Hello, all,
I'm working on the early stages of a serious Stirling engine design. There are two things that I don't know enough about.
I want to try to make this run with no lube in the crankcase. (The reason is that the high temperatures in the hot heat exchanger (about 700 - 800 C) will make most oils coke up and block the tubes. The design of the engine makes it possible to keep the really hot gas away from the sliding seal on the piston. (The displacer seal also runs at a moderate temperature, and some leakage there will not hurt performance much.) The power piston is on the cold side of the engine, and shouldn't see temperatures over 100 C.
So, does anyone have any ideas for a piston seal that would be fairly easy to make, or stock materials that can be had readily?
And, second, I will need to assemble a crank in pieces, so roller bearings can be placed on the crank pins. I sort of have an idea on how to do this: Make the crank pins an interference fit into the crank throws, but have slanted flats, making the end of the pin into a sort of wedge shape. That sounds pretty easy. Making the mating socket in the crank throws sounds like a perfect EDM job. I can't think of any other way to make it that has a chance of working. There would be bolts coaxial to the pins that would hold the crank and pins together. The flats should hold the crank in alignment.
Is there a better way to do this? I'm looking at a 1-2 Hp output engine running 800 PSI of Hydrogen in it, if I can get it to hold that. (The idea is to put a PM alternator inside the crankcase, and make the engine-alternator a semi-hermetic unit, with copper O-rings at every place it opens up.)
Any and all suggestions welcome!
Thanks,
Jon