JPH1099728A - Nozzle device in liquid for forming cavitation bubbles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a liquid jet stream just after jetting from an ejecting hole due to a wall effect from adhering to a wall surface by providing a tapered shape gradually increasing a diameter toward the front and providing a tapered space communicated with an expanded space at the back end and passing the liquid jet stream from the ejecting hole to an opening at the front end. SOLUTION: High pressure water jetted from an orifice 30 becomes a water jet stream 50 and passes through an expanded cylindrical space 32 and a truncated cone space 34, and jets forward from the opening 36. The water 52 in the outside becomes a relative water stream 56 from the periphery of the opening 36 in accordance with discharge of the water jet stream 50 and enter the truncated cone space 34 and goes forward toward the interior in the vicinity of the wall of the truncated cone space 34, and advances toward the opening 36 in accordance with the water jet stream 50 in the vicinity of the water jet stream 50. Since the space between the wall surface and the water jet, stream 50 becomes narrower at the deeper place of the truncated cone space 34, reduction in an advancing speed of the relative water stream 56 toward the expanded cylindrical space part 32 is suppressed and reduction in the relative speed of the water jet stream 50 against the relative water stream 56 at the boundary between the water jet stream 50 and the water 52 in the truncated cone space 34, is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cavitation bubble for performing operations such as cleaning, cutting, peening, and deburring using cavitation bubbles (= decompression bubbles) generated by injecting a high-pressure jet in a liquid. The present invention relates to a submerged nozzle device for production.

[0002]

2. Description of the Related Art In a submerged nozzle device for generating cavitation bubbles disclosed in Japanese Patent Publication No. 4-43712, a conical space portion whose diameter gradually increases forward is continuously provided immediately before an injection hole for ejecting a liquid jet. The liquid jet from the injection hole passes through the conical space and is discharged outside from the front end opening of the conical space. In the cavitation bubble generating submerged nozzle apparatus disclosed in Japanese Patent Application Laid-Open No. 5-212317, a cylindrical space having a constant diameter is provided in front of an injection hole for ejecting a liquid jet, and a liquid jet from the injection hole is formed. , And passes through the cylindrical space, and is discharged to the outside through the front end opening of the cylindrical space.

[0003]

In a submerged nozzle apparatus for generating cavitation bubbles in which a conical space portion is provided in front of the injection hole, if the center lines of the injection hole and the conical space portion are shifted from each other,
Due to the wall effect, the liquid jet immediately after exiting from the injection hole partially adheres to the portion of the wall of the conical space part that is deviated to the vicinity, and the frictional loss lowers the momentum of the liquid jet and reduces the cavitation bubbles. The production efficiency decreases. In order to avoid this, it is necessary to sufficiently increase the processing accuracy, but this leads to complication of manufacturing.

In a submerged nozzle for cavitation bubble generation, in which a cylindrical space is continuously provided in front of an injection hole, there is no problem as in the case of a conical space, but with the discharge of a liquid jet from the space, An appropriate relative velocity is not generated between the relative liquid flow entering the space from the front end opening of the space and the liquid jet, and as a result, the relative velocity effect cannot be fully utilized,
Cavitation bubble generation efficiency is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cavitation bubble generating submerged nozzle device for increasing cavitation bubble generation efficiency by utilizing a relative liquid flow entering from a front end opening. The purpose is to prevent the jet from adhering to the wall surface.

[0006]

In the submerged nozzle device for generating cavitation bubbles (10) which is a premise of the present invention, a liquid jet (50) is injected from an injection hole (30) disposed in a liquid (52). To generate cavitation bubbles (64). The cavitation bubble generating submerged nozzle device (10) has the following elements (a) and (b). (A) The diameter of the injection hole (30) becomes sufficiently larger than the diameter of the injection hole (30) immediately before the injection hole (30) so that the liquid jet (50) immediately after injection from the injection hole (30) is prevented from adhering to the wall surface. (B) a tapered shape that gradually increases in diameter toward the front side and communicates with the enlarged diameter space (32) at the rear end to form an injection hole (30); ) Through which the liquid jet (50) passes toward the front end opening (36).

The injection hole (30) faces the enlarged diameter space (32), and the injection hole (3)
The liquid jet (50) from (0) is jetted into the enlarged-diameter space (32). The diameter-enlarged space (32) has a diameter corresponding to the diameter of the injection hole (30).
The liquid jet (50) from the injection hole (30) passes through the large-diameter space (32) without adhering to the wall surface of the large-diameter space (32) because it is sufficiently larger than immediately before. And the tapered space (3
4). In the tapered space (34), the liquid jet flows from the enlarged diameter space (32) toward the front end opening (36) of the tapered space (34).
With the passage of the liquid (50), the liquid outside the tapered space (34) (5
2) enters the tapered space (34) from the periphery of the front end opening (36) and becomes a relative liquid flow (56) to the liquid jet (50).
As a result, the liquid jet flows in the tapered space (34).
In the periphery of (50), an appropriate relative velocity is generated between the liquid jet (50) and the relative liquid flow (56), and cavitation bubbles (64) are appropriately generated. In this way, the cavitation bubble (6) is utilized by utilizing the relative liquid flow (56) of the tapered space (34).
While increasing the generation efficiency of 4), the enlarged diameter space (32) immediately before the injection hole (30) allows the liquid jet (50)
Can be prevented from adhering.

Another cavitation bubble generating submerged nozzle device (10) of the present invention further has the following element (c). (C) A throttle (38) existing between the enlarged diameter space (32) and the tapered space (34).

Due to the presence of the throttle (38) between the enlarged diameter space (32) and the tapered space (34), the tapered space enters the tapered space (34) from the front end opening (36). The liquid (52) that proceeds toward the back of the tapered space (34) flows from the tapered space (34)
Approach to (32) is suppressed. As a result, the pressure in the enlarged diameter space (32) is appropriately reduced, and the generation efficiency of the cavitation bubbles (64) in the enlarged diameter space (32) is increased. Also, the aperture
A step is formed on the side of the expanded space portion (32) of (38), and the liquid (52) stays in the step, and the liquid jet (50) that passes through the throttle (38) is formed. The cavitation bubble (64) is efficiently generated in the step portion. Since the cavitation bubbles (64) are entrained and carried by the liquid jet (50), the cavitation bubbles (64) in the liquid jet (50) can be further increased.

According to another submerged-nozzle device for generating cavitation bubbles of the present invention, the enlarged-diameter space portion (32) is capable of adjusting the length of the liquid jet (50) in the flow direction. .

[0011] The distance between the injection hole (30) and the tapered space (34) in the flow direction of the liquid jet (50) at which the generation efficiency of the cavitation bubbles (64) is maximized, and hence the liquid jet (50) The length of the radially enlarged space portion (32) in the flow direction changes depending on the speed, injection pressure, and the like of the liquid jet (50). In the cavitation bubble generating submerged nozzle device (10), by adjusting the length of the liquid jet (50) in the flow direction of the enlarged-diameter space (32), the speed of the liquid jet (50), the injection pressure, etc. Despite the change in the situation, the generation efficiency of the cavitation bubbles (64) can be made accurate.

According to another cavitation bubble generating submerged nozzle device (10) of the present invention, the taper angle (θ / 2) of the vertical section of the tapered space (34) is set so that the taper angle (θ / 2) from the injection hole (30) increases. Liquid jet
It is larger than the taper angle (γ / 2) of the spread of (50).

The liquid (52) which has entered the tapered space (34) from the front end opening (36) tends to have a lower traveling speed toward the inside of the tapered space (34). However, the taper angle (θ / 2) of the vertical section of the tapered space (34) is
Since the expansion of the liquid jet (50) from (30) is larger than the taper angle (γ / 2), the depth of the tapered space (34), the wall surface of the tapered space (34) and the liquid jet (50) ) Is narrowed, whereby a decrease in the traveling speed of the liquid (52) traveling deep inside the tapered space (34) can be suppressed. In this way, even in the back of the tapered space (34), the relative liquid flow (5
An appropriate relative speed is maintained between 6) and the liquid jet (50), and the generation efficiency of the cavitation bubbles (64) is increased.

According to another cavitation bubble generating submerged nozzle apparatus (10) of the present invention, the following dimensional relationship is obtained. 4 · d ≦ D1 ≦ 8 · d, 0 <La ≦ 5 · d, 2 · d ≦ D2
≦ 7 · d, 10 ° ≦ θ / 2 ≦ 45 °, 2 · d ≦ Lb ≦ ・
12d. However, the meaning of each symbol is as follows. d: Diameter of injection hole (30) D1: Diameter of enlarged diameter space portion (32) D2: Diameter of throttle portion (38) La: Length of enlarged diameter space portion (32) in center line direction Lb: Center line direction Length of tapered space (34) θ / 2: Angle of inclination of wall surface with respect to center line in longitudinal section of tapered space (34)

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of the underwater nozzle device 10.
The underwater nozzle device 10 includes a nozzle mounting pipe 12, and high-pressure water from a high-pressure water generator 14 is supplied to a base end side of the nozzle mounting pipe 12 via a high-pressure water pipe 16. The nozzle mounting tube 12 has a screw portion 18 on the outer peripheral portion of the front end portion, and a circular orifice tip 20 having a predetermined thickness and a predetermined thickness is applied to the front surface. The cap 22 is fitted on the outside of the orifice tip 20, and the screw groove 24 of the concave portion of the rear end opening is screwed into the screw portion 18 of the nozzle mounting pipe 12, and the orifice tip 20 is fastened to the front face of the nozzle mounting pipe 12. . The passage hole 26 is formed inside the nozzle mounting pipe 12 along the center line, and guides high-pressure water from the high-pressure water generator 14. The reverse taper portion 28, the orifice 30, the large-diameter cylindrical space portion 32, the truncated cone space portion 34, and the opening 36 are aligned with the center line of the passage hole 26, and from the passage hole 26 to the front of the submerged nozzle device 10. They are installed in sequence. The inverted taper portion 28 and the orifice 30 are bored in the orifice tip 20, and the enlarged cylindrical space portion 32 and the truncated conical space portion 34 are connected to the cap 22. The diameter of the reverse tapered portion 28 is made equal to the diameter of the passage hole 26 at the rear end, gradually decreases toward the front, and the diameter at the front end is d. The orifice 30 has the same diameter (= d) in the length direction. Large-diameter cylindrical space 32
Has a diameter sufficiently larger than that of the orifice 30, and the diameter of the truncated cone space 34 gradually increases from the rear end toward the opening 36. The diameter of the front end of the truncated cone space portion 34 is smaller than the diameter of the enlarged cylindrical space portion 32.
And at the boundary between the truncated cone space portion 34.

FIG. 2 shows an enlarged cylindrical space 32 and a truncated cone space.
The specifications of each part of 34 are shown. The meaning of each symbol in FIG. 2 is as follows. d: Diameter of the orifice 30 D1: Diameter of the expanded cylindrical space 32 D2: Diameter of the throttle 38 La: Length of the expanded cylindrical space 32 in the centerline direction Lb: Truncated conical space 34 in the centerline direction Length θ / 2: The inclination angle of the wall surface with respect to the center line in the longitudinal section of the truncated cone space portion 34

The relationship between the specifications is defined, for example, as follows. 4 · d ≦ D1 ≦ 8 · d, 0 <La ≦ 5 · d, 2 · d ≦ D2
≦ 7 · d, 10 ° ≦ θ / 2 ≦ 45 °, 2 · d ≦ Lb ≦ ・
12d.

The following is a typical example of each dimension. d = 1 mm, D1 = 6 mm, D2 = 4 mm, La = 2 mm, Lb
= 5mm.

The length xc of the jet core (the high-density portion extending from the orifice 30 into the water jet 50) is visually observed by an experiment, and the dimensions of each portion are defined so that xc / d is approximately 5.5. It is known that cavitation bubbles having high processing ability are generated even if d and the injection pressure slightly change. The injection pressure is 100 kgf / cm ^ 2 and the Reynolds number is 11.
Observed under 2.times.10@4, xc was about 5.5 mm. In this specification, ^ indicates a power, and ^ n indicates the nth power.

FIG. 3 shows the velocity distribution of the relative water flow 56 between the wall surface of the truncated cone space 34 and the water jet 50. θ / 2, γ
/ 2 indicates the angle of the bundle of the water jet 50 and the wall surface of the frustoconical space 34 with respect to the center line of the submersible nozzle device 10 (= the center line of the water jet 50) in the vertical cross section of the submersible nozzle device 10.
> Γ. The underwater nozzle device 10 is submerged in water 52 of a predetermined tank, and supplied with high-pressure water from the high-pressure water generator 14. The high-pressure water injected from the orifice 30 becomes a water jet 50, and the expanded cylindrical space portion 32 and the truncated cone space portion 34
Through the opening 36 of the truncated cone space 34
It is fired toward an object (not shown) in front of the object.
With the release of the water jet 50 from the opening 36, the underwater nozzle device 10
Outside water 52 becomes a relative water flow 56 from the periphery of the opening 36,
It enters into the truncated cone space 34. The relative velocity of the relative water flow 56 in the truncated cone space 34 is shown at three places in the truncated cone space 34 in the direction of the center line of the submerged nozzle device 10,
The relative water flow 56 advances toward the inside of the truncated cone space 34 near the wall surface of the truncated cone space 34, and the water jet flows near the water jet 50.
Followed by 50, proceed towards opening 36. The relative water flow 56 is
Normally, as the depth of the truncated cone space 34 increases, the traveling speed tends to decrease. However, due to the relationship of θ> γ, the depth of the truncated cone space 34, the wall surface of the truncated cone space 34 Since the distance between the water jet 50 and the water jet 50 is reduced, a decrease in the traveling speed of the relative water flow 56 toward the enlarged cylindrical space 32 is suppressed, and the water at the boundary between the water jet 50 and the water 52 in the truncated cone space 34 is suppressed. Jet 50 and relative water flow 56
The decrease in relative speed with respect to is suppressed. As a result, cavitation bubble generation efficiency can be increased.

FIG. 4 shows a state in which cavitation bubbles 64 and the like are generated. The water jet 50 causes the relative water flow 56 to open 36
Flows into the frusto-conical space 34, and a large relative velocity is generated at the boundary between the water jet 50 and the relative water flow 56 in the expanded cylindrical space 32 and the frusto-conical space 34, and the water jet 50 is in a turbulent state. And cavitation bubbles 64 are generated in the water jet 50. Further, since the relative water flow 56 is difficult to enter into the enlarged cylindrical space 32 due to the presence of the throttle portion 38, the pressure in the enlarged cylindrical space 32 is sufficiently reduced. Then, a small amount of entering water 58 passes through the constricted portion 38 and penetrates into the enlarged-diameter cylindrical space 32, and generates a vortex in the enlarged-diameter cylindrical space 32, so that cavitation bubbles 66 are formed outside the water jet 50. Is generated efficiently. This cavitation bubble 66 is entrained in the water jet 50 and is carried by the water jet 50 together with the cavitation bubble 64 to an object (not shown) in front of the submerged nozzle device 10 to clean, cut, peen, Perform processing such as deburring.

FIG. 5 is an enlarged view of the vicinity of the diaphragm 38 in FIG. Due to the presence of the constricted portion 38, the enlarged cylindrical space 32 of the constricted portion 38
A step is formed on the side, and water 52 stays in the step, and the relative speed difference between the water jet 50 and the water jet 50 increases, thereby promoting the generation of the cavitation bubbles 68. This cavitation bubble 68
4 is similar to the cavitation bubble 66 in FIG.
And heads for the object together with the cavitation bubbles 64.

FIG. 6 shows the prior art (broken line) and the present invention (solid line).
The relationship between the processing distance (the distance from the underwater nozzle device 10 to the target object) and the amount of erosion caused by cavitation bubbles is shown in comparison with FIG. The dimensions of each part employed in the present invention are those shown in the above-mentioned typical example. The injection pressure was 100 kgf / cm ^ 2 and 300 kgf / cm ^ 2, but under the injection pressure of 100 kgf / cm ^ 2, the erosion amount of the present invention was higher than that of the prior art under the injection pressure of 100 kgf / cm ^ 2. The upturn rate reaches a maximum of about 30%. Under the injection pressure of 300 kgf / cm ^ 2, although the erosion amount of the present invention is lower than the erosion amount of the prior art in the intermediate inter-work distance range, the maximum inter-work distance is larger in the present invention than in the prior art. Therefore, the maximum erosion amount in the region where the distance between the processes is large is larger in the present invention than in the conventional technology.

FIG. 7 is a longitudinal sectional view of another underwater nozzle device 10. Only the differences will be described. Orifice tip
20 is omitted, and the reverse tapered portion 28 and the orifice 30 are formed in the nozzle mounting tube 12. The circumferential groove 74 is formed at the front end of the nozzle mounting pipe 12 in a circle centered on the orifice 30 and opens at the front of the nozzle mounting pipe 12. The circumferential ridge 76 is formed on the cap 22 and can be closely fitted and inserted into the circumferential groove 74. Thus, the enlarged cylindrical space portion 32 is defined by the circumferential ridge 76 in the radial direction, and is defined by the front surface of the nozzle mounting tube 12 and the bottom surface of the deep portion of the enlarged cylindrical space portion 32 in the axial direction. ,It is formed. The lock nut 78 is screwed into the screw portion 18 adjacent to the rear end of the cap 22 to suppress the rotation of the cap 22. By changing the screwing position of the screw groove 24 of the cap 22 to the screw portion 18 of the nozzle mounting tube 12, the length of the enlarged cylindrical space portion 32 in the center line direction of the underwater nozzle device 10 changes. Water jet
When the operating conditions such as speed, injection pressure, etc. change, the diameter of the expanded cylindrical space 32 maximizes the generation efficiency of the cavitation bubbles 64.
Also varies slightly. In this underwater nozzle device 10,
By appropriately changing the length of the enlarged cylindrical space 32 in accordance with the use conditions, the generation efficiency of the cavitation bubbles 64 can be increased.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an underwater nozzle device.

FIG. 2 is a diagram showing the specifications of each part of a large-diameter cylindrical space portion and a truncated cone space portion.

FIG. 3 is a diagram showing a velocity distribution of a relative water flow between a wall surface of a truncated cone space portion and a water jet.

FIG. 4 is a diagram showing a state of generation of cavitation bubbles and the like.

FIG. 5 is an enlarged view of the vicinity of a diaphragm in FIG. 4;

FIG. 6 compares the prior art (broken line) with the present invention (solid line) and compares the distance between processing (the distance from the underwater nozzle device to the object).
FIG. 4 is a diagram showing a relationship between the erosion amount due to cavitation bubbles.

FIG. 7 is a longitudinal sectional view of another underwater nozzle device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Underwater nozzle apparatus (submerged nozzle apparatus for cavitation bubble generation) 30 Orifice (injection hole) 32 Expanded cylindrical space section (expanded space section) 34 Truncated cone space section (tapered space section) 36 Opening (front end opening) 38 Restrictor 50 Water jet (liquid jet) 52 Water (liquid) 56 Relative water flow (relative liquid flow) 64 Cavitation bubbles (cavitation bubbles)

Claims (5)

[Claims] A cavitation bubble generating submerged nozzle device (10) that is disposed in a liquid (52) and injects a liquid jet (50) from an injection hole (30) to generate a cavitation bubble (64). (A) Immediately before the injection hole (30), the diameter of the injection hole (30) becomes sufficiently larger so that the liquid jet (50) immediately after injection from the injection hole (30) is prevented from adhering to the wall surface. (B) a tapered shape which gradually increases in diameter toward the front, and communicates with the enlarged diameter space (32) at the rear end. A tapered space (34) for passing the liquid jet (50) from the injection hole (30) toward the front end opening (36),
A submerged nozzle device for generating cavitation bubbles, comprising: 2. The method according to claim 1, further comprising: (c) a throttle section (38) existing between the enlarged diameter space section (32) and the tapered space section (34). A submerged nozzle device for generating cavitation bubbles as described in the above. 3. The liquid for generating cavitation bubbles according to claim 1, wherein the diameter of the enlarged space portion (32) is adjustable in length in a flow direction of the liquid jet (50). Medium nozzle device. 4. The taper angle (θ / 2) of the longitudinal section of the tapered space portion (34) is larger than the taper angle (γ / 2) of the spread of the liquid jet (50) from the injection hole (30). The submerged nozzle device for generating cavitation bubbles according to any one of claims 1 to 3, which is large. 5. The submerged nozzle device for generating cavitation bubbles according to claim 1, wherein the dimensional relationship is as follows. 4 · d ≦ D1 ≦ 8 · d, 0 <La ≦ 5 · d, 2 · d ≦ D2
≦ 7 · d, 10 ° ≦ θ / 2 ≦ 45 °, 2 · d ≦ Lb ≦ ・
12d. However, the meaning of each symbol is as follows. d: Diameter of injection hole (30) D1: Diameter of enlarged diameter space portion (32) D2: Diameter of throttle portion (38) La: Length of enlarged diameter space portion (32) in center line direction Lb: Center line direction Length of tapered space (34) θ / 2: Angle of inclination of wall surface with respect to center line in longitudinal section of tapered space (34)