3D Printed Regenerative Compressor (Supercharger) 25Amp Pressure Test

Regenerative compressors provide good pressure head and medium flow at low RPMs. I designed this 3D printed one from scratch in Sketchup to play with the concept for potential CPAP cooling on my printer. It starts to build pressure head at fairly low RPMs, but it needs plenty of power ... so after a lame smoke test with a 1 Amp DC motor from an inkjet printer, I decided to try out a 25-30 Amp cordless drill motor belted down by 3:1. Now THAT'S some BRRRRRRRR!
*8.30.2022 CORRECTION/UPDATE: the highest pressure I have MEASURED on this unit is 0.75 PSI at around 7-8k RPMs (estimated) with the flow nearly stalled.
I even posted the files this time, so if you want your own, head to www.printables.com/model/2543...
I genuinely think this regenerative direction might be a viable path for higher-head 3D printed air compressors. The efficiency even on commercial versions isn't awesome, BUT you can get usable pressure without needing 50-100k RPM like a small-diameter centrifugal compressor needs, meaning the stress on the plastic parts is MUCH lower and there's little/no risk of exploding wheels or suddenly friction welding force-expanded parts and blowing up the motor. The sound on this one is pretty awful (or awesome, in small bursts), but it really does start working at very low RPMs. You can actually feel it start to work even just spinning the shaft with your fingers. I think a multi-stage version might be able to build a lot of head without needing these jet engine-screaming RPMs (which aren't actually all that high -- I would guess only a few K tops). And even if this one does scream, you'd need real screamer of a centrifugal / turbo compressor to get the same boost, and 3D printed positive displacement pumps like roots blowers and screw compressors seem to sound universally awful ... blah blah blah, but yeah, I'd have to figure out the noise issue before putting this to any daily printing use.
I will probably explore this direction further in the future, maybe with a proper brushless motor, and maybe even get a real pressure dial and a tach to quantify results! I may also play with printed intake/exhaust silencers, which some commercial versions use for reasons that are much more obvious after these tests (ha). Let me know in the comments if these (or other ideas) interest you, or whatever.
Check out my other designs at:
www.printables.com/social/237...
I'm also a writer! I genuinely don't care if you mash dat like or smash dat subscribe, but if you like sci-fi adventure stories, check out my debut novel, JONESY FLUX AND THE GRAY LEGION: bit.ly/JonesyFluxAZ
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www.jamespray.com
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[@stefanguiton]

Great results! What CFM stats do you reckon you are getting with such a setup? The pressure is impressive

[@jamespray]

If we assume the 13-gallon trash bag was more like 7 gallons of volume because of being rubber banded around the hose, that would be 0.936 cu ft. If we say the fill starts at 0:41 and ends between 0:47 and 0:49 (when it's only just full, not pressurizing), so 6-8 seconds, that would be 7.02 to 9.36 CFM average.
Safe to say the actual CFM at full speed would be higher since the demo spooled up from 0, but probably not a *lot* higher. So that explains why the smoke test looks almost like nothing's happening! This type of compressor really doesn't act intuitively at all... and it's a very interesting middle ground between radial / centrifugal blowers and positive displacement compressors. Particularly interesting to me is that it works this well with gaps of .6 to .8mm between the impeller wheel and the housing's "sealing" surfaces.

[@stefanguiton]

@@jamespray Nice! With the pressure that it is able to achieve, a lower cfm must not matter as much, since it opens the posibility of forcing air better through small vents near the nozzle, whereas other high cfm/low pressure fans would struggle.

[@mitchellstrobbe7779]

What is that sound!

[@jamespray]

Pretty bad, ain't it? I toned down the sound a lot (detailed in a more recent video), but suffice to say that although this may be a low-RPM compressor, quiet it is not!

[@beanMosheen]

@@jamespray I once took some 2" corrugated plastic raceway thinking it would make great vacuum hose. I think it deafened my neighbors too when I tested it on a shopvac the first time!

[@jamespray]

@@beanMosheen Oh, yeah, when it's just the wrong airflow rate the noise is TERRIBLE 😫