# The workings of a Stirling engine

1. Feb 13, 2012

### magicacid

Hi
As a school project, I want to construct a Stirling engine (particularly this kind : http://monsterguide.net/how-to-build-a-stirling-engine [Broken]). The execution is quite simple, but I do not fully understand the theoretical background.
Can someone give me an explanation?

Last edited by a moderator: May 5, 2017
2. Feb 13, 2012

### 256bits

3. Feb 13, 2012

### Staff: Mentor

Put simply, the engine uses a heat source to make a cold gas (such as air) expand. Expanding gas does work on a piston. The piston then pushes the air to a heat sink where it is cooled. Then the cooled air is pushed back to the hot piston where it is compressed and heated again.

See here: http://en.wikipedia.org/wiki/Stirling_engine
And here: http://en.wikipedia.org/wiki/Heat_engine

4. Feb 13, 2012

### AlephZero

The key point to understand is that there are actually two pistons, which operate out of phase with each other, moving like graphs of $\sin t$ and $\cos t$.

As the Wiki page shows, both pistons can be in one cylinder if you want, but it's probably mechanically simpler to have two cylinders.

5. Feb 13, 2012

### Staff: Mentor

Ah yes, I had forgotten to mention the very important 2nd piston.