Double-heat-source Brayton cycle design method of laser fusion reactor

Abstract

The invention discloses a double-heat-source Brayton cycle design method for a laser fusion reactor, and the method comprises the steps: considering the design demands of the laser fusion reactor, employing two cooling systems with different operation parameters to work in series, and enabling the two cooling systems to serve as double heat sources of a Brayton cycle system; firstly, a working condition analysis matrix is established and comprises a working medium, circulation configuration, heat source temperature difference and an energy ratio; a circulating system thermodynamic calculation method is adopted, conjugate gradient optimization is carried out, and system performance under different working conditions is obtained; the optimal efficiency under different working conditions is compared, enthalpy analysis and effective energy analysis are combined, and the double-heat-source Brayton cycle characteristics are analyzed; and establishing an equivalent single-heat-source model, comparing performance advantage intervals of the double-heat-source Brayton cycle system, and performing sensitivity analysis on parameters of the double-heat-source system. Aiming at a laser fusion reactor multi-cooling system, a genetic algorithm is adopted to optimize design parameters, and the efficient double-heat-source Brayton cycle system design method is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of laser inertial confinement fusion reactor cycle system design, and in particular to a dual-heat source Brayton cycle design method for a laser fusion reactor. Background Art

[0002] The closed Brayton cycle is renowned for its compact structure and excellent thermodynamic efficiency, particularly at medium and high temperatures. In recent years, this cycle has been extensively researched and applied in a variety of cutting-edge energy fields.

[0003] In the engineering design of nuclear fusion reactors, extracting fusion energy inevitably requires the use of multiple cooling systems. Therefore, achieving efficient and economical utilization of multiple heat sources has become a core issue in the design of fusion reactor thermal cycle systems. The dual-heat-source Brayton cycle, an optimized and improved version of the Brayton cycle, was first applied in the European nuclear fusion project, TECNO FUS. This cycle system achieves significant improvements in thermodynamic performance while maintaining system compactness through innovative heat source configuration. Specifically, high-temperature and low-temperature heat sources can be flexibly integrated in series or parallel to optimize heat source utilization efficiency.

[0004] Existing research has systematically explored various Brayton cycle configurations, categorizing them primarily based on whether the working fluid flow path is split. Non-split configurations include intercooling, reheating, and pre-compression, while split configurations include recompression, improved recompression, preheating, and turbine splitting.

[0005] Currently, the analysis of the dual-heat source Brayton cycle is mainly carried out for specific engineering applications, and there are relatively few comprehensive performance analyses that integrate cycle working fluids, cycle configurations, and various operating conditions. Summary of the Invention

[0006] To fill the gap in the above-mentioned prior art, the purpose of the present invention is to provide a dual-heat source Brayton cycle design method for laser fusion reactors, providing a reference for optimizing cycle design and improving overall system performance in applications such as nuclear fusion.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A dual-heat source Brayton cycle design method for a laser fusion reactor, characterized by comprising the following steps:

[0009] Step 1: Establish a dual-heat source Brayton cycle system operating condition analysis matrix, including the following:

[0010] Based on the operating characteristics of laser fusion reactors, two cooling systems with different operating parameters were connected in series as the high-temperature and low-temperature heat sources, respectively, of the Brayton cycle system. To comprehensively evaluate the thermodynamic performance of the dual-heat-source Brayton cycle system, key design dimensions were identified, including cycle configuration, cycle working fluid, heat source temperature difference, heat source energy ratio, and heat source inlet and outlet temperature difference, and a parameterized operating condition analysis matrix was constructed.

[0011] Step 2: Calculation and optimization of thermodynamic parameters of the dual-heat source Brayton cycle system, including the following:

[0012] 1) Construct a nonlinear system of equations for the key equipment of the Brayton cycle and its complete control equations;

[0013] 2) Establish thermodynamic models for dual-heat-source Brayton cycle systems with different configurations and determine global setting parameters based on the fusion reactor power, operating temperature, pressure, and characteristics of key system equipment. These parameters do not change during iterations.

[0014] 3) Using a nonlinear equation solver and combining it with the heat transfer pinch point theory, the optimization range for parameter iteration is defined. The parameters include the working fluid operating pressure, temperature, and split ratio. During the calculation process, a genetic algorithm is used to iteratively optimize the optimal efficiency and formulate judgment conditions to filter out unreasonable operating conditions that do not conform to the entropy increase law and have only zero solutions under the operating condition analysis matrix, thereby obtaining effective results.

[0015] Step 3: Analysis of the characteristics of the dual-heat source Brayton cycle system, including the following:

[0016] 1) Based on the optimal thermal efficiency of different operating conditions, the impact of different dimensions on the thermodynamic characteristics of the system is analyzed. The effective results are globally compared from five key design dimensions. Typical cases are selected for detailed analysis, and the effective results are analyzed locally.

[0017] 2) Simplify the results, calculate the average efficiency under each single dimension, and calculate the deviation of each result from the two average efficiencies to evaluate the impact of each single dimension on the optimal thermal efficiency level;

[0018] 3) Further analyze the characteristics of the dual-heat source Brayton cycle system. Select typical operating conditions that reflect the characteristics of the dual-heat source Brayton cycle system to conduct temperature-entropy analysis and effective energy analysis. This will reflect the thermodynamic behavior and efficiency change trends of different circulating working fluids under different cycle configurations. It will further reflect the impact of these five key design dimensions on the thermodynamic performance of the dual-heat source Brayton cycle system, providing a reference for system design.

[0019] Step 4: Analysis of the advantage range and parameter sensitivity of the dual-heat source Brayton cycle system, including the following:

[0020] 1) Establish an equivalent single heat source model. That is, by constructing a virtual heat exchanger, the energy of the high-temperature heat source in the dual heat source is transferred to the low-temperature heat source, making it the single heat source of the system. In other words, a single heat source model equivalent to the dual-heat source Brayton cycle system in terms of heat source power is obtained. Then, the corresponding cycle configuration of the dual-heat source Brayton cycle is used for optimization calculation, and these results are used as the evaluation benchmark. The efficiency of the equivalent single heat source model and the dual-heat source Brayton cycle system under different configurations is compared when the heat source temperature and energy ratio change. The range of heat source temperature and energy ratio under the condition of optimal thermal efficiency of the dual-heat source Brayton cycle system is obtained.

[0021] 2) Conduct parameter sensitivity analysis on the dual-heat source Brayton cycle system, that is, analyze the impact of changes in heat source temperature and energy ratio on the optimal thermal efficiency level of the dual-heat source cycle, compare and obtain the changing trends of the dual-heat source Brayton cycle system with respect to heat source temperature and energy ratio, determine the optimal value point of the parameters within the above value range, and design an efficient dual-heat source Brayton cycle system.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. Compared with the traditional analysis of the dual-heat source Brayton cycle for specific engineering applications, the method of the present invention comprehensively considers multiple indicators such as the cycle working fluid, cycle configuration and various operating conditions to obtain a more accurate system optimization result, which more comprehensively reflects the performance of the dual-heat source Brayton system.

[0024] 2. Comprehensively considering the comparison of single heat source equivalent Brayton cycle system models and various performance analysis methods, the applicability of the dual heat source Brayton cycle system is highlighted, providing more reliable, comprehensive and efficient guidance for system design. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of a dual-heat source Brayton cycle design method for a laser fusion reactor according to the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings.

[0027] The present invention is a dual-heat source Brayton cycle design method for a laser fusion reactor. The specific process is as follows: Figure 1 As shown, the following steps are included:

[0028] Step 1: Establish a dual-heat source Brayton cycle system operating condition analysis matrix, including the following:

[0029] Based on the operating characteristics of the laser fusion reactor, two cooling systems with different operating parameters are connected in series as the high-temperature heat source and low-temperature heat source of the Brayton cycle system, respectively. To comprehensively evaluate the thermodynamic performance of the dual-heat-source Brayton cycle system, key design dimensions are determined, including cycle configuration, cycle working fluid, heat source temperature difference, heat source energy ratio, and heat source inlet and outlet temperature difference. By permuting and combining the specific ranges of these key design dimensions, a parameterized operating condition analysis matrix can be constructed. The specific ranges of the key design dimensions of the operating condition analysis matrix are as follows:

[0030] 1) Heat source temperature difference: The maximum outlet temperature of the high temperature heat source (HTHS) is 700℃, while the minimum outlet temperature of the low temperature heat source (LTHS) is 400℃. HS ) are set to 100℃ and 300℃.

[0031] 2) Heat source energy ratio (ε L / ε H ) are: 30% / 70%, 50% / 50%, and 70% / 30%. The numerator is the proportion of low-temperature heat source energy, and the denominator is the proportion of high-temperature heat source energy. There are three cases in total.

[0032] 3) Temperature difference between heat source inlet and outlet (ΔT c ) are 50℃ and 100℃ respectively. When ΔT HS =300℃, the outlet temperatures of HTHS and LTHS are set to 700℃ / 400℃ respectively. HS =100℃, the outlet temperatures of HTHS and LTHS are set to 500℃ / 400℃ and 700℃ / 600℃ respectively, for a total of 6 cases.

[0033] 4) Circulating working fluids: This includes eight fluids: air, nitrogen (N2), helium (He), argon (Ar), carbon dioxide (CO2), sulfur hexafluoride (SF6), propane (C3H8), and xenon (Xe). The first four fluids are considered far-critical fluids, characterized by design conditions above their critical point. The last four fluids are considered near-critical fluids, characterized by design conditions above but close to their critical point.

[0034] 5) Cycle Configuration: Integrate the reheating and recompression processes to efficiently utilize heat sources. Simple heating (SH) and reheating (RH) configurations are considered for the hot side. Four cold side configurations are considered: simple cooling (SC), reheating (RH), recompression 1 (RC1), and recompression 2 (RC2). Combining hot and cold side options yields a total of eight configurations.

[0035] The two dimensions of heat source temperature difference and heat source inlet and outlet temperature difference yielded a total of 18 operating conditions; the circulating fluid dimension included eight fluids; and the combination of hot-side and cold-side circulation configurations yielded eight configurations. By permuting and combining these conditions, a parametric analysis matrix containing 18 × 8 × 8 = 1,152 operating conditions was constructed.

[0036] Step 2: Calculation and optimization of thermodynamic parameters of the dual-heat source Brayton cycle system, including the following:

[0037] 1) For the key equipment of the Brayton cycle, including the turbine, heat exchanger, cooler, main compressor, auxiliary compressor, heat source, etc., a complete set of control equations covering energy conservation, pressure drop, irreversible compression, irreversible expansion, physical property equations, pinch point temperature difference, irreversible loss and system thermal efficiency are established. The above equations constitute a nonlinear equation group.

[0038] 2) Establish thermodynamic models for dual-heat-source Brayton cycle systems of different configurations, and determine global setting parameters based on the fusion reactor power, operating temperature, pressure, and key system equipment characteristics, including pinch point temperature difference, ambient temperature, equipment pressure drop, and turbine machinery efficiency. These parameters do not change during iteration.

[0039] 3) Using a nonlinear equation solver and combining it with the heat transfer pinch point theory, the optimization range for parameter iteration is defined. The parameters mainly include the working fluid operating pressure, temperature, and split ratio. During the calculation process, a genetic algorithm is used to iteratively optimize the optimal efficiency, and judgment conditions are formulated to filter out unreasonable operating conditions that do not conform to the entropy increase law and have only zero solutions under the operating condition analysis matrix, thereby obtaining effective results.

[0040] Step 3: Analysis of the characteristics of the dual-heat source Brayton cycle system, including the following:

[0041] 1) Based on the optimal thermal efficiency of different operating conditions, we analyze the impact of different dimensions on the system's thermodynamic characteristics. We analyze the impact of temperature settings on the computational feasibility of operating condition settings from two perspectives: the heat source temperature difference and the heat source inlet and outlet temperature difference. We globally compare the effective results from three perspectives: the circulating working fluid, the heat source energy ratio, and the circulation configuration. We select typical cases for detailed analysis, examining the impact of heat source quality on optimal thermal efficiency and the differences in average thermal efficiency between near-critical and far-critical working fluids.

[0042] 2) Perform a local analysis of the effective results to analyze the efficiency level of the dual heat source configuration when there is a significant temperature difference between the two heat sources.

[0043] 3) Simplify the results, calculate the average efficiency of each cycle configuration and circulating working fluid separately, and calculate the deviation of each result from the two average efficiencies to evaluate the impact of these two factors.

[0044] 4) Further analyze the characteristics of the dual-heat source Brayton cycle system, select typical operating conditions that reflect the characteristics of the dual-heat source Brayton cycle system for temperature-entropy (Ts) analysis and effective energy analysis, reflect the thermodynamic behavior and efficiency change trend of different circulating working fluids under different cycle configurations, and further reflect the influence of these five key design dimensions on the thermodynamic performance of the dual-heat source Brayton cycle system, providing a reference for system design.

[0045] Step 4: Analysis of the advantage range and parameter sensitivity of the dual-heat source Brayton cycle system, including the following:

[0046] 1) Establish an equivalent single-heat source model. This involves constructing a virtual heat exchanger to transfer the energy of the high-temperature heat source in the dual-heat source to the low-temperature heat source, making it the sole heat source in the system. This results in a single-heat source model equivalent to the dual-heat source Brayton cycle system in terms of heat source power. Optimization calculations are then performed using the corresponding cycle configuration for the dual-heat source Brayton cycle, and these results serve as an evaluation benchmark. The cycle configuration uses a recompression configuration, with air and carbon dioxide as the circulating working fluids. The calculations maintain a fixed minimum heat source inlet temperature. The efficiencies of the equivalent single-heat source model and the dual-heat source Brayton cycle system under different configurations are compared when the heat source temperature and energy ratio vary. This provides the range of heat source temperature and energy ratio values ​​that achieves a higher optimal thermal efficiency level for the dual-heat source Brayton cycle system.

[0047] A parameter sensitivity analysis was conducted on the dual-heat source Brayton cycle system. Focusing on the changing trend of the system's optimal thermal efficiency when the energy ratio of the low-temperature heat source LTHS is in the range of 0.2 to 0.6 and the heat source temperature difference is in the range of 100℃ to 400℃, the influence of different parameters on the optimal thermal efficiency levels of the single heat source cycle and the dual heat source cycle was analyzed. The optimal value point of the parameter within the above value range was determined, and an efficient dual-heat source Brayton cycle system was designed.

Claims

1. A dual-heat source Brayton cycle design method for a laser fusion reactor, characterized by: The steps include: Step 1: Establish a dual-heat source Brayton cycle system operating condition analysis matrix, including the following: Based on the operating characteristics of laser fusion reactors, two cooling systems with different operating parameters were connected in series as the high-temperature and low-temperature heat sources, respectively, of the Brayton cycle system. To comprehensively evaluate the thermodynamic performance of the dual-heat-source Brayton cycle system, key design dimensions were identified, including cycle configuration, cycle working fluid, heat source temperature difference, heat source energy ratio, and heat source inlet and outlet temperature difference. The specific ranges of these key design dimensions were arranged and combined to construct a parameterized operating condition analysis matrix. Step 2: Calculation and optimization of thermodynamic parameters of the dual-heat source Brayton cycle system, including the following: 1) Construct a nonlinear system of equations for the key equipment of the Brayton cycle and its complete control equations; 2) Establish thermodynamic models for dual-heat-source Brayton cycle systems with different configurations and determine global setting parameters based on the fusion reactor power, operating temperature, pressure, and characteristics of key system equipment. These parameters do not change during iterations. 3) Using a nonlinear equation solver and combining it with the heat transfer pinch point theory, the optimization range for parameter iteration is defined. The parameters include the working fluid operating pressure, temperature, and split ratio. During the calculation process, a genetic algorithm is used to iteratively optimize the optimal efficiency and formulate judgment conditions to filter out unreasonable operating conditions that do not conform to the entropy increase law and have only zero solutions under the operating condition analysis matrix, thereby obtaining effective results. Step 3: Analysis of the characteristics of the dual-heat source Brayton cycle system, including the following: 1) Based on the optimal thermal efficiency of different operating conditions, the impact of different dimensions on the thermodynamic characteristics of the system is analyzed. The effective results are globally compared from five key design dimensions. Typical cases are selected for detailed analysis, and the effective results are analyzed locally. 2) Simplify the results, calculate the average efficiency under each single dimension, and calculate the deviation of each result from the two average efficiencies to evaluate the impact of each single dimension on the optimal thermal efficiency level; 3) Further analyze the characteristics of the dual-heat source Brayton cycle system. Select typical operating conditions that reflect the characteristics of the dual-heat source Brayton cycle system to conduct temperature-entropy analysis and effective energy analysis. This will reflect the thermodynamic behavior and efficiency change trends of different circulating working fluids under different cycle configurations. It will further reflect the impact of these five key design dimensions on the thermodynamic performance of the dual-heat source Brayton cycle system, providing a reference for system design. Step 4: Analysis of the advantage range and parameter sensitivity of the dual-heat source Brayton cycle system, including the following: 1) Establish an equivalent single heat source model, that is, by constructing a virtual heat exchanger, the energy of the high-temperature heat source in the dual heat source is transferred to the low-temperature heat source, making it the single heat source of the system, that is, obtaining a single heat source model equivalent to the dual heat source Brayton cycle system in terms of heat source power; Then, optimization calculations were performed using the corresponding cycle configurations of the dual-heat-source Brayton cycle, and these results served as an evaluation benchmark. The efficiencies of the equivalent single-heat-source model and the dual-heat-source Brayton cycle system under different configurations were compared when the heat source temperature and energy ratio varied. The range of heat source temperature and energy ratio values ​​for the dual-heat-source Brayton cycle system, which provides the optimal thermal efficiency, was determined. 2) Conduct parameter sensitivity analysis on the dual-heat source Brayton cycle system, that is, analyze the impact of changes in heat source temperature and energy ratio on the optimal thermal efficiency level of the dual-heat source cycle, compare and obtain the changing trends of the dual-heat source Brayton cycle system with respect to heat source temperature and energy ratio, determine the optimal value point of the parameters within the above value range, and design an efficient dual-heat source Brayton cycle system.

2. The dual-heat source Brayton cycle design method for a laser fusion reactor according to claim 1, characterized in that: In step 2, 1), a nonlinear equation group is constructed for the key equipment of the Brayton cycle and its complete control equations. Specifically, for the key equipment of the Brayton cycle, including the steam turbine, heat exchanger, cooler, main compressor, auxiliary compressor, and heat source, a complete control equation covering energy conservation, pressure drop, irreversible compression, irreversible expansion, physical property equations, pinch point temperature difference, irreversible loss, and system thermal efficiency is established. The above equations constitute a nonlinear equation group.

3. The dual-heat source Brayton cycle design method for a laser fusion reactor according to claim 1, characterized in that: In step 2, 2), global parameters are set, including pinch temperature difference, ambient temperature, equipment pressure drop, and turbomachinery efficiency.

4. The dual-heat source Brayton cycle design method for a laser fusion reactor according to claim 1, characterized in that: In step 3 (1), the impact of different dimensions on the system's thermodynamic characteristics is analyzed based on the optimal thermal efficiency of different operating conditions, and the effective results are globally compared from five key design dimensions. Specifically, the impact of different dimensions on the system's thermodynamic characteristics is analyzed based on the optimal thermal efficiency of different operating conditions, and the impact of temperature settings on the feasibility of operating condition settings is analyzed from the two dimensions of heat source temperature difference and heat source inlet and outlet temperature difference; The effective results are globally compared from three dimensions: circulating working fluid, heat source energy ratio and circulation configuration.

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