Water pulsejet

Off topic posts are welcome in this forum!
No smear campaign, or you will be banned!

Moderator: Mike Everman

Mark
Posts: 10931
Joined: Sat Oct 11, 2003 10:14 pm

re: Water pulsejet

Post by Mark » Wed Aug 16, 2006 1:48 am

I wonder if a bundle of little tubes would be better than a single tube?
Mark
Presentation is Everything

Mike Everman
Posts: 5007
Joined: Fri Oct 31, 2003 7:25 am
Antipspambot question: 0
Location: santa barbara, CA
Contact:

Re: re: Water pulsejet

Post by Mike Everman » Wed Aug 16, 2006 2:16 am

Greg O'Bryant wrote:Mike that is true with the smaller putt putt engines. The problem is when you try to upscale them the water just runs out when steam is produced. The vacuum phase doesn't happen. So I am under the impression that it actually is partly due to capillary action. That is why I inverted my engine. This solved the problem of getting the water back in but they still aren't that forceful. If you have any ideas on how to super heat the water before it flashes into steam I think you would solve the mistery of upscaling putt putt's :)
I don't think it can be capillary action... never seen water jump up a soda straw, and you can certainly get one that diameter to go. I'd like to think that it's just the starting procedure that needs to be modified.
Lately, I've been thinking "why scale it up?" Just make a strip of hundreds of 1/4 inchers on a bar, have a string of propane jets, and away your little fishing boat goes! Why not?
Oh, I had a thought. You don't need the pipes to run under water, they get cooled by the incoming water.
Mike Often wrong, never unsure.
__________________________

Greg O'Bryant
Posts: 209
Joined: Mon Mar 14, 2005 4:03 am

re: Water pulsejet

Post by Greg O'Bryant » Wed Aug 16, 2006 3:10 am

Capillary action is not a good description. You are right that it is too large for that to happen. I am just trying to explain what I am seeing. The small diameter does have an effect on how they operate and it seems to be related to the surface tension. In my larger engines the hot water in the boiler will actually rise up through the pipe on one side and cool water will go down the other. This doesn't seem to happen in the smaller ones. Perhaps the small diameter and increased surface tension holds the water in a stratified configuration. Last I have read on the internet that the diaphragm engines work the best, and from my observations I would agree. Both for small and large engines. You simply get a lot more power out of them for what you put in. I think that this may be related to surface tension too. At first I thought that this might be caused by the diaphragm popping and causing more water to splash on the hot metal of the boiler. This isn't the case with a large inverted engine. It is completely full of water from the start. As the water turns into steam it increases the volume of the boiler. The bubbles of steam in the boiler will then get bigger and just like blowing up a balloon it eases up on the pressure. This would then release more steam and provide more power. Anyway do you think that a couple hundred small tubes would provide enough force to be worth it? At the moment it seems to be the most sensible thing to try.

Mike Everman
Posts: 5007
Joined: Fri Oct 31, 2003 7:25 am
Antipspambot question: 0
Location: santa barbara, CA
Contact:

re: Water pulsejet

Post by Mike Everman » Wed Aug 16, 2006 3:34 am

Yeah, the diaphragm type ar far superior to the coil type, I think because the flash boiler expands as the charge of water is expelled, and then it shrinks, squeezing out even more. Neeto. I'll bet there is an optimum diaphragm diameter for a given water mass that you want to expel. I think Forrest did some calcs on that(?)

Another opportunity to match frequencies in our daily lives. Ah, people just don't know what they're missing, and go back to their collecting of commemorative plates. ;-)
Mike Often wrong, never unsure.
__________________________

multispool
Posts: 125
Joined: Thu Jan 19, 2006 10:59 pm
Antipspambot question: 0
Location: UK

re: Water pulsejet

Post by multispool » Thu Sep 14, 2006 8:51 pm

The silly season must have arrived because I was tickled by the water pulsejet idea. I remember them but soo long ago!

Decided to make one, Tried a closed end tube with a flame on the end but no dice.
Second attempt was 12" long pipes with a three turn coil, this sprung into life using a small blowlamp. The tube must have got too hot because the pulsing ceased. Removed the heat and as the tubes cooled, t sprung into life and ran on it's own for several seconds. I think the heat originally pushed the water too far from the boiler area.

As it cooled, and started working, it seemed to have a broad range of working stability before it finally became too cool.
This engine was made from 3mm brass tubing. I'll make a 4mm one tomorrow and see if it still works!

And to hell with safety, I think I'll make a twin candle one!

Mark
Posts: 10931
Joined: Sat Oct 11, 2003 10:14 pm

re: Water pulsejet

Post by Mark » Fri Sep 15, 2006 7:20 pm

Presentation is Everything

multispool
Posts: 125
Joined: Thu Jan 19, 2006 10:59 pm
Antipspambot question: 0
Location: UK

re: Water pulsejet

Post by multispool » Fri Sep 15, 2006 11:24 pm

Tried a 4mm diameter tube version today with two boiler coils! It worked, at one stage it even jumped out of the water tray it was in but quite a limited working temperature range. Think the 3mm tube is the best overall size to go for.
Three coils for the boiler and 12" long tubes. The best working position was sloping about 15-20 degrees with the boiler at the top.

hagent
Posts: 413
Joined: Sun Feb 06, 2005 9:01 pm
Antipspambot question: 0
Location: Simi Valley CA

re: Water pulsejet

Post by hagent » Sat Sep 16, 2006 7:20 am

How about this idea?

Have a Tesla valve on the intake. The intake is pointing towards the front.

Have a "CC" chamber that houses a small coil that can be pulsed with electricity.


This is what I envision happening.

A small area right around the coil which is in the middle of the CC chamber is pulse with lots of energy. Just around the coil area, bubbles spontaniously appear and therefore displace some water. Water has a hard time going through the intake because of the Tesla valve but a very easy route to the exhaust. The bubbles then shrink because they cool down and the volume drops pulling in water from the intake.

Any focused energy source could be used. So long as it can vaporize water without having to heat up the whole chamber.

Let me know what you think.
Hagen Tannberg

Nick
Posts: 371
Joined: Fri Oct 17, 2003 10:36 am
Antipspambot question: 0
Location: Somerset, UK
Contact:

re: Water pulsejet

Post by Nick » Sat Sep 16, 2006 8:58 am

What you want guys is a fluidyne. add a little compexity in the form of 2 ball valves and you can happily have a 300gph pump (yes 300gph).
Look up fluidyne on google, build one out of std plumbing parts. A brilliant simple water jet propulsion system.!!

Nick

Mr.B
Posts: 36
Joined: Sat Apr 15, 2006 3:45 pm
Antipspambot question: 0
Location: Berlin, Germany

re: Water pulsejet

Post by Mr.B » Wed Oct 25, 2006 1:33 pm

This is perhaps what Mark was referring to.
We build one after reading something here.
http://www.newscientist.com/article.ns?id=dn3321

To provide enough steam I heated up an old CO2 welding-tank (1/2)filled with water to 16 Bar. It propelled a very crude and heavy raft for about 5 meters in 3 sec but then it ran out of pressure.
Looking for a good van Reynst style combuster where I can ran a stainless steam coil through. Any practical designs??
Thanks

The first a view into the exhaust.
The second pict shows the jet with the air-snorkel attached
Attachments
steamOB.jpg
steamOB.jpg (55.5 KiB) Viewed 7091 times
CIMG0479.JPG
CIMG0479.JPG (170.99 KiB) Viewed 7091 times

Post Reply