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catalogue:
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Rotor machines
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topic:
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Backward precession during horizontal rotor's movement.
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author:
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Phd Eng. J.Zachwieja
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summary:
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In this work a model of rotor rotating in bearings characterized by transverse anisotropy stiffness has been analyzed. Displacement path of the rotor's center of mass which is affected by forced rotation with the rotor revolutions frequency is an ellipse whose semi-axes reach the highest dimension for resonance frequencies in horizontal and vertical directions.
For definite periodicities of the exciting force, movement trajectories assume a shape of a straight line or a circle. For rotation periodicity lying between two resonance periodicities the rotor precession is of backward character. Thus, it should be noted that for forced periodicity changes occurring during the rotor starting or its stopping , the precession is concurrent with the rotation direction. In practice the rotor resonance frequencies in the horizontal and vertical directions are very similar, thus, the concurrent precession occurs in a narrow range of revolutions frequencies and it might be even not noticed. A machine working frequency should not occur in the area between resonance frequencies.
During examining the movement of a stiff rotor supported by bearings characterized by distinct anisotropic susceptibility in the conditions of disk unbalance the expected shape of the movement trajectory was achieved for different revolutions frequencies. However, no rotor's backward precession was observed in the conditions in which it should have occurred. This observation encouraged the author to consider the probability of occurrence of such a movement under the influence of damping.
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file:
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