Geometry of pancake medium temperature stirling

[staska]

Yes, i will post some pictures/sketches, it looks that i had finally figured type of engine and possible technologies. Sadly, vermiculite boards are not suitable for displacer, they did not survive pressure swing. For heat exchanger i will try to use corrugated foil and spot welder, i have a mould for it.

[zhivko]

I also thought of corrugated foils... It would be very interesting project to see. what is your piston diameter? What stirling type you are building?

[Ian S C]

Probably, if your displacer is of conventional diamentions, ie., length three times the diameter, the best way I see of making a regenerative displacer would be one with a thin walled cylinder as usual, but with holes top and bottom, inside, fill with the stainless foil, either corrugated, or dimpled. Ian S C

[staska]

Thanks for suggestions. I try to use materials ad technology common to me. I thought about annulus regenerator with filler, but it is way out of my experience - you must have displacer with compression ring to direct air there it mus be. Other way it will go shortest path - along displacer. So - or simple annulus or displacer with compression ring and properly designed air path.

Currently i have two path, none of them clear.

1. Copy of NAS 2 engine, thich is ok by performance for me, but i must find TAICALITE or analogous material. I will try to look at ceramic insulation boards. It should be "pancake", like 200 diameter of displacer with 50 stroke.

2. "Classic stirling" from spot welded SS 0.5 stell. Long horizontal displacer with some sort of roller to support weight of it. Low rpm, in 50-100 rpm range.

[Ian S C]

Try not to need the roller support for the displacer, but rely on the gland bearing on the displacer rod, and if need be, an extra bearing ahead of that, the weight of the displacer should not be great enough to cause it to sag to much. The other way to over come the sagging problem, is to mount the displacer vertically, hot end top or bottom depending on the type of heater used. You could use less than .5 mm stainless, .25/.3 mm is quite OK, I'v used .007", it is getting to the size that needs a good TIG job. Ian S C

[staska]

Back again to work.

I have managed to get this piece of software running: http://www.ohio.edu/mechanical/stirling/me422.html And now, i could answer a question of engine geometry. In short - 3 mm gap in heater will work, but will not produce any high usable power or allow regenerator placing without piston ring on displacer. To got realistic rpm in 150-300 range you shall go to 1-1,5 mm annular heater "deph" or use multitube heater, at least 30 cm long. Also - it is possible to use alpha type stirling engine. To wary compression ratio, we should wary an angle between hot side and cold side of pistons. 120 degree instead of 90 will give about 1.5 compression ratio.