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

[TinselKoala]

Sigh.

Note the oscillation of the Ringbom Stirling's free displacer, which is demonstrated without the engine running, and listen to the explanation of how the connecting tube diameter affected the stable oscillation frequency of the engine. Watch it operate with and without a load.
http://www.youtube.com/watch?v=Qdq7XAyhk7A

Now read about thermoacoustic engines and resonance.
http://en.wikipedia.org/wiki/Thermoacoustic_heat_engine
http://www.aster-thermoacoustics.com/wp/wp-content/uploads/2012/08/Presentation_Multi-stage-traveling-wave-feedback.pdf
http://www.sciencedirect.com/science/article/pii/S001122750200019X
http://proceedings.aip.org/resource/2/apcpcs/823/1/1109_1?isAuthorized=no

http://www.youtube.com/watch?v=M9aUiojteys

Yes, mechanical resonance is an important feature of these engines; yes, the linear inertia of the moving parts is used just as the rotational inertia of a flywheel is used, to store energy which is interchanged with stored energy in compression/rarefaction of the working fluid.  Just exactly as hanging a weight from a coiled spring exchanges stored energy between GPE and the stretch of the spring: bounce the weight and you will see the system oscillate at its natural resonant frequency. And if a tiny bit of energy is added at just the right time, the amplitude... hence the stored energy in the system... will increase.... but the system will still "want" to oscillate at the same natural resonant frequency. Unless the masses change or the "spring constant" of the compressible working fluid changes.

[bugler]

I would like to know, does this idea have any merit ?

Peter Lindeman has written an article about this.


He mentioned two companies working on this idea.
I guess we will never see it (like with the rest of free energy devices).

[Tom Booth]

Sigh.

Harray! my hero has arrived! yay!

Note the oscillation of the Ringbom Stirling's free displacer, which is demonstrated without the engine running, and listen to the explanation of how the connecting tube diameter affected the stable oscillation frequency of the engine. Watch it operate with and without a load.
http://www.youtube.com/watch?v=Qdq7XAyhk7A

Now read about thermoacoustic engines and resonance.
http://en.wikipedia.org/wiki/Thermoacoustic_heat_engine
http://www.aster-thermoacoustics.com/wp/wp-content/uploads/2012/08/Presentation_Multi-stage-traveling-wave-feedback.pdf
http://www.sciencedirect.com/science/article/pii/S001122750200019X
http://proceedings.aip.org/resource/2/apcpcs/823/1/1109_1?isAuthorized=no

http://www.youtube.com/watch?v=M9aUiojteys

Yes, mechanical resonance is an important feature of these engines; yes, the linear inertia of the moving parts is used just as the rotational inertia of a flywheel is used, to store energy which is interchanged with stored energy in compression/rarefaction of the working fluid.  Just exactly as hanging a weight from a coiled spring exchanges stored energy between GPE and the stretch of the spring: bounce the weight and you will see the system oscillate at its natural resonant frequency. And if a tiny bit of energy is added at just the right time, the amplitude... hence the stored energy in the system... will increase.... but the system will still "want" to oscillate at the same natural resonant frequency. Unless the masses change or the "spring constant" of the compressible working fluid changes.

Very interesting.

I can see from the above material (most of which I've seen before) several things, and there may be a few additional things that are of some importance which you haven't brought out.

First of all, there is a vast difference between a "free displacer" and a "free piston". Entirely different functions.

Naturally a "free displacer" suspended in a magnetic field or "levitated" on a magnetic spring will bob up and down when you tap on it. The displacer does not touch the walls of the displacer cylinder. It is not a power piston so there is no friction to restrict its movement.

"Mechanical resonance" in a Stirling Engine at say 100 RPM with a piston and crankshaft is vastly different than acoustic resonance in a REAL acoustic engine at 150 Hz with no moving parts.

The last video of an engine that the guy calls a Thermo-acoustic engine is not a thermo-acoustic engine. It is just a big Lamina Flow Stirling, regardless of what the guy thinks it is or calls it. This should be plain to see by comparing the documents you presented relating to actual thermo-acoustic engines with any kind of Stirling Engine.

As far as the connecting tube. It connects the displacer chamber to the power cylinder. He put in a bigger tube which let the air flow more freely, as a result the engine ran faster. That was his own explanation. Just because he used the term "resonant frequency" does not mean the thing is being driven by sound waves or that it is "thermo-acoustic".

As far as it running with and without a load, it runs much faster without a load and barely chugs along with a load. Naturally.

If it was a variable load with a dial you could no doubt make it run at a range of speeds. If the connecting tube had anything to do with the "frequency" at which the engine ran then you would need some kind of adjustable tube to change the "frequency" there.

You then generalize and say "Yes, mechanical resonance is an important feature of these engines;..." without differentiating between the various types of engines presented as if they were all the same, which they most certainly are not. Personally I would not generally consider sound waves as "mechanical", at least not like piston and crankshaft mechanical.

A piston driven by pressure differentials in an engine is not "exactly the same" as a weight suspended by a spring. A piston in a cylinder of an engine does not swing freely back and forth like a pendulum, nor does it bounce up and down on its own accord like a weight on a spring. It is DRIVEN linearly down a cylinder by an expansive force like a cannon ball shot from a cannon in one direction.

A weight on a spring has gravity balanced by the spring tension. A pendulum swings back and forth due to gravity pulling it downward. A piston is driven by the explosive force of an expanding gas on one side. The only thing on the other side, in the engine we have been talking about is atmospheric pressure.

This seems to me something more along the lines of a man pushing a heavy cart up a hill.

The expanding gas pushes the piston "up hill" against atmospheric pressure, which we might equate with gravity. Heat is the energy exerted by the man pushing the cart up the hill.

At some point the man gets exhausted and collapses and the cart goes rolling back down the hill. It will tend to pick up momentum so that it will roll down the hill and want to keep going beyond the resting point where it started at the bottom of the hill.

The man, or his "energy" has in effect vanished from the equation. Just as the heat that pushed the piston down the cylinder against atmospheric pressure suddenly "disappears" The heat/energy having been exhausted. With the man gone the cart rolls back down the hill by gravity, the thing the man was working against. Without the heat expanding the gas in the cylinder, atmospheric pressure pushes the piston back.

If you have more men, then another man can take the first mans place and push the cart up the hill again until the second man's energy gets exhausted and he collapses, then the cart rolls back down the hill again. Continue this enough times and you have what looks like an "oscillation" or "frequency" but it would be a mistake to believe or suppose that the cart was therefore oscillating up and down the hill on its own accord, just as it is a mistake to believe that a piston in a Stirling Engine is somehow moving up and down or back and forth by its own mass or momentum.

Anyway, welcome.

Perhaps you can say how any of the material you presented relates to Tesla's theory, or does it ?

With an engine running on "supplied" heat. Heat that you have to make. You have to in effect pay every man you hire to push your cart up the hill.

With ambient heat you have an inexhaustible army of men. When one gets exhausted there is always another to take his place.

If the "sink" is the top of the hill, notice that the cart never gets there. but if you attached a generator to the carts wheel you could still get power as the cart was pushed up the hill as well as on its return trip back down the hill.

[Tom Booth]

Perhaps the observed action of Mr mowerofdoom's engine running with no flyweel might more clearly and accurately be explained by this illustration:

Take our cannon and cannonball.

Imagine that a cannon with a long barrel is tilted up at an angle, having been given too feeble a charge of gunpowder so that when fired, the cannonball is only projected a short distance but never actually leaves the barrel. The ball then rolls back down the barrel reaching the bottom with a "clunk".

If we could quickly replace the first charge with another, just the same as the first the process could be repeated. But if it were possible to devise some mechanism to quickly replace the charges one after the other and time them so that their detonation would coincide with the balls return to the bottom of the tube going off at the precise moment that the ball arrives at the bottom of the tube we might set up an "oscillation" of sorts.

It seems to me however that we would be loosing some of the available energy.

Remember the piston "banging into the orifice" and the jittery motion of the engine towards the source of heat or towards the "charge" similar to the cannonball clunking against the bottom of the barrel. The cannon might also, if it were not so heavy likewise make some backward motion due to the momentum of the cannonball upon its return down the barrel, the stored momentum being transferred to the cannon. If the cannonball were slowed down on its return trip by causing it to do some work for us then it would land much more gently and the power derived could be utilized.

We might imagine the cannonball as a magnet and the barrel of the cannon wrapped with wires in the manner of a linear generator. Then we could increase the charge slightly and get energy in both directions of travel.

Or suppose we could lengthen the barrel and tilt the cannon at a greater angle. We could then increase the charge even more and get more energy back on both legs of the trip. This might be equated with pressurizing the cold box and lowering the temperature if you follow the reasoning.

But the important thing to consider in this context I think is that the energy supplied by the charge never actually leaves the barrel, it is always trapped behind the cannonball. That is, if we assume that the canon and cannonball are machined with such precision that the cannonball makes a perfect air tight seal within the cylinder but is yet free to move.

We are then burdened with no other labor than that of occasionally removing the ash from the bottom of the barrel. In the case of HEAT however, when used as a charge, we are dealing with a form of pure energy which leaves no ash.

If our charges of "gunpowder" are delivered automatically and the charges themselves are inexhaustible in number then it would seem we have set up something of a "perpetual motion machine" that could run almost indefinitely with no further attention given to it.

The set up would however have to be carefully balanced. The various factors involved would have to be regulated with some precision. The length of the barrel, the angle at which the cannon is set, the volume of gunpowder measured out for each charge, the exact trimming of the firing of the charge, the magnetic force of the cannon ball and the number of windings of wire on the barrel for our generator and perhaps most importantly the electrical LOAD on the power output.

If any of these factors go out of balance with one another the system would fail or might even lead to some minor disaster.

To strong a charge and the cannonball is actually discharged from the barrel, too weak and it does not move at all, if the system is set up for maximum power output the charge might be great and the ball projected with great energy only to be slowed down due to the energy extracted from it. If the load were removed, again , the cannonball might leave the barrel. And of course the timming of the charges etc.

All these factors have their corollaries in our (or Tesal's) theoretical ambient heat engine.

[Tom Booth]

I might add, that if you read Tesla's article previously posted or linked to it is apparent that he did work with some diligence towards building such an engine but I think his efforts were perhaps too ambitious from the start.

That is, it seems he was working on something to power cities.

Many of his inventions were a result of work on this engine, his infamous "earthquake machine", his turbine, "valvular conduit" and so forth were were actually spin offs, or should I say ELEMENTS of this ambient heat engine.

I really don't have a clear picture of just how he intended to put all these elements together into a working engine so at this point I'm not looking to reproduce whatever it was Tesla had in mind but rather go back to the basic principle he outlined and perhaps devise a small "proof of concept" prototype based on that.

If his idea was actually correct and workable than it should be scalable. In this case my idea is to scale it down to as small and simple a construction as possible.

In Teslas description of his concept he says merely:

Conceive, for the sake of illustration, [a cylindrical] enclosure T, as illustrated in diagram b, such that energy could not be transferred across it except through a channel or path O, and that, by some means or other, in this enclosure a medium were maintained which would have little energy, and that on the outer side of the same there would be the ordinary ambient medium with much energy.  Under these assumptions the energy would flow through the path O, as indicated by the arrow, and might then be converted on its passage into some other form of energy.

This is his theory reduced to the bare essentials without much of any clue provided in regard to how this is to be accomplished other than "by some means or other" which is not particularly helpful.

It is evident however from his description that he was talking about heat and in the above statement he doubtless had some kind of heat engine in mind.

There are many, many, many different possible configurations when it comes to a Heat engine. The "Lamina Flow" Stirling is, it seems to me, the simplest possible mechanical heat engine there is, especially if we can reduce the number of moving parts by eliminating the flywheel.

I would venture to say that if Tesla's idea cannot be applied using the simplest possible configuration, a larger more complicated machine would have no more success. At any rate, it would be but a relatively small investment in time and effort to test the theory by actual experiment using such a small engine of simple construction.