Design of Tilting-Pad Journal Bearings Considering Bearing Clearance Uncertainty and Reliability Analysis

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Heitor Antonio Pereira da Silva ◽  
Rodrigo Nicoletti
Keyword(s):  
Reliability Analysis ◽  
Dynamic Characteristics ◽  
Stochastic Analysis ◽  
Design Procedure ◽  
Journal Bearings ◽  
Dynamic Coefficients ◽  
Bearing Clearance ◽  
Tilting Pad ◽  
Tilting Pad Bearings ◽  
Tilting Pad Journal Bearings

The dynamic characteristics of tilting-pad journal bearings (TPJBs) are strongly related to their geometric parameters, most importantly the bearing clearance. In turn, the bearing clearance in TPJBs is strongly dependent on the machining tolerances of the bearing parts and their assembling. Considering that, the machining tolerances of the pads can be of the same magnitude order of the oil film thickness in the bearing, it is uncertain that the TPJB will have the originally designed geometry after assembling. Therefore, the resultant dynamic characteristics of the TPJB also become uncertain. In this work, we present an investigation of tilting-pad bearings and their equivalent dynamic coefficients when subjected to dimensional variability. First, we perform a stochastic analysis of the system using a thermo-hydrodynamic (THD) model of the tilting-pad bearing and considering the bearing clearance in each pad as an independent random variable (varying between minimum and maximum values). We show that the scattering of the results of the dynamic coefficients is limited by the values obtained from TPJBs with all pads with maximum or minimum possible clearances. Second, we apply the concepts of reliability analysis to develop a design procedure for tilting-pad bearings. This design methodology considers the results obtained in the stochastic analysis and it allows the Engineer to appropriately design the bearing for a given probability of success or, inversely, a given probability of failure. Such approach assures a level of reliability to the dynamic coefficients of designed TPJBs in face of their dimensional variability.

Frequency Effects on Dynamic Characteristics of Tilting-Pad Journal Bearings due to Pivot Flexibility

2017 ◽  
Author(s):  
Tian Jiale ◽  
Yu Lie ◽  
Zhou Jian
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Dynamic Coefficients ◽  
Stability Performance ◽  
Limit Value ◽  
Tilting Pad ◽  
Perturbation Frequency ◽  
Tilting Pad Journal Bearings

The stable working condition of high speed, heavy loaded rotating machinery depends strongly on the stability provided by the journal bearing. Tilting pad journal bearings (TPJB) are widely used under such situation due to their inherent stability performance. However, because of the complexity of the TPJB structure, obtaining a reliable prediction of the journal bearing’s dynamic characteristics has always been a challenging task. In this paper, a theoretical analysis has been done to investigate the dynamic performance of a 4 pad TPJB with ball-in-socket pivot, emphasizing on the frequency dependency due to pivot flexibility. The analytical model containing the complete set of dynamic coefficients of the TPJB is built and the pivot stiffness is calculated and used to evaluate the equivalent dynamic coefficients of the bearing. In general, at lower perturbation frequency, the equivalent stiffness and damping increase with frequency. While for higher perturbation frequency, the dynamic coefficients are nearly independent of the frequency. Moreover, the results also show the limit value of the dynamic characteristics of the TPJB when the perturbation frequency is set to 0+ and ∞.

Numerical and experimental study on dynamic characteristics of tilting-pad journal bearings considering pivot stiffness in a vertical rotor system

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fan Zhang ◽  
Peng Yin ◽  
Yuyang Liu ◽  
Jianmei Wang
Keyword(s):  
Dynamic Characteristics ◽  
Journal Bearings ◽  
Rotor System ◽  
Obvious Effect ◽  
Content Type ◽  
Vertical Rotor ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
The Stability ◽  
Tilting Pad Journal Bearings

Purpose The purpose of this paper is to study the influence of pivot stiffness on the dynamic characteristics of tilting-pad journal bearings (TPJBs) and the stability of the bearing-rotor system. Design/methodology/approach A theoretical numerical model is established, and the influences of pivot stiffness on TPJBs and a bearing-rotor system are analyzed. Then, two kinds of pivot structures with different stiffness are designed and the vibration characteristics are tested on the vertical rotor bearing test bench. Findings The pivot stiffness has an obvious effect on the dynamic characteristics of the TPJBs and the stability of the bearing-rotor system. As a result of appropriate pivot stiffness, the critical speed and the vibration amplification factor can be reduced, the logarithmic decay rate and the stability of the rotor system can be effectively increased. While the journal whirl orbit is smoother and the rubbing is obviously reduced when the bearings have flexible pivots. Originality/value The influence of pivot stiffness on TPJBs and a vertical rotor-bearing system is studied by theoretical and experimental methods.

Dynamic characteristics of polymer faced tilting pad journal bearings

2014 ◽  
Vol 74 ◽  
pp. 20-27 ◽  
Author(s):  
Gregory F. Simmons ◽  
Alejandro Cerda Varela ◽  
Ilmar Ferreira Santos ◽  
Sergei Glavatskih
Keyword(s):  
Dynamic Characteristics ◽  
Journal Bearings ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearings

Frequency Dependent Dynamic Properties of Tilting Pad Journal Bearings: Experimental Results and Uncertainty Analysis

2005 ◽  
Author(s):  
Waldemar Dmochowski ◽  
Jacek Dmochowski
Keyword(s):  
Spectral Density ◽  
Dynamic Properties ◽  
Journal Bearings ◽  
Data Uncertainty ◽  
Dynamic Coefficients ◽  
Power Spectral ◽  
Tilting Pad ◽  
Spectral Density Method ◽  
Tilting Pad Journal Bearings ◽  
Inertia Forces

The paper presents experimentally obtained TPJB response to multifrequency excitation and its comparison with theoretically obtained data. Uncertainty considerations for the results obtained using the power spectral density method are also presented. It has been concluded that inertia forces and pivot flexibility effects are behind the variations of dynamic coefficients with frequency of excitation.

Effect of Uncertainties in the Estimation of Dynamic Coefficients on Tilting Pad Journal Bearings

2016 ◽  
Author(s):  
Rafael O. Ruiz ◽  
Sergio E. Diaz
Keyword(s):  
Surrogate Model ◽  
Journal Bearing ◽  
Deterministic Model ◽  
Journal Bearings ◽  
Kriging Interpolation ◽  
Manufacturing Tolerance ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearing ◽  
Tilting Pad Journal Bearings

It has been identified that small variations in the pad clearance and preload of a Tilting Pad Journal Bearing lead to important variations in their dynamic coefficients. Although this variation trend is already identified, a more robust statistical analysis is required in order to identify more general tendencies and quantify it. This work presents a framework that helps to identify the relation between the manufacturing tolerance of the bearing (reflected in the pad clearance and preload) and the expected variations on the dynamic coefficients. The procedure underlies the adoption of a surrogate model (based on Kriging interpolation) trained by any deterministic model available to predict dynamic coefficients. The pad clearance and preload are considered uncertain parameters defined by a proper probability density function. All statistical quantities are obtained using stochastic simulation, specifically adopting a Monte Carlo simulation employing the surrogate model. The framework is illustrated through the study of a five pad bearing.

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