Cheating at pulse-detonation

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ace_fedde
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Re: Cheating at pulse-detonation

Post by ace_fedde » Fri Aug 21, 2009 9:15 pm

Latrocinium wrote: I have to take mike at his word on some of it. His name is all over this board,...
And he's the owner of this forum!!
Latrocinium wrote:I've read the article by beck-technologies.

Uh, or do you mean by Bruno O., not by Eric (Beck)?
Latrocinium wrote:I'm currently trying to find a good copy of Reynst book. Hoping that will fill in the blanks.
Look in the essential reading topic in the valveless forum (the sticky topic on top)

Fedde
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Re: Cheating at pulse-detonation

Post by Mike Everman » Sat Aug 22, 2009 3:17 pm

Oh, I may own the place, but I know just above zero about PDE's.
Reynst's book is here:
viewtopic.php?f=3&t=2256#p39501
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Latrocinium
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Re: Cheating at pulse-detonation

Post by Latrocinium » Sun Aug 23, 2009 4:25 am

Thanks for the info. This is the stuff I was looking for.

And thanks for the board Mike.

James OS
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Re: Cheating at pulse-detonation

Post by James OS » Sat Sep 05, 2009 8:25 pm

I'm pretty new here and very inexperienced - but this topic caught my eye...
Has anyone here experimented with injecting acetylene charges into a standard pulsejet?
According to wikipedia, acetylene gas explodes violently at pressures above 39psi.
Is there not a way to modify a pulsejet to produce these kinds of pressures (maybe try starting it on enriched/pure oxygen) ?
Then maybe you could inject the gas along with your standard fuel and produce a detonation wave that would ignite a standard fuel charge - no need to worry about huge tailpipes if the detonation occurs instantly. It would also be safer (relatively speaking) in comparison to using nitroglycerine or some other explosive as it still requires oxygen to burn - you could inject it like any other fuel.

However, I know next to nothing about the details - I've just read about it a little. It's just a thought - I know there'll be loads of problems with this.

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Re: Cheating at pulse-detonation

Post by ace_fedde » Sat Sep 05, 2009 8:47 pm

James,
Try! :D
But first build a stronger PJ :lol:
Fedde
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Re: Cheating at pulse-detonation

Post by James OS » Sat Sep 05, 2009 9:27 pm

Fedde
If someone doesn't get there first, maybe I will give it a try - but right now its beyond my means. I'd love to experiment with these ideas, but first I'll need more experience, and alot more money... I'd need a superalloy like inconel or something, or maybe titanium. Right now I can't even weld! :D
James

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Re: Cheating at pulse-detonation

Post by ace_fedde » Sat Sep 05, 2009 9:35 pm

James,
Mind the following:
First: Experiments with acetylene are highly dangerous, don't do nothing if you don't know exactly what you can and can't do with acetylene.
Secondly: Explosions are mostly not detonations but deflagrations. Detonations occur when the shockwave is - and energetic and long (duration) - enough fed to accelerate till past the speed of sound.
A batch of acetylene will not do, a (long enough) pipe full of acetylene/air mixture will do.
Please read the Gexcon Gas Handbook about detonations.
Fedde
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Re: Cheating at pulse-detonation

Post by James OS » Sun Sep 06, 2009 11:21 am

Don't worry - I'm a long way off doing anything with acetylene - I'm not even sure if it's legal to sell round here.
Also - it was only a thought... I knew there'd be some sort of problem with it - I was just putting the idea out there.

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Re: Cheating at pulse-detonation

Post by durg » Sat Sep 25, 2010 7:46 pm

A while ago I saw a patent for creating a continuous detonation, by means of two extra combustion chambers. One of these were fed too rich fuel/air mix, the other too lean. The two combustion chambers function was to accelerate, pressurize and preheat the two mixtures. When the two mixes were mixed inside the main combustion chamber, the result was stochiometric - diluted by combustion products, but fast, hot and pressurized enough to detonate.
Do you think this is a viable idea for a PDE?

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Re: Cheating at pulse-detonation

Post by ace_fedde » Sun Sep 26, 2010 2:56 pm

I believe that system is described somewhere in this forum, look for CDE. It only works with hydrogen/oxygen mixtures because they can burn/explode while not being a close to stochiometric mixture.

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Re: Cheating at pulse-detonation

Post by John Werner » Sun Jun 26, 2011 12:56 pm

An Exercise In Deflageration to Detonation

Copyright © 2011 By John Werner

This is a method to produce a detonation using empty food
cans.

The first thing that may come to mind is the "TennisBall
Cannon" Where empty food cans are taped together and fire a
tennis ball up into the air. It takes a little more then
this to produce a detonation as you will see.

Without getting into a long winded discussion I'll cut to the
chase on how to produce detonation. This model will get you
started and at your own risk you can carry it further.

The materials you will need are:

1) a ream of 8 1/2" X 11" 110 weight cardstock
Sams Club, Office Max
2) 1/2" masking tape and packing tape 2"
Office Max
3) one butane barbecue lighter
Home Depot
4) one pint of S-L-X brand denatured alcohol
Home Depot
5) two empty enchilada cans
Super market
6) one empty green bean can
Super market
7) Sharp nail used as a punch

What this model will do, it will show what a baffle will do
to increase combustion pressure and I'm really surprised that
no one in this forum has ever tried this with pulsejets.

In scouring the US patent office there are several patents
that use the baffel system in combustion.They are:
1) The Brown Patent awarded to Samuel Brown Jr 1972
#3,745,691

This patent now expired will allows anyone to build and sell
combustion devices using the baffle system.

2) December 28, 1982 #4365471 Joseph S. Adams

3) E. B. Meyers 1946 #2647365

The baffle is not as apparent in the Meyers jet engine but
it's there.

The baffel used in these patents is similar to the shchelkin
spiral which is still a baffle.

All of the PDE patents use some form of the shchelkin spiral.

OK back to the model. What it won't do with the three cans is
detonate, for that you need several more stages! And
electronic ignition with 20 feet of wire so you can get
behind a barricade. It will blow the cans into shrapnel.

Building the Model

Tape the two enchilada cans together end to end to form a
mandrel. Cut 4 pieces of the card stock 5 1/2" X 8 1/2 then
tape them to form one long piece 5 1/2" X 68".

Cut a piece of tape 3/4" long and tape the card stock to the
mandrel so that 3/16" holds the cardstock to the mandrel with
the rest on the cardstock. Start rolling to the end. It will
most likely be crooked, just clamp with your hand the roll
against the mandrel and twist against the direction you
rolled. This will loosen the roll so you can straighten it
then twist in the direction you rolled to make the tube nice
and tight and tape the seem with masking tape. Cover the
masking tape with a piece of the packing tape.

Dismantle the mandrel and punch a hole with the nail in the
center of one of the enchilada cans then enlarge it to 1/4".
In the other enchilada can punch a hole in the side 1" up
from the closed end, this will be the igniter can. No holes
are punched in the bean can.

Fueling the Model

Get an empty jam jar or any small jar with a lid and pour in
about 1/4" of alcohol. Pour a small amount of alcohol into
the igniter can, rock the can back and forth to cover the
bottom then pour out ALL of the alcohol back into the jar
for this first test.

Push the empty compressor can into the tube (center hole can)
then follow it with the igniter can (side hole can).
Orientate the cans so the compressor can with the center hole
is against the open end of the igniter can. Both cans should
stick out from each end of the tube. The cans must be
against each other. Place a tennis ball into the open
compressor can and ignite with the barbecue lighter at the
side hole with the cans standing on the igniter can.

Not much will happen, the ball may not even shoot out of the
cannon. Remove the cans and this time fuel both cans. Hold
the compressor can at a 45 degree angle when you pour in a
little alcohol then hold it over the jar as you rock it to
catch any spill through the center hole.

With both cans fueled place them back into the tube and add
the tennis ball and ignite. The ball should go up 50 feet or
more.

Now for the third and last test fuel the enchilada cans as
before and also the bean can and be sure to always pour out
to the last drop of alcohol, all you want is to coat the
bottom of each can.

Place the enchilada cans in the tube then place the bean can
over the open end of the tube, this should be a snug fit and
stand the tube on the igniter can and fire.

The bean can will shoot up 100 or more feet straight up and
you can calculate the height by timing with a stopwatch from
the time of the explosion till the can comes back down and
hits the ground. Divide the total time by 2 then multiply by 9.8
which gives the height in meters. Be sure to wear a hard hat to
protect your head from the falling can.

It takes a longer tube which must be reinforced with steel
and multiple stages of compressor cans to get a true detonation.
Do this at your own Risk!!

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