Thermodynamic Analysis Of Space Nuclear Power System Based On Liquid Metal Rankine Cycle

With the continuous development of deep space exploration,space nuclear power system has been used as the future of space exploration of the most potential power energy,its development has been much attention at home and abroad.The space nuclear power supply has many advantages,such as large energy density,stable working performance and environment adaptability,governments and research institutions in many country have invested a great deal of manpower and financial in research and development.In this paper,the thermodynamic characteristics of the space nuclear liquid metal Rankine cycle system are analyzed.Energy analysis and exergy analysis were carried out on the system with the first law of thermodynamics and the second law of thermodynamics,respectively.The thermodynamic parameters of the system are obtained,such as thermal efficiency,energy efficiency,output power and the energy and exergy loss in various component of system.The influence of the ambient temperature,the system operating parameters and the system structure on the thermodynamic properties is analyzed.The thermodynamic characteristics of the system are compared when the four liquid metals are selected.In this thesis,the thermodynamic analysis of the 5MW space nuclear energ y nuclear system in the typical working conditions is carried out.The energy loss and loss of each component in the system are studied and the efficiency of each component is calculated.As a comparison,energy loss mainly occurred in the condenser,accounting for 77.28%,exergy loss of the system mainly occurred in the condenser and the reactor,which accounted for 40.47% and 33.11% respectively.Then select the different space temperature for analysis,with the space ambient temperature increases,the exegy efficiency of the condenser is increased by 45%,The impact on steam generators,reheaters and turbines is not noticeable.The four kinds of liquid metal working materials for potassium,sodium,cesium and rubidium were used in the space nuclear Rankine cycle.First,the thermophysical properties of the four kinds of liquid metals were analyzed,And then by comparing the system's thermal efficiency,output power and the use of liquid metal,it can be seen that the rubidium and cesium working fluid systems have great thermal efficiency,but the output power is low,the output power of the sodium working fluid system is large,but the thermal efficiency is low and the potassium working fluid has good comprehensive performance.At the same time,it can be found that the cesium working fluid system is most susceptible to the change of the temperature of the space environment,and the sodium working fluid is the most stable.Through the analysis of the influence of operating parameters on the system,it can be seen that when the higher temperature is used,the system has better thermodynamic performance,but at the same time,it is necessary to consider the bearing capacity of the material.Finally,the influence of the system structure on the thermodynam ic characteristics of the liquid nuclear Rankine cycle is studied,and select the potassium as the circulating working fluid.By adding the reheat and regenerative cycles in the basic cycle,five kinds of system schemes were proposed to analyze the thermal efficiency,output power and heat absorption of the system.Each stage regenerative cycles can increase the thermal efficiency by 0.4% to 0.5%.When the reheat cycle is added to the system,the output power and thermal efficiency of the system are greatly increased.