www.pulse-jets.com

Well, more that I want to do liqid fuel for pulsejet and gaseous fuel for pulsepots...
I'm in Costa Rica atm, so not doing anything but dreaming...

Mike Everman wrote:Well, more that I want to do liqid fuel for pulsejet and gaseous fuel for pulsepots...
I'm in Costa Rica atm, so not doing anything but dreaming...

Hey, Costa Rica seems like a good place to do some dreaming

I'm only a week off blasting down through Europe on my KTM990! - so I'm dreaming of the alpine passes and the French Riviera.

Seems like a good place to look for blue morphos.
https://www.youtube.com/watch?v=29Ts7CsJDpg#t=1m17s

Looks like one for "natures children", mark.

Have fun, Nick!

I asked Axel Borg (amazingdiyprojects.com) about the fueling on his pulsejet rocket, and got this interesting reply:

Hi Mike, and thanks for hosting such a great forum.

Well, the fuel system challenge was really one of the most joyful and cumbersome difficulties to overcome.
Since the overall structure had to be as light as possible it had to be a liquid fuel system rather than a pulse jet running from a heavy vaporized propane source. My solution was to preheat the propane stored in a WD40 canister fitted with a car tire valve to about 40 degrees Celsius, both to achieve a adequate fuel pressure and partly to make the primary start squirt of liquid propane to vaporize before entering the engine. The fuel is fed into a vaporize chamber which also is the front double walled bulkhead of the pulse jet engine From there three brass fuel tubes goes trough the combustion chamber exiting the tree air intakes, than the tube is bent 180 degrees to direct the now vaporized propane back into the flared intakes. The brass tube is squeezed to a 0.1mm (I think) slit to allow for reliable self start sucking air in whit the propane stream. The engine has to be gradually throttled up and set at idle throttle for 2-3 seconds to allow the vaporizing chamber to build up enough heat to handle the full throttle fuel flow. You will find a more comprehensive and illustrated description of it all in the e- book up for sale on amazingdiyprojects.com

Kind regards/Axel

So I've got this notion to make a PJ powered bike out of a 1L pocket jet I have. Just go for a simple free turbine and gear it all down. I do not care about how fast I go, gearing it for 10-15ish MPH(?), assuming 100m/sec achievable tangential velocity(?)
I do not have any interest in using a PJ big enough to push you around by main thrust; rather I want to putt-putt around the salt flats talking to motorheads with something that is not entirely uncomfortable to be around.

To that end, I'm again interested in self starting fueling setups for my pocketjets. Pocketjets take a good deal of starting air and finesse at the valve to get running; an air source not easy to manage in the field, complicated by wanting to start anywhere when power is lost.

What's known is that it should be a jet of proper tiny diameter, situated at the inlet to entrain air. I've ordered an assortment of 3d printing nozzles: https://www.amazon.com/gp/product/B07DL ... UTF8&psc=1
to try and home in on this proper jet diameter.
Since I ordered those, however I found a Holley carb jet assortment that would be more appropriate, more expensive and complete and ordered that. https://www.amazon.com/gp/product/B0006 ... UTF8&psc=1

The carb jets set will be good to adapt in the field to different elevations and conditions. I'm hoping this can be simple, but does bring to mind the possible eventuality of applying the same starting smarts that we find on turbojets: temp transducers, proportional valves, multiple fuel sources all controlled by a processor for one touch starting. I don't think I've ever seen that applied to a pulsejet, and want to avoid it.

Hey Mike - sounds like a great idea look forward to seeing that come on!!

Cheers

Nick

Hey Nick, hope all is well! Need to come out there in '19 for sure.
I'd like to see this one too as it's been percolating for a long time, so am laying in some supplies. But anyone that reads this thread knows I'm all talk until I am not!
I've had to scale back on work a bit for my sanity, so am imagining a bit of hobby work.

All good thanks mate
Always welcome here mate, look forward to seeing in 19

Oh yeah, I suppose we did talk about this
viewtopic.php?f=3&t=4190&hilit=chicken+ ... =15#p59619

I think I'm favoring the simple free turbine idea better now. I can imagine the Coriolis and centrifugal forces going on are going to massively hurt flow on the "spin around the intake" type. I've seen simple convection amid the chaos inside a valveless.

Way to go I think, - John Wallis tried a turbine on a PJ once - it worked but not enough power for what he wanted.

Looking forward to seeing more of this!

Cheers

Nick

Ah yessss, pushbutton starting works! I’ll get a youtube up of the successful result.

I ran out of fittings, so decided to try a direct line to the starting stinger, and adjusting the needle valve going to the main feed.

The next iteration needs ability to shut off and get the starting stinger out of there, or leave it on to cool it, IDK

Here are the raw notes from the test site:

Pulsejet tests
Basic set up: line direct to starting stinger, needle valve branched to main feed, starting pressure 135psi, 120psi by the end.
.4 mm nozzle One and a half inches in, just barely
4 mm nozzle, 1/2 inch in, starts with ramp up of main feed!
.3 mm nozzle, at entrance, nice consistently burning warm-up, bangs, increasing main fuel feed does not resonate, though
.3 mm nozzle, 1/2 inch in, Again good burner, pop starts well, still no main fuel feed resonance
.3 mm nozzle one and a half inches in,Same no resonance on main fuel feed
Same, 2 1/2 inches submerged,Same result
Same, 3 1/2 inches submerged, same
.4 mm nozzle, 2 1/2 inches submerged, Unsteady, energetic bangs, requires continuous spark but definitely goes with careful ramp up of main fuel feed
.4 mm nozzle, 3 1/2 inches submerged, nope
.6 nozzle 1/2 inch sub merged, energetic pops, needs ignition, main fuel feed at a low level as well becomes instant starting!
.6 submerged 1 1/2 inches, still energetic pops, though no low level main feed really low
.6 mm nozzle 2 1/2 inches submerged
.6 mm not also at Inlet, sporadic pops, no good
.5 mm, 1/2 inch submerged, a pop or two nothing going
.5 mm 1 1/2 inches submerged, definitely start up or by working the main fuel feed sporadic pops
.5 mm 2 1/2 inches submerged,About 80 psi with a little bit of main becomes instant starting
.8 mm 2 1/2 inches submerged, can work with a flow restrictor

Nice one Mike, those measurements don't half high-light the precision needed with the fuelling volume and position
turnkey starting enroute!

You know, once you let go of any dreams of high performance pushing a bike around with 5 lb of thrust, the problem opens up and gets really fun. Doing some math, I realized that making a larger diameter free turbine gets me very little. My original thought was that the thrust acting on a bigger radius would get me more. Not so. Going with a smaller turbine is merely a reduction ratio issue. I was also very determined to make it not "pump air" in the sectors that were not being impinged by the jetstream. Let go, Mike, it's all ready horribly inefficient! Grasping at a few percents here and there is a "someday never".
Just saying to myself that I'll only go on level ground and be proud of a ludicrously low HP/Db ratio was so liberating!

That decided, the thought becomes: where can I get a turbine for next to nothing that is made out of stainless at least, and can take a higher RPM? I was originally looking at steel squirrel cages, but no good dimensions available cheaply. Started thinking "make it" again.

Then it went to random searches for "impeller", and LO, doesn't a Jet Ski impeller look so nice. Put the word out, and I got two from friends over the weekend. Popular change-out item, as it turns out.
Look to Ebay for a right angle drive, and get two for $75. A bit big, but heh? It may explode from high rpm's or not, who cares?