Synchronous Unbalance Response of an Overhung Rotor With Disk Skew

1979 ◽  
Author(s):  
O. J. Salamone ◽  
E. J. Gunter
Keyword(s):  
Phase Angle ◽  
Critical Speed ◽  
Rapid Phase ◽  
Single Plane ◽  
Unbalance Response ◽  
Flexible Rotors ◽  
All Speeds

This paper deals with the influence of disk skew on the synchronous unbalance of flexible rotors in damped bearings. A simple overhung rotor 1E treated to illustrate the effects of various combinations of unbalance and disk skew on the amplitude and phase angle response at the disk and bearings. The paper shows that it is impossible to balance the rotor at all speeds by single plane balancing even if three correction planes are employed. The presence of disk skew may be best detected by monitoring the far bearing for a rapid phase angle decrease after passing through the first critical speed.

Synchronous Unbalance Response of an Overhung Rotor with Disk Skew

1980 ◽  
Vol 102 (4) ◽  
pp. 749-755 ◽  
Author(s):  
D. J. Salamone ◽  
E. J. Gunter
Keyword(s):  
Phase Angle ◽  
Critical Speed ◽  
Rapid Phase ◽  
Single Plane ◽  
Unbalance Response ◽  
Flexible Rotors ◽  
All Speeds

This paper deals with the influence of disk skew on the synchronous unbalance response of flexible rotors in damped bearings. A simple overhung rotor is treated to illustrate the effects of various combinations of unbalance and disk skew on the amplitude and phase angle response at the disk and bearings. The paper shows that it is impossible to balance the rotor at all speeds by single plane balancing even if three correction planes are employed. The presence of disk skew may be best detected by monitoring the far bearing for a rapid phase angle decrease after passing through the first critical speed.

Optimum Bearing and Support Damping for Unbalance Response and Stability of Rotating Machinery

1978 ◽  
Vol 100 (1) ◽  
pp. 89-94 ◽  
Author(s):  
L. E. Barrett ◽  
E. J. Gunter ◽  
P. E. Allaire
Keyword(s):  
Approximate Method ◽  
Critical Speed ◽  
Exact Methods ◽  
Mass Model ◽  
Unbalance Response ◽  
Flexible Rotors ◽  
Bearing Stiffness ◽  
Single Mass ◽  
Internal Rotor ◽  
Stability Limits

This paper presents a rapid approximate method for calculating the optimum bearing or support damping for multimass flexible rotors to minimize unbalance response and to maximize stability in the vicinity of the rotor first critical speed. A multimass rotor is represented by an equivalent single-mass model for purposes of the analysis. The optimum bearing damping is expressed as a function of the bearing stiffness and rotor modal stiffness at the rigid bearing critical speed. Stability limits for aerodynamic cross coupling and viscous internal rotor friction damping are also presented. Comparison of the optimum damping obtained by this approximate method with that obtained by full scale linearized transfer matrix methods for several rotor-bearing configurations shows good agreement. The method has the advantage of being quickly and easily applied and can reduce analysis time by eliminating a time consuming search for the approximate optimum damping using more exact methods.

Effect of Residual Shaft Bow on Unbalance Response and Balancing of a Single Mass Flexible Rotor—Part II: Balancing

1976 ◽  
Vol 98 (2) ◽  
pp. 182-187 ◽  
Author(s):  
J. C. Nicholas ◽  
E. J. Gunter ◽  
P. E. Allaire
Keyword(s):  
Critical Speed ◽  
Direct Method ◽  
Influence Coefficient ◽  
Unbalance Response ◽  
Influence Coefficient Method ◽  
Single Mass ◽  
All Speeds ◽  
Optimum Balance ◽  
Coefficient Method ◽  
Speed Method

Three methods of balancing a rotor with a residual shaft bow were presented. Method I balanced the total shaft amplitude to zero at the balance speed. Method II balanced the elastic deflection to zero at the balance speed leaving the residual bow amplitude. Method III balanced the total shaft amplitude to zero at the critical speed without actually operating the rotor at the critical. After balancing by Method I, a large amplitude remained near the critical. Method II balanced the rotor to the residual bow amplitude at all speeds except near the critical where the amplitude is slightly larger than the residual amplitude. The optimum balance resulted from balancing by Method III. In this case, the amplitude was less than or equal to the residual bow amplitude for all speeds except at the critical where the amplitude was zero. Method III required that the critical speed be known prior to balancing. For all three balancing methods, the unbalance influence coefficient must be determined. Two procedures for determining this coefficient were discussed. One was the familiar trial weight influence coefficient method and the other was the direct method which does not require trial weights. Part I of this paper discussed the effect of shaft bow on unbalance response.

Secondary critical speed of flexible rotors with inertia slots

1983 ◽  
Vol 87 (1) ◽  
pp. 61-70 ◽  
Author(s):  
M. Sakata ◽  
M. Endo ◽  
K. Kishimoto ◽  
N. Hayashi
Keyword(s):  
Critical Speed ◽  
Flexible Rotors

Steady-State Performance of Squeeze Film Damper Supported Flexible Rotors

1977 ◽  
Vol 99 (4) ◽  
pp. 552-558 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Rolling Element Bearing ◽  
Squeeze Film ◽  
Response Curves ◽  
Flexible Rotors ◽  
Steady State Operation ◽  
Bearing Life ◽  
Rolling Element ◽  
Single Mass

The synchronous steady-state operation of a centrally preloaded single mass flexible rotor supported in squeeze film bearing dampers is examined theoretically. Assuming the short bearing approximation and symmetric motions, frequency response curves are presented exhibiting the effect of relevant system parameters on rotor excursion amplitudes and unbalance transmissibilities for both pressurized and unpressurized lubricant supply. Hence, the influence of rotor flexibility, rotor mass distribution, rotor speed, bearing dimensions, lubricant viscosity, support flexibility can be readily determined, allowing for optimal rotor bearing system design. It is shown that with pressurized bearing mounts, the possibility of undesirable operation modes is eliminated and a smooth passage through the first pin-pin critical speed of the rotor is feasible, while absence of pressurization significantly limits the maximum safe unbalance in the vicinity of this critical speed. Significant decrease in transmissibility and rotor excursion amplitudes over those obtainable with rigid mounts are shown to be a practical possibility, with consequent decrease in the vibration level of the rotor mounts and prolongation of rolling element bearing life, while maintaining acceptable rotor vibration amplitudes. A design example is included to illustrate the use of the data.

Multi Objective Optimisation of an Aero Engine Rotor System Using Nondominated Sorting Genetic Algorithm (NSGA)

2017 ◽  
Author(s):  
Joseph Shibu Kalloor ◽  
Ch. Kanna Babu ◽  
Girish K. Degaonkar ◽  
K. Shankar
Keyword(s):  
Genetic Algorithm ◽  
Critical Speed ◽  
Rotor System ◽  
Pareto Optimal ◽  
Multi Objective ◽  
Rayleigh Beam ◽  
Unbalance Response ◽  
Aero Engine ◽  
Nondominated Sorting ◽  
Engine Rotor

A comprehensive multi-objective optimisation methodology is presented and applied to a practical aero engine rotor system. A variant of Nondominated Sorting Genetic Algorithm (NSGA) is employed to simultaneously minimise the weight and unbalance response of the rotor system with restriction imposed on critical speed. Rayleigh beam is used in Finite Element Method (FEM) implemented in-house developed MATLAB code for analysis. The results of practical interest are achieved through bearing-pedestal model and eigenvalue based Rayleigh damping model. Pareto optimal solutions generated and best solution selected with the help of response surface approximation of the Pareto optimal front. The outcome of the paper is a minimum weight and minimum unbalance response rotor system which satisfied the critical speed constraints.

Effect of Higher-Than-Rated-Speed Rotordynamic Modes on Rotor Balancing

2015 ◽  
Author(s):  
John J. Yu ◽  
Siddharth Ashar
Keyword(s):  
Critical Speed ◽  
Measured Data ◽  
Vibration Response ◽  
Vibration Level ◽  
Generator Rotor ◽  
Vibration Data ◽  
Unbalance Response ◽  
Nodal Points ◽  
Rotor Balancing

It was surprisingly reported that a generator rotor could not be balanced to an acceptable vibration level by weights at two balance planes at the drive end (DE) and the non-drive end (NDE) fan rings. Both real measured vibration data and rotordynamic calculations indicate that the rotor at rated speed of 3600 rpm appears to run just above the 2nd critical speed (couple or conical mode). However, couple weights (same weights placed at both DE and NDE with 180-degree-out-of-phase) have little effect on 1X vibration response. A third balance plane had to be utilized to effectively reduce vibration. This paper uses measured data and rotordynamic modelling to explain these findings. It is found that the 4th mode could affect synchronous vibration response at rated speed significantly besides the 3rd mode. The two fan ring balance planes appear to be near the nodal points of the 4th mode, which explains ineffectiveness of the couple weights to vibration response at rated speed in the field. Measured data from real machines including influence vectors are presented from third balance planes such as the coupling and the exciter ends, besides the fan ring wheels. The 3rd and 4th rotordynamic modes are also given along with unbalance response studies.

The Mathematical Theory of the Snaking of Two-wheeled Trailers, with Practical Rules and Devices for Preventing Snaking

1951 ◽  
Vol 5 (1) ◽  
pp. 175-190 ◽  
Author(s):  
D. Williams
Keyword(s):  
General Solution ◽  
Detailed Analysis ◽  
Mathematical Analysis ◽  
Mathematical Theory ◽  
Degrees Of Freedom ◽  
Critical Speed ◽  
Elastic System ◽  
Practical Experience ◽  
Dynamical Equations ◽  
All Speeds

It is well known that a prime essential in bringing about unstable motion in any elastic system is the presence of at least two degrees of freedom. A trailer and its towing vehicle constitute a mechanical system with a number of degrees of freedom, and a main feature of the present problem is the necessity for deciding which are essential factors in the unstable motion and which are trivial or merely incidental. The idea of including all the possible degrees of freedom in the dynamical equations, thereby obtaining a general solution in which the part played by the several parameters can be seen, is quite impracticable. In Part I of the paper the results obtained from the mathematical analysis of the problem are given and discussed. There is a general agreement with practical experience. Part II contains the detailed analysis on which the conclusions in Part I are based. It is emphasized that the main purpose of the analysis is not to enable calculations to be made of the precise critical speed at which snaking begins for any particular combination of tractor and trailer, but to discover what factors make for stability and for instability, and how to design for immunity from snaking at all speeds.

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