This application is the US National Stage of International Application No. PCT/EP2010/053325, filed Mar. 16, 2010 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 09155341.2 EP filed Mar. 17, 2009. All of the applications are incorporated by reference herein in their entirety.
The present invention relates to methods for operating a burner, to a burner and to a gas turbine.
Because of their distributed heat release zones and the absence of swirl-induced vortex, premixed jet flame based combustion systems offer advantages compared to swirl-stabilized systems, in particular from a thermoacoustic point of view. By appropriate selection of the jet momentum, small-scale flow structures can be produced which dissipate acoustically induced heat release fluctuations and therefore suppress pressure pulsations that are typical of swirl-stabilized flames.
The jet flames are stabilized by mixing-in hot recirculating gases. The fuel distribution in the premixing section is an important parameter for setting the DOC-specific combustion state, which is characterized by delayed ignition of the fresh gas mixture and a distributed heat release zone. As the fuel distribution in the premixing section depends not only on the fuel distributor used but also on the air flow to the jet nozzle, which can also be load-dependent, additional measures must be taken to set the desired fuel profile reliably.
Against this background, a first object of the present invention is to provide an advantageous method for operating a burner. A second object consists in providing an advantageous burner. A third object of the present invention consists in providing an advantageous gas turbine.
The first object is achieved by a method as claimed in the claims, the second object by a burner as claimed in the claims and the third object by a gas turbine as claimed in the claims. The dependent claims contain further advantageous embodiments of the invention.
The method according to the invention for operating a burner relates to a burner which comprises a burner axis and at least one jet nozzle. Typically, however, a number of jet nozzles disposed around the burner axis will be present. The at least one jet nozzle comprises a central axis, a jet nozzle outlet and a wall running in a radial direction from the central axis and facing the burner axis. A fluid mass flow containing a fuel passes through the at least one jet nozzle to the jet nozzle outlet. The method according to the invention is characterized in that an air or inert gas film is formed at the jet nozzle outlet between the fuel-containing fluid mass flow and the wall facing the burner axis by air or inert gas being injected along the wall facing the burner axis into the at least one jet nozzle.
In the context of the present invention, at least the region of the jet nozzle wall located between the central axis of the jet nozzle and the burner axis will be termed the wall facing the burner axis.
It is particularly advantageous in the context of the method according to the invention to have no or very little fuel in the region of the jet nozzle outlet facing the burner axis. This is because too much fuel in this region can result in excessively rapid ignition of the flame which in this case is undesirable. Since in the present method no or only very little fuel is present in this region, ignition is delayed. Delayed ignition allows on the one hand a greater mixing length, resulting in a lower nitrogen oxide value. On the other hand delayed ignition allows distributed heat release, which is advantageous from a thermoacoustic standpoint.
With the aid of the present invention, by selective air or inert gas injection for film formation in the jet nozzle, the fuel profile is basically modified such that, for example, the part of the profile facing the burner axis contains no or only very little fuel. The objective here should be to use as little air or inert gas as possible for setting the profile.
The at least one jet nozzle can have a circumferential direction running around the central axis. In this case the air or the inert gas can be injected into the jet nozzle in the circumferential direction in an angular range of at least ±15°, referred to a radial connecting line between the burner axis and the central axis. The effect of this is that the part of the fuel profile facing the burner axis contains no or only very little fuel.
In addition, the air or the inert gas can be injected into the jet nozzle in the circumferential direction in an angular range of at most ±135°, in particular in an angular range of at most between ±90° and more particularly of at most ±45°, referred to a radial connecting line between the burner axis and the central axis. In this case, if adjacent jet nozzles are present, air or inert gas can also be injected at the sides facing the adjacent jets. This air or inert gas prevents the jet flames from coalescing and therefore provides an advantageous heat release zone, as is the objective for jet flame based burner systems. The air or inert gas injection on the sides facing the adjacent jets can be implemented bilaterally or only unilaterally.
In addition, the air can be injected into the jet nozzle in the circumferential direction about the central axis in an asymmetrical angular range of at most −135° to +45° or at most −45° to +135°, referred to a radial connecting line between the burner axis and the central axis, thereby achieving unilateral air or inert gas injection on the sides facing the adjacent jets.
The at least one jet nozzle can basically comprise a central axis. The air or the inert gas can be advantageously injected into the jet nozzle at an angle of between 0° and 60° to the central axis.
The burner according to the invention comprises a burner axis and at least one jet nozzle. However, it can also comprise a number of jet nozzles disposed about the burner axis. The at least one jet nozzle comprises a central axis and a wall area extending around same in an angular range of at most −135° to +135° and of at least −15° to +15°, referred to a radial connecting line between the burner axis and the central axis (hereinafter also referred to as the wall facing the burner axis). The burner according to the invention is characterized in that only the wall area extending around the central axis in an angular range of at most −135° to +135° and of at least −15° to +15° comprises at least one flow channel feeding into the jet nozzle to supply air or inert gas. The burner according to the invention is suitable for implementing the above-described inventive method. In particular, the flow channel can be connected to an air reservoir or an inert gas source.
The wall area comprising the at least one flow channel feeding into the jet nozzle can in particular also extend around the central axis in an angular range of at most ±90, in particular at most ±45 or at most −45° to +135° or at most −135° to +45°. In the two latter variants, unilateral air or inert gas injection on the sides facing the adjacent jets is achieved in each case.
The flow channel can be advantageously embodied as a bore or partial annular gap. In particular, the bore can comprise a central axis which, with the central axis of the jet nozzle, includes an angle of between 0° and 60°, in particular between 20° and 40°. The injected air or the injected inert gas entrained by the main flow in the jet nozzle then forms a particularly advantageous film. The bore can have, for example, a circular, an elliptical or any other cross-section. The bore can advantageously have a profiled outlet cross-section corresponding to that of film cooling holes. Similarly to the film cooling air, the requirement for the injected air or the injected inert gas is that it mixes as little as possible with the core flow.
If the flow channel is embodied as a partial annular gap, the partial annular gap can constitute a notional partial cone envelope which, with the central axis of the jet nozzle, can include an angle of between 0° and 60°, in particular between 20° and 40°. Advantageously, the partial annular gap can comprise a plurality of partial annular gap segments, thereby providing better controllability of the gap size.
In addition, the partial annular gap can be embodied such that it closes or opens as a function of the operating conditions. For example, it can be implemented such that it closes or opens due to thermal expansion of a structural element, in particular due to thermal expansion of the adjacent components. For example, the burner can comprise a pilot fuel nozzle and the partial annular gap can be embodied such that the partial annular gap closes or opens as a function of the temperature of the pilot fuel nozzle. Thus, in particular a hot pilot fuel nozzle in the partial load range can cause the gap to close, whereas in the case of very little pilot gas, i.e. with a cooler pilot fuel nozzle compared to the partial load range, the gap attains a maximum size close to base load.
The burner according to the invention permits the use of air films or inert gas films in order to model the mixture profile for a jet burner in an optimum manner for the operation thereof.
The gas turbine according to the invention comprises at least one previously described burner according to the invention. Its characteristics and advantages derive from those of the already described burner according to the invention. Altogether, through the use of air films or inert gas films, the present invention allows the mixture profile to be modeled for a jet burner so as to optimize said profile for operation of the gas turbine.
Further features, characteristics and advantages of the present invention will be described in greater detail below with reference to an exemplary embodiment taken in conjunction with the accompanying drawings, the features described being advantageous both individually and in combination with one another.
Exemplary embodiments of the invention will be explained in greater detail below with reference to
The combustion system 151 communicates with an annular hot gas path where a plurality of series-connected turbine stages constitute the turbine 105. Each turbine stage is composed of blade rings. Viewed in the flow direction of a working fluid, a stationary blade ring 117 is followed in the hot gas path by a rotor blade ring composed of rotor blades 115. Said stationary blades 117 are mounted on an internal housing of a stator, whereas the rotor blades 115 of a rotor blade ring are mounted on the rotor e.g. by means of a turbine disk. Coupled to the rotor is a generator or a driven machine.
During operation of the gas turbine, air is sucked in through the intake housing 109 and compressed by the compressor 101. The compressed air provided at the turbine end of the compressor 101 is fed to the combustion system 151 where it is mixed with a fuel. The mixture is then burned in the combustion system 151 using the jet burner 1 with the formation of the working fluid. From there the working fluid flows along the hot gas path past the stationary blades 117 and the rotor blades 115. At the rotor blades 115, the working fluid expands in a pulse-transmitting manner so that the rotor blades 115 drive the rotor and the latter the driven machine or the generator coupled thereto (not shown).
The combustion system 151 comprises at least one burner according to the invention and can basically incorporate an annular combustion chamber or a plurality of cylindrical can-type combustion chambers.
The
The jet nozzle 2 is fluidically connected to a compressor. The compressed air from the compressor is fed via an annular gap 22 to the jet nozzle inlet 8 and/or fed radially with respect to the central axis 5 of the jet nozzle 2 via an air inlet orifice 23 to the jet nozzle inlet 8. In the event that the compressed air is fed through the annular gap 22 of the jet nozzle 2, the compressed air flows through the annular gap 22 in the direction of the arrow denoted by the reference numeral 15, i.e. parallel to the central axis 5 of the jet nozzle 2. The air flowing in the direction of the arrow 15 is then deflected through 180° by the back wall 24 of the burner 1 and subsequently flows through the jet nozzle inlet 8 into the jet nozzle 2. The flow direction of the air inside the jet nozzle 2 is indicated by an arrow 10.
In addition or alternatively to supplying the compressed air through the annular gap 22, the compressed air coming from the compressor can also be fed through an orifice 23 disposed radially in the housing 6 of the burner 1 with respect to the central axis 5 of the jet nozzle 2. The flow direction of the compressed air flowing through the orifice 23 is indicated by an arrow 16. In this case the compressed air is next deflected through 90° and then flows through the jet nozzle inlet 8 into the jet nozzle 2.
Also located at the jet nozzle inlet 8 is a fuel nozzle 19 through which a fuel 12 is injected into the jet nozzle 2. The flow direction of the fuel is denoted by the reference numeral 17. At its circumference, the fuel nozzle 19 can additionally or alternatively have fuel outlet orifices 119 via which fuel can be introduced in the direction of the dashed arrows 117 shown in
The jet nozzle 2 additionally comprises a wall 7 facing the burner axis 4. By wall 7 facing the burner axis 4 is meant at least the area of the jet nozzle wall located between the central axis 5 of the jet nozzle 1 and the burner axis 4. The wall 7 facing the burner axis can in particular extend around the central axis 5 in an angular range of at most −135° to +135° and at least −15° to +15°, referred to the radial connecting line 26 between the burner axis 4 and the central axis 5.
In the region of the wall 7 facing the burner axis there is located, inside the housing 6, an air supply line 13 connected to the compressor. From the air supply line 13, air inlet orifices 14 lead into the interior of the jet nozzle 2. In the present embodiment variant the air inlet orifices 14 are implemented as bores with a circular cross-section. They each comprise a central axis 27 which, with the central axis 5 of the jet nozzle 2, include an angle β which can be, for example, between 0° and 60°, in particular between 20° and 40°. Instead of air, an inert gas can also be supplied via the supply line. In this case the line 13 is not connected to the compressor, but to an inert gas reservoir or an inert gas source.
Through the air supply line 13 and the air inlet orifices 14, air is injected into the jet nozzle 2 such that it is entrained by the main flow indicated by the arrow 10 and therefore forms an air film along the wall 7 facing the burner axis 4. The flow direction of the injected air is denoted by the reference numeral 20.
The burner according to the invention 1 can basically be implemented even without the outer housing section 127, i.e. without an outer housing 127. In this case the compressed air can flow directly into the “plenum”, i.e. the area between the back wall 24 and the jet nozzle inlet 8. In addition, the burner according to the invention 1 can also be implemented without the back wall 24.
The burner profile schematically illustrated in
Using the method according to the invention, i.e. by injecting air along the wall 7 facing the burner axis with the formation of an air film, the fuel profile schematically illustrated in
The fuel profile shown in
The fuel profile shown in
The jet nozzle 2 shown in
The partial annular gap 28 forms a notional partial cone envelope which is denoted by the reference numeral 29 and forms an angle β of between 0° and 60°, in particular of between 20° and 40°, with the central axis 5 of the jet nozzle 2.
The partial annular gap 28 can be implemented such that it closes or opens as a function of the operating conditions, e.g. as a result of thermal expansion of a structural element. In particular, the burner 1 can comprise at least one pilot fuel nozzle and the partial annular gap 28 can be implemented and be in thermal contact with the pilot fuel nozzle such that it closes or opens as a function of the temperature of the pilot fuel nozzle. For example, a hot pilot fuel nozzle during partial load operation can cause the partial annular gap 28 to close, while the partial annular gap 28 attains a maximum size when there is very little pilot gas close to base load, i.e. in the case of a cooler pilot fuel nozzle.
Number | Date | Country | Kind |
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09155341 | Mar 2009 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2010/053325 | 3/16/2010 | WO | 00 | 9/13/2011 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2010/106034 | 9/23/2010 | WO | A |
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