Modal Balancing of Quasi-Rigid Jet Engine Rotors With Exchangeable Rotor Modules

1995 ◽  
Author(s):  
Hatto Schneider
Keyword(s):  
Flexible Rotor ◽  
Index Procedure ◽  
Jet Engine ◽  
Vibration Problems ◽  
Rotor Balancing ◽  
Rigid Rotors ◽  
Engine Rotors

Abstract Flexible rotor assemblies often consist of two or more rotor modules which are index-balanced against each other with the purpose of eliminating the need for re-balancing if a module should have to be exchanged. However, the index procedure may cause vibration problems because it ignores certain flexible rotor balancing requirements. This paper describes a modal balancing approach based on jet engine rotors which are typically balanced as ISO Class 2 (quasi-rigid) rotors. Appreciation is expressed to Prof. R. Gasch of TU Berlin for his valuable suggestions.

Design of Jet Engine Rotors for Long Life

1975 ◽  
Author(s):  
S. A. Sattar ◽  
J. T. Hill
Keyword(s):  
Jet Engine ◽  
Long Life ◽  
Engine Rotors

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.

Chaos of a Flexible Rotor in Journal Bearings

1995 ◽  
Author(s):  
R. D. Brown ◽  
G. Drummond
Keyword(s):  
Theoretical Models ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
Rigid Rotor ◽  
Flexible Rotor ◽  
Hydrodynamic Bearings ◽  
Stress Reversals ◽  
Oil Films ◽  
Rigid Rotors ◽  
Rotor Model

Abstract Nonlinear systems can give rise to chaotic behaviour, essentially unpredictable. Oil film forces arising from hydrodynamic bearings in rotating machinery can be extremely nonlinear under conditions of large unbalance. Chaotic response has been demonstrated in theoretical models of rigid rotors supported in hydrodynamic bearings. The behaviour of a rigid rotor can be extended by looking at a flexible rotor model supported on journal bearings and subject to large unbalance levels. The introduction of a flexible shaft yields chaotic regions which are less extensive than those obtained from a rigid rotor model. This is not surprising as the nonlinearity in the model is confined to the oil films at the end of the shaft. However if this level of unbalance is experienced in service then shaft fatigue could occur because of the sustained nature of the non-synchronous response and the effect of the resulting stress reversals.

Improved Fabrication Methods of Jet Engine Rotors

1970 ◽  
Author(s):  
George Korton ◽  
Kenneth W. Stalker
Keyword(s):  
Jet Engine ◽  
Engine Rotors

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.

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.

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.

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.

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