10 kWe空间堆闭式布雷顿系统驱动单元设计

Design of drive unit in closed Brayton system for 10 kWe space reactor

针对空间反应堆要求能量密度高和长寿命等特点,提出一种以气体箔片轴承作为支承,高效率径流式叶轮作为驱动的离心式压气机设计方案。以特定流量、压力、功率和效率作为设计依据,进行叶轮的气动设计,得到高效率压气机和高效率径流式涡轮模型。基于有限元法,对径向气箔轴承的顶箔变形分别采用欧拉梁和厚板模型进行表达,并结合Reynolds方程进行求解,厚板模型的计算结果准确反映了顶箔沿轴向的变形,由此得到的气膜厚度、气膜压力和承载力更加符合实际,在厚板模型基础上求得轴承动态刚度和阻尼系数更为合理。选取合理的轴承模型获取了转子系统的临界转速和闭式布雷顿系统的最低起飞转速,并由线性轴心轨迹得知转子系统在额定工况具有更好的稳定性。最后对止推箔片轴承的承载特性进行了分析,提出了装配注意事项,为10 kWe空间堆闭式布雷顿系统驱动单元样机研制提供了理论指导。

According to the characteristics of high energy density and long life of space reactor,a design scheme of centrifugal compressor driven by gas foil bearing and high efficiency radial flow impeller is proposed.Based on the specific flow rate,pressure,power and efficiency,the aerodynamic design of the impeller is carried out,and the high efficiency compressor and the high efficiency radial turbine model are obtained.Based on the finite element method,the top foil deformation of the radial air foil bearing is expressed by Euler beam and thick plate model,and solved by the Reynolds equation.The calculation results of the thick plate model accurately reflect the deformation of the foil along the axial direction.It is more reasonable to obtain the dynamic stiffness and damping coefficient of the bearing based on this thick plate model.Based on the thick plate model,the dynamic stiffness and damping coefficient of the bearing are obtained.In this paper,the critical speed of rotor system and the minimum take-off speed of closed Brayton system are obtained by using a reasonable bearing model.The rotor system has better stability under rated conditions from the linear axis trajectory.At last,the load-bearing characteristics of thrust foil bearing are analyzed,and the attention points for assembly are put forward.This research provides theoretical guidance for the development of a prototype driving unit of 10 kWe space reactor closed Brayton system.