Non Linear Transient Response of a Flexible Shaft Controlled by Electro-rheological Hydrostatic Squeeze Film Dampers

2012 ◽  
pp. 33-40 ◽  
Author(s):  
Ahmed Bouzidane ◽  
Marc Thomas
Keyword(s):  
Transient Response ◽  
Squeeze Film ◽  
Flexible Shaft ◽  
Squeeze Film Dampers ◽  
Non Linear

Response of a Squeeze Film Damper-Elastic Structure System to Multiple and Consecutive Impact Loads

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Luis San Andrés ◽  
Sung-Hwa Jeung
Keyword(s):  
Transient Response ◽  
Damping Ratio ◽  
Test System ◽  
Elastic Structure ◽  
Squeeze Film ◽  
Radial Clearance ◽  
System Response ◽  
Fluid Inertia ◽  
Squeeze Film Dampers ◽  
Structural Isolation

Squeeze film dampers (SFDs) are common in aircraft gas turbine engines, customized to provide a desired level of damping while also ensuring structural isolation. This paper presents measurements obtained in a test rig composed of a massive cartridge, an elastic structure, and an open-ends SFD with length L = 25.4 mm, diameter D = 127 mm, and radial clearance c = 0.267 mm. ISO VG 2 oil at room temperature lubricates the thin film. The measurements quantify the system transient response to sudden loads for motions departing from various static eccentricity displacements, es/c = 0–0.6. The batch of tests include recording the system response to (a) one single impact, (b) two (and three) impacts with an elapsed time of 30 ms in between, and (c) two or more consecutive impacts, without any delay, each with a load magnitude at 50% of the preceding impact. The load actions intend to reproduce, for example, a hard landing on an uneven surface or plunging motions from sudden contacts in a machine tool. The test system transient responses due to one or more impacts, each 30 ms apart, show the peak amplitude of motion (ZMAX) is proportional to the magnitude of applied load (FMAX). The identified system damping ratio (ξ) is proportional to the peak dynamic displacement as a linear system would show. Predictions of transient response from a physical SFD model accounting for fluid inertia correlate best with the experimental results as they produce greatly reduced peak dynamic motions when compared to predictions from a purely viscous SFD model. For the responses due to consecutive impacts, one after the other with no delay, the system motion does not decay immediately but builds to produce larger motion amplitudes than in the earlier cases. Eventually, as expected, after several oscillations, the system comes to rest. For an identical damper having a smaller clearance cs = 0.213 mm (0.8c), its damping ratio (ξs) is ∼1.3 to ∼1.7 times greater than the damping ratio for the damper with a larger film clearance (ξ). Hence, the experimentally derived (ξs/ξ) scales with (c/cs)2. The finding demonstrates the importance of manufacturing precisely the components in a damper to produce an accurate clearance.

Response of a Squeeze Film Damper-Elastic Structure System to Multiple and Consecutive Impact Loads

2016 ◽  
Author(s):  
Luis San Andrés ◽  
Sung-Hwa Jeung
Keyword(s):  
Transient Response ◽  
Damping Ratio ◽  
Test System ◽  
Elastic Structure ◽  
Squeeze Film ◽  
Radial Clearance ◽  
System Response ◽  
Fluid Inertia ◽  
Squeeze Film Dampers ◽  
Structural Isolation

Squeeze Film Dampers (SFDs) are common in aircraft gas turbine engines, customized to provide a desired level of damping while also ensuring structural isolation. This paper presents measurements obtained in a test rig composed of a massive cartridge, an elastic structure, and an open ends SFD with length L=25.4 mm, diameter D=127 mm, and radial clearance c=0.267 mm. ISO VG 2 oil at room temperature lubricates the thin film. The measurements quantify the system transient response to sudden loads for motions departing from various static eccentricity displacements, es/c=0 to 0.6. The batch of tests include recording the system response to (a) one single impact, (b) two (and three) impacts with an elapsed time of 30 ms in between, and (c) two or more consecutive impacts, without any delay, each with a load magnitude at 50% of the preceding impact. The load actions intend to reproduce, for example, a hard landing on an uneven surface or plunging motions from sudden contacts in a machine tool. The test system transient responses due to one or more impacts, each 30 ms apart, show the peak amplitude of motion (ZMAX) is proportional to the magnitude of applied load (FMAX). The identified system damping ratio (ξ) is proportional to the peak dynamic displacement as a linear system would show. Predictions of transient response from a physical SFD model accounting for fluid inertia correlate best with the experimental results as they produce greatly reduced peak dynamic motions when compared to predictions from a purely viscous SFD model. For the responses due to consecutive impacts, one after the other with no delay, the system motion does not decay immediately but builds to produce larger motion amplitudes than in the earlier cases. Eventually, as expected, after several oscillations the system comes to rest. For an identical damper having a smaller clearance cs=0.213 mm (0.8c), its damping ratio (ξs) is ∼1.3 to ∼1.7 times greater than the damping ratio for the damper with a larger film clearance (ξ). Hence, the experimentally derived (ξs/ξ) scales with (c/cs)2. The finding demonstrates the importance of manufacturing precisely the components in a damper to produce an accurate clearance.

Non-linear behavior of a flexible shaft partly supported by a squeeze film damper

Wear ◽  
1997 ◽  
Vol 206 (1-2) ◽  
pp. 244-250 ◽  
Author(s):  
Olivier Bonneau ◽  
Jean Frêne
Keyword(s):  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Flexible Shaft ◽  
Linear Behavior ◽  
Non Linear

Nonlinear Dynamic Behavior of a Flexible Shaft Supported by Smart Hydrostatic Squeeze Film Dampers

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
A. Bouzidane ◽  
M. Thomas
Keyword(s):  
Electric Field ◽  
Dynamic Behavior ◽  
Nonlinear Model ◽  
Nonlinear Dynamic ◽  
Electrorheological Fluid ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Flexible Shaft ◽  
Squeeze Film Dampers ◽  
Nonlinear Dynamic Behavior

The aim of this research is to study the nonlinear dynamic behavior of a flexible shaft supported by smart hydrostatic squeeze film dampers, which are filled with a negative electrorheological fluid (NERF). A nonlinear model of the hydrostatic squeeze film damper has been developed in order to study the effect of the electrorheological fluid on the dynamic behavior of a flexible shaft. The results obtained are discussed and compared with the linear model, which is restricted to only small vibrations around the equilibrium position. A new smart hydrostatic squeeze film damper is proposed to reduce the transient response of the shaft and transmitted forces by applying an electric field to the NER fluid, which results in modifying its viscosity. The results show that it is possible to effectively monitor the electric field and the viscosity of the fluid inside the hydrostatic squeeze film dampers (HSFD) for a better control of flexible shaft vibration and bearing transmitted forces.

Nonlinear Response of Rotors Supported on Squeeze Film Dampers

1999 ◽  
Author(s):  
Krishnaswamy Ramesh ◽  
R. Gordon Kirk
Keyword(s):  
Nonlinear Response ◽  
Forced Response ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Linear Behavior ◽  
Linearized Stability ◽  
Squeeze Film Dampers ◽  
Dynamic Forces ◽  
Speed Range ◽  
Non Linear

Abstract The ability of a squeeze film damper (SFD) to attenuate the amplitude of vibration and to decrease the dynamic forces transmitted to the support system, makes it an attractive means of supporting turbomachinery. The main reasons for using a squeeze film damper on a rotor are to improve the dynamic stability and also to reduce the forces transmitted to the foundation. Generally the squeeze film damper ring is centered by a retainer spring. For linearized stability evaluation this is an acceptable assumption. While evaluating the forced response of a rotor having a squeeze film damper, the damper ring is usually assumed to be centralized in the clearance space through the entire running speed range. During the actual running condition the damper does not remain in the centered position and the damper ring tends to find its own eccentric position. This paper discusses the effect of this non-linear behavior of the damper and on the response. A overhung compressor is used as an example to illustrate the influence of the non-linear damper as compared to the centered damper assumption.

An Energy Approach to Linearizing Squeeze-Film Damper Forces

1985 ◽  
Vol 199 (1) ◽  
pp. 57-63
Author(s):  
E J Hahn
Keyword(s):  
Parametric Design ◽  
Squeeze Film ◽  
Transient Solution ◽  
Equivalent Stiffness ◽  
Design Studies ◽  
Damping Coefficients ◽  
Squeeze Film Dampers ◽  
Non Linear ◽  
Linear Elements ◽  
Stiffness And Damping

Analyses of multi-degree of freedom rotor-bearing systems incorporating non-linear elements, such as squeeze-film dampers, generally necessitate time consuming transient solution. Consequently, it is often too expensive to carry out parametric design studies on such systems. This paper presents a general technique for linearizing the non-linear element forces using equivalent stiffness and damping coefficients with energy dissipation and energy storage-release concepts. The approach is illustrated and tested for both centrally preloaded squeeze-film dampers and for squeeze-film dampers without centralizing springs under a combination of unidirectional and unbalance loading. The results predicted by using such equivalent stiffness and damping coefficients agree quite well with those obtained from the full transient solution, even where the unidirectional load exceeds the dynamic load and the damper is operating at high eccentricity. An iterative procedure is proposed which, with the aid of such stiffness and damping coefficients, should significantly reduce the computation time presently needed to carry out parametric design studies on general multi-degree of freedom systems incorporating non-linear elements such as squeeze-film dampers.

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