JPH10274027A - Resonance muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save an arrangement space of a resonance muffler used for an exhaust duct by reducing capacity of a resonator or shortening the length of a branched pipe. SOLUTION: An opening 2 is formed on a wall surface of an exhaust duct 1 of a gas turbine, while a branched pipe 3 and a resonance box 4 are installed being communicated. A pressure receiving plate 5 is arranged inside the branched pipe 3 with a gap therearound. Sliding pieces are projected from the ends of the pressure receiving plate 5, and movably engaged with a guide rail arranged on an inner peripheral surface of the branched pipe 3. By attaching the pressure receiving plate 5, resonance frequency can be reduced without enlarging a device when low frequency component is eliminated while reducing the resonance frequency. It is also possible to actually reduce the capacity of the resonance box 4, and shorten the length of the branched pipe 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonance type silencer which is used for silencing exhaust ducts of gas turbines, blower ducts for boilers, and the like.

[0002]

2. Description of the Related Art FIG. 14 shows an example in which a conventional Helmholtz resonance type silencer is applied to a duct 1. FIG.
2 shows a layout diagram of the silencer main body 7 and the branch pipe 3. The silencer main body 7 has a volume V, and the branch pipe 3 has a diameter 2 a and a length l. (B) is a principle diagram of the Helmholtz resonator, (c) is a vibration model diagram of (b), and (d) is a frequency characteristic of sound reduction obtained by the silencer.

In the principle of the Helmholtz resonator shown in FIG. 14B, M is the mass of the gas contained in the branch pipe, R is the damping caused by friction with the pipe wall when the gas in the branch pipe moves. , C is the spring action of the gas in the resonator, P
Is the pressure of the sound wave propagating in the duct 1, (c)
Is replaced by a vibration model as shown in FIG.

FIG. 14D shows the transmittance of the silencer (reduced sound volume).
By giving the dimensions shown in the figure in the calculation example of
The resonance frequency of the vibration model shown in (b) and (c) is 250 Hz. The feature of the Helmholtz resonance type silencer is that the maximum volume reduction is obtained at this resonance (resonance) frequency.

FIGS. 15 and 16 show a resonance type silencer conventionally used for a duct of a gas turbine or the like. FIG. 15 is a side view and FIG. 16 is a plan view thereof. In these figures, 1 is a duct, 2 is an opening of a silencer main body, and 8 is a branch pipe, which has the same principle as in the example of FIG. 14, but in this example, a single resonance box is attached in the middle of the duct. . This operation is as described above.

FIGS. 17 and 18 show a resonance type silencer in a case where there are a plurality of frequencies to be silenced. FIG. 17 is a side view and FIG. 18 is a plan view thereof. In this example, two resonance boxes 3 ', 3 "having frequencies corresponding to each are provided.

As described above, the prior art includes a single resonance box 3 'in the middle of a duct and two resonance boxes 3' and 3 ".
Is attached, the sound wave is attenuated by the frictional action between the gas and the pipe wall inside the branch pipe 8, and the resonance box 3 'or 3'
And a noise effect can be obtained by the spring action of the gas within 3 ″.

[0008]

As for the volume reduction of the conventional Helmholtz resonance type silencer, the maximum volume reduction near the resonance frequency of the Helmholtz resonator is obtained as shown in FIG. This resonance frequency f ₀ is represented by the following equation <1>.

[0009]

(Equation 1)

Next, as shown in the measurement examples of FIGS. 11, 12 and 13 described later, the sound propagating through the exhaust duct of the gas turbine contains many low frequency components, and the low frequency noise problem Is the cause. Therefore, in order to reduce this sound, it is necessary to lower f ₀ .

[0011] As can be seen from the above formula <1>, in order to lower the f ₀ is l ', it is necessary to increase the V, which inevitably dimensions of the muffler becomes larger, cost, location of Challenges arise.

When the frequency of the low-frequency sound in question is a single frequency, the silencer provided with one resonance box tuned to that frequency can be used, but in practice, the frequency of the low-frequency sound in question is low. In many cases, a plurality of silencers tuned to the respective frequencies as shown in FIGS. 17 and 18 must be individually provided.
High cost and large installation space.

Accordingly, a first object of the present invention is to provide (1) a resonance type silencer which reduces the length of the resonance tube of the resonance type silencer to reduce the installation space and does not increase the cost. Is to do.

Another object of the present invention is to provide a configuration in which the position of the pressure receiving plate can be easily adjusted in order to realize the above-mentioned resonance type silencer (1).

A third object is to improve the sound reduction performance by coping with a plurality of resonance frequencies to be reduced, to improve sound reduction characteristics by adding acoustic resistance, and
An object of the present invention is to provide a resonance type silencer that can reduce the installation space.

Further, as a fourth problem, it is possible to cope with a plurality of resonance frequencies to be reduced, to select a frequency to be attenuated and to perform accurate tuning, thereby expanding the applicable range of the silencer. Another object of the present invention is to provide a resonance type silencer that can reduce the space.

[0017]

The present invention provides the following means (1) to (4) in order to solve the first to fourth problems.

(1) In a resonance type silencer, a pressure receiving plate is mounted at a desired position in a resonance box branch pipe or a resonance pipe so as to adjust a front and rear position thereof while maintaining a predetermined gap with a periphery of a pipe inner wall. Type silencer.

(2) In the above (1), a guide rail is provided on the inner wall of the branch pipe or the resonance pipe in the front-rear direction, and a sliding piece is provided around the pressure receiving plate to engage with the guide rail. A resonance type silencer characterized in that the pressure receiving plate is movably and flexibly supported.

(3) A resonance type silencer in which a resonance box divided into a plurality of parts having different sizes and a net and a protection member of the net are provided at an entrance of the resonance box. vessel.

(4) In a resonance type silencer connected to an exhaust duct requiring silencing, the resonance silencer is provided in a resonance box communicating with the duct, and comprises a net and a protection member of the net.
A partition plate movable in the front-rear direction, a connecting rod connected to the partition plate to enable the partition plate to move in the front-rear direction, a net provided at the entrance of the resonance box, and a protection member for the net. The resonance type silencer characterized by having a.

Lowering the resonance frequency of a Helmholtz resonator corresponds to lowering the resonance frequency of a vibration model, for which it is necessary to weaken the spring or increase the mass. In order to weaken the spring, it is necessary to increase the volume of the silencer main body. It is not appropriate to simply increase the length of the branch pipe in order to increase the mass, because this also leads to an increase in the size of the apparatus.

Therefore, as in (1) and (2) of the present invention, a pressure receiving plate is provided in a branch pipe or a resonance pipe, and the length of the branch pipe is kept constant by softly supporting the pressure receiving plate. It is possible to increase the mass in the branch pipe as it is.

The principle of the inventions (1) and (2) described above will now be described. When a pressure receiving plate having an areal density (mass per unit area) m is inserted into the branch pipe, the resonance frequency of the resonator is given by the following equation <2>.

[0025]

(Equation 2)

Sb, l 'is the same in the resonator with the pressure receiving plate inserted and in the resonator without the pressure receiving plate, and the same resonance frequency f
_In order to obtain ₀ , the relationship of the following expression <3> is derived from the expressions <1> and <2>, where Vp is the internal volume of the silencer main body into which the pressure receiving plate is inserted.

[0027]

(Equation 3)

Similarly, assuming that Sb and V are the same, the following equation <4> is derived.

[0029]

(Equation 4)

FIG. 8 shows the relationship between the above expressions <3> and <4>. From FIG. 8, if a plate having an area density m is inserted into a branch pipe of a Helmholtz resonator, the same resonance frequency can be obtained. To
It can be seen that the required resonator volume or branch length can be reduced.

Next, the principle of the resonance type silencer (3) of the present invention will be described. First, the noise reduction target frequency f ₀ is given by the following equation <5>.

[0032]

(Equation 5)

It has been confirmed by an experiment that the frontage area of the resonance box inlet does not affect the noise reduction performance up to half of the cross-sectional area of the exhaust duct to be installed.

On the other hand, a net provided at the entrance of the resonance box, for example, a wire net, adds acoustic resistance to sound waves entering the resonance box, thereby improving sound reduction performance. The appropriate sound value R is given by the following equation (6).

[0035]

(Equation 6)

In addition, a protective member, for example, a perforated plate or the like is used, which has a role of protecting the wire mesh for preventing the wire mesh from being exhausted and damaged by pressure, and has an opening ratio of 30% or more. If so, it does not affect the sound reduction performance.

Next, the principle of the resonance type silencer (4) of the present invention will be described. First, two noise reduction target frequencies f ₀₁ and f ₀₂
Is given by the following formulas <7> and <8>, respectively, as in formula <5>.

[0038]

(Equation 7)

As described above, even though the resonance box is a single resonance box, by providing a partition plate inside the resonance box, it is possible to reduce two frequency components. On the other hand, a net provided at the entrance of the resonance box and the partition plate, for example, a wire net, adds acoustic resistance to sound waves entering the resonance box, thereby improving sound reduction performance. The optimum acoustic resistance value R is given by the above-mentioned expression (6).

As the protective member, for example, a perforated plate is used, and the perforated plate has a role of protecting the wire net from preventing the wire net from exhausting and being damaged by pressure, and has an aperture ratio of 30%. If it is above, it does not affect the sound reduction performance.

[0041]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a configuration diagram of a resonance type silencer according to a first embodiment of the present invention, and FIG. 2 is a configuration diagram showing an application example thereof. In FIG. 1, an opening 2 is provided in a wall surface of a gas turbine exhaust duct 1, and a resonator composed of a branch pipe 3 and a resonance box 4 is attached to the opening 2 to constitute a Helmholtz resonator. A pressure receiving plate 5 is set in the branch pipe 3 of the resonator. The pressure receiving plate 5 is supported so as to freely move in a direction perpendicular to the surface of the plate by the pressure of the sound wave.

FIG. 2 shows an applied example of the first embodiment shown in FIG. 1, in which a pressure receiving plate 5 is attached to an inlet of a resonance box 6 of a resonance type silencer attached to an exhaust duct 1 of a gas turbine. Things.

Pressure receiving plate 5 in muffler shown in FIGS. 1 and 2
The same material as that of the gas turbine exhaust duct is used to withstand high temperature and corrosive gas turbine exhaust gas.

Since the pressure receiving plate 5 receives the static pressure in the exhaust duct, a slight gap is provided around the pressure receiving plate to equalize the pressure on both surfaces of the pressure receiving plate. As described above, since the pressure on both sides of the pressure receiving plate 5 is the same, no special strength is required. However, it is necessary to provide a certain degree of rigidity and strength to withstand sudden pressure fluctuations. In order to provide the necessary rigidity and strength by minimizing the weight increase of the pressure receiving plate, it is preferable to adopt a honeycomb structure.

FIGS. 3A and 3B show a mounting portion for supporting the pressure receiving plate 5 in the branch pipe 3, wherein FIG. 3A is a front view, FIG. 3B is a detailed view of a portion A in FIG. FIG. In FIG. 3, a guide rail 14 is provided inside the branch pipe 3.
So that the sliding piece 15 attached to the end of the pressure receiving plate 5 can slide freely along the guide rail 14 in the axial direction of the branch pipe 3. Also, by changing the friction between the guide rail 14 and the sliding piece 15, the damping C shown in FIGS. 14B and 14C can be adjusted.

There are no particular restrictions on the location where the resonance type silencer of the first embodiment is attached to the duct. That is, as in the first embodiment shown in FIGS.
May be attached to the bend portion, or may be attached to a straight portion of the duct.

In the first embodiment as described above,
By installing the pressure receiving plate 5 at the branch tube 3 or at the inlet of the resonance tube, the volume of the resonator or the length of the branch tube 5 required to obtain the same resonance frequency can be reduced.

FIG. 11 is a diagram showing a measurement example of the exhaust noise of the gas turbine and the noise reduction effect of the silencer in the first embodiment, in which the horizontal axis represents the frequency and the vertical axis represents the sound pressure level. . In the figure, the thick line X represents the sound pressure level without the resonance type silencer, and the thin line Y represents the sound pressure level when the resonance type silencer is provided. Accordingly, the hatched portion in the figure indicates the amount of attenuation, and the frequency at which the required sound reduction is maximized is about 10H.
9 shows the sound reduction characteristics of the silencer tuned to z and 27 Hz.

FIGS. 4 and 5 show a resonance type silencer according to a second embodiment of the present invention. FIG. 4 is a side view and FIG. 5 is a plan view. This is an example in which a resonance type silencer for reducing two frequency components is installed.

In both figures, an opening 12 is provided in the wall surface of the exhaust duct 1, and the resonance box 23 is vertically divided by resonance boxes 23 'and 23 "having different lengths as shown in the side view of FIG. Between the exhaust duct 1 and the resonance box 23, there is provided a wire mesh 24 for adding acoustic resistance and a protection member for protecting the wire mesh 24, that is, a perforated plate 25.

FIGS. 6 and 7 show a resonance type silencer according to a third embodiment of the present invention. FIG. 6 is a side view, and FIG. 7 is a plan view thereof. This is an example in which a resonance silencer for reducing a frequency component is installed.

In both figures, an opening 12 is provided in the wall surface of the exhaust duct 1, and a resonance type silencer 33 is provided on the left and right sides by resonance boxes 33 'and 33 "having different lengths as shown in the plan view of FIG. A wire mesh 2 for adding acoustic resistance between the exhaust duct 1 and the resonance box as in the second embodiment.
4 and a perforated plate 25 for protecting the wire mesh.

In the above-described resonance type silencers according to the second and third embodiments, sound waves traveling through the exhaust duct 1 enter the resonance boxes 23 'and 23 "or 33' and 33" from the opening 12, respectively. , Resonance boxes 23 'and 23 "or 33' and 3
Sound reduction can be obtained at a frequency that resonates with the depth and length of 3 ″. The depth and length of the resonance box are tuned to frequencies that require sound reduction.

On the other hand, the wire mesh 24 provided at the entrance of the resonance box acts to add acoustic resistance to the sound wave entering the resonance box and to improve the sound reduction performance. The perforated plate 25 also functions to protect the wire mesh 24 from being damaged by the exhaust gas flow or pressure fluctuation. The resonance boxes 23 'and 23 "or 33' and 3
By lining a sound absorbing material, such as rock wool, on the inner surface of the 3 ″, it is possible to reduce higher frequency sounds.

FIG. 12 is a diagram showing a measurement example of the exhaust noise of the gas turbine and the noise reduction effect by the silencer in the second and third embodiments of the present invention. As in FIG. The thick line X 'indicates the sound pressure level without the resonance type silencer, and the thin line Y' indicates the sound pressure level when the resonance type silencer is attached. Accordingly, the hatched portions in the figure indicate the attenuation, and it can be seen that the resonance type silencers in the second and third embodiments of the present embodiment are effective.

9 and 10 show a resonance type silencer according to a fourth embodiment of the present invention. FIG. 9 is a side view and FIG. 10 is a plan view thereof. The fourth embodiment is a resonance type silencer for reducing two frequency components as in the second and third embodiments, and a resonance box 43 is provided in the exhaust duct 1. An opening 42 is provided in the wall surface of the exhaust duct 1 so that the resonance box 4
3 is divided into two chambers by a partition plate 46. The partition plate 46 is a wire mesh 44 for adding acoustic resistance and a wire mesh 44.
Is constituted by a perforated plate 45 for protecting.

Between the exhaust duct 1 and the resonance box 43, a wire netting 44 for adding acoustic resistance and a perforated plate 45 for protecting the wire netting 44 are provided. In addition, the partition plate 46 is connected to the opening 42 of the resonance box 43 and the wall on the opposite side by the connecting rod 7, so that the partition plate 46 can be slid back and forth to make fine adjustment of the sound reduction frequency. ing.

[0058] In the above-described fourth embodiment of the arrangement, sound waves traveling exhaust duct 1 enters the resonance box 43 through the opening 42, reduced sound resonance frequency corresponding to the depth length L ₁ and L ₂ of the resonance box 43 Is obtained. The depth lengths L ₁ and L ₂ are tuned to frequencies that require sound reduction. Additionally L ₂ can be changed to any length by sliding the partition plate 46 by a connecting rod 7, and tuned to increase or frequency of noise reducing effect by optimal tuning, reduces the frequency component Is possible.

[0059] Adjust the lengths L _1, L ₂ so as to correspond to the two resonant frequencies, as described above, the partition plate 4 once the L ₂
Fix 6 so that it does not move. As a fixing method, for example, the connecting rod 7 is fixed outside the resonance box 43 with a lock nut or the like.

On the other hand, the wire mesh 44 provided at the partition plate 46 and the entrance of the resonance box 43 has an effect of adding acoustic resistance to the sound wave entering the resonance box 43 and improving the sound reduction performance. In addition, perforated plate 4
Numeral 5 functions to protect the wire mesh 44 from being damaged by the exhaust gas flow or pressure fluctuation. Further, the perforated plate 43 also performs an attenuating function of sound waves due to a frictional action between the gas and the perforated plate hole. By lining a sound absorbing material, for example, rock wool or the like on the inner surface of the resonance box 43, it is possible to reduce higher frequency sounds.

FIG. 13 is a diagram showing a measurement example of gas turbine exhaust noise and a noise reduction effect by the silencer according to the fourth embodiment of the present invention. As in FIGS.
The vertical axis indicates the sound pressure level. The thin line X ″ indicates the sound pressure level without the resonance type silencer, and the thick line Y ″ indicates the sound pressure level when the resonance type silencer is attached. Accordingly, the hatched portion in the figure indicates the amount of attenuation, and it can be seen that the resonance type silencer according to the fourth embodiment is effective.

FIG. 13 shows the noise reduction characteristics tuned so that the frequency at which the required volume reduction becomes maximum is about 12 Hz and 26 Hz. In this way, two frequencies to be reduced can be reduced by one silencer. As a result, cost can be reduced and installation space can be saved.

[0063]

As described above, according to the first aspect of the present invention, in the resonance type silencer, a predetermined clearance is maintained at a desired position in the resonance box branch pipe or the resonance pipe with the periphery of the pipe inner wall. It is characterized by mounting the pressure receiving plate so that the position can be adjusted back and forth,
Since the position of the pressure receiving plate can be adjusted according to the resonance frequency to be silenced, it is equivalent to a conventional silencer without increasing the length of the branch pipe or increasing the volume of the resonance box of the silencer Is obtained. For this reason, if the required silencing frequency is the same, the length of the branch pipe or the resonance box of the silencer can be reduced, and cost and installation space can be reduced.

According to (2) of the present invention, a guide rail is provided on the inner wall of the branch pipe or the resonance pipe in the front-rear direction, and a sliding piece is provided around the pressure receiving plate to engage with the guide rail. Since the pressure receiving plate is movably and flexibly supported, the pressure receiving plate can move the sliding piece along the guide rail, so that the adjustment can be easily performed.

A third aspect of the present invention is characterized in that, in the resonance type silencer, a resonance box divided into a plurality of parts having different sizes, and a net and a protection member of the net are provided at an entrance of the resonance box. So that the net adds acoustic resistance,
In addition, it is possible to prevent the protection member from damaging the net due to the flow of exhaust gas or pressure, and to reduce a plurality of noise reduction frequencies in one resonance box.

A fourth aspect of the present invention is directed to a resonance type silencer connected to an exhaust duct which requires silencing, which is provided in the resonance box communicating with the duct, comprising a net and a protection member of the net. A partition plate movable in the front-rear direction, a connecting rod connected to the partition plate to enable the partition plate to move in the front-rear direction, a net provided at the entrance of the resonance box, and a protection member for the net. It is characterized by having provided. With such a configuration, two noise reduction frequencies can be obtained with one resonance box, and the partition plate can be slid back and forth, so that optimum tuning can be performed for the frequency to be reduced, and the maximum noise reduction effect can be obtained, and the space can be reduced. Can also be planned. Tuning to another frequency is also possible, and the applicable range of the silencer can be expanded.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a resonance type silencer according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing an application example of FIG. 1 in the resonance type silencer according to the first embodiment of the present invention.

3A and 3B show a pressure receiving plate mounting portion of the resonance type silencer according to the first embodiment of the present invention, wherein FIG. 3A is a front view and FIG.
7A is a detailed view of a portion A, and FIG. 7C is a sectional view taken along line BB in FIG.

FIG. 4 is a side view of a resonance type silencer according to a second embodiment of the present invention.

FIG. 5 is a plan view of the resonance silencer shown in FIG.

FIG. 6 is a side view of a resonance type silencer according to a third embodiment of the present invention.

FIG. 7 is a plan view of the resonance silencer shown in FIG.

8A and 8B are explanatory diagrams of the operation of the present invention, wherein FIG. 8A shows the relationship between the volume of the resonance box and the pressure receiving plate, and FIG. 8B shows the relationship between the length of the branch pipe and the pressure receiving plate.

FIG. 9 is a side view of a resonance type silencer according to a fourth embodiment of the present invention.

FIG. 10 is a plan view of the resonance type silencer shown in FIG.

FIG. 11 is a diagram illustrating a relationship between frequency and attenuation in a measurement example of gas turbine exhaust noise by the resonance type silencer according to the first embodiment of the present invention.

FIG. 12 is a diagram illustrating a relationship between frequency and attenuation in a measurement example of gas turbine exhaust noise by the resonance type silencers according to the second and third embodiments of the present invention.

FIG. 13 is a diagram showing a relationship between frequency and attenuation in a measurement example of a gas turbine exhaust sound by a resonance type silencer according to a fourth embodiment of the present invention.

FIG. 14 shows a conventional Helmholtz resonance type silencer,
(A) is the configuration diagram, (b) is the principle diagram, (c) is (b)
FIG. 4D is a diagram showing the relationship between the frequency and the volume reduction.

FIG. 15 is a side view showing a conventional resonance type silencer.

FIG. 16 is a plan view of the resonance silencer shown in FIG.

FIG. 17 shows a conventional resonance type silencer in which the frequency to be reduced is 2;
FIG.

FIG. 18 is a plan view of the resonance silencer shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust duct 2,12,42 Opening 3 Branch pipe 4,23,33 Resonance box 5 Pressure receiving plate 6 Resonant pipe 7 Connecting rod 14 Guide rail 15 Sliding piece 24,44 Wire mesh 25,45 Perforated plate

Claims (4)

[Claims] 1. A resonance type silencer wherein a pressure receiving plate is mounted at a desired position in a resonance box branch pipe or a resonance pipe so as to adjust a position in front and rear thereof while maintaining a predetermined gap with a circumference of a pipe inner wall. Silencer. 2. A guide rail is provided on the inner wall of the branch pipe or the resonance pipe in the front-rear direction, and a sliding piece is provided around the pressure receiving plate to be engaged with the guide rail, and the pressure receiving plate is movably movable. 2. The support according to claim 1, wherein
The described resonance type silencer. 3. A resonance type silencer comprising: a resonance box divided into a plurality of parts having different sizes; and a net and a protection member of the net provided at an entrance of the resonance box. . 4. A resonance type silencer connected to an exhaust duct requiring silencing, which is provided in the middle of a resonance box communicating with the duct, comprises a net and a protection member of the net, and is movable in the front-rear direction. A partition plate, a connecting rod connected to the partition plate to enable the partition plate to move in the front-rear direction, and a net provided at an entrance of the resonance box and a protection member of the net are provided. And a resonance type silencer.