A gas turbine system, comprising: a fuel nozzle, comprising: a first body comprising: a central passage extending from a mixing region to a central outlet at a first downstream end portion of the first body, wherein the central passage is defined by a first annular wall, and wherein the first annular wall radially diverges relative to a central axis of the central passage in a downstream directions toward the first downstream end portion; an annular pilot fuel outlet extending axially from an upstream end portion of the first body into the mixing region, wherein the annular pilot fuel outlet is oriented parallel to the central axis and surrounds a central pilot fuel passage configured to deliver air and fuel into the mixing region; an oxidant outlet in the mixing region; and an outer passage comprising a first passage extending in the downstream direction toward the first downstream end portion and a second passage extending in an upstream direction from the first downstream end portion into the mixing region, wherein the second passage radially diverges relative to the central axis in the upstream direction such that a first radial dimension of the second passage adjacent to the first downstream end portion is smaller than a second radial dimension of the second passage adjacent to the mixing region, and wherein the fuel nozzle is configured to flow a fluid through the first passage, the second passage, the oxidant outlet, and into the mixing region. a fuel nozzle, comprising: a first body comprising: a central passage extending from a mixing region to a central outlet at a first downstream end portion of the first body, wherein the central passage is defined by a first annular wall, and wherein the first annular wall radially diverges relative to a central axis of the central passage in a downstream directions toward the first downstream end portion; an annular pilot fuel outlet extending axially from an upstream end portion of the first body into the mixing region, wherein the annular pilot fuel outlet is oriented parallel to the central axis and surrounds a central pilot fuel passage configured to deliver air and fuel into the mixing region; an oxidant outlet in the mixing region; and an outer passage comprising a first passage extending in the downstream direction toward the first downstream end portion and a second passage extending in an upstream direction from the first downstream end portion into the mixing region, wherein the second passage radially diverges relative to the central axis in the upstream direction such that a first radial dimension of the second passage adjacent to the first downstream end portion is smaller than a second radial dimension of the second passage adjacent to the mixing region, and a central passage extending from a mixing region to a central outlet at a first downstream end portion of the first body, wherein the central passage is defined by a first annular wall, and wherein the first annular wall radially diverges relative to a central axis of the central passage in a downstream directions toward the first downstream end portion; an annular pilot fuel outlet extending axially from an upstream end portion of the first body into the mixing region, wherein the annular pilot fuel outlet is oriented parallel to the central axis and surrounds a central pilot fuel passage configured to deliver air and fuel into the mixing region; an oxidant outlet in the mixing region; and an outer passage comprising a first passage extending in the downstream direction toward the first downstream end portion and a second passage extending in an upstream direction from the first downstream end portion into the mixing region, wherein the second passage radially diverges relative to the central axis in the upstream direction such that a first radial dimension of the second passage adjacent to the first downstream end portion is smaller than a second radial dimension of the second passage adjacent to the mixing region, and wherein the fuel nozzle is configured to flow a fluid through the first passage, the second passage, the oxidant outlet, and into the mixing region.