A 3D Printed Jet Engine Appears to Function

[amazingdiyprojects] has been working on a 3D printable jet engine. You may remember seeing a 3D printed jet engine grace our front page back in October. That one was beautiful didn’t function. This one flips those values around.¬†[amazingdiyprojects] seems to make a living from selling plans for his projects, so naturally most of the details of the build are hidden from us. But from what we can see in the video clips there are some really interesting solutions here.

Some of the parts appear to be hand-formed sheet metal. Others are vitamins like bearings and an electric starter. We really liked the starter mechanism, pressing in the motor to engage with a spline, or perhaps by friction, to give the starting rotation.

What really caught our attention was casting the hot parts of the printer in refractory cement using a 3D printed mold. It reminds us of the concrete lathes from¬†World War 1. We wonder what other things could be built using this method? Flame nozzles for a foundry? A concrete tea-kettle. It’s pretty cool.

We’re interested to see how the jet engine performs and how others will improve on the concept. Video of it in action after the break.

UPDATE: [amazingdiyprojects] posted a video of the engine being disassembled.

UPDATE:

24 thoughts on “A 3D Printed Jet Engine Appears to Function

    1. Looking at the second video, not sure if it’s common-parlance “jet engine” as I can’t see any Brayton cycle-style compressor + combustor, just the exhaust fan; i.e. the spin on the hot end doesn’t actually do anything apart from.. well.. spin.

      The inlet probably has to be small so that the exhaust goes out the other end. I think it’s more of a self-sustaining gas turbine than fully-fledged “Jet Engine”? – althou ghI could be wrong; there may be a single-stage / some rotor vanes at the front of the unit that we don’t see.

    2. Small inlet works to his advantage: as the interior cross section increases, the air pressure goes up and the velocity drops. He’s also using a single stage centrifugal compressor, which is like a turbo charger compressor. Adding an exhaust nozzle would increase the thrust a bit, but as the efficiency of this design is probably low, it may not self-sustain without the full pressure-drop across the exhaust turbine.

      1. I don’t think the proportions of diameter vs inlet looks too far of for a single stage centrifugal compressor. 3d-printing a centrifugal compressor seems like a really smart way to be able to make a compressor that actually works an build it yourself (think hoover compressor/fan).

        Now, I think the compression ratio is extremely low, but it self-sustains and it runs, pretty cool :).

  1. Very nice, but I will stick to the made from a car\ lorry turbo version. Easier cheaper and dare I say it safer? All that plastic looks like a recipe for melting PLA and an explody fireball. That and you can have a closed oil loop for a turbo so you can run it longer.

  2. There’s no glow from the thrust end while it’s running, and then he picks it up with his bare hands and touches the expansion turbine a few seconds after running it? Something funny’s going on. Running off compressed gas only with no flame, maybe? Squirting enough gas into the ‘combustion chamber’ will cause it to spool up even if it wouldn’t be thermodynamically self-sustaining.

      1. Yeah, I take it back – the third video definitely shows flames. The first video looks like it’s just powered by expanding butane and I still think this contributes significantly to it sustaining. I’d be curious what the fuel-to-air ratio is and what pressure it’s reaching in the combustion chamber.

    1. That’s what I was thinking.

      Point a blowtorch at a turbine wheel, and the wheel will spin. The whole thing can be running on a gas mixer which pulls air in using the pressure from the bottle, basically replacing the compressor stage with a venturi pump, and the expansion of the combusting gasses then turn the turbine wheel.

      It works and spools up as long as there is sufficiently little back pressure at the turbine – i.e. no load and little bearing friction so the turbine spins freely. It also blows only the amount of air that the venturi can draw in, instead of acting like a proper jet engine. That would basically make it just a fancy version of this:

        1. In the second video at 2:23 it appears he may have added a compression stage. My untrained eye tells me it was some sort of fan attached near the rear in front of his starter motor. How well it works is unknown, maybe he could take some pressure measurements through his ignition hole.

  3. Turn the lights down low or off. I would have thought that if it had any reasonable thrust it would be a good idea to use it as a hair dryer. I’m sure UL listing is out of the question. lol

  4. This is a fairly sweet design! I like how he uses a 3d printed mandrel to press the turbine blades into shape. For those doubting… it appears to be a single stage centrifugal compressor (like a turbocharger) driven by a single stage axial turbine. The small intake and large exhaust probably enable it to work with very low required efficiency. The compressor just has to help the air intake enough to let Bernoulli change the pressure by 2:1 or maybe 3:1 depending on the cross section area change. That also helps by reducing the velocity through the combustor. Then he’s not really decreasing the area any, which would keep the internal pressure fairly high, so he gets the full pressure drop across the exhaust turbine stage. It’s kind of like blowing into the small end of a funnel.

    To maximize thrust of this engine, progressively smaller nozzles can be added until it won’t self sustain. The nozzles added after the turbine steal pressure drop from the turbine and convert the pressure into velocity.

    If you look at early aircraft jet designs, they did the same thing – put a small opening at the front and let Bernoulli’s principle help out with compression since compressor efficiency sucked back then.

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