Test · 2024-01-21
Thermoacoustic turbine test
Can a Wells turbine extract rotary work from the oscillating flow of a 2-inch thermoacoustic engine?
Not in this test. A metal-printed stainless Wells turbine on a ceramic bearing spun freely by hand but did not turn under the engine's acoustic flow, at either end of the tube. The long shaft is the first suspect.
- Kind
- Test
- Status
- Retired
- Date
- 2024-01-21
- Turbine
- Wells, metal-printed 316 stainless
- Bearing
- Ceramic
- Resonator
- 2 in tri-clamp
- Stack
- 5.9 in ceramic
Video
What it is
A stainless-steel, metal-3D-printed Wells turbine on a low-friction ceramic bearing, mounted on a long shaft so it could be slid along the resonator. Plus a supply-chain update on stacks and diaphragms, and a recap of failed piston attempts.
Results
- →No rotation observed with the turbine at the end of the tube or repositioned.
- →Pressure waves are strong enough to feel by hand at the open end.
- →Next: shorter shaft, retest.
Lab notes
Why not pistons
Several pistons were tried in a tri-clamp sight glass: a glass/nylon piston and an Airpot graphite-in-glass piston. Both barely moved. A thermoacoustic engine delivers acoustic power, not the pressure swing a piston needs; a diaphragm works because its natural frequency can match the engine's, so it resonates.
Coil gap is deliberate
The gap between coil and diaphragm equals the magnet length, so the magnet fully exits and re-enters the coil each stroke, maximizing flux change.
Engine proportions
The 18 in reference design is three 6 in sections: hot base, stack, cold top, sized to the stack's resonant frequency. A shorter base works on a desk but would overheat the cold end in a campfire.
Supply
New vendors for the 5.9 in ceramic stack (~500 in stock) and for high-temperature silicone diaphragms, now vacuum-sealed and clearer than earlier batches.
Notes transcribed from the build video.
Related
Questions about this one? Ask in the Discord. It's the fastest way to reach me.