Fuel and air are injected in a first poloidal flow in a first poloidal direction within a first annular zone of an annular combustor. A first combustion gas from the at least partial combustion of the fuel and air is discharged into an annular transition zone of the annular combustor and transformed to a second combustion gas therein within an at least partial second poloidal flow followed by an at least partial third poloidal flow in the annular transition zone, wherein the direction of the second poloidal flow is opposite to that of the first and third poloidal flows. The second combustion gas is discharged into a second annular zone of the annular combustor, and then transformed to a third combustion gas therein before being discharged therefrom, responsive to which a back pressure is generated in the annular combustor.