Vibration analysis of a misaligned rotor—coupling—bearing system passing through the critical speed

2001 ◽  
Vol 215 (12) ◽  
pp. 1417-1428 ◽  
Author(s):  
S Prabhakar ◽  
A S Sekhar ◽  
A R Mohanty
Keyword(s):  
Transient Response ◽  
Vibration Analysis ◽  
Critical Speed ◽  
Rotor System ◽  
Continuous Wavelet ◽  
The Finite Element Method ◽  
System A ◽  
Different Types ◽  
Stiffness And Damping ◽  
Bearing System

The transient response of a misaligned rotor—coupling—bearing system passing through the critical speed has been analysed by using the finite element method (FEM) for flexural vibrations. The coupling has been modelled in two ways: a frictionless joint and a joint with stiffness and damping. From the vibration analysis, the subcritical speeds at one-half, one-third and one-fourth the critical speed have been found when the misaligned rotor—coupling—bearing system passes through its critical speed. The continuous wavelet transform (CWT) has been used as a tool to extract the silent features from the time response of the rotor system. A parametric study has been carried out to investigate the transient response of this rotor system for different angular accelerations in different types of misalignment.

scholarly journals Dynamic Analysis of Flexible Rotor Based on Transfer Symplectic Matrix

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Hao Deng ◽  
Xi Fang ◽  
Huachun Wu ◽  
Yiming Ding ◽  
Jinghu Yu ◽  
...  
Keyword(s):  
Transfer Matrix ◽  
Matrix Method ◽  
Critical Speed ◽  
Reference Method ◽  
Rotor System ◽  
High Order ◽  
Symplectic Matrix ◽  
Hamilton System ◽  
System A ◽  
Relative Errors

In view of the numerical instability and low accuracy of the traditional transfer matrix method in solving the high-order critical speed of the rotor system, a new idea of incorporating the finite element method into the transfer matrix is proposed. Based on the variational principle, the transfer symplectic matrix of gyro rotors suitable for all kinds of boundary conditions and supporting conditions under the Hamilton system is derived by introducing dual variables. To verify the proposed method in rotor critical speed, a numerical analysis is adopted. The simulation experiment results show that, in the calculation of high-order critical speed, especially when exceeding the sixth critical speed, the numerical accuracy of the transfer symplectic matrix method is obviously better than that of the reference method. The relative errors between the numerical solution and the exact solution are 0.0347% and 0.2228%, respectively, at the sixth critical speed. The numerical example indicates the feasibility and superiority of the method, which provides the basis for the optimal design of the rotor system.

An Experimental Investigation on the Static and Dynamic Characteristics of Journal Bearings Under the Influence of Twisting Misalignment

1997 ◽  
Vol 119 (1) ◽  
pp. 188-192 ◽  
Author(s):  
P. Arumugam ◽  
S. Swarnamani ◽  
B. S. Prabhu
Keyword(s):  
Finite Element Method ◽  
Vertical Direction ◽  
Journal Bearings ◽  
Response Functions ◽  
The Finite Element Method ◽  
Static And Dynamic Characteristics ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Different Levels ◽  
Bearing System

The misalignment between the journal and the bearing in a rotor-bearing system may be due to manufacturing error, elastic deflection, thermal expansion etc. In the present work, the eight linearized stiffness and damping coefficients of the cylindrical and three lobe bearings are identified at different levels of bearing misalignment (twisting misalignment) and at different speeds of the rotor. The identification method used here needs FRFs (Frequency Response Functions) obtained by the measurements and the finite element method. The twisting misalignment changes the stiffness and damping coefficients in the vertical and horizontal directions. In the case of three lobe bearings, for 0.7 degree of misalignment, the stiffness in the vertical direction is increased by about 12 percent.

scholarly journals Blade Loss Simulation of Multi Mass Rotor Model With Nonlinear Tilt Pad Journal Bearings

1995 ◽  
Author(s):  
R. K. Gadangi ◽  
A. B. Palazzolo
Keyword(s):  
Natural Frequency ◽  
Transient Response ◽  
Critical Speed ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Flexible Rotor ◽  
Equilibrium Location ◽  
Rotor Model ◽  
Limiting Value ◽  
Bearing System

Prediction of rotor vibrations due to large imbalance requires nonlinear solution of the supporting bearings. This paper presents a methodology and results for the effects of large, sudden imbalance on the response of a multi mass rotor model supported on tilt pad journal bearings. For a given imbalance, response is obtained for rotor speeds below, above and at the rotor natural frequency. The maximum peak to peak amplitude is larger at the critical speed than at a speed above or below the critical. The imbalance response is compared with two other methods used for predicting the transient response of a rotor bearing system. The rigid rotor and nonlinear bearing model shows a response similar in shape to that obtained with a flexible rotor and nonlinear bearing model, but the magnitude is different, which reached a limiting value as the imbalance was increased. The flexible rotor and linearized bearing model predicts a similar trend as the flexible rotor and nonlinear bearing model, with increasing speed for a given imbalance, but the shape and magnitude of the orbit is completely different. The motion of rotor to static equilibrium location for the flexible rotor and nonlinear bearing model showed oscillations which diminished with time, while the rigid rotor and nonlinear bearing model does not show any oscillations.

Based on One-Dimensional Model to Calculate the Critical Speed

2012 ◽  
Vol 203 ◽  
pp. 427-431
Author(s):  
Jun Feng Wang ◽  
Kang Sun
Keyword(s):  
Critical Speed ◽  
Early Stage ◽  
Reference Value ◽  
Dimensional Model ◽  
Lumped Mass ◽  
One Dimensional ◽  
Rotor Bearing ◽  
Continuous Mass ◽  
Stiffness And Damping ◽  
Bearing System

Use the simple geometric features of a one-dimensional model to calculate the rotor critical speed, the shaft use the beam element to simulate, considering the shear deformation, continuous mass, the rotation inertia and gyro effect, bearing simplified as linear stiffness and damping element, disc use the lumped mass element to simulate, considering the mass and the effect of inertia, finite element method is applied, established the rotor-bearing system dynamics model, through the example to validate, the results show that the model is the advantage of calculation on a smaller scale, solution speed and high precision, easy to adjust the parameters for the model, suitable for large needs to adjust the parameters in the early stage of design and analysis of the rotor-bearing system, it has great reference value for the design and analysis of rotor dynamics.

scholarly journals Influence of roundness error screw on running characteristics of sliding bearing based on SDT

2022 ◽  
Vol 355 ◽  
pp. 01021
Author(s):  
Zhenyu Chen ◽  
Wubin Xu ◽  
Bing Li
Keyword(s):  
Critical Speed ◽  
Journal Bearing ◽  
Rotor System ◽  
Small Displacement ◽  
Promoting Effect ◽  
Sliding Bearing ◽  
Roundness Error ◽  
System A ◽  
Film Characteristics ◽  
Generalized Roundness

In order to study the influence of roundness error on the oil film characteristics of journal bearing rotor system, a dynamic model of journal bearing rotor system with roundness error was established, and a new generalized roundness error equation is derived based on the small displacement screw (SDT) theory. And the influence of roundness error screw parameter dx represented by SDT on critical speed and stability of sliding bearing is analyzed emphatically. The results show that the existence of journal roundness error is beneficial to the bearing capacity and stability of sliding bearing rotor system to a certain extent, and with the increase of roundness error screw parameter, its promoting effect is more obvious; At the same time, the critical speed of the system will increase with the increase of screw parameter, especially when eccentricity ε>0.6; And when Sommerfeld number S>0.6, the roundness error of journal has little influence on stability.

scholarly journals Transmissibility Analysis of a Regenerated Rotor System

2021 ◽  
Vol 9 (8) ◽  
pp. 1102-1107
Author(s):  
Akanksha Dhurvey
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Rotor System ◽  
Jet Engines ◽  
Simply Supported ◽  
Rotor Bearing ◽  
Unbalance Force ◽  
Force Transmissibility ◽  
Very High ◽  
Bearing System

Abstract: The aim of this paper is to represents a dynamic behavior of rotor bearing system wirth simply supported beam for three different position disc. rotating machinery such as compressors, turbines, pumps, jet engines, turtobo chargers, etc. are subject to vibrations. rotating machines are operated in very high speed and they are subjected to some unbalance force due to vibration from that machine pass to the foundation of machine.so the analysis of the dynamics parameter of rotor it is important to determine force transmissibility, natural frequency, critical speed and amplitudes of rotor system. Keywords: force transmissibility, vibration, critical speed, rotor bearing system etc.

scholarly journals Chaos of flexible rotor system with critical speed in magnetic bearing based on the improved precise Runge–Kutta hybrid integration

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401880085 ◽  
Author(s):  
Xi Fang ◽  
Dongbo Zhang ◽  
Xiaoyu Zhang ◽  
Huachun Wu ◽  
Fei Gao ◽  
...  
Keyword(s):  
Critical Speed ◽  
Integration Method ◽  
Magnetic Bearing ◽  
Rotor System ◽  
Kutta Method ◽  
Hybrid Integration ◽  
Flexible Rotor ◽  
Runge Kutta Method ◽  
Runge Kutta ◽  
Bearing System

Magnetic rotor-bearing system has drawn great attention because of its several advantages compared to existent rotor-bearing system, and explicit Runge–Kutta method has achieved good results in solving dynamic equation. However, research on flexible rotor of magnetic bearing is relatively less. Moreover, explicit Runge–Kutta needs a smaller integral step to ensure the stability of the calculation. In this article, we propose a nonlinear dynamic analysis of flexible rotor of active magnetic bearing established by using the finite element method. The precise Runge–Kutta hybrid integration method and the largest Lyapunov exponent are used to analyze the chaos of the rotor system at the first- and second-order critical speed of the rotor. Experiment on chaos analysis has shown that compared with the explicit Runge–Kutta method, the precise Runge–Kutta hybrid integration method can improve the convergence step of calculation significantly while avoiding iterative solution and maintain high accuracy which is four times the increase of the integral step.

Theoretical and experimental dynamics analysis of rotor-bearing system supported by elliptical bearings

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zhiming Zhao ◽  
Rui Zhang ◽  
Feng Ji ◽  
Xiaoyang Yuan
Keyword(s):  
Peer Review ◽  
Dynamic Characteristics ◽  
Critical Speed ◽  
Design Method ◽  
Large Diameter ◽  
Rotor System ◽  
Content Type ◽  
Vibration Data ◽  
Rotor Bearing ◽  
Bearing System

Purpose High power and speed are new demands for rotating machinery which needs the journal bearings with high dynamic characteristics. The critical speed of the rotor-bearing system is one of the most significant parameters to evaluate the dynamic characteristics. This paper aims to investigate the theoretical and experimental analysis of a rotor system supported by large diameter elliptical bearings. Design/methodology/approach To obtain the theoretical and experimental support for rotor-bearing system design, dynamic characteristics theoretical analysis based on the finite difference method is given and an experiment focuses on critical speed identification is carried out. Findings The theoretical calculation results indicate that the critical speed is near to 800 rpm and there is no large vibration amplitude round working speed (1,500 rpm). Using the test bench in the factory unit, vibration data including three experimental processes are obtained. According to the vibration data, the critical speed is identified which also indicates that it is stable when working at 1,500 rpm. Originality/value The design method for the rotor system supported by large diameter elliptical bearing can be obtained by the theoretical and experimental results shown in this paper. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2020-0122/

The Analyses of the Critical Speed and Unbalance Response in the Rotor System

2014 ◽  
Vol 607 ◽  
pp. 515-518
Author(s):  
Jun Li Liu ◽  
Zong Rui Hao ◽  
Juan Xu ◽  
Qing Ming Meng
Keyword(s):  
Finite Element ◽  
Critical Speed ◽  
Rotor System ◽  
Rigid Support ◽  
The Finite Element Method ◽  
Analysis Model ◽  
Element Analysis ◽  
Resonance Amplitude ◽  
Finite Element Analysis Model ◽  
Linear Finite Element

Linear finite element analysis model of the typical rotor system is established by the finite element method. Considering the gyroscopic effect of the rotor, critical speed in the rotor system is solved. Then the effect of the rotor system by the unbalanced force on dynamic characteristic is analyzed by frequency response curve. The result shows that support damping coefficient has a great effect on critical speed in the rotor system. With the support from rigid support to elastic support, the critical speed greatly reduces. Because of the unbalance exciting force, maximum resonance amplitude of the disk is near the critical speed of the rotor.

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