Nanosoft: New Chinese Project

[NanoSoft]

Well here is my latest creation. It is a dual intake Chinese style engine. I built the entire thing in one day. As always, all pieces are formed by hand, hammer, and anvil. All pieces were MIG welded and hand sanded and polished. I designed it using my own program and then UFlow to check. But apparently my program and Uflow are both wrong because it won't run. My program checks the acoustics of the jet and tells you if it will run but I seemed to have messed up some equations because the jet won’t run.

I have posted the dimensions and pictures to look at. Does anyone have any ideas of what I should change to get it to work? I think the Throat between CC and Exhaust needs to be a larger diameter. Ideas? I tried plugging one intake while leaving the other open, which helped significantly but not enough wouldn't run. The jet will resonate when one intake is plugged otherwise it just howls and groans. Help is appreciated. I would really like to get this one going.

Nanosoft

[hinote]

Well here is my latest creation. It is a dual intake Chinese style engine. I built the entire thing in one day. As always, all pieces are formed by hand, hammer, and anvil. All pieces were MIG welded and hand sanded and polished. I designed it using my own program and then UFlow to check. But apparently my program and Uflow are both wrong because it won't run. My program checks the acoustics of the jet and tells you if it will run but I seemed to have messed up some equations because the jet won’t run.

I have posted the dimensions and pictures to look at. Does anyone have any ideas of what I should change to get it to work? I think the Throat between CC and Exhaust needs to be a larger diameter. Ideas? I tried plugging one intake while leaving the other open, which helped significantly but not enough wouldn't run. The jet will resonate when one intake is plugged otherwise it just howls and groans. Help is appreciated. I would really like to get this one going.

Hi Nanosoft:

Good grief, man!! I thought I was starting to build better quality--but you're making me look like a serious slacker here.

Please accept my congratulations on a great-looking project. For the rest of you Forum guys--you're looking at the product of a fine young man in his last year of high school (is that right, Nano?). IMHO he's putting the rest of us to shame here.

I'll try to look at the dimensions--but I'm not (yet) well-versed in the Chinese config. I hope Mike E. and maybe Eric, will chime-in to help you improve your results.

Don't give up--this project is just too nice to take lightly!!

Congratulations, again.

Bill H.
Acoustic Propulsion Concepts

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

[hinote]

I have posted the dimensions and pictures to look at. Does anyone have any ideas of what I should change to get it to work? I think the Throat between CC and Exhaust needs to be a larger diameter. Ideas?

My first impression is that the throat is too short.

Please, DON'T change anything until you get several days of comments, from interested and qualified participants!!

Bill H.
Acoustic Propulsion Concepts

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

[hinote]

I thought I was starting to build better quality

I'll bet there's some "Chinese" engine builders who are very jealous, right now. In particular the frustrum after the combustion chamber apears to be a near work of art. The blend into the twin intakes as well as the throat tube is very nice.

Sorry 'bout the excessive posts here--I'm just very impressed.

I'll be quiet now and let somebody else post.

Bill H.
Acoustic Propulsion Concepts

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

[Eric]

Nice job with the intake junction.

The intakes look to be the same size as the throat area, although that probably isnt the biggest problem.

The expanded section at the end of the tailpipe looks like it has way way too much volume. If you are going to go for a much larger exhaust expansion you have to play around so that you dont have too much volume.

You want most of the expansion to be discharged, and each pulse can only do so much, have to keep in mind the length of time the engine has for each part of the cycle. If you really want to keep the expansion much larger than the throat I think that you are going to need to make it about 1/4 - 1/3 its current length and make the cone section longer to compensate.

Otherwise the engine should be capable of running with the throat that diameter. I have run engines with 4x as much intake as throat area, and Im sure Bills Kentfield is probably in the same boat.

I will have more to comment on in a little while.

Eric

[Viv]

Pitty your not Candian I would give you a job based on the quality of that project:-) were starting to hire now but the work permit for you would be a pain to sort out.

Nice job though well done, to my eye with out doing any more than look the proportions seem a bit off off for the tube from the combustion chamber to the exhaust cone.

Viv

[Eric]

Something along this line would only require you to change the length of the tailpipe cone and chop the end a bit shorter.

With an idea of the dimensions and ratios Im sure we could all be a lot more help.

The intakes might be a bit long for having dual intakes, but I cant quite tell from the pics alone.

Eric

[larry cottrill]

Nanosoft -

Man, what a beautiful piece! That is an engine to be proud of, indeed!

The next thing I would do is lathe turn a couple of full-length brass sleeves (like super-long venturis) that would slip down inside your intakes to reduce the free area to about 70 percent of what they are now, i.e. cutting the total intake volume down to the original single-intake value. Just to see if that altered mass imbalance might be what's killing you, without making a permanent alteration.

What a wondeful build - congratulations!

L Cottrill

[Mike Everman]

Nice work, Mikhail!... I'm with Ben and Larry. Theirs are nice ideas to keep from cutting too soon.

Then I'd suggest the throat tube increase in diameter by a factor of root2, and change that tube's mid-length to be 1/3 of the (acoustically corrected) over-all-length.

The more I think on it Ben, the better that sounds, just butting different exhaust tubes into the rear cone to try different volumes for the expander. Very nice.

[milisavljevic]

Hello Mikhail,

I will not waste your time by complimenting your obvious skill in working with sheet metal, so let us cut to the chase:

1. There are at least two (2) dimensioning errors in your schematic; please find and correct each, and then present
the corrected dimensions here. (hint: think "power of ten")

2. On the assumption that your unit of measurement is the meter, I have already modeled your latest creation;
however, I had to "guess" correct values for each of the mis-stated dimensions in the schematic you provided.

3. If you would like to have mathematically sound assistance from me with this engine, please provide either:
(a) a sound file of the engine resonating with one inlet plugged;
or
(b) the resonating frequency (as previously determined by you).
(by "resonating", I mean the same condition that you observed)

I have identified two (2) candidate stable resonant points (so far): (a) a 4.8:1 lock-up at 324 Hz (712 K); and
(b) a far more probable 5:1 lock-up at 287 Hz (558 K). (assumes an ICAO standard day at sea-level and 15 C)

4. To be brief, this duct is suffering from a variation of "PJ-MAPD" (Pulsejet Multiple Acoustic Personality Disorder).

With due respect to your home-grown acoustic analysis program (and the hapless UFlow1D), your "as-is" duct has
three (3) critical resonance modes, each in conflict with the other two. (enough to keep an orchestra out on strike)

5. Is this a straight derivative of the classic "chinese" type, or a new Escopeta hybrid? (hint: overly long intakes)

Even if this duct were to self-sustain "as-is", the SFC would be rather poor: 3.4 lbs/lbf/hr at an equivalence ratio of 1.0.
The probability of creating near-stoichiometric fuel-air charges within the combustor of this duct is needless to say, low.

6. For a "chinese" style duct of similar dimensions, your tailpipe's L/D ratio is too low, at less than 12:1;
the relative lengths of the three tailpipe segments are also out of whack, but this is a minor nit to pick.

More interesting are the anemic-looking flares on the intakes; the diameter ratio for the flares should not be less
than about 1.25:1, with respect to the the intake ID. This can strongly affect aspiration, so it is worth looking at.

7. Setting the previous six (6) items aside, your pulsejet can easily be brought into a proper operating condition.
I can offer a minimal set of changes, if correctly implemented, that I guarantee will make your project a success.

Please let me know if you wish to have any additional assistance from me.

Best regards,
Störgröße M.
__________________
Hey pezman, who deleted your most excellent "piñata" post?
[ http://www.pulse-jets.com/phpbb2/viewto ... c&start=30 ]

[NanoSoft]

Wow! Thanks for all the replies everyone, this is why I like this forum so much. So today I will try to get some testing in. First I will try Ben's idea with the tailpipe and then tinker with the intakes. I don't have much time today so that probably all I will get done. I have college apps to do.

milisavljevic, Thanks for the long reply. You always seem to be there when I screw up. I guess I don't see the dimensional error. Those are the dimensions of my jet in meters correct. "Power of Ten", hmmm... I guess you'll have to help me on this one, sorry. This jet was supposed to be a short yet fat mix of and Chinese and Escopeta but didn't turn out as planned. I will get some sound files for you today. And yes I think I will probably need some further assistance. Thanks, once again.

Nanosoft

PS Here are a couple more pictures for your enjoyment

[marksteamnz]

Nanosoft at a guess M is refering to the cross sections two at 0.8485 and two at 0.07071. Should be 0.08485??

[NanoSoft]

Wow! Apparently I am as blind as a bat. Yes its supposed to say .08485. Here are the updated plans. Sorry about that.

Nanosoft

[NanoSoft]

So here is the update:

I played with the lengths of the intakes and tried sticking things as Ben suggested and I tried sticking solid pipes in the exhaust to get the same effect. What I have come up with so far is better but not running right. The best configuration I tried was just blocking one of the intakes with the right sized bolt. I could get it revved up and running with compressed air but not without. I think I am close but just a little off. Any more ideas?

I'll try what ever you suggest during the weekdays because I leave on the 17 to go to Maui for a week. YEAH!!

Here is the sound file you wanted milisavljevic. It was taken with one intake blocked but everything else the same. Hope it helps.

Mikhail Jones

[Fricke]

Nano-

Wery nice work! Nothing beats a shiny engine!

I wish You luck in getting her to run!

//Fredrik