Agnes Muszynska

Bio: Agnes Muszynska is an academic researcher from Dynamics Research Corporation. The author has contributed to research in topics: Rotor (electric) & Bearing (mechanical). The author has an hindex of 14, co-authored 35 publications receiving 1050 citations.

Parameter Identification With Noncollocation of Force and Measurement Locations Using Nonsynchronous Perturbation and Optimization Techniques

Abstract: Nonsynchronous perturbation techniques developed over the last few years have proven to be a very powerful tool for parameter identification of rotating systems. In order to obtain interpretable results, some limitations have had to be imposed on the analytical models and rotor systems used in the process, such as applied forces, and measurement transducers had to be located near major masses on the rotor. In the laboratory environment these limitations can usually be accommodated, but not always, while in the field, compliance is almost impossible. This paper explores the use of finite element modeling, measured vibration response data, and optimization techniques to extend the applicability of parameter identification through nonsynchronous perturbation techniques to those systems in which the perturbation forces and/or resultant response measurements cannot be conveniently located at the mass centers. In this technique, a finite element model of the rotor system is constructed, and all known information about the system parameters input to a computer program designed to operate on a personal computer. The program then computes the theoretical response of the system, by processing user-supplied initial conditions for the unknown system parameters, and compares these results with the vibration responses measured on the machine, and collected by the data acquisition system. The unknown parameters are then modified using local convergence optimization techniques until the error between the theoretical and measured responses is acceptably small. If the system parameters under investigation coincide with the unknown parameters in the computer program, they are identified in the process.This technique was applied to an experimental rotor system constructed such that the parameters under investigation, the direct and quadrature dynamic stiffness components for a plain oil-lubricated journal bearing operating at low eccentricity, could be determined by both this technique and conventional unbalance force testing. The results of the nonsynchronous tests are presented in the paper.© 1994 ASME

Stability and Instability of a Two-Mode Rotor Supported by Two Fluid-Lubricated Bearings

Abstract: This paper is a continuation of the series of papers on application of the improved fluid force model for lightly loaded shafts rotating in a fluid environment. The fluid force model is based on the strength of the circumferential flow. The considered two–mode rotor is supported in two fluid–lubricated bearings, thus it contains two potential sources of instability. The eigenvalue solution predicts thresholds of stability and provide natural frequencies and modes of the system, including the flow–induced modes The nonlinear model of the rotor/bearing system allows for evaluation of parameters of after instability onset self–excited vibrations (whirl and whip). Experimental data illustrate the dynamic phenomena predicted by the model. In particular, they show an undocumented new phenomenon, the simultaneous existence of two whip vibrations with frequencies corresponding to two modes of the rotor. A radial preload of the rotor results in specific changes of the fluid forces (an increase of radial stiffness and reduction of circumferential velocity) providing better stability of the rotor. This effect predicted by the model is illustrated by the experimental data.Copyright © 1991 by ASME

Influence of rubbing on rotor dynamics, part 2

Abstract: Rotor dynamic behavior depends considerably on how much the specific physical phenomena accompanying rotor rubbing against the stator is involved The experimental results of rotor-to-stator rubbing contact are analyzed The computer code is described for obtaining numerical calculations of rotor-to-stator rubbing system dynamic responses Computer generated results are provided The reduced dynamic data from High Pressure Fuel Turbo Pump (HPFTP) hot fire test are given The results provide some significant conclusions Information is provided on the electronic instrumentation used in the experimental testing

Stability and Instability of a Two-Mode Rotor Supported by Two Fluid-Lubricated Bearings

Abstract: This paper is a continuation of the series of papers on application of the improved fluid force model for lightly loaded shafts rotating in a fluid environment. The fluid force model is based on the strength of the cir- cumferential flow. The considered two—mode rotor is supported in two fluid—lubricated bearings, thus it contains two potential sources of instabi- lity. The eigenvalue solution predicts thresholds of stability and provide natural frequencies and modes of the system, including the flow—induced modes The nonlinear model of the rotor/bearing system allows for evalua- tion of parameters of after instability onset self—excited vibrations (whirl and whip). Experimental data illustrate the dynamic phenomena predict- ed by the model. In particular, they show an undocumented new phe- nomenon, the simultaneous existence of two whip vibrations with frequen- cies corresponding to two modes of the rotor. A radial preload of the rotor results in specific changes of the fluid forces (an increase of radial stiffness and reduction of circumferential velocity) providing better stability of the rotor. This effect predicted by the model is illustrated by the experimental data.

Applications of Sweep Frequency Rotating Force Perturbation Methodology in Rotating Machinery for Dynamic Stiffness Identification

Abstract: This paper outlines the sweep frequency rotating force perturbation method for identifying the dynamic stiffness characteristics of rotor/bearing/seal systems. Emphasis is placed on nonsynchronous perturbation of rotating shafts in a sequence of constant rotative speeds. In particular, results of the identification of flexible rotor multi–mode parameters and identification of fluid forces in seals and bearings are given. These results, presented in the direct and quadrature dynamic stiffness formats, permit the separation of components for easy identification. Another example of the perturbation method application is the identification of the lateral–torsional coupling due to shaft anisotropy. Results of laboratory rig experiments, the identification algorithm, and data processing techniques are discussed.Copyright © 1992 by ASME

Dynamics of rotating machines

Abstract: This book equips the reader to understand every important aspect of the dynamics of rotating machines. Will the vibration be large? What influences machine stability? How can the vibration be reduced? Which sorts of rotor vibration are the worst? The book develops this understanding initially using extremely simple models for each phenomenon, in which (at most) four equations capture the behavior. More detailed models are then developed based on finite element analysis, to enable the accurate simulation of the relevant phenomena for real machines. Analysis software (in MATLAB) is associated with this book, and novices to rotordynamics can expect to make good predictions of critical speeds and rotating mode shapes within days. The book is structured more as a learning guide than as a reference tome and provides readers with more than 100 worked examples and more than 100 problems and solutions.

Stick-Slip Whirl Interaction in Drillstring Dynamics

Abstract: A Stick-slip Whirl Model is presented which is a simplification of an oilwell drillstring confined in a borehole with drilling fluid. The disappearance of stick-slip vibration when whirl vibration appears is explained by bifurcation theory. The numerical results are compared with the experimental data from a full-scale drilling rig.

Rotating Machinery Vibration: From Analysis to Troubleshooting

Abstract: Part I: Primer on Rotor Vibration Vibration Concepts and Methods One-Degree-of-Freedom Model Multi-DOF Models Modes, Excitation, and Stability of Multi-DOF Models Lateral Rotor Vibration Analysis Models Simple Linear Models Formulations for RDA Software Insights into Linear LRVs Nonlinear Effects in Rotor Dynamical Systems Torsional Rotor Vibration Analysis Models Rotor-Based Spinning Reference Frames Single Uncoupled Rotor Coupled Rotors Semidefinite Systems Part II: Rotor Dynamic Analyses RDA Code for Lateral Rotor Vibration Analyses Unbalance Steady-State Response Computations Instability Self-Excited-Vibration Threshold Computations Additional Sample Problems Bearing and Seal Rotor Dynamics Liquid-Lubricated Fluid-Film Journal Bearings Experiments to Measure Dynamic Coefficients Annular Seals Rolling Contact Bearings Squeeze-Film Dampers Magnetic Bearings Compliance Surface Foil Gas Bearings Turbo-Machinery Impeller and Blade Effects Centrifugal Pumps Centrifugal Compressors High-Pressure Steam Turbines and Gas Turbines Axial Flow Compressors Part III Monitoring and Diagnostics Rotor Vibration Measurement and Acquisition Introduction to Monitoring and Diagnostics Measured Vibration Signals and Associated Sensors Vibration Data Acquisition Signal Conditioning Vibration Severity Guidelines Casing and Bearing Cap Vibration Displacement Guidelines Standards, Guidelines, and Acceptance Criteria Shaft Displacement Criteria Signal Analysis and Identification of Vibration Causes Vibration Trending and Baselines FFT Spectrum Rotor Orbit Trajectories Bode, Polar, and Spectrum Cascade Plots Wavelet Analysis Tools Chaos Analysis Tools Symptoms and Identification of Vibration Causes Part IV Trouble-Shooting Case Studies Forced Vibration and Critical Speed Case Studies HP Steam Turbine Passage through First Critical Speed HP-IP Turbine Second Critical Speed through Power Cycling Boiler Feed Pumps: Critical Speeds at Operating Speed Nuclear Feed Water Pump Cyclic Thermal Rotor Bow Power Plant Boiler Circulating Pumps Nuclear Plant Cooling Tower Circulating Pump Resonance Generator Exciter Collector Shaft Critical Speeds Self-Excited Rotor Vibration Case Studies Swirl Brakes Cure Steam Whirl in a 1300 MW Unit Bearing Unloaded by Nozzle Forces Allows Steam Whirl Misalignment Causes Oil Whip/Steam Whirl "Duet" Additional Rotor Vibration Cases and Topics Vertical Rotor Machines Vector Turning from Synchronously Modulated Rubs Air Preheater Drive Structural Resonances Aircraft Auxiliary Power Unit Commutator Vibration-Caused Uneven Wear Impact Tests for Vibration Problem Diagnoses Bearing Looseness Effects Tilting-Pad versus Fixed-Surface Journal Bearings Base-Motion Excitations from Earthquake and Shock Parametric Excitation: Nonaxisymmetric Shaft Stiffness Rotor Balancing Index

Cracked shaft detection and diagnostics: A literature review

Abstract: Cracks in shafts have long been identified as factors limiting the safe and reliable operation of turbomachines. They can sometimes result in catastrophic failure of equipment (rotor bursts) and, more often, in costly process upsets, repairs and premature scrapping and replacement of equipment. Cracked shafts still pose a significant and real threat to equipment in spite of the great advances made in the areas of metallurgy, manufacturing and design. In the past two decades, much research and many resources have gone into developing various on-line and off-line diagnostic techniques to effectively detect cracks before they cause serious damage. Because of the enormous amount of ongoing research in this area (more than 500 technical papers have been published in English alone in the past 30 years), there is a real need to periodically condense and summarize the information. This paper reviews literature on cracked shaft detection and diagnostics published after 1990.