Littérature scientifique sur le sujet « Rotor dynamics, Tilting Pad Journal Bearing, Turbomachinery »
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Articles de revues sur le sujet "Rotor dynamics, Tilting Pad Journal Bearing, Turbomachinery"
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Dimond, T. W., P. N. Sheth, P. E. Allaire et M. He. « Identification Methods and Test Results for Tilting Pad and Fixed Geometry Journal Bearing Dynamic Coefficients – A Review ». Shock and Vibration 16, no 1 (2009) : 13–43. http://dx.doi.org/10.1155/2009/708363.
Texte intégralRésumé :
Fluid film journal bearings (FFBs) are used to support high-speed rotors in turbomachinery which often operate above the rotor first bending critical speed. The FFBs provide both lateral support and dynamic coefficients: stiffness, damping, and mass terms, related to machine vibrations. Detailed numerical values of the bearing dynamic characteristics are necessary for proper design and operation of rotating machinery.The methods of the identification of fluid film journal bearing static and dynamic characteristics, particularly the bearing stiffness, damping, and mass coefficients, from measured data, obtained from different measurement systems, is reviewed. Many bearing tests have been performed to validate a number of different theoretical models, including the classical Reynolds isoviscous model. More advanced bearing models include the thermohydrodynamic (THD), and thermoelastohydrodynamic (TEHD) approaches. The advanced models also include turbulence effects which are important as rotor speeds continue to increase. The range of measured bearing data no longer includes current operational conditions.The various approaches to the bearing identification problem are discussed, including the different force excitation methods of incremental loading, sinusoidal, pseudorandom, impulse, known/additional unbalance, and non-contact excitation. Also bearing excitation and rotor excitation approaches are discussed. Data processing methods in the time and frequency domains are presented. Methods of evaluating the effects of measurement uncertainty on overall bearing coefficient confidence levels are reviewed.In this review, the relative strengths and weaknesses of bearing identification methods are presented, and developments and trends in improving bearing measurements are documented. Future trends in journal bearing identification improvement are discussed.
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Ciulli, Enrico, Paola Forte, Flavio Antonelli, Roberto Minelli et Daniele Panara. « Tilting Pad Journal Bearing Ball and Socket Pivots : Experimental Determination of Stiffness ». Machines 10, no 2 (23 janvier 2022) : 81. http://dx.doi.org/10.3390/machines10020081.
Texte intégralRésumé :
Tilting pad journal bearings (TPJB) are used in turbomachinery for their stability at high speeds. For design purposes, it is necessary to preliminarily investigate the turbomachine rotor dynamic behavior by simulation. The dynamic characteristics of all components must be known as precisely as possible and experimental validation of each single model is required. While a lot of work has been carried out on bearings, the ball-and-socket stiffness is still estimated by means of Hertzian formulas. Recently, some authors have used the finite element method, but it seems that nothing has been done experimentally to date. This paper describes the test rig designed to determine the stiffness of a TPJB ball-and-socket pivot by equipping the grippers of a tensile universal testing machine with specifically designed interfaces. A methodology for evaluating the stiffness from the experimental results is reported. Preliminary compression results are presented and compared with the analytical ones obtained using Hertz’s formula showing significant differences for the ball-and-socket conformal contact.
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Chan, D. S. H. « Nonlinear Analysis of Rotordynamic Instabilities in High-Speed Turbomachinery ». Journal of Engineering for Gas Turbines and Power 118, no 1 (1 janvier 1996) : 122–29. http://dx.doi.org/10.1115/1.2816527.
Texte intégralRésumé :
A nonlinear approach based on the method of averaging has been developed to study unstable lateral vibrations of rotors in high-speed turbomachinery. The method makes use of an extended concept of bearing dynamic coefficients, which are defined by applying small perturbations to the dynamic equilibrium positions. The approach has been applied to determine the stability threshold of flexible rotors supported on short and tilting-pad journal bearings, respectively. Stability performance of systems supported on short journal bearings is improved by the presence of mass unbalance. However, for flexible rotors supported on tilting-pad journal bearings, increased unbalance can lead to lower rotordynamic stability margins. This has the significant implication that stability estimates from linear analysis are not always conservative. The present method provides a computationally more efficient way to understand the nonlinear vibration behavior of high-speed turbomachinery.
4
Ying, Jiayang, Yinghou Jiao et Zhaobo Chen. « Nonlinear Dynamics Analysis of Tilting Pad Journal Bearing-Rotor System ». Shock and Vibration 18, no 1-2 (2011) : 45–52. http://dx.doi.org/10.1155/2011/213742.
Texte intégralRésumé :
The nonlinear dynamics theory is increasingly applied in the dynamics analysis of tilting pad journal bearing-rotor system. However, extensive work on system dynamics done previously neglects the influence caused by the moment of inertia of the pad. In this paper, a comparison is made between the responses of the rotor in the bearings with and without pad inertia effect. Taking the Jeffcott rotor system as an example, the characteristics of bearing-rotor system, such as bifurcation diagram, cycle response, frequency spectrum, phase trajectories, and Poincaré maps, were attained within a certain rotation rate range. The pivotal oil-film force of tilting pad journal bearing was calculated by database method. The results directly demonstrate that considering the influence of the pad moment of inertia, system dynamics characteristics are found more complicated when rotor-bearing system works around natural frequency and system bifurcation is observed forward when rotor-bearing system works on high-speed range.
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Kirk, R. G., et S. W. Reedy. « Evaluation of Pivot Stiffness for Typical Tilting-Pad Journal Bearing Designs ». Journal of Vibration and Acoustics 110, no 2 (1 avril 1988) : 165–71. http://dx.doi.org/10.1115/1.3269494.
Texte intégralRésumé :
The manufacturers of high speed turbomachinery are concerned with the accurate prediction of rotor response and stability. One major factor in the placement of system critical speeds and amplification factors is the stiffness and damping of both the fluid-film bearing and support structure. Typical calculated results for tilting-pad fluid-film bearings have neglected the influence of the point or line contact of the pivot support for the individual pads. This paper will review the equations developed considering the Hertzian contact stress and deformation theory and present the equations for pivot stiffness necessary for inclusion in tilting pad bearing computer programs. In addition, the influence of various standard pivot designs will be compared for typical fluid-film bearing stiffness and damping characteristics.
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Brancati, Renato, Stefano Pagano, Ernesto Rocca, Michele Russo et Riccardo Russo. « Experimental Investigations on Tilting Pad Journal Bearings ». International Journal of Rotating Machinery 5, no 3 (1999) : 181–91. http://dx.doi.org/10.1155/s1023621x99000160.
Texte intégralRésumé :
The results of a survey conducted on an experimental system consisting of a rigid rotor supported on two radial bearings each with five tilting pads is presented. In particular, the system was set up in order to assess the dynamic behaviour of the bearing in unusual operating conditions. The response of the bearing to different unbalance values was determined after acquiring and analysing the orbits described by the journal axis for assigned unbalance values in different operating conditions. Analysis of the results shows some particular operating features that were not entirely predicted by the theoretical model and which may give rise to malfunctions in the rotor-tilting pad bearings system. The tests were carried out in the rotor dynamics laboratory of the Dipartimento di Ingegneria Meccanica per l'Energetica at the University of Naples.
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Vázquez, J. A., et L. E. Barrett. « Modeling of Tilting-Pad Journal Bearings with Transfer Functions ». International Journal of Rotating Machinery 7, no 1 (2001) : 1–10. http://dx.doi.org/10.1155/s1023621x0100001x.
Texte intégralRésumé :
Tilting-pad journal bearings are widely used to promote stability in modern rotating machinery. However, the dynamics associated with pad motion alters this stabilizing capacity depending on the operating speed of the machine and the bearing geometric parameters, particularly the bearing preload. In modeling the dynamics of the entire rotor-bearing system, the rotor is augmented with a model of the bearings. This model may explicitly include the pad degrees of freedom or may implicitly include them by using dynamic matrix reduction methods. The dynamic reduction models may be represented as a set of polynomials in the eigenvalues of the system used to determine stability. All tilting-pad bearings can then be represented by a fixed size matrix with polynomial elements interacting with the rotor. This paper presents a procedure to calculate the coefficients of polynomials for implicit bearing models. The order of the polynomials changes to reflect the number of pads in the bearings. This results in a very compact and computationally efficient method for fully including the dynamics of tilting-pad bearings or other multiple degrees of freedom components that interact with rotors. The fixed size of the dynamic reduction matrices permits the method to be easily incorporated into rotor dynamic stability codes. A recursive algorithm is developed and presented for calculating the coefficients of the polynomials. The method is applied to stability calculations for a model of a typical industrial compressor.
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Feng, N. S., et E. J. Hahn. « Vibration Analysis of Statically Indeterminate Rotors With Hydrodynamic Bearings ». Journal of Tribology 120, no 4 (1 octobre 1998) : 781–88. http://dx.doi.org/10.1115/1.2833779.
Texte intégralRésumé :
In statically indeterminate rotor bearings systems, where the rotor is supported by one or more hydrodynamic bearings, the reactions at each hydrodynamic bearing, and hence its stiffness and damping properties depend not only on the bearing type, the operating conditions and the bearing dimensions but also on the relative lateral alignment between the journal and the bearing housing; the alignment, therefore, has a significant influence on the system stability and unbalance response. Additional complications arise if nonsymmetric bearing types such as elliptic or tilting pad bearings are present. An iterative procedure is outlined which enables the bearing reactions to be determined at any speed, thereby enabling even large systems such as turbomachinery to be rapidly analyzed in conjunction with existing linear rotor bearing vibration analysis software. Sample numerical examples show how misalignment and bearing type can affect the natural frequencies, the stability threshold, and the unbalance response of such statically indeterminate systems.
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Ma, Hui, Zhao Hui Ren, Ji Shuang Dai et Bang Chun Wen. « Research on Dynamics of Rotor Systems in Large Centrifugal Compressor ». Key Engineering Materials 419-420 (octobre 2009) : 121–24. http://dx.doi.org/10.4028/www.scientific.net/kem.419-420.121.
Texte intégralRésumé :
It is important to study system vibration characteristics for improving product quality and ensuring safety operation of units. In this paper, some dynamics of rotor systems are studied in large centrifugal compressor. The models of diaphragm coupling and tilting pad bearing are established by appropriate simplification. The finite element model of rotors with bearing and coupling is set up by taking interrelation of these subsystems into account. The unbalance responses of journal are computed based on the relative standard. The effect of bearing parameters (length-diameter ratio, clearance ratio and lubricating oil number) to journal vibration of rotor systems is analyzed. Finally test results and theoretical results are compared and errors are analyzed. The research results will provide theoretical basis for improving the bearing design of compressor rotor systems.
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Abu-Mahfouz, Issam, et Maurice L. Adams. « Numerical Study of Some Nonlinear Dynamics of a Rotor Supported on a Three-Pad Tilting Pad Journal Bearing (TPJB) ». Journal of Vibration and Acoustics 127, no 3 (1 juin 2005) : 262–72. http://dx.doi.org/10.1115/1.1888593.
Texte intégralRésumé :
The use of tilting pad journal bearings (TPJBs) has increased in the recent past due to their stabilizing effects on the rotor bearing system. However, in this paper two mechanisms capable of producing instabilities in terms of subharmonic and chaotic motions are suggested. The first one is that of a centrally loaded pad with rotor unbalance excitations. The second one represents a concentric rotor (or a vertical rotor) acted upon by centering sprigs and large unbalance excitations. Extensive numerical experimentation shows, for certain parameters, subharmonic, quasi-periodic, and chaotic motions. The pad state space trajectory, in many cases, resembles that of the two-well potential case as in Duffing’s oscillator. Time trajectories, Poincare maps, fast Fourier transform (FFT) plots, and the max Lyapunov exponent are utilized to examine the periodicity (order) of the nonsynchronous rotor orbits and pad trajectories. The TPJB problem belongs to a family of nonlinear rotor-dynamical phenomena that are potentially of a considerable value as diagnostic tools in assessing rotating machinery condition monitoring.
Thèses sur le sujet "Rotor dynamics, Tilting Pad Journal Bearing, Turbomachinery"
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NOCCIOLINI, DANIELE. « Development and Validation of an Efficient TEHD Model of Tilting Pad Journal Bearings ». Doctoral thesis, 2017. http://hdl.handle.net/2158/1080940.
Texte intégralRésumé :
The constant increase of turbomachinery rotational speed has brought the design and the use of journal bearings to their very limits: tilting pad journal bearings (TPJBs) have been introduced for high-speed/high-load applications due to their intrinsic stability properties and can be used both in transient and steady-state operations obtaining superior performances. TPJBs operation involves different physical aspects, like the pads flexibility and the heat exchange between solids and fluids. An accurate analysis of the TPJBs behavior is essential for a successful design and operation of the system; however, it is necessary to reach a compromise between the accuracy of the results provided by the TPJB model and its computational cost. The present thesis exposes the development of an innovative and efficient quasi-3D TPJB modeling approach that allows an accurate analysis of the interactions between the fluid dynamic and thermal phenomena with the elastic behaviour of the solid components (ThermoElastoHydroDynamic analysis); the majority of existing models describes these aspects separately but their complex interactions must be taken into account to obtain a more accurate characterization of the system.
The main objective of the proposed model is to provide accurate 3D results with low computational times; furthermore, it is characterized by a strong modularity, allowing for complex transient simulations of the complete plant and for the representation of different kinds of bearings.
In this thesis, the whole model has been developed and experimentally validated in collaboration with Nuovo Pignone General Electric S.p.a., which provided the required technical and experimental data.
Chapitres de livres sur le sujet "Rotor dynamics, Tilting Pad Journal Bearing, Turbomachinery"
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Chatterton, Steven, Paolo Pennacchi, Phuoc Vinh Dang et Andrea Vania. « Identification Dynamic Force Coefficients of a Five-Pad Tilting-Pad Journal Bearing ». Dans Proceedings of the 9th IFToMM International Conference on Rotor Dynamics, 931–41. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-06590-8_76.
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Chatterton, Steven, Paolo Pennacchi, Phuoc Vinh Dang et Andrea Vania. « A Test Rig for Evaluating Tilting-Pad Journal Bearing Characteristics ». Dans Proceedings of the 9th IFToMM International Conference on Rotor Dynamics, 921–30. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-06590-8_75.
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He, Minhui, C. Hunter Cloud et José A. Vázquez. « The Effects of Temporal Fluid Inertia on Tilting Pad Journal Bearing Dynamics ». Dans Proceedings of the 9th IFToMM International Conference on Rotor Dynamics, 805–19. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-06590-8_66.
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Hagemann, Thomas, et Hubert Schwarze. « A Theoretical Study on Frequency Effects on Tilting-Pad Journal Bearing Dynamic Coefficients ». Dans Proceedings of the 9th IFToMM International Conference on Rotor Dynamics, 1069–80. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-06590-8_87.
Texte intégralActes de conférences sur le sujet "Rotor dynamics, Tilting Pad Journal Bearing, Turbomachinery"
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Dang, Phuoc Vinh, Steven Chatterton, Paolo Pennacchi, Andrea Vania et Filippo Cangioli. « Behavior of Tilting–Pad Journal Bearings With Large Machining Error on Pads ». Dans ASME Turbo Expo 2016 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56674.
Texte intégralRésumé :
The use of tilting pad journal bearings (TPJBs) has increased in recent years due to their stabilizing effects on the rotor bearing system. Most of the studies addressing steady state and dynamic behaviors of TPJBs have been evaluated by means of thermo-hydrodynamic (THD) models, assuming nominal dimensions for the bearing, (i.e., the physical dimensions of all pads are identical and loads applied along the vertical direction). However machining errors could lead to actual bearing geometry and dimensions different from the nominal ones. In particular, for TPJB the asymmetry of the bearing geometry has not been well-investigated and can lead to an unexpected behavior of the bearing. The asymmetry of the bearing geometry can arise from large machining errors on only one or more pads, as a consequence of a pivot failure or after bad-mounting of the pads during assembly. These conditions can sometimes be detected by high values of the pad temperature, as measured by the temperature probes installed on the bearing pads, or by the abnormal vibration caused by pad-flutter phenomena. In this paper the authors investigate large machining errors on the pad thickness for a five-pad TPJB and analyze their effects on the bearing operating characteristics. Pad thickness errors correspond to a different preload factor or clearance for each pad. A sensitivity analysis was performed for several combinations of pad thickness using a THD model and the behavior of the bearing was analyzed, including dynamic stiffness and damping coefficients, clearance profile, shaft locus, minimum oil-film thickness, power loss, flow rate, and maximum pressure. The experimental case of a five pads TPJB with an intentional large machining error on the thickness of the pads is also described in the paper. The bearing has a nominal diameter of 100 mm, a diameter to length ratio (L/D) equal to 0.7 and can run at up to 3000 rpm. The experimental measurements are compared with the results obtained from the analytical model. The results show that the effects of asymmetry of the bearing geometry are more evident if the direction of the static load applied on the rotor bearing system, which is different from the vertical load, is also considered. For instance, the shape of shaft locus obtained by experimental tests changing the static load direction at a constant speed is an irregular pentagon if it is compared to the case of the nominal bearing. Based on our findings, we concludes that the machining error on the pads has a large influence on the shaft locus, minimum oil-film thickness and maximum pressure on pads, especially at high rotational speed, but has little effect on the flow rate and power loss. In addition, this error significantly affects the dynamic stiffness and damping coefficients, both in terms of rotational speed and load direction.
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Liu, Binbin, Weimin Wang, Jinji Gao et Jian Zhang. « Influence of Bearing Load on the Performance of Tilting-Pad Journal Bearing Under High Surface Velocity ». Dans ASME Turbo Expo 2017 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64263.
Texte intégralRésumé :
Tilting-pad journal bearings (TPJBs) are dominant as shaft support in high-parameter turbomachinery, particularly in highspeed applications. Bearing test technology and high-precision model simulation are the key technologies for the development of high-end bearings. A bearing test platform which is based on the active magnetic bearing (AMB) loading and excitation is first designed and developed. Two large AMBs are used in the test rig as loader and exciter, and the system has a whole loading capacity up to 20000 N. As the bearing load is not always along the vertical direction, the performance of five-pads TPJBs with inner diameter of 140 mm is tested under the different load directions and load magnitudes in the speed range of 2000 to 12000 r/min. The results indicate that the direction and magnitude of the bearing load have a considerable effect on the experimental characteristics of TPJBs, especially under high-speed and heavy-load operation conditions. The bearing load has less influence on power loss than the rotation speed. By changing the direction of load, the bearing pad in the load direction has much higher temperature than the opposite pad. The change of pad temperature caused by the change of bearing load direction becomes greater under a larger bearing load. By analyzing the influence of the magnitude and direction of the bearing load on the rotor vibration, the mutual relationship among the dynamic stiffness, bearing load and rotor vibration are revealed. The performance test of TPJBs under different load directions with the AMB loading is beneficial to design the tilting pad bearing with high performance, to reduce the power loss of bearing, and to verify the correctness of the numerical model analysis. The results can be used for the performance prediction of the integrally geared centrifugal compressor because of their ever varying bearing load direction and load magnitude.
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Zemella, Philipp, Thomas Hagemann, Bastian Pfau et Hubert Schwarze. « Identification of Dynamic Coefficients of a Five-Pad Tilting Pad Journal Bearing up to Highest Surface Speeds ». Dans ASME Turbo Expo 2020 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14991.
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Abstract Tilting-pad journal bearings are widely used in turbomachinery industry due to their positive dynamic properties at high rotor speeds. However, the exact description of this dynamic behavior is still part of current research. This paper presents measurement results for a five-pad tilting-pad journal bearing in load between pivot configuration. The bearing is characterized by a nominal diameter of 100 mm, a length of 90 mm, and a pivot offset of 0.6. Investigations include results for surface speeds between 25 and 120 m/s and specific bearing loads ranging from 0.0 to 3.0 MPa. Results of theoretical predictions are commonly derived from perturbation of stationary operation under static load. Therefore, experimental results for stationary operation including pad deflection under static load are presented first to characterize the investigated bearing. Measured results indicate considerable non-laminar flow in the upper region of the investigated range of rotor speeds. Second, dynamic excitation test are performed with excitation frequencies up to 400 Hz to evaluate dynamic coefficients of a stiffness (K) and damping (C) KC-model, and additionally, a KCM-model using additional virtual mass (M) coefficients. KCM-coefficients are obtained by fitting frequency dependent KC-characteristics to the KCM-model structure using least square approach. The wide range of rotating and excitation frequencies leads to subsynchronous as well as supersynchronous vibrations. Excitation forces are applied with multi-sinus and single-sinus characteristics. The latter one allows evaluation of KC-coefficients at the particular frequency ratio in the time domain. Here, frequency and time domain evaluation algorithms for dynamic coefficients are used in order to assess their special properties and quality. The impact of surface speed, bearing load, and oil flow rate on measured and predicted KCM-coefficients is investigated. Measured and predicted results can be well fitted to a KCM-model and show a significant influence of the ratio between fluid film and pivot support stiffness on the speed dependent characteristic of bearing stiffness coefficients. However, the impact of this ratio on damping coefficients is considerably lower. Further investigations on the impact of oil flow rates indicate that a significant decrease of direct damping coefficients exists below a certain level of starvation. Above this limit, direct damping coefficients are nearly independent of oil flow rate. Results are analyzed in detail and demands on improvements for predictions are derived.
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Conti, R., A. Frilli, E. Meli, D. Nocciolini, S. Panconi, L. Pugi, A. Rindi et S. Rossin. « Development and Validation of an Efficient TEHD Model of Tilting Pad Journal Bearings ». Dans ASME Turbo Expo 2016 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57401.
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The large success of Tilting Pad Journal Bearings (TPJBs) for the use in high speed/high load applications is due to their intrinsic stability properties, which allow superior rotor dynamic performances. TPJBs operation involves different physical phenomena, like the pads flexibility and the heat exchange between solids and fluids: an accurate analysis of these phenomena is fundamental in order to successfully employ TPJBs. In this paper, the authors, in cooperation with General Electric Nuovo Pignone, develop an innovative 3D TPJB modelling approach that allows an accurate analysis of the interactions between the fluid dynamic and thermal phenomena with the elastic behaviour of the solid components (ThermoElastoHydroDynamic analysis). The main objective of the proposed model is to provide accurate 3D results with low computational times. The TPJB model has been also experimentally validated, focusing on the thermal characteristics of the system and the interactions due to the TEHD behaviour of the bearing system.
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San Andrés, Luis, Bonjin Koo et Makoto Hemmi. « A Flow Starvation Model for Tilting Pad Journal Bearings and Evaluation of Frequency Response Functions : A Contribution Towards Understanding the Onset of Low Frequency Shaft Motions ». Dans ASME Turbo Expo 2017 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64822.
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Direct lubrication tilting pad journal bearings (TPJBs) require of less oil flow, reduce power consumption and offer cooler pad temperatures for operation at high surface speeds. Although apparently free of a hydrodynamic instability, the literature shows that direct lubrication TPJBs exhibit unexpected shaft vibrations with a broadband low frequency range, albeit small in amplitude. Published industrial practice demonstrates the inlet lubrication type, a reduced supply flow rate causing film starvation, and the bearing discharge conditions (evacuated or end sealed) affect the onset, gravity and persistency of the sub synchronous (SSV) hash motions. The paper presents a physical model to predict the performance of TPJBs with flow conditions ranging from over flooded to extreme starvation. Lubricant starvation occurs first on an unloaded pad, thus producing a (beneficial) reduction in drag power. As the supplied flowrate decreases further, fluid starvation moves towards the loaded pads and affects the film temperature and power loss, increases the journal eccentricity, and modifies the dynamic force coefficients of each tilting pad and thus the whole bearing. For a point mass rotor supported on a TPJB, the analysis produces eigenvalues and frequency response functions (FRFs) from three physical models for lateral rotor displacements: one with frequency reduced (4×4) bearing stiffness (K) and damping (C) coefficients and another with constant K-C-M (inertia) coefficients over a frequency range. The third model keeps the degrees of freedom (tilting) of each pad and incorporates the full matrices of force coefficients including fluid inertia. Predictions of rotordynamic performance follow for two TPJBs: one bearing with load between pads (LBP) configuration, and the other with a load on a pad (LOP) configuration. For both examples, under increasingly poor lubricant flow conditions, the damping ratio for the rotor-bearing low frequency (SSV) modes decreases, thus producing an increase in the amplitude of the FRFs. For the LOP bearing, a large static load produces a significant asymmetry in the force coefficients; the rotor-bearing has a small stiffness and damping for shaft displacements in the direction orthogonal to the load. A reduction in lubricant flow only exacerbates the phenomenon; starvation reaches the loaded pad to eventually cause the onset of low frequency (SSV) instability. The bearing analyzed showed similar behavior in a test bench. The predictions thus show a direct correlation between lubricant flow starvation and the onset of SSV.
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Ding, Aoshuang, et Xuesong Li. « Numerical Investigation for Characteristics and Oil-Air Distributions of a Tilting-Pad Journal Bearing Under Different Loads ». Dans ASME Turbo Expo 2020 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15151.
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Abstract This paper analyses the flow characteristics and oil-air distributions of oil flows in a tilting-pad journal bearing under different bearing loads. This titling-pad journal bearing is working at 3000 rpm rotation speed and its minimum film thicknesses have been measured under different loads from 180 kN to 299 kN. Based on the previous researches of this bearing under 180 kN, the gaseous cavitation and low-turbulence flow exists in this bearing flow. A suitable gaseous cavitation model and the SST model with low-Re correction are used in the film flow simulations. With the rotor and pads assumed to be rigid, the dynamic mesh and motion equations are applied to simulate the motions of the rotor and the rotations of the pads. Based on the simulation results under different bearing loads, the simulated minimum film thicknesses agrees well with the measured data. It indicates that the simulation results can catch the film geometries and flows correctly. With the load increasing, the rotor moves closer to the loaded pads and the minimum film thickness decreases. Taking the effect of boundary layers into consideration, the turbulence has a negative relationship with the film thickness and decreases in the loaded area under higher bearing load. It can be verified by the simulated lower turbulent viscosity ratio distributions in the loaded pads. In the unloaded area, both the film thickness and turbulence viscosity ratio are positively related to the bearing loads. Thus, the higher bearing load may lead the flow to be more different in the loaded and unloaded area, and the turbulence in the loaded pads may transfer to laminar in the end. As for the oil-air distributions, in the unloaded pads, with the bearing load increasing, the simulated air volume fraction increases in the unloaded pads with lower pressure. It should be caused by the higher film thickness of the unloaded pads under higher loads. In sum, the flow turbulence and cavitation process changes with the bearing load. With a higher load, the cavitation becomes more in the unloaded pads and the flow changes sharper from the high-turbulence unloaded area to the low-turbulence loaded area. As the simulation results is in good accordance with the experimental data, the SST model with low-Re correction and the gaseous cavitation model are verified to be suitable for bearing film simulations under different loads.
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Chatterton, Steven, Filippo Cangioli, Paolo Pennacchi, Andrea Vania et Phuoc Vinh Dang. « Development of an Active Control System for Rotating Machinery by Means of Tilting Pad Journal Bearings ». Dans ASME Turbo Expo 2016 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56632.
Texte intégralRésumé :
The current design trend of rotating machines like turbo-generators, compressors, turbines, and pumps is focused on obtaining both high dynamic performances and high versatility of machines in different operating conditions. The first target is nowadays achieved by equipping machines with tilting pad journal bearings. For the second target, State-of-the-Art researches are focused on the development of active systems able to adapt the dynamic behavior of the machine to the external environment and new operating conditions. Typical causes of large vibration in rotating machines are faults, residual unbalance, resonance condition and instabilities. Aiming at vibration reduction, in recent years many studies are carried out to investigate different solutions; one of them is based on active tilting pad journal bearing. In this paper, the authors investigate, by simulations, the reduction of shaft vibration by controlling the motion of the pads of a tilting pad journal bearing. The basic idea is to balance the exciting force on the shaft with a suitable resulting force of the oil-film pressure distribution. In particular, a sliding mode controller has been considered and both angular rotation of the pads about the pivot and the radial motion of the pivot have been analyzed. Sliding mode control guarantees high robustness of the control system in real applications that can be characterized by a strong non-linear behavior. In the paper a general consideration about the bearing, the actuating methods and the control system have been provided. A numerical analysis of large size rotor equipped with active pads has been carried out in order to verify the effectiveness of the system in several conditions, even during the most critical operating phase, i.e. the lateral critical speed.
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Arihara, Hirotoshi, Yuki Kameyama, Yoshitaka Baba et Luis San Andrés. « A Thermoelastohydrodynamic Analysis for the Static Performance of High-Speed Heavy Load Tilting-Pad Journal Bearing Operating in the Turbulent Flow Regime and Comparisons to Test Data ». Dans ASME Turbo Expo 2018 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-77151.
Texte intégralRésumé :
Tilting-pad journal bearings (TPJBs) ensure rotordynamic stability that could otherwise produce dangerously large amplitude rotor oil-whirl/whip motions in high speed rotating machinery. Currently, highly efficient turbo compressors demand an ever increasing rotor surface speed and specific load on its support bearings. The accurate prediction of bearing performance is vital to guarantee reliable products, specifically with regard to reducing maximum bearing pad temperature and drag power losses, and operating with the least flow rate while still maximizing load capacity. The hydrodynamic pressure and heat generation in an oil film acting on a bearing pad produce significant mechanical and thermal deformations that change the oil film geometry (clearance and preload) to largely affect the bearing performance, static and dynamic. In addition, a high surface speed bearing often operates in the turbulent flow regime that produces a notable increase in power loss and a drop in maximum pad temperature. This paper details a thermoelastohydrodynamic (TEHD) analysis model applied to TPJBs, presents predictions for their steady-load performance, and discusses comparisons with experimental results to validate the model. The test bearing has four pads with a load between pads configuration; its length L = 76.2 mm and shaft diameter D = 101.6 mm (L/D = 0.75). The rotor top speed is 22.6 krpm, i.e. 120 m/s surface speed, and the maximum specific load is 2.94 MPa for an applied load of 23 kN. The test procedure records shaft speed and applied load, oil supply pressure/temperature and flow rate, and also measures the pads’ temperature and shaft temperature, as well as the discharge oil (sump) temperature. The TEHD model couples a generalized Reynolds equation for the hydrodynamic pressure generation with a three-dimensional energy transport equation for the film temperature. The pad mechanical deformation due to pressure utilizes the finite elemental method, whereas an analytical model estimates thermally induced pad crowning deformations. For operation beyond the laminar flow regime, the analysis incorporates the eddy viscosity concept for fully developed turbulent flow operation. Current predictions demonstrate the influence of pressure and temperature fields on the pads mechanical and thermally induced deformation fields, and also show static performance characteristics such as bearing power loss, flow rate, and pad temperatures. The comparisons of test results and analysis results reveal that turbulent flow effects significantly reduce the pads’ maximum temperature while increasing the bearing power loss. Turbulent flow mixing increases the diffusion of thermal energy and makes more uniform the temperature profile across the film.
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Kim, Tae Ho, Kyung Eun Jang et Tae Gyu Choi. « Rotordynamic Performance Predictions of Flexure Pivot Tilting Pad Bearings and Comparison to Published Test Data ». Dans ASME Turbo Expo 2016 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56284.
Texte intégralRésumé :
This paper presents performance predictions for a Flexure Pivot® tilting pad bearing (FPTPB) and comparisons to published test data. The FPTPB has pads that tilt about a web pivot. The pivot is designed to have little rotational stiffness, which improves its rotordynamic stability. The Reynolds equation for an isothermal and isoviscous fluid was used to calculate the film pressure using the finite element method. The Newton–Raphson method was used to determine the journal eccentricity, journal attitude angle, and pivot deflections (tilting angle, and radial and circumferential displacements) simultaneously. A small perturbation of the journal center around its equilibrium position was employed to calculate the stiffness and damping coefficients. The whirl frequency ratio (WFR), which is the ratio of the frequency of unstable whirl motion to the rotor threshold speed, was calculated using the predicted dynamic coefficients. The predictive model used was for a four-pad FPTPB with a journal diameter of 116.81 mm and axial length of 76.2 mm. Each pad had a preload of 0.25, pivot offset of 0.5, and web pivot thickness of 2.125 mm. The rotor speed and specific load were varied up to 16 krpm and 345 kPa, respectively. Predictions were performed for the load-on-pad (LOP) and load-between-pad (LBP) configurations. The results show that the predicted journal eccentricity and attitude angle decrease as the rotor speed increases. The direct stiffness coefficients increase as the rotor speed increases, but the cross-coupled stiffness coefficients change little. As the static load increases, the direct stiffness coefficient in the vertical direction increases, but the other stiffness coefficients change little. The damping coefficients are affected little by the rotor speeds and static loads. A comparison of the predictions with published test data shows that the predictive model slightly overestimates the journal eccentricities and underestimates the absolute values of the journal attitude angles. The predicted stiffness coefficients agree well with the test data. However, large discrepancies in the damping coefficients were observed between the predictions and published data. The effect of the pivot thickness on the rotordynamic performance of the FPTPB was also studied. Predictions were performed for changes in the pivot thickness up to ± 20 percent in increments of 10 percent from the original value of 2.125 mm. The results show that the predicted maximum pressure, journal eccentricity, and attitude angle decrease with decreasing pivot thickness, but the minimum film thickness increases. As the pivot thickness decreases, the direct stiffness coefficients, direct damping coefficients, and absolute values of the cross-coupled damping coefficients increase. The whirl frequency ratio (WFR), which was found to be in reasonable agreement with the test data, decreases significantly with decreasing pivot thickness, which suggests improvement in rotordynamic stability.
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Ferraro, Riccardo, Alice Innocenti, Mirko Libraschi, Michele Barsanti, Enrico Ciulli, Paola Forte et Matteo Nuti. « Dynamic Identification of 280mm Diameter Tilting Pad Journal Bearings : Test Results and Measurement Uncertainties Assessment of Different Designs ». Dans ASME Turbo Expo 2020 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14718.
Texte intégralRésumé :
Abstract Tilting pad journal bearings (TPJBs) are crucial elements in turbomachinery applications providing stiffness and damping characteristics that determine rotor system dynamic behavior. Hence, a correct design and an accurate dynamic properties prediction is fundamental for the successful industrial operation of rotating machinery. Current design trends in turbomachinery aiming at higher efficiency and power through weight optimization and higher operating speeds determine the development of large flexible rotors that are particularly important from the rotordynamic standpoint. The dynamic feasibility of this type of machine relies on bearing stiffness and damping characteristics that must be predicted with a certain level of confidence in order to increase the accuracy of the expected rotordynamic behaviour and avoid unpredicted vibration issues when rotors are operated. Furthermore, large centrifugal compressors commonly used in Liquified Natural Gas (LNG) applications make the bearings operate at very high peripheral speed where the transition from laminar to turbulent regime occurs, increasing the necessity of predictions accuracy. In this paper a test campaign on different large TPJB solutions operating in turbulent lubrication regime has been performed on a dedicated test rig designed for investigations on large size high-performance oil bearings. In the present work both static performance and dynamic identification of the tested TPJB solutions are presented and compared to numerical model predictions. The results of an uncertainty quantification, performed to validate the experimental results, are also shown.