BURNER FOR A GAS TURBINE AND METHOD FOR REDUCING THERMOACOUSTIC OSCILLATIONS IN A GAS TURBINE

Abstract

A burner for a gas turbine, has an air passage supplied with compressed air and a fuel passage supplied with fuel gas, each passage has a main outlet opening leading into the combustion chamber of the gas turbine, the air and fuel passages connected fluidically together via a connection duct arranged upstream of the main outlet openings. The burner is configured such that, when air passage is supplied with compressed air and fuel passage is supplied with fuel gas, a portion of the fuel gas flowing in the fuel passage flows via at least one connection duct into the air passage and, for combustion thereof, is introduced through the main outlet opening of the air passage into the interior of the combustion chamber and a remaining portion of the fuel gas is introduced through the main outlet opening of the fuel passage into the interior of the combustion chamber.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2014/070168 filed Sep. 23, 2014, and claims the benefit thereof. The International Application claims the benefit of European Application No. EP13185537 filed Sep. 23, 2013. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a burner for a gas turbine which is intended in particular for the combustion of low calorie fuel gas. The invention also relates to a method for reducing thermoacoustic oscillations in a gas turbine, wherein the burner is suitable for carrying out the method.

BACKGROUND OF INVENTION

In a combustion chamber interaction may arise between acoustic oscillations (pressure fluctuations) and fluctuations in heat release, which may amplify one another. Such thermoacoustic oscillations, which arise in particular in the combustion chamber of a gas turbine, may lead to considerable damage to the components during operation of the gas turbine and force shutdown of the installation.

In a method for reducing thermoacoustic oscillations in a gas turbine comprising at least one burner, a dwell time profile of a fuel stream flowing in a first fuel passage of the burner is adapted to reduce the thermoacoustic oscillations.

To provide a fuel gas to be combusted in the combustion chamber of the gas turbine, the burner of the type in question comprises at least the above-stated first fuel passage to which fuel gas may be supplied and, to provide the air required for combustion, an air passage to which compressed air may be supplied. The two passages each comprise a main outlet opening leading into the combustion chamber of the gas turbine. The fuel passage may take the form of a premixing passage or a diffusion passage. To this end, the fuel passage is connected to at least one feed for the fuel gas. The fuel passage is preferably configured to provide synthesis gas—in particular in the form of an annular space passage. The burner may comprise further passages, for example in order to introduce a plurality of different fuels into the combustion chamber with the burner for combustion. The individual passages may also be connected to a plurality of feed systems, in order to supply different fuels or flushing fluids to the passages, depending on the operating state of the burner.

So that such burners may also without risk adopt operating states in which fuel feed to the above-stated fuel passage is shut off (so as to supply another passage with another fuel), it is known from the prior art to provide such burners with flushing air ducts, so as to avoid flareback into the fuel passage. In known burners, compressed air from the air passage is introduced into the fuel passage through these flushing air ducts when fuel feed has been shut off. In these known burners, fuel gases penetrating via the main outlet opening into the passage are flushed out of the passage by the compressed air. This prevents flareback into the burner.

A burner of the type in question comprises at least one connection duct which is arranged upstream of the main outlet openings and connects the air passage and the fuel passage together fluidically.

Burners are known from the prior art which, to widen a dwell time profile of a fuel gas stream flowing in a first fuel passage, comprise a number of fuel nozzles which lead into the first fuel passage and are arranged offset relative to one another in the direction of flow.

SUMMARY OF INVENTION

The object of the present invention is to provide a burner and a method of the above-stated type which allow an alternative way of reducing thermoacoustic oscillations in a combustion chamber of a gas turbine.

The object is achieved according to the invention for a burner of the above-stated type in that the burner is configured such that in at least one first operating state of the burner, when compressed air is supplied to the air passage and fuel gas is supplied to the fuel passage, a portion of the fuel gas flowing in the fuel passage flows into the air passage via at least one connection duct. The branched-off portion of the fuel stream may be introduced for combustion thereof into the interior of the combustion chamber through the main outlet opening of the air passage. A portion remaining in the fuel passage of the fuel gas may be introduced into the interior of the combustion chamber through the main outlet opening of the fuel passage. The amount and radial fuel distribution of the branched-off portion of the fuel stream is such that fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

The invention is based on the recognition that the radial distribution of the fuel, in particular in the case of a synthesis gas/air mixture, plays a crucial role in the acoustic stability of the burner. The burner according to the invention allows better acoustic stability, so widening the operating range of the burner with regard to load and fuel quality.

In the burner according to the invention, the radial fuel/air distribution of a fuel stream flowing in a fuel passage may be adapted without fundamental aerodynamic design parameters of the fuel passage, such as swirl number, pressure drop and main dimensions of the passages, having to be modified significantly. The invention also makes it possible to adapt the burner to the thermoacoustic behavior of the combustion chamber for different fuel compositions without adaptation of the entire fuel passage being necessary for this purpose.

The burner according to the invention is such that, in at least one first operating state of the burner, when compressed air is supplied to the air passage and fuel gas is supplied to the fuel passage, the static pressure prevailing at the connection ducts serving in branching off the fuel is greater on the fuel passage side than on the air passage side.

According to the invention, the burner is configured such that the fuel stream is divided once it is flowing in the fuel passage. Thus, according to the invention, no division takes place in the region of the fuel feed system; rather, the division/branching off takes place after introduction of the fuel into the fuel passage but upstream of the main outlet opening.

According to the invention, the burner is configured such that, through the division/branching off of the fuel stream flowing in the first fuel passage, fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

By dividing and branching off the fuel stream flowing in the first fuel passage, the flame front in front of the burner is modified. This may be adjusted by means of the amount and radial distribution of the branched-off portion of the fuel stream such that fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber. To achieve an appropriate modification of the flame front, the radial fuel distribution of the branched-off portion of the fuel stream extends substantially beyond the thickness of a shear layer arising between the exiting streams into the air passage.

The invention thus does not relate to manipulation of the thickness of the shear layer between the compressed air stream exiting from the air passage and the fuel stream exiting from the main outlet opening of the fuel passage. Instead, to ensure that fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber, the invention takes another course, in that the amount and radial fuel distribution of a branched-off portion of the fuel gas flowing in the fuel passage is such that, through modification of the flame front (which accompanies modification of the dwell time profile of the fuel stream), fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

To bring about the desired branching off of the portion of the fuel stream, the position of the connection ducts and their diameter may be selected accordingly in the two passages. However, to produce suitable pressure conditions at the connection ducts, the invention is in particular based on the burner comprising flow guide means in the fuel passage and/or adjusting elements in the region of the connection ducts, which suitably determine the static pressure in the inlet region of the connection ducts. The flow guide means and/or adjusting elements may be modified for example in position or shape or be exchanged to adapt the division/branching off of the fuel stream. In this way, the position of the connection ducts in the passages is freely and widely selectable. The connection ducts are in this case arranged downstream of the air feed lines and/or fuel gas feed line used in the first operating state and upstream of the two main outlet openings of the two passages, so that fuel gas may be branched off into the air stream.

The main outlet opening may for example take the form of an annular opening at the outlet orifice of the passage. According to a further exemplary embodiment, the main outlet opening may consist of a plurality of holes in a metal plate (covering the outlet orifice of the burner passage). The main outlet opening is arranged at the combustion chamber end of the passage.

The connection ducts are arranged along a wall delimiting the fuel passage, for example in a circumferential sequence, such that their inlet openings are arranged in a circumferential row in the fuel passage and the ducts extend through the wall as far as the air passage. The pressure conditions in the burner may be configured such that the connection ducts also counteract flareback into the burner when the supply of fuel into the first fuel passage has been shut off.

Advantageous configurations of the invention are indicated in the following description and the subclaims, the features of which may be applied individually and in any desired combination.

Provision may advantageously be made for the burner to be configured such that the common dwell time profile, brought about by the branching off, of the remaining portion and the branched-off portion of the fuel stream is adapted to the thermoacoustic behavior of the combustion chamber, such that fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

By dividing and branching off the fuel stream flowing in the first fuel passage, the flame front in front of the burner is modified. A modified common dwell time profile of the branched-off and remaining portions of the fuel stream may thus be established. The dwell time is here the interval of time which the fuel needs from outlet from the burner to the flame front. Since the fuel in the fuel stream has different dwell times (depending on exit location at the burner outlet and depending on the position of the flame in front of the exit location), a dwell time profile of the fuel stream is established for the respective operating state. Undesired feedback of fluctuations in heat release into pressure fluctuations in the combustion chamber may be reduced by means of the division and branching off of the fuel stream, since the common dwell time profile may be modified depending on amount and radial fuel profile of the branched-off portion of the fuel stream. If for example the fraction of the profile is reduced the dwell time of which corresponds substantially to the frequency of a particular fuel chamber pressure fluctuation, this reduces feedback of fluctuations in heat release into pressure fluctuations in the combustion chamber.

The configuration according to the invention of the burner is thus such that, at least in the first operating state, a dwell time profile of the fuel stream having a damping or non-amplifying effect on the thermoacoustic behavior of the fuel chamber is brought about.

The phrase “thermoacoustic oscillation behavior” means that gas turbine combustion chambers tend, depending on power range, in particular at specific frequencies/frequency bands, to amplify thermoacoustic oscillations (characteristic ripple behavior). These frequencies may also be referred to as particular combustion chamber pressure fluctuations. If the dwell time profile of a burner is appropriately adjusted, in particular widened, this may counteract amplification of the oscillations in the range of at least one such characteristic ripple frequency/frequency band. In this respect, the dwell time profile may be adapted to or harmonized with the thermoacoustic behavior of the combustion chamber and counteract amplification of thermoacoustic oscillations in the combustion chamber. The dwell time profile may be influenced for example by means of the fraction and/or penetration depth (radial profile) and/or division over the individual connection ducts of the branched-off fuel stream. In relation to the first fuel passage, the burner comprises appropriately configured branching-off which, at least in the first operating state, brings about a fuel stream dwell time profile which has a damping effect on the thermoacoustic behavior of the combustion chamber.

In one advantageous configuration of the invention, the first fuel passage may be designed at least for supply with low calorie fuel gas.

A low calorie fuel should (in contrast to a standard fuel) be understood in particular to mean a fuel with a calorific value of less than 20 MJ/kg, in particular of less than 10 MJ/kg. This could for example be a very low calorie natural gas or a “synthesis gas”. Synthesis gas conventionally comprises main fractions of CO and H₂ and optionally secondary fractions such as N₂ and CO₂ together with water vapor. Standard fuel is conventionally a normal and/or high calorie fuel, the calorific value of which is far higher than 30 MJ/kg. Normal natural gas for example has as a rule a calorific value of between 40 and 50 MJ/kg. The combustible component of standard fuels for gas turbines consists substantially of hydrocarbons. In contrast, the combustible components of synthesis gas are substantially CO and H₂. Due to the low calorific value, high volumetric flow rates of fuel gas must consequently be supplied to the combustion chamber by the burner. The consequence of this is that, for the combustion of low calorie combustion fuels, such as for example synthesis gas, one or more separate fuel passages must be provided. Because of the high reactivity of synthesis gases compared to conventional combustion fuels such as natural gas and oil, there is a distinctly higher risk of flareback.

The present invention may be applied particularly advantageously to this fuel passage for low calorie fuels.

The fuel passage may be configured for diffusion operation or for premixing operation to introduce the low calorie fuel gas into the combustion chamber. In premixing operation, the low calorie fuel gas, which may in particular be synthesis gas, is premixed with air to yield a low calorie fuel/air mixture and reaction of the low calorie fuel/air mixture in the fuel passage is avoided, such that the fuel/air mixture is reacted to yield a hot gas only in the combustion chamber. The invention is in particular based on a synthesis gas passage for diffusion operation in which by means of swirlers swirl is imparted to the fuel stream by vanes. The synthesis gas passage in particular takes the form of an annular space passage and may taper conically downstream.

The burner may be arranged substantially rotationally symmetrically about a longitudinal axis, such that a main direction of flow of the fluid flowing in the passages of the burner points substantially in the direction of the longitudinal axis (in particular in the passages arranged radially closer to the longitudinal axis) or has at least one component in the direction of the longitudinal axis (in particular in the passages located radially more to the outside, which upstream may extend initially substantially diagonally to the longitudinal axis and downstream follow a course which is approximately parallel to the longitudinal axis). The air passage and the fuel passage may be arranged coaxially to one another at least in places, in particular the air passage may be arranged coaxially around the fuel passage.

Provision may advantageously also be made for the main outlet openings of the air passage and fuel passage to be arranged such that the coaxially surrounding passage is arranged around the other main outlet opening relative to a projection plane extending perpendicular to the longitudinal axis.

This generates flames arranged coaxially to one another from a common fuel stream with adapted dwell time profile.

A particularly simple structure is obtained if the air passage and the fuel passage adjoin one another at least in places along a wall which substantially takes the form of a cylindrical casing and/or of a truncated cone-shaped casing, wherein the connection ducts take the form of holes in the wall.

According to a particularly advantageous configuration, at least one adjusting element may be arranged in the region of the connection ducts, such that the fraction and/or the radial inflow profile and/or the division over the connection ducts of the fuel gas branched off from the fuel passage into the air passage is adjusted and/or adjustable by means of the at least one adjusting element.

The adjusting element may influence the static pressure in the region of the inlet opening of at least one connection duct, such that a suitable position of the inlet opening is not exclusively determined by the pressure conditions established in the fuel passage in the first operating state. In addition, the adjusting element may be more readily adapted to a desired dwell time profile (for example by exchange or by modification of the shape thereof) than the position or size of the at least one connection duct.

According to a particularly advantageous configuration of the adjusting element, a flow guide means is arranged in the fuel gas passage downstream of at least one fuel passage-side inlet opening of a connection duct, which flow guide means increases the static pressure in the region of the inlet openings of the connection duct when the fuel passage is supplied with fuel gas.

It may also be considered advantageous for the flow guide means to comprise a substantially annular metal plate, wherein the metal plate is arranged circumferentially on an inside of a wall delimiting the fuel passage. (The term “metal plate” relates to the shape, but should not be understood to be limiting for the purposes of the present invention in respect of the material selected).

This configuration of the flow guide means has a particularly simple structure and thus low manufacturing costs.

To achieve a particularly marked increase in pressure, the metal plate may extend into the interior of the fuel passage at an angle contrary to a main direction of flow in the fuel passage. For example, it may project beyond at least one sub-region of the inlet openings of the connection ducts.

To have the least possible effect on the flow profile between the inlet openings of the connection ducts, the substantially annular metal plate may in each case have a cut-out between the regions located downstream of the inlet openings of the connection ducts, such that the metal plate comprises triangular or trapezoidal crenellations for example downstream of the inlet openings.

Provision may for example be made for the adjusting element to comprise a number of flow guide means, which take the form of triangular or trapezoidal metal plates. The triangular metal plates may be arranged on the inside of the fuel passage similarly to the above-mentioned substantially annular metal plate. The individual metal plates certainly have the advantage that no regions of a flow guide means which disadvantageously increase the pressure drop are arranged downstream of the regions between the inlet openings.

An alternative, advantageous configuration of the flow guide means may comprise at least one cupped element with entry opening, which is arranged with the entry opening pointing towards the inlet opening of a connection duct downstream of the inlet opening on an inside of a wall delimiting the fuel passage.

The cupped element may advantageously substantially take the form of a hollow quarter-sphere. This may project at least in part beyond the inlet opening.

Provision may further advantageously be made for at least one adjusting element to be of tubular configuration, wherein the tubular adjusting element is in each case arranged in particular at least in part in one of the connection ducts.

According to a first exemplary embodiment of the configuration of the invention, the at least one tubular adjusting element may be partially inserted in each case into a connection duct and protrude into the air passage, such that the radial position of the inflow of the branched-off sub-stream flowing through the respective connection duct may be precisely positioned. The amount by which the tubular adjusting element protrudes into the air passage may also vary from tubular adjusting element to tubular adjusting element depending on the desired radial inflow profile. According to a further exemplary embodiment of the configuration of the invention, the at least one tubular adjusting element may be arranged for example in each case completely in one connection duct. To adjust the radial inflow profile of the branched-off fuel stream, the wall thicknesses of the at least one tubular adjusting element may for example be selected accordingly. According to a further exemplary embodiment of the invention, the at least one tubular adjusting element may be fixed to the inside of the air passage as an extension of a connection duct. According to a further exemplary embodiment, the at least one tubular adjusting element may, in addition or as an alternative to the above-mentioned exemplary embodiments, protrude into the fuel passage and for example comprise an inflow dish at the end thereof protruding into the fuel passage. The inflow dish may for example be configured similarly to the triangular metal plates or the hollow quarter-spheres. The stated exemplary embodiments of the tubular adjusting element may for example be combined together or used individually. If a plurality of such tubular adjusting elements are provided, these may, depending on the desired radial inflow profile of the branched-off fuel stream, all be configured the same or differ from one another, for example in accordance with the stated exemplary embodiments and combinations thereof.

A further object of the invention is to provide a method of the above-stated type which allows an alternative way of reducing thermoacoustic oscillations in a combustion chamber of a gas turbine.

The object is achieved according to the invention for a method of the above-stated type in that, to adapt the dwell time profile of a fuel stream flowing in a first fuel passage, a remaining portion of the fuel stream is introduced into the combustion chamber through at least one main outlet opening of the first passage and a branched-off portion of the fuel stream is introduced, downstream of introduction thereof into the fuel passage and upstream of the main outlet opening, into at least one second passage via at least one connection duct, wherein the branched-off portion of the fuel stream is introduced into the combustion chamber separately from the remaining fuel stream, such that the sub-streams, after exit thereof from the burner, are combusted in the combustion chamber with different dwell times or dwell time profiles, wherein, to adapt the dwell time profile, the fraction of the branched-off sub-stream and/or the inflow profile thereof and/or the division thereof over the at least one connection duct is adjusted such that fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

With regard to the possible configurations and advantages of the method, reference is made to the above explanations relating to the burner according to the invention.

Provision may advantageously further be made for the remaining fuel stream and the branched-off portion of the fuel stream to be introduced substantially coaxially to one another into the combustion chamber.

To adapt the thermoacoustic behavior of the combustion chamber comprising the burner, the fraction and/or the inflow profile and/or the division over the at least one connection duct of the branched-off portion of the fuel stream may be adjusted prior to start-up of the burner and/or during operation of the burner.

Advantageously, adjustment of the fraction and/or the penetration depth and/or the division over the at least one connection duct proceeds by adapting at least one flow guide means arranged in the fuel passage and/or one adjusting element arranged in the region of the connection ducts.

According to one advantageous configuration of the invention, adaptation of the at least one flow guide means and/or adjusting element may proceed by exchange and/or adaptation of the shape and/or position thereof.

A further object of the invention is to provide a combustion chamber with at least one burner and a gas turbine with at least one such combustion chamber, which allows an alternative way of suppressing thermoacoustic oscillations in a combustion chamber of a gas turbine.

The object is achieved according to the invention for a combustion chamber of the above-stated type in that the burner is configured as claimed.

The object is achieved according to the invention for a gas turbine of the above-stated type in that the combustion chamber is configured as claimed.

Further convenient configurations and advantages of the invention constitute the subject matter of the description of exemplary embodiments of the invention with reference to the figures of the drawings, wherein the same reference numerals refer to identically acting components.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings

FIG. 1 is a schematic representation of a longitudinal section through a gas turbine according to the prior art, and

FIG. 2 is a schematic representation of a longitudinal section through a burner according to the invention according to a first exemplary embodiment,

FIG. 3 is a schematic representation of a longitudinal section through a burner according to the invention according to a second exemplary embodiment, and

FIG. 4 is a schematic representation of a longitudinal section through a burner according to the invention according to a third exemplary embodiment.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a schematic sectional view of a gas turbine 1 according to the prior art. In its interior, the gas turbine 1 comprises a rotor 3 mounted so as to rotate about an axis of rotation 2 and having a shaft 4, said rotor also being known as a turbine wheel. The following succeed one another along the rotor 3: an intake housing 6, a compressor 8, a combustion system 9 with a number of combustion chambers 10, a turbine 14 and a waste gas housing 15. The combustion chambers 10 each comprise a burner arrangement 11 and a housing 12, which is lined with a heat shield 20 to provide protection from hot gases.

The combustion system 9 communicates with a for example annular hot gas duct. A plurality of series-connected turbine stages there form the turbine 14. Each turbine stage is formed of rings of blades or vanes. When viewed in the direction of flow of a working medium, a row formed of guide vanes 17 is followed by a row of rotor blades 18 in the hot duct. The guide vanes 17 are here fastened to an inner housing of a stator 19, whereas the rotor blades 18 of a row are mounted for example by means of a turbine disk on the rotor 3. A generator (not shown) is for example coupled to the rotor 3.

During operation of the gas turbine, air is drawn in by the compressor 8 through the intake housing 6 and compressed. The compressed air provided at the turbine-side end of the compressor 8 is guided to the combustion system 9 and there is mixed with a fuel in the region of the burner arrangement 11. The mixture is then combusted in the combustion system 9 with the assistance of the burner arrangement 11, forming a working gas stream. From there the working gas stream flows along the hot gas duct past the guide vanes 17 and the rotor blades 18. At the rotor blades 18 the working gas stream expands in a pulse-transmitting manner, such that the rotor blades 18 drive the rotor 3 and the latter drives the generator (not shown) coupled thereto.

FIG. 2 is a schematic representation, in longitudinal section, of a detail of a burner 24 according to the invention for a gas turbine according to a first exemplary embodiment.

The burner 24 comprises an air passage 26 in the form of an annular channel and to which compressed air can be supplied, a fuel passage 28 configured to be supplied with synthesis gas and a secondary feed unit 30, which may comprise a pilot burner (not shown explicitly) and further passages (not shown explicitly) for introducing a fluid. The burner has a substantially rotationally symmetrical structure about a longitudinal axis 32. In this respect, the air passage 26 coaxially encompasses the fuel passage 28 designed for synthesis gas, which in turn coaxially surrounds the secondary feed unit 30. The secondary feed unit 30 and the two passages 26 and 28 each respectively comprise a main outlet opening 36, 38, 40 leading into the combustion chamber 34.

The main outlet opening 36 is here arranged around the main outlet opening 38 relative to the projection plane 50 extending perpendicular to the longitudinal axis 32.

Compressed air entering the air passage 26, the main direction of flow of which is indicated in the inlet region by an arrow L″, is swirled by a swirler 42 arranged in the air passage. The vanes of the swirler extend from an inner wall 44 delimiting the passage to an outer wall 46 delimiting the passage, wherein the vanes are arranged in a ring over the circumference of the wall. The air stream exits the air passage 26 through the main outlet opening 36. To introduce synthesis gas into the combustion chamber 34, a synthesis gas stream 48 (which may also be premixed with compressed air prior to entry into the illustrated portion of the fuel passage 28) is fed to the fuel passage 28 via a feed line system. The feed line system is not shown in the figure, since it is located outside the detail illustrated. To swirl the synthesis gas stream 48, vanes 52 of a swirler are likewise arranged in the fuel passage 28. Downstream of the vanes 52 the fuel passage 28 and the air passage 26 are connected fluidically together via connection ducts 54. In the exemplary embodiment illustrated, the connection ducts 54 are arranged in a region in which the air passage 26 and the fuel passage 28 adjoin one another along a wall 56 which substantially takes the form of a cylindrical casing, wherein the connection ducts 54 are formed as holes in the wall 54 which takes the form of a cylindrical casing.

The burner 24 is configured such that, in at least one first operating state of the burner, when air passage 26 is supplied with compressed air and fuel passage 28 is supplied with fuel gas a portion of the fuel gas flowing in the fuel passage flows via the connection ducts 54 into the air passage 26 and, for combustion thereof, may be introduced through the main outlet opening 36 of the air passage into the interior of the combustion chamber 34.

Branching off proceeds such that the common dwell time profile of the fuel stream prevents or reduces in at least one frequency band any amplification of thermoacoustic oscillations which occur in characteristic frequency bands in the respective combustion chamber 34 of the gas turbine as a function of the power range. Thus, fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

The dwell time profile is adapted by means of an adjusting element 60 to the thermoacoustic behavior of the combustion chamber 34. In the first exemplary embodiment, the adjusting element 60 consists of a flow guide means 62, which is arranged in the fuel passage 28 downstream of the fuel passage-side inlet openings 64 of the connection ducts 54 and, on supply of fuel gas to the fuel passage 28, increases the static pressure in the region of the inlet openings 64 of the connection ducts 54. The flow guide means 62 takes the form of a substantially annular metal plate 66. This is arranged circumferentially on the inside 68 of the wall 56 delimiting the fuel passage 28 and extends into the interior of the fuel passage 28 at an angle contrary to a main direction of flow 70 in the fuel passage. The metal plate 66 here projects, maintaining a spacing, over at least a sub-region of the inlet openings 64. Depending on proximity, height, angle of attack and shape of the metal plate 66, the fraction and/or radial inflow profile and/or division over the individual connection ducts of the fuel gas branched off from the fuel passage 28 into the air passage 26 may be adjusted by means of the at least one adjusting element 60.

A disadvantageous increase in the pressure drop in the passage due to the flow guide means may be advantageously reduced for example by cut-outs (not shown) in the metal plate 66, which are each arranged between the regions located downstream of the inlet openings of the connection ducts.

Segmentation of the metal plate is an even more advantageous way of preventing a disadvantageous increase in the pressure drop. The adjusting element 60 may consist of a number of metal plates each arranged downstream of the inlet openings 64. These may for example, as illustrated in FIG. 3, take the form of triangular metal plates 74, which are curved over the inlet openings. For clarity's sake, only one such metal plate 74 is shown in FIG. 3.

According to a further exemplary embodiment, which is illustrated in FIG. 4, the adjusting element 60 may consist of a row of cupped elements 84, which each comprise an entry opening 86 and are arranged, with this pointing towards the inlet opening 64 of a connection duct 54, downstream of the inlet opening 64 on an inside 68 of a wall 56 delimiting the fuel passage 28 and in particular project at least in part beyond the inlet opening 64. In the exemplary embodiment illustrated in FIG. 4, the cupped element 84 substantially takes the form of a hollow quarter-sphere. FIG. 4 likewise shows for clarity's sake just one such hollow quarter-sphere.

The burners 24 according to the invention illustrated in FIGS. 2 to 4 are suitable for carrying out the method according to the invention. With reference to FIG. 3, to adapt the dwell time profile of a fuel gas stream 78 flowing in a fuel passage 28, a remaining portion 80 of the fuel stream is introduced through at least one main outlet opening 38 of the fuel passage 28 into the combustion chamber 34. A branched-off portion 82 of the fuel stream is introduced, downstream of introduction thereof into the fuel passage and upstream of the main outlet openings 36 and 38, via the connection ducts 54 into the air passage 26. The branched-off portion 82 of the fuel stream is introduced into the combustion chamber 34 separately from the remaining fuel stream 80, such that the sub-streams are combusted in the combustion chamber 34 with different dwell times or dwell time profiles after exiting from the burner 24, wherein the burner 24 is configured such that the common dwell time profile of the fuel streams 82 and 80 is adapted via the fraction of the branched-off sub-stream 82 and/or the inflow profile thereof and/or division thereof over the at least one connection duct 54 to the thermoacoustic behavior of the combustion chamber 34, such that fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

Claims

1.-22. (canceled)

23. A burner for a gas turbine, comprising:

at least one air passage to which compressed air is supplied and at least one fuel passage to which at least one fuel gas is supplied, the two passages each comprising a main outlet opening leading into the combustion chamber of the gas turbine, the air passage and the fuel passage being connected fluidically together via at least one connection duct arranged upstream of the main outlet openings,

wherein the burner is configured such that, in at least one first operating state of the burner, when air passage is supplied with compressed air and fuel passage is supplied with fuel gas, a portion of the fuel gas flowing in the fuel passage flows via at least one connection duct into the air passage and, for combustion thereof, is introduced through the main outlet opening of the air passage into the interior of the combustion chamber and a remaining portion of the fuel gas is introduced through the main outlet opening of the fuel passage into the interior of the combustion chamber, and

at least one adjusting element arranged in the region of the connection ducts, such that the fraction and/or the radial inflow profile and/or the division over the connection ducts of the fuel gas branched off from the fuel passage into the air passage is adjusted and/or adjustable by the at least one adjusting element, such that fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

24. The burner as claimed in claim 23,

wherein the burner is configured such that the common dwell time profile, brought about by the branching off, of the remaining portion and of the branched-off portion of the fuel stream is adapted to the thermoacoustic behavior of the combustion chamber, such that fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

25. The burner as claimed in claim 23,

wherein the burner is arranged substantially rotationally symmetrically about a longitudinal axis, such that a main direction of flow of the fluid flowing in the passages of the burner points in the direction of the longitudinal axis or has at least one component in the direction of the longitudinal axis, and the air passage and the fuel passage are arranged coaxially to one another at least in places.

26. The burner as claimed in claim 23,

wherein the main outlet openings of the air passage and fuel passage are arranged such that the coaxially surrounding passage is arranged around the other main outlet opening relative to a projection plane extending perpendicular to the longitudinal axis.

27. The burner as claimed in claim 23,

wherein the air passage and the fuel passage adjoin one another at least in places along a wall which substantially takes the form of a cylindrical casing and/or of a truncated cone-shaped casing, wherein the connection ducts take the form of holes in the wall.

28. The burner as claimed in claim 23, further comprising:

a flow guide arranged in the fuel gas passage downstream of at least one fuel passage-side inlet opening of a connection duct, wherein the flow guide increases the static pressure in the region of the inlet openings of the connection duct when the fuel passage is supplied with fuel gas.

29. The burner as claimed in claim 28,

wherein the flow guide comprises a substantially annular metal plate, wherein the metal plate is arranged circumferentially on an inside of a wall delimiting the fuel passage.

30. The burner as claimed in claim 29,

wherein the metal plate extends into the interior of the fuel passage at an angle contrary to a main direction of flow in the fuel passage.

31. The burner as claimed in claim 29,

wherein the metal plate in each case has a cut-out between the regions located downstream of the inlet openings of the connection ducts.

32. The burner as claimed in claim 28,

wherein the adjusting element comprises a number of flow guides, which take the form of triangular or trapezoidal metal plates.

33. The burner as claimed in claim 28,

wherein the flow guide comprises at least one cupped element with an entry opening, which is arranged with the entry opening pointing towards the inlet opening of a connection duct downstream of the inlet opening on an inside of a wall delimiting the fuel passage.

34. The burner as claimed in claim 33,

wherein the cupped element substantially takes the form of a hollow quarter-sphere.

35. The burner as claimed in claim 23,

wherein at least one adjusting element is of tubular configuration, wherein the tubular adjusting element is in each case arranged at least in part in one of the connection ducts.

36. A combustion chamber, comprising:

at least one burner,

wherein the burner is configured as in claim 23.

37. A gas turbine, comprising:

at least one combustion chamber,

wherein the combustion chamber is configured as in claim 36.

38. A method for reducing thermoacoustic oscillations in a gas turbine comprising at least one burner, the method comprising:

adapting a dwell time profile of a fuel stream flowing in a first fuel passage of the burner to the thermoacoustic behavior of the combustion chamber, wherein, to adapt the dwell time profile, a remaining portion of the fuel stream is introduced into the combustion chamber through at least one main outlet opening of the first passage and a branched-off portion of the fuel stream is introduced, downstream of introduction thereof into the fuel passage and upstream of the main outlet opening, into at least one second passage via at least one connection duct branching off from the first passage, wherein the branched-off portion of the fuel stream is introduced into the combustion chamber separately from the remaining fuel stream, such that the sub-streams, after exit thereof from the burner, are combusted in the combustion chamber with different dwell times or dwell time profiles,

adjusting the fraction and/or the inflow profile and/or the division over the at least one connection duct of the branched-of portion of the fuel stream prior to start-up of the burner and/or during operation of the burner, wherein adjustment of the fraction and/or the penetration depth and/or the division over the at least one connection duct proceeds by adapting at least one flow guide arranged in the fuel passage and/or one adjusting element arranged in the region of the connection ducts, such that fluctuations in heat release are fed back to a lesser extent into the pressure fluctuations in the combustion chamber.

39. The method as claimed in claim 38, further comprising:

introducing the remaining fuel stream and the branched-off portion of the fuel stream substantially coaxially to one another into the combustion chamber.

40. The method as claimed in claim 38,

wherein adaptation of the at least one flow guide and/or of the at least one adjusting element proceeds by exchange of the flow guide and/or the adjusting element and/or adaptation of the shape and/or position thereof.