A Mechanism of Low Subharmonic Response in Rotor/Stator Contact—Measurements and Simulations

2002 ◽  
Vol 124 (3) ◽  
pp. 350-358 ◽  
Author(s):  
Go¨tz von Groll ◽  
David J. Ewins
Keyword(s):  
Numerical Simulation ◽  
Rotating Machinery ◽  
Squeeze Film ◽  
Vibration Frequencies ◽  
Interaction Dynamics ◽  
Squeeze Film Dampers ◽  
Rotor Stator Interaction ◽  
Subharmonic Response ◽  
Subharmonic Vibration ◽  
Aero Engines

There are a variety of abnormal running conditions in rotating machinery that lead to rotor/stator interaction dynamics which, in turn, have a range of effects associated with them. One of these effects is steady vibration response at frequencies which are different from the excitation. This paper describes a mechanism of generating subharmonic vibration frequencies in both numerical simulation and measurements, which are obtained from a study of the relatively new problem of “windmilling imbalance” in aero-engines. What is different from other nonlinear systems with, say, clearance or squeeze film dampers, is the richness of the frequency spectrum.

Experimental and Analytical Investigation of Hybrid Squeeze Film Dampers

1993 ◽  
Vol 115 (2) ◽  
pp. 353-359 ◽  
Author(s):  
A. El-Shafei
Keyword(s):  
High Speed ◽  
Extreme Case ◽  
Analytical Investigation ◽  
Rotating Machinery ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Controlling Mechanism ◽  
Squeeze Film Dampers ◽  
Oil Flow ◽  
Hybrid Damper

A new concept for actively controlling high-speed rotating machinery is investigated both analyically and experimentally. The controlling mechanism consists of a hybrid squeeze film damper (patent pending) that can be adaptively controlled to change its characteristics according to the instructions of a controller. In an extreme case the hybrid damper can act as a long damper, which is shown to be effective in reducing the amplitude of vibration of rotating machinery. In the other extreme the hybrid damper acts as a short damper, which is shown to be effective in reducing the force transmitted to the support. In the long damper configuration the oil flow is circumferential, while in the short damper configuration the oil flow is predominantly axial. The hybrid damper is designed to operate in either the short or the long damper configuration by controlling the positions of two movable sealing rings. The hybrid damper was tested on a Bently Nevada Rotor Kit and it is shown experimentally that the long damper configuration is extremely efficient at controlling the amplitude of vibration and the short damper configuration reduces the force transmitted to the support.

Design of Electromagnetic Dampers for Aero-Engine Applications

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Andrea Tonoli ◽  
Nicola Amati ◽  
Angelo Bonfitto ◽  
Mario Silvagni ◽  
Bernard Staples ◽  
...  
Keyword(s):  
Electrorheological Fluid ◽  
Working Environment ◽  
Squeeze Film ◽  
Steam Turbines ◽  
Rolling Bearings ◽  
Displacement Sensors ◽  
Squeeze Film Dampers ◽  
Passive Dampers ◽  
Quantitative Performance ◽  
Aero Engines

The vibration control of rotors for gas or steam turbines is usually performed using passive dampers when hydrodynamic bearings are not used. In layouts where the rotating parts are supported by rolling bearings, the damping is usually provided by squeeze film dampers. Their passive nature and the variability of their performances with temperature and frequency represent the main disadvantages. Dampers with magnetorheological and electrorheological fluid allow solving only a part of the abovementioned drawbacks. Active magnetic bearings (AMBs) are promising since they are very effective in controlling the vibration of the rotor and offering the possibility of monitoring the rotor’s behavior using their displacement sensors. However they show serious drawbacks related to their stiffness. Electromagnetic dampers seem to be a valid alternative to visco-elastic, hydraulic dampers due to, among the others, the absence of all fatigue and tribology issues resulting from the absence of contact, the small sensitivity to the working environment, the wide possibility of tuning even during operation, the predictability of the behavior, the smaller mass compared with AMBs, and the failsafe capability. The aim of the present paper is to describe a design methodology adopted to develop electromagnetic dampers to be installed in aero-engines. The procedure has been validated using a reduced scale laboratory test rig. The same approach has then been adopted to design the electromagnetic dampers for real civil aircraft engines. The results in terms of achievable vibration reductions, mass, and overall dimensions are hence presented. A trade-off between the various proposed solutions has been carried out evaluating quantitative performance parameters together with qualitative aspects that this “more electric” technology implies.

Perturbation Solutions for Eccentric Operation of Squeeze Film Damper Systems

1986 ◽  
Vol 108 (4) ◽  
pp. 619-623 ◽  
Author(s):  
Xuehai Li ◽  
D. L. Taylor
Keyword(s):  
Numerical Simulation ◽  
Experimental Results ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Squeeze Film Damper ◽  
Synchronous Motion ◽  
Squeeze Film Dampers ◽  
Large Speed ◽  
Good Agreement ◽  
Perturbation Solutions

The study focuses on the effect of a small unidirectional load such as comes from imperfect balance between preloading on centering springs and gravitational load on squeeze film dampers. A rigid rotor-squeeze film damper system is considered, and a thorough study of the synchronous motion of the system is performed. Two perturbation solutions are developed: one for large speed and one for small speed. The perturbation solutions are shown to be in good agreement with numerical simulation and published experimental results.

A Dynamic Analysis of a Dual Clearance Squeeze Film Damper

2010 ◽  
Author(s):  
L. Moraru ◽  
T. G. Keith ◽  
F. Dimofte ◽  
S. Cioc ◽  
N. Ene ◽  
...  
Keyword(s):  
High Speed ◽  
Reynolds Equation ◽  
Numerical Solutions ◽  
Rotating Machinery ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Squeeze Film Dampers ◽  
Abnormal Operating Conditions ◽  
Oil Films

Squeeze film dampers (SFD) are devices utilized to control the shafts of high-speed rotating machinery. A dual squeeze film damper (DSFD) consists of two squeeze film bearings that are separated by a sleeve, which is released when the rotor experiences abnormal operating conditions. In this part of our study of DSFD we analyze the case when both the inner and the outer oil films are active. We present computed and measured unbalance responses of a shaft supported in DSFD. The oil forces which are utilized in the calculation of the unbalance response are obtained from numerical solutions of the Reynolds equation. A finite-difference algorithm is utilized for solving the pressure equation within the calculation of the dynamic response of the shaft.

scholarly journals Experimental and Analytical Investigation of Hybrid Squeeze Film Dampers

1991 ◽  
Author(s):  
A. El-Shafei
Keyword(s):  
High Speed ◽  
Extreme Case ◽  
Analytical Investigation ◽  
Rotating Machinery ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Controlling Mechanism ◽  
Squeeze Film Dampers ◽  
Oil Flow ◽  
Hybrid Damper

A new concept for actively controlling high speed rotating machinery is investigated both analytically and experimentally. The controlling mechanism consists of a hybrid squeeze film damper (patent pending) that can be adaptively controlled to change its characteristics according to the instructions of a controller. In an extreme case the hybrid damper can act as a long damper which is shown to be effective in reducing the amplitude of vibration of rotating machinery. In the other extreme the hybrid damper acts as a short damper which is shown to be effective in reducing the force transmitted to the support. In the long damper configuration the oil flow is circumferential, while in the short damper configuration the oil flow is predominantly axial. The hybrid damper is designed to operate in either of the short or the long damper configurations by controlling the positions of two movable sealing rings. The hybrid damper was tested on a Bently Nevada Rotor Kit and it is shown experimentally that the long damper configuration is extremely efficient at controlling the amplitude of vibration and the short damper configuration reduces the force transmitted to the support.

Active Control Algorithms for the Control of Rotor Vibrations Using Hybrid Squeeze Film Dampers

2002 ◽  
Vol 124 (3) ◽  
pp. 598-607 ◽  
Author(s):  
A. El-Shafei
Keyword(s):  
Active Control ◽  
Gain Scheduling ◽  
Rotating Machinery ◽  
Squeeze Film ◽  
Control Algorithms ◽  
Critical Stage ◽  
Squeeze Film Damper ◽  
Squeeze Film Dampers ◽  
Active Vibration

The hybrid squeeze film damper (HSFD) has proven itself to be an effective controlling device of vibration in rotating machinery. The critical stage in the development of the HSFD as an active vibration suppressant, is the development of the control algorithms for active control of rotor vibrations. This paper summarizes, evaluates, and compares the control algorithms for HSFD-supported rotors. Quantitative as well as qualitative measures of the effectiveness of the control algorithms are presented. The study includes the PID-type controllers, LQR, gain scheduling, adaptive and bang-bang controllers. The adaptive, gain scheduling, and nonlinear proportional controllers have proved to be quite effective in the active control of HSFD supported rotors, with impressive results.

Dynamic Modeling of a Dual Clearance Squeeze Film Damper: Part III

2005 ◽  
Author(s):  
L. Moraru ◽  
F. Dimofte ◽  
S. Cioc ◽  
T. G. Keith ◽  
D. P. Fleming
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Rotating Machinery ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Squirrel Cage ◽  
Squeeze Film Dampers ◽  
Abnormal Operating Conditions ◽  
Oil Films

Squeeze film dampers (SFD) are devices utilized to control vibrations of the shafts of high-speed rotating machinery. A dual squeeze film damper (DSFD) consists of two squeeze film bearings that are separated by a sleeve, which is released when the rotor experiences abnormal operating conditions. In this part of our study of DSFD we analyze the case when both the inner and the outer oil films are active and the separating sleeve is supported by a squirrel cage. Numerical results are compared with the experimental data.

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.

Influence of different flow regimes on the performance characteristics of a four-pad hydrostatic squeeze film damper loaded between pads

2019 ◽  
Vol 71 (3) ◽  
pp. 440-446
Author(s):  
Amina Nemchi ◽  
Ahmed Bouzidane ◽  
Aboubakeur Benariba ◽  
Hicham Aboshighiba
Keyword(s):  
Turbulent Flow ◽  
Load Capacity ◽  
Flow Regimes ◽  
Performance Characteristics ◽  
Squeeze Film ◽  
Eccentricity Ratio ◽  
Flow Conditions ◽  
Content Type ◽  
Turbulent Flow Regime ◽  
Squeeze Film Dampers

Purpose The purpose of this paper is to study the influence of different flow regimes on the dynamic characteristics of four-pad hydrostatic squeeze film dampers (SFDs) loaded between pads. Design/methodology/approach A numerical model based on Constantinescu’s turbulent lubrication theory using the finite difference method has been developed and presented to study the effect of eccentricity ratio on the performance characteristics of four-pad hydrostatic SFDs under different flow regimes. Findings It was found that the influence of turbulent flow on the dimensionless damping of four-pad hydrostatic SFDs appears to be essentially controlled by the eccentricity ratio. It was also found that the laminar flow presents higher values of load capacity compared to bearings operating under turbulent flow conditions. Originality/value In fact, the results obtained show that the journal bearing performances are significantly influenced by the turbulent flow regime. The study is expected to be useful to bearing designers.

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