A vibration assembly of a coal rock permeability testing device

Abstract

The utility model discloses a kind of coal rock permeability testing device's vibration assembly, specifically related to coalbed gas seepage characteristic test technical field.Coal rock permeability testing device's vibration assembly includes: modal exciter, it is used to generate vibration;Connecting pipe, it is cylindrical member, is suspended and fixed below the upper telescopic rod by connecting piece, and the connecting pipe and the modal exciter are not directly contacted physically;Jacks, it is slidably arranged in the inner hole of the connecting pipe, for transmitting vibration to coal rock core sample;The top end of the jacks is fixedly arranged with limit plate;Annular groove is opened on the inner wall of the connecting pipe, and the limit plate is contained in the first annular groove and can slide up and down along it.The utility model provides coal rock permeability testing device's vibration assembly, to solve the problem that existing tester cannot simulate mining disturbance, cannot study the influence of vibration on coal rock gas seepage characteristic.

Description

Technical Field

[0001] This utility model relates to the field of coal seam gas seepage characteristic testing technology, and in particular to a vibration component of a coal and rock permeability testing device. Background Technology

[0002] Coal core permeability is a key parameter for assessing coal seam gas extraction efficiency and predicting coal and gas outburst risk. In the laboratory, researchers typically use a coal core permeability analyzer to simulate the stress state of underground coal seams by applying axial and circumferential stresses (confining pressure) to coal samples, thereby measuring their gas seepage characteristics.

[0003] Existing testing instruments are relatively mature in simulating and controlling static stress fields. However, the real environment underground in coal mines is far from static. During mining operations, the continuous vibrations generated by drilling rigs, coal mining machines, and other equipment significantly disturb the surrounding coal seam. Practice shows that this vibration alters the internal fracture structure of the coal seam, directly affecting the desorption and flow behavior of gas. Therefore, to obtain permeability data in the laboratory that truly reflects field conditions, it is necessary to introduce controllable vibration loads on top of applying static stress.

[0004] Currently, traditional permeability testers lack dedicated vibration loading structures. Simply installing a vibration source on the outer casing results in significant absorption and dissipation of vibration energy during transmission, failing to effectively and controllably transfer it to the coal core specimen, leading to distorted experimental data. Designing a vibration assembly that can efficiently and directly apply vibration energy to the coal sample without interfering with the accuracy of existing axial and confining pressure loading, and that can be easily integrated with existing testers, has become a pressing technical challenge in this field. Utility Model Content

[0005] In order to overcome the shortcomings of the existing technology, this utility model provides a vibration component of a coal and rock permeability testing device to solve the problem that existing testing instruments cannot simulate mining disturbances and cannot study the impact of vibration on the seepage characteristics of coal and rock gas.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0007] The vibration component of the coal permeability testing device, located between the upper telescopic rod and the mounting cylinder of the testing instrument, includes: a modal exciter for generating vibration; a connecting pipe, which is a cylindrical component, suspended and fixed below the upper telescopic rod by a connector, and the connecting pipe and the modal exciter are not in direct physical contact; a top rod, which is slidably disposed in the inner hole of the connecting pipe for transmitting vibration to the coal core sample; a limiting plate is fixedly disposed at the top end of the top rod; a first annular groove is circumferentially formed on the inner wall of the connecting pipe, the limiting plate is accommodated in the first annular groove and can slide up and down along it; the telescopic rod of the modal exciter can extend downward and strike the limiting plate.

[0008] Preferably, the modal exciter is an electromagnetic exciter with a frequency control range of 10Hz to 5000Hz and a maximum excitation force of not less than 500N.

[0009] Preferably, the connector includes: one set of connecting rods fixed near the lower end of the upper telescopic rod; another set of connecting rods fixed near the upper end of the connecting pipe, the axes of the two sets of connecting rods being corresponding and the external threads being rotated in opposite directions; and a threaded sleeve, the inner hole of which is provided with reverse threads matching the two sets of connecting rods, and the upper telescopic rod and the connecting pipe are connected and fixed by screwing the threaded sleeve into it.

[0010] Preferably, it further includes an anti-loosening structure, which includes: a second annular groove opened on the outer wall of the threaded sleeve; an annular retaining spring, the two sides of which are punched inward to form multiple retaining holes, the retaining spring being able to be engaged into the second annular groove of the multiple threaded sleeves, so that the retaining holes are in close contact with the outer wall of the threaded sleeve outside the groove bottom.

[0011] Preferably, the retaining ring is made of 60Si2Mn spring steel.

[0012] Preferably, the inner surface of the bayonet is knurled or has a fluororubber layer bonded to it.

[0013] Preferably, both ends of the retaining ring have extension sections, and each extension section has a through hole. After installation, a metal wire or fatigue-resistant cable tie is passed through the two through holes and pulled tight to fix the ring.

[0014] Preferably, the vibration assembly further includes a vibration excitation control unit and a data acquisition unit. The vibration excitation control unit is electrically connected to the modal exciter and is used to drive it to generate vibrations with specific frequencies, amplitudes, and waveforms. The data acquisition unit is used to synchronously acquire vibration parameters, stress, and seepage data.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) By designing the vibration component as an independent module, this utility model can be easily integrated into the existing standard testing instrument, upgrading it into an advanced device capable of conducting stress-vibration-seepage multi-field coupling experiments, effectively simulating the downhole mining disturbance environment.

[0017] (2) Through the structural design of the connecting pipe suspension and fixing, the sliding cooperation between the top rod and the limiting plate, and the first annular groove, this utility model realizes that static axial compression loading and dynamic vibration excitation do not interfere with each other, which not only ensures the accuracy of static stress loading, but also ensures that vibration energy can be efficiently and directly transmitted to the coal core sample.

[0018] (3) This utility model adopts unique connectors and anti-loosening structure to ensure the firmness of the connection between the vibration component and the main body of the tester, effectively overcome the problem of loose connection that may be caused by long-term vibration, and improve the reliability of the equipment and the accuracy of experimental data. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of this utility model when installed on a traditional testing instrument;

[0020] Figure 2 This is a schematic diagram of the structure of this utility model;

[0021] Figure 3 This is a cross-sectional structural diagram of the present invention;

[0022] Figure 4 This is a frontal sectional view of the present invention.

[0023] Figure 5 This is an exploded cross-sectional view of the present invention;

[0024] Figure 6 This is a schematic diagram of the assembly of the snap ring and the threaded sleeve in this utility model;

[0025] Figure 7 for Figure 6 Enlarged view of section A;

[0026] Figure 8 This is a schematic diagram of the snap ring in this utility model.

[0027] The corresponding names of the reference numerals in the attached drawings are as follows: 1. Housing; 2. Upper telescopic rod; 3. Lower telescopic rod; 4. Mounting cylinder; 5. Modal exciter; 6. Connecting pipe; 7. Top rod; 8. First annular groove; 9. Limiting plate; 10. Connecting rod; 11. Threaded sleeve; 12. Snap ring; 13. Second annular groove; 14. Bayonet; 15. Extension section; 16. Through hole. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0029] A traditional automatic coal core permeability tester includes at least an upper telescopic rod 2 and a lower telescopic rod 3 installed inside a housing 1, and an installation cylinder 4 fixed inside the housing 1 and located between the upper and lower telescopic rods 2 and 3. The installation cylinder 4 also has a rubber sleeve (not shown in the figure) inside, which is hydraulically controlled and provides lateral sealing and confining pressure (hereinafter referred to as confining pressure) to the coal core. The lower telescopic rod 3 pushes the cylindrical coal core upwards into the installation cylinder 4, providing an upward thrust, while the upper telescopic rod 2 applies a downward thrust, thus forming axial pressure (hereinafter referred to as axial pressure). In this way, under the action of the upper telescopic rod 2, the lower telescopic rod 3, and the installation cylinder 4, the axial pressure and confining pressure of the coal core are simulated. This allows for subsequent steps such as vacuuming, gas injection, and permeability measurement.

[0030] The core of this invention lies in providing a vibration component specifically designed for a coal core permeability tester. This component aims to solve the key problems of existing testers being unable to simulate mining disturbances and study the impact of vibration on the seepage characteristics of coal and rock gas. By integrating this component into a standard tester, it can be upgraded into an advanced device capable of conducting multi-field coupled experiments.

[0031] See Figures 1 to 8 The vibration component, as a relatively independent module, is installed between the original upper telescopic rod 2 and the mounting cylinder 4 of the testing instrument. The top end of the vibration component is detachably fixed to the upper telescopic rod 2, and the top rod 7 at its bottom end acts on the coal core sample placed inside the mounting cylinder 4.

[0032] The vibration assembly mainly includes: modal exciter 5, connecting pipe 6, push rod 7, and connecting parts.

[0033] The modal exciter 5 serves as a vibration source and is fixed to the bottom end of the upper telescopic rod 2 via a flange and bolts. In a preferred embodiment of this invention, the modal exciter 5 is an electromagnetic exciter with a frequency control range of 10Hz to 5000Hz and a maximum excitation force of not less than 500N.

[0034] The connecting pipe 6 is a cylindrical component that serves as the structural framework of the entire assembly. It is suspended and fixed below the upper telescopic rod 2 via connectors. The connecting pipe 6 is located below the modal exciter 5, and the two are not in direct physical contact. This ensures that the vibration excitation and the static pressure servo control system of the upper telescopic rod 2 do not interfere with each other.

[0035] The top rod 7 is slidably disposed in the inner hole of the connecting pipe 6. A limiting plate 9 is fixed at its top end. Correspondingly, a first annular groove 8 is formed circumferentially on the inner wall of the connecting pipe 6, and the limiting plate 9 is accommodated in the first annular groove 8 and can slide up and down along it.

[0036] When the telescopic rod of the modal exciter 5 extends downward, it directly strikes the limiting plate 9, and the impact force is efficiently transmitted to the coal core sample below through the top rod 7.

[0037] The first annular groove 8 provides the push rod 7 with a predetermined downward movement space, ensuring an effective impact amplitude, while avoiding interference between the push rod 7 and the exciter in the non-excited state.

[0038] When only static axial pressure is applied, the upper telescopic rod 2 moves downward, pressing the upper surface of the first annular groove 8 through the upper end face of the connecting pipe 6. The force is transmitted to the top rod 7 via the limiting plate 9, and finally acts stably on the coal core. This process ensures the accuracy and stability of the static axial pressure loading, which is no different from before the installation of this component.

[0039] The connector is used to achieve a detachable connection between the vibration assembly and the upper telescopic rod 2. It includes two sets of connecting rods 10. One set of connecting rods is fixed near the lower end of the upper telescopic rod 2, and the other set is fixed near the upper end of the connecting pipe 6. The axes of the two sets of connecting rods are corresponding, but the directions of their external threads are opposite.

[0040] By screwing in the threaded sleeve 11 (whose inner hole is provided with a reverse thread that matches the connecting rod), the upper telescopic rod 2 and the connecting pipe 6 can be firmly connected as one unit.

[0041] To overcome the loosening of the threaded pair caused by vibration, this utility model is designed with a special anti-loosening structure.

[0042] A second annular groove 13 is provided on the outer wall of each threaded sleeve 11.

[0043] A ring-shaped retaining spring 12 has multiple retaining slots 14 formed by inward stamping on both sides. During installation, the retaining spring 12 is inserted into the second annular groove 13 of multiple threaded sleeves, so that the retaining slots 14 are in close contact with the outer wall of the threaded sleeve outside the groove bottom, and the rotation of the threaded sleeve 11 is effectively suppressed by friction.

[0044] To further enhance the anti-loosening effect, the retaining spring 12 is preferably made of 60Si2Mn spring steel, and its inner surface of the retaining groove 14 can be knurled or bonded with a fluororubber layer to increase the coefficient of friction.

[0045] Both ends of the retaining ring 12 have extension sections 15, and each extension section 15 has a through hole 16. After installation, a metal wire or fatigue-resistant cable tie can be passed through the two through holes 16 and pulled tight to fix it, which can fundamentally prevent the retaining ring 12 from coming off due to vibration, forming a double safety measure.

[0046] The vibration component, as a module, can be easily integrated into existing testing instruments via the aforementioned connectors.

[0047] To achieve multi-field coupling experiments involving vibration, stress, and seepage, the following are also included:

[0048] The system includes a vibration excitation control unit and a data acquisition unit. The vibration excitation control unit is electrically connected to the modal exciter 5 and is used to drive it to generate vibrations with specific frequencies, amplitudes, and waveforms. The data acquisition unit is used to synchronously acquire vibration parameters, stress, and seepage data.

[0049] Experimental procedure:

[0050] 1. Install the vibration assembly between the upper telescopic rod 2 and the mounting cylinder 4 of the testing instrument.

[0051] 2. Load the coal core sample according to the standard procedure and apply the predetermined axial pressure and confining pressure.

[0052] 3. Conduct initial gas permeability testing.

[0053] 4. Start the modal exciter 5 and apply the set vibration load to the coal core while maintaining the stability of the static stress field.

[0054] 5. Simultaneously monitor and record the changes in gas permeability during vibration, thereby quantifying the impact of vibration on seepage characteristics.

[0055] The vibration assembly of this invention, through the cooperation of the top rod, limiting plate, and annular groove structure, allows strong static pressure and small-amplitude high-frequency vibration to act simultaneously on the coal core without interfering with each other. This simulates the actual stress state of underground coal seams, enabling precise research into the impact of vibration on gas flowability.

Claims

1. A vibration component of a coal and rock permeability testing device, disposed between the upper telescopic rod (2) and the mounting cylinder (4) of the testing instrument, characterized in that, include: Modal exciter (5), which is used to generate vibration; The connecting pipe (6) is a cylindrical component, which is suspended and fixed below the upper telescopic rod (2) by a connector, and the connecting pipe (6) and the modal exciter (5) are not in direct physical contact. The top rod (7) is slidably disposed in the inner hole of the connecting pipe (6) for transmitting vibration to the coal core sample; a limit plate (9) is fixedly disposed at the top end of the top rod (7). The inner wall of the connecting pipe (6) is provided with a first annular groove (8), the limiting plate (9) is accommodated in the first annular groove (8) and can slide up and down along it; the telescopic rod of the modal exciter (5) can extend downward and strike the limiting plate (9).

2. The vibration component of the coal and rock permeability testing device according to claim 1, characterized in that: The modal exciter (5) is an electromagnetic exciter with a frequency control range of 10Hz to 5000Hz and a maximum excitation force of not less than 500N.

3. The vibration component of the coal and rock permeability testing device according to claim 1, characterized in that: The connector includes: One set of connecting rods is fixed near the lower end of the upper telescopic rod (2); Another set of connecting rods is fixed near the upper end of the connecting tube (6). The axes of the two sets of connecting rods are corresponding and the external threads are rotated in opposite directions. The threaded sleeve (11) has a reverse thread in its inner hole that matches the two sets of connecting rods. By screwing the threaded sleeve (11), the upper telescopic rod (2) is connected and fixed to the connecting pipe (6).

4. The vibration component of the coal and rock permeability testing device according to claim 3, characterized in that: It also includes an anti-loosening structure, which comprises: A second annular groove (13) is formed on the outer wall of the threaded sleeve (11); The ring-shaped retaining spring (12) has multiple slots (14) formed by inward stamping on both sides. The retaining spring (12) can be inserted into the second annular groove (13) of the multiple threaded sleeves (11), so that the slots (14) are in close contact with the outer wall of the threaded sleeves (11) outside the groove bottom.

5. The vibration component of the coal and rock permeability testing device according to claim 4, characterized in that: The snap ring (12) is made of 60Si2Mn spring steel.

6. The vibration component of a coal and rock permeability testing device according to claim 4 or 5, characterized in that: The inner surface of the bayonet (14) is knurled or has a fluororubber layer bonded to it.

7. The vibration component of the coal and rock permeability testing device according to claim 4, characterized in that: Both ends of the snap ring (12) have extension sections (15), and each extension section (15) has a through hole (16). After installation, a metal wire or fatigue-resistant cable tie is passed through the two through holes (16) and tightened to fix it.

8. The vibration component of the coal and rock permeability testing device according to claim 1, characterized in that: The vibration assembly also includes a vibration excitation control unit and a data acquisition unit. The vibration excitation control unit is electrically connected to the modal exciter (5) and is used to drive it to generate vibrations of a specific frequency, amplitude and waveform. The data acquisition unit is used to synchronously acquire vibration parameters, stress and seepage data.

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