I'm currently messing around with the idea of a steam turbine made out
of 3D printed plastic.

Early design test shows that it's practical, and can meet the goal of
being able to charge a cell phone (5V at 3A like a typical USB 2 charger)

The actual design is on github as an OpenSCAD file: https://github.com/bombasticbob/3DObjects/blob/master/turbine_rotor1.scad

The rendered result looksl like this:
http://bigbadbob.name/turbine.wheel.jpg


I did a basic experiment of pressing a DC motor shaft into the center
[slightly off due to 3D printer bad behavior], and spinning it using
compressed air. The wheel speed was at least 10,000 RPM (really spun
the hell out of that motor). The motor normally runs on 6-12V DC, but
when spun, was producing more than 50V as a generator!

I put a 100 ohm 10 W resistor across motor output, and was able to spin
it to produce more than 40V (careful not to overspin though).

Then I tried it with steam from a capuccino machine (a Mr. Espresso
type) and, estimating less than 50psi steam, spun the thing at a
slightly higher RPM than it was when I was getting 40V.

In short, the steam from the capuccino maker, when spinning the wheel by
hand, produced enough power (16W) to charge a cell phone.

And the steam temp at 50psi is about 285F, somewhat below th3e melting
point of PLA plastic. [it _is_ in the "glass" range though, so I don't
know how long it will last with 50PSI steam on it).

Given that P.O.C. it should be possible to make a steam turbine for 50
psi steam from PLA plastic, as a design P.O.C. at any rate.

One thing worth pointing out, the steam cools when it does work. In
this case, I held onto the motor with the turbine wheel on it in my
naked hand. Spinning it with steam produced a "wet fog" all around the turbine, which was only slightly warm [in addition to the amount of
entrained air involved]. In short, steam cools when you do work with
it. Basic heat transfer equations, enthalpy becomes kinetic energy.


So I'd guess that the hot steam could melt turbine blades, but the cool
steam would protect them... and it might be interesting to see how long
plastic blade turbines would last in this kind of environment!








--
(aka 'Bombastic Bob' in case you wondered)

'Feeling with my fingers, and thinking with my brain' - me

'your story is so touching, but it sounds just like a lie'
"Straighten up and fly right"

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On 2021-03-26 11:31, Big Bad Bob wrote:

I'm currently messing around with the idea of a steam turbine made out
of 3D printed plastic.

Early design test shows that it's practical, and can meet the goal of
being able to charge a cell phone (5V at 3A like a typical USB 2 charger)

The actual design is on github as an OpenSCAD file: https://github.com/bombasticbob/3DObjects/blob/master/turbine_rotor1.scad

The rendered result looksl like this:
http://bigbadbob.name/turbine.wheel.jpg

working on 3D objects, more in github site

https://github.com/bombasticbob/3DObjects

added an 'eductor' test drawing to use a steam or air jet to create vacuum.

https://github.com/bombasticbob/3DObjects/blob/master/eductor.scad

and

https://github.com/bombasticbob/3DObjects/blob/master/eductor.stl

(the STL file is the output you 3D print with)

You can view STL files online here if you want:
https://www.viewstl.com/

This one's pretty large [file size] because of all of the smooth
transition shapes you have to make to render it.

An eductor is an interesting mechanical device that creates a vacuum by blasting a "moving fluid" from one end into a convergent-divergent
nozzle and an inlet manifold. You can typically get a vacuum of about
3:1 output pressure to manifold pressure with something like this. I
figured it would need at least 50psi to work, and if I need a harder
vacuum, their can be multiple stages [each with significantly higher
flow rates on the 'moving fluid'].

So yeah it's a bit of mechanical hacking, 3D CAD hacking, and plastic
printing (which nearly always involves at least SOME hardware hacking).

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