A helium phase transition cycle cryogenic heat engine system based on the magneto-caloric effect

Abstract

This invention discloses a helium phase change cycle cryogenic heat engine system based on the magnetocaloric effect. The system includes a vacuum insulated container, a liquid helium tank, a plunger pump, a cold source replacement countercurrent heat exchanger, a magnetocaloric regenerator assembly, a cryogenic helium temporary storage and transfer pipeline, an ambient heat energy countercurrent heat exchanger, an expander, a pressure stabilizing tank, and at least two cryogenic circulation pumps. The system includes a main working flow path, a low-pressure cold source flow path, and a cryogenic compensation flow path, forming a closed-loop helium working fluid phase change cycle. The beneficial effects of this invention are: (1) the cold and heat sources share the magnetic bed heat exchange channel, improving heat exchange efficiency; (2) the recovered cryogenic helium is used as a supplementary cold source, enabling the magnetocaloric material to work efficiently close to the Curie temperature; (3) the magnetic bed retains cryogenic helium to participate in the tail gas condensation, compensating for insufficient tail gas liquefaction rate; (4) the closed-loop stable operation continuously outputs mechanical energy and / or electrical energy. The superconducting magnetic source cooling can be replaced by other cryogenic liquids through heat exchange, thereby reducing the amount of liquid helium used.

Description

Technical Field

[0001] This invention relates to the fields of cryogenic engineering, magnetocaloric effect application, cryogenic heat engine and energy conversion technology, and particularly to a helium phase change cycle cryogenic heat engine system based on the magnetocaloric effect. Background Technology

[0002] Liquid helium, due to its extremely low boiling point and excellent cryogenic properties, is widely used in superconducting magnets, quantum computing, particle accelerators, and cryogenic scientific devices. Current research focuses primarily on the refrigeration and liquefaction processes of helium, i.e., how to obtain a liquid helium cold source through external energy input, while research on the utilization of the cryogenic environment formed by liquid helium itself as a thermodynamic cooling sink is relatively limited.

[0003] The magnetocaloric effect (MCE) is a physical phenomenon in which magnetic materials reversibly release or absorb heat under varying external magnetic fields. Current technologies primarily utilize it in magnetic refrigeration, with the core objective of lowering the temperature of the target object. However, the magnetocaloric effect is essentially a reversible heat exchange mechanism and is not limited to refrigeration applications. With appropriate thermodynamic cycle design, it can also be used in energy conversion processes.

[0004] On the other hand, helium has extremely low latent heat of liquefaction and high specific heat capacity at constant pressure in the cryogenic region, making its phase transition process under cryogenic conditions extremely sensitive to temperature changes. This characteristic provides a unique physical basis for constructing efficient thermodynamic cycles in the cryogenic region.

[0005] There are existing theoretical studies on the conversion of liquid helium into mechanical energy at low temperatures through the magnetocaloric effect (e.g., invention application "A Helium Magnetocaloric Phase Change Cyclic Power Device" (CN120556993A)). However, the principle of this method has the following shortcomings: (1) Due to the different pressures of the cold and hot helium sources, they are usually divided into different heat exchange channels, which limits the lateral heat exchange efficiency of the magnetocaloric material in different channels. (2) In the helium liquefaction temperature range, the initial temperature of the magnetocaloric material before demagnetization and cooling is difficult to maintain stably in the optimal Curie temperature range, and the magnetocaloric effect is not fully utilized. (3) It is not easy to completely reliquefy the exhaust gas, which leads to an imbalance in the phase change quality and makes it impossible to maintain closed-loop operation.

[0006] Therefore, there is an urgent need for a new system structure and working cycle to extend the magnetocaloric effect from a single refrigeration application to a heat engine application, and to deeply couple it with the helium phase change process, thereby achieving efficient utilization of low-temperature thermal energy. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a helium phase change cycle cryogenic heat engine system based on the magnetocaloric effect. The system includes a liquid helium tank, a cold source displacement countercurrent heat exchanger, a magnetocaloric regenerator assembly, a cryogenic helium annular temporary storage and transfer pipeline, an ambient heat energy countercurrent heat exchanger, an expander, and a pressure stabilizing tank. The system comprises mutually coupled first, second, and third flow paths, forming a closed-loop helium working fluid phase change cycle. The first flow path, the main working fluid flow path: The liquid phase outlet of the liquid helium tank is connected in sequence to the high-pressure side of the cold source displacement countercurrent heat exchanger, the working fluid side of the ambient heat energy countercurrent heat exchanger, and the expander via a plunger pump; the expander is connected to the magnetic bed heat exchange channel of the magnetocaloric regenerator assembly via a pressure stabilizing tank; the magnetocaloric regenerator assembly is provided with a gas-liquid mixed phase outlet that returns to the liquid helium tank, thereby forming a circulating flow path for the main working fluid; this first flow path allows the pressurized high-pressure helium working fluid to be heated in the cold source displacement countercurrent heat exchanger and the ambient heat energy countercurrent heat exchanger, and then enter the expander to expand and do work to form low-pressure exhaust gas, which releases heat and condenses back to the liquid helium tank under the action of magnetocaloric effect in the magnetocaloric regenerator assembly; The second flow path, the low-pressure cold source circulation flow path: the magnetic bed heat exchange channel of the magnetic thermal regenerator assembly is also connected to the low-pressure side of the cold source displacement counterflow heat exchanger, and a circulation pump A is connected in series between the magnetic bed heat exchange channel and the low-pressure side of the cold source displacement counterflow heat exchanger, thereby forming a low-pressure cold source circulation flow path; wherein, the low-pressure side and the high-pressure side of the cold source displacement counterflow heat exchanger form a counterflow heat exchange relationship within the cold source displacement counterflow heat exchanger; The third flow path, the cryogenic helium temporary storage and transfer compensation flow path: The cryogenic helium annular temporary storage and transfer pipeline is connected to the magnetic bed heat exchange channel of the magnetothermal regenerator assembly via valve control. The cryogenic helium annular temporary storage and transfer pipeline is divided into multiple temperature zones along the circumference. The valve group is used to control the connection between the multiple temperature zones and the magnetothermal regenerator assembly, thereby forming a cryogenic helium temporary storage, transfer and supply flow path. It is used to replenish cryogenic helium step by step and buffer pressure fluctuations. In the later stage of magnetic bed demagnetization and refrigeration, it temporarily stores the unliquefied cryogenic helium. After the magnetic bed is magnetized and releases heat, it provides cryogenic precooling to the magnetothermal material. It is the first to condense when the magnetothermal material is demagnetized and refrigerated, and flows back to the liquid helium tank together with the exhaust gas.

[0008] The magnetic bed heat exchange channel has valves at both ends that are selectively connected to the first flow path, the second flow path, and the third flow path, respectively, forming a connection structure between the first flow path, the second flow path, and the third flow path and the same magnetic bed heat exchange channel at different operating stages. This allows the low-pressure high-temperature helium gas in the first flow path or the low-pressure low-temperature helium gas in the second and third flow paths to flow through the same magnetic bed heat exchange channel alternately or selectively at similar pressure levels for heat exchange.

[0009] Preferably, the system further includes: The fourth flow path, the superconducting magnetic source cooling flow path: The liquid helium tank is connected to the liquid helium cooling channel of the superconducting magnetic source coil in the magnetocalor regenerator assembly via a circulation pump B. The return end of the liquid helium cooling channel is connected to the liquid helium tank, thereby forming a superconducting magnetic source cooling circuit. Depending on its superconducting critical temperature, the superconducting magnetic source coil in the magnetocalor regenerator assembly can use other liquid gases besides liquid helium as the cooling medium. After the alternative cooling medium absorbs heat and vaporizes, its heat is released through a pipeline heat exchanger to the low-pressure cold source helium in the second flow path, achieving heat exchange. The condensed cooling medium returns to the superconducting coil for heat exchange after passing through the circulation pump.

[0010] Preferably, the liquid helium tank, plunger pump, cold source replacement countercurrent heat exchanger, magnetothermal regenerator assembly, circulation pump A, circulation pump B, and cryogenic helium annular temporary storage transfer pipeline are all located in an insulated vacuum chamber or vacuum insulated tank to isolate the thermal influence of external heat sources on the internal components. The exposed parts of each component are coated with an infrared reflective coating to reduce mutual radiative heat conduction.

[0011] Preferably, the cold source displacement countercurrent heat exchanger includes a high-pressure side channel and a low-pressure side channel. The high-pressure side channel is located in the first flow path and is connected to the outlet of the plunger pump. The low-pressure side channel is located in the second flow path and is connected to the circulating pump A. The high-pressure side channel and the low-pressure side channel exchange heat in countercurrent within the cold source displacement countercurrent heat exchanger.

[0012] Preferably, the magnetocaloric regenerator assembly includes a magnetic bed and one, two, or more sets of internal and external magnetic sources uniformly distributed along the inside and outside of the magnetic bed. The magnetic bed is a hollow cylindrical structure composed of multiple unit magnetic beds. Magnetothermal material is disposed within each unit magnetic bed, and the pores between the material particles form heat exchange channels for the flow of helium working fluid. The magnetocaloric material is arranged in layers along the flow direction of the helium working fluid, with different layers corresponding to different temperature ranges, forming a magnetocaloric regeneration temperature gradient to cover a wide temperature range from the liquid helium temperature range to above the exhaust gas temperature.

[0013] Each set of magnetic sources includes: an inner magnetic source disposed on the central cavity side of the magnetic bed and an outer magnetic source disposed on the outer periphery side of the magnetic bed, wherein the opposite poles of the inner magnetic source and the outer magnetic source are placed opposite each other on the magnetic bed to generate a magnetic field in the magnetic bed region. Preferably, the inner magnetic source includes double-C or multi-C shaped body structures arranged back-to-back to form a multi-pole equidistant opposite-pole arrangement, and the outer magnetic source includes two or more C-shaped body structures, each corresponding to the opposite pole of the inner magnetic source. The magnetic source is provided with a reinforcing structure to limit the displacement of the magnetic source.

[0014] The inner and outer magnetic sources are superconducting magnetic sources or permanent magnet magnetic sources, and the coils of the inner and outer magnetic sources are equipped with liquid gas cooling channels at corresponding temperatures.

[0015] The magnetothermal regenerator assembly further includes a composite rotating pipeline assembly, which, when the magnetothermal regenerator assembly is rotating, forms a connection structure between the first flow path, the second flow path, and the magnetic bed heat exchange channel. The composite rotating pipeline assembly is provided with a multi-layer rotating sealing structure, which includes at least two sealing rings, and a leakage collection chamber is provided between adjacent sealing rings. The leakage collection chamber is connected to a low-pressure cold source helium pipeline at a similar temperature through a leakage recovery pipeline to recover leaked helium.

[0016] The cryogenic helium annular temporary storage and transfer pipeline is a closed annular pipeline, which is divided into multiple temperature zones along the annular direction. Each temperature zone is used to temporarily store and transfer cryogenic helium within the corresponding temperature range. The cryogenic helium annular temporary storage and transfer pipeline is selectively connected to the magnetic bed heat exchange channel of the magnetothermal regenerator assembly through a valve group. The valve group includes multiple valves, each corresponding to a different temperature section of the cryogenic helium annular temporary storage and transfer pipeline. The valve group is configured to switch open sequentially according to the temperature zone from low temperature to high temperature or from high temperature to low temperature, so as to realize the hierarchical connection between different temperature zones and the magnetic bed of the magnetothermal regenerator unit. This is used for the hierarchical heat exchange and reflux of cryogenic helium between different temperature zones, thereby providing cooling compensation for the deep pre-cooling of the magnetothermal material in the later stage of magnetization and heat release, so that its temperature before demagnetization and cooling is close to the optimal Curie temperature.

[0017] Preferably, when the exhaust gas in the first flow path enters the magnetic bed heat exchange channel, it flows together with the existing helium gas in the magnetic bed heat exchange channel through the magnetic thermal material channel during the flow process, and participates in heat exchange together, so as to increase the total mass of helium gas before condensation and balance the amount of helium gas condensed per unit time with the mass flow rate of exhaust gas. The gas-liquid mixture flowing out of the magnetic bed heat exchange channel undergoes gas-liquid separation in the liquid helium tank. Unliquefied gaseous helium is temporarily stored in different temperature sections of the cryogenic helium annular storage and transfer pipeline, and in subsequent cycles, it is returned to the corresponding unit's magnetic bed heat exchange channel to participate in the pre-cooling of the magnetocaloric material after the magnetic bed releases heat. Furthermore... The system is equipped with a detection mechanism for monitoring the amount of exhaust gas entering the magnetic bed heat exchange channel and the liquid phase flow rate flowing out of the magnetic bed heat exchange channel. When the deviation between the mass of the exhaust gas and the mass of the liquid phase produced is detected to exceed a preset threshold within a set control cycle, the system controls the flow rate and quality of condensed helium by adjusting the rotation frequency of the magnetic bed and / or adjusting the helium flow rate of the cold and hot sources.

[0018] Preferably, the system further includes a control system, which is signal-connected to the valve group, the circulating pump A, and the circulating pump B. The control system is configured to adjust the switching of the valve group and / or the operating status of the circulating pump A and the circulating pump B based on the temperature, flow rate, and / or pressure parameters of the system.

[0019] The beneficial effects of this invention are as follows: By constructing a stable phase change cycle and heat exchange path, this invention achieves efficient conversion of ambient thermal energy into mechanical and electrical energy, significantly improving the system's heat exchange efficiency, cycle stability, and continuous operation capability under low-temperature conditions, and enhancing the energy utilization efficiency and system operational reliability of the helium working fluid phase change cycle process. Specifically: 1. Effect of shared heat exchange channel: Low-pressure cold source helium, low-pressure exhaust gas, and cryogenic helium share the same magnetic bed heat exchange channel and contact the magnetothermal material for heat exchange under similar pressure, which simplifies the structure and improves heat exchange efficiency and cycle stability.

[0020] 2. Cryogenic compensation precooling and temperature zone temporary storage transfer effect: The cryogenic helium ring transfer pipeline temporarily stores unliquefied cryogenic helium gas according to temperature zones and returns it in an orderly manner. This achieves cryogenic precooling and compensation for the magnetocaloric material in the liquefied temperature zone, fills the gap in the cryogenic temperature zone after heat exchange, and keeps the magnetocaloric material always working close to the optimal Curie temperature, thereby improving the magnetocaloric effect and circulation efficiency. 3. Enhanced effect of retained gas helium participating in condensation: The retained gas helium in the magnetic bed heat exchange channel participates in the condensation process together with the exhaust gas, increasing the total mass of helium participating in the phase change and improving the mass of helium in the condensate after heat exchange.

[0021] 4. Cooling capacity matching and effective magnetic thermal temperature range maintenance: By configuring the types and quality of magnetic thermal materials with different Curie temperatures, the magnetic cooling capacity of the magnetic bed is matched with the heat released by the exhaust gas. By utilizing the low latent heat of helium liquefaction, the magnetic thermal materials remain within the effective magnetic thermal response temperature range after absorbing the latent heat of helium phase change, thereby improving condensation efficiency and cycle energy utilization efficiency.

[0022] 5. Comprehensive effect of closed-loop operation and energy conversion: With the above structure and operation mechanism, a closed-loop cycle of helium working fluid phase change and stable work output are realized, improving the feasibility of system engineering and operational reliability. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the principle and flow of Embodiment 1 of the present invention.

[0024] Figure 2 This is a schematic diagram of the magnetic bed and superconducting magnetic source in Embodiment 1 of the present invention.

[0025] Figure 3 This is a schematic diagram illustrating the principle and flow of Embodiment 2 of the present invention.

[0026] Figure 4 This is a schematic diagram of the structure of the magnetothermal regenerator assembly and its composite rotating pipeline and cryogenic annular transfer pipeline in Embodiment 2 of the present invention.

[0027] The attached diagram is labeled as follows: 1. Liquid helium tank; 2. Plunger pump; 3. Cold source replacement countercurrent heat exchanger; 4. Ambient thermal energy countercurrent heat exchanger; 5. Expander; 6. Pressure stabilizing tank; 10. Cryogenic helium annular temporary storage and transfer pipeline; 11. Insulated vacuum chamber; 7. Magnetothermal regenerator assembly; 8. Circulation pump A; 9. Circulation pump B; 71. Magnetic bed; 72. Superconducting magnetic source. Detailed Implementation

[0028] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0029] Example 1 This invention provides a helium phase change cycle cryogenic heat engine system based on the magnetocaloric effect. The system includes: a liquid helium tank 1, a cold source displacement countercurrent heat exchanger 3, a magnetocaloric regenerator assembly 7, a cryogenic helium annular temporary storage and transfer pipeline 10, an ambient heat energy countercurrent heat exchanger 4, an expander 5, and a pressure stabilizing tank 6; wherein... Liquid helium tank 1 is used to store liquid helium and cryogenic helium; cold source replacement countercurrent heat exchanger 3 is used to transfer the heat of low-pressure cold source helium to high-pressure cryogenic helium, realizing low-pressure cold source replacement, so that the low-pressure cold source and low-pressure heat source share the magnetic bed heat exchange channel of the magnetothermal regenerator assembly 7 under the same pressure; magnetothermal regenerator assembly 7 is used to realize reverse temperature heat exchange of cold and hot source helium using the magnetothermal effect, thereby realizing the phase change cycle liquefaction of helium; cryogenic helium annular temporary storage and transfer pipeline 10 is located at the lower end of the magnetic bed 71 of magnetothermal regenerator assembly 7, used for temperature zone storage and transfer of cryogenic helium; ambient heat energy countercurrent heat exchanger 4 is used to absorb ambient heat energy and heat high-pressure helium; expander 5 is a turbine expander used to expand high-pressure helium to do work and output low-pressure exhaust gas; pressure stabilizing tank 6 is used to stabilize the exhaust gas pressure and transport it into magnetothermal regenerator assembly 7. Details: like Figure 1 As shown, the system includes a first flow path, a second flow path, and a third flow path that are coupled to each other, forming a closed-loop cycle of helium working fluid phase change: The first flow path, the main working fluid flow path: The liquid phase outlet of liquid helium tank 1 is connected sequentially to the high-pressure side of cold source displacement countercurrent heat exchanger 3, the working fluid side of ambient heat energy countercurrent heat exchanger 4, and expander 5 via plunger pump 2; expander 5 is connected to the magnetic bed heat exchange channel of magnetothermal regenerator assembly 7 via pressure stabilizing tank 6, and magnetothermal regenerator assembly 7 is provided with a gas-liquid mixed phase outlet that returns to liquid helium tank 1, thus forming a circulation path for the main working fluid; this first flow path allows the pressurized high-pressure helium working fluid to be heated in cold source displacement countercurrent heat exchanger 3 and ambient heat energy countercurrent heat exchanger 4, and then enter expander 5, expand and do work to form low-pressure exhaust gas, and in magnetothermal regenerator assembly 7, under the action of magnetothermal effect, release heat and condense back to liquid helium tank 1; wherein, plunger pump 2 is used to pressurize liquid helium to form high-pressure supercritical helium gas. The second flow path, the low-pressure cold source circulation flow path: the magnetic bed heat exchange channel of the magnetothermal regenerator assembly 7 is also connected to the low-pressure side of the cold source replacement counterflow heat exchanger 3, and a circulation pump A8 is connected in series between the magnetic bed heat exchange channel and the low-pressure side of the cold source replacement counterflow heat exchanger 3, thereby forming a low-pressure cold source circulation flow path; wherein, the low-pressure side and the high-pressure side of the cold source replacement counterflow heat exchanger 3 form a counterflow heat exchange relationship within the cold source replacement counterflow heat exchanger 3; The third flow path, the cryogenic helium temporary storage and transfer compensation flow path: the cryogenic helium annular temporary storage and transfer pipeline 10 is connected to the magnetic bed heat exchange channel of the magnetothermal regenerator assembly 7 via valve control. The cryogenic helium annular temporary storage and transfer pipeline 10 is divided into multiple temperature zones along the circumference. The valve group is used to control the connection between the multiple temperature zones and the magnetothermal regenerator assembly 7, thereby forming the cryogenic helium temporary storage, transfer and supply flow path. In the above three helium flow paths, some of the helium undergoes functional conversion within the magnetothermal regenerator. This mainly involves some of the exhaust gas being converted into cryogenic helium and low-pressure cold source helium. The cryogenic helium is partially converted into low-pressure cold source helium and condensed and liquefied, while the cold source helium is partially converted into retained cryogenic helium, forming a mutually coupled relationship.

[0030] The fourth flow path, superconducting magnetic source cooling flow path: the liquid helium tank 1 is connected to the liquid helium cooling channel of the superconducting magnetic source coil in the magnetocalor regenerator assembly 7 via the circulation pump B9. The return end of the liquid helium cooling channel is connected to the liquid helium tank 1, thereby forming a superconducting magnetic source cooling circuit. The magnetic bed heat exchange channel has valves at both ends that are selectively connected to the first flow path, the second flow path, and the third flow path, respectively, forming a connection structure between the first flow path, the second flow path, and the third flow path and the same magnetic bed heat exchange channel at different operating stages. This allows the low-pressure high-temperature helium gas in the first flow path or the low-pressure low-temperature helium gas in the second flow path to flow through the same magnetic bed heat exchange channel alternately or selectively at similar pressure levels for heat exchange.

[0031] In addition, the liquid helium tank 1, plunger pump 2, cold source replacement countercurrent heat exchanger 3, magnetothermal regenerator assembly 7, circulating pump A8, circulating pump B9, and cryogenic helium annular temporary storage and transfer pipeline 10 are all located inside the insulated vacuum chamber 11 or a vacuum insulated tank to isolate the thermal effects of external heat sources on the internal components. Exposed parts of each component are coated with an infrared reflective coating to reduce radiative heat conduction between them. The expander and pressure stabilizing tank inside the insulated vacuum chamber 11 or outside the vacuum insulated tank also require insulation treatment to reduce the impact of external heat sources.

[0032] The cold source displacement countercurrent heat exchanger 3 includes a high-pressure side channel and a low-pressure side channel. The high-pressure side channel is located in the first flow path and is connected to the outlet of the plunger pump 2. The low-pressure side channel is located in the second flow path and is connected to the circulating pump A8. The high-pressure side channel and the low-pressure side channel exchange heat in countercurrent within the cold source displacement countercurrent heat exchanger 3.

[0033] like Figure 2 As shown, the magnetocaloric regenerator assembly 7 includes a magnetic bed 71 and a superconducting magnetic source 72. The magnetic bed 71 is a hollow cylindrical structure arranged in a ring around the circumference. Magnetothermal material is disposed within the magnetic bed 71, forming a heat exchange channel for the flow of helium working fluid. The heat exchange channel is located within the annular wall thickness of the magnetic bed 71. The superconducting magnetic source 72 includes an inner magnetic source located on the central cavity side of the magnetic bed 71 and an outer magnetic source located on the outer periphery of the magnetic bed 71. The inner and outer magnetic sources are radially opposite to each other, facing each other on the magnetic bed 71, to generate a magnetic field in the region of the magnetic bed 71. The inner magnetic source includes back-to-back double-C or multi-C-shaped structures to form a multi-pole equidistant opposite-pole arrangement. The outer magnetic source includes two or more C-shaped structures, each corresponding to the opposite pole of the inner magnetic source. The magnetic sources are equipped with reinforcing structures to limit relative displacement. The coils of the inner and outer magnetic sources are equipped with liquid gas cooling channels.

[0034] The magnetic bed 71 is composed of multiple independent magnetic bed units spliced ​​together in the circumferential direction. Each magnetic bed unit is filled with magnetothermal material in layers. The magnetothermal material is arranged in layers along the flow direction of the helium working fluid, and different layers correspond to different temperature ranges to form a magnetothermal regeneration temperature gradient, so as to connect and cover the temperature range from the cryogenic temperature zone to the exhaust temperature zone.

[0035] The superconducting magnetic source 72 is a set, two sets or more sets of opposing magnetic sources distributed along the axial direction of the magnetic bed 71. When the size of the magnetic bed increases, multiple sets of opposing magnetic sources can be added axially according to the size of the magnetic bed.

[0036] The magnetothermal regenerator assembly 7 also includes a composite rotating pipeline assembly. When the magnetothermal regenerator assembly 7 is rotating, the composite rotating pipeline assembly forms a connection structure between the first flow path, the second flow path, and the magnetic bed heat exchange channel. The composite rotating pipeline assembly is provided with a multi-layer rotating sealing structure, which includes at least two sealing rings, and a leakage collection chamber is provided between adjacent sealing rings. The leakage collection chamber is connected to a low-pressure cold source helium pipeline at a similar temperature through a leakage recovery pipeline to recover leaked helium.

[0037] The cryogenic helium annular temporary storage and transfer pipeline 10 is a closed annular pipeline, which is divided into multiple temperature zones along the annular direction. Each temperature zone is used to temporarily store and transfer cryogenic helium within the corresponding temperature range. The cryogenic helium annular temporary storage and transfer pipeline 10 is selectively connected to the magnetic bed heat exchange channel of the magnetothermal regenerator assembly 7 through the shortest distance valve and pipeline group. The valve group includes multiple valves, each valve corresponding to a different temperature section of the cryogenic helium annular temporary storage and transfer pipeline 10. The valve group is configured to switch open sequentially according to the temperature zone from low temperature to high temperature or from high temperature to low temperature, so as to realize the staged connection between different temperature zones and the magnetothermal regenerator assembly 7, so as to enable the staged heat exchange and reflux of cryogenic helium between different temperature zones, thereby compensating for heat exchange at the cryogenic end of the magnetothermal regenerator assembly 7 and reducing the fluctuation of circulating pressure.

[0038] When the exhaust gas from the first flow path enters the magnetic bed heat exchange channel, it flows through the magnetothermal material and participates in heat exchange with the existing helium gas in the channel during the demagnetization and refrigeration process, resulting in partial condensation. The gas-liquid mixture flowing out of the magnetic bed heat exchange channel undergoes gas-liquid separation in the liquid helium tank, and the unliquefied helium gas is successively introduced into different temperature sections of the cryogenic helium annular transfer pipeline for temporary storage and transfer. In addition, the system is equipped with a detection mechanism for monitoring the amount of exhaust gas entering the magnetic bed heat exchange channel and the flow rate of the liquid phase flowing out of the magnetic bed heat exchange channel. When the deviation between the mass of the incoming exhaust gas and the mass of the liquid phase produced is detected to exceed a preset threshold within a set control cycle, the magnetic field switching frequency and / or the amount of exhaust gas entering the channel are adjusted to balance the flow rate and mass of the exhaust gas and the condensed liquid helium within the preset threshold range.

[0039] The system also includes a control system, which is signal-connected to the valve group, circulation pump A8 and circulation pump B9. The control system is configured to adjust the switching of the valve group and / or the operating status of circulation pump A8 and circulation pump B9 based on the system's temperature, flow and / or pressure parameters.

[0040] Example 2 This invention provides a helium magnetocaloric phase change cycle cryogenic heat engine system. The system employs a structure with a fixed superconducting magnetic source and a rotating magnetic bed. By rotating the magnetic bed and moving it into and out of the fixed magnetic field, the magnetocaloric material is excited to generate a magnetocaloric effect and execute an active magnetic reheating process, achieving exothermic condensation of the exhaust gas. See also... Figure 1 , Figure 2 , Figure 3 and Figure 4 The details are as follows: I. System Composition and Connections The system in this embodiment includes an adiabatic vacuum chamber 11, a liquid helium tank 1, a plunger pump 2, a cold source displacement countercurrent heat exchanger 3, an ambient heat energy countercurrent heat exchanger 4, a turbine expander 5, a pressure stabilizing tank 6, a magnetothermal regenerator assembly 7, and a cryogenic circulating pump A8 and a circulating pump B9.

[0041] The specific connection relationships are as follows: The liquid phase outlet of liquid helium tank 1 is connected to the high-pressure side of the cold source displacement countercurrent heat exchanger via a plunger pump; The high-pressure side outlet of the cold source replacement countercurrent heat exchanger 3 is connected to the working fluid side inlet of the ambient heat energy countercurrent heat exchanger. The outlet of the ambient thermal energy countercurrent heat exchanger 4 is connected to the inlet of the turbine expander, and the outlet of the turbine expander is connected to the hot end of the magnetic bed heat exchange channel of the magnetic thermal regenerator assembly via the pressure stabilizing tank. The cold end outlet (gas-liquid mixed phase) of the magnetic bed heat exchange channel of the magnetothermal regenerator assembly 7 flows back to the liquid helium tank; The cold end of the magnetic bed heat exchange channel of the magnetothermal regenerator assembly 7 is also connected to the low-pressure side of the cold source replacement counterflow heat exchanger. The low-pressure side outlet returns to the magnetothermal regenerator assembly via circulating pump A to form a low-pressure cold source circulation. The cold end of the magnetic bed heat exchange channel of the magnetothermal regenerator assembly 7 is connected to the cryogenic helium annular temporary storage and transfer pipeline through valve control, forming a cryogenic helium temporary storage and transfer compensation flow path. The inlet of the cooling channel for the superconducting magnetic source coil is connected to the liquid helium tank via the circulation pump B9, and the return end returns to the liquid helium tank, forming a cooling circuit for the superconducting magnetic source.

[0042] Insulated vacuum chamber 11: Dewar flask structure, double-layer vacuum shell, maintains high vacuum inside to suppress convective and conductive heat exchange between components; exposed surfaces and inner walls of each component are covered with infrared radiation shielding material to reduce the impact of radiant heat and ensure the temperature stability of low-temperature core components.

[0043] Liquid helium container 1: A sealed Dewar flask structure with an inner insulation layer and a safety valve. It stores liquid helium and gaseous helium, serving as the system's cold source and working fluid source, continuously replenished through exhaust gas phase change reflux. The gas phase space serves as a temporary storage area for reflux cryogenic helium (approximately 5K). If the superconducting magnetic source uses liquid helium cooling, it also includes cooling reflux helium. The mixed helium temperature is approximately 5K, and the pressure is set according to operating conditions (e.g., 0.1-0.12MPa).

[0044] Plunger Pump 2: A high-efficiency liquid pump that pressurizes liquid helium to a set pressure (e.g., 3.0 MPa) to provide a high-pressure working fluid. The pump has an isentropic efficiency of approximately 90% and is designed with minimal heat loss.

[0045] Cold Source Replacement Countercurrent Heat Exchanger 3: A high-efficiency countercurrent heat exchanger that transfers heat from the high-temperature end of the low-pressure cold source helium to the high-pressure low-temperature supercritical helium, while simultaneously converting the low-pressure helium into the low-pressure cold source required by the magnetothermal regenerator. The high-pressure end connects to the plunger pump outlet and the ambient heat energy countercurrent heat exchanger, while the low-pressure end connects to the magnetothermal regenerator and the circulating pump A8, ensuring minimal heat exchange temperature difference (approximately 4K at the cold end and approximately 5K at the hot end).

[0046] Ambient thermal energy countercurrent heat exchanger 4: Absorbs thermal energy from external heat sources (such as the atmosphere or seawater), and heats high-pressure helium gas to the target temperature of the expander (such as 270K) through the heat exchange medium.

[0047] Turbine Expander 5: A high-efficiency expander with an isentropic efficiency of approximately 85%. It converts the thermal energy of high-pressure helium gas into mechanical work, and discharges low-pressure exhaust gas as a heat source into a pressurization tank. The output mechanical work drives an external load (such as a generator). External insulation is required.

[0048] Pressure stabilizing tank 6: Stabilizes exhaust gas pressure (e.g., 0.12MPa), ensuring stable expander efficiency and heat source pressure entering the magnetothermal regenerator. The tank and pipelines are insulated.

[0049] Magnetothermal Regenerator Assembly 7: The core of the system, consisting of a magnetic bed 71, a composite rotating pipeline, a ring-shaped closed pipeline, a cryogenic helium ring-shaped temporary storage and transfer pipeline, a control valve group, and connecting pipelines. It utilizes the magnetocaloric effect (MCE) and active magnetic regeneration (AMR) principles to achieve helium phase change circulation liquefaction. By optimizing the structure, materials, and the timing control of cold and heat source flow, it achieves efficient heat exchange, dynamic balance of the working fluid, and long-term stability.

[0050] II. Structure of Magnetothermal Regenerator The magnetothermal regenerator assembly 7 includes a magnetic bed 71, a superconducting magnetic source 72, a composite rotating pipeline assembly, and a cryogenic helium annular temporary storage and transfer pipeline 10.

[0051] Magnetic bed structure and support drive: The hollow cylindrical structure is composed of multiple independent magnetic bed units spliced ​​together circumferentially. The modular design allows each unit to expand and contract freely, mitigating thermal stress caused by temperature changes. The magnetic bed is placed vertically, facilitating the natural reflux of liquid helium under gravity and pressure difference. Stable support and precise positioning are achieved through axial pressure bearings in the base and radial rolling bearings between the inner and outer magnetic sources. Precise rotation is driven by a motor via a transmission device, and the heat from the motor is transferred to the high-pressure helium pipeline to prevent heat buildup.

[0052] The number of each magnetic bed unit (e.g., 25 units) is matched with the magnetic source poles in a non-integer multiple to form a staggered arrangement, ensuring a smooth transition between the hot and cold helium gas switching sequences. This design smooths the heat exchange process of the entire system, significantly shortens the transit time of cryogenic helium in the intermediate storage pipeline, effectively improves the heat exchange rate and suppresses pressure fluctuations (controlled to <0.02 MPa), which is crucial for improving system efficiency and stability. The geometric dimensions of the magnetic bed unit (e.g., thickness, width) are optimized in conjunction with the magnetic field strength (5-7T), magnetic pole width, and field transition time (frequency approximately 0.167 Hz) to ensure sufficient heat exchange and reduce thermal hysteresis.

[0053] Magnetocaloric material filling: Each unit magnetic bed is layered with composite magnetocaloric materials (MCMs) with different Curie temperatures to cover a wide temperature range from the highest temperature of the low-pressure cold source (approximately 125K) to the liquid helium temperature range (approximately 2K). Magnetocaloric materials are selected and optimized based on the magnetic source field strength. For example, when using permanent magnets, more layers (e.g., 10-16 layers) and different material combinations (e.g., Gd-Al alloy, Er3Ni, etc.) are required; when using superconducting magnetic sources, the number of layers can be reduced, but the field strength needs to be increased (>5T). Material layering includes a hot end (high Curie temperature, such as Gd), an intermediate layer (transitional material, such as GdY), and a cold end (low Curie temperature, such as DyAl2). Magnetocaloric materials are processed into microparticles, flakes, or filaments to improve specific surface area and heat transfer efficiency; if the magnetic field conversion frequency is too high, the metal-based material needs surface oxidation or coating insulation treatment to reduce eddy current heat loss.

[0054] In the low-temperature region, the specific surface area is increased by gradually reducing the material thickness or particle size (from 0.5-2.0 mm at the hot end to 0.2-0.5 mm at the cold end), thereby enhancing the heat transfer rate between the material and helium. Simultaneously, the density of helium increases significantly with decreasing temperature, leading to a corresponding increase in its flow rate per unit mass. This characteristic partially offsets the increased flow resistance caused by the reduced gaps in the magnetocaloric material, thus ensuring the overall heat transfer and flow performance of the system. The gradation and selection of the magnetocaloric material are based on the exhaust gas temperature and actual operating conditions to ensure seamless temperature transition between the cold and hot helium sources, meeting the temperature difference requirement (<6K) between the low-pressure cold source and the high-pressure helium after heat exchange.

[0055] Dynamic equilibrium mechanism of circulating working fluid: To maintain steady-state operation of the system, the mass of liquid helium condensed in each power cycle must be dynamically balanced with the mass of liquid helium pumped out of the liquid helium tank (including the working fluid liquid helium and the superconducting coolant liquid helium). If a deviation in the total mass inside the liquid helium tank is detected, the control system automatically adjusts the flow rate of the heat source and the magnetic field switching frequency to restore phase change equilibrium.

[0056] This system achieves this goal through the following three core designs: Helium retained in the channel: During the demagnetizing refrigeration stage, the gaseous helium retained in the channel participates in condensation along with the exhaust gas, increasing the total mass of helium participating in the phase change. This enhances the magnetic bed's ability to complete its rated condensation task and improves the system's robustness to changes in operating conditions. The retained cryogenic helium has a low temperature and high density, significantly improving the mass of liquid helium after condensation.

[0057] Helium has a very low latent heat of liquefaction: approximately 20.7 kJ·kg⁻¹. - ¹ This means that a relatively small magnetocaloric effect can drive an efficient phase change process, providing a physical basis for precise control of condensation. The release of latent heat only causes the temperature of the helium gas of the same mass to rise by about 4K, which ensures that after the magnetocaloric material has fully absorbed the latent heat, its temperature change remains within the effective magnetocaloric range of all temperature zones.

[0058] Optimize cooling capacity matching: Precisely configure the type and quality of magnetocaloric materials in each temperature zone to match the total "cooling capacity" with the total heat release of the exhaust gas when the operating conditions are set. At the same time, considering the potential performance degradation of magnetocaloric materials during use, a certain degree of redundancy (such as increasing material mass or using spare configurations) needs to be introduced into the design to ensure long-term stable operation and efficient liquefaction.

[0059] The system is equipped with a detection mechanism for monitoring the amount of exhaust gas entering the magnetic bed heat exchange channel and the flow rate of liquid phase flowing out of the magnetic bed heat exchange channel. When the deviation between the mass of the exhaust gas and the mass of the liquid phase produced is detected to exceed a preset threshold within a set control cycle, the system adjusts the magnetic field switching frequency and / or the amount of exhaust gas or cold source introduced to maintain the balance of the helium phase change cycle.

[0060] Distributed cryogenic helium transfer and storage structure: In the later stages of each magnetocaloric material cooling process, some unliquefied helium (e.g., 5-11K) is recovered as part of the cryogenic cold source temperature distribution zone to supplement the gap in the low-pressure cold source helium cryogenic temperature zone (e.g., 5-12K). This is used for deep pre-cooling of the magnetocaloric material in the later stages of magnetization and heat release, bringing its operating temperature closer to the optimal Curie temperature, thereby enhancing the magnetocaloric effect and improving thermal cycle efficiency. Simultaneously, as stored helium, it participates in the liquefaction process along with the exhaust gas during the demagnetization cooling stage, increasing the overall helium liquefaction rate.

[0061] To efficiently manage cryogenic helium, the system employs a distributed transfer and storage pipeline structure consisting of a closed-loop ring system. These pipelines are directly fixed to the rotating magnetic bed, extending outward from the center of the rotating magnetic bed to the external magnetic source base. They can be arranged in single or multiple layers and divided according to temperature zones (e.g., subdivided temperature zones: 5K, 6K, 7K…11K; or coarsely divided temperature zones: 5K, 7K, 9K, 11K, etc.). Valves with the shortest path are connected to all magnetic bed units to reduce flow resistance and delay. The helium in the 5K temperature zone pipeline originates from the gas phase space of the liquid helium tank.

[0062] The annular transfer and storage pipeline is designed with a certain volume to buffer pressure pulses during the entry and exit of cryogenic helium, keeping fluctuations within a small range (e.g., <0.02MPa). The capacity can be set according to the density of helium at different temperatures and actual operating conditions. The pressure of cryogenic helium entering all transfer and storage pipelines comes from the exhaust gas (e.g., 0.12MPa), and the specific pressure value can be adjusted according to actual operating conditions. Because the pressure within the magnetic bed unit decreases due to the closure of valve F4, a pressure difference is formed (for example, when the same magnetic bed unit enters the cryogenic heat exchange process, valve F4 is closed, other magnetic beds have F4 open, while valve F3 of this magnetic bed remains open, and the booster pump B1 operates, reducing the pressure within this magnetic bed unit to approximately 0.09MPa, at which point a pressure difference of approximately 0.02-0.03MPa is formed with the exhaust gas). Cryogenic helium can return to the magnetic bed unit using this pressure difference, achieving cryogenic circulating heat exchange.

[0063] III. Operating Method and Control Timing The system, coordinated by the control system, sequentially completes the following multi-stage cycles, forming a closed-loop helium magnetocaloric phase change dynamic cycle: (1) Pressurization and heat absorption stage: Liquid helium is pressurized to the working pressure from the liquid helium tank by a plunger pump, becoming high-pressure supercritical helium. This high-pressure helium first flows through a cold source displacement countercurrent heat exchanger, where it exchanges heat with low-pressure cold source helium, thereby cooling the low-pressure helium and converting it into a low-pressure cold source that can directly enter the magnetothermal regenerator. Subsequently, the high-pressure helium further enters the ambient thermal energy countercurrent heat exchanger, absorbing low-grade external thermal energy (such as atmospheric or seawater thermal energy), and heating up to the set inlet temperature of the expander.

[0064] (2) Expansion and work stage: The heated high-pressure helium gas enters the turbine expander and expands and cools down during the near isentropic expansion process, converting its thermal energy into mechanical work to drive an external load (such as a generator). The expanded exhaust gas becomes a low-pressure heat source, which is then regulated by a pressure stabilizing tank and delivered to the hot end of the magnetothermal regenerator.

[0065] (3) Condensation Stage (Demagnetization Refrigeration): Exhaust gas (low-pressure heat source) enters the magnetic bed unit in a demagnetized state under the control of the valve group. During this process, the cryogenic helium gas and exhaust gas remaining in the channel flow through the magnetocaloric material one after another, releasing heat to it, and a fixed amount of helium gas is condensed into liquid. After the gas-liquid mixture flows out of the magnetic bed, it is introduced into the liquid helium tank through the valve for separation. The liquid helium flows back into the tank to maintain the mass balance of the circulating working fluid. The returned gaseous helium enters the corresponding closed loop transfer and storage pipelines to form cryogenic cold sources at different temperatures (such as 5 K-11 K) to fill the temperature gap in the cryogenic temperature range after the heat replacement of the low-pressure cold source.

[0066] (4) Regeneration Stage (Magnetic Heat Release): When the magnetic bed rotates to the magnetization zone, the magnetocaloric material is magnetized and releases heat. At this time, low-pressure cold source helium flows through the magnetic bed unit driven by circulating pump A, absorbs the magnetization heat, and is heated. The heated low-pressure cold source helium returns to the cold source displacement countercurrent heat exchanger, transferring heat to the high-pressure helium through the temperature difference, thus completing heat recovery and circulation closure. After the magnetic bed is magnetized and the cold source helium heat exchange is completed, the cryogenic helium temporarily stored in the transfer pipeline enters the magnetic bed sequentially according to the temperature from high to low through the pressure difference, further reducing the magnetic bed temperature and ensuring the magnetocaloric effect of the magnetocaloric material is close to the optimal Curie temperature.

[0067] (5) Continuous cyclic operation: The system adopts a multi-unit magnetic bed alternating operation mode: when some units are in the condensation stage, other units are in the regeneration stage. The rotation of the magnetic bed and the switching of the valve group (F1-F11) are coordinated in real time by the control system to ensure the continuity and balance of the flow of cold and heat sources, thereby maintaining the overall stable operation of the system.

[0068] Through the above cycle, the system realizes the vaporization and re-condensation phase change process of the working medium, helium. During the cycle, ambient thermal energy is converted into mechanical work by an expander, and finally output as electrical energy. The entire process is carried out under the protection of an adiabatic vacuum chamber and multiple layers of thermal management measures to minimize the interference of external heat on the internal structure and stabilize the temperature of each internal component.

[0069] IV. Optimized Design and Selective Structure (I) Rotating Composite Piping and Valve System: When the magnetic bed rotates, the cold and hot source helium gas passes through a non-metallic, low thermal conductivity composite rotating main pipeline, and then splits into branch pipelines (the same number as the unit magnetic bed) via a ring-shaped pipeline (heat source end, non-cryogenic helium gas transfer and storage pipeline). This accelerates helium gas flow and stabilizes the pressure fluctuations caused by the opening and closing of valves. The branch pipelines connect to the corresponding unit cold and hot source control valves (F1, F3) on the magnetic bed, and the other end of the valves connects to the unit magnetic bed. The magnetic bed valve control system is fixed to the magnetic bed, and its main control power supply is set in the center hole of the composite rotating pipeline at the cold and hot ends of the magnetic bed through the rotating pipeline. This center hole is also used to set up the internal magnetic source cooling pipeline, and the axial position of the internal superconducting magnetic source can be fixed by ropes; the center hole or reserved lines are used to supplement the internal coil current.

[0070] The hot-end composite rotating pipeline of the magnetic bed consists of two composite lines (exhaust gas pipeline and low-pressure cold source hot section pipeline); the cold source end consists of three composite rotating pipelines (gas-liquid mixed gas outlet pipeline, low-pressure cold source booster circulation pump A outlet pipeline, and liquid helium tank cryogenic helium pipeline, approximately 5K). The gas-liquid mixed pipeline requires enhanced insulation. To reduce helium leakage caused by poor cryogenic sealing, 2-3 layers of rotary seals (such as indium or PTFE spring-loaded seals, or fluorosilicone rubber sealing rings wrapped with insulation material, with built-in resistance heating to maintain temperature) are installed at the rotation points of the composite rotating pipelines. Interlayer leakage helium is collected by a vacuum pump and sent to the low-pressure cold source pipeline or liquid helium tank.

[0071] (II) Circular Transfer Pipeline Control Valve Assembly (F5-F11) and Temperature Zone Classification Control: This valve assembly is used for precise reciprocating flow control and temperature classification management of cryogenic helium. All valves are connected at one end to the magnetic bed unit and at the other end to the corresponding temperature zone transfer and storage pipeline. F5-F11 control the inflow and outflow of cryogenic helium in different temperature zones. The temperature zone setting is determined based on the temperature of the low-pressure cold source at the outlet of the booster circulation pump A. For example, when the outlet temperature of A is 12K, the highest temperature of the cryogenic cold source is adjusted to 11K to compensate for the lack of a temperature zone below 12K for the low-pressure cold source helium. The other end of the F5 transfer and storage pipeline is connected to the 5K gas helium tank via a rotating pipeline. The protruding pipelines of the low-pressure cold source and cryogenic helium within the magnetic bed are higher than the gas-liquid mixing pipe and are equipped with caps to prevent liquid helium from flowing in. Helium dispersion devices are also installed at the upper and lower ends of the magnetic bed to avoid heat exchange blind spots.

[0072] (III) Valve Sequence Control: The control system integrates a state machine, PID controller, or mechanical linkage to monitor temperature, time, and flow thresholds in real time, precisely controlling the sequential opening and closing of all valves (F1-F11). A sequential execution strategy is employed to achieve seamless temperature transitions between the refrigeration and heat exchange stages (e.g., the state machine triggers valve switching based on temperature and time), and PID controllers compensate for fluctuations, or mechanical linkages serve as a simplified backup. Multi-mode control enhances system response speed, stability, and optimizability, reduces human intervention, and ensures efficient and redundant operation.

[0073] Demagnetizing and Cooling Stage: When the magnetocaloric material enters the demagnetizing and cooling stage, after the gas-liquid mixed helium in pipeline F2 is completely released, approximately 4.3-6K cryogenic helium enters the gas phase space of the liquid helium tank, mixing to form approximately 5K cryogenic gaseous helium. Subsequently, depending on the approach of the gaseous helium in the pipeline to different set thresholds (preset temperature, time, or flow rate thresholds, primarily time-based), temperature zone switching is performed sequentially: F2 is closed, F6 is opened, and gaseous helium enters the 6K intermediate storage pipeline; when the gaseous helium temperature rises to approximately 7K, F6 is closed, F7 is opened, and gaseous helium enters the 7K intermediate storage pipeline; and so on, until the gaseous helium temperature rises to approximately 11K, at which point F10 is closed, F11 is opened, and gaseous helium enters the 11K intermediate storage pipeline, completing the temperature zone switching for this magnetic bed unit. Other magnetic bed units sequentially execute the above temperature zone classification process, achieving multi-unit cyclic control.

[0074] Cryogenic heat exchange stage: When the magnetic bed unit enters the cryogenic heat exchange stage, the cryogenic helium at its highest temperature flows in reverse: valve F11 opens, and 11K cryogenic helium returns to the magnetic bed for heat exchange via the intermediate storage pipeline through F11; after a set time (temperature or flow rate threshold), F11 closes and F10 opens, allowing 10K cryogenic helium to enter the magnetic bed; this process continues until F5 closes, completing the cryogenic cycle. This design fills the gap in the cryogenic range (5-11K) of the low-pressure displacement cold source, lowering the temperature of the magnetocaloric material to near its optimal Curie temperature before it enters the demagnetization refrigeration stage, ensuring optimal magnetocaloric effect and thus improving the overall heat exchange efficiency and liquefaction rate of helium.

[0075] (iv) Magnetic source structure configuration: A double C-shaped opposite pole arrangement is adopted to provide a uniform high magnetic field (5-7T). The number of magnetic bed units is odd (e.g., 25 magnetic bed units, 4 pole pairs of magnetic source), which is matched with a non-integer multiple of the magnetic poles; the width of the unit magnetic bed is approximately 32% of the width of the magnetic poles. The magnetic source can be rotated or fixed, and the cooling channel supports the replacement of the cryogenic medium, which is released to the low-pressure cold source helium gas through heat exchange.

[0076] V. Recondensation and Heat Balance Design The system achieves heat balance through heat exchange by recondensing an equal amount of exhaust gas. As a calculation example (helium thermophysical property data were calculated using REFPROP 10.0 model software): The helium cycle begins in the initial state of liquid helium. Assume an average pressure P0 = 0.11 MPa, a temperature T0 = 4.31 K, and a specific enthalpy h0 = 0.48 kJ·kg⁻¹. - ¹, mass flow rate =0.01kg / s. The first step of the cycle involves pressurizing the helium using a plunger pump (approximately 90% efficiency), increasing the pressure to P = 3.0MPa. After pressurization, the helium temperature rises to T = 6.95K, and the specific enthalpy increases to h = 22.55kJ·kg⁻¹. - ¹.

[0077] High-pressure, low-temperature helium gas first enters a cold source displacement counter-current heat exchanger, where it exchanges heat counter-currently with cold source helium gas from the low-pressure side, absorbing its heat and increasing in temperature. This high-pressure helium gas then continues to exchange heat indirectly with an ambient heat source (ambient temperature approximately 290 K) through a heat exchange medium, further absorbing ambient heat energy and ultimately reaching a temperature of 270 K, a pressure of 3.0 MPa, and an enthalpy of 1417 kJ / kg. The heated high-pressure helium gas then enters an expander (with an isentropic efficiency of approximately 85%) to expand and perform work, reducing its pressure to a set value P = 0.12 MPa, and its temperature and specific enthalpy to T = 104 K and h = 546 kJ / kg, respectively. - ¹. The net work done during the expansion process is approximately 8.71 kW (based on Δh = 1417 – 546 = 871 kJ·kg). - ¹, Power = ×Δh). The enthalpy change energy that the exhaust gas needs to release during the condensation process is 546 kJ·kg. - ¹. The total system heat load includes exhaust gas enthalpy change, booster pump power of approximately 0.04 kW, hysteresis, eddy currents, friction, and heat leakage (estimated at 0.11 kW), calculated based on mass flow rate. The total heat load is approximately 561 kJ·kg⁻¹. - ¹.

[0078] In a cold source displacement countercurrent heat exchanger, assuming a hot-end heat exchange temperature difference of 5K, the average temperature at the hot end of the low-pressure cold source must reach at least 115K to complete heat exchange. The average outlet pressure is approximately P = 0.11 MPa, corresponding to a specific enthalpy of 602.5 kJ·kg⁻¹. - ¹. After heat exchange with helium from the low-pressure cold source, the outlet temperature of the countercurrent heat exchanger drops to T=11K (a temperature difference of approximately 4K with the high-pressure helium at 6.95K). Assume the inlet pressure of the booster circulation pump A (efficiency approximately 85%) is P=0.10MPa (considering the pressure drop after heat exchange), and the specific enthalpy is h=60.4kJ·kg⁻¹. - ¹, The heat released is 602.5 – 60.4 = 542.1 kJ·kg - ¹. This value is higher than the 561 kJ·kg absorbed by high-pressure helium. - ¹18.9 kJ·kg less - ¹, accounting for approximately 3.4% of the total heat exchange, mainly due to the difference in isobaric specific heat capacity of helium at different pressures for the same flow rate and mass. After pressurization, the outlet pressure at A is P = 0.12 MPa, the temperature is T = 12 K, and h = 64 kJ·kg⁻¹. - ¹(Circulation pump power is approximately 0.04kW).

[0079] To achieve complete liquefaction of an equal amount of exhaust gas during operation, the following solutions can be adopted: Increase the mass flow rate of the low-pressure cold source: make the low-pressure cold source flow rate 3.4% higher than the high-pressure helium mass flow rate to compensate for the heat difference, while maintaining a 5K heat exchange temperature difference at the hot end and a 4K heat exchange temperature difference at the cold end. This scheme adjusts the flow rate through program control, operates stably, and the 3.4% increase in flow rate has a negligible impact on the cold end temperature (temperature fluctuation <0.2K).

[0080] Increasing the initial temperature of the low-pressure cold source: Under the condition that the high-pressure helium and the low-pressure cold source helium flow rates are equal, increasing the temperature of the low-pressure cold source before heat exchange increases the heat transfer. This requires simultaneously increasing the mass of the magnetocaloric material at the hot end of the magnetic bed, or adding another stage of magnetocaloric material to increase the temperature of the final magnetic bed.

[0081] Before demagnetization and cooling, the magnetocaloric material had undergone heat exchange through a low-pressure cold source and then through cryogenic helium. The cold end temperature of the magnetic bed dropped to 5.5K, a temperature difference of 0.5K from the lowest temperature of the cryogenic helium (5K). The hot end temperature dropped to 110K. After demagnetization and cooling, the lowest temperature of the cold end magnetocaloric material could be reduced to approximately 2K, a temperature drop of about 3.5K at this stage. The hot end magnetocaloric material temperature was approximately 90K, a temperature drop of about 20K. The above calculations are based on experimental data from literature on cold and hot end magnetocaloric materials.

[0082] The exhaust gas first enters the magnetothermal regenerator unit through the pre-opened valve F1. When liquid helium is detected, F2 opens, and the helium retained in the magnetic bed and the exhaust gas flow through the magnetic bed successively. The gas-liquid mixture is separated after entering the liquefaction tank. When the helium entering the liquefaction tank reaches the set time threshold, corresponding to a temperature close to 6K, F2 closes. The 6-11K cryogenic helium enters the pipeline gas tank for temporary storage and transfer through the corresponding valves. When F1 and F11 are closed, the refrigeration and heat exchange ends. At this time, the temperature of the cold-end magnetothermal material is about 10K, with a temperature difference of about 0.5-1K with the cryogenic helium. The temperature difference between the hot-end magnetothermal material and the exhaust gas is about 1-2K, approximately 103K.

[0083] To ensure system stability, the mass flow rate of liquid helium generated during condensation in each cycle is... The liq must be balanced with the pump output mass flow rate. Specifically, the mass of liquid helium generated by condensation should be equal to the sum of the plunger pump output mass flow rate and the B2 pump mass flow rate. liq= plunger pump+ B2). If a deviation in the total mass inside the liquid helium tank is detected, the control system will automatically adjust the flow rate of the cold and heat sources and the switching frequency of the magnetic field to restore dynamic balance.

[0084] Magnetic heating stage After the cooling and heat exchange are complete, the magnetic bed enters the magnetization and heat release stage. The initial temperature of the cold end of the magnetic bed is approximately 10K, and the temperature of the hot end is approximately 103K. After magnetization, the cold end temperature rises to 25K (a 15K increase), and the hot end temperature rises to 125K (a 22K increase). F4 is activated early, followed by F3. The low-pressure cold source enters the magnetic bed for heat exchange via drive A. Once the set threshold is reached, F4 is closed, and F3 remains open. Cryogenic helium gas enters the magnetic bed sequentially from high temperature to low temperature (11K-5K) through corresponding valves to continue heat exchange. When F3 and F11 are closed, heat exchange ends, and the final temperature of the cold end of the magnetic bed drops to 5.5K, and the temperature of the hot end drops to 110K. The low-pressure cold source, through circulation A8, transfers the high heat to the high-pressure helium gas via the cold source heat exchanger. After heat exchange, the next demagnetization and cooling stage begins.

[0085] The low-pressure cold source helium gas is circulated, and the flow rate can be flexibly adjusted via program control. Considering the temperature change of the magnetocaloric material during the heat exchange process, the average temperature of the hot-end magnetocaloric material after magnetization and heat release should be higher than 115 K, with a minimum temperature difference of approximately 11 K between it and the exhaust gas. The larger the temperature difference, the better the heat exchange effect and speed. Therefore, the maximum temperature during the magnetization and heat release stage of the hot-end magnetocaloric material is set to be greater than 125 K to optimize heat exchange efficiency.

[0086] The above calculation examples show that the system can achieve stable closed-loop operation within a reasonable parameter range. The specific values ​​can be optimized according to the actual working conditions, which does not limit the scope of protection of this invention.

[0087] VI. Selection and Layering of Magnetothermal Materials This embodiment of the system can use layered filling of magnetocaloric material to cover the temperature range of 2-125K, and provides two material combination schemes suitable for permanent magnet magnetocaloric regenerators and superconducting magnetocaloric regenerators, respectively.

[0088] Combination 1: For permanent magnet magnetothermal regenerators (field strength 1-2T, 10-16 layers): Extremely low temperature layer (2-4K): Dy2Ti2O7+Gd3Ga5O 12 (GGG); Al-doped GGG; Low temperature layer (4-10K): Eu2SiO4+GdPO4; Mid-to-low temperature layer (10-30K): ErAl2+HoCu2; with added Er4PtAl; Mid-temperature layer (30-60K): HoNi2+DyNi2; Medium-high temperature layer (60-100K): DyAl2+TbAl2 (nanocomposite); High-temperature layer (100-125K): GdAl2+La(Fe0) 92 Co0. 08 ) 11.9Si1.1; Added LaFe 13-x Si x .

[0089] Combination 2: For superconducting magnetothermal regenerators (field strength 5-7T, 6-12 layers): Extremely low temperature layer (2-4K): Dy2Ti2O7+RE2Cr2C3 (Er / Ho variant); Low temperature layer (4-10K): EuTiO3+GdPO4; with added Eu(Ti,Nb,Zr)O3; Mid-to-low temperature layer (10-30K): ErAl2+DyNi2; Mid-temperature layer (30-60K): ErCo2+HoMn2; Medium-high temperature layer (60-100K): DyAl2+TbNi2; High-temperature layer (100-125K): MnFe(P,As)+Fe82Hf6Zr7B4Cu1.

[0090] The above materials can be optimized in terms of thermal conductivity and magnetocaloric effect coverage through composite methods (e.g., layered / hot-pressed Sn / Cu network). The material filling ratio can be optimized according to the heat load and heat exchange requirements of each temperature zone to adapt to the liquefaction and regeneration process under continuous circulation.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A magnetic heat effect based helium gas phase transition cycle cryogenic heat engine system, characterized in that, The system includes a liquid helium tank, a cold source displacement countercurrent heat exchanger, a magnetothermal regenerator assembly, a cryogenic helium annular temporary storage and transfer pipeline, an ambient heat energy countercurrent heat exchanger, an expander, and a pressure stabilizing tank; wherein, the system includes a first flow path, a second flow path, and a third flow path coupled together to form a closed-loop helium working fluid phase change cycle: The first flow path, the main working fluid flow path: the liquid phase outlet of the liquid helium tank is connected in sequence to the high-pressure side of the cold source displacement countercurrent heat exchanger, the working fluid side of the ambient heat energy countercurrent heat exchanger, and the expander via a plunger pump; the expander is connected to the magnetic bed heat exchange channel of the magnetothermal regenerator assembly via a pressure stabilizing tank; the magnetothermal regenerator assembly is provided with a gas-liquid mixed phase outlet that returns to the liquid helium tank, thereby forming a circulating flow path for the main working fluid; The second flow path, the low-pressure cold source circulation flow path: the magnetic bed heat exchange channel of the magnetic thermal regenerator assembly is also connected to the low-pressure side of the cold source displacement counterflow heat exchanger, and a circulation pump A is connected in series between the magnetic bed heat exchange channel and the low-pressure side of the cold source displacement counterflow heat exchanger, thereby forming a low-pressure cold source circulation flow path; wherein, the low-pressure side and the high-pressure side of the cold source displacement counterflow heat exchanger form a counterflow heat exchange relationship within the cold source displacement counterflow heat exchanger; The third flow path, the cryogenic helium temporary storage and transfer compensation flow path: the cryogenic helium annular temporary storage and transfer pipeline is connected to the magnetic bed heat exchange channel of the magnetothermal regenerator assembly via valve control. The cryogenic helium annular temporary storage and transfer pipeline is divided into multiple temperature zones along the circumferential direction. The valve group is used to control the connection between the multiple temperature zones and the magnetothermal regenerator assembly, thereby forming a cryogenic helium temporary storage, transfer and supply flow path. The magnetic bed heat exchange channel has two ends connected to the first flow path, the second flow path, and the third flow path respectively through valves, forming a connection structure between the first flow path, the second flow path, and the third flow path and the same magnetic bed heat exchange channel at different operating stages.

2. The system according to claim 1, characterized in that, The system also includes: The fourth flow path, superconducting magnetic source cooling flow path: the liquid helium tank is connected to the liquid helium cooling channel of the superconducting magnetic source coil in the magnetocalor regenerator assembly via the circulation pump B. The return end of the liquid helium cooling channel is connected to the liquid helium tank, thereby forming a superconducting magnetic source cooling circuit.

3. The system according to claim 1 or 2, characterized in that, The liquid helium tank, plunger pump, cold source displacement countercurrent heat exchanger, magnetothermal regenerator assembly, circulation pump A, circulation pump B, and cryogenic helium annular temporary storage and transfer pipeline are all located in a vacuum-insulated environment.

4. The system according to any one of claims 1-3, characterized in that, The cold source displacement countercurrent heat exchanger includes a high-pressure side channel and a low-pressure side channel. The high-pressure side channel is located in the first flow path and is connected to the outlet of the plunger pump. The low-pressure side channel is located in the second flow path and is connected to the circulating pump A. The high-pressure side channel and the low-pressure side channel exchange heat in countercurrent within the cold source displacement countercurrent heat exchanger.

5. The system according to any one of claims 1-4, characterized in that, The magnetothermal regenerator assembly includes a magnetic bed and one, two, or more sets of magnetic sources distributed along the axial direction of the magnetic bed; The magnetic bed is a hollow cylindrical structure that is enclosed in a ring along the circumference. Magnetothermal material is disposed inside the magnetic bed, and the gaps in the magnetothermal material form a magnetic bed heat exchange channel for the flow of helium working fluid. The magnetic bed heat exchange channel is located inside the annular wall of the magnetic bed. The magnetic source includes an inner magnetic source disposed on the central cavity side of the magnetic bed, and an outer magnetic source disposed on the outer periphery side of the magnetic bed, wherein the inner magnetic source and the outer magnetic source are disposed opposite to each other and are placed on the magnetic bed.

6. The system according to claim 5, characterized in that, The magnetic bed is composed of multiple independent magnetic bed units spliced ​​together circumferentially. Each magnetic bed unit is filled with the magnetothermal material in layers. The magnetothermal material is arranged in layers along the flow direction of the helium working fluid, and different layers correspond to different temperature ranges to form a magnetothermal regeneration temperature gradient, so as to connect and cover the temperature range from the liquid helium temperature range to above the exhaust gas temperature range.

7. The system according to claim 5 or 6, characterized in that, The magnetothermal regenerator assembly includes a composite rotating pipeline assembly, which, when the magnetothermal regenerator assembly is rotating, forms a connection structure between the first flow path, the second flow path, and the magnetic bed heat exchange channel. The composite rotary pipeline assembly is provided with a multi-layer rotary sealing structure, which includes at least two sealing rings and a leakage collection chamber between adjacent sealing rings. The leakage collection chamber is connected to a low-pressure cold source helium pipeline at a similar temperature through a leakage recovery pump and pipeline to recover leaked helium.

8. The system according to any one of claims 1-4, characterized in that, The cryogenic helium annular temporary storage and transfer pipeline is a closed annular pipeline, which is divided into multiple temperature zones along the annular direction. Each temperature zone is used to temporarily store and transfer cryogenic helium within the corresponding temperature range. The cryogenic helium annular temporary storage and transfer pipeline is selectively connected to the magnetic bed heat exchange channel of the magnetothermal regenerator assembly through a valve group. The valve group includes multiple valves, each corresponding to a different temperature section of the cryogenic helium annular temporary storage and transfer pipeline. The valve group is configured to switch open sequentially according to temperature zones, from low temperature to high temperature or from high temperature to low temperature, so as to achieve hierarchical connection between different temperature zones and the magnetothermal regenerator assembly.

9. The system according to any one of claims 1-8, characterized in that, When the exhaust gas from the first flow path enters the magnetic bed heat exchange channel, it flows through the magnetothermal material and participates in heat exchange with the existing helium gas in the magnetic bed heat exchange channel during the heat exchange process, and some condensation occurs. The gas-liquid mixture flowing out of the magnetic bed heat exchange channel undergoes gas-liquid separation in the liquid helium tank. Unliquefied gaseous helium is temporarily stored in different temperature sections of the cryogenic helium annular storage and transfer pipeline, and then enters the corresponding heat exchange stage of the magnetic bed unit in subsequent cycles. Furthermore... The system is equipped with a detection mechanism for monitoring the amount of exhaust gas entering the magnetic bed heat exchange channel and the flow rate of liquid phase flowing out of the magnetic bed heat exchange channel. When the deviation between the mass of the exhaust gas and the mass of the liquid phase produced is detected to exceed a preset threshold within a set control cycle, the system adjusts the magnetic bed rotation frequency and / or the amount of helium gas introduced from the cold and heat sources to keep the mass flow rates of the condensed liquid helium and the exhaust gas in balance.

10. The system according to any one of claims 1-9, characterized in that, The system also includes a control system, which is signal-connected to the valve group, the circulating pump A, the circulating pump B, and the circulating pump B. The control system is configured to adjust the switching of the valve group and / or the operating status of the circulating pump A and the circulating pump B based on the temperature, flow rate, and / or pressure parameters of the system.

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