The Fuel rollout controls the simulation of burning. The fuel is used mostly for gasoline explosions, propagating fire or other special effects. There is no need to use fuel for simple fire, it can be made pretty well with simple hot air. The burning process in Phoenix FD converts the fuel into smoke (only in oxygen presence), releasing heat and increasing the volume. The produced heat is controlled by the Energy parameter, the volume growth is controlled by the Propagation parameter. There is no separate oxygen channel, but it is calculated as complementary substance up to the value of 1. This means, if the fuel is 0.3 and the smoke is 0.2 the oxygen is the rest up to 1, i.e. it is 0.5.
Enable burning (MXS: burning) - enables the fuel channel and the simulation of burning.
Energy (MXS: fl_energy) - specifies the energy released from burning a unit of fuel.
Ignition (MXS: fl_ignition) - ignition temperature (keep in mind that the environment temperature is 300).
Propagation (MXS: fl_propg) - controls the propagation speed of the ignition front.