弹性流体动压润滑高速低温透平稳定性机理研究

In order to solve the key issues against the stable operation of a high speed cryogenic turboexpander(HSCTP), study will be carried out to explore the mechanism of the stability characteristics of the HSCTP with hydrodynamic lubrication.The HSCTP is configured with the stiffness controllable multi-elastic layers gas foil bearing(MLGFB) which was developed and studied by our group. A fluid-solid numerical model which coupled the multi-elastic layer gas foil deformation with the hydrodynamics of lubrication fluid will be developed to predict the characteristics of the MLGFB. The adjustable features of the overall and local stiffness and structural damping of the MLGFB will be properly considered. Combined the dynamic characteristics of MLGFB with the axial and circumferential vortex motion of HSCTP at the first order critical speed, a transient model that coupled the elastic hydrodynamic lubrication with the motion of high speed rotor will be established to investigate the influence of hydrodynamic lubrication on high speed stability of the HSCTP. The interaction mechanism of the aerodynamic performance in the processes of startup, shut down and high speed running of HSCTP can also be determined. Experiments will be carried out to study the static, dynamic characteristics and stability of the high speed rotor-bearing system. Based on the theoretical and experimental studies, this project is aimed to explore the load bearing mechanism and interrelationship between the coupled vibrations of the hydrodynamic lubrication bearings and high speed rotor of cryogenic turbo-expanders.The results and findings can serve as important guidelines to solve the issue of the high speed unstable vortex motion of HSCTP.

为解决高速低温透平膨胀机稳定性关键问题，以自主提出的可控刚度多层弹性箔片动压气体轴承为基础，进行流体动压润滑支承高速低温透平稳定性机理研究。考虑新型轴承整体和局部刚度及阻尼可调、多重刚度及多重阻尼的特性，建立弹性结构力学特性与狭窄空间内动压润滑气膜动态物理特性分布的耦合模型，对动压润滑刚度和阻尼的产生、构成及作用机理进行研究。继而综合考虑跨一临界高速低温透平转子的轴向及周向涡动，建立流体动压润滑耦合高速转子的瞬态运动模型，揭示弹性流体动压润滑特性对低温透平气动性能和高速稳定性的作用规律。在此基础上，进行高速轴承-转子系统静、动特性及稳定性实验研究，最终掌握高速低温透平气动性能与弹性流体动压润滑稳定性的相互作用机理。通过理论与实验研究，揭示弹性流体动压润滑承载机理，探明流体动压润滑－低温透平转子振动耦合传递的基本规律和影响关系，为解决高速低温透平膨胀机稳定性问题提供重要依据。

本课题研究背景为高速低温透平膨胀机稳定性技术。其应用涉及氦低温系统、中小型空分系统、采用逆布雷顿循环的空气制冷循环包括装甲、潜艇、飞行器环控系统等的关键核心部件-高速透平膨胀机的稳定性。本课题的研究方向为制冷低温领域，高速低温透平机械，特别涉及新一代气体动压润滑作用机理及润滑轴承结构技术准则，及其支承高速低温透平膨胀极转子的动力学模型构建和相关实验研究。本研究的主要内容为（1）多层弹性箔片元件刚度和阻尼的产生、构成及作用机理研究。（2）力学特性对流体动压润滑特性的影响机理研究。（3）建立并求解流体动压润滑与高速低温透平转子运转的瞬态耦合运动模型。（4）进行流体动压润滑轴承-高速转子系统动力学特性及稳定性实验研究。本课题的重要结果（1）成功开发出具有优异性能和我国自主知识产权的新一代可控刚度多层弹性箔片动压气体轴承技术，包括止推箔片轴承技术、径向箔片轴承技术。在25mm主轴转子上进行了实验，证明了可行性和可靠性。（2）完成了上述新型流体动压润滑技术的理论模型构建，包括多层（2层和3层）弹性箔片动压气体径向和止推轴承静态特性、动态特性，多层箔片耦合的形变特性。（3）基于理论模型，完成了多层弹性箔片动压气体轴承阻尼和刚度特性预测与比较、掌握了多层弹性结构流体动压润滑轴承局部和整体刚度特性、结构阻尼及库伦阻尼特性的调节及控制的基本原则。（4）初步形成了弹性流体动压润滑-高速透平转子系统理论结构设计、性能预测、改进及实验研究的完整方法。关键数据及其科学意义(1)多层鼓泡箔片动压径向和止推轴承结构参数，掌握该新型流体动压润滑结构的设计方法。（2）多层鼓泡箔片动压气体径向和止推轴承特性参数，掌握了该种结构轴承的全套性能测试方法，获得了轴承主要性能参数。（3）该结构轴承支承25 mm主轴150标方每小时工业制氧机高速低温透平转子，最高转速达到8.5万转/分钟，最大振幅小于4微米。