JPH08257997A - Method for treating material with hydro-jet - Google Patents

Abstract

PURPOSE: To perform surface treatments and washing at low cost by mixing a gas into a liquid pressurized to high pressure, injecting the mixture, breaking a jet structure for promotion of atomization, and colliding this broken flow with a subject, for processes such as material machining, cutting, or washing, etc. CONSTITUTION: A pressurization means 2, such as a high-pressure pump, for pressurizing water to high pressures and injecting it into a water tank 1, is provided, and water is pressurized by the actuation of the pressurization means 2 and supplied to a nozzle 4 via a pressure-resisting hose 3. The nozzle 4 is fitted with a mixing mechanism 4a for mixing into the injected water another fluid, e.g. a gas, such as air or carbon dioxide, from a compressor 7, etc. In the mixing mechanism 4a, the gas is mixed into the jet of water to break the jet structure to promote atomization, and the broken flow promoted for atomization is collided against the surface of a subject 5 from the nozzle 4 to perform processes such as machining, cutting or washing on the subject 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention artificially disintegrates a jet structure of a liquid which is pressurized to a high pressure to collide with a surface of an object as a collapsing flow in which droplet formation is promoted.
The present invention relates to a method of treating a material by a hydrojet, which performs processing such as machining, cutting or cleaning of the material.

[0002]

2. Description of the Related Art As a means for cutting hard rock, metal, glass, ceramics, reinforced concrete and the like, an abrasive jet in which an abrasive material (abrasive) is mixed in a water jet has been put into practical use. However, conventional abrasive jets have many problems such as high cost of abrasives, remarkable consumption of nozzles by abrasives, and inability to cut thick objects with high accuracy. Further, although it is considered to use it for dismantling an abandoned nuclear reactor, cutting solid materials having radioactivity, etc., in that case, there is a problem in reprocessing the activated abrasive.

Further, as a method for surface treatment or cleaning of a material, a rotary jet in which one or a plurality of nozzles are rotated has been put into practical use, and in this method, a wide surface can be treated by rotating the nozzle portion. However, since it does not use abrasives, it has advantages such as cost reduction compared to the above abrasive jet, but since it has a rotating part in the flow path of high pressure fluid, there is a problem in service life and reliability of the equipment. It is left.

On the other hand, according to the conventional research on the water jet, as shown in FIGS. 1 and 2, the position where the cutting of the material by the jet becomes remarkable (the mass reduction amount M becomes large) is closer to the nozzle than the nozzle. Rather, it has been clarified that it is located some distance from the nozzle [Edited by the Japan Water Jet Society, "Water Jet Technical Dictionary", p.73, Maruzen (1993)]. FIG. 1 shows a mass reduction amount M according to a distance x / d from a nozzle (a dimensionless distance obtained by dividing a distance x from a nozzle to a sample piece by a nozzle outlet diameter d).
2 shows the change of the discharge pressure P ₀ , and FIG. 2 also shows the influence by changing the material.

Looking at the relationship between the structure of the water jet (Fig. 3) and the position where the amount of mass reduction is maximum, which was revealed by Yanaida et al. In "Encyclopedia of Water Jet", p. The position where the mass reduction amount is the maximum is a droplet flow region where the flow of the water jet is droplets or liquid masses of about 100 μm, and there is a water hammer phenomenon caused by collision of the droplets or liquid masses. It has also been clarified that erosion occurs due to impact pressure and cutting of the material becomes remarkable [Fumio Seino, et al .: Transactions of the Japan Society of Mechanical Engineers, Volume B, Vol. 60, No. 573
(1994)].

However, as can be seen from FIG. 4, in this region, the pressure on the central axis of the water jet is significantly attenuated as compared with the pressure in the vicinity of the nozzle. Figure 4 shows the distance from the nozzle x /
3 shows changes in the pressure P _m / P ₀ on the central axis of the water jet due to d [Katsuya Yanaida et al., The Mining Industry Journal, Vol.
93 No. 1072 (1977)]. Therefore, if the state corresponding to the droplet flow region is obtained when the pressure of the water jet is not attenuated, a further erosion effect on the surface of the object can be expected.

[0007]

SUMMARY OF THE INVENTION The technical problem of the present invention is to modify the structure of the water jet without using the abrasive or the mechanism having a rotating part in the flow path of the high-pressure fluid employed in the above-mentioned prior art. Efficiently processing, cutting or cleaning materials,
It is to provide a means that can be performed at low cost. Another technical problem of the present invention is to further enhance the erosion effect on the surface of the object by making it possible to obtain a state corresponding to the droplet flow region when the pressure of the water jet jetted from the nozzle is small. Another object of the present invention is to provide a method of performing processing for processing, cutting, cleaning or the like of the material.

[0008]

A method for treating a material by a hydrojet of the present invention for solving the above-mentioned problems is a method of mixing a gas into a liquid pressurized to a high pressure and injecting the gas,
By collapsing the jet structure, a collapsing flow that promotes the formation of droplets is collided with an object, and processing such as processing, cutting or cleaning of the material is performed. As the gas mixed into the liquid pressurized to a high pressure, a liquefied gas that is vaporized after mixing into the liquid can be used.

More specifically, in the method of the present invention, in the vicinity of a nozzle for injecting a liquid such as water, in a region where the ejection pressure is less attenuated, the ejection of the ejected liquid is promoted. By mixing another fluid at an appropriate time before and after the injection of, the jet structure is collapsed, and droplets or liquid masses are artificially generated in the region where the pressure attenuation is small. As the other fluid, air, a gas such as carbon dioxide, or a liquid that is vaporized early after being mixed with a liquefied gas such as liquid carbon dioxide can be used, and they are supplied as a fluid pressurized from a cylinder or a compressor. However, it is also possible to mix the fluid ejected from the nozzle at a normal pressure so that the fluid is caught in the fluid.

In this way, another fluid is mixed with the liquid ejected from the nozzle so that a state corresponding to the droplet flow region, that is, a collapsing flow can be obtained in a region where the ejection pressure is less attenuated, and the collapsing flow is collapsed. When the flow collides with the target object, it is possible to perform processing for processing, cutting, cleaning, or the like of a material having a higher erosion effect on the surface of the target object. In particular, when a low-temperature fluid such as liquid carbon dioxide is mixed in the liquid jet, it can be expected that the surface treatment effect of the object is improved due to the decrease in the liquid temperature. As a means for improving the cutting effect by mixing other fluids into the water jet, there is also a method of adding a polymer material (polymer) to the water jet [the above-mentioned "Water Jet Technical Dictionary", p. 135 and p. 146], an improvement in cutting efficiency has been recognized, but it has been reported that the macroscopic jet structure does not change even when a polymer is added, and the above collapse flow as in the present invention cannot be obtained.

FIG. 5 shows the structure of an apparatus for carrying out the method for treating a material with a hydrojet according to the present invention. In FIG. 5, reference numeral 1 denotes a water tank, and the water tank 1 is provided with a pressurizing means 2 such as a high-pressure pump for pressurizing and ejecting water to a high pressure. 4 is connected. The nozzle 4 is provided with a mixing mechanism 4a for mixing another fluid with the jetted water. The fluid mixed in the mixing mechanism 4a is
It is mixed as a gas in the jet of water jetted by pressurization by the pressurizing means 2 to promote the formation of droplets by collapsing the jet structure, and a gas such as air or carbon dioxide gas can also be mixed. However, it is also possible to mix a liquid such as liquid carbon dioxide gas that is vaporized after mixing. Further, the mixing mechanism 4 a can mix the mixed fluid into the water in the nozzle 4, but can also mix the mixed fluid in the jet flow immediately after jetting from the nozzle 4. The other fluid to be mixed in the jet flow is supplied as a pressurized fluid from a mixed fluid supply source 7 including a cylinder and a compressor, but is positioned near the outlet of the nozzle 4 by being caught in the fluid ejected from the nozzle 4. It is also possible to mix them under normal pressure.

The water pressurized and jetted from the nozzle 4 collides with the surface of the object 5 as a collapsing flow in which the jet structure is collapsed due to the mixing of the gas and droplet formation is promoted. Thereby, processing such as processing, cutting or cleaning of the target object 5 can be performed. The used water that has been made to collide with the target object 5 by jetting is separated from the target object 5 as well as the water tank 6
Will be collected.

[0013]

EXAMPLE FIG. 6 and FIG. 7 show an example of the result of an experiment conducted by the present inventor. FIG. 6 shows how the mass reduction amount m of an aluminum plate sample (JIS H4000, A1050P) depends on the distance x from the nozzle outlet to the sample piece when compressed air or liquid carbon dioxide gas is mixed in the jet nucleus region near the nozzle. It shows how to change. In addition, FIG.
When the mixing amount of the liquid carbon dioxide gas is constant (0.6 kg / min), the change in the mass reduction amount m due to the difference of the mixing position (the jet core region and the continuous flow region downstream thereof) is shown. In the figure, the horizontal axis is the dimensionless distance x / d obtained by dividing the distance x from the nozzle to the sample piece by the nozzle outlet diameter d (here, 0.8 mm). The injection time was 30 seconds, and the injection environment was in the air. From these figures, it can be seen that the mass reduction amount is increased by the mixing of the compressed air or the liquid carbon dioxide, that is, the mixing effect is recognized. Further, as is clear from FIG. 7, there is a difference in the mixing effect due to the difference in the supply position, and the efficiency is better when mixed in the jet core region.

Further, in FIG. 8, the discharge pressure of the pump is 4
The relationship between the amount of liquid carbon dioxide gas mixed and the amount of mass reduction when liquid carbon dioxide gas is mixed in the jet nucleus region is shown at 00 kgf / cm ² . In the figure, the vertical axis represents a dimensionless amount m / m ₀ obtained by dividing the mass reduction amount m by the mass reduction amount m ₀ when liquid carbon dioxide gas is not mixed. When these figures and examples of other experimental results are also evaluated, the amount of mass reduction when liquid carbon dioxide gas is mixed in the jet core region is about 1.5 to 2 times that in the case where liquid carbon dioxide gas is not mixed. It is clear.

[0015]

As is apparent from the above detailed description, according to the present invention, the collapsing flow can be obtained at the time when the pressure attenuation of the water jet jetted from the nozzle is small, and the collapsing flow with respect to the object surface can be obtained. Not only can the erosion effect be enhanced, but there are the following advantages. (1) It is possible to operate at low cost as compared with the conventional abrasive jet. (2) There is no rotation mechanism and the like, and the device configuration is simple. (3) No foreign matter is attached to the object to be processed. (4) Wastewater treatment becomes easy. (5) By promoting the formation of droplets, a uniform pressure distribution can be obtained as compared with a normal jet flow, which is advantageous for surface treatment and cleaning.

[Brief description of drawings]

FIG. 1 is a graph showing an influence of a discharge pressure P ₀ on a change in a mass reduction amount M according to a distance x / d from a nozzle.

FIG. 2 is a graph showing the influence of the material on the change in the mass reduction amount M depending on the distance x / d from the nozzle.

FIG. 3 is a structural conceptual diagram of a known high-speed water jet in the air.

FIG. 4 is a graph showing a change in pressure P _m / P ₀ on a central axis of a water jet flow depending on a distance x / d from a nozzle.

FIG. 5 is a block diagram of an apparatus for carrying out the method of the present invention.

FIG. 6 is a graph showing an experimental example by the inventors of the present invention regarding changes in the mass reduction amount m (influence of pressure and mixing amount) depending on the distance x / d from the nozzle.

FIG. 7 is a graph showing an example of experiments by the inventors with respect to changes in the mass reduction amount m (influence of pressure and mixing position) depending on the distance x / d from the nozzle.

FIG. 8: Mass reduction amount m / m due to mixing amount of liquid carbon dioxide gas
It is a graph which shows the experiment example of the inventors about the change of _o .

[Explanation of reference numerals] 2 pressurizing means 4 nozzle 4a mixing mechanism 5 object 7 mixing fluid supply source

Claims (2)

[Claims] 1. A high-pressure liquid is mixed with a gas and jetted to break the jet structure to collide with an object as a collapsing flow that promotes the formation of droplets, thereby processing the material,
A method for treating a material by hydrojet, which is characterized by performing treatment such as cutting or cleaning. 2. The method for treating a material by a hydrojet according to claim 1, wherein a liquefied gas that is vaporized after being mixed into the liquid is used as the gas mixed into the liquid pressurized to a high pressure.