What is the difference between thermal lag and lamina flow engines

Discussion on Stirling or "hot air" engines (all types)
Crazyguy
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Re: What is the difference between thermal lag and lamina flow engines

Post by Crazyguy » Mon Feb 22, 2016 6:59 am

Test#2.
My heat tube is 3/4" diameter and about 8" long. Half filled with pot scrubber. Larger choke hole no better.
Tried tea light candle n/g, then propane torch, red hot, n/g.
Wondering what I should be looking for if I'm going in the right direction or just spinning my wheels.

mhe
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Re: What is the difference between thermal lag and lamina flow engines

Post by mhe » Mon Feb 22, 2016 7:49 am

Not being critical but I don't think I've ever seen a TA LF or Tl engine that bends the air. Stretch and compress but never bend. Kind of gets you thinking about the lamina part of lamina flow.

Crazyguy
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Re: What is the difference between thermal lag and lamina flow engines

Post by Crazyguy » Mon Feb 22, 2016 9:03 am

Hi mhe
This is supposed to be a TLE not a LFE. Thats why I asked the original question of " what's the differrence".
Well ive seen an thermoacoustic engine with two diaphrams and they were at 90 degrees to the pipe so i figured this would be okay also. One diaphragm had a weight and one a magnet. Also some kind of rubber cone diaphragm inside.

Like the below video by tibsim

Crazyguy
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Re: What is the difference between thermal lag and lamina flow engines

Post by Crazyguy » Wed Feb 24, 2016 5:18 am

Larger choke no good. Trying longer heat tube.

mastrovetraio
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Re: What is the difference between thermal lag and lamina flow engines

Post by mastrovetraio » Wed Feb 24, 2016 7:44 am

The horn as an "impedance coupler" https://en.m.wikipedia.org/wiki/Horn_loudspeaker

Crazyguy
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Re: What is the difference between thermal lag and lamina flow engines

Post by Crazyguy » Wed Feb 24, 2016 8:22 am

I guess I'll try the impedance matching if I can detect whether I'm anywhere in the ballpark to getting a sustained oscillation. The diaphram is showing two states, when cool it bounces when I tap it. When hot it's puffed out and doesn't bounce very much.

mastrovetraio
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Re: What is the difference between thermal lag and lamina flow engines

Post by mastrovetraio » Wed Feb 24, 2016 10:36 am

is a tube of Blade Attila. The difference between his experiment and your is that water is much more dense that air is. That's the reason why I think that's necessary an impedance coupler and (maybe) a longer tube, a "trombone" ..... If this stuff is "thermo-acoustic", well, we have to respect the acoustic's laws. I apologize that at the age of 64 I'm still working, so I've no time to experiment...

Ian S C
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Re: What is the difference between thermal lag and lamina flow engines

Post by Ian S C » Mon Feb 29, 2016 6:33 pm

Test #1 ditto, only thing noted so far, the diaphragm was drawn in as the motor was heated!!
Ian S C

Crazyguy
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Re: What is the difference between thermal lag and lamina flow engines

Post by Crazyguy » Mon Feb 29, 2016 7:34 pm

No. The membrane was pushed out.

derwood
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Re: What is the difference between thermal lag and lamina flow engines

Post by derwood » Mon Feb 29, 2016 10:05 pm

You need to have a bleeder valve to equalize the pressure after the engine heats up. If you use a piston it leaks just enough to equalize. When the engine is heated and not running the pressure needs to be the same as the atmospheric pressure. if the pressure inside the engine is greater it will not run. Good luck!

Ian S C
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Re: What is the difference between thermal lag and lamina flow engines

Post by Ian S C » Tue Mar 01, 2016 2:28 am

Tested again, and found a leak in the diaphragm. Made another diaphragm, and it inflated on heating, but not oscillation, I think the problem lies in the steel wool, I'll try some adjustments there.
Ian S C

Crazyguy
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Re: What is the difference between thermal lag and lamina flow engines

Post by Crazyguy » Tue Mar 01, 2016 4:51 am

@derwood
That's good information. Thank you. I have never seen that tip in any of the video's I've watched. Thank goodness for this forum.

Tom Booth
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Re: What is the difference between thermal lag and lamina flow engines

Post by Tom Booth » Wed Jun 08, 2016 2:28 pm

In all engines I've previously seen of this or similar type, the choke is located very close to the heat source.. My impression being that this is necessary in order to force an air stream into the regenerator for heat exchange. If this is the case then the hole in the bottom of the tuna can would only direct an air stream down into the relatively cold pipe far from the heat source/regenerator.

cbstirling2
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Re: What is the difference between thermal lag and lamina flow engines

Post by cbstirling2 » Mon Dec 19, 2016 10:33 pm

I have an old 0.35 McCoy airplane engine, I was thinking of converting to a thermal lag engine. It still has compression, so I assume the piston would do the trick. Approx ~16mm bore and stroke there abouts.

What would it take to convert that?
CBStirling2


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