Will water or ATF absorb helium?
Posted: Sun Aug 03, 2008 8:30 pm
I am contemplating the problems with using helium as the medium in a Stirling to see if its worth the trouble.
I believe the displacer can be moved with external magnets, so there will be no possible shaft seal leakage from the displacer cylinder. This leaves the power-piston rings and the power piston rod seal.
If I put the expanding/retracting helium into the top of a "U" pipe with fluid in it, a piston on the other side would be raised and lowered by the cycling fluid.
Even the first version should have two side by side "U"-tubes, with the two piston rod ends attached by a rocking beam to each other. This would prevent the lifting piston from trying to draw a cavity void from the liquid.
Hydraulic actuator pistons and rods are easily available off-the-shelf. The piston seals are well-designed to seal while sliding in a cylinder with high-pressure hydraulic oil.
I know from reading about ram water-pumps, that a snifter valve must be included to keep some air bubbles in the accumulator (an upside down cup) so it can act as an air-spring.
Without this snifter valve, the air pocket will be absorbed over time by the water. Also, carbonated beverages are another example of a pressurized gas (CO2) being absorbed into a liquid.
I can envision this working on a high-pressure/low-RPM engine. Helium is non-flammable, cheap, and easy to get from baloon suppliers, but leakage past seals on most conventional Stirlings can be a major roadblock to making an easy-to-build high-power Stirling.
The magnetic seal-less displacer and liquid U-tube seal might fix this problem,...IF the gas is not absorbed by the liquid.
I am leaning towards synthetic Automatic Transmission Fluid (ATF)
Any thoughts on this? Thanks in advance...
I believe the displacer can be moved with external magnets, so there will be no possible shaft seal leakage from the displacer cylinder. This leaves the power-piston rings and the power piston rod seal.
If I put the expanding/retracting helium into the top of a "U" pipe with fluid in it, a piston on the other side would be raised and lowered by the cycling fluid.
Even the first version should have two side by side "U"-tubes, with the two piston rod ends attached by a rocking beam to each other. This would prevent the lifting piston from trying to draw a cavity void from the liquid.
Hydraulic actuator pistons and rods are easily available off-the-shelf. The piston seals are well-designed to seal while sliding in a cylinder with high-pressure hydraulic oil.
I know from reading about ram water-pumps, that a snifter valve must be included to keep some air bubbles in the accumulator (an upside down cup) so it can act as an air-spring.
Without this snifter valve, the air pocket will be absorbed over time by the water. Also, carbonated beverages are another example of a pressurized gas (CO2) being absorbed into a liquid.
I can envision this working on a high-pressure/low-RPM engine. Helium is non-flammable, cheap, and easy to get from baloon suppliers, but leakage past seals on most conventional Stirlings can be a major roadblock to making an easy-to-build high-power Stirling.
The magnetic seal-less displacer and liquid U-tube seal might fix this problem,...IF the gas is not absorbed by the liquid.
I am leaning towards synthetic Automatic Transmission Fluid (ATF)
Any thoughts on this? Thanks in advance...