JP5996348B2 - Cavitation nozzle - Google Patents

Description

  The present invention relates to a nozzle that generates a cavitation jet by jetting a high-pressure liquid in the liquid.

  Conventionally, by jetting a highly pressurized liquid from a small-diameter orifice, the high-pressure liquid is converted into a high-speed liquid flow, and the energy of the high-speed liquid flow is used for processing, thereby cleaning an object. Exfoliation and excavation were performed effectively. As a method of converting the energy of the high-pressure liquid into processing energy, there are a method of processing mainly in the air and a method of processing in the liquid.

  As the submerged processing method, for example, a so-called horn type nozzle 11 having an injection hole 13 having a conical internal shape whose diameter is increased in a tapered shape from the downstream end opening of the orifice portion 12 as shown in FIG. 3 is used. (See Patent Document 1), or a nozzle having a cylindrical shape in which the cross-sectional area is rapidly enlarged at the injection hole introduction part that follows the orifice part and the injection hole opening end that follows the inlet part (see FIG. Patent Document 2).

  In any of the above-described submerged systems, shock waves caused by jet cavitation are used as machining energy. Cavitation is a physical phenomenon in which microbubbles are generated and disappeared in a short time due to a pressure difference in the liquid flow, and the impact caused by the disappearance of the bubbles when colliding with an object erodes the member. . When such a cavitation effect is used for processing, bubbles are generated and grow due to fluctuations in speed and pressure in the mixing region of the jet fluid and the surrounding liquid. The surrounding liquid is appropriately introduced toward the high shear layer having a large velocity gradient that generates many surrounding bubbles.

JP-A-60-168554 Japanese Patent No. 3277214

  However, in any of the conventional nozzles, when the jet flow collides with the inner wall surface of the nozzle hole, the nozzle member is also damaged by the erosion due to the cavitation effect, and the generation and growth of bubbles are also suppressed. There was a problem. As a result, the cavitation effect is reduced and processing energy cannot be obtained efficiently, and the life of the nozzle itself is shortened. As a result, frequent replacement of the entire nozzle is required, resulting in complicated labor and cost. Was supposed to accompany high.

  Therefore, it is possible to manufacture the nozzle itself with a corrosion-resistant alloy, but since the material is expensive, an increase in cost is unavoidable, and the manufacturing itself is difficult due to the difficult workability of the material. There are also challenges.

  Even in jet cleaning that does not require processing energy as much as excavation, it is necessary to stably maintain the formation of a strong cavitation jet to some extent in order to ensure a more efficient and reliable cleaning effect. However, in the middle of the cleaning liquid supply channel to the nozzle, various piping elements such as elbow piping for changing the flow direction depending on the piping layout and joints for obtaining a step are often attached. In some cases, a secondary flow such as turbulent flow is generated before the liquid is introduced into the nozzle due to various piping elements, and the cavitation effect is attenuated.

  In view of the above problems, the object of the present invention is to stably form powerful cavitation that can be efficiently converted into processing energy without suppressing generation and growth of bubbles for causing cavitation inside the nozzle. An object of the present invention is to provide a cavitation nozzle having a longer life than conventional ones.

In order to achieve the above object, a cavitation nozzle according to the first aspect of the present invention is a cylindrical orifice into which high-pressure liquid supplied from a high-pressure liquid supply means flows from a flow path having a relatively large diameter on the upstream side. and parts, communicates with the downstream of the orifice, generating bubbles fast fluid ejected from the downstream end thereof through said orifice portion, the injection holes by growing injected into the second liquid as a cavitation jet In a cavitation nozzle equipped with
The injection hole has a flat part extending in an annular shape on a plane orthogonal to the orifice central axis in the outer circumferential direction from the downstream end opening of the orifice part, and is tapered from the periphery of the flat part toward the downstream side. A horn portion that expands at a taper angle of 60 ° to 120 ° , and a parallel portion that is connected in a cylindrical shape coaxial with the orifice central axis from the downstream peripheral edge of the horn portion to the injection hole opening end side, It is what it has.

  A cavitation nozzle according to a second aspect of the present invention is the cavitation nozzle according to the first aspect, wherein the flat portion has an inner diameter 2 to 5 times the inner diameter of the orifice portion.

  A cavitation nozzle according to a third aspect of the present invention is the cavitation nozzle according to the first or second aspect, wherein the parallel portion has an inner diameter of 15 to 30 mm when the inner diameter of the orifice portion is 1 to 4 mm. It is.

  A cavitation nozzle according to a fourth aspect of the present invention is the cavitation nozzle according to the first aspect, wherein the second horn portion that expands in a taper shape from the downstream peripheral edge of the parallel portion to the injection hole opening end is provided. In addition.

The present invention provides a flat portion in which an injection hole communicated downstream of the orifice portion extends in an annular shape on a plane perpendicular to the central axis of the orifice in the outer circumferential direction from the downstream end opening of the orifice portion, A horn portion that expands in a tapered shape from the periphery toward the downstream side, and a parallel portion that is connected in a cylindrical shape coaxial with the orifice central axis from the downstream periphery of the horn portion to the injection hole opening end side, Since the cavitation nozzle is equipped with a high-speed fluid ejected from the orifice part and collides with the introduction part of the injection hole, the impact may damage the member, and the generation and growth of bubbles in the subsequent horn part are suppressed. In addition, a powerful cavitation jet can be formed by introducing and rectifying the surrounding liquid into the horn part due to the parallel part. It is possible to obtain the Yabiteshon effect.
Therefore, according to the cavitation nozzle of the present invention, the damage to the member is greatly reduced as compared with the conventional case. Therefore, it is possible to extend the life of the member without using an expensive member, and it is necessary for frequent member replacement. There is also an effect of reducing the labor and cost.

It is a schematic longitudinal cross-sectional view which shows the structure of the cavitation nozzle used in the experiment in the Example of this invention. In the line graph which shows the result of the erosion experiment with respect to the member which contrasted the conventional horn nozzle in Example 1 of this invention (horizontal axis: injection time (hour), vertical axis: erosion part maximum depth (mm)). is there. It is a schematic longitudinal cross-sectional view which shows the structure of the conventional horn nozzle. It is a schematic block diagram of the experimental apparatus which performed the processing experiment in the Example of this invention. It is a bar graph (vertical axis | shaft: erosion amount (g)) which shows the influence on the cavitation effect by the presence or absence of a parallel part in Example 2 of this invention. It is a line graph (horizontal axis: parallel part internal diameter (mm), vertical axis: peak erosion amount (g)) which shows the influence on the cavitation effect by the parallel part internal diameter in Example 3 of this invention. It is a line graph (horizontal axis: angle (alpha) (degree), vertical axis: peak erosion amount (g)) which shows the influence on the cavitation effect by the taper angle of the horn part in Example 4 of this invention. It is a bar graph (vertical axis: erosion amount (g)) which shows the influence on the cavitation effect by the presence or absence of the flat part in Example 5 of this invention. It is a line graph (horizontal axis: injection pressure (MPa), vertical axis: peak erosion amount (g)) which shows the change of the cavitation effect with respect to the injection pressure area | region which contrasted the conventional horn nozzle in Example 6 of this invention. It is a schematic longitudinal cross-sectional view which shows the structure of the cavitation nozzle provided with the 2nd horn part as another Example of this invention.

  In the cavitation nozzle of the present invention, the injection hole communicated downstream of the orifice portion, a flat portion extending annularly on a plane perpendicular to the orifice central axis in the outer peripheral direction from the downstream end opening of the orifice portion, A horn portion whose diameter increases in a taper shape from the peripheral edge of the flat portion toward the downstream side, and a cylindrical shape coaxial with the orifice central axis from the downstream peripheral edge of the horn portion to the injection hole opening end side. When the bubbles contributing to cavitation are generated and grown in the high-speed fluid ejected from the orifice portion and are grown and ejected from the opening end of the ejection hole as a cavitation jet flow. Thus, an injection flow that exhibits a stronger cavitation effect than before can be obtained by the internal shape of the injection hole.

  That is, since the flat portion is first provided at the downstream end of the orifice portion, the high-speed fluid is ejected to the opened peripheral region, and the inner wall surface of the injection hole introducing portion is exposed to the impact immediately after the high-speed fluid ejection. Without damage, member damage is avoided. And since the downstream horn part starts from the periphery of the flat part and the upstream opening has a larger diameter than before, the velocity gradient that generates many bubbles around the jet fluid by setting the taper angle and distance of the horn part The surrounding liquid flows in toward the high shear layer having a large diameter, and the bubbles that contribute to cavitation are favorably grown without being suppressed by the inner wall surface of the injection hole. In addition, the jet flow in which good bubbles are generated and grown not only has a rectifying effect that causes a group of bubbles in the cylindrical parallel part on the downstream side to be jetted together, but also effectively flows the surrounding liquid into the horn part. The liquid is introduced into the liquid from the opening end of the injection hole as a stronger cavitation jet flow.

  In the cavitation nozzle of the present invention having the injection hole configured as described above, the damage to the member due to the collision of the jet flow against the inner wall surface of the injection hole and the suppression of the generation and growth of bubbles contributing to cavitation are avoided. It is possible to form a cavitation jet that can efficiently obtain a powerful cavitation effect that can be converted into energy, to realize a long life of the member, and to reduce labor and cost required for member replacement.

  Further, in the case where a piping element such as an elbow pipe is generated in the pipe upstream of the nozzle, even if the cavitation is attenuated by the secondary flow generated in the pipe element, the cavitation of the present invention In the nozzle, since the cavitation attenuation due to erosion in the exit area of the orifice is avoided by the flat portion, a jet flow having a stronger cavitation effect than the conventional one is stably formed.

  As a preferred design of the injection hole in the present invention, the flat portion preferably has an inner diameter 2 to 5 times the inner diameter of the orifice portion. For example, when the inner diameter of the orifice portion is 1 to 4 mm, the inner diameter of the flat portion is 2 to 20 mm. If the ratio of the inner diameter of the flat part to the orifice part is smaller than this condition, the impact when the high-speed fluid is ejected from the orifice part at the introduction part of the injection hole cannot be satisfactorily avoided and the member may be eroded. Yes, if it is larger than the above condition, the shock wave can be avoided, but the introduction opening of the subsequent horn part is too large to form a high shear layer that promotes good bubble growth, and the nozzle becomes larger than necessary. May become impractical.

  Further, as shown in the examples described later, the parallel portion following the horn portion increases the cavitation effect as the processing capability by the jet flow as the inner diameter increases under a certain level of injection pressure condition. Therefore, the cavitation effect corresponding to the desired processing capability can be selectively adjusted by appropriately setting the inner diameter of the parallel portion at an arbitrary injection pressure. However, the preferable range of the inner diameter of the parallel part that enables such adjustment is 15 to 30 mm when the inner diameter of the orifice part is 1 to 4 mm.

  In the injection hole of the cavitation nozzle of the present invention, a second horn part may be further provided downstream of the parallel part. Due to this second horn portion, further bubble generation and growth occur in the jet flow from the parallel portion, and a stronger cavitation jet flow can be obtained. The configuration including the second horn portion is particularly effective in a nozzle that performs injection at a relatively low injection pressure, for example, near 20 MPa.

  As a first embodiment of the present invention, the results of an erosion experiment by continuous injection using the cavitation nozzle 1 shown in FIG. 1 using the conventional horn nozzle 11 shown in FIG. 3 as a control are shown below. The cavitation nozzle 1 in this embodiment includes a cylindrical orifice portion 2 having an inner diameter of 1.5 mm and an injection hole 3 communicating with the downstream of the orifice portion 2. The injection hole 3 is a downstream end of the orifice portion 3. A flat portion 5 extending annularly on a plane perpendicular to the central axis of the orifice in the outer peripheral direction from the opening, a horn portion 6 that expands in a tapered shape from the periphery of the flat portion 5 toward the downstream side, And a parallel portion 7 connected in a cylindrical shape coaxial with the central axis of the orifice from the downstream peripheral edge of the horn portion 6 to the injection hole opening end 4 side. In this embodiment, the inner diameter D1 of the flat portion 5 is 8 mm, the inner diameter D2 of the parallel portion 7 is 28 mm, and the distance L along the central axis direction of the orifice portion is 8 mm.

  The injection hole 13 of the horn nozzle 11 as a control is composed of a substantially conical horn part 16 that expands in a taper shape from the downstream end opening of the cylindrical orifice part 12 to the injection hole opening end 14. The orifice portion 12 has an inner diameter of 1.5 mm and has the same dimensions as the orifice portion 2 of the cavitation nozzle 1 in this embodiment.

  In the erosion experiment, water was continuously sprayed using each nozzle at an injection pressure of 48 MPa, and the change with time of the maximum depth of the erosion portion was measured. The measurement method is to measure the cross-sectional shape of the erosion part by traversing the laser by traversing the erosion part by the laser displacement diameter, and measuring the exit area of the orifice part where erosion is most likely to proceed. The maximum depth of the shape was determined.

  The measurement results are shown in the line graph of FIG. 2 (horizontal axis: injection time (hour), vertical axis: maximum depth of erosion (mm)). Specifically, in the cavitation nozzle 1 of the present embodiment, the flat portion 5 (white square: □ in FIG. 2) and the vicinity of the entrance of the horn portion 6 (white triangle: Δ in FIG. 2), the control horn nozzle 11, the vicinity of the entrance of the horn part 16 (white circle in FIG. 2: ◯) was measured.

  From the result of FIG. 2, in the conventional horn nozzle 11, the depth of the erosion portion suddenly increased after about 5 hours of continuous injection, whereas in the cavitation nozzle 1 of this embodiment, the flat portion 5 It can be seen that the progress of the erosion part was very slow in the vicinity of the entrance of the horn part 6. Further, when observing the target portion, a local erosion portion is generated near the entrance of the horn portion 16 of the horn nozzle 11 after 8 hours of continuous injection (time A in FIG. 2). Although the erosion part was expanding at the starting point, the erosion area was uniform in the cavitation nozzle 1 after 11 hours of continuous injection (time B in FIG. 2) in all cases.

  From the above results, in the cavitation nozzle 1 of the present embodiment, when the flat portion 5 is provided at the inlet of the injection hole 3, the high pressure liquid is ejected from the orifice portion which has been a problem with the conventional horn nozzle. It has been found that the damage of the member due to the impact of this is greatly reduced, and that it is possible to extend the life of the member.

  As a second embodiment of the present invention, the effectiveness of providing a parallel portion on the opening end side of the injection hole of the cavitation nozzle is shown in an object processing experiment by underwater injection with a cavitation nozzle having no parallel portion as a control. The examination results are shown below. The cavitation nozzle 1 shown in FIG. 1 was used in this example, and the parallel portion 7 has an inner diameter D2 of 28 mm and a distance L of 8 mm. The control nozzle is a nozzle having the same dimensional configuration from the orifice part to the horn part only without the parallel part 7.

  The processing experiment was conducted in an experimental apparatus whose schematic configuration is shown in FIG. That is, high-pressure water that is pressurized and supplied from a supply water tank 30 via a plunger pump P to an object, which is vertically fixed in the experimental water tank 20, in this case, a work W made of an aluminum plate (A1050 plate). Is jetted underwater from the jet nozzle N in a substantially horizontal direction. Using the cavitation nozzle 1 and the control nozzle as the injection nozzle N, continuous injection was performed for 30 minutes at an injection pressure of 36 MPa. And the workpiece | work defect | deletion amount in the meantime was measured from the mass change before and behind injection as the amount of erosion, and the result was shown in the bar graph (vertical axis: amount of erosion (g)) of FIG. A nozzle with a larger amount of erosion can be evaluated as having a higher cavitation effect as processing capability.

  From the result of FIG. 5, the amount of erosion by the cavitation nozzle 1 having the parallel portion 7 was about twice that of the nozzle having no parallel portion. From this result, in the nozzle in which the cavitation jet is injected through the parallel portion 7, the generation and growth of bubbles in the horn portion 6 are further promoted and the bubbles are more efficient than the nozzle having no parallel portion. It was found that they were jetted together as a stronger cavitation jet.

  Next, as a third embodiment of the present invention, the results of examining the influence of the inner diameter D2 on the cavitation effect of the parallel portion 7 in the cavitation nozzle 1 of FIG. 1 are shown below. In the present embodiment, the cavitations in which the inner diameter D2 of the parallel portion 7 is changed from 7 mm to 28 mm while the inner diameter of the orifice portion 2 and the flat portion 5 and the distance between the parallel portion 7 and the injection hole 3 are the same as the nozzle dimensions of the first embodiment. Using the nozzle 1, the same processing experiment as in Example 2 was performed, and the peak erosion amount of the workpiece W at each nozzle was measured. The results are shown in the line graph of FIG. 6 (horizontal axis: parallel part inner diameter (mm), vertical axis: peak erosion amount (g)).

  In this example, injection was performed under three conditions of injection pressures of 8 MPa, 20 MPa, and 28 MPa with each nozzle having different inner diameters of parallel portions, and the cavitation effect as each processing ability was evaluated from the obtained peak erosion amount. The peak erosion amount is a peak value obtained by plotting the distribution of the mass defect amount as the erosion amount with respect to the distance between the nozzle tip and the surface of the workpiece W (standoff distance). In addition, although the taper angle of the horn part 6 will also be changed with the change of the internal diameter of the parallel part 7, in this Example, the nozzle was evaluated on the basis of the parallel part internal diameter.

  From the results shown in FIG. 6, the amount of erosion, that is, the cavitation effect was increased with the increase in the inner diameter of the parallel portion under the condition of a certain injection pressure or more, in this embodiment, 20 MPa or more. As a result, if the inner diameter D2 of the parallel portion is adjusted within a range of substantially 15 mm to 30 mm under the conditions of the present embodiment at an arbitrary injection pressure, a desired processing capability can be selectively set. I understood.

  Furthermore, as a fourth embodiment of the present invention, the results of examining the influence of the taper angle α on the cavitation effect of the horn portion 6 in the cavitation nozzle 1 of FIG. 1 are shown below. In this embodiment, the taper angle α of the horn portion 6 is changed from 60 ° to 120 ° while the inner diameter of the orifice portion 2 and the flat portion 5 and the distance between the parallel portion 7 and the injection hole 3 are the same as the nozzle size of the first embodiment. Using each of the cavitation nozzles 1, the same processing experiment as in Example 2 was performed, and the peak erosion amount of the workpiece W at each nozzle was measured.

  The results are shown in the line graph of FIG. 7 (horizontal axis: horn taper angle (°), vertical axis: peak erosion amount (g)). In addition, although the internal diameter of the parallel part 7 will also be changed with the change of the taper angle (alpha) of this horn part 6, in the present Example, the nozzle was evaluated on the basis of the taper angle (alpha) of the horn part 6. FIG. From the results of FIG. 7, it was found that when the taper angle is in the range of 60 ° to 120 °, there is no significant difference in the amount of erosion and there is almost no influence on the cavitation effect.

  As a fourth embodiment of the present invention, the results of examining the influence of the cavitation effect on the presence or absence of the flat portion of the flat portion 5 in the cavitation nozzle 1 of FIG. 1 are shown below. In the present embodiment, a cavitation nozzle 1 having the same nozzle size as in the first embodiment is compared with a nozzle having the same orifice inner diameter, horn taper angle, and parallel portion distance as the cavitation nozzle 1 but without a flat portion. The same processing experiment as in Example 2 was performed, and the amount of erosion of the workpiece W at both nozzles was measured.

  The results are shown in the bar graph (vertical axis: erosion amount (g)) in FIG. From the results of FIG. 8, the nozzle with the flat part 5 has an amount of erosion that is 6 times or more that of the nozzle without the flat part, so that the high-pressure liquid ejected from the orifice part collides with the member near the injection hole inlet part. It was found that the generation and growth of bubbles due to the cavitation effect were greatly inhibited. That is, it has been confirmed that the presence of the flat portion 5 avoids such obstruction and provides a cavitation effect that is efficiently converted into processing energy.

  Further, as a fifth embodiment of the present invention, the results of examination of the change of the cavitation effect with respect to the injection pressure of 5 to 60 MPa in the cavitation nozzle according to the present invention by using a conventional horn nozzle as a control are shown below.

  In this embodiment, although the basic shape is the same as that of the cavitation nozzle 1 shown in FIG. 1, it is optimized so that the cavitation effect becomes strong in the high-pressure region and the low-pressure region by changing the dimensions of some parts, respectively. The two types of nozzles (C1, C2) are prepared, and the conventional horn nozzle used as a reference also has the same basic shape as each other, but the dimensions of some parts are changed to enhance the cavitation effect. Two types of optimized horn nozzles (H1, H2) were prepared.

  A processing experiment similar to that of Example 2 was performed using these four types of nozzles, the peak erosion amount with respect to the injection pressure at each nozzle was measured, and the result was plotted in the line graph of FIG. 9 (horizontal axis: injection pressure (MPa), Vertical axis: peak erosion amount (g)). From the results shown in FIG. 9, in the conventional horn nozzle, there was an injection region where the cavitation effect was greatly reduced, whereas in the cavitation nozzle according to the present invention, in the arbitrary injection pressure region, compared with the conventional horn nozzle. It was also found that the cavitation effect can be strengthened. In particular, it has been confirmed that the cavitation effect can be obtained more stably than in the past without significant drop in the high pressure region.

  According to the nozzle configuration of the present invention, for example, in a cavitation nozzle that performs injection in a high pressure region where the injection pressure is 30 to 60 MPa, a sufficiently strong cavitation injection flow can be stably formed, for example, in a low pressure region around an injection pressure of 20 MPa. A cavitation jet can be stably formed even in a nozzle that performs jetting. However, also in the cavitation jet flow by the nozzle for the low pressure region, the cavitation effect can be enhanced by providing the second horn portion 28 further downstream of the parallel portion 27 as shown in FIG.

  In addition, when the high pressure water is supplied through the straight pipe and the high pressure water is supplied through the elbow pipe arranged immediately before using the cavitation nozzle 1 of the present invention shown in FIG. As a result of experiments, it was confirmed that the erosion amount similar to that obtained through the straight pipe can be obtained even when the elbow pipe is used. This is because in conventional horn nozzles, the amount of erosion is greatly reduced even when the standoff distance is shortened when the elbow pipe is used, compared to the case where the straight pipe is used. This shows that the cavitation effect is enhanced by the injection through the cavitation nozzle of the present invention even when cavitation attenuation occurs due to turbulent flow or the like generated in the piping element.

1, 2: Cavitation nozzle 11: Horn nozzle 2, 12, 22: Orifice portion 3, 13, 23: Injection hole 4, 14, 24: Injection hole opening end 5, 25: Flat portion 6, 16, 26: Horn portion 7, 27: Parallel portion 28: Second horn portion L: Parallel portion distance D1: Flat portion inner diameter D2: Parallel portion inner diameter 20: Experimental water tank 30: Supply water tank

Claims (4)

An orifice portion of the cylindrical high-pressure liquid supplied from the high-pressure liquid supply means is introduced from a large flow path of relatively diameters upstream, communicates with the downstream of the orifice, its through said orifice portion In a cavitation nozzle comprising: an injection hole that generates and grows a bubble in a high-speed fluid ejected from a downstream end and injects it into the second liquid as a cavitation jet flow;
The injection hole has a flat part extending in an annular shape on a plane orthogonal to the orifice central axis in the outer circumferential direction from the downstream end opening of the orifice part, and is tapered from the periphery of the flat part toward the downstream side. A horn portion that expands at a taper angle of 60 ° to 120 ° , and a parallel portion that is connected in a cylindrical shape coaxial with the orifice central axis from the downstream peripheral edge of the horn portion to the injection hole opening end side, Cavitation nozzle characterized by having.   The cavitation nozzle according to claim 1, wherein the flat portion has an inner diameter that is 2 to 5 times an inner diameter of the orifice portion.   3. The cavitation nozzle according to claim 1, wherein the parallel portion has an inner diameter of 15 to 30 mm when the inner diameter of the orifice portion is 1 to 4 mm.   2. The cavitation nozzle according to claim 1, further comprising a second horn portion that expands in a tapered shape from a downstream peripheral edge of the parallel portion to an opening end of the injection hole.

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