Linearized Fluid Film Forces for Squeeze Film Dampers Executing Small Amplitude Circular-Centered Orbits in Aero-Engines

2017 ◽  
Author(s):  
Sina Hamzelouia ◽  
Kamran Behdinan
Keyword(s):  
Small Amplitude ◽  
Fluid Film ◽  
Squeeze Film ◽  
Squeeze Film Dampers ◽  
Aero Engines

scholarly journals Squeeze Film Dampers Executing Small Amplitude Circular-Centered Orbits in High-Speed Turbomachinery

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Sina Hamzehlouia ◽  
Kamran Behdinan
Keyword(s):  
Pressure Distribution ◽  
Small Amplitude ◽  
High Speed ◽  
Fluid Film ◽  
Distribution Model ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Squeeze Film Dampers ◽  
Reaction Forces

This work represents a pressure distribution model for finite length squeeze film dampers (SFDs) executing small amplitude circular-centered orbits (CCOs) with application in high-speed turbomachinery design. The proposed pressure distribution model only accounts for unsteady (temporal) inertia terms, since based on order of magnitude analysis, for small amplitude motions of the journal center, the effect of convective inertia is negligible relative to unsteady (temporal) inertia. In this work, the continuity equation and the momentum transport equations for incompressible lubricants are reduced by assuming that the shapes of the fluid velocity profiles are not strongly influenced by the inertia forces, obtaining an extended form of Reynolds equation for the hydrodynamic pressure distribution that accounts for fluid inertia effects. Furthermore, a numerical procedure is represented to discretize the model equations by applying finite difference approximation (FDA) and to numerically determine the pressure distribution and fluid film reaction forces in SFDs with significant accuracy. Finally, the proposed model is incorporated into a simulation model and the results are compared against existing SFD models. Based on the simulation results, the pressure distribution and fluid film reaction forces are significantly influenced by fluid inertia effects even at small and moderate Reynolds numbers.

First Order Perturbation Technique for Squeeze Film Dampers Executing Small Amplitude Circular Centered Orbits With Aero-Engine Application

2016 ◽  
Author(s):  
Sina Hamzehlouia ◽  
Kamran Behdinan
Keyword(s):  
Pressure Distribution ◽  
Small Amplitude ◽  
Slenderness Ratio ◽  
Order Perturbation ◽  
Squeeze Film ◽  
Zeroth Order ◽  
Flow Equations ◽  
First Order ◽  
Squeeze Film Dampers ◽  
First Order Perturbation

This work develops inertial expressions for the lubricant pressure distribution and fluid velocity components for squeeze film dampers (SFDs) executing small amplitude circular centered orbits (CCO), by applying a first order perturbation to the fluid equations. For small amplitude motions of the journal center, it is assumed that the fluid convective inertia terms are negligible relative to the unsteady (temporal) inertia terms. Firstly, a first order perturbation is applied to the pressure and velocity components in the flow equations. Subsequently, the flow equations are solved for the zeroth-order (i.e. non-inertial) velocities and the first-order (i.e. inertial) velocities. The velocity components are incorporated into the flow equations to develop separate expressions for the zeroth-order and the first order pressures. Furthermore, the pressure expressions are numerically solved by applying finite difference approximations to the equations. Finally, a simulation model is developed to determine the lubricant pressure distribution and fluid film reaction forces for different damper operating parameters, including Reynold’s number (i.e. inertia effect), journal eccentricity ratio, and bearing slenderness ratio.

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.

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.

Cavitation and Air Entrainment Effects on the Response of Squeeze Film Supported Rotors

1990 ◽  
Vol 112 (2) ◽  
pp. 347-353 ◽  
Author(s):  
F. Zeidan ◽  
J. Vance
Keyword(s):  
Nonlinear Response ◽  
Wide Spectrum ◽  
Air Entrainment ◽  
Operating Conditions ◽  
Fluid Film ◽  
Squeeze Film ◽  
Experimental Measurements ◽  
Inertial Effects ◽  
Squeeze Film Dampers ◽  
Rigid Rotors

This paper analyzes the effects of air entrainment and cavitation on the synchronous response of squeeze film supported rigid rotors. The fluid film force coefficients are obtained from experimental measurements corresponding to a wide spectrum of operating conditions. These conditions include regimes in which air entrainment effects are dominant. Other conditions where vapor cavitation and fluid inertial effects are dominant are included for comparison. The effects of air entrainment are shown to produce a nonlinear response representative of a softening spring effect not previously known to exist in squeeze film dampers.

Squeeze film dampers supporting high-speed rotors: Fluid inertia effects

2019 ◽  
Vol 234 (1) ◽  
pp. 18-32 ◽  
Author(s):  
Sina Hamzehlouia ◽  
Kamran Behdinan
Keyword(s):  
Thin Film ◽  
Pressure Distribution ◽  
Closed Form ◽  
Hydrodynamic Pressure ◽  
Fluid Film ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Thin Film Equations ◽  
Squeeze Film Dampers ◽  
Reaction Forces

This work represents closed-form analytical expressions for the operating parameters for short-length open-ended squeeze film dampers, including the lubricant velocity profiles, hydrodynamic pressure distribution, and lubricant reaction forces. The proposed closed-form expressions provide an accelerated calculation of the squeeze film damper parameters, specifically for rotordynamics applications. In order to determine the analytical solutions for the squeeze film damper parameters, the thin film equations for lubricant are introduced in the presence of the influence of lubricant inertia. Subsequently, two different analytical techniques, namely the momentum approximation method, and the perturbation method are applied to the thin film equations. Moreover, the solution for the lubricant flow equations are analytically determined to represent closed-form expressions for the hydrodynamic pressure distribution and the velocity component profiles in squeeze film dampers. Additionally, the expressions for the hydrodynamic pressure distribution are integrated over the journal surface, either numerically or analytically by using Booker’s integrals, to develop expressions for the fluid film reaction forces. Lastly, the developed squeeze film damper models are incorporated into simulation models in Matlab and Simulink®, and the results are compared against a well-established force coefficient model to verify the accuracy of the calculations. The results of the simulations verify the effect of the lubricant inertia components, namely the convective and temporal (i.e., unsteady) inertia components on the squeeze film damper dynamics, including hydrodynamic pressure distribution and fluid film reaction forces. Additionally, the simulation results suggest a close agreement between the proposed models and the results in the literature.

Numerical Analysis of Flexible Rotor With Nonlinear Bearings and Squeeze Film Dampers

2014 ◽  
Author(s):  
Jianming Cao ◽  
Timothy Dimond ◽  
Paul Allaire
Keyword(s):  
Fluid Film ◽  
Squeeze Film ◽  
Steam Turbines ◽  
Flexible Rotor ◽  
Time Step ◽  
Closed Form Solutions ◽  
Wide Range ◽  
Squeeze Film Dampers ◽  
Nodal Displacements ◽  
Nonlinear Components

This paper presents dynamic behaviors of a flexible rotor supported on nonlinear bearings and nonlinear squeeze film dampers. The nonlinear bearing and damper forces, which depend on instantaneous nodal displacements and velocities, are calculated at each time step through closed form solutions of Reynolds equation. Such combinations of fluid film bearings and squeeze film dampers are often used in industrial machines such as compressors and steam turbines to increase system damping. No previous works have studied the nonlinear time transient analysis of a fluid film bearing and damper combination. To describe the coupled motion of shaft, bearing and squeeze film damper, a method of assembling both the linear rotor and the nonlinear components is developed. The numerical transient analyses are applied to a 3-disk rotor supported with nonlinear short plain journal bearings and nonlinear short squeeze film dampers. Squeeze film dampers, introduced to the system, increase dynamic stability of the system under a wide range of system rotational speeds, and decrease the bearing forces under severe unbalance forces. Different nonlinear rotor dynamic behavior, such as sub-harmonic, super-harmonic and torus orbits are shown in transient analyses. This type of analysis can be employed to study whether a centering spring is required in the damper or not.

Magnetohydrodynamic Squeeze Film Characteristics Between Parallel Circular Plates Containing a Single Central Air Bubble in the Inertial Flow Regime

1999 ◽  
Vol 66 (4) ◽  
pp. 1021-1023 ◽  
Author(s):  
R. Usha ◽  
P. Vimala
Keyword(s):  
Magnetic Field ◽  
Differential Equation ◽  
Nonlinear Differential Equation ◽  
Bubble Radius ◽  
Fluid Film ◽  
Squeeze Film ◽  
Parallel Plates ◽  
Circular Plates ◽  
Air Bubble ◽  
Approximate Analytical Solutions

In this paper, the magnetic effects on the Newtonian squeeze film between two circular parallel plates, containing a single central air bubble of cylindrical shape are theoretically investigated. A uniform magnetic field is applied perpendicular to the circular plates, which are in sinusoidal relative motion, and fluid film inertia effects are included in the analysis. Assuming an ideal gas under isothermal condition for an air bubble, a nonlinear differential equation for the bubble radius is obtained by approximating the momentum equation governing the magnetohydrodynamic squeeze film by the mean value averaged across the film thickness. Approximate analytical solutions for the air bubble radius, pressure distribution, and squeeze film force are determined by a perturbation method for small amplitude of sinusoidal motion and are compared with the numerical solution obtained by solving the nonlinear differential equation. The combined effects of air bubble, fluid film inertia, and magnetic field on the squeeze film force are analyzed.

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