An Experimental Investigation on the Misalignment Effects in Journal Bearings
TL;DR: In this paper, the experimental performance of misaligned cylindrical and three-lobe journal bearings was evaluated using a double-disc rotor system with a test bearing in the middle and driven by a variable speed DC motor through an electromagnetic coupling.
Abstract: In this paper an investigation is made to evaluate the experimental performance of misaligned cylindrical and three-lobe journal bearings. A three-bearing double-disc rotor system with a test bearing in the middle and driven by a variable speed DC motor through an electromagnetic coupling is used. Various parameters which have been studied are friction through coastdown analysis, unbalance response and film thickness. The system damping also has been evaluated. The film thickness decreases, friction increases and system damping increases as the bearing misalignment increases. While the first, third and fourth harmonics vibration response is found to be almost steady with a increasing degree of misalignment, the second harmonics vibration response tends to decrease slightly. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996
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TL;DR: In this article, the effect of parallel misalignment on the lateral and torsional responses of two rotating shafts (Jeffcott rotors) is examined with theoretical and numerical analysis.
131 citations
TL;DR: Major emphasis is given to vibration-based identification methods and the review encompasses descriptions of experimental measurement techniques, mathematical modeling, parameter extraction algorithms and uncertainty in the estimates applied to a variety of bearings.
Abstract: In this paper, we present a review of the experimental identification of dynamic parameters of bearings in a rotating machine. Major emphasis is given to vibration-based identification methods and the review encompasses descriptions of experimental measurement techniques, mathematical modeling, parameter extraction algorithms and uncertainty in the estimates applied to a variety of bearings. The parameter extraction algorithms include the descriptions of governing equations of the rotor-bearing system and identification methods in both time and frequency domains. The identification techniques have been classified based on methods used to excite the system. The review includes a variety of bearings and similar components, which play an active link between the rotating and stationary parts of a machine. Based on the state of the art in bearing identification, conclusions are made and future directions are suggested.
127 citations
Cites background from "An Experimental Investigation on th..."
...(frequency) Damping, stiffness and uncertainty Prabhu (1997) HDJ Sinusoidal Displ....
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...Prabhu (1997) obtained, experimentally, the effect of misalignment on direct damping coefficients for cylindrical and three-lobed journal bearings....
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TL;DR: In this paper, the performance of a 100 mm diameter plain journal bearing submitted to a misalignment torque was evaluated for rotational speeds ranging from 1500 to 4000 rpm with a maximum static load of 9000 N and a misaligned torque varying from 0 to 70 N.
Abstract: The present study deals with the experimental determination of the performance of a 100 mm diameter plain journal bearing submitted to a misalignment torque. Hydrodynamic pressure and temperature fields in the mid-plane of the bearing, temperatures in two axial directions, oil flow rate, and minimum film thickness, were all measured for various operating conditions and misalignment torques. Tests were carried out for rotational speeds ranging from 1500 to 4000 rpm with a maximum static load of 9000 N and a misalignment torque varying from 0 to 70 N.m. The bearing performances were greatly affected by the misalignment. The maximum pressure in the mid-plane decreased by 20 percent for the largest misalignment torque while the minimum film thickness was reduced by 80 percent. The misalignment caused more significant changes in bearing performance when the rotational speed or load was low. The hydrodynamic effects were then relatively small and the bearing offered less resistance to the misalignment.
115 citations
TL;DR: In this article, a finite element model is used for the hyperstatic shaft-line, while bearing characteristics are calculated by integrating Reynolds equation as a function of the instantaneous load acting on the bearings, caused also by the coupling misalignment.
55 citations
Cites result from "An Experimental Investigation on th..."
...A similar case was analyzed by Prabhu [6] that highlighted the effects of relative misalignment, between the journal and the bearing, on film thickness, friction and damping and found out superharmonics vibration response in the shaft....
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...Sekhar A.S., Prabhu B.S. (1995) Effects of coupling misalignment on vibrations of rotating machinery....
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...Prabhu B.S. (1997) An experimental investigation on the misalignment effects in journal bearings....
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...Also Sekhar and Prabhu [11] considered flexible coupling, used Gibbons’ theoretical model [12] and performed some simulations in which 2X components were evident....
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TL;DR: In this paper, the authors inspect the different types of misalignments by using diagnostic medium such as stator current signature as well as rotor vibration signal and it is being found that current signature alone can predict the misalignment effect without use of vibration signal.
Abstract: Misalignment is one of the most common faults in any rotating machine. It can cause decrease in efficiency and in the long run may cause failure of machine. Most of the researchers, consider only vibration information for the misalignment. However, this paper inspects the different types of misalignments by using diagnostic medium such as stator current signature as well as rotor vibration signal and it is being found that current signature alone can predict the misalignment effect without use of vibration signal. Diagnostic features obtained by FFT related to misalignments have been explained. Orbit plots are effectively used to explain the unique nature of misalignment fault. In this study, shaft displacement and stator current samples during machine run up under aligned as well as misaligned conditions are measured and analyzed. Result shows that misalignment is the parameter that is more responsible for the cause of instability.
41 citations
Cites background from "An Experimental Investigation on th..."
...An experimental investigation on the misalignment effect on cylindrical and three-lobe journal bearings was conducted by Prabhu [6]....
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References
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Book•
01 Jan 1965
TL;DR: In this paper, a new chapter on computational methods that present the basic principles on which most modern computer programs are developed is presented, which introduces an example on rotor balancing and expands on the section on shock spectrum and isolation.
Abstract: This edition features a new chapter on computational methods that presents the basic principles on which most modern computer programs are developed It introduces an example on rotor balancing and expands on the section on shock spectrum and isolation
2,196 citations
TL;DR: A modified version of the Elrod cavitation algorithm, which automatically predicts film rupture and reformation in bearings, is used to analyze a misaligned grooved journal bearing as mentioned in this paper, and the predicted performance of the misaligned bearing is compared with available experimental and theoretical results.
61 citations
52 citations
TL;DR: In this article, it was shown that bearing coefficients are entirely subject to test conditions, meaning not only sensor accuracy but also where in an orbit data is taken, and that stiffness coefficients had about an order of magnitude less uncertainty in their evaluation than damping coefficients.
Abstract: The goal of many experimental studies of fluid film bearings is the determination of the eight linearized stiffness and damping coefficients. These coefficients cannot be measured directly; they are derived from a series of other measurements. In many cases, the coefficients are found by applying known steady-state sinusoidal loads to excite a journal on a rigid rotor and measuring the resulting displacement, velocity, and acceleration orbits. This paper relates how uncertainties in these measurements affect the accuracy of the derived coefficients. The analysis can also be used for the proper selection of test procedures and transducers to measure the primary variables and estimate results beforehand. For an example case, it was found that bearing coefficients are entirely subject to test conditions, meaning not only sensor accuracy but where in an orbit data is taken. Stiffness coefficients had about an order of magnitude less uncertainty in their evaluation (∼3 percent) than the damping coefficients (∼...
41 citations
39 citations