Please put your "I am new and need help" question here.

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metiz
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Re: Please put your "I am new and need help" question here.

Post by metiz » Sat Aug 01, 2015 8:38 pm

Hi Gerre,

Yes. I can't comment in depth since I'm not knowledgeable enough, but Kadency, Helmholtz and Rijke are all effects that are fundamental to pulse-jets. You might also want to include the Rayleigh Criterion and Reynst's work on pulsating combustion systems.

Here's a paper I found while googling the subject to appear smarter that might be interesting to your cause https://smartech.gatech.edu/bitstream/h ... 05_phd.pdf
Here's a semi technical article about the workings of valveless pulse-jets, including some referrals to intersting source material http://exrocketman.blogspot.fr/2012/05/ ... s-for.html

Good luck!
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Re: Please put your "I am new and need help" question here.

Post by gerre » Wed Aug 12, 2015 6:16 pm

Thanks for the information!
Overwhelming that such a mechanically simple engine can be so thermodynamically complex.
And for some reason I'm not able to find the exact thermodynamic cycle. A lot of people say it's working on the Lenoir cycle, other people say it's Humphrey, some people even say Brayton and others say "We don't really know". This engine keeps suprising me :)

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Re: Please put your "I am new and need help" question here.

Post by metiz » Wed Aug 12, 2015 7:40 pm

It seems like the Lenoir cycle is the best match.
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Re: Please put your "I am new and need help" question here.

Post by Coles » Mon Oct 05, 2015 5:36 pm

Hello,
I am an 8th grader and for a school project I am trying to make a fairly large Lockwood-Hiller pulse jet engine that may or may not be mounted on the back of a bicycle. My designs right now include a J shaped stainless steel pipe and two four foot long stainless steel pipes with a diameter of three inches as my exhaust and intake pipe. Any ideas for a combustion chamber besides sheet metal? I also wanted to know what the best fuel would be. As of right now I'm using propane but if there's any thing better I would like to know.
Thank you,
Coles

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Re: Please put your "I am new and need help" question here.

Post by metiz » Mon Oct 05, 2015 5:45 pm

I'd suggest trying a smaller 50 pound lockwood first with a proven design. I deduce that you have a welder, so at least try to get some sheet metal. Also try "pyrojoe's recipe for beginners" for easy to follow instructions for your own design
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Re: Please put your "I am new and need help" question here.

Post by Bclark215 » Thu Dec 31, 2015 9:23 pm

Hello I am looking to make a pulse jet to put on a bike or small riding kart as a project for a school fair. I am looking for dimensions/plans for a Lockwood-hiller style valvless pulse jet with enough thrust to get our bike or kart moving. Obviously the more thrust the happier we will be, but we still need it to be somewhat practical. We will most likely be using direct injection propane as a fuel. We have access to a cnc table plasma and ideally would like flat 2d dimensions that we could plug into the machine and cut out our flat pieces, however we could easily make do with 3d conical dimensions and figure it out from there.
I believe we have access to a sheet metal roller as well, however I'm not %100 sure of this as of right now, so we may be rolling this by hand. We also have access to a mig welder and a tig welder, however my tig welding experience is minimal, and limited to carbon steel. Considering these factors, what metals and gauges would be best for this project? We're also on somewhat of a budget, so stainless and other high dollar metals are probably out. Sorry for the large post, and numerous questions, but any help you can offer would be greatly appreciated! Also I wouldn't be opposed to a Chinese style or some other style if you think they'd be easier. Thanks

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Re: Please put your "I am new and need help" question here.

Post by metiz » Sat Jan 02, 2016 1:18 am

Bclark215 wrote:Hello I am looking to make a pulse jet to put on a bike or small riding kart as a project for a school fair. I am looking for dimensions/plans for a Lockwood-hiller style valvless pulse jet with enough thrust to get our bike or kart moving. Obviously the more thrust the happier we will be, but we still need it to be somewhat practical. We will most likely be using direct injection propane as a fuel. We have access to a cnc table plasma and ideally would like flat 2d dimensions that we could plug into the machine and cut out our flat pieces, however we could easily make do with 3d conical dimensions and figure it out from there.
I believe we have access to a sheet metal roller as well, however I'm not %100 sure of this as of right now, so we may be rolling this by hand. We also have access to a mig welder and a tig welder, however my tig welding experience is minimal, and limited to carbon steel. Considering these factors, what metals and gauges would be best for this project? We're also on somewhat of a budget, so stainless and other high dollar metals are probably out. Sorry for the large post, and numerous questions, but any help you can offer would be greatly appreciated! Also I wouldn't be opposed to a Chinese style or some other style if you think they'd be easier. Thanks
There's a thread called "Looking for plans, look here" directly under this thread. It has a bunch of plans you can use, including one for a lockwood download/file.php?id=11410&mode=view
You can use mild steel but beware that it won't last long (long enough for some fun) You can use any thickness of sheet steel you want, but for practical reasons and because you will be using mild steel, I'd suggest 1-1.5mm. You can go thicker but then hand rolling will be almost impossible. You can mig 1mm stainless. If you keep blowing holes through the metal, weld small, overlapping beads, like *zap zap* (don't leave holes) Also, with mild steel and U-bent designs, make sure you support the tailcone to prevent sagging. Depending on material thickness, also consider welding fins (think submarine) on the larger cones and pipe (cc, tailcone) to prevent imploding. All the dimensions in plans posted are, unless mentioned otherwise, internal so make sure you compensate for the material thickness when you create the flat pattern layouts.
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Re: Please put your "I am new and need help" question here.

Post by Bclark215 » Sat Jan 02, 2016 1:31 am

Thanks for the reply! I had looked through the "looking for plans" section of the forum, however the majority of the links wouldn't open. In the link for the Lockwood jet you put above, are the measurements in metric? I'm in the us and use customary inches. Converting is no problem I just didn't see any units that specified. Also can those measurements be used to scale up or down to any size as long as the same ratio us used? And lastly how much longer than mild steel will stainless last? I weld thin 18 gauge steel with the mig all the time. Im actually working in a level one U.S. ASNT level one welding certification. Tig is just the last portion of the certification tests and I haven't quite made it there yet.

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Re: Please put your "I am new and need help" question here.

Post by Mike Everman » Sun Jan 03, 2016 3:00 am

You can get those links to work by editing them to say phpbb3 instead of 2. Sorry, lazy admin.
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Re: Please put your "I am new and need help" question here.

Post by Mike Everman » Sun Jan 03, 2016 3:08 am

Inches. So, really it all starts with whatever u-bend you can find, between 2.5 and 3". Scaling within that range to match the actual inside diameter of u-bend is fine.
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Re: Please put your "I am new and need help" question here.

Post by Joris » Mon Jan 18, 2016 4:04 pm

I'm planning on building a pulse jet in the near future, for the design i used the 1967 lockwood patent, using all the proportions in this patent i came up with the following sizes. Because i can't make a inwards tapering cone bend i instead decided to end the inward tapering cone before the bend and i also made the exhaust and inlet end at the same height. I would appreciate it if someone would take a look and guess whether or not they think it'll work, mostly whether the non inward tapering bend will work with the pipe in between the combustion chamber and the bend.

Also the diameter of the bend is the diameter from the middle of the tube to the middle of the opposite tube.

The proportions (all gotten from the lockwood patent, Combustion chamber has a 45º angle on both sides)
O means towards the exhaust
I means towards the inlet
L means length
M means average diameter
NozzleM=4,15"
CombustionM=11"
ExhaustM=3,825"
ExhaustO/ExhaustI=1,55
ExhaustL=28*ExhaustM
CombustionO/CombustionI=1,0625
CombustionL=CombustionM*1,45
NozzleO/NozzleI=1,083
NozzleL=NozzleM*3,85
CombustionI/NozzleO=2,46
ComustionO/ExhaustI=3,66

i do not own the rights to this picture i took it from the valveless pulsejets 1,5 pdf i got from this site, as said i got the dimensions from a patent in 1967 which i believe has expired. The patent has been included the file's called pulsejet proporties forgot to change the title. I've included the excel file i made for the size calculations if required i can easily change all the proportions, it also includes the circles and degrees i'm planning on using to make the cones.

Thanks in advance
Attachments
Sizes pdf.pdf
(47.83 KiB) Downloaded 66 times
Pulse jet proporties.pdf
pulse jet patent
(836.8 KiB) Downloaded 57 times
Pulse jet dimensions.jpg

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Re: Please put your "I am new and need help" question here.

Post by Joris » Thu Jan 21, 2016 10:36 am

Whilst looking around to see if my answer was in some other section i found a patent in the pulsejet designs section, this design comes pretty close to my design apart from my tailpipe being quite allot longer about 34 inches and the diameter of my combustion chamber was quite allot bigger a difference of 4,28 inches on the tailpipe side. I noticed that the angles on both sides of the combustion chamber towards the tailpipe and towards the nozzle aren't 45º where as my design is based on a 45º angle.

To fix the length of the tailpipe i could i it isn't functioning take out the piece between the combustion chamber and the bend which is part of the tailpipe. I've included the other design from the forum.
Attachments
Lockwood designs.JPG

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Re: Please put your "I am new and need help" question here.

Post by Joris » Thu Jan 21, 2016 11:12 am

After tweeking my design to match up with the design i posted in my previous reply i'm quite sure i've got one working now with a few slight differences, for one i'm still using a 45º angle the combustion chamber and both the exhaust and the intake. and as i've already got a 180º bend i've tweeked so the total exhaust length comes up to the 72,7 inches long (i used the outer radius of the bend like they did in the design drawing which isn't actually the length in the tube but that doesn't matter) but because i've already got the bend the exhaust pipe after the bend is 44" long instead of 42" and the length of the pipe between the bend and the combustion chamber is also 13" instead of 11", both vary by 2" which means both pipe's are still as long. Also i used my own program to calculate it all so both pipes are the same length exactly.

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Re: Please put your "I am new and need help" question here.

Post by emile » Mon Mar 28, 2016 6:13 pm

I am new and need help

OK, so before I create a new topic in this forum, I thought I'd check for objections.
I'm assessing the feasibility of the following:
A "valveless" pulse jet that can run at several discrete pulse-per-minute rates.
It doesn't have to fly, so weight, aerodynamics, and thrust are irrelevant. I've seen some jets control PPM via fuel throttle and some via harmonic length ratio adjustments.

So what I am looking for here is if I can go ahead and start a new thread with more detail to solicit feedback, or if I should take my bag of crazy elsewhere.

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Re: Please put your "I am new and need help" question here.

Post by metiz » Mon Mar 28, 2016 7:13 pm

You can start a new thread
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