Philippe Schutt wrote:In general, the octane number increases when:
- the length of the carbon chains decreases
- the number of secondary chains increases (for the same number of atoms of C)
- the number of cyclic structures (cycloalkanes and aromatics) increases
so if the reactor is cracking as many people think, it's normal for it to ignite less.
Completely agree I will simply say that for your third dash (increase in aromatics) this poses a problem: they resist the detonation so much that they are sources of unburnt enough. Oil tankers have a habit of adding aromatics which promotes the creation of unburnt ... (ppm HC)
Your remarks also mean that the simpler a compound, the better its octane number ... see the index of GNV octane 130 or methanol (which I don't know ... ethanol varies between 110 and 120 depending on the source ... I think methanol must exceed 140 ... advice to connoisseurs?) which allows incredible compression rates on a petrol engine (up to 17 - 18) and therefore better yields and lighter engines. These simple compounds have not only this advantage but also that of burning very easily (hence the danger of methanol) unlike aromatics.
So why the builders so reluctant to use on-board reformers that would ONLY have advantages (make a simpler fuel with a heavier fuel directly: better octane and better combustion) .... The answer must be found on the side of their friends the tankers ...