真空环境下静压气体轴承内流场分析

发布时间：2018-05-31 10:14

本文选题：真空环境 + 静压气体轴承　；参考：《中国计量大学》2016年硕士论文

【摘要】：因具有摩擦小、精度高、无污染、寿命长等优点,气体轴承被广泛应用于微电子制造和超精密定位设备中,而随着下一代光刻曝光、激光干涉测量和半导体检测技术的发展,超精密运动定位不仅要求定位精度更高,还要求必须在真空或超洁净环境中进行,但真空环境下静压气体轴承性能与大气环境下相比较变化显著。目前对于真空条件下静压气体轴承润滑理论的研究比较少,而且多以单一的连续流为基础,未考虑过渡流和分子流对轴承内部流场的影响。针对此问题,本文以单供气孔应用于真空环境的盘型静压止推轴承作为研究对象,对真空环境下轴承的气体内流场进行了理论分析和实验研究,主要完成了以下几方面的工作:(1)将真空环境气体轴承内流场分为入口区域、承载区域和密封区域三个部分分别进行分析,其中,根据气体薄膜的润滑原理,采用D-T模型和一阶滑移模型对真空环境下气体轴承承载区的润滑问题进行了重点研究。将轴承的参数无量纲化后,通过D-T模型分析得到,增大承载区无量纲入口压力、无量纲入口区域半径,减小轴承外径和气膜厚度的比值,可以使连续流到分子流转变位置外移,提高了气体轴承的相对承载能力,通过一阶滑移模型分析认为,在其他条件不变的情况下,增大边界克努森数会使轴承的承载能力下降;(2)建立了以真空环境为边界条件的仿真模型,采用COMSOL软件模拟了入口区域、承载区域和密封区域的压力场分布,分析认为,入口区域的流动复杂,但由于所占比重比较小,为轴承提供的承载力有限,而承载区域是轴承承载力的主要来源,与大气环境下相比,真空环境下气体轴承的承载能力有所提高,由于气体稀薄效应,提高量少于大气环境时轴承上表面所受的大气压力,密封区域的气体压力由于抽气系统的作用变得很稀薄,需要用分子流模块来模拟,模拟得到了不同排气槽尺寸和气膜厚度是的压力分布,结果显示气膜厚度增大,排气槽处的压力降低,减小排气槽深度有利于提高轴承的密封性能,减小排气槽宽度,排气槽处的压力会增加,对轴承的密封性能的影响需综合考虑密封宽度的增加产生的结果;(3)对加工的实验真空环境气体轴承进行了数值计算,并通过搭建的真空环境下静压气体轴承的性能实验装置,加载不同负载时,测量了气膜厚度、承载区入口压力、一级排气槽轴承和两级排气槽轴承排气槽处压力相应情况下真空室的压力,实验结果表明,相同负载下,真空环境时的气膜厚度比大气环境下有了很大增加,气膜厚度增加时,气体轴承的泄漏量先增大后减小;(4)将实验结果和理论分析与数值仿真相结合来分析,总结了理论方法和数值仿真方法,对比结果表明一阶滑移模型和COMSOL仿真结果与实验符合得比较好,另外还对真空气体轴承的设计提出了优化的方法,结果认为增大排气系统泵的抽速有利于降低排气槽出的压力,提高轴承的密封性,但要兼顾实际情况和经济成本来选取,对于两级排气槽轴承,还需合理地分配第一级和第二级密封宽度。通过本课题的研究,期望利用对真空环境气体轴承的内部流场的理论分析、仿真和实验研究,获得性能计算方法和减少气体泄漏提高轴承密封性能的方法,其中主要考虑了气体稀薄效应的影响,为气体轴承在真空环境下的应用提供一定的理论支撑,为气体轴承的发展和进步添砖加瓦。
[Abstract]:Because of the advantages of small friction, high precision, no pollution and long life, gas bearings are widely used in microelectronic manufacturing and ultra precision positioning equipment. With the development of the next generation photolithography, laser interferometry and semiconductor detection technology, ultra precision motion positioning requires not only higher positioning accuracy, but also the need to be vacuum or super clean. In the net environment, the performance of the static pressure gas bearing in the vacuum environment is more significant than that under the atmospheric environment. At present, there are few studies on the theory of hydrostatic bearing lubrication under the vacuum condition, and on the basis of a single continuous flow, there is no consideration of the influence of the transition flow and molecular flow on the internal flow field of the bearing. In this paper, a disc type static thrust bearing with a single supply hole should be used as the research object, the inner flow field of the gas bearing in the vacuum environment is analyzed theoretically and experimentally. The following work is completed mainly: (1) the internal flow field of the vacuum environment gas bearing is divided into the entrance area, the bearing area and the three parts of the seal area. According to the lubrication principle of the gas film, the D-T model and the first order slip model are used to study the lubrication problem of the bearing area of the gas bearing in the vacuum environment. After the dimensionless bearing parameters are dimensionless, the D-T model is obtained to increase the dimensionless entrance pressure in the bearing area, and there is no dimension entrance area half. The diameter, reducing the ratio of the outer diameter of the bearing and the thickness of the gas film, can move the continuous flow to the transition position of the molecular flow and improve the relative bearing capacity of the gas bearing. By the first order slip model, it is believed that the bearing capacity of the shaft will be reduced by the increase of the boundary kunson number in the condition that other conditions are constant; (2) the vacuum environment is established. The simulation model of boundary condition is used to simulate the pressure field distribution of the entrance area, the bearing region and the sealing area by COMSOL software. It is found that the flow of the entrance area is complex, but the bearing capacity of the bearing is limited because of the small proportion of the occupied area, and the bearing area is the main source of the bearing capacity of the bearing, compared with the atmospheric environment. In the air environment, the bearing capacity of the gas bearing is improved. Because of the gas thinning effect, the air pressure on the upper surface of the bearing is increased less than the atmospheric environment. The gas pressure in the sealing area becomes thin because of the function of the pumping system. The molecular flow module is needed to simulate the gas pressure. The size of the exhaust tank and the thickness of the gas film are simulated. It is the pressure distribution. The results show that the thickness of the gas film increases and the pressure of the exhaust groove is reduced. Reducing the depth of the exhaust groove is beneficial to improving the sealing performance of the bearing, reducing the width of the exhaust slot, increasing the pressure at the exhaust slot, and considering the effect of the increase of the seal width on the seal performance of the bearing. (3) the experiment is true for the processing. The air bearing gas bearing was numerically calculated, and the pressure of the gas film thickness, the inlet pressure of the bearing area, the pressure of the bearing area and the pressure of the two stage exhaust tank under the pressure of the vacuum chamber were measured. The experimental results showed that the pressure of the vacuum chamber under the load of the static pressure gas bearing under the vacuum environment was measured. Under the same load, the film thickness of the vacuum environment is greatly increased than that in the atmospheric environment. When the film thickness increases, the leakage of the gas bearing increases first and then decreases. (4) the theoretical method and numerical simulation method are summarized by combining the experimental results with the numerical simulation, and the comparison results show that the first order slip model and the CO are the first order slip model and the numerical simulation method. The simulation results of MSOL are in good agreement with the experiment. In addition, the optimization method for the design of the vacuum gas bearing is also put forward. The result is that increasing the pumping speed of the exhaust system pump is beneficial to reduce the pressure of the exhaust tank and improve the seal of the bearing, but the actual situation and the economic cost should be taken into consideration, and the bearing of the two stage exhaust tank must be combined. Through the research of this subject, we expect to make use of the theoretical analysis, simulation and experimental study of the internal flow field of the vacuum environment gas bearing, to obtain the method of performance calculation and to reduce the gas leakage to improve the sealing performance of the bearing. The main consideration is the effect of the gas thinning effect. The application of body bearings in vacuum environment provides some theoretical support, which will contribute to the development and progress of gas bearings.
【学位授予单位】：中国计量大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH133.36

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