Process And Appratus For The Production Of Hydroelectric Pulsed Liquids Jets

Abstract

Process and apparatus for producing high energy pulsed liquid jets by the discharge of electrical energy through a relatively incompressible liquid in an essentially closed chamber having a shaped outlet nozzle.

Description

BACKGROUND OF THE INVENTION

1. Scope of the Invention

This invention relates generally to a method and apparatus for generating pulsed water jets and, more particularly to a method and apparatus for the generation of high repetition rate pulsed water jets by the discharge of electrical energy.

2. The Prior Art

In the field of subterranean mining there has heretofore been employed conventionally a "moil" which is a metal cutting tool used for cutting away hard rock material in the mining area. These cutting tools are made of hard metal, but they erode during the cutting process, thereby limiting the amount of material removed and curtailing the speed of mining.

In recent years, due to the increased need for rapid underground excavation for the removal of valuable material and for the development of subterranean channels for rapid transit and for materials handling, hydraulic mining techniques have been developed with the goal of long life, low cost and easily maintainable equipment. Such hydraulic techniques have included the use of hydraulic amplifiers and jack hammer type oscillators to generate the requisite peak pressures for accelerating water missiles to high velocities. Such equipment is bulky and has an inherent high noise factor producing unsuitable working conditions.

SUMMARY OF THE INVENTION

In accordance with the present invention, it has been discovered that the discharge of stored electrical energy from a capacitor or other suitable source into a closed container of a suitable fluid such as water by means of proper coupling electrodes will generate high temperature channel between the electrodes. This discharge will produce three effects: (1) a high pressure sonic front travelling outward from the discharge channel: (2) a high temperature expanding gaseous bubble containing superheated steam and a substantial amount of ionized species and neutral molecules: and (3) a continuum of high intensity light coincident with the time of discharge. A study of a typical system according to the present invention has revealed that the conversion from electrical energy to heat, sound and light is highly efficient, utilizing about fifty percent (50 percent) of the total discharge energy, the remainder being lost in the external circuitry.

Delivery of the high voltage electric energy to the spark gap is at a faster rate than the ability of the fluid medium to absorb the heat generated thereby. Consequently, the fluid medium in the gap is vaporized, undergoing at least partial ionization. Upon discharge of the electrical energy, a gaseous bubble is formed in the channel between the electrodes. Expansion of the bubble takes place during the relatively short time period of energy release, producing a shock wave in the relatively incompressible liquid. Since the reaction vessel is effectively a closed container except for the jet nozzle at the time of discharge, this shock wave meets mechanical resistance at all directions except through the nozzle opening. Thus a pulsed liquid jet is forced through the jet nozzle opening. This pulsed liquid jet is in the form of a liquid slug and is under extremely high pressure. When directed onto or against a desired surface, the Kinetic energy of the liquid slug is capable of useful work such as shaping, fracture and the like.

Several methods can be employed to supply the liquid to the reaction chamber. A suitable method would include a continuous liquid feed through the jet opening, producing a continuous stream out of the nozzle when unpulsed and an automatically pulsed stream when the electrical circuitry is actuated.

The apparatus of the present invention can also function in an open system whereby the electrode gap area is replenished by the action of the surrounding fluid medium. A mechanical shutter can be employed for the nozzle opening in such a manner that uncovering the nozzle opening automatically triggers the electrical discharge.

A continuous and predictable electrical discharge is important to the successful application of the present application. This can be provided by suitable electrode design. The use of ungrounded sleeves for the electrodes will produce a capacitive voltage divider across the electrode gap with the shell of the apparatus connected to the central junction point of the capacitors. Thus upon initiation of the discharge cycle, the high voltage starting gradients from the side wall of the apparatus to the sleeves will be half the gradient to the electrodes, providing a controlled and predictable streamer discharge.

A freely accelerating piston can also be employed to supply the liquid to the reaction chamber. In such an application, the piston will deliver the liquid at a high pressure, which pressure will be even further increased by the discharge of electric energy. Thus the magnitude of the force possessed by the resultant liquid jet is markedly increased over that supplied by the piston.

The electrohydraulic liquid jet units of the present invention can also be used in combination with known mining techniques and equipment. The device of the present invention can be used in combination with tungsten carbide or very hard steel bits in the cutting of hard rock to ease the job of cutting and to increase the life of the bits. In such an application, a multiplicity of electrohydraulic jet units can be arranged vertically for travel along a mine wall preceding the travel of the cutter bits along the mine face. By this arrangement, the water slugs will lacerate and weaken the wall by forming horizontal slabs. Subsequent cutting by the bits is much easier and the resultant reduction in bit wear and erosion increases bit life.

The electrohydraulic jet units can also be employed to drive a water-soluble resin into the bedding planes of a mine wall when such resin is added to the liquid supplied to the jet. These water-soluble resins, such as Polyox, will reduce the coefficient of friction between adjacent surfaces by as much as 68 percent when dispersed in water to a concentration of 30 ppm. The use of such a mixture will cause the bedding planes to part more easily and will also serve as a lubricant for cutting bits which follow the electrohydraulic jets.

The application of heat to weaken rock and cause it to spall and crack in depth is well known. If the percentage of water in the rock is proper, the spalling, weakening and cracking of the rock is greatly enhanced. Where strata are encountered which are deficient in water content, the electrohydraulic jets of the present invention can be used to saturate the bedding planes prior to the application of heat. In such application, the heat and high pressure jets can be applied simultaneously or alternately, the heat causing expansion stresses in the rock and the slugs of water tending to cool and crack the rock. Subsequent cutting by mechanical bits can be employed where desired.

In some applications of mining techniques, a rock slab will break loose but will hang up on the mine face due to an effect known as "keystoning." Such problems are eliminated by the present invention since the liquid jets act to pry loose the rock.

The electrohydraulic jet units of the present invention can be arranged in any desired configuration to achieve a desired result. For example, when positioned vertically and arranged in a circle, several units will act as a drill. When used alone or in combination with a standard metal rotary bit, a self flushing drill is achieved.

DESCRIPTION OF THE DRAWINGS

The features of this invention together with further objects and advantages thereof, may best be understood by reference to the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of one embodiment of an electrohydraulic jet apparatus according to the present invention;

FIG. 2 is a cross-sectional view of a second embodiment of an electrohydraulic jet apparatus according to the present invention;

FIG. 3 is a schematic illustration of a plow assembly employing a plurality of electrohydraulic jet apparatus according to the present invention in combination with a plurality of metal moils; and

FIG. 4 is a schematic illustration of a plow assembly employing a plurality of electrohydraulic jet apparatus according to the present invention, in combination with a plurality of heating units and a plurality of metal moils.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The process and apparatus can best be described with reference to the drawings. For purposes of illustration, a single electrohydraulic jet apparatus will be described. It will be readily understood that such jets may be employed singly or in any desired number arranged in any configuration designed to achieve a desired result.

Specifically, the apparatus includes a container 10 which defines a reaction chamber 11 having a nozzle 12. Liquid is supplied to the container through a pressurized line 13 and enters the reaction chamber 11. The liquid preferably is water but may comprise any suitable non-explosive fluid having characteristics tailored for a particular operation such as improved lubricating qualities for enhancing the performance of mechanical moils. The fluid enters reaction chamber 11 through a port 14. This port may be provided with valve means 15 operable to seal the reaction chamber 11 during production of the jet. Coupling electrodes 16, 17 extend into the reaction chamber 11. These electrodes 16, 17 are insulated from the container 10 by insulating means 18, 19. Metallic sleeves 20, 21 are provided for each electrode 16, 17. The sleeves 20, 21 are mechanically and electrically connected to container 10 and are not grounded. The electrodes 16, 17 are connected through switch means 22 to a source of electrical energy which may be a capacitor bank 23 which is in turn connected across a high voltage power source (not shown). Any suitable source of electrical energy can be employed in this embodiment. In addition to the preferred capacitor bank, induction coils, transformers and the like may be used. For illustration purposes the source of electrical energy has been shown as a capacitance 23. Because the electrode sleeves 20, 21 and container 10 are not grounded, they serve as a capacitive voltage divider across the gap between the electrodes 16, 17 when the switch means 22 is actuated. One plate of the capacitance 23 is connected to ground at to the electrode 17. Upon actuation of the switch means 22 which can be a gas discharge tube, a triggered gap or the like, the high voltage starting gradients from the side walls of the container 10 to electrodes 16, 17 are always half the gradient across the electrodes. This ensures a controlled and predictable streamer discharge across the electrode gap. The insulating means 18, 19 also serve to prevent unpredictable firing across the gap after erosion of the electrodes by ensuring that the gradient between the electrodes is greater than the electrode to wall gradient.

Prior to actuation of the device, the reaction chamber is substantially completely filled with liquid supplied through the port 14. When the electrical energy stored in the capacitance 23 is discharged across the electrodes 16, 17 by actuation of the switch means 22, a high temperature channel is generated between the electrodes 16, 17 with the following effects: (1) a high pressure sonic front travelling outward from the discharge channel: (2) a high temperature expanding gaseous bubble containing superheated steam and a substantial amount of ionized species and neutral molecules: and (3) a continuum of high intensity light coincident with the time of discharge. Studies have shown that the conversion from electrical energy to heat, sound and light is highly efficient, utilizing about fifty percent (50 percent) of the total discharge energy, the remainder being lost in the external circuitry. Some of the sound produced within the container 10 and all light produced therein is absorbed in the liquid and reconverted into usable heat. The time of discharge of the capacitor circuit is of the order of 50 microseconds. During this interval about 27,000 horsepower of total energy per kilojoule of energy supplied is released into the liquid in the reaction chamber 11 while the liquid is in a substantially static condition. The extremely high temperatures (20,000.degree. - 30,000.degree. K) and pressures (100,000- 200,000psi) developed in the channel between the electrodes 16, 17 cause the gaseous bubble formed therein to expand at a very rapid rate. Check means such as ball valve 15 serve to close the liquid entry port 14 and thus the liquid confined within the reaction chamber 11 meets mechanical resistance in all directions except through the nozzle opening 12. This nozzle opening 12 is preferably located on-center with the position of the spark discharge between the electrodes 16, 17.

If desired, shutter means 24 may be employed to close the nozzle opening 12 between pulses. The shutter means 24 can be actuated electrically or mechanically and may be connected through a circuit 25 to a sensor 26 which is in turn connected to the switch means 22. The sensor 26 acts to synchronize the opening of the shutter 24 with the discharge of the capacitance 23 to effect proper operation. Valve means or the like can be employed in place of the shutter 24. For example, an electromagnetically actuated solenoid valve could be used to alternately open and close the nozzle opening 12.

Referring to FIG. 2, an embodiment is shown in which a freely accelerating piston 30 is employed to compress the liquid in the reaction chamber 11 prior to discharge of the capacitor 23 between the electrodes 16, 17. The liquid is supplied to the reaction chamber 11 through suitable means such as port 31. In this embodiment, the piston 30 is driven at a high rate of speed through a cylinder 32 by external power means (not shown). The piston 30 picks up the liquid supplied by the port 31 and accelerates this liquid during delivery into reaction chamber 11. The liquid thus enters the reaction chamber 11 at a high rate of speed and with considerable force. It fills the reaction chamber 11 and at the instant that the chamber is filled with the substantially incompressible fluid, i.e. at top-dead-center of the piston, switch means 22 cause discharge of the capacitance 23 between the electrodes 16, 17. The rapidly expanding gaseous bubble created by the electric discharge adds even greater force to that already transferred to the liquid by the piston 30 which is instantaneously locked in its forwardmost position so as to confine the space of reaction chamber 11 and is then retracted by an appropriate connecting rod and accelerating mechanism. Since at the instant of electric discharge the reaction chamber 11 is essentially a closed vessel having only a nozzle opening, all of the force will be directed in driving a slug of water through the nozzle opening.

In FIG. 3 there are shown a multiplicity of electrohydraulic jet units 10 arranged serially one above the other on a common "plow" or stand 40. A suitable number of metal cutting bits or moils 41 are also arranged on the stand 40 in cooperative relationship with the jet units 10. The stand is mounted on a suitable means such as rails 42 for travel laterally across a mine wall or the like so that the surface thereof is acted on by the electrohydraulic jet units 10 and then the metal cutting bits 41. Suitable transport means 43, such as wheels or tracks or the like, suitably powered may be employed to advance the stand 40 in the direction of the mine wall after each pass across the mine face so that the units are repositioned to remove additional material. The rock is fractured by the action of the electrohydraulic jet units 10 and then complete removal is effected by the action of the cutting bits 41.

Referring to FIG. 4 there are shown a multiplicity of electrohydraulic jet units 10 arranged serially one above the other on a common "plow" or stand 40. A bank 50 of infrared heating units 51 each having a filament 52 surrounded by a reflector 53 is mounted adjacent the electrohydraulic jet units 10. In the operation of this embodiment, the stand 40 is advanced toward the mine face by the motive means 43. The stand 40 travels across the mine face on rails 42. The rock of the mine face is first heated by the heating units 51 and then the action of the electrohydraulic jet units 10 acts to cool the rock. The resulting thermal shock acts in combination with the force of the electrohydraulic jet units to fracture the rock. Metal cutting bits 41 may also be used after the rock has been fractured effectuate the complete removal of the rock. The arrangement of the electrohydraulic jet units 10 and the heating units 51 can be reversed on the stand 40 so that the liquid used to fracture the rock by the jet units 10 also permeates the rock, is heated by the heating units 51 and expands as it turns to steam and subjects the rock to both thermal shock and fracturing. Again metal cutting bits 41 can be employed to aid in removal of the rock.

FIGS. 5, 6, and 7 of the drawings illustrate one known form of an electrohydraulic jet unit constructed in accordance with the invention and suitable for use in the overall systems shown in FIGS. 1. In FIG. 5, a pair of relatively thick, flat, circular steel plates are shown at 31 and 32 for supporting insulating sleeves 18 and 19 and the opposed central conducting electrodes 16 and 17. The relatively thick plates 31 and 32 have an inner, or central flat, circular, cavity defining, thick plate 33 sandwiched between them that also is constructed of steel. The plates 31, 32 and 33 are held together in assembled relation by means of a plurality of relatively large, threaded bolts and nuts 34 and 35 arranged around the periphery of the plates and inserted through aligned apertures formed in the plates. The two inner faces of the outer plates 31 and 32 have suitable O-ring grooves formed therein (best shown in FIG. 7) which coact with coresponding grooves formed in the two faces of the inner steel plate 33 and support O-ringe seals 36 and 38 for sealing closed the space or cavity 39 formed by a central opening in the inner steel plate 33. The ends of the central electrodes 16 and 17 extend into the central cavity 39.

As best shown in FIG. 6, the central steel plate 33 has a small passageway 14 formed therein for supplying liquid to the interior of the cavity 39 as described earlier, and the discharge opening or nozzle 12 is formed approximately 90 arcuate degrees from the discharge opening or nozzle 12 as best shown in FIG. 7. FIG. 7 is an exploded view of the assembled structure shown in FIGS. 5 and 6 and illustrates in greater detail the construction of each of the outer plates 31 and 32 together with the subtended insulating sleeves 18 and 19 and their central conducting electrodes 16 and 17 as well as the construction of the inner or central cavity defining plate 33. All of the elements are of heavy thick steel plate construction so as to withstand the extremely high pressures built up during operation of the electrohydraulic jet unit as described earlier in the application.

Although the present invention has been described in connection with the preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. To be particular, while the embodiments of the invention herein disclosed have been described as adapted primarily for use in mining the vertical surfaces of a laterally extending underground mine shaft or tunnel, the invention is in no way restricted to such use but readily may be adapted for use in open pit mining and excavation, drilling, descallng, deicing, use as a pneumatic hammer, use in the manner of sand blasting equipment, and other similar applications as would be obvious to one skilled in the art in the light of the above teachings. Accordingly, any such modifications and variations are considered to be within the purview and scope of the invention as defined by the appended claims.

Claims

We claim:

1. A process for producing a high energy liquid jet with a confined chamber provided with an electrical discharge channel and an outlet opening which comprises:

a. supplying a relatively incompressible liquid to said chamber;

b. confining the liquid within said chamber;

c. discharging electric energy across the discharge channel through the liquid to create a shock wave in said liquid; and

d. directing at least a portion of the liquid directionally through the outlet opening under action of the shock wave whereby the liquid emerges as a high energy liquid jet.

2. The process of claim 1, including the step of applying mechanical force to the liquid to increase the energy level of the liquid prior to the discharge of electrical energy therein.

3. A process for producing a high energy liquid jet with an electrohydraulic chamber having a shaped outlet nozzle and at least one pair of spaced apart electrodes insulatingly supported within the chamber to define an electric channel, the process comprising:

a. confining a relatively incompressible liquid in the electrohydraulic chamber;

b. charging a capacitance to a desired level of electrical energy from an electrical power supply;

c. initiating a wave within the electrohydraulic chamber by discharging the electrical energy stored in the capacitance across the electrodes defining the discharge channel while the electrodes are surrounded by the liquid in the chamber; and

d. directing at least a portion of the liquid within the chamber out through the outlet nozzle under action of the shock wave as a high energy liquid jet.

4. The process of claim 3, further including capacitance dividing the electric energy appearing between the electrohydraulic chamber and the electrodes defining the electric discharge channel.

5. A process for producing repetitively pulsed high energy liquid jets with an electrohydraulic chamber having a shaped outlet nozzle and a pair of spaced apart electrodes insulatingly supported with the chamber to define an electric discharge channel, the process comprising:

a. providing a continuously available supply of a relatively incompressible liquid to the electrohydraulic chamber;

b. repetitively charging a capacitance connected to an electrical power supply to a desired level of electrical energy;

c. repetitively triggering the capacitance to discharge the same across the electrodes while surrounded by the liquid in the chamber to create a series of shock waves within said chamber; and

d. directing at least a part of the liquid within the chamber out through the nozzle under action of each shock wave as a pulsed liquid jet.

6. The process of claim 5, including the step of isolating the liquid supply from the chamber during electrical discharge.

7. Apparatus for producing a high energy liquid jet comprising:

a. electrohydraulic chamber means having liquid jet outlet means;

b. electric spark discharge means positioned within said chamber means;

c. supply means connected to said chamber for supplying liquid to said chamber;

d. electric circuit means connected to said electric spark discharge means for supplying electric energy to said electric spark means; and

e. switch means in said electric circuit means for selectively supplying electric energy to the electric spark discharge means whereby a shock wave is created in the liquid in the chamber means and at least a portion of the liquid is directed out through the outlet means as a high energy liquid jet.

8. Apparatus according to claim 7, wherein said electric circuit means includes,

f. capacitance means;

g. high voltage means connected to said electric circuit means for charging said capacitance means to a desired level of electrical energy; and

h. Wherein said switch means in said electric circuit means selectively discharges the capacitance means across the electric discharge means whereby a shock wave is created in the liquid in the chamber means and at least a portion of the liquid is directed out through the outlet means as a high energy liquid jet.

9. Apparatus according to claim 8, wherein the outlet means is shaped to force the liquid directed therethrough into a relatively cohesive mass.

10. Apparatus according to claim 9, wherein check valve means are included for making the electrohydraulic chamber a substantially closed chamber except for the outlet means at the time of electrical discharge.

11. Apparatus according to claim 10, wherein the electric spark discharge means comprises a pair of electrodes insulatingly supported within the electrohydraulic chamber so as to be surrounded by the liquid.

12. Apparatus according to claim 10, wherein each electrode is supported within a conductive shell electrically insulated therefrom and mechanically and electrically connected to the electrohydraulic chamber to form a capacitance voltage divider between the electrodes and the electrohydraulic chamber means.

13. Apparatus according to claim 12, wherein the chamber means and the capacitance means are not connected to a common electrical ground and the electrical discharge means is connected to a common electrical ground.

14. Apparatus according to claim 7, wherein the supply means includes check valve means for preventing reverse flow of the liquid.

15. Apparatus according to claim 7, including valve means selectively actuatable to open said jet outlet means upon electrical discharge of the capacitance means.

16. Apparatus according to claim 7, wherein said supply means includes cylinder means communicating directly with said electrohydraulic chamber means, port means for delivering liquid to the cylinder means and piston means freely acceleratible within said cylinder means for delivering the liquid from said port means to the chamber means.