CN115247984B - Electrode structure capable of focusing impact wave energy and electrode device composed of electrode structure - Google Patents

Abstract

The invention discloses an electrode structure that can focus shock wave energy under the hydroelectric effect and an electrode device composed of it. The electrode structure includes a high-voltage electrode, a ground electrode, a polypropylene insulating sleeve, a rubber gasket, a fixing nut, and an electrode shell; the electrode device includes a charging power supply, an energy storage capacitor, a current-limiting protection resistor, a power switch, and a high-voltage electric pulse switch. Gas gap switch, ultra dynamic strain gauge, electrode structure. Under the action of the hydroelectric effect, the invention uses the area size and distribution of the prefabricated holes in the electrode shell to focus the shock wave energy generated during the discharge of the hydroelectric effect and realize the directionality of the released energy. It has certain application in fields such as directional rock crushing. applicability.

Description

Electrode structure that can focus shock wave energy and its composed electrode device

Technical field

The invention relates to an electrode structure that can focus shock wave energy under the hydroelectric effect and an electrode device composed of it. It belongs to high-voltage electric pulse technology and can be applied to high-voltage electric pulse rock breaking, gas drainage and other fields.

Background technique

In the process of coal mining, rock formation control is an important link in the safe and efficient production of coal mines. As mining depth continues to increase, geological conditions gradually deteriorate, and the probability of causing mine safety accidents also continues to increase. During the mining process, coal and rock masses under high stress can easily accumulate huge energy. Under certain circumstances, the release of energy will be accompanied by the generation of impact mine pressure. The generation of impact mine pressure will instantly destroy the coal and rock mass, cause damage to the tunnel system, and even endanger personal safety.

The prevention and control of mine pressure shock is the most important link in the coal mining process, which has a serious impact on the safety and efficiency of coal mining. At present, the more mature stress control technologies include drilling and blasting technology and hydraulic fracturing technology. Hydraulic fracturing is used due to the large size of the equipment, the large flow of water required, and the difficulty in sealing holes under high pressure. The rock efficiency is low; drilling and blasting technology requires the use of chemical explosives, which has certain risks when the coal mine is rich in gas. The direction of the blasted rock fragments is uncontrollable and a large amount of dust will be generated, resulting in drilling and blasting with certain risks. limitation.

At present, the emerging technology - high-voltage electric pulse has been studied by many scholars and applied in the field of rock crushing, and it also has certain prospects in the field of coal mining anti-collision. The technology of using high-voltage electric pulses to crack hard roofs is safer and can effectively avoid the problem of coal mine gas explosions caused by blasting. It also avoids the high-pressure problem of hydraulic fractures and can effectively weaken hard roofs with less water flow.

High-voltage electric pulse technology in water refers to charging high-voltage electric equipment through a capacitor bank, and then releasing it through electrodes in water in a very short time, generating a pulse discharge in the water, and forming a plasma channel that penetrates both electrode poles and continuously expands, thereby Create a shock wave. Under the action of high temperature and high pressure during the discharge process, the bubble pulsation caused by the generation and collapse of bubbles will also generate a part of the shock wave. However, the generation of the shock wave is based on the formation of the plasma channel. The shock wave is generated between the two electrodes. The space spreads out in a shape similar to a sphere, and the energy release has no specific direction and is relatively scattered.

For the stress concentration problem caused by the hard roof of the underground well, not only cracking means are needed to weaken the stress, but also directional cracking needs to be carried out through different situations, so as to form an efficient stress control technology. Therefore, the energy generated by electrode discharge is focused to maximize energy release and controllability of the release direction, which has good application prospects for downhole stress control.

Contents of the invention

The present invention aims to provide an electrode structure that can focus shock wave energy under the hydroelectric effect and an electrode device composed of the same, and to study the changing relationship between the shock wave released by high-voltage electric pulses and the electrode structure.

The invention provides an electrode structure that can focus shock wave energy under the hydroelectric effect, including a high-voltage electrode, a ground electrode, a polypropylene insulating collar, a rubber gasket, an electrode shell, a fixing nut and a fixing ring;

The upper end of the high-voltage electrode is threaded, and the middle part of the high-voltage electrode is connected and fixed with a polypropylene insulating collar through a fixing nut. The high-voltage electrode is located inside the polypropylene insulating collar. The polypropylene insulating collar is fixed on the upper part of the electrode shell. The polypropylene insulating collar and the electrode The shell is tightly connected through a fixed ring; a rubber gasket is placed at the contact point between the polypropylene insulating collar and the electrode shell to increase the tightness of the contact between the two;

The ground electrode is fixed to the lower end of the electrode housing through threads; the ground electrode is screwed in through the threads at the bottom of the electrode housing, and then fixed with a nut;

The high-voltage electrode and the ground electrode are set opposite each other in the hole of the electrode shell. By rotating the thread on the lower end of the ground electrode, the distance between the ground electrode and the high-voltage electrode can be adjusted. The distance between the two electrodes is set to 1mm-5mm.

The total length of the high-voltage electrode is 74mm, which is composed of three parts: the upper end, the middle end, and the lower end. The upper end is a cylinder with a diameter of 4mm and a length of 70mm. An M8 thread with a length of 25mm is machined on the top of the cylinder, which is the upper end of the high-voltage electrode thread; the middle end is a diameter A 5mm, 2mm length cylinder with a 30° chamfer for the lower 1mm length; a 2mm diameter, 2mm length cylinder with a 45° tip chamfer at the bottom.

The ground electrode is composed of a smooth cylinder and a threaded cylinder; the upper part of the smooth cylinder has a diameter of 2mm, a length of 3mm, and a tip with a 45° chamfer at the top; the lower part is an M8 threaded cylinder with a length of 17mm.

The polypropylene insulating collar is a cylinder with a diameter of 8mm and a length of 95mm; the diameter of the built-in cavity is 4mm; 35mm from the top, add a polypropylene ring with a diameter of 12mm and a length of 4mm to fix it on the electrode housing.

The electrode shell has a cylindrical appearance and a hollow interior, through which the electrode passes. The electrode shell is composed of three cylinders with different outer diameters. The first cylinder in the upper part is connected to a fixed ring, and the second cylinder in the middle has a Rubber gasket, the outside of the third section of the lower cylinder is a smooth structure; the first section of the cylinder of the electrode housing is equipped with external threads for connecting to the fixed ring; the center of the top of the first section of the cylinder is a step hole, and the upper hole of the step hole is insulated with polypropylene Ring connection; there is a hole in the inner bottom of the second section of the cylinder for placing a rubber gasket; there is an internal thread in the center of the bottom of the third section of the cylinder for fixing the ground electrode, and there is an electrode housing cavity on the cylindrical surface above it. hole to expose the electrode.

The electrode housing hole 20 is provided with one or more holes. The cross-section of the electrode housing hole is rectangular, and the size is 2mm×10mm, 3mm×10mm or 5mm×10mm (this refers to the drilled hole). The cross-sectional dimensions corresponding to the front view); only one empty hole, two empty holes (set correspondingly before and after the electrode) or three empty holes (along the 120° direction) can be drilled at the bottom of the third cylinder of the electrode housing. drill three empty holes). The shock wave direction controllability and energy focusing of the electrode structure are achieved through the holes provided at the lower end of the electrode shell.

The fixed ring has a diameter of 22mm and a length of 13mm. It has a built-in thread with a length of 11mm and a diameter of M13. A round hole with a diameter of 8mm is drilled on the top of the fixed ring for the polypropylene insulating collar to pass through.

The high-voltage electrode passes through the built-in cavity from the lower part of the polypropylene insulating collar, and the high-voltage electrode and the polypropylene insulating collar are fixed with nuts; then the polypropylene insulating collar is placed in the built-in cavity of the electrode shell; a fixing ring is used Secure the polypropylene insulating collar to the electrode housing; screw the ground electrode through the thread at the bottom of the electrode housing and secure it with a nut. When fixing the electrode structure, the electrode spacing can be adjusted by adjusting the distance between the screw-in ground electrode and the high-voltage electrode. The distance between the two electrodes can be 1mm-5mm for testing.

The shock wave generated by the connection of two electrodes is the key to breaking rocks, and the discharge channel is determined by the distance between the two electrodes. During research, the amount of pulse energy released can be achieved by changing the distance between the two electrodes, and monitoring and analysis can be performed to obtain Find the optimal electrode spacing.

The invention also provides an electrode device made of the above electrode structure that can focus shock wave energy under the hydroelectric effect, including a charging power supply, an energy storage capacitor, a current limiting protection resistor, a power switch, a high-voltage electric pulse switch, and a gas gap. Switch, super dynamic strain gauge, electrode structure; the electrode structure is placed inside the rock cavity, and the high-voltage cable connects the charging power supply, energy storage capacitor, current limiting protection resistor, power switch, high-voltage electric pulse switch, gas gap switch, super dynamic strain The instrument and electrode structures are connected in turn.

The monitoring objects of the electrode device of the present invention can select granite samples of 100mm×100mm×100mm, 150mm×150mm×150mm, or 300mm×300mm×300mm. Select one surface of the granite sample and drill a hole with a diameter of 12mm and a length of 12mm at the center. It is a 75mm cylindrical cavity used for injecting conductive solutions and placing electrode structures. In order to tightly contact the electrode structure with the cavity, a sealing gasket is placed at the bottom of the electrode ring to achieve a sealed effect between the electrode and the rock material cavity.

To inject conductive liquid into the above granite cavity, different types of solutions can be used, such as tap water, NaCl solutions of different concentrations, CaCl ₂ solutions of different concentrations, AlCl ₃ solutions of different concentrations, etc.; the concentration of the three conductive liquids can be 1mol/ Five gradients of L, 1.5mol/L, 2mol/L, 3mol/L, and 5mol/L were tested; when selecting conductive liquids, green safety, wide sources, cost-effectiveness, etc. were considered. Tap water was selected as the conductive liquid. Tap water is currently considered. The most practical in actual application environment. During research, you can consider replacing different conductive liquids and monitor the magnitude of the pulse energy generated by different conductive liquids during the discharge process, so as to analyze the best conductive liquid that can be used to break rocks, making the damage effect more beneficial.

Paste strain gauges on both sides of the granite sample. Choose two models: BFH120-80AA-D150 and BFH120-20AA-D150. Select the side in the same direction as the electrode shell pore to paste two BFH120-20AA-D150 strain gauges. Select the center line for the position. One up and one down, paste a BFH120-80AA-D150 strain gauge on the symmetry plane, select the exact center position, and paste a BFH120-20AA-D150 strain gauge on the rock wall in the direction perpendicular to the pores of the electrode shell. The position is the same as the upper position of the same model. The strain gauges are the same.

A super dynamic strain gauge is used to connect the strain gauge to collect the frequency during high-voltage electric pulse discharge. When the two electrodes are connected in the sealed cavity, the shock wave generated by the connection of the two electrodes can be collected and analyzed by the ultra-dynamic strain gauge to study the size and direction of the holes in the electrode shell and the direction of pulse propagation under the condition of conductive liquid. Correlation between frequency sizes, thereby exploring the relationship between electrode hole size and direction and shock wave energy release and propagation direction.

The present invention provides the application of an electrode device capable of focusing shock wave energy under the above-mentioned hydroelectric effect, which includes the following steps:

a. For this test material, granite samples of 100mm × 100mm × 100mm, 150mm × 150mm × 150mm, and 300mm × 300mm × 300mm can be selected. A cylindrical cavity hole is drilled in the center of a surface, and the electrode is selected for the hole size. diameter and length.

b. Select the axis position of one side arbitrarily, and paste two strain gauges, one above the other. Paste one strain gauge on the opposite side, and the paste position should be horizontal to the electrode gap; on the other side of the adjacent Attach a strain gauge to one side, level with the electrode gap.

c. Place the high-voltage electrode into the cavity of the polypropylene insulating collar, and fix the upper end with a nut; place the polypropylene insulating collar in the electrode cavity; in order to ensure good sealing performance, connect the ring of the insulating collar and the electrode At the contact point of the shell, insert a rubber washer and then use a fixing ring to connect and fix it; the ground electrode is screwed into the bottom of the electrode shell through threads, and the distance between the high-voltage electrode and the ground electrode is adjusted. The electrode distance can be between 1mm and 5mm. After adjusting the gap distance, fix the ground electrode with a fixing nut.

d. The hole size of the electrode shell can be of various specifications such as 2mm×10mm, 4mm×10mm, 5mm×10mm, etc. One hole, two holes, three holes, etc. can be selected to form different electrode structures. .

e. Inject conductive solution into the cavity drilled in granite. Different types of solutions can be used, such as tap water, NaCl solutions of different concentrations, CaCl ₂ solutions of different concentrations, AlCl ₃ solutions of different concentrations, etc.; three conductive liquid concentrations Five gradients of 1mol/L, 1.5mol/L, 2mol/L, 3mol/L, and 5mol/L can be used for testing. In order to enhance the sealing effect, a sealing gasket is placed at the bottom of the ring of the electrode housing, and the sealing gasket is used to increase the tightness between the electrode and the granite cavity.

f. Use the upper and lower cover plates to assemble and fix the electrode and the granite sample. Rotate the nuts at the four corners of the upper and lower cover plates to fix the tightness of the sample, electrode and cover plate. Connect the high-voltage cable to the upper end of the high-voltage electrode, and connect the ground cable to the fixed ring between the upper cover plate and the electrode.

g. Connect the fixed electrodes and samples to the high-voltage electric pulse discharge device, and connect the pasted strain gauges to the collection ports of the hyperdynamic strain gauge.

h. Use high-voltage cables to connect the charging power supply, energy storage capacitor, current-limiting protection resistor, power switch, high-voltage electric pulse switch, gas gap switch, hyperdynamic strain gauge and electrode structure in sequence. Start the hyperdynamic strain gauge first, and then Turn on the power switch and observe the voltage value of the charging power supply. The charging voltage can be selected according to the actual situation. The initial range is 5kV-20kV. When the voltage value is reached, turn off the power switch and turn on the high-voltage pulse switch for discharge. After the discharge is completed, the hyperdynamic strain gauge stops collecting data, leaks the residual voltage, and analyzes the data.

i. Repeat the above a-h process, explore the collected data under different electrode shell hole sizes and cavity placement angles, and analyze the relationship between the pulse energy size and cracking direction and the electrode shell holes.

Beneficial effects of the present invention:

(1) Depending on the electrode structure, pulse energy release in different situations can be achieved by simply replacing the electrode shell, which changes the previous way of releasing energy in a spherical shape and focuses the energy to a certain position and direction for release, which can meet the needs of engineering projects. The need for field-directed fragmentation;

(2) Based on the data obtained from ultra-dynamic strain gauge monitoring, the impact energy can be analyzed, and the relationship between changing the electrode gap, conductive solution, etc. and the pulse energy under the condition of a hole in the electrode shell can also be monitored;

(3) The device can also be used in true triaxial pressure tests. The electrodes are built into the material sample and the true triaxial press is used to simulate the stress in the real working environment. The optimal parameters can be explored. Provide a new technology for the field of underground coal mining energy.

Description of drawings

Figure 1 is a schematic structural diagram of an electrode device capable of focusing shock wave energy under the hydroelectric effect of the present invention;

Figure 2 is a schematic diagram of the pasting position of the strain gauge on the side of the granite sample in the example of the present invention;

Figure 3 is an electrode structure diagram of the present invention;

Figure 4 is a cross-sectional view of the central axis of Figure 3;

Figure 5 is a schematic diagram of the hollow holes in the electrode housing of different sizes; (a) the hollow hole size is 2mm×10mm, (b) the hollow hole size is 5mm×10mm;

Figure 6 is a diagram of high-voltage electrode parts;

Figure 7 is a diagram of the ground electrode parts;

Figure 8 is a diagram of the parts of the polypropylene insulating collar;

In the picture: 1 is the charging power supply, 2 is the current limiting protection resistor, 3 is the energy storage capacitor, 4 is the gas gap switch, 5 is the discharge electrode, 6 is the upper cover, 7 is the sample, 8 is the strain gauge, 9 is Under the cover, 10 is the super dynamic strain gauge, 11 is the high-voltage electric pulse switching device, 12 is the power switch, 13 is the upper end of the high-voltage electrode thread, 14 is the fixing nut, 15 is the polypropylene insulating collar, and 16 is the fixing ring. , 17 is the rubber gasket, 18 is the electrode shell, 19 is the high voltage electrode tip, 20 is the hole in the electrode shell, 21 is the ground electrode tip, 22 is the lower end of the ground electrode thread.

Detailed ways

The present invention is further described below through examples, but is not limited to the following examples.

Example:

As shown in Figure 1-8, an electrode structure that can focus shock wave energy includes a high-voltage electrode, a ground electrode, a polypropylene insulating collar, a rubber gasket, an electrode shell, a fixing nut, and a fixing ring;

The upper end of the high-voltage electrode is provided with a thread. The middle part of the high-voltage electrode is connected and fixed with a polypropylene insulating collar 15 through a fixing nut 14. The high-voltage electrode is located inside the polypropylene insulating collar 15. The polypropylene insulating collar 15 is fixed on the upper part of the electrode shell 18. The polypropylene The insulating collar 15 and the electrode housing 18 are tightly connected through a fixed ring 16; a rubber gasket 17 is placed at the contact point between the polypropylene insulating collar 15 and the electrode housing 18 to increase the tightness of the contact between the two;

The ground electrode is fixed to the lower end of the electrode housing 18 through threads; the ground electrode is screwed in through the threads at the bottom of the electrode housing 18, and then fixed with a fixing nut 14;

The high-voltage electrode and the ground electrode are installed opposite each other in the hole 20 of the electrode housing (the hole 20 is the hole drilled in the electrode housing 18). The distance between the ground electrode and the high-voltage electrode is adjusted by rotating the thread at the lower end of the ground electrode. The electrode distance is set to 1mm-5mm.

Specifically, the total length of the high-voltage electrode is 74mm, which is composed of three parts: the upper end, the middle end, and the lower end. The upper end is a cylinder with a diameter of 4mm and a length of 70mm. The upper end is the part exposed on the polypropylene insulating collar 15, and the middle end is a polypropylene insulating collar. 15, the lower end is the part exposed under the polypropylene insulating collar 15 (the lower part of the polypropylene insulating collar 15 is located inside the electrode housing 18); the top of the high-voltage electrode is machined with an M8 size thread with a length of 25mm, and is processed as The upper end of the high-voltage electrode thread is 13; the middle end is a cylinder with a diameter of 5mm and a length of 2mm, and the lower 1mm length is chamfered at 30°; the lower end is a cylinder with a diameter of 2mm and a length of 2mm, and the tip is chamfered at 45° at the bottom.

The ground electrode is composed of a smooth cylinder and a threaded cylinder; the upper part of the smooth cylinder has a diameter of 2mm, a length of 3mm, and a tip with a 45° chamfer at the top; the lower part is an M8 threaded cylinder with a length of 17mm.

The polypropylene insulating collar is a cylinder with a diameter of 8mm and a length of 95mm; the diameter of the built-in cavity is 4mm; 35mm from the top, add a polypropylene ring with a diameter of 12mm and a length of 4mm to fix it on the electrode housing.

The electrode shell has a cylindrical appearance and a hollow interior (the electrode passes through it). The electrode shell is composed of three cylinders with different outer diameters. The upper first cylinder (outer diameter is 14mm, inner diameter is 8mm, and height is 12mm). Fixed ring connection, the second section of the middle cylinder (outer diameter is 22mm, inner diameter is 8mm, height is 3mm) with a rubber gasket inside (outer diameter is 16mm, inner diameter is 10mm, height is 2mm), and the third section of the lower cylinder is (The outer diameter is 10mm, the inner diameter is 8mm, and the height is 62mm) The outside is a smooth structure; the first section of the cylinder of the electrode housing is equipped with an external thread (M14 external thread with a height of 10mm), which is used to connect the fixed ring 16; the first The center of the top of the segment cylinder is a step hole (the diameter of the upper hole of the step hole is 12mm and the height is 2mm; the diameter of the lower hole is 8mm). The top of the step hole is connected to the polypropylene insulating collar 15; there is a hole in the bottom of the second segment of the cylinder. It is used to place the rubber gasket 17; there is an internal thread (M8) in the center of the bottom of the third section of the cylinder, which is used to fix the ground electrode. There is an electrode shell hole 20 on the cylindrical surface above it to expose the electrode.

The electrode housing hole 20 is provided with one or more holes. The cross-section of the electrode housing hole is rectangular, and the size is 2mm×10mm, 3mm×10mm or 5mm×10mm (this refers to the drilled hole). The cross-sectional dimensions corresponding to the front view); you can drill only one empty hole at the bottom of the third cylinder of the electrode housing, or you can drill two empty holes (corresponding to the front and rear of the electrode) or three empty holes (along the 120° direction line Drill three empty holes). The shock wave direction controllability and energy focusing of the electrode structure are achieved through the holes provided at the lower end of the electrode shell.

The fixed ring 16 connected to the upper end of the electrode housing has a diameter of 22mm and a length of 13mm. There is a thread with a length of 11mm and a diameter of M13 inside the fixed ring 16. A circular hole with a diameter of 8mm is drilled on the top of the fixed ring for Polypropylene insulating collar passes through.

The invention also provides an electrode device made of the above electrode structure that can focus shock wave energy under the hydroelectric effect, including a charging power supply 1, an energy storage capacitor 3, a current limiting protection resistor 2, a power switch 12, and a high-voltage electric pulse switch 11 , gas gap switch 4, super dynamic strain gauge 10, electrode structure; the electrode structure is placed inside the rock borehole, and the high-voltage cable sequentially connects the charging power supply 1, the power switch 12, the current limiting protection resistor 2, the energy storage capacitor 3, the gas gap The switch 4, the discharge electrode 5, the super dynamic strain gauge 10, and the high-voltage electric pulse switch 11 are structurally connected.

When in use, the electrode device is placed into the sample (i.e., the cavity of the rock drill hole). The sample is selected from a granite sample of 100mm×100mm×100mm, 150mm×150mm×150mm, or 300mm×300mm×300mm. On one surface, a cylindrical cavity with a diameter of 12mm and a length of 75mm is drilled in the center for injecting the conductive solution and placing the electrode structure. In order to tightly contact the electrode structure with the cavity, a sealing gasket is placed at the bottom of the electrode ring to achieve a sealed effect between the electrode and the rock material cavity.

The present invention provides the application of an electrode device capable of focusing shock wave energy under the above-mentioned hydroelectric effect, which includes the following steps:

To inject conductive liquid into the above granite cavity, different types of solutions can be used, such as tap water, NaCl solutions of different concentrations, CaCl ₂ solutions of different concentrations, and AlCl ₃ solutions of different concentrations; the concentration of the latter three conductive liquids can be 1 mol /L, 1.5mol/L, 2mol/L, 3mol/L, 5mol/L five gradients were tested;

Paste strain gauges on both sides of the sample, choose BFH120-80AA-D150 and BFH120-20AA-D150. Select the side in the same direction as the electrode shell pore to paste two BFH120-20AA-D150 strain gauges. Select the center line as the position. Next, paste a BFH120-80AA-D150 strain gauge on the symmetry plane, select the exact center position, and paste a BFH120-20AA-D150 strain gauge on the rock wall perpendicular to the pore direction of the electrode shell. The position is the same as the upper position of the same model. The strain gauges are the same;

The super dynamic strain gauge 10 is used to connect the strain gauge 8 to collect the frequency during high-voltage electric pulse discharge; when the two electrodes are connected in the sealed cavity, the shock wave generated by the connection of the two electrodes can be collected through the super dynamic strain gauge 10 , analyze and study the correlation between the size and direction of the electrode shell hole and the pulse propagation direction and frequency under the condition of conductive liquid, thereby exploring the relationship between the size and direction of the electrode hole and the shock wave energy release and propagation direction.

The above application specifically includes the following steps:

a. This test material selects a 150mm×150mm×150mm granite sample, and drills a cavity cylinder with a diameter of 12mm and a length of 75mm at the center of a surface.

b. Select the axis position of any side and paste the strain gauge model BFH120-20AA-D150. The pasting positions are 75mm and 120mm away from the bottom surface; paste the strain gauge model BFH120-80AA-D150 on the opposite side. , choose the pasting position 75mm away from the bottom surface; paste a BFH120-20AA-D150 strain gauge on the other adjacent side, the position is the same as the strain gauge 75mm away from the adjacent surface.

c. Place the high-voltage electrode into the cavity of the polypropylene insulating collar, and fix the upper end with a nut; place the polypropylene insulating collar in the electrode cavity; in order to ensure good sealing performance, connect the ring of the insulating collar and the electrode At the contact point of the shell, insert a rubber washer and then use a fixing ring to connect and fix it; the ground electrode is screwed into the bottom of the electrode shell through threads, and the distance between the high-voltage electrode and the ground electrode is adjusted. The electrode distance can be between 1mm and 5mm. In this step, 2mm is selected as the discharge gap. After adjusting the gap distance, fix the ground electrode with a fixing nut.

d. The hole size of the electrode shell can be a through hole of 5mm×10mm. The direction of the hole in the electrode shell is consistent with the horizontal connection direction of two BFH120-20AA-D150 strain gauges and BFH120-80AA-D150 strain gauges.

e. Inject the conductive solution into the cavity drilled in the granite. The conductive solution selected in this step is tap water; place the assembled electrode inside the sample cavity. In order to enhance the sealing effect, a sealing gasket is placed at the bottom of the ring of the electrode housing, and the sealing gasket is used to increase the tightness between the electrode and the granite cavity.

f. Use the upper and lower cover plates to assemble and fix the electrode and the granite sample. Rotate the nuts at the four corners of the upper and lower cover plates to fix the tightness of the sample, electrode and cover plate. Connect the high-voltage cable to the upper end of the high-voltage electrode, and connect the ground cable to the fixed ring between the upper cover plate and the electrode.

g. Connect the fixed electrodes and samples to the high-voltage electric pulse discharge device, and connect the pasted strain gauges to the collection ports of the hyperdynamic strain gauge.

h. The high-voltage cable connects the charging power supply 1, power switch 12, current limiting protection resistor 2, energy storage capacitor 3, gas gap switch 4, discharge electrode 5, super dynamic strain gauge 10, and high-voltage electric pulse switch 11 in sequence. Start the super dynamic strain gauge first, then turn on the power switch, and observe the voltage value of the charging power supply. The charging voltage can be selected according to the actual situation. The initial range can be between 5kV and 20kV. When the voltage value is reached, turn off the power switch and turn on the high-voltage pulse. The switch discharges. After the discharge is completed, the hyperdynamic strain gauge stops collecting data, leaks the residual voltage, and analyzes the data.

i. Repeat the above a-h process, explore the collected data under different electrode shell hole sizes and cavity placement angles, and analyze the relationship between the pulse energy size and cracking direction and the electrode shell holes.

The effect of focusing and directional release of energy generated during electrode discharge can be achieved only by replacing the electrode shell. Because different electrode shell holes can achieve different energy focusing, the electrode shell can be replaced.

Claims (10)

1. An electrode structure capable of focusing shock wave energy, characterized in that: the electrode structure comprises a high-voltage electrode, a grounding electrode, a polypropylene insulating collar, a rubber gasket, an electrode shell, a fixing nut and a fixing circular ring;

the upper end of the high-voltage electrode is provided with threads, the middle part of the high-voltage electrode is fixedly connected with the polypropylene insulation sleeve ring through a fixing nut, the high-voltage electrode is positioned in the polypropylene insulation sleeve ring, the polypropylene insulation sleeve ring is fixedly arranged on the upper part of the electrode shell, and the polypropylene insulation sleeve ring is fixedly connected with the electrode shell through a fixing circular ring; a rubber gasket is sleeved at the contact part of the polypropylene insulating collar and the electrode shell; increasing the tightness of the contact between the two;

the grounding electrode is fixed at the lower end of the electrode shell through threads; the grounding electrode is screwed in through threads at the bottom of the electrode shell, and then is fixed by using a nut;

the high-voltage electrode and the grounding electrode are arranged in the hollow hole of the electrode shell relatively to the device, and the distance between the grounding electrode and the high-voltage electrode is adjustable by rotating the threads at the lower end of the grounding electrode, and the distance between the grounding electrode and the high-voltage electrode is set to be 1mm-5mm;

the direction of the shock wave of the electrode structure is controllable, and the energy focusing is realized through a hollow hole arranged at the lower end of the electrode shell; the shock wave generated by the connection of the two electrodes is the key of breaking rock, and the released pulse energy is realized by changing the distance between the two electrodes; injecting conductive solution into the hollow hole of the electrode shell, placing the electrode structure, and when the two electrodes are conducted in the sealed cavity, the two electrodes are connected to generate shock waves.

2. The focused shockwave energy electrode structure according to claim 1, wherein: the total length of the high-voltage electrode is 74mm, and the high-voltage electrode consists of an upper end, a middle end and a lower end, wherein the upper end is a cylinder with the diameter of 4mm and the length of 70mm, and the top of the cylinder is provided with a thread with the length of 25mm and the size of M8, so that the upper end of the thread of the high-voltage electrode is processed; the middle end is a cylinder with the diameter of 5mm and the length of 2mm, and the length chamfer of the lower part of 1mm is 30 degrees; the lower end is a cylinder with the diameter of 2mm and the length of 2mm, and the bottom is chamfered to be a tip with 45 degrees.

3. The focused shockwave energy electrode structure according to claim 1, wherein: the grounding electrode consists of a smooth cylinder and a threaded cylinder; the smooth cylinder of the upper half part has a diameter of 2mm and a length of 3mm, and the top chamfer is a tip with an angle of 45 degrees; the lower half is a threaded cylinder of M8 and the length is 17mm.

4. The focused shockwave energy electrode structure according to claim 1, wherein: a cylinder with the diameter of 8mm and the length of 95mm of the polypropylene insulating collar; the diameter of the built-in cavity is 4mm; at a distance of 35mm from the top, a polypropylene ring of 12mm diameter and 4mm length was added, which served to secure it to the electrode housing.

5. The focused shockwave energy electrode structure according to claim 1, wherein: the electrode shell is cylindrical in appearance, hollow in the interior and through which an electrode passes, the electrode shell consists of three sections of cylinders with different outer diameters, the upper first section of cylinder is connected with a fixed circular ring, the middle second section of cylinder is internally provided with a rubber gasket, and the outer side of the lower third section of cylinder is of a smooth structure; the first section cylinder of the electrode shell is provided with external threads for connecting and fixing the circular ring; the center of the top of the first section of cylinder is a step hole, and an upper hole of the step hole is connected with a polypropylene insulation lantern ring; the bottom of the second section of cylinder is provided with a hole for placing a rubber gasket; an internal thread is arranged at the center of the bottom of the third section of cylinder and used for fixing the grounding electrode, and an electrode shell hollow hole is arranged on the cylindrical surface above the grounding electrode to expose the electrode;

the fixed ring is internally provided with threads, a round hole with the diameter of 8mm is drilled at the top of the fixed ring, and the polypropylene insulation lantern ring passes through the round hole.

6. The focused shockwave energy electrode structure according to claim 5, wherein: one or more electrode shell holes are arranged, the section of each electrode shell hole is rectangular, and the size of each electrode shell hole is 2mm multiplied by 10mm, 3mm multiplied by 10mm or 5mm multiplied by 10mm; drilling a hollow hole at the bottom of a third section of cylinder of the electrode shell, or symmetrically arranging two hollow holes back and forth or uniformly distributing three hollow holes along the circumference; the direction of the shock wave of the electrode structure is controllable and the energy is focused by setting the size and the position of the hollow hole.

7. An electrode device capable of focusing shock wave energy under a hydro-electric effect, which adopts the electrode structure as set forth in any one of claims 1 to 6, and is characterized in that: the device comprises a charging power supply, an energy storage capacitor, a current-limiting protection resistor, a power switch, a high-voltage pulse switch, an air gap switch, an ultra-dynamic strain gauge and an electrode structure; the electrode structure is arranged in the cavity of the rock sample, and the high-voltage cable sequentially connects the charging power supply, the power switch, the current-limiting protection resistor, the energy storage capacitor, the gas gap switch, the discharge electrode, the super-dynamic strain gauge and the high-voltage pulse switch structure;

the rock sample is prepared by selecting a granite sample with the diameter of 100mm multiplied by 100mm, the diameter of 150mm multiplied by 150mm, the diameter of 300mm multiplied by 300mm, selecting one surface of the granite sample, and drilling a cylindrical cavity with the diameter of 12mm and the length of 75mm at the right center position for injecting conductive solution and placing an electrode structure; in order to tightly contact the electrode structure with the cavity, a sealing gasket is arranged at the bottom of the electrode ring and used for achieving the effect of sealing the electrode and the rock material cavity.

8. A method of using an electrode assembly for focusing shock wave energy under the electro-hydraulic effect as defined in claim 7, wherein:

injecting conductive liquid into the cavity of the rock sample, and using different types of solutions; pasting strain gauges on two sides of a sample, selecting BFH120-80AA-D150 and BFH120-20AA-D150, pasting two BFH120-20AA-D150 strain gauges on one surface of the same direction as the hole of the electrode shell, selecting a center line from top to bottom, pasting one BFH120-80AA-D150 strain gauge on the symmetrical surface, selecting a right-centered position, pasting one BFH120-20AA-D150 strain gauge on the rock wall surface vertical to the hole direction of the electrode shell, wherein the positions are the same as those of the strain gauge on the upper position with the same size;

the ultra-dynamic strain gauge is connected with the strain gauge to collect the frequency during high-voltage pulse discharge; when the two electrodes are conducted in the sealed cavity, shock waves generated by the connection of the two electrodes are collected and analyzed through the super-dynamic strain gauge, and the correlation between the size and the direction of the holes of the electrode shell and the pulse propagation direction and the frequency is researched under the condition of conductive liquid, so that the relation between the size and the direction of the holes of the electrode and the energy release and propagation directions of the shock waves are explored.

9. The method of using an electrode assembly capable of focusing shock wave energy under the electro-hydraulic effect according to claim 8, wherein: the method comprises the following steps:

a. the test material selects granite samples of 100mm×100mm, 150mm×150mm or 300mm×300mm, drilling a cylindrical cavity hole in the center of the surface of the sample, wherein the size of the hole is determined according to the diameter and the length of the electrode;

b. the axis position of one side surface of the sample is arbitrarily selected, two strain gauges are stuck, and the sticking position is selected from top to bottom; sticking a strain gauge on the other opposite side surface, wherein the sticking position is selected from the position horizontal to the electrode gap; sticking a strain gauge on the other adjacent side surface, wherein the position of the strain gauge is horizontal to the electrode gap;

c. the high-voltage electrode is placed in a cavity of the polypropylene insulating sleeve ring, and the upper end of the high-voltage electrode is fixed by a nut; placing a polypropylene insulating collar in the electrode cavity; in order to ensure good sealing performance, a rubber gasket is sleeved at the contact position of the circular ring of the insulating sleeve ring and the electrode shell, and then the rubber gasket is connected and fixed by a fixed circular ring; the grounding electrode is screwed into the bottom of the electrode shell through threads, the distance between the high-voltage electrode and the grounding electrode is adjusted, the electrode distance is 1mm-5mm, and the grounding electrode is fixed by a fixing nut after the gap distance is adjusted;

d. the size of the hollow hole of the electrode shell is 2mm multiplied by 10mm, 4mm multiplied by 10mm or 5mm multiplied by 10mm, and one hollow hole, two hollow holes or three hollow holes are selected to form different electrode structures;

e. injecting conductive solution into the granite drilled cavity, using different types of conductive solution, placing a sealing gasket at the bottom of the circular ring of the electrode shell for enhancing the sealing effect, and improving the tightness degree of the electrode and the granite cavity by using the sealing gasket;

f. the electrodes and granite samples are assembled and fixed by using the upper cover plate and the lower cover plate, and the tightness degree of the samples, the electrodes and the cover plate is fixed by rotating nuts at four vertex angles of the upper cover plate and the lower cover plate; the upper end of the high-voltage electrode is connected with a high-voltage cable, and the upper cover plate is connected with a grounding cable at the fixed circular ring of the electrode;

g. connecting the fixed electrode and the sample to a high-voltage pulse discharge device, and respectively connecting the adhered strain gauges to acquisition ports of the super-dynamic strain gauge;

h. the high-voltage cable connects the electrode structures of the charging power supply, the energy storage capacitor, the current-limiting protection resistor, the power switch, the high-voltage pulse switch, the gas gap switch and the super-dynamic strain gauge in sequence, the super-dynamic strain gauge is started firstly, the power switch is turned on, the voltage value of the charging power supply is observed, the charging voltage is selected according to actual conditions, the range of 5kV-20kV is selected, after the charging voltage reaches the voltage value, the power switch is turned off, the high-voltage pulse switch is turned on to discharge, and after the discharging is finished, the super-dynamic strain gauge stops collecting data, leaks residual voltage and analyzes the data;

i. repeating the steps a-h, exploring the collected data under the conditions of different electrode shell hole sizes and angles when the cavity is placed, and analyzing the relation between the pulse energy size and the fracturing direction and the electrode shell hole.

10. The method of using an electrode assembly capable of focusing shock wave energy under the electro-hydraulic effect according to claim 9, wherein: the conductive solution comprises tap water, naCl solution and CaCl ₂ Solutions or AlCl ₃ A solution; the concentrations of the three salt solutions were measured in five gradients of 1mol/L, 1.5mol/L, 2mol/L, 3mol/L and 5 mol/L.