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dimensions for displacer on a Stirling engine? Answered

I want to make a low temperature Stirling engine. I was looking at some different designs for them and none really have a set dimension for the displacer. All the ones I see must just be guesswork. I  have a glass tube that I was going to use for the power cylinder about 16mm diameter I will build it like this. I have no idea what size the displacer cylinder and displacer will need to be for it to be effective. can anyone guess for me?

I also need to know how much the piston should move for it to be effective.

Thanks, David.

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rickharrisBest Answer (author)2013-06-24

The displacer can displace more air then the power cylinder holds, the extra will just stay in the displacer cylinder. In some - Low temp for example there is an advantage in displacing a lot of air at once and they usually have a wide shallow displacer cylinder.

The displace should be as light as possible. BUT be able to withstand the temperature of the heat source. I have used crushed aluminium foil - a sort of crude honeycomb aluminium as well as empty cans.

Low temp generally use foam as a displacer because of the very light weight and low temperatures.

http://www.john-tom.com/StirlingPlans/LiveSteamStirling.pdf

http://www.john-tom.com/StirlingPlans/KoichiHiataStirling2.pdf

http://www.john-tom.com/StirlingPlans/KoichiHiataStirling.pdf

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energybroadcast (author)2013-06-24

There's a page on LTD Stirling engines here: http://diystirlingengine.com/ltd-stirling-engine/

There is good info on that page. At the bottom of the page there is a link to a good book on this topic.

I've read it and it's short and easy to understand a will give a much better perspective on low temperature differential Stirling engines.

Hope this helps.

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Kiteman (author)2013-06-24

The displacer cylinder should be the size you can manage - unless you are going to splash out on a custom-made cylinder, you're going to have to use a reclaimed cylinder, like a soda can or a bean tin. Either way, all the displacers I have seen have been around a third the height of the inside of the cylinder.

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