CN113156079B - Experimental device for testing space-time evolution and mechanical parameters of liquid nitrogen immersed coal sample cracks - Google Patents

Experimental device for testing space-time evolution and mechanical parameters of liquid nitrogen immersed coal sample cracks Download PDF

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CN113156079B
CN113156079B CN202110344249.4A CN202110344249A CN113156079B CN 113156079 B CN113156079 B CN 113156079B CN 202110344249 A CN202110344249 A CN 202110344249A CN 113156079 B CN113156079 B CN 113156079B
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liquid nitrogen
coal sample
coal
sample
temperature
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CN113156079A (en
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林海飞
李树刚
罗荣卫
严敏
李博涛
秦雷
丁洋
王裴
成连华
李莉
刘思博
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Xian University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/22—Fuels, explosives
    • G01N33/222—Solid fuels, e.g. coal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D21/00—Measuring or testing not otherwise provided for
    • G01D21/02—Measuring two or more variables by means not covered by a single other subclass
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/44—Sample treatment involving radiation, e.g. heat
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Abstract

The invention discloses a device for testing space-time evolution and mechanical parameters of cracks of a liquid nitrogen immersed coal sample, which comprises a coal sample vacuum drying system, a coal sample water bath constant temperature system, a coal sample water saturation system, a liquid nitrogen injection system, a liquid nitrogen immersion reaction system and a monitoring acquisition processing system. The liquid nitrogen leaching reaction system comprises a waveguide rod sensor coupling cavity and a liquid nitrogen reaction kettle, wherein the liquid nitrogen reaction kettle comprises a sensor clamping groove, a sound insulation cover, a waste liquid cavity, a waste liquid outlet, a sample placing table, an electromagnetic valve, an exhaust hole, a reaction kettle base and a supporting frame, all parts are fixedly connected, and small uniformly distributed holes and ribs are arranged below the sample placing table. The monitoring, collecting and processing system comprises a strain testing subsystem, a pressure monitoring subsystem and an acoustic emission collecting subsystem. The experimental data monitoring of the whole process of immersing the coal sample in the liquid nitrogen can be realized in real time, the microscopic structural change of the coal sample under the action of the liquid nitrogen is monitored, and the rules and effects of damage, deformation and fracture of the coal body are dynamically analyzed when the coal sample is subjected to liquid nitrogen fracturing.

Description

Experimental device for testing space-time evolution and mechanical parameters of liquid nitrogen immersed coal sample cracks
Technical Field
The invention relates to the field of coal sample experimental equipment, in particular to a device for testing the space-time evolution and mechanical parameters of liquid nitrogen immersed coal sample cracks.
Background
The primary energy consumption structure of China is mainly based on coal, and along with the steady development of economy of China, the demand for coal is increased, and coal becomes an important resource foundation for industrial and economic development of China. At present, most of coal mine production modes in China are underground mining, and potential resources are increasingly exhausted along with the transition of shallow coal mining time and the need of energy sources, so that the mine mining in China gradually enters a deep mining stage. The mine enters deep mining, the gas content and the gas emission amount of the coal bed are rapidly increased, particularly under special conditions of high ground stress, high ground temperature and the like, the phenomena of gas overrun, coal and gas outburst and the like are more frequent, the phenomena of coal and gas outburst become one of main factors restricting the safe and efficient production of the mine, the temperature of the shallow stratum is often referred to as ground temperature for short, the temperature of the shallow stratum is increased along with the increase of depth, and the ground temperature is increased by 1 degree every 33 meters when the buried depth is increased.
Coal is a natural geologic body with the defects of micro-cracks, pores, low strength and the like. Most of mining area gas reservoirs in China have the occurrence characteristics of 'three high and two low' (three high: high gas content of coal layers, high plasticity structure and high gas adsorption capacity, two low: low coal layer permeability and low conventional fracture crack ratio of coal layers under reinforcing measures), and according to statistics, high gas mines in China account for more than 37 percent in mines in China, wherein 95 percent of mined coal layers belong to low permeability coal layers, so how to improve the permeability of low permeability coal layers is one of the keys of gas extraction and gas disaster prevention in China, and the expansion of micro cracks and new crack initiation of coal bodies can directly influence the permeability of coal.
The liquid nitrogen has no pollution to the environment, is easy to prepare and low in cost, has extremely low temperature (-196 ℃) and can weaken freezing damage of the coal body, expand primary micro-cracks and generate new cracks after the low-temperature liquid nitrogen is injected into the coal body, so that a freeze-thawing fracture zone is formed. In the limited space of the coal bed, the volume of the gasified liquid nitrogen is rapidly expanded to generate a huge expansion force to crack the coal bed, the gasification volume of the 1m < 3 > liquid nitrogen is expanded by 696 times at the temperature of 21 ℃ to form a gasification high-pressure fracturing zone, meanwhile, high-pressure nitrogen can drive and partial pressure replace coal bed gas, gas desorption seepage is promoted, particularly, liquid nitrogen is circularly frozen and thawed to crack the coal bed repeatedly, the permeability effect of the coal bed is more remarkable, and meanwhile, the absorption of heat required by liquid nitrogen volatilization can play a certain role in cooling the coal bed.
The gas is a main factor causing coal mine gas accidents and is also a strong greenhouse gas, and the damage to an ozone layer and the generated greenhouse effect respectively reach 7 times and 21 times of CO 2. Compared with disastrous, the gas is available clean energy in the coal seam, has wide development prospect, has a shallow gas resource amount of about 36.8 trillion m3 for the buried depth of 2000m in China, and has remarkable exploitation value. Therefore, the coal and gas resources are safely and efficiently co-mined, not only can the disaster of the gas be effectively prevented and controlled and the pollution to the atmosphere is reduced, but also the gas is used as clean energy, and the aims of mine safety production, environmental protection, new energy supply and the like can be realized.
Along with the development of scientific technology, in order to solve the problem of insufficient technology in the conventional coal seam permeability improvement, the coal seam gas is efficiently pre-pumped and utilized, the problems of gas accidents and environmental pollution reduction are prevented, the economic benefit is maximized, and the anhydrous fracturing technology using ultralow-temperature fluid such as liquid nitrogen and the like as fracturing fluid is gradually paid attention to.
In order to improve the permeability of the coal seam, related scholars at home and abroad propose explosion permeability-increasing technologies such as presplitting explosion, gas explosion and the like, and the technology operation is relatively complex and easy to generate secondary hazard. There are also hydraulic fracturing, high pressure water injection, hydraulic slotting, etc. and the fracturing fluid has certain environmental pollution and water locking effect and great water consumption. With the development of technology, many new technologies are proposed by expert students, such as: ultrasonic excitation, solvent extraction, microbial fermentation, electrochemical methods, etc., have been rapidly developed, however, the complicated and expensive costs of the technology process make it difficult to popularize or apply these technologies.
Because the occurrence condition of the coal seam is complex, the natural coal seam contains moisture, and the coal seam has different temperatures due to the buried depth, the surrounding rock air permeability and other reasons, and the liquid nitrogen freezes and melts the coal body under the condition, so that the fracturing and permeability increasing and gas displacement effects are more obvious, and the efficient gas extraction is more facilitated. How to simulate the consistency of the properties of experimental coal samples and occurrence coal samples in a laboratory, and provide effective basis and theory for on-site application of liquid nitrogen to coal seam anti-reflection gas extraction, and still needs to be perfected at present. Meanwhile, the laboratory can only observe the change of the liquid nitrogen before and after the coal body is acted, but cannot effectively monitor the whole process of freezing and thawing the coal body by the liquid nitrogen.
Disclosure of Invention
The invention aims to provide a device for testing the space-time evolution and mechanical parameters of cracks of a liquid nitrogen immersed coal sample, which has the advantages of solving the problems in the prior art.
In order to achieve the above purpose, the present invention provides the following technical solutions: the experimental device for the space-time evolution of the cracks of the liquid nitrogen immersed coal sample and the mechanical parameter test comprises a coal sample vacuum drying system, a coal sample water bath constant temperature system, a coal sample water saturation system, a liquid nitrogen injection system, a liquid nitrogen immersion reaction system and a monitoring acquisition processing system.
The liquid nitrogen leaching reaction system comprises a waveguide rod sensor coupling cavity 28, an electromagnetic valve switch 29 and a liquid nitrogen reaction kettle 31, wherein the liquid nitrogen reaction kettle comprises a sensor clamping groove 31-1, a sound insulation cover 31-2, a waste liquid cavity 31-3, a base fixing hole 31-4, a sample placing table 31-5, a waste liquid outlet 31-6, an ultralow temperature resistant electromagnetic valve 31-7, an exhaust hole 31-8, a reaction kettle base 31-9 and a support frame 31-10, the parts are fixedly connected, and the ultralow temperature resistant electromagnetic valve 31-7 controls liquid nitrogen to flow out from the waste liquid outlet 31-6 after experiments; the solenoid valve switch 29 is electrically connected with the ultra-low temperature resistant solenoid valve 31-7.
According to the structure, the waste liquid cavity 31-3 is used for containing liquid nitrogen which is used for soaking the coal sample after the experiment is finished, so that the soaking time is better controlled, and the coal sample is convenient to separate from the liquid nitrogen; the sound insulation cover 31-2 is used for isolating the influence of external sound on experiments; the base fixing holes 31-4 facilitate fixing of the experimental device.
Small holes and ribs are uniformly distributed below the sample placing table 31-5. The direct contact area between the bottom of the sample and the liquid nitrogen is increased, and a hole is formed in the center of the sample so as to facilitate placement of the pressure sensor. The six sides of the coal sample can be directly acted by the liquid nitrogen, and compared with the prior art that the bottom surface cannot be directly contacted with the liquid nitrogen, the experimental environment of each side of the coal sample is the same, the fracture influence caused by different side actions is avoided, and the experimental error is reduced.
The monitoring, collecting and processing system comprises a strain testing subsystem, a pressure monitoring subsystem and an acoustic emission collecting subsystem.
Further, the sample coal vacuum drying system comprises a vacuum drying box 7, a sealing door 5, a vacuumizing pump 2, a temperature setting area 3 and a gas release knob 4. According to the structure, when the vacuum drying device is operated, the sealing door 5 is opened to put the coal sample 14 into the vacuum drying box 7, the sealing ring is arranged in the sealing door 5, the air release knob 4 is rotated to be in a closed state, the vacuum drying box 7 is subjected to vacuum treatment through the vacuumizing pump 2, and the temperature required by vacuum drying is set by using the keys of the temperature setting area 3; the drying time is determined according to the experimental requirement; the vacuum drying oven 7 is arranged above the laboratory experiment table 6; after the coal sample is dried, the air release knob 4 is rotated slowly to be in a semi-open state for air release for a period of time and then is completely opened, so that the damage to an instrument caused by overlarge pressure difference is avoided.
Further, the coal sample water bath constant temperature system comprises a water bath box main body 13, a water bath sealing cover 9, a water discharging switch 8, a temperature display screen 10, a water bath switch 11 and a temperature setting button 12. As can be seen from the above structure, when operating, firstly, a proper amount of water is added into the water bath tank, and the water bath tank is opened by the temperature setting button 12; the temperature display screen 10 displays the water bath temperature in real time; the temperature setting button 12 is used for setting the required temperature, and the temperature range is room temperature to 100 ℃; then covering a water bath sealing cover 9; the constant-temperature water bath is finished, and the wastewater is discharged through a water discharge switch 8; different heating chambers of the water bath box can be provided with different temperatures.
Further, the coal sample saturation system comprises a sample tank 22, a pressurizing device 19, a vacuum pressurizing and saturating device 20, a pressure display 21-1 and a vacuum display 21-2. According to the structure, during operation, the coal sample 14 is placed 22 in the sample tank, the tank is sealed again, and the vacuum display of the vacuumized 21-2 is stopped by a required value; the pressurization by 19 manual pressurization devices is carried out until the pressure of 21-1 shows the required pressure, and the pressure is ensured to be constant in the water retention process.
Further, the liquid nitrogen injection system comprises a self-pressurization liquid nitrogen tank 1, an ultralow temperature flowmeter 32, an ultralow temperature heat preservation pipe 33, a self-pressurization liquid nitrogen tank valve 34, a pressure regulating valve 35, a pressure gauge 36 and a liquid inlet valve 37. According to the structure, during operation, liquid nitrogen is injected into the customized reaction kettle from the self-pressurizing liquid nitrogen tank 1; the ultra-low temperature flowmeter 32 can monitor the flow rate of the liquid nitrogen conveyed into the reaction kettle in real time; 34, controlling a liquid nitrogen conveying switch by a self-pressurizing liquid nitrogen tank valve; the 35-regulator valve controls the pressure at which liquid nitrogen is injected.
Further, the heat-insulating materials are externally attached to each part of the reaction kettle 31. Avoiding volatilization of liquid nitrogen during transportation.
Further, the strain testing subsystem comprises an ultralow temperature strain gauge 16, a low temperature resistant signal transmission line 16-1, a USB data line 24, a computer 23 and a strain tester 30. The ultralow temperature strain gauge 16 is attached to the surface of the coal sample 14, and the signal transmission line is made of a low temperature resistant material, so that failure caused by ultralow temperature is avoided.
Further, the number of ultralow temperature strain gauges is 3, and the ultralow temperature strain gauges are distributed on the vertical, horizontal and oblique directions of the surface of the coal sample. According to the structure, the vertical, horizontal and oblique distribution can completely measure the stress performance of the coal sample in all directions in the mechanical change process.
Further, the pressure monitoring subsystem comprises an ultralow temperature pressure sensor 15, a low temperature resistant signal transmission line 15-1, a pressure receiving device 25, a data line 24 and a computer 23.
Further, the acoustic emission acquisition subsystem comprises a waveguide rod 17, an acoustic emission signal amplifier 18, an acoustic emission processor 26, an acoustic emission receiving line 27, an acoustic emission sensor 27-1, a waveguide rod sensor coupling cavity 28 and a computer 23.
In the above structure, the ultra-low temperature pressure sensor 15, the ultra-low temperature strain gauge 16, the waveguide rod 17 and the coal sample 14 need to be bonded; the acoustic emission sensor 27-1 needs to be smeared with a couplant at the butt joint interface of the waveguide rod and the contact end 17-2 of the experiment table shell, and the coupling is completed between the waveguide rod and the sensor coupling cavity 28; six waveguide rods of the waveguide rods 17 are welded on the reaction kettle corresponding to the contact ends 17-1 of the coal sample and the setting positions of the computer, and are used for releasing conduction signals to the acoustic emission sensor when the coal sample is immersed and fused by liquid nitrogen, one end of the waveguide rods is clung to the sensor, and the interface of the waveguide rods is required to be coupled with the coupling agent; the positions of the wave guide rods on each surface are collinear with the position of the contact end 17-1 of the coal sample, and all the connecting lines are not coplanar with each other, so that the acoustic emission energy of the coal sample can be obtained, the ringing count can be carried out, and meanwhile, the acoustic emission event generated by the raw coal in the liquid nitrogen immersing process can be positioned in real time in three-dimensional space; the low temperature resistant signal transmission line 15-1 and the low temperature resistant signal transmission line 16-1 are FEP wires, and the coating material is made of low temperature resistant materials.
In the use process of the whole experimental equipment,
firstly, preparing coal samples with different factors:
single-factor preparation of completely dried coal samples: opening a 5 sealing door of a vacuum drying box to put a 14 coal sample into a 7 vacuum drying box, tightly closing the sealing door, then rotating a 4 air release knob to a closed state, opening a 2 vacuumizing pump to vacuumize the inside, then closing the 2 vacuumizing pump, setting the required temperature for drying through a 3 temperature setting area, rotating the 4 air release knob slowly after the drying time is finished to be in a semi-open state to release air for a period of time, then completely opening the air release knob, taking out the coal sample, putting the coal sample into a sample bag for sealing for standby, and if the humidity of the coal sample is overlarge, distributing water drops on the 5 sealing door in the drying process, opening a towel for the vacuum drying box to wipe the internal water drops, and then drying.
Single factor initial temperature coal sample preparation: taking out the completely dried coal sample, at this time, carrying out water-proof treatment on the 14 coal sample at room temperature, opening a 9 water bath sealing cover to put the coal sample in, closing an 8 water discharge switch, adding a proper amount of water to submerge the 4 coal sample, opening an 11 water bath switch 10 temperature display screen to display real-time water bath temperature and set temperature, using a 12 temperature setting button to set the required sample temperature, covering the 9 water bath sealing cover, and discharging the wastewater through the 8 water discharge switch after the constant-temperature water bath is finished.
And (3) preparing a single-factor fully saturated water coal sample: opening a 22 sample tank to put a 14 coal sample into a rotary 22 sample tank, sealing the upper end of the 22 sample tank, opening a 2 vacuumizing pump of a coal sample water saturation system to vacuumize the 22 sample tank, displaying at 21-2 vacuum, rotating a 19 manual pressurizing device to pressurize the 22 sample tank until 21-1 pressure is displayed until the pressure is required, ensuring constant pressure in the water retention process, opening the 22 sample tank to take out the coal sample after water retention is finished, and placing the coal sample in a water-filled vessel for standby.
Preparing coal samples with different water contents: opening a 5 sealing door of a vacuum drying box to put a 14 coal sample into a 7 vacuum drying box, tightly closing the sealing door, rotating a 4 air release knob to a closed state, opening a 2 vacuumizing pump to vacuumize the inside, closing the 2 vacuumizing pump, setting a drying temperature through a 3 temperature setting area, slowly rotating the 4 air release knob to a semi-open state after the drying time is finished, deflating for a period of time, fully opening, taking out the 14 coal sample, weighing on an electronic scale, recording as m0, opening a 22 sample tank to put the 14 coal sample into the upper end of the 22 sample tank for sealing, filling the 2 vacuumizing pump of a water saturation system of the 22 sample tank, vacuumizing in the 22 sample tank for 21-2 vacuum display, rotating a 19 manual pressurizing device to pressurize the 22 sample tank until 21-1 pressure displays the pressure, ensuring that the pressure is constant in the water retention process, opening the 22 sample tank to take out the 14 coal sample, weighing again with a wet towel, recording as m, and measuring the water content
Figure GDA0003105076940000061
The calculated water content is the maximum water content of the 14 coal samples, and then the 14 coal samples are put into a 7 vacuum drying oven for drying for different time and weighing to obtain mn, and the mn is calculated to obtainTo different water contents->
Figure GDA0003105076940000062
Preparing water-containing coal samples at different prefabrication temperatures: opening a 5 sealing door of a vacuum drying box to put a 14 coal sample into a 7 vacuum drying box, tightly closing the sealing door, then rotating a 4 air release knob to a closed state, opening a 2 vacuumizing pump to vacuumize the inside, then closing the 2 vacuumizing pump, setting a drying temperature through a 3 temperature setting area, after the drying time is over, rotating the 4 air release knob to slowly rotate to a semi-open state to release air for a period of time, then completely opening the vacuum drying box, taking out the 14 coal sample, weighing the 14 coal sample on an electronic scale, recording as m0, opening a 22 sample tank to put the 14 coal sample into the upper end of the rotary 22 sample tank for sealing, opening a 2 vacuumizing pump of a coal sample saturation system to vacuumize the 22 sample tank until the pressure of 21-2 is required, rotating a 19 manual pressurizing device to pressurize the 22 sample tank until the pressure of 21-1 is required for displaying, ensuring the pressure in a water retention process to be constant, opening the 22 sample tank to take out the 14 coal sample, using a towel to wet the surface water bead of the 14 coal sample, then putting the 14 coal sample into the 7 vacuum drying box for drying for different time, weighing to obtain an mn, calculating the water content, using a bathroom film to put the 14 coal sample into a water bath cover, completely sealing the 14 water bath 10, and then placing the 14 water bath cover to be completely at least 9, and setting a water bath cover for sealing the 14 water bath 10 for a water bath, and sealing the water bath cover for at least 9 h, setting the temperature water bath cover for at least, and sealing the water bath cover for setting the temperature for at least 9, and sealing the water bath cover for setting the temperature.
Different leaching times of coal samples: and the liquid nitrogen injection system injects liquid nitrogen into the 31 liquid nitrogen reaction kettle, starts timing when the 14 coal sample is completely immersed, and operates a 29 electromagnetic valve switch to open a 31-7 ultralow temperature resistant electromagnetic valve after the immersion time is reached to control liquid nitrogen from a 31-6 waste liquid outlet to a 31-3 waste liquid cavity, so that the immersion time of the 14 coal sample is controlled.
Again, the test data were tested:
the method comprises the steps of attaching a 15 ultralow temperature pressure sensor and a 16 ultralow temperature strain gauge to the surface of a prepared 14 coal sample by using ultralow temperature resistant resin glue as shown in a graph 3, connecting one end of the 15-1 ultralow temperature resistant signal transmission line and the 16-1 ultralow temperature resistant signal transmission line, opening the 15-1 ultralow temperature resistant signal transmission line by a 23 computer, opening the 23 computer, a 26 acoustic emission processor, a 30 strain tester and a 25 pressure receiving device, simultaneously opening the pressure monitoring software and the strain monitoring software, closing a 31-7 ultralow temperature resistant electromagnetic valve by a 29 electromagnetic valve switch, closing a 37 liquid nitrogen inlet valve on a 1 self-pressurizing liquid nitrogen tank, opening a 34 self-pressurizing liquid nitrogen tank valve, regulating the pressure regulating valve by a 35 valve, and injecting the 27-1 acoustic emission sensor surface coating coupling agent into a 28 wave guide rod and a sensor coupling cavity according to the corresponding position, opening 23 computer, 26 acoustic emission processor, 30 strain tester and 25 pressure receiving device, opening the 31-7 ultralow temperature resistant electromagnetic valve, closing a 37 liquid nitrogen inlet valve on the 1 self-pressurizing liquid nitrogen tank, opening the 34 self-pressurizing liquid nitrogen valve, and regulating the 35 valve, and quickly injecting the 17-1 acoustic emission sensor surface coating coupling agent into the 27 acoustic emission sensor surface coupling agent into the 28 wave guide rod and the sensor coupling cavity, opening 23 computer, closing the 23 computer, the 26 acoustic emission processor, the 30 strain tester and the pressure meter, closing the 25 pressure meter, closing the pressure meter, and the 25 pressure liquid nitrogen inlet sensor, closing the pressure meter, and the 37 liquid nitrogen inlet valve and the pressure sensor valve, and the 37 liquid nitrogen inlet valve and the pressure valve, and the 37 liquid valve and the pressure valve Processing the position to generate data in 23 computer software; the strain generated by the surface skeleton of the 14 coal sample is received by a 16 ultralow temperature strain gauge, transmitted to a 30 strain tester for pretreatment through a 16-1 low temperature resistant signal transmission line, and transmitted to 23 computer software through a 24USB data line; the environmental pressure received by the surface of the 14 coal sample is received by a 15 ultra-low temperature pressure sensor, and is transmitted to a 25 pressure receiving device through a 15-1 low temperature resistant signal transmission line and reaches 23 computer software through a 24USB data line; and when the soaking time is about to end, closing a 35 pressure regulating valve and a 34 self-pressurizing liquid nitrogen tank valve on the 1 self-pressurizing liquid nitrogen tank, stopping the test on a 23 computer, opening a 31-7 ultralow temperature resistant electromagnetic valve through a 29 electromagnetic valve switch to control liquid nitrogen to be discharged from a 31-6 waste liquid outlet to a 31-3 waste liquid cavity, and volatilizing the liquid nitrogen to be discharged from a 31-8 exhaust hole. The 31-2 sound-proof cover covers the whole liquid nitrogen leaching reaction system in the sound-proof cover, so that the influence of external environment noise on the receiving of the internal 14 coal sample cracking sound signal can be reduced, and more stable and accurate data can be obtained.
The experimental device can monitor the generation times and energy of cracks and the generation and expansion positions of cracks in the space of the coal sample in real time in the time change process of the coal sample soaking and melting through the process, so as to obtain the time-space evolution rule of the cracks of the liquid nitrogen immersed coal body, dynamically analyze the effect of the liquid nitrogen cracking coal sample in the soaking and melting process, monitor the environmental pressure condition and the combination strain of the surface of the coal sample and analyze the stress deformation cracking rule of the surface cracks of the coal sample in the liquid nitrogen immersing process through the elastic modulus calculated by the strain.
Compared with the prior art, the invention has the following beneficial effects:
(1) The experimental device for testing the space-time evolution and mechanical parameters of the cracks of the complete liquid nitrogen immersed coal sample is provided.
(2) Liquid nitrogen-like coal with different factors can be prepared in a laboratory, and the low-temperature freeze thawing fracturing anti-reflection effect of the liquid nitrogen of the coal is systematically researched.
(3) The experimental data monitoring of the whole process of immersing the coal sample in the liquid nitrogen can be realized, the microscopic structural change of the coal sample under the action of the liquid nitrogen can be monitored in real time, and the rules and effects of damage, deformation and fracture of the coal body can be dynamically analyzed when the coal sample is subjected to liquid nitrogen fracturing.
(4) And on the basis of the acquisition of elastic wave release times, intensity, energy and waveform in the whole liquid nitrogen leaching and fusion process of the coal sample based on acoustic emission, three-dimensional space positioning is realized.
(5) The six sides of the coal sample can be directly acted by the liquid nitrogen, and compared with the prior art that the bottom surface cannot be directly contacted with the liquid nitrogen, the experimental environment of each side of the coal sample is the same, the fracture influence caused by different side actions is avoided, and the experimental error is reduced.
(6) And combining the surface pressure and the surface shape variable of the coal sample and the poisson ratio to obtain the relationship between the characteristic parameters of liquid nitrogen freezing and thawing, the mechanical parameters and the fracture deformation.
Drawings
Fig. 1 is a diagram showing the overall structure of the present invention.
FIG. 2 is an enlarged view of the waveguide rod and sensor coupling cavity.
FIG. 3 is a diagram of a contact end arrangement of a coal sample surface sensor and a waveguide rod.
FIG. 4 is an enlarged view of the reaction vessel and the coal sample.
Fig. 5 is a top cut-away view of a waveguide rod installation.
In the figure: 1 self-pressurizing liquid nitrogen tank, 2 vacuumizing pump, 3 temperature setting area, 4 deflation knob, 5 sealing door, 6 experiment table, 7 vacuum drying oven, 8 water release switch, 9 water bath cover, 10 temperature display screen, 11 water bath switch, 12 temperature setting button, 13 water bath box main body, 14 coal sample, 15 ultralow temperature pressure sensor, 15-1 low temperature resistant signal transmission line, 16 ultralow temperature strain gauge, 16-1 low temperature resistant signal transmission line, 17 waveguide rod, 17-1 waveguide rod and coal sample contact end, 17-2 waveguide rod and experiment table shell contact end, 18 acoustic emission signal amplifier, 19 manual pressurizing device, 20 vacuum pressurizing saturation device, 21-1 pressure display, 21-2 vacuum display 22 sample tank, 23 computer, 24USB data line, 25 pressure receiving device, 26 acoustic emission processor, 27 acoustic emission receiving line, 27-1 acoustic emission sensor, 28 waveguide rod and sensor coupling cavity, 29 electromagnetic valve switch, 30 strain tester, 31 liquid nitrogen reaction kettle, 31-1 sensor clamping groove, 31-2 sound insulation cover, 31-3 waste liquid cavity, 31-4 base fixing table, 31-5 sample placing table, 31-6 waste liquid outlet, 31-7 ultra-low temperature resistant electromagnetic valve, 31-8 exhaust hole, 31-9 reaction kettle base, 31-10 support frame, 32 ultra-low temperature flowmeter, 33 ultra-low temperature heat preservation pipe, 34 self-pressurizing liquid nitrogen tank valve, 35 pressure regulating valve, 36 pressure gauge and 37 liquid inlet valve
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.
Embodiment one:
referring to fig. 1 and 2, an experimental device for testing the space-time evolution and mechanical parameters of cracks of a liquid nitrogen immersed coal sample comprises a coal sample vacuum drying system, a coal sample water bath constant temperature system, a coal sample water saturation system, a liquid nitrogen injection system, a liquid nitrogen immersion reaction system and a monitoring acquisition processing system.
The liquid nitrogen leaching reaction system comprises a waveguide rod sensor coupling cavity 28, an electromagnetic valve switch 29 and a liquid nitrogen reaction kettle 31, wherein the liquid nitrogen reaction kettle comprises a sensor clamping groove 31-1, a sound insulation cover 31-2, a waste liquid cavity 31-3, a base fixing hole 31-4, a sample placing table 31-5, a waste liquid outlet 31-6, an ultralow temperature resistant electromagnetic valve 31-7, an exhaust hole 31-8, a reaction kettle base 31-9 and a support frame 31-10, the parts are fixedly connected, and the ultralow temperature resistant electromagnetic valve 31-7 controls liquid nitrogen to flow out from the waste liquid outlet 31-6 after experiments; the solenoid valve switch 29 is electrically connected with the ultra-low temperature resistant solenoid valve 31-7.
According to the structure, the waste liquid cavity 31-3 is used for containing liquid nitrogen which is used for soaking the coal sample after the experiment is finished, so that the soaking time is better controlled, and the coal sample is convenient to separate from the liquid nitrogen; the sound insulation cover 31-2 is used for isolating the influence of external sound on experiments; the base fixing holes 31-4 facilitate fixing of the experimental device.
Small holes and ribs are uniformly distributed below the sample placing table 31-5. The direct contact area between the bottom of the sample and the liquid nitrogen is increased, and a hole is formed in the center of the sample so as to facilitate placement of the pressure sensor. The six sides of the coal sample can be directly acted by the liquid nitrogen, and compared with the prior art that the bottom surface cannot be directly contacted with the liquid nitrogen, the experimental environment of each side of the coal sample is the same, the fracture influence caused by different side actions is avoided, and the experimental error is reduced.
The monitoring, collecting and processing system comprises a strain testing subsystem, a pressure monitoring subsystem and an acoustic emission collecting subsystem.
The using process comprises the following steps:
preparing sample coal with different factors by using a coal sample vacuum drying system, a coal sample water bath constant temperature system and a coal sample water saturation system;
according to different leaching time of coal sample: and the liquid nitrogen injection system injects liquid nitrogen into the 31 liquid nitrogen reaction kettle, starts timing when the 14 coal sample is completely immersed, and operates a 29 electromagnetic valve switch to open a 31-7 ultralow temperature resistant electromagnetic valve after the immersion time is reached to control liquid nitrogen from a 31-6 waste liquid outlet to a 31-3 waste liquid cavity, so that the immersion time of the 14 coal sample is controlled.
The monitoring, collecting and processing system monitors the generation times and energy of cracks in real time in the time change process of the coal sample soaking and the generation and expansion positions of cracks in the coal sample space to obtain the time-space evolution rule of cracks of the liquid nitrogen soaking coal body, dynamically analyzes the effect of the liquid nitrogen cracking coal sample in the soaking and melting process, and simultaneously monitors the environmental pressure condition and the strain of the surface of the coal sample and analyzes the stress deformation and cracking rule of cracks of the surface of the coal sample in the liquid nitrogen soaking process through the elastic modulus calculated by the strain.
Embodiment two:
referring to fig. 1-5, an experimental device for testing the space-time evolution and mechanical parameters of cracks of a liquid nitrogen immersed coal sample comprises a coal sample vacuum drying system, a coal sample water bath constant temperature system, a coal sample water saturation system, a liquid nitrogen injection system, a liquid nitrogen immersion reaction system and a monitoring acquisition processing system.
The liquid nitrogen leaching reaction system comprises a waveguide rod sensor coupling cavity 28, an electromagnetic valve switch 29 and a liquid nitrogen reaction kettle 31, wherein the liquid nitrogen reaction kettle comprises a sensor clamping groove 31-1, a sound insulation cover 31-2, a waste liquid cavity 31-3, a base fixing hole 31-4, a sample placing table 31-5, a waste liquid outlet 31-6, an ultralow temperature resistant electromagnetic valve 31-7, an exhaust hole 31-8, a reaction kettle base 31-9 and a support frame 31-10, the parts are fixedly connected, and the ultralow temperature resistant electromagnetic valve 31-7 controls liquid nitrogen to flow out from the waste liquid outlet 31-6 after experiments; the solenoid valve switch 29 is electrically connected with the ultra-low temperature resistant solenoid valve 31-7.
According to the structure, the waste liquid cavity 31-3 is used for containing liquid nitrogen which is used for soaking the coal sample after the experiment is finished, so that the soaking time is better controlled, and the coal sample is convenient to separate from the liquid nitrogen; the sound insulation cover 31-2 is used for isolating the influence of external sound on experiments; the base fixing holes 31-4 facilitate fixing of the experimental device.
Small holes and ribs are uniformly distributed below the sample placing table 31-5. The direct contact area between the bottom of the sample and the liquid nitrogen is increased, and a hole is formed in the center of the sample so as to facilitate placement of the pressure sensor. The six sides of the coal sample can be directly acted by the liquid nitrogen, and compared with the prior art that the bottom surface cannot be directly contacted with the liquid nitrogen, the experimental environment of each side of the coal sample is the same, the fracture influence caused by different side actions is avoided, and the experimental error is reduced.
The monitoring, collecting and processing system comprises a strain testing subsystem, a pressure monitoring subsystem and an acoustic emission collecting subsystem.
Further, the sample coal vacuum drying system comprises a vacuum drying box 7, a sealing door 5, a vacuumizing pump 2, a temperature setting area 3 and a gas release knob 4. According to the structure, when the vacuum drying device is operated, the sealing door 5 is opened to put the coal sample 14 into the vacuum drying box 7, the sealing ring is arranged in the sealing door 5, the air release knob 4 is rotated to be in a closed state, the vacuum drying box 7 is subjected to vacuum treatment through the vacuumizing pump 2, and the temperature required by vacuum drying is set by using the keys of the temperature setting area 3; the drying time is determined according to the experimental requirement; the vacuum drying oven 7 is arranged above the laboratory experiment table 6; after the coal sample is dried, the air release knob 4 is rotated slowly to be in a semi-open state for air release for a period of time and then is completely opened, so that the damage to an instrument caused by overlarge pressure difference is avoided.
Further, the coal sample water bath constant temperature system comprises a water bath box main body 13, a water bath sealing cover 9, a water discharging switch 8, a temperature display screen 10, a water bath switch 11 and a temperature setting button 12. As can be seen from the above structure, when operating, firstly, a proper amount of water is added into the water bath tank, and the water bath tank is opened by the temperature setting button 12; the temperature display screen 10 displays the water bath temperature in real time; the temperature setting button 12 is used for setting the required temperature, and the temperature range is room temperature to 100 ℃; then covering a water bath sealing cover 9; the constant-temperature water bath is finished, and the wastewater is discharged through a water discharge switch 8; different heating chambers of the water bath box can be provided with different temperatures.
Further, the coal sample saturation system comprises a sample tank 22, a pressurizing device 19, a vacuum pressurizing and saturating device 20, a pressure display 21-1 and a vacuum display 21-2. According to the structure, during operation, the coal sample 14 is placed 22 in the sample tank, the tank is sealed again, and the vacuum display of the vacuumized 21-2 is stopped by a required value; the pressurization by 19 manual pressurization devices is carried out until the pressure of 21-1 shows the required pressure, and the pressure is ensured to be constant in the water retention process.
Further, the liquid nitrogen injection system comprises a self-pressurization liquid nitrogen tank 1, an ultralow temperature flowmeter 32, an ultralow temperature heat preservation pipe 33, a self-pressurization liquid nitrogen tank valve 34, a pressure regulating valve 35, a pressure gauge 36 and a liquid inlet valve 37. According to the structure, during operation, liquid nitrogen is injected into the customized reaction kettle from the self-pressurizing liquid nitrogen tank 1; the ultra-low temperature flowmeter 32 can monitor the flow rate of the liquid nitrogen conveyed into the reaction kettle in real time; 34, controlling a liquid nitrogen conveying switch by a self-pressurizing liquid nitrogen tank valve; the 35-regulator valve controls the pressure at which liquid nitrogen is injected.
Further, the heat-insulating materials are externally attached to each part of the reaction kettle 31. Avoiding volatilization of liquid nitrogen during transportation.
The using process comprises the following steps:
firstly, preparing coal samples with different factors:
single-factor preparation of completely dried coal samples: opening a 5 sealing door of a vacuum drying box to put a 14 coal sample into a 7 vacuum drying box, tightly closing the sealing door, then rotating a 4 air release knob to a closed state, opening a 2 vacuumizing pump to vacuumize the inside, then closing the 2 vacuumizing pump, setting the required temperature for drying through a 3 temperature setting area, rotating the 4 air release knob slowly after the drying time is finished to be in a semi-open state to release air for a period of time, then completely opening the air release knob, taking out the coal sample, putting the coal sample into a sample bag for sealing for standby, and if the humidity of the coal sample is overlarge, distributing water drops on the 5 sealing door in the drying process, opening a towel for the vacuum drying box to wipe the internal water drops, and then drying.
Single factor initial temperature coal sample preparation: taking out the completely dried coal sample, at this time, carrying out water-proof treatment on the 14 coal sample at room temperature, opening a 9 water bath sealing cover to put the coal sample in, closing an 8 water discharge switch, adding a proper amount of water to submerge the 4 coal sample, opening an 11 water bath switch 10 temperature display screen to display real-time water bath temperature and set temperature, using a 12 temperature setting button to set the required sample temperature, covering the 9 water bath sealing cover, and discharging the wastewater through the 8 water discharge switch after the constant-temperature water bath is finished.
And (3) preparing a single-factor fully saturated water coal sample: opening a 22 sample tank to put a 14 coal sample into a rotary 22 sample tank, sealing the upper end of the 22 sample tank, opening a 2 vacuumizing pump of a coal sample water saturation system to vacuumize the 22 sample tank, displaying at 21-2 vacuum, rotating a 19 manual pressurizing device to pressurize the 22 sample tank until 21-1 pressure is displayed until the pressure is required, ensuring constant pressure in the water retention process, opening the 22 sample tank to take out the coal sample after water retention is finished, and placing the coal sample in a water-filled vessel for standby.
Preparing coal samples with different water contents: opening a 5 sealing door of a vacuum drying box to put a 14 coal sample into a 7 vacuum drying box, tightly closing the sealing door, rotating a 4 air release knob to a closed state, opening a 2 vacuumizing pump to vacuumize the inside, closing the 2 vacuumizing pump, setting a drying temperature through a 3 temperature setting area, slowly rotating the 4 air release knob to a semi-open state after the drying time is finished, deflating for a period of time, fully opening, taking out the 14 coal sample, weighing on an electronic scale, recording as m0, opening a 22 sample tank to put the 14 coal sample into the upper end of the 22 sample tank for sealing, filling the 2 vacuumizing pump of a water saturation system of the 22 sample tank, vacuumizing in the 22 sample tank for 21-2 vacuum display, rotating a 19 manual pressurizing device to pressurize the 22 sample tank until 21-1 pressure displays the pressure, ensuring that the pressure is constant in the water retention process, opening the 22 sample tank to take out the 14 coal sample, weighing again with a wet towel, recording as m, and measuring the water content
Figure GDA0003105076940000141
The calculated water content is the maximum water content of the 14 coal samples, then the 14 coal samples are put into a 7 vacuum drying oven for drying for different time and weighing to obtain mn, and the different water contents are calculated to obtain +.>
Figure GDA0003105076940000142
Preparing water-containing coal samples at different prefabrication temperatures: opening a 5 sealing door of a vacuum drying box to put a 14 coal sample into a 7 vacuum drying box, tightly closing the sealing door, then rotating a 4 air release knob to a closed state, opening a 2 vacuumizing pump to vacuumize the inside, then closing the 2 vacuumizing pump, setting a drying temperature through a 3 temperature setting area, after the drying time is over, rotating the 4 air release knob to slowly rotate to a semi-open state to release air for a period of time, then completely opening the vacuum drying box, taking out the 14 coal sample, weighing the 14 coal sample on an electronic scale, recording as m0, opening a 22 sample tank to put the 14 coal sample into the upper end of the rotary 22 sample tank for sealing, opening a 2 vacuumizing pump of a coal sample saturation system to vacuumize the 22 sample tank until the pressure of 21-2 is required, rotating a 19 manual pressurizing device to pressurize the 22 sample tank until the pressure of 21-1 is required for displaying, ensuring the pressure in a water retention process to be constant, opening the 22 sample tank to take out the 14 coal sample, using a towel to wet the surface water bead of the 14 coal sample, then putting the 14 coal sample into the 7 vacuum drying box for drying for different time, weighing to obtain an mn, calculating the water content, using a bathroom film to put the 14 coal sample into a water bath cover, completely sealing the 14 water bath 10, and then placing the 14 water bath cover to be completely at least 9, and setting a water bath cover for sealing the 14 water bath 10 for a water bath, and sealing the water bath cover for at least 9 h, setting the temperature water bath cover for at least, and sealing the water bath cover for setting the temperature for at least 9, and sealing the water bath cover for setting the temperature.
Different leaching times of coal samples: and the liquid nitrogen injection system injects liquid nitrogen into the 31 liquid nitrogen reaction kettle, starts timing when the 14 coal sample is completely immersed, and operates a 29 electromagnetic valve switch to open a 31-7 ultralow temperature resistant electromagnetic valve after the immersion time is reached to control liquid nitrogen from a 31-6 waste liquid outlet to a 31-3 waste liquid cavity, so that the immersion time of the 14 coal sample is controlled.
The monitoring, collecting and processing system monitors the generation times and energy of cracks in real time in the time change process of the coal sample soaking and the generation and expansion positions of cracks in the coal sample space to obtain the time-space evolution rule of cracks of the liquid nitrogen soaking coal body, dynamically analyzes the effect of the liquid nitrogen cracking coal sample in the soaking and melting process, and simultaneously monitors the environmental pressure condition and the strain of the surface of the coal sample and analyzes the stress deformation and cracking rule of cracks of the surface of the coal sample in the liquid nitrogen soaking process through the elastic modulus calculated by the strain.
Embodiment III:
referring to fig. 1-5, an experimental device for testing the space-time evolution and mechanical parameters of cracks of a liquid nitrogen immersed coal sample comprises a coal sample vacuum drying system, a coal sample water bath constant temperature system, a coal sample water saturation system, a liquid nitrogen injection system, a liquid nitrogen immersion reaction system and a monitoring acquisition processing system.
The liquid nitrogen leaching reaction system comprises a waveguide rod sensor coupling cavity 28, an electromagnetic valve switch 29 and a liquid nitrogen reaction kettle 31, wherein the liquid nitrogen reaction kettle comprises a sensor clamping groove 31-1, a sound insulation cover 31-2, a waste liquid cavity 31-3, a base fixing hole 31-4, a sample placing table 31-5, a waste liquid outlet 31-6, an ultralow temperature resistant electromagnetic valve 31-7, an exhaust hole 31-8, a reaction kettle base 31-9 and a support frame 31-10, the parts are fixedly connected, and the ultralow temperature resistant electromagnetic valve 31-7 controls liquid nitrogen to flow out from the waste liquid outlet 31-6 after experiments; the solenoid valve switch 29 is electrically connected with the ultra-low temperature resistant solenoid valve 31-7.
According to the structure, the waste liquid cavity 31-3 is used for containing liquid nitrogen which is used for soaking the coal sample after the experiment is finished, so that the soaking time is better controlled, and the coal sample is convenient to separate from the liquid nitrogen; the sound insulation cover 31-2 is used for isolating the influence of external sound on experiments; the base fixing holes 31-4 facilitate fixing of the experimental device.
Small holes and ribs are uniformly distributed below the sample placing table 31-5. The direct contact area between the bottom of the sample and the liquid nitrogen is increased, and a hole is formed in the center of the sample so as to facilitate placement of the pressure sensor. The six sides of the coal sample can be directly acted by the liquid nitrogen, and compared with the prior art that the bottom surface cannot be directly contacted with the liquid nitrogen, the experimental environment of each side of the coal sample is the same, the fracture influence caused by different side actions is avoided, and the experimental error is reduced.
The monitoring, collecting and processing system comprises a strain testing subsystem, a pressure monitoring subsystem and an acoustic emission collecting subsystem.
Further, the sample coal vacuum drying system comprises a vacuum drying box 7, a sealing door 5, a vacuumizing pump 2, a temperature setting area 3 and a gas release knob 4. According to the structure, when the vacuum drying device is operated, the sealing door 5 is opened to put the coal sample 14 into the vacuum drying box 7, the sealing ring is arranged in the sealing door 5, the air release knob 4 is rotated to be in a closed state, the vacuum drying box 7 is subjected to vacuum treatment through the vacuumizing pump 2, and the temperature required by vacuum drying is set by using the keys of the temperature setting area 3; the drying time is determined according to the experimental requirement; the vacuum drying oven 7 is arranged above the laboratory experiment table 6; after the coal sample is dried, the air release knob 4 is rotated slowly to be in a semi-open state for air release for a period of time and then is completely opened, so that the damage to an instrument caused by overlarge pressure difference is avoided.
Further, the coal sample water bath constant temperature system comprises a water bath box main body 13, a water bath sealing cover 9, a water discharging switch 8, a temperature display screen 10, a water bath switch 11 and a temperature setting button 12. As can be seen from the above structure, when operating, firstly, a proper amount of water is added into the water bath tank, and the water bath tank is opened by the temperature setting button 12; the temperature display screen 10 displays the water bath temperature in real time; the temperature setting button 12 is used for setting the required temperature, and the temperature range is room temperature to 100 ℃; then covering a water bath sealing cover 9; the constant-temperature water bath is finished, and the wastewater is discharged through a water discharge switch 8; different heating chambers of the water bath box can be provided with different temperatures.
Further, the coal sample saturation system comprises a sample tank 22, a pressurizing device 19, a vacuum pressurizing and saturating device 20, a pressure display 21-1 and a vacuum display 21-2. According to the structure, during operation, the coal sample 14 is placed 22 in the sample tank, the tank is sealed again, and the vacuum display of the vacuumized 21-2 is stopped by a required value; the pressurization by 19 manual pressurization devices is carried out until the pressure of 21-1 shows the required pressure, and the pressure is ensured to be constant in the water retention process.
Further, the liquid nitrogen injection system comprises a self-pressurization liquid nitrogen tank 1, an ultralow temperature flowmeter 32, an ultralow temperature heat preservation pipe 33, a self-pressurization liquid nitrogen tank valve 34, a pressure regulating valve 35, a pressure gauge 36 and a liquid inlet valve 37. According to the structure, during operation, liquid nitrogen is injected into the customized reaction kettle from the self-pressurizing liquid nitrogen tank 1; the ultra-low temperature flowmeter 32 can monitor the flow rate of the liquid nitrogen conveyed into the reaction kettle in real time; 34, controlling a liquid nitrogen conveying switch by a self-pressurizing liquid nitrogen tank valve; the 35-regulator valve controls the pressure at which liquid nitrogen is injected.
Further, the heat-insulating materials are externally attached to each part of the reaction kettle 31. Avoiding volatilization of liquid nitrogen during transportation.
Further, the strain testing subsystem comprises an ultralow temperature strain gauge 16, a low temperature resistant signal transmission line 16-1, a USB data line 24, a computer 23 and a strain tester 30. The ultralow temperature strain gauge 16 is attached to the surface of the coal sample 14, and the signal transmission line is made of a low temperature resistant material, so that failure caused by ultralow temperature is avoided.
Further, the number of ultralow temperature strain gauges is 3, and the ultralow temperature strain gauges are distributed on the vertical, horizontal and oblique directions of the surface of the coal sample. According to the structure, the vertical, horizontal and oblique distribution can completely measure the stress performance of the coal sample in all directions in the mechanical change process.
Further, the pressure monitoring subsystem comprises an ultralow temperature pressure sensor 15, a low temperature resistant signal transmission line 15-1, a pressure receiving device 25, a data line 24 and a computer 23.
Further, the acoustic emission acquisition subsystem comprises a waveguide rod 17, an acoustic emission signal amplifier 18, an acoustic emission processor 26, an acoustic emission receiving line 27, an acoustic emission sensor 27-1, a waveguide rod sensor coupling cavity 28 and a computer 23.
In the above structure, the ultra-low temperature pressure sensor 15, the ultra-low temperature strain gauge 16, the waveguide rod 17 and the coal sample 14 need to be bonded; the acoustic emission sensor 27-1 needs to be smeared with a couplant at the butt joint interface of the waveguide rod and the contact end 17-2 of the experiment table shell, and the coupling is completed between the waveguide rod and the sensor coupling cavity 28; six waveguide rods of the waveguide rods 17 are welded on the reaction kettle corresponding to the contact ends 17-1 of the coal sample and the setting positions of the computer, and are used for releasing conduction signals to the acoustic emission sensor when the coal sample is immersed and fused by liquid nitrogen, one end of the waveguide rods is clung to the sensor, and the interface of the waveguide rods is required to be coupled with the coupling agent; the positions of the wave guide rods on each surface are collinear with the position of the contact end 17-1 of the coal sample, and all the connecting lines are not coplanar with each other, so that the acoustic emission energy of the coal sample can be obtained, the ringing count can be carried out, and meanwhile, the acoustic emission event generated by the raw coal in the liquid nitrogen immersing process can be positioned in real time in three-dimensional space; the low temperature resistant signal transmission line 15-1 and the low temperature resistant signal transmission line 16-1 are FEP wires, and the coating material is made of low temperature resistant materials.
The using process comprises the following steps:
firstly, preparing coal samples with different factors:
single-factor preparation of completely dried coal samples: opening a 5 sealing door of a vacuum drying box to put a 14 coal sample into a 7 vacuum drying box, tightly closing the sealing door, then rotating a 4 air release knob to a closed state, opening a 2 vacuumizing pump to vacuumize the inside, then closing the 2 vacuumizing pump, setting the required temperature for drying through a 3 temperature setting area, rotating the 4 air release knob slowly after the drying time is finished to be in a semi-open state to release air for a period of time, then completely opening the air release knob, taking out the coal sample, putting the coal sample into a sample bag for sealing for standby, and if the humidity of the coal sample is overlarge, distributing water drops on the 5 sealing door in the drying process, opening a towel for the vacuum drying box to wipe the internal water drops, and then drying.
Single factor initial temperature coal sample preparation: taking out the completely dried coal sample, at this time, carrying out water-proof treatment on the 14 coal sample at room temperature, opening a 9 water bath sealing cover to put the coal sample in, closing an 8 water discharge switch, adding a proper amount of water to submerge the 4 coal sample, opening an 11 water bath switch 10 temperature display screen to display real-time water bath temperature and set temperature, using a 12 temperature setting button to set the required sample temperature, covering the 9 water bath sealing cover, and discharging the wastewater through the 8 water discharge switch after the constant-temperature water bath is finished.
And (3) preparing a single-factor fully saturated water coal sample: opening a 22 sample tank to put a 14 coal sample into a rotary 22 sample tank, sealing the upper end of the 22 sample tank, opening a 2 vacuumizing pump of a coal sample water saturation system to vacuumize the 22 sample tank, displaying at 21-2 vacuum, rotating a 19 manual pressurizing device to pressurize the 22 sample tank until 21-1 pressure is displayed until the pressure is required, ensuring constant pressure in the water retention process, opening the 22 sample tank to take out the coal sample after water retention is finished, and placing the coal sample in a water-filled vessel for standby.
Preparing coal samples with different water contents: opening a 5 sealing door of a vacuum drying box to put a 14 coal sample into a 7 vacuum drying box, tightly closing the sealing door, rotating a 4 air release knob to a closed state, opening a 2 vacuumizing pump to vacuumize the inside, closing the 2 vacuumizing pump, setting a drying temperature through a 3 temperature setting area, slowly rotating the 4 air release knob to a semi-open state after the drying time is finished, deflating for a period of time, fully opening, taking out the 14 coal sample, weighing on an electronic scale, recording as m0, opening a 22 sample tank to put the 14 coal sample into the upper end of the 22 sample tank for sealing, filling the 2 vacuumizing pump of a water saturation system of the 22 sample tank, vacuumizing in the 22 sample tank for 21-2 vacuum display, rotating a 19 manual pressurizing device to pressurize the 22 sample tank until 21-1 pressure displays the pressure, ensuring that the pressure is constant in the water retention process, opening the 22 sample tank to take out the 14 coal sample, weighing again with a wet towel, recording as m, and measuring the water content
Figure GDA0003105076940000191
The calculated water content is the maximum water content of the 14 coal samples, then the 14 coal samples are put into a 7 vacuum drying oven for drying for different time and weighing to obtain mn, and the different water contents are calculated to obtain +.>
Figure GDA0003105076940000192
Preparing water-containing coal samples at different prefabrication temperatures: opening a 5 sealing door of a vacuum drying box to put a 14 coal sample into a 7 vacuum drying box, tightly closing the sealing door, then rotating a 4 air release knob to a closed state, opening a 2 vacuumizing pump to vacuumize the inside, then closing the 2 vacuumizing pump, setting a drying temperature through a 3 temperature setting area, after the drying time is over, rotating the 4 air release knob to slowly rotate to a semi-open state to release air for a period of time, then completely opening the vacuum drying box, taking out the 14 coal sample, weighing the 14 coal sample on an electronic scale, recording as m0, opening a 22 sample tank to put the 14 coal sample into the upper end of the rotary 22 sample tank for sealing, opening a 2 vacuumizing pump of a coal sample saturation system to vacuumize the 22 sample tank until the pressure of 21-2 is required, rotating a 19 manual pressurizing device to pressurize the 22 sample tank until the pressure of 21-1 is required for displaying, ensuring the pressure in a water retention process to be constant, opening the 22 sample tank to take out the 14 coal sample, using a towel to wet the surface water bead of the 14 coal sample, then putting the 14 coal sample into the 7 vacuum drying box for drying for different time, weighing to obtain an mn, calculating the water content, using a bathroom film to put the 14 coal sample into a water bath cover, completely sealing the 14 water bath 10, and then placing the 14 water bath cover to be completely at least 9, and setting a water bath cover for sealing the 14 water bath 10 for a water bath, and sealing the water bath cover for at least 9 h, setting the temperature water bath cover for at least, and sealing the water bath cover for setting the temperature for at least 9, and sealing the water bath cover for setting the temperature.
Different leaching times of coal samples: and the liquid nitrogen injection system injects liquid nitrogen into the 31 liquid nitrogen reaction kettle, starts timing when the 14 coal sample is completely immersed, and operates a 29 electromagnetic valve switch to open a 31-7 ultralow temperature resistant electromagnetic valve after the immersion time is reached to control liquid nitrogen from a 31-6 waste liquid outlet to a 31-3 waste liquid cavity, so that the immersion time of the 14 coal sample is controlled.
Again, the test data were tested:
the method comprises the steps of attaching a 15 ultralow temperature pressure sensor and a 16 ultralow temperature strain gauge to the surface of a prepared 14 coal sample by using ultralow temperature resistant resin glue as shown in a graph 3, connecting one end of the 15-1 ultralow temperature resistant signal transmission line and the 16-1 ultralow temperature resistant signal transmission line, opening the 15-1 ultralow temperature resistant signal transmission line by a 23 computer, opening the 23 computer, a 26 acoustic emission processor, a 30 strain tester and a 25 pressure receiving device, simultaneously opening the pressure monitoring software and the strain monitoring software, closing a 31-7 ultralow temperature resistant electromagnetic valve by a 29 electromagnetic valve switch, closing a 37 liquid nitrogen inlet valve on a 1 self-pressurizing liquid nitrogen tank, opening a 34 self-pressurizing liquid nitrogen tank valve, regulating the pressure regulating valve by a 35 valve, and injecting the 27-1 acoustic emission sensor surface coating coupling agent into a 28 wave guide rod and a sensor coupling cavity according to the corresponding position, opening 23 computer, 26 acoustic emission processor, 30 strain tester and 25 pressure receiving device, opening the 31-7 ultralow temperature resistant electromagnetic valve, closing a 37 liquid nitrogen inlet valve on the 1 self-pressurizing liquid nitrogen tank, opening the 34 self-pressurizing liquid nitrogen valve, and regulating the 35 valve, and quickly injecting the 17-1 acoustic emission sensor surface coating coupling agent into the 27 acoustic emission sensor surface coupling agent into the 28 wave guide rod and the sensor coupling cavity, opening 23 computer, closing the 23 computer, the 26 acoustic emission processor, the 30 strain tester and the pressure meter, closing the 25 pressure meter, closing the pressure meter, and the 25 pressure liquid nitrogen inlet sensor, closing the pressure meter, and the 37 liquid nitrogen inlet valve and the pressure sensor valve, and the 37 liquid nitrogen inlet valve and the pressure valve, and the 37 liquid valve and the pressure valve Processing the position to generate data in 23 computer software; the strain generated by the surface skeleton of the 14 coal sample is received by a 16 ultralow temperature strain gauge, transmitted to a 30 strain tester for pretreatment through a 16-1 low temperature resistant signal transmission line, and transmitted to 23 computer software through a 24USB data line; the environmental pressure received by the surface of the 14 coal sample is received by a 15 ultra-low temperature pressure sensor, and is transmitted to a 25 pressure receiving device through a 15-1 low temperature resistant signal transmission line and reaches 23 computer software through a 24USB data line; and when the soaking time is about to end, closing a 35 pressure regulating valve and a 34 self-pressurizing liquid nitrogen tank valve on the 1 self-pressurizing liquid nitrogen tank, stopping the test on a 23 computer, opening a 31-7 ultralow temperature resistant electromagnetic valve through a 29 electromagnetic valve switch to control liquid nitrogen to be discharged from a 31-6 waste liquid outlet to a 31-3 waste liquid cavity, and volatilizing the liquid nitrogen to be discharged from a 31-8 exhaust hole. The 31-2 sound-proof cover covers the whole liquid nitrogen leaching reaction system in the sound-proof cover, so that the influence of external environment noise on the receiving of the internal 14 coal sample cracking sound signal can be reduced, and more stable and accurate data can be obtained.
The experimental device can monitor the generation times and energy of cracks and the generation and expansion positions of cracks in the space of the coal sample in real time in the time change process of the coal sample soaking and melting through the process, so as to obtain the time-space evolution rule of the cracks of the liquid nitrogen immersed coal body, dynamically analyze the effect of the liquid nitrogen cracking coal sample in the soaking and melting process, monitor the environmental pressure condition and the combination strain of the surface of the coal sample and analyze the stress deformation cracking rule of the surface cracks of the coal sample in the liquid nitrogen immersing process through the elastic modulus calculated by the strain.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.

Claims (7)

1. The utility model provides a liquid nitrogen submergence coal sample crackle space-time evolution and mechanical parameter test experimental apparatus which characterized in that: the device comprises a coal sample vacuum drying system, a coal sample water bath constant temperature system, a coal sample water saturation system, a liquid nitrogen injection system, a liquid nitrogen leaching reaction system and a monitoring acquisition processing system;
the liquid nitrogen leaching reaction system comprises a waveguide rod sensor coupling cavity and a liquid nitrogen reaction kettle, wherein the liquid nitrogen reaction kettle comprises a sensor clamping groove, a sound insulation cover, a waste liquid cavity, a waste liquid outlet, a sample placing table, an electromagnetic valve, an exhaust hole, a reaction kettle base and a supporting frame, all the parts are fixedly connected, and small uniformly distributed holes and ribs are arranged below the sample placing table;
The monitoring acquisition processing system comprises a strain testing subsystem, a pressure monitoring subsystem and an acoustic emission acquisition subsystem;
the acoustic emission acquisition subsystem comprises a waveguide rod, an acoustic emission signal amplifier, an acoustic emission processor, an acoustic emission receiving line, an acoustic emission sensor, a waveguide rod sensor coupling cavity and a computer;
one end of the waveguide rod is a contact end of the waveguide rod with the coal sample, the other end of the waveguide rod is a contact end of the waveguide rod with the experiment table shell, the contact end of the waveguide rod with the coal sample is tightly attached to the coal sample, a groove is arranged at the contact end of the waveguide rod with the experiment table shell, one end, matched with the contact end of the experiment table shell, of the acoustic emission sensor, the waveguide rod and the contact end of the experiment table shell can be inserted into the groove to form a butt joint interface, and a coupling agent is smeared at the butt joint interface;
the number of the waveguide rods is six, the six waveguide rods are arranged on three mutually perpendicular surfaces of the coal sample in a pairwise manner, connecting lines are formed between the waveguide rods of the two waveguide rods arranged on the same surface and the contact end of the coal sample, and the three connecting lines are not coplanar with each other;
the strain testing subsystem comprises an ultralow temperature strain gauge, a low temperature resistant signal transmission line, a USB data line, a computer and a strain tester; the number of the ultralow temperature strain gages is 3, the ultralow temperature strain gages are distributed on the vertical, horizontal and oblique directions of the surface of the coal sample, the 3 ultralow temperature strain gages are arranged on the same surface of the coal sample and form an ultralow temperature strain gage setting surface, and the ultralow temperature strain gage setting surface is a surface of the non-connecting waveguide rod on the coal sample and a contact end surface of the coal sample.
2. The experimental device for testing the space-time evolution and mechanical parameters of the crack of the liquid nitrogen immersed coal sample according to claim 1, which is characterized in that: the coal sample vacuum drying system comprises a vacuum drying box, a sealing door, a vacuumizing pump, a temperature setting area and a gas release knob.
3. The experimental device for testing the space-time evolution and mechanical parameters of the crack of the liquid nitrogen immersed coal sample according to claim 1, which is characterized in that: the coal sample water bath constant temperature system comprises a water bath box main body, a water bath sealing cover, a water discharging switch, a temperature display screen, a water bath switch and a temperature setting button.
4. The experimental device for testing the space-time evolution and mechanical parameters of the crack of the liquid nitrogen immersed coal sample according to claim 1, which is characterized in that: the coal sample saturation system comprises a sample tank, a pressurizing device, a vacuum pressurizing saturation device, a pressure display and a vacuum display.
5. The experimental device for testing the space-time evolution and mechanical parameters of the crack of the liquid nitrogen immersed coal sample according to claim 1, which is characterized in that: the liquid nitrogen injection system comprises a self-pressurization liquid nitrogen tank, an ultralow temperature flowmeter, an ultralow temperature heat preservation pipe, a self-pressurization liquid nitrogen tank valve, a pressure regulating valve, a pressure gauge and a liquid inlet valve.
6. The experimental device for testing the space-time evolution and mechanical parameters of the crack of the liquid nitrogen immersed coal sample according to claim 1, which is characterized in that: and heat preservation and insulation materials are externally adhered to each part of the reaction kettle.
7. The experimental device for testing the space-time evolution and mechanical parameters of the crack of the liquid nitrogen immersed coal sample according to claim 1, which is characterized in that: the pressure monitoring subsystem consists of an ultralow temperature pressure sensor, a low temperature resistant signal transmission line, a pressure receiving device, a data line and a computer.
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