Experimental device for researching natural convective heat transfer characteristic of magnetic liquid under uniform magnetic field

Abstract

The invention discloses an experimental device for researching natural convective heat transfer characteristics of magnetic liquid under a uniform magnetic field, and belongs to the field of magnetic liquid convective heat transfer experiments. The device comprises a thermocouple mounting rack, an experiment channel, a cold control semiconductor chilling plate, a thermal control semiconductor heating plate, a large gear, an electromagnetic coil shaft, a small gear, an infrared thermal imager, a thermocouple and other components, and the temperature accuracy of the magnetic liquid and the regulation and control convenience of a uniform magnetic field in the convective heat transfer performance experiment research of the magnetic liquid under the magnetic field are improved. The arrangement of the thermocouple mounting rack can effectively ensure that the position of a magnetic liquid temperature measuring point is accurate and stable, fluctuation during data acquisition is reduced, the measuring point arrangement is simpler, more convenient and more reliable, and the temperature value is more accurate; and the magnetic field regulation and control unit can realize connection and fixation of a plurality of magnetic sources through meshing of gears of all stages and installation of an electromagnetic coil shaft, regulation and control of magnetic field intensity and direction are realized, and the connection method is convenient to operate.

Description

TECHNICAL FIELD

[0001] The present application relates to an experimental device for studying the natural convection heat transfer characteristics of magnetic liquid in a uniform magnetic field, which is suitable for studying the natural convection heat transfer characteristics of different magnetic liquids in a magnetic field and belongs to the field of experimental research on the heat transfer performance of magnetic liquid. BACKGROUND

[0002] The convective heat transfer performance is an important physical property of magnetic liquid, and accurate measurement of the convective heat transfer coefficient is of great significance for further promoting the application of magnetic liquid in the fields of thermal energy engineering and mechanical engineering. For example, with the rapid development of artificial intelligence, the power density of supercomputing chips has broken through 300W / cm 2 . Traditional heat transfer fluids such as water and mineral oil gradually show limitations in heat transfer in high heat flux scenarios due to their low natural heat transfer performance, and there is an urgent need for fluids with higher convective heat transfer performance. Magnetic liquid has better natural convective heat transfer performance than traditional fluids because magnetic nanoparticles are uniformly dispersed in the base liquid, and has greater application potential in high-power chip cooling and large-calorie power cooling. However, the research on the natural convective heat transfer performance of magnetic liquid is still not mature. Therefore, experimental measurement of the convective heat transfer coefficient of magnetic liquid can not only improve the database of its heat transfer performance, but also provide support for building a universal theoretical model, further enrich the research on the heat transfer performance of magnetic liquid, and provide new thermal control solutions for high-power electronic devices, concentrated solar energy collectors and other high-end equipment. It has important significance for realizing the self-innovation of China's technology in the field of thermal management.

[0003] In the measurement of natural convection heat transfer of magnetic liquid, the distribution and fixation of the magnetic liquid measuring points are key factors affecting the experimental results and analysis. Currently, in the patents related to the experimental device for studying the convective performance of magnetic liquid that have been published, researchers have proposed various methods for measuring the temperature of magnetic liquid. For example, as described in the patent with publication number CN206563724U, the experimental device calculates the temperature value of the magnetic liquid inside the fluid channel by counting the temperature values of the thermometers arranged at the inlet and outlet of the magnetic liquid. However, there is a certain measurement error in indirect calculation. As described in the patent with publication number CN206563915U, the experimental device further optimizes the method for obtaining the temperature of magnetic liquid, i.e. adding a thermocouple inside the channel for directly measuring the temperature of magnetic liquid. The temperature value of magnetic liquid obtained by this method is more accurate than that of the previous method, but the thermocouple inside the magnetic liquid is not effectively fixed. The movement of the thermocouple inside the fluid will change the effective heat transfer area and the local flow structure, thereby affecting the natural convection of magnetic liquid. The current methods for fixing and measuring the temperature of magnetic liquid still need to be further optimized to improve the measurement accuracy.

[0004] Magnetic liquid has its unique properties in heat transfer characteristics due to its unique magnetic response characteristics. Magnetic liquid shows anisotropy under the action of magnetic field, and the heat transfer performance is greatly affected by the magnetic field. Therefore, the traditional experimental device for studying the heat transfer characteristics of liquid cannot meet the research of the heat transfer characteristics of magnetic liquid, and it is necessary to further study the natural convection heat transfer performance of magnetic liquid under the action of magnetic field. As disclosed in the patent with publication number CN104181194A, an experimental device for studying the natural convection heat transfer performance of magnetic liquid under the action of magnetic field is proposed, which uses a permanent magnet as a magnetic source to provide a magnetic field environment, but the magnetic field strength adjustment is cumbersome; as disclosed in the patent with publication number CN119480822A, the experimental device uses an electromagnetic coil to generate a magnetic field, and the electromagnetic coil is convenient to adjust, which further optimizes the magnetic field generating device, but due to the local arrangement of the electromagnetic coil, the uniformity of the magnetic field distribution in the fluid channel is poor, which may cause the magnetic liquid to gather or be insufficient in some areas, affecting the heat exchange effect, in addition, the device contains multiple complex components such as metal heat-conducting base and array heat-dissipation ring pipe, and the manufacturing cost is high. In the existing experimental devices for studying the heat transfer performance of magnetic liquid under the action of magnetic field, there are problems such as inconvenient magnetic field adjustment and high cost.

[0005] In summary, accurate measurement of the temperature of magnetic liquid and design of a simple magnetic field generating device are important links to accurately study the natural convection heat transfer performance of magnetic liquid under the action of magnetic field. Therefore, the present application proposes an experimental device for studying the natural convection heat transfer characteristics of magnetic liquid under uniform magnetic field, which is designed with a thermocouple mounting rack in the fluid channel to realize firm measurement of the thermocouple of magnetic liquid and improve the accuracy of temperature measurement. In addition, a gear transmission system and an electromagnetic coil are used to complete the regulation and control of uniform magnetic field. By measuring the temperature and other parameters of different magnetic liquids at different positions in the experimental channel under the action of magnetic field, the natural convection heat transfer coefficient of magnetic liquid is calculated, which provides an experimental basis for further research on the natural convection heat transfer performance of magnetic liquid, provides specific data reference for the establishment of thermal theory model of magnetic liquid and thermal analysis, and provides strong theoretical and technical support for the application of magnetic liquid in the fields of thermal energy and machinery. SUMMARY

[0006] The technical problems to be solved by the present application are that the existing magnetic field natural convection heat transfer experimental device of the magnetic liquid does not solve the problem of fixing the position of the thermocouple measuring point of the magnetic liquid layer in the heat transfer channel, it is difficult to ensure the effective measurement and stability of the temperature at the center position of the magnetic liquid, and it affects the accuracy of the research on the natural convection heat transfer performance of the magnetic liquid; and the magnetic field adjustment in the existing experimental device is complicated and depends on manual operation, it is difficult to realize the rapid and accurate switching of the dynamic magnetic field, at the same time, the arrangement mode of the permanent magnet or the electromagnetic coil leads to uneven magnetic field distribution in the working area, and there is even a magnetic field gradient mutation in the local area, and this uncontrollable magnetic field environment makes it difficult to stably reproduce the natural convection process of the magnetic liquid under the temperature-magnetic field coupling effect. Therefore, an experimental device for researching the natural convection heat transfer characteristics of the magnetic liquid under the uniform magnetic field is proposed.

[0007] The technical solution adopted by the present application to solve its technical problems is:

[0008] An experimental device for researching the natural convection heat transfer characteristics of the magnetic liquid under the uniform magnetic field, comprising: a large gear wheel 1, an experimental channel 2, a thermocouple mounting frame 3, an electromagnetic coil shaft 4, a small gear wheel 5, an upper sealing cover plate 6, an electromagnetic coil shaft 7, a small gear wheel 8, a cold end heat-conducting silicone grease layer 9, a cold control semiconductor refrigeration piece 10, a small gear wheel 11, an electromagnetic coil shaft 12, a heat insulation plate 13, a large gear wheel 14, a temperature controller 15, an infrared thermal imager 16, a multi-channel direct current power supply 17, a hot end heat-conducting silicone grease layer 18, a hot control semiconductor heating piece 19, a small gear wheel 20, an electromagnetic coil shaft 21, a small gear wheel 22, an electromagnetic coil shaft 23, a horizontal experimental operation table 24, a small gear wheel 25, an electromagnetic coil shaft 26, computer data acquisition software 27, a temperature inspection instrument 28, cold end wall surface thermocouples T1-T8, magnetic liquid layer thermocouples T9-T16, and hot end wall surface thermocouples T17-T24.

[0009] The left end face of the thermocouple mounting frame 3 is installed at the corresponding clamping groove position of the left end inner wall of the experimental channel 2, and the right end face of the thermocouple mounting frame 3 is installed at the corresponding clamping groove position of the right end inner wall of the experimental channel 2.

[0010] The magnetic liquid layer thermocouple measuring points T9-T16 are uniformly pasted on the thermocouple mounting frame 3 in sequence according to the distance;

[0011] The lower wall surface of the experimental channel 2 is uniformly punched with 8 hole grooves with a diameter of 2mm, which are used for installing the thermocouples T17-T24 to measure the temperature of the hot end wall surface of the experimental channel 2, and the hole grooves are filled with heat-conducting silicone grease.

[0012] The upper sealing cover plate 6 has eight holes with a diameter of 2 mm evenly punched along the axis, which are used to install thermocouples T1-T8 to measure the temperature of the cold end wall of the experimental channel 6. Each hole is filled with heat-conducting silicone grease. A through hole with a diameter of 8 mm is used to lead the wires of the thermocouples T9-T16 of the magnetic liquid layer. The through hole is sealed with sealing glue. The upper sealing cover plate 6 is attached to the left and right end faces of the experimental channel 2 by sealing glue.

[0013] The thermocouples T1-T24 are connected to the temperature inspection instrument 28 and the computer data acquisition software 27.

[0014] The cold-controlled semiconductor refrigeration sheet 10 is connected to the temperature controller 15 and is attached to the upper end face of the upper sealing cover plate 6 through the cold end heat-conducting silicone grease layer 9.

[0015] The heat-controlled semiconductor heating sheet 19 is connected to the multi-channel direct current power supply 17 and is attached to the lower end face of the experimental channel 2 through the hot end heat-conducting silicone grease layer 18.

[0016] The heat insulation board 13 tightly covers the outside of the cold-controlled semiconductor refrigeration sheet 10, the experimental channel 2, and the heat-controlled semiconductor heating sheet 19. The lower wall of the heat insulation board 13 is attached to the upper wall of the horizontal experimental operating table 14.

[0017] The infrared thermal imager 16 is placed on the left side of the experimental channel 2 to detect the internal temperature distribution in real time.

[0018] The electromagnetic coil shaft one 4 is installed on the pinion one 5, the electromagnetic coil shaft two 7 is installed on the pinion two 8, the electromagnetic coil shaft three 12 is installed on the pinion three 11, the electromagnetic coil shaft four 21 is installed on the pinion four 20, the electromagnetic coil shaft five 23 is installed on the pinion five 22, and the electromagnetic coil shaft six 26 is installed on the pinion six 25, forming rotating magnetic field assemblies I, II, III, IV, V, and VI. The large gear one 1 is engaged with the pinion three 11 and the pinion four 20, respectively. The large gear two 14 is engaged with the pinion six 25 and the pinion one 5, respectively.

[0019] The electromagnetic coil shaft one 4 and the electromagnetic coil shaft six 26 are connected to the positive and negative poles of the multi-channel direct current power supply 17, respectively, to realize the loading and regulation of the magnetic field.

[0020] The electromagnetic coils on the electromagnetic coil shaft one 4, the electromagnetic coil shaft two 7, the electromagnetic coil shaft three 12, the electromagnetic coil shaft four 21, the electromagnetic coil shaft five 23, and the electromagnetic coil shaft six 26 are wound in a clockwise manner.

[0021] The large gear one 1 and the large gear two 14 serve as driving wheels to drive the directional rotation of all gears, realizing the synchronous change of the direction of the magnetic source of each electromagnetic coil shaft.

[0022] The thermocouple mounting bracket 3 is 500 mm long, 3 mm wide, and 3 mm high.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] (1) The present application can directly measure the temperature of the magnetic liquid in the fluid channel while ensuring the constant temperature measurement point by fixing the magnetic liquid thermocouple at the corresponding measurement point position of the thermocouple mounting frame, so that the collection result of the magnetic liquid temperature in the experimental channel is accurate and stable;

[0025] (2) The present application uses an electromagnetic coil as a magnetic source and covers the entire channel, which can accurately control the magnetic field strength and direction of the uniform magnetic field, is simple to operate, uses gear transmission to adjust the magnetic field direction, and is simple to connect and easy to operate;

[0026] (3) The present application combines the temperature data collected by the thermocouple with the image of the infrared thermal imager to observe the heat transfer process in real time, can directly observe the temperature distribution of the magnetic liquid, and can more accurately and comprehensively study the heat transfer performance of the magnetic liquid under the action of the magnetic field;

[0027] The device has simple structure, convenient assembly and easy operation, and improves the precision and accuracy of the measurement of the heat transfer performance of the magnetic liquid under the action of the magnetic field. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A schematic diagram of an experimental device for studying the natural convection heat transfer characteristics of magnetic liquid under a uniform magnetic field;

[0029] Figure 2 A cross-sectional view of the experimental channel;

[0030] Figure 3 A cross-sectional view of the upper sealing cover plate;

[0031] Figure 4 A schematic diagram of the movement of the rotating magnetic field assembly (parallel magnetic field);

[0032] In the figure: large gear 1, experimental channel 2, thermocouple mounting frame 3, electromagnetic coil shaft 1 4, small gear 1 5, upper sealing cover plate 6, electromagnetic coil shaft 2 7, small gear 2 8, cold end heat-conducting silicone grease layer 9, cold control semiconductor refrigeration piece 10, small gear 3 11, electromagnetic coil shaft 3 12, heat insulation board 13, large gear 2 14, temperature controller 15, infrared thermal imager 16, multi-channel direct current power supply 17, hot end heat-conducting silicone grease layer 18, hot control semiconductor heating piece 19, small gear 4 20, electromagnetic coil shaft 4 21, small gear 5 22, electromagnetic coil shaft 5 23, horizontal experimental operation table 24, small gear 6 25, electromagnetic coil shaft 6 26, computer data acquisition software 27, temperature inspection instrument 28, cold end wall surface thermocouple T1-T8, magnetic liquid layer thermocouple T9-T16, hot end wall surface thermocouple T17-T24. DETAILED DESCRIPTION

[0033] The application is further illustrated with the accompanying drawings as the specific embodiment:

[0034] An experimental device for studying the heat transfer characteristics of natural convection of magnetic liquid in a uniform magnetic field, as shown in Figure 1 characterized in that:

[0035] The device is composed of a large gear 1, an experimental channel 2, a thermocouple mounting rack 3, an electromagnetic coil shaft 4, a small gear 5, an upper sealing cover plate 6, an electromagnetic coil shaft 2 7, a small gear 8, a cold end heat-conducting silicone grease layer 9, a cold control semiconductor refrigeration piece 10, a small gear 11, an electromagnetic coil shaft 3 12, a heat insulation board 13, a large gear 2 14, a temperature controller 15, an infrared thermal imager 16, a multi-channel direct current power supply 17, a hot end heat-conducting silicone grease layer 18, a hot control semiconductor heating piece 19, a small gear 20, an electromagnetic coil shaft 4 21, a small gear 22, an electromagnetic coil shaft 5 23, a horizontal experimental operating table 24, a small gear 6 25, an electromagnetic coil shaft 6 26, computer data acquisition software 27, a temperature inspection instrument 28, cold end wall surface thermocouples T1-T8, magnetic liquid layer thermocouples T9-T16, and hot end wall surface thermocouples T17-T24.

[0036] The connection between each part of the device:

[0037] The left end face of the thermocouple mounting rack 3 is installed in the corresponding clamping groove position of the left end inner wall of the experimental channel 2, and the right end face of the thermocouple mounting rack 3 is installed in the corresponding clamping groove position of the right end inner wall of the experimental channel 2.

[0038] The magnetic liquid layer thermocouples T9-T16 are evenly pasted on the thermocouple mounting rack 3 in sequence according to the distance;

[0039] The lower wall of the experimental channel 2 is evenly punched with 8 hole grooves with a diameter of 2 mm, as shown in Figure 2 , for installing thermocouples T17-T24 to measure the hot end wall surface temperature of the experimental channel 2, and the hole grooves are filled with heat-conducting silicone grease;

[0040] The upper sealing cover plate 6 is evenly punched with 8 hole grooves with a diameter of 2 mm in the central axis for installing thermocouples T1-T8 to measure the cold end wall surface temperature of the experimental channel 6, and each hole groove is filled with heat-conducting silicone grease, and a through hole with a diameter of 8 mm is provided for leading out the lead wires of the magnetic liquid layer thermocouples T9-T16, the through hole is sealed with sealing glue, and the upper sealing cover plate 6 is attached to the left and right end faces of the experimental channel 2 through the sealing glue, Figure 3 is a sectional view of the upper sealing cover plate;

[0041] The thermocouples T1-T24 are connected with the temperature inspection instrument 28 and the computer data acquisition software 27;

[0042] The cold-controlled semiconductor refrigeration sheet 10 is connected with the temperature controller 15 and is pasted on the upper end surface of the upper sealing cover plate 6 through the cold-end heat-conducting silicone grease layer 9.

[0043] The heat-controlled semiconductor heating sheet 19 is connected with the multi-channel direct-current power supply 17 and is pasted on the lower end surface of the experimental channel 2 through the hot-end heat-conducting silicone grease layer 18.

[0044] The heat-insulating plate 13 tightly covers the outside of the cold-controlled semiconductor refrigeration sheet 10, the experimental channel 2 and the heat-controlled semiconductor heating sheet 19, and the lower wall surface of the heat-insulating plate 13 is attached to the upper wall surface of the horizontal experimental operating table 14.

[0045] The infrared thermal imager 16 is placed outside the experimental channel 2 to detect the internal temperature distribution in real time.

[0046] The electromagnetic coil shaft one 4 is installed on the pinion one 5, the electromagnetic coil shaft two 7 is installed on the pinion two 8, the electromagnetic coil shaft three 12 is installed on the pinion three 11, the electromagnetic coil shaft four 21 is installed on the pinion four 20, the electromagnetic coil shaft five 23 is installed on the pinion five 22, and the electromagnetic coil shaft six 26 is installed on the pinion six 25, forming rotating magnetic field assemblies I, II, III, IV, V and VI. The large gear one 1 is engaged with the pinion three 11 and the pinion four 20 respectively, and the large gear two 14 is engaged with the pinion six 25 and the pinion one 5 respectively. When the large gear two 14 rotates counterclockwise by 90°, the magnetic field direction is parallel to the temperature gradient direction, as shown in Figure 4 ;

[0047] The electromagnetic coil shaft one 4 and the electromagnetic coil shaft six 26 are respectively connected with the positive and negative poles of the multi-channel direct-current power supply 17 to realize the loading and regulation of the magnetic field.

[0048] The electromagnetic coils on the electromagnetic coil shaft one 4, the electromagnetic coil shaft two 7, the electromagnetic coil shaft three 12, the electromagnetic coil shaft four 21, the electromagnetic coil shaft five 23 and the electromagnetic coil shaft six 26 are all wound in a clockwise manner.

[0049] The large gear one 1 and the large gear two 14 act as driving wheels to drive the directional rotation of all gears and realize the synchronous change of the magnetic source direction of each electromagnetic coil shaft.

[0050] The thermocouple mounting bracket 3 is 500mm long, 3mm wide and 3mm high, and its length-width ratio is large, so the influence on the natural convection performance of the magnetic liquid can be ignored.

Claims

1. An experimental apparatus for studying the natural convective heat transfer characteristics of magnetic fluids under a uniform magnetic field, characterized in that: include: Large Gear 1 (1), Experimental Channel (2), Thermocouple Mounting Bracket (3), Electromagnetic Coil Shaft 1 (4), Small Gear 1 (5), Upper Sealing Cover (6), Electromagnetic Coil Shaft 2 (7), Small Gear 2 (8), Cold End Thermal Grease Layer (9), Cold Control Semiconductor Cooling Chip (10), Small Gear 3 (11), Electromagnetic Coil Shaft 3 (12), Thermal Insulation Board (13), Large Gear 2 (14), Temperature Controller (15), Infrared Thermal Imager (16), Multi-channel DC Power Supply (17) ), hot end thermal conductive silicone grease layer (18), thermal control semiconductor heating element (19), pinion four (20), electromagnetic coil shaft four (21), pinion five (22), electromagnetic coil shaft five (23), horizontal experimental operating table (24), pinion six (25), electromagnetic coil shaft six (26), computer data acquisition software (27), temperature monitoring instrument (28), cold end wall thermocouples T1-T8, magnetic liquid layer thermocouples T9-T16, hot end wall thermocouples T17-T24; The thermocouple mounting bracket (3) is installed with one end face corresponding to the inner wall of one end of the experimental channel (2) at the corresponding slot position, and the other end face of the thermocouple mounting bracket (3) is installed with the other end of the experimental channel (2) at the corresponding slot position; the measuring points of the magnetic liquid layer thermocouples T9-T16 are evenly pasted on the thermocouple mounting bracket (3) at a distance in sequence. The experimental channel (2) has eight holes and slots evenly drilled along the central axis of the lower wall surface for installing thermocouples T17-T24 to measure the temperature of the hot end wall surface of the experimental channel (2). The holes and slots are filled with thermally conductive silicone grease. The upper sealing cover plate (6) has eight holes and slots evenly drilled along its central axis for installing thermocouples T1-T8 to measure the cold end wall temperature of the experimental channel (6). Each hole and slot is filled with thermally conductive silicone grease. The upper sealing cover plate (6) has a through hole for leading out the magnetic liquid layer thermocouples T9-T16 wires. This through hole is sealed with sealant. The upper sealing cover plate (6) is attached to both ends of the experimental channel (2) through the sealant. Thermocouples T1-T24 are connected to temperature monitoring instrument (28) and computer data acquisition software (27); The cold control semiconductor cooling chip (10) is connected to the temperature controller (15) and is attached to the upper end face of the upper sealing cover plate (6) through the cold end thermal conductive silicone grease layer (9); The thermal control semiconductor heating element (19) is connected to a multi-channel DC power supply (17) and is attached to the lower end face of the experimental channel (2) through a thermally conductive silicone grease layer (18); The heat insulation board (13) tightly covers the outside of the cold control semiconductor cooling chip (10), the experimental channel (2) and the heat control semiconductor heating chip (19), and the lower wall of the heat insulation board (13) is attached to the upper wall of the horizontal experimental operating table (14); The infrared thermal imager (16) is set on one side of the experimental channel (2) to detect the internal temperature distribution in real time; The electromagnetic coil shaft 1 (4) is mounted on the small gear 1 (5), the electromagnetic coil shaft 2 (7) is mounted on the small gear 2 (8), the electromagnetic coil shaft 3 (12) is mounted on the small gear 3 (11), the electromagnetic coil shaft 4 (21) is mounted on the small gear 4 (20), the electromagnetic coil shaft 5 (23) is mounted on the small gear 5 (22), and the electromagnetic coil shaft 6 (26) is mounted on the small gear 6 (25), forming rotating magnetic field components I, II, III, IV, V, and VI. The large gear 1 (1) meshes with the small gear 3 (11) and the small gear 4 (20) respectively, and the large gear 2 (14) meshes with the small gear 6 (25) and the small gear 1 (5) respectively.

2. The experimental apparatus for studying the natural convective heat transfer characteristics of magnetic fluids under a uniform magnetic field according to claim 1, characterized in that: The electromagnetic coils on the electromagnetic coil shaft one (4), electromagnetic coil shaft two (7), electromagnetic coil shaft three (12), electromagnetic coil shaft four (21), electromagnetic coil shaft five (23), and electromagnetic coil shaft six (26) are all wound in a clockwise direction.

3. The experimental apparatus for studying the natural convective heat transfer characteristics of magnetic fluids under a uniform magnetic field according to claim 1, characterized in that: The large gear one (1) and large gear two (14) serve as driving wheels, driving the directional rotation of all gears to achieve synchronous change of the magnetic source direction of each electromagnetic coil shaft.

4. The experimental apparatus for studying the natural convective heat transfer characteristics of magnetic fluids under a uniform magnetic field according to claim 1, characterized in that: Thermocouple mounting bracket (3) is 500mm long, 3mm wide, and 3mm high.

5. The experimental apparatus for studying the natural convective heat transfer characteristics of magnetic fluids under a uniform magnetic field according to claim 1, characterized in that: The electromagnetic coil shaft one (4) and electromagnetic coil shaft six (26) are respectively connected to the positive and negative poles of the multi-channel DC power supply (17) to realize the loading and control of the magnetic field.

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