EP1507119A1 - Burner and process to operate a gas turbine - Google Patents

Abstract

The burner has an annular premixing channel (21), into which fuel is fed radially. Feeding of fuel can be adjusted during operation. The premixing channel is made up of segments (31, 33), with radial rows of inlets (29) which alternately increase and decrease in diameter in adjacent segments. An independent claim is included for a method for operating a gas turbine using the burner.

Description

The invention relates to a burner with an annular Premix channel, radially distributed in the fuel introduced is. The invention also relates to a method of operation a gas turbine with a burner having an annular Premix channel has.

In a burner combustion air and fuel are brought together, mixed, ignited and burned in a flame. It is usually of great importance that Pollutant emissions such as carbon monoxide or nitrogen oxide thereby be kept low. The possibility of low nitrogen oxide Incineration consists in particular of a so-called premix combustion, at the fuel and combustion air first mixed as homogeneously as possible before they Combustion zone are supplied. Such a premix burner is disclosed in WO 02/095293 A1. This burner shows an annular Vormischkanal having a central Surrounds diffusion burner. In the premix channel are clear upstream of the combustion zone, swirl vanes in one extending over the entire cross section of the premix channel Swirl grid arranged. Such a swirl grid is used the flame stabilization. The swirl vanes of the disclosed Swirl lattices are hollow, with openings at the Surface of the swirl blades in the radial direction with Swirl blades extend. These openings become fuel embedded in the premix channel, previously the hollow Swirl blades was supplied. This will be on the radial height of the premix channel uniform inlet of Fuel in the flowing through the premixing combustion air reached. At the same time, through the inlet of the Fuel from all swirl blades also a uniform Distribution of fuel in the circumferential direction of the premix channel reached. This has a high homogeneity of then in the combustion zone flowing combustion air-fuel mixture According. Such homogeneity is desirable for low nitrogen oxide emissions, since the formation of nitric oxide exponditiell grows with the flame temperature. At a homogeneous mixture, peak local temperatures are avoided, since the energy release is uniform in the mixture distributed. This reduces the nitrogen oxide formation. In the Premix combustion is also comparatively low fuel burned in combustion air. This so-called lean Premix combustion, however, tends to burn instabilities, d. H. the flame fluctuates in its energy release or can even go out. To stabilize this Premix combustion serves the central diffusion burner, at the fuel and combustion air mixed in the flame become. To further stabilize the flame stability to reach the premix flame is proposed by the radial outer edge of the annular Vormischkanals flow blocking To provide elements at some local sites delay the flow of combustion air. This has in these Zones an enrichment of the combustion air-fuel mixture with fuel resulting in local, hot strands in the combustion zone, which is the premix combustion stabilize. Operationally dependent However, this static concept can change changing conditions do not go down.

The object of the invention is to specify a burner with an annular premixing channel, which can be adjusted with regard to its combustion stability as a function of the prevailing operating conditions.
Another object of the invention is the disclosure of a method for operating a gas turbine, in which a burner is adjusted depending on the operating state of the gas turbine so that the highest possible flame stability and lowest possible pollutant emissions result.

The task directed to a burner is according to the invention solved by a directed along an axis burner with an annular Vormischkanal, in the fuel radially distributed is introduced, wherein the radial distribution of the fuel during operation of the burner adjustable is.

The radial distribution of the fuel is the distribution of the fuel along a line perpendicular to the axis of Burner. With the invention is proposed for the first time, the to make the radial distribution of the fuel adjustable, so that it reacts to different operating conditions can. So far, only static fuel distributions by means of the geometry and inlet positions of fuel and combustion air realized. The invention works In contrast, from the knowledge that pollutant emissions and combustion stabilities at various operating conditions of the burner favorably by a changed radial Distribution of the fuel can be influenced. To the Example is usually sought in a full load operation, that fuel is as homogeneous as possible in the combustion air is distributed to keep nitrogen oxide emissions low. This requires a radial distribution of fuel at the inlet, which is higher radially outside than inside, in the annular Vormischkanal radially outside a larger To supply air mass flow is considered radially inside. Around So a uniform fuel concentration over the Vormischkanalquerschnitt to get the fuel inlet radially outside being higher than radially inside. In contrast, can in partial load operation a local accumulation of the Fuel air mixture with fuel in comparatively cold zones reduce carbon monoxide emissions. Therefore is at a partial load operation, a radial distribution of Fuel at inlet favorably, at radially inside more Fuel is taken in as radially outside. Continue to take the radial combustion profile influences combustion oscillations. Such combustion vibrations occur at Flame instabilities, the pressure fluctuations in a combustion chamber entail, in which the burner opens. By Reverse reflection from the combustion chamber walls of these pressure fluctuations in the flame area or in the mixing area of Fuel and combustion air can be in-phase Overlay a positive feedback of flame instability and pressure fluctuations occur, creating a stable Combustion vibration can be built. This leads to high sound emissions and vibrations in the combustion system, the damage may result. A change in the Distribution profile of the fuel inlet can be this positive Interrupt feedback and thus the combustion oscillation suppress.

Preferably, in the burner over the circumference of the premix channel distributed inlet devices provided for a lying at the respective circumferential position radial Inlet of fuel by means arranged in the radial direction Inlet openings with a respective opening cross-section, wherein at a first part of the inlet devices the opening cross-sections increase in the direction of the axis and in a second part of the inlet devices, the opening cross sections lose weight. By such a configuration it is possible, depending on the inlet of fuel on the one hand from the first part of the inlet devices and on the other hand from the second part of the inlet devices by the counter-rotating Change the opening cross sections a desired radial Adjust distribution of the fuel inlet.

Preferably, the inlet devices of the first part and of the second part alternately along the circumference of the premixing channel arranged. The inlet devices of the first and the second part are so alternately next to each other arranged around the circumference.

Preferably, the inlet devices of the first follow Part and the second part in the axial direction of the premixing channel each other. In this configuration so z. B. first, fuel from the intake devices of the first Partly embedded in the premix channel and in the flow direction subsequently, fuel from the inlet devices of the second part. This can in particular both from the inlet devices of the first part as well as the inlet devices of the second part with the circumference of the premix channel evenly distributed fuel can be let in. The overlay of the fuel inlet from the two Divide yields the desired radial distribution for the entire Fuel inlet.

Preferably, a first and a second around the axis the burner fuel supply line provided, wherein a pressure difference of the fuel pressure in the two Fuel supply lines to each other depending on the operating condition of the burner is adjustable. More preferred is the first Part of the inlet device with the first fuel supply line and the second part of the inlet device with the second Fuel supply connected. Through this configuration it is possible in a simple way, the fuel inlet the first part and the second part of the inlet devices independently of each other as desired. For this purpose, in each case the necessary for the desired distribution Pressure in the first and second fuel supply set. Depending on the pressure difference, there are thus different Amounts of fuel that exceed the first or the second inlet device are inserted, so that the entire fuel inlet of the desired distribution accordingly is set.

Preferably, the inlet devices are radially in the premixing channel protruding tubes, inside which the fuel is supplied. These tubes then become out of the inlet openings the fuel is admitted into the premixing channel.

Preferably, the inlet devices are radially in the Premix channel protruding swirl vanes, in the interior of the Fuel is supplied. In this case, the inlet openings on the surface of the swirl vanes, preferably in near a blade leading edge, arranged. The swirl blades thus fulfill a dual function by the impart necessary swirl for combustion stabilization and also at the same time as an inlet device for the fuel act.

Preferably, the first part of the inlet devices is off radially protruding into the premix tube and the second tube Part of the inlet devices from radially into the premixing channel protruding swirl vanes formed. It can be both the first Part and the second part of the inlet devices upstream arranged from the other part in the premix channel be. Conveniently, the tubes are upstream of the swirl vanes arranged, resulting in a higher mixing of Fuel and combustion air when passing through the vortex grid leads. With increased security against a flashback but it may be cheaper, the tubes downstream to arrange the swirl vanes.

Preferably, the burner is a gas turbine burner, in particular for a stationary gas turbine with a power greater than 50 MW. A gas turbine has a compressor on, the air is highly compressed and fed to the burner. The burner opens into a gas turbine combustor, in the the burner flame is included. That in the combustion chamber generated hot exhaust gas then flows into a turbine part, in the turbine blades are flowed around by the hot gas. On a Turbine shaft arranged moving blades, driven from the hot gas, the turbine shaft into rotation. Especially at large stationary gas turbines are demanding in terms of low pollutant emissions and in terms of low tendency to form combustion oscillations posed.

Preferably, the burner has a central, from Vormischkanal enclosed diffusion burner on.

The object directed to a method according to the invention solved by specifying a method for operating a gas turbine with a burner for burning a fuel in air, which burner is an annular Vormischkanal in which the fuel in a radial distribution is initiated, the radial distribution depending on the operating state of the gas turbine is set.

The advantages of this method are found in accordance with the above comments on the advantages of the burner.

Preferably, at a partial load operation of the gas turbine a radial distribution is set so that an area a local maximum in the radial distribution of the fuel concentration forms in the fuel-air mixture.

It is preferred for a full-load operation of the gas turbine a radial distribution adjusted so that a homogeneous mixture concentration of fuel and air results.

It is preferred when a combustion vibration occurs with an amplitude that is a predetermined limit exceeds the radial distribution changed.

The invention will become more apparent by way of example with reference to the drawings explained.

Figur 1

eine Gasturbine

Figur 2

einen Vormischbrenner nach dem Stand der Technik,

Figur 3

einen Längsschnitt durch einen Vormischkanal eines Vormischbrenners nach dem Stand der Technik,

Figur 4, 5

einen Ausschnitt eines Längsschnittes durch einen Vormischkanal,

Figur 6, 7

einen Längsschnitt durch einen Vormischkanal,

Figur 8

einen Ausschnitt eines Querschnittes durch einen Vormischkanal,

Figur 9

einen Ausschnitt eines Längsschnittes durch einen Vormischkanal.

They show partly schematically and not to scale:

FIG. 1

a gas turbine

FIG. 2

a premix burner according to the prior art,

FIG. 3

a longitudinal section through a premixing channel of a premix burner according to the prior art,

FIG. 4, 5

a section of a longitudinal section through a premixing channel,

FIG. 6, 7

a longitudinal section through a premixing channel,

FIG. 8

a section of a cross section through a premixing channel,

FIG. 9

a section of a longitudinal section through a premixing channel.

The same reference numerals have in the various figures same meaning.

FIG. 1 shows a gas turbine 1. The gas turbine 1 has a common turbine shaft 8 arranged a compressor 3 and a turbine part 7. Between compressor 3 and turbine part 7, an annular combustion chamber 5 is connected. In the Annular combustion chamber 5 open around the circumference distributed a number of premix burners 9. Premix burners 9 become air 11 supplied from the compressor 3 highly compressed. Continue supplied to the premix burner 9 fuel 13. Air 11 and Fuel 13 are mixed and via the premix burner. 9 introduced into the combustion chamber 5, where it is a hot gas 15th to be burned.

Figure 2 shows a premix burner 9. This is along an axis 10 directed. The premix burner 9 has a annular Vormischkanal 21. The premix channel 21 surrounds a central diffusion burner 23. The premix channel 21 has an annular central surface 22, which in cross section forms an angle to the burner axis 10. The premix channel 21 has a radially outer outer surface 18th and a radially inner inner surface 20. In radial Direction over the entire cross-section of the premix channel 21, i.e. extends perpendicular to Vormischkanalmittelfläche 22 an annular swirl lattice 25, which consists of individual Swirl vanes 26 is constructed. Continue to protrude in radial Direction starting from the diffusion burner 23 fuel inlet tube 27 in the premix channel 21. The fuel inlet tube 27 are hollow and have inlet openings 29 on.

In the burner of the prior art in Figure 2 is Air 11 passed through the premixing channel 21. The air 11 flows past the fuel inlet tube 27. The fuel inlet tube 27, fuel 13 is supplied to the interior, which from the inlet openings 29 into the air 11th exit. The air 11 is above the swirl blades 26 in Twist lattice 25 gives a twist, which is a combustion stabilization serves. The swirl vanes 26 are designed to that they also fuel 13 can be fed. About not inlet openings on the surface of the Swirl blade 26 is also fuel 13 in the air 11th embedded in the premix channel 21. Fuel 13 and air 11 are mixed in Vormischkanal 21 to a fuel-air mixture 28, which emerges from the premix burner 9 and burned there in a combustion zone. At a lean premix combustion, i. with relatively little fuel 13 in the air 11, such premix combustion tends to instabilities at the flame, i. it comes to fluctuations or even to extinguish the flame. For stabilization This combustion often becomes the central diffusion burner 21 used, which also air 11 and fuel 13 are supplied. These are, however, essentially first mixed in the combustion zone, with a is chosen fatter mixture. With the flame of the diffusion burner 23, premix combustion can be stabilized. The premix burner 9 shown in FIG. 2 becomes fuel 13 in a fixed, static distribution in the premix channel 21 initiated.

Figure 3 shows a section of a longitudinal section through a premixing channel according to the prior art. It is a Section through a swirl blade 26 of the swirl lattice 25 shown. From an annular, radially inward, i. in the area the inner surface 20 of the Vormischkanals 21 is an annular Fuel supply line 41 is arranged. From this annular Fuel supply line 41 becomes fuel 13 the swirl vanes 26 supplied. The swirl vanes 26 are all the same Arrangement and the same opening cross-section at their inlet openings 29 on.

Figure 4 shows in a section of a longitudinal section through the premixing channel 21 a comparison with Figure 3 changed arrangement, which becomes clear together with Figure 5. FIG. 4 and FIG FIG. 5 each show a section through two adjacent ones Swirl vanes 26, i. FIG. 4 shows a first swirl blade 26 and Figure 5 an adjacent swirl blade 26th In the swirl blade 26 of Figure 4, the opening cross sections change the inlet openings 29, and indeed the opening cross sections in the direction of the inner surface 20th of premix channel 21, i. not in the direction of here illustrated axis 10, larger. In contrast, the opening cross sections the inlet openings 29 of the illustrated in Figure 5 Twist bucket 26 smaller in the same direction. For each two adjacent swirl vanes 26 of the Twist lattice 25 thus change the opening cross sections the inlet openings 29 in the opposite direction, i. on a blade 26 will enlarge in the direction of the axis 10 Inlet openings 29 are each followed by a swirl blade 26 with inlet openings 29, whose opening cross-sections downsize in the direction of the axis 10. The swirl blades 26 of FIG. 4 form a first part 31 of inlet devices for the admission of fuel 13 in the Vormischkanal 21. The swirl vanes 26 of Figure 5 form a second part 33 of inlet devices to the inlet of fuel 13 in the premixing channel 21.

FIGS. 6 and 7 show, like the inlet devices 31, 33 are supplied with the fuel 13. The first part 31 the inlet device is made of an annular fuel supply line 43 supplied between the diffusion burner 23 and the premixing channel 21 is arranged. The second Part 33 is a second, independent annular Fuel supply line 45 supplied with fuel 13. The second annular fuel supply line 45 is the first fuel supply line 43 arranged immediately adjacent.

With the configuration introduced in this way, it is now the first time possible, during the operation of the burner, the radial distribution of fuel in the premix channel 21 to change. This happens through a changing fuel addition to the Inlet devices 31, 33 by means of the fuel supply lines 43, 45. By the opposite change in the opening cross sections in the inlet devices 31, 33, almost any one can any desired radial distribution of fuel 13 in Premix channel 21 can be adjusted. For example, in a partial load operation of the first part 31 of the inlet devices more fuel 13 are fed, due to the in the direction of the axis 10 magnifying opening cross sections the inlet opening 29 to an enrichment of Fuel toward the inner surface 20 of the Vormischkanals 21 leads. This can be done by means of local enrichment favorably acted upon a reduced carbon monoxide development become. In contrast, z. B. in a full load operation the second part of the intake devices more fuel be fed, resulting in a more homogeneous distribution of fuel 13 in Vormischkanal 21 leads. The in Direction of the outer surface 18 of the premixing channel 21 widening Inlet openings 29 carry mass flow of Air 11 in the radially outer part in the direction of the Outer surface 18 in Vormischkanal 21 account, so that by this increasing opening cross-sections a radial Distribution of fuel 13 in Vormischkanal 21 set that is the most homogeneous mixture of fuel possible 13 and 11 air entails. Further could be about also the radial distribution of the fuel 13 then changed be when a combustion vibration in the combustion chamber. 5 occurs that exceeds a certain threshold amplitude. Such combustion vibrations may be due to flame instabilities and a feedback of pressure fluctuations and form dense fluctuations in the fuel-air mixture. By changing the radial distribution of the fuel 13 in the air 11, this feedback mechanism can be interrupted and suppress the combustion vibrations thereby become.

Figure 8 shows again in a section of a cross section through the Vormischkanal 21, the changing arrangement the first part 31 of inlet devices and the second one Part 33 of inlet devices each formed as Swirl vanes 26 in the swirl lattice 25. One recognizes the opposite Change of the opening cross-section of the inlet openings 29 in the radial direction.

FIG. 9 shows another possible configuration of the arrangement the first part 31 and the second part 33 of the inlet devices. A section through a longitudinal section through the premix channel 21 points in the flow direction of the Air 11 arranged one behind the other, the first part 31 and the second part 33 of the inlet devices. The first part 31 This is made up of tubes, which are in the Vormischkanal 21 protrude. The second part 33 is made of swirl blades 26 educated. The opening cross sections of the inlet openings 29 turn in opposite directions, i. towards the Increase axis 10 or toward the inner surface 20 the inlet openings 29 of the first part 31 of the inlet devices, while the opening cross sections of the inlet openings 29 of the second part 33 of the inlet device zoom out in the direction of the axis 10. Through this axial Graduation of the first part 31 and the second part 33 of the Inlet devices may also fuel 13 in the circumferential direction be introduced very evenly in Vormischkanal 21.

Claims (15)

Along an axis (10) directed burner (9) with an annular Vormischkanal (21), in the fuel (13) radially distributed is introduced,
characterized in that
the radial distribution of the fuel (13) during operation of the burner (9) is adjustable. Burner (9) according to claim 1,
in which inlet devices (31, 33) are provided, distributed over the circumference of the premixing channel (21), for a radial inlet of fuel (13) lying at the respective circumferential position by means of inlet openings (29) arranged in the radial direction and having a respective opening cross-section a first part (31) of the inlet devices, the opening cross-sections increase in the direction of the axis (10) and in a second part (33) of the inlet devices decrease the opening cross-sections. Burner (9) according to claim 2,
in which the inlet devices of the first part (31) and the second part (33) are arranged alternately along the circumference of the premixing channel (21). Burner (9) according to claim 2,
in which the inlet devices of the first part (31) and the second part (33) follow one another in the axial direction of the premixing channel (21). Burner (9) according to one of the preceding claims,
with a first (43) and a second (45) about the axis (10) extending fuel supply, wherein a pressure difference of the fuel pressure in the two fuel supply lines (43,44) to each other depending on the operating state of the burner (9) is adjustable. Burner (9) according to claim 5 and one of claims 2 to 4,
in which the first part (31) of the inlet devices is connected to the first fuel feed line (43) and the second part (33) of the inlet devices is connected to the second fuel feed line (45). Burner (9) according to one of claims 2 to 6,
in which the inlet devices (31, 33) are tubes projecting radially into the premixing channel (21), into the interior of which the fuel (13) is supplied. Burner (9) according to one of claims 2 to 6,
in which the inlet devices (31, 33) are radially in the premixing channel (21) projecting swirl vanes (26), inside which the fuel (13) is supplied. Burner (9) according to claim 4,
in which the first part (31) of the inlet devices is formed from tubes projecting radially into the premixing channel (21) and the second part (33) of the inlet devices is formed from swirl vanes (26) projecting radially into the premixing channel (21). Burner (9) according to one of the preceding claims, designed as a gas turbine burner, in particular for a Stationary gas turbine (1) with a capacity greater than 50 MW. Burner (9) according to one of the preceding claims, with a central, by Vormischkanal (21) enclosed Diffusion burner (23). Method for operating a gas turbine (1) with a burner (9) for combustion of a fuel (13) in air (11), which burner (9) has an annular premixing duct (21) into which the fuel (13) in a radial Distribution is initiated,
characterized in that
the radial distribution is adjusted depending on an operating state of the gas turbine (1). Method according to claim 10,
wherein at a part load operation of the gas turbine (1), a radial distribution is set so that a range of a local maximum in the radial distribution of the fuel concentration in the fuel-air mixture (28) is formed. Method according to claim 10,
in which, in a full-load operation of the gas turbine (1), a radial distribution is set so that a homogeneous mixture concentration of fuel (13) and air (11) results. Method according to one of claims 12 to 14,
wherein, upon the occurrence of a combustion vibration having an amplitude exceeding a predetermined limit, the radial distribution is changed.

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