Magnetic fluid seal with sealed gap magnetic field regulation capability

Abstract

The application relates to a magnetic fluid seal with sealing gap magnetic field regulation and control capability, comprising a shell, a pole shoe ring, a permanent magnet and a winding. The application proposes a novel magnetic fluid seal, a winding with controllable current is arranged at the position of the permanent magnet ring, so that the magnetic field at the sealing gap of the magnetic fluid seal is regulated and controlled, the structure solves the problems that the permanent magnet of the commonly used magnetic fluid seal is difficult to magnetize, difficult to process, easy to demagnetize and the magnetic field is uncontrollable, meanwhile, the adjustment of the magnetic fluid state at the sealing gap is realized through the regulation of the current in the winding, wherein the reinforced current, the weakened current and the variable frequency current can respectively achieve the three purposes of high-pressure resistance, low-temperature starting and long-term preservation of the magnetic fluid, so that the magnetic fluid seal can solve the three difficult problems of high-pressure resistance, low-temperature starting and long-term preservation in engineering, and the magnetic fluid seal can simultaneously have the three functions of high-pressure resistance, low-temperature starting and long-term preservation.

Description

Technical Field

[0001] This invention belongs to the field of mechanical engineering sealing, and specifically relates to a magnetohydrodynamic seal with the ability to regulate the magnetic field of the sealing gap. Background Technology

[0002] Magnetofluid sealing utilizes the magnetic force generated by a permanent magnet within the sealing gap to firmly fix the magnetic fluid within the gap, resisting the pressure difference on both sides, thereby achieving a sealing effect. Research on magnetic fluid sealing using electromagnets as the magnetic source is relatively lacking, mainly because under normal operating conditions, the magnetic field of the sealing gap can be stabilized at a certain value to meet the sealing requirements.

[0003] In some advanced weapon applications, installed sealing devices need to be placed in working or idle states for extended periods, while maintaining stable pressure resistance in both working and idle states. When using magnetohydrodynamic (MHD) seals that lack the ability to regulate the magnetic field of the sealing gap, the stable magnetic field increases the concentration of magnetic particles in the MHD at the sealing gap when the shaft and pole shoes are relatively stationary. This causes the magnetic particles in the magnetic fluid to form a columnar structure, resulting in a significant increase in starting torque and severely hindering the start-up of the sealing spindle. Furthermore, due to the tip effect of the magnetic field, a large number of magnetic particles accumulate at the tip of the pole teeth, while the concentration of MHD at other locations decreases. Long-term accumulation can cause the magnetic particles in the MHD to separate from the carrier fluid, severely affecting the performance of the MHD. Summary of the Invention

[0004] This invention proposes a novel magnetohydrodynamic (MHD) seal. By adding a winding with a controllable current at the location of the permanent magnet, the magnetic field at the sealing gap of the MHD seal can be controlled. This structure solves the problems of difficult magnetization, difficult processing, easy demagnetization, and uncontrollable magnetic field of the permanent magnet commonly used in MHD seals. At the same time, the state of the MHD at the sealing gap can be adjusted by controlling the current in the winding. The application of strong current and weak current can achieve the three purposes of high pressure resistance, low temperature start-up, and long-term preservation of the MHD, respectively. This MHD seal effectively solves the three difficult problems of high pressure resistance, low temperature start-up, and long-term preservation in engineering, enabling a single MHD seal to have the three functions of high pressure resistance, low temperature start-up, and long-term preservation.

[0005] This patent conducts finite element simulations on a large number of magnetohydrodynamic sealing examples, analyzes the simulation results, and derives a reasonable design scheme for the number of winding turns and the ring width and ring thickness of the permanent magnet.

[0006] The technical solution of the present invention is as follows: A magnetohydrodynamic seal with the ability to regulate the magnetic field of the sealing gap includes a shell, a left pole shoe ring, a right pole shoe ring, and a permanent magnet; the pole shoe rings are disposed on the inner wall of the shell, the permanent magnet and the winding are disposed between the two pole shoe rings, and a gap is left between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft; the inner circular surface of the pole shoe ring is provided with pole teeth, which extend radially toward the inner circular surface of the pole shoe ring, and a gap is left between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft, the gap being filled with magnetohydrodynamic fluid for sealing; the winding is a cylindrical ring tightly pressed from copper wire, wherein a gap is left between the inner circular surface of the winding and the outer circular surface of the shaft, the winding... The gap between the winding and the shaft is greater than the gap between the inner surface of the shoe ring and the outer surface of the shaft. The permanent magnet is made up of small cylindrical magnets spliced ​​together and contacts the outer surface of the winding. The outer shell has a radial through hole, and an aviation plug is installed at the through hole. The wires led out from the winding are connected to the power supply through the gap of the permanent magnet and the aviation plug on the outer shell. The winding is powered by an adjustable voltage power supply, which is required to output constant current DC. Through simulation design of the dimensions of the winding and the permanent magnet, the magnetic field strength generated by the permanent magnet working alone in the sealed gap is equal to the magnetic field strength generated by the winding working alone in the sealed gap, thereby achieving zeroing of the magnetic field of the sealed gap.

[0007] The inner circular surface of the pole shoe ring has 4 to 10 pole teeth.

[0008] The gap between the outer circular surface of the shaft and the inner circular surface of the pole shoe ring is 0.05~3mm.

[0009] The magnetic fluid seal with the ability to regulate the magnetic field of the sealing gap is characterized in that: the outer circumference of the pole shoe ring is provided with an annular groove, and an O-ring is provided in the annular groove to prevent leakage along the path between the outer shell and the pole shoe ring.

[0010] The magnetohydrodynamic seal with the ability to regulate the magnetic field of the sealing gap further includes an end cap and a bearing. The end cap is used to ensure the axial positioning of the pole shoe ring and the bearing, so that the pole shoe ring and the bearing have good coaxiality with the shaft.

[0011] The bearing is mounted on the shaft. Attached Figure Description

[0012] Figure 1 The schematic diagram of a magnetohydrodynamic seal with magnetic field control capability for sealing gap provided by the present invention is shown below. The serial numbers and corresponding names in the figure are as follows: 1-shaft, 2-outer shell, 3-pole shoe ring, 4-permanent magnet, 5-winding, 6-bearing, 7-end cap; Figure 2 The magnetic field strength of the sealing gap is determined by the fact that no current flows through the winding. Figure 3 To enable the winding to carry current in the same direction as the permanent magnet's magnetic field; Figure 4To enable the winding to carry current in the direction of the magnetic field opposite to that of the permanent magnet. Detailed Implementation

[0013] The invention will now be further described with reference to the accompanying drawings.

[0014] like Figure 1 As shown, the technical solution of the present invention is as follows: A magnetohydrodynamic seal with the ability to regulate the magnetic field of the sealing gap includes a shell, a left pole shoe ring, a right pole shoe ring, and a permanent magnet; the pole shoe rings are disposed on the inner wall of the shell, the permanent magnet and the winding are disposed between the two pole shoe rings, and a gap is left between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft; the inner circular surface of the pole shoe ring is provided with pole teeth, which extend radially toward the inner circular surface of the pole shoe ring, and a gap is left between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft, which is filled with magnetohydrodynamic fluid for sealing; the winding is a cylindrical ring tightly pressed from copper wire, wherein a gap is left between the inner circular surface of the winding and the outer circular surface of the shaft, and the winding... The gap between the winding and the shaft is greater than the gap between the inner surface of the shoe ring and the outer surface of the shaft. The permanent magnet is made up of small cylindrical magnets spliced ​​together and contacts the outer surface of the winding. The outer shell has a radial through hole, and an aviation plug is installed at the through hole. The wires led out from the winding are connected to the power supply through the gap of the permanent magnet and the aviation plug on the outer shell. The winding is powered by an adjustable voltage power supply, which is required to output constant current DC. Through simulation design of the dimensions of the winding and the permanent magnet, the magnetic field strength generated by the permanent magnet working alone in the sealed gap is equal to the magnetic field strength generated by the winding working alone in the sealed gap, thereby achieving zeroing of the magnetic field of the sealed gap.

[0015] The inner circular surface of the pole shoe ring has 4 to 10 pole teeth.

[0016] The gap between the outer circular surface of the shaft and the inner circular surface of the pole shoe ring is 0.05~3mm.

[0017] The permanent magnet is an axially magnetized permanent magnet. To control the magnetic field of the sealing gap, the magnetic field of the sealing component is simulated and calculated using Maxwell software. Taking a N35H neodymium iron boron cylindrical magnet as the permanent magnet and a cylindrical ring tightly pressed with 0.2mm diameter copper wire as the winding as an example, it can be seen that when the volume of the winding is 4 times the volume of the permanent magnet, the magnetic field of the sealing gap can be zeroed. Taking an ester-based magnetic liquid seal with a shaft diameter of 20mm and an injection volume of 20ml as an example, the starting torque of the magnetic liquid seal is 0.002 N·m at room temperature without zeroing, 0.448 N·mm at -60℃ without zeroing, and 1.344 N·mm after being placed at -60℃ for 24 hours. After the magnetic field is zeroed at -60℃, the starting torque of the magnetic liquid seal is 0.082 N·mm, and 0.284 N·mm after being placed for 24 hours.

[0018] The magnetic fluid seal with the ability to regulate the magnetic field of the sealing gap is characterized in that: the outer circumference of the pole shoe ring is provided with an annular groove, and an O-ring is provided in the annular groove to prevent leakage along the path between the outer shell and the pole shoe ring.

[0019] The magnetohydrodynamic seal with the ability to regulate the magnetic field of the sealing gap further includes an end cap and a bearing. The end cap is used to ensure the axial positioning of the pole shoe ring and the bearing, so that the pole shoe ring and the bearing have good coaxiality with the shaft.

[0020] The bearing is mounted on the shaft.

Claims

1. A magnetohydrodynamic seal with the ability to regulate the magnetic field of the sealing gap, comprising a shell (2), a pole shoe ring (3), a permanent magnet (4), and a winding (5); characterized in that: The pole shoe ring (3) is located on the inner wall of the outer shell (2). The permanent magnet (4) and the winding (5) are located between the two pole shoe rings (3). There is a gap between the inner circular surface of the pole shoe ring (3) and the outer circular surface of the shaft (1). The inner circular surface of the pole shoe ring (3) is provided with pole teeth, which extend radially towards the inner circular surface of the pole shoe ring (3). There is a gap between the inner circular surface of the pole shoe ring (3) and the outer circular surface of the shaft (1). The gap is filled with a magnetic fluid for sealing. The winding (5) is made of tightly pressed copper wire. The inner circular surface of the winding (5) and the outer circular surface of the shaft (1) are separated by a gap. The gap between the winding and the shaft is greater than the gap between the inner circular surface of the pole shoe ring (3) and the outer circular surface of the shaft (1). The permanent magnet (4) is made of small cylindrical magnets spliced ​​together and is in contact with the outer circular surface of the winding (5). The outer shell (2) is provided with a radial through hole. The through hole is threaded to install an aviation plug. The wires led out from the winding (5) are connected to the power supply through the gap of the permanent magnet and the aviation plug on the outer shell. The winding is powered by an adjustable voltage power supply, which is required to output constant current DC power. By simulating the design of the winding and permanent magnet dimensions, the magnetic field strength generated by the permanent magnet working alone in the sealed gap is equal to the magnetic field strength generated by the winding working alone in the sealed gap, thus achieving zeroing of the magnetic field in the sealed gap.

2. The magnetohydrodynamic seal with magnetic field control capability for sealing gap as described in claim 1, characterized in that: The inner circular surface of the pole shoe ring (3) has 4 to 10 pole teeth.

3. A magnetohydrodynamic seal with the ability to adjust the magnetic field of the sealing gap as described in claim 1, characterized in that: The gap between the pole teeth on the inner circular surface of the pole shoe ring (3) and the outer circular surface of the shaft (1) is 0.05~3mm.

4. A magnetohydrodynamic seal with the ability to adjust the magnetic field of the sealing gap as described in claim 1, characterized in that: The outer surface of the pole shoe ring (3) is provided with an annular groove, and an O-ring is provided in the annular groove to prevent leakage along the path between the outer shell (2) and the pole shoe ring (3).

5. A magnetohydrodynamic seal with the ability to adjust the magnetic field of the sealing gap as described in claim 1, characterized in that: It also includes an end cap (7) and a bearing (6); the end cap (7) is used to ensure the axial positioning of the pole shoe ring (3) and the bearing (6), so that the pole shoe ring (3) and the bearing (6) have good coaxiality with the shaft (1).

6. A magnetohydrodynamic seal with the ability to adjust the magnetic field of the sealing gap as described in claim 5, characterized in that: The bearings (6) are respectively mounted on the shaft (1).

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