"Maybe this creates a sort of pulsating effect on thespherical flame,
contracting it when the oxygen is running out, and allowing thus the
flux of more oxygen into the core, which feeds againthe flames to its
previous size?"

In perfectly still air I would expect the core of the fire to gradually
lose heat by radiation and go out. This will take much longer than heat
loss by convection, which can't happen without gravity.

If there is any movement of air I would expect combustion to continue
to the extent that oxygen can reach the core of the fire.

I wonder if you could make a fire retardent bag for use in
microgravity. You would enclose the fire in the bag and seal it. Oxygen
in the bag would be used up quickly and the mess inside would slowly
cool.

Of course, if a fire starts on the ISS, it is unlikely to cooperate to
this extent.

Michael Smith
...who wishes he new how to quote in google groups