Rotor Bearing Solutions International

Charlottesville, VA, United States

Rotor Bearing Solutions International

Charlottesville, VA, United States

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Cao J.,Cao Consulting | Dimond T.,Rotor Bearing Solutions International | Allaire P.,University of Virginia
ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) | Year: 2014

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 subharmonic, 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. Copyright © 2014 by ASME.


Dousti S.,Rotor Bearing Solutions International | Dousti S.,University of Virginia | Fittro R.L.,University of Virginia
Proceedings of the ASME Turbo Expo | Year: 2015

Water lubricated bearings used in nuclear coolant pumps and sub-sea applications exhibit large lubricant inertia forces in the magnitude order of viscous forces. To model these bearings the traditional Reynolds equation is not adequate. An extended Reynolds equation is developed in this study which takes into account the turbulence and inertia effects: both convective and temporal. The most complete form of temporal inertia which applies to the turbulent regime as well, is developed that consists of primary and secondary temporal inertia terms. The convective inertia model follows Constantinescu's approach [1,2]. The turbulence model is also Constantinescu's which is tuned with a CFD work. The dynamic coefficients including the lubricant added mass coefficients of a full cylindrical fixed geometry water bearing are obtained. It is observed that the convective inertia increases the load capacity and stability of the bearing. Significant lubricant added mass coefficients comparable to the shaft mass are calculated, which exhibit destabilizing effects in general. Copyright © 2015 by ASME.


Cao J.,Candu Energy Inc. | Dimond T.,Rotor Bearing Solutions International | Allaire P.,University of Virginia
Proceedings of the ASME Turbo Expo | Year: 2014

This paper provides a time transient method for solving coupled lateral and torsional analysis of a flexible rotorbearing system including gyroscopic effects, nonlinear short journal bearings, nonlinear short squeeze film dampers, and external nonlinear forces/torques. The rotor is modeled as linear, and the supporting components, including bearings and dampers, are modeled as nonlinear. An implicit Runge-Kutta method is developed to solve the nonlinear equations of motion with non-constant operating speed since the unbalance force and the gyroscopic effect are related to both the rotational speed and the acceleration. The developed method is compared with previous torsional analysis first to verify the nonlinear transient solver. Then the coupled lateral and torsional analysis of a flexible 3-disk rotor with nonlinear bearings and nonlinear dampers driven by a synchronous motor is approached. The acceleration effects on lateral and torsional amplitudes is presented in the analysis. The developed method can be used to study the rotor motion with non-constant rotational speed, such as during startup, shutdown, going through critical speeds, blade loss force, or other sudden loading. Copyright © 2014 by ASME.


Gerami A.,University of Virginia | Allaire P.,Rotor Bearing Solutions International | Fittro R.,University of Virginia
Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME | Year: 2015

In this paper, a nonlinear modeling and control method for magnetic bearings is designed, considering the core material nonlinear high flux behavior for the first time. A combination of the generalized Lur'e method and linear matrix inequalities is used during the modeling and control design process. It is common to include a margin of safety in amplifiers and other active magnetic bearing (AMB) components. The nonlinear modeling makes it possible to operate an existing industrial AMB system with larger electric currents and thus achieve a larger maximum load capacity than existing AMB modeling and control practices allow. As a result, existing industrial AMB's can be tuned to become more resilient in dealing with external disturbances. In addition, smaller and lighter AMBs can be designed by using the proposed method, which enables achievement of the same maximum force requirement of present-day larger AMB systems. Copyright © 2015 by ASME.


PubMed | Cedars Sinai Medical Center, Rotor Bearing Solutions International and Drexel University
Type: Journal Article | Journal: Journal of cardiac surgery | Year: 2015

We present a review of the evolution of total artificial hearts (TAHs) and new directions in development, including the coupling of VADs as biventricular TAH support.


He F.,Dresser Rand Company | Allaire P.,Rotor Bearing Solutions International | Dimond T.,Rotor Bearing Solutions International
Proceedings of the ASME Design Engineering Technical Conference | Year: 2014

Squeeze film dampers in flexible rotors such as those in compressors, steam turbines, aircraft engines and other rotating machines are often modeled as linear devices. This linearization is valid only for a specified orbit where appropriate equivalent stiffness and damping coefficients can be found. However, squeeze film dampers are inherently nonlinear devices which complicates the analysis. This paper develops the harmonic balance method with a direct force model of the SFDs. This model is used for flexible rotors with squeeze film dampers where the rotor is treated as linear and the squeeze film damper is treated as nonlinear. The predictor-corrector method is employed to obtain the system forced response in the frequency domain after separating the nonlinear components from the linear components of the equations of motion. This approach is much more efficient than conventional full nonlinear transient analysis. The application considered in this paper is the low pressure (LP) compressor of an aircraft engine. The LP compressor rotor has two roller bearings with squeeze film dampers and one ball bearing without a squeeze film damper. Orbits at the fan end dampers and the turbine end dampers for both the harmonic balance and nonlinear transient modeling are compared for accuracy and calculation time. The HB method is shown to be 5 to 12 times faster computationally for similar results. Fast Fourier transform results were obtained for various shaft operating speeds. Results were also obtained for the unbalance response at different locations with gravity loading. Finally, unbalance response of the rotor with varying centering spring stiffness values were obtained. The results show that the centering spring stiffness for the turbine end damper is less sensitive than the fan end damper. Copyright © 2014 by ASME.


Cao J.,Rotor Bearing Solutions International | Allaire P.,Rotor Bearing Solutions International | Dimond T.,Rotor Bearing Solutions International
Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME | Year: 2015

This paper provides a time transient method for solving coupled lateral and torsional analysis of a flexible rotor-bearing system including gyroscopic effects, nonlinear short journal bearings, nonlinear short squeeze film dampers (SFDs), and external nonlinear forces/torques. The rotor is modeled as linear, and the supporting components, including bearings and dampers, are modeled as nonlinear. An implicit Runge-Kutta method is developed to solve the nonlinear equations of motion with nonconstant operating speed since the unbalance force and the gyroscopic effect are related to both the rotational speed and the acceleration. The developed method is compared with a previous torsional analysis first to verify the nonlinear transient solver. Then the coupled lateral and torsional analysis of an example flexible three-disk rotor, perhaps representing a compressor, with nonlinear bearings and nonlinear dampers driven by a synchronous motor is approached. The acceleration effects on lateral and torsional amplitudes of vibration are presented in the analysis. The developed method can be used to study the rotor motion with nonconstant rotational speed such as during startup, shutdown, going through critical speeds, blade loss force, or other sudden loading. Copyright © 2015 by ASME.


Dousti S.,Rotor Bearing Solutions International | Allaire P.,Rotor Bearing Solutions International | Dimond T.,Rotor Bearing Solutions International | Cao J.,Rotor Bearing Solutions International
Tribology International | Year: 2016

The introduction of this paper serves as a review of previous studies on extending the Reynolds equation. This paper develops an extended Reynolds equation and includes turbulence and inertia effects. Use of low viscosity lubricants and/or high rotational speed applications yield high Reynolds and high reduced Reynolds numbers. Our approach fully realizes the convective inertia effects on the static and dynamic properties of journal bearings as nonlinear with reduced Reynolds number. Two types of temporal inertia terms are identified for the first time: primary and secondary, in both laminar and turbulent regimes. The contribution of the secondary inertia effects can be up to 30% of the lubricant added mass coefficients. Lubricant added mass coefficients are potentially comparable to journal mass. © 2016 Elsevier Ltd.


Cao J.,Rotor Bearing Solutions International | Allaire P.,Rotor Bearing Solutions International | Dimond T.,Rotor Bearing Solutions International | Dousti S.,Rotor Bearing Solutions International
Proceedings of the ASME Turbo Expo | Year: 2016

For rotors supported with active magnetic bearings (AMBs), the auxiliary bearing system or backup bearing system is needed to avoid serious potential internal damaging in the event of AMB loss of power or overload. The evolution of auxiliary systems has been made a priority by the American Petroleum Institute using analytical or experimental methods. In part I of this paper, a detailed rotor drop nonlinear transient analysis method including flexible shaft, rolling element bearing components including inner/outer races and balls, as well as flexible/damped supporting structures is given. A finite element based 6-DOF flexible rotor model is used to indicate shaft motion before the drop (operating conditions) and during the rotor drop event. Un-lubricated Hertzian contact models are used between the shaft and inner/outer races, between balls and races. To avoid heavy calculating time, two different methods to calculate ball bearing contact loads are discussed and the simulation results are compared. These models are applied to predict shaft-race-ball displacements and angular speeds, contact loads and ball bearing stresses during the drop for angular contact auxiliary bearings. This method also can be used to design and optimize the auxiliary bearing system as presented in the 2nd part of this paper. © Copyright 2016 by ASME.


Cao J.,Rotor Bearing Solutions International | Allaire P.,Rotor Bearing Solutions International | Dimond T.,Rotor Bearing Solutions International | Dousti S.,Rotor Bearing Solutions International
Proceedings of the ASME Turbo Expo | Year: 2016

This paper forms Part II of the rotor drop analysis, focusing on the auxiliary bearing system design and optimization based on the rotor drop analysis methods, as introduced in Part I. Optimization focuses on shaft orbit, maximum ball bearing stress, and how to avoid possible ball bearing damage due to impact loading during rotor drop by optimizing auxiliary design including bearing selection, preload method, radial and axial damping element, and flexible bearing support. Using the detailed rotor drop model and time transient method, a variety of simulations are presented for 1) an energy storage vertical flywheel system, and 2) an 8-stage horizontal centrifugal compressor, are conducted to investigate the effects of auxiliary bearing design and to optimize the auxiliary system. Axial drops, radial drops and combination of radial/axial drops are all evaluated considering angular contact auxiliary bearing size, number of rows, preload, and flexible damped bearing supports in the axial and radial directions. The rotor drop analysis method introduced in this paper may be used as a design toolbox for the auxiliary bearing system. © Copyright 2016 by ASME.

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