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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What is the difference between thermal lag and lamina flow engines

Post by Crazyguy » Tue Feb 16, 2016 3:11 pm

I see all kinds of confusing information on the internet. Is there a difference betwern thermal lag and lamina flow engines? What are the key components of each?

Ian S C
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Location: New Zealand

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

Post by Ian S C » Wed Feb 17, 2016 12:56 am

Nothing, they are also known as Thermo Acoustic Pulse Engines, and if they don't go they probably get called a few other things as they get thrown at the dog. Quite interesting motors, and some have been built with quite a bit of power.
Ian S C

Crazyguy
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Joined: Sun Jun 07, 2015 10:39 am
Location: USA

Thermal lag hot air engine project

Post by Crazyguy » Wed Feb 17, 2016 10:03 am

@ ian sc
Thanks.
After reading, watching, and scratching my head I came up with this design. Any suggestions would be much appreciated.

Image
Last edited by Crazyguy on Fri Feb 19, 2016 8:49 am, edited 1 time in total.

Ian S C
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Location: New Zealand

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

Post by Ian S C » Thu Feb 18, 2016 3:19 am

DON'T use copper, get a bit of stainless tube. The copper conducts heat too well, and within a few minutes the whole motor will be hot. Also heated copper will flake, and before long it will bulge, and bend at the point of heating. Other than that it looks good, might even have a go myself. I think that I would cut a thread on the cold end, and in the cold end cap, then you can get the steel wool in, and if need be, adjust the amount and density.
A prototype could be made with steel tube, and you may not even need the water cooling.
Ian S C

Crazyguy
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Location: USA

Re:thermal lag hot air engines

Post by Crazyguy » Thu Feb 18, 2016 4:43 am

@ian sc
Okay, i was looking at what was readily available and easy to fabricate and i forgot about copper spreading the heat. I just wonder how i would seal the ends , maybe compression fittings? I cant weld stainless steel. I wonder if high temp silicone sealer like the type used for internal combustion engine gaskets would work?
Last edited by Crazyguy on Fri Feb 19, 2016 8:50 am, edited 1 time in total.

Ian S C
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Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

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

Post by Ian S C » Fri Feb 19, 2016 2:13 am

You can braze stainless steel quite easily, or at the LH end (your sketch), a tight plug, in fact that may do for both ends.
When it comes to welding SS I'v got a mate who runs a SS fabricating business and I get him to TIG weld my displacers, and hot caps, he doesn't like me when I bring along anything much less than .010" thick.
Ian S C

Crazyguy
Posts: 61
Joined: Sun Jun 07, 2015 10:39 am
Location: USA

Thermal lag hot air engine project

Post by Crazyguy » Fri Feb 19, 2016 4:08 am

I'll build it and report back on the results. It may be awhile since I have a lot of household chores that have been assigned to me.:-(
The only hot air engine I've been succesful with, has been the pringles can, water piston, metronome engine.
Last edited by Crazyguy on Fri Feb 19, 2016 8:51 am, edited 1 time in total.

Crazyguy
Posts: 61
Joined: Sun Jun 07, 2015 10:39 am
Location: USA

Thermal lag hot air engine project

Post by Crazyguy » Fri Feb 19, 2016 6:38 am

Wish me luck. Going to build it. Here's basically what it might look like. Components are not to scale in relation to each other.
POC.

Image

Crazyguy
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Re: Thermal lag hot air engine project

Post by Crazyguy » Fri Feb 19, 2016 8:53 am

:big smile:

Ian S C
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Location: New Zealand

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

Post by Ian S C » Sat Feb 20, 2016 1:55 am

I'm starting mine with 12" of 3/4" chrome plated steel tube, it has a wall thickness of .025", we'll see how it evolves.
Ian S C

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

Post by Crazyguy » Sat Feb 20, 2016 3:09 pm

Cool

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

Post by Ian S C » Sun Feb 21, 2016 1:09 am

Just looking at your last sketch, the container with the diaphragm on top only needs to be deep enough for the diaphragm not to touch the bottom. you may find that the stroke is fairly short.
Ian S C

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

Post by Crazyguy » Sun Feb 21, 2016 1:23 pm

Watched lots of video's on youtube. I'm going to try it as a free piston version first. Got the heat tube from a Solar garden LED light, stake. 3/4" copper cap on one end, 3/4" copper elbow other side with a small tuna can RTVed on top. Tuna can has a 1/4" hole in bottom leading to elbow as a choke. Rubber diaphram (balloon) over that with a 3/4"x3/4" neodymium magnet stuck to the top as a resonating weight. RTV is drying now. Will install stainless steel scrubby inside pipe about half way tomorrow and light the fire. Cross your phalanges.j :big smile:
Image
Im anticipating having to modify the choke hole, both in size and streamlining the flow. Also the tuna can may need to be shortened.
We'll see.
Last edited by Crazyguy on Mon Feb 22, 2016 6:54 am, edited 1 time in total.

Ian S C
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Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

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

Post by Ian S C » Mon Feb 22, 2016 1:23 am

I also am going the free piston way, don't know if it will be a piston, or diaphragm, but it will be inverted from your sketch. I'll do as I did with my free piston GAMA Stirling Engine, and fit a magnet on the piston, and under that, another magnet, and put like poles toward each other so the repel, this way is far better than a spring, and a heavy piston uses gravity to restrict the height it goes.
Ian S C

Crazyguy
Posts: 61
Joined: Sun Jun 07, 2015 10:39 am
Location: USA

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

Post by Crazyguy » Mon Feb 22, 2016 4:44 am

Test #1 = fail
No indication of running or what needs to be done next. All guess work. Working blind. :sad:
Making choke bigger.

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