EP1213538B1 - Exhaust gas system with Helmholtz resonator - Google Patents

Description

Technical area

The invention relates to an exhaust system for industrial gas turbines with an exhaust pipe and an adjoining fireplace, according to the preamble of claim 1.

Settlement areas and facilities that run on gas turbines, such as thermal power plants, are moving closer together. In order to minimize the noise pollution of the population, the limit values for noise emissions have been tightened in recent years. In addition to the existing limits for high and medium frequencies, additional limits for low-frequency noise have been introduced in many places. The noise emissions of a gas turbine plant mainly takes place via its exhaust system. The emergence of the difficult to control low-frequency noise has many causes and is due among other things to pulsations in the combustion chamber.

State of the art

In order to be able to comply with the limits for low-frequency noise emissions, absorption silencers have been incorporated into the exhaust gas system of the gas turbine plants, as mentioned, for example, in DE-A1-44 19 604 and DE-A1-40 09 072. This is intended to reduce the low-frequency noise at the place where its radiation into the environment takes place. But while sound in the high and medium frequency range can be absorbed relatively well with absorption silencers, low-frequency noise is difficult to control, since conventional silencers show only low sound attenuation at low frequencies. To be able to reduce the low-frequency noise, therefore, large absorption silencers with insulating mats of up to 800mm thickness must be installed in the exhaust system of the plants. This increases the footprint of the exhaust system, possibly reduces their performance due to pressure drop in the system and is also very expensive to install and maintain. The exhaust system is very expensive.

Presentation of the invention

The object of the invention is therefore to provide an exhaust system of the type mentioned, are efficiently reduced in the low-frequency noise emissions without the performance of the system is significantly impaired and is also easy and economical to install and Watung.

This object is achieved by an exhaust system with the features of claim 1.

In an exhaust gas system for industrial gas turbines, an exhaust pipe and a chimney adjoining it together form a continuous flow channel. In the exhaust system, a Helmholtz resonator is acoustically coupled to the flow channel. The Helmholtz resonator is exactly tuned to the low frequency that is to be damped. It takes up less space than an absorption silencer. The installation of a Helmholtz resonator is very simple and its durability at high flow rate in relation to absorption silencers much higher. Moreover, the use of Helmholtz resonators causes no reduction in performance of the system. For these reasons, the exhaust system can be installed and maintained more easily and the entire system can be operated more economically.

If the Helmholtz resonator is arranged with its inlet opening in the range of a maximum pressure of an acoustic mode in the exhaust system, its efficiency is greatest

It is very advantageous to arrange the Helmholtz resonator in the transition region between the exhaust duct and the chimney, since there are usually hardly any space problems. It is particularly advantageous to provide the Helmholtz resonator on the rear wall of the chimney which delimits the exhaust gas channel in the flow direction, since this allows a particularly simple assembly.

In a preferred embodiment, the dimensions of the exhaust duct and the chimney are selected so that a pressure maximum of the acoustic mode occurs in the transition regions between the exhaust duct and the chimney. In this way, the Helmholtz resonator, as described above, can be mounted very easily and is also extremely efficient.

A heat insulation of the Helmholtz resonator to the outside ensures an approximately constant temperature of the Helmholtz resonator and thus a frequency stability of its absorption properties.

If the Helmholtz resonator has a neck which is adjustable in its length and / or its cross section, the Helmholtz resonator can be better adjusted to the frequencies to be absorbed.

In a further preferred embodiment, the Helmholtz resonator has an adjustable volume. This also provides a simple possibility of adaptation to the frequencies to be absorbed. The adjustable volume can be realized very simply by making the height of the side walls adjustable by means of a sliding floor.

If the temperature of the Helmholtz resonator is adjustable, it can be particularly easily adapted to the frequency to be absorbed. The adjustability of the temperature can be realized, for example, simply by attaching heating elements to the outer walls of the Helmholtz resonator. Another cost-effective option is to make the Helmholtz resonator flow around, so that either hot exhaust gases are diverted from the exhaust system for temperature regulation and passed to the outer walls of the Helmholtz resonator or the same is flowed around with cold air.

In a further preferred embodiment, the Helmholtz resonator is acoustically transparent shielded from the flow in the flow channel. This allows a better sound absorption of the Helmholtz resonator. Such a shield can be implemented very simply and expediently by means of an absorption silencer arranged between the inlet opening of the Helmholtz resonator and the flow.

It is particularly advantageous to use an absorption silencer, which has approximately the following structure: A first hole cover is part of a wall bounding the flow channel. A flow-resistant fabric arranged on the side of the hole covering facing away from the flow passage and a layer of damping material adjoin this first hole cover. This is followed by a second hole cover on the side facing away from the flow passage. Laterally, the absorption silencer is comprised of sidewalls. Such an absorption silencer has a good load capacity adjacent to a flow channel with high flow velocities.

If a cavity is arranged between the absorption silencer and the inlet opening of the Helmholtz resonator, this has a positive effect on the oscillation behavior of the Helmholtz resonator and thus on its absorption capacity.

It is very advantageous to provide a plurality of Helmholtz resonators in the exhaust system. These may then be located at different locations in the exhaust system, e.g. in each case where maxima of the sound modes occur. They can also be tuned to different, low frequencies and thus contribute to an even more effective reduction of low-frequency noise. For this they can be arranged at different locations of the exhaust system or also close to each other. To ensure good sound absorption, however, the Helmholtz resonators should be separated from each other in a gas-tight manner.

Further preferred embodiments are the subject of further dependent claims.

Brief description of the drawings

Fig. 1

ein erfindungsgemässes Abgassystem mit Helmholtz-Resonator;

Fig. 2

in einem schematischen Schnitt entlang der Längsachse des Strömungskanals einen Teil eines erfindungsgemässen Abgassystems mit nebeneinander angeordneten Helmholtz-Resonatoren;

Fig.3

eine Ansicht der nebeneinander angeordneten Helmholtz-Resonator aus Fig. 2 gemäss dem Schnitt III-III in Fig. 2; und

Fig. 4

in einem schematischen Schnitt einen Helmholtz-Resonator mit Längenverstellbarem Hals und verstellbarem Volumen.

In the following, the subject invention will be explained in more detail with reference to preferred embodiments, which are illustrated in the accompanying drawings. It shows purely schematically:

Fig. 1

an inventive exhaust system with Helmholtz resonator;

Fig. 2

in a schematic section along the longitudinal axis of the flow channel, a part of an inventive exhaust system with juxtaposed Helmholtz resonators;

Figure 3

a view of the juxtaposed Helmholtz resonator of Figure 2 along the section III-III in Fig. 2. and

Fig. 4

in a schematic section a Helmholtz resonator with adjustable length neck and adjustable volume.

The reference numerals used in the drawings and their meaning are listed in the list of reference numerals. Basically, the same parts are provided with the same reference numerals in the figures. The described embodiments are exemplary of the subject invention and have no limiting effect.

Ways to carry out the invention

Figure 1 shows the sketch of an exhaust system 10 for a gas turbine plant (not shown) with an exhaust passage 12 and a chimney 14. The exhaust passage 12 and the chimney 14 together form a flow channel 16. The flow direction of the exhaust gas 18 in the flow channel 16 is indicated by arrows S. In a transition region 20 between the exhaust duct 12 and the chimney 14, the exhaust duct 12 is bounded by a rear wall 22 of the chimney 14 in its flow direction S. In the transition region 20, a Helmholtz resonator 24 is arranged on the rear wall 22 of the chimney 14. The Helmholtz resonator 24 is shielded by the flow in the flow channel 16 through a hole cover 26, which forms part of the rear wall 22 of the chimney 14, and arranged behind the hole cover 26 from the flow channel 16, acoustically transparent tissue.

The exhaust gas channel 12 and the chimney 14 are dimensioned such that a pressure maximum of a sound mode lies in the transition region 20 or in the inlet region 30 of the Helmholtz resonator 24. The Helmholtz resonator 24 is thermally insulated to the outside so that it assumes an approximately constant temperature during operation. In addition to the Helmholtz resonator 24 in the exhaust system 10 in a known manner absorption mufflers 32 are arranged to sound in the range of high and to absorb medium frequencies.

As indicated by dashed lines in Fig. 1, it is possible to the Helmholtz resonator 24 at other locations of the exhaust system 10 or even several Helmholtz resonators 24, 24 ', 24 ", ... to arrange at different locations of the exhaust system 10. In order to achieve good sound absorption efficiency, the Helmholtz resonator or resonators 24, 24 ', 24 ",... Should be arranged in the exhaust system 10 where a pressure maximum of a sound mode lies.

In FIGS. 2 and 3, a portion of an exhaust system 10 is shown in various views, in which three Helmholtz resonators 24, 24 ', 24 "are arranged side by side in the transition region 20 between the exhaust duct 12 and the chimney 14 on the rear wall 22 of the chimney 14 The exhaust gas channel 12 and the chimney 14 are in turn dimensioned such that the maximum pressure of a sound mode lies in the transition region 20 or in the inlet region 30 of the Helmholtz resonators 24, 24 ', 24 ". The three Helmholtz resonators 24, 24 ', 24 "are formed in a cylindrical hollow body 34. Against the flow channel 16, the hollow cylinder 34 is shielded by an upstream absorption silencer 36.

Spaced to this absorption silencer 36, an intermediate wall 38 is arranged in the hollow cylinder 34, which encloses a gap 44 together with the absorption silencer 36. On the opposite side of the intermediate wall 38, the hollow cylinder 34 is closed by a bottom 40 against the outside gas-tight. The entire hollow cylinder 34 and the bottom 40 are thermally insulated from the outside, so that the hollow cylinder 34 assumes approximately the temperature in operation, which prevails in the flow channel 16.

The absorption silencer 36 has essentially the usual structure: Against the flow channel 16 of the absorption silencer 36 is delimited by a hole cover 26, which forms part of the rear wall 22 of the chimney 14. The hole cover 26 is backed with a flow resistant and wear resistant fabric 28 that is acoustically transparent, such as a metal mesh. The layer 28 is followed on the fabric 28 by a layer of damping material 46, which can be constructed in one or more layers adapted to the frequency range to be absorbed. The material and the thickness of the damping material 46 are determined as required. Finally, against the gap 44 through a further hole cover 48 is arranged. The jacket of the hollow cylinder 34 also forms the side walls for the absorption silencer 36.

The remaining between the intermediate wall 38 and the bottom 40 cavity of the hollow cylinder 34 is divided by means of walls 42 into three sectors, which form the volumes 25, 25 ', 25 "of the three Helmholtz resonators 24, 24', 24". The walls 42 close off the Helmholtz resonators 24, 24 ', 24 "in a gastight manner against each other. Each Helmholtz resonator 24, 24', 24" is acoustically connected to the one between the two through a tubular neck 47, which is guided through the intermediate wall 38 connected upstream absorption silencer 36 and the intermediate wall 38 intermediate space 44. Low-frequency sound that is not absorbed by the absorption silencer 36 is conducted into the gap 44 and further into the three Helmholtz resonators 24, 24 ', 24 ". The number and shape of the Helmholtz resonators 24, 24', 24" shown here can be changed as needed. Thus, a Helmholtz resonator 24, two, three, four, or even more resonators 24, 24 ', 24 ", ... can be arranged side by side, and the shape can also vary as desired In addition, one or more Helmholtz resonators 24, 24 ', 24 ",... can be arranged next to one another at other locations of the exhaust system 10 as well.

In a particular embodiment, the three Helmholtz resonators 24, 24 ', 24 "by means of adjustable in length and / or in cross-section necks 47 and by means of an adjustable volume 25, 25', 25" set to slightly different, low frequencies , which preferably also differ from the frequency which is attenuated in the intermediate space 44. In this way, the low-frequency noise can be reduced with high efficiency.

FIG. 4 shows in section the principle of an adaptable Helmholtz resonator 24a. As can be seen from FIG. 4, the neck 47a has two tubes 50, 52 inserted into one another. But it can also be chosen any other cross-sectional shapes. The outer tube 50 with the larger diameter is firmly anchored in the intermediate wall 30. It may be welded to the intermediate wall 30, for example. The outer tube 50 has on its inside, in its two end regions in each case on circular discs, radially inwardly extending projections 54. Between the projections 54, a seal 56 is arranged, which comprises the inner tube 52 with the slightly smaller diameter gas-tight. The inner tube 52 is concentric in the outer tube 50 and slidably mounted against the resistance of the seal 56. The inner tube 52 has radially outwardly bent ends 53 which, brought into abutment with the projections 54, prevent the inner tube 52 from being pulled too far out of the outer tube 50. By displacing the inner tube 52 in the outer tube 50, the neck 47a of the Helmholtz resonator 24a is slidable in length. An adjustability of the neck diameter can be established, for example, by forming the neck with a polygonal cross-section and by pivoting the side walls of the polygon towards one another.

The volume 25a of the Helmholtz resonator 24a is adjustable by means of height-adjustable side walls 58. The height of the side walls 58 is variable by means of a sliding floor 60. The displaceable bottom 60 is cup-shaped and comprises a bottom plate 62 and of this approximately perpendicular protruding bottom walls 64 which engage around the side walls 58 of the Helmholtz resonator 24a side. At their bottom plate 62 opposite end 66, the bottom walls 64 are bent radially inwardly. Distanced from the bent ends 66, a radially inwardly extending collar 68 is provided on the bottom walls 64. Between the collar 68 and the bent ends 66 of the bottom walls 64, a bottom seal 70 is arranged, which comprises the side walls 58 of the Helmholtz resonator 24 a gas-tight. The side walls 58 have on their the bottom 60 side facing radially outwardly bent edges 72, which can be brought into abutment with the collar 68, and thus prevent the bottom of the side walls 58 of the Helmholtz resonator 24a is deductible. The volume 25a of the Helmholtz resonator 24a is thus in the context of the displacement of the bottom 60 from the stop of the bottom plate 62 to the edges 72 of the side walls 58 up to stop the edges 72 of the side walls 58 with the collar 68 of the bottom walls 64 adjustable. Thus, the Helmholtz resonator 24a can be adjusted very precisely to the frequency to be damped by the adjustable neck 47a and the adjustable volume 25a.

The distance between the two tubes 54, 56 and the bottom walls 64 and the side walls 58 of the Helmholtz resonator 24a are shown exaggerated in Fig. 4 for greater clarity.

LIST OF REFERENCE NUMBERS

10

exhaust system

12

exhaust duct

14

fireplace

16

flow channel

18

exhaust

20

Transition area

22

rear wall

24, 24 ', 24 "

Helmholtz resonator

25, 25 ', 25 "

volume

26

hole cover

28

tissue

30

entry area

32

absorption silencer

34

hollow cylinder

36

upstream absorption silencer

38

partition

40

ground

42

walls

44

gap

46

damping material

48

further hole cover

50

Pipe outside

52

Pipe inside

54

head Start

56

poetry

58

side walls

60

sliding floor

62

baseplate

64

bottom walls

66

bent ends

68

collar

70

floor seal

72

bent edges

Claims (11)

1. Exhaust gas system for industrial gas turbines with an exhaust gas conduit (12) and a chimney (14) connected to it, which together form a continuous flow duct (16), and having a device for noise reduction, characterized in that a Helmholtz resonator (24, 24', 24", 24a), is provided for suppressing the low frequencies of the noise, the inlet region (30) of which resonator is arranged in the region of a pressure maximum of an acoustic mode in this frequency range.
2. Exhaust gas system according to claim 1, characterized in that the dimensions of the exhaust gas duct (12) and the chimney (14) are selected in such a way that the pressure maximum of the acoustic mode occurs in the transition region (20) between exhaust gas duct (12) and chimney (14).
3. Exhaust gas system according to one of claims 1 or 2, characterized in that the Helmholtz resonator (24, 24', 24", 24a) is located in the transition region (20) between exhaust gas duct (12) and chimney (14) and, in fact, preferably on the chimney (14) rear wall (22), which bounds the exhaust gas duct (12) in the flow direction (S).
4. Exhaust gas system according to one of the preceding claims, characterized in that the Helmholtz resonator (24, 24', 24", 24a) is thermally insulated from the outside.
5. Exhaust gas system according to one of the preceding claims, characterized in that the Helmholtz resonator (24, 24', 24", 24a) has a throat (47, 47a) which can be adjusted in its length and/or its cross section and/or in that the Helmholtz resonator (24, 24', 24", 24a) has a volume (25, 25', 25", 25a) which is adjustable and, in fact, preferably by the height of its side walls (58) being adjusted by means of a displaceable base (40, 60).
6. Exhaust gas system according to one of the preceding claims, characterized in that the temperature of the Helmholtz resonator (24) can be adjusted.
7. Exhaust gas system according to one of the preceding claims, characterized in that the inlet region (30) of the Helmholtz resonator (24, 24', 24", 24a) is screened in an acoustically transparent manner from the flow in the flow duct (16) and, in fact, preferably by means of an absorption noise suppressor (36) located between the throat (47, 47a) of the Helmholtz resonator (24, 24', 24", 24a) and the flow (S).
8. Exhaust gas system according to claim 7, characterized in that the absorption noise suppressor (36) has a first perforated cover (26), which preferably forms a part of a wall (22) bounding the flow duct (16), and in that it comprises a flow-resistant fabric (28) located on the side of the perforated cover (26) facing away from the flow duct (16), a layer of absorption material (46) adjacent to the fabric (28), a second perforated cover (48) opposite to the first perforated cover (26) and side walls.
9. Exhaust gas system according to claim 7 or 8, characterized in that an intermediate space (44) is located between the absorption noise suppressor (36) and the throat (47, 47a) of the Helmholtz resonator (24, 24', 24", 24a).
10. Exhaust gas system according to one of the preceding claims, characterized in that a plurality of Helmholtz resonators (24, 24', 24", 24a) are provided which are preferably tuned to different frequencies or modes.
11. Exhaust gas system according to claim 10, characterized in that the Helmholtz resonators (24, 24', 24", 24a) are separated from one another in a gas-tight manner.

Images