Perturbation Solutions for Eccentric Operation of Squeeze Film Damper Systems

1986 ◽  
Vol 108 (4) ◽  
pp. 619-623 ◽  
Author(s):  
Xuehai Li ◽  
D. L. Taylor
Keyword(s):  
Numerical Simulation ◽  
Experimental Results ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Squeeze Film Damper ◽  
Synchronous Motion ◽  
Squeeze Film Dampers ◽  
Large Speed ◽  
Good Agreement ◽  
Perturbation Solutions

The study focuses on the effect of a small unidirectional load such as comes from imperfect balance between preloading on centering springs and gravitational load on squeeze film dampers. A rigid rotor-squeeze film damper system is considered, and a thorough study of the synchronous motion of the system is performed. Two perturbation solutions are developed: one for large speed and one for small speed. The perturbation solutions are shown to be in good agreement with numerical simulation and published experimental results.

Eccentric Operation and Blade-Loss Simulation of a Rigid Rotor Supported by an Improved Squeeze Film Damper

1995 ◽  
Vol 117 (3) ◽  
pp. 490-497 ◽  
Author(s):  
J. Y. Zhao ◽  
E. J. Hahn
Keyword(s):  
Outer Ring ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Cavitation Model ◽  
Squeeze Film Damper ◽  
Constant Stiffness ◽  
Flexible Support ◽  
Squeeze Film Dampers ◽  
Stiffness And Damping ◽  
Blade Loss

This paper outlines an improved squeeze film damper which reduces significantly the dependence of the stiffness of conventional squeeze film dampers on the vibration amplitudes. This improved damper consists of a conventional squeeze film damper with a flexibility supported outer ring. This secondary flexible support is considered to be massless, and to have a constant stiffness and damping. Assuming the short bearing approximation and the ‘π’ film cavitation model, the performances of this damper in preventing bistable operation and sub-synchronous and nonsynchronous motions are theoretically demonstrated for a rigid rotor supported on a squeeze film damper. Blade-loss simulations are carried out numerically.

Electric-Hydraulic Actuator Design for a Hybrid Squeeze-Film Damper-Mounted Rigid Rotor System With Active Control

2005 ◽  
Vol 128 (2) ◽  
pp. 176-183 ◽  
Author(s):  
Her-Terng Yau ◽  
Chieh-Li Chen
Keyword(s):  
Dynamical Behavior ◽  
Rotor System ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Loop Gain ◽  
Hydraulic Actuator ◽  
Squeeze Film Damper ◽  
Chaotic Vibration ◽  
Squeeze Film Dampers ◽  
Actuator Design

When a squeeze-film damper-mounted rigid rotor system is operated eccentrically, the nonlinear forces are no longer radially symmetric and a disordered dynamical behavior (i.e., quasi-periodic and chaotic vibration) will occur. To suppress the undesired vibration characteristics, the hybrid squeeze-film damper bearing consisting of hydrostatic chambers and hydrodynamic ranges is proposed. In order to change the pressure in hydrostatic chambers, two pairs of electric-hydraulic orifices are used in this paper. The dynamic model of the system is established with the consideration of the electric-hydraulic actuator. The complex nonsynchronous vibration of squeeze-film dampers rotor-bearing system is demonstrated to be stabilized by such electric-hydraulic orifices actuators with proportional-plus-derivative (PD) controllers. Numerical results show that the nonchaotic operation range of the system will be increased by tuning the control loop gain.

Subharmonic and Quasi-Periodic Motions of an Eccentric Squeeze Film Damper-Mounted Rigid Rotor

1994 ◽  
Vol 116 (3) ◽  
pp. 357-363 ◽  
Author(s):  
J. Y. Zhao ◽  
I. W. Linnett ◽  
L. J. McLean
Keyword(s):  
Numerical Integration ◽  
Least Square ◽  
Harmonic Series ◽  
Squeeze Film ◽  
Maximum Speed ◽  
Rigid Rotor ◽  
Squeeze Film Damper ◽  
Squeeze Film Dampers ◽  
The Stability ◽  
Nonsynchronous Vibrations

When a squeeze-film damper is operated eccentrically, the nonlinear damper forces are no longer radially symmetric and subharmonic and quasi-periodic vibrations may be excited by the rotor unbalance. In this study, the unbalance response of a rigid rotor, supported on an eccentric squeeze film damper, is first approximated by a harmonic series whose coefficients are determined by the collocation method, together with a nonlinear least-square regression. The stability of the resulting periodic solution is then examined using the Floquet transition matrix method. For sufficiently large values of the unbalance and the damper static radial misalignment, it is shown that the approximate harmonic motion loses its stability and bifurcates into a stable subharmonic motion and a quasi-periodic motion at speeds above twice the system critical speed. This analytical finding is verified by a numerical integration in forms of the Poincare´ map, the rotor trajectory, the bifurcation diagram, and the power spectrum. It is suggested that stability analysis and numerical integration should always be incorporated into an approximate analytical method to achieve an adequate approximation. The results of this study show that the introduction of squeeze-film dampers may give rise to the undesirable nonsynchronous vibrations, which limits the maximum speed at which dampers should be used.

Pressurized Oil Squeeze Film Dampers

1980 ◽  
Vol 102 (1) ◽  
pp. 41-47 ◽  
Author(s):  
A. Kent Stiffler
Keyword(s):  
Design Methodology ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Squeeze Film Damper ◽  
Supply Pressure ◽  
Squeeze Film Dampers ◽  
Stiffness And Damping ◽  
Film Stiffness

A pressurized oil squeeze film damper supporting a rigid rotor mounted in antifriction bearings is investigated. Orifice and inherent feed inlets are examined, and it is shown that the clearance determines the inlet resistance for a groove or slot. The film stiffness and damping forces are determined as a function of the restrictor coefficient, rotor unbalance speed and the supply pressure using the short bearing approximation. These forces are related to the system transmissibility. A design methodology for low transmissibilities is presented.

Time Transient Analysis of Horizontal Rigid Rotor Supported With O-Ring Sealed Squeeze Film Damper

2013 ◽  
Author(s):  
Saeid Dousti ◽  
Timothy W. Dimond ◽  
Paul E. Allaire ◽  
Houston E. Wood
Keyword(s):  
Transient Analysis ◽  
Reynolds Equation ◽  
Equations Of Motion ◽  
Excitation Frequency ◽  
Numerical Data ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Squeeze Film Damper ◽  
Squeeze Film Dampers

This study addresses the nonlinear dynamic behavior of O-ring seals as the retaining spring in squeeze film dampers (SFDs). An analytical model is developed to predict the restoring and hysteresis forces of elastomer O-rings based on experimental and numerical data. This model takes into account the temperature softening and excitation frequency hardening effects in O-rings as well as the installation conditions in the form of radial and vertical preloads, σ and γ, respectively. Long bearing assumption is adopted for the solution of Reynolds equation. The equations of motion of horizontal unbalanced rigid rotor are derived, and a dimensional analysis is conducted on them. The numerical results substantiates the synchronizing effects of bearing parameter, B and vertical preload, γ, and the asynchronizing effects of O-ring parameter, O and radial preload, σ. It is shown that the variation of temperature and rotational speed as operating conditions influence the rotor response significantly.

Parametric Study of the Imbalance Response of a Squeeze Film Damper

2008 ◽  
Author(s):  
Changhu Xing ◽  
Minel J. Braun ◽  
Hongmin Li
Keyword(s):  
Numerical Simulation ◽  
Stability Analysis ◽  
Direct Numerical Simulation ◽  
Parametric Study ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Squeeze Film Damper ◽  
Rotor Bearing ◽  
Parametric Studies ◽  
Spring Support

Rigid rotor models are widely used for the rotor-bearing stability analysis. This paper presents parametric studies for a squeeze film damper (SFD) using as parameters pressurization, the retainer spring support, and viscosity under the 2π- and π-film assumptions. The results are then validated by direct numerical simulation of the journal orbit.

Force Coefficients for a Centrally Grooved Short Squeeze Film Damper

1996 ◽  
Vol 118 (3) ◽  
pp. 608-616 ◽  
Author(s):  
J. X. Zhang ◽  
J. B. Roberts
Keyword(s):  
Hydrodynamic Force ◽  
Theoretical Work ◽  
Experimental Results ◽  
Squeeze Film ◽  
Static Force ◽  
Squeeze Film Damper ◽  
Force Coefficients ◽  
Supply Pressure ◽  
Supply Mechanism ◽  
Good Agreement

A centrally grooved short squeeze film damper (SFD), together with its lubricant supply mechanism (LSM), is analyzed, using an integrated theoretical model. It is shown that the traditional analysis for such a damper, where the effects of the central groove and the LSM are ignored, can lead to a seven-fold underestimation of the magnitude of the hydrodynamic force coefficients. The new theory gives predictions for the damping coefficients which are in good agreement with corresponding experimental results. Moreover, a five-fold improvement is obtained for both the temporal and convective inertia coefficients, at low values of eccentricity. The new model leads to the prediction of a nonzero fluid static force which, in conformity with experimental results, is linearly related to the supply pressure. The existence of this static force has not been explained by previous theoretical work on SFDs.

The Effectiveness of Porous Squeeze Film Dampers for Suppressing Nonsynchronous Motions

1991 ◽  
Author(s):  
Shiping Zhang ◽  
Litang Yan ◽  
Qihan Li ◽  
Yoshihiko Kawazoe
Keyword(s):  
Time Domain ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Third Harmonic ◽  
Squeeze Film Damper ◽  
Outer Race ◽  
System Parameters ◽  
Highly Nonlinear ◽  
Squeeze Film Dampers ◽  
Force Characteristics

Abstract The rotor time domain orbits and the transmissibility trajectories of a rigid rotor supported on squeeze film damper (SFD) and porous squeeze film damper (PSFD) systems were investigated. Under certain system parameters, The SFD system with a centralising spring exhibits excessive nonsynchronous motions with approximate third harmonic frequencies and opposite whirling motions as well as severe transmitted forces. However, under same system parameters and with a porous permeable film outer race PSFD system could effectively attenuate the nonsynchronous motions with very small transmissibilities. The rigid rotor without a centering spring supported on SFD and PSFD systems were also investigated. The highly nonlinear film force characteristics take the major responsibility for the nonsynchronous motions of uncentralized SFD systems, and typical second and third harmonic orbits of SFD system were predicted. While under the same conditions, perfect synchronous orbits of PSFD system were resulted. PSFD through outer race permeability could provide more reasonable film force characteristics, and thus has the capability of suppressing nonsynchronous motions.

Dynamic behavior analysis of a rigid rotor supported by hydrostatic squeeze film dampers compensated with new electrorheological valve restrictors

2019 ◽  
Vol 72 (5) ◽  
pp. 611-619 ◽  
Author(s):  
Mohamed Benadda ◽  
Ahmed Bouzidane ◽  
Marc Thomas ◽  
Raynald Guilbault
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
Nonlinear Models ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Eccentricity Ratio ◽  
Content Type ◽  
Squeeze Film Damper ◽  
Transmitted Force ◽  
Squeeze Film Dampers

Purpose This paper aims to propose a new hydrostatic squeeze film damper compensated with electrorheological valve restrictors to control the nonlinear dynamic behavior of a rigid rotor caused by high unbalance eccentricity ratio. To investigate the effect of electrorheological valve restrictors on the dynamic behavior of a rigid rotor, a nonlinear model is developed and presented. Design/methodology/approach The nonlinear results are compared with those obtained from a linear approach. The results show good agreement between the linear and nonlinear methods when the unbalanced force is small. The effects of unbalance eccentricity ratio and electric field on the vibration response and the bearing transmitted force are investigated using the nonlinear models. Findings The results of simulation performed that the harmonics generated by high unbalance eccentricities can be reduced by using hydrostatic squeeze film damper compensated with electrorheological valve restrictors. Originality/value The numerical results demonstrate that this type of smart hydrostatic squeeze film damper provides to hydrostatic designers a new bearing configuration suitable to control rotor vibrations and bearing transmitted forces, especially for high speed.

scholarly journals Numerical Simulations of V-Shaped Plates Subjected to Blast Loadings: A Validation Study

2016 ◽  
Vol 10 (11) ◽  
pp. 203
Author(s):  
Mohd Zaid Othman ◽  
Qasim H. Shah ◽  
Muhammad Akram Muhammad Khan ◽  
Tan Kean Sheng ◽  
M. A. Yahaya ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Variable Mass ◽  
Blast Loading ◽  
Experimental Results ◽  
Average Difference ◽  
Simulation Results ◽  
Blast Loadings ◽  
Carrier Vehicle ◽  
Good Agreement

A series of numerical simulations utilizing LS-DYNA was performed to determine the mid-point deformations of V-shaped plates due to blast loading. The numerical simulation results were then compared with experimental results from published literature. The V-shaped plate is made of DOMEX 700 and is used underneath an armour personal carrier vehicle as an anti-tank mine to mitigate the effects of explosion from landmines in a battlefield. The performed numerical simulations of blast loading of V-shaped plates consisted of various angles i.e. 60°, 90°, 120°, 150° and 180°; variable mass of explosives located at the central mid-point of the V-shaped vertex with various stand-off distances. It could be seen that the numerical simulations produced good agreement with the experimental results where the average difference was about 26.6%.

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