One Explanation for Two-Times Running Speed Response Due to Misalignment in Rotors Connected by Flexible Couplings

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Raul D. Avendano ◽  
Dara W. Childs
Keyword(s):  
System Response ◽  
Unit Load ◽  
Running Speed ◽  
Angular Misalignment ◽  
Related Factors ◽  
Static Tests ◽  
Side Load ◽  
Fixed Direction ◽  
Parallel Misalignment ◽  
Reaction Component

Misalignment in turbomachinery is commonly thought to produce two-times running-speed (2N) response. The source of 2N vibration response was investigated, starting with the development of finite-element models for three flexible disk-pack couplings (four-bolt, six-bolt, and eight-bolt couplings). Parallel and angular misalignments were analyzed. The resultant lateral stiffness terms had 1N, 2N, and 3N harmonic components versus the shaft rotation angle. The four-bolt coupling had large 1N stiffness components under angular and parallel misalignment. The six-bolt coupling had only a 1N reaction component under angular misalignment, while parallel misalignment showed a strong 2N reaction component, larger than either the 1N or 3N components. Under angular misalignment, the eight-bolt model produced large 1N reaction components. Under parallel misalignment, it produced 1N, 2N, and 3N components that were similar in magnitude. All the couplings behaved linearly in the range studied. Some experts attribute observed 2N response to nonlinear bearing forces produced by bearings at high unit loads. Static tests for a five-pad tilting-pad journal bearing with unit loads up to 34.5 bars produced small 2N motion components that did not grow with increasing unit load. A Jeffcott-rotor model with shaft stiffness orthotropy and a fixed-direction side load predicts that 2N response depends on three related factors: (1) the degree of orthotropy (the 1N stiffness variation magnitude), (2) the magnitude of the side load, and (3) the relative ratio of running speed to rotor first natural frequency, (ω/ωn). The 2N response magnitude is largest when ω is close to ωn/2. The side load is required to create 2N response due to shaft stiffness orthotropy. Misaligned couplings create precisely the same (very old) physical model as a two-pole turbogenerator rotor with a gravity side load (gravity critical speed). The response of a two-rotor/coupling system with parallel and angular misalignment was simulated using a time-transient code. When the frequency ratio was 0.5, the system response with the four-bolt and six-bolt coupling had a synchronous 1N component as well as a significant 2N component. Parallel misalignment at a coupling produces stiffness orthotropy and a fixed-direction side load. For ranges of running speed near ωn/2, these two elements can combine to produce 2N response.

One Explanation for 2N Response due to Misalignment in Rotors Connected by Flexible Couplings

2012 ◽  
Author(s):  
Raul D. Avendano ◽  
Dara W. Childs
Keyword(s):  
System Response ◽  
Unit Load ◽  
Running Speed ◽  
Angular Misalignment ◽  
Related Factors ◽  
Static Tests ◽  
Side Load ◽  
Fixed Direction ◽  
Parallel Misalignment ◽  
Reaction Component

Misalignment in turbomachinery is commonly thought to produce two-times-running-speed (2N) response. The source of 2N vibration response was investigated, starting with the development of finite-element models for three flexible disc-pack couplings (4-bolt, 6-bolt, and 8-bolt couplings). Parallel and angular misalignments were analyzed. The resultant lateral stiffness terms had 1N, 2N, and 3N harmonic components versus the shaft rotation angle. The 4-bolt coupling had large 1N stiffness components under angular and parallel misalignment. The 6-bolt coupling had only a 1N reaction component under angular misalignment, while parallel misalignment showed a strong 2N reaction component, larger than either the 1N or 3N components. Under angular misalignment, the 8-bolt model produced large 1N reaction components. Under parallel misalignment, it produced 1N, 2N, and 3N components that were similar in magnitude. All the couplings behaved linearly in the range studied. Some experts attribute observed 2N response to nonlinear bearing forces produced by bearings at high unit loads. Static tests for a 5-pad tilting-pad journal bearing with unit loads up to 34.5bars produced small 2N motion components that did not grow with increasing unit load. A Jeffcott-rotor model with shaft stiffness orthotropy and a fixed-direction side load predicts that 2N response depends on three related factors: (1) the degree of orthotropy (the 1N stiffness variation magnitude), (2) the magnitude of the side load, and (3) the relative ratio of running speed to rotor 1st natural frequency, (ω/ωn). The 2N response magnitude is largest when ω is close to ωn/2. The side load is required to create 2N response due to shaft stiffness orthotropy. Misaligned couplings create precisely the same (very old) physical model as a two-pole turbogenerator rotor with a gravity side load (gravity critical speed). The response of a 2-rotor/coupling system with parallel and angular misalignment was simulated using a time-transient code. When the frequency ratio was 0.5, the system response with the 4-bolt and 6-bolt coupling had a synchronous 1N component as well as a significant 2N component. Parallel misalignment at a coupling produces stiffness orthotropy and a fixed-direction side load. For ranges of running speed near ωn/2, these two elements can combine to produce 2N response.

Analysis of the Effects of Parallel and Angular Misalignment in Hyperstatic Rotors Equipped With Oil-Film Bearings

2011 ◽  
Author(s):  
P. Pennacchi ◽  
A. Vania ◽  
S. Chatterton
Keyword(s):  
Reynolds Equation ◽  
Nonlinear Effects ◽  
Element Model ◽  
System Response ◽  
Angular Misalignment ◽  
Oil Film ◽  
Rotating Machine ◽  
Parallel Misalignment ◽  
Spectral Components ◽  
The Time Domain

Misalignment is one of the most common sources of trouble of rotating machinery having couplings between the shafts. Ideal alignment is a chimera and the coupling flanges of the shafts are never ideally aligned, presenting angular and/or parallel misalignment (defined also as radial misalignment or offset). In particular, during the shaft rotation, if coupling misalignment between the shafts of a statically aligned line is excessive, a periodical change, of the load on the bearings in hyperstatic shaft-lines, occurs. If the rotating machine is equipped with oil-film bearings, the change of the loads on the bearings causes also the variation of their oil-film dynamic characteristics, i.e. damping and stiffness, and the complete system cannot be considered as linear. In the paper, this phenomenon is modelled accurately and analyzed by considering the simulated response of a misaligned rotor train in the time domain. A finite element model is used for the hyperstatic rotor, while bearing characteristics are calculated by integrating Reynolds equation (considering the actual type and dimensions of the bearings) as a function of the instantaneous load acting on the bearings, caused by the coupling misalignment. Nonlinear effects are highlighted and the spectral components of system response are analyzed, in order to give pertinent diagnostic information.

scholarly journals Analisis Ketidaksesumbuan Poros (Misalignment) pada Rotordinamik Berdasarkan Sinyal Suara

2021 ◽  
Vol 12 (2) ◽  
pp. 487-495
Author(s):  
Dedi Suryadi ◽  
◽  
M Reza Febriyanto ◽  
Fitrilina Fitrilina
Keyword(s):  
Rotor Dynamics ◽  
Sound Signal ◽  
Peak Amplitude ◽  
Test Results ◽  
Motor Shaft ◽  
Angular Misalignment ◽  
Parallel Misalignment ◽  
Spectrum Characteristic ◽  
The Time Domain ◽  
Sound Spectrum

This research aims to identify misalignment of the rotor dynamics based on sound spectrum characteristic. In this study, rotor dynamics consist of motor, shaft, coupling and bearings. Three types of misalignment were considered, namely parallel, angular, and combination misalignment. In order to obtain the best signal, microphones were used as sensors to capture sound signal placed on coupling and each bearing. The signal obtained was in time series. The sound signal in the time domain is then filtered to remove noise signals, which are then transferred to be signals in the frequency domain using Fast Fourier Transform (FFT). From the test results, it is found that in the case of parallel misalignment, the sound frequency spectrum is obtained with a peak amplitude at 2x rpm. The case of angular misalignment obtained a sound spectrum with a peak amplitude value and is dominant at 1x rpm than 2x rpm. Meanwhile, in the case of a combination of parallel and angular misalignment, a peak amplitude sound spectrum appears at 1x rpm and 2x rpm with relatively close spacing between the peaks of the sound spectrum. The result shows that sound signal can be used for identification of misalignment of the rotor dynamics.

scholarly journals MISALIGNMENT DISTANCE ANALYSIS OF VIBRATION AND NOISE VALUE

2020 ◽  
Vol 5 (2) ◽  
pp. 75-94
Author(s):  
Fathur Rahman Hidayat ◽  
Mastiadi Tamjidillah
Keyword(s):  
Angular Misalignment ◽  
Distance Analysis ◽  
Parallel Misalignment

Penelitian ini bertujuan untuk mengetahui nilai vibrasi yang terjadi pada saat misalignment 0,1, 0,2, 0,3, 0,4, dan 0,5 mm dan mengetahui nilai noise yang terjadi pada saat misalignment 0,1, 0,2, 0,3, 0,4, dan 0,5 mm. Variasi yang digunkan adalah parallel misalignment, angular misalignement dan combination misalignment dengan jarak misalignment 0,1, 0,2, 0,3, 0,4, dan 0,5 mm. Hasil penelitian menunjukkan untuk parallel misalignment vibrasi dan noise tertinggi terjadi pada saat parallel misalignment 0,5 posisi pengujian horizontal sebesar 8,97 mm/s overall velocity,   65,43 µm overall displacement, noise maximum 8 dB dan carpet -6 dB, sedangkan untuk angular misalignment vibrasi dan noise tertinggi terjadi pada saat angular misalignment 0,5 posisi pengujian axial sebesar 10,95 mm/s overall velocity, 76,95 µm overall displacement, noise maximum 5 dB carpet -11 dB dan untuk combination misalignment vibrasi dan noise tertinggi terjadi pada saat combination misalignment 0,5 posisi pengujian axial sebesar 16,33 mm/s overall velocity, 100,95 µm overall displacement noise maximum 13 dB dan carpet 3 dB.

A novel health indicator developed using filter-based feature selection algorithm for the identification of rotor defects

2020 ◽  
pp. 1748006X2091695 ◽  
Author(s):  
Anil Kumar ◽  
CP Gandhi ◽  
Xiaoyang Liu ◽  
Yi Liu ◽  
Yuqing Zhou ◽  
...  
Keyword(s):  
Feature Selection ◽  
Selection Process ◽  
Signal Frequency ◽  
Health Indicator ◽  
Angular Misalignment ◽  
Time Frequency ◽  
Vibration Data ◽  
Time Domain Signal ◽  
Frequency Representation ◽  
Parallel Misalignment

In this work, a novel health indicator is developed for the identification of rotor defects. The indicator is developed by extracting features from vibration data acquired from horizontal and vertical directions of rotors. A total of 38 features were initially extracted from time-domain signal, frequency-domain signal, and time–frequency representation. Out of many features, six most important features were selected using filter-based feature selection process. Thereafter, important features were fused together using manifold learning to develop health indicator. The developed indicator is used to identify misalignments (angular misalignment and parallel misalignment), rub, and unbalance. The major benefit of the proposed method is that it not only indicates the presence of defect in the rotor but also indicates the severity of defect. The experimental study presented in this article justifies that the proposed method is sensitive to the increasing levels of horizontal and angular misalignment and unbalance. The developed indicator is sensitive enough to indicate the presence of rub.

scholarly journals Dynamic Response of a Rotating Assembly under the Coupled Effects of Misalignment and Imbalance

2020 ◽  
Vol 2020 ◽  
pp. 1-26
Author(s):  
Mohamed Desouki ◽  
Sadok Sassi ◽  
Jamil Renno ◽  
Samer Abdelazim Gowid
Keyword(s):  
Numerical Model ◽  
Rotational Speed ◽  
Rotating Machinery ◽  
Angular Misalignment ◽  
Simultaneous Effect ◽  
Frequency Responses ◽  
Parallel Misalignment ◽  
Misalignment Fault ◽  
Coupling Type ◽  
Bearing System

In rotating machinery, the second most common fault after imbalance is misalignment. Misalignment can have a severe impact on equipment and may reduce the machine’s lifetime considerably. In this paper, the simultaneous effect of imbalance and misalignment (parallel or angular) on the vibration spectra of rotating machinery will be discussed. A numerical model is developed and used to obtain the time and frequency responses of the rotor-coupling-bearing system to the simultaneous effect of these faults. The numerical model shows that the imbalance was mainly related to the peak located around 1X, whereas misalignment was linked to the peak around 2X. In addition, the parallel misalignment fault magnifies the 2X amplitude of the displacement response, whereas the response of angular misalignment is captured at the 2X and 4X amplitudes. This study also examines the effects of changing the model’s rotational speed, misalignment level, and coupling type for angular and parallel misalignments.

Testing Aircraft to Destruction

1922 ◽  
Vol 26 (138) ◽  
pp. 195-230
Author(s):  
WM. D. Douglas
Keyword(s):  
Flight Test ◽  
Strength Test ◽  
General Description ◽  
Horizontal Force ◽  
Static Tests ◽  
Side Load ◽  
Historical Outline ◽  
Strength Tests ◽  
Loading Methods ◽  
Test Loading

Necessity for strength tests to supplement calculations and to check the assumptions on which the calculations are based. Historical outline. Examples of certain types of defect which are revealed by strength, test.Assumed aerodynamic conditions. Approximations reproduced by test loading. Methods of support during test. Measurements, testing routine and technique.The usual tests are described:—Flight test, C P . forward; Flight test, C P . back; Nose dive test; Tests of auxiliary and controlling surfaces; Ailerons, elevators and rudder; Tailplane and fins; Fuselage, down load, side load, torsion ; Undercarriage, discussion of stresses which may arise during landing, pointing out presence of frictional horizontal force causing rotational acceleration of the wheels; Static tests of undercarriages, dropping tests; General description of rib tests.Description of shot bags and general principles of load application with a view to efficiency and safety.

Numerical Modeling of Copper Tube Extrusion: Process and Eccentricity Analysis

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Luigi De Pari ◽  
Wojciech Z. Misiolek
Keyword(s):  
Software Package ◽  
Severe Case ◽  
Extrusion Process ◽  
Processing Conditions ◽  
State Variables ◽  
Angular Misalignment ◽  
Tube Extrusion ◽  
Parallel Misalignment ◽  
The Impact ◽  
The Given

In order to simulate copper extrusion more closely to industrial practices and to analyze the roots of the complicated issue of tube eccentricity, the material properties and the extrusion conditions were simulated using the finite element modeling (fem) software package, DEFORMTM-3D. This allowed prediction of stress, strain, strain rate, and temperature conditions within the billet during various processing conditions. These state variables were considered when ascertaining the influence of degree of billet upset and tool misalignment on tube eccentricity. It was found that under ideal upset conditions and perfect tool alignment, the tube eccentricity was minimized. If the piercer (or mandrel) was aligned with an initial angular or parallel misalignment that was still within tolerance the impact on eccentricity initially is minor in comparison to the eccentricity produced toward the end of extrusion, with the angular misalignment scenario being the more severe case. As a result, an angular misalignment is more detrimental than a parallel misalignment for tube preform eccentricity with the given forming parameters.

scholarly journals Dynamic analysis of coupling misalignment and unbalance coupled faults

2019 ◽  
Vol 38 (2) ◽  
pp. 363-376 ◽  
Author(s):  
Haifei Wang ◽  
Junjie Gong
Keyword(s):  
Degrees Of Freedom ◽  
Vertical Displacement ◽  
Rotor System ◽  
Vertical Force ◽  
Angular Misalignment ◽  
Response Characteristics ◽  
Parallel Misalignment ◽  
Vertical Displacements ◽  
Periodic Impulse ◽  
The Moment

Misalignment is a common fault occurring in the rotor system. However, the response characteristics have not been understood comprehensively, especially the relation between forces or torques and displacements, accelerations, or moments. First, misalignment modeling is investigated in this paper. Two coupled rotor system is modeled by six degrees of freedom. Misalignment effects are considered at coupling location using nodal force vectors and moment vectors. Second, Newmark- β method is used to solve the nonlinear equations. Acceleration, displacement, and force or moment response characteristics are discussed. Some results are obtained as follows: (1) 2× will appear in the parallel misalignment forces spectrum, and 0× will appear in the vertical force spectrum; 2×, 4×, 6× will appear in the angular misalignment moment spectrum. (2) In parallel misalignment simulation, it is found that multifrequency components are more obvious, static components are showed in vertical forces and displacements, 1× is dominated and 2× is weak in the displacement spectrum, and 2× is obvious in the force spectrum; acceleration is periodic impulse signal and 1× and 2× are dominated in its spectrum; vertical displacement is truncated and its values are positive, the orbit looks like an inverted triangle. (3) In angular misalignment simulation, it is found that multifrequency components of response are more obvious, 2× is obvious in the vertical displacement spectrum, and 2× is dominated in the moment spectrum; acceleration is periodic impulse signal, horizontal and vertical displacements are periodic, the orbit looks like a moon or an eight shape, and 2× is obvious in the moment spectrum.

scholarly journals Gammaherpesvirus Alters Alveolar Macrophages According to the Host Genetic Background and Promotes Beneficial Inflammatory Control over Pneumovirus Infection

Viruses ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 98
Author(s):  
Gautier Gilliaux ◽  
Daniel Desmecht
Keyword(s):  
Alveolar Macrophages ◽  
Genetic Background ◽  
Wide Spectrum ◽  
Lethal Dose ◽  
System Response ◽  
Dependent Manner ◽  
Related Factors ◽  
Acute Interstitial Pneumonia ◽  
Innate Immunity Cells ◽  
Syncytial Virus

Human respiratory syncytial virus (hRSV) infection brings a wide spectrum of clinical outcomes, from a mild cold to severe bronchiolitis or even acute interstitial pneumonia. Among the known factors influencing this clinical diversity, genetic background has often been mentioned. In parallel, recent evidence has also pointed out that an early infectious experience affects heterologous infections severity. Here, we analyzed the importance of these two host-related factors in shaping the immune response in pneumoviral disease. We show that a prior gammaherpesvirus infection improves, in a genetic background-dependent manner, the immune system response against a subsequent lethal dose of pneumovirus primary infection notably by inducing a systematic expansion of the CD8+ bystander cell pool and by modifying the resident alveolar macrophages (AMs) phenotype to induce immediate cyto/chemokinic responses upon pneumovirus exposure, thereby drastically attenuating the host inflammatory response without affecting viral replication. Moreover, we show that these AMs present similar rapid and increased production of neutrophil chemokines both in front of pneumoviral or bacterial challenge, confirming recent studies attributing a critical antibacterial role of primed AMs. These results corroborate other recent studies suggesting that the innate immunity cells are themselves capable of memory, a capacity hitherto reserved for acquired immunity.

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