stirling engine with helium/hydrogen/other gases

[stuffandthings]

i want to either buy or build a stirling engine with a specific gas (will use several gases)
it is for a science fair, doesn't have to be very efficient
it just needs to hold in helium or any other gas for a short period of time
the working fluid will be changed

are there any tuturials, kits, or preassembled stirling engines that will let me do this?

[Triangle.Stirling]

I don't think your question is that simple.

Overall it is very difficult to make an engine that will hold such gasses, even for a short time.
I don't know of an engine that is currently available, maybe others know?
Building yourself such an engine is also not that simple. You have to start at the beginning, building simple stirling engines, before you can try a pressurized engine.

Overall, is would be nice to experiment with different gasses, but i'm afraid it is not easily done. Correct me if 'm wrong.

[scottmatthew]

The Stirling engine, like most heat-engines, cycles through four main processes: cooling, compression, heating and expansion. This is accomplished by moving the gas back and forth between hot and cold heat exchangers. The gas follows the behavior described by the gas laws which describe how a gas's pressure, temperature and volume are related. When the gas is heated, because it is in a sealed chamber, the pressure rises and this then acts on the power piston to produce a power stroke.

[vamoose]

Hey stuffandthings,
Like all elements/compounds some are more thermally conductive than others. Also different liquids/gases have better/worse viscosity relative to density (partly due to atomic properties and/or molecule shape). Spend some time and do some research into these things and it may become a bit clearer.
like looking through mud//

Coleman 'used' to sell a portable fridge using a free piston stirling 'cooler' with pressurised helium (in a sealed system) as the working gas.
If i ever come across one i intend to attempt to turn it into an engine

http://r1.coleman.com/Manuals/5726-750.pdf

also, on the subject of stirling engine working gases..
http://www.stirlingengineforum.com/view ... f=1&t=1149

A group of gases had collected together at the Air pavilion for a Stirling engine convention, to state their case for being used as a working gas in a Stirling engine. Hydrogen was the first to rise up and proclaim its superior attributes. Helium wasn't far behind and said that at the core of the matter he is twice the gas that hydrogen could ever be.
'Ha.. don’t make me laugh' proclaims Nitrous Oxide.
Anyway, A group of hydrocarbons try to make their case but Supercritical fluid cuts them down and says that they and their ideas stink. Its not us that stinks, they proclaim, but that stigma follow us everywhere we go.
Argon steps up trying to be noble by suggesting that they all have abilities that they could periodically bring to the table, so should try and combine together on this project.
To which supercritical fluid replies; Well Hydrogen doesn't tend to stick around, so has commitment issues, and when he and oxygen are under pressure things tend to become explosive,
to which oxygen meekly replies, Unfortunately I tend to have that affect on a some gases.
Anyway after alot of heated exchanges by a multitude of different gases, and after most everyone had dissipated, Air was still hanging around, taking in the atmosphere, so got the job by default because it was free and avaliable...

vamoose

[Ian S C]

As I said on another thread, try and get "The Stirling Engine Manual" vol 2 by James G. Rizzo, there are some reasonably simple pressurised motors in that book that someone with reasonable skill in the machine shop should be able to build, don't try one of these as your first motor, you have to start at the bottom and work your way up, good luck. Ian S C

[stuffandthings]

Is there any way to pressurize a Stirling engine by increasing ambient temperature?
If a Stirling engine isn't pressurized, it has an atmospheric pressure. So if you were to put the Stirling engine inside a pressure vessel, would it have the pressure of the vessel?

[Ian S C]

Basically, When you build a pressurised engine it becomes a hermetically sealed unit, so the pressure of the whole is the basic pressure, it would be difficult to imagine a motor working in a bell jar.
By raising the ambient temperature(it would need to be in a sealed container), the pressure would rise, but the ratio of temperature between hot and cold end would be reduced. Ian S C

[stuffandthings]

Thank you, that clarifies a lot!

But why would increasing pressure by increasing the mass of gas within a fixed volume have anything to do with the tenperature ratio?