Effect of Axial Force on Rotordynamics of a Rigid Rotor Supported by Foil Bearings

2018 ◽  
Author(s):  
Wanhui Liu ◽  
Daejong Kim ◽  
Kai Feng
Keyword(s):  
Natural Frequency ◽  
Axial Force ◽  
Time Domain ◽  
Rotor System ◽  
Rigid Rotor ◽  
Rotor Bearing ◽  
Asymmetric Rotor ◽  
The Asymmetry ◽  
The Stability ◽  
Bearing System

This paper investigates the effect of gas foil thrust bearing (GFTB) on the rotordynamic performance of the rotor-gas foil bearing (GFB) system. A rigid rotor supported on two gas foil journal bearings (GFJB) and a pair of GFTBs is studied using a five degree of freedom (5-DOF) model. The studies were performed in both frequency domain using excitation frequency-dependent bearing coefficients (modal analyses) and non-linear analyses (time domain orbit simulations). Modal analyses were performed for both symmetrically and asymmetrically supported rotor systems. For the symmetric rotor, the modal stiffness for the conical mode increases with the axial force, while cylindrical mode is not affected. The axial force has little effects on the modal damping for both the cylindrical mode and conical mode. Thus, the natural frequency and threshold speed (stability limit) for the conical mode increases as the axial force increases, while these values for the cylindrical mode remain almost constant. For the asymmetric rotor, the modal stiffness for both the cylindrical mode and conical mode increases with the axial force, and thus both natural frequency and threshold speed increase with the axial force. Rotor lateral vibrations were also predicted using synchronous bearing coefficients (of both GFJB and GFTB) for both conical and cylindrical modes. The predicted rotor lateral responses show the critical speed increases with axial force for both cylindrical mode and conical mode. The nonlinear analysis using time-domain orbit simulation was also performed including the effect of axial force on the GFTB. The effect of axial force on the stability of the rotor system were discussed. The predicted results showed that the stability of rotor system improved as the axial force increases for Case 1 when the out of phase imbalances were added on the rotor. However, the stability of the rotor system for Case 2 not only influenced by the axial force but also influenced by how asymmetry the rotor is. For the in phase imbalances, the onset speed of subsynchronous motion decreases as axial force increases for the large asymmetric rotor bearing system and the decrement of the onset speed of subsynchronous decreases as the asymmetry of the rotor bearing system decreases. For the out of phase imbalances, the onset speed of subsynchronous motion also decreases as axial force increases for the large asymmetric rotor, but an opposite trend was shown as the asymmetry of the rotor decreases.

Nonlinear vibration characteristics of the rotor bearing system with bolted flange joints

2019 ◽  
Vol 233 (4) ◽  
pp. 910-930
Author(s):  
Yifu Zhou ◽  
Zhong Luo ◽  
Zifang Bian ◽  
Fei Wang
Keyword(s):  
Nonlinear Vibration ◽  
Time Domain ◽  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Rolling Bearing ◽  
Vibration Characteristics ◽  
Rotor System ◽  
Rotor Bearing ◽  
Bolted Flange ◽  
Bearing System

As sophisticated mechanical equipment, the rotor system of aero-engine is assembled by various parts; bolted flange joints are one of the essential ways of joints. Aiming at the analysis of the nonlinear vibration characteristics of the rotor-bearing system with bolted flange joints, in this paper, a finite element modeling method for a rotor-bearing system with bolted flange joints is proposed, and an incremental harmonic balance method combined with arc length continuation is proposed to solve the dynamic solution of the rotor system. In order to solve the rotor system with rolling bearing nonlinearity, the alternating frequency/time-domain process of the rolling bearing element is deduced. Compared with the conventional harmonic balance method and the time-domain method, this method has the characteristics of fast convergence and high computational efficiency; solving the rotor system with nonlinear bearing force; overcome the shortcoming that the frequency–response curve of the system is too sharp to continue solving. By using this method, the influence of bearing clearance and stiffness on vibration characteristics of the rotor system with bolted flange joints is studied. The evolution law of the state of the rotor system with bolt flange is investigated through numerical simulation and experimental data. The results indicated that the modeling and solving method proposed in this paper could accurately solve the rotor-bearing system with bolted flange joints and analyze its vibration characteristics.

Stability of Two-Span Rotor-Bearing System with Coupling Faults of Crack and Rub-Impact

2007 ◽  
Vol 353-358 ◽  
pp. 2501-2504
Author(s):  
Yue Gang Luo ◽  
Song He Zhang ◽  
Xiao Dong Liu ◽  
Bang Chun Wen
Keyword(s):  
Floquet Theory ◽  
Period Doubling ◽  
Rotor System ◽  
Failure Diagnosis ◽  
Coupling Faults ◽  
Rotor Bearing ◽  
Set Up ◽  
The Stability ◽  
Shooting Algorithm ◽  
Bearing System

A dynamic model was set up for the two-span rotor–bearing system with coupling faults of crack and rub-impact. Using the continuation-shooting algorithm for periodic solution of nonlinear non-autonomous system, the stability of the system periodic motion was studied by the Floquet theory. The unstable form of the rotor system with coupling faults is Hopf bifurcation when the depth of crack is smaller. The influence to the response of the system increased along with the depth of crack, the unstable form of the rotor system with coupling faults is period-doubling bifurcation. The conclusions provide theoretic basis reference for the failure diagnosis of the rotorbearing system.

scholarly journals Analytical and Experimental Investigation of the Stability of the Rotor-Bearing System of a New Small Turbocharger

1987 ◽  
Author(s):  
H. R. Born
Keyword(s):  
Experimental Investigation ◽  
Dynamic Stability ◽  
Squeeze Film ◽  
Test Results ◽  
Flow Capacity ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
The Stability ◽  
Turbine Design ◽  
Bearing System

This paper presents an overview of the development of a reliable bearing system for a new line of small turbochargers where the bearing system has to be compatible with a new compressor and turbine design. The first part demonstrates how the increased weight of the turbine, due to a 40 % increase in flow capacity, influences the dynamic stability of the rotor-bearing system. The second part shows how stability can be improved by optimizing important floating ring parameters and by applying different bearing designs, such as profiled bore bearings supported on squeeze film dampers. Test results and stability analyses are included as well as the criteria which led to the decision to choose a squeeze film backed symmetrical 3-lobe bearing for this new turbocharger design.

Dynamic Behavior Analysis of Three-Span Rotor-Bearing System with Rub-Impact Fault

2012 ◽  
Vol 460 ◽  
pp. 160-164 ◽  
Author(s):  
Song He Zhang ◽  
Yue Gang Luo ◽  
Bin Wu ◽  
Bang Chun Wen
Keyword(s):  
Nonlinear Dynamics ◽  
Behavior Analysis ◽  
Dynamic Model ◽  
Dynamic Behavior ◽  
Rotor System ◽  
System Response ◽  
Rotor Bearing ◽  
Set Up ◽  
Bearing System ◽  
Main Influence

The dynamic model of the three-span rotor-bearing system with rub-impact fault was set up. The influence to nonlinear dynamics behaviors of the rotor-bearing system that induced by rub-impact of one disc, two discs and three discs were numerically studied. The main influence of the rotor system response by the rub-impact faults are in the supercritical rotate speed. There are mutations of amplitudes in the responses of second and third spans in supercritical rotate speed when rub-impact with one disc, and there are chaotic windows in the response of first span, and jumping changes in second and third spans when rub-impact with two or three discs.

scholarly journals Dynamic Characteristics and Experimental Research of a Two-Span Rotor-Bearing System with Rub-Impact Fault

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Rui Zhu ◽  
Guang-chao Wang ◽  
Qing-peng Han ◽  
An-lei Zhao ◽  
Jian-xing Ren ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Great Influence ◽  
Experimental Platform ◽  
Rotating Machine ◽  
Rotor Bearing ◽  
Before And After ◽  
Analysis System ◽  
The Stability ◽  
Bearing System

Rotor rub-impact has a great influence on the stability and safety of a rotating machine. This study develops a dynamic model of a two-span rotor-bearing system with rubbing faults, and numerical simulation is carried out. Moreover, frictional screws are used to simulate a rubbing state by establishing a set of experimental devices that can simulate rotor-stator friction in the rotor system. Through the experimental platform and its analysis system, the rubbing experiment was conducted, and the vibration of the rotor-bearing system before and after the critical speed is observed. Rotors running under normal condition, local slight rubbing, and severe rubbing throughout the entire cycle are simulated. Dynamic trajectories, frequency spectrum diagrams, chart of axis track, and Poincare maps are used to analyze the features of the rotor-bearing system with rub-impact faults under various parameters. The vibration characteristics of rub impact are obtained. Results show that the dynamic characteristics of the rotor-bearing system are affected by the change in velocity and degree of impact friction. The findings are helpful in further understanding the dynamic characteristics of the rub-impact fault of the two-span rotor-bearing system and provide reference for fault diagnosis.

scholarly journals Research on Periodic Motion Stability of Rotor-Bearing System with Dual-Unbalances

2011 ◽  
Vol 2-3 ◽  
pp. 728-732
Author(s):  
Chao Feng Li ◽  
Guang Chao Liu ◽  
Qin Liang Li ◽  
Bang Chun Wen
Keyword(s):  
Stability Analysis ◽  
Phase Difference ◽  
Periodic Motion ◽  
Initial Phase ◽  
Shooting Method ◽  
Small Eccentricity ◽  
Rotor Bearing ◽  
Large Eccentricity ◽  
The Stability ◽  
Bearing System

Multiple freedom degrees model of rotor-bearing system taking many factors into account is established, the Newmark-β and shooting method are combined during the stability analysis of periodic motion in such system. The paper focused on the influence law of two eccentric phase difference on the instability speed of rotor-bearing system. The results have shown that the instability speed rises constantly with the eccentric phase difference angle increasing in small eccentricity system. When the two unbalance be in opposite direction, the system reached its maximum instability speed. However, the unstable bifurcation generates mutation phenomenon for large eccentricity system with the eccentric phase difference angle increasing. In summary, the larger initial phase angle can inhibit system instability partly. The conclusions have provided a theoretical reference for vibration control and stability design of the more complex rotor-bearing system.

scholarly journals Nonlinear Dynamic Analysis of Rotor Rub-Impact System

2019 ◽  
Vol 2019 ◽  
pp. 1-20
Author(s):  
Youfeng Zhu ◽  
Zibo Wang ◽  
Qiang Wang ◽  
Xinhua Liu ◽  
Hongyu Zang ◽  
...  
Keyword(s):  
Periodic Motion ◽  
Chaotic Motion ◽  
Nonlinear Dynamic Analysis ◽  
Period Doubling ◽  
Time History ◽  
Rotor System ◽  
Quasiperiodic Motion ◽  
Rotor Bearing ◽  
Motion Period ◽  
Bearing System

A dynamic model of a double-disk rub-impact rotor-bearing system with rubbing fault is established. The dynamic differential equation of the system is solved by combining the numerical integration method with MATLAB. And the influence of rotor speed, disc eccentricity, and stator stiffness on the response of the rotor-bearing system is analyzed. In the rotor system, the time history diagram, the axis locus diagram, the phase diagram, and the Poincaré section diagram in different rotational speeds are drawn. The characteristics of the periodic motion, quasiperiodic motion, and chaotic motion of the system in a given speed range are described in detail. The ways of the system entering and leaving chaos are revealed. The transformation and evolution process of the periodic motion, quasiperiodic motion, and chaotic motion are also analyzed. It shows that the rotor system enters chaos by the way of the period-doubling bifurcation. With the increase of the eccentricity, the quasi-periodicity evolution is chaotic. The quasiperiodic motion evolves into the periodic three motion phenomenon. And the increase of the stator stiffness will reduce the chaotic motion period.

scholarly journals Nonlinear Dynamics Analysis of Tilting Pad Journal Bearing-Rotor System

2011 ◽  
Vol 18 (1-2) ◽  
pp. 45-52 ◽  
Author(s):  
Jiayang Ying ◽  
Yinghou Jiao ◽  
Zhaobo Chen
Keyword(s):  
Nonlinear Dynamics ◽  
System Dynamics ◽  
Journal Bearing ◽  
Rotor System ◽  
Moment Of Inertia ◽  
Dynamics Analysis ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
Tilting Pad Journal Bearing ◽  
Bearing System

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.

Modelling and Analysis of the Dynamic Behavior of an Active Journal Bearing

1994 ◽  
Author(s):  
Linxiang Sun ◽  
Janusz M. Krodkiewski ◽  
Nong Zhang
Keyword(s):  
Pressure Distribution ◽  
Reynolds Equation ◽  
Hydrodynamic Pressure ◽  
Chamber Pressure ◽  
Oil Film ◽  
Simulation Based ◽  
Rotor Bearing ◽  
New Type ◽  
The Stability ◽  
Bearing System

Modelling and analysis of a rotor-bearing system with a new type of active oil bearing are presented. The active bearing basically consists of a flexible sleeve and a pressure chamber. The deformation of the sleeve can be controlled by the chamber pressure during the operation, and so can the pressure distribution of the oil film. Finite Element Methods (FEMs) and the Guyan condensation technique were utilised to create mathematical models for both the rotor and the flexible sleeve. The hydrodynamic pressure distribution of the oil film, for the instantaneous positions and velocities of the flexible sleeve and rotor, was approximated by Reynolds equation. The influence of the chamber pressure on the stability of the rotor system was investigated by numerical simulation based on the nonlinear model. The results showed that the stability of the rotor-bearing system can be improved effectively by implementation of the active bearing.

Non-linear dynamic behaviour of rotor—bearing system trained by bevel gears

2008 ◽  
Vol 222 (4) ◽  
pp. 617-627 ◽  
Author(s):  
M Li
Keyword(s):  
Equilibrium Points ◽  
Rotor System ◽  
Design Stage ◽  
Oil Film ◽  
Bevel Gears ◽  
Linear Dynamic ◽  
Non Linear ◽  
Rotor Bearing ◽  
Stability And Bifurcations ◽  
Bearing System

The vibrations of parallel geared rotor—bearing system have been intensively discussed; however, little attention has been paid to the dynamic analysis of angled bevel-geared system supported on journals. In the present work, the non-linear dynamics of a bevel-geared rotor system on oil film bearings is studied. First, the dynamic model is developed under some assumptions, such as rigid rotors, short-bearings, small teeth errors, and so forth. Then, the non-linear dynamic behaviours of both the balanced and unbalanced rotor system are analysed, respectively, in which the equilibrium points, limit cycles, their stability, and bifurcations are paid more attention. Numerical results show that in the bevel-geared rotor system under the action of non-linear oil film forces there exists a series of complex non-linear dynamic phenomena of rotor orbits, such as Hopf bifurcation, torus-doubling bifurcation, and jump phenomenon. All these features can help us to understand the dynamic characteristics of bevel-geared rotor—bearing system at design stage and during running period. Finally, some concerned problems during the investigation are also present.

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