JP6488513B2 - Focused sound field generator - Google Patents

Description

  The present invention relates to a focused sound field forming apparatus.

  As a dust collection method for collecting suspended fine particles such as dust contained in a gas, a gravity method in which the suspended fine particles are settled by a gravity action, a filtration method using an air filter, or the like is generally known. However, if the particle size of the suspended particulates to be collected is very small and light, it is difficult to settle and separate directly by the gravitational method, and the suspended particulates permeate without being collected by the air filter. May end up. Therefore, in order to reliably collect suspended particles even in the gravity method or the filtration method, the suspended particles in the gas are aggregated in advance to increase the diameter, and then the aggregated suspended particles are settled or collected by an air filter. By doing so, dust collection efficiency is improved.

  Conventionally, a method using high-intensity aerial ultrasonic waves is known as one of the methods for aggregating suspended fine particles in a gas. In this method, a focused sound field is formed in the space by powerful aerial ultrasonic waves, and air is passed through the focused sound field to excite suspended particles in the gas, and these particles collide with each other to aggregate the particles. ing.

As an aggregating apparatus used for such an aggregating method, a cylindrical diaphragm (vibrating body) is attached to the vibrator, and the diaphragm is resonated by the vibration of the vibrator to generate powerful ultrasonic waves inside thereof. Airborne particle collection devices are known (see, for example, Patent Document 1 and Patent Document 2).
According to the suspended particle collecting devices disclosed in Patent Document 1 and Patent Document 2, fine particles in a gas flowing in the diaphragm are excited by exciting ultrasonic waves generated in the cylindrical diaphragm. Can aggregate.

Japanese Patent Laid-Open No. 06-47346 Japanese Patent Laid-Open No. 10-174829

However, in the above suspended particle collecting apparatus, since the dimensions of the cylindrical diaphragm are calculated from the determined mathematical formula, it is difficult to design and there is a problem in versatility.
Moreover, as an aggregating apparatus that does not use a cylindrical diaphragm, the apparatus includes a sound source that has a flat diaphragm and generates ultrasonic waves, and a plurality of wall surfaces that surround the diaphragm, and is surrounded by the wall surface. A device that generates a focused sound field in the space and aggregates the suspended fine particles by this focused sound field is conceivable.

  However, since this aggregating apparatus requires a gap between the wall surface and the sound source, the sealing property is poor, and it is not suitable for a fine particle aggregating apparatus. In addition, since a sound source and a plurality of wall surfaces are used, there are a number of elements constituting the device, which complicates the device and increases the cost accordingly.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a focused sound field forming apparatus that is versatile and has a simple apparatus configuration and can be suitably used as an aggregating apparatus. It is in.

  An apparatus for forming a focused sound field of the present invention includes an ultrasonic sound source device that includes a vibrator and a flexible vibration plate, and radiates ultrasonic waves generated by the vibrator vibrating the flexible vibration plate from the flexible vibration plate. A cylindrical rigid wall integrally provided on an outer peripheral portion which is a node position of vibration of the flexible diaphragm, and the ultrasonic sound source device is formed between the flexible diaphragm and the rigid wall. A focused sound field is formed in the internal space.

  Further, in the focused sound field forming device, the flexible diaphragm is formed in a disk shape, and the rigid wall is formed in a cylindrical shape and integrally provided on an outer peripheral edge portion of the flexible diaphragm. preferable.

  In the focused sound field forming apparatus, it is preferable that the rigid wall is provided with a lid that closes an opening on a side opposite to the flexible diaphragm.

  Further, in the focused sound field forming apparatus, the lid is a flat plate disposed in parallel to face the flexible vibration plate, and a half wavelength of vibration of the flexible vibration plate with respect to the flexible vibration plate. It is preferable that they are spaced apart by a distance corresponding to an integral multiple of.

  Further, in the focused sound field forming device, the processing object is supplied into the internal space through the internal space, and the supplied processing object is processed in the focused sound field, and the internal space is connected. It is preferable that a discharge pipe for discharging the processed object in the internal space is provided without being in contact with the flexible vibration plate.

  In the focused sound field forming apparatus, it is preferable that the object to be processed is a gas containing fine particles, and the treatment is an aggregation of the fine particles in the gas.

  In the focused sound field forming apparatus, it is preferable that the object to be processed is a reactant and the treatment is a chemical reaction.

  According to the focused sound field forming device of the present invention, the flexural diaphragm is excited by the vibration of the vibrator, so that the focused sound field is formed in the internal space formed between the flexural diaphragm and the rigid wall. . At that time, since the cylindrical rigid wall is provided on the outer periphery which is the node position of the vibration of the flexible diaphragm, the flexible diaphragm vibrates in the set vibration mode without being affected by the rigid wall and converges. Create a sound field. Therefore, the apparatus configuration is simplified by being composed of the ultrasonic sound source device and the rigid wall, and the converging sound field is formed in the internal space between the flexible diaphragm and the rigid wall, so that versatility is enhanced. . Further, since the rigid wall is integrally provided on the outer peripheral portion of the flexible diaphragm, the sealing performance is improved, and this facilitates the use as an aggregating apparatus.

It is the front view which carried out the partial cross section view of one Embodiment of the focused sound field formation apparatus which concerns on this invention. It is a top view of a diaphragm and a rigid wall, Comprising: It is a sand figure of Kladoni formed on the diaphragm. It is a graph which shows the result of having measured the flexural vibration distribution of the diaphragm of an ultrasonic sound source device. It is a figure which shows the measurement result of the sound pressure distribution of internal space. It is a figure which shows the simulation result of the sound pressure distribution of internal space. It is principal part sectional drawing of the focused sound field formation apparatus shown in FIG.

Hereinafter, the focused sound field forming apparatus of the present invention will be described in detail with reference to the drawings. In the following drawings, the scale of each member is appropriately changed to make each member a recognizable size.
FIG. 1 is a partial cross-sectional front view of an embodiment of a focused sound field forming device according to the present invention. In FIG. 1, reference numeral 1 denotes a focused sound field forming device.

  The focused sound field forming device 1 of this embodiment is applied to an aggregating device that processes a gas (gas) containing fine particles (smoke) to agglomerate the fine particles, and includes an ultrasonic sound source device 2, a rigid wall 3, and the like. It is configured with. Ultrasound generally refers to high-frequency sound that cannot be heard by humans, but may also refer to sound waves that are not intended to be heard even in the human audible range (about 20 Hz to 20 kHz). .

The ultrasonic sound source device 2 includes a vibrator 4 and a diaphragm (flexible diaphragm) 5, and ultrasonic waves generated by the vibrator 4 vibrating the diaphragm 5 are transmitted from the diaphragm 5. Radiates into space.
Specifically, the vibrator 4 is composed of an electromechanical conversion element such as a piezoelectric element, a magnetostrictive element, or an electrostrictive element. Among them, a bolt-clamped Langevin type transducer (BLT) is preferably used as the transducer 4 that generates strong ultrasonic waves. The vibrator 4 is driven by electric power supplied from a power supply circuit (power supply) (not shown).

  The vibrator 4 is connected to the diaphragm 5 via an exponential horn 6 and a resonance rod 7. The exponential horn 6 is attached to the vibrator 4 and amplifies the vibration by the vibrator 4 (increases the amplitude). The resonance rod 7 connects the exponential horn 6 and the diaphragm 5 and transmits the vibration amplified by the exponential horn 6 to the diaphragm 5. The distance from the vibrator 4 to the diaphragm 5 is an integral multiple of the half wavelength (1/2 wavelength [λ / 2]) of the vibration of the vibrator 4 in order to excite the diaphragm 5 in a predetermined mode. Is set to That is, by adjusting the length of the resonance rod 7, the distance from the vibrator 4 to the diaphragm 5 is adjusted to an integral multiple of a half wavelength.

  In this embodiment, the diaphragm 5 is a disc-shaped flexible diaphragm having a diameter of 84 mm. A resonance bar 7 is connected to the center of the diaphragm 5 and fixed to the resonance bar 7 by bolting or the like. The disk-like diaphragm 5 is not particularly limited as long as it vibrates in a mode for forming a nodal circle as described later. For example, a metal plate such as duralumin or titanium is used. Used.

  As shown in FIG. 2 which is a plan view of the diaphragm 5 and the rigid wall 3, the diaphragm 5 is a vibration mode having a nodal circle H in this embodiment. Here, FIG. 2 is a sand chart of Kladoni formed on the diaphragm 5 when the vibrator 4 is driven at 27.8 kHz. Kradoni's sand chart is used to see the mode of flexural vibration by spreading fine particles on the vibration surface. As shown in FIG. 2, since the particles are gathered in the concentric black portion, it can be seen that the black portion is a vibration node. From FIG. 2, it was found that the diaphragm 5 of the present embodiment is a vibration mode having two node circles H.

  The rigid wall 3 is a cylindrical one integrally formed on the outer peripheral edge of the diaphragm 5, and in this embodiment, the outer diameter is 100 mm and the inner diameter is 84 mm. The rigid wall 3 is formed of the same material (metal) as the diaphragm 5. That is, the rigid wall 3 may be integrally formed with the diaphragm 5 from the same metal block or the like, or may be integrally formed by being fixed to the diaphragm 5 by welding or screwing. Good. Such a rigid wall 3 is preliminarily designed in size, shape, material, and the like so that the vibration is sufficiently less than that of the diaphragm 5 when the same vibration is applied. In the present embodiment, the thickness of the diaphragm 5 is sufficiently thick (for example, three times or more), so that vibration hardly occurs compared to the diaphragm 5. That is, the vibration of the rigid wall 3 is small enough to be ignored.

  Further, the rigid wall 3 is disposed on the outer peripheral edge (outer peripheral part) which is the vibration node position of the diaphragm 5. Here, the result of measuring the flexural vibration distribution of the diaphragm 5 of the ultrasonic sound source device 2 is shown in FIG. FIG. 3 is a graph showing the measurement results, in which the horizontal axis indicates the radial distance from the center of the diaphragm 5 (the central axis of the resonance bar 7), and the vertical axis indicates the vibration displacement. The measurement was performed using a laser Doppler vibrometer with the input voltage to the vibrator 4 being constant at 5 W and the resonance frequency being 27.8 kHz.

  As shown in FIG. 3, the position of the vibration node represented by the minimum value of the vibration displacement is at two locations of 10 mm and 24 mm from the center of the diaphragm 5, and is the same as the position of the node circle H shown in FIG. Confirmed to be in position. It was also found that the maximum of the vibration displacement becomes smaller as the distance from the center increases. Further, in the present embodiment, the rigid wall 3 is disposed at a position 42 mm away from the center of the diaphragm 5 (a position slightly deviated to the right from the graph of FIG. 3). It turns out that it is the position of the vibration node.

  Generally, the outer peripheral part (outer peripheral part) of the flexure diaphragm vibrates greatly when no rigid wall is arranged as in the present embodiment. On the other hand, in the diaphragm 5 of the present embodiment, the rigid wall 3 is integrally provided on the outer peripheral portion (outer peripheral edge portion), so that the outer peripheral portion is almost free from vibration by the rigid wall 3. The node position does not vibrate.

  The size (outer diameter), thickness, and material of the diaphragm 5 are determined so as to resonate at a frequency given by the vibrator 4. In addition, when vibrating and resonating at a frequency given by the vibrator 4, the dimensions of the diaphragm 5 and the rigid wall 3 Dimensions and the like are determined based on experiments and the like. Thereby, the rigid wall 3 is disposed at the position of the vibration node of the diaphragm 5.

  As described above, the rigid wall 3 is integrally provided on the outer peripheral portion of the vibration plate 5 (flexible vibration plate) as a vibration node position, so that the vibration plate 5 is provided by the vibrator 4 without vibrating the rigid wall 3. Resonant at a high frequency, a focused sound field is formed in the internal space 8 formed between the diaphragm 5 and the rigid wall 3 shown in FIG.

  Here, the measurement result of the sound pressure distribution in the internal space 8 of the sound wave radiated from the diaphragm 5 is shown in FIG. In this measurement, sound pressure was measured using a microphone with a probe. The measurement range was a cylindrical cross-sectional range in which the internal diameter of the internal space 8 was 80 mm and the height in the axial direction was 50 mm. Measurements were made at 1 mm intervals.

In FIG. 4, the horizontal axis indicates the radial direction (diameter direction) of the diaphragm 5, and the vertical axis indicates the axial direction of the rigid wall 3. The sound pressure is indicated by a binarized bar in which the intensity is normalized by the maximum value.
As shown in FIG. 4, it was found that the sound pressure distribution was the largest near the center in the diameter direction. Further, since two nodes are seen in the radial direction, it was found that this measurement result coincided with the sound pressure distribution by the vibration mode shown in FIG.

For comparison, FIG. 5 shows the result of simulation by the finite element method.
As shown in FIG. 5, since the sound pressure near the center is high and two nodes are seen, it was found that this simulation result also coincides with the sound pressure distribution by the vibration mode shown in FIG. From this, it was found that the same sound pressure distribution can be obtained in the measurement result and the simulation result. Therefore, it was found that a strong sound pressure distribution was generated in the internal space 8 shown in FIG. 1, and thereby a focused sound field was formed in the internal space 8 mainly near the center in the diameter direction.

  In this way, a focused sound field is formed in the internal space 8, but this focused sound field is made stronger and the internal space 8 is a sealed space. In this embodiment, as shown in FIG. A lid 9 is attached to the rigid wall 3. That is, the lid 9 is provided by bolting or the like so as to cover the opening of the rigid wall 3 on the side opposite to the diaphragm 5. Thereby, the upper opening of the rigid wall 3 is closed by being covered with the lid body 9, and the internal space 8 becomes a sealed space. Since the lid body 9 is provided on the rigid wall 3 that does not vibrate, the lid body 9 itself does not vibrate, so that the vibration of the diaphragm 5 is not affected.

  The lid 9 is a flat plate disposed in parallel to face the diaphragm 5, and a lower surface (inner surface) facing the diaphragm 5 has a reflecting surface 9 a that reflects the ultrasonic waves radiated from the diaphragm 5. It has become. That is, in this embodiment, the lid 9 not only simply covers the upper opening of the rigid wall 3 and forms the internal space 8 in a closed space, but also functions as a reflector. The lid 9 is disposed such that the reflection surface 9 a is separated from the diaphragm 5 by a distance corresponding to an integral multiple of a half wavelength (λ / 2) of vibration of the diaphragm 5.

  As a result, in the internal space 8, not only a focused sound field is formed in the vicinity of the center thereof, but also a standing wave sound field is formed. A standing wave is formed by overlapping two waves that have the same wavelength, period (frequency or frequency), amplitude, and speed (absolute value of velocity) and are traveling in opposite directions. It is a wave that seems to stop and vibrate. That is, when the ultrasonic wave radiated from the diaphragm 5 and the reflected wave reflected by the reflecting surface 9a overlap each other, a standing wave, that is, a powerful aerial ultrasonic wave is formed.

  A standing wave sound field that generates such a standing wave, that is, a standing wave sound field in which the focused sound field becomes stronger, is suitable for aggregating suspended fine particles in a gas, for example. Therefore, in the present embodiment, a supply pipe 10 and a discharge pipe 11 are provided on the rigid wall 3 as shown in FIGS.

  The supply pipe 10 is provided on the rigid wall 3 so as to communicate with the internal space 8 and is connected to a gas supply source (not shown) to supply gas sent from the gas supply source to the internal space 8. is there. Further, the discharge pipe 11 discharges the object to be processed after being processed in the internal space 8 through the internal space 8. The supply pipe 10 and the discharge pipe 11 are inserted into through holes (not shown) formed in the rigid wall 3 and open to the inner surface of the rigid wall 3.

  As a result, the supply pipe 10 and the discharge pipe 11 are provided without being in contact with the diaphragm 5, and are provided on the rigid wall 3 that does not vibrate in the same manner as the lid body 9. Not to give. Moreover, the standing wave sound field formed in the internal space 8 is not disturbed by opening to the inner surface of the rigid wall 3 without protruding into the internal space 8.

In addition, the supply pipe 10 and the discharge pipe 11 are arranged so that the openings of the supply pipe 10 and the discharge pipe 11 face each other across the center of the diaphragm 5 (the central axis of the rigid wall 3). Basically, it flows through the center of the internal space 8 to the opening of the discharge pipe 11.
Here, the gas is an object to be processed in the present invention, and is a gas containing fine particles, for example, air (exhaust gas) containing fine particles such as oil mist. Such a gas (object to be treated) is not efficient when treated directly with an air filter or the like, and the amount of fine particles that cannot be collected and permeate may increase. Aggregation is performed as a pretreatment for the treatment.

  In order to perform the aggregating process by the focused sound field forming apparatus 1 of the present embodiment, first, the vibrator 4 is driven to vibrate the diaphragm 5 to form a standing wave sound field (focused sound field) in the internal space 8. . Subsequently, an object to be processed, that is, a gas containing fine particles is supplied from the supply pipe 10 to the internal space 8. Then, the fine particles in the gas (object to be processed) are excited by the powerful aerial ultrasonic waves in the standing wave sound field, and the fine particles collide with each other, thereby aggregating the fine particles. And the gas containing the aggregated particles which have aggregated and become large in this way is discharged from the discharge pipe 11 and guided to a dust collector having a subsequent dust collector, for example, an air filter.

  According to the focused sound field forming device 1 of the present embodiment, the vibration plate 5 (flexible vibration plate) is excited by the vibration of the vibrator 4, so that the internal portion formed between the vibration plate 5 and the rigid wall 3 is excited. A focused sound field is formed in the space 8. At this time, since the cylindrical rigid wall 3 is provided on the outer peripheral portion that is the vibration node position of the diaphragm 5, the diaphragm 5 forms a focused sound field without being affected by the rigid wall 3. Therefore, the apparatus configuration is simplified by comprising the ultrasonic sound source device 2 and the rigid wall 3, and a focused sound field is formed in the internal space 8 between the diaphragm 5 and the rigid wall 3. Increases nature. Further, since the rigid wall 3 is integrally provided on the outer peripheral portion of the diaphragm 5, the sealing performance is improved, and this makes it easy to use as an aggregating device.

  That is, the focused sound field forming device 1 of the present embodiment can be used for agglomeration processing of fine particles of a processing object made of a gas containing fine particles. In that case, the fine particles in the gas are excited by the powerful aerial ultrasonic waves in the standing wave sound field (focused sound field), and the fine particles collide with each other, thereby aggregating the fine particles and increasing the diameter. The degree of aggregation of the fine particles, that is, how much the diameter is increased, can be easily set, for example, by adjusting the time during which the gas stays in the internal space 8.

  In addition, since the diaphragm 5 is formed in a disc shape and the rigid wall 3 is formed in a cylindrical shape and integrally provided on the outer peripheral edge portion of the diaphragm 5, the outer peripheral edge portion of the diaphragm 5 is a vibration node. It is easy to adjust the position, and therefore, the vibration of the rigid wall 3 can be reliably suppressed by disposing the rigid wall 3 here.

In addition, since the lid 9 is provided on the rigid wall 3, the internal space 8 can be easily applied to the agglomeration process of the fine particles by making the internal space 8 a sealed space.
Furthermore, since the lid 9 is disposed at a distance corresponding to an integral multiple of a half wavelength of the vibration of the diaphragm with respect to the diaphragm 5, the lid 9 is fixed by the powerful aerial ultrasonic waves in the internal space 8. A wave sound field can be formed, and thus the fine particles can be aggregated more efficiently.

  The preferred embodiments of the present invention have been described above with reference to the drawings, but the present invention is not limited to the above-described embodiments. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are merely examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, in the above-described embodiment, the case where the focused sound field forming device 1 of the present invention is applied to the aggregating device has been described. It is applicable to.

For example, the focused sound field forming apparatus of the present invention can be expected to have an effect of promoting a chemical reaction, and thus can be applied to a processing apparatus that performs a chemical reaction process. In that case, for example, a reactant (processing object) as a raw material and an atmospheric gas (for example, nitrogen gas or argon gas) are supplied from a supply pipe, and in a focused sound field (standing wave sound field) in the internal space 8. The reactant is reacted and discharged from the discharge tube to obtain the product.
Even when applied to such a chemical reaction processing apparatus, the chemical reaction of the reactant can be promoted by the focused sound field (standing wave sound field), thereby increasing the reaction efficiency and increasing the yield of the product. be able to.

In addition to such a chemical reaction processing apparatus, the present invention can also be applied to, for example, improving the wettability of liquid with respect to solids and promoting impregnation.
In addition, when the focused sound field forming apparatus of the present invention is applied to various processing apparatuses as described above, the number of supply pipes and discharge pipes, their dimensions, mounting positions, and the like can be appropriately changed according to the purpose. For example, the attachment position of the supply pipe or the discharge pipe may be the lid 9 instead of the rigid wall 3 if it does not contact the diaphragm 5.

  Further, since a focused sound field can be formed in the internal space without providing a lid, a focused sound field forming device having such a configuration without a lid can improve the wettability of a liquid with respect to a solid, for example. It can also be applied to promote impregnation.

DESCRIPTION OF SYMBOLS 1 ... Focusing sound field formation apparatus, 2 ... Ultrasonic sound source apparatus, 3 ... Rigid wall, 4 ... Vibrator, 5 ... Vibration plate (flexible vibration plate), 8 ... Internal space, 9 ... Cover body, 9a ... Reflecting surface, 10 ... supply pipe, 11 ... discharge pipe

Claims (6)

An ultrasonic sound source device including a vibrator and a flexible diaphragm, wherein the vibrator radiates ultrasonic waves generated by vibrating the flexible diaphragm from the flexible diaphragm; and a vibration node position of the flexible diaphragm A cylindrical rigid wall integrally provided on the outer peripheral portion,
The ultrasonic sound source device forms a focused sound field in an internal space formed between the flexible diaphragm and a rigid wall ;
A supply pipe for supplying an object to be processed into the internal space through the internal space, and processing the supplied object to be processed in the focused sound field; and a processed object in the internal space through the internal space. A discharge pipe for discharging the processed material is provided without being in contact with the flexible vibration plate,
The opening of the supply pipe provided on the inner surface of the rigid wall and the opening of the discharge pipe provided on the inner surface of the rigid wall are arranged to face each other across the central axis of the rigid wall. A focused sound field forming apparatus characterized by the above.   2. The focused sound according to claim 1, wherein the flexible diaphragm is formed in a disc shape, and the rigid wall is formed in a cylindrical shape and integrally provided on an outer peripheral edge of the flexible diaphragm. Field forming device.   The focused sound field forming apparatus according to claim 1, wherein the rigid wall is provided with a lid that closes an opening on a side opposite to the flexible vibration plate.   The lid is a flat plate disposed in parallel with the flexible diaphragm, and is separated from the flexible diaphragm by a distance corresponding to an integral multiple of a half wavelength of the vibration of the flexible diaphragm. 4. The focused sound field forming device according to claim 3, wherein the focused sound field forming device is arranged. Wherein a gas to be treated contains fine particles, wherein the process is focused sound field forming apparatus according to any one of claims 1 to 4, characterized in that an aggregation of particulate matter in the gas. The object to be treated is a reaction product, wherein the process is focused sound field forming apparatus according to any one of claims 1 to 4, characterized in that a chemical reaction.