EP1918642A2 - Combustion chamber device - Google Patents

Abstract

The combustion chamber unit comprises a combustion chamber with a combustion space (14) and a number of resonator devices (22), which are arranged on the combustion chamber. The resonator devices are formed or arranged for suppression of tangential modes or combination modes with a tangential share. Two resonator devices are arranged on a combustion chamber axis at an angle, relative to one resonator device, where i is a natural odd number and n is an ordinal number of the tangential mode or the tangential share of the combination mode.

Description

The invention relates to a combustion chamber device comprising a combustion chamber with a combustion chamber and a plurality of resonator devices, which are arranged on the combustion chamber, wherein the resonator devices are designed and arranged for the suppression of tangential modes or combination modes with tangential.

In or on combustion chambers, in particular for missiles such as rockets, oscillating sub-processes of combustion can take place. The fuel supply may oscillate, the mixture formation of fuel and oxidizer may oscillate and the chemical reactions in the combustion chamber may oscillate. In the case of liquid fuel or a gel fuel, the atomization and evaporation may have oscillations.

The combustion chamber itself is a hollow body which has acoustic eigenmodes. It is basically possible that an acoustic coupling of the described oscillating processes takes place with eigenmodes of the combustion chamber. As a result, pressure pulsations may arise, which may, for example, damage the combustion chamber or disturb the combustion. It is even possible that the combustion extinguishes.

When combustion is disturbed, there is usually a reduction in performance. There is also the risk that the reliability is lowered and the service life is reduced. It can also increase the pollution and the sound pollution occur.

The acoustic properties of a combustion chamber can be influenced by the provision of one or more acoustic resonators as damping elements. These acoustic resonators can couple to eigenmodes of the combustion chamber in order to be able to shift eigenmodes into uncritical frequency ranges or to be able to dampen disturbing eigenmodes.

From the not pre-published German Patent Application No. 10 2005 035 085 dated July 20, 2005 and the not pre-published European Patent Application No. 06 117 462.9 of July 19, 2006 By the same Applicant a method for adjusting the acoustic properties of a combustion chamber is known in which the combustion chamber is provided with at least one acoustic resonator as a damping element and a first eigenmode of an output combustor-resonator combination below the eigenmode of the output combustion chamber and a second Eigenmode the output combustor-resonator combination is compared above the eigenmode of the output combustion chamber with respect to intensity and / or half width.

From the not pre-published German Patent Application No. 10 2005 050 029.3 of 14 October 2005 the same applicant is one A resonator device for a combustion chamber with a combustion chamber is known, which comprises a wall through which a resonator chamber is formed, wherein the resonator chamber is open at a first end face for connection to the combustion chamber by means of a first opening. The wall has a second opening on a second end face opposite the first end face.

Investigations on the eigenmodes of a cylindrical combustion chamber are given in the article " Resonance Frequencies and Damping in Combustion Chambers with Quarter Wave Cavities "by Z. Faragó and M. Oschwald, 6th Symposium on Launcher Technologies, November 8th to 11th, 2005, Münch en, described.

From the not pre-published German Patent Application No. 10 2006 007 711.3 of 14 February 2006 the same applicant is a combustion chamber with a combustion chamber and a resonator, which comprises one or more resonators and is used to adjust the acoustic properties of the combustion chamber, known. At least one resonator is tuned with an overtone to a natural mode of the combustion chamber.

The invention has for its object to provide a combustion chamber device of the type mentioned, which is simple in construction and for which natural vibrations of the combustion chamber can be effectively damped.

bezogen auf eine Brennraumachse angeordnet ist, wobei i eine ungerade natürliche Zahl und n die Ordnungszahl der Tangentialmode oder Tangentialbeteiligung der Kombinationsmode ist.This object is achieved according to the invention in that a first resonator device with one or more resonator devices and a second resonator device with one or more resonator devices are provided, wherein the second resonator device to the first resonator device at least approximately at an angle $\alpha =i\cdot \frac{90°}{n}$

is arranged on a combustion chamber axis, where i is an odd natural number and n is the ordinal number of the tangential mode or tangential component of the combination mode.

It has been found that by means of the arrangement according to the invention, tangential modes or combination modes with tangential participation can be effectively damped while minimizing the number of resonator devices. Each tangential mode of the combustion chamber occurs in a double version (σ-mode and π-mode). These double versions are coupled together because the print node of one mode is the speed node of the other mode. By means of the arrangement of the resonator devices according to the invention, all tangential modes of order n can be effectively damped. For example, σ modes and π modes can be effectively damped.

For damping a specific tangential mode of the combustion chamber with a specific natural frequency, basically two resonator devices are sufficient, which are arranged at an angle α to one another. The resonator devices can be tuned to the fundamental mode or an overtone of the corresponding tangential mode.

If additional tangential modes are to be damped, then the respective resonator devices should be arranged at the corresponding angle α to each other.

bezogen auf eine Brennraumachse zueinander angeordnet sind, wobei j eine gerade natürliche Zahl ist und n die Ordnungszahl der Tangentialmode oder der Tangentialbeteiligung der Kombinationsmode ist.The above-mentioned object is further achieved according to the invention in that at least one resonator device is provided with a group of resonator devices which at least approximately at an angle of 0 ° or $\mathit{\beta }=j\cdot \frac{90°}{n}$

relative to a combustion chamber axis are arranged to each other, wherein j is an even natural number and n is the ordinal number of the tangential mode or the tangential component of the combination mode.

If a plurality of resonator devices are provided in a resonator device, which are in particular adapted to one another, then an effective reduction in intensity of the corresponding tangential mode or combination mode can be achieved.

The solution in which at least one resonator device comprises a plurality of resonator devices, which are arranged correspondingly, can be combined with the solution of an angular arrangement of resonator devices.

The resonator devices are designed in particular as λ / 4 resonators or Helmholtz resonators. Such resonators can be easily produced and fixed to the combustion chamber.

In particular, the resonator devices each have a wall which delimit a resonator chamber, wherein the resonator chamber is connected to the combustion chamber via an opening. As a result, a coupling of the combustion chamber to the corresponding resonator chamber of a resonator device is possible in a simple manner.

In particular, a longitudinal axis of the respective resonator chamber is oriented transversely to the combustion chamber axis. The longitudinal axis of the respective resonator chamber is preferably perpendicular to the combustion chamber axis. As a result, a large number of resonator devices can be arranged on the combustion chamber.

It is favorable if the resonator chambers of the resonator device have substantially the same diameter. As a result, the combustion chamber device can be produced in a simple manner.

It is particularly advantageous if the first resonator device is arranged on a first sector region of the combustion chamber and the second resonator device on a second sector region of the combustion chamber. A plurality of resonator devices can also be positioned at the first sector region and correspondingly at the second sector region (per resonator device) in order, for example, to be able to take into account a variation of the speed of sound in the combustion chamber.

It is particularly advantageous if resonator devices of a group (that is to say a resonator device) have resonator chambers of different lengths. This results in an effective suppression of tangential modes or combination modes with tangential participation.

It has proved to be advantageous if the length of the longest resonator space is above an average value and the length of the shortest resonator space is below the mean value. The lengths of the resonator cavities advantageously differ only slightly from one another.

In particular, the mean value corresponds at least approximately to an anti-crossing length.

In particular, the difference between the largest length and the smallest length is k · a · d / n ^0.7 , where d is a diameter of the resonator chambers, a is a dimensionless number, k is the number of resonator devices per resonator device and n is the ordinal number of the tangential mode ,

It has been shown that it is favorable if a lies in the range between 0.25 and 0.7. This results in an effective mode suppression of the corresponding tangential mode or combination mode with tangential participation.

For example, it is favorable if a is approximately 0.4 if the at least one group (the resonator device) comprises two resonator devices. In this case, then, the resonator space of the resonator device having the largest length differs by approximately the diameter of the resonator space from the resonator device having the smallest length.

wobei d ein Durchmesser des Resonatorraums ist und b eine dimensionslose Zahl. Durch entsprechende Längenabstufung der Resonatorvorrichtung erhält man eine effektive Dämpfungswirkung pro Tangentialmode beispielsweise auch bei Verbrennungsstabilitäten; n ist die Ordnungszahl der Tangentialmode.For example, it is favorable if a length L _{k + 1 of} a resonator cavity of a resonator device k + 1 is determined by $L_{k+1}=L_k-\frac{b\cdot \mathrm{<figure-callout\; id="0"\; label="d\; n"\; filenames="imgf0005.png,imgf0006.png"\; state="\{\{state\}\}">d\; </figure-callout>}}{n^{}}.$

where d is a diameter of the resonator cavity and b is a dimensionless number. By appropriate length gradation of the resonator, one obtains an effective damping effect per tangential mode, for example, even with combustion stabilities; n is the ordinal number of the tangential mode.

It has proved to be advantageous if the dimensionless number b is in the range between 0.1 and 1.2 and in particular in the range between 0.3 and 0.7. It has proved to be particularly favorable when b is about 0.5.

The length L ₀ is determined by the fact that the natural frequency of the corresponding resonator device corresponds to the natural frequency of the corresponding tangential mode of the combustion chamber without a resonator device.

wobei r ein Brennkammerradius, c_R die Schallgeschwindigkeit im Resonatorraum der Resonatorvorrichtung, c_B die Schallgeschwindigkeit im Brennraum, l die Ordnungszahl der Eigenmode der Resonatorvorrichtung mit l = 1, 2, 3, ... und α_{n, m} Eigenwerte der Besselfunktionen sind mit m = 1, 2, 3,...und n = 0, 1, 2,...In a λ / 4 resonator L ₀ is for example given by ${\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="imgf0005.png,imgf0006.png"\; state="\{\{state\}\}">L</figure-callout>}}_0=\frac{\mathit{\pi }\cdot r\left(2l-1\right){\mathrm{<figure-callout\; id="2"\; label="c\; R"\; filenames="imgf0005.png,imgf0006.png"\; state="\{\{state\}\}">c\; </figure-callout>}}_R}{2{\alpha }_{n.m}\cdot c_B}.$

where r is a combustion chamber radius c _{R are} the speed of sound in the resonator chamber of the resonator device, c _B the speed of sound in the combustion chamber, L is the order number of the eigenmode of the resonator with l = 1, 2, 3, ..., and α _{n m} eigenvalues of Bessel functions with m = 1, 2, 3, ... and n = 0, 1, 2, ...

In particular, the angular distance between a longitudinal axis of the resonator device k + 1 and a longitudinal axis of the resonator device k is smaller than twice the diameter of a resonator cavity in order to achieve an effective damping effect.

It has proved to be advantageous if the number of resonator devices arranged on the first sector region is at least approximately ( L _max -L _min ) / ( bd / n ^0.7 ), where L _{max is} the length of a resonator cavity of the resonator device with the largest Length is and L _{min is} the length of the resonator space the resonator device with the smallest length and b is between 0.1 and 1.2. This results in the same mode suppression at the resonance frequencies f _max and f _min .

It can be provided that resonator devices are arranged axially spaced apart at the first sector region and / or second sector region. As a result, resonator devices with a small angular spacing can be positioned at a corresponding sector area.

It is favorable if the first sector region and / or the second sector region, on which length-graduated resonator devices are arranged, are limited over an angular range of less than 90 ° / (2n). For example, six resonator devices per sector are arranged in four sectors. The angular range of a sector is 15 °.

It is possible for the first sector region and / or the second sector region to have partial regions which are objected to by an angle 2α. As a result, the angular distances of resonator devices to a sector region can be kept small. For example, one half of the resonator device is arranged in a sector area in a first partial area and the other half in the second partial area.

In particular, different resonators for suppressing different tangential modes or combination modes with different tangential component are arranged at different locations of the combustion chamber. If the above-mentioned angle condition is satisfied, then the number of resonator devices can be minimized.

In an advantageous embodiment, the first resonator device is tuned to the first overtone of the first tangential mode, the second resonator device is arranged at an angle of 90 ° to the first resonator device and tuned to the first tangential mode, a third resonator device is arranged at an angle of 45 ° and on the second tangential mode is tuned, and a fourth resonator is arranged at an angle of 30 ° and tuned to the third tangential mode. Since the first overtone of the first tangent mode coincides with the second overtone of the second tangent mode and the third overtone of the third tangential mode, in this arrangement with only four resonators, both the first tangential mode and the second tangential mode and the third tangential mode can effectively be attenuated, namely for both σ-modes and π-modes.

It is possible in this case for each resonator device to comprise, for example, two resonator devices or more than two resonator devices which are arranged as close as possible to the angle β or at 0 ° to one another.

It is favorable if in the resonator chamber of a resonator device one or more resonance influencing elements are arranged, which are fluid-permeable and generate turbulence.

It is basically the case that a resonator device tuned to a eigenmode to be damped comprises a frequency protection range, with eigenmodes whose frequency falls within the frequency protection range being suppressed. This also allows eigenmodes during combustion stabilities be suppressed if their corresponding natural frequency falls within the frequency protection range. It is therefore basically desirable that the frequency protection range is as large as possible.

It has been shown that, for example, when working in the field of anticrossing (in the area of avoided crossing), as in the EP 06 117 462.9 described, the protected frequency range, which is between the T + eigenmode and the T - eigenmode is larger, the larger the ratio of resonator space diameter to combustion chamber radius. On the other hand, it has been found that the damping effect of a resonator device decreases with increasing this ratio.

In the solution according to the invention, one or more resonance influencing elements are arranged in the resonator chamber. These lead to a line broadening of the self-mode to be suppressed and thus to higher attenuation. It has been found that such resonance influencing elements do not substantially affect the frequency protection range, but have an increased damping effect with respect to the same ratio of resonator chamber diameter to combustion chamber radius. By means of a corresponding resonance influencing element, the intensity of the eigenmodes is reduced, while the corresponding frequency protection region is essentially unaffected. The one or more resonance influencing elements have no significant influence on the natural frequencies of the eigenmodes.

The described solution can provide a large frequency protection range with effective damping. This makes it possible, for example, To position a smaller number of resonator devices on the combustion chamber and thereby obtain an equal or better damping effect.

In particular, one or more gratings and / or porous structures are arranged as resonance influencing elements in the resonator space. Fluid can flow through a grid or a porous structure. As a result, an acoustic coupling between the resonator device and the combustion chamber is achieved. Through the flow, the fluid is excited to turbulence. The turbulences lead to an irreversible pressure drop, which has the described effect.

In particular, a porous structure is open-pored. It has been found that, for example, a non-porous foam material leads to an acoustic decoupling of the resonator device from the combustion chamber.

In principle, the arrangement of the resonance influencing element or elements can be arbitrary. Experiments have shown the strongest quantitative effect if the resonance influencing element or elements are arranged at or in the vicinity of the end opening.

In principle, it is possible that the one or more resonance influencing elements extend over a partial cross section or over the entire cross section of the resonator chamber. The latter case has proven to be favorable to achieve a high damping effect.

It is possible for the resonance influencing element (s) to completely or partially fill the resonator chamber.

It is advantageous if the one or more resonance influencing elements are made of a metallic or ceramic material. This makes it possible to realize a temperature-resistant resonance influencing element, which is not damaged even in a combustion operation of the combustion chamber.

It has proved favorable if a resonance influencing element comprises a porous structure made of a fiber material, the fiber density lying in the range between 5 mg / cm ³ and 300 mg / cm ³ and in particular in the range between 10 mg / cm ³ and 200 mg / cm ³ lies.

In an alternative embodiment, a lattice and in particular a flat lattice was used as the resonance influencing element, the mesh number being in the range between 300 l / cm ² and 6000 l / cm ² and in particular in the range between 400 l / cm ² and 5000 l / cm ² . With an insignificant influence on the frequency protection range, it has been possible to achieve effective damping even with a larger resonator cavity diameter.

The resonator device is designed, for example, as a λ / 4 resonator or as a Helmholtz resonator.

Figur 1

eine schematische Darstellung eines Ausführungsbeispiels einer Brennkammervorrichtung mit an einer Brennkammer angeordneten Resonatorvorrichtungen (Stand der Technik);

Figur 2

eine Draufsicht auf die Brennkammervorrichtung gemäß Figur 1 (Stand der Technik);

Figur 3

eine Teilschnittdarstellung einer Brennkammervorrichtung mit Resonatorvorrichtungen;

Figur 4

ein erstes Ausführungsbeispiel einer erfindungsgemäßen Brennkammervorrichtung in Draufsicht;

Figur 5

ein zweites Ausführungsbeispiel einer erfindungsgemäßen Brennkammervorrichtung in Draufsicht;

Figur 6

ein drittes Ausführungsbeispiel einer erfindungsgemäßen Brennkammervorrichtung in Seitenansicht;

Figur 7

eine schematische Darstellung des Klangbilds für verschiedene Eigenmoden einer zylindrischen Brennkammer;

Figur 8

ein Messdiagramm für die Intensität der Druckschwankung der 1T-Eigenmode bei unterschiedlicher Anordnung und Ausbildung von Resonatorvorrichtungen in Abhängigkeit von der Tangentialposition (Winkel χ);

Figur 9(a)

ein Intensitätsdiagramm für unterschiedliche Eigenmoden, wenn eine Resonatoreinrichtung mit zwei Resonatorvorrichtungen vorgesehen ist;

Figur 9(b)

ein ähnliches Diagramm wie in Figur 9(a), wenn die Resonatoreinrichtung drei Resonatorvorrichtungen unterschiedlicher Länge umfasst;

Figur 10

Schnittansichten für Ausführungsbeispiele von Resonatorvorrichtungen;

Figur 11

für ein Ausführungsbeispiel einer Brennkammervorrichtung die Abhängigkeit der Eigenfrequenzen der 1T+-Eigenmode und 1T--Eigenmode beim 1T-Anticrossing in Abhängigkeit von einem Resonatorraumdurchmesser bezogen auf einen Brennraumradius für einen λ/4-Resonator;

Figur 12

die Intensitätsreduktion für die entsprechenden Eigenmoden;

Figur 13

den Frequenzverlauf einer 1T+-Eigenmode und 1T--Eigenmode beim 1T-Anticrossing für einen bestimmten Resonatorraumdurchmesser (d/r = 0,18) als Funktion der Maschenzahl M eines an der Resonatorvorrichtung angeordneten Gitters;

Figur 14

die Intensitätsreduktion, wenn die Resonatorvorrichtung mit einem Gitter der Maschenzahl M versehen ist;

Figur 15

den Frequenzverlauf der 1T+-Eigenmode und 1T--Eigenmode beim 1T-Anticrossing für einen bestimmten Resonatorraumdurchmesser (d/r = 0,18) als Funktion der Länge Lp einer porösen Struktur, welche an der Resonatorvorrichtung angeordnet ist; und

Figur 16

die entsprechende Intensitätsreduktion.

The following description of preferred embodiments is used in conjunction with the drawings for a more detailed explanation of the invention. Show it:

FIG. 1

a schematic representation of an embodiment of a combustion chamber device arranged on a combustion chamber resonator devices (prior art);

FIG. 2

a plan view of the combustion chamber device according to Figure 1 (prior art);

FIG. 3

a partial sectional view of a combustion chamber device with resonator devices;

FIG. 4

a first embodiment of a combustion chamber device according to the invention in plan view;

FIG. 5

A second embodiment of a combustion chamber device according to the invention in plan view;

FIG. 6

a third embodiment of a combustion chamber device according to the invention in side view;

FIG. 7

a schematic representation of the sound pattern for different eigenmodes of a cylindrical combustion chamber;

FIG. 8

a measurement diagram for the intensity of the pressure fluctuation of the 1T eigenmode with different arrangement and formation of resonator devices as a function of the tangential position (angle χ);

FIG. 9 (a)

an intensity diagram for different eigenmodes, when a resonator device is provided with two resonator devices;

FIG. 9 (b)

a similar diagram as in Figure 9 (a), when the resonator device comprises three resonator devices of different lengths;

FIG. 10

Sectional views for embodiments of resonator devices;

FIG. 11

for an exemplary embodiment of a combustion chamber device, the dependence of the natural frequencies of the 1T + eigenmode and 1T eigenmode in 1T anticrossing as a function of a resonator chamber diameter relative to a combustion chamber radius for a λ / 4 resonator;

FIG. 12

the intensity reduction for the corresponding eigenmodes;

FIG. 13

the frequency response of a 1T + eigenmode and 1T eigenmode in 1T anticrossing for a given resonator cavity diameter (d / r = 0.18) as a function of the mesh number M of a grating disposed on the resonator device;

FIG. 14

the intensity reduction when the resonator device is provided with a mesh of mesh M;

FIG. 15

the frequency response of the 1T + eigenmode and 1T eigenmode in 1T anticrossing for a given resonator cavity diameter (d / r = 0.18) as a function of the length Lp of a porous structure disposed on the resonator device; and

FIG. 16

the corresponding intensity reduction.

An exemplary embodiment of a combustion chamber device, which is shown schematically in FIG. 1 and denoted there by 10, comprises a combustion chamber 11 with a combustion chamber wall 12 and an interior as combustion chamber 14. The combustion chamber 14 is usually designed to be rotationally symmetrical about a combustion chamber axis 16.

The combustion chamber 11 has an end 18 at which a blowing device for injecting fuel and oxidizer is arranged (not shown in FIG. 1). The end 18 is located on a cylindrical portion 19, on which a constricted neck portion 20 follows.

Fuel gases exit the combustion chamber 11 via the neck region 20.

A combustion chamber 11 has acoustic eigenmodes. Knowing and adjusting the acoustic characteristics of a combustor 11 may be important to combustion processes. Partial operations of the combustion of a fuel in the combustion chamber 11 such as fuel supply, mixture formation and chemical reaction as well as liquid fuel atomization and evaporation can be periodic or pulsating processes. If the corresponding oscillation frequency of any of these sub-processes an acoustic eigenmode of the combustion chamber 11 to vibrate, strong pressure pulsations may arise in the combustion chamber 11 due to acoustic coupling, which in turn may lead to damage to the combustion chamber 11 and may lead to disturbances of combustion.

By targeted adjustment of the acoustic properties of the combustion chamber 11 via a resonator 21 one can avoid the problems described.

On the combustion chamber 11, one or more acoustic resonator devices 22 are arranged as damping elements. When such an acoustic resonator device 22 (or a plurality of acoustic resonator devices 22) couples (ie, resonates) to an acoustic eigenmode of the combustor 11, then with proper choice, the eigenmode may be slid into a frequency range in which it is used for the combustion process is no longer disturbing, or be damped and ideally suppressed to a large extent.

It is known, for example, that an annular flange 24 is fixed to an outer side 26 of the combustion chamber 11, at which acoustic resonator devices 22 can be positioned in particular around a circumferential line on the outer side 26 of the combustion chamber 11 (preferably at the same height). The distance of the resonator devices 22 (along the combustion chamber axis 16) to the neck region 20 is preferably larger than the diameter 2 r of the combustion chamber 14.

An acoustic resonator device 22 in this case has a resonator chamber 28 (resonance chamber), which is connected via an opening 29 in connection with the combustion chamber 14 of the combustion chamber 11 (FIGS. 3, 10).

For acoustic examination of the combustion chamber 11, an acoustic excitation of the combustion chamber 11 via a loudspeaker 30 takes place. For signal generation, a signal generator 32 is provided whose signals are amplified by an amplifier 34. The amplifier 34 is coupled to the speaker 30.

For signal detection, a microphone 36 is provided, which is coupled to an amplifier 38. The amplifier 38 supplies the amplified signals to an evaluation device 40, by which in particular the frequency spectrum of the combustion chamber 11 can be determined.

As an acoustic resonator device, for example, a quarter-wave resonator 42 can be used (FIG. 10). This comprises a cylindrical tube 44, in which the cylindrical resonator chamber 28 is formed. The tube 44 opens via an open end 46 into the combustion chamber 14 of the combustion chamber 11. The tube 44 is oriented transversely and in particular perpendicular to the combustion chamber axis 16 and at least partially aligned radially.

The resonator chamber 28 is closed off at the end 48 opposite the end 46 by a wall 50. This wall 50 may be fixed or it may be displaceable, so that the length L of the resonator chamber 28 between the end 46 and the end 48 is variably adjustable.

Another example of an acoustic resonator device is a Helmholtz resonator, which is shown schematically in FIG. 10 and denoted by 52 there. A Helmholtz resonator comprises a rotationally symmetric resonator 54, which is for example partially formed in a tube 56. The tube 56 is connected via a neck 58 with the interior 14 of the combustion chamber 11. An interior 60 in the neck 58 is also part of the resonator 54. The resonator is closed via a wall 62.

The neck 58 has a smaller cross-sectional area than the tube 56.

By selective choice or adjustment of one or more acoustic resonator devices 22, the acoustic properties of the combustion chamber 11 can be adjusted. The setting is in particular such that for pulsating processes during combustion in the combustion chamber 11 no coupling with eigenmodes of the combustion chamber 11 can take place.

The eigenmodes of the combustion chamber 11 (without acoustic resonator devices 22) and the corresponding natural frequencies depend on the geometric shape of the combustion chamber 11. For an ideal cylindrical combustion chamber 11, the eigenfunctions are, for example, cylindrical Bessel functions.

In a rotationally symmetrical combustion chamber 11 with cylinder geometry exist as eigenmodes transverse modes and longitudinal modes (axial modes). The longitudinal modes are usually denoted nL such as 1L, 2L, etc. The transversal modes include radial modes (R-modes) and tangential modes (T-modes). The radial modes are usually labeled nR such as 1R, 2R, etc., and the tangential modes labeled nT are 1T, 2T, etc.

FIG. 7 shows sound images of the 1T eigenmode and 2T eigenmode of a rotationally symmetrical combustion chamber; In this case, s denotes a symmetry line, p _{n in} each case represents a pressure oscillation belly, in is an isobar of the pressure fluctuation and K _n are pressure oscillation nodes.

If no resonator device is present, the 1T eigenmode is subdivided into a 1T-σ eigenmode and 1T-π-eigenmode, in which the isobars of the pressure fluctuation are oriented at 90 ° to one another.

The 2T eigenmode is divided into a 2T-σ eigenmode and a 2T-π eigenmode, which are separated by 45 °.

The coupling of a resonator device 22 means a symmetry fault. The 1T σ eigenmode has a pressure bulge at the opening 29 of the corresponding resonator chamber 28. The 1T σ eigenmode interacts with the resonator device 22. By contrast, the 1T-π eigenmode, which has a pressure node at the opening 29, does not interact with the resonator device 22.

As will be explained in more detail below, with certain excitations of the combustion chamber two eigenmodes are present, which are close to each other and have the same resonance properties. These are shown in FIG. 1 as 1T eigenmodes and 1T + eigenmodes with their corresponding sound images. The 1T eigenmode and 1T + eigenmode can be excited when the resonant condition with respect to the frequency is satisfied, but the pressure distribution does not match the velocity distribution of the resonator device 22 and the combustion chamber.

If the cylindrical region 19 of the combustion chamber 11 has a sufficiently high height in comparison to the neck region 20, then here too the eigenfunctions are, to a good approximation, Bessel functions. The openings 46 to resonator 22 have a relatively small influence.

bestimmt, wobei α_n,m Eigenwerte der Besselfunktionen sind und c_B die Schallgeschwindigkeit im Brennraum 14 ist; r ist der Radius des Brennraums 14. (m-1) ist die Ordnung der radialen Eigenmode; n ist die Ordnung der tangentialen Eigenmode; c_B kann veränderlich sein.The natural frequencies of the combustion chamber 11 for the transverse (radial and tangential) natural oscillations are in good approximation by the equation $$\begin{array}{ll}{{\mathrm{f}}^{\mathrm{B}}}_{\mathrm{n}\mathrm{.}\mathrm{m}}=\frac{{\alpha }_{n.\mathrm{<figure-callout\; id="2"\; label="m\; c\; B"\; filenames="imgf0005.png,imgf0006.png"\; state="\{\{state\}\}">m\; </figure-callout>}}{c}_B{}_{}}{2\mathit{\pi \; r}}& \mathrm{m}\mathrm{=}\mathrm{1}\mathrm{.}\mathrm{2}\mathrm{.}\mathrm{3}\mathrm{.}\mathrm{...}\\ & \mathrm{n}\mathrm{=}\mathrm{1}\mathrm{.}\mathrm{2}\mathrm{.}\mathrm{3}\mathrm{.}\mathrm{...}\end{array}$$

where α _{n, m are} eigenvalues of the Bessel functions and c _{B is} the speed of sound in the combustion chamber 14; r is the radius of the combustion chamber 14. (m-1) is the order of the radial eigenmode; n is the order of the tangential eigenmode; c _B can be variable.

mit der Resonatorlänge L und der Schallgeschwindigkeit c_R im Resonator. l ist die Ordnungszahl der Eigenmoden des Lambda-Viertel-Resonators, wobei l = 1 dem Grundton entspricht, l = 2 ist der erste Oberton, I = 3 ist der zweite Oberton usw.; c_R kann veränderlich sein.The natural frequency of a quarter-wave resonator is $${{\mathrm{f}}^{\mathrm{R}}}_{\mathrm{l}}=\frac{\left(2l-1\right){\mathrm{<figure-callout\; id="4"\; label="c\; R"\; filenames="imgf0004.png,imgf0006.png"\; state="\{\{state\}\}">c\; </figure-callout>}}_R}{4L};\mathrm{l}=1.2.3....$$

with the resonator length L and the speed of sound c _R in the resonator. l is the ordinal number of the eigenmodes of the quarter-wave resonator, where l = 1 corresponds to the root, l = 2 is the first overtone, I = 3 is the second overtone, etc .; c _R can be variable.

The number of resonator devices 22 that can be positioned on the combustion chamber 11 is limited. If S is set as the distance between adjacent resonator devices (including resonator wall) (FIG. 3), then the possible number of resonator devices 22 which can be arranged around a circumferential line of the combustion chamber 11 is 2rπ (S + d). With a combustion chamber diameter of 2r = 220 mm, a resonator diameter of d = 9 mm and a distance S = 5.4 mm, the number of maximum resonator devices is about 50. A larger number of resonator devices can only be achieved by reducing the resonator diameter d and / or be reached by S. A reduction of d results in a reduction of the effective frequency range, as will be explained below. A reduction of S leads to design difficulties.

dann angeordnet ist. i = 1, 3, 5, ... ist dabei eine ungerade Zahl und n ist die Ordnungszahl der zu unterdrückenden Tangentialmode oder die Ordnungszahl der Tangentialbeteiligung einer Kompensationsmode; der Winkel α ist auf die Brennraumachse 16 bezogen.According to the invention, it is provided that a first resonator device 63 with at least one resonator device 64 is arranged on the combustion chamber 11 and a second resonator device 65 with at least one Resonator device 66 at an angle (at least approximately) $$\alpha =i\cdot \frac{90°}{n}$$

then arranged. i = 1, 3, 5, ... is an odd number and n is the ordinal number of the tangential mode to be suppressed or the ordinal number of the tangential component of a compensation mode; the angle α is related to the combustion chamber axis 16.

If, for example, the first tangential mode 1T is to be suppressed, then the first resonator device 63 and the second resonator device 65 are arranged at an angle of 90 ° with respect to the combustion chamber axis 16 relative to one another. (This angle can also be 270 °.)

If the second tangential mode 2T is to be suppressed, then the first resonator device 63 with resonator devices 64 'and the second resonator device 65 with resonator devices 66' apart by 45 °. (They can also be at 135 ° or 225 ° or 315 ° apart.)

If the third tangential mode 3T is to be suppressed, then the first resonator device 63 with resonator devices 64 "and the second resonator device 65 with resonator devices 66" apart by 30 °. They can also be 90 °, 150 °, 210 °, 270 ° or 330 ° apart.

In the combustion chamber 14, standing waves can form in the tangential modes, which have different characteristics. Each tangential mode occurs in duplicate. These double versions are coupled together because the print node is one mode of the other's velocity nodes. For example, there are σ modes and π modes (FIG. 7). By arranging the first resonator device 63 and the second resonator device 65 at the angle α, both the σ modes and the π modes of the corresponding tangential mode can be effectively suppressed.

The first resonator device 63 comprises a group of resonator devices which are arranged on a first sector region 68. The second resonator device 65 is arranged on a second sector region 70 of the combustion chamber 11; it also includes a plurality of resonator devices 66.

The first resonator device 63 and the associated second resonator device 65 are aligned with a specific tangential mode of the combustion chamber 11. This tangential mode can, for example, have different natural frequencies when the speed of sound varies. In order to be able to damp these modified tangential modes as well, it is advantageous if a plurality of resonator devices with different resonator cavity lengths L are arranged on the respective first sector region 68 and the second sector region 70. It is favorable if an angular distance β of resonator devices of such a group is approximately 0 ° or j * 90 ° / n , where j is an even natural number.

Correspondingly, a first group 72 of resonator devices is arranged on the first sector region 68 and a second group 74 of resonator devices on the second sector region 70. (A first group 72 'is arranged at the first sector area 68' and a second group 74 'is arranged at the second sector area 70'.) A first group 72 "is present at the first sector area 68" and a second group at the second sector area 70 " Group 74 "arranged.)

Due to the different lengths, for example, it is also possible to record transient processes effectively.

L_k+1 ist die Länge des Resonatorraums der Resonatorvorrichtung k+1 der entsprechenden Gruppe. d ist der Durchmesser des entsprechenden Resonatorraums und n ist die Ordnungszahl der entsprechenden Tangentialmode. b ist eine dimensionslose Zahl, die zwischen 0,1 und 1,2 und insbesondere zwischen 0,3 und 0,7 liegt. Besonders gute Ergebnisse haben sich erzielen lassen, wenn b bei ca. 0,5 liegt.It is intended, in order to achieve combustion stability in the combustion chamber 14 for a wide range of sound velocities, that the resonator devices, which are per tangential mode of a group of resonator devices, are graduated in their lengths. The length graduation takes place, for example, according to: $$L_{k+1}=L_k-\frac{b<figure-callout\; id="0"\; label="\cdot \; d\; n"\; filenames="imgf0005.png,imgf0006.png"\; state="\{\{state\}\}">\cdot \; </figure-callout>d}{n^{}}$$

L _{k + 1} is the length of the resonator cavity of the resonator device k + 1 of the corresponding group. d is the diameter of the corresponding resonator space and n is the ordinal number of the corresponding tangent mode. b is a dimensionless number which is between 0.1 and 1.2 and in particular between 0.3 and 0.7. Particularly good results have been achieved when b is about 0.5.

L ₀ is a basic length of the resonator device. It is determined by the fact that the natural frequency of the corresponding tangential mode of the combustion chamber 11 without resonator device corresponds to the natural frequency of the resonator device. For example, L _{0 is determined} by a λ / 4 resonator $$L_{}$$$${}_0=\frac{\mathit{\pi }\cdot r\left(2l-1\right){\mathrm{<figure-callout\; id="2"\; label="c\; R"\; filenames="imgf0005.png,imgf0006.png"\; state="\{\{state\}\}">c\; </figure-callout>}}_R}{2{\alpha }_{n.m}\cdot c_B}$$

The length graduation in associated groups 72, 74 and 72 ', 74' and 72 ", 74" is the same. In particular, each resonator of a group is assigned a resonator of the same length in the associated group.

Within the respective group 72, 72 ', 72 "(and thus also in the group 74, 74', 74"), the distance between adjacent resonator devices k + 1 and k is preferably as small as possible. Preferably, it is also smaller than a double diameter of the resonator cavity of the resonator devices.

liegt, angeordnet sind, wobei n die Ordnungszahl der Tangentialmode oder der Tangentialbeteiligung einer Kombinationsmode ist und j eine gerade natürliche Zahl.It has proved favorable if a resonator device (for example the resonator device 63 and / or the resonator device 65) has a plurality of resonator devices which have different lengths, as indicated schematically in FIG. It is advantageous if the resonator devices of such a group in an angular range which is as close as possible to 0 ° or as close to $$\mathit{\beta }=j\cdot \frac{90°}{n}$$

where n is the ordinal number of the tangential mode or the tangential component of a combination mode, and j is an even natural number.

It is furthermore advantageous if the resonator spaces of the resonator devices of a group have lengths which slightly deflect from one another, wherein a minimum length L _min lies below an average value. This average is determined by the anti-crossing length. Furthermore, a resonator device should have a resonator space with a length L _max which lies above this mean value. This gives an amplification of the resonator effect. In particular, an increased suppression of the intensity of pressure fluctuations is possible.

It is particularly advantageous if resonator devices which are spaced at an angle α are provided, which themselves in turn comprise a group of resonator devices which satisfy the above-mentioned condition for the angle β.

FIG. 8 shows a measurement diagram for the intensity of the pressure fluctuations of the 1T eigenmode at the circumference of a specific combustion chamber, the dependence on the angle γ on the circumference being measured. The measured values 160 correspond to the arrangement 162. A resonator device (λ / 4 resonator) was provided, which is tuned poorly; the resonator space of the resonator device has a length of 20 mm. This length is too short.

In comparison, the measured values 164 belong to an arrangement 166 in which a tuned resonator device (with a resonator cavity length of 90 mm) was used.

It can be seen here that at the position γ = 90 ° high pressure fluctuations exist. This is due to the 1T π eigenmode. The further you go away from this 90 °, the more effective is a suppression of the 1T eigenmode.

The measured values 168 belong to the arrangement 170, in which an additional resonator device was additionally provided. One recognizes that this has a relatively small influence.

The course of the measured values 160, 164 and 168 can be easily explained from the sound images in FIG.

The measured values 172 belong to the arrangement 174 according to the invention, in which a first resonator device (with a single resonator device) and a second resonator device (with a single resonator device) are at an angle of 90 ° apart. It can be seen that both the 1T-σ eigenmode and also the 1T-π eigenmode are effectively suppressed and thereby obtains an effective suppression of the pressure fluctuations over the entire circumference of the combustion chamber.

FIG. 9 (a) shows a measuring diagram when a single resonator device with two resonator devices is arranged on a combustion chamber is, wherein the two resonator devices are arranged at a small angle as close to 0 ° and have resonator spaces of different lengths. The length of the shorter resonator space is L _min and the length of the larger resonator space is L _max .

und $1T_3^{-}$

-Eigenmode. Diese sind abgeschwächt. Die $1T_1^{-}$

-Eigenmode entspricht einer 1T--Eigenmode und die $1T_3^{-}$

-Eigenmode entspricht der 1T+-Eigenmode. Die $1T_2^{-}$

-Eigenmode liegt mit der Eigenfrequenz zwischen den Frequenzen der beiden anderen Eigenmoden. Die $1T_2^{-}$

-Eigenmode liegt in der Intensität um ca. eine Zehnerpotenz niedriger als die der beiden anderen Eigenmoden, wenn die Länge der Resonatorräume der Resonatorvorrichtungen annähernd gleich ist. Bei Vergrößerung des Längenunterschieds sinkt die Intensität der $1T_1^{-}$

- und $1T_3^{-}$

-Eigenmode. Diejenige der $1T_2^{-}$

-Eigenmode steigt. Das Optimum der Längenabstufung liegt bei L_max - L_min ≈ k · a · d/n ^0,7 wobei d der Resonatordurchmesser ist, k die Anzahl der Resonatorvorrichtungen pro Resonatoreinrichtung (hier k = 2) und n die Ordnungszahl der Tangentialmode ist (hier n = 1); ein optimales a liegt bei ca. 0,4 bis 0,5.This arrangement creates a $1T_1^{-}.1T_2^{-}$

and $1T_3^{-}$

-Eigenmode. These are attenuated. The $1T_1^{-}$

Own-mode corresponds to a 1T-eigenmode and the $1T_3^{-}$

Own-mode corresponds to 1T + -single mode. The $1T_2^{-}$

Eigenmode lies with the natural frequency between the frequencies of the other two eigenmodes. The $1T_2^{-}$

The eigenmode is about one-decade lower in intensity than the other two eigenmodes when the length of the resonator cavities of the resonator devices is approximately equal. As the difference in length increases, the intensity of the $1T_1^{-}$

- and $1T_3^{-}$

-Eigenmode. The one who $1T_2^{-}$

-Eigenmode rises. The optimum of the length graduation is L _max - L _min ≈ k · a · d / n ^0.7 where d is the resonator diameter, k is the number of resonator devices per resonator device (here k = 2) and n is the ordinal number of the tangential mode (here n = 1); an optimal a is about 0.4 to 0.5.

und eine $1T_4^{-}$

-Eigenmode. Die optimale Längenabstufung erreicht man, wenn L_max - L_min ungefähr k · a · d/n ^0,7 ist, wobei a zwischen 0,25 und 0,7 liegt.FIG. 9 (b) corresponds to an arrangement of a single resonator device on a combustion chamber with three resonator devices which are arranged as close as possible to 0 ° in a small angular range. There is one each $1T_1^{-}-.1T_2^{-}-.1T_3^{-}-$

and a $1T_4^{-}$

-Eigenmode. The optimum length graduation is achieved when L _max - L _{min is} approximately k · a · d / n ^0.7 , where a is between 0.25 and 0.7.

The measurements which led to the diagrams according to FIGS. 8 and 9 were carried out on a model combustion chamber with air as medium under ambient conditions (cold tests). The combustion chamber diameter was 220 mm and the combustion chamber length 40 mm. The resonator diameter d was 9 mm.

If a plurality of resonator devices with a corresponding angular arrangement are arranged on the combustion chamber 11 and the length of the resonator chambers of all resonator devices is equal (this corresponds to b = 0), then the mode suppression is just as large as if only one resonator device with the same resonator cavity length was coupled. The frequency range of the mode suppression effect increases slightly more with increasing number of resonator devices than if the diameter of this single resonator device were increased so that the area of the resonator device of increased diameter would equal the sum of the area of all original diameter resonator devices.

It has been found that if, in addition to the first resonator 63 and the second resonator 65, a third resonator of equal length is connected at a "wrong" angle, the mode rejection will be degraded. If then a fourth resonator device of the same length is connected to the system, the angle between the third resonator device and the fourth resonator device corresponds to the above equation with i = 1, 3, 5, .., then the corresponding tangential mode is optimally suppressed again.

The first sector region 68 and the second sector region 70 may be formed in several parts. (This corresponds to j ≠ 0.) This is indicated in FIG. In this case, the first sector area 68 comprises subsectors 76a, 76b and the second sector area 70 comprises subsectors 78a, 78b. The subsectors 76a, 76b differ by an even multiple of the angle β. Correspondingly, the subsectors 78a, 78b differ by an even multiple of the angle α with respect to the combustion chamber axis 16. In the embodiment shown with α = 90 °, the subsectors 76a and 76b are 180 ° apart. Accordingly, the subsectors 78a and 78b are 180 ° apart. With this configuration, the angular range in which resonator devices are arranged at a sector area can be made small. For example, half of the resonator devices in the subsector 76a and 78a and the other half of the resonator devices in the subsector 76b and 78b may be arranged.

It is also possible, for example, for resonator devices, as shown in FIG. 6, to be axially offset (that is to say parallel to the combustion chamber axis 16) in a respective sector region. The axial displacement is preferably as small as possible.

In the arrangement according to the invention, it is possible that resonator devices associated therewith are tuned to the fundamental tone, that one resonator device is tuned to a fundamental tone and the other resonator device is tuned to an overtone or both resonator devices are tuned to an overtone, wherein the harmonics may also be different.

For the suppression of radial modes, a single resonator device is sufficient for a given sound velocity.

In a specific embodiment, four resonator devices are arranged on the combustion chamber 11. In the arrangement according to the invention, the first three tangential modes 1T, 2T and 3T can be effectively suppressed. For this purpose, a first resonator device is tuned to the first overtone of the first tangential mode. The first overtone of the first tangent mode coincides with the second overtone of the second tangent mode and the third overtone of the third tangent mode. At an angle of 90 ° to the first resonator device, a second resonator device is arranged, which is tuned to the first tangential mode. At an angle of 45 °, a third resonator device is arranged, which is tuned to the second tangential mode. At an angle of 30 °, a fourth resonator device is arranged, which is tuned to the third tangential mode.

Anticrossing or "avoided crossing" means that for certain excitations of the combustion chamber there are two eigenmodes which are close to each other and have the same resonance characteristics; in particular, they have a substantially equal intensity and half-width. A avoided crossing arises when the resonance condition with respect to the frequency is satisfied, but the pressure distribution and the velocity distribution in the resonator device and the combustion chamber do not match. For example, the resonant frequency conditions for a radial mode of the combustion chamber and a λ / 4 oscillation of a coupled resonator be met. However, the λ / 4 oscillation of the resonator device requires a pressure node at a resonator opening in an interior of the combustion chamber. For the radial mode, on the other hand, a pressure annotation on the cylinder wall is required.

For a tangential mode, the λ / 4 oscillation of the resonator device requires radial velocity fluctuation at the mouth of the resonator device into the combustion chamber, while the tangential mode of the combustion chamber requires azimuthal oscillation at the same location.

The avoidance of the crossing results in two eigenmodes, one of which has a slightly lower frequency than the eigenmode of the combustion chamber without resonator device, and the other has a slightly higher frequency than the corresponding eigenmode of the combustion chamber without resonator device.

If the frequency of the eigenmode with the higher frequency is designated as f ⁺ and the eigenmode with the identical frequency as f ^- and the frequency of the mode to be suppressed is designated as f ', then the protected frequency range of the combustion chamber at f' ± ( f ⁺ - f ^- ) / 6 and the protection range is approx. (f ⁺ - f ^- ) / 3. The protection range is the frequency range within which eigenmodes can be suppressed. Within the protection range, even with changes in the operating parameters of the combustion in the combustion chamber, eigenmode can be effectively suppressed. It is therefore desirable that the protection range is a wide frequency range in which one or more resonator devices are highly attenuated.

The effect of avoided crossing or anticrossing is in the not previously published European Patent Application No. 06 117 462.9 of July 19, 2006 described by the same applicant. It is expressly referred to.

FIG. 12 shows the dependence of the intensity reduction (in dB) as a function of the ratio d to r for the intensity of the 1T + eigenmode and 1T eigenmode in 1T anticrossing. It can be seen that the strongest reduction in intensity, and thus the strongest suppression of the 1T eigenmode, occurs at a ratio of d to r in the range between 0.04 and 0.065. For larger diameters of the resonator cavity of the corresponding resonator device, the intensity reduction decreases, that is to say the intensity is reduced to a lesser extent.

It can be seen from the comparison with FIGS. 11 and 12 that a large diameter d of the resonator chamber of a connected resonator device is favorable for a large protection range, but is unfavorable for intensity suppression.

According to the invention, one or more resonance influencing elements 100 are arranged in the resonator chamber 28 or 54 of the corresponding resonator device 22 or 52. Various examples are shown in FIG. The resonant influencing element or elements 100 are designed such that they are fluid-permeable and, in particular, permeable to gas, in order to enable a coupling of the medium in the corresponding resonator chamber 102 to the medium in the combustion chamber 14. Further For example, the resonance influencing element (s) 100 are designed to generate turbulence. The fluid which flows through a corresponding resonance influencing element 100 is swirled. There is a drop in pressure fluctuations. This causes a dissipation in volume.

It has been found that by providing one or more resonance influencing elements for a given diameter d of the resonator chamber 102, the frequency width and hence the protective region 94 is only slightly affected, while the intensity reduction corresponds to an effective smaller diameter d. By providing one or more resonance influencing elements 100, both a large reduction in intensity and a large protection region 94 can be achieved.

The resonant influencing element or elements 100 can fill the resonator chamber 102 completely or in a partial region.

FIG. 10 shows a resonance influencing element designated by reference numeral 104, which is formed from a porous structure 106. The porous structure is, for example, a metallic fiber structure.

The resonance influencing element 104 is arranged at an opening 108 of the resonator chamber 102 in the combustion chamber 14.

The length of the porous structure 106 parallel to an axis 110 of the resonator chamber 102 may be different. FIG. 10 shows resonance influencing elements 104, which are formed as a porous structure and have a different length, with the reference numbers 112, 114, 116, 118 and 120. The resonance influencing element 120 fills the entire volume of the resonator chamber 102, wherein the resonance influencing element 120 is fluid-permeable.

The resonance influencing elements 104 and 112 to 120 extend over the entire cross section of the respective resonator cavity 102.

It is also possible that a resonance influencing element 122 is provided, which is arranged about the axis 110 and does not extend over the entire cross section of the resonator chamber 102.

For example, it is also possible for an annular resonance influencing element 124 to have a central opening 126. The resonance influencing element 124 is arranged on a wall of the resonator chamber.

It is also possible that resonance influencing elements 128, 130, 132, 134 are formed from an open-pore foam material and in particular a metal foam.

For example, it is possible for resonance influencing elements such as the resonance influencing elements 130 and 132 to be positioned at a distance from the opening of the resonator chamber toward the combustion chamber 14.

For example, it is also possible for a resonator space 136 to be provided with a grating 138 as a resonance influencing element. This grid 138 is arranged in particular at an opening 140 of the resonator chamber 136 to the combustion chamber 14.

The grid 138 has meshes with openings therebetween.

A resonance influencing element 142 can also be positioned, for example, at an opening of a Helmholtz resonator 52 in the combustion chamber 14.

FIG. 13 shows a diagram for the natural frequency of the 1T + eigenmode and the 1T eigenmode in anticrossing when a resonator device with a grating 138 is provided at an opening 140. Shown is the dependence on the mesh size of the grating 138. It can be seen that the distance between the natural frequencies and thus the protection range is essentially independent of the mesh size.

FIG. 14 shows the intensity reduction as a function of the mesh size. It can be seen that the intensity of the 1T eigenmode to be suppressed decreases with increasing mesh size. FIG. 14 is to be compared with FIG.

It has proven advantageous if the mesh size between 300 1 / cm ² and 6000 1 / cm ² and preferably between 400 1 / cm ² and 5000 1 / cm ² .

From Figures 13 and 14 can be seen in comparison with Figures 11 and 12, that the provision of a grating 138 as a resonance influencing element leads to a greater reduction in intensity without significantly affecting the scope of protection.

Figures 13 and 14 were taken at a ratio of d to r of 0.18.

FIG. 15 shows a diagram similar to FIG. 13, wherein a porous structure, namely a metal fiber structure with a fiber density of approximately 50 mg / cm ³ , was selected as resonance influencing element 104. The frequency is represented as a function of the length Lp of the resonance influencing element 104. This frequency is arranged at the opening 108 and extends away from it into the resonator chamber 102 over the length Lp.

The measurements were carried out at a ratio of d to r of 0.18.

Figure 16 shows the intensity reduction over Lp. Again, one recognizes the stronger intensity reduction compared to a combustion chamber with a resonator without resonance influencing element (Figures 11 and 12).

According to the invention, the damping effect of a resonator device, which is arranged on the combustion chamber 11, can be increased for a given diameter d by arranging one or more resonance influencing elements in the resonator chamber of the resonator device. The resonance influencing elements are designed such that they lead to an increase in the line width of the eigenmode to be suppressed. It It has been found that such resonance influencing elements hardly affect the frequency protection range, while they lead to an effective reduction in intensity.

For example, porous structures of mineral fiber or metal fiber or an open-pore foam material may be provided as resonance influencing elements. For example, a grid can also be used. Combinations are possible.

As mentioned above, it is advantageous if resonator devices for a group are arranged at a small distance from each other. The solution according to the invention with the provision of one or more resonance influencing elements 100 in a resonator chamber gives a high protection range even for larger resonator chamber diameters with effective damping. In turn, a high protection range means that the number of necessary resonator devices can be reduced. As a result of the solution according to the invention with the resonance influencing elements, this makes it possible to reduce the number of resonator devices in a group. As a result, the effects of a larger resonator cavity diameter are less relevant.

Claims (29)

A combustor device comprising a combustor (11) having a combustion chamber (14) and a plurality of resonator devices (22) disposed on the combustor (11), the resonator devices (22) being configured and arranged to suppress tangent modes or tangential combination modes are,
characterized by a first resonator device (63) having one or more resonator devices (64) and a second resonator device (65) having one or more resonator devices (66) which are at least approximately at an angle to the first resonator device (63) $\alpha =i\cdot \frac{90°}{n}$

is arranged on a combustion chamber axis (16), where i is an odd natural number and n is the ordinal number of the tangential mode or the tangential component of the combination mode. Combustor chamber device according to claim 1 or the preamble of claim 1, characterized by at least one resonator device (63; 65) with a group of resonator devices which are at least approximately at an angle of 0 ° or $\mathit{\beta }=j\cdot \frac{90°}{n}$

relative to a combustion chamber axis (16) are arranged to each other, wherein j is an even natural number and n is the ordinal number of the tangential mode or the tangential component of the combination mode. Combustion chamber device according to claim 1 or 2, characterized in that the resonator devices (22) as λ / 4 resonators (42) or Helmholtz resonators (52) are formed. Combustion chamber device according to one of the preceding claims, characterized in that the resonator devices (22) each have a wall defining a resonator chamber (28; 54), the resonator chamber (28; 54) being connected to the combustion chamber (14) via an opening (29) ) connected is. Combustion chamber device according to claim 4, characterized in that a longitudinal axis of the respective resonator chamber (28; 54) is oriented transversely to the combustion chamber axis (16). Combustion chamber device according to one of the preceding claims, characterized in that resonator chambers (28) of the resonator devices (22) have substantially the same diameter (d). Combustion chamber device according to one of the preceding claims, characterized in that the first resonator device (63) is arranged on a first sector region (68) of the combustion chamber (11) and the second resonator device on a second sector region (70) of the combustion chamber (11). Combustion chamber device according to one of Claims 2 to 7, characterized in that resonator devices have a group of resonator chambers of different lengths. Combustion chamber device according to claim 8, characterized in that the length of the longest resonator space is above an average value and the length of the shortest resonator space is below the mean value. Combustion chamber device according to claim 9, characterized in that the mean value corresponds at least approximately to an anti-crossing length. Combustion chamber apparatus according to claim 9 or 10, characterized in that the difference between the largest length and the smallest length is k · a · d / n ^0.7 , where d is a diameter of the resonator spaces, a is a dimensionless number, k is the number the resonator devices per resonator device and n is the ordinal number of the tangential mode. Combustion chamber device according to claim 11, characterized in that a lies in the range between 0.25 and 0.7. A combustion chamber device according to claim 11 or 12, characterized in that a is about 0.4 when the at least one group comprises two resonator devices. Combustion chamber device according to one of claims 7 to 13, characterized in that resonator devices (22) are arranged axially spaced apart on the first sector region (68) and / or second sector region (70). Combustion chamber device according to one of claims 7 to 14, characterized in that the first sector region (68) and / or second sector region (70) extends over an angular range which is smaller than 90 ° / (2n). Combustion chamber device according to one of Claims 7 to 15, characterized in that the first sector region (68) and / or the second sector region (70) have partial regions (76a, 76b; 78a, 78b) which are attacked by an angle 2α. Combustion chamber device according to one of the preceding claims, characterized in that different resonators for suppressing different tangential modes or combination modes with different tangential component are arranged at different locations of the combustion chamber (11). Combustion chamber device according to one of the preceding claims, characterized in that the first resonator device is tuned to the first overtone of the first tangential mode (1T), the second resonator device is arranged at an angle of 90 ° to the first resonator device and to the first tangential mode (1T) is tuned, a third resonator is arranged at an angle of 45 ° and is tuned to the second tangential mode (2T), and a fourth resonator device is disposed at an angle of 30 ° and is tuned to the third tangential mode (3T). Combustion chamber device according to one of the preceding claims, characterized in that in the resonator chamber (28) of a resonator device (22) one or more resonance influencing elements (100) are arranged, which are fluid-permeable and turbulence-generating. Combustion chamber device according to the preamble of claim 19 or claim 19, characterized in that in the resonator (28) one or more gratings (138) and / or porous structures (106) are arranged as resonance influencing elements (100). Combustion chamber device according to claim 20, characterized in that a porous structure (106) is open-pored. Combustion chamber device according to one of claims 19 to 21, characterized in that the one or more resonance influencing elements (100) are arranged at or in the vicinity of an end opening (29). Combustion chamber device according to one of claims 19 to 22, characterized in that the or the resonance influencing elements (100) extend substantially over the entire cross section of the resonance chamber (28). Combustion chamber device according to one of claims 19 to 23, characterized in that the one or more resonance influencing elements (100) completely or partially fill the resonator chamber (28). Combustion chamber device according to one of claims 19 to 24, characterized in that the one or more resonance influencing elements (100) are made of a metallic or ceramic material. Combustion chamber device according to one of claims 19 to 25, characterized in that a resonance influencing element (100) comprises a porous structure (106) of a fiber material, wherein the fiber density is in the range between 5 mg / cm ³ and 300 mg / cm ³ . Combustion chamber device according to one of claims 19 to 26, characterized in that a resonance influencing element (100) comprises a porous structure (106) of a fiber material, wherein the fiber density is in the range between 10 mg / cm ³ and 200 mg / cm ³ . Combustion chamber device according to one of claims 19 to 27, characterized in that a resonance influencing element (100) comprises a grid (138), wherein a mesh count (M) in the range between 300 1 / cm ² and 6000 1 / cm ² . Combustion chamber device according to claim 28, characterized in that a resonance influencing element (100) comprises a grid (138), wherein a mesh count (M) in the range between 400 1 / cm ² and 5000 1 / cm ² .

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