Stability of Squeeze Film Damped Multi-Mass Flexible Rotor Bearing Systems

1985 ◽  
Vol 107 (3) ◽  
pp. 402-409 ◽  
Author(s):  
L. J. McLean ◽  
E. J. Hahn
Keyword(s):  
Performance Monitoring ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Equilibrium Solutions ◽  
Rotor Bearing ◽  
Stability Maps ◽  
Damper Design ◽  
Synchronous Orbit ◽  
And Performance

A technique is presented for investigating the stability of and the degree of damping in the circular synchronous orbit equilibrium solutions pertaining to radially symmetric multi-mass flexible rotor bearing systems. It involves the analysis of appropriate linearized perturbation equations about the equilibrium solutions and is applicable to systems with several squeeze film dampers. For a system with a single damper, stability threshold maps, independent of unbalance distribution, may be found in terms of the same damper parameters and operating conditions as the equilibrium solutions, thereby allowing for damper design and performance monitoring. The technique is illustrated for a simple symmetric four degree of freedom flexible rotor with an unpressurized damper. This example shows the utility of zero frequency stability maps for delineating multiple solution possibilities and that for low (in this case of the order of 0.06 or lower) bearing parameters, the introduction of an unpressurized squeeze film damper may promote instability in an otherwise stable system.

Unbalance Behavior of Squeeze Film Damped Multi-Mass Flexible Rotor Bearing Systems

1983 ◽  
Vol 105 (1) ◽  
pp. 22-28 ◽  
Author(s):  
L. J. McLean ◽  
E. J. Hahn
Keyword(s):  
Squeeze Film ◽  
Design Parameters ◽  
Solution Technique ◽  
System Response ◽  
Rotor Speed ◽  
Flexible Rotor ◽  
Rotor Bearing ◽  
Orbit Eccentricity ◽  
Convergence Problems ◽  
Damper Design

A solution technique is developed whereby the problem of determining the synchronous unbalance response of general multi-degree of freedom rotor bearing systems is reduced to solving a set of as many simultaneous nonlinear equations in damper orbit eccentricities are there are dampers. It is shown how, in the case of a single damper, the resulting nonlinear equation may be solved directly to determine all possible orbit eccentricity solutions as a function of the rotor speed and bearing parameter, thereby ensuring completeness of solution, eliminating convergence problems and clearly indicating all multistable operation possibilities. Design maps portraying the effect of the relevant damper design parameters on system response may be conveniently obtained, allowing for optimal damper design. The technique is illustrated for the case of a simple squeeze film damped symmetric flexible rotor.

Theoretical and Experimental Studies on Squeeze Film Stabilizers for Flexible Rotor-Bearing Systems Using Newtonian and Viscoelastic Lubricants

1990 ◽  
Vol 112 (4) ◽  
pp. 473-482 ◽  
Author(s):  
B. Halder ◽  
A. Mukherjee ◽  
R. Karmakar
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Squeeze Film ◽  
Experimental Investigations ◽  
Flexible Rotor ◽  
Stability Range ◽  
High Speeds ◽  
Flexible Rotors ◽  
Rotor Bearing

A combination of a squeeze film damper and a plane journal bearing is studied as a stabilizing scheme. The damper is made to play the role of a stabilizer to postpone the instability threshold speeds of flexible rotors. Both Newtonian and viscoelastic fluids are used in the rotor-bearing system. Dynamics of the system is theoretically analyzed using bond graphs. Analysis reveals that the use of a Newtonian fluid in the stabilizer largely improves the high speed stability range. However, viscoelastic stabilizing fluid has a detrimental effect on highly flexible rotors. Experimental investigations, conducted on a flexible rotor (natural frequency, 30 Hz), confirm the theoretical findings. In addition, experiments indicate that though the use of viscoelastic stabilizing fluids leads to instability in flexible rotors, the growth of large amplitude whirl is postponed to very high speeds.

Rotordynamic Evaluation of an Advanced Multi-Squeeze Film Damper: Imbalance Response and Bladeloss Simulation

1991 ◽  
Author(s):  
J. F. Walton ◽  
H. Heshmat
Keyword(s):  
Steady State ◽  
Rotor System ◽  
Squeeze Film ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Flexible Rotor ◽  
High Eccentricity ◽  
Squeeze Film Damper ◽  
Wide Range ◽  
Damper Design

In this paper results of rotordynamic response and transient tests of a novel, high load squeeze film damper design, are presented. The spiral foil multi-squeeze film damper has been previously shown to provide two to four fold or larger increases in damping levels without resorting to significantly decreased damper clearances or increased lengths. By operating with a total clearance of approximately twice conventional designs, the non-linearities associated with high eccentricity operation are avoided. Rotordynamic tests with a dual squeeze film configuration were completed. As a part of the overall testing program, a flexible rotor system was subjected to high steady state imbalance levels and transient simulated bladeloss events for up to 0.254 mm (0.01 in) mass c.g offset or 180 gm-cm (2.5 oz-in) imbalance. The spiral foil multi-squeeze film damper demonstrated that the steady state imbalance and simulated bladeloss transient response of a flexible rotor operating above its first bending critical speed could be readily controlled. Rotor system imbalance sensitivity and logarithmic decrement are presented showing the characteristics of the system with the damper installed. The ability to accommodate high steady state and transient imbalance conditions make this damper well suited to a wide range of rotating machinery, including aircraft gas turbine engines.

Reduced-order modelling methods to assess the overall vibration response of a flexible rotor-squeeze film damper bearing assembly

2002 ◽  
Vol 216 (11) ◽  
pp. 1081-1097
Author(s):  
C C Siew ◽  
M Hill ◽  
R Holmes ◽  
M J Brennan
Keyword(s):  
Computing Time ◽  
Three Dimensional ◽  
Vibration Response ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Reduced Order ◽  
Squeeze Film Damper ◽  
Bearing Assembly ◽  
Reduced Order Methods

This paper uses two reduced-order methods to calculate the overall non-linear vibration response of a multi-mode rotor-squeeze film damper (SFD) bearing assembly. Good agreement has been found between their computed results and those calculated by the conventional Runge-Kutta-Merson method (RKMM), yet they require less than 5 per cent of the computing time consumed by the RKMM. They are applied to compute the vibration response, three-dimensional deflection shape and the overall vibrational kinetic energy of the rotor-bearing assembly. The assembly is simulated under various operating conditions including different unbalances, oil viscosities, static misalignments and damper factors. It is concluded that effective vibration control of a flexible rotor-SFD bearing assembly can be achieved when the vertical static eccentricity ratio of the SFD is set to a certain limit.

Design of a Squeeze-Film Damper for a Multi-Mass Flexible Rotor

1975 ◽  
Vol 97 (4) ◽  
pp. 1383-1389 ◽  
Author(s):  
Robert E. Cunningham ◽  
David P. Fleming ◽  
Edgar J. Gunter
Keyword(s):  
Computer Program ◽  
Critical Speed ◽  
Lubrication Theory ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Squeeze Film Damper ◽  
Flexible Support ◽  
Single Mass ◽  
Damper Design ◽  
Stiffness And Damping

A single mass flexible rotor analysis was used to optimize the stiffness and damping of a flexible support for a symmetric five-mass rotor. The flexible support attenuates the rotor motions and forces transmitted to the support bearings when the rotor operates through and above its first bending critical speed. An oil squeeze-film damper was designed based on short bearing lubrication theory. The damper design was verified by an unbalance response computer program. Rotor amplitudes were reduced by a factor of 16 and loads reduced by a factor of 36 compared with the same rotor on rigid bearing supports.

Harmonic Balance Analysis of General Squeeze Film Damped Multidegree-of-Freedom Rotor Bearing Systems

1994 ◽  
Vol 116 (3) ◽  
pp. 499-507 ◽  
Author(s):  
E. J. Hahn ◽  
P. Y. P. Chen
Keyword(s):  
Harmonic Balance ◽  
Reference Frames ◽  
Squeeze Film ◽  
Equilibrium Solutions ◽  
Rotor Bearing ◽  
Balance Analysis ◽  
Force Components ◽  
Lift Off ◽  
Rotating Reference Frames ◽  
The Stability

Squeeze film dampers introduce nonlinear motion dependent damper forces into otherwise linear rotor bearing systems, thereby considerably complicating their analysis. Noncircular orbit type dampers, such as unsupported or uncentralized dampers, have generally necessitated transient solutions, which are computationally prohibitive for design studies of large order systems, particularly for systems with low damping. By utilizing harmonic balance with appropriate condensation, it is possible to considerably reduce the number of simultaneous nonlinear equations inherent to this approach. The stability (linear) of the equilibrium solutions may be conveniently evaluated using Floquet theory, particularly if the damper force components are evaluated in fixed, rather than rotating, reference frames. The versatility of this technique is illustrated on systems of increasing complexity with and without damper centralizing springs. Of particular interest, is its applicability to unsupported systems illustrating how such systems can lift off and, with further increase in speed, the damper forces can be linearized about the orbit center.

Experimental Investigation of the Effects of Squeeze Film Damper Design on Highspeed Rotor System

2020 ◽  
Author(s):  
Vincent Iacobellis ◽  
Kamran Behdinan ◽  
Dennis Chan ◽  
Dave Beamish
Keyword(s):  
Dynamic Testing ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Test Rig ◽  
Oil Supply ◽  
Squeeze Film Dampers ◽  
Jeffcott Rotor ◽  
Large Amplitude Motions ◽  
Damper Design ◽  
Initial Results

Abstract Squeeze film dampers (SFDs) are used in highspeed rotordynamics systems to mitigate vibrations while traversing critical speeds. SFDs are critical in dissipating large amplitude motions and dynamic loading transferred from the rotor to the bearing supports during highspeed operation. Little testing on the effect of SFDs on rotor shafts under highspeed operating conditions is available in the literature. Thus, a SFD-rotor test rig has been designed and built to study the effect of SFD oil supply pressure, oil temperature, oil inlet feed number/orientation, unbalance, and seals on the response of a Jeffcott rotor. In this paper, the test rig is introduced along with its calibration through static and dynamic testing. It was found that the rotor displacement results were improved through the addition of trial masses to provide a runout correction and that using rubber supports for the support structure generated more symmetric results in the vertical and horizontal planes compared to steel supports. Initial results for the test rig are also presented for different unbalances with and without oil supply and with and without SFD end seals. In these cases, increased unbalance produced higher amplitude motion with a corresponding increase in critical speed and decrease in damping.

Rotordynamic Evaluation of an Advanced Multisqueeze Film Damper—Imbalance Response and Blade-Loss Simulation

1993 ◽  
Vol 115 (2) ◽  
pp. 347-352 ◽  
Author(s):  
J. F. Walton ◽  
H. Heshmat
Keyword(s):  
Steady State ◽  
Rotor System ◽  
Squeeze Film ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Flexible Rotor ◽  
Squeeze Film Damper ◽  
Wide Range ◽  
Damper Design ◽  
Blade Loss

In this paper results of rotordynamic response and transient tests of a novel, high load squeeze film damper design are presented. The spiral foil multisqueeze film damper has been previously shown to provide two to fourfold or larger increases in damping levels without resorting to significantly decreased damper clearances or increased lengths. By operating with a total clearance of approximately twice conventional designs, the nonlinearities associated with high-eccentricity operation are avoided. Rotordynamic tests with a dual squeeze film configuration were completed. As a part of the overall testing program, a flexible rotor system was subjected to high steady-state imbalance levels and transient simulated blade-loss events for up to 0.254 mm (0.01 in.) mass c. g. offset or 180 g-cm (2.5 oz-in.) imbalance. The spiral foil multisqueeze film damper demonstrated that the steady-state imbalance and simulated blade-loss transient response of a flexible rotor operating above its first bending critical speed could be readily controlled. Rotor system imbalance sensitivity and logarithmic decrement are presented showing the characteristics of the system with the damper installed. The ability to accommodate high steady-state and transient imbalance conditions make this damper well suited to a wide range of rotating machinery, including aircraft gas turbine engines.

Coupled Lateral and Torsional Nonlinear Transient Solver With Application to Flexible Rotor-Bearing System

2014 ◽  
Author(s):  
Jianming Cao ◽  
Tim Dimond ◽  
Paul Allaire
Keyword(s):  
Rotational Speed ◽  
Equations Of Motion ◽  
Squeeze Film ◽  
Flexible Rotor ◽  
Rotor Bearing ◽  
Nonlinear Transient ◽  
Gyroscopic Effects ◽  
Nonlinear Equations Of Motion ◽  
Torsional Analysis ◽  
Bearing System

This paper provides a time transient method for solving coupled lateral and torsional analysis of a flexible rotor-bearing system including gyroscopic effects, nonlinear short journal bearings, nonlinear short squeeze film dampers, and external nonlinear forces/torques. The rotor is modeled as linear, and the supporting components, including bearings and dampers, are modeled as nonlinear. An implicit Runge-Kutta method is developed to solve the nonlinear equations of motion with non-constant operating speed since the unbalance force and the gyroscopic effect are related to both the rotational speed and the acceleration. The developed method is compared with previous torsional analysis first to verify the nonlinear transient solver. Then the coupled lateral and torsional analysis of a flexible 3-disk rotor with nonlinear bearings and nonlinear dampers driven by a synchronous motor is approached. The acceleration effects on lateral and torsional amplitudes is presented in the analysis. The developed method can be used to study the rotor motion with non-constant rotational speed, such as during startup, shutdown, going through critical speeds, blade loss force, or other sudden loading.

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