Vibration analysis of a misaligned rotor—coupling—bearing system passing through the critical speed

Prabhakar, S.; Sekhar, A. S.; Mohanty, A.R.

doi:10.1243/0954406011524784

Cited by 41 publications

(34 citation statements)

References 18 publications

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“…The meshing force of gear coupling has been discussed, and the misalignment forces in the y and z directions of the rotor system are expressed by Prabhakar et al (2001):…”

Section: Misalignment Faultmentioning

confidence: 99%

Dynamic characteristics analysis of a misaligned rotor-bearing system with squeeze film dampers

Zhang

Lin

et al. 2016

J. Zhejiang Univ. Sci. A

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Abstract:In this paper, a dynamic model is established for a two-stage rotor system connected by a gear coupling and supported on ball bearings with squeeze film dampers (SFDs). The nonlinear dynamic behavior of the rotor system is studied under misalignment fault condition. The meshing force of the gear coupling is calculated considering the deformation of the tooth caused by torque transmission and dynamic vibration. The contact force between the ball and race is computed based on the Hertzian elastic contact deformation theory and the elastohydrodynamic lubrication theory. The supported force of SFD is simulated by integrating the pressure distribution derived from Reynolds's equation. The equations of motion are rewritten in nondimensional differential form, and the fourth-order Runge-Kutta method is employed to solve the nonlinear dynamic equilibrium equations iteratively. To verify the validity of the dynamic model and the correctness of the numerical solution method, the experimental power spectra of the rotor system under various misalignment degrees are compared with the analytical results. The effects of several important parameters, such as the lubrication of the ball bearing, the centralizing spring stiffness, the radial clearance of SFD, and the misalignment of gear coupling, on the dynamic characteristics of the rotor system are investigated and discussed mainly focusing on the system stability. The response spectra, bifurcation diagrams, and Pointcaré maps are analyzed accordingly. These parametric analyses are very helpful in the development of a high-speed rotor system and provide a theoretical reference for the vibration control and optimal design of rotating machinery.

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“…The meshing force of gear coupling has been discussed, and the misalignment forces in the y and z directions of the rotor system are expressed by Prabhakar et al (2001):…”

Section: Misalignment Faultmentioning

confidence: 99%

Dynamic characteristics analysis of a misaligned rotor-bearing system with squeeze film dampers

Zhang

Lin

et al. 2016

J. Zhejiang Univ. Sci. A

View full text Add to dashboard Cite

show abstract

“…This additional symptom suggested to suppose that the machine failure was able to induce a shaft bending in the machine train. Also the presence of a significant 2X vibration component is a symptom of coupling misalignment [25,26,28]. Therefore, the most probable fault was a severe misalignment which affected the coupling between the generator and the steam turbine.…”

Section: Case Historymentioning

confidence: 99%

“…The fault taken into account in this paper is one of the most common in rotating machinery that present coupling between the shafts, so that handbooks are also available to perform good alignments [32]. However, literature studies are mainly devoted to theoretical analysis [25,28,30] using numerical simulation and to the validation of the theoretical assumptions on small scale test-rigs [10,18,26]. Some experimental results of coupling misalignment identification on a test-rig using wavelets are presented in [21,22].…”

Section: Introductionmentioning

confidence: 99%

Diagnosis and Model Based Identification of a Coupling Misalignment

Pennacchi

Vania

2004

Shock and Vibration

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This paper is focused on the application of two different diagnostic techniques aimed to identify the most important faults in rotating machinery as well as on the simulation and prediction of the frequency response of rotating machines. The application of the two diagnostics techniques, the orbit shape analysis and the model based identification in the frequency domain, is described by means of an experimental case study that concerns a gas turbine-generator unit of a small power plant whose rotor-train was affected by an angular misalignment in a flexible coupling, caused by a wrong machine assembling. The fault type is identified by means of the orbit shape analysis, then the equivalent bending moments, which enable the shaft experimental vibrations to be simulated, have been identified using a model based identification method. These excitations have been used to predict the machine vibrations in a large rotating speed range inside which no monitoring data were available. To the best of the authors' knowledge, this is the first case of identification of coupling misalignment and prediction of the consequent machine behaviour in an actual size rotating machinery. The successful results obtained emphasise the usefulness of integrating common condition monitoring techniques with diagnostic strategies.

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“…Ramachandran et al [14] conducted experiments to approach the misalignment using vibration, orbit, and CDT phenomenon and they found that improper alignment leads to extensive vibration and noise and the increased misalignment reduces the CDT. Prabhakar et al [15] analyzed the transient response of a misaligned rotorcoupling-bearing system passing through the critical speed using the finite element method for flexural vibrations and found that the subcritical speeds at one-half, one-third, and one-fourth of the critical speed. The mathematical model constructed for the effect of misalignment on magnetic coupling [16] derived a set of nonlinear equations for parallel misalignment effect [17] between two rotating shafts and two rotor segments with angular misalignment [18].…”

Section: Introductionmentioning

confidence: 99%

Condition Monitoring of Forward Curved Centrifugal Blower Using Coast Down Time Analysis

Rameshkumar

Rao

Ramachandran

2010

International Journal of Rotating Machinery

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Mechanical malfunctions such as, rotor unbalance and shaft misalignment are the most common causes of vibration in rotating machineries. Vibration is the most widely used parameter to monitor and asses the machine health condition. In this work, the Coast Down Time (CDT), which is an indicator of faults, is used to assess the condition of the rotating machine as a condition monitoring parameter. CDT is the total time taken by the system to dissipate the momentum acquired during sustained operation. Extensive experiments were conducted on Forward Curved Centrifugal Blower Test Rig at selected cutoff speeds for several combinations of combined horizontal and vertical parallel misalignment, combined parallel and angular misalignment, as well as for various unbalance conditions. As mechanical faults increase, a drastic decrease in CDT is found and this is represented as CDT reduction percentage. A specific correlation between the CDT reduction percentage, level of mechanical faults, and rotational cutoff speeds is observed. The results are analyzed and compared with vibration analysis for potential use of CDT as one of the condition monitoring parameter.

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Vibration analysis of a misaligned rotor—coupling—bearing system passing through the critical speed

Cited by 41 publications

References 18 publications

Dynamic characteristics analysis of a misaligned rotor-bearing system with squeeze film dampers

Dynamic characteristics analysis of a misaligned rotor-bearing system with squeeze film dampers

Diagnosis and Model Based Identification of a Coupling Misalignment

Condition Monitoring of Forward Curved Centrifugal Blower Using Coast Down Time Analysis

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