A new model to predict the behaviour of cavitated squeeze-film bearings

1987 ◽  
Vol 411 (1841) ◽  
pp. 445-466
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Lift Force ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Successful Operation ◽  
New Model ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Linear Damping

Squeeze-film bearings are used extensively to control vibration in rotor-bearing systems. No closed-form mathematical model exists to represent the stiffness and dam ping characteristics of a cavitated squeeze-film bearing when it is describing a non-circular, non-concentric orbit. In this paper nonlinear expressions are developed for the oil-film forces from which are derived two direct linear stiffness and two direct linear damping coefficients with all the cross stiffness and dam ping coefficients zero. The linearized stiffness coefficients and the damping coefficients are functions of the amplitude of the journal orbit. The dynamic lift-force which is fundamental to the successful operation of a cavitated squeeze-film bearing when designed without centralizing springs has not previously been predicted analytically. An expression is derived for this lift force. Its magnitude is shown to be dependent upon the amplitude of the steady-state orbit, that is, it is dependent upon the dynamic load. A numerical experiment is performed to assess the validity of the new model over a range of operating conditions.

Considerations about Maximum Temperature of Toroidal Transformers in Steady-State Conditions

2020 ◽  
Vol 7 (1) ◽  
pp. 22-29
Author(s):  
Adrian Pleșca ◽  
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Ambient Temperature ◽  
Electric Current ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Maximum Difference ◽  
Novel Method ◽  
Theoretical Results

In this paper, a novel method based on a thermal mathematical model which includes the main geometrical, physical and thermal parameters of the toroidal transformer has been developed in order to obtain the maximum temperature inside the transformer during steady-state operating conditions. The influence of electric current and ambient temperature on the maximum temperature has been investigated. To validate the proposed method, some experimental tests have been done. The analyzed transformer had a rated power of 2kVA and the rated primary voltage of 230V. There is a good correlation between experimental and theoretical results with a maximum difference of 3°C.

First Paper: An Investigation into the Steady-State Characteristics of Plain Slideways

1969 ◽  
Vol 184 (1) ◽  
pp. 1075-1087 ◽  
Author(s):  
R. Bell ◽  
M. Burdekin
Keyword(s):  
Cast Iron ◽  
Steady State ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Sliding Velocity ◽  
Experimental Conditions ◽  
Friction Characteristics ◽  
Feed Drive ◽  
Lubricant Viscosity

This paper describes steady-state friction tests on a scraped-cup ground combination of cast iron surfaces. The experimental conditions were representative of the operating conditions on a machine tool feed drive employing plain slideways. The range of the relative sliding velocity investigated was 0 → 1 in s-1, and the influence of lubricant viscosity of both polar and non-polar additive lubricants is shown. An investigation into the effect of oil grooves is also reported. Data obtained from squeeze film measurements enabled the characteristics, normal to the sliding plane, to be specified. These characteristics, together with measurements of the separation of the surfaces, enabled the steady-state friction characteristics to be predicted over the range of mixed and hydrodynamic lubrication covered by the tests. This work formed a basis for the investigation into the mechanism of the friction characteristics under dynamic conditions.

Rotordynamic Characteristics of a Flexure Pivot Pad Bearing With an Active and Locked Integral Squeeze Film Damper

2012 ◽  
Author(s):  
Jeff Agnew ◽  
Dara Childs
Keyword(s):  
Added Mass ◽  
Squeeze Film ◽  
Test Results ◽  
Squeeze Film Damper ◽  
Rotordynamic Coefficients ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Direct Stiffness ◽  
Active Damper ◽  
Rotordynamic Coefficient

Measured rotordynamic coefficients are presented for a flexure-pivot-pad journal bearing (FPJB) in a load-between-pad configuration with: (1) an active, and (2) locked integral squeeze film damper (ISFD). Prior rotordynamic-coefficient test results have been presented for FPJBs (alone), and rotor-response results have been presented for rotors supported by FPJBS with ISFDs; however, these are the first rotordynamic-coefficient test results for FPJBs with ISFDs. A multi-frequency dynamic testing regime is employed. For both bearing configurations, quadratic curve fits provide good representation of the real portions of the dynamic-stiffness coefficients yielding a direct stiffness and a direct added-mass coefficient. The imaginary portions are well represented by linear curve fits, implying constant, frequency-independent direct-damping coefficients. Direct stiffness coefficients are ∼50% lower for the active-damper configuration, and direct damping coefficients are only modestly lower. The combination of ∼50% reduction in direct stiffness with a modest drop in direct damping indicates a very effective squeeze-film damper application. Added-mass coefficients are normally lower for the active-damper configuration, and all coefficient trends (for changes in loading and shaft speed) are “flatter” for the active flexure pivot-pad damper bearing. The measured rotordynamic coefficients are used to calculate the whirl frequency ratio and indicate high stability for both bearing configurations.

The Damping Characteristics of Vibration Isolators Used in Gas Turbines

1977 ◽  
Vol 19 (6) ◽  
pp. 271-277 ◽  
Author(s):  
R. Holmes
Keyword(s):  
Gas Turbines ◽  
Journal Bearing ◽  
Nonlinear Damping ◽  
Common Type ◽  
Squeeze Film ◽  
Vibration Isolator ◽  
Vibration Isolators ◽  
Damping Coefficients ◽  
Damping Characteristics ◽  
Linear Damping

The linear and nonlinear damping performance of a common type of gas-turbine vibration isolator, consisting of a squeeze-film journal bearing in parallel with a linear retainer spring, is computed and used to prescribe limits to the use of linear damping coefficients.

Friction torque characteristics of an internal gear pump

2011 ◽  
Vol 225 (6) ◽  
pp. 1523-1534 ◽  
Author(s):  
Y Inaguma
Keyword(s):  
Mathematical Model ◽  
Friction Torque ◽  
Operating Conditions ◽  
Gear Pump ◽  
Operating Pressure ◽  
New Model ◽  
Pump Speed ◽  
Gear Pumps ◽  
Internal Gear ◽  
Three Components

This paper describes the influence of pump operating conditions, such as operating pressures, pump speeds, and oil temperatures, on the friction torque characteristics of internal gear pumps for automobiles. Additionally, it presents a new mathematical model reflecting the influence of the oil temperature on the friction torque. In an internal gear pump, the friction torque was affected by oil temperature as well as operating pressure and pump speed. When the operating pressure was high, the influence of oil temperature on friction torque at a pump speed of less than 1000 r/min was contrary to that at a pump speed of greater than 1000 r/min. It was considered that the friction torque is fundamentally composed of three components: the component dependent on the operating pressure, dependent on the pump speed, and independent of both the operating pressure and the pump speed. However, the component dependent on the operating pressure was affected significantly by not only the pump speed but also the oil temperature. In addition, another factor besides the viscosity of the oil existed in the component dependent on the pump speed. A mathematical model for the friction torque characteristic of the internal gear pump was newly established by adding factors including the oil temperature to the Wilson’s model. The new model was able to represent with accuracy the experimental friction torque characteristic in the internal gear pump under various pump operating conditions.

Squeeze Film Dynamics of Two-Phase Seals

1992 ◽  
Vol 114 (2) ◽  
pp. 236-246 ◽  
Author(s):  
J. A. Yasuna ◽  
W. F. Hughes
Keyword(s):  
Steady State ◽  
Dynamic Analysis ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Transient Responses ◽  
Two Phase ◽  
Thermal Transients ◽  
Face Seals

A dynamic analysis of two-phase face seals including squeeze film effects and thermal transients is presented. Axial responses to perturbations from equilibrium for various sets of typical seal operating conditions are examined, and the sensitivity of these responses to certain parameters is discussed. Sample calculations indicate damped transient responses which often decay as steady state is approached asymptotically. In some cases, however, stable and unstable oscillations are observed.

scholarly journals Steady Modeling for an Ammonia Synthesis Reactor Based on a Novel CDEAS-LS-SVM Model

2014 ◽  
Vol 2014 ◽  
pp. 1-18 ◽  
Author(s):  
Zhuoqian Liu ◽  
Lingbo Zhang ◽  
Wei Xu ◽  
Xingsheng Gu
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Differential Evolution ◽  
Ammonia Synthesis ◽  
Fast Convergence ◽  
Operating Conditions ◽  
Synthesis Process ◽  
Plant Behavior ◽  
Svm Model ◽  
Simulation Results

A steady-state mathematical model is built in order to represent plant behavior under stationary operating conditions. A novel modeling using LS-SVR based on Cultural Differential Evolution with Ant Search is proposed. LS-SVM is adopted to establish the model of the net value of ammonia. The modeling method has fast convergence speed and good global adaptability for identification of the ammonia synthesis process. The LS-SVR model was established using the above-mentioned method. Simulation results verify the validity of the method.

scholarly journals Experimental investigation and thermal analysis of coupler-rocker ball bearing

2020 ◽  
Vol 24 (6 Part A) ◽  
pp. 3781-3793
Author(s):  
Abdullah Jamil ◽  
Bin Baharom ◽  
Alemu Lemma ◽  
Tadimalla Rao
Keyword(s):  
Mathematical Model ◽  
Thermal Analysis ◽  
Experimental Investigation ◽  
Steady State ◽  
Applied Load ◽  
Ball Bearing ◽  
Linear Trend ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Ball Bearings

Ball bearings are widely used in many machineries and industrial applications. Thermal behaviour of oscillating ball bearings is unknown due to its complex pendulum-like motion and is discussed in this research. In this research, the effect of operating conditions of the oscillating bearing performing coupler-rocker motion on the heat generation is experimentally investigated and verified using mathematical model. For this purpose, a coupler-rocker bearing testing rig was designed and fabricated and the test bearing is splash-lubricated in an oil sump. The loading of test bearing was done using two extension springs. The applied load on the bearing was varied from 0 to 750 N while the crank rpm was varied from 1200 rpm to 1800 rpm. Three lubricant grades were used namely, SAE30, SAE40, and SAE50. Experimental results showed that the temperature of coupler-rocker bearing approaches steady-state at about 12 minutes for all cases. The steady-state temperatures at variable conditions are observed to follow a linear trend.

Leakage and Rotordynamic Coefficients of Brush Seals With Zero Cold Clearance Used in an Arrangement With Labyrinth Fins

2013 ◽  
Author(s):  
Manuel Gaszner ◽  
Alexander O. Pugachev ◽  
Christos Georgakis ◽  
Paul Cooper
Keyword(s):  
Dynamic Test ◽  
Operating Conditions ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Rotordynamic Coefficients ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Brush Seal ◽  
Brush Seals ◽  
Stiffness And Damping

A brush-labyrinth sealing configuration consisting of two labyrinth fins upstream and one brush seal downstream is studied experimentally and theoretically. Two slightly different brush seal designs with zero cold radial clearance are considered. The sealing configurations are tested on the no-whirl and dynamic test rigs to obtain leakage performance and rotordynamic stiffness and damping coefficients. The no-whirl tests allow identification of the local rotordynamic direct and cross-coupled stiffness coefficients for a wide range of operating conditions, while the dynamic test rig is used to obtain both global stiffness and damping coefficients, but for a narrower operating range limited by the capabilities of a magnetic actuator. Modeling of the brush-labyrinth seals is performed using computational fluid dynamics. The experimental global rotordynamic coefficients consist of an aerodynamic component due to the gas flow and a mechanical component due to the contact between the bristle tips and rotor surface. The CFD-based calculations of rotordynamic coefficients provide however only the aerodynamic component. A simple mechanical model is used to estimate the theoretical value of the mechanical stiffness of the bristle pack during the contact. The results obtained for the sealing configurations with zero cold radial clearance brush seals are compared with available data on three-tooth-on-stator labyrinth seals and a brush seal with positive cold radial clearance. Results show that the sealing arrangement with a line-on-line welded brush seal has the best performance overall with the lowest leakage and cross-coupled stiffness. The predictions are generally in agreement with the measurements for leakage and stiffness coefficients. The seal damping capability is noticeably underpredicted.

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