Jørgen W. Lund: Theories Versus Tests, Part 1: Balancing and Response of Flexible Rotors

2003 ◽  
Vol 125 (4) ◽  
pp. 482-488 ◽  
Author(s):  
Jørgen Tonnesen
Keyword(s):  
Experimental Work ◽  
Journal Bearing ◽  
Rotor Dynamics ◽  
Flexible Rotor ◽  
Late Professor ◽  
Fluid Film Bearings ◽  
Condensed Form ◽  
Flexible Rotors ◽  
The Subject ◽  
Rotor Balancing

The contribution of the late Professor Jørgen W. Lund in the field of rotor dynamics and fluid film bearings is presented in a condensed form with the emphasis on the experimental work and results that confirm and support many of Dr. Lund’s theories and analyses. Part 1(A) covers the subject of rotor balancing by the influence method and Part 1(B) the unbalance response of a flexible rotor. In Part 2(A), experiments on instability and the influence of unbalance on whirl frequency are discussed for two rotors supported in cylindrical bearings. In Part 2(B), experiments using a cylindrical, two-axial groove journal bearing over a range of loads and speeds are reviewed.

Jorgen W. Lund: Theories Versus Tests

2001 ◽  
Author(s):  
Jorgen Tonnesen
Keyword(s):  
Thermal Properties ◽  
Experimental Work ◽  
Rotor Dynamics ◽  
Fluid Film ◽  
Flexible Rotor ◽  
Late Professor ◽  
Fluid Film Bearings ◽  
Condensed Form ◽  
Flexible Rotors ◽  
Rotor Balancing

Abstract The contribution of the late Professor Jorgen W. Lund in the field of rotor dynamics and fluid film bearings is presented in a condensed form with the emphasis on the experimental work and results that confirm and support many of Dr. Lund’s theories and analyses. Included are subjects of rotor balancing by the influence method, unbalance response of a flexible rotor, damped critical speeds of flexible rotors and fluid film bearing’s static, dynamic and thermal properties.

Nonlinear Dynamics of Flexible Rotors Supported on Journal Bearings—Part I: Analytical Bearing Model

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Mohammad Miraskari ◽  
Farzad Hemmati ◽  
Mohamed S. Gadala
Keyword(s):  
Journal Bearing ◽  
Nonlinear Coefficient ◽  
Journal Bearings ◽  
Flexible Rotor ◽  
Dynamic Coefficients ◽  
Flexible Rotors ◽  
Rotor Bearing ◽  
Bearing Force ◽  
Derivatives Of ◽  
Bearing System

To determine the bifurcation types in a rotor-bearing system, it is required to find higher order derivatives of the bearing forces with respect to journal velocity and position. As closed-form expressions for journal bearing force are not generally available, Hopf bifurcation studies of rotor-bearing systems have been limited to simple geometries and cavitation models. To solve this problem, an alternative nonlinear coefficient-based method for representing the bearing force is presented in this study. A flexible rotor-bearing system is presented for which bearing force is modeled with linear and nonlinear dynamic coefficients. The proposed nonlinear coefficient-based model was found to be successful in predicting the bifurcation types of the system as well as predicting the system dynamics and trajectories at spin speeds below and above the threshold speed of instability.

Demonstration of a Unified Approach to the Balancing of Flexible Rotors

1981 ◽  
Vol 103 (1) ◽  
pp. 101-107 ◽  
Author(s):  
M. S. Darlow ◽  
A. J. Smalley ◽  
A. G. Parkinson
Keyword(s):  
Power Transmission ◽  
Substantial Reduction ◽  
Influence Coefficient ◽  
Flexible Rotor ◽  
Unified Approach ◽  
Test Rig ◽  
Multiple Mode ◽  
Flexible Rotors ◽  
Transmission Shaft ◽  
Rotor Balancing

A flexible rotor balancing procedure, which incorporates the advantages and eliminates the disadvantages of the modal and influence coefficient procedures, has been developed and implemented. This new procedure, referred to as the Unified Balancing Approach, has been demonstrated on a supercritical power transmission shaft test rig. The test rig was successfully balanced through four flexural critical speeds with a substantial reduction in effort as compared with the effort required in modal and influence coefficient balancing procedures. A brief discussion of the Unified Balancing Approach and its relationship to the modal and influence coefficient methods is presented. A series of tests which were performed to evaluate the effectiveness of various balancing techniques are described. The results of the Unified Balancing Approach tests are presented and discussed. These results confirm the superiority of this balancing procedure for the supercritical shaft test rig in particular and for multiple-mode balancing in general.

Flexible rotor balancing without trial runs using experimentally tuned FE based rotor model

2021 ◽  
Vol 21 (1) ◽  
pp. 20-26
Author(s):  
Yahya Muhammed Ameen ◽  
Jaafar Khalaf Ali
Keyword(s):  
Mode Shapes ◽  
Influence Coefficient ◽  
Flexible Rotor ◽  
Rotating Disks ◽  
Finite Elements Analysis ◽  
Response Data ◽  
Flexible Rotors ◽  
Low Efficiency ◽  
Rotor Balancing ◽  
Rotor Model

A method based on experimentally calibrated rotor model is proposed in this work for unbalance identification of flexible rotors without trial runs. Influence coefficient balancing method especially when applied to flexible rotors is disadvantaged by its low efficiency and lengthy procedure, whilst the proposed method has the advantage of being efficient, applicable to multi-operating spin speeds and do not need trial runs. An accurate model for the rotor and its supports based on rotordynamics and finite elements analysis combined with experimental modal analysis, is produced to identify the unbalance distribution on the rotor. To create digital model of the rotor, frequency response functions (FRFs) are determined from excitation and response data, and then modal parameters (natural frequencies and mode shapes) are extracted and compared with experimental analogies. Unbalance response is measured traditionally on rotor supports, in this work the response measured from rotating disks instead. The obtained results show that the proposed approach provides an effective alternative in rotor balancing. Increasing the number of balancing disks on balancing quality is investigated as well.

Separation Cavitation in Lightly Loaded Fluid Film Bearings with Both Surfaces in Motion

1974 ◽  
Vol 16 (3) ◽  
pp. 147-155 ◽  
Author(s):  
C. M. Taylor
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Experimental Work ◽  
Journal Bearing ◽  
Fluid Film ◽  
Operating Parameters ◽  
Separation Boundary ◽  
Fluid Film Bearings ◽  
Theoretical Predictions ◽  
Bounding Surfaces

For lightly loaded fluid film bearings in which gaseous cavitation occurs, application of the continuity boundary condition at the liquid-gas interface is not satisfactory. Two alternative boundary conditions have been postulated. The purpose of this paper is to examine the separation boundary condition; in particular, the effect of both bounding surfaces being in motion is studied. This situation might be used as a basis for experimental work designed to select the most appropriate boundary condition for lightly loaded bearings. In Part 2, the boundary condition is used to analyse the cylinder-plane and journal bearing configurations. The theoretical predictions for the operating parameters are examined to see if their magnitudes and/or trends could be used for comparing the available cavitation boundary conditions.

scholarly journals An Introduction to a Unified Approach to Flexible Rotor Balancing

1979 ◽  
Author(s):  
A. G. Parkinson ◽  
M. S. Darlow ◽  
A. J. Smalley ◽  
R. H. Badgley
Keyword(s):  
Theoretical Basis ◽  
Flexible Rotor ◽  
Unified Approach ◽  
Test Program ◽  
Theoretical Terms ◽  
Joint Project ◽  
Modal Characteristics ◽  
Influence Coefficients ◽  
The Subject ◽  
Rotor Balancing

Several successful methods for balancing flexible rotating shells have been developed in recent years. The methods can apparently be subdivided into a group which is based on modal characteristics and another set which employs influence coefficients. The relative merits of these two approaches have been the subject of much discussion and argument — most of it inconclusive and rather fruitless. The authors consider that in practice many of the differences are more apparent than real and that they seem to occur because the various techniques are normally presented in relatively simple and ideal, theoretical terms. This paper represents the start of a joint project which hopes to resolve the apparent differences and, eventually, develop a unified approach to such balancing. A discussion of the theoretical basis for this unified approach is presented along with a description of a test program conducted to explore the possibilities of such an approach.

scholarly journals In Situ Balancing of Flexible Rotors Using Influence Coefficient Balancing and the Unified Balancing Approach

1983 ◽  
Author(s):  
Mark S. Darlow
Keyword(s):  
Subsequent Development ◽  
Commercial Application ◽  
Influence Coefficient ◽  
Production Operation ◽  
Steam Turbines ◽  
Flexible Rotor ◽  
Large Computer ◽  
Flexible Rotors ◽  
Rotor Balancing

A number of sophisticated procedures for balancing flexible rotors have been developed during the past two decades. For a variety of reasons, none of these methods has gained general acceptance by practicing balancing engineers. Several of these balancing techniques require a great deal of operator insight and expertise. This has tended to discourage many potential users where this expertise was not already available in-house, particularly where balancing is required as a production operation. In other cases (for example large steam turbines), the machinery owner has had to rely on the manufacturer to provide this balancing expertise when it is needed often resulting in excessive downtime and maintenance costs. Other balancing methods have been developed which are more systematic so as to reduce the level of expertise required of the user. Unfortunately, these methods have invariably required the collection of large quantities of data and very complex computations. Thus, originally, this data was taken by hand and transcribed for input to a large computer. The results of the balancing calculations were returned some time later for use by the balancing engineer. Such an operation was clearly not conducive to effective commercial application. With the development of minicomputers, the situation was alleviated to a certain extent through the use of more accessible, and even on-line computers to perform these calculations. However even with these minicomputers, in-place flexible rotor balancing facilities were expensive and inconvenient to assemble, and in situ balancing of flexible rotors was impractical if not impossible. The subsequent development of the microcomputer has made in situ balancing of flexible rotors a possibility. This paper describes a completely portable, microcomputer-based flexible rotor balancing system that uses influence coefficient balancing and the Unified Balancing Approach two of the systematic methods which have been shown to be very effective for balancing flexible rotors. The results of a series of verification tests are also presented.

A Linear Programming Approach for Balancing Flexible Rotors

1976 ◽  
Vol 98 (3) ◽  
pp. 1030-1035 ◽  
Author(s):  
R. M. Little ◽  
W. D. Pilkey
Keyword(s):  
Linear Programming ◽  
Objective Function ◽  
Computer Code ◽  
Programming Approach ◽  
Flexible Rotor ◽  
New Approach ◽  
Linear Programming Approach ◽  
Flexible Rotors ◽  
Rotor Balancing ◽  
Rotor Model

The feasibility of a new flexible rotor balancing method is demonstrated. Discrete “effective” unbalance components which produce the same observed response as the actual rotor unbalance are identified, and subsequently removed, using linear programming. In addition to satisfying rotor runout observations, the unbalance may be identified such that it is potentially harmful to response at a speed above the level at which the shaft can safely run without balancing. The potentially harmful response corresponds to the linear programming objective function, while the observations become constraints. In addition, further constraints can be included to assure that the size of the calculated balance weights are within practical limits. The versatility of the new approach is demonstrated with example problems using a rotor model for which the response is obtained with a computer code.

Flexible Rotor Balancing by the Exact Point-Speed Influence Coefficient Method

1972 ◽  
Vol 94 (1) ◽  
pp. 148-158 ◽  
Author(s):  
J. M. Tessarzik ◽  
R. H. Badgley ◽  
W. J. Anderson
Keyword(s):  
Influence Coefficient ◽  
Flexible Rotor ◽  
Critical Speeds ◽  
Angle Measurements ◽  
Flexible Rotors ◽  
Speed Range ◽  
Influence Coefficient Method ◽  
Rotor Balancing ◽  
Exact Point ◽  
Coefficient Method

A test program was conducted to confirm experimentally the validity of the exact point-speed influence coefficient method for balancing rotating machinery, and to assess the practical aspects of applying the method to flexible rotors. Testing was performed with a machine having a 41-in. long, 126-lb rotor. The rotor was operated over a speed range encompassing three rotor-bearing system critical speeds: two “rigid-body” criticals and one flexural critical. Rotor damping at the flexural critical was very low due to the journal bearings being located at the nodal points of the shaft. The balancing method was evaluated for three different conditions of initial rotor unbalance. The method was found to be effective and practical. Safe passage through all the critical speeds was obtained after a reasonable number of balancing runs. Success of the balancing method was, in large part, due to the accuracy of the instrumentation system used to obtain phase-angle measurements during the balancing procedure.

scholarly journals A New Method for Field-Balancing of High-Speed Flexible Rotors without Trial Weights

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Y. A. Khulief ◽  
M. A. Mohiuddin ◽  
M. El-Gebeily
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
High Speed ◽  
Flexible Rotor ◽  
Analytical Technique ◽  
Flexible Rotors ◽  
Physical Insight ◽  
Benchmark Solutions ◽  
Rotor Balancing ◽  
Insight Into

Flexible rotor balancing, in general, relies to a great extent on physical insight into the modal nature of the unbalance response. The objective of this investigation is to develop a hybrid experimental/analytical technique for balancing high-speed flexible rotors. The developed technique adopts an approach that combines the finite element modeling, experimental modal analysis, vibration measurements, and mathematical identification. The modal imbalances are identified and then transformed to the nodal space, in order to determine a set of physical balancing masses at some selected correction planes. The developed method does not rely on trial runs. In addition, the method does not require operating the supercritical rotor in a high-speed balancing facility, while accounting for the contribution of higher significant modes. The developed scheme is applied to a multidisk, multibearing, high-speed flexible rotor, where the interaction between the rotor-bending operating deflections and the forces resulting from the residual unbalance are appreciable. Some new benchmark solutions and observations are reported. The applicability, reliability, and challenges that may be encountered in field applications are addressed.

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