The invention relates a method for mixing a dilution air with a hot main flow in a sequential combustion system of a gas turbine, wherein the gas turbine essentially comprises at least one compressor, a first combustor which is connected downstream to the compressor, and a second combustor. The hot gases of the first combustor are admitted to at least one intermediate turbine or directly or indirectly to at least one second combustor, wherein the hot gases of the second combustor are admitted to a further turbine or directly or indirectly to an energy recovery device. The method comprises a coaxial injection of first combustor liner cooling air with second combustor liner cooling air, the first combustor liner cooling air having a sufficient excess pressure margin with respect to the second combustor liner cooling air.