A Fluid Dynamic Study of Gas Bearing for High Speed Mini-Scale Turbo Machinery

从气体轴承流动的数值分析、放大模型的低速实验研究三个方面进行了研究。对直径31.8 mm、长45 mm、径向间隙20μ、转速分别为10,000，50,000和100,000转/分的主轴进行了数值研究。数值结果表明，无因次载荷系数与轴承个数之间存在着传统的关系，它们分别代表承载能力和转速。由于轴承内部的压力分布，空气通过轴端间隙进出，并被发现有助于轴承的冷却。根据数值结果，制定了低速模型试验试验台的规格。主轴直径144 mm，长100 mm，径向间隙0.12 mm，由静止型Pr…电机驱动更精致的轴承。在实验中，主轴的周向速度为7.5m/S，最大转速为1000rpm。在主轴的3个轴向位置安装3个高频压力传感器，利用锁相采样系统测量轴承周向压力分布，确定轴承个数和无量纲载荷系数。根据压力分布，无因次载荷系数因空气泄漏而减小。泄漏空气的密封在实际应用中被认为是很重要的。由于轴颈轴承的强烈剪切，产生了陡峭的周向压力梯度。压力梯度对换热特性有显著影响。在直径约为1 mm的微尺度通道进口段，换热得到了很大的强化。其换热性能与冲击换热相当，具有较高的换热性能。较少

Research was carried out from the points of view of three terms, which were a flow analysis of gas bearing by way of numerical approach, low speed experimental investigation of scale up model. and heat transfer investigation of air for mini-scale passage.The numerical investigation was executed for a spindle of 31.8mm diameter,45mm length and radial clearance of 20μ for rotational speed of 10,000,50,000 and 100,000 rpm. Numerical result showed a conventional relationship between non-dimensional load coefficient and bearing number, which represented load capability and rotational speed respectively. Air flowed in and out through the shaft end clearance due to the pressure distribution inside the bearing and was found to contribute to the cooling of the bearing.A specification of test stand for low speed model test was based on the numerical result. The spindle was designed as 144mm diameter, 100mm length and 0.12mm radial clearance and was driven by an electric motor with static type pr … More essurized bearing. The peripheral velocity of the spindle was 7.5m/s for maximum rotational speed of 1,000 rpm in the experiment. Three high frequency pressure transducer were installed in three axial points of the spindle and the pressure distribution in the peripheral direction of the bearing was measured by phase locked sampling system to decide a bearing number and non-dimensional load coefficient. The non-dimensional load coefficient decreased due to the leakage of air according to the pressure distribution. A seal of leakage air was considered to be important for practical application.A steep peripheral pressure gradient was created due to the strong shear in the journal bearing. The pressure gradient gave significant effect on the heat transfer characteristics. At the inlet portion of the mini-scale channel of about 1 mm diameter, it was found that heat transfer was greatly enhanced. The heat transfer performance was equivalent to the impingement heat transfer, which was well known to have a high heat transfer performance. Less