A method determines a largest rectangle on a display surface. The characteristics of a liquid fuel spray and the gaseous fuel and primary oxidant gas flows, as well as the geometry of the burner is adapted to shroud the liquid fuel from the primary oxidant until it exits a precombustor and to prevent the liquid fuel from contacting the walls of the precombustor. Thus, after a halt of the compressor, under-communication oil-feeding of the lubricating oil from the high-pressure region via the back pressure chamber to the compression chamber can be prevented.