A double-walled tube support structure and its control method

Abstract

This invention provides a double-walled pipe support structure and control method. The double-walled pipe consists of an inner pipe and an outer pipe coaxially sleeved outside the inner pipe. The double-walled pipe support structure includes a static pressure support structure positioned between the inner and outer pipes to provide air jet support for the outer wall of the inner pipe. The static pressure support structure includes an annular pipe for gas transmission and several air jet heads with adjustable intake volume. The annular pipe is axially sleeved around the outer circumference of the inner pipe and fixed to the inner wall of the outer pipe. The several air jet heads are arranged in a circumferential array and communicate with the annular pipe. Each air jet head radially jets air towards the outer wall of the inner pipe to form an air film, supporting and maintaining the coaxiality of the inner and outer pipes. This invention achieves non-contact support for the inner pipe by setting up a static pressure support structure, and by setting up an intermediate pipe, the outer pipe provides secondary protection and a safety shell for the interior. Non-contact support effectively reduces contact wear between the inner pipe and the support structure, improving the stability and safety of the double-walled pipe operation.

Description

Technical Field

[0001] This invention relates to the field of ship fuel supply, and more specifically, to a double-walled pipe support structure and control method. Background Technology

[0002] With the trend of green and low-carbon transformation of marine propulsion systems, LNG (liquefied natural gas), as a clean and efficient fuel, is widely used in the fuel storage and supply systems of marine main engines. Double-walled pipes, due to their core advantages of double-layer protection, leak prevention, and thermal insulation, are key transport components in marine LNG main engine fuel storage and supply systems. They are mainly used to safely transport cryogenic LNG from storage tanks to the main engine combustion chamber, with the inner pipe responsible for transporting the cryogenic LNG.

[0003] Existing technologies for LNG fuel transportation on ships impose stringent requirements on the support structure of double-walled pipes: On the one hand, the temperature of LNG medium is extremely low (usually -162℃), and the inner pipe is prone to shrinkage and deformation under low-temperature conditions. Rigid contact friction between the inner pipe and the support components must be strictly avoided to prevent friction from generating debris that contaminates the medium, damages the low-temperature protective layer of the inner pipe, or even causes the risk of LNG leakage. On the other hand, ships are subject to multiple external disturbances such as wind, waves, and engine vibration during navigation. It is necessary to ensure the central stability of the inner pipe under complex vibration conditions, prevent the inner pipe from shifting and colliding with the outer pipe, and at the same time accommodate the axial and radial displacement of the inner pipe caused by temperature changes and vibration to prevent stress concentration in the support from causing fatigue damage to the inner pipe.

[0004] Currently, the support method for LNG double-walled pipes in ships is still mainly the traditional contact support, with common structures including rigid bracket support, elastic pad support (such as polyurethane, PTFE material), and roller support. However, these contact support structures have significant drawbacks in the context of marine LNG applications: First, contact supports inevitably experience friction and wear, and materials such as elastic pads are prone to embrittlement and failure at low temperatures; simultaneously, frictional heat may be transferred to the inner pipe, causing a small amount of LNG vaporization inside the pipe, leading to pipeline pressure fluctuations and threatening system safety. Second, the fixed and rigid support points cannot adapt to the low-temperature contraction of the inner pipe, and the radial displacement of the inner pipe caused by multiple external disturbances such as wind, waves, and engine vibration during ship navigation.

[0005] Chinese Patent Application No. 202311122748.4 discloses a ventilation and gas double-wall pipe and a ship, comprising: an inner pipe having a gas passage; an outer pipe sleeved on the outside of the inner pipe, the inner and outer pipes forming a ventilation passage, one end of which is configured as an air inlet for air intake; a ventilation system connected to the other end of the ventilation passage for extracting gas from the passage; and a support member, one of the outer surface of the inner pipe and the inner surface of the outer pipe being connected to the support member, and the other of the outer surface of the inner pipe and the inner surface of the outer pipe forming a gap with the support member. This patent uses a support member between the inner and outer pipes as a support structure, with a gap between the support member and the inner or outer pipe to alleviate stress concentration between the inner and outer pipes.

[0006] The aforementioned patent achieves stress concentration between the inner and outer tubes by setting up a support structure. However, under normal conditions, the support does not contact the outer wall of the inner tube. This structure can only be considered as a protective structure when the inner tube undergoes a large displacement. At the same time, the pressure of the support is fixed, making it difficult to adapt to the complex working conditions during the dynamic navigation of ships, resulting in insufficient support accuracy and stability.

[0007] Therefore, improvements are needed to the existing structure to enhance the protection of the inner tube during use. Summary of the Invention

[0008] The main objective of this application is to provide a double-walled tube support structure and control method that can achieve jet-type static pressure support for the double-walled tube, while adjusting the local support pressure to address the radial displacement of the inner tube, so as to keep the inner and outer tubes always coaxial.

[0009] To achieve the above objectives, in a first aspect, this application provides a double-walled tube support structure, wherein the double-walled tube consists of an inner tube and an outer tube coaxially sleeved outside the inner tube. The double-walled tube support structure includes a hydrostatic support structure disposed between the inner tube and the outer tube to provide air jet support for the outer wall of the inner tube. The hydrostatic support structure includes an annular tube for transmitting gas and a plurality of air jet heads with adjustable air intake. The annular tube is axially sleeved around the outer circumference of the inner tube and fixed to the inner wall of the outer tube. The plurality of air jet heads are arranged in a circumferential array and communicate with the annular tube. Each air jet head sprays air radially toward the outer wall of the inner tube to form an air film, so as to support and keep the inner tube and the outer tube always coaxial.

[0010] By spraying air onto the outer wall of the inner tube, the inner tube maintains non-contact support during operation, reducing wear caused by friction between the inner and outer tubes and providing stability for the inner tube's operation. Furthermore, by setting an adjustable air intake nozzle, radial displacement of the inner tube can be compensated.

[0011] Optionally, the hydrostatic support structure further includes several baffles and several air intake pipes for transmitting and adjusting the air intake volume. The baffles are sealed inside the annular tube in a circumferential manner, dividing the interior of the annular tube into multiple independent chambers. The air intake pipes are connected to the chambers one by one, and each chamber is connected to at least one jet head. By setting multiple chambers inside the annular tube, the jet heads corresponding to different chambers can be adjusted accordingly. When the inner tube undergoes radial displacement, the force on the outer wall of the inner tube is indirectly adjusted by changing the air intake volume of the opposite chamber, thereby controlling the inner tube and the outer tube to always remain coaxial.

[0012] Optionally, the double-walled tube support structure further includes an intermediate tube axially sleeved between the inner tube and the outer tube. The annular tube is axially sleeved on the outer circumference of the inner tube and fixed to the inner wall of the intermediate tube. Each of the air inlet pipes passes through the intermediate tube and connects to the annular gap formed by the intermediate tube and the outer tube. Gas for air intake is continuously introduced into the annular gap. By setting the intermediate tube, a protective shell is added to the inner tube, and air is supplied to the air inlet pipe by introducing air between the intermediate tube and the outer tube.

[0013] Optionally, a limiting protection support structure is also provided on the outer periphery of the inner tube. The limiting protection support structure is fixed to the inner wall of the intermediate tube and connected to one side of the static pressure support structure. The limiting protection support structure has a support end facing the outer wall of the inner tube. The support end is closer to the outer wall of the inner tube than the air outlet of the jet head. When the radial displacement of the inner tube exceeds the effective compensation range of the static pressure support structure, the limiting protection support structure preferentially contacts the outer wall of the inner tube for support.

[0014] Optionally, the limiting protection support structure includes at least one pair of arc-shaped plates and support heads. The arc-shaped plates are symmetrically distributed and connected and fixed to the outer periphery of the annular tube. The support heads are detachably mounted on the arc-shaped plates and face the outer wall of the inner tube. The detachable support heads facilitate the replacement of support heads with different structures.

[0015] Secondly, this application provides a control method for a double-walled tube support structure according to any one of the first aspects, comprising: S1: By using sensors arranged in a circumferential array along the inner wall of the intermediate tube, the radial displacement information of the inner tube relative to the outer tube during operation is acquired in real time. S2: Determine the radial displacement direction of the inner tube based on the radial displacement information, and determine the opposite direction of the radial displacement direction as the compensation direction; S3: Calculate the target air intake volume of the chamber corresponding to the compensation direction based on the radial displacement information; S4: The controller calculates the target air intake volume of the chamber corresponding to the compensation direction and controls the gas to be introduced into the chamber corresponding to the compensation direction to match the target air intake volume. The jet head connected to the chamber sprays the gas onto the outer wall of the inner tube corresponding to the compensation direction, pushing the inner tube to move until it is coaxial with the outer tube.

[0016] By dynamically adjusting the air intake of the corresponding chamber based on the radial displacement information of the inner tube, and controlling the opening and closing of the air intake pipe of the corresponding chamber in the compensation direction to allow the corresponding air intake, the dynamic stability of the inner tube position is achieved, so that the inner tube and the outer tube are always coaxial.

[0017] Optionally, in step S1, the radial displacement information is obtained by real-time detection of the gap between the inner tube and the intermediate tube at different circumferential positions, and the accuracy of the data is ensured by detecting at different positions.

[0018] Optionally, the target air intake volume of the chamber corresponding to the compensation direction is calculated using the following formula: ; in, This represents the radial displacement of the inner tube. The effective working area of ​​the chamber. This is the conversion factor between radial displacement and radial restoring force. This is the conversion coefficient between intake volume and film pressure. To maintain the baseline intake volume of the basic static pressure support, a quantitative relationship between radial displacement and target intake volume is established, so that the target intake volume can change continuously with the magnitude of radial displacement, thereby achieving fine adjustment of the radial restoring force.

[0019] Optionally, the controller is electrically connected to an electronically controlled flow regulating valve installed on each intake pipe to control the intake air volume. In step S4, the controller controls the opening of the electronically controlled flow regulating valve of the intake pipe corresponding to the compensation direction of the chamber, and introduces the corresponding intake air volume into the current intake pipe according to the target intake air volume calculation result.

[0020] Optionally, the controller is installed on the outer wall of the outer tube and is one of an industrial controller, a programmable logic controller, an embedded controller, and a computing unit with data processing capabilities.

[0021] The present invention provides a double-walled pipe support structure and control method. Compared with the prior art, its advantages are as follows: The present invention, by setting a static pressure support structure between the inner and outer pipes and combining it with an intake volume control adjustment method based on radial displacement, not only provides jet support for the inner pipe, but also generates a radial restoring force pointing towards the center in the corresponding direction when the inner pipe undergoes radial displacement. This ensures that the inner pipe and the outer pipe remain coaxial during operation. At the same time, the set limit protection support structure mechanically limits the inner pipe in cases of insufficient static pressure support compensation or abnormal operating conditions, avoiding rigid contact between the inner and outer pipes and providing stability and safety for the operation of the double-walled pipe. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a partial explosion diagram of the present invention; Figure 3 This is a cross-sectional schematic diagram of the annular tube of the present invention; Figure 4 This is an enlarged schematic diagram of the hydrostatic support structure of the present invention; Figure 5 This is a schematic diagram of the limiting protection support structure of the present invention; Figure 6 This is a flowchart illustrating Embodiment 2 of the present invention.

[0023] Wherein: 1-inner tube, 2-middle tube, 3-outer tube, 4-static pressure support structure, 41-ring tube, 42-baffle, 43-jet head, 44-inlet pipe, 5-limiting protection support structure, 51-fixed column, 52-arc plate, 53-fixed seat, 54-fixed cylinder, 55-movable cylinder, 56-abutment plate. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0027] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0028] In addition, the term "multiple" should mean two or more.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] Example 1: like Figures 1 to 5 As shown, this embodiment provides a double-walled tube support structure, wherein the double-walled tube consists of an inner tube 1 and an outer tube 3 coaxially sleeved outside the inner tube 1. The double-walled tube support structure includes a middle tube 2, a static pressure support structure 4, and a limiting and protective support structure 5. The middle tube 2 is axially sleeved between the inner tube 1 and the outer tube 3. The static pressure support structure 4 is disposed on the inner wall of the middle tube 2, and its end faces the outer wall of the inner tube 1 for air jet support. The limiting and protective support structure 5 is fixed to the inner wall of the middle tube 2 and connected to one side of the static pressure support structure 4, while the support end used for support faces the outer wall of the inner tube 1.

[0031] In use, the static pressure support structure 4 is located on the outer periphery of the inner tube 1 to provide non-contact air jet support to the outer wall of the inner tube 1. When the inner tube 1 experiences abnormal displacement, the static pressure support structure 4 adjusts the pressure to restore it to normal. It should be noted that in this embodiment, the static pressure support structure 4 and the limiting protection support structure 5 are preferably set as two groups, each group including one static pressure support structure 4 and one limiting protection support structure 5, and each group is axially sleeved on the outside of the inner tube 1 near both ends.

[0032] refer to Figure 3 As shown, in this embodiment, the hydrostatic support structure 4 includes an annular tube 41 axially sleeved on the outer circumference of the inner tube 1. The annular tube 41 is a hollow tube with a plurality of jet heads 43 connected to its inner circumference. The jet heads 43 are preferably distributed in a circumferential array. The jet end of each jet head 43 is directed toward the outer wall of the inner tube 1. It should be noted that in this embodiment, each jet head 43 has a certain gap with the outer wall of the inner tube 1, and the gap is preferably 0.5~5mm.

[0033] refer to Figure 3 and Figure 4 As shown, in this embodiment, the interior of the annular tube 41 is sealed with baffles 42 along its axial direction. Preferably, there are four baffles 42, which divide the interior space of the annular tube 41 into four identical chambers along the circumferential direction. Each chamber is correspondingly and sealed with an air inlet pipe 44 and five jet heads 43. In this embodiment, the angle of every two adjacent jet heads 43 on the annular tube 41 is the same, and the jet ends of each jet head 43 are equidistant from each other and face the outer wall of the inner tube 1.

[0034] refer to Figure 3 As shown, in this embodiment, the intake pipe 44 is preferably connected to the upper, lower, left and right positions of the cross-section of the annular pipe 41. In addition, each intake pipe 44 in this embodiment is also connected to and installed with an electronically controlled flow regulating valve used in the prior art for flow regulation.

[0035] It should be noted that in this embodiment, the inner tube 1, the intermediate tube 2, and the outer tube 3 are arranged sequentially from the inside to the outside. The annular tube 41 is axially sleeved on the outer periphery of the inner tube 1 and fixed to the inner wall of the intermediate tube 2. The air inlet pipe 44 of the static pressure support structure 4 passes through the intermediate tube 2 and connects to the annular gap formed by the intermediate tube 2 and the outer tube 3. The air inlet pipe 44 and the tube wall of the intermediate tube 2 are sealed and welded together. Gas is continuously introduced into the annular gap formed by the intermediate tube 2 and the outer tube 3. The gas is preferably nitrogen or LNG vapor gas. By introducing nitrogen or LNG vapor gas into the annular gap, the gas supply to the air inlet pipe 44 is achieved.

[0036] In use, the air inlet pipe 44 continuously supplies gas synchronously to the four chambers of the annular pipe 41. The gas is sprayed out towards the outer wall of the inner pipe 1 through the five jet nozzles 43 corresponding to each chamber at a preset air intake volume. A uniform gas film is formed between the outer wall of the inner pipe 1 and the jet nozzles 43, realizing non-contact coaxial support between the inner pipe 1 and the static pressure support structure 4. This avoids wear caused by direct contact between the inner pipe 1 and the support structure, while reducing vibration transmission during LNG transportation and the evaporation of some LNG due to contact with the outer pipe.

[0037] refer to Figure 4 and Figure 5 As shown, in this embodiment, the limiting protection support structure 5 includes four arc-shaped plates 52, each of which is welded and fixed to the outer periphery of the annular tube 41 by a fixing column 51. The arc-shaped plates 52 fit the inner wall arc of the intermediate tube 2. In this embodiment, the arc-shaped plates 52 are in contact with and fixed to the inner wall of the intermediate tube 2. Each arc-shaped plate 52 has a fixing seat 53 welded to the arc-shaped surface facing the inner tube 1. The fixing seat 53 is equipped with a fixing cylinder 54 by welding technology in the prior art. A movable cylinder 55 is sleeved in the fixing cylinder 54. An abutment piece 56 is fixed to the end of the movable cylinder 55. The abutment piece 56 is also arc-shaped and is adapted to the outer wall of the inner tube 1.

[0038] In this embodiment, the abutment piece 56 faces the outer wall of the inner tube 1 with a gap. The gap between the abutment piece 56 and the outer wall of the inner tube 1 is smaller than the gap between the jet end of the jet head 43 and the outer wall of the inner tube 1. That is, the abutment piece 56 is closer to the outer wall of the inner tube 1 than the jet head 43.

[0039] It should be noted that a spring is provided in the fixed cylinder 54 in this embodiment. One end of the spring is fixed to the bottom of the fixed cylinder 54, and the other end is fixed to the movable cylinder 55. In order to enable the limiting protection support structure 5 to adapt to different stress requirements, the abutment piece 56 in contact with its end face can be flexibly replaced with a columnar abutment structure or a point abutment structure.

[0040] In normal use, the static pressure support structure 4 forms an air film through jetting to achieve non-contact support for the inner tube 1. At this time, the abutment piece 56 of the limiting protection support structure 5 maintains a preset small gap with the outer wall of the inner tube 1. The movable cylinder 55 is in the initial extended position inside the fixed cylinder 54, and the spring is in a naturally relaxed state. The overall limiting protection support structure 5 does not participate in the support work of the inner tube 1 and is only used as a backup protection component.

[0041] When the static pressure support structure 4 experiences a pressure loss fault (such as interruption of air supply or blockage of the jet head), or when the static pressure support structure 4 cannot withstand the pressure generated by abnormal offset, the limit protection support structure 5 will make contact with the outer wall of the inner tube 1. Since the arc shape of the abutment piece 56 is perfectly matched with the outer wall of the inner tube 1, a surface contact abutment can be formed, avoiding local stress concentration from causing scratches or deformation to the thin-walled inner tube.

[0042] As pressure is continuously applied to the inner tube 1, the abutment piece 56 pushes the movable cylinder 55 to contract inward along the axial direction of the fixed cylinder 54, compressing the spring inside the fixed cylinder 54. The elastic deformation of the spring can effectively buffer the impact kinetic energy of the inner tube 1, preventing the inner tube 1 from rigidly colliding with the hydrostatic support structure 4. At the same time, the four sets of circumferentially evenly distributed arc-shaped plates 52 and the abutment components can jointly limit the radial displacement range of the inner tube 1, preventing the inner tube 1 from colliding with the inner wall of the intermediate tube 2. In different application scenarios, the structural form of the abutment piece 56 can be flexibly changed according to the material strength of the inner tube 1 and the pressure fluctuation characteristics of the transported medium.

[0043] In use, the air intake in different directions is controlled according to the radial displacement of the inner tube 1. If the inner tube 1 shifts to one side, the air supply to the corresponding chamber of the end static pressure support structure 4 is increased, the jet intensity of the corresponding jet head 43 is increased, and the inner tube 1 is pushed back to its original position by the air film pressure difference. If the displacement of the inner tube 1 is small, the air supply to the corresponding chamber of the end static pressure support structure 4 is finely adjusted to reduce the risk of increased displacement, so as to always keep the inner tube 1, the annular tube 41, the intermediate tube 2 and the outer tube 3 coaxial.

[0044] Example 2: like Figures 1 to 6 As shown, based on Embodiment 1, this embodiment provides a control method for a double-walled tube support structure, including: S1: Sensors arranged in a circumferential array along the inner wall of the intermediate tube 2 are used to acquire, in real time, the radial displacement information of the inner tube relative to the outer tube during operation, specifically including: Multiple gap sensors are arranged in a circumferential array on the inner wall of the intermediate tube 2 near both ends. These sensors monitor the distance between the outer wall of the inner tube 1 and the inner wall of the intermediate tube 2. The gap is obtained by real-time detection of the gap between the inner tube 1 and the intermediate tube 2 at different circumferential positions. Taking four detection positions circumferentially opposite to each other on the inner tube 1 as an example, the gap data for the right side, left side, top side, and bottom side are obtained respectively, and are denoted as follows: , , and Based on the above gap data, the radial displacement components of inner tube 1 in the orthogonal direction are calculated as follows: ; ; The radial displacement of the inner tube can be calculated as follows: ; S2: Determine the radial displacement direction of the inner tube 1 based on the radial displacement information, and determine the opposite direction of the radial displacement direction as the compensation direction, specifically including: Based on the radial displacement component, the circumferential direction of the inner tube's radial displacement is determined, and its direction angle is obtained through the arctangent bivariate function: ; Because the compensation direction is the opposite direction of the radial displacement, that is: ; That is, the current angle direction is the compensation direction. The controller determines the chamber corresponding to the circumferential direction of the annular tube based on the compensation direction, and identifies the chamber as the target adjustment chamber.

[0045] S3: Calculate the target air intake volume of the chamber corresponding to the compensation direction based on the radial displacement information, specifically including: To determine the target air intake volume of the chamber corresponding to the compensation direction, it is first necessary to obtain the radial restoring force required for the inner tube 1 to return to coaxiality with the outer tube 3 in that compensation direction. For this purpose, let the radial restoring force be... It satisfies the following relationship: ; In this embodiment, the effective compensation range of the hydrostatic support is 0.1~5mm (small displacement) of the inner tube radial displacement. The radial restoring force of the gas film on the inner tube 1 is essentially the elastic support force of the gas. According to the small deformation theory of engineering mechanics, the elastic support force under small displacement is linearly proportional to the displacement. .

[0046] in, The conversion factor between radial displacement and radial restoring force is calculated using the following method for inner tube 1 under no-load conditions: Step 1: After the double-walled pipe is installed, keep inner pipe 1 unloaded (do not introduce LNG medium), and introduce the air intake volume of the foundation support into all chambers. This allows the inner tube 1 to be in a coaxial suspended state; Step 2: By controlling the electronically controlled flow regulating valve of the individual chamber through the controller, the air intake is gradually increased, so that the inner tube 1 produces a detectable small radial displacement Δr (0.1~1mm, which is detected in real time by the gap sensor). Step 3: According to the pressure-force formula in fluid mechanics By combining the air film pressure sensor of this technical solution to detect the pressure P and area S of each chamber when unloaded, the radial restoring force under this displacement is calculated. ; Step 4: Based on the linear relationship = Calculations yielded In this embodiment Preferred selection: 2002000 .

[0047] In this embodiment, since the radial restoring force is generated by the jet head in the chamber corresponding to the compensation direction, the relationship satisfies: ; in This represents the pressure generated in the corresponding chamber in the direction of compensation. This indicates the pressure generated in the corresponding chamber in other reference directions. This represents the effective area, and it also satisfies the following conditions under the jet head 43 structure and stable air supply: ; The pressure-intake volume relationship that the corresponding chamber in the compensation direction needs to satisfy is: = ( ); in This is the conversion coefficient between intake volume and film pressure. To compensate for the target air intake volume of the corresponding chamber. Regarding the air intake volume for basic support, in this embodiment, the gap between the jet head 43 and the outer wall of the inner tube 1 is preferably 0.5~5mm (effective gap for static pressure support). The gas supply medium is nitrogen or LNG vapor gas. Under this gap, the Reynolds number Re of the gas flow is <2300 (critical value for laminar flow), and the gas film flow is in a completely laminar state. According to the laminar flow theory of fluid mechanics, the gas intake volume and gas film pressure in the laminar state have a strictly linear relationship. This relationship is an inherent characteristic of laminar flow and satisfies... , Combining the above formulas, we get: ; Since the inner tube 1 and outer tube 3 are kept coaxial in each chamber during operation, the target intake volume of the chamber corresponding to the compensation direction can be obtained as follows: ; In this embodiment This indicates the effective air film area of ​​the chamber corresponding to the jet head 43 on the outer wall of the inner tube 1. , It was obtained through calculation, where Obtained through measurement.

[0048] in, Calculated directly using existing fluid dynamics formulas: ; in The number of jet heads 43 connected to this chamber. The exhaust area of ​​a single jet head 43 is given by the jet nozzle. ( (This refers to the inner diameter of the jet nozzle, which can be measured directly). The angle between the jet direction of the jet head 43 and the radial direction of the inner tube 1.

[0049] It should be noted that the conversion coefficient between intake volume and film pressure in this embodiment... Calculated using the following method: Step 1: Close the air supply to all chambers of inner tube 1, and supply air to only a single chamber, keeping the gap between the chamber and inner tube 1 at a fixed value (0.5~5mm). Step 2: Adjust the electronically controlled flow regulating valve via the controller to set different intake volumes. The preferred flow rate is 0.1~5L / min. After each intake flow rate stabilizes for 30 seconds, the air film pressure is detected by a pressure sensor installed on the intake pipe 44. ; Step 3: Based on the linear relationship of laminar flow theory Calculate the intake volume under different conditions Finally, the average value is taken, where 5002000 is preferred .

[0050] It should be noted that the air intake volume of the basic support in this embodiment is... Calculated using the following method: Step 1: After the double-walled tubes are installed on site, the inner tube 1 is unloaded, and the air intake is slowly increased synchronously to all chambers; Step 2: Monitor the status of inner tube 1 in real time using the set gap sensor. When inner tube 1 is exactly in a coaxial suspended state (gap equal in all directions, no contact), record the air intake at this time. This value is the air intake volume. In this embodiment Preferably 0.5~3 .

[0051] S4: Based on the target air intake volume calculation result of the chamber corresponding to the compensation direction, the controller controls the gas matching the target air intake volume to be introduced into the chamber corresponding to the compensation direction. The jet head 43, which is connected to the chamber, sprays the gas onto the outer wall of the inner tube 1 corresponding to the compensation direction, pushing the inner tube 1 to move until it is coaxial with the outer tube 3. Specifically: After the target intake volume is determined, the controller controls the opening of the electronically controlled flow regulating valve of the intake pipe 44 corresponding to the compensation direction, so that the chamber is filled with the target intake volume corresponding to the calculation result. The gas is injected onto the outer wall of the inner pipe 1 through the jet head 43 connected to the current chamber, generating a radial restoring force pointing towards the center on the outer wall of the inner pipe 1. Under the action of the radial restoring force, the inner pipe 1 is pushed to move. As the radial displacement of the inner pipe 1 gradually decreases, the inner pipe 1 and the outer pipe 3 become coaxial.

[0052] It should be noted that in this embodiment, the controller is installed on the outer wall of the outer tube 3, and the controller is communicatively or electrically connected to the gap sensor and the electronically controlled flow regulating valve. The sensor in this embodiment is preferably a fiber optic gap sensor or a capacitive gap sensor used in the prior art to meet the requirements of low temperature applications. The controller in this embodiment is preferably one of an industrial controller, a programmable logic controller, an embedded controller, and a computing unit with data processing capabilities, used for quantity calculation and air intake control. In this technical solution, the controller adopts the conventional PID closed-loop feedback algorithm in the field of industrial control, with the radial displacement Δr=0 of the inner tube 1 as the target value, and finely adjusts the air intake in real time.

[0053] Meanwhile, in this embodiment, as the radial displacement of the inner tube 1 decreases, the controller can correspondingly reduce the air intake of the chamber in the compensation direction, so that the radial restoring force gradually weakens. When the radial displacement of the inner tube 1 exceeds the effective compensation range of the static pressure film support, the limiting protection support structure 5 set on the outer periphery of the inner tube 1 contacts and limits the inner tube 1, thereby preventing the inner tube 1 from directly contacting the outer tube 3 under abnormal working conditions and improving the operational safety of the double-walled tube system.

[0054] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A double-walled tube support structure, wherein the double-walled tube consists of an inner tube (1) and an outer tube (3) coaxially sleeved outside the inner tube (1), characterized in that: The double-walled tube support structure includes a static pressure support structure (4) disposed between the inner tube (1) and the outer tube (3) to provide air jet support for the outer wall of the inner tube (1). The static pressure support structure (4) includes an annular tube (41) for transmitting gas and several air jet heads (43) with adjustable air intake. The annular tube (41) is axially sleeved on the outer circumference of the inner tube (1) and fixed to the inner wall of the outer tube (3). Several air jet heads (43) are arranged in a circumferential array and communicate with the annular tube (41). Each air jet head (43) sprays air radially toward the outer wall of the inner tube (1) to form an air film, so as to support and keep the inner tube (1) and the outer tube (3) always coaxial.

2. The double-walled tube support structure according to claim 1, characterized in that: The static pressure support structure (4) also includes several baffles (42) and several air intake pipes (44) for transmitting and adjusting the intake volume. Several baffles (42) are sealed inside the annular pipe (41) in a circumferential manner, dividing the interior of the annular pipe (41) in a circumferential manner to form multiple independent chambers. The air intake pipes (44) are connected to the chambers one by one, and each chamber is connected to at least one jet head (43).

3. The double-walled tube support structure according to claim 2, characterized in that: The double-walled tube support structure also includes an intermediate tube (2) axially sleeved between the inner tube (1) and the outer tube (3). The annular tube (41) is axially sleeved on the outer periphery of the inner tube (1) and fixed to the inner wall of the intermediate tube (2). Each of the air inlet pipes (44) passes through the intermediate tube (2) and connects to the annular gap formed by the intermediate tube (2) and the outer tube (3). Gas for the air inlet pipe (44) is continuously introduced into the annular gap.

4. The double-walled tube support structure according to claim 3, characterized in that: The inner tube (1) is also provided with a limiting protection support structure (5) on its outer periphery. The limiting protection support structure (5) is fixed to the inner wall of the intermediate tube (2) and connected to one side of the static pressure support structure (4). The limiting protection support structure (5) has a support end facing the outer wall of the inner tube (1). The support end is closer to the outer wall of the inner tube (1) than the air outlet of the jet head (43).

5. A double-walled tube support structure according to claim 4, characterized in that: The limiting protection support structure (5) includes at least one pair of arc plates (52) and a support head. The arc plates (52) are symmetrically distributed and connected and fixed to the outer periphery of the annular tube (41). The support head is detachably mounted on the arc plates (52) and faces the outer wall of the inner tube (1).

6. A control method for a double-walled tube support structure according to any one of claims 1-5, characterized in that, include: S1: The radial displacement information of the inner tube (1) relative to the outer tube (3) during operation is obtained in real time by sensors arranged in a circumferential array along the inner wall of the middle tube (2); S2: Determine the radial displacement direction of the inner tube (1) based on the radial displacement information, and determine the opposite direction of the radial displacement direction as the compensation direction; S3: Calculate the target air intake volume of the chamber corresponding to the compensation direction based on the radial displacement information; S4: The controller calculates the target intake volume of the chamber corresponding to the compensation direction and controls the gas to be introduced into the chamber corresponding to the compensation direction to match the target intake volume.

7. The control method for a double-walled tube support structure according to claim 6, characterized in that, In step S1, the radial displacement information is obtained by real-time detection of the gap between the inner tube (1) and the intermediate tube (2) at different circumferential positions.

8. The control method for a double-walled tube support structure according to claim 7, characterized in that, The target air intake volume of the chamber corresponding to the compensation direction is calculated using the following formula: ； in, The radial displacement of the inner tube (1) is... The effective working area of ​​the chamber. This is the conversion factor between radial displacement and radial restoring force. This is the conversion coefficient between intake volume and film pressure. To maintain the baseline intake volume for basic static pressure support.

9. The control method for a double-walled tube support structure according to claim 8, characterized in that, The controller is electrically connected to the electrically controlled flow regulating valve installed on each air intake pipe (44) to control the air intake flow. In step S4, the controller controls the opening of the electrically controlled flow regulating valve of the air intake pipe (44) corresponding to the compensation direction, and introduces the corresponding air intake gas into the current air intake pipe (44) according to the target air intake calculation result.

10. The control method for a double-walled tube support structure according to claim 9, characterized in that, The controller is installed on the outer wall of the outer tube (3) and is one of an industrial controller, a programmable logic controller, an embedded controller, and a computing unit with data processing capabilities.

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