Is there a perfect ratio between cylinder size.

Discussion on Stirling or "hot air" engines (all types)
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WildBillCody
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Joined: Mon Oct 17, 2016 10:51 am

Is there a perfect ratio between cylinder size.

Post by WildBillCody » Thu Oct 20, 2016 1:24 pm

I'm going to build a Gamma, What size should my power cylinder be compared to my displacer cylinder? I would think you would want a bigger displacer. Also is there a perfect size tube diameter between the two. I am shooting for a 10" flywheel, I am also planning on it powering it's own water pump to move cooling water around the displacer. TIA

thanh-cuibap
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Location: Việt Nam

Re: Is there a perfect ratio between cylinder size.

Post by thanh-cuibap » Thu Oct 20, 2016 6:29 pm

I think that there is one best rates! but I do not know and no one talks about it all, you do this link step by step ... and then gradually learn from experience
http://www.stirlingengineforum.com/view ... f=1&t=2124

Ian S C
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Location: New Zealand

Re: Is there a perfect ratio between cylinder size.

Post by Ian S C » Fri Oct 21, 2016 3:03 am

The ratio for GAMMA and BETA motors (high temp) is 1.5 : 1, the displacer being the larger of the two. A conventional displacer in the form of a hollow cylinder has a length three times it's diameter. The gap between the displacer and the hot cap ranges from .020/.5 mm up depending on the size of the motor, a larger motor might have 1/8"/3.5 mm.
Ian S C

Alfista
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Clarification

Post by Alfista » Fri Oct 21, 2016 5:01 am

Here is a rough outline : The classic design calls for the swept volume of the displacer to be 1.5 times the (working) volume of the power cylinder. As this ratio increases, the requirement of the temperature differential goes down. Specific output tends to go down as does the rpm range. Engines between with a ratio of 5 : 1 to 30 : 1 may be thought of as medium temperature differential engines, and those from about 50 : 1 to 100 : 1 as low temperature differential engine. As the ratio goes up, the engine must be ever larger to reach the same power level as the smaller, high temperature differential engine.

Here is a link to one of Robert Sier's pages : http://www.stirlingengines.org.uk/modeng/note.html


WildBillCody
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Joined: Mon Oct 17, 2016 10:51 am

Re: Is there a perfect ratio between cylinder size.

Post by WildBillCody » Fri Oct 21, 2016 8:26 am

Thanks everyone, very helpful.!

WildBillCody
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Joined: Mon Oct 17, 2016 10:51 am

Re: Is there a perfect ratio between cylinder size.

Post by WildBillCody » Tue Oct 25, 2016 2:36 pm

I just read over that page, very informative, one thing that comes to mind, the tube that runs from the top of the diffuser cylinder to the power cylinder, what diameter should that be? I'm thinking the bigger the better for easier transfer of air?

thanh-cuibap
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Location: Việt Nam

Re: Is there a perfect ratio between cylinder size.

Post by thanh-cuibap » Tue Oct 25, 2016 9:46 pm

I usually make the diameter of the pipe between 2 cylinders about 3 -> 5mm,

masaruneema
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Re: Is there a perfect ratio between cylinder size.

Post by masaruneema » Fri Nov 18, 2016 1:09 am

I'm thinking the bigger the better for easier transfer of air
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