to cut this tube to length anyway, you might as well make the valveplate (cause it will be the right size regardless what you do) and just stick it right onto the tube and if it doesn't work, oh well, you just built the Tiger Jet like you were planning to anyway. What are the dimensions of the tube in its present form?

Hey Mike,

The Tiger Jet Combustion chamber is approx. 1.718" I.D. by 2.50" long until it reaches the start of the taper. The resonance tube portion is .866 O.D. and the overall length from the front of the combustion chamber to the end of the resonance tube is 18.875".

The tubing I intend to use is hard-chromed carbon steel with an O.D. of .87" and wall thickness of .020" (I'll replace it later with a stainless steel tube if the design works out).

The intake/valve head assembly is being designed based upon the data from the Tiger-Jet Engine.

The design is based upon 'stacked plate' construction.

I am working for a laser cutting company and the management is willing to cut metal for the employees for free (as long as we're not too outrageous). All the metal is various gauges and thicknesses of Carbon Steel, Stainless Steel and Aluminum sheet and plate.

I'm designing with SolidWorks 2003 Personal Edition, and when I finally get my engine finished I'll post a pic and e-Drawing file so those interested can critique the design.

[Mark]

I have a Tigerjet and even though it is small, smaller than the Dynajet, it is still very, very, loud. I like holding it in my hand, it's cute in some way.
Mark