Stirlingengineforum.com

Thanks for the patient explanations.

However, this is a "typical" displacer out of one of the Stirling LTD engines I've got.
It's weight is not actually measurable on my kitchen scale.
As is, of course, it has no electrical properties, I know of. Some static electricity perhaps.

"As I said I would start with something which works, a disk of Styrofoam so that we know size, material, weight, porosity, air flow, inertia, plus the circuitry and measure power consumption. Then we might not like the results but we would know how much electrical power the displacer needs."

What circuitry? What electrical power?

If I understand the plan, which at this point is very doubtful, you are proposing a basic oscillating circuit attached in some way to a Stirling engine, which circuit includes a loop or coil of wire that acts as an inductor of sorts to repel the displacer.

For that the displacer needs to be made, at least in part, out of some diamagnetic(?) electrically conductive material, such as a loop of wire or aluminum disk. What I'm picturing is probably just some light weight aluminum foil on the surface of the displacer. The weight of which could be compensated for by removing some of the poly-foam. Or use a lighter weight connecting rod. Or, as there should be no flywheel, the weight of the connecting rod has already been eliminated. No need for it! So the new design, in all probability, does not add any weight, overall, to the displacer/connecting rod assembly. Probably, without a connecting rod, the displacer would actually be lighter than a typical displacer with a steel connecting rod.

So the displacer is lighter, has no "circuitry", no power consumption. I'm not sure what you mean by: "we would know how much electrical power the displacer needs".

Earlier you had made the comment:

"Even simpler would be to design an LTD with the displacer driven by an altogether external coaxial coil.
"A well designed coil could also work as a generator."

The problem there, in my mind at least, is; a coil that drives the displacer, if the displacer is so light and takes virtually no power to move in the first place, is hardly going to be able to return any power to the coil, however well it might be designed, the loses would far outweigh the practically non-existent power requirements we would be attempting to reclaim, which is why, I would think a small coil to drive the displacer, a larger coil to feed energy back, not around the displacer which has no driving force, but around the piston which has the full force of expanding air from the heat input to drive a magnet through a coil

I don't see any problem whatsoever as far as

if the power balance is satisfied it runs.

.

That is a given, inherent in the design of Stirling engines generally. Heat drives the piston which supplies far more power than required to move the displacer.

Perhaps, instead of an LTD type Stirling, a Beta type engine would be more suitable for a one coil arrangement, where both the piston and displacer move, at least part of the time, through the same physical space, or same cylinder.

https://youtu.be/MrArmbBIe5Q

Or this way (vertical) without all the linkage.
The coil, in either case, somewhere in the vicinity of the cooling fins.

This looks interesting, though I'm not entirely sure what exactly is being demonstrated.

The spring oscillation does not seem to diminish with time noticeably during this clip. Is there some kind of feedback from the coil, helping to maintain the oscillation.

https://youtu.be/FhnrmACxeHE

What is also rather curious is mention of the 90° phase shift.
Is it just coincidence a Stirling engine likes to run with the same phase shift between piston and displacer as an electric oscillation?

An induced EMF travels at the speed of light. Is that correct? And viewed in one way Heat is also Electromagnetic waves in the infrared band. Two sides of the same coin in some way? I wonder.

An hard-drive read/write arm would make for a well executed, already built, efficient magnetic actuator for a displacer especially a foam, pendulum like, vertical displacer.
Are you able to use arduino, or a similar processor, to drive a R/W arm with something like this https://www.adafruit.com/product/2928
I have a little bit of experience with arduino, it would be ideal for our experiment, it would simultaneously read internal pressure/temperature with an inexpensive sensor like this https://www.adafruit.com/product/4816, with exceptional resolution.
The hard part for a pendulum displacer is to build the airtight vessel with its book like shape.
This experiment would give us EFFd right away with an already excellent actuator, efficiency wise.
The measured delta P would give us the mechanical power output and though a predictable EFFg, the electrical power.
You understand one should still need the oscillator in between to provide for the flywheel effect needed to supply power to the displacer actuator with the right phase.

"Are you able to use arduino,..."

Never heard of arduino before you first made mention of it earlier in this thread and haven't really fooled around with any electronics since high school :- a long long time ago.

I'm always interested in learning something new, but it will take time and I don't really know where to begin.

I sent away for this kit, which just arrived, but have yet to do anything with it.

with what you have got you could easily replicate that wonderful experiment we talked about earlier
https://www.youtube.com/watch?v=dvomod6 ... gWS41&t=1s
it would teach you by far the most important theory about how stirtling engines work, please think about doing this project, not difficult if you already have a working engine
I would be glad to help you, in fact I would try to replicate it too if you want and compare results, much more fun than working in isolation
As I said earlier it could also become an essential part of the EM stirling project, definitely the best way to start this project in practice.
first step I think is to assemble a system to measure temperature, then add pressure. Then place the pressure sensor inside the engine and make a recording of pressure vs time during the cycle.
To complete the youtube experiment one has to acquire the crankshaft phase with an encoder, not difficult either, and acquire both simultaneously.
Just as a curiosity how old are you? Which kind of work/school curriculum do you have? It would help me to find common references while discussing. I live in Venice, Italy, by the way, do you live in the US?

Just as a curiosity how old are you? Which kind of work/school curriculum do you have?

I'll have to use my calculator.

62, retired, "jack of all trades" I guess you could say.

Did some computer programming for a while, which might help, but hardly much call for Perl these days anymore.

arduino is programmed in really basic C, you know much more than needed and can start immediately with a project without any preparatory work

Right. I've been going rather quickly through this set of tutorials:

https://youtube.com/playlist?list=PLWdh ... HrGlUED6Az

Not exactly the same kit, I don't think. Got as far as lesson #4 last night.

I can already see where this could be quite useful applied to direct engine control for a little LTD displacer. The programming involved is all, so far, surprisingly easy and familiar.

But, I have a bit of a learning curve yet to go through, but do feel like I'd like to just skip ahead to something applicable to robotic control of the displacer or something, like you described using a hard drive read/write arm, or maybe just a stepping motor, if there is one in the box.

I thought I'd send for some basic electronics kit to learn something about LC circuits, and just sent for the first thing that came up on Amazon, or Google. Didn't really know what I was getting.

Is there a Linux IDE for this thing? The video only mentions windows and mac. This kit is Arduino compatible, but not actual Arduino it seems. Anyway the only halfway decent laptop I've got is Linux. My old windows laptop is useless.

I really may need to pick up a new laptop for this project before I can really get started.

You like to do things more complicated than they are, download the arduino IDE https://www.arduino.cc/en/software/ for whichever operating system you already use, select arduino mega 2560 as your board and you should be set to go. You will soon need also a spreadsheet app, like libre office.
The main reason to go for arduino is the giant mass of users on the web, the arduino site www.arduino.cc and the arduino forum https://forum.arduino.cc/
my suggestion is that to avoid compatibility issues if you can get a plain vanilla UNO clone on amazon for ex.:
ELEGOO UNO R3 Board ATmega328P ATMEGA16U2 with USB Cable Compatible with Arduino IDE Projects
I only use Arduino Leonardo because is the only one with a precision quartz clock, not necessary in this case
your processor is compatible with all arduino software, is listed among the compatible boards in the IDE (Mega 2560), but you are looking for troubles here and there, use that processor later for already working applications, not for development
You will be able to use all the sensors though
play with a couple of self contained arduino examples and then start your real project
the main part of our project is to "measure" the characteristics of a new displacer
the simplest way to get ready do so try to set up exactly the same experiment you saw on youtube with an already existing LTD
if you don't have one buy it on amazon.
I guarantee you can complete it and that in the process you will learn the most difficult theory involved with the EM project and become familiar with the all practicalities
I have done already very similar projects, I would be very interested to replicate it, many other people on you tube would follow it and I will be able to help with any issue
believe me here, don't start looking everywhere on the web, reproduce first that dotted graph of https://youtu.be/dvomod6SsA0?list=PLyCh ... YhWX2gWS41 , it would give us exactly what we need to know about the EM displacer

try to set up exactly the same experiment you saw on youtube

The PV diagram one, I'm guessing. Or the earlier one with the spring?

Anyway, as I've tried to explain, I don't really have a working laptop at the moment. I've been posting from my phone.

A PV diagram plotted in real time with real data is certainly interesting, but I'm not sure how that relates to or could shed any light on an, as yet, non-existent, "EM displacer", the construction of which has not been worked out,and the details of which have not been set, and the working theory of which is still quite vague, in my mind, anyway.

What do you mean by "EM displacer"?

That video does not seem to describe in very much detail the "exact" setup.

Plotting a PV diagram, in itself, seems rather unremarkable to me.

That engine does not have any sort of variable timing mechanism, such as has been under discussion here. It is also not magnetic.

In other words, we have no working engine using this new oscillator principle to test, and a PV diagram of a regular LTD tells us nothing new.

Still, I'm finding all this rather compelling, though uncertain about where it is headed.

My time is also quite limited.

My "Linux computer", BTW is "Live" on a flash drive, booted up on the junk windows laptop, not an actual computer. It does not retain modifications, such as downloaded programs.

If I'm going to do any kind of serious work, run programs, save files etc. (other than just surfing the web), I really do need a new, or at least functional computer.

If I'm going to do any kind of serious work, run programs, save files etc. (other than just surfing the web), I really do need a new, or at least functional computer.
yes a functional computer helps, especially if you want to program a process computer, better an old reliable desktop than a laptop

My time is also quite limited.

same here, otherwise I would have done it myself, but if you start I promise I would follow

a PV diagram of a regular LTD tells us nothing new.

I have a couple of toy LTDs I could use to get a calibrated PV diagram out, if I had the two sensors setup working that is.
It would then be the starting point to make an EM displacer experiment, which , as explained before is the new part of an original EM stirling engine.
What is an EM displacer experiment: a vessel with an electricity driven displacer inside
Which design I don't know yet, I think we already have 3 quite different proposals, they would all work but with different efficiency.
The PV diagram we would get from the EM displacer, the engine power information, would then tell us how to design the more conventional generator side of the engine.
To me even the power balance of the LTD would be a very rewarding result. I bet one would learn a lot of stuff from it that we were not even thinking about, it's always that way with experiments.

omblauman wrote: ↑Mon May 03, 2021 5:57 am ...an electricity driven displacer inside...

My thinking on this is there is some potential for improved performance by increasing "dwell"" time.

That is, the displacer moves up quickly, then waits. Then moves down quickly, then waits again.

Or, possibly a quick up and down to release heat quickly, then wait. A regenerative displacer, (basically a displacer made of steel wool) could have time to absorb a lot of heat, then a quick rise and fall would release the heat traveling in both up and down directions, then rest at the bottom (or hot side, wherever it may be) to absorb more heat.

"Dwell" is the wait time.

My kit comes with a servo which it seems could easily be programed to do the job.

https://youtu.be/kdcOkDRBiU0

A problem I anticipate with a oscillator is, it is sinusoidal. which is what I'm trying to get away from.

The theory in this video (or "key feature" of the engine) has the right idea, but the actual cam design shown doesn't seem to do anything but follow a sinusoidal path. The implementation does not appear to match the theory about increasing dwell time. Not by much anyway

https://youtu.be/8QE-CmKxz40

I'm looking more to provide a dwell of some 3/4's or even 7/8th's or 9/10th's of the entire cycle.

My "cam" if I were to use that method, would be almost entirely flat, except for one bump. Or flat on one side with a flat plateau on the other, and very sharp inclines.

My theory of Stirling engine thermodynamics, does not include cooling, or use of a "sink", so I think just a bump, or quick rise and fall of the regenerative displacer (or maybe just call it a "heat distributing matrix".

Carnot believed that the heat entering a heat engine had to be removed, like the water flowing into a turbine must also flow out the other side. I think that theory is wrong.

The only thing that should be flowing out "the other side" of a heat engine is mechanical or electrical power output.

I don't really comprehend how some people do not see how an equal amount of heat going in, and also being removed to the "sink" along with additional energy production (power out to the load), is not a violation of the conservation of energy.

If I'm right, then a typical LTD Stirling engine uses about half of it's available energy resources just, uselessly, pushing heat to the cold side of the engine to go entirely to waste.

If that energy could instead, all be used to deliver heat, all at one time, then twice the amount of power would drive the piston/load and no energy would need to be wasted pushing hot air to the sink to all go to waste.

Probably enough power could be delivered that heat might only need to be delivered (the displacer moved up and down) every other revolution.

My theory is this:

Heat (in a Stirling engine displacer chamber) is the kinetic energy of fast moving air molecules.

A freely moving piston, acts (in relation to the fast moving air molecules) similarly to a golf simulator screen in relation to a fast moving golf ball. It absorbs the impact.

https://youtu.be/A5b5bApAnIY

Like the golf ball that falls to the floor, the hot air molecules that hit the piston and drive it outward from the cylinder, loose their kinetic energy which has been transfered to the piston.

These hot, fast moving air molecules are, theoretically, moving at near the speed of light, so fast, that as the piston travels out, nearly all of them within the displacer chamber have a chance to strike the piston and loose kinetic energy, which kinetic energy is actually heat.

In other words, as the molecules strike the piston they "drop down" cold, like a golf ball hitting a simulation screen.

So, the heat, is, in effect, GONE. It does not need to be removed or transfered to the sink.

So, by that deduction, all the energy used to move air to the cold side of the displacer chamber and back again is wasted energy that could instead be used to deliver more heat into the gas for more rapid expansion.

But that is impossible if the displacer is attached to a crankshaft. Attached to a crank it can only follow a sinusoidal motion moving air from the hot to the cold side.

The whole design of a Stirling engine is based on Carnot's old fallacy that heat is a fluid.

Decouple the displacer from the crank and it is possible to deliver heat to the engine more quickly and effectively.

In theory at least.

Programming a servo to control displacer movement should make it possible to test out the theory.

A displacer controlled by a magnet attached to the piston allows slightly more "dwell" time, but I think it could be taken further.