JP3343371B2 - Cavitation injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for modifying the surface of a metal material, in which a high-speed water jet with cavitation is injected into the surface of the metal material in water, and the collapse pressure of the cavitation bubbles generated in the water jet is measured. The present invention relates to a cavitation spraying apparatus for treating a surface of a metal material in which a tensile stress remains so that a compressive stress acts.

[0002]

2. Description of the Related Art The residual stress of an existing structural material is subjected to peening treatment using a shot blast in which steel balls are blown by an air current, a sand blast using sand grains, a cryo blast using ice grains, and the stress is reduced in a tensile direction ( From the direction of crack propagation) to the compression direction. Such a peening technique is widely used at the time of processing various mechanical structures or parts as a measure against residual stress.

[0003] However, there are many structures which must be peened by all means even in such an environment where blasting cannot be performed. For example, the nozzle portion and the offshore structure of an aged reactor pressure vessel are both in water, and it is almost physically or economically impossible to remove and treat the water. In a reactor pressure vessel, a large amount of radioactivity is released when water is drained. Recovering the blast particles is also a difficult task. If ice particles are used, collection is unnecessary,
Economic merits are unlikely.

[0004] The use of high-speed water jets is widely known as a unique processing, mining or cleaning technique.
Attempts to utilize this for surface stress modification have been made by Westinghouse (JP-A-62-63614). Peening with a water jet also has the advantage of preventing the local temperature rise due to the effect of water cooling. However, this is an operation in the atmosphere in which the axial dynamic pressure of a water jet can be effectively used, and there is no guarantee that this technology can be directly applied as a peening technology using a submerged water jet.

As shown in FIG. 19, the decay of the jet flow dynamic pressure is considerably rapid in water. This is because the diffusion is fast because it is in phase with the resistance of the surrounding water. In order to obtain an axial pressure equivalent to that of a gas-phase water jet in water, an ultra-high pressure generator is required, resulting in a very disadvantageous technique in terms of cost.

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

[0007]

FIG. 20 shows that:
It is a typical structure of a nozzle used for water jet processing. The purpose of this nozzle is to squeeze a water stream into a beam in the gas phase, and even when used as a submerged water jet, cavitation hardly occurs. The reason is that the squeezing angle θ of the contraction portion 1105 is small, and the depressurizing action here is too gentle.

In addition, the outer surface of the water jet has little disturbance, and it is difficult to generate cavitation due to shear vortex, or even if cavitation occurs, it is intermittent and poor in reproducibility, and the development state of the cavitation is unstable That's why.

In the drawing, reference numeral 1101 denotes a submerged water jet nozzle main body, 1102 denotes high-pressure supply water, 1103 denotes a water supply parallel portion, 1104 denotes a nozzle center axis, 1106 denotes a jet hole,
107 is an underwater water jet, 1108 is a solid surface of a processing object,
Reference numeral 1109 denotes surrounding water of the object to be processed.

The prior art shown in FIG. 21 (JP-A-61-81)
No. 84) attempts to remove attached contaminants by the action of cavitation generated in a submerged water jet.

In the drawing, reference numeral 1201 denotes a water tank;
2 is a part to be cleaned, 1203 is a nozzle, 1203a is nozzle cleaning, 1203b is a jet hole, 1204 is water, 1205
Is a pipeline.

The prior art shown in FIG.
No. 8554) is a nozzle developed for various operations in water, and the use of cavitation is declared.

In the drawing, reference numeral 1301 denotes a nozzle body;
1302 is an orifice portion, 1303 is a conical opening portion, 13
04 is a conical cavity, 1305 is a piping member, 1306 is a high-pressure injection device, and 1307 is an object to be injection-processed.

[0014] In these examples, there is a limit in terms of the structure of the nozzle even if the cavitation is actively generated. In order to promote cavitation, it is necessary to devise a strong turbulence in the water flow in the nozzle or to forcibly supply cavitation bubble nuclei.

FIG. 23 shows a structural example of a self-resonant cavity phenomenon promoting nozzle. In this nozzle, the cavity 1403 provided in the nozzle generates a self-resonance phenomenon, and the cutting efficiency is enhanced by utilizing the cavity generated in the gaseous water jet. The problem with this nozzle is
Since the cavitation occurs in the nozzle, the nozzle is in a bubble-locked state (actually, the bubble-locked state and the phenomenon that only bubble-free water is jetted are repeated in accordance with the resonance frequency), causing an increase in pressure loss and an increase in water flow. Violently pulsates (oscillations in the cavity feed back to the upstream side and become a state of self-excited oscillation).

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

[0017] As the nozzle showing the structure in FIG. 2 4,
Conventional nozzles intended to squeeze a water jet into a beam in order to process various materials in the atmosphere, even when used for peening in the atmosphere, as shown in FIG. Is extremely local, so peening efficiency cannot be said to be high, for example, a long time is required for construction.

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

That is, as shown in FIGS. 26A and 26B, the peening pressure generating portion 1909 moves along the locus 190 in order to peening the entire area where the peening is required 1901.
The nozzle must be moved vigorously so that it looks like 5. The structure of the tip of the manipulator for mounting the nozzle 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 a submerged water jet, the dynamic pressure on the jet axis attenuates very rapidly in water. FIG. 19 shows a comparison with characteristics in the gas phase. On the other hand, in such a submerged water jet 1803, a spiral cavity 1804 due to a shear type vortex is generated on the outer periphery of the jet. FIG. 25 schematically shows such a situation. In the case of the conventional nozzle, the turbulence due to the vortex is weak, the generation of cavitation is insufficient / unstable, and the pressure distribution 1806 caused by the collapse of the cavitation bubbles is Around the central axis 1807.

In the drawing, reference numeral 1801 denotes a water injection nozzle, 1802 denotes high-pressure water, and 1805 denotes an object to be pressurized.

As described above, the on-axis dynamic pressure of the jet is low in the water, and the pressure distribution inevitably becomes “dropout”. If the generation of the cavitation bubbles is remarkably active, the bubbles on the outer periphery are entrained into the center of the jet (entrance). However, in the unstable cavitation as shown in FIG. 25, the entrainment operation cannot be expected. As shown in FIGS. 26 (c) and (d), the required peening location 1
In order to apply the 903 evenly, the nozzle must be traversed in a complicated manner. (A) and (c) show examples of moving the nozzle in a pendulum shape, and (b) and (d) show examples of reciprocating the nozzle.

Reference numerals 1902 and 1904 denote peening-required points, reference numerals 1906 to 1908 denote nozzle movement trajectories, and reference numeral 191.
0 is a peening pressure generating portion.

In the prior art shown in FIG.
An air suction pipe 2002 that uses a suction action by accelerating a water flow is provided, and outside air is sucked into high-pressure water 2004 and mixed therewith to create a two-phase jet 2005 in a gas phase containing bubbles. In this case, it is advantageous if the sucked air bubbles act as a cavitation, but if it acts as a 'cushion'-like cushioning effect, it has an adverse effect on peening. If the peening location is deep underwater, a long air suction pipe is not practical.

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

An object of the present invention is to provide a nozzle for jetting a cavity, which has less adverse effects due to the generation of the cavity.

[0027]

[Means for Solving the Problems]

1. In the present invention, a small orifice for ejecting a jet having a large swirl velocity component is arranged around the outer periphery of a water jet for ejecting a high-speed water jet from a central axis orifice in an annular shape outside the center orifice, or the opening area is reduced. A nozzle with a small annular slit is used.

When a strong swirling jet is added to the straight water jet from the central jet, a shear vortex street, which is a generation point of the cavitation bubbles, is extremely actively generated at the boundary between these jets.
The cavitation jet generated in this manner is irradiated onto a steel material surface requiring peening.

2. The present invention utilizes a submerged water jet nozzle that generates two different types of cavitations and combines them in a submerged jet.

In the nozzle according to the present invention, first, 1) a main shaft jet is generated from a jet hole opened on the main shaft (center axis) to generate 1) separation bubble cavitation. In order to forcibly apply a swirl to the main spindle jet, a plurality of swirl spouts are provided outside the on-spindle spout in the direction of swirling slightly toward the center. Large flow velocity from here (nearly four times the spindle injection velocity)
Then, a swirling jet is created around the main jet to generate large-scale 2) swirl cavitation. When the different cavities described in 1) and 2) above interfere with each other in the jet, the bubble nuclei in the water are excited in a chain due to the interaction, and a developed cavitation jet is formed. This enables highly efficient underwater peening. 3. According to the present invention, a plurality of thin pipes for sucking environmental water around a nozzle by the action of an ejector, so to speak, into a depressurizing section, ie, a squeezing section of a nozzle for injecting a high-speed water jet into water, are provided with a suction port on the outer periphery of the nozzle and the nozzle. The aperture is opened so that the squeezed portion communicates. In the nozzle of the present invention, when water is jetted at a high pressure in water, ambient water is sucked from the thin suction communication pipe. The sucked water mixes with the water supplied from the high-pressure pump at the narrowing portion of the nozzle, where strong turbulence occurs in the water flow. By the above operation, the cavitation of the underwater water jet is remarkably promoted.

[0031]

[Action]

1. When a strongly swirling water jet is supplied around the high-speed water jet that goes straight on the center axis of the underwater nozzle, part of the outer swirling water jet flows backward, and a strong shear layer is formed between it and the straight water jet. Vortices occur in this shear layer. Capillary bubbles are actively generated from the center of the vortex. This creates a well-developed cavitation jet with a high bubble generation density.

Further, the swirling water flow on the outer periphery creates a large backflow downstream of the cavitation jet so as to be drawn into the center of the straight water jet on the central axis from the downstream side. Due to such a large backflow vortex, the cavitation bubbles generated in the vortex portion in the shear layer described above are uniformly diffused not only outside the cavitation jet but also throughout the cavitation jet.

By the mechanism described above, a cavitation jet in which the spread is large, the number density of bubbles per unit space is large, and the bubbles are uniformly dispersed 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.

If the cavity jet thus produced is used for peening, it is possible to peen a steel surface having a large area at a time in a short time, thereby achieving high peening efficiency.

2. First, in the orifice on the central axis, the water flow separates from the inner wall of the orifice due to the rapid depressurizing action in the orifice, and 1) separated bubble cavitation is generated. This is a small slug-shaped bubble flow cavitation, which is ejected from the ejection hole so as to be pushed out by the force of the water stream. On the other hand, a depressurized portion is generated in a strong and large vortex generated by the swirling water flow, and 2) vortex cavitation is generated there. 2) is generated slightly downstream from 1) at a position slightly away from the nozzle, but immediately interferes with each other in the submerged water jet. The collision between the cavitation bubbles 1) and 2) or the impact of coalescence triggers the excitation of the other bubble nuclei in the water, and the cavitation is amplified in a chain. Further, on the outer periphery of the water jet, a shear vortex cavity originating from the shear vortex also occurs. In this way, the submerged water jet becomes a developed complex type cavitation jet.

The swirling jet has an effect of expanding the submerged water jet by its centrifugal force. Also, the expanded underwater water jet is
Entrains ambient water into its own jet. The swirling jet also produces a large circulating flow downstream of the water jet. With such a combination of flow patterns, the cavitation bubbles are evenly diffused (dispersed) inside the water jet. By the above-described operation, the jet is widened and the jet is filled with air bubbles, and a cavity jet suitable for underwater peening is realized.

3. When the sucked water mixes with the mainstream jet water at the nozzle orifice and is jetted from the nozzle, the submerged water jet becomes violently disturbed from inside. In this way, in the underwater water jet, in addition to the spiral cavitation generated around the jet, a massive bubble type cavitation is also generated from inside the jet. These two types of cavities amplify each other through a synergistic action (the generation of bubbles excites the surrounding bubble nuclei).
Therefore, the entire jet becomes a developed cavity flow.

Also, the cavitation bubbles become more evenly distributed in the transverse cross section of the jet (compared to the state shown in FIG. 25), so that when they hit the surface of the structure, they will spread over a large area. Such an impact pressure is generated.

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

[0040]

FIG. 1 shows the structure of a nozzle for jetting cavitation according to the present invention as a sectional view passing through a central axis. FIG. 2 shows the structure of the nozzle as viewed from the front. The main high-pressure supply water 2 is guided to a nozzle center axis 5 of the nozzle body 1 through a high-pressure water flow path 4. The main high-pressure supply water 2 is decompressed and accelerated in the diameter contraction section 6 and is injected into the water from the main ejection hole 7 as a high-speed water flow in the axial direction having a flow velocity of at least 40 m / s. The outlet of the main ejection hole 7 is an outlet enlarged portion 8 for gradually increasing the diameter. The outer peripheral high-pressure supply water 3 is supplied through a plurality of outer peripheral high-pressure water supply channels 9 provided outside the high-pressure water channel 4, merges with the swirling water flow header 10, and then opens toward the water from the swirling jet hole 11. The fluid is guided to the swirling flow jet slit 12 and jetted at high speed into the water with a strong swirling component.

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

The structure of a nozzle according to another embodiment based on the same concept is shown in FIG.
FIG. 4 is a view from the front. Nozzle body 3
The main high-pressure supply water 302 is guided on the nozzle center axis 5 of No. 01. The main high-pressure supply water 302 is decompressed and accelerated in the diameter contraction part, 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 for gradually increasing the diameter, similarly to the embodiment shown in FIG. After being supplied with high pressure through the outer peripheral high pressure water supply channel 309 and merging with the swirling water flow header 310, the nozzle body 3
The water is injected into the water from a plurality of swirl outlets 311 opening to the outlet of No. 01. The high-speed water flow flowing straight in the axial direction from the main outlet 307 and the high-speed turning water flow from the turning outlet 311 are not mixed immediately after the jetting (the reason will be described later).
The swirling flow guide 312 for turning the jet direction from the swirling orifice 311 slightly outward is provided at the outlet enlarged portion 30 of the main orifice.
8 is provided so as to slightly protrude from the nozzle body 301.

In the figure, reference numeral 303 denotes an outer peripheral high-pressure supply water, 304 denotes a high-pressure water flow path, 305 denotes a central axis of a nozzle,
Reference numeral 6 denotes a diameter contraction portion.

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

FIGS. 5 and 6 show the injection unit (pump).
The water supply system from to the injection nozzle is schematically shown.
The example of FIG. 5 is a type in which the flow rates of the axially high-speed water flow and the swirling high-speed water flow are independently adjusted using two injection units.

In the figure, reference numeral 501 denotes a nozzle body,
502 is an injection gun, 503 and 504 are high-pressure water supply pipes,
05 and 506 are pressure regulating valves, 507 and 508 are injection units, 509 is a cavitation jet, 510 is a workpiece, and 511 is ambient water. On the other hand, in the type shown in FIG. 6, a high-pressure water supply pipe from one injection unit is branched, and each flow rate is distributed by a 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 apparatus.

In the drawing, reference numeral 601 denotes a nozzle body;
602 is a spray gun, 603 and 604 are high-pressure water supply pipes, 6
05 and 606 are pressure regulating valves, 607 is an injection unit, 608
Is a cavity jet, 609 is a workpiece, 61
0 is ambient water.

FIG. 7 is a schematic cross-sectional view showing a flow pattern of a water stream jetted into water from a nozzle for jetting cavitation according to the present invention. Between the central straight jet 7g jetted on the nozzle center axis 704 and the outer swirling jet 7a jetted by being swirled slightly outward on the outer periphery, a shear layer vortex 7c due to a strong shear flow is provided.
Is formed.

The shear layer vortex 7c is generated between the outer periphery of the center straight jet 7g and the backflow 7b from the outer swirling jet 7a. The inside of the shear layer vortex 7c becomes a vortex type cavity generation area 7d, where 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 the case of 0), the bubbles in the nozzle according to the present invention are generated very actively, continuously and stably as compared with the intermittent cavitation that occurs. The generated bubbles move to the outside downstream once accompanied by the peripheral swirling flow, but are caught in the circulating flow 7f from the outside and flow back into the inside of the cavitation jet.

Such a vortex type cavitation has a strong pressure propagating force and gives a trigger to bubble nuclei in water in a jet. Therefore, a large number of cavitation bubbles are generated in a chain so as to fill the inside of the jet. Big swirl 7
e and the resulting circulating flow 7f from the outside have the effect of diffusing the cavitation produced in a part of the jet over substantially the entire flow field of the jet.

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 optimal jet for peening. In addition, this cavity jet nozzle according to the present invention, in order to create a cavity 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, reference numeral 701 denotes a nozzle body,
702 is the main high pressure supply water, 703 is the outer high pressure supply water, 70
5 is an outlet enlarged portion of the main outlet, 706 is a swirl flow outlet, 7
Reference numeral 07 denotes 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. As described above, the profile a of the cavitation jet when the nozzle (nozzle body 801) according to the present invention is used is spread by the swirling flow, and has a characteristic that bubbles are uniformly dispersed inside the jet. Therefore, the collision pressure distribution c on the collision surface (solid surface) 802 is divergent, and there is no so-called depression where the collision pressure decreases at the center of the jet axis. On the other hand, the profile b of the cavitation jet when the conventional nozzle is used is considerably thinner, the pressure distribution d against the collision surface (solid surface) is poorly spread, and bubbles are generated on the outer periphery of the jet. The shape becomes concave in the middle. From the viewpoint of peening efficiency, the nozzle of the present invention, in which the pressure distribution is uniform and the spread is large, is more advantageous. This is because a large area can be processed by one irradiation.

FIG. 9 shows the result of an experiment for examining the effect of modifying the residual stress in the piping. Even when the conventional nozzle is used, the effect of modifying the surface stress until the component in the tensile direction substantially disappears is obtained, but the effect of modifying the surface 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 reducing the residual stress to the compression side. In the conventional nozzle, the development of the cavitation was insufficient, whereas in the nozzle according to the present invention, the collapse pressure of the bubbles in the developed cavitation jet was strong, so that a remarkable stress reforming effect was obtained. It is considered something.

The present invention utilizing the collision pressure due to the high-speed water flow in the water and the bubble collapse pressure due to the cavitation,
The present invention can be applied to other than the surface stress modification for preventive maintenance of the special heat exchange container or the chemical reaction tank described in the embodiment. Generally, in the modification of the surface stress, treatment at normal temperature without applying heat, that is, without transformation of the metal structure is much more preferable. The present invention is also advantageous from this point,
It can also be applied to surface stress modification of pressure-resistant members of boilers (thermal power). Considering that the work is underwater, the present invention 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 surface, causing considerable flow resistance to running.In the present invention, it is necessary to remove these deposits in sea water. enable. If the removal of attached organisms becomes possible in seawater in this way, (1) the ship is docked, (2) the seawater is pumped out of the dock, (3) the wastewater mixed with attached matter is discarded, and (4) ) Fill the dock again with seawater.

A series of operations described above is omitted altogether, and the maintenance of the ship can be performed more economically. It is preferable from the viewpoint of marine environment protection if the amount of the special paint used for removing the deposits is also reduced.

FIG. 10 is a longitudinal sectional view of the composite cavitation nozzle according to the present invention passing through the center axis thereof. FIG. 11 shows the opening structure of the ejection holes of the composite cavitation nozzle as viewed from the downstream side in the upstream direction. The high pressure water 201 for central axis supply is supplied through the high pressure water flow path 208 for central axis supply, and
At 09, the pressure is reduced and the fuel is injected from the main shaft outlet 210. The main shaft ejection hole 210 opens on the central axis of a slightly concave surface at the tip of the nozzle body 203. In the main-shaft ejection hole 210, a peel-type cavity is formed on the inner wall. The swirling supply high-pressure water 202 is guided to an annular swirling supply high-pressure water passage 206 around the central axis supply high-pressure water passage 208.

The high-pressure water for swirling supply 202 is jetted from eight swirling jet holes 211 into the water at an inclination 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 swirl around the jet.
High pressure water 20 for central shaft supply spouting from main shaft spout 210
The main shaft jet flow velocity Uj of 1 and the swirl jet flow velocity Uc of the swirling supply high-pressure water 202 spouted from the swirl jet hole 211 are set in a range where the relationship of 1.2 <Uc / Uj <8.0 (1) holds. Is done. However, a preferable injection condition in the practical work is Uc / Uj ≦ 4.0 (2). The reason why the swirling jet flow velocity Uc is set to be nearly four times larger than the main spindle jet flow velocity Uj is to give a strong swirl to the main spindle jet flow and to forcibly generate cavitation in the swirl flow. Although there is a large difference between the flow rates from the main spindle outlet 210 and the swirl outlet 211, the jet flow from the main outlet 210 and the swirl outlet 211 is made substantially equal. Based on such conditions, the main spindle outlet 21
0 and the ejection hole diameter of the swirl ejection hole 211 and the injection pressure of each of the high pressure water 201 for central axis supply and the high pressure water 202 for swirl supply are set. The main shaft outlet 210 is provided with the swirl outlet 2
An opening is provided at a location which is depressed to the upstream side by hi from the opening position 11.

Initially, the intention was to create a swirl cavitation due to the swirling flow at this depressed location. However, it has been found that swirl cavitation actually occurs at a position slightly downstream from the nozzle.
In this recess, the swirl cavity is filled with the main spindle outlet 21.
At present, it is known that there is an effect of preventing collision due to backflow to zero. The distance hi between the main shaft ejection hole 210 and the swirl ejection hole 211 and the diameter of the opening circle of the swirl ejection hole 211 are determined such that Dc is 1/8 <hi / Dc <1/2 (3). I do. Within this range, the structure of hi / Dc ≦ １ ／ (4) is used to create a swirling water flow, promote cavitation,
Alternatively, it is preferable from many viewpoints such as ease of processing.

In the drawing, reference numeral 204 denotes a high-pressure water supply gun, 205 denotes a locknut, and 212 denotes a conical recess at the nozzle tip.

FIG. 12 schematically shows a flow pattern of a water stream injected into water from the composite cavitation nozzle according to the present invention. The feature of this flow pattern is that, due to the strong swirling force 204a of the swirling jet 215, the swirling jet 215 itself as well as the main spindle outlet 210
The main axis (central axis) jet 214 which is jetted in the direction of the main axis (central axis) is also spread downstream by the centrifugal force of the swirl (204b).

The characteristic that the jet flow spreads is important, and bubbles generated near the nozzle or at the center of the swirling vortex are diffused (dispersed) throughout the jet flow. On the other hand, the expanded jet entrains the surrounding water into the jet (204c). Further, at this location, a shear vortex generated at the interface between the jet and the surrounding water 213 (this is smaller than the swirling flow 204a due to the water jet from the swirling orifice,
Shear vortex-type cavitation is generated at the boundary between the vortex and the vortex. 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 circulating flow 204d acts in a direction to suppress the peening collision pressure, it has an effect of uniformly dispersing the cavitation bubbles throughout the jet flow.
Plays a very important role. By the effect of the flow field as described above, a jet is created in which the cavitation having a large spread is more evenly dispersed throughout the inside thereof. FIG. 13 schematically depicts aspects of cavitation in a nozzle and a water jet. First,
In the main-shaft outlet 210, the water flow separates from the inner wall of the main-shaft outlet 210 due to the diameter-reducing portion 209 and the rapid depressurizing action caused by the contraction in the main-shaft outlet 210, thereby generating a separated bubble-type cavity 205a. The cavitation is a combination of small slag-like bubbles. When the cavitation is generated in the main-shaft ejection hole 210, the cavitation is ejected into the submerged water jet so as to be sequentially pushed downstream.

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

Although this cavitation occurs slightly downstream from the above-mentioned separation type cavitation 205a, it mixes in the vicinity of the main shaft ejection hole 210 and interferes with each other. The coalescence or repulsion caused by collision of the cavitation bubbles triggers, and a rapid pressure fluctuation propagates into the nearby water, and even the stable bubble nuclei combined in the water are excited, and the cavitation is remarkably promoted. In addition, a shear vortex cavity is also generated on the outer periphery of the jet (205).
c).

These cavitation bubbles are shown in FIG.
As shown in (1), the water is diffused throughout the submerged jet by the action of the centrifugal action 204b of the swirling flow, the entrainment of surrounding water 204c, and the large-scale circulating flow 204d generated downstream of the jet.

In the figure, reference numeral 205d denotes diffusion of the cavitation bubbles into the jet, and 205e denotes a shear vortex on the outer periphery of the jet.

FIG. 14 shows the profile of the submerged water jet and the impact pressure distribution in the composite cavity 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 wider jet flow than the conventional nozzle and has a considerably wider and more uniform impact pressure distribution. The impact pressure peak is slightly higher for the conventional nozzle, but because the water jet is squeezed into a beam, the impact of the direct impact pressure of the water flow rather than the effect of cavitation occurs. It is thought that it was.

FIG. 15 shows the structure of a submerged water jet nozzle.
It is shown as a cross-sectional view passing through the central axis. High pressure water 1
02 is supplied through a high-pressure water conduit 104 that opens as a water supply part on the upstream side of the nozzle main body 101, and is decompressed and accelerated in the nozzle contraction part 106, and the nozzle ejection port
7 into the ambient water 110. At the exit of the nozzle ejection hole 107, a nozzle account counterpart 108 is slightly cut. A plurality (three in this embodiment) of suction water thin tubes 109 having the other end opened on the outer surface of the nozzle main body 101 are opened so as to communicate with the outlet side of the nozzle outlet 107.

By the acceleration action of the high-speed water flow in the nozzle outlet 107, the surrounding water 110 is sucked into the suction water tube 109 as the suction water 103, and the nozzle outlet 1
High-pressure water 1 supplied from the pump near the outlet of 07
02 and mixed. In order to reduce the pressure loss at the time of suction, the diameter of the inlet portion of the suction water thin tube 109 is configured to increase as approaching the inlet portion. Reference numeral 105 denotes a nozzle center axis. FIG. 16 is a diagram of a nozzle for a submerged water jet .
A nozzle viewed from the line 15A-A, in which the suction water capillary (swirl type) 109b and the nozzle outlet 107 are connected in a tangential direction so as to swirl.

In this nozzle structure, the nozzle ejection holes 107
The turbulence is added to the water flow, and cavitation is likely to occur in the nozzle jet hole 107 or in the water jet immediately after jetting from the nozzle jet hole 107, and the jet flow is easily spread by the swirling action.

FIG. 17 schematically illustrates a phenomenon in the submerged water jet nozzle whose structure is shown in FIGS.

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

A large number of bubbles 403 are generated not only on the outer periphery but also inside the cavity jet. Swirling flow 401
The action causes a entrapped flow 404 from the outer periphery of the jet, and the bubbles 403 on the outer periphery of the jet are drawn into the center of the cavity jet 402. The bubble nucleus that is aligned with the center of the jet is also triggered by such a turbulence, and cavitation is generated in a chain.

FIG. 18 is a graph showing a collision pressure distribution characteristic due to a cavity jet.

In the nozzle embodying the present invention, the collision pressure is maximum on the jet center axis, and as described above,
It was confirmed that the cavitation was actively generated over the entire area of the cavitation jet. Also, compared with the conventional nozzle, the spread of the collision pressure is considerably wider,
The peening area by cavitation has expanded considerably,
It can be said that it is a characteristic that efficient peening can be expected.

[0077]

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

(1) The surface stress state of the underwater processing object can be efficiently modified.

(2) Since no blast beads are used, the trouble of collecting or discarding them can be eliminated. The result is an economic operation.

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

(4) Noise can be prevented due to peening in water.

(5) As in the case of (4), since peening is performed in water, there is no need to worry about the disposition of droplets (splashing water droplets).

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

(7) Since the cavitation jet has a large spread, a large-area steel material surface can be peened at a time. This increases the traverse speed of the nozzle,
Also, by reducing the number of repetitions of peening, the peening work time can be significantly reduced. In particular, when the construction time is limited, the effect of embodying the present invention is considerably large.

[Brief description of the drawings]

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

FIG. 2 is a view of the nozzle of FIG. 1 as viewed in the α-α direction.

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

FIG. 4 is a view of the nozzle in FIG.

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 flow injected into water from a nozzle.

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

FIG. 9 is a view showing an experimental result of examining a modification effect of a 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 viewed in the direction of arrows 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 view schematically showing aspects of cavitation in a water jet.

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

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

FIG. 16 is a view of the nozzle in FIG.

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

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

FIG. 19 is a pressure decay characteristic diagram.

FIG. 20 is a diagram showing a state of ejection of a conventional nozzle.

FIG. 21 is a view showing a conventional structure for removing adhering contaminants.

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

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

FIG. 24 is a diagram schematically showing a problem of a 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 longitudinal sectional view of a conventional nozzle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle main body 2 Main high-pressure supply water 3 Perimeter 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 head 11 Swirling ejection Hole 12 Swirl jet spurt 13 Swirl guide

Continuation of the front page (56) References JP-A-57-156200 (JP, A) JP-A-62-63614 (JP, A) JP-A-59-209767 (JP, A) JP-A-3-75971 (JP) , U) Japanese Utility Model Hei 3-75970 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B23P 17/00 B24C 1/10 B24C 5/04 B05B 1/26

Claims (8)

(57) [Claims] 1. High pressure water is applied from the nozzle body in water.
Said have you <br/> to Kiyabiteshiyon injection device to improve the surface stress state of the workpiece by jetting collide with factory object, to the nozzle body, and the straight ejection hole, outside the straight ejection hole
Swirling jets arranged in a ring on the side and opening in the swirling direction
A cavitation injection device provided with an ejection hole or an annular swirling ejection slit . 2. The cavitation injection device according to claim 1 , wherein
In location, or the swivel jet holes or pivoting ejection slit
Of swirling jet formed by high pressure water jet
Direction is formed by high-pressure water jets from the straight jet holes.
To the outside of the jet direction of the straight jet
A cavitation injection device , wherein a guide member is provided on the nozzle body . 3. The cavitation injection device according to claim 1 , wherein
In location, or the swivel jet holes or pivoting ejection slit
Of swirling jet formed by high pressure water jet
Are formed by high-pressure water jets from the straight jet holes.
The flow is distributed so that it is larger than the flow of the straight jet flow.
Kiyabiteshiyon jet apparatus characterized by that. 4. The cavitation injection device according to claim 1 , wherein
In location, or the swivel jet holes or pivoting ejection slit
Velocity of swirling jet formed by high pressure water jet
Are formed by high-pressure water jets from the straight jet holes.
The cavitation injection device is set to be faster than the flow velocity of the straight jet flow . 5. The cavitation injection device according to claim 3, wherein
In location, the swivel jet holes or pivoting ejection slit
An injection pump for supplying high-pressure water, high pressure to the straight advancing ejection hole
Separate injection pumps for supplying water are provided.
A cavitation injection device wherein the flow rate is independently adjusted by a pump. 6. The cavitation injection device according to claim 3, wherein
In location, the swivel jet holes or pivoting ejection slit
The high-pressure water to be supplied and the high-pressure water to be supplied to the straight jet hole are:
High pressure water supply pipe is branched from one injection pump and supplied.
Is, Kiyabiteshiyon jet apparatus characterized by distributing the respective flow rates through the pressure regulating valve. 7. The cavitation injection device according to claim 1 , wherein
In location, the swivel jet holes or pivoting ejection slit
A cavitation injection device , wherein a supply source of supplied water is ambient water. 8. The cavitation injection device according to claim 7 , wherein
In location, the suction port of the surrounding water on the outer surface of the nozzle body is formed, Kiyabiteshiyon injection tubules extending from the suction opening to the inside and wherein the communicating with the throttle portion of the straight ejection hole injection opening Equipment .