Silencing device for ultrasonic measuring instrument

Abstract

A silencing device (1) comprises: a sound wave decomposition unit (10) that decomposes, into a plurality of partial waves having different phases, an ultrasonic wave which has entered; and a sound wave attenuation unit (30) that is located downstream of the sound wave decomposition unit (10) in the flow direction of a fluid and that attenuates the plurality of partial waves. The sound wave decomposition unit (10) includes: a first case (11) that has an inlet (13) for the fluid; and a reflector (21) that is provided inside of the first case (11), that has a reflective surface (22) at which the reflection angles of ultrasonic waves which have entered from the inlet (13) differ according to the reflection position, and that forms a streamlined shape. The sound wave attenuation unit (30) includes: a second case (31) that has an interference space (34) in which the plurality of partial waves interfere with each other; and an outlet (33) for the fluid.

Description

Soundproofing device for ultrasonic measuring instrument

[0001] The present disclosure relates to a soundproofing device for an ultrasonic measuring instrument that measures the flow rate or the like of a fluid using ultrasonic waves.

[0002] Conventionally, a supply network for supplying fluids such as gas and water to consumer houses has been constructed. As an example, the gas supply network will be described. The gas supply network supplies gas to each consumer house through pipes such as a common pipe and a plurality of individual pipes extending from the common pipe. Further, in order to measure the amount of gas used in each consumer house, a measuring instrument for measuring the physical quantity of gas is installed at an appropriate position in the pipe.

[0003] As this type of measuring instrument, an ultrasonic measuring instrument that measures the flow rate or concentration of a fluid such as gas or water using ultrasonic waves is known. The ultrasonic measuring instrument includes a flow path through which the fluid flows and a pair of ultrasonic transceivers arranged apart from each other on the upstream side and the downstream side with respect to the flow path. Then, an ultrasonic signal is transmitted and received bidirectionally between the pair of ultrasonic transceivers, and the flow rate or the like is measured from the propagation time in one direction and the propagation time in the other direction.

[0004] However, in the supply network, a plurality of measuring instruments are connected through pipes. Therefore, an ultrasonic signal emitted from one measuring instrument may propagate through the pipe to another measuring instrument. The ultrasonic signal propagated from one measuring instrument becomes noise in another measuring instrument and deteriorates the measurement accuracy of the flow rate. Further, in a plant device having a control valve such as a fuel cell, there is one in which an ultrasonic measuring instrument is further incorporated. In such a device, since the control valve and the ultrasonic measuring instrument are located extremely close to each other, strong ultrasonic waves included in the metallic sound generated when the control valve is opened and closed become noise and can have a great influence on the measurement by the ultrasonic measuring instrument. Therefore, in Patent Document 1, a silencer for attenuating such ultrasonic noise is proposed.

[0005] Japanese Patent Application Laid-Open No. 2013-127443

[0006] However, the silencer described in Patent Document 1 has obstruction plates (a central obstruction plate and outer obstruction plates) that are substantially perpendicular to the line connecting the fluid inlet and outlet. While these obstruction plates can efficiently attenuate highly directional ultrasonic noise, they result in very high flow resistance and high pressure loss.

[0007] Therefore, the present disclosure aims to provide a noise reduction device for ultrasonic measuring instruments that can reduce ultrasonic noise and suppress the increase in fluid pressure loss.

[0008] The sound-dampening device of this disclosure is installed upstream of an ultrasonic measuring instrument in the direction of fluid flow and reduces ultrasonic noise propagating to the ultrasonic measuring instrument with the fluid, and comprises a sound wave decomposition unit that decomposes incoming ultrasonic waves into a plurality of partial waves with different phases, and a sound wave attenuation unit located downstream of the sound wave decomposition unit in the direction of fluid flow and attenuating the plurality of partial waves, wherein the sound wave decomposition unit includes a first case having a fluid inlet, and a reflector provided inside the first case having a reflective surface that has a streamlined shape and whose reflection angle of ultrasonic waves entering from the inlet differs according to the reflection position, and the sound wave attenuation unit includes a second case having an interference space in which the plurality of partial waves interfere with each other, and a fluid outlet.

[0009] According to the ultrasonic noise reduction device for ultrasonic measuring instruments described herein, ultrasonic waves entering from the inlet of the first case are reflected by the reflective surface of the reflector in the sound wave decomposition section and decomposed into multiple types of partial waves with different phases. These partial waves interfere with each other and are attenuated in the interference space of the sound wave attenuation section. On the other hand, since the reflector has a streamlined shape, the pressure loss of the fluid flowing in from the inlet can be reduced. In this way, a good balance can be achieved between the reduction of ultrasonic noise and the suppression of fluid pressure loss.

[0010] Figure 1 is a schematic diagram illustrating a fluid piping network in which a sound-dampening device is installed. Figure 2 is an external perspective view showing the configuration of the sound-dampening device according to Embodiment 1. Figure 3 is a schematic longitudinal cross-sectional view of the sound-dampening device. Figure 4 is a schematic longitudinal cross-sectional view of the sound-dampening device according to Embodiment 2. Figure 5 is a perspective view of the internal parts of the sound-dampening device. Figure 6 is a schematic longitudinal cross-sectional view of the sound-dampening device according to Embodiment 3. Figure 7 is a perspective view of the internal parts of the sound-dampening device. Figure 8 is a schematic diagram showing the configuration of various modified examples of the reflector.

[0011] (Embodiment 1) Hereinafter, embodiments of the sound-dampening device for ultrasonic measuring instruments according to the present disclosure will be specifically described with reference to the drawings. In the following, the same or corresponding elements will be denoted by the same reference numerals in all drawings, and redundant explanations will be omitted. Furthermore, the fluid (fluid to be measured) that the ultrasonic measuring instrument measures, such as flow rate and concentration, is not particularly limited, but here we will explain using an ultrasonic measuring instrument that uses a gas such as hydrogen as the fluid to be measured as an example.

[0012] [Supply Network] As shown in Figure 1, the sound-dampening device 1 according to Embodiment 1 of the present disclosure is installed on the upstream side of the gas flow direction relative to the ultrasonic measuring instrument 2 in a gas piping network 100 in which a plurality of ultrasonic measuring instruments are installed. The gas piping network 100 is an example of a fluid supply network for supplying the fluid to be measured to a customer's home. Specifically, the gas piping network 100 is composed of pipes 102 that branch at a plurality of branching points 103 as they proceed downstream from a pressure reducing valve 101 located on the upstream side, and a customer's home 104 that uses gas is located at the end of each pipe 102. An ultrasonic measuring instrument 2 is installed in the middle of the pipe 102 connecting the customer's home 104 and the branching point 103 immediately upstream, in order to measure the flow rate, concentration, etc. of the gas at the customer's home 104. The sound-dampening device 1 according to the present disclosure is installed on the upstream side of the ultrasonic measuring instrument 2 in the same pipe 102.

[0013] The ultrasonic measuring instrument 2 has a flow path 2a through which gas flows, and a pair of ultrasonic transducers 2b and 2c arranged to face this flow path. One ultrasonic transducer 2b is positioned upstream of the other ultrasonic transducer 2c in the flow path 2a in the direction of gas flow. Therefore, there is a difference in the propagation time of ultrasonic waves from one ultrasonic transducer 2b to the other ultrasonic transducer 2c and the propagation time of ultrasonic waves from the other ultrasonic transducer 2c to the one ultrasonic transducer 2b, depending on the gas flow velocity in the flow path. Consequently, by measuring this propagation time difference, physical quantities such as gas flow velocity and flow rate can be obtained.

[0014] Incidentally, as described above, the ultrasonic measuring instrument 2 is installed in the pipe 102 that constitutes the gas piping network 100. Therefore, some of the ultrasonic waves emitted by other ultrasonic measuring instruments 2 connected to the pipe 102 via the branching point 103 (shown by dashed arrows in Figure 1) may propagate to one ultrasonic measuring instrument 2. For one ultrasonic measuring instrument 2, the ultrasonic waves propagating from other ultrasonic measuring instruments 2 through the pipe 102 in this way are noise and affect the accurate measurement of physical quantities in the instrument itself. In contrast, the noise reduction device 1 of this disclosure mainly reduces ultrasonic noise propagating from the upstream side and contributes to improving the accuracy of measurement of physical quantities at the ultrasonic measuring instrument 2 located downstream.

[0015] The ultrasonic measuring instrument 2 may also be equipped with other sensors, such as a temperature sensor or a pressure sensor. When the ultrasonic measuring instrument 2 measures physical quantities such as the temperature and pressure of the gas in the flow path, the components and concentrations of the gas in the flow path can be obtained by performing calculations using these physical quantities.

[0016] [Silencer] Next, the configuration of the silencer 1 will be described in detail with reference to Figures 2 and 3. Figure 2 is a schematic external view showing the configuration of the silencer 1, with a portion (sound wave decomposition unit 10) shown transparently. Figure 3 is a schematic longitudinal cross-sectional view of the silencer 1.

[0017] [Sound Wave Decomposition Unit] As shown in Figure 2, the silencer 1 comprises a sound wave decomposition unit 10 on the upstream side in the direction of gas flow and a sound wave attenuation unit 30 on the downstream side. The sound wave decomposition unit 10 has the function of decomposing incoming ultrasonic waves into a plurality of partial waves with different phases, and comprises a first case 11 and a reflector 21 provided inside the first case 11. In Figure 2, the first case 11 is shown with a dashed line to show the external configuration of the reflector 21.

[0018] The first case 11 has an internal space 11a. The first case 11 also has a fluid inlet 13, which is an opening provided at the upstream end, and a first opening 14, which is an opening provided at the downstream end, and these inlet 13 and first opening 14 are in communication with the internal space 11a. The downstream end of the piping 102, which is provided on the upstream side of the sound-dampening device 1, is connected to the inlet 13. Therefore, the gas flowing from the piping 102 and the ultrasonic waves propagating from the piping 102 enter the internal space 11a of the first case 11 through this inlet 13.

[0019] The inlet 13 and the first opening 14 are both circular in shape when viewed from the direction of flow and are located coaxially. That is, as shown in Figure 3, the centers of the inlet 13 and the first opening 14 are located on a predetermined axis line L. Furthermore, the first opening 14 has a larger diameter than the inlet 13. The diameter dimension D1 of the internal space 11a of the first case 11 (the inner diameter dimension in the direction perpendicular to the direction of flow) gradually increases from the inlet 13 toward the first opening 14.

[0020] More specifically, the diameter D1 of the internal space 11a is at its minimum value at the inlet 13, increases at a nearly constant rate as one moves downstream from the inlet 13, then the rate of increase gradually decreases, and then the diameter D1 becomes a constant value (maximum value) when it reaches the first opening 14. Therefore, when viewing the first case 11 in terms of the diameter D1 of the internal space 11a, the first case 11 can be divided into a first part 15, a second part 16, and a third part 17, in order from the upstream side.

[0021] Here, the first portion 15 is the portion that continues from the inlet 13 and in which the diameter D1 increases at a nearly constant rate, and for example, it has a truncated cone shape. As an example, as shown in Figure 2, the portion of the inner surface 11b of the first case 11 that corresponds to the first portion 15 may have a configuration in which its inclination direction (the direction along the inner surface 11b) is closer to the flow direction than to the radial direction. The second portion 16 is the portion in which the rate of increase of the diameter D1 gradually decreases to zero. The third portion 17 is the portion in which the diameter D1 is the same constant value as the first opening 14 and continues to the first opening 14, and for example, it has a cylindrical shape. The inner surface 11b of the first case 11 in this manner has a streamlined shape with respect to the gas flow direction from the inlet 13 to the first opening 14. The cross-section of the internal space 11a (the cross-section perpendicular to the axis line L) is a coaxial circle at any position in the axial direction.

[0022] The reflector 21 is provided in the internal space 11a of the first case 11. The reflector 21 has a streamlined shape so as not to obstruct the gas flow within the first case 11 as much as possible. A suitable shape for such a reflector 21 is, for example, a teardrop shape as shown in Figure 2. The reflector 21 in Figure 2 has a rotationally symmetric shape with respect to the axis line L, and the contour shape of the longitudinal section is a teardrop shape in which the curvature of the upstream part is greater than the curvature of the downstream part.

[0023] The teardrop shape is just one example of the shape of the reflector 21, and it is not limited to this. For example, the reflector 21 can also be spherical or elliptical, or have other shapes in which the contour of the longitudinal cross-section consists of curves. However, the reflector 21 has an external shape in which the reflection angle of the ultrasonic waves that enter the case 11 from the entrance 13 differs depending on the reflection position of the reflective surface 22.

[0024] Figure 3 schematically shows the ultrasonic wave W entering the first case 11 from the entrance 13. The ultrasonic wave W has high directivity and can be viewed as a collection of multiple signal waves propagating in parallel. Therefore, Figure 3 schematically shows two arbitrary signal waves WA1 and WA2 included in the ultrasonic wave W. These signal waves WA1 and WA2 propagate parallel to each other and propagate at a predetermined distance apart in the direction perpendicular to the propagation direction. Furthermore, these signal waves WA1 and WA2 are in phase with each other.

[0025] These two signal waves WA1 and WA2 enter through the inlet 13 and are reflected at different positions on the reflective surface 22, which is mainly the upstream surface of the reflector 21. Signal wave WA1 is reflected at reflection angle A1, and signal wave WA2 is reflected at reflection angle A2, and these reflection angles A1 and A2 are different angles from each other. In addition, each signal wave WA1 and WA2 reflected by the reflective surface 22 is also reflected by the inner surface 11b of the first case 11, and in some cases, further reflected at different positions on the reflective surface 22. The "reflection angle" mentioned above is the angle formed by the direction of propagation of the reflected wave with respect to the tangent at the position where the signal wave is reflected on the reflective surface 22 (i.e., the reflective surface for the signal wave).

[0026] In other words, the signal waves WA1 and WA2 are reflected once or multiple times at different reflection angles by the reflective surface 22 before reaching the first aperture 14. Therefore, the propagation distances of the signal waves WA1 and WA2 from the inlet 13 to the first aperture 14 are different. As a result, although the signal waves WA1 and WA2 were in phase at the inlet 13, at the first aperture 14 they become signal waves (partial waves WB1 and WB2) with different phases depending on the difference in propagation distance. In this way, the ultrasonic wave W is decomposed into multiple partial waves WB1 and WB2 with different phases by propagating through the sound wave decomposition unit 10.

[0027] Such a reflector 21 is supported by an arm 23 extending from the inner surface 11b of the first case 11. The arm 23 has an elliptical or oblong cross-section and is positioned so that the major axis of the cross-section is oriented in the direction of gas flow. The base end of the arm 23 is located on the inner surface 11b of the first part 15 of the first case 11, and the arm 23 extends diagonally backward from this base end, moving backward as it approaches the axis line L. The tip of the arm 23 is connected to the outer surface (reflective surface 22) of the upstream portion of the reflector 21. In this embodiment, the arm 23 is bridged at the point where the distance between the inner surface 11b of the first case 11 and the outer surface of the reflector 21 is smallest.

[0028] The number of arms 23 is not particularly limited. There may be one or more. Figure 3 illustrates a configuration in which the reflector 21 is supported by three arms 23. In this case, the three arms 23 are arranged at equal intervals in the circumferential direction centered on the axis line L. Furthermore, different configurations may be adopted for the shape and arrangement of the arms 23.

[0029] [Sound wave attenuation section] Next, the sound wave attenuation section 30, which is provided downstream of the sound wave decomposition section 10, will be described. The sound wave attenuation section 30 has the function of attenuating the multiple partial waves decomposed by the sound wave decomposition section 10 by causing them to interfere with each other, and is equipped with a second case 31. The second case 31 has a second opening 32 and an outlet 33, and further has an interference space 34 which is an internal space communicating with these second opening 32 and outlet 33.

[0030] The second opening 32 and the outlet 33 are both circular in shape when viewed from the direction of flow and are located coaxially. The first case 11 and the second case 31 are connected with the first opening 14 and the second opening 32 facing each other. For example, a male screw threaded on the outer circumference of the downstream end of the first case 11 and a female screw threaded on the inner circumference of the upstream end of the second case 31 are screwed together to connect them. With the first case 11 and the second case 31 connected in this way, the centers of the second opening 32 and the outlet 33 are located on the axis line L. Therefore, in the silencer 1, the inlet 13 and the outlet 33 are arranged coaxially on the axis line L. This axis line L forms the center line of gas flow connecting the inlet 13 and the outlet 33.

[0031] The interference space 34 is a space with a predetermined capacitance in which multiple partial waves from the sound wave decomposition unit 10 interfere with each other. This interference space 34 has substantially the same diameter as the internal space of the third portion 17, which is the downstream portion of the internal space 11a of the first case 11. Therefore, when the first case 11 and the second case 31 are connected, the downstream portion of the first case 11 and the upstream portion of the second case 31 are flush with each other without any steps between their inner surfaces.

[0032] The interference space 34 is a cylindrical space with a nearly constant diameter and a predetermined dimension in the direction of flow. Therefore, the inner surface 34a of the second case 31 defining the interference space 34 is cylindrical. The dimension of the interference space 34 in the direction of flow is, for example, more than half of the radial dimension (inner diameter), and preferably the same or greater. Because the interference space 34 has a wide space, multiple partial waves with different phases that enter the interference space 34 interfere with each other, weaken each other, and are attenuated. In this way, the interference space 34 attenuates the partial waves separated from the sound wave, so it can also be called a sound-dampening space.

[0033] A throttling space 35 is provided at the downstream end of the interference space 34. The throttling space 35 is a space connecting the large-diameter interference space 34 and the small-diameter outlet 33, and its diameter decreases at a nearly constant rate as it moves downstream. In the case of Figure 3, the throttling space 35 is roughly the shape of a truncated cone, and the inner surface 35a of the second case 31 that defines the throttling space 35 has an inclined surface that intersects both the flow direction and the radial direction. Therefore, a portion of the partial wave that enters the interference space 34 is reflected by this inner surface 35a and propagates again within the interference space 34, and is further attenuated by interfering with other partial waves. As an example, as shown in Figure 3, the inner surface 35a may be configured such that its inclination direction (the direction along the inner surface 35a) is closer to the radial direction than to the flow direction.

[0034] The inner surface 34a of the interference space 34 and the inner surface 35a of the diaphragm space 35 are smoothly and continuously connected by a curved surface. Similarly, the inner surface 35a of the diaphragm space 35 and the inner surface 33a of the second case 31 defining the outlet 33 are smoothly and continuously connected by a curved surface. In this way, the inner surface of the second case 31 has a streamlined shape in its longitudinal cross-section. Therefore, the flow of gas entering the second case 31 is less likely to be obstructed.

[0035] The outlet 33 of the second case 31 has a cylindrical internal space defined by its inner surface 33a. That is, the outlet 33 is coaxial with the interference space 34 and has a smaller diameter than the interference space 34. If multiple partial waves enter the internal space of this outlet 33, the entered partial waves can interfere with each other and be attenuated.

[0036] [Operation and Effects] With the sound-dampening device 1 configured as described above, the ultrasonic noise is decomposed into multiple partial waves with different phases in the sound wave decomposition unit 10, and these multiple partial waves interfere with each other and are attenuated in the sound wave attenuation unit 30. Therefore, ultrasonic noise propagating from the outside can be effectively reduced. Moreover, since the internal space of the sound-dampening device 1 is streamlined, pressure loss for fluids such as gas is suppressed. Thus, a good balance can be achieved between suppressing fluid pressure loss and reducing ultrasonic noise.

[0037] In this embodiment, the sound-dampening device 1 is provided such that the reflector 21 obstructs the axial line L, which is the centerline of gas flow connecting the inlet 13 and the outlet 33. As a result, ultrasonic noise entering from the inlet 13 is reflected by the reflector 21 with a high probability, decomposed into partial waves, and attenuated through interference. Therefore, the passage of ultrasonic noise that enters from the inlet 13 and exits directly from the outlet 33 can be suppressed, and ultrasonic noise can be reduced more reliably within the sound-dampening device 1.

[0038] Furthermore, the cross-sectional shape of the reflector 21 may be made larger than the opening shape of the inlet 13, or the cross-sectional shape of the reflector 21 may be made larger than the opening shape of the outlet 33. This makes it possible to more reliably suppress the passage of ultrasonic noise and reduce it through decomposition and interference.

[0039] (Embodiment 2) Figure 4 is a schematic vertical cross-sectional view showing the configuration of the sound-dampening device 1A according to Embodiment 2 of the present disclosure, and Figure 5 is a perspective view of the internal parts of the sound-dampening device 1A.

[0040] The sound-dampening device 1A according to this embodiment has a configuration in which a divided flow channel section 50 is interposed between the sound wave decomposition section 10 and the sound wave attenuation section 30 of the sound-dampening device 1 of Embodiment 1. The following describes in detail the configuration of the sound-dampening device 1A that differs in particular from the sound-dampening device 1 according to Embodiment 1.

[0041] The silencing device A1 shown in Fig. 4 includes a first case 11A and internal parts 40 housed in the first case 11A. The first case 11A is divided into a first part 15, a second part 16, and a third part 17A in order from the upstream side. Among these, the first part 15 and the second part 16 on the upstream side have the same configuration as the first part 15 and the second part 16 of the silencing device 1. On the other hand, the third part 17A is longer in the axial direction than the third part 17 of the silencing device 1.

[0042] As shown in Fig. 5, the internal parts 40 are composed of a reflector 21 located on the upstream side and a plurality of arms 23 supporting the reflector 21, and a divided flow path portion 50 located on the downstream side. Among these, the reflector 21 and the arms 23 have the same configuration as the reflector 21 and the arms 23 of the silencing device 1.

[0043] The divided flow path portion 50 includes a cylindrical member 51 having a plurality of parallel branch flow paths 52. The downstream end of the reflector 21 is connected to the center position of the upstream end face of the cylindrical member 51, and the cylindrical member 51 is integrally formed with the reflector 21. As shown in Fig. 4, the outer diameter dimension of the cylindrical member 51 is substantially the same as the inner diameter dimension of the third part 17A of the first case 11A, and the cylindrical member 51 is fitted and fixed to the first case 11A from the downstream side.

[0044] The plurality of branch flow paths 52 are through holes provided to penetrate between the upstream end face 51u and the downstream end face 51d of the cylindrical member 51. As shown in Fig. 5, the plurality of branch flow paths 52 are arranged at concentric positions centered on the axis of the cylindrical member 51 and are arranged at equal intervals in the circumferential direction. More specifically, the axis (center) of the cylindrical member 51 coincides with the axis line L, and the branch flow paths 52 include six branch flow paths 52a arranged on a concentric circle close to the axis line L and twelve branch flow paths 52b arranged on a concentric circle far from the axis line L and outside the branch flow paths 52a.

[0045] Thus, the divided flow path portion 50 has a plurality of small-diameter branch flow paths 52 (having a diameter smaller than at least the third portion 17A of the first case 11). As a result, the partial waves decomposed in the sound wave decomposition portion 10 pass through the small-diameter branch flow paths 52 and are reflected by the inner surfaces of the branch flow paths 52 during the passage. As a result, the number of reflections of the partial waves increases, so that the distribution of the phases of the respective partial waves becomes wider, and the attenuation effect in the sound wave attenuation portion 30 can be improved.

[0046] In addition, in the divided flow path portion 50 according to the present embodiment, the center of the flow path of each branch flow path 52 is inclined with respect to the axial center of the cylindrical member 51 (refer to the axial center line L). For example, the six inner branch flow paths 52a are such that the downstream end is located on one side in the circumferential direction (for example, the counterclockwise side when viewed along the flow-through direction) centered on the axial center with respect to the upstream end. Further, the twelve outer branch flow paths 52b are such that the downstream end is located on the other side in the circumferential direction (for example, the clockwise side) with respect to the upstream end.

[0047] Thus, by inclining each branch flow path 52 so that the circumferential positions of the upstream end and the downstream end are different, the gas that has passed through these branch flow paths 52 flows downstream while forming a vortex within the sound wave attenuation portion 30. As a result, an efficient gas flow due to the swirl effect can be realized.

[0048] In the above, a configuration in which the inclination directions of the inner branch flow paths 52a and the outer branch flow paths 52b are opposite to each other has been illustrated, but the present invention is not limited to this, and the inclination directions may be the same. Further, the inclination angle of each branch flow path 52 is not particularly limited. For example, the inner branch flow paths 52a and the outer branch flow paths 52b may be set to have different inclination angles. However, it is preferable that the inclination angles of the branch flow paths 52 on the same circumference are the same.

[0049] (Embodiment 3) FIG. 6 is a schematic longitudinal sectional view showing the configuration of the silencer 1B according to Embodiment 3 of the present disclosure, and FIG. 7 is a perspective view of the internal parts included in the silencer 1B.

[0050] The silencing device 1B according to this embodiment has a configuration in which a pipe member is inserted into a through-hole that forms a branch channel 52 in the separation channel section 50 of the silencing device 1A of the second embodiment. The following describes in detail the configuration of the silencing device 1B that differs from the silencing device 1A according to the second embodiment.

[0051] The sound-dampening device 1B shown in Figure 6 comprises an internal part 41 consisting of a reflector 21, a plurality of arms 23, and a divided channel section 50. The divided channel section 50 also comprises a cylindrical member 51 having a plurality of through holes 53 (see Figure 7). These through holes 53 have substantially the same configuration as the branch channels 52 of the cylindrical member 51 of the sound-dampening device 1A, and are provided penetrating between the upstream end face and the downstream end face of the cylindrical member 51.

[0052] As shown in Figure 7, in the sound-dampening device 1B, pipe members 54 are inserted through each of these through holes 53. The longitudinal dimension of the pipe member 54 is longer than the axial dimension of the cylindrical member 51. One end (upstream end) 54u of the pipe member 54 protrudes upstream from the upstream end face 51u of the cylindrical member 51, and the other end (downstream end) 54d protrudes downstream from the downstream end face 51d of the cylindrical member 51. In the sound-dampening device 1B according to this embodiment, the internal space of such pipe member 54 forms a branch channel 52.

[0053] By using the internal space of the pipe member 54 as a branch channel 52 in this way, it becomes easier to arbitrarily set the length dimensions of the multiple branch channels 52.

[0054] The above example illustrates a configuration in which both ends of the pipe member 54 protrude from the cylindrical member 51, but the invention is not limited to this. For example, the upstream end 54u of the pipe member 54 may protrude from the upstream end face 51u of the cylindrical member 51, while the downstream end 54d of the pipe member 54 may not protrude from the downstream end face 51d of the cylindrical member 51. Conversely, the downstream end 54d of the pipe member 54 may protrude from the downstream end face 51d of the cylindrical member 51, while the upstream end 54u of the pipe member 54 may not protrude from the upstream end face 51u of the cylindrical member 51.

[0055] Furthermore, it is also possible to configure the system so that only some of the multiple pipe members 54 protrude from the cylindrical member 51, while the remaining pipe members 54 do not protrude from the cylindrical member 51.

[0056] (Modifications) Modifications of the reflector 21 applicable to the sound-dampening device according to each embodiment will be described with reference to Figure 8. In Figures 8, Modifications 1 to 5 show the configuration of the reflector 21 when viewed in the direction of airflow, and Modification 6 shows the longitudinal section of the reflector 21, but the hatching representing the cross section is omitted.

[0057] In the embodiments described above, the reflectors 21 are symmetrically arranged with respect to the axis L connecting the inlet 13 and the outlet 33, but the invention is not limited to this configuration. For example, as shown in Modification 1 of Figure 8, the reflectors 21 may be provided asymmetrically with respect to the axis L. For example, the axis 21A of the reflector 21 may be offset from the axis L. As a result, the internal space 11a of the sound wave decomposition unit 10 has different radial dimensions depending on its position, which increases the phase difference between the multiple partial waves decomposed from the ultrasound. Therefore, the attenuation of ultrasound due to interference between partial waves can be achieved more efficiently.

[0058] Furthermore, as shown in the modified example 2 of Figure 8, the area of ​​the reflector 21 projected in the direction of flow (projected area) may be set to be greater than or equal to the opening area of ​​the inlet 13 (shown by the dashed line), and the entire inlet 13 may be located within the area occupied by the reflector 21 when viewed along the direction of flow. In this case, the ultrasonic waves entering from the inlet 13 can be reflected by the reflector 21 more reliably, and the generation of partial waves can be promoted.

[0059] Furthermore, the method for increasing the phase difference between partial waves is not limited to the asymmetric arrangement of the reflector 21 with respect to the axis line L as in the modified example 1 described above. Alternatively, or in addition to this, at least one of a recessed portion that is recessed from the surface and a convex portion that protrudes from the surface may be provided on the surface that reflects the ultrasonic noise. Here, the surface that reflects the ultrasonic noise is at least one of the reflective surface 22 of the reflector 21 and the inner surface 11a of the first case 11.

[0060] Modification 3 shows a configuration in which the reflective surface 22 of the reflector 21 is provided with a recess 60. The recess 60 may be a concave groove having a predetermined length, and the recess 60 shown in Modification 3 is a groove formed so that its longitudinal direction is aligned with the direction of gas flow (the direction along the axis line L). Modification 4 shows a configuration in which the reflective surface 22 of the reflector 21 is provided with a convex portion 61. The convex portion 61 may be a convex rib having a predetermined length, and the convex portion 61 shown in Modification 4 is a rib formed so that its longitudinal direction is aligned with the direction of gas flow (the direction along the axis line L). By having such a recess 60 or convex portion 61, it is possible to increase the phase difference between the partial waves reflected by the reflective surface 22 while suppressing the increase in pressure loss during gas flow.

[0061] Furthermore, the contour shape of the cross-section of the reflector 21 is not limited to a circle. For example, as shown in Modification 5, it may be a polygon formed by connecting multiple line segments 63, or it may be a contour shape in which each side of such a polygon is curved outward. It may also be an elliptical shape, or an asymmetric shape that is not rotationally symmetric with respect to the center.

[0062] Furthermore, although the contour shape of the longitudinal cross-section of the reflector 21 is streamlined with respect to the fluid flow, it only needs to be streamlined when viewed macroscopically, and is not limited to a shape composed of continuous curves and straight lines when viewed microscopically. That is, as shown in Modification 6, as long as it is streamlined when viewed macroscopically, it may be a contour shape such as one made by connecting multiple line segments 64.

[0063] Furthermore, it is preferable that the streamlined reflector 21 has a surface (substantially the reflective surface 22) in contact with the flowing gas that is as close as possible to the axis L connecting the inlet 13 and the outlet 33. For example, it is preferable that the angle of inclination with respect to the axis L is 45 degrees or less for 60% or more of the total surface area of ​​the reflector 21, and more preferably that the angle of inclination with respect to the axis L is 45 degrees or less for 80% or more of the total surface area of ​​the reflector 21.

[0064] (Other Embodiments) The above description of embodiments discloses the following technologies.

[0065] (Technology 1) The noise reduction device of Technology 1 is provided upstream of an ultrasonic measuring instrument in the direction of fluid flow and reduces ultrasonic noise propagating to the ultrasonic measuring instrument, and comprises a sound wave decomposition unit that decomposes incoming ultrasonic waves into a plurality of partial waves with different phases, and a sound wave attenuation unit located downstream of the sound wave decomposition unit in the direction of fluid flow and attenuates the plurality of partial waves, wherein the sound wave decomposition unit includes a first case having a fluid inlet, and a reflector provided inside the first case that has a streamlined shape and has reflective surfaces whose reflection angles of ultrasonic waves entering from the inlet differ according to the reflection position, and the sound wave attenuation unit includes a second case having an interference space in which the plurality of partial waves interfere with each other, and a fluid outlet.

[0066] This reduces ultrasonic noise while suppressing pressure loss in the flowing fluid. Consequently, the propagation of ultrasonic noise to ultrasonic measuring instruments located downstream of the sound-dampening device can be suppressed, thereby improving the accuracy of physical quantity measurements by the ultrasonic measuring instruments.

[0067] (Technology 2) In the sound-dampening device of Technology 2, the reflector may be provided in such a way as to obstruct the center line of fluid flow connecting the inlet and the outlet.

[0068] This allows ultrasonic noise entering from the inlet to be more reliably reflected by the reflective surface of the reflector, and prevents it from escaping from the outlet without being reflected by the reflector.

[0069] (Technology 3) In the sound-dampening device of Technology 3, the reflector may be provided asymmetrically with respect to the fluid flow centerline connecting the inlet and the outlet.

[0070] This increases the phase difference between the multiple partial waves decomposed from the ultrasound, allowing for more efficient attenuation of the ultrasound due to interference between the partial waves.

[0071] (Technology 4) In any of the technologies 1 to 3, the sound-dampening device of Technology 4 may have at least one of a recessed portion that is recessed from the surface and a convex portion that is projected from the surface formed on at least one of the inner surface of the first case and the reflective surface of the reflector.

[0072] This increases the phase difference between the multiple partial waves decomposed from the ultrasound, allowing for more efficient attenuation of the ultrasound due to interference between the partial waves.

[0073] (Technology 5) The sound-dampening device of Technology 5 may include a divided channel section provided between the sound wave decomposition section and the sound wave attenuation section, and having a plurality of parallel branch channels, in any of Technology 1 to 4.

[0074] As a result, the partial waves decomposed in the sound wave decomposition section pass through the smaller diameter branch channel and are reflected off the inner surface of the branch channel during passage. In this way, the number of reflections of the partial waves increases, which broadens the phase distribution of each partial wave and improves the attenuation effect in the sound wave attenuation section.

[0075] (Technology 6) In the sound-dampening device of Technology 6, the divided flow channel section may have a plurality of pipe members, and the internal space of the pipe members may form the branch flow channel.

[0076] This increases the degree of freedom in setting the length dimensions of the tributary channels.

[0077] (Technology 7) In the sound-dampening device of Technology 7, the divided flow channel section has a cylindrical member provided with a plurality of through holes that form the branch flow channels, and the plurality of branch flow channels may be inclined with respect to the center line of the cylindrical member such that the downstream end is located on one side in the circumferential direction of the cylindrical member relative to the upstream end.

[0078] As a result, the fluid passing through the branch channels of the divided channel section forms vortices, enabling efficient flow through the swirl effect.

[0079] This disclosure can be applied to a sound-dampening device for ultrasonic measuring instruments that measure fluid flow rates and the like using ultrasound.

[0080] 1, 1A, 1B Silencer 2 Ultrasonic measuring instrument 10 Sound wave decomposition section 11 First case 13 Inlet 21 Reflector 22 Reflecting surface 30 Sound wave attenuation section 31 Second case 33 Outlet 34 Interference space 50 Divided flow path section 51 Cylindrical member 52 Branch flow path 53 Through hole 54 Pipe member 60 Recess 61 Protrusion

Claims

1. A sound-dampening device for an ultrasonic measuring instrument, provided upstream of the fluid flow direction to the ultrasonic measuring instrument, for reducing ultrasonic noise propagating to the ultrasonic measuring instrument, comprising: a sound wave decomposition unit that decomposes incoming ultrasonic waves into a plurality of partial waves with different phases; and a sound wave attenuation unit located downstream of the sound wave decomposition unit in the fluid flow direction to attenuate the plurality of partial waves, wherein the sound wave decomposition unit includes a first case having a fluid inlet, and a reflector provided within the first case that has a streamlined shape and has reflective surfaces whose reflection angles for ultrasonic waves entering from the inlet differ according to the reflection position; and the sound wave attenuation unit includes a second case having an interference space in which the plurality of partial waves interfere with each other, and a fluid outlet.

2. The sound-dampening device according to claim 1, wherein the reflector is provided so as to obstruct the center line of fluid flow connecting the inlet and the outlet.

3. The sound-dampening device according to claim 1, wherein the reflector is provided asymmetrically with respect to the fluid flow centerline connecting the inlet and the outlet.

4. The sound-dampening device according to claim 1, wherein at least one of the inner surface of the first case and the reflective surface of the reflector is formed on at least one of a recessed portion that is recessed from the surface and a convex portion that is projected from the surface.

5. The sound-dampening device according to claim 1, further comprising a divided channel section provided between the sound wave decomposition section and the sound wave attenuation section, having a plurality of parallel branch channels.

6. The sound-dampening device according to claim 5, wherein the divided flow channel section has a plurality of pipe members, and the internal space of the pipe members forms the branch flow channel.

7. The sound-dampening device according to claim 5, wherein the divided channel section has a cylindrical member provided with a plurality of through holes forming the branch channels, and the plurality of branch channels are inclined with respect to the center line of the cylindrical member such that their downstream ends are located on one side in the circumferential direction of the cylindrical member relative to the upstream ends.

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