Frequency-swept rotating input perturbation techniques and identification of the fluid force models in rotor/bearing/seal systems and fluid handling machines
TL;DR: In this paper, a comparison between two periodic frequency-swept perturbation methods applied in identification of fluid forces of rotating machines is presented, based on the existence and strength of the circumferential flow most often generated by the shaft rotation.
About: This article is published in Journal of Sound and Vibration.The article was published on 1990-11-22. It has received 94 citations till now. The article focuses on the topics: Rotating unbalance & Turbomachinery.
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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 or methods from "Frequency-swept rotating input pert..."
...(time) Damping and stiffness Muszynska and Bently (1990) HDJ Sine sweep Displ....
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...Muszynska (1986,1998) and Muszynska and Bently (1990) advocated two perturbation techniques (calibrated displacement or force) for non-synchronous single-mode testing used for the identification of a fluid force model in rotorbearing systems....
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...For fluid-film bearings where the dynamic characteristics change for the reverse direction of rotation of the rotor an external auxiliary means of excitation described by Muszynska and Bently (1990) can be used....
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TL;DR: In this paper, the Hopf bifurcation behavior of a symmetric rotor/seal system was investigated using Muszynska's non-linear seal fluid dynamic force model.
64 citations
TL;DR: In this article, an identification algorithm for bearing dynamic characterization by using unbalance response measurements is developed for multi-degree-of-freedom (m.d.o.f.) flexible rotor-bearing systems.
62 citations
Additional excerpts
...Muszynska and Bently [10] developed a perturbation technique (two frequency swept periodic inputs) for estimation of these parameters....
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TL;DR: In this paper, a nonlinear model of rotor/bearing/seal system based on the Hamilton principle was proposed for steam turbine systems in power plants, where the Musznyska model and unsteady bearing oil-film force model were applied to describe the nonlinear steam excitation force and oilfilm force.
51 citations
TL;DR: In this article, an efficient and high-precision direct integration scheme based on the 2 N type algorithm for the computation of exponential matrices is presented for the rotor-seal system.
44 citations
References
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TL;DR: In this paper, a mathematical model of an unloaded symmetric rotor supported by one rigid and one fluid lubricated bearing is proposed, where the rotor model is represented by generalized (modal) parameters of its first bending mode.
270 citations
TL;DR: In this article, the effect of squeeze action on the annular clearance spaces of the leakage path of a single mass rotor was analyzed. But the effect on the acceleration of the bearing and journal surfaces was not considered.
Abstract: In centrifugal pumps, the annular clearance spaces of the leakage path, i.e. impeller seals and balance piston seals, act as powerful hydrostatic bearings with turbulent flow. In the present discussion, the dynamic forces due to these bearings acting on the rotor are analysed, including the effect of squeeze action, i.e. the effect of velocities of separation or approach of the bearing and journal surfaces.Synchronous forced whirling is analysed in a simple idealization comprising a single mass rotor, including the estimation of amplitudes as well as critical speeds. Large damping forces due to squeeze action are found, in qualitative agreement with experimental work by Marcinkowskij and Karincev (3)†. A simplified treatment of the effects of fluid rotation is included in the analysis of rotor vibrations, leading to an analysis of high speed whip instability onset.
120 citations
TL;DR: In this paper, the rotordynamic coefficients for seven honeycomb seals were analyzed and compared with the labyrinth and smooth annular annular sealed cells, and the results showed that the honeycomb seal had the best sealing performance.
Abstract: Test results are presented for leakage and rotordynamic coefficients for seven honeycomb seals. All seals have the same radius, length, and clearance; however, the cell depths and diameters are varied. Rotordynamic data, which are presented, consist of the direct and cross-coupled stiffness coefficients and the direct damping coefficients. The rotordynamic-coefficient data show a considerable sensitivity to changes in cell dimensions; however, no clear trends are identifiable. Comparisons of test data for the honeycomb seals with labyrinth and smooth annular seals show the honeycomb seal had the best sealing (minimum leakage) performance, followed in order by the labyrinth and smooth seals. For prerotated fluid entering the seal, in the direction of shaft rotation, the honeycomb seal has the best rotordynamic stability followed in order by the labyrinth and smooth. For no prerotation, or fluid prerotation against shaft rotation, the labyrinth seal has the best rotordynamic stability followed in order by the smooth and honeycomb seals.
81 citations
TL;DR: In this paper, a numerical model based on a transformed, conservative form of the three dimensional Navier-Stokes equation and an analytical model based upon lumped fluid parameters are presented and compared with studies of modeled rotor bearing seal systems.
Abstract: A numerical model based on a transformed, conservative form of the three dimensional Navier-Stokes equation and an analytical model based on lumped fluid parameters are presented and compared with studies of modeled rotor bearing seal systems. The rotor destabilizing factors are related to the rotative character of the flow field. It is shown that these destabilizing factors can be reduced through a decrease in the fluid average circumferential velocity. However, the rotative character of the flow field is a complex three dimensional system with bifurcated secondary flow patterns that significantly alter the fluid circumferential velocity. By transforming the Navier-Stokes equations to those for a rotating observer and using the numerical code PHOENICS-84 with a nonorthogonal body fitted grid, several numerical experiments were carried out to demonstrate the character of this complex flow field. In general, fluid injection and/or preswirl of the flow field opposing the shaft rotation significantly intensified these secondary recirculation zones and thus reduced the average circumferential velocity; injection or preswirl in the direction of rotation significantly weakened these zones.
71 citations