PREDATOR - valveless PDE build blog

Moderator: Mike Everman

zono
Posts: 72
Joined: Wed May 28, 2008 1:03 pm

PREDATOR - valveless PDE build blog

Post by zono » Sun Oct 10, 2010 8:26 pm

Some months ago I started creating a valveless PDE , fueled by stoichiometric propane/air mixture. The already manufactured pieces are lying around and waiting for completion. Now I hope to speed up my efforts.

what has been done until now?

- applied PDE function principle: propane / air injector tube provides intermitted detonable gas mixture, that is pushed into DDT tube, where intermitted ignition is done by spark plug. Propane gas solenoid valve and ignition will be triggered by AVR ECU (timer programming)

- spreadsheet calculation of supersonic propane nozzle , air-gas injector (stoichiometry) and DDT tube dimensions has been done already.

- intake flare, injector tube and DDT tube are welded together (welding is not one of my favorite skills :lol: )
-- propane nozzle throat d = 1.15mm
-- injector tube d_i = 27mm ; L = 350mm ; high alloy stainless steel 2.8mm thickness
-- DDT tube d_i = 76mm (=minimum DDT cell size) ; L = ca 1600mm ; high alloy stainless steel 2.5mm thickness
-- 10mm thick steel Shchelkin spiral for advanced DDT (deflagration to detonation transition)

- recent gas and spark trigger technology is very crude : manual switch and piezo agitator. (AVR ECU will be completed next time)

no test run yet ! (but soon....)
Attachments
image011.jpg
image010.jpg
image008.jpg
image007.jpg
image001.jpg
___________________________
zono - the thruster buster
--------------------------------------

metiz
Posts: 1517
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: PREDATOR - valveless PDE build blog

Post by metiz » Sun Oct 10, 2010 8:35 pm

Not only an actual attempt but also a build log! I realy hope you make me swallow my words :)

Any estimation when you will have this engine done? Also, on topic more or less, what exactly is a Shchelkin spiral; what is its exact function? It's very hard to get any good info on the thing.

Good work so far!
Quantify the world.

zono
Posts: 72
Joined: Wed May 28, 2008 1:03 pm

Re: PREDATOR - valveless PDE build blog

Post by zono » Sun Oct 10, 2010 9:27 pm

I am very covered by my job, so I can't do an estimation, when we will hear the first BANG- BANGs . But I will speed-up

Shchelkin spiral helps speed-up DDT by causing turbulences, so detonation tube can be shortened. Normally DDT minimum lenth of propane/air mix is (cant remember exactly) ca 1.8 ... 2.5 meters. Good starting point on literature:

http://en.wikipedia.org/wiki/Shchelkin_spiral

Instead of Shchelkin spirals many other obstacles has been tried by research institutes. Orifices, wedges, cavities....all objects, that can cause turbulence are principally applicable.
___________________________
zono - the thruster buster
--------------------------------------

metiz
Posts: 1517
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: PREDATOR - valveless PDE build blog

Post by metiz » Sun Oct 10, 2010 9:55 pm

Ok thanks for the info. Do you know what a Tesla valveless conduit is? It constantly reverses flow back onto itself. Maybe if that same principle was incorporated inside a ddt engine tailpipe it would cause sufficient pressure build-up to do the same thing, maybe even quicker...hmm food for thought :)

Image
Last edited by metiz on Sun Oct 10, 2010 10:15 pm, edited 2 times in total.
Quantify the world.

metiz
Posts: 1517
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: PREDATOR - valveless PDE build blog

Post by metiz » Sun Oct 10, 2010 10:05 pm

Btw reading your description, am I right in asuming this engine does not breath on its own or auto-ignites?
Quantify the world.

zono
Posts: 72
Joined: Wed May 28, 2008 1:03 pm

Re: PREDATOR - valveless PDE build blog

Post by zono » Mon Oct 11, 2010 10:54 am

yes, I know the Tesla valve, but I don't make use of in on PDE construction. My PDE is quite simple: intermitting self-breathing by supersonic propane-injection (jet-pump principle = air suction by propane-jet). No auto-ignition. Ignition spark is triggered at end of propane injection. See the sketch of valveless PDE.
Attachments
Predator-PDE.png
(9.72 KiB) Downloaded 216 times
___________________________
zono - the thruster buster
--------------------------------------

metiz
Posts: 1517
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: PREDATOR - valveless PDE build blog

Post by metiz » Mon Oct 11, 2010 11:38 am

Ok thanks for the info. very professional build so far, excellent work :D
Is your knowledge on the subject purely self taught i.e for hobby purposes or does your job have something to do with propulsion/ acoustics as well?
Quantify the world.

zono
Posts: 72
Joined: Wed May 28, 2008 1:03 pm

Re: PREDATOR - valveless PDE build blog

Post by zono » Mon Oct 11, 2010 1:20 pm

Yes, its an own development for non-commercial purposes, but I have some background knowledge as I am a chemical process engineer. So far fluid dynamics and thermodynamics and propulsion touches my job in general.
___________________________
zono - the thruster buster
--------------------------------------

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: PREDATOR - valveless PDE build blog

Post by PyroJoe » Mon Oct 11, 2010 2:31 pm

Good work, and it is good to see a build log here.

Be safe, this is a high risk area with little payout for Do It Yourself folk.
Attaching the internal objects should be done with care, in the past they have been shot out the tube in bullet fashion.
In short, don't have anything of value down or up range. Secure the engine well.

Survivability is often relative to proximity, best to give some distance.

Thanks for sharing, Joe

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: PREDATOR - valveless PDE build blog

Post by Viv » Mon Oct 11, 2010 2:43 pm

Hi Zono

Looks nice to me, I like your simpler approach to getting some thing to go bang but I did wonder about your tube sizing as its pretty much on the minimum cell size for propane, my question is this, does the shchelkin coil occupy some of the space in your DDT tube that the shock cell needs to occupy? so 75mm for the cell plus the shchelkin coil = the inner DDT size?

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

zono
Posts: 72
Joined: Wed May 28, 2008 1:03 pm

Re: PREDATOR - valveless PDE build blog

Post by zono » Mon Oct 11, 2010 4:57 pm

Hi friends,

I am very glad, that you like this build ! Hopefully you get satisfying answers from myself.

Ok, I am aware, that 76mm dia and blockage by Shchelkin spiral affecting or concerning a possible run. The good news is that (on literature I read) obstacles lower the necessary cell size, so we wait and see....The simple reason is, I got this tube very cheap out of scrap metal. If it doesn't work, I will take 100mm dia.

Safety: the maximum detonation pressure of propane-air mix is by Chapman–Jouguet-condition only 18 bars, so most bicycle tires could withstand this load :wink: --- really dangerous is hydrogen or acetylene with oxygen

Now i am on travel for some days, and will continue after that. so long, guys...
___________________________
zono - the thruster buster
--------------------------------------

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: PREDATOR - valveless PDE build blog

Post by Viv » Mon Oct 11, 2010 5:03 pm

zono wrote:Hi friends,

I am very glad, that you like this build ! Hopefully you get satisfying answers from myself.

Ok, I am aware, that 76mm dia and blockage by Shchelkin spiral affecting or concerning a possible run. The good news is that (on literature I read) obstacles lower the necessary cell size, so we wait and see....The simple reason is, I got this tube very cheap out of scrap metal. If it doesn't work, I will take 100mm dia.

Safety: the maximum detonation pressure of propane-air mix is by Chapman–Jouguet-condition only 18 bars, so most bicycle tires could withstand this load :wink: --- really dangerous is hydrogen or acetylene with oxygen

Now i am on travel for some days, and will continue after that. so long, guys...
Hi Zono

Thanks for the answer, I would be interested to read the reference on cell size reduction if you can post it when you get back

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

zono
Posts: 72
Joined: Wed May 28, 2008 1:03 pm

Re: PREDATOR - valveless PDE build blog

Post by zono » Mon Oct 18, 2010 8:32 pm

Hi All !

See some useful literature regarding cell size and other dimensioning parameters (answer to Viv's question)

here "quasi-detonation" is explained for tube diameters smaller than cell-size
http://www.iwr.uni-heidelberg.de/groups ... 00/231.pdf

other useful stuff :
http://www.dtic.mil/cgi-bin/GetTRDoc?Lo ... =ADA411011

http://conference.ing.unipi.it/ichs2007 ... 1.3.40.pdf

http://www.gexcon.com/handbook/GEXHBcontents.htm

here is a good explanation of "cell size" (tube diameter may have minimum cellsize/3 ) :
http://www.gexcon.com/handbook/GEXHBchap6.htm
___________________________
zono - the thruster buster
--------------------------------------

zono
Posts: 72
Joined: Wed May 28, 2008 1:03 pm

Re: PREDATOR - valveless PDE build blog

Post by zono » Thu Nov 04, 2010 11:58 am

announcement:

in the next days I hope to start first static tests with single-shot
___________________________
zono - the thruster buster
--------------------------------------

zono
Posts: 72
Joined: Wed May 28, 2008 1:03 pm

successful run !!!!

Post by zono » Mon Jun 13, 2011 10:16 am

Hi All,

end of May I had some successful runs of valveless PDE "Predator" !

This videos don't look or sound very spectacular (bright daylight, microphone overblow...), but believe me: detonations blastwaves give a nice massage of your intestins!

So, consider these details : wiggling and trembling frame and concrete plate (weight) ; and echo of detonations. The surging sound is made by the propane injector, which provides the stoichiometric mix with air. Sometimes you can hear some self-ignition pulsations like in a normal valveless pulsejet.


http://www.youtube.com/watch?v=j7av5ae7dDI

http://www.youtube.com/watch?v=yAnFORosMPs
Attachments
pde-predator.jpg
___________________________
zono - the thruster buster
--------------------------------------

Post Reply