V twin compressor conversion

[matt brown]

Hall video is very interesting, but his engine running so well without flywheel indicates piston & crank mass are effective 'flywheel' and engine has very low power per stroke. I imagine all the pickups on engine are to gather data points for PV plot, but kinda strange we don't have temp and wattage values. Basic scheme exposes an unusual thing about adiabatic processes: adiabatic compression & expansion are only equal when work is done on and by the gas, but a 'workless' adiabatic expansion is slightly different (way beyond the context here). Hall video has xlnt PV plot, but also exposes how limited PV plots can be. However, we know that after adiabatic expansion, ambient pressure would tend to retrace adiabatic expansion curve with adiabatic compression until pressure equalizes on both sides of piston. The only way to get a different 'trace' is via heat flow. So, I'm guessing he's approximating a 3 legged cycle with isothermal compression, isochoric heating, and adiabatic expansion. This is similar the 3 legged Lenoir with isothermal compression in lieu of isobaric compression.

I'll further guess that Hall engine has temp above ambient at end of expansion which means very light gas mass enclosed. I think it's kinda sneaky to suggest (by omission) that temp at end of expansion is sub ambient like pressure. So, my bottom line is Hall has a fancy flame licker...

Most model SE run a very slight Carnot cycle, just barely wider than a thin adiabatic PV plot. This is the only way to have a point plot for T high and T low while being able to allow for various values within the same mech, and even then, mech requires careful construction (narrow performance envelope). Interestingly, while most ICE have a narrow mechanical performance envelope (fuel, ignition, idle, whatever) their thermal envelope is monsterous...Otto, Diesel, Brayton, and Atkinson are not heat 'sensitive' cycles.

[Tom Booth]

Hall video is very interesting, but his engine running so well without flywheel indicates piston & crank mass are effective 'flywheel' and engine has very low power per stroke. I imagine all the pickups on engine are to gather data points for PV plot, but kinda strange we don't have temp and wattage values. Basic scheme exposes an unusual thing about adiabatic processes: adiabatic compression & expansion are only equal when work is done on and by the gas, but a 'workless' adiabatic expansion is slightly different (way beyond the context here). Hall video has xlnt PV plot, but also exposes how limited PV plots can be. However, we know that after adiabatic expansion, ambient pressure would tend to retrace adiabatic expansion curve with adiabatic compression until pressure equalizes on both sides of piston. The only way to get a different 'trace' is via heat flow. So, I'm guessing he's approximating a 3 legged cycle with isothermal compression, isochoric heating, and adiabatic expansion. This is similar the 3 legged Lenoir with isothermal compression in lieu of isobaric compression.

I'll further guess that Hall engine has temp above ambient at end of expansion which means very light gas mass enclosed. I think it's kinda sneaky to suggest (by omission) that temp at end of expansion is sub ambient like pressure. So, my bottom line is Hall has a fancy flame licker...

Most model SE run a very slight Carnot cycle, just barely wider than a thin adiabatic PV plot. This is the only way to have a point plot for T high and T low while being able to allow for various values within the same mech, and even then, mech requires careful construction (narrow performance envelope). Interestingly, while most ICE have a narrow mechanical performance envelope (fuel, ignition, idle, whatever) their thermal envelope is monsterous...Otto, Diesel, Brayton, and Atkinson are not heat 'sensitive' cycles.

Your post, being generally dismissive and full of falsehoods and unwarranted assumptions I'm going to mostly just ignore for now. I just got up to load up the coal stove then going back to bed. I'll just say that your first objection: "his engine running so well without flywheel indicates piston & crank mass are effective 'flywheel' " This has already been addressed over and over. First a piston cannot act as a flywheel, it has no angular rotation and there are plenty of examples of similar engines running with no crankshaft whatsoever and no flywheel. I can just post my playlist of some that can be found on YouTube:

https://youtube.com/playlist?list=PLpx2 ... qzm1QCGCEW


But I primarily dropped in, as I thought of a simplified way to show how a Stirling engine behaves as a heat pump, showing just two basic steps or stages.

Sorry about the crude drawing on a brown grocery bag but it was all I had on hand to sketch on at the moment

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From known and accepted principles compressed gas gets hot and expanded gas gets cold.

The power piston alternately compresses and expands the gas in the engine.

The displacer, traditionally 90° offset can be seen to drive the hot compressed gas down to the hot side of the engine at TDC and drive the cold expanded gas up to the cold side at BDC.

That is the observable reality. Completely irrefutable IMO as anyone can make this simple direct observation for themselves.

[Tom Booth]

When I find some time, I'll respond to your comments on the Andrew Hall demonstration on another thread:

viewtopic.php?f=1&t=5497


The purpose of THIS thread is primarily just to document the compressor conversion build and I think the Hall video is important and should have a thread of its own.

[Tom Booth]

One relevant take away from Hall's experiment, as well as any other demonstration of a Stirling engine operating with no need for a flywheel, I think is; (though Hall may disagree and I make no claim that my conclusions represent his in any way);

IF, and that can be taken as a big IF, the working fluid cools and contracts "on its own" so to speak, without the need for a flywheel to push the piston in for the compression stroke, that is, if the gas gets cold as a result of work output, then the "cold side" SINK is, perhaps redundant.

From my observations over the years, I believe it very well may be true. A "displacer" only acts as a kind of valve to LET HEAT IN.

As the engine is designed to convert that heat into mechanical "WORK" output, there is no requirement for any "valve" to let the heat back out.

Anyway, that assumption; that a COLD "sink" is unnecessary has gone into the design of this Ringbom-like compressor conversion. In particular in regard to the "displacer" mechanism, which, instead of the unnecessary cold displacer chamber, instead has an Air Spring, Ideally, filled with some inert, non-heat conducting gas and insulated, so that rather than "rejecting" heat to a "sink", heat is retained for additional power output

[Tom Booth]

For all who have been waiting in anxious anticipation, the 1/4 inch steel discs (for the compressor/engine cylinder head replacements) have arrived.

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