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A fuel injection head for a fuel nozzle used in a gas turbine combustor includes a substantially hollow body formed with an upstream end face, a downstream end face and a peripheral wall extending therebetween. A plurality of pre-mix tubes or passages extend axially through the hollow body with inle

A fuel injection head for a fuel nozzle used in a gas turbine combustor includes a substantially hollow body formed with an upstream end face, a downstream end face and a peripheral wall extending therebetween. A plurality of pre-mix tubes or passages extend axially through the hollow body with inlets at the upstream end face and outlets at the downstream end face. An exterior surface of the downstream end face is formed with three-dimensional surface features that increase a total surface area of the exterior surface as compared to a substantially flat, planar downstream end face.

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1. A fuel injection head for a fuel nozzle used in a gas turbine combustor comprising: a substantially hollow body formed with an upstream end face, a downstream end face and a peripheral wall extending therebetween;a plurality of pre-mix tubes or passages extending axially through said hollow body

1. A fuel injection head for a fuel nozzle used in a gas turbine combustor comprising: a substantially hollow body formed with an upstream end face, a downstream end face and a peripheral wall extending therebetween;a plurality of pre-mix tubes or passages extending axially through said hollow body with inlets at said upstream end face and outlets flush with an exterior surface of said downstream end face; andwherein said exterior surface of said downstream end face is formed with at least one of a plurality of dimples and a plurality of grooves that increase a total surface area of said exterior surface of said downstream end face to provide an enlarged recirculation pattern that enhances fuel/air mixing as compared to a substantially flat, planar downstream end face. 2. The fuel injection head of claim 1 further comprising a center opening in the upstream end face adapted to receive a fuel feed tube for supplying fuel to said substantially hollow body; and wherein fuel injection holes are provided in each of said pre-mix tubes or passages thereby enabling fuel in said substantially hollow body to be injected into said plurality of pre-mix tubes or passages. 3. The fuel injection head of claim 1 wherein said plurality of pre-mix tubes or passages are arranged in concentric annular rows, with pre-mix tubes or passages in one row circumferentially offset from pre-mix tubes or passages in an adjacent row. 4. The fuel injection head of claim 1 wherein said exterior surface of said downstream end face is formed with a plurality of substantially concave dimples. 5. The fuel injection head of claim 1 wherein said exterior surface of said downstream end face is formed with a plurality of substantially concentric, annular grooves. 6. The fuel injection head of claim 1 wherein said exterior surface of said downstream end face is formed with a plurality of substantially radially-oriented grooves. 7. The fuel injection head of claim 5 wherein said exterior surface of said downstream end face further comprises a plurality of substantially radially-oriented grooves that intersect said plurality of concentric annular grooves. 8. The fuel injection head of claim 4 wherein said plurality of substantially concave dimples have round or oval shapes. 9. The fuel injection head of claim 4 wherein said plurality of substantially concave dimples are arranged in a lattice or grid-like pattern, substantially filling an entire space between a group of four surrounding premix tubes or passages. 10. The fuel injection head of claim 4 wherein said plurality of substantially concave dimples have different cross sectional shapes. 11. The fuel injection head of claim 10 wherein said plurality of concave dimples include at least round and oval shapes. 12. The fuel injection head of claim 1 wherein a width dimension of the annular and radial grooves, a diameter of the dimples, and a depth dimension of the grooves and the dimples lie in a range of from 0.1 to 1.5 times a diameter of the premix tubes or passages. 13. A fuel injection head for a fuel nozzle comprising: a substantially hollow body formed with an upstream end face, a downstream end face and a peripheral wall extending therebetween, a plurality of pre-mix tubes extending axially through said hollow body with inlets at said upstream end face and outlets flush with said downstream end face, said premix tubes each provided with plural injection holes adapted to permit fuel in said substantially hollow body to enter said premix tubes to mix with air in said premix tubes;a center opening in the upstream end face adapted to receive a fuel feed tube for supplying fuel to said substantially hollow center body; andwherein an exterior surface of said downstream end face is provided with a plurality of dimples or grooves to thereby increase the surface area of said downstream end face. 14. The fuel injection head of claim 13 wherein said downstream end face is formed with a plurality of substantially concave dimples. 15. The fuel injection head of claim 13 wherein said downstream end face is formed with a plurality of substantially concentric, annular grooves. 16. The fuel injection head of claim 13 wherein said downstream end face is formed with a plurality of substantially radially-oriented grooves. 17. The fuel injection head of claim 15 wherein said downstream end face is formed with a plurality of substantially radially-oriented grooves that intersect said concentric annular grooves. 18. The fuel injection head of claim 14 wherein said plurality of substantially concave dimples are round or oval in shape. 19. The fuel injection head of claim 14 wherein said plurality of substantially concave dimples are arranged in a lattice or grid-like pattern substantially filling an entire space between a group of four surrounding premix tubes or passages. 20. A method of producing a fuel injection head that provides an enlarged recirculation pattern to enhance fuel/air mixing, comprising: a) forming a substantially hollow body with an upstream end face, a downstream end face and a peripheral wall extending therebetween;(b) forming a center opening in the upstream end face adapted to receive a fuel feed tube for supplying fuel to said substantially hollow body;(c) providing a plurality of pre-mix tubes or passages extending axially through said substantially hollow body, with inlets at said upstream end face and outlets substantially flush with said downstream end face; and(d) forming said downstream end face with a pattern of three-dimensional surface features in areas between said outlets to thereby increase surface area of said downstream end face.