{
 "version": "2026-10-20",
 "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.",
 "slug": "thermoacoustic-jet-pump",
 "name": "Thermoacoustic jet pump: 2 in, Ø20 to Ø8 taper",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Thermoacoustic & fluidyne",
 "year": null,
 "question": "How do I stop the steady flow round a looped thermoacoustic engine?",
 "tags": [
  "jet pump",
  "gedeon streaming",
  "thermoacoustic",
  "tri-clamp",
  "long earth society"
 ],
 "aliases": [
  "thermoacoustic jet pump",
  "gedeon streaming suppression",
  "tashe jet pump"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/thermoacoustic-jet-pump/",
 "sheet_txt": "https://xemstudio.com/objects/thermoacoustic-jet-pump/sheet.txt",
 "sheet": {
  "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",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "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."
  ],
  "table": {
   "columns": [
    "feature",
    "value"
   ],
   "rows": [
    [
     "outside",
     "Ø47.5"
    ],
    [
     "taper",
     "Ø20 → Ø8"
    ],
    [
     "length",
     "30"
    ]
   ]
  }
 },
 "sheet_text": "Thermoacoustic jet pump: 2 in, Ø20 to Ø8 taper — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/thermoacoustic-jet-pump/  (CC BY 4.0)\nBasis: 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\nCatalog version: 2026-10-20\n\nSizes: see table below\n- 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.\n- 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.\n- Only the twin-piston engine needs it: in the ring engine the pistons themselves block the loop.\n\nfeature  value\noutside  Ø47.5\ntaper  Ø20 → Ø8\nlength  30\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- 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 license at link] — https://doi.org/10.1121/1.429343\n- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/thermoacoustic-jet-pump/index.json\nAPI: https://xemstudio.com/api/geometry?object=thermoacoustic-jet-pump\n",
 "sources": [
  {
   "publisher": "J. Acoust. Soc. Am. (S. Backhaus, G. W. Swift)",
   "title": "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",
   "url": "https://doi.org/10.1121/1.429343",
   "formats": [
    "web"
   ],
   "license": "journal article; cited",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "list-ta-twin-piston-2in",
  "thermoacoustic-buffer-tube-liner"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [
  {
   "feature": "outside",
   "exact": "Ø47.5",
   "mates": "2 in cross branch bore",
   "fit": "slide",
   "files": "all"
  },
  {
   "feature": "taper",
   "exact": "Ø20 → Ø8 over 30",
   "mates": "oscillating gas (no contact)",
   "fit": "designed",
   "files": "all"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. Typical FDM: +0.2 mm.",
  "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "Why not a membrane?",
   "a": "A membrane works too but has to survive the stroke; the jet pump has no moving part."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "jet-pump-2in-30",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/thermoacoustic-jet-pump/jet-pump-2in-30.step",
   "stl": "https://xemstudio.com/files/hardware/thermoacoustic-jet-pump/jet-pump-2in-30.stl",
   "note": "jet pump Ø47.5 × 30: conical bore Ø20 at the junction side to Ø8 at the inertance side"
  }
 ],
 "markdown": "https://xemstudio.com/objects/thermoacoustic-jet-pump/index.md"
}