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Thermoacoustic jet pump: 2 in, Ø20 to Ø8 taper
How do I stop the steady flow round a looped thermoacoustic engine? · Hardware · basis: Backhaus & Swift's jet pump: an asymmetric orifice whose minor-loss difference between the two flow directions sets a steady pressure drop that opposes Gedeon streaming
Long Earth Society build part. The jet pump in my twin-piston generator. The engines
Exact dimensions. Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part. Mating features
- sizes
- 3 in table
Notes
- A torus lets the gas drift steadily round the loop (Gedeon streaming), carrying heat from the hot exchanger straight to the ambient one. A tapered hole loses more pressure on the flow out of its small end than into it, so it sets a steady pressure difference that can cancel the drift: Backhaus & Swift's jet pump.
- Here a Ø47.5 plug, 30 long, sits in the junction cross's lower branch on the gasket lip, its taper from Ø20 (junction) to Ø8 (the ¾ in inertance line). The linear model counts it as a duct of the mean bore.
- Only the twin-piston engine needs it: in the ring engine the pistons themselves block the loop.
Sizes
| feature | value |
|---|---|
| outside | Ø47.5 |
| taper | Ø20 → Ø8 |
| length | 30 |
Mating features
Drawn at the exact size. Open press, slide, run and socket features by your process's clearance; leave designed gaps and clamp fits as drawn.
| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| outside | Ø47.5 | 2 in cross branch bore | slide | all |
| taper | Ø20 → Ø8 over 30 | oscillating gas (no contact) | designed | all |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| J. Acoust. Soc. Am. (S. Backhaus, G. W. Swift) | A thermoacoustic-Stirling heat engine: detailed study, JASA 107(6), 3148 (2000): torus with inertance and compliance, thermal buffer tube, jet pump against Gedeon streaming | web | journal article; cited verify |
| Long Earth Society | Engine builds | web, video | LES site |
Free files
★ Free files 1 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json
| jet-pump-2in-30 | jet pump Ø47.5 × 30: conical bore Ø20 at the junction side to Ø8 at the inertance side | STEP · STL |
Plain text: sheet.txt · JSON: /api/geometry?object=thermoacoustic-jet-pump
How it fits
In these build lists
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Questions
Why not a membrane?
A membrane works too but has to survive the stroke; the jet pump has no moving part.