JPH07241494A - Nozzle for water jet - Google Patents

Abstract

PURPOSE:To provide a nozzle for the water jet continuing steady cavitation even in water, having a low pressure drop and having a high treating effect. CONSTITUTION:The nozzle 1 for a water jet is provided with a hole 8 for injecting high-pressure water and a part 12 gradually expanded and extended from the outlet of the hole 8. At least one and more steps 20 are furnished on the inner wall of the part 12, a throttled part is furnished at the outlet part of the part 12, the sections of the hole 8 and part 12 vertical to the center axis 5 are made circular, and the inner diameter of the outlet of the part 12 is made 15-25 times as large as that of the hole 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water jet nozzle used for various kinds of underwater processing, and more particularly to a water jet nozzle for producing a high-speed water jet accompanied by severe cavitation in water.

[0002]

The use of high speed water jets is known as a unique processing, mining or cleaning technique such as cutting, drilling, cleaning, chipping and metal strengthening. An attempt was made to use this to strengthen the material by Westinghouse Electric Company. However, this is an operation in the atmosphere that can effectively use the axial power of the water jet, and there is no guarantee that this technology can be directly deployed as an underwater water jet.
In water, the jet axial dynamic pressure decays fairly quickly. This is due to the fact that the diffusion rate is high because of the same liquid phase as the resistance of ambient water. In water, an ultrahigh pressure device is required to obtain an axial power similar to a gas-phase water jet, which is a very disadvantageous technique in terms of cost.

On the other hand, as shown in FIG. 17, an underwater water jet 4
At 0, severe cavitation occurs due to the combined effect of the turbulence of the jet flow and the shearing action of it and the surrounding water 39. If cavitation is promoted and the impact pressure of bubbles generated in large quantities, especially the impact pressure due to collision of vortex cavitation as shown in FIG. It could be achieved with pressure. In FIG. 17, reference numeral 4 is a nozzle body, 8 is a jet hole, 38 is high pressure water, and 98 is high pressure water.
Is the beginning of cavitation, 99 is the cavitation cloud, 100 is the cavitation cloud split,
101 is vortex cavitation, 102 is cavitation cloud disappearance, and 103 is a fine bubble group.

[0004]

The problem shown in FIG. 18 is as follows.
FIG. 1 is a cross-sectional view of a general water jet nozzle 1 ′, which shows a typical structure of a nozzle used for water jet cutting. This nozzle has a diaphragm angle θ of the reduction unit 37.
The purpose is to narrow the water jet into a beam in the gas phase by reducing the water vapor, and the cavitation intensity (Intensity) cannot be said to be sufficient even if it is used as it is for an underwater water jet. The reason is that the high-pressure water 38 is not greatly disturbed in the underwater water jet ejected from the flow path 36 through the contraction portion 37 and the ejection hole 8, and the bubble nucleus in the ejected water is not excited until active cavitation. . Reference numeral 5 is the central axis. As in the structure of the water jet nozzle 1 ′ shown in FIG. 19, when θ is set large and the aperture is made sharp, cavitation is actively generated due to a rapid contraction flow in the contraction section 37, but inside the ejection hole 8. Since air bubbles are generated at, pressure loss increases due to so-called bubble lock. Although the underwater treatment performance is improved, a higher pressure pump is required, which is disadvantageous in terms of cost.

Since the cavitation jets jetted from the water jet nozzle 1'of FIGS. 18 and 19 are both produced from a single jet hole, their spread is poor. Therefore, in order to process a wide area on the surface to be processed, there remains a problem that the water jet nozzle must be traversed in a complicated manner or the processing time must be lengthened. Shortening processing time, water jet nozzle manipulation (positioning operation)
In order to simplify, the cavitation jet with large spread must be created.

A water jet nozzle 1'used for an underwater water jet of the prior art shown in FIG. 20 has been developed for various works underwater, and the use of cavitation has been shown (Japanese Patent Laid-Open No. Sho 61-242). 60-168554
Issue). In the water jet nozzle 1 ′ shown in FIG. 20, the cavitation is promoted by the action of the unstable separation vortex generated from the high-pressure jetting device 107 through the pipe 106 and the jetting hole 8 in the conical enlarged portion 12. The processing surface of the target surface 48 is processed. However, as shown in FIG. 21, the separation vortex 1 of the underwater water jet 40 is
The action of 10 has strong non-stationarity and is intermittent (in the figure,
Cavitation is not always activated violently, and unstable movement in and out indicated by arrow 111).

An object of the present invention is to solve the above-mentioned problems and to provide a water jet nozzle having a small pressure loss and a large treatment effect, in which cavitation is constantly and vigorously continued in water. .

[0008]

In order to solve the above-mentioned problems, the first aspect of the present invention is a water provided with an ejection hole for ejecting high-pressure water and an enlarged portion gradually enlarged and extended from the outlet of the ejection hole. In the jet nozzle, at least one step-like step is provided on the inner wall of the enlarged portion.

A second aspect of the present invention is a water jet nozzle including a jet hole for jetting high-pressure water and an enlarged portion gradually enlarged and extended from an outlet of the jet hole, wherein at least one inner wall of the enlarged portion is provided. That is, at least one annular groove is provided.

A third aspect of the present invention is a water jet nozzle comprising a jet hole for jetting high-pressure water and an enlarged portion that is gradually enlarged and extended from an outlet of the jet hole. A throttle portion is provided at the outlet of the enlarged portion. Is provided.

A fourth invention is that in the first invention or the second invention, a throttle portion is provided at an outlet of the expanding portion.

According to a fifth aspect of the present invention, in a water jet nozzle including a jet hole for jetting high-pressure water and an enlarged portion gradually enlarged and extended from an outlet of the jet hole, the jet hole and the enlarged portion are provided. A cross-sectional shape perpendicular to the central axis is circular, and the inner diameter of the outlet of the enlarged portion is 15 to 15 times the inner diameter of the ejection hole.
25 times.

In a sixth aspect of the present invention, in any one of the first to fourth aspects of the present invention, a cross-sectional shape perpendicular to the central axis of the ejection hole and the enlarged portion is circular, and the outlet inner diameter of the enlarged portion is It is 15 to 25 times the inner diameter of the ejection hole.

[0014]

According to the present invention, in a water jet nozzle provided with an ejection hole for ejecting high-pressure water and an enlarged portion gradually enlarged and extended from the outlet of the ejection hole, at least one is provided on the inner wall of the enlarged portion. Since the above-described step-like steps are provided, the step-like steps that are continuously arranged on the inner wall of the enlarged portion generate a separation vortex in a chain. Since the separating vortex complicatedly interferes with the shear vortex generated between the enlarged portion and the water jet, many minute low pressure portions are generated at the interface of the underwater water jet, and cavitation is greatly promoted.

Further, since at least one annular groove is provided on the inner wall of the enlarged portion, the annular groove on the inner wall of the enlarged portion is
Non-condensable gas (eg air) trapped there
Are separated one after another and become fine bubbles and are entrained in the jet flow, which has a so-called ambient nuclei supply function. That is, the annular groove has a function as a cavitation device that supplies cavitation nuclei.

Further, since the narrowed portion is provided at the outlet of the enlarged portion, the separation bubbles generated by the narrowed portion interfere with the underwater water jet flow and violently disturb the interface of the underwater water jet flow. Thus, shear vortices are actively generated at the turbulent jet interface, and powerful vortex cavitation that strongly affects the material develops.

Further, since at least one step-like step or at least one annular groove and the narrowing part are provided at the outlet of the expanding part on the inner wall of the expanding part, the separation vortices in the step-like step are chained. Along with the action of generation or entrainment of non-condensable gas (for example, air) trapped in the annular groove into the jet of the desorbing microbubbles, the defoaming bubbles generated by the narrowed part attached to the tip of the enlarged part are Interfere with each other and violently disturb the underwater water jet interface. Thus, shear vortices are actively generated at the turbulent jet interface, cavitation is greatly promoted, and the vortex cavitation acts as powerful vortex cavitation that strongly affects the surface to be treated.

The cross section of the ejection hole and the enlarged portion perpendicular to the central axis is circular, and the inner diameter of the outlet of the enlarged portion is 15 to 25 times the inner diameter of the ejection hole, so that it is generated in the jet of the enlarged portion. Cavitation becomes the most active in this range and acts as a powerful vortex cavitation that strongly affects the surface to be treated.

Further, a step-like step or an annular groove is provided on the inner wall of the enlarged portion, and a narrowed portion is provided at the outlet of the enlarged portion, and the cross-sectional shape perpendicular to the central axis of the ejection hole and the enlarged portion is circular, so that the inner diameter of the outlet of the enlarged portion is circular. Is 15 to 25 times as large as the inner diameter of the ejection hole, so that powerful vortex cavitation that more strongly influences the surface to be processed is generated.

A shear vortex is generated between the divergent, conical enlarged portion at the outlet of the jet hole and the jet flow that is jetted and spread from the jet hole, and this vortex disturbs the jet flow, thus promoting cavitation. In particular, vortex cavitation is actively generated in the shear layer at the jet interface. In particular, vortex cavitation is more powerful than other cavitations and has a strong influence on the material. As a result, the power of cavitation generated in a high-speed water jet in water is significantly improved, and the efficiency of underwater treatment is improved. Since the water jet nozzle of the present invention promotes the turbulence of the jet flow after being ejected from the ejection holes, the pressure loss of the nozzle does not increase.

All of the above-mentioned actions promote cavitation. By using the means according to the present invention, the turbulence of the interface of the underwater water jet immediately after jetting from the nozzle, that is, the generation of a shear vortex is promoted, and the generation of a large-scale vortex inside the jet is also promoted. The action of these turbulences triggers the supply of bubble nuclei through the turbulence at the jet interface. As a result, vortex cavitation that strongly acts on the material is activated. The steps of the inner wall of the enlarged portion, the annular groove, and the size of the narrowed portion at the outlet of the enlarged portion most promote the supply of vortices, turbulence, or cavitation nuclei in the optimum range described above.

[0022]

Embodiments of the water jet nozzle according to the present invention will be described below in detail with reference to the drawings. Figure 1
FIG. 1 is a sectional view of a first embodiment of a water jet nozzle according to the present invention. The water jet nozzle 1 of the first embodiment has a stepped step 20 provided on the inner wall 15 of the enlarged portion 12. The high pressure water 38 flows through the flow path 36.
Is guided through, is squeezed to the ejection hole 8 and accelerated under reduced pressure,
An enlarged portion 12 is extended to the outlet 10 and is injected into the surrounding water from here. The one-sided spread angle of the enlarged portion 12 is 30 °. Further, with respect to the inner diameter 9 (Dj) of the ejection hole 8, the outlet inner diameter 14 (Do) of the enlarged portion 12 is selected from the range of Do = (15 to 25) Dj (1). Under the condition that satisfies the expression (1), the cavitation generated in the jet in the enlarged portion 12 becomes most active. If Do is outside this range, cavitation is inactive. In this embodiment, the stepped steps 20 are provided on the inner wall 15 of the enlarged portion 12, and the number of the steps is 5.

FIG. 2 is a sectional view of the second embodiment of the water jet nozzle according to the present invention. The structure of this water jet nozzle 1 is basically the same as that of FIG. However, the inner wall 15 of the substantially conical enlarged portion 12 extended to the outlet 10 of the ejection hole is rounded,
The shape is close to a spheroid. Also in this nozzle, the inner diameter 9 (Dj) of the ejection hole and the outlet inner diameter 14 (Do) of the substantially conical enlarged portion are selected and set within a range satisfying the above expression (1). In this embodiment, the number of steps on the inner wall of the substantially conical enlarged portion 12 is 5, as in the example of FIG. Of the reference numerals in FIG. 2, the same structural parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 3 is a sectional view of the third embodiment of the water jet nozzle according to the present invention. In the water jet nozzle 1 having this structure, an annular groove 24 is provided in the inner wall 15 of the conical enlarged portion 12. In this embodiment, three rows of annular grooves 24 are provided. The annular groove 24 has the following preferable ranges for promoting cavitation. The outer diameter 26 (Dt) and the inner diameter 25 (D
The dimensional relationship of h) is

[0025]

[Equation 1]

It is preferable to determine within the range of, and more preferably,

[0027]

[Equation 2]

It may be set from. Also, the width 2 of the annular groove 24
For 7 (l),

[0029]

[Equation 3]

It is better to select from the range of

[0031]

[Equation 4]

Within the condition range of (3), it is more suitable for promoting cavitation. Also in the nozzle of this embodiment, the inner diameter 9 (Dj) of the ejection hole and the conical enlarged portion 1
The outlet inner diameter 14 (Do) of No. 2 is determined according to the condition of the above-mentioned formula (1). Further, as in the embodiment shown in FIG. 1, the cone-shaped enlarged portion 12 has a swing-out angle of 30 °. Figure 3
Of the reference numerals therein, the same structural portions as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 4 is a sectional view of a fourth embodiment of a water jet nozzle according to the present invention. This water jet nozzle 1 has a spheroidal structure in which the cone-shaped enlarged portion of the annular grooved nozzle shown in FIG. 3 is rounded. The shape of the enlarged part is
The spheroid can secure a large space between the inner wall and the jet flow, so that the interfacial shear vortex on the outer periphery of the jet flow immediately after jetting can be more actively generated. Of the reference numbers in FIG. 4,
The same structural parts as those in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 5 is a cross-sectional view of a fifth embodiment of the water jet nozzle according to the present invention, showing a conical enlarged portion 1
An orifice 30 ', which is a narrowed portion, is provided at the outlet of No.2. The opening diameter 31 (Dc) of the orifice 30 'is different from the outlet inner diameter 14 (Do) of the conical enlarged portion.

[0035]

[Equation 5]

It is preferable to select from the range of. More preferably,

[0037]

[Equation 6]

If the range is selected from the range, the cavitation generated in the jet can be remarkably activated while suppressing the increase of the pressure loss. Also in the nozzle of the fifth embodiment, the dimensions of the ejection hole inner diameter 9 (Dj) and the outlet inner diameter 14 (Do) of the conical enlarged portion are as shown in the equation (1), and the conical enlarged portion 12 is used. The unilateral swing-out angle is 30 ° like other nozzles. Of the reference numbers in FIG. 5,
The same structural parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 6 is a sectional view of a sixth embodiment of a water jet nozzle according to the present invention. The basic structure of this nozzle is the same as that of FIG. 5, and the shape of the inner wall 15 of the enlarged portion 12 having a substantially conical shape is formed into a rounded substantially spheroidal shape. Of the reference numerals in FIG. 6, the same structural parts as those in FIG.

FIG. 7 is a side view showing the relationship between the underwater water jet and the surface to be treated. When the underwater water jet 40 accompanied by intense cavitation, in which the high-pressure water 38 is jetted into the water from the nozzle 1 is collided with the surface 48 to be treated, a rebounding jet 47 is generated. The standoff distance x between the outlet of the nozzle body 4 and the surface 48 to be processed is selected as a condition under which cavitation is sufficiently developed and powerful, and erosion of the material is never caused. The injection pressure in the nozzle body 4 is, for example, 700 kgf / cm ²
(70 MPa), the preferred standoff distance is about 8
It is in the range of 0 to 150 mm. Reference numeral 46 is the contour of the jet.

FIG. 8 is a side view for explaining an underwater water jet flow in the first embodiment of the present invention. 1 is a schematic drawing showing the state of an underwater water jet 40 in the first embodiment in which a stepped step 20 is provided in a conical enlarged portion 12. Cavitation occurs in the water jet jetted from the jet holes 8 and spreads out in the conical enlarged portion 12 and jets out. An annular vortex 55 around the jet is generated between the conical enlarged portion 12 and the underwater water jet 40. The annular vortex 55 around this jet is relatively large as shown. On the other hand, also in the stepped step 20 according to the present invention, the vortex 54 generated in the step is generated.
The vortex 54 generated in the stepped step 20 interferes with the annular vortex 55 around the jet to produce the following two effects.

(A) To promote turbulence around the jet flow.

(B) The core portion 56 at the center of the jet flow is diffused.

According to (a), the shear layer 5 at the jet interface
Strongly affects 7 and promotes cavitation.
The shear layer portion 57 is a functionally important vortex cavitation generation region among several types of cavitation generated in an underwater water jet. On the other hand, the core portion 56 at the center of the jet flow has a problem of eroding the material, but due to the action of (b), this danger is considerably eliminated. As a result of the above-mentioned operation, the step-like step 20 provided in the conical enlarged portion has the developed cavitation 59.
And the structure of the underwater water jet 40 is modified.
Incidentally, reference numeral 58 is a supply of the surrounding nucleus.

FIG. 9 is a side view for explaining an underwater water jet in the fifth embodiment of the present invention. This is a case in which the state of the underwater water jet 40 in the case where an orifice 30 'is provided at the tip of the outlet 13 of the conical enlarged portion is schematically drawn. By providing the orifice 30 ′, a vortex flow 65 that is generated in the stable expanded portion 12 is formed on the outer periphery of the jet flow immediately after being jetted from the jet hole 8. Eddy current 65 generated in the enlarged portion 12
Is much more stable than it would be without the orifice 30 'at the outlet 13 of the conical enlargement and continues to provide continuous variation to the underwater water jet 40. On the outer circumference of the orifice 30 ', a vortex 64 generated in the orifice 30' and annular vortices 66a and 66b around the jet induced by the vortex 64 are formed. In this way, vortex cavitation is actively generated in the shear layer portion 57 of the underwater water jet 40. The active vortex and bubble movements in the shear layer portion 57 become more active due to the supply of peripheral nuclei 58 from the surrounding water, as indicated by the outlined arrows in the figure. Therefore, in the underwater water jet flow 40, vortex cavitation is further generated in the shear layer portion 57 on the upstream side near the nozzle body 4.
Cavitation 5 developed downstream of the underwater jet 40
9 is created inside the jet.

Next, the effects of the present invention will be concretely shown based on the characteristics of cavitation generated in the underwater water jet. Two peaks appear in the distribution of the impact pressure in the axial direction of the underwater water jet. The first peak near the nozzle body is called the "first peak", while the second peak downstream is called the "second peak". FIG. 10 is a side view showing the measurement positional relationship between the first peak and the second peak of an underwater water jet.
The jet diameters D ₁ and D ₂ at the standoff distances x ₁ and x ₂ corresponding to the first peak and the second peak of the underwater water jet 40 were measured. Cavitation generated in the underwater water jet 40 draws the contour 46 of the jet. The contour 46 of this jet flow was obtained by the following method.

FIG. 11 is a side view for explaining a method of photographing the contour of an underwater water jet. A blackout 70 is installed behind the jet,
The camera 72 uses a continuous light source 71 to illuminate the jet stream.
The contour 46 of the jet was photographed and measured by the photograph.

FIG. 12 is a relationship curve diagram between the injection pressure and the injection diameter at the first peak of the underwater water jet. Injection pressure P
To the first peak corresponding to the standoff distance X ₁ (Fig. 1
The change in the diameter D ₁ of the jet in 0) is arranged, and the thickness of the jet in the embodiment of the present invention is compared with the thickness of the jet in the prior art. The injection pressure P on the horizontal axis is made dimensionless with the reference injection pressure P * as a comparison reference. On the other hand, the jet diameter D _{1 on the} vertical axis
Also, the dimension is made dimensionless using the diameter D ₁ * of the jet at the “first peak” under the condition of P = P * as a comparison reference. Curve 76 represents the first example (first peak) and curve 7
8 represents the prior art (first peak). Both curves are P
Although D ₁ / D ₁ * gradually increases as / P * increases, the curve 76 of the present invention is overwhelmingly more D ₁ than the curve 78 of the prior art when compared at the same P / P *. / D ₁ * is large. From this result, even in the area near the nozzle,
It can be said that the effect of promoting cavitation of the water jet nozzle according to the present invention has been verified.

FIG. 13 is a relationship curve between the injection pressure and the injection diameter at the second peak of the underwater water jet. The jet pressure P / which is made dimensionless with the jet diameter D ₂ at the downstream second peak
It is organized as changes to P *. Similar to FIG. 12, D ₂ is expressed dimensionlessly by being divided by the diameter D ₂ * of the jet at the “second peak” under the condition of P = P *. Curve 77 represents the first example (second peak) and curve 79 represents the prior art (second peak). Regarding the jet at the standoff distance X ₂ (FIG. 10) corresponding to the second peak, the curve 77 of the present invention is the curve 79 of the prior art.
It is clear from this result that it is much larger than the above.

FIG. 14 is a side view showing a method for measuring the impact pressure of an underwater water jet. Using the pressure sensitive film method, the impact pressure 84 generated from the cavitation of the underwater water jet 40
In comparison with the case of using the water jet nozzle 1 according to the embodiment of the present invention and the conventional water jet nozzle 1 '. A pressure sensitive film 73 was installed in parallel with the central axis 5 at a position 5 mm away from the central axis 5 of the underwater water jet 40 accompanied by cavitation in the radial direction.

FIG. 15 is a relationship curve diagram between the standoff distance and the impact pressure. The curve 86 summarizes the results of the distribution of the impact pressure Psh with respect to the standoff distance x.
The relationship curve of the non-dimensionalized standoff distance to the non-dimensionalized impact pressure of the first embodiment is shown, and the curve 87 is the relationship curve of the non-dimensionalized stand-off distance to the non-dimensionalized impact pressure of the prior art. Show. The standoff distance x on the horizontal axis is divided by the standoff distance x * corresponding to the "first peak" in the prior art to make it dimensionless. Impact pressure Psh on the vertical axis
Also, the impact pressure Psh at the “first peak” of the conventional technique
It is expressed dimensionlessly based on *. Generally Psh / Psh
The curve of * has a distribution shape having two peaks as is clear from the figure, and the first peak near the nozzle is x / x
It shows sharp characteristics in the narrow range of *. On the contrary, the second peak in the downstream shows a fairly gentle shape. When the water jet nozzle 1 according to the embodiment of the present invention is used, Psh / Psh in the entire x / x * region.
It can be seen that the level of * is much higher and the cavitation is more powerful over the entire area than the curve 87 of the prior art. Also, the standoff distance x corresponding to the first peak
Although / x * is not much different from that in the conventional technique, x / x * corresponding to the second peak is shifted downstream.

FIG. 16 is a bar graph for explaining the effect of removing deposits on the surface to be treated, and shows the effect of removing deposits in comparison with the prior art. Ratio Δm / m of mass Δm of deposit remaining after treatment to mass m ₁ of deposit as initial condition
Evaluate as ₁ . Each bar shows the amount of deposits on the surface to be treated, rod 90 is the amount of deposits before treatment, and rod 91 is the rod 92 when the water jet nozzle 1'of FIG. 18 is used.
19 is used, when the water jet nozzle 1'of FIG. 19 is used, the rod 93 is the water jet nozzle 1'of FIG. 20, and when the water jet nozzle 1'of FIG. Is used.
The value at the head of each rod is the amount of adhesion Δm / m ₁
Indicates the value of. From the results of this test, even in the prior art shown in FIGS. 18, 19 and 20, the adhered amount Δm / m ₁ is greatly reduced and the adhering matter can be removed. However, according to the embodiment of the present invention, It was confirmed that the adhesion amount Δm / m ₁ can be significantly reduced. The applied amount Δm / m ₁ when the present invention is applied is 1/10 of that in the case of the rod 91.
It is the following.

All the above-mentioned actions promote cavitation. By using the means according to the present invention, the turbulence of the interface of the underwater water jet immediately after jetting from the water jet nozzle, that is, the generation of shear vortices is promoted, and the generation of large-scale vortices inside the jet is also promoted. The action of these turbulences triggers the supply of bubble nuclei through the turbulence at the jet interface. As a result, vortex cavitation that strongly acts on the material is activated. Stepped steps on its inner wall in the enlarged section,
The dimensions of the annular groove and the orifice, which is the narrowed portion at the outlet of the enlarged portion, are conditions that most promote the supply of vortices, turbulence, or cavitation nuclei in the optimum range described above.

As another embodiment, the present invention can be applied to marine vessels. Shells, algae, and other organisms attach to the bottom of the ship below the sea level, which causes considerable resistance to the cruise. The water jet nozzle according to the present invention,
Allows these deposits to be removed during marine navigation. If fouling can be removed in seawater in this way, a series of operations such as putting the boat in the dock, pumping seawater from the dock, discarding the wash water containing fouling, and then reintroducing seawater into the dock are all omitted. Will be
Maintenance and maintenance of ships will be carried out more economically.
If the use of special paint used to prevent deposits is reduced, it is preferable from the viewpoint of marine environment protection. In particular, it is possible to prevent marine pollution due to organic tin compounds near the dock.

Although the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited only to those embodiments by using the embodiments, and various modifications can be made without departing from the spirit of the present invention. In addition, it goes without saying that various modifications can be made.

[0056]

According to the first aspect of the present invention, in the water jet nozzle having the ejection hole for ejecting the high-pressure water and the enlarged portion gradually expanded and extended from the outlet of the ejection hole, the inner wall of the enlarged portion is provided. Since at least one step-like step is provided in the,
Generates separation vortices in a chain. This separation vortex complicatedly interferes with the shear vortex generated between the expanded part and the water jet, so many small low pressure parts are generated at the interface of the underwater water jet,
Cavitation is greatly promoted. As a result, the following effects are achieved.

(1) Since the spread of the underwater water jet accompanied by cavitation becomes large, it is possible to treat a wide portion of the surface to be treated.

(2) Since the cavitation generated in the water jet is significantly developed, the treatment can be completed in a short time, the treatment efficiency is improved, and the treatment cost is reduced.

(3) In the peening process, since strong cavitation with a large impact pressure can be used,
The strengthening of the surface to be treated extends from the surface layer to a deeper portion. Therefore, the surface to be treated can be efficiently strengthened.

(4) Since cavitation is promoted in the flow after the ejection holes of the nozzle body, there is no problem due to an increase in pressure loss such that the ejection holes are filled with cavitation bubbles and blocked.

According to the second aspect of the present invention, since at least one annular groove is provided on the inner wall of the enlarged portion, the non-condensable gas trapped therein is contained in the annular groove on the inner wall of the enlarged portion. Cavitation is greatly promoted by the fact that they are separated one after another and become fine bubbles and are entrained in the jet flow. Therefore, the same effects as the items (1) to (4), which are the effects of the first invention, can be obtained.

According to the third aspect of the present invention, since the narrowed portion is provided at the outlet of the enlarged portion, the defoaming bubbles generated by this narrowed portion violently disturb the interface of the underwater water jet and activate the generation of shear vortices. The powerful vortex cavitation that exerts a strong influence on the surface to be treated is developed, and, like the second invention, the same effects as the items (1) to (4) which are the effects of the first invention are exhibited.

According to the fourth invention, the first invention or the second invention is provided.
In the invention, since the narrowed portion is provided at the outlet of the expansion portion, the expansion of the separation vortex in the step-like step or the entrainment of the non-condensable gas trapped in the annular groove into the jet flow of the microbubbles is increased. Separation bubbles generated by the throttle attached to the tip of the section violently disturb the interface of the underwater water jet, actively generating shear vortices at the disturbed jet interface,
Cavitation is greatly promoted, and the same effects as the first invention or the second invention are more reliably exhibited.

According to the fifth aspect of the present invention, the sectional shape perpendicular to the central axes of the enlarged portion and the ejection hole is circular, and the outlet inner diameter of the enlarged portion is 15 to 25 times the inner diameter of the ejection hole. Cavitation can be greatly promoted by various means.

According to the sixth aspect of the present invention, in any one of the first to fourth aspects of the present invention, a stepped step or an annular groove is provided on the inner wall of the enlarged portion, and a narrowed portion is provided at the outlet of the enlarged portion. By making the cross-sectional shape perpendicular to the central axis of the ejection hole circular and the outlet inner diameter of the enlarged portion 15 to 25 times the inner diameter of the ejection hole, the effect of any one of the first to fourth inventions can be more surely achieved. To play.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first embodiment of a water jet nozzle according to the present invention.

FIG. 2 is a sectional view of a second embodiment of the water jet nozzle according to the present invention.

FIG. 3 is a sectional view of a third embodiment of the water jet nozzle according to the present invention.

FIG. 4 is a cross-sectional view of a fourth embodiment of a water jet nozzle according to the present invention.

FIG. 5 is a cross-sectional view of a fifth embodiment of a water jet nozzle according to the present invention.

FIG. 6 is a sectional view of a sixth embodiment of the water jet nozzle according to the present invention.

FIG. 7 is a side view showing the relationship between the underwater water jet and the surface to be treated.

FIG. 8 is a side view illustrating an underwater water jet in the first embodiment of the present invention.

FIG. 9 is a side view illustrating an underwater water jet in the fifth embodiment of the present invention.

FIG. 10 is a side view showing a measurement positional relationship between a first peak and a second peak of an underwater water jet.

FIG. 11 is a side view illustrating a method of capturing an outline of an underwater water jet.

FIG. 12 is a relationship curve diagram between an injection pressure and an injection diameter at a first peak of an underwater water jet.

FIG. 13 is a relationship curve diagram between an injection pressure and an injection diameter at a second peak of an underwater water jet.

FIG. 14 is a side view showing a method for measuring an impact pressure of an underwater water jet.

FIG. 15 is a relationship curve diagram between a standoff distance and an impact pressure.

FIG. 16 is a bar graph for explaining the effect of removing deposits on the surface to be processed.

FIG. 17 is a side view illustrating cavitation of an underwater water jet.

FIG. 18 is a cross-sectional view of a water jet nozzle according to a conventional technique.

FIG. 19 is a cross-sectional view of another water jet nozzle according to the related art.

FIG. 20 is a cross-sectional view of a water jet nozzle used for an underwater water jet according to a conventional technique.

FIG. 21 is a side view for explaining the action of the water jet nozzle used for the underwater water jet in FIG. 20.

[Explanation of symbols]

 1 Nozzle for Water Jet 5 Central Axis 8 Ejection Hole 9 Outlet Hole Inner Diameter 10 Outlet of Ejection Hole 12 Expanded Portion 13 Expanded Portion Exit 15 Inner Wall 20 Stepped Step 24 Annular Groove 30 'Orifice (Throttle Portion) 38 High Pressure Water

Claims (6)

[Claims] 1. A water jet nozzle comprising a jet hole for jetting high-pressure water and an enlarged portion gradually enlarged and extended from an outlet of the jet hole, wherein at least one staircase is provided on an inner wall of the enlarged portion. Nozzle for water jet characterized by having a stepped shape. 2. A water jet nozzle comprising a jet hole for jetting high-pressure water and an enlarged portion gradually enlarged and extended from an outlet of the jet hole, wherein at least one annular ring is formed on an inner wall of the enlarged portion. A water jet nozzle characterized by having grooves. 3. A water jet nozzle comprising a jet hole for jetting high-pressure water and an enlarged portion gradually enlarged and extended from the outlet of the jet hole, wherein a narrowed portion is provided at the outlet of the enlarged portion. Nozzle for water jet characterized by. 4. The water jet nozzle according to claim 1, wherein a narrowed portion is provided at the outlet of the enlarged portion. 5. A water jet nozzle comprising a jet hole for jetting high-pressure water and an enlarged portion gradually enlarged and extended from an outlet of the jet hole, wherein the jet hole and a central axis of the enlarged portion are perpendicular to each other. The cross-sectional shape is circular, and the inner diameter of the outlet of the enlarged portion is 15 to 25 times the inner diameter of the ejection hole. 6. The cross-sectional shape perpendicular to the central axis of the ejection hole and the enlarged portion is circular, and the outlet inner diameter of the enlarged portion is 1 of the ejection hole inner diameter.
Nozzle for water jet, which is 5 to 25 times.