Non-magnetic dewar for aerospace

Abstract

The application discloses a non-magnetic Dewar for aviation and relates to the technical field of aviation full-tensor magnetic gradient measurement. The non-magnetic Dewar comprises a straight-cylinder-shaped shell and an inner container arranged in the shell; a vacuum interlayer is formed between the shell and the inner container; a vacuum-pumping valve is arranged on the top of the shell and communicates with the vacuum interlayer; a glue-rich layer is arranged on the inner wall of the vacuum interlayer; the shell and the inner container are made of epoxy glass steel material; and the glue-rich layer is made of a mixed material of resin and low permeability. The non-magnetic Dewar is made of epoxy glass steel non-magnetic material, has the advantages of non-magnetic interference, high heat preservation, automatic liquid level maintenance and the like, can significantly reduce the volatilization rate of liquid nitrogen, and can fully meet the demand of uninterrupted area flight measurement operation of a high-temperature superconducting full-tensor magnetic gradient sensor system carried by a helicopter in the field on the premise that liquid nitrogen is supplemented once a day.

Description

Technical Field

[0001] This invention relates to the field of airborne full tensor magnetic gradient measurement technology, and in particular to an airborne non-magnetic Dewar. Background Technology

[0002] Airborne full-tensor magnetic gradient measurement technology, as an important tool in the field of geophysical exploration, is widely used due to its advantages such as strong practicality, wide applicability, and rich magnetic anomaly information. DC-SQUID superconducting quantum interference devices (DC-SQUIDs), with their superior magnetic sensitivity, are also widely used as sensors in magnetic measurement systems. Full-tensor magnetic gradient measurement systems based on DC-SQUID sensors have been extensively studied in countries such as Australia, Germany, and the United States, and are gradually being applied to geophysical exploration, military anti-submarine warfare, and unexploded ordnance detection. In high-temperature superconducting full-tensor magnetic gradient sensing systems, the non-magnetic Dewar serves to store liquid nitrogen, enabling the DC-SQUID magnetometer immersed in it to reach a superconducting state to complete magnetic measurements. The design of the non-magnetic Dewar is crucial to the safety and endurance of the airborne magnetic full-tensor magnetic gradient measurement system.

[0003] Existing non-magnetic dewars for aviation are susceptible to gas permeation in their vacuum interlayer, resulting in rapid vacuum decay and unstable thermal insulation. This leads to rapid liquid nitrogen evaporation and a gradual decrease in the liquid nitrogen level, making it difficult to sustain flight measurement operations for extended periods. The dewars require 2-3 stops per day to replenish liquid nitrogen, which is extremely inconvenient for field operations and wastes a significant amount of working time. Therefore, there is an urgent need to develop a non-magnetic dewar for aviation that is suitable for field operations, has good thermal insulation, and requires no continuous liquid nitrogen replenishment. Summary of the Invention

[0004] The main objective of this invention is to provide a non-magnetic Dewar for aviation applications to solve the aforementioned problems.

[0005] To achieve the above objectives, the present invention provides a non-magnetic Dewar for aviation, comprising a cylindrical outer shell and an inner liner disposed within the outer shell; a vacuum interlayer is formed between the outer shell and the inner liner; a vacuum valve communicating with the vacuum interlayer is disposed on the top of the outer shell; a resin-rich layer is disposed on the inner wall of the vacuum interlayer; both the outer shell and the inner liner are made of epoxy fiberglass material; the resin-rich layer is a mixture of resin and low-permeability material.

[0006] Furthermore, the adhesive-rich layer comprises, by mass fraction: 70% non-magnetic low-temperature epoxy resin, 12% nano-fumed silica, 10% hexagonal boron nitride, 8% ultrafine mica powder, and 25% by mass of low-temperature amine curing agent of non-magnetic low-temperature epoxy resin.

[0007] Furthermore, an insulation layer is provided on the outer wall of the inner liner.

[0008] Furthermore, the inner liner is provided with multiple layers of porous damping ring plates, the inner diameter of which is the same as the inner diameter of the neck of the inner liner.

[0009] Furthermore, the porous damping ring plate is made of epoxy fiberglass material.

[0010] Furthermore, a straight cylindrical component is provided below the neck of the inner liner, and there is a gap between the bottom of the straight cylindrical component and the bottom of the inner liner. The outer diameter of the straight cylindrical component is smaller than the lower inner diameter of the inner liner.

[0011] Furthermore, the cylindrical component is made of epoxy fiberglass material.

[0012] Furthermore, the inner wall of the cylindrical component is provided with multiple layers of porous damping ring plates, and the inner diameter of the porous damping ring plates is the same as the inner diameter of the neck of the inner liner.

[0013] Furthermore, the outer diameter of the outer shell is 260mm and the height is 700mm; the inner diameter of the neck of the inner liner is 130mm and the neck height is 205mm; the lower inner diameter of the inner liner is 192mm and the height is 441mm.

[0014] The present invention has the following beneficial effects: 1. This invention forms a sealed vacuum interlayer between the outer shell and the inner liner. Combined with a dense, adhesive-rich inner wall layer, this effectively inhibits the penetration of external gas molecules into the vacuum interlayer, maintaining a consistently high vacuum level over the long term. This significantly reduces heat conduction and convection within the interlayer, fundamentally slowing down the evaporation rate of liquid nitrogen and solving the problems of rapid vacuum decay and insulation failure associated with traditional Dewar flares. An additional insulation layer is added to the outer wall of the inner liner, forming a three-tiered insulation system with the vacuum interlayer and adhesive-rich layer. This system simultaneously blocks heat intrusion from three dimensions: the inner side of the liner, the interlayer space, and the inner wall penetration. The overall insulation efficiency is more than 40% higher than that of a single vacuum Dewar flare, further extending the effective operating time of liquid nitrogen and meeting the needs of long-term operation.

[0015] 2. The adhesive-rich layer is made of non-magnetic low-temperature epoxy resin, nano-fumed silica, hexagonal boron nitride, and ultrafine mica powder in precise mass fractions. After curing, it forms a continuous and dense barrier layer with extremely low gas permeability. It can also withstand the low temperature environment of liquid nitrogen at -196℃ without cracking, peeling, or powdering. It can maintain excellent airtightness even after long-term use, ensuring the long-term stability of the vacuum interlayer.

[0016] 3. The straight cylindrical design increases the storage height of liquid nitrogen inside the non-magnetic Dewar, reducing the evaporation area.

[0017] 4. The inner liner and the inner wall of the straight cylinder are both equipped with multi-layer porous damping ring plates. The inner diameter of the ring plates is consistent with the neck of the inner liner. This can effectively break up liquid nitrogen fluctuations and suppress liquid surface sloshing in the vibration environment of helicopter flight, and avoid the DC-SQUID magnetometer sensor from being partially exposed to the liquid surface due to violent fluctuations in the liquid surface, thus ensuring continuous and stable measurement.

[0018] 5. A gap is left between the straight cylindrical part and the bottom of the inner liner, and the outer wall and the inner wall of the inner liner form an annular liquid storage space, constituting a communicating vessel structure; liquid nitrogen can be pre-stored during filling, and the pre-stored liquid nitrogen is pressed back into the straight cylindrical part by the pressure difference between the inside and outside during decompression, automatically raising and maintaining the internal liquid level, ensuring that the DC-SQUID magnetometer sensor is always immersed in liquid nitrogen, greatly extending the effective working time.

[0019] 6. The outer shell, inner liner, porous damping ring plate, and straight cylindrical parts of this invention are all made of epoxy fiberglass material. The material has extremely low magnetic susceptibility and does not contain any magnetic metal components. It will not cause magnetic interference to the DC-SQUID magnetometer sensor during airborne magnetic measurement, which can ensure the authenticity and accuracy of the full tensor magnetic gradient measurement data and significantly improve the measurement accuracy and system stability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a non-magnetic Dewar for aviation applications according to the present invention.

[0021] Figure 2 This is a schematic diagram of the insulation layer and porous damping ring plate structure of a non-magnetic Dewar for aviation applications according to the present invention.

[0022] Figure 3 This is a schematic diagram of the cylindrical structure of a non-magnetic Dewar for aviation applications according to the present invention.

[0023] Figure 4 This is a graph showing the change in liquid nitrogen level in the Dewar of this invention over time.

[0024] Among them, 1-inner liner; 2-outer shell; 3-vacuum jacket; 4-vacuum valve; 5-insulation layer; 6-porous damping ring plate; 7-straight cylinder. Detailed Implementation

[0025] To achieve the above objectives and effects, the technical means and structure adopted by the present invention will be described in detail with reference to the accompanying drawings, focusing on the features and functions of the preferred embodiments of the present invention.

[0026] Example 1

[0027] like Figure 1-2As shown, the present invention provides a non-magnetic Dewar for aviation, comprising a cylindrical outer shell 2 and an inner liner 1. The outer shell has an outer diameter of 260 mm and a height of 700 mm; the inner liner has an inner neck diameter of 130 mm and a neck height of 205 mm; the lower inner liner has an inner diameter of 192 mm and a height of 441 mm; a vacuum interlayer 3 is formed between the outer shell 2 and the inner liner 1, and a vacuum valve 4 is provided on the top of the outer shell 2, which can be used to evacuate the vacuum interlayer 3 to 0.01 Pa.

[0028] The inner wall of vacuum jacket 3 is coated with a rich adhesive layer, comprising, by mass fraction: 70% non-magnetic low-temperature epoxy resin, 12% nano-fumed silica, 10% hexagonal boron nitride, and 8% ultrafine mica powder. A low-temperature amine curing agent, comprising 25% of the epoxy resin mass, is added. After curing, a dense, low-permeability rich adhesive layer is formed, inhibiting gas molecule permeation, further enhancing the insulation performance of the Dewar valence and extending the continuous operating time of the DC-SQUID magnetometer.

[0029] The outer wall of the inner liner 1 is provided with an insulation layer 5 to further enhance the heat preservation effect.

[0030] To verify the thermal insulation performance of the non-magnetic Dewar after its design and fabrication were completed, thermal insulation performance tests were conducted on the Dewar.

[0031] First, the non-magnetic Dewar is evacuated and left to stand for three days. After three days, a small amount of liquid nitrogen is poured into the Dewar to slowly lower the internal temperature. Then, liquid nitrogen is gradually poured into the Dewar until the liquid level is close to the neck of the Dewar. Once the liquid level inside the Dewar returns to calm, the test can begin.

[0032] This test uses the height of the liquid nitrogen level in the Dewar flask from the bottom of the flask as a parameter, and involves continuous observation and measurement, with the test conducted and the liquid level height recorded every hour. Figure 4 The figure shown is the test result, namely the curve of the liquid nitrogen level in Dewar changing over time.

[0033] Depend on Figure 4 It is known that the initial liquid level inside the Dewar was 39.8 cm. As time progressed, the liquid nitrogen gradually evaporated, causing the liquid level to decrease and the evaporation rate to slow down, eventually reaching a near-uniform evaporation rate. After 8 hours, the liquid nitrogen level remained at 31.2 cm. When the probe with the DC-SQUID magnetometer sensor was fixed inside the Dewar, the topmost DC-SQUID magnetometer sensor was 21.5 cm from the bottom of the Dewar. Therefore, the test experiment proves that the thermal insulation performance of the designed and manufactured non-magnetic Dewar can ensure that all eight DC-SQUID magnetometer sensors in the high-temperature superconducting full-tensor magnetic gradient sensing system probe can operate continuously for at least 8 hours. Therefore, with liquid nitrogen replenished once a day, it can fully meet the needs of uninterrupted area-based flight measurement operations carried out by a helicopter in the field using the high-temperature superconducting full-tensor magnetic gradient sensing system.

[0034] Example 2

[0035] like Figure 2 As shown, unlike Example 1, the inner wall of the inner liner 1 is provided with multiple layers of porous damping ring plates 6. The porous damping ring plates 6 are made of epoxy fiberglass and have an inner diameter that is consistent with the inner diameter of the neck of the inner liner, so as to facilitate the installation of the DC-SQUID magnetometer sensor. By setting multiple layers of porous damping ring plates 6, the sloshing of liquid nitrogen during flight is suppressed, and the liquid surface is kept stable.

[0036] Example 3

[0037] like Figure 3 As shown, unlike Embodiment 1, a straight cylindrical component 7 is provided below the neck of the inner liner 1. The straight cylindrical component 7 is made of epoxy fiberglass, and there is a gap between its bottom and the bottom of the inner liner 1. Its outer diameter is smaller than the lower inner diameter of the inner liner 1, forming a communicating vessel structure.

[0038] When adding liquid nitrogen, the liquid nitrogen first enters the internal area of ​​the straight cylinder 7. As the addition proceeds, the liquid level gradually submerges the bottom of the straight cylinder 7. As the amount added increases, under the action of liquid pressure, some liquid nitrogen enters the gap between the lower inner wall of the inner liner 1 and the outer wall of the straight cylinder 7 through the gap at the bottom of the straight cylinder 7 and is stored therein.

[0039] During operation, the evaporation of liquid nitrogen causes the pressure inside the inner liner to rise, requiring decompression through the Dewar decompression tube. However, during decompression, only the internal pressure of the straight cylinder 7 is reduced, while the pressure between the outer wall of the straight cylinder 7 and the lower inner wall of the inner liner 1 is not reduced. Under the action of the pressure difference, the pre-stored liquid nitrogen is forced back into the straight cylinder 7, causing the liquid level inside the straight cylinder 7 to rise, effectively maintaining the immersion depth of the DC-SQUID magnetometer sensor and extending the continuous working time.

[0040] In this embodiment, the multi-layer porous damping ring plate 6 structure of Embodiment 2 can also be added. The difference is that the porous damping ring plate 6 is installed on the inner wall of the straight cylinder 7.

[0041] The above description is only a preferred embodiment of the present invention and not all embodiments. Anyone should know that structural changes made under the guidance of the present invention, and any technical solutions that are the same as or similar to the present invention, are within the protection scope of the present invention.

Claims

1. A non-magnetic Dewar for aviation, characterized in that, It includes a cylindrical outer shell and an inner liner disposed within the outer shell; a vacuum interlayer is formed between the outer shell and the inner liner; a vacuum valve communicating with the vacuum interlayer is provided on the top of the outer shell; a rich adhesive layer is provided on the inner wall of the vacuum interlayer; both the outer shell and the inner liner are made of epoxy fiberglass material; the rich adhesive layer is made of a mixture of resin and low-permeability material.

2. The non-magnetic Dewar for aviation as described in claim 1, characterized in that, The adhesive-rich layer comprises, by mass fraction: 70% non-magnetic low-temperature epoxy resin, 12% nano-fumed silica, 10% hexagonal boron nitride, 8% ultrafine mica powder, and 25% by mass of low-temperature amine curing agent of non-magnetic low-temperature epoxy resin.

3. A non-magnetic Dewar for aviation as described in claim 1 or 2, characterized in that, The outer wall of the inner liner is provided with a heat insulation layer.

4. The non-magnetic Dewar for aviation as described in claim 3, characterized in that, The inner liner is provided with multiple layers of porous damping ring plates, and the inner diameter of the porous damping ring plates is the same as the inner diameter of the neck of the inner liner.

5. The non-magnetic Dewar for aviation as described in claim 4, characterized in that, The porous damping ring plate is made of epoxy fiberglass material.

6. A non-magnetic Dewar for aviation as described in claim 1 or 2, characterized in that, A straight cylindrical component is provided below the neck of the inner liner, and there is a gap between the bottom of the straight cylindrical component and the bottom of the inner liner. The outer diameter of the straight cylindrical component is smaller than the lower inner diameter of the inner liner.

7. The non-magnetic Dewar for aviation as described in claim 6, characterized in that, The cylindrical component is made of epoxy fiberglass material.

8. The non-magnetic Dewar for aviation as described in claim 7, characterized in that, The inner wall of the cylindrical component is provided with multiple layers of porous damping ring plates, and the inner diameter of the porous damping ring plates is the same as the inner diameter of the neck of the inner liner.

9. The non-magnetic Dewar for aviation as described in claim 1, characterized in that, The outer diameter of the outer shell is 260mm and the height is 700mm; the inner diameter of the neck of the inner liner is 130mm and the neck height is 205mm; the lower inner diameter of the inner liner is 192mm and the height is 441mm.

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