A combustor arrangement of a gas turbine engine or power plant is disclosed, having at least one combustion chamber, at least one mixer arrangement for admixing air or gas to the hot gas flow leaving the combustion chamber. The mixer arrangement is configured to guide combustion gases in a hot gas flow path extending downstream of the combustion chamber, wherein the mixer includes a plurality of injection pipes pointing inwards from the side walls of the mixer arrangement for admixing air portions to cool at least the hot gas flow leaving combustion chamber. The mixer arrangement is applied to at least one volume of dilution air flowing from a first plenum and at least one volume of cooling air flowing from a second plenum.