scholarly journals On the Importance of Sleeve Flexibility in Passive Control of Critical Speeds of a Rotating Shaft Using Eccentric Sleeves

Machines ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 56
Author(s):  
Antony Kirk ◽  
Jonathan Griffiths
Keyword(s):  
Finite Element ◽  
Experimental Test ◽  
High Speed ◽  
Passive Control ◽  
Finite Element Simulations ◽  
Test Facility ◽  
Rotating Shaft ◽  
Critical Speeds ◽  
Dynamic Finite Element

In this paper, the critical speeds of a rotating shaft fitted with eccentric balance sleeves are identified from a scaled, high speed experimental test facility. The results are compared with the results of dynamic finite element simulations. It is shown that the stiffness of the sleeves must be accommodated when considering passive control characteristics critical speeds of a rotating shaft using eccentric sleeves.

Passive Control of Critical Speeds of a Rotating Shaft Using Eccentric Sleeves: Model Development

2016 ◽  
Author(s):  
A. J. Kirk ◽  
J. Griffiths ◽  
C. Bingham ◽  
G. Knowles ◽  
R. Bickerton
Keyword(s):  
High Speed ◽  
Passive Control ◽  
Equations Of Motion ◽  
Variable Mass ◽  
Model Development ◽  
Three Dimensional ◽  
Practical Case ◽  
Rotating Shaft ◽  
Critical Speeds ◽  
Rotating Shafts

This paper considers the passive control of lateral critical speeds in high-speed rotating shafts through application of eccentric balancing sleeves. Equations of motion for a rotating flexible shaft with eccentric sleeves at the free ends are derived using the extended Hamilton Principle, considering inertial, non-constant rotating speed, Coriolis and centrifugal effects. A detailed analysis of the passive control characteristics of the eccentric sleeve mechanism and its impact on the shaft dynamics, is presented. Results of the analysis are compared with those from three-dimensional finite element simulations for 3 practical case studies. Through a comparison and evaluation of the relative differences in critical speeds from both approaches it is shown that consideration of eccentric sleeve flexibility becomes progressively more important with increasing sleeve length. The study shows that the critical speed of high-speed rotating shafts can be effectively controlled through implementation of variable mass/stiffness eccentric sleeve systems.

Modeling Support Effects: Finite Element and Experimental Modal Methods

1996 ◽  
Author(s):  
Jonathan R. Buckles ◽  
Keith E. Rouch ◽  
John R. Baker
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Transfer Functions ◽  
Coupling Effects ◽  
Support Effects ◽  
Critical Speeds ◽  
Modal Data ◽  
The Stability ◽  
Direct Use ◽  
Reduced Matrices

The effects of support/foundation dynamics are often significant in high speed turbomachinery, and can affect the stability and response to unbalance. In some cases additional critical speeds are introduced, related to resonances in the foundation or interaction with rotor resonances of foundation resonances. This paper reviews several methods for representing these effects, including (1) reduced matrices from finite element substructures (ANSYS, for example), (2) matrices generated from modal data, and (3) direct use of experimental transfer functions. These methods are implemented in a finite element rotor program in a PC-DOS environment. The application of the methods to two laboratory rotor configurations described and results presented. Situations with a foundation resonance above and near the rotor critical are included. The importance of including coupling effects between supports is shown.

scholarly journals Effect of Torsional Element towards High-Speed Rotating Shaft’s Critical Speed at Different Boundary Conditions

2019 ◽  
Vol 8 (4) ◽  
pp. 6787-6792
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
High Speed ◽  
Critical Speed ◽  
Element Model ◽  
Accurate Estimation ◽  
Fe Model ◽  
Rotating Shaft ◽  
Different Boundary Conditions ◽  
The Difference

Efficiency improvement that can be provided by the high-speed rotating equipment becomes a concern for designers nowadays. Since the high-speed rotating machinery was capable of rotating at very near to critical speed, the accurate estimation of critical speed needs to be considered. This paper investigated the effect of torsional element towards critical speed of high-speed rotating shaft system for pinned-pinned (P-P), clamped-free (C-F) and clamped-free (C-F) boundaries condition. The Nelson’s finite element model that considers the torsional effect was developed for formulating the finite element (FE) model. This FE model was used to derive Mathieu-Hill’s equation and then solved by applying the Bolotin’s theory. From the solution, the Campbell’s diagram of the high-speed shaft was plotted. It was found that torsional motion has significant effect on the critical speed for different boundary conditions. The difference between critical speed of 4DOF and 5DOF models can be as high as 6.91 %.

scholarly journals Tribology of High Speed Aerodynamic Foil Journal Bearings

1997 ◽  
Author(s):  
D. Sudheer Kumar Reddy ◽  
S. Swarnamani ◽  
B. S. Prabhu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
High Speed ◽  
Perturbation Technique ◽  
Journal Bearings ◽  
Rotating Shaft ◽  
Aerodynamic Pressure ◽  
Foil Bearing ◽  
Bearing Number ◽  
Element Method

Foil journal bearings come under the category of air lubricated journal bearings where the lubricant is atmospheric air. In this type of bearings the pressure developed is due to the aerodynamic wedge developed between the rotating shaft and the foil bearing surface. This paper is concerned with the analysis of the bending dominated type foil bearing, in which the compliance is effected mainly through the bending of foils. The nonlinear Reynolds equation has been used for the aerodynamic pressure solution. Effect of elastohydrodynamics on foil journal bearing has been studied. The problem has been formulated using incremental finite element method. Two types of bending dominated foil bearings have been considered for analysis, namely straight foil type and curved foil type bearings. The equations for the dynamic coefficients were obtained by a perturbation technique and the results were computed using the finite element method. The effect of bearing compliance and the bearing number on performance parameters has been studied, the results were compared with the available literature.

Stochastic Finite Element Analysis for High Speed Rotors

1993 ◽  
Vol 115 (1) ◽  
pp. 59-64 ◽  
Author(s):  
T. S. Sankar ◽  
S. A. Ramu ◽  
R. Ganesan
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Mass Density ◽  
Adjoint System ◽  
Stochastic Finite Element ◽  
Stochastic Field ◽  
Rotating Shaft ◽  
Stochastic Variation ◽  
Element Analysis ◽  
Stochastic Finite Element Analysis

The general problem of the dynamic response of highspeed rotors is considered in which certain system parameters may have a spatial stochastic variation. In particular the elastic modulus and mass density of a rotating shaft are described through one dimensional stochastic field functions so that the imperfections in manufacture and measurement can be accounted for. The stochastic finite element method is developed so that the variability of the response of the rotor can be interpreted in terms of the variation of the material property. As an illustration the whirl speed analysis is performed to determine the stochastics of whirl speeds and modes through the solution of a random eigenvalue problem associated with a non self-adjoint system. Numerical results are also presented.

Harmonic Analysis of the High Speed Direct Coupled SCO2 Turbo-Generator

2021 ◽  
Author(s):  
Ashutosh Patel ◽  
Vijay Biradar ◽  
Pramod Kumar
Keyword(s):  
Finite Element ◽  
Harmonic Analysis ◽  
High Speed ◽  
Computation Time ◽  
Lumped Mass ◽  
Axisymmetric Model ◽  
Critical Speeds ◽  
Turbo Generator ◽  
Shaft Deflection ◽  
Rotor Assembly

Abstract The rotordynamics and harmonic characteristics of the rotor assembly designed for 40-kW high-speed sCO2 direct-coupled turbo-generator pair have been evaluated numerically using finite element solver “ANSYS Mechanical”. First, the shaft geometry and dimensions have been optimized using lumped mass-inertia-based AxSTREAM RotorDynamics module followed by the bearing selection analysis using SKF SimPro expert to ensure enough separation margin from the nearby critical speeds. Equivalent 2D geometry has been used with an FEA-based ANSYS general axisymmetric model to reduce the computation time. The effect of the damping on the forces transmitting to the bearings and shaft deflection at the critical speeds are analyzed by performing harmonic analysis under various damped and undamped conditions (ζ = 0, 0.005, 0.01, and 0.02).

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