Analysis of Cracked Rotor With Gyroscopic Effects Supported on Textured Journal Bearings

2019 ◽  
Author(s):  
C. Shravankumar ◽  
K. Jegadeesan ◽  
T. V. V. L. N. Rao
Keyword(s):  
Dynamic Modelling ◽  
Journal Bearings ◽  
Cracked Rotor ◽  
Campbell Diagram ◽  
Reduced Order ◽  
Gyroscopic Effects ◽  
Stiffness And Damping ◽  
Rotor Dynamic ◽  
Element Theory ◽  
Order State

Abstract This paper present the analysis of a cracked rotor shaft with an offset disc attached to it and mounted on textured journal bearings. The bearings are modelled using linearized stiffness and damping coefficients, both direct and cross-coupled. The shaft and disc are modelled using finite element theory. The shaft and disc masses, stiffnesses and their gyroscopic effects are considered. The crack is modeled based on fracture mechanics approach. The rotor dynamic modelling and analysis of the system considering the effect of crack geometry is carried out to obtain the system whirl frequencies. The system is represented in reduced order state-space form and its critical speeds are obtained by plotting the Campbell diagram.

The Extended Modal Reduction Method Applied to Rotor Dynamic Problems

1991 ◽  
Vol 113 (1) ◽  
pp. 79-84 ◽  
Author(s):  
K. Kane ◽  
B. J. Torby
Keyword(s):  
Degrees Of Freedom ◽  
Reduction Method ◽  
Mode Shapes ◽  
Dynamic Problems ◽  
Modal Reduction ◽  
Stiffness Matrices ◽  
Space Formulation ◽  
Gyroscopic Effects ◽  
Stiffness And Damping ◽  
Rotor Dynamic

In this paper, the existing Modal Reduction Method, which was developed to handle symmetric mass and stiffness matrices, is extended utilizing state-space formulation to handle nonsymmetric mass, damping, and stiffness matrices. These type of matrices typically accompany rotor dynamic problems since journal bearings supporting the rotor have nonsymmetric stiffness and damping characteristics. The purpose of modal reduction is to eliminate unimportant modes and degrees of freedom from the analytical model after they are found, so that further numerical analysis can be accelerated. The reduction described here leaves the retained eigenvalues and mode shapes unaltered from their original values. This method is demonstrated for a simple rotor problem having nonsymmetric system matrices including gyroscopic effects.

Nonparametric Stochastic Modeling of Uncertainty in Rotordynamics—Part II: Applications

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Raghavendra Murthy ◽  
Marc P. Mignolet ◽  
Aly El-Shafei
Keyword(s):  
Standard Deviation ◽  
Stochastic Modeling ◽  
Journal Bearings ◽  
Eigenvalues And Eigenvectors ◽  
Campbell Diagram ◽  
Oil Whip ◽  
Stiffness Matrices ◽  
Symmetric Rotor ◽  
Bearing Stiffness ◽  
Stiffness And Damping

In the first part of this series, a comprehensive methodology was proposed for the consideration of uncertainty in rotordynamic systems. This second part focuses on the application of this approach to a simple, yet representative, symmetric rotor supported by two journal bearings exhibiting linear, asymmetric properties. The effects of uncertainty in rotor properties (i.e., mass, gyroscopic, and stiffness matrices) that maintain the symmetry of the rotor are first considered. The parameter λ that specifies the level of uncertainty in the simulation of stiffness and mass uncertain properties (the latter with algorithm I) is obtained by imposing a standard deviation of the first nonzero natural frequency of the free nonrotating rotor. Then, the effects of these uncertainties on the Campbell diagram, eigenvalues and eigenvectors of the rotating rotor on its bearings, forced unbalance response, and oil whip instability threshold are predicted and discussed. A similar effort is also carried out for uncertainties in the bearing stiffness and damping matrices. Next, uncertainties that violate the asymmetry of the present rotor are considered to exemplify the simulation of uncertain asymmetric rotors. A comparison of the effects of symmetric and asymmetric uncertainties on the eigenvalues and eigenvectors of the rotating rotor on symmetric bearings is finally performed to provide a first perspective on the importance of uncertainty-born asymmetry in the response of rotordynamic systems.

Reduced-Order State Space Model for Dynamic Phasors in Active Distribution Networks

2020 ◽  
Vol 11 (3) ◽  
pp. 1928-1941
Author(s):  
Huifang Wang ◽  
Kuan Jiang ◽  
Mohammad Shahidehpour ◽  
Benteng He
Keyword(s):  
State Space ◽  
State Space Model ◽  
Distribution Networks ◽  
Reduced Order ◽  
Space Model ◽  
Dynamic Phasors ◽  
Active Distribution Networks ◽  
Order State

Porous Wall Gas Lubricated Journal Bearings: Theoretical Investigation

1979 ◽  
Vol 101 (4) ◽  
pp. 458-465 ◽  
Author(s):  
E. P. Gargiulo
Keyword(s):  
Experimental Investigation ◽  
Dynamic Stiffness ◽  
Porous Wall ◽  
Companion Paper ◽  
Journal Bearings ◽  
Damping Properties ◽  
Governing Equations ◽  
Performance Curves ◽  
Unsteady Characteristics ◽  
Stiffness And Damping

A model has been developed to compute the dynamic stiffness and damping properties of externally pressurized, porous-wall, gas journal bearings which includes the effects of journal rotation and eccentricity. This paper presents the derivation of the governing equations and the perturbation analysis used to find the unsteady characteristics. Typical nondimensional performance curves are found and the influences of seven governing parameters are discussed. A companion paper describes an experimental investigation of porous journal bearings.

scholarly journals Reduced-Order State Observer-Based Feedback Control Methodologies for Doubly Fed Induction Machine

2018 ◽  
Vol 54 (3) ◽  
pp. 2845-2856 ◽  
Author(s):  
Rojan Bhattarai ◽  
Niroj Gurung ◽  
Abilash Thakallapelli ◽  
Sukumar Kamalasadan
Keyword(s):  
Feedback Control ◽  
Induction Machine ◽  
State Observer ◽  
Reduced Order ◽  
Doubly Fed Induction Machine ◽  
Doubly Fed ◽  
Order State

Modelling Fluid Inertia Forces of Short Journal Bearings for Rotordynamic Applications

1993 ◽  
Author(s):  
A. El-Shafei
Keyword(s):  
Momentum Equation ◽  
Journal Bearings ◽  
Fluid Inertia ◽  
Radial Acceleration ◽  
Damping Characteristics ◽  
Energy Approximation ◽  
Form Model ◽  
Fluid Inertia Effect ◽  
Stiffness And Damping ◽  
Inertia Forces

Abstract It has been recently suggested that fluid inertia may play an important role in the dynamic behavior of rotors supported on journal bearings. This paper presents a model for fluid inertia forces in short cylindrical journal bearings based on an energy approximation. The inertialess velocity profiles predicted by the solution of Reynolds’ equation are inserted in the axial momentum equation multiplied by the axial velocity profile and integrated across the film thickness, to obtain the pressure in short journal bearings including the fluid inertia effect. The pressure is then integrated to obtain the fluid inertia forces. It is shown that the inertia forces thus obtained are proportional to the usual radial, centripetal, tangential and coriolis accelerations of the journal, in addition to a nonlinear radial acceleration. Moreover, it is shown that the inertia forces contribute to the stiffness and damping characteristics of the journal bearings. The inertia coefficients of the bearings are obtained in cartezian and cylindrical coordinates, for both uncavitated and cavitated bearings, and are plotted versus the eccentricity ratio. The model thus obtained is an analytical closed form model for fluid inertia forces in short journal bearings. Such a model is the most suitable for rotordynamic applications, particularly for time transient rotordynamic simulations.

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