国外文献 > 1.轴承 > 1. 基础理论与机制 > 动力学与稳定性
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| 标 题： |
A comparison of techniques for identifying the configuration state of statically indeterminate rotor bearing systems
静态不确定转子轴承系统的配置状态识别技术比较 |
| 作 者： |
W. Hu
N. S. Feng
E. J. Hahn |
| 关键词： |
Turbomachinery [涡轮机械]
Configuration state identification [ 配置状态识别]
Rotordynamics [ 转子动力学]
Hydrodynamic bearings [ 水动力轴承] |
| 出版年： |
2004 |
| 期刊名： |
Tribology International
摩擦学国际 |
| 年卷期： |
2004, vol.37, no.2 |
| 摘 要： |
Turbomachinery rotors are frequently supported on several hydrodynamic bearings and so are statically indeterminate. In such cases, the relative locations of the bearing centres (viz. the system configuration state) affect the bearing reaction forces and hence their stiffness and damping properties, thereby significantly influencing the vibration behaviour of the rotor bearing system. Since this configuration state may differ from its value at time of installation, due to thermal effects and/or foundation settlement, it would be useful to identify its value under operating conditions. This paper illustrates how this can be done in principle, regardless of the unbalance, by measuring the locations of the rotor journals relative to their respective bearing housings at any speed at which the system has reached steady state operating conditions, provided one has good models of the rotor and the foundation. Two identification procedures are compared. Both methods rely, to varying degrees, on using the Reynolds equation for hydrodynamic lubrication to obtain the bearing reaction forces. The first procedure uses the Reynolds equation to evaluate both the magnitudes and directions of the forces (the 'magnitude and direction' or MAD method), whereas the second procedure uses the Reynolds equation to evaluate only the directions of the forces (the 'direction only' or DO method). Numerical experiments on a flexibly supported statically indeterminate four bearing flexible rotor prove that both the MAD and DO identification procedures are sound in principle, being able to identify the locations of the two inboard bearings relative to the two outboard bearings to within 0.1 μm assuming seven-digit accuracy in journal orbit eccentricity measurements. On the other hand, three-digit measurement accuracy, felt to be the best accuracy practically achievable, restricts identification of the bearing locations to within 10 μm, with somewhat better identification being achieved with the MAD procedure. Such identification accuracy presupposes that the Reynolds equation correctly predicts the bearing reaction forces and could be in error owing to the temperature dependence of the bearing clearance, the assumption of a mean lubricant viscosity and the uncertainty of the cavitation boundaries. It is shown that error in lubricant viscosity may introduce significant errors into the identification achievable with the MAD procedure, but has no effect on that achievable with the DO procedure; and error in clearance introduces more error into the identification achievable with the MAD procedure than the DO procedure. Identification errors due to assumed cavitation conditions still need to be addressed.
涡轮机械转子通常安装在多个流体动力轴承上，因此属于静定不确定结构。在这种情况下，轴承中心的相对位置（即系统配置状态）会影响轴承反作用力，从而影响其刚度和阻尼特性，进而显著改变转子轴承系统的振动行为。由于热效应和/或地基沉降可能导致该配置状态与安装时的数值不同，因此有必要确定其在运行工况下的实际值。本文说明了无论是否存在不平衡，只要具备良好的转子和地基模型，即可通过测量转子轴瓦相对于相应轴承座的位置，在系统达到稳态运行条件的任意转速下实现这一目标。文中比较了两种识别方法，两者均不同程度地依赖于利用雷诺方程进行流体动力润滑以求得轴承反作用力。第一种方法使用雷诺方程来评估力的大小和方向（即“大小与方向”或MAD法），而第二种方法仅使用雷诺方程来评估力的方向（即“方向仅”或DO法）。在一种柔性支承、静定四轴承柔性转子上的数值实验表明，MAD和DO两种识别方法在原理上均是可靠的，能够在轴颈轨道偏心度测量精度为七位数的情况下，将两个内轴承相对于两个外轴承的位置识别误差控制在0.1微米以内。另一方面，若测量精度达到三位数，这是目前实际可实现的最佳精度水平，则轴承位置的识别误差将限制在10微米以内，其中MAD方法的识别效果略优于此。这种识别精度的前提是雷诺方程能够正确预测轴承反力，但由于轴承间隙的温度依赖性、平均润滑剂黏度的假设以及空化边界不确定性的存在，该方法可能存在误差。研究表明，润滑剂黏度的误差可能对采用MAD方法实现的识别结果造成显著影响，但对采用DO方法实现的结果则无影响。间隙误差引入的识别误差，比DO方法通过MAD程序所能实现的识别误差更大。由于假设了空化条件而产生的识别误差仍需加以解决。 |
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