Stirlingengineforum.com

There is a lot of information on a very detailed 100W inline alpha stirling engine that was originally intended for solar use. It appears to be a master's thesis or sorts.

http://poisson.me.dal.ca/~dp_08_04/Downloads.html


It somewhat supports Ian's theory on dead air space having little effect on an alpha engine, but it opposes it also. It was destroked to reduce the compression ratio so the engine's required running effort would be minimized.

Maybe I missed something. I read the Final Report but never saw any reference about "100w" output. Also, there is no reference to type of gas used in the test and at what pressure; I will have to assume that this engine was tested with air and at 1 bar. The use of internal fins is a good idea.

It was destroked to reduce the compression ratio so the engine's required running effort would be minimized.

This is the dilemma of Stirling engines. Increase compression also increases heat conductivity of the gas. However, it would've to be a few hundred PSIs for it to be effective.

Correct me if I am wrong. From the report, it mentioned that the gas temp in the hot cylinder is only 250C (< 400 rpm). That's only half of that of the hot cap. Very disappointing.

Of course they didn't complete the development of the engine.....they were on a time schedule per the assignment. The construction techniques and methodology were sound. It is only half developed. ran at 10psi max. The power estimates were about 98w with an efficiency of 42% or so. They cheated by using ice water to cool it. You have to look at these things with better eyes than simply output. It is an excellent primer on tuning in a stirling engine to balance the dead volume with compression ratio to achieve what you want. What do you expect for free plans? All decent designs are patented and protected.


Here is a link if you like hype. http://www.superengine.de/e-lebendiges-totvolumen.html

Hi
Thanks for the link,much info to learn from.
Jan

vile_fly wrote: Here is a link if you like hype. http://www.superengine.de/e-lebendiges-totvolumen.html

That sounds like a thermoacoustic engine. Check this out too.

http://www.io.com/~frg/
Just go through their site. I think their claim is way too optimistic. (http://www.io.com/~frg/tac.htm)

Their youtube video http://www.youtube.com/watch?v=Ro6f_nmJh0E

just read some of their papers, the 98 watt output was supposed to be at 200 rpm and was the schmidt ideal, not actual. the 42 percent efficiency claim was probably derived from the 52 percent claimed carnot ideal, minus the expected friction losses. both must have assumed a higher temperature difference than was actually achieved. i recall seeing it on youtube, and it was nowhere near the desired output. sorry to break the news but it was not a 100 watt engine.

The only way to measure power output is to use a dyno. Everything else is speculation.

onecycleDan1990, I initially suspected that engine would produce 100w with that small heat exchanger surface. If you know the material used to make the hot cap, its surface, its thinness (also the temperature difference between the walls), you can find out maximum amount of heat can be pumped into system per hour. Also, if you know type and pressure of the working gas, you can calculate the maximum amount of heat that can be pumped into the gas per revolution.

Dalhousie university team 4 (designers and builders of engine in question) posted 2 videos on youtube depicting this engine

links to videos:

Running: http://www.youtube.com/watch?v=0wR6AfTO ... er&list=UL
and
details: http://www.youtube.com/watch?v=PLDwYTGZ ... re=related

I think all this tube bending is getting to me. I am beginning to make vast assumptions these days. Might be the zinc coating of the tubing polluting my system. Maybe I will develop a tick, too. Oh well, at least the machinist plans are useful. I definitely would change the hot and cold heads drastically. Tubular heads and heat exchangers are favored, but I may still be crazy from zinc poisoning.
"No sense mentioning these bats.....poor bastard will see them soon enough" --Hunter Thompson