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Integrated Thermal Analysis of Aerostatic Bearing System

空气静压轴承系统综合热分析

基本信息

批准号：
09650146
负责人：
OHISHI Susumu
金额：
$ 1.6万
依托单位：
Aoyama Gakuin University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

Air bearings have been considered to have little or no heat generation due to the low viscosity of air, and have been applied mainly to ultra precision machine tools with paying a little attention to the thermal effects. With increasing demand for high speed machining, however, the effect of heat generation in the air-film has become not negligible, because the bearing characteristics are very sensitive to the bearing clearance and it changes due to the thermal deformations of the spindle and housing. The spindle expansion by the centrifugal force also affects it. A final goal of the study is to evaluate aerostatic bearing performances under actual operating conditions, and this project has been undertaken to develop finite element programs to calculate pressure distribution in the air-film (incompressive Reynolds equation) and the air-film and housing temperature distributions (the Energy equation). An aerostatic bearing system has been built to measure temperature distributions, pressures and the spindle deflections experimentally. The air flow in the clearance of the bearing can be considered as the combination of Couette flow caused by the moving part (the rotation of the spindle) and Poiseuille flow caused by the pressure, and the calculations show very interesting results regarding to the effects of these flows. In compressive fluid like air, the temperature distributions are different from those in incompressive fluid. Generally, Couette flow always induces temperature rise regardless of incompressive and compressive fluid. On the other hand, Poiseuille flow induces temperature rise in incompressive fluid, but not in compressive fluid. Whenever the pressure gradient is positive, the temperatures always increase. However, the temperatures could decrease in case the pressure gradient is negative. These calculation results suggest that, in aerostatic bearings, there is a possibility of the temperature decrease if the pressure gradient is large and negative.

由于空气粘度低，空气轴承被认为几乎不产生热量，并且主要应用于超精密机床，而很少关注热效应。然而，随着高速加工需求的不断增加，气膜中发热的影响已变得不可忽视，因为轴承特性对轴承间隙非常敏感，并且轴承间隙会因主轴和外壳的热变形而发生变化。离心力引起的主轴膨胀也会对其产生影响。该研究的最终目标是评估实际操作条件下的空气静压轴承性能，该项目旨在开发有限元程序来计算气膜中的压力分布（非压缩雷诺方程）以及气膜和外壳温度分布（能量方程）。已经建立了一个空气静压轴承系统来通过实验测量温度分布、压力和主轴挠度。轴承间隙中的气流可以被认为是由运动部件（主轴旋转）引起的库埃特流和由压力引起的泊肃叶流的组合，并且计算显示了关于这些流的影响的非常有趣的结果。在空气等压缩流体中，温度分布与非压缩流体中的温度分布不同。一般来说，无论非压缩性流体还是压缩性流体，库埃特流总是会引起温度升高。另一方面，泊肃叶流会引起非压缩流体的温度升高，但不会引起压缩流体的温度升高。只要压力梯度为正，温度就会升高。然而，如果压力梯度为负，温度可能会降低。这些计算结果表明，在空气静压轴承中，如果压力梯度较大且为负值，则存在温度降低的可能性。