A high-voltage electric pulse induced coal rock stress shock wave monitoring device
By designing a high-voltage electric pulse-induced fracturing coal and rock stress shock wave monitoring device, the shortcomings of stress shock wave monitoring during electric crushing were solved, achieving real-time and accurate stress wave detection, providing efficient data support, and reducing equipment costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHONGQING UNIV
- Filing Date
- 2025-04-18
- Publication Date
- 2026-06-16
AI Technical Summary
In existing technologies, there are insufficient methods for monitoring stress shock waves during electro-cracking, making it impossible to achieve real-time, accurate, and direct measurement. Furthermore, these methods are severely affected by strong electric field interference, which increases the difficulty of signal acquisition.
A high-voltage pulse-induced fracturing coal and rock stress shock wave monitoring device was designed, including a high-voltage pulse capacitor, a voltage divider, a high-voltage pulse switch, and a high-voltage pulse fracturing generation chamber. Combined with a piezoelectric pressure sensor and a Faraday cage, a closed electromagnetic shielding environment is formed. The release of high-voltage pulses and stable detection of shock waves are achieved through needle electrodes and specimen clamping components.
It enables real-time, accurate, and direct monitoring of high-voltage electric pulse stress shock waves, provides accurate and reliable data support, avoids electromagnetic interference, reduces equipment costs, and improves the accuracy and real-time performance of measurements.
Smart Images
Figure CN120333981B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of coal mining technology, specifically to a high-voltage electrical pulse-induced coal and rock stress shock wave monitoring device. Background Technology
[0002] Coalbed methane (CBM), as an important unconventional natural gas resource, is characterized by its cleanliness, high efficiency, and low carbon footprint. As coal mining in my country gradually extends to deeper levels, CBM occurrence environments exhibit the characteristics of "high permeability, high energy density, high pollution, and low efficiency," with low coal seam permeability becoming a core factor restricting efficient CBM extraction. Therefore, developing efficient coal seam permeability enhancement technologies has become a key breakthrough direction for improving the development and utilization of CBM.
[0003] Currently, conventional methods for improving coal seam permeability include hydraulic fracturing, water jet permeability enhancement, deep blasting pre-fracturing, and high-voltage pulse discharge. These methods have all achieved certain results in improving coal seam permeability. However, they also have some drawbacks. For example, hydraulic fracturing has limitations in soft coal seams, such as a small fracturing range, easy closure of fractures, and insignificant permeability enhancement. Water jet permeability enhancement is limited by the jet structure, restricting its range. Deep blasting pre-fracturing may result in duds, posing safety hazards and limiting its widespread adoption. High-voltage pulse discharge, on the other hand, has advantages such as strong fracturing ability, green and controllable operation, significant fracturing effect, and ease of operation, making it particularly suitable for coal seam permeability enhancement.
[0004] Currently, high-voltage pulsed discharge technology is applied to coal seam permeability enhancement primarily through two methods: electrohydraulic fracturing and electro-fracturing. Electrohydraulic fracturing uses a liquid as the impact medium, utilizing the resulting stress shock wave front to act on the solid surface, thus inducing localized fracturing. Electro-fracturing, on the other hand, converts electrical energy into a plasma channel that directly acts on the solid medium. This plasma, combined with the resulting expansion stress, generates a larger stress shock wave within the solid material, resulting in a more pronounced fracturing effect and significantly higher energy utilization efficiency than the electrohydraulic effect. Therefore, in-depth research into the propagation mechanism and fracturing characteristics of electro-fracturing shock waves helps to reveal the mechanism by which stress shock waves affect the propagation and stress release of coal and rock fractures, thus providing theoretical support for optimizing permeability enhancement. Stress shock wave monitoring is the core means to achieve this research goal. By quantitatively analyzing the intensity, propagation path, and energy attenuation law of the shock wave, key data support is provided for studying the shock wave action mechanism, thereby optimizing electro-fracturing parameters and improving fracturing efficiency.
[0005] Existing high-voltage pulse discharge technology employs various monitoring methods, providing some support for obtaining experimental data on high-voltage pulse-induced fracturing of coal and rock masses. However, current research on stress shock wave monitoring primarily focuses on electrohydraulic fracturing, with relatively few methods specifically addressing stress shock waves during electro-fracturing. Furthermore, the presence of strong electric field interference during electro-fracturing prevents sensors from being directly attached to the specimen surface, further increasing the difficulty of signal acquisition. Simultaneously, current methods for monitoring stress shock waves in electro-pulse fracturing mainly rely on dynamic strain gauges, fiber optic grating sensors, and high-speed cameras. While these methods can capture some signals, they only obtain indirect data on the response caused by stress shock waves, failing to achieve real-time, accurate, and direct measurement of stress shock waves. Summary of the Invention
[0006] This invention aims to solve the technical problems existing in the prior art, and innovatively proposes a high-voltage electric pulse fracturing coal and rock stress shock wave monitoring device, which can capture the propagation characteristics of high-voltage electric pulse stress shock waves in coal and rock mass in real time, accurately and directly, and provide accurate and reliable data support for in-depth research on the mechanism of high-voltage pulse electric fracturing.
[0007] To achieve the above objectives, the present invention provides a high-voltage pulse fracturing coal and rock stress shock wave monitoring device, comprising a high-voltage pulse capacitor, a voltage divider, a high-voltage pulse switch, and a high-voltage pulse fracturing chamber connected in sequence to form a closed loop. A high-voltage probe and a Rogowski coil are installed on the wire connecting the high-voltage pulse fracturing chamber and the high-voltage pulse capacitor. The signal output terminals of the high-voltage probe and the Rogowski coil are both connected to an oscilloscope. A specimen is fixed in the high-voltage pulse fracturing chamber. A specimen clamping assembly is provided in the high-voltage pulse fracturing chamber corresponding to the specimen. Needle-shaped electrodes are provided on both sides of the specimen where the specimen clamping assembly is not provided, and the needle-shaped electrodes abut against the specimen and release high-voltage pulses.
[0008] Each specimen clamping assembly in the high-pressure pulse fracturing chamber is equipped with a piezoelectric pressure sensor. The output terminals of all piezoelectric pressure sensors are connected to the pressure detection signal input terminal of the stress wave signal acquisition device. Each piezoelectric pressure sensor in the high-pressure pulse fracturing chamber is provided with a Faraday cage for covering the piezoelectric pressure sensor. Each Faraday cage is connected to the power ground via a wire.
[0009] Each specimen clamping assembly includes a fixed base and a transmission rod slidably connected to the fixed base. One end of the transmission rod faces the specimen and is provided with a clamping plate for abutting against the specimen. All the clamping plates are combined to form a clamp. The other end of the transmission rod extends into the Faraday cage and abuts against the piezoelectric pressure sensor. The fixed base is provided with an insertion hole for the transmission rod to pass through, and a linear bearing is provided in the insertion hole.
[0010] In the above scheme: a fixing sleeve is provided on the outside of the needle electrode and it is fixed to the side wall of the high-voltage pulse fracturing chamber by the fixing sleeve. A clamping plate is also provided at one end of the fixing sleeve near the specimen, and the ends of the two needle electrodes pass through the clamping plate and abut against the specimen.
[0011] In the above scheme: the outer wall of the fixed sleeve is provided with threads, and two nuts are threadedly connected to the fixed sleeve. The two nuts are located on the inner and outer sides of the high-pressure pulse fracturing chamber, respectively, and the fixed sleeve is fixed by the inner and outer nuts pressing against the two sides of the side wall of the high-pressure pulse fracturing chamber.
[0012] In the above scheme: the fixed base includes a fixed panel, on which a pair of fixed bolts are fixed, and the fixed base is fixed to the side wall of the high-pressure pulse fracturing chamber by the fixed bolts. The structure is simple and the fixation is stable.
[0013] In the above scheme, both the transmission rod and the fixing sleeve are integral with the clamping plate, which can improve the structural rigidity.
[0014] In the above scheme: the high-voltage pulse capacitor is equipped with a high-voltage pulse power supply and a centralized control computer. The control output terminal of the centralized control computer is connected to the control signal input terminal of the high-voltage pulse power supply, and the power supply terminal of the high-voltage pulse power supply is connected to the power input terminal of the high-voltage pulse capacitor. The centralized control computer can adjust the power supply quantity and voltage of the high-voltage pulse power supply, and can charge the high-voltage pulse capacitor with the required amount of electricity through the gaps in the high-voltage pulse power supply.
[0015] In the above scheme, the installation distance between the needle electrode and the piezoelectric pressure sensor is greater than 50mm, which can ensure the safe operation of the equipment.
[0016] In the above scheme, there are four specimen clamping assemblies, which are respectively arranged on the front, rear, top, and bottom sides of the specimen. This allows for the detection of impacts in both the vertical and horizontal directions.
[0017] In the above scheme: the transmission rod, fixing sleeve, clamping plate, nut, linear bearing and fixing base are all made of PEEK material.
[0018] In summary, the beneficial effects of this invention are as follows: The needle-shaped electrode can release high-voltage pulses to the specimen, thereby electrically fracturing it. The specimen clamping assembly can fix the specimen and also serves as a transmission medium for the electric fracturing shock wave. Combined with a piezoelectric pressure sensor, it ensures stable acquisition of the impact force during the high-voltage pulse fracturing process, and transmits the data to a stress wave signal acquisition device for dynamic analysis. The Faraday cage reduces electromagnetic interference to the piezoelectric pressure sensor during high-voltage pulse discharge, forming a closed electromagnetic shielding environment that effectively blocks high-frequency electromagnetic waves and improves data accuracy. The structure is simple, enabling real-time, accurate, and direct capture of the propagation characteristics of high-voltage pulse stress shock waves in coal and rock masses, providing accurate and reliable data support for in-depth research on the high-voltage pulse electric fracturing mechanism. The equipment has low investment costs and can achieve faster and more accurate real-time signal feedback, effectively avoiding the limitations of conventional methods. Attached Figure Description
[0019] Figure 1 This is a system schematic diagram of the present invention.
[0020] Figure 2 This is a cross-sectional view of the high-voltage pulse fracturing chamber of the present invention. Figure 1 .
[0021] Figure 3 This is a cross-sectional view of the high-voltage pulse fracturing chamber of the present invention. Figure 2 . Detailed Implementation
[0022] The present invention will be further described below with reference to the embodiments and accompanying drawings:
[0023] like Figures 1-3 As shown, a high-voltage pulse fracturing coal and rock stress shock wave monitoring device includes a high-voltage pulse capacitor 3, a voltage divider 4, a high-voltage pulse switch 5, and a high-voltage pulse fracturing chamber 6 connected in sequence to form a closed loop. A high-voltage probe 16 and a Rogowski coil 17 are installed on the wire connecting the high-voltage pulse fracturing chamber 6 and the high-voltage pulse capacitor 3. The signal output terminals of both the high-voltage probe 16 and the Rogowski coil 17 are connected to an oscilloscope 19.
[0024] The high-voltage pulse capacitor 3 is equipped with a high-voltage pulse power supply 2 and a centralized control computer 1. The control output terminal of the centralized control computer 1 is connected to the control signal input terminal of the high-voltage pulse power supply 2, and the power supply terminal of the high-voltage pulse power supply 2 is connected to the power input terminal of the high-voltage pulse capacitor 3. The centralized control computer 1 can adjust the power supply and voltage of the high-voltage pulse power supply 2, and can charge the high-voltage pulse capacitor 3 with the required amount of electricity through the gaps in the high-voltage pulse power supply 2. The pulse release signal output terminal of the centralized control computer 1 is connected to the pulse release signal input terminal of the high-voltage pulse switch 5.
[0025] The high-pressure pulse fracturing chamber 6 contains a specimen, and four specimen clamping assemblies are provided in the high-pressure pulse fracturing chamber 6 corresponding to the specimen, respectively located on the front, rear and upper and lower sides of the specimen.
[0026] Each specimen clamping assembly in the high-pressure pulse fracturing chamber 6 is equipped with a piezoelectric pressure sensor 14, which, in conjunction with the piezoelectric pressure sensor 14, can detect impact stress in both the vertical and horizontal directions. The output terminals of all piezoelectric pressure sensors 14 are connected to the pressure detection signal input terminal of the stress wave signal acquisition unit 18. Within the high-pressure pulse fracturing chamber 6, a Faraday cage 15 is provided to cover each piezoelectric pressure sensor 14, and each Faraday cage 15 is connected to the power ground via a wire. Figure 1 To better showcase the fixing panel 11 and fixing bolts 12, only one side of the Faraday cage 15 is depicted, while the Faraday cages 15 on the other three sides are omitted.
[0027] Each specimen clamping assembly includes a fixed base and a transmission rod 10 slidably connected to the fixed base. The fixed base includes a fixed panel 11, on which a pair of fixing bolts 12 are fixed, and the fixed base is fixed to the side wall of the high-pressure pulse fracturing chamber 6 by the fixing bolts 12. The structure is simple and the fixation is stable. One end of the transmission rod 10 faces the specimen and is provided with a clamping plate 9 for abutting against the specimen. All the clamping plates 9 are combined to form a clamp. The transmission rod 10 and the clamping plate 9 are an integral structure, which can improve the structural rigidity. The other end of the transmission rod 10 extends from the gap of the Faraday cage 15 into the Faraday cage 15 and abuts against the piezoelectric pressure sensor 14. The fixed panel 11 is provided with an insertion hole for the transmission rod 10 to pass through, and a linear bearing 13 sleeved on the transmission rod 10 is provided in the insertion hole.
[0028] Both sides of the specimen without a specimen clamping assembly are equipped with needle-shaped electrodes 7. The ends of both needle-shaped electrodes 7 extend outside the high-pressure pulse fracturing chamber 6 and serve as wire connection terminals for the high-pressure pulse fracturing chamber 6. The needle-shaped electrodes 7 are in contact with the specimen and release high-pressure pulses. Each needle-shaped electrode 7 is equipped with a fixing sleeve and is fixed to the side wall of the high-pressure pulse fracturing chamber 6. The fixing sleeve has through holes for accommodating the needle-shaped electrodes 7. A clamping plate 9 is also provided at the end of the fixing sleeve near the specimen, with the two ends of the needle-shaped electrodes 7 located outside the fixing sleeve and outside the clamping plate 9, respectively. The installation distance between the needle-shaped electrodes 7 and the piezoelectric pressure sensor 14 is greater than 50 mm to ensure safe operation of the equipment.
[0029] The outer wall of the fixing sleeve is threaded, and two nuts 8 are threadedly connected to the fixing sleeve. The two nuts 8 are located on the inner and outer sides of the high-pressure pulse fracturing chamber 6, respectively, and are secured to the fixing sleeve by pressing against the side walls of the high-pressure pulse fracturing chamber 6. The fixing sleeve and the clamping plate 9 are also an integrated structure.
[0030] The components inside the high-pressure pulse fracturing chamber 6, such as the transmission rod 10, the fixed sleeve, the clamping plate 9, the nut, the linear bearing 13, the fixed panel 11, and the fixing bolt 12, are all made of high-pressure insulating, high-temperature resistant, and high-strength PEEK material to meet the experimental requirements of the equipment in high-pressure and high-temperature environments.
[0031] In use, the centralized control computer 1 controls the high-voltage charging power supply 2 to determine the charging voltage and charging speed to the high-voltage pulse capacitor 3. When the voltage across the high-voltage pulse capacitor 3 reaches the set threshold, the centralized control computer 1 triggers the high-voltage pulse switch 5 to close, and discharges the specimen into the holder 9 through the tip of the needle electrode 7. During the discharge process, the waveform signals on the stress wave signal receiver 18 and the oscilloscope 19 should be monitored in real time to determine whether the specimen has broken down.
[0032] If the specimen does not break down, only a weak noise signal will be displayed on the stress wave signal receiver 18, and no significant changes in breakdown voltage and current will appear on the oscilloscope 19. When the specimen breaks down, its fracture causes it to compress the clamping plate 9 in all directions. Subsequently, the stress on the clamping plate 9 is transmitted to the piezoelectric pressure sensor 14 through the transmission rod 10, and the stress waveform signal of the specimen breakdown process within a μs time scale is dynamically displayed on the stress wave signal receiver 18. At the same time, the voltage and current signals at the time of specimen breakdown will be clearly displayed on the oscilloscope 19.
[0033] During the test, stress waveform data needs to be acquired from the stress wave signal receiver 18, and current and voltage signals from the oscilloscope 19 should be acquired simultaneously. After the test, the negative terminal of the high-voltage pulse capacitor 3 should be grounded to release its residual voltage to ensure test safety.
Claims
1. A high-voltage pulse-induced fracturing coal and rock stress shock wave monitoring device, comprising a high-voltage pulse capacitor (3), a voltage divider (4), a high-voltage pulse switch (5), and a high-voltage pulse fracturing generation chamber (6) connected in sequence to form a closed loop, characterized in that: A high-voltage probe (16) and a Rogowski coil (17) are provided on the wire connecting the high-voltage pulse fracture generation chamber (6) and the high-voltage pulse capacitor (3). The signal output terminals of the high-voltage probe (16) and the Rogowski coil (17) are both connected to an oscilloscope (19). A specimen is fixed inside the high-voltage pulse fracture generation chamber (6). Multiple specimen clamping assemblies are provided in the high-voltage pulse fracture generation chamber (6) in the circumferential direction of the specimen. Needle electrodes (7) are provided on both sides of the specimen where no specimen clamping assembly is provided. The needle electrodes (7) are all in contact with the specimen and release high-voltage pulses. Each specimen clamping assembly in the high-pressure pulse fracturing chamber (6) is equipped with a piezoelectric pressure sensor (14). The output terminals of all piezoelectric pressure sensors (14) are connected to the pressure detection signal input terminal of the stress wave signal acquisition device (18). Each piezoelectric pressure sensor (14) in the high-pressure pulse fracturing chamber (6) is provided with a Faraday cage (15) for covering the piezoelectric pressure sensor (14). Each Faraday cage (15) is connected to the power ground through a wire. Each specimen clamping assembly includes a fixed base and a transmission rod (10) slidably connected to the fixed base. One end of the transmission rod (10) faces the specimen and is provided with a clamping plate (9) for abutting against the specimen. All the clamping plates (9) are combined to form a clamp. The other end of the transmission rod (10) extends into the Faraday cage (15) and abuts against the piezoelectric pressure sensor (14). The fixed base is provided with an insertion hole for the transmission rod (10) to pass through. A linear bearing (13) is provided in the insertion hole.
2. The high-voltage electrical pulse-induced fracturing coal and rock stress shock wave monitoring device according to claim 1, characterized in that: The needle electrode (7) is provided with a fixing sleeve, and is fixed to the side wall of the high-voltage pulse fracture generation chamber (6) by the fixing sleeve. The end of the fixing sleeve near the specimen is also provided with a clamping plate (9), and the ends of the two needle electrodes (7) pass through the clamping plate (9) and abut against the specimen.
3. The high-voltage electrical pulse-induced fracturing coal and rock stress shock wave monitoring device according to claim 2, characterized in that: The outer wall of the fixed sleeve is provided with threads, and two nuts (8) are threadedly connected to the fixed sleeve. The two nuts (8) are located on the inner and outer sides of the high-pressure pulse fracturing chamber (6), respectively, and the fixed sleeve is fixed by the inner and outer nuts (8) pressing against the two sides of the side wall of the high-pressure pulse fracturing chamber (6).
4. The high-voltage electrical pulse-induced fracturing coal and rock stress shock wave monitoring device according to claim 3, characterized in that: The transmission rod (10) and the fixing sleeve are both integral with the clamping plate (9).
5. The high-voltage electrical pulse-induced fracturing coal and rock stress shock wave monitoring device according to claim 1, characterized in that: The fixed base includes a fixed panel (11), on which a pair of fixing bolts (12) are provided, and the fixing bolts (12) are fixed to the side wall of the high-pressure pulse fracturing chamber (6).
6. The high-voltage electrical pulse-induced fracturing coal and rock stress shock wave monitoring device according to claim 1, characterized in that: The high-voltage pulse capacitor (3) is equipped with a high-voltage pulse power supply (2) and a central control computer (1). The control output terminal of the central control computer (1) is connected to the control signal input terminal of the high-voltage pulse power supply (2), and the power supply terminal of the high-voltage pulse power supply (2) is connected to the power input terminal of the high-voltage pulse capacitor (3).
7. The high-voltage electrical pulse-induced fracturing coal and rock stress shock wave monitoring device according to claim 1, characterized in that: The installation distance between the needle electrode (7) and the piezoelectric pressure sensor (14) is greater than 50 mm.
8. The high-voltage electrical pulse-induced fracturing coal and rock stress shock wave monitoring device according to claim 1, characterized in that: The specimen clamping components consist of four parts, which are respectively located on the front, rear, upper, and lower sides of the specimen.
9. A high-voltage electrical pulse-induced fracturing coal and rock stress shock wave monitoring device according to claim 3, characterized in that: The transmission rod (10), the fixing sleeve, the clamping plate (9), the nut, the linear bearing (13) and the fixing base are all made of PEEK material.