Theoretical–experimental study on a rotor with a residual shaft bow

Guo

Transactions of the Canadian Society for Mechanical Engineering

2016

Bearing is the key component in rotating machine. It is important to assess the performance degradation degree of bearings for making proactive maintenance and realizing near-zero downtime. A methodology based on orthogonal local preserving projection (OLPP) and continuous hidden Markov model (CHMM) is introduced in bearing performance degradation assessment. Firstly, the time domain, frequency domain and time-frequency domain features are extracted from the vibration signals. Then, the multi-dimensional features are reduced by OLPP. And the selection of the adjacent paragraph parameters in OLPP is optimized adaptively by minimizing the ratio of between-class distance to within-class distance. A CHMM is trained by using the reduced feature in normal condition. At last, the test bearing data are input into the pre-trained CHMM to calculate the log-likelihood of the test data, which can assess the performance degradation of bearings quantitatively. A bearing accelerated life experiment is performed to validate the feasibility and validity of the proposed method.

“…The normal data (1 to 300 group) are adopted to calculate the CHMM parameters in Eq. (13). Then, the full life time testing data are input into CHMM.…”

Section: Results and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bearing Performance Degradation Assessment by Orthogonal Local Preserving Projection and Continuous Hidden Markov Model

Guo

Transactions of the Canadian Society for Mechanical Engineering

2016

International Journal of Rotating Machinery

“…Pang and Yang [27] studied the coupled vibration responses caused by load changes of one support to the other supports in a multisupport rotor-bearing system. Song et al [28] studied the effects of various torque loads on the bending characteristics of rotor systems, taking into account the impact of bearing loads. Sun et al [29] studied the law of axis changes of rotor systems subjected to abrupt torque loads, considering the effects of torque loads on bearing loads.…”

Section: Introductionmentioning

confidence: 99%

Investigation on Lubrication State of Sliding Bearings in Low-Speed Rotor System Subjected to Torque Load

Pang

Jiang

Jin

2019

In order to study the influence of torque load on the lubrication and wear of the sliding bearing of the rigid rotor system, the theoretical and experimental researches on the single-span rotor system with low speed were carried out. A special force sensor was used to measure the bearing load under different torque excitations, and the oil film pressure was calculated. The oil film pressure and thickness of sliding bearing under low speed (210r/min) were simulated by combining the lubrication theory. Based on the film thickness ratio theory, the corresponding relationship between the lubrication state and the torque load value was deduced. In addition, the wear rate and abrasive grain morphology of sliding bearing with different torque values were analyzed by means of oil sample preparation to verify this correspondence. The results show that the film thickness ratio has a logarithmic function relationship with the constant torque load, and the film thickness ratio curve can be used to determine the corresponding torque values under different lubrication states. The wear rate under mixed lubrication state increases exponentially with the torque load, and the main wear mechanism is adhesive wear and abrasive wear. The research results have certain guiding significance to the adjustment of the actual running condition of sliding bearing and its life prediction.

“…Nicholas et al [18] carried out a systematic study on the effect of the residual shaft bow on unbalance response of a single mass flexible rotor. Song et al [19] presented a theoretical-experimental study on the dynamic response of a rotor with the residual shaft bow. The results indicated that the residual shaft bow can obviously affect the rotor vibration as the eccentricity and the damping ratio are relatively small.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Coupled Dynamics of a Rod Fastening Rotor under Rub-Impact and Initial Permanent Deflection

Teng

et al. 2016

Energies

Abstract:A nonlinear coupled dynamic model of a rod fastening rotor under rub-impact and initial permanent deflection was developed in this paper. The governing motion equation was derived by the D'Alembert principle considering the contact characteristic between disks, nonlinear oil-film force, rub-impact force, unbalance mass, etc. The contact effects between disks was modeled as a flexural spring with cubical nonlinear stiffness. The coupled nonlinear dynamic phenomena of the rub-impact rod fastening rotor bearing system with initial permanent deflection were investigated by the fourth-order Runge-Kutta method. Bifurcation diagram, vibration waveform, frequency spectrum, shaft orbit and Poincaré map are used to illustrate the rich diversity of the system response with complicated dynamics. The studies indicate that the coupled dynamic responses of the rod fastening rotor bearing system under rub-impact and initial permanent deflection exhibit a rich nonlinear dynamic diversity, synchronous periodic-1 motion, multiple periodic motion, quasi-periodic motion and chaotic motion can be observed under certain conditions. Larger radial stiffness of the stator will simplify the system motion and make the oil whirl weaker or even disappear at a certain rotating speed. With the increase of initial permanent deflection length, the instability speed of the system gradually rises, and the chaotic motion region gets smaller and smaller. The corresponding results can provide guidance for the fault diagnosis of a rub-impact rod fastening rotor with initial permanent deflection and contribute to the further understanding of the nonlinear dynamic characteristics of the rod fastening rotor bearing system.