EP0990851B1 - Gas turbine combustor - Google Patents

Description

TECHNICAL AREA

The present invention relates to the field of gas turbines. It affects a combustion chamber for a gas turbine, in which combustion chamber the hot combustion gases a combustion zone are enclosed by inner walls, which by cooling air, which by outside of the inner walls by a The outer wall of the combustion chamber and the inner walls formed cooling air channels is introduced, cooled.

Such a combustion chamber is in the form of a secondary combustion chamber e.g. from the Document EP-A1 0 669 500 of the applicant is known.

STATE OF THE ART

More conventional in the combustion chambers, especially the secondary combustion chambers Gas turbines can cause pressure vibrations during operation under certain conditions or acoustic vibrations that occur in terms of frequency Range of several kHz, e.g. are in the range of 2-6 kHz. Such vibrations prove to be disruptive to the operation and are therefore undesirable. There is a possibility of damping or suppressing such vibrations in providing fluidic means in the combustion chamber which influence the flow of hot gases in such a way that the acoustic Vibrations are not excited or only to a small extent. Another One possibility is to have so-called Helmholtz resonators on the combustion chamber to attach, which couple to the vibrations as damping elements and dampen the vibrations or make them disappear completely.

Various examples of the use of are from the prior art Helmholtz resonators known. In US-A 5,373,695 a Annular combustion chamber for a gas turbine described, in which on the front side individual Helmholtz resonators flushed with cooling air are arranged next to the burners are, each comprising an external damping volume, the is connected to the combustion chamber via a damping tube and for prevention a heat-related frequency detuning over a thin one Cooling air is applied to the supply pipe from the outside.

A gas turbine combustor is described in US Pat. No. 5,644,918, with the leading within the cooling air surrounding the combustion chamber Double jacket and on the front of the combustion chamber in the area of the burner by pulling in additional dividing walls Helmholtz resonators 48 and 56 are formed, the constrictions 50 and 58 in connection with the combustion chamber stand, but are otherwise completely completed, so that a Flow of cooling air through the resonator rooms does not take place.

Another solution that specifically relates to a secondary combustion chamber is in US-A 5, 431,018. A Helmholtz resonator flushed with cooling air surrounds concentrically the one that opens radially into the combustion chamber Fuel line through which the fuel for afterburning in the combustion chamber is injected.

The known solutions working with Helmholtz resonators are complex in the construction, is difficult to retrofit with existing gas turbines, take up considerable space when used in a plurality a, and are not compatible with cooling concepts where the inner wall of the Combustion chamber is cooled by cooling air brought in from the outside. additionally solutions using Helmholtz resonators usually have the disadvantage on that their sound absorption profile is pretty narrow-band in the frequency domain and is not approximately the above and typically relevant Can cover the range from 2-6 kHz. The resonators can individually or in groups, which then becomes one leads to inhomogeneous broadening of the absorption profile, but has such a solution inherent the disadvantage that less power absorbs at a certain frequency can be.

European publication EP-A1-0 576 717 discloses a gas turbine combustor. In this combustion chamber the flame tube is located away from the combustion chamber Side exposed to an air flow supplied by the gas turbine compressor. The flame tube is essentially composed of wall parts, the combustion chamber outer wall parts facing away from each have a plurality of inlet openings distributed over the circumference have, introduced via the cooling air into an intermediate space arranged in the flame tube becomes. From the intermediate space, the cooling air is passed through outlet bores into the combustion chamber facing inner wall parts introduced into the combustion chamber. The The space between the wall parts is on to form a Helmholtz resonator large, closed additional volume coupled, with the inlet openings in the outer wall parts as feed pipes and the outlet bores as damping pipes of the Helmholtz resonator, are formed.

EP-A1-0 971 172 discloses a gas turbine. In this combustion chamber, in which the hot combustion gases of a combustion zone are enclosed by inner walls, which is cooled by cooling air brought in outside the inner walls a simultaneous efficient acoustic damping and cooling achieved that at least in a partial area on the outside of the inner walls, a distance from the inner walls, perforated plate arranged essentially parallel to the inner walls which, together with the associated inner wall, is a closed damping volume forms that the inner walls in the region of the damping volume a plurality of distributed first openings through which the damping volume with the combustion zone of the combustion chamber communicates that the perforated plate is a Has a plurality of distributed second openings through which cooling air from flows into the outside of the damping volume and in the manner of an impingement cooling between the first openings meets the opposite outside of the inner wall, and that the Distance between the perforated plate and the inner wall and the geometric dimensions of the first openings are selected so that the first openings together with the damping volume form a plurality of interconnected Helmholtz resonators and act as a silencer for acoustic vibrations arising in the combustion chamber.

PRESENTATION OF THE INVENTION

It is therefore an object of the invention to use a combination of Helmholtz resonators and a sound-absorbing perforated plate acoustically damped To create combustion chamber for gas turbines, which have the disadvantages of the known Avoids solutions and especially by a small additional Characterized effort and space requirements for the integrated resonators, and at the same time allows effective cooling of the inner walls of the combustion chamber, and which has the broadest possible sound absorption profile in the frequency range.

The task is thereby in a combustion chamber of the type mentioned solved that at least in a partial area of the inner walls of the inner wall at least two perforated plates arranged essentially parallel to one another is formed that a first perforated plate borders directly on the cooling air channels and is provided with a plurality of first openings through which cooling air from the cooling air channels into a first intermediate volume lying behind the first perforated plate flows that behind the first perforated plate, towards the combustion zone, a further perforated plate is arranged, which with a plurality of further openings is provided that the distance between the first perforated plate and the other perforated plate and the geometric dimensions of the others Openings and are selected so that the openings together with between the perforated plates existing intermediate volumes a plurality of one another connected Helmholtz resonators and as a silencer for in acoustic vibrations arising in the combustion chamber act, and that in addition there are other agents which have a sound-absorbing effect. The The essence of the invention is therefore that the combination of Helmholtz resonators with further sound-absorbing means for a broad sound absorption characteristic leads to a small footprint.

A first preferred embodiment of the invention is characterized by that at least in a partial area of the inner walls, the inner wall of three, in perforated plates arranged substantially parallel to each other is formed that a first perforated plate directly adjoins the cooling air ducts and with a plurality is provided by first openings through which cooling air from the cooling air channels into a first intermediate volume lying behind the first perforated plate flows, which on the side facing the cooling air ducts from the first Perforated plate and on the opposite side of a second perforated plate is limited, which second perforated plate with a plurality of second openings is provided that on the side facing away from the first intermediate volume of the second perforated plate, a third perforated plate is arranged, which has a plurality is provided by third openings, and which to the combustion zone borders, and that at least one of the perforated plates additionally sound-absorbing acts. In other words, the essence of the embodiment is that a of the three perforated plates by appropriate hole design, or by appropriate Contraction ratio, the most possible reflection-free sound transmission has, and that the combination and the geometric design of two further perforated plates a plurality of interconnected Helmholtz resonators creates a phase shift. In addition, the whole Absorption system flushed by cooling air, making the resonators thermal and frequency stabilized. The additional effort to create of the absorption system - if there is effusion cooling the large openings in the inner wall already exist - only from attaching two more perforated plates.

A second preferred embodiment of the combustion chamber according to the invention is characterized in that the contraction ratio, defined as the Ratio between the area of the opening and that towards the combustion zone surface in front, for the second or third openings in the is essentially the same as the largest Mach number that occurs in the combustion chamber, which is defined as the ratio of the source velocity and the Speed of sound, and that the perforated plate provided with such openings has a sound-absorbing effect. This way either the second or the third Perforated panel for sound-absorbing panel, in that a frequency-independent, echo-free transmission is set.

A second preferred embodiment of the combustion chamber according to the invention is characterized in that the distance between the first perforated plate and of the second perforated plate and the geometric dimensions of the second openings be chosen such that the second openings in combination with the first space arranged between the first and the second perforated plate Helmholtz resonators result in their resonance frequency essentially in the area of acoustic vibrations occurring in the combustion chamber lies, and that further preferably the third perforated plate is designed to be sound-absorbing is. The third perforated plate leads to anechoic transmission of the Noise and the Helmholtz resonators behind it in the direction of sound propagation push its phase.

For common frequency values of combustion chamber vibrations in the range of 2-6 kHz, the second perforated plate has a thickness in the range from 0.1 to 1 cm, in particular preferably from 0.6 cm, the area ratio of the acoustically relevant Partial areas of the first intermediate volume and the areas of the second openings are in the range from 5 to 10, particularly preferably from 8, the distance between the first of the second perforated plate is 0.1 to 1 cm, particularly preferred 0.6 cm, the product of the contraction ratio of the third openings and the largest Mach number ranges from 1 to 0.5, and the area ratio of the acoustic relevant areas in the combustion chamber and the acoustically relevant areas the first intermediate volume is in a range from 1 to 2.

Another preferred embodiment of the combustion chamber according to the invention is characterized in that the distance between the first perforated plate and of the third perforated plate and the geometric dimensions of the third openings be chosen such that the third openings in combination with the between the first and the third perforated plate arranged Helmholtz resonators result, whose resonance frequency is essentially in the range the acoustic vibrations occurring in the combustion chamber, and that the second perforated plate is preferably also sound-absorbing. This creates a sound-absorbing arrangement in which the sound-absorbing Perforated plate in the actual damping volume of the Helmholtz resonators is arranged, which proves to be space-saving and yet efficient.

Particularly space-saving and optimal in terms of cooling technology without significant losses the sound-absorbing arrangement can be designed acoustically, if, according to a further embodiment, the second and the third Perforated plate with even and concentric arrangement of the holes in the two perforated plates can be joined directly and without spacing, or that the two perforated plates can even be covered by a single perforated plate holes drilled on both sides with different diameters become.

Further embodiments result from the dependent claims.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

im vereinfachten Längsschnitt eine Sekundärbrennkammer, wie sie aus dem Stand der Technik, insbesondere der EP-A1 0 669 500, bekannt ist;

Fig. 2

einen vergrösserten Ausschnitt der Brennkammer nach Fig. 1 im Bereich des stufenartigen Übergangs zwischen Zuströmzone und Verbrennungszone mit einer integrierten Helmholtzresonator-Anordnung und einem extern angeordneten Dämpfungsblech gemäss einem bevorzugten Ausführungsbeispiel der Erfindung;

Fig. 3

eine schematische Darstellung eines Schnittes der Anordnung nach Figur 2;

Fig. 4

eine vereinfachte kleinste Berechnungseinheit für eine Anordnung gemäss Fig. 2 mit externem Dämpfungsblech;

Fig. 5

die quadrierten Reflexionskoeffizienten als Funktion der Frequenz in verschiedenen Anordnungen mir externem Dämpfungsblech;

Fig. 6

einen vergrösserten Ausschnitt der Brennkammer nach Fig. 1 im Bereich des stufenartigen Übergangs zwischen Zuströmzone und Verbrennungszone mit einer integrierten Helmholtzresonator-Anordnung und einem intern angeordneten Dämpfungsblech gemäss einem bevorzugten Ausführungsbeispiel der Erfindung;

Fig. 7

eine schematische Darstellung eines Schnittes der Anordnung nach Figur 6;

Fig. 8

eine vereinfachte kleinste Berechnungseinheit für eine Anordnung gemäss Fig. 6 mit internem Dämpfungsblech;

Fig. 9

die quadrierten Reflexionskoeffizienten als Funktion der Frequenz in verschiedenen Anordnungen mir internem Dämpfungsblech; und

Fig. 10

einen Schnitt durch ein Lochblech, welches das zweite und das dritte Lochblech ersetzt für den Fall eines internen Dämpfungsblechs.

The invention will be explained in more detail below on the basis of exemplary embodiments in connection with the drawing. Show it

Fig. 1

in a simplified longitudinal section, a secondary combustion chamber, as is known from the prior art, in particular EP-A1 0 669 500;

Fig. 2

an enlarged section of the combustion chamber of Figure 1 in the region of the step-like transition between the inflow zone and combustion zone with an integrated Helmholtz resonator arrangement and an externally arranged damping plate according to a preferred embodiment of the invention.

Fig. 3

is a schematic representation of a section of the arrangement of Figure 2;

Fig. 4

a simplified smallest calculation unit for an arrangement according to FIG 2 with an external damping plate.

Fig. 5

the squared reflection coefficients as a function of frequency in various arrangements with an external damping plate;

Fig. 6

an enlarged section of the combustion chamber of Figure 1 in the region of the step-like transition between the inflow zone and combustion zone with an integrated Helmholtz resonator arrangement and an internally arranged damping plate according to a preferred embodiment of the invention.

Fig. 7

is a schematic representation of a section of the arrangement of Figure 6;

Fig. 8

a simplified smallest calculation unit for an arrangement according to FIG 6 with an internal damping plate.

Fig. 9

the squared reflection coefficients as a function of frequency in various arrangements with an internal damping plate; and

Fig. 10

a section through a perforated plate, which replaces the second and third perforated plate in the case of an internal damping plate.

WAYS OF CARRYING OUT THE INVENTION

In Fig. 1 a secondary combustion chamber is shown in a simplified longitudinal section, which is known from EP-A1 0 669 500, and which is preferred for implementation the invention is suitable. The combustion chamber 10 includes a combustion zone 23, which of an inner wall extending in the axial direction 12 and a radial inner wall 17 is limited. In the combustion zone 23 the hot gases of an upstream combustion stage pass through a Inflow zone 20 in and out through a hot gas outlet 13. The inflow zone 20 is delimited by an inner wall 15. Protrudes into the inflow zone 20 a fuel lance 18 from the side, a nozzle at the front end 19 for fuel injection. The inner walls 12, 15 and 17 are from an outer wall 11 extending in the axial direction. Between a cooling air duct 14 remains free through the inner wall 12 and the outer wall 11 which cooling air against the flow direction of the hot gases in between the inner wall 15 and the outer wall 11 formed rear cooling air duct 16 streams. The inner wall 12 is convectively cooled by the cooling air. The cooling air flows from the rear cooling air duct 16 through openings 21 in the inner wall 15 in the inflow zone 20, and through further openings 22 in the radial Inner wall 17 into the combustion zone 23, thereby causing effusion cooling.

On the radial inner wall 17, i.e. the step-like expansion between the inflow zone 20 and combustion zone 23 can now according to a preferred Embodiment of the invention, as shown in Fig. 2, a Helmholtz resonator arrangement in combination with a sound-absorbing third perforated plate 29 are integrated, which at the same time effective cooling of the arrangement guaranteed. This is done on the outside of the previously radial inner wall 17a 2 a first perforated plate 24 is arranged in parallel at a distance (L in FIG. 4), which together with the actual radial inner wall, which is a forms second perforated plate 17a, includes a first (annular) intermediate volume 26. The second perforated plate 17a has a plurality of more or less regularly distributed openings 27a, which are identical to the openings 22 for the effusion cooling in the combustion chamber according to FIG. 1 can be, but also deviating can have geometric dimensions. The as through holes with a diameter a and a length I (Fig. 4) formed openings 27a each act individually as a damping tube of a Helmholtz partial resonator, that of the respective opening 27a and the partial volume behind it first intermediate volume 26 is formed. The first intermediate volume 26 in total and the entirety of the openings 27a can be used as individual Helmholtz resonators understand, the individual damping volumes with each other to first intermediate volume 26 are connected.

The first perforated plate 24 has in addition to the limitation of the first intermediate volume two other important tasks. Those provided in the first perforated plate 24 Openings 25 let cooling air from the rear cooling air duct 16 into the first intermediate volume 26 flow in. The incoming cooling air cools the one hand Helmholtz arrangement. This is the geometry and thus the Damping frequency of the arrangement kept stable. On the other hand, the openings 25 offset relative to the second openings 27a or arranged "on gap". As a result, the cooling air flowing into the first intermediate volume 26 hits the outside of the second perforated plate opposite the openings 25 17a, which leads to an effective impact cooling of the second perforated plate 17. The The diameter of the openings 25 is compared to the diameter a small (Fig. 4). This ensures that the cooling air flowing through one suffers sufficient pressure drop.

On the inside of the second perforated plate 17a, according to FIG a distance (X in Fig. 4) a third perforated plate 29 arranged in parallel, which together with the second perforated plate 17a a second (ring-shaped) intermediate volume 30 includes. The third perforated plate 29 has a plurality of distributed ones Openings 28 on. These openings 28 are preferably designed such that the third perforated plate 29 the sound generated in the combustion zone 23 transmits echo-free, i.e. that no sound is reflected and therefore this third Perforated plate has a sound-absorbing effect. The second intermediate volume 30 and the third perforated plate are the by the first intermediate volume and the Cooling air flowing through second openings 27a and cooled accordingly.

Figure 3 shows schematically the structure of the embodiment shown in Figure 2 the invention again. The incoming from the combustion zone 23 Sound 31 first passes through the openings 28 of the third perforated plate in an echo-free manner 29 into the second intermediate volume 30. Then the sound hits that from the first 24 and the second 17a perforated plate with the Helmholtz resonators formed with the openings 27a, which push the phase of the sound waves. Flows at the same time by the arrangement in the opposite direction to the sound of the cooling air flow 22 after he through the openings 25 in the first perforated plate 24 into the first intermediate volume 26 has arrived.

A schematic representation of the arrangement, which can be used to calculate its Properties is particularly suitable, together with the specification of the dimensions shown in Figure 4. The main characteristics of this series of elements can be easily calculated by calculating the transformation behavior the Riemannin variants for each element and subsequent determine sequential sequence of transformations. As in this context particularly important property of the sound absorbing perforated plate applies that the transmission of the sound absorbing perforated plate for flow lower Mach numbers then echo-free, i.e. is reflection-free if the contraction ratio, defined as the ratio of the area of the aperture or opening b to the area B in front of the aperture (b / B) is essentially the same as the largest in the Mach number that occurs in the chamber.

The resonance frequency of the resonator arrangement or the partial resonators is in the essentially by the area A, the thickness I of the second perforated plate 17a or Length of the openings 27a, the diameter of the openings 27a and spacing L of the plates determined. For attenuation of frequencies in the range of several kHz are the openings 27a as through holes with a length I of a few millimeters and a diameter a of a few millimeters. The distance L between the first 24 and the second 17a perforated plate is a few millimeters, and the ratio of area A to hole area a is in the range from 5 to 10.

For the attenuation of frequencies in the range from 2 to 6 kHz, the exemplary values listed in the following table can be given: input values Temperature of the air 770 K Hole length I 6 mm Distance between plates L 6 mm Plate spacing X 6 mm Area ratio A / a 8th Area ratio B / A 1 Product of Mach number and inverse contraction ratio 1 Mass flow of the cooling air 3.88 kg / (s * m ^ 2) Burner pressure 16.6 bar output values Flow rate in the openings 27a 4.13 m / s Inverse contraction ratio 32.81 Flow speed through the third perforated plate 29 16.94 m / s

The damping behavior of the arrangement for the values from the table from Helmholtz resonators and sound-absorbing perforated plate 29 is in Fig. 5a) reproduced. 5 shows the squared reflection coefficient in each case (reflection coefficient squared) over the frequency in Hz. One can see Fig. 5a), that for the above values in the whole range from 2 to 6 kHz significant absorption takes place, and that resonant absorption occurs at 4720 Hz. Very strong Absorption is in the range from 3.5 to 5.5 kHz, where more than 75% of the acoustic Power to be absorbed.

If you change the area ratio B / A to 2 from the above input values alone, ie if you reduce the ratio of burner area to damping area, the result is an absorption behavior as indicated in FIG. 5b), while the output values given in the table do not change. Sound absorption generally decreases and there is no longer any resonant absorption. This shows that the whole arrangement must always be taken into account and that one should not consider Helmholtz resonators and sound absorbing plates separately. In order to remedy the detuning of the system by the above change, the third perforated plate must be changed, namely besides B / A = 2 the product of Mach number and inverse contraction ratio must be set to 0.5. The following new initial values then result: output values Inverse contraction ratio 23:21 Flow speed through the third perforated plate 29 11.98 m / s

This reduction in the flow velocity through the third perforated plate 29 the result is a behavior according to FIG. 5c), again a resonant is observed Absorption at approximately the same frequency, albeit the area is stronger Absorption has become narrower compared to Figure 5a) because of the contraction ratio is no longer optimally adapted to the maximum Mach number.

Another embodiment of an embodiment of the invention is shown in FIG 6 shown. In this case it is a so-called internal absorber, i.e. the sound-absorbing sheet is in the actual damping volume of the Helmholtz resonators. The Helmholtz resonators are in in this case from a first perforated plate facing the rear cooling air duct 16 24 and a third perforated plate directly adjacent to the combustion zone 23 17b formed. The first perforated plate 24 in turn has openings 25, through which cooling air 22 flows into the arrangement. The third perforated plate 17b has Openings 27b, which serve as damping tubes of the Helmholtz resonators. The damping volume of the Helmholtz resonators exposes itself in this case the two intermediate volumes 32 and 35 together, which by the between the first 24 and the third 17b perforated plate retracted second perforated plate 34 be formed. The second perforated plate 34 is provided with openings 33 which are designed such that this second perforated plate 34 is sound-absorbing, i.e. appears anechoic. As described above, this is done by adjusting to the highest Mach number Contraction ratio.

FIG. 7 again shows a schematic illustration of how the sound 31 from the Combustion zone 23 strikes the arrangement with internal absorber, and how the cooling air 22 through the openings 25 from the opposite side flows. The one used to calculate the main characteristic properties of a Such an arrangement of the simplest representation of the elements is analogous to FIG. 4 given in Figure 8 along with the dimensions. The resonance frequency of the In this case, the resonator arrangement or the partial resonators essentially becomes by the area A, the thickness I1 of the third perforated plate 17b or the length of the openings 27b, the diameter of the openings 27b and spacing L1 of the plates. For attenuation of frequencies in the range of several kHz are the openings 27b as through holes with a length I1 of a few Millimeters and a diameter of a few millimeters. The distance L1 between the first 24 and the third 17b perforated plate is a few Millimeters, and the ratio of area A to hole area a is in the range from 5 to 10.

For the attenuation of frequencies in the range from 2 to 6 kHz, the exemplary values listed in the following table can be given: input values Temperature of the air 770 K Hole length I1 6 mm Plate spacing L1 8th mm Plate spacing Y 3 mm Area ratio A / a 8th Area ratio B / A 1 Product of Mach number and inverse contraction ratio 2025 Mass flow of the cooling air 3.88 kg / (s * m ^ 2) Burner pressure 16.6 bar output values Flow rate in openings 27b 4.13 m / s Inverse contraction ratio 46.68 Flow velocity through the second perforated plate 34 24.10 m / s

The damping behavior of the arrangement for the values from the table from Helmholtz resonators and internal sound-absorbing perforated plate 34 is shown in Fig. 9a). Fig. 9 again shows the squared Reflection coefficient squared over frequency in Hz. It can be seen in FIG. 9 a) that for the above values in the entire range from 2 to 6 kHz significant absorption takes place, and that at 3880 Hz resonant absorption occurs. One has very strong absorption in the range from 2.9 to 5.2 kHz, where more than 75% of the acoustic power is consumed.

If you change the area ratio B / A to 2 from the above input values as above, i.e. if you reduce the ratio of burner area to damping area, the result is an absorption behavior as indicated in FIG. 9b), while the output values given in the table do not change , Sound absorption generally decreases and there is no longer any resonant absorption. In order to remedy the detuning of the system by the above change, the second perforated plate 34 has to be changed. In addition to B / A = 2, the product of Mach number and inverse contraction ratio has to be set to 0.981. The following new initial values then result: output values Inverse contraction ratio 32.50 Flow velocity through the second perforated plate 34 16.78 m / s

By reducing the flow rate through the second perforated plate 34 results in a behavior according to FIG. 9c), again a resonant is observed Absorption at approximately the same frequency, albeit the area is stronger Absorption has become narrower compared to Figure 9a) because of the contraction ratio is no longer optimally adapted to the maximum Mach number.

If you compare the characteristics of the internal and external absorber in each case for the first input values, you can see that the absorption at the external Absorber increases relatively slowly between 2 and 4.5 kHz and decreases rapidly above 5.2 kHz, while the absorption in the internal absorber is between 2 and 3.5 kHz increases quickly and decreases slowly above 4.5 kHz. The absorption behavior an arrangement with an internal absorber is therefore not only more symmetrical, but it also generally has a broader absorption. ever depending on the application and the sound frequencies involved, one or the other the other arrangement is more suitable.

Because in an arrangement with three spaced perforated plates, the cooling in particular the wall exposed to the combustion zone 23 is no longer optimal can be accomplished, it can prove to be advantageous, according to another Embodiment of the invention, the sound-absorbing perforated plate and the perforated plate, which forms the damping tubes of the Helmholtz resonators, immediately to be placed next to each other, or even by one, with special, stepped Openings provided perforated plate 37 to be replaced. Such a perforated plate 37 is for an arrangement with internal absorber shown in Figure 10. The perforated plate 37 has openings of different diameters from the two sides, wherein the second stage part 39 facing the combustion zone 23 to the damping tubes 27b from FIG. 6, and the other, first step part 38 ensures anechoic transmission and corresponds to the openings 33 from FIG. 6. In this way you have the advantage of only having to provide two perforated plates, which greatly simplifies cooling and construction, and still one efficient combined arrangement of Helmholtz resonators and sound absorbers to have.

All of the above exemplary embodiments are distinguished in that they are based on can be easily installed in an existing combustion chamber. In The exemplary embodiments described here become the former radial Inner wall 17 once as the second 17a and once as the third 17b perforated plate three-part arrangement used. Of course, the former radial Inner wall 17 but take over the task of each of the three perforated plates or else that of the perforated plate 37 with stepped openings. Depending on space and already existing bores 22 in the radial inner wall 17 can thus Retrofitting can be done in one way or another.

LIST OF REFERENCE NUMBERS

10

secondary combustion chamber

11

outer wall

12

Inner wall (combustion zone)

13

hot gas outlet

14

Cooling air duct

15

Inner wall (inflow zone)

16

rear cooling air duct

17

radial inner wall

17a

second perforated plate

17b

third perforated plate

18

fuel lance

19

Nozzle (fuel lance)

20

inflow zone

21

Opening (wall 15)

22

Opening (wall 17)

23

combustion zone

24

first perforated plate

25

first opening

26

first intermediate volume

27a

second opening

27b

third opening

28

third opening

29

perforated plate

30

second intermediate volume

31

sound waves

32

first intermediate volume

33

Opening in 34

34

second perforated plate

35

second intermediate volume

36

perforated sheet

37

stepped opening

38

first stage part

39

second stage

L

Length of the damping volume

I

Neck length

X

Distance of the external perforated sheet of 17

L1

Length of the damping volume

I1

Neck length

Y

Internal perforated sheet spacing of 17

Claims (12)

1. Combustion chamber (10) for a gas turbine, in which combustion chamber (10) the hot combustion gases of a combustion zone (23) are surrounded by inner walls (12, 17) which are cooled by cooling air, which is introduced through cooling air ducts (14, 16) outside the inner walls (12, 17), which cooling air ducts (14, 16) are formed by an outer wall (11) of the combustion chamber (10) and the inner walls (12, 17), the inner wall (17) being formed, at least in a partial region of the inner walls (12, 17), from at least two perforated plates (24, 17a; 24, 17a) arranged essentially parallel to one another, a first perforated plate (24) bordering directly on the cooling air ducts (14, 16) and being provided with a plurality of first openings (25) through which cooling air (22) from the cooling air ducts (14, 16) flows into a first intermediate volume (26, 32) located behind the first perforated plate, a further perforated plate (17a, 17b) being arranged behind the first perforated plate (24), in the direction of the combustion zone (23), which further perforated plate (17a, 17b) is provided with a plurality of further openings (27a, 27b), the distance (L, L1) between the first perforated plate (24) and the further perforated plate (17a, 17b) and the geometrical dimensions (I, I1, a, A) of the further openings (27a, 27b) being selected in such a way [sic], characterized in that the openings (27a, 27b), together with intermediate volumes (26, 32, 35) present between the perforated plates (24, 17a, 17b), form a plurality of mutually connected Helmholtz resonators and act as noise dampers for acoustic vibrations (31) occurring in the combustion chamber, and in addition further means (29, 34) which act to absorb noise are present.
2. Combustion chamber (10) according to Claim 1, characterized in that, at least in a partial region of the inner walls (12, 17), the inner wall (17) is formed from three perforated plates (24, 17a, 29; 24, 34, 17a) arranged essentially parallel to one another, the first perforated plate (24) bordering directly on the cooling air ducts (14, 16) and being provided with a plurality of first openings (25) through which cooling air (22) from the cooling air ducts (14, 16) flows into a first intermediate volume (26, 32) located behind the first perforated plate, which first intermediate volume (26, 32) is bounded, on the side facing towards the cooling air ducts (14, 16), by the first perforated plate (24) and, on the opposite side, by a second perforated plate (17a, 34), which second perforated plate (17a, 34) is provided with a plurality of second openings (27a, 33), in that a third perforated plate (17b, 29) is arranged on the side of the second perforated plate (17a, 34) facing away from the first intermediate volume (26, 32), which third perforated plate (17b, 29) is provided with a plurality of third openings (27b, 28) and borders on the combustion zone (23), and in that at least one of the perforated plates (29, 34) is configured to absorb noise.
3. Combustion chamber (10) according to Claim 2, characterized in that the contraction ratio, defined as the ratio between the area (b) of the opening (28, 33) and the area (B) located in front of it in the direction of the combustion zone (23), is essentially the same for the second (33) or the third (28) openings as the maximum Mach number occurring in the combustion space (23), which is defined as the ratio of the source velocity and the sonic velocity, and in that the perforated plate (29, 34) provided with such openings (33, 28) acts in a noise-absorbing manner.
4. Combustion chamber (10) according to one of Claims 2 or 3, characterized in that the second (17a, 34) and the third (17b, 29) perforated plates are at such a distance from one another that a second intermediate volume (30, 35) is formed.
5. Combustion chamber (10) according to one of Claims 2 to 4, characterized in that the distance (L) between the first perforated plate (24) and the second perforated plate (17a) and the geometrical dimensions (I, a, A) of the second openings (27a) are selected in such a way that the second openings (27a), in combination with the first intermediate space (26) arranged between the first (24) and the second (17a) perforated plates, provide Helmholtz resonators whose resonant frequency is essentially located within the range of the acoustic vibrations (31) occurring in the combustion space (23).
6. Combustion chamber (10) according to Claims 3 and 5, characterized in that the third perforated plate (29) is configured to noise absorb.
7. Combustion chamber (10) according to Claim 6, characterized in that the second perforated plate (17a) has a thickness (I) in the range from 0.1 to 1 cm, in particular preferably 0.6 cm, in that the area ratio of the acoustically relevant partial areas (A) of the first intermediate volume (26) and the areas (a) of the second openings (27a) is in the range from 5 to 10, in particular preferably 8, in that the distance (L) of the first (24) from the second (17a) perforated plate is 0.1 to 1 cm, in particular preferably 0.6 cm, in that the product of the contraction ratio of the third openings (28) and the maximum Mach number is in the range from 1 to 0.5, and in that the area ratio of the acoustically relevant partial areas (B) in the combustion space (23) and the acoustically relevant partial areas (A) of the first intermediate volume (26) is in a range from 1 to 2, so that the Helmholtz resonators, in combination with the noise-absorbing perforated plate (29), absorb acoustic vibrations (31) occurring in the combustion space (23) with frequencies in the range from 2 to 6 kHz.
8. Combustion chamber (10) according to one of Claims 2 to 4, characterized in that the distance (L1) between the first perforated plate (24) and the third perforated plate (17b) and the geometrical dimensions (I1, a, A) of the third openings (27b) are selected in such a way that the third openings (27b), in combination with the intermediate space arranged between the first (24) and the third (17b) perforated plate, provide Helmholtz resonators whose resonant frequency is essentially located within the range of the acoustic vibrations (31) occurring in the combustion space (23).
9. Combustion chamber (10) according to Claims 3 and 8, characterized in that the second perforated plate (34) is configured to absorb noise.
10. Combustion chamber (10) according to Claim 9, characterized in that the third perforated plate (17b) has a thickness (I1) in the range from 0.1 to 1 cm, in particular preferably 0.6 cm, in that the area ratio of the acoustically relevant partial areas (A) of the intermediate space and the areas (a) of the third openings (27b) is in the range from 5 to 10, in particular preferably 8, in that the distance (L1) of the first (24) from the third (17b) perforated plate is 0.1 to 1 cm, in particular preferably 0.6 cm, in that the product of the contraction ratio of the second openings (33) and the maximum Mach number is in the range from 2.5 to 0.5, and in that the area ratio of the acoustically relevant partial areas (B) in the combustion space (23) and the acoustically relevant partial areas (A) of the first intermediate volume (26) is in a range from 1 to 2, so that the Helmholtz resonators, in combination with the noise-absorbing perforated plate (34), absorb acoustic vibrations (31) occurring in the combustion space (23) with frequencies in the range from 2 to 6 kHz.
11. Combustion chamber (10) according to one of Claims 2 to 10, characterized in that the second (17a, 34) and the third (29, 17b) perforated plates lie directly one above the other, and in that the second (27a, 33) and the third (28, 27b) openings are arranged to be equally distributed and concentric.
12. Combustion chamber (10) according to Claim 11, characterized in that the second (17a, 34) and the third (29, 17b) perforated plates are formed by a perforated diaphragm (36) which has stepped openings (37), whose first stepped parts (38) facing towards the first perforated plate (24) correspond to the second openings (27a, 33) and whose stepped parts (39) facing towards the combustion space (23) correspond to the third openings (28, 27b).

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