An Experimental Study of the Steady-State Response of Oil-Film Dampers

1978 ◽  
Vol 100 (2) ◽  
pp. 216-221 ◽  
Author(s):  
R. K. Sharma ◽  
M. Botman
Keyword(s):  
Experimental Study ◽  
Steady State ◽  
High Speed ◽  
Maximum Amplitude ◽  
Dynamic Responses ◽  
Steady State Response ◽  
Main Bearing ◽  
Oil Film ◽  
State Response ◽  
Mass Eccentricity

Oil-film dampers are an integral feature of most high-speed, lightweight turbo engines, in which they are used to suppress undesirable shaft dynamic responses. They are generally located at the antifriction main bearings. An experimental study of the steady-state response of an oil-film damper at a main bearing was conducted on the high-speed rig developed for this purpose. The rig and some typical test results on a damper with a discreet number of oil-inlet ports were described in an earlier publication [1]. In this paper, the experimental results are presented on dampers with different geometries and oil-supply arrangements. The results are presented in terms of transmissibility, deflection and damping coefficient plots. The response of the damper with radial springs to simulate gravity effects in a vertical rotor arrangement is compared to that without radial springs. It is shown that there is a range of speeds up to which the response of the damper is synchronous and beyond which it becomes nonsynchronous. No nonsynchronous behavior was observed for damper amplitudes not exceeding the mass eccentricity of the rotor, that is, the displacement of the rotor center of gravity from the geometric center for a given unbalance. It appears that in a good damper design the maximum amplitude does not exceed the mass eccentricity of the rotor.

An Efficient Algorithm for Computing the Steady-State Dynamic Response of High-Speed Mechanisms

1994 ◽  
Author(s):  
Tyler J. Selstad ◽  
Kambiz Farhang
Keyword(s):  
Steady State ◽  
High Speed ◽  
Steady State Solution ◽  
Time Varying ◽  
Initial Condition ◽  
Steady State Response ◽  
Periodicity Condition ◽  
Varying Coefficients ◽  
State Response ◽  
Time Varying Coefficients

Abstract An efficient method for obtaining the steady-state response of linear systems with periodically time varying coefficients is developed. The steady-state solution is obtained by dividing the fundamental period into a number of intervals and establishing, based on a fourth-order Rung-Kutta formulation, the relation between the response at the start and end of the period. Imposition of periodicity condition upon the response facilitates computation of the initial condition that yields the steady-state values in a single pass; i.e. integration over only one period. Through a practical example, the method is shown to be more accurate and computationally more efficient than other known methods for computing the steady-state response.

Synthesis and Steady State Analysis of High-Speed Elastic Cam-Follower Linkages With Concentrated Masses: Part II — Steady State Analysis

1991 ◽  
Author(s):  
Hsin-Ting J. Liu ◽  
Donald R. Flugrad
Keyword(s):  
Steady State ◽  
High Speed ◽  
Steady State Response ◽  
Steady State Analysis ◽  
State Response ◽  
Periodic Linear ◽  
Cam Follower ◽  
Concentrated Masses ◽  
Characteristic Multipliers ◽  
State Analysis

Abstract The responses for different design and simulation conditions, including various speed and damping ratios, are investigated for an elastic cam-follower system discussed in Part I. The location of a single dominant pair of characteristic multipliers of the inhomogeneous periodic linear system is found to have significant influence on the steady state response.

A Nonlinear Analysis of the Axial Steady State Response of the Hydrodynamic Thrust Bearing-Rotor System Subjected to a Harmonic Excitation

2005 ◽  
Author(s):  
T. N. Shiau ◽  
W. C. Hsu
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Thrust Bearing ◽  
Harmonic Excitation ◽  
Rotor System ◽  
Time Dependent ◽  
Steady State Response ◽  
Harmonic Force ◽  
Oil Film ◽  
State Response

The purpose of this study is to investigate the nonlinear axial response of a thrust bearing-rotor system, which is subjected to an axial harmonic force. For the axial vibration of the rotor, the system forces include the external axial harmonic force and the reacting oil film forces, which are obtained by solving a time-dependent Reynolds Equation within the thrust pads of the thrust bearing. The time-dependent Reynolds Equation is solved by a finite difference method, and the system equation of motion is solved by the fourth-order Runge-Kutta method. A linear analysis is attempted in to evaluate its suitability for the situation under consideration. And the bearing stiffness and damping coefficients are investigated with parameters including the dimensionless wedge thickness, the initial oil film thickness and the rotor spin speed. The results show that the average steady state response will decrease as the harmonic axial force intensifies its fluctuating magnitude. The results also indicate that it will induce ultra-super harmonics when the axial harmonic force intensifies its fluctuating magnitude.

Trigonometric Collocation for Computation of Steady State Response of a Cracked Beam

2013 ◽  
Author(s):  
Bakeer Bakeer ◽  
Oleg Shiryayev
Keyword(s):  
Steady State ◽  
Fatigue Cracks ◽  
Equations Of Motion ◽  
Dynamic Responses ◽  
Steady State Response ◽  
Cracked Beam ◽  
Vibration Period ◽  
State Response ◽  
Trigonometric Collocation ◽  
Alternative Techniques

Development of vibration-based structural health monitoring techniques requires the use of various computational methods to predict dynamic responses of damaged structures. The method described in this work can be used for prediction of steady state harmonic responses for structures with fatigue cracks and may have several advantages over alternative techniques. The method appears to be relatively easy to implement and computationally inexpensive. The steady state response of the system at a given number of time points distributed over one vibration period is represented in terms of Fourier series containing higher frequency harmonics. Equations of motion are formulated in the form that allows for easy computation of Fourier coefficients for all terms in the series. Iterative procedure is used for determining the time of stiffness change in order to capture bilinear dynamic behavior. We present results of initial investigation by applying the method to a model of a cantilever beam with a crack.

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