  Stefan problems relevant to burning oil-water systems are formulated. Two
moving boundary sub-problems are defined: burning liquid surface and formation
of a distillation ("hot zone") layer beneath it. The basic model considers a
heat transfer equation with internal heat generation due to radiation flux
absorbed in the fuel depth. In verse Stefan problem corresponding to the first
case solved by the heat balance integral method and dimensionless scaling of
semi-analytical solutions are at issue.
