How small?

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zeptoon
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How small?

Post by zeptoon » Mon Dec 26, 2005 2:50 pm

How small is it possible to build a Valveless pulse jet?

Mike Everman
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re: How small?

Post by Mike Everman » Mon Dec 26, 2005 3:56 pm

to make noise, or one that will actually do some work?
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re: How small?

Post by Mark » Mon Dec 26, 2005 4:39 pm

If it puts money in your bank account, does that count as work? ; )
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zeptoon
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re: How small?

Post by zeptoon » Mon Dec 26, 2005 5:35 pm

To do some work, although not necessarily a whole lot...

For instance would it be possible to power a small r/c airplane using a pulsejet?

Or could a pulsejet possibly be used for a really teensy airplane (microflyer)?

Mainly I am just interested in what would start to limit you first.

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re: How small?

Post by Mark » Mon Dec 26, 2005 5:41 pm

Sure, you could do all of the above. But it would take some work. Work is something that is rather defining. If you are lazy, the project won't be easy.
I once heard a female comedian who said, "You really have to want it." It's not going to fall into your lap, that's for sure. She was just speaking in generalities, whatever you do in life. I remember hearing her on the radio, an interview, and I had seen her at the Riviera at "The Improv."
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re: How small?

Post by Mark » Tue Dec 27, 2005 4:02 am

I made a copy of this article back in 2000. I wonder how he's coming along with his dream?
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re: How small?

Post by El-Kablooey » Tue Dec 27, 2005 4:36 am

"This engine will produce a tiny ultrasonic sound"

????????????

What kind of fuel would you use in an engine operating above 20khz?


That would be cool though, a quiet PJ. What fun I could have with my neighbors #@$#%#%&'n blue-tick's.
On an endless quest in search of a better way.

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re: How small?

Post by Mike Everman » Tue Dec 27, 2005 6:36 am

Back on topic...
Well, Bill Robert's team did an 80mm long valveless at 1.6KHz on Hydrogen.

Steve Here did a 290mm at 585 Hz on acetylene.

I've only gone as short as 26" with propane, gets tricky going shorter with that fuel. Some of Larry's motors are that short.

It's all about flamespeed at those shorter lengths. I'll bet you could get one down to 18" length or so on MAPP gas. Methanol is probably good that short, too. Methanol would be a great flight-ready fuel.

As to doing work, all are low thrust. These days, I think any useful work will come from simple turbines with pulsejet gas generators, and several contributors here are building such to find out. Very exciting times!
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re: How small?

Post by Mark » Tue Dec 27, 2005 1:20 pm

Did you notice all his gallery of flow images? You can view them by clicking on the top left of this page. Lots of pretty pictures, food for thought. Hmmm, can't access them today but last night I did, and they were quite interesting.
Mark
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re: How small?

Post by Steve Wallington » Thu Jan 12, 2006 8:09 pm

Hi all
Be gentle with me, it's my first time
The first PJ i built was scaled from a picture i found on ebay,early last year.
The cc is 50mm dia and total length is 350mm and it runs on propane.
It starts very easy and is good at annoying the neighbours.
Is mine the smallest?
Hope i attach pic and vid
Attachments
jet injun 004.mpg
(1.34 MiB) Downloaded 570 times

hinote
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Re: re: How small?

Post by hinote » Thu Jan 12, 2006 8:30 pm

Steve Wallington wrote:Hi all
Be gentle with me, it's my first time
The first PJ i built was scaled from a picture i found on ebay,early last year.
The cc is 50mm dia and total length is 350mm and it runs on propane.
It starts very easy and is good at annoying the neighbours.
Steve:

Welcome to the club!

You don't need any gentling--you've done a great job of building a nice-performing engine.

BTW it's running at an amazing 380Hz.

Now, the questions: How long is the intake--and does it protrude into the combustion chamber? (that would make it a "thermojet", BTW). Also, it looks like there's only one intake (please confirm).

Looks like the fuel probe is inserted directly into the intake; can you tell us how far the probe extends into the intake--and how large is the opening at the end?

Again, congratulations!

Bill H.
Acoustic Propulsion Concepts

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

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re: How small?

Post by larry cottrill » Thu Jan 12, 2006 9:06 pm

Steve W -

Yes, congratulations! That's a nice piece of work.

However, it is not the smallest, though it might possibly be the smallest to self-sustain on propane. Another Steve, Steve Bukowsky, built one so small it will only run on acetylene. However, I can't seem to find his original Pocket Lockwood thread ... somebody help me, here ...

L Cottrill

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re: How small?

Post by Steve Wallington » Thu Jan 12, 2006 9:41 pm

Hi Bill

Thanks for the welcome.

Answer time
The intake's, there are 2, are 55mm long and 12mm dia
They do not protrude into the combustion chamber,they are flush with inside of the cone.
The fuel pipes are 4mm i/d tube tapering to 3mm i/d.
They go into the intakes about 3mm.

After i built this PJ i bought plans from Eric Beck. My other builds are on his website. (I'm Steve from England).

I'm glad i'm not the smallest

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Re: re: How small?

Post by hinote » Thu Jan 12, 2006 10:43 pm

Steve Wallington wrote: The fuel pipes are 4mm i/d tube tapering to 3mm i/d.
They go into the intakes about 3mm.

My other builds are on his website. (I'm Steve from England).
Well, PJ fans--there's your answer!! The mixing length is surprisingly long, given the overall size of the engine. I'll bet this PJ wouldn't run at all if the fuel supply was inserted farther into the intakes.

Steve: How did you find the optimum location for the fuel feed?

Also--I wouldn't be too shy about participating on this Forum; you're in the 90th percentile, given the experience you've got building and operating pulsejets.

Bill H.
Acoustic Propulsion Concepts

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

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