Supercritical carbon dioxide cycle system for laser fusion reactor and design method thereof

Abstract

The application discloses a supercritical carbon dioxide cycle system of a laser fusion reactor and a design method thereof, and is used for establishing a high-efficiency power cycle system suitable for a large temperature difference of a multi-heat source of a laser fusion reactor primary loop; the cycle system comprises a heat exchanger connected with heat sources of different temperature ranges, a turbine, a regenerator, a compressor and a cooling device; a high-temperature heat exchanger and a low-temperature heat exchanger are arranged respectively and used for leading out heat of a high-temperature lithium-lead alloy loop and a low-temperature supercritical carbon dioxide loop in the laser fusion reactor; the design method firstly establishes a multi-stage thermodynamic model based on thermodynamic system parameters and a specific configuration of the cycle system; then, the thermodynamic equations of each device are calculated to obtain a cycle system thermal efficiency and thermodynamic parameters of each device; finally, a particle swarm algorithm is used for optimization. The application provides two cycle systems suitable for a large temperature difference of a laser fusion reactor primary loop and a design method for realizing optimal system cycle thermal efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser inertial confinement fusion reactor cycle system design, in particular to two kinds of supercritical carbon dioxide cycle systems of fusion reactors and design methods thereof BACKGROUND

[0002] One of the key problems of laser fusion reactors is the design of the thermoelectric conversion system, and the current mainstream design adopts supercritical carbon dioxide as the main working medium of the dynamic hot spot conversion system, and the working interval of supercritical carbon dioxide is usually 300-400 DEG C; liquid lithium lead is used as the tritium breeding and local cooling medium of the fusion reactor, and the working interval is usually 500-700 DEG C; the temperature range of the two cycles is quite different, and a solution needs to be provided for the cycle characteristics.

[0003] The supercritical carbon dioxide power cycle is a Brayton cycle with carbon dioxide as the working medium. The key of the cycle is to compress the supercritical carbon dioxide near the critical point, which greatly reduces the compression power consumption, so that the supercritical carbon dioxide Brayton cycle can realize high thermal efficiency. In order to improve the cycle thermal efficiency, a reheat cycle is proposed; in the reheat cycle, the working medium on both sides of the low-temperature regenerator has a nearly constant temperature difference, and the high-temperature regenerator works in a relatively high temperature environment, and the reheat cycle reduces the heat transfer temperature difference between the two ends of the regenerator in the cycle system through the shunt, improves the heat transfer performance of the regenerator, and improves the cycle thermal efficiency of the system; although the reheat cycle can achieve very high efficiency, the system heat source needs to be kept at a low temperature difference.

[0004] Because there are multiple heat sources in the laser fusion reactor primary loop, the temperature range is quite different, so the reheat cycle system thermal efficiency decreases. Therefore, how to effectively couple the heat sources of different temperature ranges in the laser fusion reactor primary loop and maintain high cycle efficiency is an important problem in the design of the laser fusion reactor cycle system. SUMMARY

[0005] In order to solve the above problems in the design of the laser fusion reactor cycle system, the purpose of the present application is to provide a supercritical carbon dioxide cycle system of a laser fusion reactor and a design method thereof, to design a multi-stage simple reheat supercritical carbon dioxide cycle system, which is suitable for a laser fusion reactor with small occupied space and simple structure; according to different application requirements, the present application adds devices to the multi-stage simple reheat cycle system to obtain a multi-stage reheat cycle system with relatively complex structure but higher cycle efficiency; a design method is provided to make the system have optimal cycle efficiency; and the deficiencies in the design of the existing laser fusion reactor cycle system are made up.

[0006] The present application achieves the above-mentioned purposes by adopting the following technical solutions:

[0007] The application discloses a supercritical carbon dioxide cycle system of a laser fusion reactor, and relates to the field of laser fusion reactors.

[0008] The multi-stage simple regenerative cycle system comprises a first intermediate heat exchanger 3, a second intermediate heat exchanger 4, a low-temperature heat exchanger 5, a high-temperature regenerator 6, a high-temperature heat exchanger 7, a turbine 8, a low-temperature regenerator 9, a cooler 10 and a main compressor 11.

[0009] In the multi-stage simple regenerative cycle system, the high-temperature heat exchanger 7 and the low-temperature heat exchanger 5 are arranged in a dispersed manner and are coupled with heat sources in different temperature ranges of a laser fusion reactor loop.

[0010] In the multi-stage simple regenerative cycle system, supercritical carbon dioxide working medium flows through the high-temperature heat exchanger 7, the turbine 8, the high-temperature regenerator 6, the low-temperature regenerator 9, the cooler 10 and the main compressor 11 in sequence, and then returns to the high-temperature heat exchanger 7 through the low-temperature regenerator 9, the low-temperature heat exchanger 5 and the high-temperature regenerator 6 to complete a cycle.

[0011] The multi-stage reheat cycle system is more complex than the multi-stage simple reheat cycle system, and the first shunt 12, the second shunt 14 and the auxiliary compressor 13 are added on the basis of the multi-stage simple reheat cycle system, so that a higher dynamic thermoelectric conversion efficiency can be provided for the laser fusion reactor; the inlet and outlet of the auxiliary compressor 13 are respectively connected with the first shunt 12 and the second shunt 14, the first shunt 12 is arranged at the hot side outlet of the low-temperature regenerator 9, and the second shunt 14 is arranged at the cold side outlet of the low-temperature heat exchanger 5;

[0012] In the multi-stage reheat cycle system, the high-temperature heat exchanger 7 and the low-temperature heat exchanger 5 are dispersedly arranged and coupled with heat sources of different temperature ranges in the laser fusion reactor primary loop; the first intermediate heat exchanger 3 and the low-temperature heat exchanger 5 are responsible for leading out the heat of the supercritical carbon dioxide cooling loop 1 in the fusion chamber cladding, and the temperature range is 620K to 690K; the second intermediate heat exchanger 4 and the high-temperature heat exchanger 7 are responsible for leading out the heat of the liquid lithium-lead alloy cooling loop 2 in the fusion chamber cladding, and the temperature range is 770K to 970K; the first intermediate heat exchanger 3 and the second intermediate heat exchanger 4 are used to prevent tritium leakage in the laser fusion reactor;

[0013] In the multi-stage reheat cycle system, the supercritical carbon dioxide working medium flows through the hot side of the high-temperature heat exchanger 7, the turbine 8, the hot side of the high-temperature regenerator 6 and the hot side of the low-temperature regenerator 9 in sequence, and then passes through the first shunt 12; most of the working medium flows through the cooler 10 and the main compressor 11 in the main loop, and then passes through the cold side of the low-temperature regenerator 9 and the cold side of the low-temperature heat exchanger 5; a small part of the working medium is shunted to the auxiliary compressor 13 and is combined with the main loop working medium at the cold side outlet of the low-temperature heat exchanger 5 through the second shunt 14; after the combination, the working medium flows through the cold side of the high-temperature regenerator 6 and returns to the hot side of the high-temperature heat exchanger 7 to complete the cycle;

[0014] The cycle system couples two heat sources with large temperature range difference in the low-temperature supercritical carbon dioxide cooling loop 1 in the fusion chamber cladding of the laser fusion reactor and the high-temperature liquid lithium-lead alloy cooling loop 2 in the fusion chamber cladding, and converts the heat generated in the reactor core into electric energy through the supercritical carbon dioxide working medium; the multi-stage simple reheat cycle system meets the design requirements of the fusion reactor with small construction space, and the multi-stage reheat cycle system meets the design requirements of the fusion reactor with high thermoelectric conversion efficiency.

[0015] The design method of the supercritical carbon dioxide cycle system of the laser fusion reactor comprises the following steps:

[0016] Step 1: confirming the thermodynamic parameters of the supercritical carbon dioxide cycle system

[0017] Confirm the thermodynamic parameters of the laser fusion reactor and supercritical carbon dioxide cycle system, including the rated output power of the laser fusion reactor, the inlet and outlet temperatures of the low-temperature supercritical carbon dioxide cooling circuit 1 and the high-temperature liquid lithium-lead alloy cooling circuit 2 in the blanket of the fusion chamber, the pressure drops of various devices in the cycle system, the adiabatic efficiency of the compressor and the isentropic efficiency of the turbine, the minimum approach temperature of the heat exchanger, the pressure range and temperature range of the supercritical carbon dioxide in the cycle system;

[0018] Step 2: Establish a thermodynamic model of the supercritical carbon dioxide cycle system

[0019] Based on the specific structure of the cycle system, a thermodynamic model is established, including: establishing a heat exchanger pinch point temperature difference model for the high-temperature heat exchanger 7, the low-temperature heat exchanger 5, the high-temperature regenerator 6, the low-temperature regenerator 9 and the cooler 10. The point with the minimum temperature difference inside the heat exchanger is the pinch point. The pinch point temperature difference model divides the enthalpy field of the hot side and the cold side of the heat exchanger into n units. The temperature is calculated using the inlet and outlet pressures on both sides of each unit. The corresponding temperature difference on both sides is calculated, and the minimum temperature difference is compared with the set value to ensure that the heat exchanger exchanges heat in the right direction. An irreversible constant pressure model is established for the turbine 8, the main compressor 11 and the auxiliary compressor 13. The heat balance equations of various devices in the cycle system are established.

[0020] Step 3: Calculation of the thermodynamic parameters of the supercritical carbon dioxide cycle system

[0021] Based on the supercritical carbon dioxide cycle pressure and temperature range in step 1, the temperature and pressure of the supercritical carbon dioxide at the outlet of the cooler 10 are first determined. The maximum pressure of the system is taken as the outlet pressure of the main compressor 11. Combined with the irreversible constant pressure model of the main compressor established in step 2, the enthalpy value and temperature of the supercritical carbon dioxide at the outlet of the main compressor 11 are obtained. Secondly, considering the pressure drops of various devices in the cycle system determined in step 1, the pressures of all nodes in the thermodynamic model of the supercritical carbon dioxide cycle system are obtained.

[0022] Combined with the supercritical carbon dioxide state equation provided by the CoolProp property library and the system thermodynamic parameters determined in step 1, the nonlinear equation solver is used to calculate the thermodynamic model established in step 2. After multiple iterations, the cycle system thermal efficiency and the thermodynamic parameters of each node in the cycle system thermodynamic model are given, including pressure, temperature, enthalpy, working fluid flow rate, turbine and compressor work.

[0023] Step 4: System design optimization

[0024] The decision variables affecting the optimal thermal efficiency of the circulating system include the minimum pressure, the maximum pressure and the minimum temperature of the circulating system; the particle swarm optimization algorithm is adopted, the values near the decisive parameters are randomly selected, the iterative calculation of the thermodynamic model of the circulating system constructed in step 2 is repeatedly carried out through a nonlinear equation solver, the global optimal solution is sought, and the optimal circulating efficiency is obtained until the optimal circulating efficiency is obtained; the parameters corresponding to the optimal circulating thermal efficiency are the best values of the decision variables, and the supercritical carbon dioxide circulating system with the optimal circulating efficiency is determined in combination with the design standard of the supercritical carbon dioxide circulating system of the laser fusion reactor.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. The present application designs a supercritical carbon dioxide circulating system suitable for the laser fusion reactor according to the characteristics that the primary loop of the laser fusion reactor has two heat sources with a large temperature difference. The circulating system adopts the method of arranging high-temperature heat exchangers and low-temperature heat exchangers to couple the supercritical carbon dioxide heat sources and lithium-lead alloy heat sources with different temperature ranges, thereby improving the heat transfer performance of the loop and converting the heat generated by the reactor core into electrical energy.

[0027] 2. The present application designs a multi-stage simple regenerative circulating system, which provides a simple circulating system design for the laser fusion reactor with a tight construction space.

[0028] 3. The present application designs a multi-stage re-regenerative circulating system, which adds equipment to the multi-stage simple regenerative circulating system and can effectively improve the circulating efficiency, thereby providing a more efficient circulating system design for the laser fusion reactor with a relatively loose construction space and high circulating efficiency requirements.

[0029] 4. Unlike the previous fusion reactor design which focuses on fusion principle design and reactor core device design, the present application designs a dynamic thermoelectric conversion scheme suitable for the heat source characteristics of the laser fusion reactor and a system design method with optimal circulating efficiency, thereby making up for the shortcomings of the existing laser fusion reactor circulating system design.

[0030] In summary, the present application designs a supercritical carbon dioxide circulating system suitable for the characteristics of the laser fusion reactor and different application requirements, and provides a corresponding design method, which can establish a design process of the laser fusion reactor circulating system based on model construction and calculation, and can also provide guidance for the actual operation of the laser fusion reactor circulating system. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a schematic diagram of the multi-stage simple regenerative and multi-stage re-regenerative supercritical carbon dioxide circulating system. DETAILED DESCRIPTION

[0032] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the present application will be described clearly and completely below with reference to the drawings in the examples of the present application.

[0033] The laser fusion reactor has two temperature ranges with a large difference, and different cooling circuits using different cooling working substances are used to lead out the heat generated in the laser fusion reactor, which are a low-temperature supercritical carbon dioxide cooling circuit 1 in the fusion chamber cladding and a high-temperature liquid lithium-lead alloy cooling circuit 2 in the fusion chamber cladding; the circulation system adopts a multi-stage simple regenerative cycle based on an improved simple regenerative cycle.

[0034] As shown in Figure 1 The main devices of the multi-stage simple regenerative cycle system include an intermediate heat exchanger 3, an intermediate heat exchanger 4, a low-temperature heat exchanger 5, a high-temperature regenerator 6, a high-temperature heat exchanger 7, a turbine 8, a low-temperature regenerator 9, a cooler 10 and a main compressor 11; the cold side outlet of the low-temperature regenerator 9 is connected to the cold side of the low-temperature heat exchanger 5, and then connected to the cold side inlet of the high-temperature regenerator 6; the cold side outlet of the high-temperature regenerator 6 is connected to the cold side of the high-temperature heat exchanger 7, and then connected to the inlet of the turbine 8; the outlet of the turbine 8 is connected to the hot side of the high-temperature regenerator 6 and the hot side of the low-temperature regenerator 9 in sequence; the hot side outlet of the low-temperature regenerator 9 is connected to the inlet of the cooler 10; the outlet of the cooler 10 is connected to the main compressor 11; and the outlet of the main compressor 11 is connected to the cold side inlet of the low-temperature regenerator 9 to form a loop; the hot side of the low-temperature heat exchanger 5 is connected to the cold side of the first intermediate heat exchanger 3 to form a first intermediate loop; and the hot side of the first intermediate heat exchanger 3 is connected to the low-temperature supercritical carbon dioxide cooling circuit 1 in the fusion chamber cladding; the hot side of the high-temperature heat exchanger 7 is connected to the cold side of the second intermediate heat exchanger 4 to form a second intermediate loop; and the hot side of the second intermediate heat exchanger 4 is connected to the high-temperature lithium-lead alloy cooling circuit 2 in the fusion chamber cladding.

[0035] In the multi-stage simple regenerative cycle system, the high-temperature heat exchanger 7 and the low-temperature heat exchanger 5 are arranged dispersedly and coupled to the heat sources of different temperature ranges of the laser fusion reactor loop; the first intermediate heat exchanger 3 and the low-temperature heat exchanger 5 are responsible for leading out the heat of the low-temperature supercritical carbon dioxide cooling circuit 1 in the fusion chamber cladding, and the temperature range is 620K to 690K; the second intermediate heat exchanger 4 and the high-temperature heat exchanger 7 are responsible for leading out the heat of the high-temperature liquid lithium-lead alloy cooling circuit 2 in the fusion chamber cladding, and the temperature range is 770K to 970K; and the first intermediate heat exchanger 3 and the second intermediate heat exchanger 4 are used to prevent tritium leakage in the laser fusion reactor.

[0036] In the multi-stage simple regenerative cycle system, the supercritical carbon dioxide working substance flows through the hot side of the high-temperature heat exchanger 7, the turbine 8, the hot side of the high-temperature regenerator 6, the hot side of the low-temperature regenerator 9, the cooler 10 and the main compressor 11 in sequence, and then returns to the hot side of the high-temperature heat exchanger 7 through the cold side of the low-temperature regenerator 9, the cold side of the low-temperature heat exchanger 5 and the cold side of the high-temperature regenerator 6 to complete the circulation.

[0037] AsFigure 1 As shown, the multi-stage regenerative cycle system is more complex in structure than the multi-stage simple regenerative cycle system. By adding a first distributor 12, a second distributor 14, and an auxiliary compressor 13 to the multi-stage simple regenerative cycle system, it can provide higher dynamic thermoelectric conversion efficiency for the laser fusion reactor. The inlet and outlet of the auxiliary compressor 13 are respectively connected to the first distributor 12 and the second distributor 14. The first distributor 12 is located at the hot side outlet of the cryogenic regenerator 9, and the second distributor 14 is located at the cold side outlet of the cryogenic heat exchanger 5.

[0038] In the multi-stage reheat cycle system, the high-temperature heat exchanger 7 and the low-temperature heat exchanger 5 are distributed and coupled to heat sources with different temperature ranges in the primary loop of the laser fusion reactor. The first intermediate heat exchanger 3 and the low-temperature heat exchanger 5 are responsible for removing heat from the supercritical carbon dioxide cooling circuit 1 in the fusion chamber cladding, with a temperature range of 620K to 690K. The second intermediate heat exchanger 4 and the high-temperature heat exchanger 7 are responsible for removing heat from the liquid lithium-lead alloy cooling circuit 2 in the fusion chamber cladding, with a temperature range of 770K to 970K. The first intermediate heat exchanger 3 and the second intermediate heat exchanger 4 are used to prevent tritium leakage from the laser fusion reactor.

[0039] In the multi-stage reheat cycle system, supercritical carbon dioxide working fluid flows sequentially through the hot side of high-temperature heat exchanger 7, turbine 8, hot side of high-temperature regenerator 6, and hot side of low-temperature regenerator 9. After passing through the first distributor 12, most of the working fluid flows through cooler 10 and main compressor 11 in the main loop, and then through the cold side of low-temperature regenerator 9 and cold side of low-temperature heat exchanger 5. A small portion of the working fluid is diverted to auxiliary compressor 13, and merges with the working fluid in the main loop at the cold side outlet of low-temperature heat exchanger 5 through the second distributor 14. After merging, the working fluid flows through the cold side of high-temperature regenerator 6 and returns to the hot side of high-temperature heat exchanger 7 to complete the cycle.

[0040] The circulation system couples two heat sources with large temperature differences: a low-temperature supercritical carbon dioxide cooling circuit 1 inside the fusion chamber blanket of the laser fusion reactor and a high-temperature liquid lithium-lead alloy cooling circuit 2 inside the fusion chamber blanket. The heat generated in the reactor core is converted into electrical energy through supercritical carbon dioxide working fluid. The multi-stage simple regenerative circulation system meets the design requirements of fusion reactors with small construction space, while the multi-stage regenerative circulation system meets the design requirements of fusion reactors with high thermoelectric conversion efficiency.

[0041] The design method for the supercritical carbon dioxide cycle system of the laser fusion reactor includes the following steps:

[0042] 1. Based on the core design requirements of CFETR Phase I and the requirements of laser fusion projects such as LIFE and HiPER, the main thermodynamic boundary parameters of the circulation system are determined, including: constant fusion core thermal power of 200MW, high-temperature liquid lithium-lead alloy cooling loop 2 outlet temperature of 970.15K, inlet temperature of 770.15K, low-temperature supercritical carbon dioxide cooling loop 1 outlet temperature of 690.15K, low-temperature heat source inlet temperature of 620.15K, adiabatic efficiency of main compressor 11 and auxiliary compressor 13 of 0.83, isentropic efficiency of turbine 8 of 0.87, minimum heat transfer temperature difference of high-temperature regenerator 6 and low-temperature regenerator 9 of 10K, pressure drop of heat exchanger and regenerator equipment of 0.1MPa, minimum system temperature of 308.15K, minimum pressure of 7.39MPa, and maximum pressure of 25MPa.

[0043] 2. Establish a thermodynamic model based on the specific configuration of the circulating system, including: establishing a heat exchanger pinch temperature difference model for the high-temperature heat exchanger 7, low-temperature heat exchanger 5, high-temperature regenerator 6, low-temperature regenerator 9 and cooler 10 in the circulating system; establishing an irreversible constant pressure model for the turbine 8, main compressor 11 and auxiliary compressor 13; and establishing the heat balance equations for each device in the circulating system.

[0044] 3. The temperature of the supercritical carbon dioxide at the outlet of cooler 10 is determined to be 308.15 K and the pressure to be 7.39 MPa; the maximum system pressure is taken as the pressure at the outlet of main compressor 11, which is 25 MPa; combining the compressor's irreversible constant pressure model and the CoolProp property library, the enthalpy and temperature of the supercritical carbon dioxide at the outlet of main compressor 11 are obtained; secondly, based on the pressure drop of each device in the circulation system, the pressure of all nodes in the thermodynamic model of the supercritical carbon dioxide circulation system is obtained.

[0045] Combining the heat balance equations of all devices, the heat exchanger pinch temperature difference model, the irreversible isobaric model of the turbine and compressor, thermodynamic parameters, and the supercritical carbon dioxide equation of state, a nonlinear equation solver is used to calculate the thermodynamic model. After multiple iterations, the nonlinear equation solver scipy provides the thermal efficiency of the cycle system and the thermodynamic parameters of each node of the cycle system thermodynamic model, including pressure, temperature, enthalpy, working fluid flow rate, and turbine and compressor work.

[0046] Step 4: Decision variables affecting the thermal efficiency of the cycle system include the minimum pressure, maximum pressure, and minimum temperature of the cycle system; invoke the particle swarm optimization algorithm to randomly select values ​​near the three decision variables, and perform repeated iterative calculations using the nonlinear equation solver SciPy to seek the global optimal solution until the particle swarm optimization algorithm finishes iterating and the optimal cycle efficiency is obtained; based on the parameters corresponding to the optimal cycle thermal efficiency, obtain a supercritical carbon dioxide cycle system that meets the requirements of high-efficiency cycle efficiency.

Claims

1. A supercritical carbon dioxide cycle system for a laser fusion reactor, characterized in that: The circulation system is a multi-stage simple regenerative cycle or a multi-stage reheat cycle, which is suitable for laser fusion reactors in different application environments; the multi-stage simple regenerative cycle provides the laser fusion reactor with a small footprint and simple structure for dynamic thermoelectric conversion; Multi-stage reheat cycles, with their relatively complex structural design, provide higher energy conversion efficiency for laser fusion reactors. The multi-stage simple regenerative cycle system includes a first intermediate heat exchanger (3), a second intermediate heat exchanger (4), a low-temperature heat exchanger (5), a high-temperature regenerator (6), a high-temperature heat exchanger (7), a turbine (8), a low-temperature regenerator (9), a cooler (10), and a main compressor (11). The cold-side outlet of the low-temperature regenerator (9) is connected to the cold side of the low-temperature heat exchanger (5), and then connected to the cold-side inlet of the high-temperature regenerator (6). The cold-side outlet of the high-temperature regenerator (6) is connected to the cold side of the high-temperature heat exchanger (7). Then, the turbine (8) inlet is connected, and the turbine (8) outlet is connected in sequence to the hot side of the high-temperature regenerator (6) and the hot side of the low-temperature regenerator (9). The hot side outlet of the low-temperature regenerator (9) is connected to the inlet of the cooler (10), and the cooler (10) outlet is connected to the main compressor (11). The main compressor (11) outlet is connected to the cold side inlet of the low-temperature regenerator (9) to form a loop. The hot side of the low-temperature heat exchanger (5) is connected to the cold side of the first intermediate heat exchanger (3) to form the first intermediate loop. The hot side of the first intermediate heat exchanger (3) is connected to the low-temperature supercritical carbon dioxide cooling loop (1) inside the fusion chamber cladding. The hot side of the high-temperature heat exchanger (7) is connected to the cold side of the second intermediate heat exchanger (4) to form the second intermediate loop. The hot side of the second intermediate heat exchanger (4) is connected to the high-temperature lithium-lead alloy cooling loop (2) inside the fusion chamber cladding. In the multi-stage simple regeneration cycle system, the high-temperature heat exchanger (7) and the low-temperature heat exchanger (5) are arranged separately to couple heat sources of different temperature ranges in the first loop of the laser fusion reactor. Heat exchanger (3) and low-temperature heat exchanger (5) are responsible for removing heat from the low-temperature supercritical carbon dioxide cooling circuit (1) inside the fusion chamber cladding, with a temperature range of 620K to 690K; second intermediate heat exchanger (4) and high-temperature heat exchanger (7) are responsible for removing heat from the high-temperature liquid lithium-lead alloy cooling circuit (2) inside the fusion chamber cladding, with a temperature range of 770K to 970K; first intermediate heat exchanger (3) and second intermediate heat exchanger (4) are used to prevent tritium leakage inside the laser fusion reactor; In a multi-stage simple regenerative cycle system, supercritical carbon dioxide working fluid flows sequentially through the hot side of the high-temperature heat exchanger (7), turbine (8), hot side of the high-temperature regenerator (6), hot side of the low-temperature regenerator (9), cooler (10), and main compressor (11), and then returns to the hot side of the high-temperature heat exchanger (7) via the cold side of the low-temperature regenerator (9), the cold side of the low-temperature heat exchanger (5), and the cold side of the high-temperature regenerator (6) to complete the cycle. The multi-stage regenerative cycle system is more complex in structure than the multi-stage simple regenerative cycle system. It adds a first splitter (12), a second splitter (14) and an auxiliary compressor (13) to the multi-stage simple regenerative cycle system, which can provide higher dynamic thermoelectric conversion efficiency for laser fusion reactors. The inlet and outlet of the auxiliary compressor (13) are connected to the first splitter (12) and the second splitter (14) respectively. The first splitter (12) is located at the hot side outlet of the low-temperature regenerator (9), and the second splitter (14) is located at the cold side outlet of the low-temperature heat exchanger (5). In the multi-stage reheat cycle system, the high-temperature heat exchanger (7) and the low-temperature heat exchanger (5) are distributed and coupled with heat sources of different temperature ranges in the primary loop of the laser fusion reactor; the first intermediate heat exchanger (3) and the low-temperature heat exchanger (5) are responsible for removing the heat from the supercritical carbon dioxide cooling circuit (1) in the fusion chamber cladding, with a temperature range of 620K to 690K; the second intermediate heat exchanger (4) and the high-temperature heat exchanger (7) are responsible for removing the heat from the liquid lithium-lead alloy cooling circuit (2) in the fusion chamber cladding, with a temperature range of 770K to 970K; the first intermediate heat exchanger (3) and the second intermediate heat exchanger (4) are used to prevent tritium leakage in the laser fusion reactor; In the multi-stage reheat cycle system, the supercritical carbon dioxide working fluid flows sequentially through the hot side of the high-temperature heat exchanger (7), the turbine (8), the hot side of the high-temperature regenerator (6), and the hot side of the low-temperature regenerator (9). After passing through the first distributor (12), most of the working fluid flows through the cooler (10) and the main compressor (11) in the main loop, and then through the cold side of the low-temperature regenerator (9) and the cold side of the low-temperature heat exchanger (5). A small portion of the working fluid is diverted to the auxiliary compressor (13) and merges with the working fluid in the main loop at the cold side outlet of the low-temperature heat exchanger (5) via the second distributor (14). After merging, the working fluid flows through the cold side of the high-temperature regenerator (6) and returns to the hot side of the high-temperature heat exchanger (7) to complete the cycle. The circulation system couples two heat sources with large temperature differences: a low-temperature supercritical carbon dioxide cooling circuit (1) in the fusion chamber blanket of the laser fusion reactor and a high-temperature liquid lithium-lead alloy cooling circuit (2) in the fusion chamber blanket. The heat generated in the reactor core is converted into electrical energy through supercritical carbon dioxide working fluid. The multi-stage simple regenerative circulation system meets the design requirements of fusion reactors with small construction space, while the multi-stage regenerative circulation system meets the design requirements of fusion reactors with high thermoelectric conversion efficiency.

2. The design method of the supercritical carbon dioxide cycle system for laser fusion reactors according to claim 1, characterized in that: Includes the following steps: Step 1: Confirm the thermodynamic parameters of the supercritical carbon dioxide cycle system Confirm the thermodynamic parameters of the laser fusion reactor and the supercritical carbon dioxide cycle system, including the rated output power of the laser fusion reactor, the inlet and outlet temperatures of the low-temperature supercritical carbon dioxide cooling circuit (1) and the high-temperature liquid lithium-lead alloy cooling circuit (2) in the fusion chamber, the pressure drop of each device in the cycle system, the adiabatic efficiency of the compressor and the entropy efficiency of the turbine, the minimum terminal difference of the heat exchanger, and the pressure and temperature range of supercritical carbon dioxide in the cycle system. Step 2: Establish a thermodynamic model for the supercritical carbon dioxide cycle system A thermodynamic model is established based on the specific structure of the circulating system, including: establishing a pinch temperature difference model for the heat exchanger (7), the low temperature heat exchanger (5), the high temperature regenerator (6), the low temperature regenerator (9), and the cooler (10). The point with the smallest internal temperature difference of the heat exchanger is the pinch point. The pinch temperature difference model divides the enthalpy field of the hot and cold sides of the heat exchanger into n units. The temperature is calculated using the inlet and outlet pressures on both sides of each unit. The corresponding temperature difference on both sides is calculated, and the minimum temperature difference is compared with the set value to ensure positive heat exchange of the heat exchanger; an irreversible constant pressure model is established for the turbine (8), the main compressor (11), and the auxiliary compressor (13); and the heat balance equations of each device in the circulating system are established. Step 3: Calculation of thermodynamic parameters of the supercritical carbon dioxide cycle system Combining the supercritical carbon dioxide circulation pressure and circulation temperature range in step 1, the temperature and pressure of supercritical carbon dioxide at the outlet of cooler (10) are first determined; the maximum system pressure is taken as the pressure at the outlet of main compressor (11); combined with the irreversible constant pressure model of main compressor established in step 2, the enthalpy and temperature of supercritical carbon dioxide at the outlet of main compressor (11) are obtained; secondly, considering the pressure drop of each device in the circulation system determined in step 1, the pressure of all nodes in the thermodynamic model of the supercritical carbon dioxide circulation system is obtained; Combining the supercritical carbon dioxide equation of state provided by the CoolProp property library and the system thermodynamic parameters determined in step 1, the thermodynamic model established in step 2 is calculated using a nonlinear equation solver. After multiple iterations, the nonlinear equation solver provides the thermal efficiency of the cycle system and the thermodynamic parameters of each node of the cycle system thermodynamic model, including pressure, temperature, enthalpy, working fluid flow rate, turbine and compressor work. Step 4: System Design Optimization The decision variables affecting the optimal thermal efficiency of the circulating system include the minimum pressure, maximum pressure, and minimum temperature of the circulating system. Using a particle swarm optimization algorithm, values ​​near the decisive parameters are randomly selected, and the thermodynamic model of the circulating system constructed in step 2 is iteratively calculated repeatedly through a nonlinear equation solver to seek the global optimal solution until the optimal circulating efficiency is obtained. The parameter corresponding to the optimal circulating thermal efficiency is the best value of the decision variables. Combined with the design standards of the supercritical carbon dioxide circulating system of laser fusion reactor, the supercritical carbon dioxide circulating system with the optimal circulating efficiency is determined.

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