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Just curious here...has anyone ever tried using a spark plug or diesel glow plug mounted inside the hot cylinder as the heat source? It sure seems that you'd gain a lot of efficiency by having the heat source inside the hot cylinder versus outside the cylinder. (I'm not saying ignite any fuel inside the cylinder, just use the spark plug or glow plug to heat the air or other gas inside the cylinder.)

I don't now the thermodynamics calculations, but I'd imagine a glow plug would work nicely. I know the spark of a spark plug has a very high temperature, but I honestly don't know the calcs to determine if a short spark would actually put enough heat into the air inside the cylinder to do the trick.

Any thoughts?
Dave

Thanks for the reply Ian. Overall, I can't see how putting the heat source inside the hot cylinder (if possible) wouldn't be beneficial. True? I'm trying to think out of the box on ways to do that.

Cheers,
Dave

theropod2 wrote: External combustion, more than just a phrase.

Indeed.

Yeah, some sort of electric heating element might be worth a try.

Now, I wonder...if the flywheel were set up to function as a Faraday wheel (ie. generate electric current from it's spinning), how much efficiency that might add by supplementing the current to the heating element (Faraday wheel's can produce high current, but low voltage...hmmm). Of course, any energy used to generate additional electricity = less mechanical energy available to use for something else.

Dave

Ian, I gather you are thinking along the lines of a Gamma-type Stirling with the electric heating pad. I'm thinking more along the lines of the two-cylinder Alpha-type Stirling and putting an electric (or some sort of non-combustion) heat source INSIDE the hot cylinder (presumably at the end). Diesel glow plugs won't work, regular spark plugs don't impart enough heat...what is a similar point-source of high heat that you guys can think of?

Something like this might work:
http://cgi.ebay.com/Replaceable-30W-Wel ... 3a5f542dbd
http://cgi.ebay.com/Replaceable-Solderi ... 3a5ff3c34f

Hmmm...I have one of those electronic soldering irons at home that uses a carbon electrode with a spark gap.

Anyone got a lump sum of spare Uranium lying around?

Nichrome wire...good thought! I wonder how much current I would need?

Cheers,
Dave

What about one of those little hot plates designed for keeping your coffee cup warm? Or an immersible heating element used for warming a cup of coffee? They may not get real hot, but they would have more surface area than a soldering iron.

You can take the heating element out of a steam iron or an electric dryer.

The only problem I see with any of these approaches is that you are just making an electric motor, and there are many designs for electric motors that are far more efficient.

Good point about creating a less efficient "electric motor".

Still thinking "out of the box" here...external combustion, electrical resistance, electrical arcs, concentrated/point-focused sunlight, geothermal heat, nuclear reactions, chemical reactions, friction...what other ways are there of producing substantial amounts of heat? (Maybe this should become a separate thread?)

Dave

The first thought that comes to mind is geothermal heat. If you are lucky enough to have access to it, that would be an awesome application of a Stirling engine. You could generate electricity from a hot spring.

few years ago,

I read, somewhere ( in the internet ), about stirling engine using spark plugs.

I think it was for a Ph.D degree. but I can not find it.

anyway, now I found another link, by using google patents:

http://www.google.com/patents/US5050570

I hope it will be useful.

aiad7

Interesting perhaps, but not really anything like our closed cycle, external combusion, hot air and stirling engines. Iamn S C