Reheat burner and method of mixing fuel/carrier air flow within a reheat burner

1. A reheat burner between a high pressure turbine and a low pressure turbine comprising:

a flow channel for a hot gas flow with a lance arranged along said flow channel, protruding into the flow channel for injecting a fuel over an injection plane perpendicular to a channel longitudinal axis, wherein the flow channel and lance define a vortex generation zone upstream of the injection plane and a mixing zone downstream of the injection plane in the hot gas flow direction, the mixing zone including changing cross sectional areas by continuous rotation of a non-circular cross section area shape along the longitudinal axis of the mixing zone starting at a first non-circular cross section area shape and ending at an inlet of the low pressure turbine with a non-circular last cross section area shape rotated by an angle between 0 and 180 degrees around the channel longitudinal axis.

2. The reheat burner of claim 1 wherein the flow channel encircles the mixing zone with an inner channel wall, which is smooth without any protrusions extending beyond the inner wall surface.

3. A stationary gas turbine using sequential combustion having a reheat combustor that is equipped with a reheat burner according to claim 1 .

4. A reheat burner comprising:

a flow channel for a hot gas flow with a lance arranged along said flow channel, protruding into the flow channel for injecting a fuel over an injection plane perpendicular to a channel longitudinal axis, wherein the flow channel and lance define a vortex generation zone upstream of the injection plane and a mixing zone downstream of the injection plane in the hot gas flow direction, the mixing zone a) having different cross sectional areas along a longitudinal axis of the mixing zone with continuously changing shape, or b) having non circular cross section areas which change location along the longitudinal axis of the mixing zone by continuously rotation around the longitudinal axis, wherein the mixing zone provides at least two axially regions with a first axially region having the different cross sectional areas along the longitudinal axis of the mixing zone with continuously changing shape, and a second axially region having the non-circular cross section area which changes location along the longitudinal axis by continuously rotation around the longitudinal axis.

5. The reheat burner of claim 4 , wherein the first and second axially regions are related axially directly or indirectly.

6. The reheat burner of claim 4 , wherein the cross sectional area of an upstream end of the mixing zone is greater than the cross sectional area of a downstream end of the mixing zone.

7. The reheat burner of claim 4 , wherein the cross sectional area of a downstream end of the mixing zone is greater than the cross sectional area of an upstream end of the mixing zone.

8. A method for mixing a fuel and a carrier air flow within a reheat burner between a high pressure turbine and a low pressure turbine, in which the carrier air flow enters the reheat burner and being swirled by vortex generators inside the reheat burner before fuel is injected into the carrier air flow and producing a flow of fuel/carrier air mixture by injecting fuel into the swirled carrier air flow comprising:

propagating of said flow of fuel/carrier air mixture along a flow channel downstream to said fuel injection; and

introducing shear stress to the flow of fuel/carrier air by passing the flow of fuel/carrier air through a mixing zone of the flow channel, the mixing zone extending downstream from an injection plane perpendicular to a longitudinal axis of the flow channel, the mixing zone including changing cross sectional areas by continuous rotation of a non-circular cross section area shape along the longitudinal axis of the mixing zone starting at a first non-circular cross section area shape and ending at an inlet of a low pressure turbine with a non-circular last cross section area shape rotated by an angle between 0 and 180 degrees around the longitudinal axis.

9. A method for mixing a fuel and a carrier air flow within a reheat burner, in which the carrier air flow enters the reheat burner and being swirled by vortex generators inside the reheat burner before fuel is injected into the carrier air flow and producing a flow of fuel/carrier air mixture by injecting fuel into the swirled carrier air flow comprising:

propagating of said flow of fuel/carrier air mixture along a flow channel downstream to said fuel injection; and

introducing shear stress to the flow of fuel/carrier air by passing the flow of fuel/carrier air through a mixing zone of the flow channel, the mixing zone extending downstream from an injection plane perpendicular to a longitudinal axis of the flow channel, the mixing zone a) having different cross sectional areas along a longitudinal axis of the mixing zone with continuously changing shape, or b) having non circular cross section areas which change location along the longitudinal axis of the mixing zone by continuously rotation around the longitudinal axis, and wherein the mixing zone provides at least two axially regions with a first axially region having the different cross sectional areas along the longitudinal axis of the mixing zone with continuously changing shape, and a second axially region having the non-circular cross section area which changes location along the longitudinal axis by continuously rotation around the longitudinal axis.

10. The method of claim 9 , wherein the first and second axially regions are related axially directly or indirectly.

11. The method of claim 9 , wherein the cross sectional area of an upstream end of the mixing zone is greater than the cross sectional area of a downstream end of the mixing zone.

12. The method of claim 9 , wherein the cross sectional area of a downstream end of the mixing zone is greater than the cross sectional area of an upstream end of the mixing zone.