This is a question for spark ignition engines, NOT diesels.
For engines running regular gas (87 octane) a 7/1 to 9/1 compression ratio will suffice under most conditions (older engines with deposits in the combustion chamber may require Plus…89-91 octane).
High performance engines in sports cars running on Premium 93 octane generally have 11/1 CR.
Alcohol and Gaseous Fueled engines with octanes in excess of 110 often have 12, 13, or even 14/1 CRs.
If you had a fuel with a high enough octane rating (hydrogen?) is there any upper limit to the compression ratio an engine can run?
20/1? 50/1? 100/1?
Or is there an optimum compression ratio, beyond which, pumping losses detracts from net power and torque output?
I am not an automotive engineer, but since nobody else has addressed this, I’ll give it a SWAG and we can discuss it until someone chimes in to tell me how wrong I am.
I can see from your question’s wording that you are aware of the problem with premature ignition due to compression. If we could ignore that for the moment, I think the next problem with a super high CR would probably stem from failure of rings and valves to seal completly. Any defect would be greatly magnified by increases in CR, to the point where proper metering of fuel and air might be out of the range of practical equipment.
Mechanically, we might have a problem with our connecting rod/crankshaft geometry. With a short stroke, we would have problems with precision getting the piston as close to the head as possible, due to thermal expansion. Going the other way with a long stroke requires more crank offset, which might cause the connecting rod to bum the block in mid-travel. That would require a crankshaft to be much further away from the piston to avoid interferences. This could get impractical fast.
To get back to the fuel… I really don’t know what limitaions there are, but I found a Gasoline FAQ which, while being mostly wayyyy over my head is very informative.
Just my rambling guesses. Thank you for a very stimulating question.
I have at least two references which claim that due to balancing thermal efficiency with mechanical efficiency, that close to 17:1 is the “ideal” compression ratio. Now I will see if I can find said resources…
Lemme address at least the octane rating part of the question. Octane is one of the carbon chains that make up gasoline (along with heptane, etc) Octane happens to be the most stable chain found in pump gas.
So octane rating is a measure of the realive “stability” of the gasoline based on the percentage of octane it contains.
Thus, to talk about “octane” rating of fuels other than gasoline (e.g. hyrdogen) is impossible.
I’m not an engineer either, but yes, I’m sure there are limits. On a production car, the most compression I ever seen coming out of Detroit was 12.5/1 during the muscle car era. The hot rodder‘s I used to know rarely went much past 14/1. Expect more pollutants and shorter life span’s for spark plugs at those higher CR’s too. I’m currently doing search engines, and noticed one study is experimenting with a 25/1 ratio on a converted diesel engine that runs on hydrogen. So my guess to your question, is, you can forget any of those higher CR ratio’s you listed. At some point, you would no longer need that spark ignition system, but would have to have the fuel forced into the pumped air much like diesels because the fuel would be ignited well before the spark ignited it.