EP1463911B1 - Burner with sequential fuel injection - Google Patents

Description

TECHNICAL AREA

The present invention relates to a burner, e.g. a double-cone burner, with special injection of fuel into the combustion air stream, in which the formation of thermoacoustic vibrations is largely avoided. Furthermore, the present invention relates to a fuel lance for such a burner and a method for operating a premix burner, which reduces the formation of thermoacoustic vibrations.

STATE OF THE ART

In burners, which supply liquid or gaseous fuel to a combustion chamber where the fuel burns at a flame front, so-called thermoacoustic fluctuations often occur. This is especially true if the burners are operated with high air numbers. So also, for example, but not exclusively, in the very successfully used so-called double-cone burner, as in the EP 0 321 809 is described. Also, such thermoacoustic vibrations occur Premix burners with downstream mixing section, as for example in the EP 0 704 657 be described on. In addition to the fluidic stability, mixture rupture fluctuations are a major reason for the occurrence of such thermoacoustic instabilities. Fluid-mechanical instability waves, which arise at the burner, lead to the formation of vortices (coherent structures), which influence the combustion and can lead to periodic heat release with the associated pressure fluctuations. The fluctuating air column in the burner leads to fluctuations in the mixing fraction with the associated fluctuations in the heat release. Such fluctuations can also be caused by alternating flame front positions.

Another excitation mechanism for thermoacoustic oscillations is given if, with proper phase position (the so-called Rayleigh criterion must be met, see below), local variations in heat release are coupled with variations in the mixture fraction across the fluctuating air column in the burner.

Frequently, in such burners several fuel injectors are provided which are arranged in groups, so as to ensure stable combustion in different load ranges, for. B. special pilot nozzles for the lower load range. In this case, the flame position can shift significantly depending on the type of piloting, and in such a case, it can also come in transition areas to thermoacoustic fluctuations by periodic change in the flame front positions.

These thermoacoustic vibrations pose a threat to any type of combustion application. They result in high amplitude pressure oscillations, a limitation of the operating range, and can increase pollutant emissions. This is especially true for combustion systems with low acoustic attenuation, such. B. annular combustion chambers with reverberant walls. In order to allow high power conversion over a wide operating range in terms of pulsations and emissions, active control of combustion oscillations may be necessary.

Coherent structures play a crucial role in mixing processes between air and fuel. The dynamics of these structures consequently influence the combustion and thus the heat release. By influencing the shear layer between the fresh gas mixture and the recirculated exhaust gas, a control of the combustion instabilities is possible (eg. Paschereit et al., 1998, "Structure and Control of Thermoacoustic Instabilities in a Gas Turbine Burner", Combustion, Science & Technology, Vol. 138, 213-232 ). One possibility is the acoustic stimulation ( EP 0 918 152 A1 ).

By means of fuel staging, the flame position can be influenced and thus the influence of flow instabilities as well as time lag effects reduced (eg in the EP 0 999 367 A1 described). Another method with multiple fuel holes describes the WO0196785A1 , at least one first fuel supply having a first group of fuel outlets for a first amount of premix fuel, wherein the first group of fuel outlets is arranged substantially in the direction of a burner axis, and at least one second fuel supply with a second group of fuel Outlets for a second quantity of premix fuel, wherein the second group of fuel discharge openings is arranged substantially in the direction of the burner axis.

Another mechanism that can lead to thermoacoustic oscillations are fluctuations in the mixture break between fuel and air.

PRESENTATION OF THE INVENTION

The invention is therefore an object of the invention to provide a burner, means for injecting fuel into a burner, and a method for operating a burner, in which the occurrence of such thermoacoustic vibrations is reduced or even avoided.

This object is achieved by a method according to claim 1 and a burner according to claim 5.

In such a burner or such method, according to the invention, thermoacoustic oscillations are reduced or even completely avoided by means projecting from the burner base in the direction of the combustion chamber into the interior, which means injecting fuel over at least two fuel injection holes distributed over the length of the means allow the combustion air flow, so that the delay time between injection of the fuel and its combustion at the flame front corresponds to a, in particular systematically varying, distribution, which avoids combustion-driven vibrations in premixing. The injected fuel may be liquid or gaseous fuel.

In a conventional burner, experience has shown that the delay time τ between injection location and effective combustion at the flame front is essentially the same for all fuel nozzles distributed over the burner length. One finds one from the one unsystematic slight variation around a mean value. As a result, thermoacoustic vibrations can easily build up. The essence of the invention is thus to inject the fuel into the combustion air flow via means arranged in the interior in such a way that the same delay time τ between injection location and effective combustion at the flame front does not occur for all fuel nozzles distributed essentially over the burner length Delay takes a particular on the burner length systematically varying distribution.

A first preferred embodiment of the burner is characterized in that the means is a fuel lance which is arranged substantially on the axis of the burner and which has fuel injection holes in particular along its surface. Preferably, the fuel lance has a substantially cylindrical cross-section, wherein the fuel injection holes are distributed on the fuel lance both with respect to the length of the fuel lance and with respect to its circumferential arrangement. In this case, the delay time dispersion can be set almost arbitrarily with a suitable choice of the injection location and the fuel penetration depth, so that different streamlines can be fed. About this central, projecting into the interior pipe, which z. B. from coaxial nested tubes can be formed, the stepped injection can be made in a simple and efficient manner. If coaxial nested tubes find application, then z. B. in the central tube with the smallest diameter of the pilot fuel (gaseous or liquid) are supplied, since typically a pilot nozzle is arranged at the top of the lance, and in the outermost space between the pipe with the largest diameter and the next inner tube of the fuel, which in premixing is to be injected through the fuel injection holes in the interior. In other words, the often existing pilot lance, which is provided for the piloted operation of the burner, can be advantageously used as a fuel lance after slight modification for injecting fuel in a staged manner during premixing operation. For this purpose, in particular an elongated pilot lance, as used for example in the writings EP-A2-0 778 445 in the case of a double-cone burner and in WO 93/17279 such as EP-A2-0 833 105 for premix burner without resp. be described with downstream mixing section.

According to the present invention, the means protrude far into the mixing section of the burner. In essence, the length of the fuel lance is limited by the length of the lance base to the flame position in the combustion chamber in premix operation. The further the fuel lance protrudes into the interior of the burner, the more distributions of the delay time can be achieved. The more fuel that can be introduced in a distributed manner via the fuel lance into the combustion air flow in relation to the fuel injected, for example, at air inlet slots, the more efficiently thermoacoustic vibrations can be avoided.

According to a further preferred embodiment, the burner is a cone burner, in particular a double-cone burner, in which the burner is arranged offset from one another by at least two hollow partial cone bodies positioned one above the other in the flow direction, and which partial cone bodies are arranged offset from one another, so that the Combustion air flows through a gap between the part cone bodies in the interior, is formed. In other words, the inventive concept in burners, as described for example in the EP-B1-0 321 809 , of the EP-A2-0 881 432 or in a very general form in the EP-A1-0 210 462 are described, find application.

According to another preferred embodiment, it is a four-slot burner, in other words, the inventive concept in a burner, as for example in the EP-A2-0 704 657 or in the EP-A2-0 780 629 is described, find application.

Another embodiment of the burner is characterized in that the fuel injection holes are divided into groups each having a group of fuel injection holes is arranged such that all nozzles of the group feed a specific area of the flame front with different time delay. Typically, it is possible, for example, to provide a total of 2n fuel injection holes on the means, which in particular are divided into n groups with 2 nozzles each and can be individually controlled as groups.

Further preferred embodiments of the burner according to the invention are described in the dependent claims.

The present invention also relates to a method for injecting fuel into a burner, according to claim 1. Here, fuel is at least partially projecting from the burner base substantially in the direction of the combustion chamber into the interior means which injecting fuel over at least two of the Length of the means allow distributed fuel injection holes in the combustion air flow, injected, so that the delay time between injection of the fuel and its combustion at the flame front corresponds to a distribution which avoids combustion-driven vibrations in premixing operation. Typically, the maximum time delay (τ _max ) between injection location and flame front is in the range of τ _max = 5-50 ms, and at a flow rate of the fuel / air mixture in the interior in the range of 20-50 m / s is the maximum time delay (τ _max ) in the range of τ _max = 5 - 15 ms.

In the method according to the invention, the fuel is injected in such a way that the time delay distribution over the burner length towards the burner end is designed to be substantially linearly decreasing from the maximum value τ _max by a maximum draft difference Δτ to a minimum value at the burner end of τ _max -Δτ. This is delay difference Δτ in the range of 10-90% of the maximum value τ _max , in particular in the range of more than 50% of the maximum value τ _max .

Further preferred embodiments of the method according to the invention are described in the dependent claims.

BRIEF EXPLANATION OF THE FIGURES

Fig.1a

einen konventionellen Doppelkegelbrenner mit typischer Brennstoffeindüsung;

Fig. 1b

die bei einem Brenner nach Fig. 1a auftretende schematisierte Verzugszeitverteilung über die Brennerlänge;

Fig. 2

eine lineare Verzugszeitverteilung;

Fig. 3

eine zweidimensionale Stabilitätsanalyse von Verzugszeitverteilungen;

Fig. 4

einen Doppelkegelbrenner mit im Innenraum des Brenners angeordneten Mitteln zur Eindüsung von Brennstoff;

Fig. 5

einen Vierschlitzbrenner mit nachgeschalteter Mischstrecke mit im Innenraum des Brenners angeordneten Mitteln zur Eindüsung von Brennstoff.

Fig. 6

eine erste Ausführungsform eines weiteren Brenners mit erfindungsgemässen zentralen Mitteln zur Eindüsung von Brennstoff und

Fig. 7

eine zweite Ausführungsform eines weiteren Brenners mit erfindungsgemässen zentralen Mitteln zur Eindüsung von Brennstoff.

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. Show it:

1a

a conventional double-cone burner with typical fuel injection;

Fig. 1b

after a burner Fig. 1a occurring schematized delay time distribution over the burner length;

Fig. 2

a linear delay time distribution;

Fig. 3

a two-dimensional stability analysis of delay time distributions;

Fig. 4

a double-cone burner with arranged in the interior of the burner means for injection of fuel;

Fig. 5

a four-slot burner with downstream mixing section with arranged in the interior of the burner means for the injection of fuel.

Fig. 6

a first embodiment of another burner with inventive means for injecting fuel and

Fig. 7

a second embodiment of another burner with inventive means for injecting fuel.

Only the elements essential to the invention are shown. Identical elements are denoted the same in different figures.

WAYS FOR CARRYING OUT THE INVENTION

nicht mehr erfüllt ist, d.h. Wärmefreisetzung und Druckmaximum nicht mehr in Phase sind. Damit ist ein wesentlicher treibender Mechanismus für die Anregung von thermoakustischen Schwingungen unterbunden, da sonst bei entsprechendem Zeitverzug bzw. entsprechender Phasenlage die Druckfluktuationen an der Brennstoffeindüsung zu Variationen im Mischungsbruch und damit zu fluktuierender Wärmefreisetzung führen können. Die Darstellung des Rayleigh-Kriteriums nach Fouriertransformation im Frequenzbereich zeigt diesen Zusammenhang noch deutlicher: $$G\left(x\right)=2\int \left|S_{\mathit{pq}}\left(x,f\right)\right|\cos \left({\phi }_{\mathit{pq}}\right)\mathit{df}$$

wobei S_pq (x,f) das Kreuzspektrum zwischen Druckfluktuationen p' (x,t) und Fluktuationen der Wärmefreisetzung q' (x,t) darstellt und φ_pq die Phasendifferenz. Durch Wahl der korrekten Phasendifferenz zwischen Wärmefreisetzung (beeinflussbar durch den Zeitverzug) und dem Drucksignal kann der Rayleigh-Index auf G(x) < 0 eingestellt werden und damit ist das System gedämpft.If one influences the time lag between the fuel injection and the periodic heat release, ie the flame front, one can control the combustion instabilities. The basic idea of the invention is to disrupt the time delay τ between the periodic heat release at the flame front and the pressure fluctuation during the injection, so that the Rayleigh criterion $$G\left(x\right)=\frac{1}{T}\underset{0}{\overset{T}{\int }}\mathit{p\text{'}}\left(x,y\right)\mathit{q\; \text{'}}\left(x,t\right)\mathit{dt}<0$$

is no longer satisfied, ie heat release and maximum pressure are no longer in phase. This prevents an essential driving mechanism for the excitation of thermoacoustic oscillations, since otherwise the pressure fluctuations at the fuel injection can lead to variations in the mixing fraction and thus to fluctuating heat release with a corresponding time delay or corresponding phase position. The representation of the Rayleigh criterion after Fourier transformation in the frequency domain shows this relationship even more clearly: $$G\left(x\right)=2\int \left|S_{\mathit{pq}}\left(x,f\right)\right|\cos \left({\phi }_{\mathit{pq}}\right)\mathit{df}$$

where S _pq (x, f) represents the cross spectrum between pressure fluctuations p '(x, t) and fluctuations in heat release q' (x, t) and φ _{pq represents} the phase difference. By choosing the correct phase difference between heat release (influenced by the time delay) and the pressure signal, the Rayleigh index can be set to G (x) <0 and thus the system is muted.

It now appears that the time delay from the injection location at the fuel nozzles to the flame front in existing premix burners is constant over the entire injection length of the premix gas at certain operating points. For example, in a double-cone burner according to the prior art as in Fig. 1a shown.

In this example to be understood longitudinal section through a double-cone burner 1, as for example from the EP 0 321 809 is known, the upper gap 7 between the two conical burner shells 8 and 9 can be seen. The combustion air 23 passes through this gap 7 to the distributed over the burner length fuel nozzles 6 over into the interior 22, wherein the fuel is detected and enclosed by the passing air 23. In the interior 22 of the burner 1, the combustion air stream flows to form a conical fuel column which propagates in the direction of flow along the stomina lines 5. The fuel / air mixture then enters the combustion chamber 2, where it ignites at a flame front 3. The flow in the burner interior 22 to the flame front 3 follows the streamlines as in Fig. 1a shown.

In such a double-cone burner, the delay time τ, which elapses between the injection at the fuel nozzles 6 to the ignition at the flame front 3, nearly constant for all positions of the fuel nozzles, as in Fig. 1b is shown schematically (the coordinate x extends from the output 10 of the burner 1 to its rear end, ie to the burner base 27, ie in the FIG. 1 a from right to left). In other words, no systematic variation of the delay times τ as a function of the fuel nozzle position along the burner 1 can be observed (eg shorter delay times for nozzles 6 near the burner exit 10), but rather a more or less random distribution which fluctuates only a little as a function of injection location x.

As in Fig. 2 is shown, it is now proposed to set a distribution of the delay time over the burner length instead of the previously substantially constant time delay from the fuel injection 6 to the flame front 3. The distribution is set in a first choice so that the delay times τ linearly varies by a delay time difference Δτ, linearly increasing from a minimum τ _max -Δτ to the maximum in the rear burner region of τ _max .

In a two-dimensional representation is in Fig. 3 the burner stability as a function of the parameters Δτ (x-axis) and τ _max (y-axis) for a delay time distribution as in Fig. 2 specified. Basically, it can be seen that both changes in the maximum value as well as variations in the time delay spread can strongly influence the stability of the burner. As an example, three values for the behavior at different flow velocities in the burner are given as individual measured values: for low flow velocity 17, for average flow velocity 18, and for high flow velocity 19. In general, it turns out that two fundamentally unstable, in Fig. 3 train hatched areas. On the one hand, an unstable region 16 short delay times. Almost regardless of the choice of Δτ, the burner is not acoustically stable here for such high flow velocities. A second, island-like region 13 of unstable behavior is found for low velocities, ie high values of τ _max , and for small values of Δτ.

In principle, it can be seen that the stability of a burner, which operates with its typical operating values mostly close to the island 13, can be stabilized both by an increase in the flow velocity according to arrow 15, and by an increase in the delay time difference Δτ, ie by a shift in the Operating point in the graph according to arrow 14 to the right. Because of practical reasons the value of τ _max can not always be shifted into the stable low range according to Fig. 15 (see below) is a shift by setting increased delay time differences Δτ ie over more spread delay times, often an efficient and viable alternative. Typically, the operating point for operating a gas turbine at base load is at Fig. 3 This point lies in the boundary between stable and unstable combustion and can be stabilized in principle both by variations in the maximum value, as well as by a change in the scattering. Variations in the maximum value generally depend on different flow velocities in the burner, ie with variations in performance. These are generally given by the operation of the gas turbine and are often difficult to influence in existing gas turbine designs.

Typically, the delay times for burners are in the range of τ = 5-50 ms, for double-cone burners normally in the range of 5-15 ms at flow rates of 10-50 m / s. In four-slot burners with a downstream mixing section, the delay times are usually in the range of 5 to 50 ms at flow velocities of 10 to 100 m / s. Δτ can now be varied within a wide range, typically variations of Δτ = 0.5 τ _max or more prove to be particularly advantageous, both in double-cone burners and in four-slot burners with a downstream mixing section.

Technically, such a distribution can be implemented on a double-cone burner serving as an exemplary embodiment, as already described in US Pat Fig. 1 represented by a fuel injection into the combustion air stream 23 by means of a fuel lance 24, as in Fig. 4 is shown. The fuel lance 24 protrudes from the burner base 27, starting in the interior 22 of the double-cone burner 1. The fuel lance is arranged substantially on the axis of the double-cone burner 1, has a cylindrical shape and distributed on its radial surface fuel injection holes 25. The fuel injection holes 25 are over the length of the fuel lance 24 distributed. In addition, the holes 25 are also distributed on the circumference, either in the form of rings, or, as in Fig. 4 shown in offset form. In this case, the delay time spread can be set almost as desired with an appropriate choice of the injection location and the fuel penetration depth. Also different streamlines 5 within the burner 1 can be spied. The maximum delay time τ _max occurring in such a burner 1 is, as in FIG Fig. 4 indicated by the ratio of the maximum distance L between fuel injection and flame front 3 given the flow velocity U in the burner. The maximum distance L is usually the distance between nearest to the burner base 27 arranged fuel nozzle 6 and the flame front 3. Considering now fuel which is injected via the Brennstoffindüsungslöcher 25 of the fuel lance 24 in the combustion air stream 23, it turns out that about the distance of two Brennstoffindüsungslöchern 25 a time delay Δτ comes about, which corresponds to the ratio of the distance .DELTA.L between two Brennstoffindüsungslöchern 25 and the flow velocity U of the combustion air stream 23 in the burner 1 (Δτ = .DELTA.L / U). In this way, by the distribution of the holes 25, the desired distribution profile 12 can be adjusted. In particular, a scattering of the delay time should be aimed at, which reaches or exceeds half the maximum value, Δτ ≥ 0.5 τ _max . Depending on the extent to which thermoacoustic oscillations effectively represent a problem in a certain operating state, the ratio of fuel injected via fuel nozzles 6 at the air inlet slots 7 to fuel injected via the fuel injection holes 25 can be adjusted and regulated in situ. In any case, it is provided that the fuel injected via the fuel lance 24 at least partially replaces the fuel which is injected via the fuel nozzles 6.

In particular, the maximum scattering Δτ proves to be important with regard to the prevention of thermoacoustic oscillations, while the distribution function of τ usually plays a rather minor role. Even a small proportion of in the range of 5 - 30% of the total fuel mass flow, which is injected via the lance, may be sufficient to stabilize the flame by the scattering.

The maximum width over which a distribution 12 is adjustable is essentially predetermined by the length of the fuel lance 24. Satisfactory results with respect to the prevention of thermoacoustic vibrations can be achieved with fuel lances 24 which extend at least to half the conical section of the burner, but the lance 24 is preferably longer and extends over 3/4 of the length of the burner or even over the entire length of the burner. In principle, the lance can extend to the location at which the flame front 3 is located in the premixing mode.

Advantageously, the fuel lance 24 is simultaneously used as a pilot lance, that is, the fuel lance 24 also has the ability to produce a diffusion flame as close as possible to the existing during premixing flame position for the piloted operation in the lower load range. Or it can be used a lance, which is intended for the oil operation of the premix burner. Suitable is, for example, an extended pilot lance, as z. B. in the writings EP-A2-0 788 445 in the case of a double-cone burner, in WO 93/17279 in the case of an inverted double cone burner with a cylindrical outer shape and in EP-A2-0 833 105 in the case of an inverted double-cone burner with cylindrical outer shape and downstream mixing section is described. Two exemplary different embodiments of a reverse bicone burner according to the present invention are in the two Fig. 6 and Fig. 7 shown. With regard to the geometry and the dimensioning of such a pilot lance, in particular the disclosure of the EP-A2-0 788 445 explicitly included in this application.

The fuel lance 24 is advantageously formed in the form of nested, concentric cylindrical tubes, wherein in the central tube with the smallest diameter of the pilot fuel (gaseous or liquid) respectively the oil fuel flows in the case of piloted operation respectively oil operation, while in the space between the outer tube and the next inner Pipe the fuel is supplied to the injection via the fuel injection holes 25. It is also possible to divide the individual fuel injection holes 25 into individually controllable groups in order, if appropriate, to be able to adjust or regulate the distribution 12 variably and the operating conditions of the premix burner.

Another embodiment is in Fig. 5 shown. This is a four-slot burner, ie a premix burner, which has four conical elements and thus four air inlet slots 7. The burner also has a downstream mixing section 26, which is cylindrical and also in Fig. 5 having not shown, extending in the flow direction transition channels. Such a burner is for example in the EP-A2-0 704 657 and in the EP-A2-0 780 629 shown. Even with such burners, a similar problem arises, namely that the delay time dispersion in the fuel injection via the fuel nozzles 6 is small in comparison to the maximum value τ _max . The fuel lance 24 protrudes in this case not only over the length of the conical section in the burner, but still far into the mixing channel 26 into it. In principle, it is also desirable in this case to make the fuel lance so long that at least one time delay Δτ is attained, which reaches or exceeds half the maximum value, ie Δτ ≥ 0.5 τ _max . This means that the lance 24 should have a length which corresponds to at least half the length of conical portion + mixing distance 26. Due to the large length of the fuel lance 24, the delay time spread can be varied within a wide range, which allows a stable burner behavior over an extended operating range.

NAME LIST

1

Double-cone burner

2

combustion chamber

3

flame front

4

Wall of the combustion chamber

5

Streamlines of the fuel / air mixture

6

fuel nozzles

7

Gap between the conical burner shells

8th

Inner conical burner bowl at 7

9

Outer conical burner bowl at 7

10

Front end of the double cone burner

11

Constant time delay

12

Delay distribution

13

Unstable range of high delay times

14

Stabilizing shift after large distribution widths

15

Stabilizing shift after short delay times

16

Unstable range of short delay times

17

Behavior at low flow velocity

18

Behavior at medium flow rate

19

Behavior at high flow velocity

21

Adjustable time delay range

22

inner space

23

Combustion air flow

24

pilot lance

25

Holes in pilot lance, fuel injection holes

26

downstream mixing section

27

Brenner base

Claims (13)

1. A method for injecting fuel into a burner (1), which burner (1) comprises an inner space (22) enclosed by at least one shell (8, 9), in which fuel is injected through fuel nozzles (6) into a combustion air flow flowing in the inner space (22), the fuel/air mixture formed flows within a delay time (T) to a flame front (3) into a combustion chamber (2) and ignites there, wherein the fuel is injected, at least partially, through means (24) projecting from the burner base (27) essentially in the direction of the combustion chamber (2) into the inner space (22) via at least two fuel injection holes (25) distributed over the length of the means (24), wherein the burner (1) has a mixing section (26) arranged downstream of the inner space (22), wherein the delay time (T) between the injection of the fuel and its combustion on the flame front (3) varies to the extent that a partial delay distribution (12) takes place over the burner length (x) from the burner base (27) to the burner end (10), reducing from the maximum value T_max by a maximum delay difference (ΔT) to a minimum value at the burner end (10) of T_max - ΔT, and wherein the delay difference (ΔT) ranges from 10-90% of the maximum value (T_max), characterised in that the means (24) project far into the mixing section (26).
2. The method according to Claim 1, characterised in that fuel is injected into different flow lines (5) inside the burner (1) through different fuel injection holes (25).
3. The method according to Claim 1, characterised in that the fuel is injected in such a manner that the partial delay distribution (12) takes place over the burner length (x) to the burner end (10) reducing essentially linearly by a maximum delay difference (ΔT) from the maximum value T_max to a minimum value at the burner end (10) of T_max - ΔT.
4. The method according to Claim 1, characterised in that the delay difference (ΔT) lies within the range of over 50% of the maximum value (T_max).
5. A burner (1) for implementing the method according to any one of Claims 1 to 4, comprising an inner space (22) enclosed by at least one shell (8, 9), in which burner (1) fuel is injected through fuel nozzles (6) arranged on the burner shells (8, 9) into a combustion air flow (23) flowing in the inner space (22), the fuel/air mixture formed flows within a delay time (T) to a flame front (3) into a combustion chamber (2), and ignites there, and comprising means (24) with fuel injection holes (25) projecting from the burner base (27) essentially in the direction of the combustion chamber (2) into the inner space (22), wherein the means (24) have at least two fuel injection holes (25) distributed over the length of the means (24), through which fuel injection holes (25) a fuel can be injected into the combustion air flow (23) so that the delay time (T) between injection of the fuel and its combustion on the flame front (3) is different, and wherein the burner (1) has a mixing section (26) arranged downstream from the inner space (22), characterised in that the means (24) project far into the mixing section (26).
6. The burner (1) according to Claim 5, characterised in that the means (24) consist of a fuel lance which is arranged essentially on the axis of the burner (1).
7. The burner (1) according to Claim 6, characterised in that the fuel lance (24) has an essentially cylindrical cross-section, wherein the fuel injection holes (25) are distributed in relation to the length of the fuel lance (24) and in relation to its circumferential arrangement on the fuel lance (24).
8. The burner (1) according to any one of Claims 5 to 7, characterised in that fuel can be injected through different fuel injection holes (25) into different flow lines (5) inside the burner (1).
9. The burner (1) according to any one of Claims 5 to 8, characterised in that the means (24) comprise a pilot lance for the piloted operation of the burner.
10. The burner (1) according to any one of Claims 5 to 9, characterised in that the burner (1) is a cone burner, in particular a double cone burner, in which the burner (1) is formed from at least two hollow partial cone bodies (8, 9) positioned one on top of the other, which partial cone bodies (8, 9) are arranged offset to each other so that the combustion air (23) flows through a gap (7) between the partial cone bodies (8, 9) into the inner space (22).
11. The burner (1) according to Claim 10, characterised in that it is a four-slot burner.
12. The burner (1) according to any one of Claims 5 to 11, characterised in that the fuel injection holes (25) are divided into groups, wherein each group of fuel injection holes (25) is arranged so that all the nozzles (25) of the group feed a certain area of the flame front (3) with a variable time delay (7).
13. The burner (1) according to Claim 12, characterised in that the fuel injection holes (25) are individually controlled.

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