JPH07301386A - Device for preventing generation of resonance sound in cavity - Google Patents

Abstract

PURPOSE:To have an effect on the prevention of resonance sound generation for frequencies in a wide range by disposing a sound damping plate having the plane crossing the axial direction of a main pipe to extend inside a cavity in the proximity of the opening part of the cavity formed to cross a main pipe. CONSTITUTION:A sound damping plate 7 having the plane crossing the axial direction of a main pipe 1 to extend inside a cavity is disposed in the proximity of an opening part 4 of the cavity 2 formed to cross the main pipe 1. The sound damping plate 7 has a linear shaped end face 9 on the inner surface side of the main pipe 1 so that both ends of the end face 9 coincide with corner parts of the inner surface of the main pipe 1 and the opening part 4 of the cavity 2. Thus, the exciting frequency of a swirl S generated on the interface between fluid 3 in the cavity 2 and fluid 3 flowing in the main pipe 1 is disturbed by the sound damping plate 7. Thus, since the fluid 3 in the cavity 2 is disturbed, the resonance with an air column resonance frequency which the cavity 2 has is not generated so that the generation of resonance sound caused by the cavity is prevented in a wide range of frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonance noise generation device for a cavity for preventing resonance noise of the cavity and an abnormal pressure fluctuation which causes the resonance noise.

[0002]

2. Description of the Related Art As shown in FIG. 36, a safety valve pipe stand of a boiler steam pipe, a blow pipe for blowing steam, or a branch pipe for an inspection hole or the like generally crosses the main pipe 1 at a right angle. The cavity 2 is formed in.

When the fluid 3 is caused to flow through the main pipe 1 having such a cavity 2, a large resonance sound (noise) is often generated due to the presence of the cavity 2.
Such a resonance sound is generally in the audible range of 1 to several KHz, which is a nuisance and a serious noise problem.

The resonance sound generated by the cavity 2 is a self-excited sound generated by the fluid 3 flowing along the cavity 2 and the inner surface of the main pipe 1. The self-excited sound is generated by a vortex formed in the fluid flowing through the opening 4 of the cavity 2. It is considered that the excitation frequency promotes a phenomenon similar to the principle of whistling, and when the excitation frequency and the air column resonance frequency of the cavity come into resonance, a large abnormal noise is generated.

Further, the generation of the resonance sound is caused by the cavity 2
It is considered that this is due to the abnormal pressure fluctuation of the fluid inside. When this pressure fluctuation increases, the vibration energy adversely affects the valve connected to the cavity 2, the measuring instrument, and the like, such as damage or malfunction.

Conventionally, in order to prevent the occurrence of the resonance noise due to the cavity 2 and the pressure fluctuation which is the cause thereof as described above, as shown in FIG. 36, the corner between the inner surface of the main pipe 1 and the opening 4 of the cavity 2 is formed. Cut out part and reducer shape 5
It is considered to be.

Further, as shown in FIG. 37, by providing a branch pipe 6 in the middle of the cavity 2 so as to be orthogonal to the cavity 2, generation of resonance sound by the cavity 2 is prevented.

[0008]

However, in the former of the above-mentioned conventional devices, a sufficient effect of preventing resonance noise has not been confirmed, and in the latter, the fluid 3 in the cavity 2 and the main pipe 1 flow. A method in which the resonance frequency is prevented by shifting the air column resonance frequency by the branch pipe 6 so that the excitation frequency generated by the vortex formed at the interface with the fluid 3 does not match the air column resonance frequency of the cavity 2. Therefore, when the diameters of the main pipe 1 and the cavity 2 change or the flow velocity of the fluid 3 changes, it is necessary to change the design dimension and the arrangement position of the branch pipe 6 each time, and the trial work for that is required. It had problems such as becoming very difficult.

The present invention has been made in view of the above circumstances, and provides a resonance sound generation preventing device for a cavity, which has a simple structure and can exert a resonance sound generation prevention effect for a wide range of frequencies. It is an object.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a sound reducing plate is provided near the opening of a cavity formed so as to intersect with a main pipe and extends into the cavity with its plane intersecting the axial direction of the main pipe. The present invention relates to a cavity resonance noise generation preventing device.

According to the present invention, the end surface of the sound-reducing plate on the inner surface of the main pipe is linear, both ends of the end surface are aligned with the corners of the cavity of the inner surface of the main pipe, and the sound-reducing plate has a cavity in the cavity depth direction. The present invention relates to a resonance sound generation preventing device for a cavity, characterized in that the device extends substantially the same size as the inner diameter of the cavity.

In the inner surface of the main pipe having a cavity formed so as to intersect with the main pipe, a convex portion protruding toward the inside of the main pipe at the same position in the circumferential direction as the installation position of the cavity is provided at the upstream side position of the cavity. The present invention relates to a cavity resonance sound generation preventing device.

According to the present invention, an inner surface of a main pipe having a cavity formed so as to intersect with the main pipe is provided at a position upstream of the cavity so as to project toward the inside of the main pipe with a required space in the inner circumferential direction of the main pipe. The present invention relates to a resonance noise generation preventing device for a cavity, which is provided with a plurality of convex portions.

The present invention relates to a cavity resonance noise generation preventing apparatus, characterized in that a plurality of convex portions are arranged in a staggered pattern.

According to the present invention, the convex portion has about 2 of the inner diameter of the cavity.
It has a cylindrical shape having a diameter of 0% to 70%, the protruding height of the convex portion is about 20% or more of the inner diameter of the cavity, and the convex portion has a space within about 5 times the inner diameter of the cavity. In addition, the present invention relates to a resonance sound generation preventing device for a cavity, which is installed at a position upstream of the cavity.

[0016]

According to the first means, a sound reducing plate extending in the cavity is disposed in the vicinity of the opening of the cavity formed so as to intersect the main pipe so that the flat surface intersects the axial direction of the main pipe. Since the noise reduction plate can disturb the excitation frequency generated by the vortex formed at the interface between the fluid in the cavity and the fluid flowing in the main pipe, the fluid in the cavity will also be disturbed, and Resonance with the column resonance frequency is eliminated, and resonance noise due to the cavity is prevented over a wide range of frequencies.

In the second means, the end surface of the noise reduction plate on the inner surface of the main pipe is linear, both ends of the end surface are aligned with the cavity corners of the inner surface of the main pipe, and the noise reduction plate is in the cavity depth direction. Since it extends substantially the same size as the inner diameter of the cavity, the excitation frequency generated by the vortex formed at the interface between the fluid in the cavity and the fluid flowing in the main pipe is more reliably disturbed by the noise reduction plate. Since the fluid in the cavity is also reliably disturbed, the effect of preventing resonance noise from being generated by the cavity is further enhanced.

[0018] In the third means, a protrusion protruding toward the inside of the main pipe at a position upstream of the cavity on the inner surface of the main pipe having a cavity formed so as to intersect the main pipe, at the same circumferential position as the installation position of the cavity. Since the section is provided, the Karman vortex generated by the convex portion can effectively disturb the excitation frequency generated by the vortex formed at the interface between the fluid in the cavity and the fluid flowing in the main pipe. Disturbance is also eliminated, and resonance with the air column resonance frequency of the cavity is eliminated, so that generation of resonance sound by the cavity is prevented in a wide frequency range.

In the fourth means, a plurality of convex portions are provided at a position upstream of the cavity on the inner surface of the main tube having a cavity formed so as to intersect with the main tube, with a required interval in the inner circumferential direction of the main tube. Since it is provided, Karman vortices generated from a plurality of convex portions complicatedly disturb the excitation frequency generated at the interface between the fluid in the cavity and the fluid flowing in the main pipe, which further ensures the generation of resonance sound by the cavity. To be prevented.

In the fifth means, since the plurality of convex portions are arranged in a staggered pattern, the Karman vortices generated from the plurality of convex portions become more complicated, and the fluid in the cavity and the fluid flowing in the main pipe are mixed. The excitation frequency generated by the vortex at the interface with and is further complicatedly disturbed, and thereby the generation of resonance noise by the cavity is more reliably prevented.

In the sixth means, the protrusion has a cylindrical shape having a diameter of about 20% to 70% of the inner diameter of the cavity, and the protrusion height of the protrusion is about 20% or more of the inner diameter of the cavity. Since the convex portion is installed at a position upstream of the cavity with a space within about 5 times the inner diameter of the cavity, the fluid in the cavity and the fluid flowing in the main pipe are caused by the Karman vortex caused by the convex portion. The excitation frequency generated by the vortex formed at the interface of can be effectively disturbed.

Since the above-mentioned means can prevent the resonance sound from being generated by the cavity, it is also possible to prevent the abnormal pressure fluctuation which is the cause of the resonance sound from being generated, so that the cavity is connected. The safety of valves and measuring instruments can be improved.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 show an embodiment of the present invention as claimed in claims 1 and 2, wherein a flat surface is formed on the main pipe 1 at a position near an opening 4 of a cavity 2 formed so as to intersect the main pipe 1. A noise reduction plate 7 is provided that extends in the cavity 2 so as to intersect the axial direction of.

Reference numeral 8 in the figure denotes a reinforcing plate provided in the axial direction of the main pipe 1 (a direction perpendicular to the sound reducing plate 7) for reinforcing the sound reducing plate 7, and the sound reducing plate 7 and the reinforcing plate 8 are welded. It is fixed to the inner surface of the cavity 2 by the above.

The sound reduction plate 7 has a straight end surface 9 on the inner surface of the main pipe 1, and both ends of the end surface 9 coincide with the inner surface of the main pipe 1 and the corner 2a of the opening 4 of the cavity 2. ing.
Further, the noise reduction plate 7 extends in the depth direction of the cavity 2 with a size L ₁ which is substantially equal to the inner diameter D of the cavity 2. Further, as shown in FIG. 4, two or more noise reduction plates 7 may be provided.

In the above-mentioned cavity 2, the cavity 2
F = D / 4L × N, where D is the inner diameter and L is the depth
It has an inherent air column resonance frequency of (N = 1, 3, 5 ...). On the other hand, when the fluid 3 flows in the direction of the arrow in the main pipe 1,
A vortex S is generated from the upstream end 4a of the opening 4 toward the downstream end 4b, and the frequency of this vortex S (excitation frequency) becomes larger when the flow velocity V of the fluid 3 flowing in the main pipe 1 increases. Therefore, when the excitation frequency matches the air column resonance frequency, a resonance sound is generated.

In the above-described embodiment, the sound reducing plate 7 is arranged in the vicinity of the opening 4 of the cavity 2 formed so as to intersect with the main pipe 1 so that the plane intersects with the axial direction of the main pipe 1. , The fluid 3 in the cavity 2 by the noise reduction plate 7
The excitation frequency generated by the vortex formed at the interface between the cavity 2 and the fluid 3 flowing in the main pipe 1 is disturbed, and as a result, the cavity 2
Since the fluid 3 inside is also disturbed, the resonance with the air column resonance frequency of the cavity 2 is eliminated, and the generation of resonance sound by the cavity 2 is prevented in a wide frequency range.

At this time, the end surface 9 on the inner surface of the main pipe 1 of the noise reduction plate 7 is linear, and both ends of the end surface 9 coincide with the corners 2a of the opening 4 of the cavity 2 on the inner surface of the main pipe 1. In addition, the noise reduction plate 7 has a shape extending in the depth direction of the cavity 2 with a size substantially equal to the inner diameter D of the cavity 2,
Fluid 3 in the cavity 2 and fluid 3 flowing in the main pipe 1
The excitation frequency generated by the vortex formed at the interface with can be effectively disturbed, so that the generation of resonance sound can be prevented more reliably.

That is, in FIG. 5, the sound reducing plate 7 is installed in the cavity 2
In the case of the present invention (circle mark) and the countermeasure (triangle mark) prepared for the above, an example of the change in noise level (broken line) and frequency (solid line) when the flow velocity V of the fluid 3 in the main pipe 1 is changed According to the present invention, the noise level can be suppressed to a small level as shown by II, although the peak P of a very large noise level such as I occurs without any countermeasure as shown in the figure. . At this time, if the main pipe flow velocity V is increased, the frequency gradually increases as indicated by III in the case of no countermeasure, whereas the present invention maintains a substantially constant frequency as indicated by IV. I knew it would be done.

FIGS. 6 to 9 show a comparison between the present invention in which the noise reduction plate 7 is provided in the cavity 2 and the relationship between the frequency and the noise level in the case where no countermeasure is taken. When the main pipe flow velocity V is 39 m / s and the main pipe flow velocity V in FIG. 7 is 90
In the case of no countermeasure at m / s, a large noise level peak P occurs, whereas in the present invention at the same main pipe flow velocity V as shown in FIGS. 8 and 9, In both cases, there is no peak of noise level,
From this, it is clear that the generation of resonance sound was prevented.

FIGS. 10 and 11 show an embodiment of the present invention as claimed in claims 3 and 4, wherein an upstream side of the cavity 2 on the inner surface of the main pipe 1 having a cavity 2 formed so as to intersect the main pipe 1. At the position, the convex portion 10 protruding toward the inside of the main pipe 1 is provided at the same position (on the same line S) in the circumferential direction as the installation position of the cavity 2.

The protrusion 10 has a cylindrical shape having a diameter d of about 20% to 70% of the inner diameter D of the cavity 2, and the protrusion height L ₂ of the protrusion 10 is about the inner diameter D of the cavity 2. The convex portion 10 having such a shape is formed so as to have a ratio of 20% or more, and the convex portion 10 having the shape of approximately 5
It is installed at a position upstream of the main pipe 1 in the cavity 2 with a distance L ₃ within twice.

Further, the convex portion 10 can have substantially the same effect even if it has a polygonal column shape other than the illustrated columnar shape.

In the above embodiment, the main pipe 1 has the cavity 2 formed so as to intersect with the main pipe 1, at the upstream side position of the cavity 2 in the inner surface of the main pipe 1, and in the main pipe 1 at the same position in the circumferential direction as the installation position of the cavity 2. Since the convex portion 10 projecting toward the side is provided, the Karman vortex 11 generated by the convex portion 10 prevents the excitation frequency generated by the vortex S at the interface between the fluid in the cavity 2 and the fluid flowing in the main pipe 1. The convex portion 10 can create a turbulence in the flow of the fluid, and thus the cavity 2
The fluid inside will also be disturbed, and resonance with the air column resonance frequency of the cavity 2 will be eliminated, and therefore resonance noise will be prevented from being generated by the cavity 2 in a wide range of frequencies.

At this time, the convex portion 10 has an inner diameter D of the cavity 2.
A cylindrical shape having a diameter d of about 20% to 70% of
Projection height L of the convex portion 10₂Is the inner diameter D of the cavity 2
Is about 20% or more of the
Interval L within about 5 times inner diameter D ₃Has a cavity 2
Since it is installed at the upstream side,
At the interface between the fluid in 2 and the fluid 3 flowing in the main pipe 1.
The excitation frequency generated by the vortex S
The Karman vortex 11 prevents it even more effectively,
The turbulence of the fluid 3 in the tee 2 can be reliably retained,
The effect of preventing the generation of resonance noise by the cavity 2 can be further enhanced.
It

That is, FIG. 12 shows that the convex portion 10 is provided on the main pipe 1 having the cavity 2 which has a noise level peak (resonance sound) at the main pipe flow velocity V of 35 to 40 m / s without any countermeasure. The results of examining the state of the noise level in the case where the diameter d and the protrusion height L ₂ of the convex portion 10 are variously changed are shown.

From FIG. 12, the noise level increases when the diameter d of the convex portion 10 is larger than the inner diameter D of the cavity 2 (28 mm in FIG. 12). Therefore, the diameter d of the convex portion 10 is smaller than the inner diameter D of the cavity 2. Must be and also the diameter d
Is too small, the effect cannot be expected.
The diameter d of 0 is 20 to 70% of the inner diameter D of the cavity 2, preferably about 50% of the inner diameter D of the cavity 2.

Further, the protrusion height L ₂ of the convex portion 10 is as shown in FIG.
Therefore, it was found that the noise level can be significantly reduced by setting the inner diameter D of the cavity 2 to 20% or more. However, if the protrusion height L ₂ is too high, it may adversely affect the fluid 3 flowing in the main pipe 1. Therefore, it is preferable to keep the protrusion height L ₂ as low as possible.

At the position where the convex portion 10 is installed, the Karman vortex 11 generated by the convex portion 10 is the cavity 2
It is necessary to set the range so that static pressure does not recover by erasing without reaching
The convex portion 10 has an interval L within about 5 times the inner diameter D of the cavity 2.
_It has been found that it is better to install it at a position upstream of the cavity 2 having the cavity ₃ .

In FIG. 13, the inner diameter D of the cavity 2 is 39 m.
m, the diameter d of the convex portion 10 is 28 mm, the main pipe flow velocity V is 40 m
/ S, the distance L ₃ between the cavity 2 and the convex portion 10 is 1
The noise levels when the protrusion height L ₂ of the convex portion 10 is variously changed are shown for the cases of 50 mm and 65 mm. It is clear that the noise level can be reduced also in the case of FIG. 13, and when the distance L ₃ is long such as L ₃ = 150 mm, the protrusion height L ₂ is increased (60 mm in the figure).
It is clear that the above) should be done.

FIG. 14 shows the noise when the flow velocity V of the fluid 3 in the main pipe 1 is changed in the case of the present invention (circle mark) provided with the convex portion 10 upstream of the cavity 2 and no countermeasure (triangle mark). This is an example showing changes in level (dashed line) and frequency (solid line). As shown in the figure, in the present invention, a peak P having a very large noise level such as I occurred without any countermeasure. According to this, the noise level can be suppressed to a low level like II. At this time, it was found that when the main pipe flow velocity V was increased, the frequency gradually increased in both cases III and IV of the present invention without any countermeasure.

FIGS. 15 and 16 show a comparison between the present invention in which the convex portion 10 is provided in the cavity 2 and the relationship between frequency and noise level when no countermeasure is taken. The diameter d of the convex portion 10 is 22 mm, and the protrusion height L is
₂ is 5 mm, distance L ₃ is 114 mm, main pipe flow velocity V is 40 m
/ S is shown, and a large noise level peak P occurs in the case of no countermeasure in FIG.
In the present invention of FIG. 16, there is no peak of the noise level, and it is clear that the generation of resonance sound is prevented.

FIGS. 17, 18 and 19 and 20 show an embodiment of the invention of claim 5, respectively. In FIGS. 17 and 18, the cavity 2 formed so as to intersect the main pipe 1 is shown. At the upstream side of the cavity 2 (L ₃ = 123 mm in FIG. 10) on the inner surface of the main pipe 1, the two convex portions 12 a are arranged so as to face the center O of the main pipe 1 at intervals in the inner circumferential direction of the main pipe 1. , 12b are formed. In the illustrated case, the cavity 2 has an inner diameter D = 40 mm, a convex portion diameter d = 16 mm, a protrusion height L ₂ = 30 mm, and a convex portion sandwiching angle θ ₁ = 32 °. In the figure, reference numeral 15 is a fixture for the convex portions 12a and 12b.

19 and 20, the main pipe 1 having the cavity 2 is provided at an upstream position of the cavity 2 on the inner surface of the main pipe 1 at equal intervals in the inner circumferential direction of the main pipe 1.
Of the three convex portions 13a, 13b, 13 facing the center O of the
The case where c is formed is shown. In the case shown, the convex portion 13
An example in which the mutual angle θ ₂ between a, 13b, and 13c is 32 ° is shown, and the others are the same as those in FIGS. 17 and 18.

21 and 22 show an embodiment of the invention of claim 6 in which the inner circumferential direction of the main pipe 1 is at the upstream side position of the cavity 2 on the inner surface of the main pipe 1 having the cavity 2. 2 convex portions 14 with a required space between
a and 14b are formed at an included angle θ ₃ = 44 °, and the convex portions 14a and 14b at the upstream side positions of the convex portions 14a and 14b are
A zigzag arrangement is formed by forming one convex portion 13c at a position between 14b and 14b.

Regarding the configuration of each of the above-described embodiments, as shown in FIG. 23 showing the side views of the apparatus of FIGS. 17 and 18 as an example, the measuring apparatus 16 is provided at the bottom of the nozzle that forms the cavity 2. After installation, the sound pressure level, the magnitude of pressure fluctuation, the pressure fluctuation width, and the flow velocity fluctuation spectrum at the opening 4 were measured.

FIG. 24 shows the measurement result of the sound pressure level when the flow velocity of the fluid 3 in the main pipe 1 is changed in the embodiment of FIGS. 17 to 22 and no countermeasure is taken. Example 3 (circle) of 18 in series 3; Example II (x) of 2 in series in FIGS. 19 and 20; Example III (square) of 3 staggered in FIGS. 21 and 22; The case of no countermeasure IV (triangle mark) is shown for comparison.

As is apparent from FIG. 24, a very large sound pressure level is generated in the non-measure IV, whereas in the above-mentioned embodiments, the noise level is increased as indicated by I, II and III. The level can be suppressed small in a wide frequency range. As a result, the noise due to the resonance sound can be significantly reduced.

FIG. 25 shows the magnitude of pressure fluctuation ξ = g · Δp /
a · γ · U (g: gravitational acceleration, Δp: pressure fluctuation range, a:
The sonic fluid γ: specific weight of gas, U: average flow velocity in the main pipe) are shown as an example, and those denoted by the same reference numerals as in FIG. 24 have the same meaning.

As is clear from FIG. 25, the magnitude of the pressure fluctuation is very large in the non-measure IV, but in the respective embodiments of the present invention described above, I, I
As indicated by I and III, the magnitude of pressure fluctuation is small.

FIGS. 26 and 27 show the pressure fluctuation width ΔP in the conventional case where no countermeasure is taken. FIG. 26 shows the case where the average flow velocity U of the fluid 3 is about 44 m / s.
Shows the case where the average flow velocity U of the fluid 3 is set to about 85 m / s, and FIGS. 28 and 29 show the case where the three convex portions 13a, 13b, 13c of FIGS. 19 and 20 are provided. Average flow velocity U of the fluid 3 is approximately 44 m /
The pressure fluctuation width ΔP was examined at s and 85 m / s.

As is clear from the comparison between FIG. 26 and FIG. 28 and the comparison between FIG. 27 and FIG. 29, the case where no countermeasure (FIG. 26, FIG. 27) causes a very large pressure fluctuation range, the present invention ( 28 and 29), the pressure fluctuation range is extremely small.

FIGS. 30, 31, and 32 show the flow velocity fluctuation spectrum in the conventional case where no countermeasure is taken. FIG. 30 shows the case where the average flow velocity U of the fluid 3 is about 55 m / s. 31 shows the case where the average flow velocity U of the fluid 3 is about 70 m / s, FIG. 32 shows the case where the average flow velocity U of the fluid 3 is about 85 m / s, and FIG. 33, FIG. 34, and FIG. 19, three convex portions 13a, 13b, 13 in FIG.
When c is provided, the flow velocity fluctuation spectrum is investigated with the average flow velocity U of the fluid 3 being the same as the above-mentioned no countermeasure, about 55 m / s, 70 m / s, and 85 m / s.

As is clear from the comparison between FIG. 30 and FIG. 33, the comparison between FIG. 31 and FIG. 34, and the comparison between FIG. 32 and FIG. 35, the strong spectrum peak is observed without any countermeasure (FIG. 30, FIG. 31, FIG. 32). While P occurred, the present invention (Fig. 33,
In FIG. 34 and FIG. 35), the peak of the spectrum was not seen at all.

From the results of FIGS. 25 to 35 described above, according to the present invention, the pressure fluctuation in the cavity 2 can be greatly reduced without any countermeasure, and therefore the vibration energy causes the connection to the cavity 2. It is possible to prevent the occurrence of problems such as damage to valves and measuring devices, malfunctions and the like.

The present invention is not limited to the above-mentioned embodiment, and the number of noise reducing plates and the number of convex portions, the positions where
The size, shape and the like can be variously changed without departing from the scope of the present invention.

[0058]

According to the first aspect of the present invention, a noise reduction plate extending in the cavity is disposed in the vicinity of the opening of the cavity formed so as to intersect the main pipe so that the flat surface intersects the axial direction of the main pipe. Since it is installed, the excitation frequency generated by the vortex formed at the interface between the fluid in the cavity and the fluid flowing in the main pipe can be disturbed by the noise reduction plate, which also disturbs the fluid in the cavity. The generation of resonance with the air column resonance frequency of the is eliminated, and the generation of resonance sound by the cavity is prevented in a wide range of frequencies.

According to the second aspect of the present invention, the end surface of the noise reduction plate on the inner surface of the main pipe is linear, both ends of the end surface coincide with the cavity corners of the inner surface of the main pipe, and the sound reduction plate has the cavity depth. Since it extends in the same direction as the inner diameter of the cavity, the excitation frequency generated by the vortex formed at the interface between the fluid in the cavity and the fluid flowing in the main pipe is more reliably disturbed by the noise reduction plate. As a result, the fluid in the cavity is also reliably disturbed, so that the effect of preventing resonance noise from being generated by the cavity is further enhanced.

According to the third aspect of the present invention, the inner surface of the main pipe having the cavity formed so as to intersect with the main pipe projects toward the inside of the main pipe at the upstream side position of the cavity at the same circumferential position as the installation position of the cavity. Since the convex part is provided, due to the Karman vortex generated by the convex part,
The excitation frequency generated by the vortex created at the interface between the fluid in the cavity and the fluid flowing in the main pipe can be effectively disturbed, and the fluid in the cavity is also disturbed, which causes Outbreak disappeared,
Therefore, generation of resonance sound due to the cavity is prevented in a wide frequency range.

According to the fourth aspect of the invention, a plurality of convex portions are provided at a position upstream of the cavity on the inner surface of the main tube having a cavity formed so as to intersect with the main tube, with a required interval in the inner circumferential direction of the main tube. Since the Karman vortex generated from the plurality of convex portions is provided, the excitation frequency generated at the interface between the fluid in the cavity and the fluid flowing in the main pipe is complicatedly disturbed, which further causes the generation of resonance sound by the cavity. Certainly prevented.

According to the fifth aspect of the invention, since the plurality of convex portions are arranged in a staggered manner, the Karman vortices generated from the plurality of convex portions become more complicated and flow in the fluid in the cavity and in the main pipe. The excitation frequency generated by the vortex at the interface with the fluid is disturbed in a more complicated manner, so that the generation of resonance noise by the cavity is more reliably prevented.

According to the sixth aspect of the invention, the convex portion has a cylindrical shape having a diameter of about 20% to 70% of the inner diameter of the cavity,
Moreover, the protruding height of the convex portion is about 20% of the inner diameter of the cavity.
As described above, since the convex portion is installed at a position upstream of the cavity with a space within about 5 times the inner diameter of the cavity, the fluid inside the cavity and the main pipe are separated by the Karman vortex by the convex portion. The excitation frequency generated by the vortex formed at the interface with the flowing fluid can be effectively disturbed.

Further, according to each of the above-mentioned inventions, it is possible to prevent the resonance sound from being generated by the cavity. Therefore, it is possible to prevent the abnormal pressure fluctuation which is the cause of the resonance sound from being generated. It is possible to enhance the safety of connected valves and measuring instruments.

[Brief description of drawings]

FIG. 1 is a cut side view showing an embodiment of the inventions of claims 1 and 2. FIG.

FIG. 2 is a front view taken along line II-II of FIG.

FIG. 3 is a plan view taken along the line III-III of FIG.

FIG. 4 is a plan view showing another example of FIG.

FIG. 5 is a graph showing the relationship between noise level and frequency when the flow velocity of the main pipe is changed in the case of the present invention provided with a sound reduction plate and no countermeasure.

FIG. 6 is a graph showing the relationship between noise level and frequency when the main pipe flow velocity is 39 m / s without any measures.

FIG. 7 is a graph showing the relationship between noise level and frequency when the main pipe flow velocity is 90 m / s without any measures.

FIG. 8 shows a main pipe flow velocity of 39 in the present invention equipped with a sound reduction plate.
It is a graph which shows the relationship between the noise level at the time of m / s, and frequency.

FIG. 9 shows a main pipe flow velocity of 90 in the present invention equipped with a sound reduction plate.
It is a graph which shows the relationship between the noise level at the time of m / s, and frequency.

FIG. 10 is a cut side view showing an embodiment of the inventions of claims 3 and 4.

11 is a sectional plan view taken along line XI-XI of FIG.

FIG. 12 is a graph showing the noise level when the flow velocity of the main pipe is changed in the case where the diameter of the convex portion in the present invention having the convex portion is variously changed.

FIG. 13 shows a case where the cavity and the convex portion have different intervals,
It is a graph which shows a noise level when the protrusion height of a convex part is changed.

FIG. 14 is a graph showing the relationship between the noise level and the frequency when the flow velocity of the main pipe is changed in the case of the present invention having a convex portion and the case where no countermeasure is taken.

FIG. 15 is a graph showing the relationship between frequency and noise level when no countermeasure is taken.

FIG. 16 is a graph showing the relationship between frequency and noise level when a convex portion is provided.

FIG. 17 is a cut front view showing an embodiment of the invention of claim 5;

FIG. 18 is a sectional plan view of FIG.

FIG. 19 is a cut front view showing another embodiment of the invention of claim 5;

20 is a sectional plan view of FIG.

FIG. 21 is a cut front view showing an embodiment of the invention of claim 6;

22 is a sectional plan view of FIG. 21. FIG.

FIG. 23 is a side view showing an example of measuring a sound pressure level of a cavity, a magnitude of pressure fluctuation, a pressure fluctuation width, and a flow velocity fluctuation spectrum at an opening.

FIG. 24 shows the results of sound pressure level measurement for the devices of FIGS. 17 and 18, the devices of FIGS. 19 and 20, and the devices of FIGS. It is a diagram showing.

FIG. 25 is a graph showing the magnitude of pressure fluctuation in the case of the apparatus shown in FIGS. 17 and 18, the apparatus shown in FIGS. 19 and 20, the apparatus shown in FIGS. It is a diagram showing a result.

FIG. 26 shows an average flow velocity of about 4 in the case of the conventional no countermeasure.
It is a diagram of the result of having measured the pressure fluctuation width at 4 m / s.

FIG. 27: The average flow velocity is about 8 in the case of the conventional no countermeasure.
It is a diagram of the result of having measured the pressure fluctuation width at 5 m / s.

28 is a diagram showing the results of measuring the pressure fluctuation range when the average flow velocity is about 44 m / s in the apparatus of FIGS. 19 and 20. FIG.

FIG. 29 is a diagram showing a result of measuring a pressure fluctuation width when the average flow velocity is about 85 m / s in the apparatus of FIGS. 19 and 20.

FIG. 30: The average flow velocity is about 5 in the conventional case without countermeasures.
It is a diagram of the result of having measured the flow velocity fluctuation spectrum at 5 m / s.

FIG. 31 shows an average flow velocity of about 7 in the conventional case of no countermeasure.
It is a diagram of the result of having measured the flow velocity fluctuation spectrum at 0 m / s.

FIG. 32: The average flow velocity is about 8 in the case of the conventional no countermeasure.
It is a diagram of the result of having measured the flow velocity fluctuation spectrum at 5 m / s.

33 is a diagram showing a result of measuring a flow velocity fluctuation spectrum when the average flow velocity is about 55 m / s in the apparatus of FIGS. 17 and 18. FIG.

FIG. 34 is a diagram showing a result of measuring a flow velocity fluctuation spectrum when the average flow velocity is about 70 m / s in the apparatus of FIGS. 17 and 18.

FIG. 35 is a diagram showing a result of measuring a flow velocity fluctuation spectrum when the average flow velocity is about 85 m / s in the apparatus of FIGS. 17 and 18.

FIG. 36 is a cut side view showing an example of a conventional device.

FIG. 37 is a cut side view showing another example of the conventional device.

[Explanation of symbols]

1 Main Pipe 2 Cavity 2a Corner 4 Opening 7 Noise Reduction Plate 9 Inner Surface End Face 10 Convex 12a Convex 12b Convex 13a Convex 13b Convex 13c Convex 14a Convex 14b Convex 14c Convex D Inside Diameter of Cavity d Diameter of convex part L ₂ Projection height of convex part L ₃ Distance between cavity and convex part

Claims (6)

[Claims] 1. A sound-reducing plate extending inward of the cavity, the plane of which intersects the axial direction of the main pipe, is disposed in the vicinity of the opening of the cavity formed so as to intersect the main pipe. Resonance sound prevention device. 2. A main pipe inner surface side end surface of the sound reducing plate is linear, both ends of the end surface coincide with a cavity corner of the main pipe inner surface, and the sound reducing plate has an inner diameter of the cavity in the cavity depth direction. The cavity resonance noise generation preventing apparatus according to claim 1, wherein the cavity resonance sound generation prevention apparatus has a size substantially equal to 3. A convex portion projecting toward the inside of the main pipe is provided at an upstream side position of the cavity on the inner surface of the main pipe having a cavity formed so as to intersect with the main pipe at the same position in the circumferential direction as the installation position of the cavity. A device for preventing resonance sound generation in a cavity, which is characterized in that 4. A plurality of protrusions are provided in a main pipe inner surface having a cavity formed so as to intersect with the main pipe, at a position upstream of the cavity at a predetermined interval in the inner circumferential direction of the main pipe, and projecting into the main pipe. A device for preventing resonance noise generation in a cavity, which is provided with a convex portion. 5. The cavity resonance noise preventing apparatus according to claim 4, wherein the plurality of convex portions are arranged in a staggered manner. 6. The convex portion is about 20% to 7% of the inner diameter of the cavity.
A cavity having a cylindrical shape with a diameter of 0%, the protruding height of the convex portion being about 20% or more of the inner diameter of the cavity, and the convex portion having a space within about 5 times the inner diameter of the cavity. The cavity resonance sound generation preventing device according to claim 3, 4 or 5, wherein the device is installed at a more upstream position.