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VincentG wrote: ↑Tue Jun 04, 2024 9:48 am If you slow the second video down you will see that the "power stroke" of the actuator is actually just barely after "tdc". So not 90 degrees out of phase as the analog is suggesting.

VincentG wrote: ↑Tue Jun 04, 2024 11:39 am Show us a combustion piston engine whos timing is at 90 degrees before TDC.

A Stirling engine is not a 'combustion piston engine

That has been another long held assumption about Stirling engines.

I remember somewhere, sometimes, when I first started learning about Stirling engines, knowing how critical timing is on IC engines generally, Not sure if it was here or another forum, but I said something about changing timing and got a rather strident reprimand., to the effect of hundreds of years of testing has shown that a 90° phase angle gives the best performance.

To some degree this inspired awe and wonder, how well worked out all these "rules" seemed to be. but on another level I remained a bit skeptical. If true, there had to be a reason.

Once I started working on my own model Stirling engines, one of the first "experiments" in putting the kits together was to try and find the best timing position.

I found it made very little if any difference if the timing was off of exactly 90° by a pretty wide margin. 90° just seemed a midway point between extremes where the engine would no longer run.

I theorized that the heat input and "output" was just too spread out and mixed due to the sinusoidal displacer action. All timing positions were just generally equally bad as there simply was no identifiable heat input "event" to actually use as a basis for "timing". Rather heat input was spread out over nearly the entire 360°'s of rotation.

I struggled to find some good reason why this might actually be beneficial in some way.

The theoretically "ideal" isothermal heat input is spread out over 180°'s. Even in an IC engine it takes time for the fuel to fully burn so heat generation does continue after ignition through the entire expansion stroke, to one degree or another. In that case though, you do end up with rather low efficiency and a lot of "waste heat" out the exhaust.

It seemed at a minimum, restricting heat input to the 180° expansion stroke by introducing a definite "dwell" so there would be no heat input during "compression" at all, should produce some beneficial effect

Restricting heat input a bit further to the begining of the expansion should give the engine some time to fully utilized the heat as the heat must take some time to propagate through the gas.

Further restricting heat input to a more definite "ignition-like" event could possibly prove beneficial in allowing the engine to actually cool down in preparation for "contraction" reducing "waste heat".

Jack wrote: ↑Tue Jun 04, 2024 8:33 pm Looking at these engines theoretically I wouldn't expect it to be the best angle either.
Did you test if there's any difference in the ideal angle with and without a regenerator?

VincentG wrote: ↑Wed Jun 05, 2024 3:53 am

A Stirling engine is not a 'combustion piston engine

A Stirling engine can only dream of being like an IC engine.

The spring and the standard Stirling engine are both eventless wishy-washy cycles, where "timing" is a poor choice of words.

You said it yourself.

That has been another long held assumption about Stirling engines.
...
I remember somewhere, sometimes, when I first started learning about Stirling engines, knowing how critical timing is on IC engines generally, Not sure if it was here or another forum, but I said something about changing timing and got a rather strident reprimand., to the effect of hundreds of years of testing has shown that a 90° phase angle gives the best performance.

To some degree this inspired awe and wonder, how well worked out all these "rules" seemed to be. but on another level I remained a bit skeptical. If true, there had to be a reason.

Once I started working on my own model Stirling engines, one of the first "experiments" in putting the kits together was to try and find the best timing position.

I found it made very little if any difference if the timing was off of exactly 90° by a pretty wide margin. 90° just seemed a midway point between extremes where the engine would no longer run.

I theorized that ...