Isolated cold hole

[Tom Booth]

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And the hot side is boiling water at 87F?

Sounds very inaccurate.

Your a confused moron. This has already been posted, probably a dozen times, both photos and two complete videos and you still don't have a clue what you are even looking at.

That 87°F reading is the side of the engine in the area of the regenerator. The water, which was boiled and poured into a cup was not "boiling".

The temperature reading of the previously boiled water was about 170°F at that point in the experiment.

If you were not completely brain dead however, you should already know all this.

Compress_20241117_083458_8173.jpg (23.15 KiB) Viewed 591 times

[Fool]

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So you are saying the area of the regenerator is only 87F?

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[Tom Booth]

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So you are saying the area of the regenerator is only 87F?

That is the reading on the outside of the displacer chamber in the area exposed (that had been insulated by an aerogel blanket).

Logically, I think, assuming a gradient the bottom of the regenerator inside the chamber and lower down, still under the insulation in more direct contact with the hot working fluid on the hot side would likely have been hotter, but direct readings of the regenerator inside the engine were not taken.

[Tom Booth]

The reading at the crosshairs is 86.5°F just below that "Max" is 87°F a difference of just 1/2 a degree

Presumably the trend continued on down.

On the other hand moving up there is a rather dramatic 24° drop in temperature to an apparent below ambient temperature of 62°F

Screenshot_20241110-201054.jpg (180.84 KiB) Viewed 581 times

Of course, that is only a "snapshot" from a three hour run.

As explained and shown in the 2nd video, the hot water was refreshed with boiling water every 30 minutes.

[matt brown]

Matt, I think your depiction of the Stirling cycle is not accurate. At least not by traditional design standards.

You don't appear to include, or account for, in any way, the standard 90° advance which IMO changes the dynamics considerably.

Using distinct events exposes the most ideal PVT values per event. Typical 90deg phasing results in out-of-phase events that tax both output and efficiency (hence dwell buzz).

Also, you don't appear to make adjustments for the temperature and pressure drop that results, or "theoretically" should result from work output during expansion (power stroke).

Take a close look at this graphic...

A 300-450k.png (25.45 KiB) Viewed 575 times

You must of missed this cartoon (lol) where I divide 600cc DP volume into six 100cc volumes and sequence volumes thru the expansion process. This indicates that during expansion, DP gas expands during heating (note density m/100cc) but then compresses thru regen prior PP. Assuming ideal everything, the gas during regen will compress proportional to the temperature differential which here is 450k in and 300k out (Ian-Hall values). Thus, in this example, the 450k DP gas is compressed 1/3 by the time it leaves regen into 300k PP.

The conventional view is that this heat of regen during expansion plus the heat of regen after expansion (DP hot space to DP cold space) will equal the heat of regen within DP when all gas moves from DP cold space to DP hot space just prior input (ideally). This view is based on molar mass ("m") being equal on both sides of the cycle and leads to conventional conclusion of constant volume regen.

However, this graphic reveals that the gas expands after reaching the PP and it doesn't take a rocket scientist to grasp that DP and PP pressure will tend to equalize REGARDLESS OF TEMPERATURE. Now, assuming PP is constant 300k, when PP gas expands then it needs heat input to maintain 300k. My original idea was ambient backflow where the 300k "sink" becomes the 300k "source" and that a self induced cold hole of some type might be possible (nothing major, but enough to wake Carnot).

Returning to regen issues, I later concluded that "constant volume" regen buzz is total BS and that ALL regen is constant pressure. Once I assumed isobaric regen, I quickly concluded work loss during regen due to gas compression between DP and PP. Now I was forced to conclude that conventional regen was not merely a transfer of internal energy between Thigh and Tlow, but also would include the work of isobaric compression which could only be supplied by further DP input.

Returning to potential ambient input, after I concluded isobaric regen, I concluded that the work of isobaric compression during regen could pass thru regen and nix or supplement ambient input. Any drop in PP pressure during expansion could be restored via heat 'sneaking' thru regen (since DP and PP pressures are equal, both have the same expansion rate).

So overall, for these reasons as well as actual observations and readings of running engines, I'm not so sure about "massive work loss when DP gas passes thru regen to PP" though admittedly, not too long ago I was thinking along the same lines.

Without valid regen this is a non issue, but without regen any "Stirling" cycle is worthless.

Note in graphic that Vincent's "zero point" is where PP density after expansion equals DP density prior expansion...

[matt brown]

The end goal of a power piston driven off the hot end is to have it be larger than the displacer, or at least the same size, within a 300k-600k cycle. I have little doubt that my new engine will run with a power piston of 50cc or greater and a displacer of 150cc, within a 275k-373k cycle, so the enormous ratios of an LTD are irrelevant IMO.

I agree, the larger the working chamber, the larger the output. As DP/PP increases, more heat is required and wasted per cycle. And if the cycle includes regen, then a massive DP/PP ratio has a massive regen heat load.

This type of thinking quickly favors a larger expansion ratio which nixes regen advantage. The gimmick here is scheming different mech than typical SE which allows T and V values to coincide.

[VincentG]

Matt, I think your depiction of the Stirling cycle is not accurate. At least not by traditional design standards.

You don't appear to include, or account for, in any way, the standard 90° advance which IMO changes the dynamics considerably.

Also, you don't appear to make adjustments for the temperature and pressure drop that results, or "theoretically" should result from work output during expansion (power stroke).

These two things combined tend to minimize or eliminate the transfer of heat through the regenerator.

It should be clear by now that the standard 90 degree advance is merely a consequence of crank driven mechanisms and not a design standard that should be met.

There are not "adjustments" made because using PV=nRT already factors in the maximum work output the system can deliver given the starting and ending states. Any less "load" and you've simply wasted energy, and any more load will not allow the end state to be reached. Thus, the ideal starting external "load"(measured as the sum of buffer pressure and the mass of the actual load) is always equal to the internal starting pressure.

I'd like to see someone draw a gas flow diagram through a single regenerator for a Gamma or Beta engine that makes any sense.

[Tom Booth]

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So overall, for these reasons as well as actual observations and readings of running engines, I'm not so sure about "massive work loss when DP gas passes thru regen to PP" though admittedly, not too long ago I was thinking along the same lines.

Without valid regen this is a non issue, but without regen any "Stirling" cycle is worthless.
....

Not sure why you are making this comment.

I assume by "regen" you're referring to regenerator.

So, are you saying my regenerator is "invalid" so my test results can be ignored or don't count so that makes your "cartoon" figuring more real or more valid than actual physical test results? Or what's your point exactly.

[Tom Booth]

Matt, I think your depiction of the Stirling cycle is not accurate. At least not by traditional design standards.

You don't appear to include, or account for, in any way, the standard 90° advance which IMO changes the dynamics considerably.

Also, you don't appear to make adjustments for the temperature and pressure drop that results, or "theoretically" should result from work output during expansion (power stroke).

These two things combined tend to minimize or eliminate the transfer of heat through the regenerator.

It should be clear by now that the standard 90 degree advance is merely a consequence of crank driven mechanisms and not a design standard that should be met.

...

No, it isn't "clear" IMO.

What is clear, from my observations is that a Stirling engine is a kind of mass spring system or driven damped oscillator..

Such systems "resonate" when the "driver" is advanced by 90°, exactly like the traditional 90° advance for a Stirling engine.

This applies to such a wide diversity of different systems and different fields it could hardly be a coincidence.

Also my own testing of small model engines shows dramatic increases in torque when the engine is "tuned" to the "in resonance" precise 90° advance.

Previously, for example, this engine, "out of the box" could not light the LED and would stall with the slightest touch on the flywheel and would not operate at all with liquid lubricant as it could not handle the high pressure that developed.

https://youtu.be/D6F_cDjrEEU

With a slight timing adjustment however, everything changed.

Compress_20241118_080735_5619.jpg (35.34 KiB) Viewed 528 times

https://youtu.be/D6F_cDjrEEU

I tried every other timing setting possible without improvement.

When I accidently hit upon a timing setting that ran, and ran remarkably well, it just "by coincidence" was at the 90° "in resonance" offset for a driven oscillator, which just "by coincidence" happens to be the traditional Stirling offset.

Too many "coincidences" IMO.

[VincentG]

This video shows how timing is best at 0 degrees. The only reason for advanced timing on a piston engine is to allow air temperature to rise. So 0 degrees is way too late, and 90 degrees is way too early. Hence why most IC engines and my own tests have favored from 10-30 degrees BTDC, with distinct events!



https://youtu.be/WCKt405t9V8?si=JypH17JCZuirkSQd

[Tom Booth]

This video shows how timing is best at 0 degrees. The only reason for advanced timing on a piston engine is to allow air temperature to rise. So 0 degrees is way too late, and 90 degrees is way too early. Hence why most IC engines and my own tests have favored from 10-30 degrees BTDC, with distinct events!

https://youtu.be/WCKt405t9V8?si=JypH17JCZuirkSQd

Apples to oranges (IMO)

Two different theories of operation.

You are basing conclusions on the idea that the operation of a Stirling engine is based on, or has something to do with wave propagation. A vibrating string type system. i..e "thermoacoustic" I suppose.

I'm basing my conclusions on the idea that a Stirling engine is mass-sprong type driven oscillator.

The piston (mass) bouncing between air springs driven by the periodic introduction of heat to expand the gas (the driver).

https://youtu.be/jewSVEBkI_s

[Tom Booth]

Personally I see no merit in the thermoacoustic model as acoustical wave phenomenon does not occur in a cylinder containing a moving mass.

The practical results of going with the 90° advance of a driven oscillator system is a previously pretty useless toy engine that could not overcome any resistance or drive a load at all when carefully "tuned" with exactly 90° displacer advance.was transformed into a little power house from which I could charge my cell phone from a candle flame.

https://youtu.be/546LT0AnL40

https://youtu.be/X825itoQn_I

[Fool]

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The best that can be done is to measure real working engines with an indicator diagram.

Of course yes, a dynamometer, many many thermometers, pressure sensors, tachometer, computers, etc...

Yes they tend to average things out, but better than guessing. Way better.

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[Tom Booth]

After about 7:30 in this video

https://youtu.be/LzF2Ov8w0to

[Fool]

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Tom, I get little to nothing out of your videos. It appears as if other people have the same issues, as you have very few followers. I read the comments on the first of the last two you linked.

@sierraecho884 and you had one of your usual spats with people. Neither of you had the correct version of what was happening. I will admit the point you were trying to make was valid, but the why was lost.

Engines have a power to rpm curve, easy to measure with a simple and cheap home dynamometer. In fact, the electric motor/generator on that model can be used if you know what you are measuring.

Yes voltage reflects RPM. Voltage times current equals power/Watts. = Dynamometer.

Anyway, the power verses rpm curve for an engine will have a peak. That peak will be the maximum power an engine will put out at a specific rpm. Matching that power to a generator is the job of gear ratio.

Making the output increase in rpms to the generator is a higher gear ratio. (Depends on how you look at it.) Just like putting a car in high gear, allowing the engine to slow down, at the same speed.

Generators produce more power at higher rpm s. True because, both more Volts and more Amps, hence more Watts, at higher rpms.

So why not just boost the gear ratio way high? As @sierraecho884, basically said, torque. At some point, boosting the rpms out of the engine and into the generator, also increasing the torque necessary from the engine, over torques the engine slowing it down. Basically asking for more power than the engine can deliver.

So getting the maximum electrical power out of a engine requires knowing how much it can produce and at what rpm. Hence my harping on getting a dynamometer.

If a generator is too big, the engine will be lugged down by friction and windage (Efficiency decreased dramatically.). If too small, not enough power can be generated to lug it down to the power peak rpms. Fortunately, generators that are a bit too big, have friction and windage that is not much higher than a perfect sized generator. Since they are electric, the power out they provided can be adjusted by load. Keep adding LEDs until at peak Watts, to get a measurement of peak power rpms. Dyno realized.

Your candle experiment, as impressive as it is, showed that, as designed the engine came with an inefficient gear ratio. You proved that. Well done.

As far as getting more followers, improve the professionalism of your videos. People get motion sick from watching a lot of camera waving, waving things in front of the camera, zooming in and out, and worse combined with poor focus. Use a tripod. Discus with someone what the real reason is for the phenomenon you are presenting. Don't argue with your commenters, a real turn off. Let them argue with themselves, you will build supporters. Ask them questions. Example: Why does it power more LEDs after the gear change?

People lose interest if they don't know what is going on, talk them through the presentation. Like Alpha Phoenix, or Veritasium. Or others.

Your presentation needs sharpening. Your phenomenon is excellent. Thanks.

Charging a cellphone from a candle with a tiny model Stirling after gear ratio change, excellent. I bought one of those engines for my nephew thinking it was just a useless demonstrator. They are cheap enough, I may buy one for myself now, just to have a power outage fueled back up that runs off emergency candle lighting. Excellent. Thanks.

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