Abstract: An apparatus for premixing fuel and air prior to combustion in a gas turbine engine, including: a linear mixing duct having a circular cross-section defined by a wall; a centerbody located along a central axis of the mixing duct and extending substantially the full length of the mixing duct, the centerbody having a plurality of orifices therein to inject fuel into the mixing duct with an axial velocity component; a fuel supply in flow communication with the centerbody orifices; an outer annular swirler located adjacent an upstream end of the mixing duct and including a plurality of circumferentially spaced vanes oriented so as to swirl air flowing therethrough in a first direction; an inner annular swirler located adjacent the mixing duct upstream end and including a plurality of circumferentially spaced vanes, the vanes having an outer radial portion having a leading edge and a trailing edge oriented so as to swirl air flowing therethrough in a second direction opposite the first swirl direction by the outer