LTD model "Stirling" uses Lenoir Cycle

[Tom Booth]

No rocket can ever be built that could escape the gravitational pull of the earth.

Here is my proof:

The Carnot rocket, most efficient rocket possible!

Resize_20220321_115548_8423.jpg (112.83 KiB) Viewed 3601 times

[Nobody]

Opps

[Goofy]

Hi guys,

I just think this is a VERY interesting note, from The Master himself :

https://www.ohio.edu/mechanical/thermo/ ... erview.pdf

[Tom Booth]

Hi guys,

I just think this is a VERY interesting note, from The Master himself :

https://www.ohio.edu/mechanical/thermo/ ... erview.pdf

I would think that a spacing of 1/80 to 1/50 of an inch, due to boundary layer "drag" or resistance to fluid flow through a narrow passage, in a long reciprocating displacer/cylinder, certainly would almost entirely negate fluid transfer through the "regenerator", in effect, creating a kind of "air spring" at either end of the displacer, rather than actual air displacement between the hot and cold ends.

That spacing would be about the same as, or slightly narrower than what is recommended spacing for the plates in a boundary layer turbine.

[matt brown]

I would think that a spacing of 1/80 to 1/50 of an inch, due to boundary layer "drag" or resistance to fluid flow through a narrow passage, in a long reciprocating displacer/cylinder, certainly would almost entirely negate fluid transfer through the "regenerator", in effect, creating a kind of "air spring" at either end of the displacer, rather than actual air displacement between the hot and cold ends.

I've often wondered about similar drag issues for any regenerator with tiny tubes or closely spaced plates, so I tend to favor the 'steel wool' concept. My main objection to forcing gas thru tiny tubes is akin filling ICE cylinder during intake from relatively small valve in a split second. However, my objection seems bogus as studies claim 85-90% volumetric efficiency with half of the 'missing' 10-15% likely due to cylinder wall temp far exceeding ambient temp.

OK, so there's going to be some drag loss, and there's going to be some thermal shorting, but these aren't as drastic as some inherent thermodynamic issues. Consider an alpha SE with perfect phasing due to a magical discontinuous motion and 2:1 compression ratio. If regen vol was dead vol, then compression vol would experience pressure drop when 'filling' the regen during transfer to expansion cyl. This would be obvious if same SE had 5:1 compression and regulated valves, but this work loss passes by usually unnoticed when unregulated. The Schmidt analysis assumes equal pressure thruout engine at all times, so the regen vol is really not a dead vol, and Urieli pointed out yrs ago that ~70% of the working gas never leaves the regen (in comm'l SE). In effect, the modern regen is a fluctuating 'reservoir', where the paltry real vs predicted eff is due to the 'reservoir effect'.

[Tom Booth]

I would think that a spacing of 1/80 to 1/50 of an inch, due to boundary layer "drag" or resistance to fluid flow through a narrow passage, in a long reciprocating displacer/cylinder, certainly would almost entirely negate fluid transfer through the "regenerator", in effect, creating a kind of "air spring" at either end of the displacer, rather than actual air displacement between the hot and cold ends.

...

OK, so there's going to be some drag loss,....

I wasn't thinking of drag "loss" so much. Robert Stirlings "respirator" afaik consisted of a long close fitting cylinder within a cylinder.

With such a narrow air gap, the air in the gap would behave like a frictionless seal rather than a passage air could actually flow through.

If all that is true, (and I'm not entirely certain what Kelvin was referring to as "respirator" but anyway), Stirling's report is that this very small gap gave the best performance.

That would, I think, be the opposite of a "loss".

I don't think anyone at that time was very cognizant of bounty later adhesion. The tendency for moving air to "stick" to a surface. (I could be wrong about that too).

Anyway, my speculation was, or is, that air transfer from the hot to cold end would constitute actual "loss". So the impassable gap prevented such loss. From his report, Stirlings' engine ran better without the passage, effectively. (If my assumptions are correct).

Anyway, my "air spring" membrane displacer, derived or inspired largely by TK motor's work, would be a development in that direction: eliminate air transfer to the cold side / have the cold side act as a simple "air spring".

In that paper, it appears that Stirling and Thompson are talking about efficiencies approaching "perpetual motion".

The too small to allow air passage, air gap was in some way a gain or advantage rather than a loss.