Method and device for judging boiling criticality of cooling surface of superconducting magnet cooled by liquid helium

Abstract

The present invention provides a method and device for judging the boiling criticality of a cooling surface of a superconducting magnet cooled by liquid helium, and relates to the field of thermal simulation technology. The superconducting magnet is immersed in the liquid helium. The method comprises: establishing a three-dimensional physical model of the superconducting magnet, and obtaining the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model; obtaining the critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field; obtaining the AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, performing thermal simulation analysis on the AC loss heat power distribution, and determining the heat flux density distribution of the cooling surface of the superconducting magnet; and comparing the heat flux density distribution with the critical heat flux density distribution to determine the boiling state of liquid helium on the surface of the superconducting magnet.

Description

Technical Field

[0001] The invention relates to the field of thermal simulation technology, and in particular to a method and device for judging the boiling criticality of a cooling surface of a superconducting magnet cooled by liquid helium. Background Art

[0002] Superconducting magnets generally use the special properties of superconducting coils at extremely low temperatures (4.2K) to generate strong magnetic fields. In order to obtain the extremely low temperature working environment required by superconducting magnets, superconducting magnets can usually be immersed in liquid helium. However, the magnetic field provided by the operation of fast pulse superconducting magnets changes periodically. During the rapid change of the magnetic field, AC losses will be generated on the coils and metal structural parts, thereby generating internal heat sources, increasing the heat flux density of the corresponding superconducting magnets in contact with liquid helium. In addition, the temperature of liquid helium is low and the latent heat of vaporization is small, which may cause the liquid helium to be converted into a film boiling state at the contact part of the superconducting magnet corresponding to the internal heat source, reducing the heat exchange efficiency between liquid helium and the superconducting magnet, and thus causing the local temperature of the superconducting magnet to rise.

[0003] The critical heat flux is a key parameter for the conversion of liquid helium nucleate boiling to film boiling, and plays an important role in the thermal stability evaluation of superconducting magnets, which can be used to optimize the cooling design of superconducting magnets. At present, the critical heat flux of liquid helium is generally calculated by the empirical relationship method, but this method is proposed by summarizing experimental data and is limited by experimental conditions and has a limited scope of application. In particular, the strong magnetic field generated by the superconducting magnet can produce an electromagnetic field force on the bubbles of liquid helium, affecting the dynamic behavior of the bubbles on the boiling wall, which further interferes with the accuracy of the empirical relationship method to calculate the critical heat flux of liquid helium for cooling the superconducting magnet, and increases the difficulty of judging the boiling state of liquid helium on the surface of the superconducting magnet. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method and device for determining the boiling criticality of the cooling surface of a superconducting magnet cooled by liquid helium.

[0005] The present invention provides a method for judging the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium, wherein the superconducting magnet is immersed in the liquid helium; the method comprises:

[0006] Establishing a three-dimensional physical model of the superconducting magnet, and obtaining the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model;

[0007] The critical heat flux density distribution of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution and the gravity field; the AC loss heat power distribution of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution, and a thermal simulation analysis is performed on the AC loss heat power distribution to determine the heat flux density distribution of the cooling surface of the superconducting magnet;

[0008] The heat flux density distribution and the critical heat flux density distribution are compared to determine the boiling state of the liquid helium on the surface of the superconducting magnet.

[0009] According to a method for determining the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the present invention, the critical heat flux density distribution of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution and the gravity field, specifically comprising:

[0010] A liquid helium boiling state model of the superconducting magnet is established based on the three-dimensional magnetic field distribution and the gravity field, and a critical heat flux density distribution of the superconducting magnet is obtained through the liquid helium boiling state model of the superconducting magnet.

[0011] According to a method for judging the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the present invention, a liquid helium boiling state model of the superconducting magnet is established based on the three-dimensional magnetic field distribution and the gravity field, specifically comprising:

[0012] An equivalent gravity field is obtained based on the three-dimensional magnetic field distribution and the gravity field, and a liquid helium boiling state model of the superconducting magnet is established based on the equivalent gravity field.

[0013] According to a method for judging the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the present invention, an equivalent gravity field is obtained based on the three-dimensional magnetic field distribution and the gravity field, specifically comprising:

[0014] Obtaining the electromagnetic force density vector distribution of the superconducting magnet based on vacuum magnetic permeability, the magnetic change rate of the superconducting magnet and the three-dimensional magnetic field distribution;

[0015] An equivalent gravitational field is obtained based on the electromagnetic force density vector distribution and the gravitational field.

[0016] According to a method for judging the boiling criticality of a cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the present invention, the liquid helium boiling state model is used to characterize the dynamic change of the liquid helium from nucleate boiling to film boiling; the liquid helium generates liquid helium bubbles under the nucleate boiling;

[0017] A liquid helium boiling state model of the superconducting magnet is established based on an equivalent gravitational field, specifically comprising:

[0018] Determining an equivalent inclination of the equivalent gravity field relative to the gravity field based on the direction of the equivalent gravity field and the direction of the gravity field;

[0019] Obtaining an equivalent gravity of the liquid helium bubbles on the surface of different positions of the superconducting magnet based on the equivalent gravity field, and determining an equivalent buoyancy of the liquid helium bubbles in a direction parallel to the surface of different positions of the superconducting magnet based on the equivalent gravity and the equivalent inclination;

[0020] A liquid helium boiling state model of the superconducting magnet is established based on the equivalent buoyancy of the liquid helium bubbles in directions parallel to the surfaces of different positions of the superconducting magnet and the corresponding surface tension and evaporation force.

[0021] According to a method for judging the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the present invention, before establishing a liquid helium boiling state model of the superconducting magnet based on the equivalent buoyancy of the liquid helium bubbles in the direction parallel to the surface of different positions of the superconducting magnet and the corresponding surface tension and evaporation force, the method further comprises:

[0022] determining a latent heat of vaporization of the liquid helium;

[0023] Based on the heat flux density distribution of the cooling surface of the superconducting magnet, the heat flux density distribution of the gas-liquid interface of the liquid helium is obtained, and the evaporation force of the liquid helium bubble in the direction parallel to the surface of different positions of the superconducting magnet is determined in combination with the latent heat of vaporization of the liquid helium;

[0024] The critical heat flux density distribution of the superconducting magnet is obtained by using the liquid helium boiling state model of the superconducting magnet, specifically including:

[0025] The evaporation force distribution of the liquid helium bubbles under critical conditions is obtained through the liquid helium boiling state model, and the critical thermal density distribution of the superconducting magnet is obtained according to the evaporation force distribution.

[0026] According to a method for judging the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the present invention, before establishing a liquid helium boiling state model of the superconducting magnet based on the equivalent buoyancy of the liquid helium bubbles in the direction parallel to the surface of different positions of the superconducting magnet and the corresponding surface tension and evaporation force, the method further comprises:

[0027] Obtaining contact angles between the gas-liquid interface of the liquid helium and surfaces at different positions of the superconducting magnet;

[0028] The surface tension of the liquid helium bubble in a direction parallel to the surface of the superconducting magnet at different positions is obtained based on the contact angle and the surface tension coefficient of the superconducting magnet.

[0029] According to a method for judging the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the present invention, the AC loss heat power distribution of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution, and a thermal simulation analysis is performed on the AC loss heat power distribution, which specifically includes:

[0030] AC loss parameters are obtained based on the three-dimensional magnetic field distribution, online AC loss and metal structure eddy current loss of the superconducting magnet are obtained according to the AC loss parameters, and thermal simulation analysis is performed on the online AC loss and metal structure eddy current loss of the superconducting magnet.

[0031] According to a method for judging the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the present invention, the three-dimensional magnetic field distribution of the superconducting magnet is obtained based on the three-dimensional physical model, specifically comprising:

[0032] Performing meshing processing on the three-dimensional physical model to obtain a three-dimensional physical mesh;

[0033] The current parameters and current density distribution of the superconducting magnet are obtained, and based on the current parameters and current density distribution, finite element analysis is performed on each of the three-dimensional physical grids to obtain the three-dimensional magnetic field distribution of the superconducting magnet.

[0034] The present invention also provides a device for judging the boiling criticality of the cooling surface of a liquid helium-cooled high-magnetic field superconducting magnet, which is used to implement any of the above-mentioned methods for judging the boiling criticality of the cooling surface of a liquid helium-cooled high-magnetic field superconducting magnet, and the device comprises:

[0035] A magnetic field distribution acquisition module, used to establish a three-dimensional physical model of the superconducting magnet, and acquire the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model;

[0036] A heat flux density acquisition module is used to obtain the critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field; obtain the AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, perform thermal simulation analysis on the AC loss heat power distribution, and determine the heat flux density distribution of the cooling surface of the superconducting magnet;

[0037] The boiling state determination module is used to compare the heat flux density distribution with the critical heat flux density distribution to determine the boiling state of the liquid helium on the surface of the superconducting magnet.

[0038] The present invention provides a method and device for judging the boiling criticality of the cooling surface of a liquid helium-cooled superconducting magnet. The three-dimensional magnetic field distribution of the superconducting magnet is obtained based on the three-dimensional physical model of the superconducting magnet; the critical heat flux density distribution of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution and the gravity field, and the critical heat flux density distribution of the superconducting magnet can be obtained based on the actual working condition of the superconducting magnet, thereby increasing the accuracy of the obtained critical heat flux density; the AC loss heat power distribution of the superconducting magnet can be obtained based on the three-dimensional magnetic field distribution, and the AC loss heat power distribution is subjected to thermal simulation analysis to determine the heat flux density distribution of the cooling surface of the superconducting magnet; the heat flux density distribution is compared with the critical heat flux density distribution to determine the boiling state of liquid helium on the surface of the superconducting magnet, thereby reducing the difficulty of judging the boiling state of liquid helium on the surface of the superconducting magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 This is one of the flow diagrams of the method for judging the boiling criticality of the cooling surface of a high magnetic field superconducting magnet cooled by liquid helium provided by the present invention.

[0041] Figure 2 It is a schematic diagram of the cooling surface of the high magnetic field superconducting magnet cooled by liquid helium provided by the present invention.

[0042] Figure 3 It is one of the schematic diagrams of the force acting on the cooling surface of the superconducting magnet in the method for judging the boiling criticality of the cooling surface of the high magnetic field superconducting magnet cooled by liquid helium provided by the present invention.

[0043] Figure 4 This is the second schematic diagram of the force acting on the cooling surface of the superconducting magnet in the method for judging the boiling criticality of the cooling surface of the high magnetic field superconducting magnet cooled by liquid helium provided by the present invention.

[0044] Figure 5 This is the third schematic diagram of the force acting on the cooling surface of the superconducting magnet in the method for judging the boiling criticality of the cooling surface of the high magnetic field superconducting magnet cooled by liquid helium provided by the present invention.

[0045] Figure 6 This is the second flow chart of the method for judging the boiling criticality of the cooling surface of a high magnetic field superconducting magnet cooled by liquid helium provided by the present invention.

[0046] Figure 7 This is the third flow chart of the method for judging the boiling criticality of the cooling surface of a high magnetic field superconducting magnet cooled by liquid helium provided by the present invention.

[0047] Figure 8 The present invention is a schematic structural diagram of a device for judging the boiling criticality of a cooling surface of a liquid helium-cooled high-magnetic field superconducting magnet provided by the present invention.

[0048] Fig. 9 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Combine the following Figure 1-Figure 8 The present invention describes a method and device for determining the boiling criticality of a cooling surface of a superconducting magnet cooled by liquid helium.

[0051] Figure 1 This is one of the flow charts of the method for judging the boiling criticality of the cooling surface of a high magnetic field superconducting magnet cooled by liquid helium provided by the present invention, such as Figure 1 As shown, the method includes the following:

[0052] Step 101: Establish a three-dimensional physical model of the superconducting magnet, and obtain the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model.

[0053] A superconducting magnet may also be referred to as a superconducting magnet, which refers to a high-performance magnet that includes a superconducting coil and can generate a strong magnetic field in a short time when the superconducting coil is excited by an electric current. For example, the superconducting magnet may be a fast pulse superconducting magnet or a high field superconducting magnet.

[0054] like Figure 2 As shown, liquid helium can be placed in a cryogenic Dewar, and two groups of superconducting coils of a superconducting magnet can be immersed in the liquid helium symmetrically along the axis of the cryogenic Dewar.

[0055] The three-dimensional physical model of a superconducting magnet refers to a model that describes the solid structure of the superconducting magnet and facilitates the analysis of the magnetic field distribution of the superconducting magnet. For example, the three-dimensional physical model of a superconducting magnet can be a three-dimensional model drawn and established by modeling software such as CAD based on the parameters of the superconducting magnet by calling a pre-established template, or can be a three-dimensional model established based on image conversion of the superconducting magnet, etc.

[0056] Exemplarily, an image of a superconducting magnet can be obtained, a three-dimensional physical model of the superconducting magnet can be established based on the image conversion of the superconducting magnet, and an expression of the magnetic field generated by the superconducting magnet can be obtained based on the three-dimensional physical model to obtain magnetic field parameters such as the intensity and direction of the magnetic field generated by the superconducting magnet at different positions in three-dimensional space.

[0057] Step 102: obtaining a critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field; obtaining an AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, performing a thermal simulation analysis on the AC loss heat power distribution, and determining a heat flux density distribution of a cooling surface of the superconducting magnet.

[0058] The gravity field refers to a force field generated by a mass body. The gravity field causes surrounding objects to be attracted and move toward the mass body. In this embodiment, the gravity field can be the real gravity field of the area, or it can be a conventional gravity field treated as a constant. For example, in this embodiment, the gravity field is the value of gravity acceleration, which can be 9.8m / s 2 The conventional gravitational field.

[0059] The critical heat flux density of a superconducting magnet can also be called the critical heat flux density of the cooling surface of a superconducting magnet, which refers to the heat flux density that characterizes whether the liquid helium on the surface of the superconducting magnet enters a modal boiling state.

[0060] The superconducting magnet cooling surface refers to the surface of the superconducting magnet in contact with liquid helium.

[0061] For example, when the critical heat flux density distribution characterizes whether the liquid helium on the surface of the superconducting magnet enters a modal boiling state, the stress conditions of the liquid helium bubbles on the surface of the superconducting magnet can be obtained based on the three-dimensional magnetic field distribution and the gravitational field, and the critical heat flux density distribution of the superconducting magnet can be obtained by analyzing the stress conditions of the liquid helium bubbles.

[0062] AC loss is the heat generated by the rapid change of magnetic field during the excitation process. Therefore, the AC loss heat power distribution of the three-dimensional solid model can be obtained based on the three-dimensional magnetic field distribution of the magnetic field generated by the superconducting magnet. It can be understood that the AC loss heat power distribution can also be called the internal heat source distribution.

[0063] Exemplarily, after obtaining the AC loss heat power distribution of the superconducting magnet, a thermal simulation analysis can be performed based on relevant software in combination with the three-dimensional physical model of the superconducting magnet to determine the heat flux density distribution on the cooling surface of the superconducting magnet. A thermal simulation analysis can also be performed based on finite element analysis in combination with the three-dimensional physical model of the superconducting magnet to determine the heat flux density distribution on the cooling surface of the superconducting magnet, etc.

[0064] Step 103: Compare the heat flux density distribution with the critical heat flux density distribution to determine the boiling state of the liquid helium on the surface of the superconducting magnet.

[0065] Exemplarily, in the case where the critical heat flux density distribution characterizes whether the liquid helium on the surface of the superconducting magnet enters a modal boiling state, it may be that the heat flux density on the cooling surface of the superconducting magnet is less than the critical heat flux density, and the liquid helium on the surface of the superconducting magnet does not enter the modal boiling state; the heat flux density on the cooling surface of the superconducting magnet is greater than the critical heat flux density, and the liquid helium on the surface of the superconducting magnet enters a modal boiling state.

[0066] The method for judging the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided in an embodiment of the present invention obtains the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model of the superconducting magnet through the three-dimensional physical model; obtains the critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field, and can obtain the critical heat flux density distribution of the superconducting magnet based on the actual working condition of the superconducting magnet, thereby increasing the accuracy of the obtained critical heat flux density; can obtain the AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, perform thermal simulation analysis on the AC loss heat power distribution, and determine the heat flux density distribution of the cooling surface of the superconducting magnet; compare the heat flux density distribution with the critical heat flux density distribution, determine the boiling state of liquid helium on the surface of the superconducting magnet, and reduce the difficulty of judging the boiling state of liquid helium on the surface of the superconducting magnet.

[0067] Based on the above embodiment, the critical heat flux density distribution of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution and the gravity field, specifically including: establishing a liquid helium boiling state model of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field, and obtaining the critical heat flux density distribution of the superconducting magnet through the liquid helium boiling state model of the superconducting magnet.

[0068] The liquid helium boiling state model refers to a model that describes the boiling state of liquid helium through the dynamic behavior of liquid helium bubbles during the cooling process of superconducting magnets.

[0069] Exemplarily, in the case where the critical heat flux density distribution characterizes whether the liquid helium on the surface of the superconducting magnet enters a modal boiling state, the stress conditions of the liquid helium bubbles on the surface of the superconducting magnet can be analyzed based on the three-dimensional magnetic field distribution and the gravity field, and a liquid helium boiling state model of the superconducting magnet is established according to the stress conditions of the liquid helium bubbles on the surface of the superconducting magnet. The critical heat flux density distribution of the superconducting magnet is obtained through the liquid helium boiling state model of the superconducting magnet in the critical state.

[0070] Compared with the method of numerically analyzing the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field, in this embodiment, the physical process and mechanism of the boiling state of liquid helium in the cooling process of the superconducting magnet can be better reflected by establishing the boiling state model of liquid helium. And the boiling state model of liquid helium of the superconducting magnet is established based on the stress of the liquid helium bubbles on the surface of the superconducting magnet, which avoids the complex numerical simulation calculation process, simplifies the analysis steps, and can reduce the calculation time and calculation resources required to obtain the boiling state of liquid helium of the superconducting magnet under different working conditions.

[0071] like Figure 3 and Figure 4 As shown, based on any of the above embodiments, a liquid helium boiling state model of the superconducting magnet is established based on the three-dimensional magnetic field distribution and the gravity field, specifically including: obtaining an equivalent gravity field based on the three-dimensional magnetic field distribution and the gravity field, and establishing the liquid helium boiling state model of the superconducting magnet based on the equivalent gravity field.

[0072] The equivalent gravitational field refers to the comprehensive force field obtained by combining the gravitational field and the magnetic field. The effect of the equivalent gravitational field is similar to that of the gravitational field, except that the size of the equivalent gravitational field is different from that of the gravitational field, and the direction of the equivalent gravitational field is different from that of the gravitational field.

[0073] In this embodiment, the equivalent gravity field of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution and the gravity field, and the force conditions of the liquid helium bubbles on the surface of the superconducting magnet are analyzed according to the equivalent gravity field, which reduces the number of objects that need to be analyzed, simplifies the mechanical analysis process, reduces the error and uncertainty of the liquid helium boiling state model of the superconducting magnet, and improves the reliability and accuracy of the critical heat flux density distribution of the superconducting magnet obtained based on the liquid helium boiling state model.

[0074] Based on any of the above embodiments, obtaining an equivalent gravity field based on the three-dimensional magnetic field distribution and the gravity field specifically includes:

[0075] Obtaining the electromagnetic force density vector distribution of the superconducting magnet based on vacuum magnetic permeability, the magnetic change rate of the superconducting magnet and the three-dimensional magnetic field distribution;

[0076] An equivalent gravitational field is obtained based on the electromagnetic force density vector distribution and the gravitational field.

[0077] The magnetic rate of change can also be called the rate of change of magnetic flux, which refers to the rate at which magnetic flux changes over time.

[0078] Volume force can also be called fluid volume force, which refers to the non-contact force on each unit volume in the fluid. Volume force density vector refers to the vector of volume force on a unit volume, including the magnitude and direction of the volume force. In this embodiment, gravity, electromagnetic force, etc. on each unit volume in liquid helium belong to volume force.

[0079] Exemplarily, the vacuum magnetic permeability, the magnetic change rate of the superconducting magnet, and the three-dimensional magnetic field distribution can be used to obtain the electromagnetic force density vector of the superconducting magnet based on the following formula:

[0080]

[0081] in, is the electromagnetic force density vector of the superconducting magnet, is the magnetic change rate of the superconducting magnet, is the vacuum permeability, is the three-dimensional magnetic induction intensity, is the gradient operator.

[0082] The magnetic field generated by the superconducting magnet is non-uniform, for example, the magnetic field generated by the superconducting magnet can be a gradient distribution. Based on the non-uniform three-dimensional magnetic field distribution generated by the superconducting magnet, the electromagnetic force density vector distribution of the superconducting magnet can be obtained in combination with the electromagnetic force density vector.

[0083] The direction of gravity in the gravity field is vertically downward, and the gravity density vector in the gravity field can be obtained by the following expression:

[0084]

[0085] in, is the gravity density vector, is the density, is the gravitational acceleration vector.

[0086] The equivalent gravity density vector can be obtained by vector synthesis based on the gravity density vector and the electromagnetic force density vector of the superconducting magnet. Specifically, the multiplication vector of the equivalent gravity density vector relative to the gravity density vector can be defined first: , as shown in the following formula:

[0087]

[0088] in, is the electromagnetic force density vector of the superconducting magnet, is the gravity density vector, is the gravity density.

[0089] Based on the multiplication vector The equivalent gravitational acceleration is obtained as shown in the following formula:

[0090]

[0091] in, is the equivalent gravitational acceleration, is the acceleration due to gravity, is the multiplication vector.

[0092] After obtaining the equivalent gravitational acceleration, similar to the method of obtaining the gravity density vector in the gravity field, the equivalent gravity density vector can be obtained based on the equivalent gravitational acceleration, and then the equivalent gravity field can be obtained.

[0093] like Figure 5As shown, based on any of the above embodiments, the liquid helium boiling state model is used to characterize the dynamic change of the liquid helium from nucleate boiling to film boiling; the liquid helium generates liquid helium bubbles under the nucleate boiling.

[0094] Nucleate boiling refers to a boiling state in which bubbles of liquid helium form and collapse on the cooling surface of a superconducting magnet. Film boiling refers to a boiling state in which the cooling surface of a superconducting magnet is covered by a vapor film. The vapor film refers to a liquid film surrounding the cooling surface of a superconducting magnet, which prevents bubbles from contacting the cooling surface of the superconducting magnet, reducing the heat transfer efficiency of the cooling surface of the superconducting magnet.

[0095] A liquid helium boiling state model of the superconducting magnet is established based on an equivalent gravitational field, specifically comprising:

[0096] Determining an equivalent inclination of the equivalent gravity field relative to the gravity field based on the direction of the equivalent gravity field and the direction of the gravity field;

[0097] Obtaining an equivalent gravity of the liquid helium bubbles on the surface of different positions of the superconducting magnet based on the equivalent gravity field, and determining an equivalent buoyancy of the liquid helium bubbles in a direction parallel to the surface of different positions of the superconducting magnet based on the equivalent gravity and the equivalent inclination;

[0098] A liquid helium boiling state model of the superconducting magnet is established based on the equivalent buoyancy of the liquid helium bubbles in directions parallel to the surfaces of different positions of the superconducting magnet and the corresponding surface tension and evaporation force.

[0099] The equivalent inclination refers to the angle of the equivalent inclination angle. The equivalent inclination angle refers to the inclination angle between the equivalent gravity density vector of the equivalent gravity field and the gravity density vector of the gravity field. Exemplarily, the equivalent inclination of the equivalent gravity field relative to the gravity field can be determined by the following formula:

[0100]

[0101] in, is the equivalent inclination, is the equivalent gravitational acceleration, is the multiplication vector.

[0102] Exemplarily, the equivalent gravity acceleration of the equivalent gravity field is used to obtain the equivalent gravity of the liquid helium bubble on the surface of the superconducting magnet, and the equivalent bubble height, equivalent tilt angle and , , the equivalent buoyancy of the liquid helium bubble on the surface of the superconducting magnet can be obtained based on the following formula:

[0103]

[0104] in, is the equivalent buoyancy of the liquid helium bubble on the surface of the superconducting magnet, is the equivalent gravitational acceleration, is the density of liquid helium, is the gas density, is the equivalent bubble height, is the equivalent tilt angle.

[0105] It can be understood that, by combining the above formula and the equivalent gravitational field at different positions on the surface of the superconducting magnet, the equivalent buoyancy of the liquid helium bubble in the direction parallel to the surface of the superconducting magnet at different positions can be obtained.

[0106] For example, the equivalent diameter of the bubble can be obtained based on the following formula to obtain the equivalent bubble height of the bubble:

[0107]

[0108] in, is the equivalent bubble height, is the equivalent diameter of the bubble, It is the contact angle between the vapor-liquid surface of liquid helium and the cooling surface of the superconducting magnet.

[0109] The equivalent diameter of the bubble can be obtained based on the following formula:

[0110]

[0111] in, is the equivalent diameter of the bubble, is the Taylor instability length, is an empirical constant, is the surface tension, is the acceleration due to gravity, is the density of liquid helium, is the gas density.

[0112] In this embodiment, by selecting the equivalent buoyancy of the liquid helium bubbles in the direction parallel to the surface of the superconducting magnet at different positions and the corresponding surface tension and evaporation force, a liquid helium boiling state model of the superconducting magnet is established. This can reduce the physical quantities involved in analyzing the boiling state of liquid helium while describing the boiling mechanism of liquid helium, thereby simplifying the mechanical analysis process.

[0113] Based on any of the above embodiments, before establishing the liquid helium boiling state model of the superconducting magnet based on the equivalent buoyancy of the liquid helium bubbles in directions parallel to the surface of different positions of the superconducting magnet and the corresponding surface tension and evaporation force, the method further includes:

[0114] determining a latent heat of vaporization of the liquid helium;

[0115] The heat flux density distribution of the gas-liquid interface of liquid helium is obtained based on the heat flux density distribution of the cooling surface of the superconducting magnet, and the evaporation force of the liquid helium bubble in the direction parallel to the surface of different positions of the superconducting magnet is determined in combination with the latent heat of vaporization of the liquid helium.

[0116] For example, after obtaining the latent heat of vaporization of liquid helium and the heat flux density of the liquid helium bubble at the gas-liquid interface of liquid helium, the evaporation force of the liquid helium bubble in the direction parallel to the surface of the superconducting magnet at different positions can be calculated based on the following formula:

[0117]

[0118] in, is the evaporation force of the liquid helium bubble in the direction parallel to the surface of the superconducting magnet at different positions, is the heat flux density of the liquid helium bubble at the gas-liquid interface of liquid helium, is the latent heat of vaporization, is the equivalent bubble height, is the gas density.

[0119] After obtaining the heat flux density distribution on the cooling surface of the superconducting magnet, the heat flux density distribution of the liquid helium bubble at the gas-liquid interface of the liquid helium can be obtained based on the following formula:

[0120]

[0121] in, is the heat flux density of the liquid helium bubble at the gas-liquid interface of liquid helium, is the contact angle between the vapor-liquid surface of liquid helium and the cooling surface of the superconducting magnet, is the equivalent diameter of the bubble, is the heat flux density on the cooling surface of the superconducting magnet, is the average diameter of the bubbles.

[0122] It can be understood that, by combining the above formula and the heat flux density distribution on the cooling surface of the superconducting magnet, the heat flux density distribution of the liquid helium bubble at the gas-liquid interface of the liquid helium can be obtained, and then the evaporation force of the liquid helium bubble in the direction parallel to the surface of the superconducting magnet at different positions can be determined.

[0123] In one embodiment, the critical heat flux density distribution of the superconducting magnet is obtained by using the liquid helium boiling state model of the superconducting magnet, specifically including:

[0124] The evaporation force distribution of the liquid helium bubbles under critical conditions is obtained through the liquid helium boiling state model, and the critical thermal density distribution of the superconducting magnet is obtained according to the evaporation force distribution.

[0125] Exemplarily, the critical condition can be obtained, and the evaporation force of the liquid helium bubble can be obtained according to the critical condition in combination with the above formula. The heat flux density of the liquid helium bubble at the gas-liquid interface of the liquid helium under the critical condition can be obtained through the evaporation force of the liquid helium bubble, thereby obtaining the heat flux density of the cooling surface of the superconducting magnet.

[0126] Different parts of the liquid helium bubble are subjected to different surface tensions. In order to obtain the surface tensions exerted on the bottom of the liquid helium bubble in directions parallel to the surface of different positions of the superconducting magnet, based on any of the above embodiments, before establishing a liquid helium boiling state model of the superconducting magnet based on the equivalent buoyancy of the liquid helium bubble in directions parallel to the surface of different positions of the superconducting magnet and the corresponding surface tension and evaporation force, the method further includes:

[0127] Obtaining contact angles between the gas-liquid interface of the liquid helium and surfaces at different positions of the superconducting magnet;

[0128] The surface tension of the liquid helium bubble in a direction parallel to the surface of the superconducting magnet at different positions is obtained based on the contact angle and the surface tension coefficient of the superconducting magnet.

[0129] For example, the contact angle between the gas-liquid interface of liquid helium and the surface of the superconducting magnet at different positions can be obtained by surface energy calculation or simulation analysis, etc. The surface of the superconducting magnet at different positions refers to the cooling surface of the superconducting magnet at the location of the liquid helium bubble.

[0130] The surface tension of the liquid helium bubble bottom in the direction parallel to the surface of the superconducting magnet at different positions can be obtained based on the following formula:

[0131]

[0132] in, is the surface tension at the bottom of the liquid helium bubble, is the surface tension coefficient, It is the contact angle between the vapor-liquid surface of liquid helium and the cooling surface of the superconducting magnet.

[0133] In another embodiment, the surface tension of the top of the liquid helium bubble in the direction parallel to the surface of the superconducting magnet at different positions can be obtained based on the following formula:

[0134]

[0135] in, is the surface tension at the bottom of the liquid helium bubble, is the surface tension coefficient.

[0136] For example, the critical condition can be expressed by the following formula:

[0137]

[0138] in, is the evaporation force of the liquid helium bubble in the direction parallel to the surface of the superconducting magnet at different positions, is the surface tension at the bottom of the liquid helium bubble, is the surface tension at the bottom of the liquid helium bubble, is the equivalent buoyancy of the liquid helium bubble on the surface of the superconducting magnet.

[0139] like Figure 6 As shown, when obtaining the critical heat flux density of the superconducting magnet, the heat flux density of the corresponding superconducting magnet cooling surface can be determined first, and the heat flux density of the liquid helium bubble at the gas-liquid interface of the liquid helium can be calculated, so as to obtain the evaporation force of the liquid helium bubble in the direction parallel to the surface of the superconducting magnet at different positions, and judge whether the critical condition is met. If not, and the evaporation force The surface tension at the bottom of the liquid helium bubble + the surface tension at the bottom of the liquid helium bubble + the equivalent buoyancy of the liquid helium bubble on the surface of the superconducting magnet will expand the heat flux density on the cooling surface of the superconducting magnet, and make subsequent judgments. If not and the evaporation force The surface tension at the bottom of the liquid helium bubble + the surface tension at the bottom of the liquid helium bubble + the equivalent buoyancy of the liquid helium bubble on the surface of the superconducting magnet will reduce the heat flux density on the cooling surface of the superconducting magnet, and subsequent judgment will be made until the critical condition is met to obtain the critical heat flux density of the superconducting magnet; then, the critical heat flux density distribution of the superconducting magnet is obtained in combination with the heat flux density distribution on the cooling surface of the superconducting magnet.

[0140] Based on any of the above embodiments, obtaining the AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, and performing thermal simulation analysis on the AC loss heat power distribution specifically include:

[0141] AC loss parameters are obtained based on the three-dimensional magnetic field distribution, online AC loss and metal structure eddy current loss of the superconducting magnet are obtained according to the AC loss parameters, and thermal simulation analysis is performed on the online AC loss and metal structure eddy current loss of the superconducting magnet.

[0142] Exemplarily, AC loss parameters may include superconductor critical current density, superconducting filament diameter, magnetic field change rate, operating current density, time constant, vacuum permeability, etc. After obtaining the AC loss parameters, the three-dimensional AC loss thermal power distribution of the superconducting magnet can be obtained by the following formula.

[0143] The online AC loss of a superconducting magnet can also be referred to as magnet AC loss. The magnet AC loss may include the hysteresis loss of the superconducting magnet and the coupling loss of the superconducting magnet.

[0144] The hysteresis loss of a superconducting magnet can be obtained according to the following formula.

[0145]

[0146] in, is the hysteresis loss of the superconducting magnet, is the critical current density of the superconductor (A / m 2 ), is the superconducting wire diameter (m), is the rate of change of magnetic field (T / s), is the operating current density (A / m 2 ),

[0147] The coupling loss of the superconducting magnet can be obtained according to the following formula.

[0148]

[0149] in, is the coupling loss of the superconducting magnet, is the time constant (s), is the vacuum permeability (H / m), is the rate of change of magnetic field (T / s).

[0150] The eddy current loss of metal structures can be obtained based on the following formula:

[0151]

[0152] in, is the eddy current loss of the metal structure, E is the electric field intensity, and J is the current density.

[0153] For example, after obtaining the online AC loss and the eddy current loss of the metal structure of the superconducting magnet, the heat flux density distribution on the cooling surface of the superconducting magnet can be determined based on the three-dimensional steady-state thermal balance.

[0154] Exemplarily, the heat flux distribution on the cooling surface of the superconducting magnet may be determined based on the following formula:

[0155]

[0156] in, is the thermal conductivity, is the temperature, is the length direction, is the width direction, is the height direction, and q is the sum of the AC loss of the magnet and the eddy current loss of the metal structure.

[0157] Based on any of the above embodiments, obtaining the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model specifically includes:

[0158] Performing meshing processing on the three-dimensional physical model to obtain a three-dimensional physical mesh;

[0159] The current parameters and current density distribution of the superconducting magnet are obtained, and based on the current parameters and current density distribution, finite element analysis is performed on each of the three-dimensional physical grids to obtain the three-dimensional magnetic field distribution of the superconducting magnet.

[0160] Exemplarily, the three-dimensional magnetic field distribution of the superconducting magnet is obtained based on the following formula:

[0161]

[0162] in, is the three-dimensional magnetic induction intensity distribution of the superconducting magnet, is the current density distribution, is the curl algorithm, is the magnetic vector potential, is the magnetic permeability.

[0163] A three-dimensional physical model can be established using three-dimensional finite element software, and the three-dimensional physical model can be processed by finite element meshing to obtain the finite element mesh of the three-dimensional physical model of the superconducting magnet, and the three-dimensional magnetic field distribution of the superconducting magnet can be obtained by solving the above equation based on finite element analysis. For example, boundary conditions are set, and the three-dimensional finite element software is used to discretely solve the above equation to obtain the magnetic field distribution in three-dimensional space.

[0164] In order to specifically illustrate the function of the method for determining the boiling criticality of the cooling surface of a liquid helium-cooled high-magnetic field superconducting magnet provided in this embodiment, a specific example is provided below.

[0165] Performing meshing processing on the three-dimensional physical model to obtain a three-dimensional physical grid; obtaining current parameters and current density distribution of the superconducting magnet, and performing finite element analysis on each of the three-dimensional physical grids based on the current parameters and current density distribution to obtain the three-dimensional magnetic field distribution of the superconducting magnet;

[0166] The electromagnetic force density vector distribution of the superconducting magnet is obtained based on the vacuum magnetic permeability, the magnetic change rate of the superconducting magnet and the three-dimensional magnetic field distribution; the equivalent gravity field is obtained based on the electromagnetic force density vector distribution and the gravity field; the equivalent inclination of the equivalent gravity field relative to the gravity field is determined based on the direction of the equivalent gravity field and the direction of the gravity field; the equivalent gravity of the liquid helium bubbles on the surface of different positions of the superconducting magnet is obtained based on the equivalent gravity field, and the equivalent buoyancy of the liquid helium bubbles in the direction parallel to the surface of different positions of the superconducting magnet is determined based on the equivalent gravity and the equivalent inclination;

[0167] Determine the latent heat of vaporization of the liquid helium; obtain the heat flux density distribution of the gas-liquid interface of the liquid helium based on the heat flux density distribution of the cooling surface of the superconducting magnet, and determine the evaporation force of the liquid helium bubble in the direction parallel to the surface of different positions of the superconducting magnet in combination with the latent heat of vaporization of the liquid helium;

[0168] Obtaining the contact angle between the gas-liquid interface of the liquid helium and the surface of the superconducting magnet at different positions; obtaining the surface tension of the liquid helium bubble in the direction parallel to the surface of the superconducting magnet at different positions based on the contact angle and the surface tension coefficient of the superconducting magnet;

[0169] A liquid helium boiling state model of the superconducting magnet is established based on the equivalent buoyancy of the liquid helium bubbles in the direction parallel to the surface of different positions of the superconducting magnet and the corresponding surface tension and evaporation force; so as to obtain the critical thermodynamic density distribution of the superconducting magnet;

[0170] Based on the three-dimensional magnetic field distribution, AC loss parameters are obtained, and according to the AC loss parameters, online AC loss and metal structure eddy current loss of the superconducting magnet are obtained, and thermal simulation analysis is performed on the online AC loss and metal structure eddy current loss of the superconducting magnet to determine the heat flux density distribution on the cooling surface of the superconducting magnet;

[0171] The heat flux density distribution and the critical heat flux density distribution are compared to determine the boiling state of the liquid helium on the surface of the superconducting magnet.

[0172] The following is a description of the device for judging the boiling criticality of the cooling surface of a liquid helium-cooled high-magnetic field superconducting magnet provided by the present invention. The device for judging the boiling criticality of the cooling surface of a liquid helium-cooled high-magnetic field superconducting magnet described below and the method for judging the boiling criticality of the cooling surface of a liquid helium-cooled high-magnetic field superconducting magnet described above can be referred to each other.

[0173] Figure 8 1 is a schematic diagram of a structure of a device for judging the boiling criticality of a cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium according to an embodiment of the present invention, and is used to implement a method for judging the boiling criticality of a cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium as described above, such as Figure 8 As shown, the device comprises:

[0174] A magnetic field distribution acquisition module 801 is used to establish a three-dimensional physical model of the superconducting magnet, and acquire the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model;

[0175] The heat flux density acquisition module 802 is used to obtain the critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field; obtain the AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, perform thermal simulation analysis on the AC loss heat power distribution, and determine the heat flux density distribution of the cooling surface of the superconducting magnet;

[0176] The boiling state determination module 803 is used to compare the heat flux density distribution with the critical heat flux density distribution to determine the boiling state of the liquid helium on the surface of the superconducting magnet.

[0177] Fig. 9 An example of a structural diagram of an electronic device is shown in FIG. Fig. 9 As shown, the electronic device may include: a processor 910, a communication interface 920, a memory 930 and a communication bus 940, wherein the processor 910, the communication interface 920 and the memory 930 communicate with each other through the communication bus 940. The processor 910 may call the logic instructions in the memory 930 to execute a method for determining the critical boiling of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium, the method comprising: establishing a three-dimensional physical model of the superconducting magnet, obtaining the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model; obtaining the critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field; obtaining the AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, performing thermal simulation analysis on the AC loss heat power distribution, and determining the heat flux density distribution of the cooling surface of the superconducting magnet; comparing the heat flux density distribution with the critical heat flux density distribution, and determining the boiling state of liquid helium on the surface of the superconducting magnet.

[0178] In addition, the logic instructions in the above-mentioned memory 930 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0179] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the method for determining the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the above methods. The method includes: establishing a three-dimensional physical model of the superconducting magnet, and obtaining the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model; obtaining the critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field; obtaining the AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, performing thermal simulation analysis on the AC loss heat power distribution, and determining the heat flux density distribution of the cooling surface of the superconducting magnet; comparing the heat flux density distribution with the critical heat flux density distribution, and determining the boiling state of liquid helium on the surface of the superconducting magnet.

[0180] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the method for determining the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium provided by the above-mentioned methods, the method comprising: establishing a three-dimensional physical model of the superconducting magnet, and obtaining the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model; obtaining the critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravitational field; obtaining the AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, performing thermal simulation analysis on the AC loss heat power distribution, and determining the heat flux density distribution of the cooling surface of the superconducting magnet; and comparing the heat flux density distribution with the critical heat flux density distribution to determine the boiling state of liquid helium on the surface of the superconducting magnet.

[0181] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0182] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0183] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the boiling criticality of a liquid helium-cooled high-magnetic field superconducting magnet cooling surface, characterized in that: The superconducting magnet is immersed in the liquid helium; the method comprises: Establishing a three-dimensional physical model of the superconducting magnet, and obtaining the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model; The critical heat flux density distribution of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution and the gravity field; the AC loss heat power distribution of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution, and a thermal simulation analysis is performed on the AC loss heat power distribution to determine the heat flux density distribution of the cooling surface of the superconducting magnet; Comparing the heat flux density distribution with the critical heat flux density distribution to determine the boiling state of liquid helium on the surface of the superconducting magnet; The step of obtaining the critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field specifically includes: A liquid helium boiling state model of the superconducting magnet is established based on the three-dimensional magnetic field distribution and the gravity field, and a critical heat flux density distribution of the superconducting magnet is obtained through the liquid helium boiling state model of the superconducting magnet; A liquid helium boiling state model of the superconducting magnet is established based on the three-dimensional magnetic field distribution and the gravity field, specifically comprising: Obtaining an equivalent gravity field based on the three-dimensional magnetic field distribution and the gravity field, and establishing a liquid helium boiling state model of the superconducting magnet based on the equivalent gravity field; The liquid helium boiling state model is used to characterize the dynamic change of the liquid helium from nucleate boiling to film boiling; the liquid helium generates liquid helium bubbles under the nucleate boiling; A liquid helium boiling state model of the superconducting magnet is established based on an equivalent gravitational field, specifically comprising: Determining an equivalent inclination of the equivalent gravity field relative to the gravity field based on the direction of the equivalent gravity field and the direction of the gravity field; Obtaining an equivalent gravity of the liquid helium bubbles on the surface of different positions of the superconducting magnet based on the equivalent gravity field, and determining an equivalent buoyancy of the liquid helium bubbles in a direction parallel to the surface of different positions of the superconducting magnet based on the equivalent gravity and the equivalent inclination; A liquid helium boiling state model of the superconducting magnet is established based on the equivalent buoyancy of the liquid helium bubbles in directions parallel to the surfaces of different positions of the superconducting magnet and the corresponding surface tension and evaporation force.

2. The method for determining the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium according to claim 1, characterized in that: The equivalent gravity field is obtained based on the three-dimensional magnetic field distribution and the gravity field, specifically including: Obtaining the electromagnetic force density vector distribution of the superconducting magnet based on vacuum magnetic permeability, the magnetic change rate of the superconducting magnet and the three-dimensional magnetic field distribution; An equivalent gravitational field is obtained based on the electromagnetic force density vector distribution and the gravitational field.

3. The method for determining the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium according to claim 1, characterized in that: Before establishing the liquid helium boiling state model of the superconducting magnet based on the equivalent buoyancy of the liquid helium bubbles in directions parallel to the surface of different positions of the superconducting magnet and the corresponding surface tension and evaporation force, the method further includes: determining a latent heat of vaporization of the liquid helium; Based on the heat flux density distribution of the cooling surface of the superconducting magnet, the heat flux density distribution of the gas-liquid interface of the liquid helium is obtained, and the evaporation force of the liquid helium bubble in the direction parallel to the surface of different positions of the superconducting magnet is determined in combination with the latent heat of vaporization of the liquid helium; The critical heat flux density distribution of the superconducting magnet is obtained by using the liquid helium boiling state model of the superconducting magnet, specifically including: The evaporation force distribution of the liquid helium bubbles under critical conditions is obtained through the liquid helium boiling state model, and the critical thermal density distribution of the superconducting magnet is obtained according to the evaporation force distribution.

4. The method for determining the boiling criticality of the cooling surface of a high magnetic field superconducting magnet cooled by liquid helium according to claim 1, characterized in that: Before establishing the liquid helium boiling state model of the superconducting magnet based on the equivalent buoyancy of the liquid helium bubbles in directions parallel to the surface of different positions of the superconducting magnet and the corresponding surface tension and evaporation force, the method further includes: Obtaining contact angles between the gas-liquid interface of the liquid helium and surfaces at different positions of the superconducting magnet; The surface tension of the liquid helium bubble in a direction parallel to the surface of the superconducting magnet at different positions is obtained based on the contact angle and the surface tension coefficient of the superconducting magnet.

5. The method for determining the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium according to claim 1, characterized in that: The AC loss heat power distribution of the superconducting magnet is obtained based on the three-dimensional magnetic field distribution, and a thermal simulation analysis is performed on the AC loss heat power distribution, specifically including: AC loss parameters are obtained based on the three-dimensional magnetic field distribution, online AC loss and metal structure eddy current loss of the superconducting magnet are obtained according to the AC loss parameters, and thermal simulation analysis is performed on the online AC loss and metal structure eddy current loss of the superconducting magnet.

6. The method for determining the boiling criticality of the cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium according to claim 1, characterized in that: Acquiring the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model specifically includes: Performing meshing processing on the three-dimensional physical model to obtain a three-dimensional physical mesh; The current parameters and current density distribution of the superconducting magnet are obtained, and based on the current parameters and current density distribution, finite element analysis is performed on each of the three-dimensional physical grids to obtain the three-dimensional magnetic field distribution of the superconducting magnet.

7. A device for judging the boiling criticality of the cooling surface of a liquid helium-cooled high-magnetic field superconducting magnet, characterized in that: A method for determining the boiling criticality of a cooling surface of a high-magnetic field superconducting magnet cooled by liquid helium as claimed in any one of claims 1 to 6, the device comprising: A magnetic field distribution acquisition module, used to establish a three-dimensional physical model of the superconducting magnet, and acquire the three-dimensional magnetic field distribution of the superconducting magnet based on the three-dimensional physical model; A heat flux density acquisition module is used to obtain the critical heat flux density distribution of the superconducting magnet based on the three-dimensional magnetic field distribution and the gravity field; obtain the AC loss heat power distribution of the superconducting magnet based on the three-dimensional magnetic field distribution, perform thermal simulation analysis on the AC loss heat power distribution, and determine the heat flux density distribution of the cooling surface of the superconducting magnet; A boiling state determination module, used for comparing the heat flux density distribution with the critical heat flux density distribution to determine the boiling state of the liquid helium on the surface of the superconducting magnet; The heat flux density acquisition module is specifically used for: A liquid helium boiling state model of the superconducting magnet is established based on the three-dimensional magnetic field distribution and the gravity field, and a critical heat flux density distribution of the superconducting magnet is obtained through the liquid helium boiling state model of the superconducting magnet; A liquid helium boiling state model of the superconducting magnet is established based on the three-dimensional magnetic field distribution and the gravity field, specifically comprising: Obtaining an equivalent gravity field based on the three-dimensional magnetic field distribution and the gravity field, and establishing a liquid helium boiling state model of the superconducting magnet based on the equivalent gravity field; The liquid helium boiling state model is used to characterize the dynamic change of the liquid helium from nucleate boiling to film boiling; the liquid helium generates liquid helium bubbles under the nucleate boiling; A liquid helium boiling state model of the superconducting magnet is established based on an equivalent gravitational field, specifically comprising: Determining an equivalent inclination of the equivalent gravity field relative to the gravity field based on the direction of the equivalent gravity field and the direction of the gravity field; Obtaining an equivalent gravity of the liquid helium bubbles on the surface of different positions of the superconducting magnet based on the equivalent gravity field, and determining an equivalent buoyancy of the liquid helium bubbles in a direction parallel to the surface of different positions of the superconducting magnet based on the equivalent gravity and the equivalent inclination; A liquid helium boiling state model of the superconducting magnet is established based on the equivalent buoyancy of the liquid helium bubbles in directions parallel to the surfaces of different positions of the superconducting magnet and the corresponding surface tension and evaporation force.

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