Focused wave engine runs!

Moderator: Mike Everman

Focused wave engine runs!

Postby steve » Wed Sep 22, 2004 7:21 pm

I just fired it up and it ran great!!!

It seemed to pe producing a good amount of thrust and made a sound Ive never heard before: there was the traditional pulsejet buzz but with undertones that sounded like an almost melodic humming. as mike would say, "Faaaaaaaaaaaaaaaasinating"

Although there was not supposed to be much flame out the intake, as it turns out, there is a lot. Actually it is only about the amount that I would expect from my mini lockwood (check my file list under .wmv)

I only let it run for about 5 seconds before I shut it off because I was using the "patented bukowsky clamp stand" and I was afraid that without a proper test stand, excessive heat might cause it to deform.

Once I make a beter stand I'll do some duration runs and get some videos and pictures for you.

IT RUNS! IT RUNS! IT RUNS! IT RUNS!

my brother claims that the sound of the engine didn't scare him as the sound of my psychotic laughter after I shut it down :-)
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Re: Focused wave engine runs!

Postby jmhdx » Wed Sep 22, 2004 7:44 pm

Congratulations on another successfull build Steve, I was quite exited by the title Focused Wave Engine Runs but then remembered the breif. Not a bcvp or some other wizardry but a practical attempt to find an effective combustion chamber form. In that respect its a success and comparative measurements may show it a good performer.
You noticed that the gas gets out the intake, I wouldn't be disheartened as far as I know it always does and many have tried but not found the trick yet.
Things are only impossible until they are not and with your speed of construction you have a good chance at finding the solution. I wouldn't have thought it possible to have a single reel audio cassette but some clever swine invented the mobius tape loop.
I may have tooling soon and be able to contribute more than encouragement.
Mike.
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Congratulations !!!

Postby larry cottrill » Wed Sep 22, 2004 7:53 pm

Steve -

Well done, my man, well done!

Yes, hurry up and get some vids and audio. What was it like to start it?

(Now ... where the heck are my cones? Man, get with it ... ;-)

Very nice work, sir! Congratulations, once again!

L Cottrill
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Re: Focused wave engine runs!

Postby tufty » Wed Sep 22, 2004 8:03 pm

Oh, that rocks, that rocks, that rocks.

Well done Steve (& Larry).

Awesome work.

Simon
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Re: Focused wave engine runs!

Postby steve » Wed Sep 22, 2004 8:52 pm

as promised pics:

starting is very easy when compared to the elektra- spray the air, turn on the spark and adjust the gas untill it sustains, no warm up time required!

BTW my nice little stand caught on fire after about two minutes of run time. Damn the varnish! no big deal though, I just need to make a heat shield next time. I got it on video and it was really funny but for some reason I can't post it! I'll try again later.

enjoy the pics!!!!
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Re: Focused wave engine runs!

Postby larry cottrill » Wed Sep 22, 2004 10:19 pm

steve wrote:as promised pics:

starting is very easy when compared to the elektra- spray the air, turn on the spark and adjust the gas untill it sustains, no warm up time required!

Steve -

I praise God for your dedication and skill. The pics make me apprecate your efforts even more.

Unbelievable ... unbelievable ...

The most astonishing thing about these shots to me is that there is no visible heating of the tailpipe -- it's as if ALL the combustion is taking place with amazing speed right within that conical chamber. Steve, that is worlds apart from anything I have experience with; in the Dynajet, for example, the nozzle zone, right where it narrows down into the pipe, is the hottest running section by far -- and that's what I expected here. What a surprise! I just can't believe how that heat is concentrated in the chamber ... I mean, I think that's good, but ... how? Why is it happening like this?

The only disappointment to me is all that blue and purple feather hanging out of the intake. Rats!!! However ... you'll note that the intake pipe itself is remaining a "cold tube" -- no visible sign of heating at all, at least in your shots. Steve, that's very, very good, I'm sure. I know you understand this, but I'll explain for some others: The only reason I'm bothered by flame ejection from the intake is that it doesn't fit very well with scale modeling requirements where the engine is fully enclosed within a hollow fuselage. Of course, it might be possible to mount a lightweight 'thrust tube' right behind it to channel it rearward. Or, an augmentor to dilute it with cold air. Lots of possibilities ...

One thing you might try on your next run: Bring the head of a wooden match slowly forward toward the intake, and see where it has to be positioned to catch and burn. I'd like to know that.

Steve, from what I see here it looks to me to be far better than I could have expected. AND, it starts right up and runs! What more could a man ask for?

Thank you, thank you!

L Cottrill
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Re: Focused wave engine runs!

Postby Mike Everman » Wed Sep 22, 2004 10:30 pm

FAAAAAAASCINATING!

Congratulations, Boyz! ah, theory and function! Well done!
Mike
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Significance, Speculations and Gratitude

Postby larry cottrill » Wed Sep 22, 2004 10:59 pm

I'm going to step back for a moment from further congratulations to Steve for his building skills and speak to what I think are the couple of most significant gains in doing this project up to the present point. Remember that what we have here is an apparently successful engine built as close as possible to a carefully contrived set of dimensions based on a fairly simple hypothesis.

First of all, I think we have validated the 'Hinote Criteria' as a design hypothesis for a certain class of valveless engines. I am now willing to state this as follows:

For a valveless pulsejet where the main tube can be considered a 'closed pipe resonator' of length L, an 'open pipe' resonator can be added as a properly tuned intake under the following conditions:
- The intake pipe is large enough and well-flared enough at its outer end that it can be considered to function as a low-impedance duct
- The intake pipe is not heated significantly by combustion or radiation
- The intake pipe length, including appropriate acoustic corrections at both open ends, is L/5
- The interior end station of the intake tube [acoustically corrected for the end condition] is positioned at a station L/8 behind the inside surface of the closed end of the main tube, at any desired orientation that provides good flow of air/fuel mixture into the explosion zone of the main tube

The other element that at least seems true is vindication of the 'focused wave' design concept. It at least appears true that such a geometry produces easy starting and good self-sustaining operation, with a high degree of localization of combustion within the chamber volume.

Of course, at this point we have no hard evidence of good performance in terms of thrust per unit area of tailpipe throat or fuel consumption per unit thrust. It will be interesting to see how such measurements pan out, and also how much the engine can be lightened with the use of higher-grade materials.

All comments welcome.

Gentlemen, I wish to acknowledge here and now that the only reason for this apparent success is that I have "learned from the best", and I humbly and sincerely thank my God for you all! I especially wish to acknowledge Bruno, Graham, Mike E, Mark 'Thixis', Bill H, Mike K, Rossco and Bruce Simpson. I have learned a lot from some, and a little from every one of you. You guys are great mentors, and it's no wonder that this forum is the place to go for anyone in the world who wants to know pulsejets on intimate terms.

L Cottrill
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Re: Focused wave engine runs!

Postby steve » Wed Sep 22, 2004 11:31 pm

I have been thinking about it for a while and I can't figure out why the tailpipe dosn't get hot enough to glow. I't makes no sense to me whatsoever! Obviously it is a good thing that the hot zone is so localized, but even that has something very odd about it- you probably couldn't tell from the pictures but the hottest area on the entire engine was directly in the path of the intake air. This also defys conventional pulsejet wisdom because anyone who has ever seen a picture of a running chinese knows that this is one of the coldest areas on the engine. (WHAT is going on here!!!!????!!)
The cold tailpipe really bothers me, especially since I clearly saw flames shooting out of it. Unless fresh air somehow flows all the way back to the combustion chamber through the tailpipe (as in the intake) I don't see how It could stay so cool. It defys logic! (AAAAHHHHHH!!!) That is another strange thing- why are there flames comming out the tailpipe? I have never seen this happen on any other VALVELESS engine EVER! (the lockwood dosn't do it, the chinese dosn't do it, the escopette dosn't do it, the list goes on and on) (Scratch that- I have seen a little bit of flame comming out the elektra1 tailpipe)

Bruno (or anyone) could you attempt an explanation? am I going insane?

;-P
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Re: Focused wave engine runs!

Postby Mike Everman » Wed Sep 22, 2004 11:46 pm

Ah, you guys are going to sleep well tonight, or maybe not, visions of sugarplums and all. ;-)

Steve, I don't have a pic of a running Chinese, got one? The heating pattern on Lady doesn't surprise me, I'm sure the closed end becomes the main acoustic antinode, where all the action wants to happen.

I think it's time for some fuel stinger experiments to see if you can move that fuel feed farther down the intake and get rid of the intake flame...
Mike
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Re: Focused wave engine runs!

Postby Mark » Thu Sep 23, 2004 2:08 am

What fuel are you using? To me, and it is a pleasant shape, but reminds me of a nostalgic street lamp, the spark plug being the ornate top of the gas light lamp fixture. A spiffy little engine you have there.
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Re: Significance, Speculations and Gratitude

Postby hinote » Thu Sep 23, 2004 3:20 am

Larry Cottrill wrote:
What we have here is an apparently successful engine built as close as possible to a carefully contrived set of dimensions based on a fairly simple hypothesis.

First of all, I think we have validated the 'Hinote Criteria' as a design hypothesis for a certain class of valveless engines.


Larry--I would like to offer my personal congrats to you.

For the rest of the crowd, consider this--How many of us have been able to conceive a pulsejet concept, solve the engineering to create the actual hardware--and then have the darned thing fire, on the first try??

In my limited exposure to this discipline, the count is considerably less than the fingers of one hand.

In addition, we should admire the effort Larry has put into presenting his concepts to this Forum--even if they weren't workable PJ designs, they represented a lot of original thought and daring foresight, IMHO.

We should all try to follow Larry's fine example in our efforts.

I'm honored (and humbled) by your naming of the criteria after me--but I wish I could take more credit for what they may represent. A fortunate circumstance, I suppose.

Bill H.
Acoustic Propulsion Concepts

P.S.: See the following post for my opinions about the operation of the engine.
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Re: Focused wave engine runs!

Postby hinote » Thu Sep 23, 2004 3:33 am

steve wrote:I just fired it up and it ran great!!!

It seemed to pe producing a good amount of thrust and made a sound Ive never heard before: there was the traditional pulsejet buzz but with undertones that sounded like an almost melodic humming

Although there was not supposed to be much flame out the intake, as it turns out, there is a lot.


Steve--

Congratulations on your fine effort in running Larry's PJ design. I'm sure you feel the satisfaction of knowing that you have successfully built and operated an original pulsejet concept.

My opinion is that you're running this engine well in excess of its max rated thrust capability. Please consider running the engine at lower power levels--especially until you can verify thrust numbers, and thrust related to fuel consumption.

I'm betting that you'll find the max thrust can be obtained at considerably reduced fueling rates. Remember, the max thrust isn't related to how much fuel you can feed the engine. You may be exceeding the max fuel/max thrust value by a considerable amount.

Practical considerations (extended material life) will usually dictate an operating limit at something like 75-80% of max thrust--so you're 'way beyond that value.

Easy does it--until you get some working numbers.

Bill H.
Acoustic Propulsion Concepts
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Re: Focused wave engine runs!

Postby resosys » Thu Sep 23, 2004 7:13 am

Out of lurking....

Congratulations guys. Very nice work. I've been following all the recent threads and am giddy that this engine worked so well.

As a note, with the propane bottle open all the way, my lockwood's certainly throw flame out the tailpipe. Of course, the entire tailpipe glows except for the last 4 or so inches.

You may want to crank up the throttle a bit and let it run a little longer to see if the tailpipe heats up.


Good work!

Cheers,

Chris
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Re: Focused wave engine runs!

Postby Graham C. Williams » Thu Sep 23, 2004 11:03 am

steve wrote:I have been thinking about it for a while and I can't figure out why the tailpipe dosn't get hot enough to glow. I't makes no sense to me whatsoever! ;-P


Dear Steve.

Think about this in terms of the Total combustion time (as determined by the rate of combustion etc) as a fraction of the Total cycle time of the motor. This is not the complete answer but it'll help you sleep at night.
As this fraction tends towards 1 more combustion must take place later in the cycle and thus further down the pipe.

As to the 'Easy' starting characteristics of the motor I think this must be linked to the Q or quality factor of the underlying standing wave.

Congratulations and Respect to you and Larry.

Graham.
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