A Numerical Study of the Stable Dynamic Behavior of Radial Face Seals With Grooved Faces

1997 ◽  
Vol 119 (3) ◽  
pp. 507-513 ◽  
Author(s):  
V. Person ◽  
B. Tournerie ◽  
J. Freˆne
Keyword(s):  
Dynamic Behavior ◽  
Numerical Study ◽  
Steady State Response ◽  
Kinematic Parameters ◽  
State Response ◽  
Dynamic Tracking ◽  
Principal Effect ◽  
Face Seals ◽  
The Stability ◽  
Hydrodynamic Effects

This paper presents a simple numerical method for modeling the dynamic tracking modes of a grooved face seal. The stability is verified using a method derived from that developed for smooth face seals. The method, enabling the calculation of the kinematic parameters which describe the steady-state response of the grooved seal, is of interest in designing this type of seal. A parametric study is presented for the case of a rotor face with eight semicircular grooves. The principal effect of the grooves is to increase the hydrostatic component of the load. In turn, this makes the seal less sensitive to fluctuations of the hydrodynamic phenomena. Sinusoidal waviness is used to simulate the periodic distortions induced by the grooves and affects the dynamic behavior only in the presence of cavitation. This occurs for very small values of the film thickness and, consequently, for very small leakage flow. In this case, the dynamic response of the seal is then strongly dependent upon the hydrodynamic effects.

Influence of Interaction Between Torsion and Bending on Long-Term Nonlinear Rotor Dynamics

1999 ◽  
Author(s):  
Jiazhong Zhang ◽  
Bram de Kraker ◽  
Dick H. van Campen
Keyword(s):  
Critical Speed ◽  
Floquet Theory ◽  
Rotor Dynamics ◽  
Steady State Response ◽  
Bending Vibrations ◽  
Bending Vibration ◽  
State Response ◽  
Stability And Bifurcation ◽  
The Stability

Abstract An elementary system with gears and excited by unbalance mass has been constructed for analyzing the interaction between torsion and bending vibration in rotor dynamics. For this system, only the interaction caused primarily by unbalance mass has been investigated. The stability and bifurcation characteristics of the system have been studied by numerical computation based on Hopf bifurcation and Floquet theory. The results show that the interaction between torsion and bending vibrations can affect the stability and bifurcation of the unbalance response, in particular the onset speed of instability. In addition to the above, the interaction also affects the steady-state response. To investigate the influence of unbalance mass, the periodic solution and its stability have been studied near the first bending critical speed of the decoupled system. All the results show that the coupling of torsion and bending vibrations can have a significant influence on the nonlinear dynamics of the whole system.

An Experimental Investigation of the Steady-State Response of a Noncontacting Flexibly Mounted Rotor Mechanical Face Seal

1995 ◽  
Vol 117 (1) ◽  
pp. 153-159 ◽  
Author(s):  
An Sung Lee ◽  
Itzhak Green
Keyword(s):  
Experimental Investigation ◽  
Steady State ◽  
Dynamic Behavior ◽  
Amplitude Ratio ◽  
Theoretical Work ◽  
Operating Conditions ◽  
Superior Performance ◽  
Steady State Response ◽  
State Response ◽  
Operation Conditions

Recent theoretical work on the dynamics of the noncontacting flexibly mounted rotor (FMR) seal has shown that it is superior in every aspect of dynamic behavior compared to the flexibly mounted stator (FMS) seal. The FMR seal is inherently stable regardless of the operating speed, the maximum relative misalignment response is smaller, and the critical stator misalignment is larger. All these are measures of superior performance. This work undertakes the experimental investigation of the dynamic behavior of a noncontacting FMR seal. The steady-state response of the FMR seal was measured at various operating conditions. The results are given in terms of dynamic and static transmissibilities, i.e., amplitude ratio of responses to two forcing inputs: the initial rotor and fixed stator misalignments. These are then compared to the analytical predictions. Further, operation maps are drawn for each set of operation conditions. The maps indicate how safely (away from contact) the seal operates. It is shown that the combination of the seal parameters that maximize the fluid film stiffness is optimal for safe noncontacting operation.

Parametric Vibrations in a Magneto-Thermo-Elastic Layer of Finite Thickness

1995 ◽  
Author(s):  
Jörg Wauer
Keyword(s):  
Magnetic Field ◽  
Finite Thickness ◽  
Elastic Field ◽  
Steady State Response ◽  
Bias Magnetic Field ◽  
Parametric Vibrations ◽  
State Response ◽  
Parametric Resonances ◽  
The Stability ◽  
The Magnetic Field

Abstract The dynamic behavior of a magneto-thermo-elastic planar layer subjected to a bias magnetic field is examined. The magnetic field acts parallel to the layer surfaces and is composed of a constant and a harmonically oscillating part. In particular, the small coupled magneto-thermo-elastic vibrations superimposed on the basic steady state response due to the stationary magnetic excitation are analyzed. Attention is focused on the influence of the pulsating part of the bias magnetic field on the governing variational equations to prove the stability of the basic state. In general, the stability equations describing the perturbations of the magnetic, thermal and elastic field properties are coupled in a special form and also the parametric excitation acts in a non-classical manner. Hence the variety of possible parametric resonances seems to be limited.

Stability Analysis and Complex Dynamics of a Gear-Pair System Supported by a Squeeze Film Damper

1997 ◽  
Vol 119 (1) ◽  
pp. 85-88 ◽  
Author(s):  
Chin-Shong Chen ◽  
S. Natsiavas ◽  
H. D. Nelson
Keyword(s):  
Steady State ◽  
Periodic Solutions ◽  
Squeeze Film ◽  
Time Behavior ◽  
Steady State Response ◽  
Squeeze Film Damper ◽  
State Response ◽  
Mass Unbalance ◽  
Periodic Steady State ◽  
The Stability

The stability properties of periodic steady state response of a nonlinear geared rotordynamic system are investigated. The nonlinearity arises because one support of the system includes a cavitated squeeze film damper, while the excitation is caused by mass unbalance. The dynamical model and the procedure which leads to periodic steady state response of the system examined have been developed in an earlier paper. Here, the emphasis is placed on analyzing the stability characteristics of located periodic solutions. Also, within ranges of the excitation frequency where no stable periodic solutions are detected, the long time behavior of the system is investigated by direct integration of the equations of motion. It is shown that large order subharmonic, quasiperiodic and chaotic motions may coexist with unstable periodic response in these frequency ranges. Finally, attention is focused on practical consequences of these motions.

Dynamic Response of Eccentric Face Seals to Synchronous Shaft Whirl

2004 ◽  
Vol 126 (2) ◽  
pp. 301-309 ◽  
Author(s):  
J. Wileman
Keyword(s):  
Steady State ◽  
Dynamic Response ◽  
Solution Technique ◽  
Steady State Response ◽  
Analytical Technique ◽  
State Response ◽  
Flexible Supports ◽  
Simple Matrix ◽  
The Stability ◽  
Degenerate Cases

This work provides an analytical technique for computing the seal face misalignment which results from synchronous whirl of the shaft. The eccentric dynamic response is obtained for seals in which both mating faces are mounted on flexible supports. Responses for seals with a single flexibly mounted stator or rotor are also obtained as degenerate cases of the more general result. Synchronous shaft whirl is shown to have a significant effect on the steady-state response of all these seals, while not affecting the stability threshold. The steady-state response is obtained by solution of a simple matrix equation for the general case, and can be obtained in closed form for the degenerate cases of the flexibly mounted stator or flexibly mounted rotor. A numerical example of the solution technique is presented, and the influence of speed is examined. Extension of the method to shaft motions other than synchronous whirl is briefly discussed.

The Steady-State Response of a Two-Degree-of-Freedom Bilinear Hysteretic System

1965 ◽  
Vol 32 (1) ◽  
pp. 151-156 ◽  
Author(s):  
W. D. Iwan
Keyword(s):  
Approximate Solution ◽  
Steady State ◽  
Degree Of Freedom ◽  
Finite Limit ◽  
Steady State Response ◽  
Varying Parameters ◽  
Hysteretic System ◽  
State Response ◽  
The Stability ◽  
Two Degree Of Freedom

The method of slowly varying parameters is used to obtain an approximate solution for the steady-state response of a two-degree-of-freedom bilinear hysteretic system. The stability of the system is investigated and it is shown that such a system exhibits unbounded amplitude resonance when the level of excitation is increased beyond a certain finite limit.

Steady-State Analysis of Mechanical Seals With Two Flexibly Mounted Rotors

1997 ◽  
Vol 119 (1) ◽  
pp. 200-204 ◽  
Author(s):  
J. Wileman ◽  
I. Green
Keyword(s):  
Steady State ◽  
Dynamic Behavior ◽  
Reference Frames ◽  
Rapid Determination ◽  
Equations Of Motion ◽  
Steady State Response ◽  
Mechanical Seals ◽  
State Response ◽  
Forcing Functions ◽  
Flexible Supports

The dynamic behavior of a mechanical face seal with two flexibly mounted rotors is investigated. The equations of motion are derived using linearized rotor dynamic coefficients to model the dynamic behavior of the fluid film. The equations are shown to be linear in the inertial reference with harmonic forcing functions which result from the initial misalignment of the flexible supports. A method for obtaining the steady-state response in the system is derived by transforming the equations of motion into reference frames which rotate with the shafts. The resulting equations contain constant forcing functions and can be readily solved for the magnitude of the steady-state response. The method presented allows a rapid determination of the steady-state misalignment of a seal without resorting to numerical modeling.

The Steady-State Response of the Double Bilinear Hysteretic Model

1965 ◽  
Vol 32 (4) ◽  
pp. 921-925 ◽  
Author(s):  
W. D. Iwan
Keyword(s):  
Steady State ◽  
Nonlinear Systems ◽  
Steady State Solution ◽  
Degree Of Freedom ◽  
State Solution ◽  
Steady State Response ◽  
Hysteretic Model ◽  
Jump Phenomenon ◽  
State Response ◽  
The Stability

The steady-state response of a one-degree-of-freedom double bilinear hysteretic model is investigated and it is shown that this model gives rise to the jump phenomenon which is associated with certain nonlinear systems. The stability of the steady-state solution is discussed and it is shown that the model predicts an unbounded resonance for finite excitation.

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