SpudFiles

So I was watching Myth Busters tonight and learned something that pertains to combustion cannons. The myth was that the gas produced in sewers could send man hole covers sky high (and yes, it can!). The small scale was almost the equivalent to a super size combustion cannon. The first test had no debris and the deflagration was remarkably slow even with the fan mixing things up. They tried it again with a bunch of large springs and the combustion was easily ten times faster. The theory stated was that the coils increased the flame front area thereby increasing the speed of the burn. Maybe we should start creating these disturbances into every day cannons?

I saw this as well. I intend to throw some random bs into my combustion and see what happens.

I think I've heard something about that here on SF.
Got a link to that episode ?

I would say "crinkle" some wire and put it in there. That should easily do the trick.
By the way, I am a major Myth Busters fan.
PS, It's a new episode. It just aired today.

This has been a common finding in research related to deflagration to detonation transition in pipes, ducts, tube and other long items... Good to see the mythbusters at it proving it experimentally though! I'm sad I missed it, I'll have to see if it's on demand.

Edit - just so I don't say without showing... here's some previous DDT studies and a good "book" (more of a field book) on the concept.

Book
http://www.gexcon.com/handbook/GEXHBchap10.htm

Studies
http://www.lsc.phy.cam.ac.uk/research/ddt.shtml
(You'll have to google this url for it to work...) http://pbadupws.nrc.gov/docs/ML0717/ML071700076.pdf
http://www.hit.no/eng/HiT/Research/Rese ... cal-Safety

From this you can see why DDT is still something we don't 100% understand, It's something I've considered for a senior thesis since we have a combustion lab on campus! And professors willing to study it...

This in a way goes back to earlier discussions of screen mesh in chamber similar to coal lanterns. Maybe it will help.

This is the only link I could find. The "Drain Disaster Aftershow" actually has side by side footage of the small scale version.

Mr.Tallahassee wrote:This is the only link I could find. The "Drain Disaster Aftershow" actually has side by side footage of the small scale version.

Cool... I love their high speed stuff, they did a great job on this one.

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It looks like we could totally use that to increase combustion speed. Although many combustions already have spark strips with multiple sparks and that would cause the entire flame to wrap around and speed up i would think.

It was a relatively small fan but they let it run for two or so minutes straight so it may have done the same thing that a larger fan would do as to mixing the fuel and air. Either way, the debris boosted the burn rate quite drastically even with a well mixed chamber. This really requires a lot of testing that I am not capable of currently.

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It works- the same thing is used in experimental PDE's (albeit with more reactive oxidants) to great effect.

I'm sure JSR would love to do some tests with the HS camera and some clear tube

If there's little merit for combustions equipped with fans, what about for hybrids where fans are unable to be used? Though, if it's significantly increasing the risk of DDT it might not be a good idea.

Edit: On reflection, I assume not. Multiple spark gaps didn't seem to make much difference when modelling my hybrid in HGDT (though this could have been effected by several variables). And of course, hybrids have valves.

i watched that too the sewer explosion was a burn but they were aiming for a deflagration so uncoil a transformer or get lots of copper wire or wire and stuff up your combustion