It seems to me that I recall, years ago, seeing a clear "test tube" type heat engine, similar to what is commonly now called "thermo-acoustic" but without any steel wool regenerator.
I've been searching videos on YouTube and searching through the forum here, but have not been able to find a video of any such engine.
Anyway, I was curious about the necessity/benefits etc.
Is this plug of steel wool actually necessary? Can such an engine, infact run without the steel wool or is my memory of having seen such an engine in error?
As I recall, the "test tube" was not as long as the engines seen today and was heated out at the end of the glass tube rather than in the middle near the steel wool somewhere.
Is it possible the steel wool is just taking up extra space in the long test tubes reducing the air volume allowing the engine to run?
If anyone knows of such an engine running without the regenerator mesh, has a video, or just knows what I'm talking about and can confirm that this is possible, or that such an engine actually exists, or existed, I'd be grateful.
Thermal Lag without regenerator
Re: Thermal Lag without regenerator
Ah!
I found the patent for the Thermal Lag engine.
Apparently, though fairly recent, the patent has expired due to failure to pay the renewal fee? (I'm guessing)
Anyway, the inventor was a Peter L. Tailer.
Odd that I find almost no mention of this inventer here on the forum, or much of anywhere else in relation to Stirling engines or heat engines in general aside from the patent itself and some passing mentions here and there in university or government papers.
As I seem to have remembered, the original "Thermal Lag" engine did not have any steel wool regenerator. Infact, the only mention of regenerator in the patent is the distinguishing feature that makes it NOT a Stirling engine.
Quite interestingly also, the same individual is also the inventor of another rather obscure type of Stirling engine, which of late has been called a "Two Can" Stirling engine.
The patents include some interesting illustrated variations, background information and descriptive commentary.
Why, I wonder, has this work been so seemingly neglected?
I've been rather skeptical of the "thermo-acoustic" theory of operation that seems to have captured everyone's imagination. How could any kind of coherent acoustic "standing wave" be maintained in a test tube stuffed full of steel wool? That makes no sense to me and seems like a literal impossibility.
Anyway, some links to the two patents:
The "Two Can" engine:
https://patents.google.com/patent/US4676066
Thermal Lag:
https://patents.google.com/patent/US5414997A/en
I was only able to find one mention of the inventor here on the forum, which at the time, received no response, in connection with the "Two Can" engine, which was originally called "plunging cylinder liquid piston engine".
Here:
viewtopic.php?f=1&t=1930
BTW, the Plunging Cylinder engine patent includes mention of a variation where instead of just one pipe, a cluster of pipes is used in the fluid baths for extra surface area which, according to the patent, and the above post, allows this engine to operate at low temperature differentials, which makes it even more interesting.
I found the patent for the Thermal Lag engine.
Apparently, though fairly recent, the patent has expired due to failure to pay the renewal fee? (I'm guessing)
Anyway, the inventor was a Peter L. Tailer.
Odd that I find almost no mention of this inventer here on the forum, or much of anywhere else in relation to Stirling engines or heat engines in general aside from the patent itself and some passing mentions here and there in university or government papers.
As I seem to have remembered, the original "Thermal Lag" engine did not have any steel wool regenerator. Infact, the only mention of regenerator in the patent is the distinguishing feature that makes it NOT a Stirling engine.
Quite interestingly also, the same individual is also the inventor of another rather obscure type of Stirling engine, which of late has been called a "Two Can" Stirling engine.
The patents include some interesting illustrated variations, background information and descriptive commentary.
Why, I wonder, has this work been so seemingly neglected?
I've been rather skeptical of the "thermo-acoustic" theory of operation that seems to have captured everyone's imagination. How could any kind of coherent acoustic "standing wave" be maintained in a test tube stuffed full of steel wool? That makes no sense to me and seems like a literal impossibility.
Anyway, some links to the two patents:
The "Two Can" engine:
https://patents.google.com/patent/US4676066
Thermal Lag:
https://patents.google.com/patent/US5414997A/en
I was only able to find one mention of the inventor here on the forum, which at the time, received no response, in connection with the "Two Can" engine, which was originally called "plunging cylinder liquid piston engine".
Here:
viewtopic.php?f=1&t=1930
BTW, the Plunging Cylinder engine patent includes mention of a variation where instead of just one pipe, a cluster of pipes is used in the fluid baths for extra surface area which, according to the patent, and the above post, allows this engine to operate at low temperature differentials, which makes it even more interesting.
Re: Thermal Lag without regenerator
There actually are thermo-acoustic engines. Forum member Tibsim has done some interesting work there. It’s not the thermal lag principal and yes, using correct terminology would aid understanding for those trying to inventioneer original designs or modify existing designs to fit different materials or skills. Thermal lag engines do not have a regenerator. I reckon the mesh used in some is a heat exchanger absorbing radiant heat to pass convectively to the air. It can be used in the same way at either end of the regenerative zone in a Stirling except of course the cold end does the reverse, absorbing heat convectively and passing it on radiantly. Pretty cool for those seeking an effective exchanger on the cheap and simple.
I didn’t know that Tailor also invented that dipping two-can engine. Thanks for that. Pretty neat how deeper understanding can lead to simpler developments.
Bumpkin
I didn’t know that Tailor also invented that dipping two-can engine. Thanks for that. Pretty neat how deeper understanding can lead to simpler developments.
Bumpkin
Re: Thermal Lag without regenerator
What I'm hoping to find is an actual video of one or these thermal Lag engines running, without any regenerator.
In the patent, there does not seem to be the typical choke point or washer between the hot and cold chambers either, just a straight tube (or tubes).
I've been curious, ever since seeing these type of physics videos demonstrating "adiabatic bounce".
This appears to me to be the same sort of oscillation that takes place in a Stirling engine.
https://youtu.be/vLtU7_AofrM
Just a pipe and a jug, similar to the original Thermal Lag in some ways.
What would happen if some heat were applied to the bottom of the jug, or perhaps somewhere along the length of the attached pipe? Could this adiabatic oscillation be made continuous?
Maybe put a coil around the pipe and use a strong tight fitting magnet to drop down the tube. (Not too tight of course. Free to move but air tight)
IMO, I can only logically deduce that at the furthest extent of travel of the piston in a "thermo-acoustic" engine running "free piston" without a flywheel, the gas, expanded by the momentum of the piston, must be subject to adiabatic cooling. A drop in temperature that results in the gas cooling, if but very briefly,below the outside ambient temperature.
That drop in temperature resulting in the air in the chamber contracting and the piston reversing direction.
If that is the case, then, if anything, heat would be traveling into the gas from the ambient at that point.
This seems to be somewhat supported by the text of the patent describing the theory of operation of the thermal Lag engine.
It describes the gas as being cold during compression.
In the patent, there does not seem to be the typical choke point or washer between the hot and cold chambers either, just a straight tube (or tubes).
I've been curious, ever since seeing these type of physics videos demonstrating "adiabatic bounce".
This appears to me to be the same sort of oscillation that takes place in a Stirling engine.
https://youtu.be/vLtU7_AofrM
Just a pipe and a jug, similar to the original Thermal Lag in some ways.
What would happen if some heat were applied to the bottom of the jug, or perhaps somewhere along the length of the attached pipe? Could this adiabatic oscillation be made continuous?
Maybe put a coil around the pipe and use a strong tight fitting magnet to drop down the tube. (Not too tight of course. Free to move but air tight)
IMO, I can only logically deduce that at the furthest extent of travel of the piston in a "thermo-acoustic" engine running "free piston" without a flywheel, the gas, expanded by the momentum of the piston, must be subject to adiabatic cooling. A drop in temperature that results in the gas cooling, if but very briefly,below the outside ambient temperature.
That drop in temperature resulting in the air in the chamber contracting and the piston reversing direction.
If that is the case, then, if anything, heat would be traveling into the gas from the ambient at that point.
This seems to be somewhat supported by the text of the patent describing the theory of operation of the thermal Lag engine.
It describes the gas as being cold during compression.
Re: Thermal Lag without regenerator
My rationale is;
If the gas inside the engine was only heated and expanded, there would be no oscillation, the gas would simply expand until it reached equilibrium with the outside ambient atmosphere and stop. It would then absolutely require a flywheel to drive the piston back down the cylinder for the compression.
For an oscillation to take place, the gas in the engine would have to go beyond the point of equalization with the outside air. The pressure, and logically I think, also the temperature would have to dip below that of the ambient for the piston to suddenly completely reverse direction and effect a compression "on its own", without any help from stored energy in a flywheel.
Also, the gas, at the extreme extent of the compression, logically, the gas must get hotter than the heat source, the oscillation caused by the piston "bouncing" between these two extremes, otherwise, as with the adiabatic expansion, during such a "free piston" compression, the piston would simply slow down and stop at the point of equilibrium with the heat source, but the momentum of the piston carries it a bit further down the tube, compressing the air and creating the high heat and pressure that results in the piston bouncing back again.
So a Stirling engine, operating in such a way, actually draws heat in at the cold end and releases heat to the hot end.
The heat, released into the hot gas only heats up the gas more, not really having anywhere to go the energy returns to the piston, like dropping a heavy ball on a strong spring, the energy is absorbed, then returned to the ball.
Likely this is why attempts to use a Stirling engine to cool a data center fail. The engines act as insulation, preventing the heat from escaping.
If the gas inside the engine was only heated and expanded, there would be no oscillation, the gas would simply expand until it reached equilibrium with the outside ambient atmosphere and stop. It would then absolutely require a flywheel to drive the piston back down the cylinder for the compression.
For an oscillation to take place, the gas in the engine would have to go beyond the point of equalization with the outside air. The pressure, and logically I think, also the temperature would have to dip below that of the ambient for the piston to suddenly completely reverse direction and effect a compression "on its own", without any help from stored energy in a flywheel.
Also, the gas, at the extreme extent of the compression, logically, the gas must get hotter than the heat source, the oscillation caused by the piston "bouncing" between these two extremes, otherwise, as with the adiabatic expansion, during such a "free piston" compression, the piston would simply slow down and stop at the point of equilibrium with the heat source, but the momentum of the piston carries it a bit further down the tube, compressing the air and creating the high heat and pressure that results in the piston bouncing back again.
So a Stirling engine, operating in such a way, actually draws heat in at the cold end and releases heat to the hot end.
The heat, released into the hot gas only heats up the gas more, not really having anywhere to go the energy returns to the piston, like dropping a heavy ball on a strong spring, the energy is absorbed, then returned to the ball.
Likely this is why attempts to use a Stirling engine to cool a data center fail. The engines act as insulation, preventing the heat from escaping.