The first part of this paper presents results of numerical simulation of the dynamic behavior of a one-lateral-mode unbalanced and radially side-loaded rotor with either a loose pedestal (looseness in a stationary joint), or with occasional rotor-to-stator rubbing. The nonlinearities of these systems (variable stiffness, impacting, and friction) are associated with the rotor intermittent contacts with the stationary element. The results, based on a newly developed local impact model [P. Goldman and A. Muszynska, Analytical and experimental simulation of loose pedestal dynamic effects on a rotating machine vibrational response, Rotating Machinery Dynamics, DE-Vol. 35, ASME, Miami, Florida, pp. 11–17 (1991); P. Goldman and A. Muszynska, Analytical model of the impact between rotating and nonrotating elements and its application in rotor-to-stator rubbing, BRDRC Report 1, (1992); P. Goldman and A. Muszynska, Chaotic behavior of rotor-to-stator systems with rubs, ASME Turbo EXPO Conference, 93-GT-34, Cincinnati, Ohio, Transactions of the ASME (to appear); P. Goldman and A. Muszynska, Dynamic effects in mechanical structures with gap and impacting: Order and chaos, Trans. of ASME, J. Vibration and Acoustics (1994)] exhibit regular periodic vibrations of synchronous (1×) and subsynchronous ( 1 2 ×, 1 3 × , …) orders, as well as chaotic vibration patterns of the rotor, all accompanied by higher harmonics. The second part of the paper presents experimental vibration characteristics of rotors with looseness or rubs, obtained from rotor rigs. The results display similar patterns as those obtained analytically.

Chaotic responses of unbalanced rotor/bearing/stator systems with looseness or rubs

This paper outlines the dynamic behavior of externally excited rotor/stator systems with occasional, partial rubbing conditions. The observed phenomenon have one major source of a strong nonlinearity: transition from no contact to contact state between mechanical elements, one of which is rotating. This results in variable stiffness and damping, impacting, and intermittent involvement of friction. A new model for such a transition (impact) is developed. In case of the contact between rotating and stationary elements, it correlates the local radial and tangential ("super ball") effects with global behavior of the system. The results of numerical simulations of a simple rotor/stator system based on that model are presented in the form of bifurcation diagrams, rotor lateral vibration time—base waves, and orbits. The vibrational behavior of the considered system is characterized by orderly harmonic and subharmonic responses, as well as by chaotic vibrations. A new result (additional subharmonic regime of vibration) is obtained for the case of heavy rub of an anisotropically supported rotor. The correspondence between numerical simulation and previously obtained experimental data supports the adequacy of the new model of impact.

Chaotic Behavior of Rotor/Stator Systems With Rubs

The thermal effects of rotor-to-stator rub, and their influence on the rotor vibrational response, are discussed in this paper. Based on machinery observations, it is assumed in the analysis that velocities of transient thermal effects are considerably lower than that of rotor vibrations, and thermal effects affect only rotor steady-state vibrational responses. These responses would change due to thermally induced bow of the rotor, which can be considered slowly varying in time for the purposes of rotor vibration calculation. Thus uncoupled from the thermal problem, the rotor vibration is analyzed. The major consideration is given to the rotor, which experiences intermittent contact with the stator due to predetermined thermal bow of the rotor, unbalance force, and radial constant load force. In the case of an inelastic impact, this causes an on/off step-change in the stiffness of the system. A specially developed transformation is applied to the system model which contains discontinuities, and an averaging technique is then used to analyze stability of the different resonance regimes of rotor motion that were obtained. These regimes are further used to calculate the heat generated during rotor-to-stator contact stages, as a function of thermal conditions and rotor thermal bow modal parameters. The calculated heat input is used as a boundary condition for the rotor heat transfer problem. The latter is treated as quasi-static, which allows the application of an asymptotic method to the problem. The solution at its first approximation is used to adjust the rotor thermal bow value. As a result of this calculation, an ordinary differential equation with complex variables is obtained for the thermal bow, and it is investigated from the stability standpoint.

/pdf/rotor-to-stator-rub-related-thermal-mechanical-effects-in-389yn4ln54.pdf

Rotor-to-stator, rub-related, thermal/mechanical effects in rotating machinery

Dynamic behavior of the full rotorstop rubbing: numerical simulation and experimental verification

Mechanism of Fast Time-Varying Vibration for Rotor–Stator Contact System: With Application to Fault Diagnosis

Results from experimental and analytical studies on rotor to stationary element partial rubbings at several locations and their effects on rotor dynamic responses are presented. The mathematical model of a rubbing rotor is given. The computer program provides numerical results which agree with experimentally obtained rotor responses.

Rotor-to-stator Partial Rubbing and Its Effects on Rotor Dynamic Response

Rotor dynamic behavior depends considerably on how much the specific physical phenomena accompanying rotor rubbing against the stator is involved The experimental results of rotor-to-stator rubbing contact are analyzed The computer code is described for obtaining numerical calculations of rotor-to-stator rubbing system dynamic responses Computer generated results are provided The reduced dynamic data from High Pressure Fuel Turbo Pump (HPFTP) hot fire test are given The results provide some significant conclusions Information is provided on the electronic instrumentation used in the experimental testing

Influence of rubbing on rotor dynamics, part 2

The results of analytical and experimental research on rotor-to-stationary element rubbing in rotating machines are presented. A characterization of physical phenomena associated with rubbing, as well as a literature survey on the subject of rub is given. The experimental results were obtained from two rubbing rotor rigs: one, which dynamically simulates the space shuttle main engine high pressure fuel turbopump (HPFTP), and the second one, much simpler, a two-mode rotor rig, designed for more generic studies on rotor-to-stator rubbing. Two areas were studied: generic rotor-to-stator rub-related dynamic phenomena affecting rotating machine behavior and applications to the space shuttle HPFTP. An outline of application of dynamic stiffness methodology for identification of rotor/bearing system modal parameters is given. The mathematical model of rotor/bearing/seal system under rub condition is given. The computer program was developed to calculate rotor responses. Compared with experimental results the computed results prove an adequacy of the model.

Influence of rubbing on rotor dynamics, part 1

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Rotor-to-stator Partial Rubbing and Its Effects on Rotor Dynamic Response

Influence of rubbing on rotor dynamics, part 2

Influence of rubbing on rotor dynamics, part 1