Combustion – With means attenuating sound or pulsation
Reexamination Certificate
1999-12-10
2001-10-23
Price, Carl D. (Department: 3743)
Combustion
With means attenuating sound or pulsation
C431S350000, C060S725000
Reexamination Certificate
active
06305927
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of burners, in particular burners for use in gas turbines. It relates to a burner with fuel supply system, in which the fuel supply system transports fuel to the burner, and the fuel in the burner is injected into a combustion chamber where the fuel is burned.
2. Discussion of Background
Burners of gas turbines serve the purpose of injecting the fuel and the combustion air in a way which is controlled and can be regulated into a combustion chamber, and of burning the fuel there, For this purpose, the burners can be recessed in a most varied arrangement in the wall of the combustion chamber, and are charged with fuel by means of a fuel supply system. In order to ensure optimum control of the combustion process in the various operating states of the turbine, the injection of the fuel in the burner must be performed controllably and as optimally as possible. Precisely the regulations to be observed ever more strictly in recent time and relating to the emission from combustion processes are now rendering mandatory a highly specialized and complicated injection and mixing of combustion air and fuel in the burner.
For example, EP-B1-0 321 809 -has disclosed a so-called double-cone burner for liquid and gaseous fuels without a pre-mixing section, in which combustion air fed from outside enters tangentially, through at least two entrance slots, between hollow half cones arranged in a displaced fashion, and flows there in the direction of the combustion chamber, and in which, on the tapered side, averted from the combustion chamber, of the half cones, fuel is injected centrally, or from distribution channels, which run along the air entry slots, through rows of bores transversely into the air which is entering.
A problem with the injection of the fuel and its subsequent combustion are, inter alia, acoustic oscillations, which are also known under the term of “singing flame”. These are mostly oscillations which come about from the interplay between the inflow of the combustion mixture and the actual combustion process in the combustion chamber. These largely coherently periodic pressure fluctuations can lead in the case, for example, of a burner of the above-named type under typical operating conditions to acoustic fluctuations with frequencies of approximately 80 to 100 Hz. Since these frequencies can coincide with typical fundamental natural modes of combustion chambers of gas turbines, these thermo-acoustic oscillations constitute a problem.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to provide a novel burner with at least one fuel supply system through which the burner is fed a fuel flow, the fuel fed is injected via fuel nozzles and subsequently burned in a combustion chamber, and is capable of preventing at least partially the formation and amplification of periodic pressure fluctuations in the combustion chamber.
This object is achieved in the case of a burner of the type mentioned at the beginning by supplying means which prevent periodic pressure fluctuations which occur in the combustion chamber from leading to fluctuations in the fuel flow in the fuel supply system. The substantial prevention of the coupling of the periodic pressure fluctuations to fluctuations in the fuel flow can prevent the undesired, escalating amplification of the pressure fluctuations by the fuel flow in the combustion chamber. In particular, such means are of great advantage when the periodic pressure fluctuations occurring in the combustion chamber are acoustic oscillations and, quite particularly, when these are situated in the range of the acoustic natural oscillations of the combustion chamber. If the oscillations in the fuel flow in the fuel supply system are periodic, and if, in particular, the frequency of these periodic fluctuations in the fuel flow is situated in the range of the acoustic natural oscillations in the combustion chamber, this escalating effect can be exceptionally pronounced, and prevention of the same can be particularly indicated.
A first preferred embodiment of the invention is typified in that the means comprise at least a first volume arranged directly upstream of the fuel nozzles, through which volume the fuel flow flows, and this first volume is connected upstream via a first constriction to the fuel supply system, which is arranged further upstream. It is preferred in this case for this first volume to be selected essentially smaller than a specific critical volume and, furthermore, in particular for the cross-sectional area of the first constriction to be constructed smaller than a specific critical cross-sectional area. Each of these measures reduces the extent of the coupling of the pressure fluctuations to the fluctuations in the fuel flow and, moreover, the measures can be built into, or even retrofitted in conventional burners without a large design outlay.
Another embodiment of the invention is typified in that arranged upstream of the first constriction is a second volume, through which the fuel flow flows, and this second volume is connected upstream via a second constriction to the fuel supply system, which is arranged further upstream. This arrangement permits the effective prevention of coupling under specific, essentially unchanging design stipulations of the burner and of the fuel supply system.
Further embodiments of the burner with fuel supply system follow from the dependent claims.
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Frutschi, H., “Advanced Cycle System With New GT24 and GT26 Gas Turbines—Historical Background”, ABB Review, Jan. 1994, pp. 20-25.
Neuhoff, H., et al., “GT24 and GT26 Gas Turbines—Sequential Combustion the Key to High Efficiencies”, ABB Review, Feb. 1994, pp. 4-7.
Keller Georg
Keller Jakob J.
ABB Alstom Power ( Schweiz) AG
Burns Doane Swecker & Mathis L.L.P.
Keller Georg
Price Carl D.
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