CN113433223B - Acoustic emission monitoring experiment system for whole process of liquid nitrogen freeze thawing coal - Google Patents
Acoustic emission monitoring experiment system for whole process of liquid nitrogen freeze thawing coal Download PDFInfo
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- CN113433223B CN113433223B CN202110695536.XA CN202110695536A CN113433223B CN 113433223 B CN113433223 B CN 113433223B CN 202110695536 A CN202110695536 A CN 202110695536A CN 113433223 B CN113433223 B CN 113433223B
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 220
- 239000007788 liquid Substances 0.000 title claims abstract description 203
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 110
- 238000010257 thawing Methods 0.000 title claims abstract description 90
- 239000003245 coal Substances 0.000 title claims abstract description 70
- 238000000034 method Methods 0.000 title claims abstract description 42
- 230000008569 process Effects 0.000 title claims abstract description 36
- 238000002474 experimental method Methods 0.000 title claims abstract description 29
- 238000012544 monitoring process Methods 0.000 title claims abstract description 27
- 230000008014 freezing Effects 0.000 claims abstract description 52
- 238000007710 freezing Methods 0.000 claims abstract description 52
- 238000007789 sealing Methods 0.000 claims abstract description 32
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052742 iron Inorganic materials 0.000 claims abstract description 5
- 239000000565 sealant Substances 0.000 claims description 6
- 238000009413 insulation Methods 0.000 claims description 5
- 239000002699 waste material Substances 0.000 claims description 5
- 229920002635 polyurethane Polymers 0.000 claims description 3
- 239000004814 polyurethane Substances 0.000 claims description 3
- 229940099259 vaseline Drugs 0.000 claims description 3
- 229910000589 SAE 304 stainless steel Inorganic materials 0.000 claims description 2
- 238000007599 discharging Methods 0.000 claims 1
- 239000013589 supplement Substances 0.000 claims 1
- 230000000007 visual effect Effects 0.000 abstract description 2
- 230000006378 damage Effects 0.000 description 5
- 238000011161 development Methods 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000035699 permeability Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000002734 clay mineral Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000005325 percolation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 230000002277 temperature effect Effects 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/14—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object using acoustic emission techniques
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/023—Solids
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
The invention discloses a full-process acoustic emission monitoring experiment system for a liquid nitrogen freeze-thaw coal body, which comprises a liquid nitrogen freeze-thaw box, an experiment table, a data receiver and an intelligent control terminal, wherein the liquid nitrogen freeze-thaw box is arranged on the experiment table, an objective table and a liquid level monitor are arranged in the liquid nitrogen freeze-thaw box, and a coal sample is arranged on an iron wire net; the liquid level monitor is connected with the data receiver through a liquid level connecting wire, and the data receiver is connected with the intelligent control terminal; screw thread waveguide rods are arranged on the front, the back, the left and the right of the liquid nitrogen freezing and thawing box; the inner end surfaces of the 6 threaded waveguide rods are adhered to the coal sample, and the outer end surfaces are connected with an acoustic emission sensor; a liquid inlet electromagnetic valve is arranged above the liquid nitrogen freezing and thawing box, and the liquid nitrogen tank is externally connected below the liquid inlet electromagnetic valve through a liquid inlet hose; the top of the liquid nitrogen freezing and thawing box is provided with a freezing and thawing box sealing cover. The liquid feeding device can accurately control liquid feeding, utilizes the liquid level meter to carry out automatic control or visual control, and can realize the real-time monitoring of the whole process of expansion and evolution of the internal cracks of the liquid nitrogen freeze-thaw coal sample through the multichannel acoustic emission system.
Description
Technical Field
The invention relates to the technical field of experiments of liquid nitrogen freeze-thawing coal bodies, in particular to an acoustic emission monitoring experiment system for the whole process of the liquid nitrogen freeze-thawing coal bodies.
Background
The coal resources of China are rich, and a large amount of coal bed gas is formed in the coal bed. Along with the increase of the exploitation depth, the permeability of the coal bed is reduced, and the gas extraction effect is poor, which provides a great technical challenge for exploitation of coalbed methane in China. Numerous technical attempts have been made by engineering technicians over the past several decades, such as hydraulic fracturing techniques, anhydrous fracturing techniques. However, these techniques still have some limitations. During hydraulic fracturing, not only is a significant amount of water consumed, but also the swelling of the clay mineral can block the percolation path due to the action of the water. In the high-pressure gas fracturing process, the cracks formed by fracturing are very short (only a few meters), propping agents are not used, the influence of the sealing of the cracks after fracturing on the permeability is very small, the gas extraction rate is low, and the gas control effect is not ideal. The liquid nitrogen has the characteristics of low temperature (-195.8 ℃), no pollution, simple preparation, wide raw material sources and the like, can be used as an efficient fracturing fluid in the process of improving the permeability of a coal bed, and has good application prospect.
In the process of freezing and thawing the coal body by liquid nitrogen, the internal structure of the coal body can be damaged under the action of the extremely low temperature of the liquid nitrogen, so that the development of cracks or the generation of new cracks is caused, and the energy is quickly released to generate acoustic emission signals when the development of cracks and the generation of new cracks in the coal body are generated. The acoustic emission can continuously monitor the generation and development of cracks in the coal body in the freeze thawing damage process of the coal body in real time, and realize the spatial positioning of the damage position of the coal body, thereby being an advanced experimental method. However, the prior method for monitoring and positioning the whole process emission of the liquid nitrogen freeze-thawing coal body has certain defects under the experimental conditions, and is mainly characterized in that:
in the past liquid nitrogen freeze thawing test coal sample need all submergence in liquid nitrogen, and conventional reation kettle is uncovered and air direct contact, and liquid nitrogen consumes too fast, need not stop to add liquid nitrogen to reation kettle in, only can observe the liquid level condition through the naked eye, because produce the mist because of the liquid nitrogen gasification when adding liquid, need wait for fog desalination, carry out the liquid feeding again, cause the liquid feeding time to become long, not only waste time and energy, still can cause the liquid nitrogen extravagant. In the liquid adding process of experimenters, the experimenters need to contact with liquid nitrogen, and the ultra-low temperature risk exists. In addition, as the conventional acoustic emission sensor with extremely low temperature of liquid nitrogen can deform under the ultralow temperature effect of the liquid nitrogen, the acoustic emission sensor cannot be directly contacted with a coal sample for normal measurement due to the reduction of the density, and at present, the research and the development of acoustic emission monitoring experiment research and related equipment for the whole process of freezing and thawing the coal body by the liquid nitrogen are not reported yet. Therefore, an intelligent and accurate liquid nitrogen filling control experiment system for monitoring acoustic emission in the whole liquid nitrogen freezing and thawing process is necessary to meet the technical requirements.
Disclosure of Invention
The invention aims to provide an acoustic emission monitoring experimental system for the whole process of a liquid nitrogen freeze-thawing coal body, which solves the problems in the prior art, has the advantages of intelligent and accurate regulation and control of liquid nitrogen filling, high degree of automation, simple operation, economy, high efficiency and high safety performance.
In order to achieve the above object, the present invention provides the following solutions: the invention provides a full process acoustic emission monitoring experiment system for a liquid nitrogen freeze-thawing coal body, which comprises a liquid nitrogen freeze-thawing box, an experiment table, a data receiver and an intelligent control terminal,
the liquid nitrogen freezing and thawing box is placed on the experiment table, a liquid discharge electromagnetic valve is arranged below the experiment table, the liquid nitrogen freezing and thawing box is connected with the liquid discharge electromagnetic valve through a liquid discharge hole, the liquid discharge hole penetrates through the experiment table, and a waste liquid tank is arranged right below the liquid discharge electromagnetic valve;
an objective table and a liquid level monitor are arranged in the liquid nitrogen freezing and thawing box, an iron wire net is arranged at the top of the height-adjustable objective table, and a coal sample is placed on the iron wire net; the liquid level monitor is connected with the data receiver through a liquid level connecting wire, and the data receiver is connected with the intelligent control terminal;
the front side surface and the rear side surface of the liquid nitrogen freezing and thawing box are respectively and horizontally provided with a threaded waveguide rod, the threaded waveguide rods are positioned at the centers of the front side surface and the rear side surface of the box body, and the left side and the right side of the liquid nitrogen freezing and thawing box are respectively and symmetrically provided with 2 threaded waveguide rods; the 6 threaded waveguide rods can move relative to the liquid nitrogen freezing and thawing box; the inner end surfaces of the 6 threaded waveguide rods are adhered to a coal sample to be tested through ultralow-temperature sealant, and the outer end surfaces are connected with an acoustic emission sensor;
a liquid inlet electromagnetic valve is arranged above the liquid nitrogen freezing and thawing box, the liquid inlet electromagnetic valve is connected with the data receiver through a liquid inlet control line number, a liquid inlet hose is arranged below the liquid nitrogen electromagnetic valve, and the liquid inlet hose is externally connected with a liquid nitrogen tank; the top of the liquid nitrogen freeze-thawing box is provided with a freeze-thawing box sealing cover.
Preferably, four feet of the objective table are provided with 4 bolt threads, and the height of the coal sample is adjusted by adjusting the connection heights of the bolt threads and four supporting legs of the objective table.
Preferably, the outer side of each threaded waveguide rod is connected with a threaded sleeve in a threaded mode, and the threaded sleeve is horizontally arranged and installed on the box body of the liquid nitrogen freezing and thawing box in a penetrating mode.
Preferably, the freezing and thawing box sealing cover is provided with a safety vent, the bottom of the freezing and thawing box sealing cover and the top of the liquid nitrogen freezing and thawing box are provided with corresponding ultralow temperature sealing rings, and the liquid nitrogen freezing and thawing box and the freezing and thawing box sealing cover are sealed and closed through a sealing cover buckle and a freezing and thawing box clamping groove.
Preferably, the outside cover of liquid nitrogen freeze thawing box is equipped with transparent sound-proof housing, open there is the round hole side top of transparent sound-proof housing, and liquid level connecting wire and feed liquor hose get into in the transparent sound-proof housing through the round hole.
Preferably, the liquid nitrogen freeze thawing tank and the freeze thawing tank sealing cover both contain polyurethane heat insulation layers.
Preferably, the threaded waveguide rod and the object stage are both made of 304 steel with low temperature resistance.
Preferably, the liquid draining electromagnetic valve and the liquid feeding electromagnetic valve are low-temperature resistant electromagnetic valves.
Compared with the prior art, the invention has the following beneficial technical effects:
1. the electromagnetic valve is used for accurately controlling liquid adding, the liquid level gauge is used for automatic control or visual control, and the electromagnetic valve is matched for liquid level control.
2. The liquid nitrogen freezing and thawing box and the sealing cover of the freezing and thawing box contain polyurethane heat insulation layers, and the sealing cover of the freezing and thawing box and the ultralow temperature sealing ring are arranged, so that the heat insulation effect in the box is ensured, and the consumption of liquid nitrogen is reduced.
3. Remote control, not contact with liquid nitrogen, reduced the ultralow temperature risk.
4. The problem that the acoustic emission sensor cannot be directly contacted with the coal sample is solved by utilizing the threaded waveguide rod, and the whole process of expansion and evolution of the internal cracks of the liquid nitrogen freeze-thaw coal sample can be monitored in real time by utilizing the multichannel acoustic emission system.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an acoustic emission monitoring experiment system for the whole process of freezing and thawing a coal body by liquid nitrogen;
FIG. 2 is a schematic diagram of a liquid nitrogen freeze-thaw chamber;
FIG. 3 is a cross-sectional view of a liquid nitrogen freeze-thaw chamber;
FIG. 4 is a schematic view of a stage;
wherein 1 a waste liquid tank; 2, a liquid discharge electromagnetic valve; 3, a test bench; 4, an objective table; a 41-thread base; 42 wire netting; 43 bolt threads; 5, testing the coal sample; 6, a liquid nitrogen freezing and thawing box; 61 ultra-low temperature sealing rings; 62 a liquid level monitor; 63 freeze thawing tank clamping groove; 64 liquid inlet electromagnetic valve; 65 drain holes; 7, sealing a cover of the freeze thawing box; 71 sealing cover buckles; 72 a safety vent; 8, a transparent sound-proof cover; 9 liquid inlet control lines; 10 liquid level connecting lines; 11 liquid inlet hose; 12 thread waveguide rod; 13 a threaded sleeve; 14 a liquid discharge control line; 15 a data receiver; 16 intelligent control terminals; 17 ultra-low temperature sealant; 18 acoustic emission sensor.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide an acoustic emission monitoring experimental system for the whole process of a liquid nitrogen freeze-thawing coal body, which solves the problems in the prior art, has the advantages of intelligent and accurate regulation and control of liquid nitrogen filling, high degree of automation, simple operation, economy, high efficiency and high safety performance.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
As shown in fig. 1-4, this embodiment provides a whole process acoustic emission monitoring experiment system of liquid nitrogen freeze-thaw coal body, liquid nitrogen freeze-thaw box 6 is wholly put on laboratory bench 3, laboratory bench 3 below is equipped with flowing back solenoid valve 2, liquid nitrogen freeze-thaw box 6 passes through flowing back hole 65 with flowing back solenoid valve 2 and is connected, flowing back hole 65 runs through laboratory bench 3, be equipped with waste liquid groove 1 directly under the flowing back solenoid valve 2, liquid nitrogen freeze-thaw box 6 inside is equipped with objective table 4 and liquid level monitor 62, objective table 4 top is equipped with wire netting 42, coal sample 5 is placed on wire netting 42, objective table 4 below is equipped with 4 bolt threads 43, can adjust the height of coal sample 5 through bolt threads 43.
The front side and the rear side of the liquid nitrogen freezing and thawing box 6 are respectively and horizontally provided with a threaded waveguide rod 12, the threaded waveguide rods 12 are arranged at the centers of the front side and the rear side of the box body, the left side and the right side are respectively and diagonally provided with 2 threaded waveguide rods 12, the threaded waveguide rods 12 are externally provided with threaded sleeves 13 with matched sizes, and the threaded waveguide rods 12 and the threaded waveguide rods are connected through threads, and the threaded sleeves 13 are horizontally arranged and penetrate through the box body on the side face of the liquid nitrogen freezing and thawing box 6. The inner end face of the threaded waveguide rod 12 is adhered to the coal sample 5 to be tested through ultralow temperature sealant 17, and the outer end face of the threaded waveguide rod 12 is connected with an acoustic emission sensor 18 through vaseline. The 4 sides of the liquid nitrogen freezing and thawing box 6 are provided with 6 threaded waveguide rods 12 in total, and threaded sleeves 13 are fixed on the four sides of the liquid nitrogen freezing and thawing box 6.
The liquid level monitor 4 is connected with a data receiver 15 through a liquid level connecting wire 10, and the data receiver 15 is connected with an intelligent control terminal 16. A liquid inlet electromagnetic valve 64 is arranged above the left side surface of the liquid nitrogen freezing and thawing box 6, the liquid inlet electromagnetic valve 64 is connected with the data receiver 15 through a liquid inlet control line number 9, a liquid inlet hose 11 is arranged below the liquid inlet electromagnetic valve 64, and the liquid inlet hose 11 is externally connected with a liquid nitrogen tank; the liquid level monitor 4 can monitor the liquid level in real time, and when the liquid level is lower than a set value, the liquid level can be automatically added through the intelligent control terminal.
The top of the liquid nitrogen freeze-thawing box 6 is provided with a freeze-thawing box sealing cover 7, the freeze-thawing box sealing cover 7 is provided with a safety vent 72, the safety of experiments is guaranteed, the bottom of the freeze-thawing box sealing cover 7 and the top of the liquid nitrogen freeze-thawing box 6 are provided with corresponding ultralow temperature sealing rings 61, the liquid nitrogen freeze-thawing box 6 and the freeze-thawing box sealing cover 7 are sealed and closed through sealing cover buckles 71 and freeze-thawing box clamping grooves 63, the heat insulation of the liquid nitrogen freeze-thawing box 6 is guaranteed, the volatilization of liquid nitrogen is reduced, the liquid nitrogen freeze-thawing box 6 is integrally positioned in a transparent sound-proof cover 8, noise in the experimental process can be isolated, the acoustic emission measurement precision is guaranteed, a round hole is formed in the upper side face of the transparent sound-proof cover 8, and a connecting wire and a liquid nitrogen hose enter the transparent sound-proof cover 8 through the round hole.
The working principle of the liquid nitrogen freeze-thawing coal body whole process acoustic emission monitoring experiment system is as follows:
when an experiment is carried out, firstly, the coal sample 5 is placed at the center of the objective table 4, the vertical height of the coal sample 5 is adjusted through the screw thread 43, the center height of the coal sample 5 is consistent with the center height of the front and rear screw thread waveguide rods 12, after the height adjustment of the coal sample 5 is completed, the screw thread waveguide rods 12 are rotated, the end faces of the screw thread waveguide rods 12 are tightly attached to the coal sample 5, ultralow temperature sealant 17 is smeared at the joint of the coal sample 5 and the screw thread waveguide rods 12 and the joint of the screw thread sleeve 13 and the screw thread waveguide rods 12, liquid nitrogen exudation in the test process is prevented, and after the coal sample 5 is assembled, sealing and closing are carried out through the sealing cover buckle 71 and the freezing and thawing box clamping groove 63. The liquid inlet hose 11 is connected with a liquid nitrogen tank, and the outside of the waveguide rod is connected with the acoustic emission sensor 18 through vaseline. The liquid level can be set in the system through the intelligent control terminal 16, after the set liquid level is reached, the liquid inlet electromagnetic valve 64 is powered off, liquid adding is stopped, and when the liquid level of liquid nitrogen is lower than the lowest set liquid level, the liquid inlet electromagnetic valve 64 is opened for automatic liquid supplementing. And then, performing an acoustic emission monitoring experiment on the whole process of freezing and thawing the coal body by liquid nitrogen, closing self-pressurization after the test is finished, disconnecting the metal hose from the equipment, and opening a liquid discharge electromagnetic valve 2 to perform liquid discharge operation.
The whole process of the liquid nitrogen freeze thawing coal sample is monitored in real time through the multichannel acoustic emission monitoring system, the multichannel acoustic emission monitoring system can realize simultaneous use of at most 6 acoustic emission channels, when the development condition of the internal pore cracks of the coal sample 5 is monitored, only the front threaded waveguide rod 12 and the rear threaded waveguide rod 12 can be connected, acoustic emission signals generated in the process of crushing the coal sample are monitored in real time through 2 channels, and after the acoustic emission signals are received by the acoustic emission monitoring system, the acoustic emission signals are processed, so that acoustic emission response characteristics of the internal pore cracks of the coal sample 5 can be obtained.
When the internal hole crack expansion space positioning of the coal sample 5 is carried out, the 6 threaded waveguide rods 12 and the 6 acoustic emission channels are connected for simultaneous use, and the coal sample 5 is consistent with the internal microcrack evolution process during the destruction process. The 6 acoustic emission sensors 18 receive acoustic emission signals in real time, and the acoustic emission system can locate a large number of acoustic emission source positions through a specific algorithm. The number of the locating points can quantitatively represent the number of cracks and internal damage of the sample in the liquid nitrogen injection process, and the range of the locating points can invert the expansion and evolution process of the cracks in the sample. By collecting and analyzing acoustic emission locating points in the sample, the dynamic damage process of crack generation and expansion in the process of freezing and thawing the coal body by liquid nitrogen can be deduced, and the internal mechanism of the coal body by freezing and thawing the coal body by liquid nitrogen is revealed.
It should be noted that it will be apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, but may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
The principles and embodiments of the present invention have been described in detail with reference to specific examples, which are provided to facilitate understanding of the method and core ideas of the present invention; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (5)
1. The utility model provides a liquid nitrogen freeze thawing coal body overall process acoustic emission monitoring experiment system which characterized in that: the liquid nitrogen freezing and thawing device comprises a liquid nitrogen freezing and thawing box, a laboratory bench, a data receiver and an intelligent control terminal, wherein the liquid nitrogen freezing and thawing box is placed on the laboratory bench, a liquid draining electromagnetic valve is arranged below the laboratory bench, the liquid nitrogen freezing and thawing box is connected with the liquid draining electromagnetic valve through a liquid draining hole, the liquid draining hole penetrates through the laboratory bench, and a waste liquid tank is arranged right below the liquid draining electromagnetic valve;
an objective table and a liquid level monitor are arranged in the liquid nitrogen freezing and thawing box, an iron wire net is arranged at the top of the height-adjustable objective table, and a coal sample is placed on the iron wire net; the liquid level monitor is connected with the data receiver through a liquid level connecting wire, and the data receiver is connected with the intelligent control terminal;
the front side surface and the rear side surface of the liquid nitrogen freezing and thawing box are respectively and horizontally provided with a threaded waveguide rod, the threaded waveguide rods are positioned at the centers of the front side surface and the rear side surface of the box body, and the left side and the right side of the liquid nitrogen freezing and thawing box are respectively and symmetrically provided with 2 threaded waveguide rods; the 6 threaded waveguide rods can move relative to the liquid nitrogen freezing and thawing box; the inner end surfaces of the 6 threaded waveguide rods are adhered to a coal sample to be tested through ultralow-temperature sealant, and the outer end surfaces are connected with an acoustic emission sensor;
a liquid inlet electromagnetic valve is arranged above the liquid nitrogen freezing and thawing box, the liquid inlet electromagnetic valve is connected with the data receiver through a liquid inlet control line number, a liquid inlet hose is arranged below the liquid nitrogen electromagnetic valve, and the liquid inlet hose is externally connected with a liquid nitrogen tank; the top of the liquid nitrogen freeze-thawing box is provided with a freeze-thawing box sealing cover;
four feet of the objective table are provided with 4 bolt threads, and the height of the coal sample is adjusted by adjusting the connection heights of the bolt threads and four supporting legs of the objective table;
the outer side of each threaded waveguide rod is in threaded connection with a threaded sleeve, and the threaded sleeve is horizontally arranged and penetrates through the box body of the liquid nitrogen freezing and thawing box;
the freezing and thawing box sealing cover is provided with a safety vent, the bottom of the freezing and thawing box sealing cover and the top of the liquid nitrogen freezing and thawing box are provided with corresponding ultralow temperature sealing rings, and the liquid nitrogen freezing and thawing box and the freezing and thawing box sealing cover are sealed and closed through a sealing cover buckle and a freezing and thawing box clamping groove;
when the acoustic emission monitoring experiment system is adopted for experiments, the experimental steps are as follows:
the first step: the coal sample is placed in the center of the objective table, and the vertical height of the coal sample is adjusted through screw threads of the bolts, so that the center of the coal sample is consistent with the center height of the front and rear screw thread waveguide rods;
and a second step of: rotating the threaded waveguide rod to enable the end face of the threaded waveguide rod to be clung to the coal sample, and smearing ultra-low temperature sealant at the joint of the coal sample and the threaded waveguide rod and the joint of the threaded sleeve and the threaded waveguide rod;
and a third step of: sealing and closing the freezing and thawing box clamping groove through the sealing cover buckle; the liquid inlet hose is connected with the liquid nitrogen tank, and the outside of the waveguide rod is connected with the acoustic emission sensor through vaseline;
fourth step: setting the liquid level through the intelligent control terminal system, powering off the liquid inlet electromagnetic valve after the set liquid level is reached, stopping adding liquid, and opening the liquid inlet electromagnetic valve to automatically supplement liquid when the liquid level of liquid nitrogen is lower than the lowest set liquid level;
fifth step: and (3) performing an acoustic emission monitoring experiment of the whole process of the liquid nitrogen freeze-thawing coal body, and monitoring the whole process of the liquid nitrogen freeze-thawing coal sample in real time through a 6-channel acoustic emission monitoring system.
2. The liquid nitrogen freeze-thaw coal body overall process acoustic emission monitoring experiment system according to claim 1, wherein: the outside cover of liquid nitrogen freeze thawing case is equipped with transparent sound-proof housing, open the side top of transparent sound-proof housing has the round hole, and liquid level connecting wire and feed liquor hose get into in the transparent sound-proof housing through the round hole.
3. The liquid nitrogen freeze-thaw coal body overall process acoustic emission monitoring experiment system according to claim 1, wherein: the liquid nitrogen freeze-thawing box and the freeze-thawing box sealing cover both contain polyurethane heat insulation layers.
4. The liquid nitrogen freeze-thaw coal body overall process acoustic emission monitoring experiment system according to claim 1, wherein: the threaded waveguide rod and the objective table are both made of 304 steel.
5. The liquid nitrogen freeze-thaw coal body overall process acoustic emission monitoring experiment system according to claim 1, wherein: the liquid discharging electromagnetic valve and the liquid feeding electromagnetic valve are low-temperature resistant electromagnetic valves.
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| US10753821B2 (en) * | 2018-08-30 | 2020-08-25 | William C. Baird, IV | System and method for monitoring and reporting liquid nitrogen container level |
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| CN105136837A (en) * | 2015-07-24 | 2015-12-09 | 中国矿业大学 | Liquid nitrogen circulating freeze-thawing permeability-increasing simulation test system and method for coal rock sample |
| CN105134284A (en) * | 2015-08-03 | 2015-12-09 | 中国矿业大学 | Gas extraction method based on horizontal orientation boring liquid nitrogen cycle freeze-thaw anti-reflection |
| CN108761025A (en) * | 2018-05-29 | 2018-11-06 | 西安科技大学 | A kind of monitoring liquid nitrogen fracturing coal sample effect experiment device in real time |
| CN209556993U (en) * | 2019-01-15 | 2019-10-29 | 河南理工大学 | The molten leaching coal body fracturing permeability improvement device of liquid nitrogen can be pressurized |
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