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Burner with exhaust gas recirculation

Imported: 24 Feb '17 | Published: 06 Jan '04

Klaus Doebbeling, Bettina Paikert, Christian Oliver Paschereit

USPTO - Utility Patents

Abstract

In a premixing burner (

1) for a gas turbine or hot-gas generation for the combustion of liquid or gaseous fuel, in which fuel is mixed with combustion air (

9

a

, 9

b) in a burner interior (

14), is fed to a combustion chamber (

3) and is burnt in this combustion chamber (

3), stabilization in the part-load model is achieved in a simple and efficient way in that means (

15) are provided which make it possible to recirculate hot exhaust gas (

17) out of the combustion chamber (

3) into the burner interior (

14) and to stabilize the flame by means of selfignition processes. The means (

15) are preferably a recirculation line which picks up hot exhaust gas (

17) from the outer backflow zone (

10) and feeds it to the burner interior (

14) in the region of a burner tip (

2) facing away from the combustion chamber (

3), additional fuel (pilot fuel

21) being admixed with the exhaust gas (

17) in the recirculation line upstream of the feed to the burner interior (

14).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail below with reference to exemplary embodiments, in conjunction with the drawings, in which:

FIG. 1 shows a double-cone burner in axial section and the backflow zones occurring during operation;

FIG. 2 shows a double-cone burner according to FIG. 1 with exhaust gas recirculation;

FIG. 3 shows the selfignition time of a fuel/air mixture as a function of the temperature;

FIG. 4 shows a double-cone burner according to FIG. 2, in which the central backflow zone is prevented; and

FIG. 5 shows a double-cone burner according to FIG. 4, in which pilot air can be supplied in addition to the hot recirculated exhaust-gas air.

Claims

1. A premixing burner for a gas turbine or hot-gas generation for the combustion of liquid or gaseous fuel, in which fuel is mixed with combustion air in a burner interior, is fed to a combustion chamber and is burnt in this combustion chamber, wherein means are provided which make it possible to recirculate hot exhaust gas out of the combustion chamber into the burner interior for stabilization in the part-load mode, and

2. The burner as claimed in claim 1, wherein the burner has an inner backflow zone.

3. The burner as claimed in claim 1, wherein it is a burner without an additional premixing zone.

4. The burner as claimed in claim 1, wherein the burner is a double-cone burner with at least two part-cone bodies positioned one on the other and having a conical shape opening toward the combustion chamber in the flow direction, the center axes of these part-cone bodies running, offset to one another in the longitudinal direction, in such a way that tangential inflow slots into the burner interior are formed over the length of the burner, through which inflow slots combustion air flows in, fuel being injected at the same time into the burner interior, so as to form a conical swirling fuel column, and, subsequently, the mixture flows out, so as to form an inner backflow zone, into the combustion chamber and is burnt there.

5. The burner as claimed in claim 4, wherein, in addition, fuel is injected centrally, near the burner tip, on the tapered side of the part-cone bodies which faces away from the combustion chamber.

6. The burner as claimed in claim 1, consisting of a swirl generator for a combustion-air stream and of means for injecting a fuel into the combustion-air stream, which burner has, downstream of the swirl generator, a mixing zone, which has, within a first zone part, transitional ducts, running in the flow direction, for transferring a flow formed in the swirl generator into a pipe located downstream of the transitional ducts, the outflow plane of this pipe into the combustion chamber being designed with a breakaway edge for stabilizing and enlarging a backflow zone formed downstream.

7. The burner as claimed in claim 6, wherein the swirl generator is in the form of a double cone.

8. The burner as claimed in claim 7, wherein the swirl generator is configured cylindrically and, in its interior, has a conical inner body running in the flow direction, the outer casing of the interior being pierced by tangentially arranged air inflow ducts, through which a combustion-air stream flows into the interior, and fuel being injected via a central fuel nozzle arranged at the tip of the inner body.

9. The burner as claimed in claim 1, wherein the hot exhaust gas is supplied to the burner interior centrally in the vortex core, essentially on the burner axis.

10. The burner as claimed in claim 9, wherein recirculation in the part-load mode, leads to a stabilization of the inner backflow zone.

11. The burner as claimed in claim 9, wherein recirculation in the part-load mode, leads to prevention of the inner backflow zone.

12. The burner as claimed in claim 1, wherein second means are provided which make it possible to admix additional fuel to the hot recirculated exhaust gas.

13. The burner as claimed in claim 12, wherein fuel injection, exhaust-gas temperature and flow velocity can be coordinated with one another in such a way that selfignition of the fuel occurs in the combustion chamber.

14. The burner as claimed in claim 13, wherein pilot air can be admixed with hot exhaust gas.

15. The burner as claimed in claim 14, wherein pilot air can be admixed with hot exhaust gas, and wherein this admixing takes place based on the injection principle.

16. The burner as claimed in claim 15, wherein the admixing of pilot air can be utilized for setting the optimum with regard to fuel injection, exhaust-gas temperature, flow velocity and, consequently, the selfignition location in the combustion chamber.

17. A method for operating a burner as claimed in claim 1, wherein exhaust gas recirculation is cut in and cut out, depending on the instantaneous power output stage of the burner.

18. The method as claimed in claim 17, wherein the pilot-air stream is used for controlling the formation of the inner recirculation zone.

19. The method as claimed in claim 18, wherein the pilot air can be used for blocking the exhaust-gas air, so that the swirl of the main airflow is sufficient to cause a breakdown of the vortex.

20. A method for operating a burner as claimed in claim 1, the recirculation of hot exhaust gas is employed in the part-load mode.

21. The burner as claimed in claim 1, wherein there are no additional premixing zones other than the premixing that occurs within the burner.