Tesla's Ambient Heat Engine Theory - Right or Wrong ?

[Tom Booth]

If you studied electronics, then you know that electricity is also, in fact a kind of Kinetic energy as well and carries a kind of momentum of its own. An oscillating circuit for example utilizes this electrical "momentum" of electricity. The electrons bouncing back and forth through the circuit like a rubber ball into a capacitor or some such and out again from one end of the circuit to the other.

So, theoretically then, the load on the generator attached to the engine might, once established, act something like a siphon drawing off energy or in other words, continuing the flow or train of energy transformation.

Just maybe.

[Tom Booth]

Of course, there is the possibility that this type of engine is in some way "thermoacoustic". In that case, the regenerator or "stack" as it is called in a thermoacoustic engine may require a temperature gradient to function.

Personally I don't think so. For one, I read a report on a Stirling Engine Forum. A poster there, experimenting with a large lamina flow Stirling stated:

The heat tube volume to piston stoke volume ratio has to be very close to get it to show signs of life. You guys that build the test tube models and can't get them to run, just remember that a couple of mm of heat tube length means everything. The tube diameter does not seem to be as important. Although mine is running this ratio still needs to be fine tuned so that the power of the expansion stroke is matched to the power of the contraction stroke. I think that when this balance of power is achieved the engine will accelerate more and the fly wheel weight will not be as important. I have found that the closer I get to this balance of power the fly wheel weight can be lowered to achieve more rpm's. As far as steel wool goes, I stopped using it. The volume of the steel wool is almost impossible to calculate and does not seem to be of any benefit other than a volume fine tuning tool.

http://stirlingengineforum.com/viewtopic.php?f=1&t=1052

The fact that the volume ratio has to be "fine tuned" seems to indicate that there may be some "acoustic" or "standing wave" type phenomenon involved (like a pipe organ) but apparently this does not involve the regenerator if it can actually be eliminated.

But if there is a requirement for some temperature gradient in the heat delivery end of the tube perhaps some modification as illustrated could provide this.

Basically the entire engine might be enclosed in a "cold box" with just a portion of the tube exposed to ambient by way of an air duct or passage.

This however would probably let too much heat into the refrigerated space. At any rate, it is something to play around with.

[Tom Booth]

Personally, I think that the way heat is delivered to this kind of engine (Lamina Flow Stirling) involves the sudden release of heat (from the regenerator or stack or from the heat cylinder walls) due to the way the piston "bounces" back when the expanding air gives up its kinetic energy to the piston and contracts "pulling" the piston with it. As the piston returns, near the end of the return stroke, I imagine that there is a rather sudden increase in pressure, the gas having become compacted. The effect being like the piston suddenly hitting a "wall" of dense air. This would then cause a concussion wave in the heating chamber which would tend to cause a sudden release of heat from the regenerator or "stack" or from the heat cylinder walls as the air in the heating chamber moves or "vibrates" and so a very rapid expansion of the air results delivering another blow of kinetic energy to the piston.

More than likely though IMO this "concussion wave"  would be a singular phenomenon, (once per cycle) not necessarily a continuous "tone" or "sound wave" as in an acoustic engine.

"Timing" may be important. That is, it may be that these concussion waves need to be delivered with a certain rhythm to be maximally effective.

Is this "acoustic" ? Well sort of. A concussion wave in the air is a sound wave I suppose, technically, maybe.

Any engine of any kind has a certain "rhythm", frequency, or simply RPM. Call it what you will.

[Tom Booth]

Here is another idea, probably not applicable to this type of Stirling Engine but it might be useful for helping to maximize the efficiency of any Stirling Engine where a regenerator is used. I recently posted this to the Stirling Engine Forum so I wont repeat it all here.

Elastic (Nitinol?) Regenerator:

http://stirlingengineforum.com/viewtopic.php?f=1&t=1450

If a Stirling Type engine can be made to act in the way Tesla envisioned perhaps this would help. The idea is to take advantage of the efficiency improvement possible with a regenerator while compensating for the losses that are introduced by its use.

[Tom Booth]

Another way to keep the hot (ambient) air out while allowing pressure equalization might be to use a trap, like under a sink.