Power plants – Combustion products used as motive fluid – Plural combustion products generators in ring coaxial with...
Reexamination Certificate
2001-02-28
2003-03-25
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Plural combustion products generators in ring coaxial with...
Reexamination Certificate
active
06536204
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a burner configuration including a burner which opens into a combustion chamber. The burner configuration is, in particular, a burner configuration for a gas turbine.
A method for suppressing thermoacoustic oscillations in the combustion chamber of a gas turbine is described in German Published, Non-Prosecuted Patent Application DE 43 39 094 A1. During the combustion of fuels in the combustion chamber of a stationary gas turbine, an aircraft engine or the like, instabilities or pressure fluctuations may occur due to combustion processes, and those instabilities or pressure fluctuations, under unfavorable conditions, excite thermoacoustic oscillations, which are also referred to as combustion oscillations. The latter not only constitute an undesirable acoustic source, but they may also lead to inadmissibly high mechanical loads on the combustion chamber. Such a thermoacoustic oscillation is actively damped by controlling a location of a heat-release fluctuation associated with the combustion by injecting a fluid.
European Patent Application EP A 0 931 979 A1 discloses a configuration for suppressing flame/pressure oscillations in a firing system, in particular a gas turbine. In that configuration, a flame is enclosed by a gas-envelope flow having a higher flow velocity. That prevents an annular vortex formation. In order to be able to obtain smaller gas volumes for the gas-envelope flow, a screen is provided which surrounds the gas-discharge openings of the burner and runs at a distance around the burner. Therefore, a flue-gas recirculation region connected to the combustion space is separated from the discharge location of the gas-envelope flow and thus from the gas-envelope flow. It is also proposed to use such configurations at each burner in an annular combustion chamber of a gas turbine.
U.S. Pat. No. 4,373,342 discloses a burner chamber of a gas-turbine engine. An inlet region of the gas-turbine combustion chamber is provided with a screen which projects into the combustion chamber. The screen reduces a carbon deposition in a head region of the combustion chamber and likewise reduces smoke emission.
2. Summary of the Invention
It is accordingly an object of the invention to provide a burner configuration, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which has a favorable behavior in particular with regard to the avoidance of thermoacoustic oscillations.
With the foregoing and other objects in view there is provided, in accordance with the invention, a burner configuration, comprising a common combustion chamber and a multiplicity of burners disposed in the combustion chamber. Each of the burners has an outlet opening into the combustion chamber. Flow-guidance elements each at least partly form a respective one of the outlets of at least some of the burners. The flow-guidance elements project into the combustion chamber for guiding a fuel-gas flow discharging from the burners into the combustion chamber.
The fuel-gas flow may be a mixture of combustion air and, for example, oil or natural gas. The flow-guidance element serves to direct the fuel-gas flow discharging from the outlet. As a result, the zone of the combustion of the fuel-gas flow is displaced further into the combustion chamber. In addition, the flame shape of the combustion is influenced. The burner configuration, i.e. a system of the burner and the combustion chamber, is acoustically detuned by the effect on the shape and location of the combustion at some of the burners. This acoustic detuning prevents combustion oscillations or at least attenuates them. If a multiplicity of burners are present in a common combustion chamber, combustion oscillations cannot be predicted and are thus especially difficult to control. The complex system being formed of the multiplicity of burners in the common combustion chamber can be acoustically detuned simply and efficiently through the use of a flow-guidance element at a burner or even at a plurality of burners, in such a way that combustion oscillations occur at most with a small amplitude. In addition, a separation edge for vortices from the fuel-gas flow is provided by the flow-guidance element projecting into the combustion chamber. These vortices result in a backflow zone for at least some of the fuel-gas flow. This has a favorable effect on stabilization of the flame and on a reduction in the nitrogen-oxide emissions. The reduction in the nitrogen-oxide emission results from the flame temperatures being made more uniform by the mixing vortices.
In accordance with another feature of the invention, the flow-guidance element is a hollow cylinder or hollow truncated cone directed along a flow-guidance-element axis. The hollow cylinder or the hollow truncated cone also preferably ends at an imaginary top surface, in which case the top surface is not oriented perpendicularly to the flow-guidance-element axis. In other words: the hollow cylinder or the hollow truncated cone ends at a sloping top surface. The fuel-gas flow is therefore directed over a longer distance at a long side of the hollow cylinder or hollow truncated cone than at a short side opposite the long side.
In accordance with a further feature of the invention, the flow-guidance element is disposed around approximately half the outlet. A contact surface is therefore offered to the fuel-gas flow on one side. In addition to the effect on the shape of the combustion, the fuel-gas flow is thereby deflected by a short distance toward the open area. This in turn results in a displacement of the location of the combustion. Acoustic detuning and thus suppression of a combustion oscillation are thereby achieved in an especially effective manner.
In accordance with an added feature of the invention, the flow-guidance element is a sheet made of a high-temperature-resistant metal, in particular a steel.
In accordance with an additional feature of the invention, the combustion chamber is an annular combustion chamber of a gas turbine. In a gas turbine, in particular in a stationary gas turbine, a very high power release occurs during combustion. Combustion oscillations may not only have an acoustically disturbing effect in that case, they may even have a damaging effect. Suppression of combustion oscillations is therefore especially important in that case.
In accordance with a concomitant feature of the invention, the outlet has an outlet diameter and the flow-guidance element has a longest extent along the element axis. The longest extent has a length which is between one-sixth and one-half of the outlet diameter. The length of the longest extent preferably is between one and ten centimeters.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a burner configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
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Rolls Royce Ltd. The Jet Engine, 1973, p. 167.*
Japanese Patent Abstract No. 08303779 (Osamu), dated Nov. 22, 1996.
Lenz Manfred
Lenze Martin
Tiemann Carsten
Casaregola Louis J.
Greenberg Laurence A.
Locher Ralph E.
Siemens Aktiengesellschaft
Stemer Werner H.
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