Effect of Pressurization on the Vibration Isolation Capability of Squeeze Film Bearings

1976 ◽  
Vol 98 (1) ◽  
pp. 109-117 ◽  
Author(s):  
S. Simandiri ◽  
E. J. Hahn
Keyword(s):  
Vibration Isolation ◽  
Rolling Element Bearing ◽  
Squeeze Film ◽  
Vibration Level ◽  
Design Data ◽  
Supply Pressure ◽  
Rolling Element ◽  
Approximation Constant ◽  
Unbalance Force ◽  
Lubricant Viscosity

This paper investigates theoretically the effect of pressurization on the vibration isolation capability of centrally preloaded squeeze film bearings supporting a rigid rotor which in turn is mounted in rolling element bearings. Assuming the short bearing approximation, constant lubricant properties, and that steady state conditions have been reached with the journal center describing synchronous circular orbits about the bearing center, the theory is developed for the general case of arbitrary pressurization at either end of the bearing. The design data are for bearings pressurized at one end only as in circumferentially grooved bearings and conservatively assume that the saturation vapor pressure of the lubricant is atmospheric. These design curves show the effect of the relevant system parameters on the possibility of undesirable operation modes, on the unbalance force transmissibility and on rotor vibration amplitudes. Hence, the influence of lubricant viscosity, lubricant supply pressure, bearing dimensions, rotor speed, rotor mass, rotor unbalance and support flexibility may be readily determined, allowing for optimal system design. It is shown that significant unbalance force isolation is a practical possibility with consequent decrease in the vibration level of the rotor mounts and increase in rolling element bearing life, while maintaining rotor excursion amplitudes at an acceptable level, even with relatively high unbalance loading. In particular, with increased pressurization, the likelihood of bistable operation can be considerably reduced. The data suggest that by varying the supply pressure and/or the lubricant viscosity, the rotor bearing system may be gainfully controlled to run at minimum vibration level and/or with minimum unbalance transmissibility.

Steady-State Performance of Squeeze Film Damper Supported Flexible Rotors

1977 ◽  
Vol 99 (4) ◽  
pp. 552-558 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Rolling Element Bearing ◽  
Squeeze Film ◽  
Response Curves ◽  
Flexible Rotors ◽  
Steady State Operation ◽  
Bearing Life ◽  
Rolling Element ◽  
Single Mass

The synchronous steady-state operation of a centrally preloaded single mass flexible rotor supported in squeeze film bearing dampers is examined theoretically. Assuming the short bearing approximation and symmetric motions, frequency response curves are presented exhibiting the effect of relevant system parameters on rotor excursion amplitudes and unbalance transmissibilities for both pressurized and unpressurized lubricant supply. Hence, the influence of rotor flexibility, rotor mass distribution, rotor speed, bearing dimensions, lubricant viscosity, support flexibility can be readily determined, allowing for optimal rotor bearing system design. It is shown that with pressurized bearing mounts, the possibility of undesirable operation modes is eliminated and a smooth passage through the first pin-pin critical speed of the rotor is feasible, while absence of pressurization significantly limits the maximum safe unbalance in the vicinity of this critical speed. Significant decrease in transmissibility and rotor excursion amplitudes over those obtainable with rigid mounts are shown to be a practical possibility, with consequent decrease in the vibration level of the rotor mounts and prolongation of rolling element bearing life, while maintaining acceptable rotor vibration amplitudes. A design example is included to illustrate the use of the data.

Development of Compact Damper Bearing

2005 ◽  
Author(s):  
Hiroshi Kanki ◽  
Yosichika Sato ◽  
Takayuki Ueshima
Keyword(s):  
Rotating Machinery ◽  
Rolling Element Bearing ◽  
Squeeze Film ◽  
Test Results ◽  
Thin Ring ◽  
Compact Size ◽  
Standard Design ◽  
Rolling Element ◽  
Aero Engine ◽  
Element Bearing

The squeeze film damper bearings have been successfully applied for important rotating machinery such as aero engine, high pressure centrifugal compressors[1] and steam turbine[2]. This paper proposes the expansion of application of the damper bearing for small and medium sized rotating machinery. The new damper has a compact size that enable standard design combined with rolling element bearing. A new design of the damper is presented. The new design consists of thin ring and special patterned wire cut grooves. The design analysis and experimental study are presented. The dynamic tests were carried out for this model damper, one is no side seal and the other is with side seals in both ends. Test results showed the sufficient damping effect for actual applications.

Transmissibility Study of a Flexibly Mounted Rolling Element Bearing in a Porous Bearing Squeeze-Film Damper

1977 ◽  
Vol 99 (1) ◽  
pp. 50-56 ◽  
Author(s):  
C. Cusano ◽  
P. E. Funk
Keyword(s):  
Steady State ◽  
Wall Thickness ◽  
Rolling Element Bearing ◽  
Squeeze Film ◽  
State Data ◽  
Squeeze Film Damper ◽  
Porous Bearing ◽  
Rolling Element ◽  
Element Bearing ◽  
Transient And Steady State

The purpose of this investigation is to study the transmissibility characteristics of a centrally preloaded porous bearing squeeze-film damper supporting a rolling element bearing. Using the short-bearing approximation and isothermal, incompressible lubrication, transient and steady-state data are presented which show that, for the range of parameters considered, porous bearing dampers exhibit superior transmissibility characteristics over equivalent dampers using solid bearings. The data presented are for squeeze-film porous bearings having a wall thickness-to-length ratio of 0.1 and three degrees of permeability, including the case of zero permeability which corresponds to a solid bearing.

Stability and Unbalance Response of Centrally Preloaded Rotors Mounted in Journal and Squeeze Film Bearings

1979 ◽  
Vol 101 (2) ◽  
pp. 120-128 ◽  
Author(s):  
E. J. Hahn
Keyword(s):  
Steady State ◽  
Vibration Isolation ◽  
Journal Bearings ◽  
Squeeze Film ◽  
State Behavior ◽  
Unbalance Response ◽  
Radial Stiffness ◽  
Rolling Element ◽  
Orbit Eccentricity ◽  
Vertical Bearing

The unbalance response and stability of centrally preloaded symmetric rigid rotors are investigated. Steady state solutions for unbalance transmissibilities, orbit eccentricity radii, and stability are presented for rotors running in hydrodynamic journal bearings and in rolling element bearings which are supported in squeeze film bearings. The Ocvirk and Warner approximations are used to evaluate the fluid film forces, rendering the data applicable to any length/diameter ratio. Both pressurized (2π film) and unpressurized (π film) oil supply are considered. Pressurization has a far reaching influence on the steady state behavior of both journal and squeeze film bearings. For unpressurized bearings, conditions of multistable operation and for stability are depicted, with journal bearings exhibiting ‘half frequency whirl’ possibilities as well. The error involved in predicting vertical bearing behavior by assuming an equivalent unidirectional load equal to the unbalance load is demonstrated. For pressurized bearings multistable operation is eliminated but both squeeze film and journal bearings are unstable for most length/diameter ratios in the absence of external radial stiffness. The stabilizing effect of superimposed external radial stiffness on pressurized bearings is clearly demonstrated. While pressurized journal bearings can run stably, they are less suited than pressurized squeeze film bearings for vibration isolation.

A New Lateral Vibration Damper Using Leaf Springs

1999 ◽  
Vol 121 (3) ◽  
pp. 343-350 ◽  
Author(s):  
Yang-Gyu Jei ◽  
Jong-Soo Kim ◽  
Seong-Wook Hong ◽  
Si-Young Jung
Keyword(s):  
Rolling Element Bearing ◽  
Squeeze Film ◽  
Leaf Spring ◽  
Lateral Vibration ◽  
Vibration Damper ◽  
Damping Coefficients ◽  
Leaf Springs ◽  
Rolling Element ◽  
Element Bearing ◽  
Stiffness And Damping

The present paper introduces a new lateral vibration damper using leaf springs and oil. This damper, named as a leaf spring damper (LSD), has several beneficial rotordynamic advantages. The leaf spring vibration damper, unlike the well-known squeeze film damper, is simple and easy enough to design the required stiffness and damping coefficients. Furthermore, the damper can be designed as a unit product joined with a rolling element bearing. A theoretical modeling procedure for leaf spring damper is presented in detail. Prototypes of the leaf spring damper are manufactured to test the dynamic characteristics of the damper. Experiments are performed to measure the stiffness and the damping coefficients of the damper.

Design of Squeeze Film Damper Supports for Rigid Rotors

1974 ◽  
Vol 96 (3) ◽  
pp. 976-982 ◽  
Author(s):  
S. Mohan ◽  
E. J. Hahn
Keyword(s):  
Operating Conditions ◽  
Squeeze Film ◽  
Design Data ◽  
Start Up ◽  
Bearing Life ◽  
Wide Range ◽  
Unbalance Force ◽  
Design Speed ◽  
Consequent Increase ◽  
Rigid Rotors

This paper investigates squeeze film bearings supporting a centrally preloaded rigid rotor mounted in antifriction bearings. Assuming the short bearing approximation and isothermal, incompressible lubrication, design data are presented for such a system over a wide range of operating conditions. Design considerations include the possibility of undesirable operation modes, the maximum unbalance for which the squeeze film support is superior to the rigid mount, the transmissibility at design speed and the forces transmitted during start-up. It is shown that unbalance force attenuations by factors of three or more are a practical possibility with a consequent increase in antifriction bearing life. A numerical example is included.

On the Frictional Damping Characterization of Compliant Bump Foils

2003 ◽  
Vol 125 (4) ◽  
pp. 804-813 ◽  
Author(s):  
Mohsen Salehi ◽  
Hooshang Heshmat ◽  
James F. Walton
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Elevated Temperatures ◽  
Hysteresis Loops ◽  
Rolling Element Bearing ◽  
Squeeze Film ◽  
Dynamic Friction Coefficient ◽  
Frictional Damping ◽  
Rolling Element ◽  
Stiffness And Damping

High-speed rotor systems use either fluid film or rolling element bearing supports, depending upon their design and operating constraints. Regardless of bearing type used, these systems require specific bearing and support stiffness and damping characteristics to achieve the desired stable and low vibration operation. Building upon the technology of thin metallic corrugated bump foils presently used in a particular class of film riding hydrodynamic bearings, a novel corrugated bump foil damped mount is introduced which provides stiffness and damping for application with rolling element bearings. These damping elements are capable of operating at elevated temperatures where implementation of conventional squeeze film dampers is ruled out. The frictional damping results from micro-slip motions between the bump foils and the mating surfaces. A semi-empirical model, based on a one degree of freedom model was developed in which damping is replaced by an equivalent frictional force in order to gain insight into the dynamic friction coefficient of the individual damping element interfaces. Experimental results, obtained in the form of hysteresis loops were compared to the developed model with good agreement. The variation in damping and dynamic coefficient of friction was found to be dependent primarily upon three factors: vibration frequency, amplitude of motion and applied static load. These parameters were tested within the range of 50–1400 Hz, 2.54–12.7 micron and 45–135 N, respectively. The tests were conducted at room and 538°C ambient temperatures under both dry and vapor phase lubricated conditions. Using the resulting empirical data, several bearing dampers were designed, built and tested in a small, high-speed gas turbine engine simulator. The tested novel foil dampers were capable of operating reliably under extremely high levels of shaft imbalance (i.e., 320 times greater than the air bearing supported with specification of 0.0002 oz-in) even while operating at temperatures to 560°C. These results show the great potential for wide application of these dampers on gas turbine engines and high-speed rotating machinery.

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