Modified "Hot" Beta engine

[stephenz]

compression ratio is a geometric figure. I mentioned this a couple of pages ago. It has nothing to do with gas whatsoever.
Don't confuse ratio (i.e. volumetric compression ratio) and pressure ratio.

This is simply not true for an ECE hot air engine and is fundamentally the single most misunderstood aspect of them.

And you're obviously not going to back that up with anything? ../..

They're two different things...
So much hate for Allan Organ. A shame.

what-now-04.jpg

Literally first page after the preface of his book.

- (Volumetric) Compression Ratio is geometric as it's the ratio of Max and Min volumes.
- Compression Ratio is affected by temperature and obviously by the pressurization of the engine.

by temperature, being a first order improvement it's obvious.
by pressurization of the engine, not as obvious as second order improvement, but in part because thermal properties of the fluid improve with temperature meaning you gain more pressure from heat supplier to the heater if the gas is pressurized.

[VincentG]

You got me there, I view compression ratio in an ECE as "effective compression ratio" and not "volumetric compression ratio".

[Tom Booth]

compression ratio is a geometric figure. I mentioned this a couple of pages ago. It has nothing to do with gas whatsoever.
...

LOL, you've got to be kidding me, you're going to double down on this?

With compression ratio, what is being compressed?

You can't compress a solid cylinder of aluminium or whatever the displacer is made of.

If the displacer is not regenerative, if it is a solid substance it can't be included as part of the gas to be compressed. Use some common sense!

[stephenz]

LOL, you've got to be kidding me, you're going to double down on this?

With compression ratio, what is being compressed?

You can't compress a solid cylinder of aluminium or whatever the displacer is made of.

If the displacer is not regenerative, if it is a solid substance it can't be included as part of the gas to be compressed. Use some common sense!

I think I've done my part. The result is not surprising but I expected nothing less from you, Tom.

Hint: I didn't come with that term. Much smarter people came up with that term decades ago.

[stephenz]

You got me there, I view compression ratio in an ECE as "effective compression ratio" and not "volumetric compression ratio".

No worries!

[Tom Booth]

LOL, you've got to be kidding me, you're going to double down on this?

With compression ratio, what is being compressed?

You can't compress a solid cylinder of aluminium or whatever the displacer is made of.

If the displacer is not regenerative, if it is a solid substance it can't be included as part of the gas to be compressed. Use some common sense!

I think I've done my part. The result is not surprising but I expected nothing less from you, Tom.

Hint: I didn't come with that term. Much smarter people came up with that term decades ago.

What do you think the V stands for?

Volume?

Volume of what?

Not the solid parts of the engine certainly. With compression ratio your supposed to be measuring the initial and final volume of the gas, not any solid parts of the engine. If the displacer is solid and does not have gas within it in association with the working fluid it should not be included in the compression ratio.

[stephenz]

Swept volume of piston (or displacer) is given by the formula I wrote down by hand on the drawing/anotation:

V = surface of piston * stroke

Stroke = 2 x R
Surface of piston = A

V = 2 x R x A




For a Gamma/Beta, the volume in the displacer cylinder is constant and is equal to 2RA. Always.
the volume in the piston cylinder is not constant and varies with the crank angle and varies from 0 to 2RA in an harmonic manner described precisely by the formula I wrote in my drawing.

In an Alpha, you don't have a displacer but have 2 pistons. Their cylinder volume varies with crank angle from 0 to 2RA, in the same harmonic manner, although off by a 90 degree phase angle in this example. These 2 harmonic responses result in a lower minimum engine volume (compared to gamma/delta) which is the main reason why the volumetric compression ratio is higher.

[Tom Booth]

...
For a Gamma/Beta, the volume in the displacer cylinder is constant and is equal to 2RA. Always.
...

I agree, typically this is true. But the topic here is "Modified "Hot" Beta engine"

What I've noticed is that if the throw and timing of the piston and displacer are adjusted in such a way that they both sandwich together at TDC as I previously illustrated then that displacer volume disappears. Tha displacer has effectively become part of the piston.

You can see that in the second frame of the illustration:

Resize_20231221_124135_5991.jpg (138.94 KiB) Viewed 1850 times

[VincentG]

For a Gamma/Beta, the volume in the displacer cylinder is constant and is equal to 2RA. Always.

This is not always true. Specific to Betas, "negative dead space" refers to the volume in which the power piston infringes upon the space that the displacer acts on.

https://youtu.be/WYY-Pn2-uzg?si=NmKDt9fz9WSgxIPV

[Tom Booth]

As I've also previously shown, the same effect could be produced in an LTD type engine:

Resize_20231224_124400_0612.jpg (120.75 KiB) Viewed 1849 times

[VincentG]

Yes infact even my long stroke ltd piston extends into the displacer chamber over 1/4".

[stephenz]

I agree, typically this is true. But the topic here is "Modified "Hot" Beta engine"

What I've noticed is that if the throw and timing of the piston and displacer are adjusted in such a way that they both sandwich together at TDC as I previously illustrated then that displacer volume disappears. Tha displacer has effectively become part of the piston.

You can see that in the second frame of the illustration:


Resize_20231221_124135_5991.jpg

We've already cleared that up. I replied to a general statement you made.
Now that everybody is clear on the math and why Alpha's offer greater volumetric compression ratio let me give you my opinion about your modified beta idea.

- you are basically more or less using the beta for its geometry of 2 coaxial pistons and its natural annular piping.
- usually the ports connecting the compression space to the regenerator are located roughly where at the piston TDC and the displacer BDC. they do that for the very purpose of allowing gas to circulate seamlessly and not getting "stuck" between the piston and displacer.

in effect, by moving these ports up, these ports become blocked by the displacer as soon as it covers them.
effectively you separated your engine volume in 2:
- one volume between the piston and displacer
- one volume above the displacer (i.e. heater volume)

Assuming this is what you were envisioning I do see merit in this concept. In fact I have a non-working prototype of this same concept using an opposed-piston-alpha configuration. I am using electronic sensor (hall effect) to measure the position of the pistons to open and close valves to achieve just that.
Amusingly, I had this idea when I was first CAD'ing my first engine which was a Beta.

I will take a picture of my setup shortly.

Again, it does not work. Granted I have never tried to run it as a heat engine. I always test my engines in refrigerator first to see if there is any merit to a concept/prototype. And I could never measure any relevant temperature drop. Oh and as actuator I am using a linear oscillator and custom made flexures. That part works really well, and the main reason why I never dismantled the experiment.


edit: I forgot it was partially dismanted (removed the modified glass syringes)
attached 2 pics + 1 video.
https://file.io/EctSdCVnLcFK

excuse the video, it's able to capture the true oscillations as the frequency is close to that of the camera fps.



edit: why it doesn't work, it's hard to know for sure but I'm pretty sure it has to do with compression ratio being a bit too high. My setup was not equipped with pressure sensor so I don't know why it gets but the oscillator slows down significantly. Being fully electronics I was able to play with timing/phase with no good results. Separating the engine in 2 distinct volumes has some undesired consequences from a pressure delta (pressure difference on both sides of the pistons) and how not only it gets increasingly harder to push as pressure increases, but it's also getting increasingly harder to pull on the other side.

[Tom Booth]

....
Assuming this is what you were envisioning I do see merit in this concept. In fact I have a non-working prototype of this same concept ...
....

You're hilarious.

First you are all in a rage about my "mistake" and demand I make a retraction for something I never said, now that you have egg on your face and realize you were wrong, why, lo and behold, you've already invented, built and tested the same concept. LOL.

[stephenz]

Are you really going to go there? Both you and Vincent asked for the math to prove my point. I did, didn't I? How was that wrong? Because I got hung up on a false statement of yours which I proved wrong with teenage math? Seriously, was that this difficult to do or understand? Come on. How does it hurt to correct you on that one?

As for the "experiment", I had solenoids lying around and really wanted to build a linear oscillator. I tested it, it was fun but it didn't work. It's ok to have weird ideas, we live in a world where it's not easy to come up with anything original. Most of the time, it's a stupid idea, best case scenario it's reinventing the wheel.

I don't necessarily think we thought of the same concept, at least your description of how it "would work" isn't how I was describing mine.

[Tom Booth]

Are you really going to go there? Both you and Vincent asked for the math to prove my point. I did, didn't I? How was that wrong? ...

Because your "math" does not take into account the volume overlap potential in the Beta that VincentG pointed out, as I pointed out, as can be seen also in Robert Stirlings original patent. So your statement "Always" regarding the Beta compression ratio is wrong, which should have been obvious to anyone who actually read this thread from the begining. So you were wrong, are wrong, you know your wrong but continue to double and triple down about how you were really right.

Please start your own thread and stop trying to Garner attention by piggybacking on and derailing this one.

Thank you.

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