On the Adjusting of the Dynamic Coefficients of Tilting-Pad Journal Bearings

1995 ◽  
Vol 38 (3) ◽  
pp. 700-706 ◽  
Author(s):  
Ilmar Ferreira Santos
Keyword(s):  
Journal Bearings ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearings

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 ∞.

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.

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.

Prediction of nonlinear dynamic coefficients of tilting-pad journal bearings with pad perturbation

2021 ◽  
pp. 135065012110548
Author(s):  
Mohammad Hojjati ◽  
Seyed Younes Farzanmehr ◽  
H. M. Navaz ◽  
Hassan Haddadpour
Keyword(s):  
Partial Derivative ◽  
Nonlinear Dynamic ◽  
Perturbation Technique ◽  
Journal Bearings ◽  
Eccentricity Ratio ◽  
Linear Dynamic ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Derivative Method ◽  
Tilting Pad Journal Bearings

In this paper, a modified partial derivative method is developed to predict the linear and nonlinear dynamic coefficients of tilting-pad journal bearings with journal and pad perturbation. To this end, Reynolds equation and its boundary conditions along with equilibrium equations of the pad are used. Finite difference, partial derivative method, and perturbation technique have been employed simultaneously for solving these equations. The accuracy of the results is investigated by comparing the linear dynamic coefficients of three types of tilting-pad journal bearings with those published the literature. It is shown that the nonlinear dynamic coefficients depend on Sommerfeld number, eccentricity ratio, and length to diameter ratio. Similar to the case of linear dynamic coefficients of TPJB, it is observed that the eccentricity ratio effects on nonlinear dynamic coefficients are more notable when the eccentricity ratio is higher than 0.8 or less than 0.2.

A method for the experimental estimation of direct and cross-coupled dynamic coefficients of tilting-pad journal bearings of vertical hydro-generators

2021 ◽  
pp. 147592172110265
Author(s):  
Geraldo C Brito ◽  
Roberto D Machado ◽  
Anselmo C Neto ◽  
Leonardo Y Kimura
Keyword(s):  
Journal Bearing ◽  
Random Noise ◽  
Turbine Rotor ◽  
Journal Bearings ◽  
Order Model ◽  
Vibration Signals ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Bearing Vibration ◽  
Tilting Pad Journal Bearings

This article presents a method to experimentally estimate the direct and cross-coupled dynamic coefficients of tilting-pad journal bearings of vertical hydro-generators and other similar rotating machinery for damage detection purposes. Based on a simplified second-order model of a journal bearing in the state-space, the method employs only the usually monitored vibrations, the shaft radial relative, and the bearing radial absolute vibrations originated by the hydro-generator residual unbalance or by hydraulic excitations in the turbine rotor. This article shows that the method was successfully tested using the shaft and bearing vibration signals synthesized by a mathematical model of a 700 MW hydro-generator, even when these signals are contaminated with random noise. This article also shows the method’s performance when applied to real vibration signals acquired from the modeled hydro-generator. Finally, it discusses the possible measures to improve the method’s efficiency.

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