An experimental device for observing the whole-process of cold shock fracturing coal mass

Abstract

The present invention belongs to the technical field of cold shock fracturing of coal bodies, and particularly relates to an experimental device for observing the whole process of cold shock fracturing of coal bodies, including a coal sample storage system, a liquid nitrogen injection system, a liquid nitrogen cold shock system, an ultrasonic acquisition and processing system, and a thermal imaging acquisition and processing system; the coal sample storage system consists of a constant temperature and humidity box and a coal body, and the liquid nitrogen injection system consists of a self-pressurizing liquid nitrogen tank, a valve, a pressure gauge, a pressure regulating valve, an ultra-low temperature flow meter, an ultra-low temperature heat preservation pipe, and a liquid nitrogen cold shock fracturing device; the liquid nitrogen cold shock system includes a liquid nitrogen cold shock fracturing device, and the liquid nitrogen cold shock fracturing device includes a device housing; the beneficial effect of the present invention is that the experimental device of the present invention can quickly immerse the coal sample in liquid nitrogen and quickly remove it from the liquid nitrogen, effectively control the time for the coal body to be cold shocked by liquid nitrogen in the cold shock experiment, and ensure the accuracy of the variable cold shock time.

Description

Technical Field

[0001] The present invention belongs to the technical field of cold shock fracturing coal bodies, and particularly relates to an experimental device for observing the whole process of cold shock fracturing coal bodies. Background Art

[0002] With the development of science and technology, in order to solve the problems of insufficient technology in previous coal seam permeability enhancement, efficiently pre-extracting and utilizing coal seam gas, preventing gas accidents and reducing environmental pollution problems, and maximizing economic benefits, the waterless fracturing technology using ultra-low temperature fluids such as liquid nitrogen as fracturing fluids has gradually received attention. However, there is a lack of observation instruments in the laboratory for the energy and structural changes of coal bodies during the whole process of liquid nitrogen cold shock on coal bodies, and the theory of liquid nitrogen enhancing the permeability of coal bodies in the laboratory still needs to be further explored to provide guiding significance for coal seam permeability enhancement. Summary of the Invention

[0003] The purpose of the present invention is to provide an experimental device for observing the whole process of cold shock fracturing coal bodies in view of the problems raised in the background art, so as to improve the observation of the internal structure changes of coal bodies before and after the action of liquid nitrogen in the laboratory, and at the same time effectively monitor the whole process of liquid nitrogen cold shock on coal bodies.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is:

[0005] An experimental device for observing the whole process of cold shock fracturing coal bodies, characterized in that: it includes a coal sample storage system, a liquid nitrogen injection system, a liquid nitrogen cold shock system, an ultrasonic acquisition and processing system, and a thermal imaging acquisition and processing system.

[0006] The coal sample storage system consists of a constant temperature and humidity box 22 and a coal body 7, and the coal body 7 is placed in the constant temperature and humidity box 22. After the coal body 7 is prepared according to the required experimental conditions, the temperature and humidity of the constant temperature and humidity box 22 are set, and the coal body 7 is put in for standby. The coal body 7 is a 70×70×70mm cube.

[0007] The liquid nitrogen injection system consists of a self-pressurizing liquid nitrogen tank 1, a valve 2, a pressure gauge 3, a pressure regulating valve 4, an ultra-low temperature flow meter 5, an ultra-low temperature heat preservation pipe 6, and a liquid nitrogen cold shock fracturing device 9. A valve 2 and a pressure gauge 3 are installed on the top of the self-pressurizing liquid nitrogen tank 1. The liquid nitrogen injection system is connected to the liquid nitrogen cold shock system through the ultra-low temperature heat preservation pipe 6, and a pressure regulating valve 4 and an ultra-low temperature flow meter 5 are installed on the ultra-low temperature heat preservation pipe 6. The liquid nitrogen is injected from the self-pressurizing liquid nitrogen tank 1 into the liquid nitrogen cold shock fracturing device 9 through the pressure gauge 3, the ultra-low temperature flow meter 5, and the ultra-low temperature heat preservation pipe 6. The ultra-low temperature flow meter 5 can monitor the liquid nitrogen flow rate delivered to the liquid nitrogen cold shock fracturing device 9 in real time; the valve 2 is the conveying switch for controlling the self-pressurizing liquid nitrogen tank 1, and the universal wheels at the bottom of the self-pressurizing liquid nitrogen tank 1 are used to control the movement of the tank body; the pressure regulating valve 4 controls the pressure when injecting liquid nitrogen, and heat preservation and insulation materials are provided outside the ultra-low temperature heat preservation pipe 6 to prevent liquid nitrogen from volatilizing during transportation and ensure the transportation of ultra-low temperature fluid during cold shock.

[0008] The liquid nitrogen cold shock system includes a liquid nitrogen cold shock fracturing device 9. The liquid nitrogen cold shock fracturing device 9 includes a device housing 9-1. An ultra-low temperature heat preservation pipe 6 communicating with its interior is welded to the top of the device housing 9-1. A waste liquid outlet 9-7 is opened at the bottom of the device housing 9-1. The waste liquid outlet 9-7 is connected to a waste liquid storage tank 9-4 through a waste liquid pipe 9-5, and an ultra-low temperature resistant valve 9-6 is installed on the waste liquid pipe 9-5; the device housing 9-1 includes a liquid nitrogen cold shock fracturing device bottom surface 9-102, two opposite guide rod penetrating shell surfaces 9-101, and a device opening coal sample probing surface 9-103; an opening is provided on the device opening coal sample probing surface 9-103. A perforated carrier ring 9-3 is installed on the liquid nitrogen cold shock fracturing device bottom surface 9-102. A coal body 7 is placed on the perforated carrier ring 9-3, and the coal body 7 protrudes from the notch on the device opening coal sample probing surface 9-103. The device housing 9-1 is connected to the coal body 7 through a sealant 24; installation holes are opened on two opposite guide rod penetrating shell surfaces 9-101, and ultra-low temperature ultrasonic guide rods 9-2 are installed in the two installation holes. One end of the ultra-low temperature ultrasonic guide rod 9-2 is a first planar transducer coupling end 9-201, and the first planar transducer coupling end 9-201 is connected to an ultrasonic acquisition and processing system. The other end of the ultra-low temperature ultrasonic guide rod 9-2 is a coal sample coupling end 9-202, and the coal sample coupling end 9-202 is connected to the coal body 7.

[0009] The ultra-low temperature ultrasonic guide rod 9-2 is threadedly connected to the guide rod penetration shell surface 9-101. Threads are provided on the ultra-low temperature ultrasonic guide rod 9-2. The ultra-low temperature ultrasonic guide rod 9-2 and the guide rod penetration shell surface 9-101 are rotationally and fittingly sealed. The two ultra-low temperature ultrasonic guide rods 9-2 are on a straight line in the same horizontal plane. The material of the liquid nitrogen cold shock fracturing device 9 is 316 steel; the ultra-low temperature ultrasonic guide rod 9-2 is made of 15Mn26Al4 ultra-low temperature steel. The perforated load-bearing ring 9-3 is a steel pipe with holes 9-301 all around. The perforated load-bearing ring 9-3 is a hollow 316 steel pipe with a specification of φ25×8. The function of the holes 9-301 is to increase the contact area between the bottom of the coal body and the liquid nitrogen. The waste liquid pipe 9-5 is a hollow 316 steel pipe. One end of the waste liquid pipe 9-5 is welded to the bottom surface 9-102 of the liquid nitrogen cold shock fracturing device, and the other end of the waste liquid pipe 9-5 is connected to the waste liquid storage tank 9-4. A 70×70mm square opening is cut on the device opening coal sample probing surface 9-103, and the square opening extends the coal body observation surface 7-1. Sealing glue 24 is applied at the contact points between the inside and outside of the device opening coal sample probing surface 9-103 and the coal body 7. The sealing glue 24 is an ultra-low temperature resistant epoxy resin glue. After being applied, the sealing glue 24, the coal body 7, and the device opening coal sample probing surface 9-103 are in the state as Figure 8 shown, and sealing can be achieved when the coal body 7 undergoes slight shrinkage due to liquid nitrogen cold shock.

[0010] The ultrasonic acquisition and processing system consists of a non-metallic ultrasonic tester 8, a system computer 12, and an acoustic wave data processor 13. The non-metallic ultrasonic tester 8 and the acoustic wave data processor 13 are electrically connected, and the acoustic wave data processor 13 and the system computer 12 are electrically connected. The non-metallic ultrasonic tester 8 is electrically connected to a planar transducer 11 through a signal line 10. The end of the planar transducer 11 is the second planar transducer coupling end 11-1. There are two planar transducers 11, one is the ultrasonic generating end and the other is the receiving end; the second planar transducer coupling ends 11-1 of the two planar transducers 11 are respectively closely attached to the first planar transducer coupling ends 9-201 of the two ultra-low temperature ultrasonic guide rods 9-2. During acquisition, coupling agent is applied to the two first planar transducer coupling ends 11-1 and they are closely attached to the two second planar transducer coupling ends 9-201. The coupling agent is vaseline.

[0011] The thermal imaging acquisition and processing system is composed of a system display screen 14, a thermal imaging data processor 15, an infrared thermal imaging collector 16, an infrared detector 17, a thermocouple temperature processor 20, and a K-type thermocouple 21. The infrared detector 17, the infrared thermal imaging collector 16, the thermal imaging data processor 15, and the system display screen 14 are electrically connected. An infrared detector lifting platform 19 is installed at the bottom of the infrared detector 17, and the infrared detector lifting platform 19 is connected to the thermal imaging data processor 15 through a control line 18. The position of the infrared detector 17 corresponds to the coal body observation surface 7-1 of the coal body 7, facilitating the infrared detector 17 to collect the data energy change of the coal body observation surface 7-1. The system display screen 14 is used to operate the thermal imaging data processor 15 to control the infrared detector lifting platform 19 to adjust the height through the control line 18, so that the infrared detector 17 is in an appropriate position relative to the coal body observation surface 7-1. The K-type thermocouple 21, the thermocouple temperature processor 20, the thermal imaging data processor 15, and the system display screen 14 are electrically connected. The K-type thermocouple 21 is composed of a K-type thermocouple temperature sensing end 21-1 and a signal input end 21-2. The K-type thermocouple temperature sensing end 21-1 is attached to the coal body observation surface 7-1, and the signal input end 21-2 is connected to the thermocouple temperature processor 20.

[0012] Compared with the disadvantages and deficiencies of the prior art, the present invention has the following beneficial effects:

[0013] 1. The experimental device of the present invention can quickly submerge the coal sample in liquid nitrogen and quickly remove it from liquid nitrogen, effectively controlling the time of the coal body being cold-shocked by liquid nitrogen in the cold shock experiment, and ensuring the accuracy of the variable cold shock time.

[0014] 2. The experimental device of the present invention can monitor the experimental data of the whole process of submerging the coal sample in liquid nitrogen in real time, realizing the acquisition of data throughout the cold shock process.

[0015] 3. The experimental device of the present invention obtains the variation laws of the wave velocity and pore volume of the coal body with time throughout the cold shock process based on ultrasonic testing technology.

[0016] 4. The experimental device of the present invention can observe the infrared radiation energy distribution pattern on the surface of the coal body throughout the cold shock process based on infrared thermal imaging technology to obtain an infrared thermal image, and further calibrate it according to the temperature change measured by the K-type thermocouple, so as to obtain the thermal distribution field on the surface of the coal body throughout the cold shock process.

[0017] 5. The experimental device of the present invention can obtain the liquid nitrogen cold shock acting on 5 surfaces of the coal body, observe the law of the temperature of the 6th surface being transmitted from the periphery to the center of the coal body, as well as the law of the surface temperature change.

[0018] 6. The experimental device of the present invention can monitor the structural and energy changes of coal samples under the action of liquid nitrogen in real time, and dynamically analyze the laws and effects of coal body fracture and damage during the liquid nitrogen fracturing of coal samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To understand the present invention more clearly, the present disclosure will be further introduced by combining the specification drawings with schematic embodiments. The drawings and embodiments are used for explanation and do not constitute a limitation to the disclosure.

[0020] Figure 1 It is the overall system diagram of the present invention;

[0021] Figure 2 It is the coupling mode diagram of ultrasonic detection and cold shock device in the present invention;

[0022] Figure 3 It is the coupling diagram of ultrasonic generating and receiving planar ring energy transducer and fracturing device in the present invention;

[0023] Figure 4 It is the coal sample placement diagram in the fracturing device of the present invention;

[0024] Figure 5 It is the schematic diagram of the perforated load-bearing ring in the present invention;

[0025] Figure 6 It is the diagram of the ultrasonic guide rod reaching the coal body surface through the fracturing device in the present invention;

[0026] Figure 7 It is the schematic diagram of the customized patch-shaped K-type thermocouple in the present invention;

[0027] Figure 8 It is the schematic diagram of the coupling of ultra-low temperature glue with the device shell and the coal body surface in the present invention.

[0028] As shown in the figure: 1. Self-pressurizing liquid nitrogen tank; 2. Valve; 3. Pressure gauge; 4. Pressure regulating valve; 5. Ultra-low temperature flow meter; 6. Ultra-low temperature heat preservation pipe; 7. Coal body; 7-1. Coal body observation surface; 7-2. Coupling end of coal sample and ultra-low temperature acoustic waveguide rod; 7-3. Contact surface between coal sample and perforated carrier ring; 8. Non-metallic ultrasonic tester; 9. Liquid nitrogen cold shock cracking device; 9-1. Device housing; 9-101. Guide rod penetrating the housing surface; 9-102. Bottom surface of the liquid nitrogen cold shock cracking device; 9-103. Coal sample exploration surface of the device opening; 9-2. Ultra-low temperature ultrasonic waveguide rod; 9-201. Second plane transducer coupling end; 9-202. Coal sample coupling end; 9-3. Perforated carrier ring; 9-301. Hole; 9-4. Waste liquid storage tank; 9-5. Waste liquid pipe; 9-6. Ultra-low temperature resistant valve; 9-7. Waste liquid outlet; 10. Signal line; 11. Plane transducer; 11-1. First plane transducer coupling end; 12. System computer; 13. Acoustic wave data processor; 14. System display screen; 15. Thermal imaging data processor; 16. Infrared thermal imaging collector; 17. Infrared detector; 18. Control line; 19. Infrared detector lifting platform; 20. Thermocouple temperature processor; 21. K-type thermocouple; 21-1. Temperature sensing end of K-type thermocouple; 21-2. Signal input end; 22. Constant temperature and humidity box; 24. Sealing glue. Specific implementation mode

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in combination with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Embodiment 1

[0031] An experimental device for observing the cold shock cracking of coal body throughout the process, as Figure 1 shown, includes a coal sample storage system, a liquid nitrogen injection system, a liquid nitrogen cold shock system, an ultrasonic acquisition and processing system, and a thermal imaging acquisition and processing system.

[0032] The coal sample storage system consists of a constant temperature and humidity box 22 and a coal body 7, and the coal body 7 is placed in the constant temperature and humidity box 22. After the coal body 7 is prepared according to the required experimental conditions, the temperature and humidity of the constant temperature and humidity box 22 are set, and the coal body 7 is put in for standby. The coal body 7 is a 70×70×70mm cube.

[0033] As Figure 1As shown in the figure, the liquid nitrogen injection system consists of a self-pressurizing liquid nitrogen tank 1, a valve 2, a pressure gauge 3, a pressure regulating valve 4, an ultra-low temperature flow meter 5, an ultra-low temperature heat preservation pipe 6, and a liquid nitrogen cold shock fracturing device 9. A valve 2 and a pressure gauge 3 are installed on the top of the self-pressurizing liquid nitrogen tank 1. The liquid nitrogen injection system is connected to the liquid nitrogen cold shock system through an ultra-low temperature heat preservation pipe 6. A pressure regulating valve 4 and an ultra-low temperature flow meter 5 are installed on the ultra-low temperature heat preservation pipe 6. The liquid nitrogen is injected from the self-pressurizing liquid nitrogen tank 1 into the liquid nitrogen cold shock fracturing device 9 through the pressure gauge 3, the ultra-low temperature flow meter 5, and the ultra-low temperature heat preservation pipe 6. The ultra-low temperature flow meter 5 can monitor the liquid nitrogen flow rate delivered to the liquid nitrogen cold shock fracturing device 9 in real time; the valve 2 is a control switch for the delivery of the self-pressurizing liquid nitrogen tank 1, and the universal wheels at the bottom of the self-pressurizing liquid nitrogen tank 1 are used to control the movement of the tank body; the pressure regulating valve 4 controls the pressure during liquid nitrogen injection. The ultra-low temperature heat preservation pipe 6 is provided with heat preservation and heat insulation materials on the outside to prevent the liquid nitrogen from volatilizing during transportation and ensure the transportation of ultra-low temperature fluids during cold shock.

[0034] As Figure 2 shown in the figure, the liquid nitrogen cold shock system includes a liquid nitrogen cold shock fracturing device 9. The liquid nitrogen cold shock fracturing device 9 includes a device housing 9-1. An ultra-low temperature heat preservation pipe 6 communicating with its interior is welded to the top of the device housing 9-1. A waste liquid outlet 9-7 is opened at the bottom of the device housing 9-1. The waste liquid outlet 9-7 is connected to a waste liquid storage tank 9-4 through a waste liquid pipe 9-5. A cryogenic-resistant valve 9-6 is installed on the waste liquid pipe 9-5; the device housing 9-1 includes a bottom surface 9-102 of the liquid nitrogen cold shock fracturing device, two opposite guide rod penetrating surfaces 9-101, and a device opening coal sample probing surface 9-103; an opening is provided on the device opening coal sample probing surface 9-103. A perforated carrier ring 9-3 is installed on the bottom surface 9-102 of the liquid nitrogen cold shock fracturing device. A coal body 7 is placed on the perforated carrier ring 9-3. The coal body 7 protrudes from the notch on the device opening coal sample probing surface 9-103. The device housing 9-1 and the coal body 7 are connected through a sealant 24; two opposite guide rod penetrating surfaces 9-101 are provided with mounting holes. Two ultra-low temperature ultrasonic guide rods 9-2 are installed in the two mounting holes. One end of the ultra-low temperature ultrasonic guide rod 9-2 is a first planar transducer coupling end 9-201, and the first planar transducer coupling end 9-201 is connected to an ultrasonic acquisition and processing system. The other end of the ultra-low temperature ultrasonic guide rod 9-2 is a coal sample coupling end 9-202, and the coal sample coupling end 9-202 is connected to the coal body 7.

[0035] As Figure 6As shown, the ultra-low temperature ultrasonic guide rod 9-2 is threadedly connected to the guide rod penetration shell surface 9-101. The ultra-low temperature ultrasonic guide rod 9-2 is provided with threads, and the ultra-low temperature ultrasonic guide rod 9-2 and the guide rod penetration shell surface 9-101 are rotationally and fittingly sealed. Two ultra-low temperature ultrasonic guide rods 9-2 are on a straight line in the same horizontal plane. The material of the liquid nitrogen cold shock fracturing device 9 is 316 steel; the ultra-low temperature ultrasonic guide rod 9-2 is made of 15Mn26Al4 ultra-low temperature steel.

[0036] As Figure 4 and Figure 5 shown, the perforated load-bearing ring 9-3 is a steel pipe with holes 9-301 all around. The perforated load-bearing ring 9-3 is a hollow 316 steel pipe with a specification of φ25×8, and the function of the holes 9-301 is to increase the contact area between the bottom of the coal body and the liquid nitrogen.

[0037] The waste liquid pipe 9-5 is a hollow 316 steel pipe. One end of the waste liquid pipe 9-5 is welded to the bottom surface 9-102 of the liquid nitrogen cold shock fracturing device, and the other end of the waste liquid pipe 9-5 is connected to the waste liquid storage tank 9-4.

[0038] As Figure 8 shown, a 70×70mm square opening is cut on the device opening coal sample exploration surface 9-103. The square opening extends the coal body observation surface 7-1. Sealant 24 is applied at the contact points between the inside and outside of the device opening coal sample exploration surface 9-103 and the coal body 7. The sealant 24 is an ultra-low temperature resistant epoxy resin glue. After being applied, the state of the sealant 24, the coal body 7, and the device opening coal sample exploration surface 9-103 is as Figure 8 shown, and sealing can be achieved when the coal body 7 undergoes a slight contraction due to liquid nitrogen cold shock.

[0039] The ultrasonic acquisition and processing system consists of a non-metallic ultrasonic tester 8, a system computer 12, and an acoustic wave data processor 13. The non-metallic ultrasonic tester 8 and the acoustic wave data processor 13 are electrically connected, and the acoustic wave data processor 13 and the system computer 12 are electrically connected. The non-metallic ultrasonic tester 8 is electrically connected to a planar transducer 11 through a signal line 10. The end of the planar transducer 11 is the second planar transducer coupling end 11-1. There are two planar transducers 11, one is the ultrasonic generation end and the other is the receiving end; as Figure 3 shown, the second planar transducer coupling ends 11-1 of the two planar transducers 11 are respectively in close contact with the first planar transducer coupling ends 9-201 of the two ultra-low temperature ultrasonic guide rods 9-2.

[0040] During acquisition, apply a coupling agent (vaseline) to the two coupling ends 11-1 of the first planar transducers and closely attach them to the two coupling ends 9-201 of the second planar transducers. The acoustic wave data processor 13 converts the collected ultrasonic wave velocity into coal porosity through a set formula, and draws ultrasonic wave velocity-time curve graphs and porosity-time curve graphs on the software of the system computer 12. Relevant data can be exported as text. The ultrasonic wave velocity is the longitudinal wave, with the unit km / s; the porosity formula is , where φ is the coal porosity, V is the acoustic wave velocity measured during the experiment, Vcs is the propagation velocity of the acoustic wave in the coal skeleton, Vca is the propagation velocity of the acoustic wave in the coal pore medium, Vcs is a fixed value, and Vca is input on the software of the system computer 7 according to the experimental situation. To avoid continuous ultrasonic acquisition and damage to the internal pores of the coal by ultrasonic waves, the ultrasonic acquisition time cannot be continuous and requires a time interval. The system default time interval is 2 minutes, which can be modified on the software of the system computer 12.

[0041] The thermal imaging acquisition and processing system consists of a system display screen 14, a thermal imaging data processor 15, an infrared thermal imaging collector 16, an infrared detector 17, a thermocouple temperature processor 20, and a K-type thermocouple 21. The infrared detector 17, the infrared thermal imaging collector 16, the thermal imaging data processor 15, and the system display screen 14 are electrically connected. An infrared detector lifting platform 19 is installed at the bottom of the infrared detector 17, and the infrared detector lifting platform 19 is connected to the thermal imaging data processor 15 through a control line 18. The position of the infrared detector 17 corresponds to the coal observation surface 7-1 of the coal body 7, facilitating the infrared detector 17 to collect the energy change of the data on the coal observation surface 7-1; use the system display screen 14 to operate the thermal imaging data processor 15 to control the infrared detector lifting platform 19 to adjust the height through the control line 18, so that the infrared detector 17 is in an appropriate position relative to the coal observation surface 7-1. The K-type thermocouple 21, the thermocouple temperature processor 20, the thermal imaging data processor 15, and the system display screen 14 are electrically connected. As Figure 7 shown, the K-type thermocouple 21 consists of a K-type thermocouple temperature sensing end 21-1 and a signal input end 21-2. The K-type thermocouple temperature sensing end 21-1 is attached to the coal observation surface 7-1, and the signal input end 21-2 is connected to the thermocouple temperature processor 20.

[0042] When liquid nitrogen is used for cold shock on the coal body, the energy change of the data on the coal body observation surface 7-1 is collected by the infrared detector 17, transmitted to the infrared thermal imaging collector 16 for preprocessing and then to the thermal imaging data processor 15. At the same time, the temperature sensing end 21-1 of the K-type thermocouple is attached to the coal body observation surface 7-1, and the collected temperature is conducted to the thermal imaging data processor 15 through the thermocouple temperature processor 20. The thermal imaging data processor 15 combines the temperature to correct the preprocessed data of the infrared thermal imaging collector 16 and draws a real-time surface heat energy distribution graph.

[0043] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An experimental device for observing the whole process of cold shock fracturing coal bodies, characterized in that: It includes a coal sample storage system, a liquid nitrogen injection system, a liquid nitrogen cold shock system, an ultrasonic acquisition and processing system, and a thermal imaging acquisition and processing system: The coal sample storage system consists of a constant temperature and humidity box (22) and a coal body (7), and the coal body (7) is placed inside the constant temperature and humidity box (22); The liquid nitrogen injection system consists of a self-pressurizing liquid nitrogen tank (1), a valve (2), a pressure gauge (3), a pressure regulating valve (4), an ultra-low temperature flow meter (5), an ultra-low temperature heat preservation pipe (6), and a liquid nitrogen cold shock cracking device (9). A valve (2) and a pressure gauge (3) are installed on the top of the self-pressurizing liquid nitrogen tank (1). The liquid nitrogen injection system is connected to the liquid nitrogen cold shock system through the ultra-low temperature heat preservation pipe (6), and a pressure regulating valve (4) and an ultra-low temperature flow meter (5) are installed on the ultra-low temperature heat preservation pipe (6); The liquid nitrogen cold shock system includes a liquid nitrogen cold shock cracking device (9). The liquid nitrogen cold shock cracking device (9) includes a device housing (9-1). An ultra-low temperature heat preservation pipe (6) communicating with its interior is welded to the top of the device housing (9-1). A waste liquid outlet (9-7) is opened at the bottom of the device housing (9-1). The waste liquid outlet (9-7) is connected to a waste liquid storage tank (9-4) through a waste liquid pipe (9-5), and an ultra-low temperature resistant valve (9-6) is installed on the waste liquid pipe (9-5); The device housing (9-1) includes a liquid nitrogen cold shock cracking device bottom surface (9-102), two opposite guide rod penetrating shell surfaces (9-101), and a device opening coal sample probing surface (9-103); An opening is provided on the device opening coal sample probing surface (9-103). A perforated carrier ring (9-3) is installed on the liquid nitrogen cold shock cracking device bottom surface (9-102). The coal body (7) is placed on the perforated carrier ring (9-3), and the coal body (7) protrudes from the opening on the device opening coal sample probing surface (9-103). The device housing (9-1) is connected to the coal body (7) through a sealant (24); Installation holes are opened on the two opposite guide rod penetrating shell surfaces (9-101). Ultra-low temperature ultrasonic guide rods (9-2) are installed in the two installation holes. One end of the ultra-low temperature ultrasonic guide rod (9-2) is a first planar transducer coupling end (9-201), and the first planar transducer coupling end (9-201) is connected to the ultrasonic acquisition and processing system. The other end of the ultra-low temperature ultrasonic guide rod (9-2) is a coal sample coupling end (9-202), and the coal sample coupling end (9-202) is connected to the coal body (7); The ultra-low temperature ultrasonic guide rod (9-2) is threadedly connected to the guide rod penetration shell surface (9-101); the ultrasonic acquisition and processing system consists of a non-metallic ultrasonic tester (8), a system computer (12) and an acoustic wave data processor (13). The non-metallic ultrasonic tester (8) and the acoustic wave data processor (13) are electrically connected, and the acoustic wave data processor (13) and the system computer (12) are electrically connected. The non-metallic ultrasonic tester (8) is electrically connected to a planar transducer (11) through a signal line (10). The end of the planar transducer (11) is the second planar transducer coupling end (11-1). There are two planar transducers (11), one is the ultrasonic generating end and the other is the receiving end; the second planar transducer coupling ends (11-1) of the two planar transducers (11) are respectively in close contact with the first planar transducer coupling ends (9-201) of the two ultra-low temperature ultrasonic guide rods (9-2).

2. The experimental device for observing the whole-process cold shock-induced coal mass cracking according to claim 1, wherein: The perforated carrier ring (9-3) is a steel pipe with holes (9-301) all around it.

3. An experimental device for observing the whole-process cold shock-induced coal mass cracking according to claim 1, characterized in that A square opening is cut on the device opening coal sample probing surface (9-103), and the coal body observation surface (7-1) extends out through the square opening. Sealant (24) is applied at the contact points between the inside and outside of the device opening coal sample probing surface (9-103) and the coal body (7).

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