Vibration of asymmetric rotor supported by oil film bearings
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Rigid rotor
Magnetic bearing
Suspension
Rigid rotor
Electromagnetic suspension
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Semiclassical physics
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Planar dynamics of a rotor supported by long hydrodynamic journal bearing is investigated theoretically. An analytical model of the long journal bearing system is numerically integrated for analysis of fixed point and periodic oscillations. The nonlinearities in the system arise due to a nonlinear fluid film force acting on the journal. The influences of three dimensionless parameters, viz. bearing parameter, unbalance, and rotor speed, on the dynamic behavior of the rotor bearing system is studied and compared with the short journal bearing. For the same bearing parameter, short bearing has large operating speed compared to a long bearing. The results are presented in the form of a bifurcation diagram and Poincaré map of the oscillations based on numerical computation. The considered unbalanced system shows periodic, multiperiodic, and quasi-periodic motion in different speed range. Jumping phenomenon is also observed for a high value of bearing parameter with unbalance.
Dimensionless quantity
Rigid rotor
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This paper proposes a fixed-angle rotor design for a vacuum chamber-free ultracentrifuge using a rigid shaft and magnetic bearings. The rotor is designed for a stable operation in the ultracentrifugation region with air friction. And the optimal design parameters and optimized connection method of the rotor and rigid shaft are proposed. The proposed rotor structure can withstand a maximum rotation speed of 100 000 rpm and achieves a maximum relative centrifugal force of 600 000 g. To verify the performance of the proposed rotor design with a rigid shaft, finite-element analysis, an impact test, and a drive operating experiment were conducted.
Centrifugal force
Magnetic bearing
Rigid rotor
Optimal design
Vacuum chamber
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Dynamics
Magnetic bearing
Helicopter rotor
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This paper treats dynamic and static features of a sliding circular bearing with tapered grooves on its upper and lower sides. This bearing is called a tapered pressure-dam bearing in the present paper and designed in order to reduce lubricant pressure at high rotational speed. The preceding features of the bearing are analyzed by numerically solving the Reynolds equation and a heatconduction equation, considering the change of the ludricant temperature. The results show the designed bearing has a smaller value of cross-coupled stiffness coefficients when it is compared with a full circular bearing. Moreover, a Jeffcott rotor is used to investigate the stability characteristics of the bearing, and some design paremeters of the bearing are numerically determined to achieve good stability at high rotational speed. A comparison of the stability with a full circular bearing shows the proposed bearing possesses a better stability feature for a higher frequency region.
Rigid rotor
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It is experimentally observed and studied the phenomena of stability loss of rotor rotation in tilting pad bearings of different designs. The trends of changing by stability limiting rotational speed of rotor depending on its unbalance and type of journal bearing are obtained. The results of spectral analysis and phase paths of rotor motion are presented, features of rotor dynamics in range of unstable rotational speed are analyzed. The methods of building and identification of discrete non-linear mathematical models of rotor are developed, permitting to analyze polyharmonic vibrations.
Rigid rotor
Critical speed
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Higher-order semiclassical phase integral methods are applied to the determination of rigid asymmetric rotor eigenlevels from the eigenvalues of Lamé’s equation. The method yields accurate eigenvalues for moderate J, J larger than ten, but is especially valuable for very large J because the accuracy of the method improves with increasing J with practically no increase in the computational cost per eigenlevel.
Semiclassical physics
Rigid rotor
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Magnetic bearing
Rigid rotor
Rotordynamics
Helicopter rotor
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