That takes me back to diesel theory: Lift off, diffusion flame, cool flame soot, oxidisation etc etc. But it also makes that noise or rattle that Yr Right spoke of.
By the use of modern fuels, with better matching cetane number for swirl chambers and cylinder head design, CI engines can now be produced almost vibration free. Note almost, they all seem to have a frequency that resonates, a car can be geared to avoid that RPM