Optimized Lockwood-Hiller Style Valveless Pulse Jet.

Print V9 for best results.

Update: V9 runs well on gasoline with canned air. See the video below for reference. Will slightly pulse without air assist when running on isopropyl alcohol. A small amount of air assist results in decent reciprocation.

I would highly recommend PPE, goggles, gloves, and a respirator if possible. If you use compressed air from an air compressor, it is probably better for you. The terrible smell is very bad to breathe in. Use in a well-ventilated area. Do not run it if you value your arm hair.

Video of it running:

https://youtube.com/shorts/uwhEAB0an6s

Tips to get it to run:

• Spray fuel into the combustion chamber and swirl it around so it fumes. This makes initial ignition easier. Be prepared for a large backfire.
• Blow air into the intake (the smaller hole). Sometimes you may need to blow it out into the exhaust; if there's too much smoke inside, it'll snuff itself, and you need to clear it.
• Keep a small pool of fuel in the combustion chamber.
• If possible, a small pilot burner in front of the intake may help for sustained runs.
• Play around with the amount of air you assist. Start small and build up. It is possible to get it to run well.
• Be mindful of how long it runs for. Much longer than 15-20 seconds continuously will begin to melt it. If you let it cool off between runs, you can get ~3-6 solid runs out of it. I'd estimate it can handle about 1 minute of run time.

Tips for printing:

• Orient it so the intake and exhaust are on the build plate.
• Scale to ~415%. This will make it ~230mm tall. The bigger you can print it, the better.
• Strength settings may affect run time, i.e., it will melt faster with thinner walls, though I doubt it changes by much.

By far my best design to date. Any tips, videos, or images of it running would be greatly appreciated.

My current plan is to reduce the exhaust taper angle from 12 degrees to ~8 degrees. As you can see in the video, it spits a lot of flame out of the exhaust. I believe this is because the exhaust is too wide. It also leaves a ton of residue, so I think it isn't burning very clean, could also be due to burning gas in plastic.