JP2005098566A - Noise absorbing duct type silencer and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently reduce the air noise to be generated when gas passes through inside a duct. <P>SOLUTION: This noise absorbing duct type silencer is provided with a tubular framework 4 for taking the gas inside for circulation from a suction opening and for discharging it from a blow-out opening, a noise absorbing member 3 arranged to be brought in contact with the air flowing inside a case to absorb the noise transmitted in the gas, and a smoothing material 6 provided in a circulating flow generative area, wherein a circulation flow is generated when the gas passes through, to reduce the generation of air noise due to the circulating flow. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sound absorbing duct type silencer and a method for manufacturing the same.

  When a gas is jetted from the outlet of a duct used for ventilation, air conditioning, or the like in tunnels or indoors, wind noise is generated by the high-speed gas jet. The magnitude of this wind noise depends on the strength of the shear flow around the air stream (rate of change in flow velocity), and the strength of this shear flow is affected by the state of the boundary layer on the inner surface of the duct. In Patent Document 1, the area of the air outlet is gradually reduced toward the outlet end, and a protrusion is provided on the inner wall surface in the vicinity of the outlet end of the air outlet so that the boundary layer in the duct is partially turbulent. An airflow outlet is disclosed that transitions to a boundary layer, reduces the strength of the shear flow, and reduces wind noise at the outlet.

Japanese Patent No. 3139588

  As shown in FIG. 8, the present inventor generates a phenomenon called contracted flow when the gas flows in the duct, and the effective area of the gas flow is narrowed by the contracted flow, and at the same time, a circulating flow is generated. It has been found that this circulating flow is engaged with the inner wall of the duct to generate wind noise. In the air outlet described in Patent Document 1, it is difficult to reduce the wind noise depending on the circulation flow, and therefore the wind noise cannot be sufficiently reduced.

  Therefore, an object of the present invention is to provide a sound absorbing duct type silencer capable of reducing wind noise generated when gas flows in a duct.

Means and effects for solving the problems

  The present invention has a tubular casing that discharges from a blower outlet after the gas is circulated from the suction port to the inside, and is disposed so as to contact the gas flowing in the casing, and propagates in the gas. A sound absorbing mechanism that absorbs the noise generated, and a wind noise reducing mechanism that is provided in a region where a circulating flow is generated when the gas is circulated and reduces wind noise caused by the circulating flow. To do.

  According to this configuration, since the wind noise reduction mechanism is provided in the region where the circulation flow generated when the gas is circulated, the wind noise can be reduced appropriately.

  In the wind noise reduction mechanism of the present invention, the surface of the wind noise reduction mechanism that is in contact with the circulating flow is made smoother than the surface in a region other than the region where the circulating flow is generated so that the flow resistance is reduced. It is preferable. In the present invention, the sound absorbing mechanism includes a sound absorbing member that absorbs noise propagating in the gas, a plurality of the sound absorbing members that surround the sound absorbing member, and that contacts the sound absorbing member and the gas flowing through the housing. And the wind noise reduction mechanism is formed so that there is no hole in contact with the circulating flow in the circulating flow generation region. It is preferable. According to this, it can suppress that a circulating flow and the surface which contacts a circulating flow engage, and generate | occur | produce a wind noise.

  In the present invention, the suction port may be provided with a guide member for guiding the gas to the suction port. According to this, gas can be circulated efficiently.

  In this invention, in order to reduce a wind noise accurately, it is preferable that the surface which contacts the said circulation flow has the distance of 0.25-1.5 with respect to the aperture diameter of the said suction inlet.

  In the sound absorbing duct type silencer of the present invention, it is preferable that the gas flow area in the circulation flow generation region is the same as the opening area of the suction port. According to this configuration, it is possible to reduce the possibility of generating wind noise caused by other than the circulation flow.

  The method of manufacturing a sound absorbing duct type silencer according to the present invention includes a step of forming a tubular casing that takes in a gas from a suction port and circulates the gas and then discharges the gas from the outlet, and absorbs noise propagating in the gas. And a wind noise reduction mechanism for reducing wind noise caused by the circulation flow generated when the gas is circulated. Is inserted into the housing from the suction port.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. First, a conventional sound absorbing duct type silencer will be described. As shown in FIGS. 7 and 8, the duct-type silencer 10 includes a duct 2, a sound absorbing member 3, and a frame body 4. The duct 2 has a rectangular cross section, is open at both ends, and is formed so as to surround the gas flow path 5. A sound absorbing member 3 having a rectangular cross section is disposed on the outer periphery of the duct 2 so as to surround the duct 2. The sound absorbing member 3 is made of glass wool or the like, and absorbs noise caused by a device (not shown) such as a fan that is propagated by the gas flowing through the flow path 5. The duct 2 has a plurality of holes 2a, and the flow path 5 and the sound absorbing member 3 are joined via the holes 2a. Thereby, the noise in the flow path 5 can be absorbed by the sound absorbing member 3.

  A frame 4 is disposed on the outer periphery of the sound absorbing member 3. The frame body 4 is disposed so as to surround the sound absorbing member 3. That is, the sound absorbing member 3 is sandwiched between the duct 2 and the frame body 4 so as not to be exposed to the outside, and is protected. As described above, the sound absorbing duct type silencer 10 is configured.

  Next, wind noise generated when gas flows through the duct 5 will be described. As shown in FIG. 8, when an external gas is taken into the duct 2 from the suction port of the duct 2, the gas flows from the outside into the narrow suction port, so that a contracted flow is generated in the vicinity of the suction port of the duct 2. To do. Due to the occurrence of the contracted flow, the effective flow path area of the gas flowing through the flow path 5 is narrowed. That is, in the vicinity of the suction port, the gas flows through the flow path 5 so as to be slightly separated from the inner wall surface of the duct 2. At this time, a circulating flow is generated in the isolated portion. This circulating flow is engaged with a hole 2a provided on the surface of the duct 2 to generate wind noise.

  Next, the duct type silencer 1 according to the present embodiment will be described. As described above, in order to reduce wind noise, it is necessary to prevent the circulating flow generated at the suction port of the duct 5 from engaging with the hole 2 a of the duct 2. For this reason, the sound absorbing duct type silencer 1 according to the present embodiment smoothes the surface of the duct 2 within the distance L from the inlet of the duct 2 in addition to the sound absorbing duct type silencer 10 described in FIG. A smoothing material 6 is provided. The smooth material 6 is smooth with no irregularities on the surface, and has a substantially similar shape to the hollow duct 2 with a rectangular cross section. Moreover, the one edge part of the smoothing material 6 is provided with the ring edge 6a one size larger than the suction inlet of the duct 2 (refer FIG. 3).

  The smoothing material 6 has a length L, and by arranging the smoothing material 6 on the inner wall of the duct 2, the hole 2 a within the distance L from the suction port of the duct 2 is blocked. Yes. Since the surface near the suction port of the duct 2 becomes smooth when the hole 2a of the duct 2 is blocked by the smoothing material 6, the circulating flow generated near the suction port of the duct 2 is engaged with the hole 2a. No longer. Thereby, wind noise can be reduced. Further, within the distance L from the suction port of the duct 2, the flow path area is always constant, and the possibility of generating wind noise caused by other than the circulation flow can be reduced.

  When the length of L is 0.25 to 1.5 with respect to the suction port diameter D of the duct 2, the wind noise can be reduced efficiently. In FIG. 2, the hole 2 a within the distance L from the suction port of the duct 2 is blocked from the inside (surface contacting the flow path 5) by the smoothing material 6. The region L is not shown for easy understanding. Moreover, the broken line of the duct 2 in FIG. 1 is a line for easily understanding the area of the distance L, and is not a line that actually exists.

  The above-described sound absorbing duct type silencer 1 can be manufactured by manufacturing the conventional sound absorbing duct type silencer 10 and inserting the above-described smoothing material 6 from the suction port of the duct 2. Since the ring edge 6a of the smoothing material 6 is larger than the suction port of the duct 2 when the smoothing material 6 is inserted, the ring edge 6a hits the frame body 4, and the smoothing material 6 enters the inside of the duct 2 more than necessary. There is no such thing.

  Next, the measurement performed in order to confirm the effect that the wind noise by a circulation flow can be reduced by arrange | positioning the smoothing material 6 in the suction inlet of the duct 2 in this Embodiment is demonstrated. The sound absorbing duct type silencer 1, the sound absorbing duct type silencer 10 and the sound absorbing duct type silencer 11 shown in FIG. 4 are installed in the wind tunnel device, and noise of wind noise at the duct inlet is provided. The power level was measured. The sound absorbing duct type silencer 11 of FIG. 4 is configured in a bell mouth shape in which the circulation flow generation region gradually increases in opening area toward the outlet end. Here, the wind tunnel device is an experimental device that can artificially adjust the flow of air.

  FIG. 5 is a graph in which the vertical axis represents the noise power level of wind noise at the suction port, and the horizontal axis represents the wind speed value generated by the wind tunnel device. As can be seen from FIG. 5, when the wind speed is changed in the sound absorbing duct type silencer 10 (□ mark) and 11 (● mark), both noise power levels draw substantially the same trajectory. In contrast to this, the noise absorbing duct type silencer 1 (Δ mark) according to the present embodiment has a noise power level that is reduced by about 5 dB compared to the other sound absorbing duct type silencers 10 and 11. Thereby, it turns out that it has the reduction effect of a wind noise by providing the smoothing material 6 in the suction inlet vicinity of the duct 2 which is a generation | occurrence | production area | region of a circulating flow.

  Next, the measurement performed in order to confirm that the length of the distance L is preferably 0.25 to 1.5 with respect to the suction port diameter D will be described. The sound absorption duct type silencer 1 according to the present embodiment was installed in a wind tunnel device, and the ratio of the distance L to the suction port diameter D was changed to measure the amount of noise reduction of wind noise. Note that the wind tunnel device measures the wind speeds of 10, 14, 19, and 24 m / s, respectively.

  FIG. 6 is a graph with the vertical axis representing the noise reduction amount of wind noise and the horizontal axis representing L / D. In this measurement, when L / D is 0, that is, when the distance L is 0, the reference noise power level is set, and how much the wind noise is reduced from this reference is measured. As can be seen from FIG. 6, at any wind speed, the wind noise of 5 dB at maximum is reduced in the range of L / D of 0.25 to 1.5. Further, if the distance L from the suction port of the duct 2 is increased, the noise reduction effect of wind noise is improved, but even if the suction port diameter D exceeds 1.5, the noise reduction effect cannot be obtained. Therefore, the distance L is preferably 0.25 to 1.5 with respect to the suction port diameter D.

  As described above, in the present embodiment, by providing the smooth member 6 in the generation region of the circulation flow generated when the gas is circulated through the duct 2, the wind noise due to the circulation flow is reduced. Can do. Further, the distance L from the suction port of the duct 2 is efficiently within the range of 0.25 to 1.5 with respect to the suction port diameter D, and wind noise can be reduced. Furthermore, by making the flow path area within the distance L from the suction port of the duct 2 always constant, it is possible to reduce the possibility of generating wind noise caused by other than the circulation flow.

  In the above-described embodiment, the sound absorbing duct type silencer has a rectangular cross section, but the present invention is not limited to this. For example, a cylindrical sound absorbing duct type silencer may be used. Moreover, although the smooth member is provided in order to smooth the duct surface within the distance L from the suction port, the holes may not be provided in the duct. Furthermore, in the above-described embodiment, only the wind noise at the duct inlet is described. However, the wind noise is reduced by smoothing the duct surface in the region where the circulation flow is generated without being limited to the inlet. You may make it do.

  As a modification of the present embodiment, as shown in FIG. 9, a structure in which a guide member 7 is provided at the suction port of the duct 2 may be used. The guide member 7 has a rectangular cross section and is open at both ends. One end of the guide member 7 is the same as the inlet port diameter of the duct 2 and the opening area gradually increases toward the other end, making it easy to take in external gas into the inlet port. Furthermore, as another modification, a structure in which a plurality of flow paths are formed may be used. Specifically, as shown in FIG. 10, a structure in which a plurality of ducts forming a flow path are arranged up and down may be used.

It is a see-through | perspective perspective view of the sound absorption duct type silencer which concerns on the 1st Embodiment of this invention. It is side surface sectional drawing of the sound absorption duct type silencer drawn by FIG. It is the figure which drew the manufacturing method of the sound absorption duct type silencer drawn by FIG. It is a figure showing one of the sound absorption duct type silencers used for the measurement performed in order to confirm the effect that the wind noise by circulating flow can be reduced. It is a graph showing the result of the measurement performed in order to confirm the effect that the wind noise by a circulating flow can be reduced. It is the graph showing the result of the measurement performed in order to confirm that it is preferable that the length of the distance L shall be 0.25-1.5 with respect to the inlet port diameter D. It is a see-through | perspective perspective view of the conventional sound absorption duct type silencer. It is the figure showing the flow of the airflow in the sound absorption duct type silencer drawn by FIG. It is a modification of the sound absorption duct type silencer which concerns on this Embodiment. It is another modification of the sound absorption duct type silencer which concerns on this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sound absorption duct type silencer 2 Duct 2a Hole 3 Sound absorption member 4 Frame 5 Flow path 6 Smoothing material

Claims (7)

A tubular casing that discharges gas from the air outlet after the gas is taken in from the inlet and circulated;
A sound absorbing mechanism disposed so as to contact the gas flowing through the housing and absorbing noise propagating in the gas;
A sound-absorbing duct-type silencer, comprising a wind noise reduction mechanism that is provided in a generation area of a circulation flow that is generated when the gas is circulated, and that reduces wind noise caused by the circulation flow.   2. The surface of the wind noise reduction mechanism that is in contact with the circulating flow is made smoother than a surface in a region other than the region where the circulating flow is generated so that the flow resistance is reduced. The sound absorption duct type silencer described in 1. The sound absorbing mechanism is
A sound absorbing member that absorbs noise propagating in the gas;
A protective member that surrounds the sound absorbing member and has a plurality of holes for contacting the sound absorbing member and the gas flowing through the housing;
The wind noise reduction mechanism is
2. The sound absorbing duct type silencer according to claim 1, wherein in the region where the circulating flow is generated, the hole is formed so as not to contact the circulating flow.   The sound-absorbing duct-type silencer according to any one of claims 1 to 3, wherein the suction port includes a guide member for guiding the gas to the suction port.   The sound-absorbing duct according to any one of claims 1 to 4, wherein the surface in contact with the circulating flow has a distance of 0.25 to 1.5 with respect to the diameter of the suction port. Mold silencer.   The sound absorption duct-type silencer according to any one of claims 1 to 5, wherein a flow area of the gas in the generation region of the circulation flow is the same as an opening area of the suction port. Forming a tubular casing for discharging gas from the air outlet after the gas is taken in from the inlet and circulated;
Arranging a sound absorbing mechanism for absorbing noise propagating in the gas so as to contact the gas flowing in the housing;
A wind noise reduction mechanism for reducing wind noise due to the generation of a circulation flow generated when the gas is circulated, and a step of fitting into the housing from the suction port. A method of manufacturing a sound absorbing duct type silencer.

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