Stability analysis of long hydrodynamic journal bearings based on the journal center trajectory
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ISSN 2223-7690 CN 10-1237/TH
SHORT COMMUNICATION
Stability analysis of long hydrodynamic journal bearings based on the journal center trajectory Yu HUANG1, Haiyin CAO1, Zhuxin TIAN2,* 1
State Key Lab of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
2
School of Mechanical Engineering, Hubei University of Arts and Science, Xiangyang 441053, China
Received: 23 April 2020 / Revised: 13 July 2020 / Accepted: 21 August 2020
© The author(s) 2020. Abstract: In this study, we observe that there are two threshold speeds (stability threshold speed and second threshold speed) for the long journal bearing, which is different for the short bearing. When the rotating speed is below the stability threshold speed, the stability boundary nearly coincides with the clearance circle, and the journal center gradually returns to the equilibrium point after being released at an initial point. If the rotating speed is between the stability threshold speed and the second threshold speed, after being released at an initial point, the journal center converges to a contour containing the equilibrium point. In this situation, for a higher rotating speed, the corresponding contour is also larger. When the rotating speed exceeds the second threshold speed, the journal gradually moves towards the bearing surface after being released at an initial point. Keywords: long journal bearings; stability threshold speed; stability boundary; journal center trajectory
1 Introduction Hydrodynamic bearings are widely used in high‐speed rotating machinery and equipment. During high‐speed rotation, the oil whirl cannot be ignored, which restricts the rotating speed of the bearings. Over the last few decades, several studies have been conducted to discuss the nonlinear stability of oil film bearings considering the oil whirl. Hollis and Taylor [1] discussed the critical speed stability boundary of short bearings by applying Hopf bifurcation and linear stability theory. Khonsari and Chang [2] studied the stability boundary of short hydrodynamic bearings lubricated with Newtonian fluids applying the fourth order RungeKutta method and the RouthHurwitz stability criterion. Bouaziz et al. [3]
discussed the dynamic performances of a misaligned rotor supported by hydrodynamic bearings. Jang and Yoon [4] analyzed the stability of hydrodynamic journal bearings with herringbone grooves. Smolík et al. [5] investigated the threshold speed and threshold curve of nonlinear hydrodynamic bearings by applying a short bearing approximation. Kushare and Sharma [6] displayed the nonlinear stability of hybrid journal bearings with valve restrictors lubricated using non‐Newtonian fluids, and Li et al. [7] illustrated the nonli
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