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.

A Preliminary Study of Whirl Instability for Pressurized Gas Bearings

1962 ◽  
Vol 84 (4) ◽  
pp. 511-518 ◽  
Author(s):  
R. H. Larson ◽  
H. H. Richardson
Keyword(s):  
Experimental Data ◽  
Natural Frequency ◽  
Stability Criterion ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Gas Bearings ◽  
Preliminary Study ◽  
Bearing System

Experimental data are presented for the threshold of whirl instability for a short, rigid rotor supported in externally pressurized compensated gas journal bearings. The effects of supply pressures from zero to 200 psig and of radial clearances from 0.0006 to 0.0032 in. are discussed for one type of bearing configuration. A simple stability criterion is presented which explains qualitatively the observed trends. Whirl instability was observed when the frequency of rotation of the shaft exceeded from two to six times the lowest natural frequency of the shaft-bearing system.

Chaos of a Flexible Rotor in Journal Bearings

1995 ◽  
Author(s):  
R. D. Brown ◽  
G. Drummond
Keyword(s):  
Theoretical Models ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
Rigid Rotor ◽  
Flexible Rotor ◽  
Hydrodynamic Bearings ◽  
Stress Reversals ◽  
Oil Films ◽  
Rigid Rotors ◽  
Rotor Model

Abstract Nonlinear systems can give rise to chaotic behaviour, essentially unpredictable. Oil film forces arising from hydrodynamic bearings in rotating machinery can be extremely nonlinear under conditions of large unbalance. Chaotic response has been demonstrated in theoretical models of rigid rotors supported in hydrodynamic bearings. The behaviour of a rigid rotor can be extended by looking at a flexible rotor model supported on journal bearings and subject to large unbalance levels. The introduction of a flexible shaft yields chaotic regions which are less extensive than those obtained from a rigid rotor model. This is not surprising as the nonlinearity in the model is confined to the oil films at the end of the shaft. However if this level of unbalance is experienced in service then shaft fatigue could occur because of the sustained nature of the non-synchronous response and the effect of the resulting stress reversals.

Nonlinear Dynamics of Flexible Rotors Supported on Journal Bearings—Part I: Analytical Bearing Model

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Mohammad Miraskari ◽  
Farzad Hemmati ◽  
Mohamed S. Gadala
Keyword(s):  
Journal Bearing ◽  
Nonlinear Coefficient ◽  
Journal Bearings ◽  
Flexible Rotor ◽  
Dynamic Coefficients ◽  
Flexible Rotors ◽  
Rotor Bearing ◽  
Bearing Force ◽  
Derivatives Of ◽  
Bearing System

To determine the bifurcation types in a rotor-bearing system, it is required to find higher order derivatives of the bearing forces with respect to journal velocity and position. As closed-form expressions for journal bearing force are not generally available, Hopf bifurcation studies of rotor-bearing systems have been limited to simple geometries and cavitation models. To solve this problem, an alternative nonlinear coefficient-based method for representing the bearing force is presented in this study. A flexible rotor-bearing system is presented for which bearing force is modeled with linear and nonlinear dynamic coefficients. The proposed nonlinear coefficient-based model was found to be successful in predicting the bifurcation types of the system as well as predicting the system dynamics and trajectories at spin speeds below and above the threshold speed of instability.

Experimental research on suppressing unbalanced vibration of rotor by integral squeeze film damper

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wei Yan ◽  
Lidong He ◽  
Zhe Deng ◽  
Xingyun Jia
Keyword(s):  
Rotational Speed ◽  
Critical Speed ◽  
Structural Characteristics ◽  
Experimental Studies ◽  
Rotor System ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Flexible Rotor ◽  
Test Rig ◽  
Squeeze Film Damper

Abstract As a novel structural damper, the unique structural characteristics of the integral squeeze film damper (ISFD) solve the nonlinear problem of the traditional squeeze film damper (SFD), and it has good linear damping characteristics. In this research, the experimental studies of ISFD vibration reduction performance are carried out for various working conditions of unbalanced rotors. Two ball bearing-rotor system test rigs are built based on ISFD: a rigid rotor test rig and a flexible rotor test rig. When the rotational speed of rigid rotor is 1500 rpm, ISFD can reduce the amplitude of the rotor by 41.79%. Under different unbalance conditions, ISFD can effectively improve the different degrees of unbalanced faults in the rotor system, reduce the amplitude by 43.21%, and reduce the sensitivity of the rotor to unbalance. Under different rotational speed conditions, ISFD can effectively suppress the unbalanced vibration of rigid rotor, and the amplitude can be reduced by 53.51%. In the experiment of the unbalanced response of the flexible rotor, it is found that ISFD can improve the damping of the rotor system, effectively suppress the resonance of the rotor at the critical speed, and the amplitude at the first-order critical speed can be reduced by 31.72%.

Bifurcation and Chaos Behavior of Rotor-Bearing System With Crack and Pedestal Looseness Faults

2007 ◽  
Author(s):  
Yuegang Luo ◽  
Songhe Zhang ◽  
Feng Wen ◽  
Bangchun Wen
Keyword(s):  
Critical Speed ◽  
Journal Bearings ◽  
Cracked Rotor ◽  
Bifurcation And Chaos ◽  
Coupling Faults ◽  
Speed Range ◽  
Rotor Bearing ◽  
Set Up ◽  
Bearing System ◽  
Main Influence

A dynamic model was set up for the two-span rotor-bearing system with coupling faults of crack and pedestal looseness supported on three plain journal bearings. The nonlinear dynamic behaviors that induced by crack, pedestal looseness and coupling faults are numerically studied. There is quasi-periodic motion appearing in the cracked rotor-bearing system, and it within the sub-critical speed range in the pedestal looseness rotor-bearing system. There is chaotic motion appearing within the supper-critical speed range in the pedestal looseness rotor-bearing system. The pedestal looseness fault is the main influence on the coupling faults system, and there is Period-3 motion appearing in the system. The results may bring up theoretical references for fault diagnoses, dynamic design, and security running to rotor-bearing system.

A dynamic response test rig of a full-scale rotor–journal bearing system

2018 ◽  
Vol 233 (4) ◽  
pp. 649-659
Author(s):  
Qiang Li ◽  
Shuo Zhang ◽  
Yujun Wang ◽  
Weiwei Xu ◽  
Zhenbo Wang
Keyword(s):  
Dynamic Response ◽  
Natural Frequency ◽  
Journal Bearing ◽  
Dynamic Balance ◽  
Journal Bearings ◽  
Full Scale ◽  
Test Rig ◽  
Field Dynamic ◽  
Bearing Structure ◽  
Bearing System

A design strategy of a test rig for the dynamic behavior of a rotor supported by two full-scale journal bearings was proposed. A special part, called “intermediate”, was set up to allow the convenient changing of the bearing structure. An electromagnetic exciter was used to obtain the natural frequency, and software running on the Microsoft Visual C++6.0 operating platform was programmed for signal acquisition and analysis. Then, the test rig was constructed. The field dynamic balance and natural frequency testing were carried out. The journal orbits and frequency spectrums were used to measure the dynamic response of different structure full-scale journal bearings. The experimental results showed that an acceptable balance effect was achieved after the field dynamic balance. The natural frequency of the rig agreed with the numerical results. Stability was improved through changing the bearing structure. This revealed that this rig can effectively test the dynamic behavior of a rotor supported by a full-scale journal bearing system, which is critical to the design of journal bearings.

Some Experiments on Oil Whirl and Oil Whip

2004 ◽  
Author(s):  
A. El-Shafei ◽  
S. H. Tawfick ◽  
M. S. Raafat ◽  
G. M. Aziz
Keyword(s):  
Twentieth Century ◽  
Critical Speed ◽  
Journal Bearings ◽  
Flexible Rotor ◽  
Angular Misalignment ◽  
Oil Whip ◽  
Early Twentieth Century ◽  
Oil Whirl

The oil whirl and oil whip phenomena are well known since the early twentieth century. However, there is a lot of confusion on the parameters that affect the onset of instability. In this study, we investigate the onset of instability on a flexible rotor mounted on two plain cylindrical journal bearings. The rotor is run through the first critical speed, the instability, and the second critical speed. Tests are conducted at various unbalance levels, pressures, and misalignment conditions on the coupling. It is shown that, by far, the misalignment of the coupling is the parameter that is most effective on the onset of instability. In particular angular misalignment resulted in the smoothest rotor response.

Stability analysis of a rigid rotor supported by two-lobe hydrodynamic journal bearings operating with a non-Newtonian lubricant

2018 ◽  
Vol 233 (6) ◽  
pp. 884-898 ◽  
Author(s):  
Saurabh K Yadav ◽  
Arvind K Rajput ◽  
Nathi Ram ◽  
Satish C Sharma
Keyword(s):  
Reynolds Equation ◽  
Pressure Field ◽  
Equation Of Motion ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Linear Finite Element ◽  
Runge Kutta Method ◽  
The Stability ◽  
Ellipticity Ratio ◽  
Bearing System

In the present work, an investigation has been performed on a rigid rotor supported by two-lobe journal bearings operating with a non-Newtonian lubricant. The governing Reynolds equation for pressure field is solved by using non-linear finite element method. Further to study the dynamic stability of the bearing system, governing equation of motion for the rotor position is solved by fourth order Runge–Kutta method. Bifurcation and Poincaré maps of two-lobe bearings are presented for different values of the non-Newtonian parameter and bearing ellipticity ratio. The numerical results illustrate that the ellipticity of a bearing with a dilatant lubricant improve the stability of the rotordynamic system.

Sign in / Sign up

Export Citation Format

Share Document