CN114062141A - High-voltage electric pulse in-situ fracturing coal seam crack real-time nondestructive observation device - Google Patents
High-voltage electric pulse in-situ fracturing coal seam crack real-time nondestructive observation device Download PDFInfo
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- CN114062141A CN114062141A CN202111442229.7A CN202111442229A CN114062141A CN 114062141 A CN114062141 A CN 114062141A CN 202111442229 A CN202111442229 A CN 202111442229A CN 114062141 A CN114062141 A CN 114062141A
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
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- G01N23/083—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption the radiation being X-rays
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
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Abstract
The invention discloses a high-voltage electric pulse in-situ fracturing coal seam fracture real-time nondestructive observation device, which comprises a stress loading system, a high-voltage electric pulse fracturing operation system and an in-situ CT scanning system; the stress loading system comprises a pressure chamber, an axial pressure loading module and a confining pressure loading module; the high-voltage electric pulse fracturing operation system comprises a high-voltage electric pulse generating module, a high-voltage electric pulse signal monitoring module and a protection module; the in-situ CT scanning system comprises a ray source, a flat panel detector and a CT scanning detection mechanism. The coal body test under the conditions of different stresses, different voltages and the like is simulated, the physical test of the high-voltage electric pulse fracturing coal body under the coupling action of multiple physical fields is simulated, and in-situ real-time scanning analysis is carried out by combining industrial CT, so that the high-voltage electric pulse in-situ fracturing coal seam fracture real-time nondestructive observation can be carried out.
Description
Technical Field
The invention relates to the field of coal bed gas (mine gas) exploitation, in particular to a real-time nondestructive observation device for high-voltage electric pulse in-situ fracturing coal bed cracks.
Background
The high-voltage electric pulse rock breaking technology is used as a novel reservoir exploitation technology and is rapidly and widely applied to the fields of oil gas exploitation, mineral processing, coal bed gas exploitation and the like in recent decades. The cracking effect of the high-voltage electric pulse is to crush the solid by using the shock wave generated in the discharge process and the mechanical effect caused by the high temperature generated in the plasma channel. In the technical field of coal bed gas (mine gas) exploitation, the high-voltage electric pulse fracturing coal bed fracture technology has a series of advantages of low energy consumption, high efficiency and the like compared with the conventional fracturing coal bed fracture technology. At present, the high-voltage electric pulse technology has a certain effect in the field application of fracturing coal seam fractures, but the basic theory research is still in the exploration stage.
CT scanning is taken as a popular detection means in recent years, has the characteristics of nondestructive detection and three-dimensional visualization, CT imaging mainly utilizes the principle of ray attenuation, X rays are emitted through a ray source, and the attenuation degree is different when the X rays penetrate through materials with different thicknesses and different densities. The X-rays with different ray doses generate images with different light and shade degrees on the detector, and the images are processed by the computer to form a visual image, so that the internal microscopic structure of the test piece can be obtained, and meanwhile, the internal structure of the detection object can be visually displayed on the display.
Although the existing electric pulse cracking coal seam fracture system realizes the research on high-voltage electric pulse cracking coal bodies to a certain extent, the system cannot carry out in-situ real-time lossless visible information capture on a loaded test piece in the test process, the information acquisition amount in the test process is small, the research on the action response mechanism in the electric pulse cracking coal body process is limited, and simultaneously the ground stress environment of a coal rock body which is exploited deeply is difficult to simulate.
Disclosure of Invention
The invention aims to develop the high-voltage electric pulse in-situ fractured coal seam crack real-time nondestructive observation device which can realize in-situ observation, has a wider simulation range, is simple to operate and has accurate test data.
Therefore, the technical scheme adopted by the invention is as follows: a high-voltage electric pulse in-situ fracturing coal seam fracture real-time nondestructive observation device comprises a stress loading system, a high-voltage electric pulse fracturing operation system and an in-situ CT scanning system;
the stress loading system comprises a pressure chamber, an axial pressure loading module and a confining pressure loading module; the pressure chamber is of a circular tube structure, and a test piece is arranged in the middle of the pressure chamber; the axial compression loading module comprises an axial compression pump, a first slide bar, a second slide bar, a third slide bar, a fourth slide bar, a fifth slide bar, an oil cylinder and an axial compression pipeline, wherein the first slide bar, the second slide bar, the third slide bar, the fourth slide bar, the fifth slide bar, the oil cylinder and the axial compression pipeline are symmetrically arranged at the upper end and the lower end of a test piece and are sequentially connected; the confining pressure loading module comprises a confining pressure pump, an isolation rubber sleeve and two confining pressure pipelines, wherein two confining pressure channels are symmetrically formed in the side wall of the pressure chamber from top to bottom, one end of each confining pressure pipeline is connected with the confining pressure pump, the other end of each confining pressure pipeline is connected into the inner cavity of the test piece through the corresponding confining pressure channel to provide confining pressure for the periphery of the test piece, the isolation rubber sleeve is wrapped outside the two first slide bars and the test piece, and a sealing ring is arranged between the isolation rubber sleeve and the first slide bars to prevent hydraulic oil from being immersed into the test piece through the upper end and the lower end of the isolation rubber sleeve;
the high-voltage electric pulse fracturing operation system comprises a high-voltage electric pulse generating module, a high-voltage electric pulse signal monitoring module and a protection module; the high-voltage electric pulse generating module comprises a high-voltage pulse power supply, a high-voltage capacitor, a high-voltage electric pulse switch, a first lead segment, a second lead segment, a third lead segment, an electrode needle and a conductive bolt; the high-voltage pulse power supply charges the high-voltage capacitor through the first lead segment, the upper end and the lower end of the test piece are both provided with an electrode needle and a conductive bolt, one end of the electrode needle is abutted against the test piece, the other end of the electrode needle sequentially penetrates through the first slide bar, the second slide bar and the third slide bar coaxially and then is inserted into a blind hole of the fourth slide bar, one end of the conductive bolt is connected with the electrode needle, the other end of the conductive bolt transversely penetrates out of the fourth slide bar, the outer side end of one conductive bolt is connected with the positive electrode of the high-voltage capacitor through the second lead segment, the outer side end of the other conductive bolt is connected with the negative electrode of the high-voltage capacitor through the third lead segment, and the second lead segment is connected with a high-voltage pulse switch in series; the high-voltage electric pulse signal monitoring module comprises a Rogowski coil, a high-voltage probe and an oscilloscope, the Rogowski coil is sleeved on the third lead section, the high-voltage probe is connected in series on the third lead section, and the Rogowski coil and monitoring signals of the high-voltage probe are connected to the oscilloscope through signal transmission lines; the protection module comprises an electromagnetic shielding field and is used for isolating high-energy static electricity generated by a high-voltage electric pulse fracturing operation system and X rays generated by an in-situ CT scanning system in the electromagnetic shielding field;
the in-situ CT scanning system comprises a ray source, a flat panel detector and a CT scanning detection mechanism, wherein the ray source and the flat panel detector are respectively arranged on two sides of a pressure chamber, the pressure chamber can be horizontally and rotatably arranged on an insulating fixed base by 360 degrees, the pressure chamber is made of materials meeting the CT scanning requirements, and the flat panel detector is connected with the CT scanning detection mechanism through a data transmission line.
Preferably, the first sliding rod, the second sliding rod, the third sliding rod and the fourth sliding rod are high-density insulating rods, and the axial compression pump is a displacement precision injection pump with a servo control system.
In order to ensure the electricity utilization safety in the test process, the first lead section, the second lead section and the third lead section are wrapped by insulating materials meeting the 100kV insulation standard, and the joints of the second lead section and the third lead section and the conductive bolts are completely wrapped by insulating tapes meeting the 100kV insulation standard.
Preferably, the end part of the electrode needle, which is in contact with the test piece, is designed into a circular truncated cone shape, and the other end of the electrode needle is tightly abutted through a compression spring arranged in a blind hole of the fourth sliding rod, so that the test piece of the electrode needle is ensured to be tightly attached all the time.
Preferably, the radiation source is an X-ray tube with a high-power micro focus and a high-resolution nano focus, the radiation source is obliquely arranged at the lower part of a tube support, the upper end of the tube support is suspended at the top of the electromagnetic shielding field, the flat panel detector is arranged on the side wall of the electromagnetic shielding field, and a radiation penetrating pressure chamber of the radiation source forms a scanning image on the CT scanning detection mechanism after being received by the flat panel detector.
Preferably, a positioning circular truncated cone is arranged at the center of the top of the insulating fixing base, and a positioning groove for the positioning circular truncated cone to be inserted into is formed at the center of the bottom of the oil cylinder at the lower end.
Preferably, the electrode needle is provided with a platform for inserting a conductive bolt for surface-mounted conduction, and the conductive bolt is separated from the fourth sliding rod by a stainless steel sealing sleeve. If the conductive bolt is in point contact with the electrode needle, the contact point position can generate discharge in the electric pulse process, and the surface-mounted installation is adopted, so that the electric arc generated by point contact is effectively prevented from influencing the discharge effect.
Preferably, the contact position of the fourth slide bar and the fifth slide bar is installed in a matched mode through a positioning circular truncated cone and a positioning groove.
Preferably, before loading, the far end of the second slide bar is flush with the end of the pressure chamber, the confining pressure channel is opposite to the near end of the second slide bar, the axial pressure channel is opposite to the far end of the fifth slide bar, and the near end of the fifth slide bar extends out of the oil cylinder.
Preferably, the outer diameter of the stainless steel sealing sleeve is enlarged at the far end position to be used as a flanging, and the flanging just covers the outer wall of the fourth sliding rod, so that the pressing-in installation is convenient, and the pressing-in is controlled to be in place through the flanging; the stainless steel sealing sleeve has small inner diameter near end and large far end, and a step surface is formed in the middle of the length; correspondingly, the section of the conductive bolt in the fourth slide bar is small at the near end and large at the far end; and the section of the conductive bolt outside the fourth sliding rod is provided with an annular groove for winding and connecting the corresponding second wire section or the third wire section.
The invention has the beneficial effects that:
(1) the stress loading system comprises a pressure chamber, an axial pressure loading module and a confining pressure loading module, the rest parts except an axial pressure pump, a confining pressure pump, an axial pressure pipeline and an axial pressure pipeline form a core holder whole body, the whole core holder is integrally arranged on an insulating fixed base and can horizontally rotate for 360 degrees, and a high-voltage electric pulse fracturing operation system and an in-situ CT scanning system are combined on the basis, so that in-situ CT real-time scanning can be performed after high-voltage electric pulses in a pressure maintaining state and in a loading process, influence on a test piece in the process of stress unloading and test piece assembling and disassembling is avoided, macro-microscopic analysis can be performed on a coal body more accurately, and the research result can provide advanced and reliable support for basic research of high-voltage electric pulse coal bed fracturing and even coal bed gas exploitation;
(2) the core holder is detachably arranged on the insulating fixed base, can be transferred or used for nuclear magnetic resonance detection and the like in a pressure maintaining state, provides a foundation for multi-aspect analysis of a test piece, and further provides a more complete basic theoretical analysis condition for the high-voltage electric pulse coal bed permeability increasing technology;
(3) the multistage slide bar is combined with the oil cylinder to provide equal axial pressure loading for the test piece, the slide bar with the larger diameter is ensured to be in sliding fit with the pressure chamber, the slide bar with the smaller diameter can reduce the influence of pipe wall friction on the axial pressure loading, the hole is formed in the side wall of the oil cylinder, and the transmission of the axial pressure is realized through the multistage slide bar, so that the processing and the replacement of a single slide bar are facilitated, and the disassembly and the assembly of the test piece in the test process are facilitated; holes are formed in the upper end and the lower end of the pressure chamber at intervals to serve as confining pressure supply channels, and an isolation rubber sleeve and a sealing ring are combined to prevent hydraulic oil from being immersed into a test piece through the upper end and the lower end of the isolation rubber sleeve, so that the structure is simple, and loading is reliable; the axial pressure loading ingeniously utilizes the side wall opening of the oil cylinder, the confining pressure loading ingeniously utilizes the side wall opening of the pressure chamber, the whole layout is reasonable, compact, simple and easy to control, the confining pressure and the axial pressure loaded at the same time are high, the research on high-voltage electric pulse fracturing of coal rock mass under the deep stress environment can be carried out, the maximum 100kV high-voltage electric pulse output is realized, the maximum confining pressure is 60MPa, and the maximum confining pressure is far higher than the condition that the current can only meet the 25kV high-voltage electric pulse output and is below 10 MPa;
(4) the upper end and the lower end of the test piece are both provided with an electrode needle and a conductive bolt, so that high-voltage electric pulses are introduced into the test piece, the electrode needle and the conductive bolt are both installed by utilizing a multistage transmission slide bar, and all the slide bars for installing the electrode needle adopt high-density insulating bars in consideration of insulation; in addition, the key part of the whole system is arranged in an electromagnetic shielding field and used for isolating high-energy static electricity generated by a high-voltage electric pulse fracturing operation system and X rays generated by an in-situ CT scanning system, and the system is safe and reliable.
In conclusion, the coal body test under the conditions of different stresses, different voltages and the like is simulated, the high-voltage electric pulse fracturing coal body physical test under the coupling action of multiple physical fields is simulated, and in-situ real-time scanning analysis is carried out by combining industrial CT. The development rule and the phase response characteristics of the pore cracks after the gas-containing coal high-voltage electric pulse technology is acted are accurately and deeply researched, the internal mechanism and the essence of multi-field coupling of an electric field, a stress field and the like in the action process are disclosed, and theoretical support and engineering parameter guidance are provided for using the high-voltage electric pulse to crack the coal body and improving the exploitation efficiency of the coal bed gas.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a cross-sectional view of the pressure chamber of the present invention.
Fig. 3 is an enlarged view of a portion a of fig. 2.
The device comprises a test piece 1, a pressure chamber 2, a shaft-pressing pump 3, an oil cylinder 4, a shaft-pressing pipeline 5, a first slide bar 6, a second slide bar 7, a third slide bar 8, a fourth slide bar 9, a fifth slide bar 10, a confining pressure pump 11, an isolating rubber sleeve 12, a confining pressure pipeline 13, a sealing ring 14, a high-voltage pulse power supply 15, a high-voltage capacitor 16, a high-voltage pulse switch 17, a first lead section 18, a second lead section 19, a third lead section 20, an electrode needle 21, a conductive bolt 22, a stainless steel sealing sleeve 23, a Rogowski coil 24, a high-voltage probe 25, an oscilloscope 26, an electromagnetic shielding field 27, a radiation source 28, a flat panel detector 29, a CT scanning detection mechanism 30, an insulating fixing base 31, a ray tube support 32 and a compression spring 33.
Detailed Description
The invention will be further illustrated by the following examples in conjunction with the accompanying drawings:
referring to fig. 1-3, a high-voltage electric pulse in-situ fracturing coal seam fracture real-time nondestructive observation device mainly comprises a stress loading system, a high-voltage electric pulse fracturing operation system and an in-situ CT scanning system.
The stress loading system mainly comprises a pressure chamber 2, an axial pressure loading module and a confining pressure loading module.
The axial compression loading module is composed of an axial compression pump 3, a first slide bar 6, a second slide bar 7, a third slide bar 8, a fourth slide bar 9, a fifth slide bar 10, an oil cylinder 4 and an axial compression pipeline 5 which are symmetrically arranged at the upper end and the lower end of the test piece 1 and are sequentially connected. The second slide bar 7 is in sliding fit with the pressure chamber 2, the diameters of the first slide bar 6, the third slide bar 8 and the fourth slide bar 9 are all smaller than the diameter of the second slide bar 7, and the fifth slide bars 10 extend into the corresponding oil cylinders 4 to be in sliding fit. A shaft pressure channel 4a is formed in the side wall of the oil cylinder 4, one end of a shaft pressure pipeline 5 is connected with the shaft pressure pump 3, the other end of the shaft pressure pipeline is connected into the corresponding oil cylinder 4 through the shaft pressure channel 4a, and shaft pressure which is equal to the shaft pressure of the test piece 1 is provided for the test piece 1 through all the slide bars (a first slide bar 6, a second slide bar 7, a third slide bar 8, a fourth slide bar 9 and a fifth slide bar 10 transmit the shaft pressure in sequence).
In order to prevent high-voltage electric energy from dissipating, the first slide bar 6, the second slide bar 7, the third slide bar 8 and the fourth slide bar 9 are high-density insulating bars. In order to realize accurate control of axial compression loading, the axial compression pump 3 adopts a displacement precision injection pump with a servo control system. In addition, the contact position of the fourth slide bar 9 and the fifth slide bar 10 is installed in a matching way through a positioning circular table and a positioning groove.
When the axial pressure is loaded, hydraulic oil flowing out of the axial pressure pump flows through the axial pressure pipeline to reach the oil cylinder, the hydraulic oil reaching the oil cylinder pushes the multi-stage slide rods to be sequentially transmitted to the test piece, and the effect of loading the axial pressure is achieved.
The confining pressure loading module comprises a confining pressure pump 11, an isolation rubber sleeve 12, two confining pressure pipelines 13 and the like. Two confining pressure channels 2a are symmetrically arranged on the side wall of the pressure chamber 2 up and down, one end of a confining pressure pipeline 13 is connected with a confining pressure pump 11, and the other end of the confining pressure pipeline is connected into the inner cavity of the test piece 1 through the corresponding confining pressure channel 2a to provide confining pressure for the periphery of the test piece 1. In order to enhance the sealing effect and ensure the smooth proceeding of the test, the isolation rubber sleeve 12 is wrapped outside the two first sliding rods 6 and the test piece 1, and a sealing ring 14 is arranged between the isolation rubber sleeve 12 and the first sliding rods 6 to prevent the hydraulic oil from immersing into the test piece 1 through the upper end and the lower end of the isolation rubber sleeve 12, so that the high-voltage electric pulse fails to discharge the test piece.
When confining pressure is loaded, hydraulic oil flows through a confining pressure pipeline through a confining pressure pump to reach a pressure chamber, a confining pressure channel is closed after the pressure chamber is filled with the hydraulic oil, and the confined pressure is applied to the periphery of a test piece by the hydraulic oil with pressure in the pressure chamber.
Preferably, before loading, the far end of the second slide bar 7 is flush with the end of the pressure chamber 2, the confining pressure channel 2a is opposite to the near end of the second slide bar 7, the axial pressure channel 4a is opposite to the far end of the fifth slide bar 10, and the near end of the fifth slide bar 10 extends out of the oil cylinder 4, so that the installation and control are convenient.
The high-voltage electric pulse fracturing operation system mainly comprises a high-voltage electric pulse generating module, a high-voltage electric pulse signal monitoring module and a protection module.
The high-voltage electric pulse generating module is composed of a high-voltage pulse power supply 15, a high-voltage capacitor 16, a high-voltage electric pulse switch 17, a first lead section 18, a second lead section 19, a third lead section 20, an electrode needle 21 and a conductive bolt 22. A high voltage pulsed power supply 15 charges a high voltage capacitor 16 through a first wire segment 18. Both the upper and lower ends of the test piece 1 are equipped with an electrode pin 21 and a conductive bolt 22. One end of the electrode needle 21 is abutted against the test piece 1, and the other end of the electrode needle is inserted into a blind hole of the fourth slide bar 9 after sequentially coaxially penetrating through the first slide bar 6, the second slide bar 7 and the third slide bar 8. A blind hole is formed in the fourth slide bar 9, and through holes are formed in the first slide bar 6, the second slide bar 7 and the third slide bar 8 for the electrode needle 21 to pass through. One end of each conductive bolt 22 is connected with the electrode needle 21, the other end of each conductive bolt transversely penetrates out of the fourth sliding rod 9, the outer end of one conductive bolt 22 is connected with the positive electrode of the high-voltage capacitor 16 through the second lead section 19, and the outer end of the other conductive bolt 22 is connected with the negative electrode of the high-voltage capacitor 16 through the third lead section 20. The second wire segment 19 is connected in series with a high-voltage electric pulse switch 17.
Preferably, the first, second and third conductor segments 18, 19, 20 are wrapped with an insulating material meeting the insulation standard of 100kV, and the joints between the second and third conductor segments 19, 20 and the conductive bolts 22 are completely wrapped with an insulating tape meeting the insulation standard of 100 kV.
In addition, the end part of the electrode needle 21, which is in contact with the test piece 1, is designed into a circular truncated cone shape, the other end of the electrode needle 21 is tightly propped against the test piece through a compression spring 33 installed in a blind hole of the fourth sliding rod 9, the electrode needle is ensured to be in close contact with the test piece, and the electrode is prevented from damaging the end part of the test piece in the axial compression loading process while discharging in a concentrated manner. The electrode needles at the upper and lower ends of the test piece need to be made of metal materials with good electrical conductivity.
The electrode needle 21 is provided with a platform for the conductive bolt 22 to be inserted for surface-mounted conduction, and the conductive bolt 22 is separated from the fourth sliding rod 9 by a stainless steel sealing sleeve 23. The outer diameter of the stainless steel sealing sleeve 23 is enlarged at the far end position to be used as a flanging 23a, and the flanging 23a just covers the outer wall of the fourth sliding rod 9; the stainless steel sealing sleeve 23 has a small inner diameter near end and a large distal end, and a step surface is formed in the middle of the length; correspondingly, the section of the conductive bolt 22 in the fourth sliding rod 9 is also small at the near end and large at the far end; the section of the conductive bolt 22 located outside the fourth sliding rod 9 is provided with a circumferential groove 22a for winding and connecting the corresponding second wire segment 19 or third wire segment 20.
The high-voltage electric pulse signal monitoring module consists of a Rogowski coil 24, a high-voltage probe 25 and an oscilloscope 26. The Rogowski coil 24 is sleeved on the third lead section 20, and the high-voltage probe 25 is connected in series on the third lead section 20 to test a circuit voltage change signal in the high-voltage pulse discharging process. The monitoring signals of the Rogowski coil 24 and the high-voltage probe 25 are connected to an oscilloscope 26 through signal transmission lines. The Rogowski coil and the high-voltage probe monitoring signal are transmitted to the oscilloscope through the signal transmission line, the waveforms of the pulse current and the pulse voltage are displayed on the screen of the oscilloscope and stored into a data file, comparison and analysis of historical pulse current and voltage data are conveniently carried out, and the optimal pulse current and voltage waveform of the high-voltage electric pulse fracturing test piece is determined. And subsequently, the optimal pulse current and voltage waveform are reduced by adjusting the discharge form of the high-voltage electric pulse generation module, so that the parameter reduction of the optimal high-voltage electric pulse cracking effect of the test piece is realized.
Because the induction of the Rogowski coil is sensitive, the place where the Rogowski coil is not easy to touch in the test process is selected as much as possible, and meanwhile, the Rogowski coil and the second lead segment keep a certain distance, so that the electromagnetic interference in the pulse current signal data acquisition process is reduced.
The main body of the protection module is an electromagnetic shielding field 27, and because high-energy static electricity generated by a high-voltage electric pulse cracking operation system and X-rays generated by an in-situ CT scanning system can both cause life threats to human bodies, the electromagnetic shielding field needs to be established, so that the high-energy static electricity generated by the high-voltage electric pulse cracking operation system and the X-rays generated by the in-situ CT scanning system in the test process are isolated in the electromagnetic shielding field, and the health and safety of operators in the test process are guaranteed.
The in-situ CT scanning system mainly comprises a ray source 28, a flat panel detector 29 and a CT scanning detection mechanism 30. The radiation source 28 and the flat panel detector 29 are arranged on both sides of the pressure chamber 2, respectively, with the flat panel detector 29 as a receiver. The pressure chamber 2 is horizontally rotatably mounted on the insulating fixed base 31 by 360 °. In order to obtain clearer scanning image data, the pressure chamber 2 is made of a material meeting the requirements of CT scanning, and meanwhile, in order to meet the loading requirements of a stress loading system on a test piece, the material is required to have the property of high mechanical strength. The flat panel detector 29 is connected with the CT scanning detection mechanism 30 through a data transmission line.
Preferably, the radiation source 28 is an X-ray tube with a high power microfocus and a high resolution nanofocus, and the radiation source 28 is mounted in an inclined manner on the lower portion of the tube support 32. The upper end of the tube support 32 is suspended from the top of the electromagnetic shield 27 and the flat panel detector 29 is mounted on the side wall of the electromagnetic shield 27. The ray penetrating the pressure chamber 2 of the ray source 28 is received by the flat panel detector 29 to form a scanning image on the CT scanning detection mechanism 30.
The ray tube can observe tiny details below 0.5 mu m, not only can scan a small-scale test piece, but also can complete scanning imaging of a large-size or irregular test piece. The pressure chamber axial pressure channel and the confining pressure channel are closed in the scanning process, so that a test piece in the pressure chamber maintains a stable stress environment, the insulating fixing base is controlled to drive the pressure chamber to horizontally rotate by 360 degrees, data are collected once when the pressure chamber rotates by one angle, and the scanning data collection is completed simultaneously after the rotation is completed.
The receiver in the in-situ CT scanning system is a flat panel detector, X-rays emitted from a ray tube penetrate through a pressure chamber and then are attenuated, images with different light and shade are left on the bottom sheet of the flat panel detector after the attenuated X-rays are received by the flat panel detector, the data are transmitted to a CT scanning detection mechanism through a data transmission line, and the data are processed and then visually displayed to be a test piece scanning picture.
In addition, a positioning circular truncated cone is arranged at the center of the top of the insulating fixing base 31, and a positioning groove for the positioning circular truncated cone to be inserted is arranged at the center of the bottom of the oil cylinder 4 at the lower end.
The high-voltage pulse power supply is connected with the high-voltage capacitor through the first lead segment, the input energy of the high-voltage pulse circuit system can be controlled by adjusting the voltage and current input values in the input circuit according to requirements during experiments, so that high-voltage electric pulses with different energies are generated to carry out pulse discharge fracturing on a test piece, and the optimal fracturing parameters of a coal layer containing gas are determined by comparing the fracturing effects of the different high-voltage pulse input energies on the test piece. In the process of charging the high-voltage capacitor, the charging current and voltage can be remotely operated and adjusted, and the safety and reliability of the test process are ensured.
The high-voltage capacitor adopts a mode of parallel connection of combined capacitors and a method of selecting capacity, and changes capacitance parameters in the high-voltage electric pulse circuit by changing the number of different access capacitors.
The high-voltage electric pulse switch is connected with the second lead segment in series, and the release of the high-voltage electric pulse to the energy of the test piece is realized by controlling the closing of the high-voltage electric pulse switch. After the high-voltage pulse power supply charges the voltage meeting the test requirement to the high-voltage capacitor, the high-voltage electric pulse switch is closed, so that the high-voltage capacitor releases specific high-voltage pulse energy to act on the test piece in a short time. The frequency of the pulse discharge action of the high-voltage pulse energy on the test piece can be controlled by controlling the closing frequency of the high-voltage electric pulse switch, so that the research on the cracking effect of the test piece by the high-voltage pulse energy with specific frequency is realized.
Claims (10)
1. The utility model provides a high-voltage electric pulse normal position sends and splits real-time nondestructive observation device of coal seam crack which characterized in that: the device comprises a stress loading system, a high-voltage electric pulse fracturing operation system and an in-situ CT scanning system;
the stress loading system comprises a pressure chamber (2), an axial pressure loading module and a confining pressure loading module; the pressure chamber (2) is of a circular tube structure, and a test piece (1) is arranged in the pressure chamber (2) in the middle; the axial compression loading module comprises an axial compression pump (3), a first slide bar (6), a second slide bar (7), a third slide bar (8), a fourth slide bar (9), a fifth slide bar (10), an oil cylinder (4) and an axial compression pipeline (5) which are symmetrically arranged at the upper end and the lower end of the test piece (1) and are sequentially connected, wherein the second slide bar (7) is in sliding fit with the pressure chamber (2), the diameters of the first slide bar (6), the third slide bar (8) and the fourth slide bar (9) are all smaller than that of the second slide bar (7), and the fifth slide bar (10) extends into the oil cylinder (4) which respectively corresponds to the first slide bar, the second slide bar (7), the third slide bar and the fourth slide bar (9), a shaft pressing channel (4a) is formed in the side wall of the oil cylinder (4), one end of the shaft pressing pipeline (5) is connected with the shaft pressing pump (3), the other end of the shaft pressing pipeline is connected into the corresponding oil cylinder (4) through the shaft pressing channel (4a), and the shaft pressing channel provides equal shaft pressing for the test piece (1) through all the sliding rods; the confining pressure loading module comprises a confining pressure pump (11), an isolation rubber sleeve (12) and two confining pressure pipelines (13), wherein two confining pressure channels (2a) are symmetrically formed in the side wall of the pressure chamber (2) from top to bottom, one end of each confining pressure pipeline (13) is connected with the confining pressure pump (11), the other end of each confining pressure pipeline is connected into an inner cavity of the test piece (1) through the corresponding confining pressure channel (2a) to provide confining pressure for the periphery of the test piece (1), the isolation rubber sleeve (12) is wrapped outside the two first sliding rods (6) and the test piece (1), and a sealing ring (14) is arranged between the isolation rubber sleeve (12) and the first sliding rod (6) to prevent hydraulic oil from being immersed into the test piece (1) through the upper end and the lower end of the isolation rubber sleeve (12);
the high-voltage electric pulse fracturing operation system comprises a high-voltage electric pulse generating module, a high-voltage electric pulse signal monitoring module and a protection module; the high-voltage electric pulse generating module comprises a high-voltage pulse power supply (15), a high-voltage capacitor (16), a high-voltage electric pulse switch (17), a first lead section (18), a second lead section (19), a third lead section (20), an electrode needle (21) and a conductive bolt (22); a high voltage pulse power supply (15) charges a high voltage capacitor (16) through a first wire segment (18), the upper end and the lower end of the test piece (1) are both provided with an electrode needle (21) and a conductive bolt (22), one end of the electrode needle (21) is abutted against the test piece (1), the other end of the electrode needle sequentially and coaxially penetrates through the first slide bar (6), the second slide bar (7) and the third slide bar (8) and then is inserted into a blind hole of the fourth slide bar (9), one end of the conductive bolt (22) is connected with the electrode needle (21), the other end of the conductive bolt transversely penetrates out of the fourth sliding rod (9), the outer end of one of the conductive bolts (22) is connected with the anode of the high-voltage capacitor (16) through a second lead segment (19), the outer end of the other conductive bolt (22) is connected with the cathode of the high-voltage capacitor (16) through a third lead segment (20), a high-voltage electric pulse switch (17) is connected in series on the second lead segment (19); the high-voltage electric pulse signal monitoring module comprises a Rogowski coil (24), a high-voltage probe (25) and an oscilloscope (26), the Rogowski coil (24) is sleeved on the third lead segment (20), the high-voltage probe (25) is connected in series on the third lead segment (20), and monitoring signals of the Rogowski coil (24) and the high-voltage probe (25) are connected to the oscilloscope (26) through signal transmission lines; the protection module comprises an electromagnetic shielding field (27) for isolating high-energy static electricity generated by a high-voltage electric pulse fracturing operation system and X rays generated by an in-situ CT scanning system in the electromagnetic shielding field (27);
the in-situ CT scanning system comprises a ray source (28), a flat panel detector (29) and a CT scanning detection mechanism (30), wherein the ray source (28) and the flat panel detector (29) are respectively arranged on two sides of a pressure chamber (2), the pressure chamber (2) can be horizontally and rotatably arranged on an insulating fixed base (31) by 360 degrees, the pressure chamber (2) is made of materials meeting the CT scanning requirements, and the flat panel detector (29) is connected with the CT scanning detection mechanism (30) through a data transmission line.
2. The high-voltage electric pulse in-situ coal seam fracture real-time nondestructive observation device according to claim 1, characterized in that: the first sliding rod (6), the second sliding rod (7), the third sliding rod (8) and the fourth sliding rod (9) are high-density insulating rods, and the axial pressure pump (3) adopts a displacement precision injection pump with a servo control system.
3. The high-voltage electric pulse in-situ coal seam fracture real-time nondestructive observation device according to claim 1, characterized in that: the first lead section (18), the second lead section (19) and the third lead section (20) are wrapped by insulating materials meeting the 100kV insulation standard, and the joints of the second lead section (19) and the third lead section (20) and the conductive bolts (22) are completely wrapped by insulating tapes meeting the 100kV insulation standard.
4. The high-voltage electric pulse in-situ coal seam fracture real-time nondestructive observation device according to claim 1, characterized in that: the end part of the electrode needle (21) contacting the test piece (1) is designed to be in a circular truncated cone shape, and the other end of the electrode needle (21) is tightly propped against the compression spring (33) arranged in the blind hole of the fourth sliding rod (9).
5. The high-voltage electric pulse in-situ coal seam fracture real-time nondestructive observation device according to claim 1, characterized in that: the X-ray source (28) is an X-ray tube with a high-power micron focus and a high-resolution nanometer focus, the X-ray source (28) is obliquely arranged at the lower part of a tube support (32), the upper end of the tube support (32) is suspended at the top of an electromagnetic shielding field (27), the flat panel detector (29) is arranged on the side wall of the electromagnetic shielding field (27), and a ray penetrating pressure chamber (2) of the X-ray source (28) is received by the flat panel detector (29) to form a scanning image on a CT scanning detection mechanism (30).
6. The high-voltage electric pulse in-situ coal seam fracture real-time nondestructive observation device according to claim 1, characterized in that: the top of the insulating fixing base (31) is provided with a positioning round table in the middle, and the bottom of the oil cylinder (4) at the lower end is provided with a positioning groove for the positioning round table to be inserted in.
7. The high-voltage electric pulse in-situ coal seam fracture real-time nondestructive observation device according to claim 1, characterized in that: the electrode needle (21) is provided with a platform for a conductive bolt (22) to be inserted for surface-mounted conduction, and the conductive bolt (22) is separated from the fourth sliding rod (9) through a stainless steel sealing sleeve (23).
8. The high-voltage electric pulse in-situ coal seam fracture real-time nondestructive observation device according to claim 1, characterized in that: the contact position of the fourth sliding rod (9) and the fifth sliding rod (10) is installed in a matched mode through a positioning circular table and a positioning groove.
9. The high-voltage electric pulse in-situ coal seam fracture real-time nondestructive observation device according to claim 1, characterized in that: before loading, the far end of the second sliding rod (7) is flush with the end of the pressure chamber (2), the confining pressure channel (2a) is over against the near end of the second sliding rod (7), the axial pressure channel (4a) is over against the far end of the fifth sliding rod (10), and the near end of the fifth sliding rod (10) extends out of the oil cylinder (4).
10. The high-voltage electric pulse in-situ coal seam fracture real-time nondestructive observation device according to claim 7, characterized in that: the outer diameter of the stainless steel sealing sleeve (23) is enlarged at the far end position to be used as a flanging (23a), and the flanging (23a) just covers the outer wall of the fourth sliding rod (9); the stainless steel sealing sleeve (23) is small in inner diameter near end and large in far end, and a step surface is formed in the middle of the length; correspondingly, the section of the conductive bolt (22) positioned in the fourth sliding rod (9) is small at the near end and large at the far end; and the section of the conductive bolt (22) outside the fourth sliding rod (9) is provided with a circumferential groove (22a) for winding and connecting the corresponding second wire segment (19) or third wire segment (20).
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