Abstract
To analyze the nonlinear dynamics of a tilting-pad journal bearing (TPJB)-rotor system with high accuracy and speed, the database method (DM) is modified to rapidly determine the nonlinear fluid film force (NFFF) of a TPJB while considering turbulent and thermal effects. A high-accuracy, large-capacity NFFF database for a single pad is constructed by numerically solving the turbulent adiabatic hydrodynamic model for five equivalent state variables of the journal, which are discretized in the pad coordinates. The remaining variables are not discretized in the DM. A combined linear and parabolic interpolation polynomial based on the database is established to accurately calculate the NFFF of the tilting pads; thus, the NFFF of a four-pad TPJB is obtained in the bearing coordinates. The DM is applied to analyze and compare the nonlinear dynamic behavior of a water-lubricated TPJB-Jeffcott rotor system with and without turbulent and thermal effects. The present DM solution without these effects and the previous DM solution are shown to be consistent. The results demonstrate the importance of the flow regime and the negligibility of temperature increases in the nonlinear dynamics of a water-lubricated TPJB. This work contributes to the accurate and efficient analysis of the nonlinear dynamics of high-speed TPJBs and low-viscosity-fluid-lubricated TPJBs.
Highlights
Owing to good stability and adaptability, tilting-pad journal bearings (TPJBs) have been widely used in large rotating components, such as those in steam turbines, compressors, and nuclear reactor coolant pumps
The primary novelty of this work is as follows: i) the previous database method (DM) is modified by considering turbulent and thermal effects, but these effects are not introduced as discretized variables in the present DM; ii) the database capacity is far larger, and the nonlinear fluid film force (NFFF) data in the database are more accurate than in the previous database; iii) a combined linear and parabolic interpolation polynomial based on the database is established to calculate the NFFF of a TPJB more accurately
The current work builds upon the DM to calculate the NFFF of a TPJB while considering turbulent and thermal effects
Summary
Owing to good stability and adaptability, tilting-pad journal bearings (TPJBs) have been widely used in large rotating components, such as those in steam turbines, compressors, and nuclear reactor coolant pumps. Some researchers have reported an alytical models and calculation methods for the NFFF and pressure distribution and for nonlinear dynamic analysis of finite-length journal bearing-rotor systems. Zhang et al [14] expressed the pressure distribution of an infinitely long journal bearing as a circumferential separable function of pressure distribution and obtained an axial separable function of pressure distribution through the variational principle, providing an approximate analytical method for calculating the NFFF of a turbulent journal bearing. Based on the above research, the NFFF models and calculation methods can be categorized as follows: i) infinitely long and short bearing models; ii) analytical models of finite-length journal bearings; iii) numerical methods; iv) the DM. The nonlinear dynamic behaviors of a water-lubricated TPJB-Jeffcott rotor system with and without the turbulent and thermal effects are compared and analyzed using the DM. The primary novelty of this work is as follows: i) the previous DM is modified by considering turbulent and thermal effects, but these effects are not introduced as discretized variables in the present DM; ii) the database capacity is far larger, and the NFFF data in the database are more accurate than in the previous database; iii) a combined linear and parabolic interpolation polynomial based on the database is established to calculate the NFFF of a TPJB more accurately
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