| Space exploration technology has become a significant signal of national comprehensive capabilities.With the steady advancement of China’s space industry,our country is moving to an advanced level in the field of space exploration.The rapid development of space application capabilities and deep space exploration technologies has led to a dramatic increase in the demand for energy for space missions.Liquid metal lithium-cooled reactor coupled with helium-xenon gas(He-Xe gas)closed Brayton cycle is an ideal solution for megawatt-level nuclear power deep space detection system,which can meet the requirements of space missions for high cycle efficiency,large output specific power,light system quality and long service life.It is a hot field for future high-power space energy utilization.This thesis focuses on the optimization design and operation characteristics of high-power deep space exploration nuclear reactor power generation systems and takes the He-Xe closed Brayton cycle power generation system coupled with the megawatt space lithium-cooled reactor as the research object.Firstly,the thermodynamic model and mass model of space lithium-cooled reactor He-Xe Brayton power system with non-ideal gas characteristics are constructed.According to the non-ideal gas characteristics of He-Xe gas,the thermophysical model of He-Xe gas under the non-ideal gas state is established.The deviation of thermophysical parameters caused by non-ideal gas characteristics and the influence of deviation on key parameters of the cycle are clarified and summarized.Through the one-dimensional design of the heat exchangers,six parameters including the temperature of turbine and compressor,and the pressure loss rates,are used as iterative parameters to develop the thermodynamic model and mass model with higher accuracy and stronger component coupling.On this basis,the range of decision parameters and the system optimization directions are clarified by studying the influence of key parameters on system efficiency,output specific power and mass.The results show that there is a significant mutual constraint between different system performance indicators,and there is no certain operating condition that makes multiple performance indicators of the system achieve the best-expected state at the same time.Secondly,the NSGA-Ⅱ method is adopted to solve the problem of mutual restriction among multiple performance indexes of the system.With maximizing energy utilization efficiency,maximizing system output specific power and minimizing system mass as optimization objectives,the multi-objective optimization analysis of the space lithium-cooled reactor Brayton cycle power system is carried out using Python language to obtain the optimal set of solutions for the Pareto frontier under the constraints.The optimal solution of the space nuclear power generation system after multi-objective optimization is determined within three decision algorithms,LINMAP,TOPSIS,and Shannon entropy.These solve the problem of mutual restriction of performance indicators in the process of system optimization and provide a reference for multi-objective system optimization.Finally,based on the simulation requirements in the application process of deep space exploration,the simulation program of He-Xe closed Brayton cycle power system for megawatt space lithium-cooled reactor is developed with Matlab/Simulink.The simulation operation and dynamic response process of the system under different working conditions are analyzed,including starting condition,variable speed condition,variable load condition and reactivity introduction.The research results show that the dynamic process simulation analysis of the megawatt-level space lithium-cooled reactor power generation system can be realized.This model can provide reference and support for the subsequent simulation research on the Brayton... |
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