多重复合节流高速超精密气浮主轴的稳定悬浮机理与技术实现方法研究

The unstable suspension mechanism of high-speed air spindle caused by the strongly nonlinear coupling multiple physical fields will be researched in this project. Moreover, the theoretical and technical methods for improving the limiting rotation speed and radial accuracy of the spindle through multiple complex restrictors will be explored. Further, the design theory parameters optimization method of high-speed and ultra-precision spindle will be investigated: 1) The time-variation flow field coupling influenced by gas flow, spindle motion and temperature change will be calculated by using the Direct Numerical Simulation (DNS). And the instability causes of high-speed spindle will be discovered by analyzing the effect of rotating speed, temperature increasing and gas characteristics on the flow status and crucial flow parameters. 2) The relationship between flow parameters and high-speed centrifugal force, uniformity gas film thickness and external disturb force will established. In addition, the quantitative calculation method for limiting rotation speed and radial errors will be investigated by analyzing the dynamic behavior of the spindle acted by time-variation gas pressure. 3) Improve the static and dynamic stiffness and damping by using porous compensator, intersect compensator and asymmetric restrictors. Increase the flow field stability by using flow disturbing technology and cooling system inside stator. Further, a high-speed and ultra-precision gas spindle with multiple complex restrictors will be developed. 4) Research the direct measuring methods for flow velocity and temperature inside gas film. Investigate the high precision testing methods for dynamic stiffness, damping coefficients and radial errors. Further, the performance testing device, calculation and parameters optimization software for gas spindle will be developed.

研究气浮主轴气膜内多物理场非线性强耦合作用导致转子高速运动失稳的内在机理，探索多重复合节流提高极限转速和径向精度，获得高速超精密气浮主轴的设计理论与参数优化方法：1)采用直接数值模拟求取气体流动、转子运动、温度变化耦合作用下气膜内时变流场，分析转速、温升以及气体性质对流动状态和关键流场参数的直接影响，揭示高速转子失稳的内在原因；2)建立高速离心力、非均匀气膜、外部干扰与流场参数之间的内在关系，研究动态气压作用下转子的动力学行为，探索极限转速和径向误差的定量计算方法；3)采用多孔材料、交错节流、非对称节流改善转子静动态刚度和阻尼，扰流诱导与定子冷却提高流场稳定性，结合转子非接触式供气，气膜与工作环境非接触式密封，研制多重复合节流高速超精密气浮主轴；4)研究气膜内气体流速和温度直接测量，转子动态刚度、阻尼和径向误差高精度检测方法，搭建气浮主轴性能实验平台，开发主轴性能计算和设计参数优化软件。

针对高速超精密静压气浮转子性能计算，稳定悬浮机理和性能检测等方面的问题，开展了理论分析、数值计算和实验方法研究，研究内容和取得的成果如下。. 采用有限差分法计算转子静动态性能，纠正了现有文献中理论推导方面存在的错误，得出了快速收敛计算方法；提出了非均匀分布变节流孔直径新型静压气浮转子，对比分析了新型转子和传统转子性能；结果表明，新型转子承载能力和刚度大幅提高，稳定性更好，进一步分析了新型转子参数对其性能的影响，给出了转子性能优化方法。. 首次在有限元法计算气浮转子性能的刚度矩阵中引入转速项，纠正了相关文献理论推导存在的错误；首次分析了转子参数对高度角的影响，定性和定量研究了气体动压效应与高度角之间的关系，从微观流场角度解释了影响转子承载能力、刚度和高度角的内在机理。.推导了气浮转子高速转动时的动力学特性，建立动态刚度和动态阻尼数学模型，研究转子动力学行为，分析转子参数对极限转速和稳定转动的影响；得出了转子极限转速、跳动和不平衡响应等特征，为转子动态性能优化提供依据。. 采用计算流体力学方法对比简单孔式节流(有气腔)、环面节流(无气腔)、沟槽节流、多孔材料节流气浮转子端面止推轴承内气体流场特性，分析了轴承参数对其性能的影响；采用大涡模拟计算轴承表面气体压力波动，分析轴承微幅自激动。提出了复合节流、新型节流、转子表面节流等新型气浮转子结构。. 研制了高速超精密气浮转子性能检测装置，电磁非接触加载克服了接触式加载对无摩擦/极低摩擦气浮系统静动态性能的影响；利用多个高精度传感器，基于数据采集平台，实时检测转子静动态性能；实验结果表明，检测装置在转子450krpm工况下，能稳定可靠工作。