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.

scholarly journals Applications of Biocatalysts for Sustainable Oxidation of Phenolic Pollutants: A Review

2021 ◽  
Vol 13 (15) ◽  
pp. 8620
Author(s):  
Sanaz Salehi ◽  
Kourosh Abdollahi ◽  
Reza Panahi ◽  
Nejat Rahmanian ◽  
Mozaffar Shakeri ◽  
...  
Keyword(s):  
Phenolic Compounds ◽  
Operating Conditions ◽  
Phenolic Pollutants ◽  
Petroleum Refinery Wastewater ◽  
Start Up ◽  
Low Concentrations ◽  
Effective Removal ◽  
Wide Range ◽  
Loading Effects ◽  
Spent Caustic

Phenol and its derivatives are hazardous, teratogenic and mutagenic, and have gained significant attention in recent years due to their high toxicity even at low concentrations. Phenolic compounds appear in petroleum refinery wastewater from several sources, such as the neutralized spent caustic waste streams, the tank water drain, the desalter effluent and the production unit. Therefore, effective treatments of such wastewaters are crucial. Conventional techniques used to treat these wastewaters pose several drawbacks, such as incomplete or low efficient removal of phenols. Recently, biocatalysts have attracted much attention for the sustainable and effective removal of toxic chemicals like phenols from wastewaters. The advantages of biocatalytic processes over the conventional treatment methods are their ability to operate over a wide range of operating conditions, low consumption of oxidants, simpler process control, and no delays or shock loading effects associated with the start-up/shutdown of the plant. Among different biocatalysts, oxidoreductases (i.e., tyrosinase, laccase and horseradish peroxidase) are known as green catalysts with massive potentialities to sustainably tackle phenolic contaminants of high concerns. Such enzymes mainly catalyze the o-hydroxylation of a broad spectrum of environmentally related contaminants into their corresponding o-diphenols. This review covers the latest advancement regarding the exploitation of these enzymes for sustainable oxidation of phenolic compounds in wastewater, and suggests a way forward.

Optimal Design of Squeeze Film Supports for Flexible Rotors

1983 ◽  
Vol 105 (3) ◽  
pp. 487-494 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Optimal Design ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Rotor Vibration ◽  
Design Constraints ◽  
Supply Pressure ◽  
Flexible Rotors ◽  
Wide Range ◽  
Film Lubrication

Assuming central preloading, operation below the second bending critical speed, and full film lubrication, this paper presents a theoretical model which allows one, with minimum computation, to design squeeze film damped rotors under conditions of high unbalance loading. Closed form expressions are derived for the maximum vibration amplitudes pertaining to optimally damped conditions. The resulting vibration amplitude and transmissibility data of design interest are presented for a wide range of practical operating conditions on a single chart. It can be seen that for a given rotor, the lighter the bearing the more easily one can satisfy design constraints relating to allowable rotor vibration levels and lubricant supply pressure requirements. The data presented are shown to be applicable to a wide variety of rotors, and a recommended procedure for optimal design is outlined.

Analysis of Measured and Predicted Turbine Maps From Start-Up to Design Point

2020 ◽  
Author(s):  
Alberto Scotti del Greco ◽  
Sara Biagiotti ◽  
Vittorio Michelassi ◽  
Tomasz Jurek ◽  
Daniele Di Benedetto ◽  
...  
Keyword(s):  
Full Range ◽  
Velocity Ratio ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Turbine Stage ◽  
Design Point ◽  
Start Up ◽  
Wide Range ◽  
Constant Shape ◽  
Ratio Versus

Abstract This paper describes a coupled experimental and CFD campaign conducted on a 1.5 intermediate turbine stage in the full range of operating conditions, from start-up to design point under variable expansion ratio and physical speed. The test maintains engine similitude conditions and allows direct comparison with CFD data to assess the predictions accuracy. The choice of variables to describe the speedlines is also addressed by using both measured and predicted data. A discussion on velocity ratio versus corrected speed illustrates the advantages of the former parameter the adoption of which produces constant shape curves in a very wide range of operating conditions. The comparison between measurements and predictions suggests that CFD, in conjunction with performance correlations, is a viable tool to predict speedlines in a fairly wide range of conditions, provided that geometrical and operational details are carefully matched.

Ten years of industrial and municipal membrane bioreactor (MBR) systems – lessons from the field

2014 ◽  
Vol 70 (2) ◽  
pp. 279-288 ◽  
Author(s):  
Asun Larrea ◽  
Andre Rambor ◽  
Malcolm Fabiyi
Keyword(s):  
Wastewater Treatment ◽  
Industrial Wastewater ◽  
Municipal Wastewater ◽  
Membrane Bioreactors ◽  
Operating Conditions ◽  
Industrial Plant ◽  
Municipal Wastewater Treatment ◽  
Design Data ◽  
Wide Range ◽  
Process Controls

The use of membrane bioreactors (MBRs) in activated sludge wastewater treatment has grown significantly in the last decade. While there is growing awareness and knowledge about the application of MBR technology in municipal wastewater treatment, not much information is available on the application of MBRs in industrial wastewater treatment. A comparative study of design data, operating conditions and the major challenges associated with MBR operations in 24 MBR plants treating both municipal and industrial wastewater, built by and/or operated by Praxair, Inc., is presented. Of the 24 MBR systems described, 12 of the plants used high purity oxygen (HPO). By enabling a wide range of food/microorganism ratios and loading conditions in the same system, HPO MBR systems can extend the options available to industrial plant operators to meet the challenges of wide fluctuations in organic loading and footprint limitations. While fouling in industrial MBR systems can be an issue, adequate flux and permeability values can be reliably maintained by the use of good maintenance strategies and effective process controls (pretreatment, cleaning and membrane autopsies).

scholarly journals An Improved Squeeze Film Damper for Rotor Vibration Control: Theoretical Results

1994 ◽  
Author(s):  
J. Y. Zhao ◽  
I. W. Linnett ◽  
E. J. Hahn
Keyword(s):  
Operating Conditions ◽  
Outer Ring ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Constant Stiffness ◽  
Wide Range ◽  
Squeeze Film Dampers ◽  
Secondary Support ◽  
Stiffness And Damping ◽  
Theoretical Results

This paper proposes an improved squeeze film damper which will prevent the bistable operation associated with conventional squeeze film dampers at large unbalances and/or at small bearing parameters. It consists of a conventional squeeze film damper with a flexibly supported outer ring. This secondary flexible support is considered to be massless, and to have a constant stiffness and damping. The effectiveness of this damper in preventing bistable operation is investigated over a wide range of operating conditions for a rigid rotor supported on a centrally preloaded squeeze film damper. It is shown that depending on relevant parameters such as the stiffness ratio between the secondary support and the retaining spring, the damping coefficient of the support, and the mass ratio between the damper outer ring and the rotor, this proposed damper is very effective in preventing bistable operation even for high unbalance conditions.

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.

scholarly journals Optimal Design of Squeeze Film Supports for Flexible Rotors

1982 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Optimal Design ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Rotor Vibration ◽  
Design Constraints ◽  
Supply Pressure ◽  
Flexible Rotors ◽  
Wide Range ◽  
Film Lubrication

Assuming central preloading operation below the second bending critical speed and full film lubrication, this paper presents a theoretical model which allows one, with minimum computation, to design squeeze film damped rotors under conditions of high unbalance loading. Closed form expressions are derived for the maximum vibration amplitudes pertaining to optimally damped conditions. The resulting vibration amplitude and transmissibility data of design interest are presented for a wide range of practical operating conditions on a single chart. It can be seen that for a given rotor, the lighter the bearing the more easily one can satisfy design constraints relating to allowable rotor vibration levels and lubricant supply pressure requirements. The data presented are shown to be applicable to a wide variety of rotors, and a recommended procedure for optimal design is outlined.

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.

Analysis and Design of Segmented Dampers for Rotor Dynamic Control

1982 ◽  
Vol 104 (1) ◽  
pp. 84-90 ◽  
Author(s):  
D. L. Taylor ◽  
V. S. Fehr
Keyword(s):  
Pressure Distribution ◽  
Dynamic Control ◽  
Design Procedure ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Fluid Viscosity ◽  
Damping Force ◽  
Analysis And Design ◽  
Wide Range ◽  
Parameter Values

Dampers have become of increasing importance in the control of shaft vibration of rotating equipment which must operate through one or more critical speeds. This paper presents the analytical results for the study of a new class of damper, the segmented film damper. A series of isolated segments of fluid are used rather than a continuous film as in the traditional squeeze film damper. This configuration provides energy dissipation through fluid viscosity within the film segments and through oriface flow in the supply and exit ports for each segment. The pressure distribution within an individual segment is developed on the basis of Reynolds equation with appropriate boundary conditions. The effects of various parameters are discussed in terms of this pressure distribution. The geometric effects of multiple segments are derived for both input, how shaft motion excites each segment, and output, how the segments’ pressure distributions combine to provide a net force. The damping force is shown to be linear for a wide range of operating conditions, speed and unbalance, and thus validly expressed in terms of a damping coefficient. Additionally, this class of damper is shown to have no radial stiffness. The limitations and implications for the designer are discussed in detail. A structured design procedure is given for the selection of parameter values, and a design example with numerical values is included.

Stability of Squeeze-Film-Damper Supported Flexible Rotors

1977 ◽  
Vol 99 (4) ◽  
pp. 545-551 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Steady State ◽  
System Stability ◽  
Squeeze Film ◽  
Design Data ◽  
Flexible Rotors ◽  
Wide Range ◽  
Single Mass ◽  
The Stability ◽  
Rotor Mass

Assuming the short bearing approximation and symmetric motions, the stability of the steady-state synchronous operation of centrally preloaded single-mass flexible rotors supported in squeeze-film bearing dampers is theoretically investigated. The stability regions are depicted over a wide range of system parameters and allow for easy determination of the stability of existing steady-state design data. The influence of rotor flexibility, rotor speed, bearing dimensions, lubricant viscosity, rotor mass distribution, and rotor unbalance on rotor-bearing system stability may be readily seen. In the absence of pressurization, instability regions were possible even with relatively high support damping, though no instability was indicated for speeds below the support natural frequency, or for bearing eccentricity ratio <0.4 at any speed. Pressurization of the lubricant supply was found to stabilize the system over the whole range of parameters investigated, regardless of unbalance, which would then be limited only by the bearing clearance. Data are presented which enable the minimum supply pressure to ensure full film lubrication to be conveniently determined.

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