JPH0647671A - Nozzle for cavitation jet - Google Patents

Abstract

PURPOSE:To reform the surface stress condition of an under-water metallic material efficiently by providing injection openings to form a straight jet and a rotary jet rotating around the straight jet. CONSTITUTION:At the ambiance of the water jet injected from a central exhaust nozzle 7, small exhaust nozzles to exhaust jets having a large rotation speed components are arranged in a circular form at the outer side of the central exhaust nozzle 7, or a circular slit 12 with small opening area is provided. By adding a strong rotating jet from the circular slit 12 to the straight jet from the central exhaust nozzle 7, a shearing whirlpool array to be the producing positions of cavitation bubbles at the border of both jets is generated very actively. The cavitation jet generated in such a way is applied to the surface of a steel material which requires a peening process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface modification technique for a metal material, and irradiates a surface of the metal material with a high-speed water jet accompanied by a cavitation in water, and the collapse pressure of the cavitation bubbles generated in the water jet is used. The present invention also relates to a nozzle for a cavitation jet, which is intended to treat a surface of a metallic material on which tensile stress remains so that a compressive stress acts.

[0002]

2. Description of the Related Art Residual stress of an existing structural material is treated by peening with a shot blast that blows a steel ball with the force of an air stream, a sand blast that uses sand grains, a cryoblast that uses ice grains, and the stress is applied in the tensile direction ( It is modified from the direction of expanding cracks) to the direction of compression. Such a peening technique is widely used as a measure against residual stress when processing various mechanical structures or parts.

However, there are many structures that must be peened by all means in such an environment where blasting cannot be performed. For example, the nozzle portion of an aged reactor pressure vessel and an offshore structure are both in water, and it is physically or economically impossible to perform treatment by removing water. In the reactor pressure vessel, a large amount of radioactivity is released when water is drained. Moreover, collecting blast particles is also a difficult task. If ice particles are used, no recovery is necessary,
It is difficult to get an economic advantage.

The use of high speed water jets is widely known as a unique processing, mining or cleaning technique,
An attempt to utilize this for surface stress modification was made by Westinghouse (Japanese Patent Laid-Open No. 62-63614). Peening with a water jet has the merit of preventing local temperature rise due to the effect of water cooling. However, this is an operation in the atmosphere that can effectively use the axial dynamic pressure of the water jet, and there is no guarantee that this technology can be directly applied as a peening technology by an underwater water jet.

As shown in FIG. 19, in water, the damping of the jet axial dynamic pressure is fairly fast. This is because the diffusion is fast because it is in phase with the resistance of ambient water. In order to obtain an axial dynamic pressure similar to that of a gas-phase water jet in water, an ultrahigh pressure generator is required, which is a very disadvantageous technique in terms of cost.

On the other hand, in the underwater water jet, cavitation occurs due to the shearing action of the jet and the surrounding water. If the cavitation is well controlled and the generated bubbles can be used effectively, there is a possibility that an effect similar to that of a water jet in a gas phase can be realized at a low injection pressure.

[0007]

The problem shown in FIG. 20 is as follows.
This is a typical structure of a nozzle used for water jet processing. This nozzle is intended to make the water flow into a beam in the gas phase, and even if it is used as an underwater water jet, cavitation is unlikely to occur. The reason is that the squeezing angle θ of the contracting portion 1105 is small and the pressure reducing action here is too gradual.

In addition, the outer surface of the water jet has little turbulence, and the shear vortex-induced cavitation is difficult to occur, or even if the cavitation occurs, the cavitation development is unstable because the cavitation is intermittent and reproducible. This is because.

In the figure, 1101 is a water jet nozzle body, 1102 is high-pressure supply water, 1103 is a water supply parallel portion, 1104 is a nozzle center axis, 1106 is an ejection hole, 1
107 is water injection, 1108 is a solid surface of the workpiece,
1109 is water around the object to be processed.

The prior art shown in FIG. 21 (Japanese Patent Laid-Open No. 61-81)
No. 84) discloses an attempt to remove adhered contaminants by the action of a cavitation generated in a jet of water in water.

In the figure, 1201 is a water tank, and 120
2 is a part to be cleaned, 1203 is a nozzle, 1203a is nozzle cleaning, 1203b is an ejection hole, 1204 is water, and 1205.
Is a pipeline.

The prior art shown in FIG. 22 (JP-A-60-16)
The nozzle of Japanese Patent No. 8554) is a nozzle developed for various operations in water, and the use of a cavitation is claimed.

In the figure, 1301 is a nozzle body,
1302 is an orifice part, 1303 is a conical opening part, 13
Reference numeral 04 is a conical hollow portion, 1305 is a pipe member, 1306 is a high-pressure injection device, and 1307 is an injection processing object.

In these examples, there is a limit in the structure of the nozzle even if it is attempted to actively generate the cage. In order to promote the cavitation, it is necessary to create a strong turbulence in the water flow in the nozzle or to forcibly supply the cavitation bubble nucleus.

FIG. 23 shows a structural example of a self-resonant cavity phenomenon promoting type nozzle. In this nozzle, a self-resonance phenomenon is generated by a cavity 1403 provided in the nozzle, and the cavitation generated in the water jet in the gas phase is used to improve the cutting efficiency. The problem with this nozzle is
Because cavitation occurs in the nozzle, the nozzle becomes a bubble lock state (actually, the bubble lock state and the phenomenon that only water without bubbles is ejected repeats according to the resonance frequency), which causes an increase in pressure loss and causes the water flow. Pulsates violently (oscillation in the cavity feeds back to the upstream side and becomes a self-oscillating state).

In these figures, 1401 is water,
1402 is a nozzle body.

Further, like the nozzle whose structure is shown in FIG. 22,
With a conventional nozzle intended to narrow a water jet into a beam for processing various materials in the atmosphere, even when used for peening in the atmosphere, as shown in FIG. Since it is extremely local, it cannot be said that the peening efficiency is high because it takes a long time for construction.

In FIG. 24, 1701 is a high-pressure water jet nozzle, 1702 is high-pressure water, 1703 is a gas-phase water jet, 1704 is an object to be processed, 1705 is pressure distribution, 1
706 is a central axis.

That is, as shown in FIGS. 26 (a) and 26 (b), in order to peen the entire peening required portion 1901, the peening pressure generating portion 1909 is the locus 190.
The nozzle must be moved violently so that it looks like 5. The structure of the tip of the manipulator to which the nozzle is attached will also be complicated.

When water is jetted from a conventional nozzle as shown in FIG. 22 in water, that is, in the case of an underwater water jet, the damping of the on-jet dynamic pressure in water is extremely fast. FIG. 19 shows the comparison with the characteristics in the gas phase. On the other hand, in such an underwater water jet 1803, a vortex cavitation 1804 caused by a shear type vortex is generated on the outer periphery of the jet. FIG. 25 schematically shows such an aspect. In the case of the conventional nozzle, the turbulence due to the vortex is weak, the generation of the cavitation is insufficient and unstable, and the pressure distribution 1806 generated by the collapse of the cavitation bubbles is , A donut shape around the central axis 1807.

In the figure, 1801 is a water jet nozzle, 1802 is high-pressure water, and 1805 is an object to be pressurized.

As described above, in water, the axial dynamic pressure of the jet flow is low, and the pressure distribution inevitably becomes "middle void". If the cavitation bubbles are remarkably active, the bubbles on the outer circumference are entrained (entrained) in the center of the jet flow, but with the unstable cavitation as shown in FIG. 25, the entrainment work cannot be expected easily. As shown in FIGS. 26 (c) and 26 (d), the peening point 1 required
In order to install 903 evenly, the nozzle must also be traversed in a fairly complicated manner. Examples of moving the nozzle like a pendulum are shown in (a) and (c), and examples of reciprocating the nozzle are shown in (b) and (d).

Numerals 1902 and 1904 are required peening points, 1906 to 1908 are movement loci of nozzles, 191
0 is a peening pressure generation part.

In the prior art shown in FIG. 27, the ejection hole of the nozzle is
An air suction pipe 2002 that utilizes a suction action by accelerating a water flow is provided, and outside air is sucked and mixed into high-pressure water 2004 to create a gas-phase two-phase jet flow 2005 including bubbles. In this case, it is convenient if the sucked air bubbles act as a cavitation, but if it becomes a "cushion" -like buffering action, it is counterproductive to peening. When the peening part is deep in the water, a long air suction pipe is not practical.

Reference numeral 2001 denotes an annular nozzle body, 200
3 is air.

It is an object of the present invention to provide a nozzle for jetting a cavitation which causes less adverse effects due to the occurrence of the cavitation.

[0027]

[Means for Solving the Problems]

1. In the present invention, small jet holes for jetting a jet having a large swirl velocity component are arranged in an outer annular shape of the central jet hole, or the outer surface of the water jet for jetting the high-speed water jet from the central jet nozzle is arranged in an annular shape outside the central jet hole. A nozzle with a small annular slit is used.

When a strong swirl jet is added to the straight water jet from the central jet hole, a shear vortex train, which is a generation point of the cavity bubble, is extremely actively generated at the boundary of these jets.
The cavitation jet generated in this way is applied to the surface of the steel material requiring peening.

2. The present invention utilizes an underwater water injection nozzle that produces two different types of cavitations and combines them in an underwater jet.

In the nozzle according to the present invention, first of all, 1) a main jet is generated from a jet hole that opens on the main axis (central axis). 1) A separation bubble cavitation is generated. In order to forcibly add a swirl to the main jet, a plurality of swirl jet holes that open in the swirl direction toward the center are provided outside the main spindle jet holes. Large flow velocity from here (close to 4 times the main jet flow velocity)
Then, a swirling jet is created around the main jet, and a large-scale 2) vortex cavitation is generated. When the different cages 1) and 2) are interfered with each other in the jet, the bubble nuclei in the water are sequentially excited by the interaction, and a developed jet jet is formed. This enables highly efficient underwater peening. 3. The present invention provides a plurality of thin pipes for sucking environmental water around the nozzle by the action of an ejector to the depressurizing portion, that is, the squeezing portion of the nozzle that jets a high-speed water jet into the water. The squeezed portion is opened so as to communicate with each other. In the nozzle of the present invention, when water is injected under high pressure in water, ambient water is sucked through the thin suction communication pipe. This sucked water mixes with the water supplied from the high-pressure pump in the squeezing part of the nozzle, where strong turbulence occurs in the water flow. Due to the above action, the cavitation of the underwater water jet is remarkably promoted.

[0031]

[Action]

1. When a strongly swirling water jet is supplied to the outer periphery of a high-speed water jet that travels straight on the central axis of the submerged nozzle, a part of the outer swirling water jet flows backward, creating a strong shear layer between the jet water jet and the straight water jet. Occurs and vortices are generated in this shear layer. A cavity bubble is actively generated from the center of this vortex. This creates a fully developed cavitation jet with high bubble formation density.

Further, the swirling water flow on the outer periphery creates a large backflow that is caught from the downstream side to the center of the straight water jet on the central axis, downstream of the cavitation jet. Due to such a large backflow vortex, the cavitation bubbles generated in the vortex portion in the shear layer are not only diffused to the outside of the cavitation jet but also diffused to the entire cavitation jet.

By the mechanism as described above, a cavity jet having a large spread, a large number density of bubbles per unit space, and a uniform dispersion of bubbles is created. In this nozzle, the pressure loss does not increase because the cavitation is developed in the jet flow after jetting from the nozzle.

By using the cavity jet generated in this way for peening, it is possible to peening a large area steel material surface at a time in a short time, thereby achieving high efficiency of peening work.

2. First, in the ejection hole on the central axis, the water flow is separated from the inner wall of the ejection hole due to the sudden depressurizing action in the ejection hole, and 1) a separation bubble cavitation occurs. This is a small slag-like bubble flow cavitation, which is ejected from the ejection hole so as to be pushed out by the force of the water flow. On the other hand, there is a decompression part in the strong and large vortex generated by the swirling water flow, so there is a 2) vortex cavitation. 2) is generated slightly downstream from 1) at a position slightly away from the nozzle, but immediately interferes in the underwater water jet. The collisions of bubbles 1) and 2) and the impact of coalescence trigger the other bubbles nuclei in the water to be excited, and the chains are amplified in a chain. In addition, a shear vortex cavitation derived from a shear vortex also occurs on the outer circumference of the water jet. In this way, the underwater water jet becomes a developed compound type jet jet.

The swirling jet has the effect of spreading the underwater water jet by its centrifugal force. In addition, the spreading underwater water jet,
Entrain ambient water into its own jet. Further, due to the swirling jet flow, a large circulation flow is generated on the downstream side of the water jet flow. By combining such flow patterns, the cavitation bubbles are uniformly diffused (dispersed) inside the water jet. With the above-described actions, the jet flow having a large spread is filled with the bubbles, and a cavity jet flow suitable for underwater peening is realized.

3. When the sucked water mixes with the mainstream jet water in the nozzle jet holes and is jetted from the nozzle, the underwater jet jet becomes violently disturbed from the inside. In this way, this submerged water jet generates a lumpy bubble type cavitation from inside the jet in addition to the vortex cavitation generated around the jet. These two types of cavities synergistically amplify each other (when bubbles occur, the surrounding bubble nuclei are excited).
Therefore, the jet flow becomes a well-developed cavitation flow.

Further, the cavitation bubbles become more evenly distributed in the transverse cross section of the jet flow (compared with the state of FIG. 25), so when they hit the surface of the structure, they spread over a large area. Such impact pressure will be generated.

As described above, it can be said that the cavitation jet from the nozzle according to the present invention is suitable for efficiently removing the residual stress particularly over a large area.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a structure of a nozzle for cavitation jet according to the present invention as a sectional view passing through a central axis. FIG. 2 shows the structure of the nozzle as a front view. The main high-pressure supply water 2 is guided to the nozzle center axis 5 of the nozzle body 1 through the high-pressure water flow path 4. The main high-pressure supply water 2 is decompressed and accelerated by the diameter contracting portion 6, and is injected from the main ejection hole 7 into the water as an axially straight forward high-speed water flow having a flow velocity of at least 40 m / s. The outlet of the main ejection hole 7 serves as an outlet expansion portion 8 whose diameter gradually increases. The outer periphery high-pressure supply water 3 is supplied through a plurality of outer periphery high-pressure water supply passages 9 provided outside the high-pressure water passage 4, merges with the swirl water flow header 10, and then opens toward the water from the swirl ejection hole 11. It is guided to the swirling flow jetting slit 12 and is jetted at high speed into the water with a strong swirling component.

The velocity of the axial component of this swirling jet is considerably smaller than the velocity from the main jet hole 7, and is about 1/10.
Is. However, the turning speed component is large. The swirling high-speed water jet from the swirling jet jet is guided by the swirling flow guide 13 so as to be slightly outward with respect to the nozzle center axis 5. Therefore, the axially straight high-speed water flow and the swirling high-speed water jet do not mix immediately after jetting from the nozzle.

The structure of a nozzle according to another embodiment based on the same idea is shown in FIG. 3 as a sectional view passing through the central axis.
4 is a front view. Nozzle body 3
The main high-pressure supply water 302 is guided on the nozzle central axis 5 of 01. The main high-pressure supply water 302 is decompressed and accelerated in the diameter contraction portion, and is injected into the water from the main ejection hole 307 as a high-speed water flow. The outlet of the main ejection hole 307 forms an enlarged portion 308 that gradually widens the diameter, as in the embodiment shown in FIG. The high pressure water is supplied through the outer circumference high pressure water supply flow path 309, and the swirling water flow header 310 joins the high pressure water supply flow path 309.
The water is jetted into the water through a plurality of swirl jet holes 311 opening at the outlet of 01. In order not to mix the axially straight high-speed water flow from the main jet holes 307 and the swirl high-speed water flow from the swirl jet holes 311 immediately after jetting (the reason will be described later),
The swirl flow guide 312 for directing the jet direction from the swirl jet hole 311 to the outside slightly is provided with the outlet expansion portion 30 of the main jet hole.
It is provided outside the nozzle body 8 so as to slightly project from the nozzle body 301.

In the figure, 303 is high-pressure outer peripheral water supply, 304 is a high-pressure water channel, 305 is a central axis of the nozzle, and 30 is a central axis.
6 is a diameter contraction part.

In the above embodiment, the flow rate ratio between the axially straight high-speed water jet and the swirling high-speed water jet is approximately 3: 7 to 4 :.
Set the range up to 6. This flow distribution is convenient for promoting cavitation and controlling the jet shape.

5 and 6, the injection unit (pump) is shown.
The water supply system from the nozzle to the injection nozzle is schematically shown.
The example of FIG. 5 is a type in which two jetting units are used to independently adjust the flow rates of the axially straight traveling high-speed water flow and the swirling high-speed water flow.

In the figure, 501 is a nozzle body,
502 is an injection gun, 503 and 504 are high pressure water supply pipes, 5
Reference numerals 05 and 506 are pressure regulating valves, 507 and 508 are injection units, 509 is a cavitation jet, 510 is an object to be processed, and 511 is ambient water. On the other hand, in the type shown in FIG. 6, the high-pressure water supply pipe from one injection unit is branched and the respective flow rates are distributed by the pressure regulating valve. The adjustment of the flow rate is easier in the example of FIG. 5, but the type of FIG. 6 is more advantageous in terms of the cost of the device.

In the figure, reference numeral 601 denotes the nozzle body,
602 is an injection gun, 603 and 604 are high pressure water supply pipes, 6
Reference numerals 05 and 606 are pressure regulating valves, 607 is an injection unit, 608.
Is a jet jet, 609 is an object to be processed, 61
0 is ambient water.

FIG. 7 is a cross-sectional view schematically showing the flow pattern of the water flow injected into the water from the cavitation jet nozzle according to the present invention. A shear layer vortex 7c due to a strong shear flow is formed between the central straight jet 7g jetted on the central axis 704 of the nozzle and the outer circumferential swirl jet 7a which is swirled toward the outer periphery and is jetted slightly outward.
Is formed.

The shear layer vortex 7c is generated between the outer circumference of the central straight jet 7g and the backflow 7b from the outer swirl jet 7a. Inside the shear layer vortex 7c, a vortex type cavity generation region 7d is formed, in which a large number of bubbles having a relatively large diameter and a high impact pressure at the time of disappearance are generated. Conventional nozzle (Fig. 2
In 0), as compared with the intermittent cavitation that occurs, the bubbles in the nozzle according to the present invention are extremely actively, continuously and stably generated. The generated bubbles are entrained in the outer peripheral swirl flow and once move to the outside downstream, but are entrained in the circulation flow 7f from the outside and flow back into the cavitation jet.

Such a vortex type cavitation has a strong pressure propagating force and gives a trigger to the bubble nucleus in the water inside the jet flow. Therefore, a large number of cavitation bubbles are generated in a chain so as to fill the inside of the jet. Big swirling flow 7
The e and the resulting circulating flow 7f from the outside have a function of diffusing the cavitation generated in a part of the jet flow into almost the entire flow field of the jet flow.

As described above, when the cavity jet nozzle according to the present invention is used, the cavity bubbles are uniformly dispersed in the jet. That is, it is possible to create an optimum jet flow for peening. In addition, since the nozzle for jetting the cavitation according to the present invention creates the cavitation in the water flow after jetting from the nozzle,
No pressure loss occurs in the nozzle due to so-called bubble lock (blockage of bubbles in the nozzle). That is, the burden on the high-pressure injection pump does not increase.

In the figure, 701 is a nozzle body,
702 is the main high pressure supply water, 703 is the outer high pressure supply water, 70
Reference numeral 5 denotes an outlet enlarged portion of the main ejection hole, 706 denotes a swirling flow ejection portion, and 7
Reference numeral 07 is a swirling flow guide.

FIG. 8 compares the profile and impact pressure distribution of the cavitation jet in the nozzle according to the present invention with those in the conventional nozzle. The profile a of the cavitation jet when the nozzle according to the present invention (nozzle body 801) is used has the characteristic that the swirl flow spreads the air bubbles uniformly inside the jet as described above. Therefore, the collision pressure distribution c on the collision surface (solid surface) 802 is divergent, and there is no so-called dent portion where the collision pressure decreases at the center of the jet axis. On the other hand, the profile b of the cavitation jet when using the conventional nozzle is considerably thin, the pressure distribution d with respect to the collision surface (solid surface) is not wide enough, and bubbles are generated on the outer periphery of the jet, so that it is a double shoulder type. The shape becomes hollow in the middle. From the viewpoint of peening efficiency, the nozzle of the present invention, which has a uniform pressure distribution and a large spread, is more advantageous. This is because a large area can be processed by one irradiation.

FIG. 9 shows the experimental results of examining the effect of modifying the residual stress in the pipe. Even when the conventional nozzle is used, the effect of modifying the surface stress until the component in the tensile direction is substantially eliminated is obtained, but the effect of modifying the stress in the tensile direction to the compression side is not sufficient.

On the other hand, it can be seen that the use of the nozzle embodying the present invention has the effect of significantly modifying the residual stress toward the compression side. In the conventional nozzle, the cavitation is not sufficiently developed, whereas in the nozzle according to the present invention, the collapse pressure of the bubbles in the developed cavitation jet is strong, so that a remarkable stress reforming effect is obtained. Thought to be

The present invention utilizing the collision pressure due to the high-speed water flow in water and the bubble collapse pressure due to the cavitation is
The present invention can be applied to other than the special heat exchange container or the surface stress modification for preventive maintenance of the chemical reaction tank described in the embodiment. Generally, for surface stress modification, it is much more preferable to perform the treatment at room temperature without applying heat, that is, without the transformation of the metal structure. From this point as well, the present invention is advantageous,
It can also be applied to surface stress modification of pressure resistant members of boilers (thermal power). Further, considering that it is an underwater operation, it can be applied to marine structures and ships in seawater. Shells, algae, and other small organisms adhere to the bottom of the ship below the sea level, resulting in considerable flow resistance to traveling.However, in the present invention, it is necessary to remove these adhered substances in sea water. to enable. If removal of attached organisms is possible in seawater, (1) ship is put in the dock, (2) seawater is pumped out of the dock, (3) wastewater containing adhering substances is discarded, and (4) ) Add seawater to the dock again.

The series of operations described above will be omitted altogether, and the maintenance of the ship will be carried out more economically. It is preferable from the viewpoint of protection of the marine environment if the amount of the special paint used for removing the deposit is reduced.

FIG. 10 shows a composite cavitation nozzle according to the present invention as a vertical cross-sectional view passing through the central axis of the composite cavitation nozzle. FIG. 11 shows the opening structure of the ejection holes of this composite cavitation nozzle as a view looking from the downstream side to the upstream direction. The high-pressure water 201 for supplying the central shaft is supplied through the high-pressure water passage 208 for supplying the central shaft, and the diameter contracting portion 2
It is decompressed at 09 and is ejected from the spindle ejection hole 210. The main-shaft ejection hole 210 opens on the central axis of the slightly recessed surface of the tip of the nozzle body 203. In the main shaft ejection hole 210, a peeling type cavity is generated on the inner wall thereof. The swirling supply high-pressure water 202 is guided to an annular swirl supply high-pressure water flow passage 206 around the central axis supply high-pressure water flow passage 208.

The high-pressure water 202 for swirl supply is jetted into the water from the eight swirl ejection holes 211 at a tilt angle θ ₁ = 40 ° with respect to the nozzle center axis 207 and at a swirl angle θ ₂ = 60 ° into the main shaft. Creates a strong swirling flow around the jet.
High-pressure water 20 for central axis supply, which is ejected from the main axis ejection hole 210
The main jet velocity Uj of 1 and the swirl velocity Uc of the swirling supply high-pressure water 202 jetted from the swirl jet hole 211 are set within the range of 1.2 <Uc / Uj <8.0 (1). To be done. However, the preferable injection condition in the actual work is Uc / Uj ≦ 4.0 (2). The reason why the swirl jet flow velocity Uc is set to be four times as large as the spindle jet flow velocity Uj is to give a strong swirl to the spindle jet flow and forcibly generate the cavitation in the vortex flow. Although the flow velocities from the main spindle ejection hole 210 and the swirl ejection hole 211 are greatly different, the ejection flow rates are substantially equal to each other. Based on these conditions, the main shaft ejection hole 21
0 and the ejection hole diameters of the swirl ejection holes 211, and the injection pressures of the central axis supply high-pressure water 201 and the swirl supply high-pressure water 202 are set. The spindle ejection hole 210 is the swirl ejection hole 2
The opening is made at a location that is recessed upstream from the opening position of 11 by hi.

Initially, it was intended to create a vortex cavitation by a swirling flow at this recessed portion. However, it was found that the vortex flow cage could actually be formed at a position slightly distant from the nozzle toward the downstream side.
A vortex flow cage is provided in the hollow portion of the main shaft ejection hole 21.
At present, it is known that it has an effect of preventing collision due to backflow to zero. The distance hi between the spindle ejection hole 210 and the swirl ejection hole 211 and the diameter Dc of the opening circle of the swirl ejection hole 211 are determined so that the relationship of 1/8 <hi / Dc <1/2 (3) holds. To do. Within this range, a structure that satisfies hi / Dc ≦ 1/4 (4) forms a swirling water flow, promotes cavitation,
Alternatively, it is preferable from many viewpoints such as ease of processing.

In the figure, reference numeral 204 is a high pressure water supply gun, 205 is a lock nut, and 212 is a conical concave portion at the nozzle tip.

FIG. 12 schematically shows a flow pattern of a water flow injected into water from the composite cavity nozzle according to the present invention. This flow pattern is characterized by the strong swirling force 204a generated by the swirling jet 215, and the main jetting holes 210 as well as the swirling jet 215 itself.
The main axis (center axis) jet flow 214 injected from the main axis (center axis) direction also spreads downstream due to the centrifugal force due to the swirling (204b).

It is important for such a characteristic that the jet flow spreads, and the bubbles generated near the nozzle or in the center of the swirling vortex diffuse (disperse) throughout the jet flow. On the other hand, the widened jet entrains ambient water into the jet (204c). Furthermore, at this point, a shear vortex that occurs at the interface between the jet and the ambient water 213 (this is smaller than the swirl flow 204a due to the water jet spouting from the swirl jet holes, but the jet and the ambient water 213
A lot of them are generated at the boundary between and) Shear vortex type cavitation. Since a strong swirling force is applied to the jet flow itself, a large-scale circulation flow 204d is generated downstream. Although this large-scale circulation flow 204d acts in a direction to suppress the collision pressure of peening, it has the effect of evenly distributing the cavitation bubbles throughout the jet flow.
It plays a very important role. Due to the effect of the flow field as described above, a jet flow in which the cavitation having a large spread is evenly dispersed in the entire inside thereof is created. FIG. 13 is a schematic drawing of the appearance of the cavitation in the nozzle and the water jet. First,
In the main shaft ejection hole 210, the water flow is separated from the inner wall of the main shaft ejection hole 210 due to the rapid pressure reducing action in the diameter contraction portion 209 and the contraction flow in the main shaft ejection hole 210, and the separation bubble type cavitation 205a is generated. This cavitation is a combination of small slag-like bubbles, and when it is generated in the main shaft ejection hole 210, it is ejected into the underwater water jet so as to be pushed out to the downstream one after another.

Further, a low-pressure cavity is also generated in the vortex generated by the swirling jet flow 215, and a vortex type cage is generated by the effect of pressure fluctuation due to strong turbulence (205b).

Although this cavitation occurs slightly downstream of the above-described peeling type cavitation 205a, they mix in the vicinity of the main shaft ejection hole 210 and interfere with each other. The cavitation is triggered by coalescence or repulsion caused by the collision of bubbles, and rapid pressure fluctuation propagates to nearby water, exciting even stable bubble nuclei that have merged in the water, and the cavitation is significantly promoted. Shear vortex cavitation is also generated on the outer circumference of the jet (205).
c).

These cavitation bubbles are shown in FIG.
As described above, the centrifugal action 204b of the swirl flow, the entrainment of ambient water 204c, and the action of the large-scale circulation flow 204d generated on the downstream side of the jet flow diffuse the water into the entire underwater jet flow.

In the figure, 205d is diffusion of cavitation bubbles into the jet, and 205e is a shear vortex on the outer circumference of the jet.

FIG. 14 shows the contour of the underwater water jet and the distribution of impinging pressure in the composite cavitation according to the present invention in comparison with those in the conventional nozzle (FIG. 20).
It can be seen that the composite cavitation nozzle according to the present invention has a larger jet spread than the conventional nozzle, and the impact pressure distribution is considerably wider and more even. The peak of the collision pressure is slightly higher in the conventional nozzle, but this is due to the direct jet pressure of the water flow rather than the effect of the cavitation because the water jet is constricted in the shape of a beam. It is believed that

FIG. 15 shows the structure of a nozzle for an underwater water jet,
It is shown as a sectional view passing through the central axis. High pressure water 1
02 is supplied to the upstream side of the nozzle body 101 through a high-pressure water conduit 104 that opens as a water supply unit, and is decompressed and accelerated in the nozzle contracting unit 106, so that the nozzle ejection hole 10
7 is injected into the ambient water 110. At the exit of the nozzle ejection hole 107, a slightly nozzle advancing hole 108 is engraved. A plurality of suction water pipes 109 (three in this embodiment) having the other end opening to the outer surface of the nozzle body 101 are opened so as to communicate with the outlet side of the nozzle ejection hole 107.

Due to the accelerating action of the high-speed water flow in the nozzle ejection hole 107, the ambient water 110 is sucked into the suction water thin tube 109 as the suction water 103, and the high pressure water 102 supplied from the pump near the outlet of the nozzle ejection hole 107. Combine and mix. In order to reduce the pressure loss at the time of suction, the diameter of the inlet portion of the suction water pipe 109 is configured to increase as it approaches the inlet portion. 105 is a central axis of the nozzle. FIG. 16 is an embodiment showing a continuous state of the suction water tube opening as a cross-sectional view perpendicular to the central axis 105 of the underwater water jet nozzle. That is, it is a nozzle in which the suction water tube (swirl type) 109b and the nozzle ejection hole 107 are connected in a tangential direction so as to swirl.

In this nozzle structure, the nozzle ejection hole 107
The swirling turbulence is added to the water flow, and the cavitation easily occurs in the nozzle jet hole 107 or in the water jet immediately after jetting from the nozzle jet hole 107, and the jet flow easily spreads due to the swirling action.

FIG. 17 schematically illustrates a phenomenon in the underwater water jet nozzle having the structure shown in FIGS. 15 and 16.

The nozzle shown in FIG. 16 is of a type in which thin tubes for sucking ambient water are connected in the tangential direction of the nozzle ejection holes. Nozzle ejection hole 107 through suction water pipe 109
The water sucked inside merges and mixes with the high-pressure water 102 while swirling in the nozzle ejection hole 107, and creates a mixing section 400 of the water streams. The water jet spouted into the water from this nozzle has a swirling flow 40 in the vicinity of the nozzle jet hole 107.
1 is generated, and due to the action of the strong shear vortex flow caused by the swirling flow 401, the developed cavity jet 402 is generated.

A large number of bubbles 403 are generated not only on the outer circumference of the cavitation jet but also on the inside. Swirling flow 401
By the action of, the entrainment flow 404 is generated from the outer circumference of the jet flow, and the bubble group 403 on the outer circumference of the jet flow is drawn into the center portion of the cavitation jet flow 402. Even in the bubble nuclei that meet the center of the jet flow, such swirling disorder is triggered to cause chain cavitation.

FIG. 18 is a characteristic diagram of collision pressure distribution by the jet jet of cavitation.

In the nozzle embodying the present invention, the collision pressure is maximum on the central axis of the jet flow, and as described above,
It was confirmed that the cavitation was actively generated over the whole area of the cavitation jet. In addition, the spread of collision pressure is considerably wider than when using the conventional nozzle,
The peening area by the cab has expanded considerably,
It can be said that this is a characteristic that can be expected to have efficient peening.

[0077]

The effects of implementing the present invention can be summarized as follows.

(1) The surface stress state of the underwater steel material can be efficiently modified.

(2) Since blast beads are not used, the trouble of collecting or discarding them can be saved. The result is an economical operation.

(3) Since peening is performed in water, the temperature of the peening portion does not rise locally, and the temperature of the target structure can be kept low and more uniform. Thermal adverse effects such as transformation of the metal structure disappear.

(4) Since peening is performed in water, noise can be prevented.

(5) Since peening is performed in water as in the case of (4), there is no need to worry about disposing of splashes (water droplets).

(6) Since the cavitation generated in the underwater water jet is effectively used, the predetermined effect can be obtained at a relatively low pressure. An ultra-high pressure water supply system (pump, piping, valve, etc.) is not required, and equipment cost (initial cost) and operation cost (running cost) can be suppressed.

(7) Since the jet jet of the cage spreads widely, it is possible to peening a large area steel surface at once. This increases the traverse speed of the nozzle,
Also, by reducing the number of times peening is repeated, the peening construction time can be significantly shortened. Especially when the construction time is limited, the effect of embodying the present invention is considerably large.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a nozzle.

FIG. 2 is an α-α direction view of the nozzle of FIG.

FIG. 3 is a vertical sectional view of a nozzle.

FIG. 4 is a view of the nozzle of FIG. 3 as seen in the aa direction.

FIG. 5 is a schematic diagram of a water supply system using two injection units.

FIG. 6 is a schematic diagram of a water supply system using one injection unit.

FIG. 7 is a diagram schematically showing a flow pattern of a water stream injected into water from a nozzle.

FIG. 8 is a diagram schematically showing the profile and collision pressure distribution of a cavitation jet in comparison with those in a conventional nozzle.

FIG. 9 is a diagram showing an experimental result of investigating a modification effect of residual stress in a pipe.

FIG. 10 is a vertical sectional view of a nozzle.

11 is a view of the nozzle of FIG. 10 as seen from the direction AA.

FIG. 12 is a diagram schematically showing a flow pattern of a water stream injected into water from a nozzle.

FIG. 13 is a diagram schematically showing the appearance of a cavitation in a water jet.

FIG. 14 is a diagram schematically showing the profile and collision pressure distribution of a cavitation jet in comparison with those in a conventional nozzle.

FIG. 15 is a vertical sectional view of a nozzle.

16 is a view of the nozzle of FIG. 15 taken along the line AA.

17 is a diagram schematically showing a phenomenon in the nozzle of FIG.

FIG. 18 is a collision pressure distribution characteristic diagram due to a cavitation jet.

FIG. 19 is a pressure attenuation characteristic diagram.

FIG. 20 is a diagram showing a state of jetting from a nozzle of a conventional example.

FIG. 21 is a diagram showing a structure for removing adhered contaminants in a conventional example.

FIG. 22 is a vertical sectional view of a conventional nozzle.

FIG. 23 is a vertical sectional view of a conventional nozzle.

FIG. 24 is a diagram schematically showing a problem of the conventional example.

FIG. 25 is a diagram schematically showing a problem of the conventional example.

FIG. 26 is a diagram schematically showing a problem of the conventional example.

FIG. 27 is a vertical sectional view of a conventional nozzle.

[Explanation of symbols]

 1 Nozzle body 2 Main high-pressure supply water 3 Peripheral high-pressure supply water 4 High-pressure water flow path 5 Nozzle center axis 6 Diameter contraction part 7 Main ejection hole 8 Main ejection hole outlet opening 9 Peripheral high-pressure water supply flow path 10 Swirling water flow Hedda 11 Swirling ejection Hole 12 Swirling flow jetting slit 13 Swirling flow guide

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Kurosawa, 3-1-1, Saiwaicho, Hitachi, Ibaraki Pref., Hitachi Works, Hitachi Works

Claims (8)

[Claims] 1. A nozzle for a cavitation jet that improves the surface stress state of a workpiece by jetting water in water to form a straight jet flow and a swirl jet flow that swirls around the straight jet flow. A nozzle for a cavitation jet, which has an injection opening for 2. The nozzle for a cage jet according to claim 1, wherein the straight jet flow and the swirl jet flow are divided near the jet opening. 3. The nozzle for cage jet according to claim 1, further comprising a guide member for directing the jetting direction of the swirl jet flow to the outside with respect to the jetting direction of the straight jet flow. 4. The method according to claim 1, wherein the total water injection amount is 4
A nozzle for a cavitation jet, which distributes not less than 80% and less than 80% as the swirl jet flow. 5. The nozzle for a cage jet according to claim 1, wherein the straight jet flow and the swirl jet flow interfere with each other in water. 6. The nozzle for a cage jet according to claim 1, wherein the flow velocity of the swirl jet flow is 1.2 times or more and less than 8.0 times the flow velocity of the straight jet flow. 7. The nozzle for cavitation jet according to claim 1, wherein the supply source of the swirling jet is ambient water. 8. A suction port for surrounding water is formed on an outer surface of a nozzle according to claim 7, and a thin tube extending inward from the suction port communicates with a squeezed portion of a jet opening forming the straight-flow jet flow. A nozzle for a jet jet that is characterized by