Stirlingengineforum.com

Hi
What material is preferred for a displacer body for a Stirling engine ?
Can this be aluminium?
I need to machine this on my hobby lathe.
The tube is about 16mm dial by about 40mm long with a minimal wall thickness.
Thanks

Kayjas wrote: ↑Mon Nov 18, 2024 3:24 pm Hi
What material is preferred for a displacer body for a Stirling engine ?
Can this be aluminium?
I need to machine this on my hobby lathe.
The tube is about 16mm dial by about 40mm long with a minimal wall thickness.
Thanks

Personally I try to avoid metal for a displacer, especially aluminum.

A lightweight refractory material of one sort or another has better thermal properties.

infact, I ordered a new material that came out recently I haven't seen before. Vermiculite soldering bricks.

Link in the video description:

https://youtu.be/JAzGwZOy2UI

Real or man made pumice usually works well. This can be found in stores as callous remover stones or as barbecue grill cleaner blocks or as chew blocks in pet stores.

Or ceramic if you have the means for firing clay.

I think ceramic fiber might also be a good choice or certain other lightweight insulating firebrick.

I think of a displacer as a "heat valve" to let heat into the engine intermittently.

So it also needs to be able to shut heat off or insulate. Aluminum has no insulating properties.

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Oops, this version already has a response. I missed that happening. Putting my post here to make this the main one.

Fool wrote: ↑Tue Nov 19, 2024 10:26 am .

Usually, if available stainless steel. It can be found in thrift stores in various items, like pots, thermoses, thermos coffee cups, etc. it is thin strong and heat, and rust, resistant.

You want it to be conductive into the gas, yet non conductive lengthwise. Longer cylinders are better for high temperatures. Pancake shaped cylinders are better for low temperatures. The compression ratio should match the temperature ratio that you plan to operate the engine.

Other displacer cylinder materials would be thin walled steel, like a tin can. Thin walled aluminum, like a pop can. Propane or butane bottles, glass, test tubes. Even acrylic has been used in low temperature engines. Copper pipe is too conductive length wise, unless a thermally insulated mid section is used.

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Many thanks.

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Welcome.

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https://www.boydhouse.com/stirlingengine/index.html

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