Experimental Evaluation of Multiplane-Multispeed Rotor Balancing Through Multiple Critical Speeds

1976 ◽  
Vol 98 (3) ◽  
pp. 988-998 ◽  
Author(s):  
J. M. Tessarzik ◽  
R. H. Badgley ◽  
D. P. Fleming
Keyword(s):  
Experimental Tests ◽  
Influence Coefficient ◽  
Critical Speeds ◽  
Vibration Data ◽  
Vibration Sensors ◽  
Flexible Rotors ◽  
Speed Range ◽  
Full Speed ◽  
Influence Coefficient Method ◽  
Rotor Balancing

Experimental tests have been conducted to further demonstrate the ability of the Influence Coefficient Method to achieve precise balance of flexible rotors of virtually any design for operation through virtually any speed range. Four distinct practical aspects of flexible-rotor balancing were investigated in the present work: (1) Balancing for operation through multiple bending critical speeds; (2) balancing of rotors mounted in both rigid and flexible bearing supports, the latter having significantly different stiffnesses in the horizontal and vertical directions so as to cause severe ellipticity in the vibration orbits; (3) balancing of rotors with various amounts of measured vibration response information (e.g., numbers of vibration data sets, and numbers and types of vibration sensors), and with different number of correction planes; (4) balancing of rotors with different (though arbitrary) initial unbalance configurations. Tests were made on a laboratory quality machine having a 122-cm (48-in.) long rotor weighing 50 kg (110 lb) and covering a speed range up to 18,000 rpm. The balancing method was found in every instance to be effective, practical, and economical, permitting safe rotor operation over the full speed range covering four rotor bending critical speeds.

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.

Experimental Evaluation of the Exact Point-Speed and Least-Squares Procedures for Flexible Rotor Balancing by the Influence Coefficient Method

1974 ◽  
Vol 96 (2) ◽  
pp. 633-643 ◽  
Author(s):  
J. M. Tessarzik ◽  
R. H. Badgley
Keyword(s):  
Least Squares ◽  
Influence Coefficient ◽  
Critical Speeds ◽  
Flexible Rotors ◽  
Operating Region ◽  
Influence Coefficient Method ◽  
Identical Test ◽  
Slow Passage ◽  
Rotor Balancing ◽  
Exact Point

An experimental test program was conducted to extend the verified operating region of the Influence Coefficient Method’s Exact Point-Speed procedure for balancing of flexible rotating machinery. Also, the Least-Squares procedure (of which the Exact Point-Speed procedure is a particular case) was applied to several test cases which were identical to those investigated by the Exact Point-Speed procedure. A comparison of the effectiveness of both balancing procedures under identical test conditions was thus obtained. The practical aspects of balancing real, flexible rotors were investigated through inclusion of rotor out-of-roundness data at the measurement probe locations. The computer program was demonstrated to be fully capable of handling out-of-roundness data in the investigation. Testing was performed predominantly with a machine having a 41-in. (104 cm) long, 126-lb (57 kg) rotor. This rotor was operated over a speed range encompassing three rotor-bearing system critical speeds. Both balancing procedures were evaluated for several different conditions of initial rotor unbalance. Safe (and slow) passage through all the critical speeds was obtained after two or three balancing runs in most cases. The Least-Squares procedure was found to be generally equivalent in capability to the Exact Point-Speed procedure for the configurations studied.

scholarly journals Review of Rotor Balancing Methods

Machines ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 89
Author(s):  
Liqing Li ◽  
Shuqian Cao ◽  
Jing Li ◽  
Rimin Nie ◽  
Lanlan Hou
Keyword(s):  
Research Progress ◽  
Stable Operation ◽  
Influence Coefficient ◽  
Future Studies ◽  
Advantages And Disadvantages ◽  
Speed Range ◽  
Influence Coefficient Method ◽  
Rotor Balancing ◽  
Coefficient Method

This review is dedicated to balancing methods that are used to solve the rotor-balancing problem. To ensure a stable operation over an operating speed range, it is necessary to balance a rotor. The traditional methods, including the influence coefficient method (ICM) and the modal balancing method (MBM) are introduced, and the research progress, operation steps, advantages and disadvantages of these methods are elaborated. The classification of new balancing methods is reviewed. Readers are expected to obtain an overview of the research progress of existing balancing methods and the directions for future studies.

Influence Coefficients Obtained by Hammer Beat Permit Significant Time Savings When Balancing Simple Flexible Rotors

1999 ◽  
Author(s):  
D. Wiese ◽  
M. Breitwieser
Keyword(s):  
Influence Coefficient ◽  
Significant Time ◽  
Flexible Rotors ◽  
Influence Coefficients ◽  
Flexible Roll ◽  
Influence Coefficient Method ◽  
Time Savings ◽  
Positive Results ◽  
Coefficient Method

Abstract The following paper presents a method for balancing simple flexible rotors with the help of influence coefficients obtained by hammer beat. The method permits time savings of approx. 50% compared to the conventional influence coefficient method. Initial positive results obtained on a flexible roll are also presented.

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.

Stabilizing a 46 MW Multistage Utility Steam Turbine Using Integral Squeeze Film Bearing Support Dampers

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Bugra Ertas ◽  
Vaclav Cerny ◽  
Jongsoo Kim ◽  
Vaclav Polreich
Keyword(s):  
Steam Turbine ◽  
Critical Speed ◽  
Stability Margin ◽  
Experimental Tests ◽  
Turbine Rotor ◽  
Squeeze Film ◽  
Full Load ◽  
Vibration Data ◽  
Full Speed ◽  
Full Load Operation

A 46 MW 5500 rpm multistage single casing utility steam turbine experienced strong subsynchronous rotordynamic vibration of the first rotor mode; preventing full load operation of the unit. The root cause of the vibration stemmed from steam whirl forces generated at secondary sealing locations in combination with a flexible rotor-bearing system. Several attempts were made to eliminate the subsynchronous vibration by modifying bearing geometry and clearances, which came short of enabling full load operation. The following paper presents experimental tests and analytical results focused on stabilizing a 46 MW 6230 kg utility steam turbine experiencing subsynchronous rotordynamic instability. The paper advances an integral squeeze film damper (ISFD) solution, which was implemented to resolve the subsynchronous vibration and allow full load and full speed operation of the machine. The present work addresses the bearing-damper analysis, rotordynamic analysis, and experimental validation through waterfall plots, and synchronous vibration data of the steam turbine rotor. Analytical and experimental results show that using ISFD improved the stability margin by a factor of 12 eliminating the subsynchronous instability and significantly reducing critical speed amplification factors. Additionally, by using ISFD the analysis showed significant reduction in interstage clearance closures during critical speed transitions in comparison to the hard mounted tilting pad bearing configuration.

Lateral Rotordynamic Analysis of a Large Alternator/Flywheel/Motor Train

2010 ◽  
Author(s):  
Jawad Chaudhry ◽  
Tim Dimond ◽  
Amir Younan ◽  
Paul Allaire
Keyword(s):  
Critical Speed ◽  
Operating Speed ◽  
Response Level ◽  
Critical Speeds ◽  
The Third ◽  
Unbalance Response ◽  
Speed Range ◽  
Stress Levels ◽  
Full Speed ◽  
Working Day

A large alternator/flywheel/motor train is employed as part of the power system for the ALCATOR C-MOD experiment at the MIT Plasma Fusion Center. The alternator is used to provide peak pulse power of 100 MW to the magnets employed in the fusion experiment. The flywheel diameter is 3.3m and the alternator is 1.8 m in diameter. After being driven up to full speed over a long period of time by a 1491 kW motor, the alternator is rapidly decelerated from approximately 1800 rpm to 1500 rpm during a 2 second interval. This sequence is repeated about six times per working day on average. A full lateral rotordynamic analysis of the including the rotors, fluid film bearings and unbalanced motor magnetic force was carried to assess the effects of rotor modifications in the alternator shaft bore. This paper provides a more detailed analysis of a complicated rotor train than is often performed for most rotors. Critical speeds, stability and unbalance response were evaluated to determine if lateral critical speeds might exist in the operating speed range in the existing or modified rotor train and if unbalance levels were within acceptable ranges. Critical speeds and rotor damping values determined for the rotor system with the existing and modified rotor. The first critical speed at 1069 rpm is an alternator mode below the operating speed range. The second critical speed is also an alternator mode but, at 1528 rpm, is in the rundown operating speed range. The third critical speed is a flywheel mode at 1538 rpm, also in the rundown operating speed range but well damped. The predicted highest rotor amplitude unbalance response level is at 1633 rpm, again in the operating speed range. Direct comparisons were made with measured bearing temperature values, with good agreement between calculations and measurements. Stress levels in the rotor were evaluated and found to be well below yield stress levels for the material for both original and modified rotors. Comparisons we carried out between standard vibration specifications and measured vibration levels which indicated that the third critical speed amplification factors were much higher than API standards indicate they should have been. Corrective actions to reduce unbalance were taken for the modified rotor.

On the Overhung Rigid Rotor Balancing

2000 ◽  
Author(s):  
José A. Méndez-Adriani
Keyword(s):  
Efficient Technique ◽  
Influence Coefficient ◽  
Rigid Rotor ◽  
Cross Effect ◽  
Calibration Process ◽  
The Third ◽  
Influence Coefficient Method ◽  
The Cross ◽  
Rotor Balancing ◽  
Coefficient Method

Abstract This article develops a more efficient technique for the balancing of the overhung rigid rotor, which is a variation of the exact influence coefficient method, that gives directly the correction weights for both balancing planes. During the calibration process, one trial weight is used for the second run and, to reduce the cross effect, only one trial weight to form a couple is used for the third run, improving the field balancing method for maintenance works.

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.

Application of the Principle of Reciprocity to Flexible Rotor Balancing

1982 ◽  
Vol 104 (2) ◽  
pp. 329-333 ◽  
Author(s):  
M. S. Darlow ◽  
A. J. Smalley
Keyword(s):  
Numerical Study ◽  
Influence Coefficient ◽  
Theoretical Discussion ◽  
Vibration Level ◽  
Flexible Rotor ◽  
Stabilization Time ◽  
Vibration Sensors ◽  
Start Up ◽  
Desirable Feature ◽  
Rotor Balancing

The least desirable feature of most flexible rotor balancing procedures is the considerable number of trial mass runs required. This is of particular importance in the balancing of machines which require a substantial stabilization time during start-up. Using an adaptation of the principle of reciprocity, it is possible to significantly reduce the required number of trial mass runs for certain rotors when using either influence coefficient balancing or the Unified Balancing Approach. When applied to flexible rotor balancing, the principle of reciprocity states that, given two rotor axial locations, A and B (at which both balancing planes and vibration sensors are located), the influence coefficient relating the vibration level at A to the unbalance at B is identical to that relating the vibration level at B to the unbalance at A. This is true even in the presence of damping. This paper begins with a theoretical discussion of the principle of reciprocity and its application to flexible rotor balancing. The particular means by which reciprocity can be applied to improve the influence coefficient and Unified Balancing Approach procedures are then described in detail. A numerical study was conducted to verify this application of reciprocity, as well as to investigate any possible limitations. The results of this study are reported along with those of a similar experimental study using two substantially different test rotors.

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