Dewar structure of superconducting motor based on dryness monitoring to realize quench early warning

Abstract

The application discloses a superconducting motor Dewar structure based on dryness monitoring to realize quench early warning, which comprises a Dewar body, wherein the Dewar body is provided with a Dewar outer wall and a Dewar inner wall, the Dewar body is sealed through a left end cover and a right end cover at two ends thereof respectively, the lower part of the left end cover is provided with a liquid nitrogen inlet, the upper part of the right end cover is provided with a liquid nitrogen outlet, the Dewar inner wall is uniformly provided with a plurality of superconducting coils along the circumferential direction thereof, and the inner side of the Dewar outer wall is provided with a probe mounting hole and a dryness monitor optical fiber; the superconducting motor Dewar structure is combined with the dryness monitor, the dryness of each measuring point is measured to realize real-time monitoring on the quench condition of the Dewar, and the superconducting motor Dewar structure has the advantages of strong real-time performance, high sensitivity and simple and reliable structure.

Description

Technical Field

[0001] This invention relates to a superconducting motor Dewar structure for quenching early warning based on dryness monitoring, and relates to the field of superconducting motor technology. Background Technology

[0002] The armature winding of a superconducting motor is made of superconducting material. Thanks to the high current-carrying capacity and low loss characteristics of superconducting materials, superconducting motors can achieve higher power density and efficiency compared to conventional motors. The superconducting winding must operate below the superconductor's critical temperature to function properly; therefore, a cooling system must be designed into the superconducting motor to cool the winding and remove the heat load caused by AC losses and system leakage, preventing quench failure. Currently, superconducting windings using high-temperature superconducting materials are generally cooled by atmospheric pressure liquid nitrogen. This cooling method maintains the superconducting winding temperature at around 77K, and the heat load generated by AC losses and system leakage is carried away by the flowing liquid nitrogen.

[0003] A common practice for cooling the stator superconducting winding is to immerse the superconducting winding in liquid nitrogen within a Dewar flask. When using a horizontal Dewar flask, the liquid nitrogen flows in from the lower side and out from the upper side. The problem with this method is that the top of the Dewar flask is often not fully immersed in liquid nitrogen, and the liquid nitrogen at the top reaches a relatively high temperature after heat exchange, which can easily cause the coil to lose quench. Furthermore, localized quenching in the coil can lead to rapid temperature rise, causing positive feedback that results in a surge in coil resistance, preventing the superconducting motor from operating normally.

[0004] When the coil is working normally, a small amount of heat will be generated inside the Dewar due to AC loss and heat leakage from the Dewar, and a small amount of liquid nitrogen will vaporize. When the coil fails to quench, the local resistance will increase significantly, the coil will generate a large amount of heat, and a large amount of liquid nitrogen will vaporize. Summary of the Invention

[0005] This invention provides a superconducting motor Dewar structure based on dryness monitoring to achieve quench warning, thereby overcoming the defect of the coil in the existing superconducting motor Dewar structure being prone to quench.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] This invention discloses a superconducting motor Dewar structure for quenching early warning based on dryness monitoring, comprising a Dewar body, an outer wall and an inner wall, and a left and right end cap at each end. The lower part of the left end cap has a liquid nitrogen inlet, and the upper part of the right end cap has a liquid nitrogen outlet. The inner wall of the Dewar is evenly distributed with several superconducting coils along its circumference. The inner side of the outer wall of the Dewar is provided with a probe mounting hole and a dryness monitoring fiber.

[0008] Furthermore, the outer wall of the Dewar includes an outer Dewar outer wall and an inner Dewar outer wall that cooperate with each other; the inner wall of the Dewar includes an inner Dewar inner wall and an outer Dewar inner wall that cooperate with each other.

[0009] Furthermore, the probe mounting hole is located on the outer wall of the inner Dewar layer, and a hub is provided between the outer wall of the outer Dewar layer and the outer wall of the inner Dewar layer, where the optical fiber of the dryness monitor is installed.

[0010] Furthermore, the left end cap includes a left outer end cap and a left inner end cap that cooperate with each other; the right end cap includes a right inner end cap and a right outer end cap that cooperate with each other.

[0011] Furthermore, the probe mounting hole is a rotating body, and the dryness monitor probe is matched with the step of the probe mounting hole. The axis of each dryness monitor probe is in the same plane as the Dewar axis for fixing and sealing. The axis of the probe mounting hole forms an angle α with the wall surface, with the angle ranging from 15.0° to 25.8°. Four dryness monitor probes are evenly arranged in the circumference as a group, and several groups are arranged along the axial direction.

[0012] Furthermore, the optical fiber of the dryness monitor is connected to the dryness monitor probe. The optical fibers connected to the dryness monitor probes at the same position in the circumference of each group of dryness monitor probes are integrated into a bundle by a hub tube and pass through the countersunk hole on the right outer end cover. The hub tube adopts a stepped structure to cooperate with the countersunk hole for fixation and sealing.

[0013] Furthermore, the empirical relationship for the axial position L of the probe mounting hole of the dryness monitor in each group is as follows:

[0014]

[0015] Where L is the axial distance between the mounting hole of a certain group of probes of the dryness monitor and the front end of the superconducting coil. When L is not a rational number, it is retained to one decimal place. n is the probe group number from left to right, and S is the axial length of the superconducting coil.

[0016] The beneficial effects achieved by this invention are: the superconducting motor Dewar structure is combined with a dryness monitor, and the Dewar quenching situation is monitored in real time based on the dryness measured at each measuring point. It has the advantages of strong real-time performance, high sensitivity, and simple and reliable structure. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This is a schematic diagram of the structure of the present invention;

[0019] Figure 2This is a side view schematic diagram of the present invention.

[0020] In the diagram: 1. Left outer end cap; 2. Left inner end cap; 3. Inner wall of the inner Dewar layer; 4. Inner wall of the outer Dewar layer; 5. Outer wall of the inner Dewar layer; 6. Outer wall of the outer Dewar layer; 7. Probe mounting hole; 8. Liquid nitrogen inlet; 9. Liquid nitrogen outlet; 10. Fiber optic cable for the dryness monitor; 11. Hub; 12. Right inner end cap; 13. Right outer end cap; 14. Superconducting coil. Detailed Implementation

[0021] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0022] Example 1

[0023] like Figures 1-2 As shown, a superconducting motor Dewar structure for quenching warning based on dryness monitoring includes a Dewar body, which has an outer wall and an inner wall. The Dewar body is sealed by a left end cap and a right end cap at both ends. The lower part of the left end cap has a liquid nitrogen inlet 8, and the upper part of the right end cap has a liquid nitrogen outlet 9. Several superconducting coils 14 are evenly distributed along the circumference of the inner wall of the Dewar. The inner side of the outer wall of the Dewar has a probe mounting hole 7 and a dryness monitor optical fiber 10.

[0024] The probe mounting hole 7 is located on the outer wall 5 of the inner Dewar layer, and a hub 11 is provided between the outer wall 6 of the outer Dewar layer and the outer wall 5 of the inner Dewar layer, in which the optical fiber 10 of the dryness monitor is installed.

[0025] The outer wall of the Dewar includes an outer Dewar outer wall 6 and an inner Dewar outer wall 5 that fit together.

[0026] The inner wall of the Dewar includes an inner Dewar inner wall 3 and an outer Dewar inner wall 4 that fit together.

[0027] The left end cap includes a left outer end cap 1 and a left inner end cap 2 that cooperate with each other;

[0028] The right end cap includes a right inner end cap 12 and a right outer end cap 13 that cooperate with each other.

[0029] The liquid nitrogen inlet 8 is located at the bottom of the left end cap, through which liquid nitrogen flows in; the liquid nitrogen outlet 9 is located at the top of the right end cap, through which liquid nitrogen and nitrogen gas generated by heating flows out. This design allows liquid nitrogen to fill the entire Dewar, ensuring that the entire Dewar remains at a low temperature.

[0030] The probe mounting hole 7 of this invention is a rotating body, such as... Figure 1As shown in the enlarged view on the left, the probe shape includes a hemispherical top and a small and a large cylinder to fit into the countersunk hole. After complete assembly, the probe mounting hole 7 is fixed and sealed with ultra-high vacuum sealant to fill the entire countersunk hole. The probes of the dryness monitor are arranged on the outer wall of the inner Dewar, with four probes evenly arranged in groups of four in the four directions of up, down, left, and right around the perimeter, and multiple groups of probes arranged along the axial direction. The probes are positioned with the countersunk hole structure on the wall and seal the inner Dewar and vacuum layer within the countersunk hole. To ensure the normal operation of the dryness monitor fiber 10, the radius of curvature of the fiber 10 is required to be greater than 50mm. However, according to the design of the Dewar structure, the height of the vacuum layer is generally less than 50mm. Therefore, the probe is installed obliquely on the outer wall of the inner Dewar in the normal plane of the Dewar, so that the probe-connected dryness monitor fiber 10 passes through the vacuum layer, extends to the outer end cap in the normal plane, and exits from the outer Dewar end cap. The optical fiber 10 of the dryness monitor connected to the probes at the same circumferential position in each group of probes is fixed with a hub tube 11, passes through the same countersunk hole of the Dewar end cap, and is fixed and sealed.

[0031] The axis of the probe mounting hole 7 forms an angle α with the wall surface, and the angle ranges from 15.0° to 25.8°.

[0032] The empirical relationships for the axial positions L of each group of probes are as follows:

[0033]

[0034] Where L is the axial distance between the mounting hole 7 of a certain group of probes of the dryness monitor and the front end of the superconducting coil 14 (L is not a rational number and is rounded to one decimal place), n is the probe group number from left to right, and S is the axial length of the superconducting coil 14 (S is 100mm in this example).

[0035] Based on this formula, the dryness values ​​measured by the probe mounting holes 7 at various axial positions of the superconducting motor Dewar under normal operating conditions can be obtained, and the trend is that the dryness gradually increases along the axial direction.

[0036] It should be noted that: 1. Under normal working conditions, the vaporization of liquid nitrogen in the Dewar mainly comes from AC loss and a small amount of heat leakage. The amount of vaporization is very small. Therefore, the dryness values ​​measured by the probes at various locations are small. However, when the superconducting coil 14 experiences local quench, a large amount of heat will be generated, and the amount of vaporization will increase dramatically. Therefore, the above relationship does not hold under the quench state. It is only necessary to set the maximum dryness threshold.

[0037] 2. The formula is derived on the premise that the supercooling of liquid nitrogen is not considered (which is negligible compared to the latent heat of vaporization), the volume change after vaporization is not considered, and the superconducting coil 14 is regarded as a hollow cylinder with uniform heating. These simplifications do not affect the sensitivity and accuracy of quench detection.

[0038] 3. The liquid nitrogen-nitrogen gas two-phase flow pattern inside the Dewar is complex. Therefore, four probes are evenly arranged in the circumference to take the average dryness value to ensure the accuracy of dryness monitoring.

[0039] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The terminology used in the description of this application is only for describing specific embodiments and is not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings indicate similar items, and therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0040] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0041] It should be noted that in the description of this application, the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

Claims

1. A superconducting motor Dewar structure for quenching early warning based on dryness monitoring, characterized in that, The device includes a Dewar body, which has an outer wall and an inner wall. The Dewar body is sealed by a left end cap and a right end cap at both ends. The lower part of the left end cap has a liquid nitrogen inlet, and the upper part of the right end cap has a liquid nitrogen outlet. The inner wall of the Dewar has several superconducting coils evenly distributed along its circumference. The inner side of the outer wall of the Dewar has a probe mounting hole and a dryness monitor fiber.

2. The superconducting motor Dewar structure for quenching early warning based on dryness monitoring according to claim 1, characterized in that, The outer wall of the Dewar includes an outer Dewar wall and an inner Dewar wall that fit together; the inner wall of the Dewar includes an inner Dewar wall and an outer Dewar wall that fit together.

3. The superconducting motor Dewar structure for quench warning based on dryness monitoring according to claim 2, characterized in that, The probe mounting hole is located on the outer wall of the inner Dewar layer, and a hub is provided between the outer wall of the outer Dewar layer and the outer wall of the inner Dewar layer, where the optical fiber of the dryness monitor is installed.

4. The superconducting motor Dewar structure for quench warning based on dryness monitoring according to claim 1, characterized in that, The left end cap includes a left outer end cap and a left inner end cap that cooperate with each other; the right end cap includes a right inner end cap and a right outer end cap that cooperate with each other.

5. The superconducting motor Dewar structure for quenching early warning based on dryness monitoring according to claim 3, characterized in that, The probe mounting hole is a rotating body, and the dryness monitor probe mates with the step of the probe mounting hole. The axis of each dryness monitor probe is in the same plane as the Dewar axis for fixation and sealing. The axis of the probe mounting hole forms an angle with the wall surface. α The angle range is between 15.0° and 25.8°. Four dryness monitoring probes are evenly arranged in the circumference as a group, and several groups are arranged along the axis.

6. The superconducting motor Dewar structure for quench warning based on dryness monitoring according to claim 3, characterized in that, The optical fiber of the dryness monitor is connected to the dryness monitor probe. The optical fibers connected to the dryness monitor probes at the same position in the circumference of each group of dryness monitor probes are integrated into a bundle by a hub tube and pass through the countersunk hole on the right outer end cover. The hub tube adopts a stepped structure to cooperate with the countersunk hole for fixation and sealing.

7. The superconducting motor Dewar structure for quench warning based on dryness monitoring according to claim 5, characterized in that, Axial position of the probe mounting hole of each group of dryness monitors L The empirical formula is as follows: in, L The axial distance between the mounting holes of a certain group of probes in the dryness monitor and the front end of the superconducting coil is given by the following formula: L If the number is not rational, retain one decimal place. n The probe groups are numbered from left to right. S denoted as axial length of the superconducting coil.

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