scholarly journals Studi Prediksi Analitik Posisi Bantalan (Journal Bearing) Pada Turbin Gas

2021 ◽  
Vol 6 (1) ◽  
pp. 52-59
Author(s):  
Rizky Arman ◽  
Yovial Mahyoedin
Keyword(s):  
Gas Turbines ◽  
Journal Bearing ◽  
Helical Gear ◽  
Force Balance ◽  
The Other ◽  
Analytical Prediction ◽  
Mass Unbalance ◽  
Dynamic Forces ◽  
Main Support ◽  
Stiffness And Damping

AbstrakBantalan menyediakan antarmuka utama antara bagian-bagian mesin yang bergerak dan tidak bergerak. Bantalan memberikan sebagian besar kekakuan dan redaman untuk struktur yang bergerak. Dapat dimengerti bahwa gaya dinamis yang dikembangkan pada bagian yang bergerak ditransmisikan ke bagian stasioner melalui bantalan penyangga utama ini. Gaya tersebut dapat berupa beban radial statis karena berat rotor, atau mungkin gaya dinamis karena mekanisme seperti ketidakseimbangan massa. Dalam kedua kasus tersebut, bantalan radial harus membawa beban yang diterapkan, atau mesin akan mengalami kegagalan. Dalam kebanyakan kasus, secara teknis sulit (jika bukan tidak mungkin) untuk secara langsung memeriksa validitas atau akurasi dari koefisien bantalan yang dihitung. Namun, setiap perhitungan harus diakhiri dengan keseimbangan gaya, ditambah keseimbangan posisi jurnal dalam jarak bebas bantalan. Karena jurnal dalam bantalan film-oli dapat diukur secara langsung dengan proximity probes, logis untuk melakukan pemeriksaan prediksi analitik versus data mesin yang sebenarnya. Proximity probe sensorik dipasang pada ± 450 dari garis tengah vertikal sebenarnya. Pada bantalan ujung saluran masuk turbin # 1, probe dipasang di atas poros. Sebaliknya, di exhaust # 2 bantalan, probe terletak di bawah poros. Untuk penelitian pada kasus ini dilakukan pada empat turbin gas poros tunggal yang beroperasi antara 5.000 dan 5.350 RPM. Unit ini memiliki daya 40.000 HP, dan digunakan untuk menggerakkan kompresor sentrifugal bertekanan tinggi melalui satu kotak roda gigi heliks. Dapat dimengerti bahwa jika posisi eksentrisitas yang dihitung benar, maka parameter yang dihitung lainnya juga mewakili karakteristik bantalan. Kata kunci: journal bearing, turbin gas, proximity probe, posisi eksentrisitas. Abstract Bearings provide the primary interface between the moving and the stationary parts of a machine. Although the seal and the process fluids (or magnetic fields) coexist, the bearings provide the majority of the stiffness and damping for the moving assembly. It is understandable that dynamic forces developed on the moving part are transmitted to the stationary part across these main support bearings. The forces may be the static radial loads due to the rotor weight, or they may be dynamic forces due to mechanisms such as mass unbalance. In either case, the radial bearings must carry the applied loads, or the machine will fail. In most cases, it is technically difficult (if not impossible) to directly check the validity or accuracy of the computed bearing coefficients. However, each calculation must conclude with a force balance, plus a position balance of the journal within the bearing clearance. For this case history, consider a group of four single shaft gas turbines that operate between 5,000 and 5,350 RPM. These units are rated at 40,000 HP, and they are used to drive high pressure centrifugal compressors through a single helical gear box. The shaft sensing proximity probes are mounted at ±450 from the true vertical centerline. At turbine inlet end#1 bearing, the probes are mounted above the shaft. Conversely, at the exhaust end #2 bearing, the probes are located below the shaft. Since journal within an oil film bearing can be measured directly with proximity probes, it is logical perform a check of the analytical prediction versus actual machine data. It is reasonable to believe that if the calculated eccentricity position is correct, than the other computed parameters are also representative of the bearing characteristics. Keywords: journal bearing, gas turbine, proximity probes, eccentricity position.

Effects of Frequency on Structural Stiffness and Damping in a Self-Acting Compliant Foil Journal Bearing

1994 ◽  
Author(s):  
C.-P. Roger Ku ◽  
Hooshang Heshmat
Keyword(s):  
Journal Bearing ◽  
Excitation Frequency ◽  
Operating Conditions ◽  
Test Facility ◽  
Structural Stiffness ◽  
Damping Term ◽  
Equivalent Viscous Damping ◽  
Wide Range ◽  
Dynamic Forces ◽  
Stiffness And Damping

This paper presents the results of an investigation into the dynamic structural properties of self-acting compliant foil journal bearings. A test facility with a journal supported by a compliant foil journal bearing was built. The nonrotating journal was driven by two shakers which were used to simulate the dynamic forces acting on the bump foil strips. The structural stiffness and equivalent viscous damping coefficients are calculated based on the experimental measurements for a wide range of operating conditions. The results are compared to the analytical predictions obtained by a theoretical model developed earlier, and the effects of frequency are investigated. Both theoretical and experimental results show that an increase in the excitation frequency decreases the direct damping term. The effect of frequency on the cross-coupling terms is much less than on the direct terms.

Experimental and Theoretical Rotordynamic Characteristics of a Hybrid Journal Bearing

1997 ◽  
Vol 119 (1) ◽  
pp. 132-141 ◽  
Author(s):  
J. T. Sawicki ◽  
R. J. Capaldi ◽  
M. L. Adams
Keyword(s):  
Journal Bearing ◽  
Operating Conditions ◽  
Dynamic Force ◽  
Test Results ◽  
Force Measurements ◽  
Lubrication Equation ◽  
Load Cells ◽  
Theoretical Predictions ◽  
Stiffness And Damping

This paper describes an experimental and theoretical investigation of a four-pocket, oil-fed, orifice-compensated hydrostatic bearing including the hybrid effects of journal rotation. The test apparatus incorporates a double-spool-shaft spindle which permits independent control over the journal spin speed and the frequency of an adjustable-magnitude circular orbit, for both forward and backward whirling. This configuration yields data that enables determination of the full linear anisotropic rotordynamic model. The dynamic force measurements were made simultaneously with two independent systems, one with piezoelectric load cells and the other with strain gage load cells. Theoretical predictions are made for the same configuration and operating conditions as the test matrix using a finite-difference solver of Reynolds lubrication equation. The computational results agree well with test results, theoretical predictions of stiffness and damping coefficients are typically within thirty percent of the experimental results.

Tilting Pad Journal Bearings: A Discussion on Stability Calculation, Frequency Dependence, and Pad and Pivot Flexibility

2012 ◽  
Author(s):  
Jason C. Wilkes ◽  
Dara W. Childs
Keyword(s):  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Operating Temperature ◽  
Excitation Frequency ◽  
Full Model ◽  
Stability Calculation ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing

For several years, researchers have presented predictions showing that using a full tilting-pad journal bearing (TPJB) model (retaining all of the pad degrees of freedom) is necessary to accurately perform stability calculations for a shaft operating on TPJBs. This paper will discuss this issue, discuss the importance of pad and pivot flexibility in predicting impedance coefficients for the tilting-pad journal bearing, present measured changes in bearing clearance with operating temperature, and summarize the differences between measured and predicted frequency dependence of dynamic impedance coefficients. The current work presents recent test data for a 100 mm (4 in) five-pad TPJB tested in load on pad (LOP) configuration. Measured results include bearing clearance as a function of operating temperature, pad clearance and radial displacement of the loaded pad (the pad having the static load vector directed through its pivot), and frequency dependent stiffness and damping. Measured hot bearing clearances are approximately 30% smaller than measured cold bearing clearances and are inversely proportional to pad surface temperature; predicting bearing impedances with a rigid pad and pivot model using these reduced clearances results in overpredicted stiffness and damping coefficients that are several times larger than previous comparisons. The effect of employing a full bearing model versus a reduced bearing model (where only journal degrees of freedom are retained) in a stability calculation for a realistic rotor-bearing system is assessed. For the bearing tested, the bearing coefficients reduced at the frequency of the unstable eigenvalue (subsynchronously reduced) predicted a destabilizing cross-coupled stiffness coefficient at the onset of instability within 1% of the full model, while synchronously reduced coefficients for the lightly loaded bearing required 25% more destabilizing cross-coupled stiffness than the full model to cause system instability. The same stability calculation was performed using measured stiffness and damping coefficients at synchronous and subsynchronous frequencies. These predictions showed that both the synchronously measured stiffness and damping and predictions using the full bearing model were more conservative than the model using subsynchronously measured stiffness and damping, an outcome that is completely opposite from conclusions reached by comparing different prediction models. This contrasting outcome results from a predicted increase in damping with increasing excitation frequency at all speeds and loads; however, this increase in damping with increasing excitation frequency was only measured at the most heavily loaded conditions.

Condition Monitoring of Combustion System on Industrial Gas Turbines Based on Trend and Noise Analysis

2017 ◽  
Author(s):  
Yu Zhang ◽  
Miguel Martínez-García ◽  
Mike Garlick ◽  
Anthony Latimer ◽  
Samuel Cruz-Manzo
Keyword(s):  
Condition Monitoring ◽  
Gas Turbines ◽  
Noise Analysis ◽  
Warning System ◽  
The Other ◽  
Training Data ◽  
Combustion System ◽  
Industrial Gas Turbines ◽  
Industrial Level ◽  
Experimental Trials

In this paper, a scheme of an ‘early warning’ system is developed for the combustion system of Industrial Gas Turbines (IGTs), which attains low computational workload and simple programming requirements, being therefore employable at an industrial level. The methodology includes trend analysis, which examines when the measurement shows different trends from the other measurements in the sensor group, and noise analysis, which examines when the measurement is displaying higher levels of noise compared to those of the other sensors. In this research, difficulties encountered by other data-driven methods due to temperature varying with load conditions of the IGT’s have also been overcome by the proposed approach. Furthermore, it brings other advantages, for instance, no historic training data is needed, and there is no requirement to set thresholds for each sensor in the system. The efficacy and effectiveness of the proposed approach has been demonstrated through experimental trials of previous pre-chamber burnout cases. And the resulting outcomes of the scheme will be of interest to IGT companies, especially in condition monitoring of the combustion system. Future work and possible improvements are also discussed at the end of the paper.

The Stick Motion of a Harmonically Excited, Friction-Induced Oscillator on a Sinusoidally Traveling Surface

2006 ◽  
Author(s):  
Albert C. J. Luo ◽  
Brandon C. Gegg ◽  
Steve S. Suh
Keyword(s):  
Dynamical Systems ◽  
Numerical Simulations ◽  
Dry Friction ◽  
The Other ◽  
Linear Oscillator ◽  
Analytical Prediction ◽  
Nonlinear Friction ◽  
Friction Forces

In this paper, the methodology is presented through investigation of a periodically, forced linear oscillator with dry friction, resting on a traveling surface varying with time. The switching conditions for stick motions in non-smooth dynamical systems are obtained. From defined generic mappings, the corresponding criteria for the stick motions are presented through the force product conditions. The analytical prediction of the onset and vanishing of the stick motions is illustrated. Finally, numerical simulations of stick motions are carried out to verify the analytical prediction. The achieved force criteria can be applied to the other dynamical systems with nonlinear friction forces possessing a CO - discontinuity.

An Analytical Complete Model of Tilting-Pad Journal Bearing Considering Pivot Stiffness and Damping

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Zhiyong Yan ◽  
Yi Lu ◽  
Tiesheng Zheng
Keyword(s):  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Local Coordinate System ◽  
Dynamical Behavior ◽  
Complete Model ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Generalized Force ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing

Considering the freedom of pad tilting and pad translation along preload orientation, an analytical complete model, as well as mathematical method, which contains 2n+2 degrees of freedom, is presented for calculating the dynamical characteristics of tilting-pad journal bearing. Based on the motion relationship of shaft and pad, the local coordinate system, the generalized displacement, and the generalized force vector are chosen. The concise transformation of generalized displacement, generalized force, and its Jacobian matrix between the local and global coordinate systems are built up in matrix form. A fast algorithm using the Newton–Raphson method for calculating the equilibrium position of journal and pads is proposed. The eight reduced stiffness and damping coefficients can be obtained assuming that the journal and all pads are subject to harmonic vibration. Numerical results show that the reduced damping coefficients and the threshold speed can be effectively enhanced by giving suitable pad pivot stiffness and damping simultaneously, and this analytical method can be applied to analyze dynamical behavior of the tilting-pad journal bearing rotor system.

scholarly journals High-Speed Rotor Analytical Dynamics on Flexible Foundation Subjected to Internal and External Excitation

2016 ◽  
Vol 46 (4) ◽  
pp. 3-18
Author(s):  
Venelin S. Jivkov ◽  
Evtim V. Zahariev
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Asymptotic Methods ◽  
Numerical Procedure ◽  
Rigid Bodies ◽  
Dynamics Simulation ◽  
Geometrical Approach ◽  
Rotating Machine ◽  
Exciting Frequency ◽  
Stiffness And Damping

Abstract The paper presents a geometrical approach to dynamics simulation of a rigid and flexible system, compiled of high speed rotating machine with eccentricity and considerable inertia and mass. The machine is mounted on a vertical flexible pillar with considerable height. The stiffness and damping of the column, as well as, of the rotor bearings and the shaft are taken into account. Non-stationary vibrations and transitional processes are analyzed. The major frequency and modal mode of the flexible column are used for analytical reduction of its mass, stiffness and damping properties. The rotor and the foundation are modelled as rigid bodies, while the flexibility of the bearings is estimated by experiments and the requirements of the manufacturer. The transition effects as a result of limited power are analyzed by asymptotic methods of averaging. Analytical expressions for the amplitudes and unstable vibrations throughout resonance are derived by quasi-static approach increasing and decreasing of the exciting frequency. Analytical functions give the possibility to analyze the influence of the design parameter of many structure applications as wind power generators, gas turbines, turbo-generators, and etc. A numerical procedure is applied to verify the effectiveness and precision of the simulation process. Nonlinear and transitional effects are analyzed and compared to the analytical results. External excitations, as wave propagation and earthquakes, are discussed. Finite elements in relative and absolute coordinates are applied to model the flexible column and the high speed rotating machine. Generalized Newton - Euler dynamics equations are used to derive the precise dynamics equations. Examples of simulation of the system vibrations and nonstationary behaviour are presented.

A Variable Viscosity Approach for the Analysis of Steady State and Dynamic Characteristics of Two-Lobe Journal Bearing With TiO2 Based Nanolubricant

2017 ◽  
Author(s):  
Ashutosh Kumar ◽  
Sashindra Kumar Kakoty
Keyword(s):  
Steady State ◽  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Volume Fraction ◽  
Variable Viscosity ◽  
Flow Coefficient ◽  
Viscosity Model ◽  
Nano Lubricant ◽  
The Stability ◽  
Stiffness And Damping

Steady-state and dynamic characteristics of two-lobe journal bearing, operating on TiO2 based Nano-lubricant has been obtained. The effective viscosity is obtained by using Krieger-Dougherty viscosity model for a given volume fraction of nanoparticle in the base fluid. Various bearing performance characteristics are then obtained by solving modified Reynolds equation for variable viscosity model and couple stress model. The stiffness and damping coefficients are also determined for various values of the volume fraction of the nanoparticle in the nanofluid. Results reveal that load carrying capacity and flow coefficient increase whereas friction variable decreases without affecting the stability condition of two-lobe journal bearing operating on TiO2 based nanolubricant. On the other hand attitude angle and dynamic coefficients remains constant for all the values of volume fraction of nanoparticle.

Dynamic Characteristics of TEHD Tilt Pad Journal Bearing Simulation Including Multiple Mode Pad Flexibility Model

1993 ◽  
Author(s):  
Jinsang Kim ◽  
Alan Palazzolo
Keyword(s):  
Heat Transfer ◽  
Elastic Deformation ◽  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Variable Viscosity ◽  
Global Analysis ◽  
Analysis Method ◽  
Stiffness And Damping ◽  
Modal Coordinates ◽  
Good Agreement

Abstract An approach for incorporating the heat transfer and elastic deformation effects into dynamic coefficient calculation is presented. A global analysis method is used, which finds the equilibrium pad tilt angles at each eccentricity position and includes cross-film variable viscosity, heat transfer effects in the lubricant, elastic deformation, heat conduction effects in the pads, and elastic deformation effect in the pivots. Deflection modes are used to approximate deformation of the top surface of the pads. The dynamic coefficients of a single pad are calculated at the equilibrium state of the bearing, based on numerical perturbation with respect to the bearing degrees of freedom. These include journal position, pad rotation, pivot deformation, and modal coordinates. The stiffness and damping coefficients are calculated and show very good agreement with experimental and numerical results from the existing literature.

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