【作者】 王志伟；

【导师】 严利明；

【作者基本信息】 哈尔滨工业大学 ， 动力工程（专业学位）， 2021， 硕士

【摘要】 随着太空探索的不断深入,对航天器的功率密度、运行寿命等方面提出了更高的要求,传统能源已不再适用于大功率的动力系统,核反应堆电源系统成为当下世界各国的研究热点。在大功率空间核电源系统中,布雷顿循环能量转换系统是能满足兆瓦级核电系统的理想热电转换技术。本文以技术相对成熟且优势明显的空间布雷顿循环作为研究对象,合理设计堆芯结构,以氦氙混合气体为工质,建立布雷顿循环的热力学模型。选取关键参数对循环特性进行热力学分析,并采用遗传算法对循环特性进行优化。选择几种特定成分的工质进行具体性能分析,从多方面探讨不同成分的工质对实际应用的可行性。本文选择了液态金属冷却快中子堆的反应堆方案。燃料元件采用棒状结构,燃料为二氧化铀芯块,包壳材料为锆-4合金,芯块两端存在Be O反射层,并在上端装有压紧弹簧。堆芯内部为正六边形结构,装有360根燃料棒,冷却方式为液态金属钠冷却,采用控制鼓控制。堆芯等效直径为43.8cm,高48.18cm。对比不同惰性气体物性,选择氦氙混合气体作为循环工质,分析了氦氙混合工质的热力学性能和输运性质在不同压力和温度下随摩尔质量的变化情况。在此基础上,建立了空间布雷顿循环的热力学模型,根据各主要部件的数学模型推导出效率和比功的函数模型。在影响循环效率和比功的几个参数变量中,绝热系数、回热度、压损系数会随工质成分的改变而改变,因此选择以上三个参数作为循环的关键参数,而其余参数作为固有参数通过已知条件给出。以压气机压比为变量,分析了关键参数对循环效率和比功的影响。绝热系数对效率和比功影响不大,回热度对效率和比功有积极影响,而压损系数会大幅降低效率和比功。利用遗传算法对循环进行双目标优化,得到帕累托最优解集,可根据不同任务需求选择合适的工况参数。最后,对纯氦气体、15.5g/mol的氦氙混合气体和40.9g/mol的氦氙混合气体从多方面比较其性能,表明40.9g/mol的氦氙混合气体最适合作为空间布雷顿循环的工作流体。更多还原

【Abstract】 With the deepening of space exploration,higher requirements have been put forward on the power density and service life of spacecraft.Traditional energy is no longer suitable for high-power power system,and nuclear reactor power system has become a research hotspot in the world.In the high-power space nuclear power supply system,the Brayton cycle energy conversion system is an ideal thermoelectric conversion technology which can meet the needs of megawatt nuclear power system.In this paper,the space Brayton cycle with relatively mature technology and obvious advantages is taken as the research object.The core structure of the reactor is designed reasonably,and the thermodynamic model of the Brayton cycle is established with He-Xe gas mixture as the working medium.The key parameters were selected for the thermodynamic analysis of the cycle characteristics,and the genetic algorithm was used to optimize the cycle characteristics.Several specific components of the working medium were selected for specific performance analysis,and the feasibility of different components of the working medium for practical application was discussed from many aspects.In this paper,the reactor scheme of liquid metal cooled fast neutron reactor is chosen.The fuel element is of rod structure,the fuel is uranium dioxide pellets,a nd the cladding material is zirconium-4 alloy.There is a Be O reflection layer at both ends of the pellets,and a compression spring is installed at the upper end.The hexagonal structure inside the reactor core contains 360 fuel rods,cooled by liquid metal sodium and controlled by control drums.The core has an equivalent diameter of 43.8cm and a height of 48.18 cm.By comparing the physical properties of different inert gases,the binary mixture of helium and xenon was selected as the circulating working medium.The thermodynamic properties and transport properties of the binary mixture of helium and xenon were analyzed with the change of molar mass under different pressures and temperatures.On this basis,the thermodynamic model of the space Brayton cycle is established,and the function models of efficiency and specific work are derived from the mathematical models of the main components.Among the several parameter variables affecting cycle efficiency and specific work,the adiabatic coefficient,recuperator effectiveness and pressure loss coefficient will change with the change of working medium composition,so the above three parameters are selected as the key parameters of the cycle,while the rest parameters are given as the inherent parameters through known conditions.The influence of key parameters on cycle efficiency and specific work was analyzed with compressor pressure ratio as variable.The adiabatic coefficient has little effect on efficiency and specific work,while the recuperator effectiveness has a positive effect on efficiency and specific work,while the pressure loss coefficient will significantly reduce efficiency and specific work.The double-objective optimization of the cycle was carried out by using genetic algorithm,and the Pareto optimal solution set was obtained.The appropriate operating parameters could be selected according to different task requirements.Finally,the performance of pure helium gas,15.5g/mol He-Xe binary mixture and 40.9g/mol He-Xe binary mixture is compared in many ways,and it is shown that 40.9g/mol He-Xe binary mixture is the most suitable working fluid for the space Brayton cycle.更多还原