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Here's an easy to view this open cycle scheme. The typical closed cycle gamma is always envisioned as starting with

(1) 1 bar buffer pressure in cold space
(2) displacer at hot plate
(3) power piston at TDC (after compression)

vs my open cycle scheme starting with

(1) 1 bar buffer pressure in hot space
(2) displacer at cold plate
(3) power piston at TDC (after exhaust)

matt brown wrote: ↑Mon May 29, 2023 1:09 pm Here's an easy to view this open cycle scheme. The typical closed cycle gamma is always envisioned as starting with

(1) 1 bar buffer pressure in cold space
(2) displacer at hot plate
(3) power piston at TDC (after compression)

vs my open cycle scheme starting with

(1) 1 bar buffer pressure in hot space
(2) displacer at cold plate
(3) power piston at TDC (after exhaust)

The sweet thing is that this open gamma cycle is not limited to LTD and largely removed from regen issues. Meanwhile, there's various ways to game the inherent 'dwell' of an ideal event cycle.

I think the real potential in a well engineered open cycle is achieving higher than ambient air density on the hot cycle, and lower than ambient air density on the cold cycle.

Consider the piston port at bdc equalizing pressure to atm with the displacer on the cold plate as the start of the cold cycle. Now consider equalizing pressure to atm with the piston at tdc and the displacer on the hot plate as the start of the hot cycle.

Now add the benefits of port tuning for fixed rpm power generation.

VincentG wrote: ↑Mon May 29, 2023 1:51 pm I think the real potential in a well engineered open cycle is achieving higher than ambient air density on the hot cycle, and lower than ambient air density on the cold cycle.

Consider the piston port at bdc equalizing pressure to atm with the displacer on the cold plate as the start of the cold cycle. Now consider equalizing pressure to atm with the piston at tdc and the displacer on the hot plate as the start of the hot cycle.

Now add the benefits of port tuning for fixed rpm power generation.

Bingo, you got it !!! Now image if your said 1 atm volumes were greater than 1 atm by connecting this open cycle to a reservoir with greater pressure. It reduces to a game of ratios vs finite values. When I was playing with volumes early in this thread, I never noticed this, but reviewing Kiochi's monster enticed me to tinker with some numbers. The good news: I have the basic scheme, but the bad news: it's constrained and I'm clueless as to the relationship between swept volume ratios vs thermal ratios. For now, all I'm doing is tracking mass thru different volume ratios and thermal ratios while hoping a simple pattern will emerge.

What's odd about this open cycle scheme is how close it is to your early LTD mods. I don't think port tuning will work due to slow rpm. I'm more concerned with gamma expansion requiring isothermal input from ambient where dT is nil vs dT of source input for alpha. Gadz, no one ever mentions that gamma expansion requires input !!! So, gamma expansion is more challenging (for efficiency) and regen issues remain unchanged. However, there's something in this open cycle scheme that should make all the treehuggers (and some others) happy. Can you spot it ???

VincentG wrote: ↑Mon May 29, 2023 1:51 pm I think the real potential in a well engineered open cycle is achieving higher than ambient air density on the hot cycle, and lower than ambient air density on the cold cycle.

Yikes, I read this too fast earlier. Yes, this is true for alphas where the hot gas is expanding like ICE. However, gammas & betas expand cold gas when the cold gas (prior expansion) has the greatest density during cycle. Nevertheless, you hit on why I'm an alpha guy (usually).

Yes, this is true for alphas where the hot gas is expanding like ICE. However, gammas & betas expand cold gas when the cold gas (prior expansion) has the greatest density during cycle. 

Sure but are we really dealing with a "gamma" anymore here?

However, there's something in this open cycle scheme that should make all the treehuggers (and some others) happy. Can you spot it ???

Have something to do with methane?

The good news: I have the basic scheme, but the bad news: it's constrained and I'm clueless as to the relationship between swept volume ratios vs thermal ratios.

I think this hybrid open cycle may allow much higher than standard compression ratios. What I envision(assuming full electronic control like modern ICE), is an engine that can go from power production to heat pump, and anywhere in between. A complete home energy solution.

The main advantage to a high compression ratio with isothermal cycles is gaming regen 'load'. Otherwise they tend to be less efficient mechanically since more power comes from the start of expansion. Indeed, once open cycle, gamma buzz sounds goofy.

Nope, not methane, but kinda close.

This popped up in my youtube feed, so thought I'd share it...

https://www.youtube.com/watch?v=o6i9Ckm2Z5E

This is a simplified copy of the original 'computer' by Charles Babbage. If unfamiliar, Lord Byron's only (legitimate) daughter Ada met Babbage at a party and they became close friends. Ada was very well schooled for a girl in those days (heck, even by today's standards) and persuaded him to continue with this daunting project. Meanwhile, she took notes which is how we know about this computer because he only finished part of it due to time, money and limited machining abilities in the early 1800s. BTW any computer nerds that happen by might recognize ADA which was named after Ada who wrote the first computer algorithm (yep, her original manuscript survives).

I encountered Tim in the early 2000's when I was acquiring some Meccano to use for sequencing ECE stuff. Back then, computer software was limited and pricey, so I figured I'd do it the old fashioned way. For Meccano fans, I ended up with 3 double "L" sets of brass plus similar sets of all the other mech stuff (racks, quadrants, couplers, etc). i wanted to be able to do a few models simultaneously, for comparison. At the time, Tim was working on expanding a smaller version, so I gave him all my spare gears & sprockets, since I only needed a small horde vs he needed a monster horde. While watching this video, few will probably wonder the most important issue...no, it's not how he designed this, but how did he solve the lash problem among various gear trains. When I asked, he said that's why he needs such a large stock, since he picks and chooses gears to game slight inaccuracies. Oddly, I never used my Meccano and resolved my timing issue on paper via another lucky altered state.

Here's a nice video of the full blown Babbage engine...

https://www.youtube.com/watch?v=BlbQsKpq3Ak

Pretty incredible stuff. The world may owe more to altered states/dreams than we would like to admit.

Have you been able to make a pv plot for your 720 degree cycle? I think it might be time to add a 3rd and 4th dimension to visualize whats really happening.

Here's my weird 720 deg 'open' cycle gamma scheme with 2 displacers alternately feeding 1 piston. Consider up towards TDC and down towards BDC with layout similar Solar Engines 1 model (vs LTD):

2 displacers - identical, vertical with conrod to bottom, hot space at top, cold space at bottom. Motion only as indicated with each displacer having 2 valves at bottom (1) an ambient intake snifter valve (2) a regulated one-way outlet valve with conduit connecting piston cylinder head

1 single-acting piston in power cylinder, vertical with conrod to bottom, regulated ambient exhaust valve in cylinder head

With careful design of volumes and thermal ratio, this could be a closed cycle by removing the 3 'ambient' valves while replacing each one-way displacer 'outlet' valve with a two-way valve and modified regulation sequence. Either way, this achieves a clean cycle while affording a prolonged heating period. The only bugger is dwell scheme for displacers, but at least this nixes piston dwell issues.

I hope you can decipher scheme from this timeline. Kinda like a musical stanza where this 4 bar cycle looks more like a fubar cycle - lol. I'm starting to see more options...

(1) if closed cycle with single two-way valve per each displacer, then Dis A could connect piston cylinder thruout 0-360 deg, and Dis B could connect piston cylinder thruout 360-720 deg

(2) since expansion in piston cylinder requires 'some' heating, so conduits connecting displacers to piston cylinder could be 'slightly' heated

(3) careful choice of volumes vs thermal ratio could avoid 'compression' of gas from piston cylinder to displacers (thus nixing heat sink/s)

(4) displacer conduits could likely connect single multi-port rotary valve at cylinder head as pseudo manifold where valve rotates at 1/2 engine speed (similar ICE) with 2x 180 deg durations

Anyone who studies this will wonder how any clean cycle could be so easy vs typical out-of-phase claptrap. Well, sketch the sequences and stare at ONE sequence sketch long enough and you'll find the answer...then an altered state might kick in, 'cause the answer is staring back at you. I merely borrowed 2 tricks from my old alpha widget to...dream this up, no pixie dust req'd. Most won't get it (for various reasons) but I suspect Vincent will see how this 'magic' works...