A helium transmission sealing structure for a high-temperature superconducting motor

Abstract

The present invention discloses a helium transmission sealing structure for a high-temperature superconducting motor, comprising a stationary air inlet pipe, a rotating air inlet pipe, an air return pipe, a vacuum sandwich pipe, a magnetic fluid sealing device comprising a rotating portion and a stationary portion, and a Tesla sealing structure comprising an outer ring and an inner ring. While ensuring that the topological structure of the existing helium transmission rotating seal of the superconducting motor remains unchanged, the present invention combines the unidirectional flow principles of the jet and Tesla valves, and proposes a nozzle and Tesla valve structure. The nozzle increases the flow velocity at the throat of the stationary air inlet pipe, thereby increasing the dynamic pressure, and greatly reduces the static pressure at the gap. The unidirectional flow characteristics of the Tesla valve are particularly effective for helium with high density and low viscosity, thereby further reducing the leakage rate compared to a labyrinth seal.

Description

Technical Field

[0001] The present invention relates to the field of high-temperature superconducting motors, and in particular to a helium transmission sealing structure based on a Tesla valve structure. Background Art

[0002] In a high-temperature superconducting motor, the helium transmission device transmits helium from the stationary refrigerator integrated device to the rotating rotor. The helium circulates in a closed pipeline. The helium transmission device must have good sealing, high transmission efficiency, high pressure resistance and low heat leakage. It is a key equipment in the high-temperature superconducting motor.

[0003] After years of development, the existing helium transmission device has been improved and developed based on the non-contact mechanical sealing structure. Structures combining nozzles based on the jet principle with a maze and nozzles based on the jet principle with a honeycomb have been developed. While ensuring the leakage rate, the difficulty of processing and assembly is greatly reduced, and the engineering process of high-temperature superconducting motors is accelerated, such as the Chinese patent CN109742922A.

[0004] This structure increases the flow velocity at the throat of the stationary intake manifold, thereby increasing the dynamic pressure. This altered pressure distribution ensures that the vast majority of the helium flows directly into the motor to cool the magnets, while a small portion flows into the sealing gap, where it is then sealed by the labyrinth seal structure for secondary sealing. However, this combined structure has its drawbacks. Because a high velocity is required to produce the jet effect, and the airway throat dimensions are designed based on the rated flow rate, a stable seal leakage rate cannot be guaranteed when the helium flow rate varies widely. Summary of the Invention

[0005] The present invention proposes a helium transmission sealing structure for a high-temperature superconducting motor, which solves the problems existing in the existing helium transmission sealing structure for a high-temperature superconducting motor.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a helium transmission sealing structure for a high-temperature superconducting motor, comprising a stationary air inlet pipe for connecting to a refrigerator, a rotating air inlet pipe for transporting refrigerant to the superconducting motor, and a return air pipe for returning the heated refrigerant to the refrigerator, wherein the stationary air inlet pipe and the rotating air inlet pipe are connected and form a convergent-divergent nozzle flow channel at the connection, the stationary air inlet pipe has a tapered shape and forms an outlet throat with a small diameter, the rotating air inlet pipe has an inlet portion with a tapered and divergent shape, the stationary air inlet pipe is inserted into the inlet portion, the diameter of the outlet throat of the stationary air inlet pipe is 0.5 to 0.6 times the diameter of the rotating air inlet pipe, the stationary air inlet pipe and the return air pipe are connected. A vacuum sandwich tube for heat insulation is provided between the air pipes, and a magnetic fluid sealing device consisting of a rotating part and a stationary part is provided on the outer wall of the vacuum sandwich tube. The rotating part is connected to the return air pipe, and the stationary part is connected to the vacuum sandwich tube. The rotating part and the stationary part are positioned by bearings. A Tesla valve sealing structure for isolating the intake and return air is provided in the fluid area of ​​the zoom nozzle flow channel. The Tesla valve sealing structure consists of an outer ring and an inner ring, and is 3D printed using low-temperature resistant aluminum alloy or stainless steel. A plurality of arc-shaped depressions are provided on the outer surface of the inner ring in the circumferential direction, and a plurality of arc-shaped depressions are processed on the inner surface of the outer ring in the circumferential direction. The arc-shaped depressions of the inner and outer rings are staggered.

[0007] The helium transmission sealing structure of the high-temperature superconducting motor has strict requirements on the shape angle and staggered distance of the arc-shaped recesses. The arc-shaped recesses have an incidence angle α of 40 to 50 degrees, the number of groups is more than 4, the staggered distance L is 0.2 mm, the dynamic and static gap H is less than 1 mm, and the hook angle β is less than 10 degrees. Other parameters can be adjusted according to actual needs.

[0008] The helium transmission sealing structure of the high-temperature superconducting motor has an outer ring welded to the rotating air inlet pipe of the stainless steel light tube, and an inner ring welded to the stationary air inlet pipe of the stainless steel light tube, and then the inner surfaces of the inner and outer rings at the gap are finely processed.

[0009] The technical solution adopted by the present invention for the helium transmission rotary seal of the superconducting motor has the following advantages and improvements compared with previous and existing sealing structures.

[0010] First, the present invention combines the jet and Tesla valve unidirectional flow principles without changing the topological structure of the existing superconducting motor helium transmission rotary seal, and proposes a nozzle and Tesla valve structure. The nozzle increases the flow velocity at the throat of the static intake pipe, thereby increasing the dynamic pressure, and greatly reduces the static pressure at the gap. The unidirectional flow characteristics of the Tesla valve are particularly effective for helium with high density and low viscosity, thereby further reducing the leakage rate compared to the labyrinth seal, and the leakage rate is further reduced from 5% to 2% under the same working conditions and dimensions.

[0011] Secondly, a more important advantage of the present invention is that it can maintain a low leakage rate even when the helium flow rate varies widely. At higher flow rates, the nozzle's jet effect is obvious, and the main role of the seal depends on the nozzle. At low flow rates, the nozzle's jet effect weakens, and the main role of the seal depends on the one-way flow characteristics of the Tesla valve structure. At a helium flow rate of 5 to 12 m / s, the leakage rate is still low. 3 / h range, the leakage rate can be maintained at about 2%, which solves the problem of difficulty in ensuring a low leakage rate under changing working conditions and lays a good foundation for the practical application of high-temperature superconducting motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the external structure of the present invention;

[0013] Figure 2 Schematic diagram of the internal structure of the present invention;

[0014] Figure 3 for Figure 2 A partial enlarged view of the ABC part;

[0015] Figure 4 An exploded view of the dynamic and static components of the present invention;

[0016] Figure 5 This is a fluid area parameter diagram of the Tesla valve structure of the present invention.

[0017] Explanation of the marks in the figure: 1—static air intake pipe, 2—rotating air intake pipe, 3—return air pipe, 4—vacuum sandwich pipe, 5—magnetic fluid sealing device, 5.1—rotating part, 5.2—static part, 6.1—outer ring, 6.2—inner ring. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementations.

[0019] like Figure 1 、 Figure 2 and Figure 3As shown, the present invention utilizes the unidirectional flow characteristics of the Tesla valve and the nozzle jet principle to disclose a helium transmission seal structure for a high-temperature superconducting motor. The structure comprises a stationary inlet pipe 1, a rotating inlet pipe 2, a return pipe 3, a vacuum sandwich pipe 4, a magnetic fluid seal device 5 comprising a rotating portion 5.1 and a stationary portion 5.2, and a Tesla seal structure comprising an outer ring 6.1 and an inner ring 6.2. The rotating portion 5.1 of the magnetic fluid seal device 5 is connected to the rotating return pipe 3, while the stationary portion 5.2 is connected to the stationary vacuum sandwich pipe 4. The diameter of the outlet throat of the stationary inlet pipe 1 is 0.5 to 0.6 times the diameter of the rotating inlet pipe 2. The rotating portion 5.1 and the stationary portion 5.2 of the magnetic fluid seal device 5 are positioned together by a bearing. The outer wall of the stationary inlet pipe 1 is designed with a pipeline similar to the return pipe 3. The vacuum sandwich pipe 4 is provided on the upper and lower inner walls of the pipeline. The magnetic fluid seal device 5 is also provided on the outer wall of the vacuum sandwich pipe 4. The operating principle of the magnetic fluid seal device 5 can be found in Chinese Patent CN109742922A.

[0020] Helium gas flows from the cryogenic refrigerator through the stationary inlet pipe 1 into the rotating inlet pipe 2, which then flows into the superconducting motor, cooling the superconducting magnet. After being heated, the gas returns to the refrigerator through the return pipe 3 and other circuits for further cooling. The rotating inlet pipe 2 and return pipe 3 are insulated by a vacuum interlayer tube 4, and the inlet and return gases are isolated by a Tesla seal at the stationary and rotating connection. With the Tesla seal in place, the return gas and any leaks from the Tesla seal are almost completely isolated from the outside world by a magnetic fluid seal 5.

[0021] The fluid channel formed by the stationary intake pipe 1 and the rotating intake pipe 2 is in the shape of a convergent nozzle. This structure increases the flow velocity at the throat and thus the dynamic pressure, and greatly reduces the static pressure. The changed pressure distribution ensures that most of the helium directly flows into the motor for magnet cooling, and a small part of the helium flows into the sealing gap. After secondary sealing through the Tesla sealing structure, the sealing effect can be enhanced.

[0022] like Figure 4 As shown, the static intake pipe 1 is tapered, and the outer wall of the static intake pipe 1 is welded with a Tesla seal structure made of low-temperature resistant stainless steel or aluminum alloy. This combined structure can maintain a low leakage when the relative rotation gap is 1mm, and at the same time, when the helium flow rate is 5-12m 3 / h variation range, when the gap is 0.6mm, the leakage rate is about 2%.

[0023] The outer ring 6.1 and the inner ring 6.2 are made of low-temperature resistant aluminum alloy or stainless steel by 3D printing. The outer surface of the inner ring 6.2 is provided with a plurality of arc-shaped depressions in the circumferential direction, and the inner surface of the outer ring 6.1 is processed with a plurality of arc-shaped depressions in the circumferential direction. The arc-shaped depressions of the inner and outer rings are staggered. The shape, angle and staggered distance of the arc-shaped depressions have strict requirements, such as Figure 5 As shown, the arc-shaped recesses have an angle of incidence α of 40-50°, are in four or more groups, have an offset distance L of 0.2mm, a dynamic / static clearance H of less than 1mm, preferably 0.6mm (to ensure a low leakage rate within 1mm), and a hook angle β of less than 10°. Other parameters can be adjusted according to actual needs. The outer ring 6.1 is welded to the rotating intake pipe 2 of the stainless steel smooth tube, and the inner ring 6.2 is welded to the stationary intake pipe 1 of the stainless steel smooth tube. The inner surfaces of the inner and outer rings at the gap are then fine-machined.

[0024] Through experimental testing, it was found that only when the helium flow rate exceeds a certain level (10m 3 / h), the leakage rate will decrease, and when it is lower than 10m 3 When the flow rate is less than 1000 / h, the labyrinth seal alone creates a seal. To ensure installation, the labyrinth seal gap is larger, resulting in a higher leakage rate. The throat of the trachea that produces the jet effect is fixed in size and designed based on the rated flow rate. Therefore, when the helium flow rate varies widely, a stable sealing leakage rate cannot be guaranteed.

[0025] Compared with patent CN109742922A, the difference between the present invention and the patent CN109742922A is that the labyrinth seal component is replaced with a Tesla valve sealing structure. The unidirectional flow characteristics of the Tesla valve structure make it significantly better than the labyrinth seal under the same sealing gap. After testing, it was found that the structure of the present invention has a better sealing performance at a helium gas flow rate of 5 to 12 m 3 / h, the leakage rate can be maintained at about 2%, which is of great significance for the application of high-temperature superconducting motors in engineering. Therefore, the nozzle structure based on the jet principle and the Tesla seal structure of the present invention can ensure that the existing superconducting motor helium transmission rotary seal topology is not changed, and the helium flow rate is between 5 and 12m 3 When the flow rate changes within the range of / h, the leakage rate always remains below 2%.

[0026] The invention solves the problem that the existing high-temperature superconducting motor helium transmission sealing structure cannot always maintain low leakage when the helium flow rate varies over a large range; and solves the problem of high processing difficulty caused by reducing the sealing gap.

[0027] The nozzle structure generates a jet at a higher helium flow rate, which increases the dynamic pressure of the gas in the intake pipe and greatly reduces the static pressure at the gap, but the effect is not obvious at low flow rates; the Tesla valve structure has a one-way flow characteristic, which is particularly suitable for sealing low-temperature helium with low viscosity and high density. Therefore, after passing through the first-stage nozzle structure, the low leakage rate of helium is guaranteed at high flow rates. The second-stage Tesla valve sealing structure ensures the low leakage rate of the system when the nozzle fails at low helium flow rates. This structure is easy to manufacture and has been process-verified, providing support for the engineering application of high-temperature superconducting motors.

[0028] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A helium transmission sealing structure for a high-temperature superconducting motor, comprising a stationary air inlet pipe (1) for connecting to a refrigerator, a rotating air inlet pipe (2) for conveying a refrigerant to the superconducting motor, and a return air pipe (3) for conveying the heated refrigerant back to the refrigerator, wherein the stationary air inlet pipe (1) and the rotating air inlet pipe (2) are connected and form a convergent nozzle flow channel at the connection, the stationary air inlet pipe (1) has a tapered shape and forms an outlet throat with a small diameter, the rotating air inlet pipe (2) has an inlet portion with a tapered and divergent shape, and the stationary air inlet pipe (1) is inserted into the inlet The diameter of the outlet throat of the static air inlet pipe (1) is 0.5 to 0.6 times that of the rotating air inlet pipe (2). A heat-insulating vacuum sandwich pipe (4) is provided between the static air inlet pipe (1) and the return air pipe (3). The outer wall of the vacuum sandwich pipe (4) is provided with a magnetic fluid sealing device (5) consisting of a rotating part (5.1) and a static part (5.2). The rotating part (5.1) is connected to the return air pipe (3), and the static part (5.2) is connected to the vacuum sandwich pipe (4). The rotating part (5.1) and the static part (5.2) are positioned by bearings. The invention is characterized in that: The convergent-convergent nozzle flow channel is provided with a Tesla valve sealing structure for isolating the intake and return air. The Tesla valve sealing structure is composed of an outer ring (6.1) and an inner ring (6.2), and is made of aluminum alloy or stainless steel. The outer surface of the inner ring (6.2) is provided with a plurality of arc-shaped depressions in the circumferential direction, and the inner surface of the outer ring (6.1) is processed with a plurality of arc-shaped depressions in the circumferential direction. The arc-shaped depressions on the inner ring (6.2) and the arc-shaped depressions on the outer ring (6.1) are staggered. The arc-shaped depressions have an incidence angle of 40 to 50 degrees, are in groups of four or more, have a staggered distance of 0.2 mm, a dynamic clearance of less than 1 mm, and a hook angle β of less than 10 degrees.

2. The helium transmission sealing structure of a high-temperature superconducting motor according to claim 1, characterized in that: The outer ring (6.1) is welded to the rotating air inlet pipe (2) of the stainless steel light tube, and the inner ring (6.2) is welded to the stationary air inlet pipe (1) of the stainless steel light tube.

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