Stirling Engines

I was hoping some kind soul out there could provide me with a very dumbed-down version of how a Stirling engine works (bearing in mind that the explanation on the howstuffworks webpage was over my head).
I’ve been intrigued by them ever since the whole Dean Kamen/Segue thing but I can’t wrap my tiny head around how they work or why they aren’t in general use. Is there a flywheel involved somehow?

Thanking you in advance for enlightenment.

I’m not so good with clarification, but I’ll do what I can if you ask.

First things first, you have to understand that as you heat a gas the pressure goes up. Heating makes the gas particles move faster, meaning it pushes out harder on the sides of it’s container. It’s kind of like those after Thanksgiving sales - as you increase the discount, the heat, you also increase the amount of force people are willing to exert to get to the discount.

The second part you need to understand will require you to look at the HSW’s picture of the cycle here. Know this: as the left piston goes up, the right piston goes down and vice versa.

Lastly, the Stirling engine is completely sealed with a gas in it, meaning that the gas can not escape.

Now, for how it works. Basically, a heat source (say a lamp) is applied to the left side of that picture. The right side has no heat source, so relatively speaking it is “cold.” Cold, in this instance, is just a lack of heat.

Well, when heat is applied the gas expands as described above. This pushes the piston down, causing work. This is the only stage of the engine that produces work.

Next, the piston is pushed back up, making the right one push down. When the heated air enters the right, cooler chamber it does the opposite of expand - it condenses. This condensed gas is then pushed with the right piston back into the left chamber, where the cycle is then repeated.

How did I do?

Excellent, seriously, thank you very much.

I think I had trouble with the idea of an external heat source not to mention I thought that a flywheel played some part in the whole contraption.

Thanks again.

I’m just curious what Dean and the Segway have to do with this?

Kamen originally wanted the Segway to be powered by a Stirling engine. IIRC, I believe he also has patented a few variations on the Stirling as well.

Flywheels are used in all sorts of engines. A flywheel is just a big mass that rotates. Once you get it rotating, it wants to stay at the same speed. It takes more effort to make it spin faster or slower. This is useful when you have something like an engine that provides power during only part of its cycle, because the intertia of the flywheel is going to keep the mechanism moving during the non-power part of the cycle. The intertia of the flywheel keeps things moving and makes the engine’s output more smooth.