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.

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.

Nonlinear Analysis of Rotor-Bearing Systems Using Component Mode Synthesis

1983 ◽  
Vol 105 (3) ◽  
pp. 606-614 ◽  
Author(s):  
H. D. Nelson ◽  
W. L. Meacham ◽  
D. P. Fleming ◽  
A. F. Kascak
Keyword(s):  
Forced Response ◽  
Component Mode Synthesis ◽  
Squeeze Film ◽  
System Response ◽  
Reduced Order ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
System Equations ◽  
Transient System ◽  
Blade Loss

The method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled with the nonlinear supports and interconnections to form a set of nonlinear system equations of reduced order. These equations are then numerically integrated to obtain the system response. A computer program, which is presently restricted to single shaft systems has been written and results are presented for transient system response associated with blade loss dynamics, with squeeze film dampers, and with interference rubs.

scholarly journals The Dynamic Response of Tuned Impact Absorbers for Rotating Flexible Structures

2005 ◽  
Vol 1 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Steven W. Shaw ◽  
Christophe Pierre
Keyword(s):  
Dynamic Response ◽  
Flexible Structures ◽  
Experimental Studies ◽  
Analytical Investigation ◽  
Design Parameters ◽  
System Response ◽  
Rotor Speed ◽  
Flexible System ◽  
Restoring Forces ◽  
And Performance

This paper describes an analytical investigation of the dynamic response and performance of impact vibration absorbers fitted to flexible structures that are attached to a rotating hub. This work was motivated by experimental studies at NASA, which demonstrated the effectiveness of these types of absorbers for reducing resonant transverse vibrations in periodically excited rotating plates. Here we show how an idealized model can be used to describe the essential dynamics of these systems, and used to predict absorber performance. The absorbers use centrifugally induced restoring forces so that their nonimpacting dynamics are tuned to a given order of rotation, whereas their large amplitude dynamics involve impacts with the primary flexible system. The linearized, nonimpacting dynamics are first explored in detail, and it is shown that the response of the system has some rather unique features as the hub rotor speed is varied. A class of symmetric impacting motions is also analyzed and used to predict the effectiveness of the absorber when operating in its impacting mode. It is observed that two different types of grazing bifurcations take place as the rotor speed is varied through resonance, and their influence on absorber performance is described. The analytical results for the symmetric impacting motions are also used to generate curves that show how important absorber design parameters—including mass, coefficient of restitution, and tuning—affect the system response. These results provide a method for quickly evaluating and comparing proposed absorber designs.

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.

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.

Field Methods for Identification of Bearing Support Parameters: Part I — Identification From Transient Rotor Dynamic Response Due to Impacts

2003 ◽  
Author(s):  
Oscar C. De Santiago ◽  
Luis San Andre´s
Keyword(s):  
Simple Procedure ◽  
Low Frequency ◽  
System Stability ◽  
Squeeze Film ◽  
Rotor Speed ◽  
Field Methods ◽  
Frequency Dependent ◽  
Force Coefficients ◽  
Rotor Bearing ◽  
Bearing System

A simple procedure, with potential as a field resource, for identification of bearing support parameter from recorded transient rotor responses due to impact loads follows. The method is applied to a test rotor supported on a pair of mechanically complex bearing supports, each comprising a tilting pad bearing in series with an integral squeeze film damper. Identification of frequency dependent bearing force coefficients is good at a rotor speed of 2,000 rpm. Stiffness coefficients are best identified in the low frequency range (below 25 Hz) while damping coefficients are best identified in the vicinity of the first natural frequency (48 Hz) of the rotor bearing system. The procedure shows that using multiple-impact frequency averaged rotor responses reduces the variability in the identified parameters. The identification of frequency-dependent force coefficients at a constant rotor speed is useful to assess rotor-bearing system stability.

Field Methods for Identification of Bearng Support Parameters—Part I: Identification From Transient Rotor Dynamic Response due to Impacts

2003 ◽  
Vol 129 (1) ◽  
pp. 205-212 ◽  
Author(s):  
Oscar C. De Santiago ◽  
Luis San Andrés
Keyword(s):  
Simple Procedure ◽  
Low Frequency ◽  
System Stability ◽  
Squeeze Film ◽  
Rotor Speed ◽  
Field Methods ◽  
Frequency Dependent ◽  
Force Coefficients ◽  
Rotor Bearing ◽  
Bearing System

A simple procedure, with the potential as a field resource, for identification of a bearing support parameter from recorded transient rotor responses due to impact loads follows. The method is applied to a test rotor supported on a pair of mechanically complex bearing supports, each comprising a tilting pad bearing in series with an integral squeeze film damper. Identification of frequency dependent bearing force coefficients is good at a rotor speed of 2000 rpm. Stiffness coefficients are best identified in the low frequency range (below 25 Hz) while damping coefficients are best identified in the vicinity of the first natural frequency (48 Hz) of the rotor bearing system. The procedure shows that using multiple-impact frequency averaged rotor responses reduces the variability in the identified parameters. The identification of frequency-dependent force coefficients at a constant rotor speed is useful to assess rotor-bearing system stability.

Nonlinear Characteristics Analysis of a Rotor-Bearing-Brush Seal System

2018 ◽  
Vol 18 (05) ◽  
pp. 1850063 ◽  
Author(s):  
Yuan Wei ◽  
Zhaobo Chen ◽  
Earl H. Dowell
Keyword(s):  
Periodic Motion ◽  
Nonlinear Dynamic ◽  
Operating Conditions ◽  
Design Parameters ◽  
Force Model ◽  
Rotor Speed ◽  
Nonlinear Characteristics ◽  
Disk Mass ◽  
Brush Seal ◽  
Rotor Bearing

The vibration response and nonlinear dynamic behavior of a rotor-bearing-brush seal system were investigated with a new seal force model of the brush seal. The nonlinear oil–film force model was adopted based on a short bearing assumption. The dimensionless equation of motion was solved using the fourth order Runge–Kutta method. The effects of key parameters including rotor speed, installation spacing of the brush seal, disk eccentricity, disk mass, and journal mass on the nonlinear dynamic characteristics of rotor-bearing-brush seal system were determined and compared under different operating conditions with a bifurcation diagram, time history, axis orbit, poincaré map, frequency spectrum, and spectrum cascade. The results showed that the system response contained various nonlinear phenomena, such as periodic motion, multi-periodic motion, and quasi-periodic motion. The interaction of the rotor speed, installation spacing of the brush seal, disk eccentricity, disk mass, and journal mass could seriously affect the stability and working condition of the system. This study provides a theoretical support for the selection of key design parameters and further understanding of the nonlinear characteristics of rotor-bearing-seal systems with a brush seal.

The Optimal Design of Squeeze Film Dampers for Flexible Rotor Systems

1988 ◽  
Vol 110 (2) ◽  
pp. 166-174 ◽  
Author(s):  
W. J. Chen ◽  
M. Rajan ◽  
S. D. Rajan ◽  
H. D. Nelson
Keyword(s):  
Design Procedure ◽  
Optimization Techniques ◽  
Squeeze Film ◽  
Design Parameters ◽  
Element Formulation ◽  
Rotor Systems ◽  
Transmitted Force ◽  
Squeeze Film Dampers ◽  
Speed Range ◽  
Damper Design

Optimization techniques are employed to design squeeze film dampers for minimum transmitted load to the bearing and foundation in the operational speed range. The rotor systems are modeled by finite element formulation. The maximum transmitted load in the operational speed range is the objective function that is minimized using mathematical nonlinear programming (NLP) techniques. The damper design parameters are the radius, length, and radial clearance. Stability of the equilibrium solutions are investigated in the design procedure. Design derivatives have been determined in closed form expressions without resolution of the inherently nonlinear problem. A parametric study of the transmitted force is carried out to show the influence of damper parameters on the response and to demonstrate the merits of applying optimization techniques in damper design. Two numerical examples are presented that illustrate the effectiveness of optimizing squeeze film damper designs for reducing transmitted load.

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