Double Action Stirling

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Double Action Stirling

Postby sgraehl » Wed Feb 13, 2008 10:32 pm

I've been thinking of building a model that uses two displacer
chambers and one power piston mounted between them. The displacers
would run opposite hot cold cycles from each other and that way as
one is pushing the piston down the other will be pulling it as
well. My question is; would it be worth doing since I would be
trading the atmosphere part of the cycle for another displacer
chamber? Has this ever been tried?
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Double Action Stirling

Postby stan.hornbaker » Thu Feb 14, 2008 9:08 am

"Would it be worth doing?" Absolutely YES. It would be of imeasureble worth from the experience alone regardless of results. Arm chair designs are worthless till proof of concept hardware is produced.

What do you mean by referring to the "atmosphere part of the cycle"?

How do you implement the ~90 deg. phase shifts between displacers and piston?
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Response to Double Action Stirling

Postby sgraehl » Thu Feb 14, 2008 1:29 pm

On cold cycle, isn't the piston being pushed back tward the displacer chamber by atmosphere pressure as much as it is by the drop in pressure in the chamber? If I have each end of my piston ported to a displacer then I will have a truely sealed engine, does that make sense? So with that I'm wondering if the extra linkage and weight of an additional displacer will actually provide enough benefit.

As for phase; I haven't thought that out completely, but what comes to mind is that the two displacers simply are linked together moving oppositely and providing their own balance compensation. I know what you mean by the timing though and like I said, I have not thought that part through as to if it would work like that. I have established a way to connect the chambers to the piston cylinder and all linkage will go internal with a minimum of dead air provided the displacers could work in the way I mention above. Even in my simplest layout, I see several more points of friction and moving parts. As for the main concern, since the Stirling is a "one stroke" engine by nature then isn't it really already double action?
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Response to Double Action Stirling

Postby jgroves467 » Tue Mar 18, 2008 7:16 pm

Building a double action Stirling would be great. You are correct about the increased friction levers and bearings, but still a worthwhile project. Robert and James Stirling built one in 1827 which operated for several years. There is an illustration of this engine on page 54 and 55 of G. Walker's book "Stirling Cycle Machines".
Jerry Groves
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