Optimum Design of Squeeze Film Dampers Supporting Multiple-Mode Rotors

2002 ◽  
Vol 124 (4) ◽  
pp. 992-1002 ◽  
Author(s):  
A. El-Shafei ◽  
R. Y. K. Yakoub
Keyword(s):  
Optimum Design ◽  
Critical Speed ◽  
Aircraft Engine ◽  
Squeeze Film ◽  
Operating Speed ◽  
Spring Stiffness ◽  
Search Technique ◽  
Amplitude Response ◽  
Design Program ◽  
Squeeze Film Dampers

In this paper a study of the optimum design of squeeze film dampers for multimode rotors is presented. The optimum design program obtains the best possible damper parameters for a given rotor to satisfy the minimization requirements for the objective function. The objectives are to minimize the amplitude response of the rotor at the critical speed, minimize the force transmitted to the support at the operating speed, or maximize the power dissipated by the damper. A combination of these objectives can also be used, with weighting factors to weigh the importance of each of these objectives. These are the possible objectives for the design of squeeze film dampers for aircraft engine applications. The basis of the optimum design program is an extremely fast algorithm which is able to quickly calculate the unbalance response of a rotor, for circular centered orbits of the journal in the damper. A commercial routine is used for the optimization, and is based on a complex direct search technique. The variation of the optimum clearance, length, and retainer spring stiffness are plotted against various rotor parameters. Recommendations for the design of squeeze film dampers are made. Applications to an aircraft engine illustrate the power of the developed algorithm.

Optimum Design of Squeeze Film Dampers Supporting Multiple-Mode Rotors

2001 ◽  
Author(s):  
A. El-Shafei ◽  
R. Y. Yakoub
Keyword(s):  
Optimum Design ◽  
Critical Speed ◽  
Aircraft Engine ◽  
Squeeze Film ◽  
Spring Stiffness ◽  
Search Technique ◽  
Amplitude Response ◽  
Design Program ◽  
Squeeze Film Dampers ◽  
Multi Mode

In this paper a study of the optimum design of squeeze film dampers for multi-mode rotors is presented. The optimum design program obtains the best possible damper parameters for a given rotor to satisfy the minimization requirements for the objective function. The objectives are to: minimize the amplitude response of the rotor at the critical speed, minimize the force transmitted to the support at the operating speed or maximize the power dissipated by the damper. A combination of these objectives can also be used, with weighting factors to weigh the importance of each of these objectives. These are the possible objectives for the design of squeeze film dampers for aircraft engine applications. The basis of the optimum design program is an extremely fast algorithm which is able to quickly calculate the unbalance response of a rotor, for circular centered orbits of the journal in the damper. A commercial routine is used for the optimization, and is based on a complex direct search technique. The variation of the optimum clearance, length, and retainer spring stiffness are plotted against various rotor parameters. Recommendations for the design of squeeze film dampers are made. Application to an aircraft engine, illustrate the power of the developed algorithm.

Use of the Harmonic Balance Method for Flexible Aircraft Engine Rotors With Nonlinear Squeeze Film Dampers

2014 ◽  
Author(s):  
Feng He ◽  
Paul Allaire ◽  
Timothy Dimond
Keyword(s):  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Aircraft Engine ◽  
Balance Method ◽  
Squeeze Film ◽  
Spring Stiffness ◽  
Squeeze Film Damper ◽  
Flexible Rotors ◽  
Squeeze Film Dampers ◽  
Nonlinear Transient

Squeeze film dampers in flexible rotors such as those in compressors, steam turbines, aircraft engines and other rotating machines are often modeled as linear devices. This linearization is valid only for a specified orbit where appropriate equivalent stiffness and damping coefficients can be found. However, squeeze film dampers are inherently nonlinear devices which complicates the analysis. This paper develops the harmonic balance method with a direct force model of the SFDs. This model is used for flexible rotors with squeeze film dampers where the rotor is treated as linear and the squeeze film damper is treated as nonlinear. The predictor-corrector method is employed to obtain the system forced response in the frequency domain after separating the nonlinear components from the linear components of the equations of motion. This approach is much more efficient than conventional full nonlinear transient analysis. The application considered in this paper is the low pressure (LP) compressor of an aircraft engine. The LP compressor rotor has two roller bearings with squeeze film dampers and one ball bearing without a squeeze film damper. Orbits at the fan end dampers and the turbine end dampers for both the harmonic balance and nonlinear transient modeling are compared for accuracy and calculation time. The HB method is shown to be 5 to 12 times faster computationally for similar results. Fast Fourier transform results were obtained for various shaft operating speeds. Results were also obtained for the unbalance response at different locations with gravity loading. Finally, unbalance response of the rotor with varying centering spring stiffness values were obtained. The results show that the centering spring stiffness for the turbine end damper is less sensitive than the fan end damper.

Design of Nonlinear Squeeze-Film Dampers for Aircraft Engines

1977 ◽  
Vol 99 (1) ◽  
pp. 57-64 ◽  
Author(s):  
E. J. Gunter ◽  
L. E. Barrett ◽  
P. E. Allaire
Keyword(s):  
Reynolds Equation ◽  
Nonlinear Effects ◽  
Aircraft Engine ◽  
Squeeze Film ◽  
Aircraft Engines ◽  
Transient Method ◽  
Squeeze Film Damper ◽  
Wide Range ◽  
Squeeze Film Dampers ◽  
Bearing Stiffness

This paper examines the effect of squeeze-film damper bearings on the steady state and transient unbalance response of aircraft engine rotors. The nonlinear effects of the damper are examined, and the variance of the motion due to unbalance, static pressurization, retainer springs, and rotor preload is shown. The nonlinear analysis is performed using a time-transient method incorporating a solution of the Reynolds equation at each instant in time. The analysis shows that excessive stiffness in the damper results in large journal amplitudes and transmission of bearing forces to the engine casing which greatly exceed the unbalance forces. Reduction of the total effective bearing stiffness through static pressurization and rotor preload is considered. The reduction in stiffness allows the damping generated by the bearing to be more effective in attenuating rotor forces. It is observed that in an unpressurized damper, the dynamic transmissibility will exceed unity when the unbalance eccentricity exceeds approximately 50 percent of the damper clearance for the relatively wide range of conditions examined in this study.

Fault Diagnosis on an Aircraft Engine Model Equipped With Self-Sensing Piezoelectric Actuators

2016 ◽  
Author(s):  
Ramakrishnan Ambur ◽  
Xiaonan Zhao ◽  
Stephan Rinderknecht
Keyword(s):  
Fault Diagnosis ◽  
Piezoelectric Materials ◽  
Piezoelectric Actuators ◽  
Aircraft Engine ◽  
Axial Direction ◽  
Squeeze Film ◽  
Sensors And Actuators ◽  
Rotor Systems ◽  
Engine Model ◽  
Squeeze Film Dampers

Piezoelectric actuators provide an active solution for vibration control in aircraft engines compared to the state-of-the-art squeeze film dampers. The property of piezoelectric materials enable them to be used as sensors and actuators simultaneously. This self-sensing property of the actuator is analyzed in this paper for its ability to detect unbalance faults, which are common in rotor systems. In this paper two different actuator configurations are studied for its ability to diagnose unbalance faults in an aircraft engine. Three parameters of unbalances such as its magnitude, its position in the circumferential and axial direction in a rotor are estimated through simulations. Finally a suitable position to achieve a better fault diagnosis is identified.

Squeeze-Film Damper Predictions for Simulation of Aircraft Engine Rotordynamics

2004 ◽  
Author(s):  
Cyril Defaye ◽  
Franck Laurant ◽  
Philippe Carpentier ◽  
Mihai Arghir ◽  
Olivier Bonneau ◽  
...  
Keyword(s):  
Reynolds Equation ◽  
Aircraft Engine ◽  
Theoretical Work ◽  
Analytical Models ◽  
Squeeze Film ◽  
Design Parameters ◽  
Aircraft Engines ◽  
Predictive Tool ◽  
Squeeze Film Dampers ◽  
Inertia Forces

On aircraft engines, a common recurring problem is excessive vibration levels generated by unbalance. With rotors mounted on usual undamped ball bearings, an amount of damping is required to limit peak amplitudes at traversed critical speeds: a solution is to introduce external damping with squeeze-film dampers. Such dampers can be added with minor modifications of the rotor system design. This paper presents experimental and theoretical work in progress focused on the analysis of squeeze film dampers (SFD) based on serial aircraft engines design. Several squeeze-film geometries were tested to measure the influence of different design parameters as the fluid clearance and the groove feeding system. Next, a damper model based on the numerical solution of the Reynolds equation is correlated with the experimental data to obtain predictive global forces. It is shown that the theoretical model is a good predictive tool if it is correctly adjusted and if temporal inertia forces are negligible. The present damper model is further compared with analytical models taken from the literature which are obviously more appropriate to be used in whole engine rotordynamic analysis. The limits of the models are then underlined by comparisons with experimental results.

The Oscillation Attenuation of an Accelerating Jeffcott Rotor Damped by Magnetorheological Dampers Affected by the Delayed Yielding Phenomenon in the Lubricating Oil

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Jaroslav Zapoměl ◽  
Petr Ferfecki
Keyword(s):  
Mathematical Model ◽  
Shear Stress ◽  
Magnetic Induction ◽  
Transient Analysis ◽  
Lubricating Oil ◽  
Squeeze Film ◽  
Operating Speed ◽  
Squeeze Film Damper ◽  
Squeeze Film Dampers ◽  
Computational Procedures

Adding damping devices to the rotor supports is a frequently used technological solution for reducing vibrations of rotating machines. To achieve their optimum performance, their damping effect must be adaptable to the current operating speed. This is offered by magnetorheological squeeze film dampers. The magnetorheological oils are liquids sensitive to magnetic induction and belong to the class of fluids with a yielding shear stress. Their response to the change of a magnetic field is not instantaneous, but it is a process called the delayed yielding. The developed mathematical model of the magnetorheological squeeze film damper is based on the assumptions of the classical theory of lubrication. The lubricant is represented by a bilinear material, the yielding shear stress of which depends on magnetic induction. The delayed yielding process is described by a convolution integral with an exponential kernel. The developed mathematical model of the damper was implemented in the computational procedures for transient analysis of rotors working at variable operating speed. The carried-out simulations showed that the delayed yielding effect could have a significant influence on performance of magnetorheological damping devices. The development of a novel mathematical model of a magnetorheological squeeze film damper, the representation of the magnetorheological oil by bilinear material, taking the delayed yielding phenomenon into consideration, increased numerical stability of the computational procedures for transient analysis of flexible rotors, and extension of knowledge on behavior of rotor systems damped by magnetorheological squeeze film dampers are the principal contributions of this paper.

Backward Whirl and Its Suppression of a Squeeze Film Damper Mounted Rotor/Casing System in Passage through Critical Speed with Rubs

2004 ◽  
Vol 10 (4) ◽  
pp. 561-573 ◽  
Author(s):  
Qian Ding
Keyword(s):  
Critical Speed ◽  
Angular Acceleration ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Internal Support ◽  
Squeeze Film Dampers ◽  
Jeffcott Rotor ◽  
Backward Whirl ◽  
Pass Through ◽  
Second Peak

In this paper we consider a flexible Jeffcott rotor mounted at the ends by identical squeeze film dampers (SFDs). The rotative speed is supposed to increase at a constant angular acceleration. There can be one-peak and two-peak solutions for different values of SFD parameters during passage through the critical speed. Calculation shows that the rotor cannot pass through the critical speed due to the occurrence of diverging backward whirl in passage of the first or second peak, if the level of acceleration is lower than the critical ones. A flexible internal support, which can be activated or deactivated at a certain position along the rotor to change the stiffness of the system to suppress large vibration, is then applied to avoid the occurrence of backward whirl. The method is found to be effective if applied in a suitable way

scholarly journals Effect of Lateral Disk Flexibility on the Dynamics of Squeeze Film Damper Supported Rotors

1993 ◽  
Author(s):  
Huajun Xie ◽  
George Flowers ◽  
Fangsheng Wu
Keyword(s):  
Critical Speed ◽  
Dynamical Behavior ◽  
Rotor System ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Operating Speed ◽  
Wide Range ◽  
Balance Analysis ◽  
Coupling Dynamics ◽  
Flexible Disk

This paper investigates the influence of disk flexibility on the dynamical behavior of a flexible disk/shaft rotor system supported with squeeze film dampers. A simplified nonlinear rotor model incorporating disk/shaft coupling dynamics is developed for lateral vibration of a rotor system. The steady state performance of the system is explored over a wide range of operating conditions using numerical integration and harmonic balance analysis. It is shown that disk flexibility may significantly affect the dynamical behavior of the system at high operating speed by creating an additional critical speed. It is observed that both the SFD journal motion and the disk motion associated with the additional critical speed are aperiodic and of large amplitudes. It is demonstrated that the influence of disk flexibility can be shifted out of the operating speed range by increasing the retainer spring stiffness.

scholarly journals The Optimum Design of Stepped Shafts: A Study in Computational Optimization

1982 ◽  
Author(s):  
C. J. Maday
Keyword(s):  
Optimum Design ◽  
Critical Speed ◽  
Numerical Solutions ◽  
Boundary Value ◽  
Minimum Principle ◽  
Problem Formulation ◽  
Rayleigh Quotient ◽  
Computational Optimization ◽  
Stepped Shaft ◽  
Determine Step

Optimum stepped shaft designs are obtained through an application of Pontryagin’s Minimum Principle. Optimum designs are obtained for a given critical speed of specified order. Indexes of Performance to be minimized include mass and rotating inertia. A general problem formulation illustrates how constraints on stress, deflections, and geometric design are taken in account. Numerical solutions are obtained to nonlinear multi-point-boundary-value-problems. A Newton-Raphson algorithm was developed to determine step locations precisely in order to facilitate the convergence of the shooting method used to solve the boundary value problem. Numerical solutions are determined with an assumed critical speed; a Rayleigh quotient calculation is used to verify that the optimum design possesses the assumed value.

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.

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