If you are like me, when you come across something that is inadequately explained, the matter goes into an 'unsolved case' file indefinitely, and any future reference to its contents brings up a flag. So, in a book on gaseous detonations I found one little answer; the question had been, why is it important for Orbital Engine Company's air-blast injector to achieve a fuel droplet size of 10 microns? The answer seems to be that, at this size, the combustion of a droplet/air suspension becomes identical with that of a fully-evaporated mixture. That, in turn, probably indicates that the evaporation of such tiny droplets can be accomplished in the reaction zone of a flame without producing any significant delay. More things to think about...