General Design Scheme for 200 W Stirling Engine

[Alfista]

If you build a gamma engine using standard dimensions with a 6" power pistion, reasonably well built with the usual attention to friction and good sealing, The output should exceed 200W.

[burnit0017]

If you build a gamma engine using standard dimensions with a 6" power piston, reasonably well built with the usual attention to friction and good sealing, The output should exceed 200W.

Hi, I am fabricating a large gamma. What are the standard dimensions for a 6" power piston? I am new to stirling engines.

[Alfista]

Burnit0017,
If you were making a piston rod guide, then you could make the piston as short in length as you would like. The longer it is, the better it tends to seal and the more friction it has. If I were buiding a 6" diameter piston with the normal connecting rod and wrist pin combination, I would make the length at least 6.8". Naturally the geometry of the crank throw must be taken into account but if your stroke is 6.625 and the crank throw is 3.3125, then it should be about right. Make the effective length of the connecting rod about 20.27 inches. That is just an approximation to get you close to the right geometry.

[burnit0017]

[youtube]https://youtu.be/cYm-SpDLyZU[/youtube]

Current attempt, piston 4 inch diameter, displacer 9 inch diameter, both are 3 inch stroke. Working on scotch yoke crank shaft.
Gamma configuration, smaller version of this design: https://www.nmri.go.jp/eng/khirata/stir ... strct.html

Thanks you for the help.

[Alfista]

Burnit0017,
I have the impression that you would like some feedback on your project. First, since you are using rod guides and diaphragm(s)? and scotch yokes, piston length is pretty irrelevant. It looks like a serious effort and a sturdy build. Can you say why you chose such a large difference in swept volume between the power piston and the displacer ? I get something like 1: 2.25 ... I understand the choice of the scotch yoke although I have never had much success with them but they look a bit heavy, are they ? I can tell you that reducing the mass of any reciprocating parts is a great advantage. I am impressed with your work so far. I cannot be sure that I completely understand what I am looking at but it appears that you have come up with a very good rod guiding system and even though things look a bit sticky at this stage, I can imagine a low friction build here with good sealing.

One more observation, if this is a vertical engine, it looks like you could reduce the diameter of the rods to get less friction, especially since you have worked out a nice guide for the rods. I have no doubt that you will work out the obstacles with your impressive building skills. To summarize the primary challenges, they are good sealing with low friction, effective temperature differential, proper ratios for the designed temperature range, good balancing of the reciprocating parts which can be VERY light given the low power output of most engines, and an appropriate flywheel. The better the balance or counterweight system in the reciprocating parts, the lighter the flywheel can be.