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Handbook of Turbomachinery Second Edition Revised - Ventech!

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Figure 2 Rotor system displacements.<br />

equations <strong>of</strong> motion are then developed and analyzed by either the direct<br />

stiffness or transfer matrix method, Ehrich [6]. Classical linear analysis<br />

techniques apply for those systems where the nonlinear mechanisms are<br />

weak and linear modeling assumptions are acceptable. Fortunately, this<br />

condition exists in many practical applications. Linear system response<br />

analyses may be conducted using established classical techniques, and<br />

several commercial numerical and/or symbolic computer s<strong>of</strong>tware packages<br />

are available for conducting these analyses. The analysis <strong>of</strong> strongly<br />

nonlinear systems, however, is more limited in terms <strong>of</strong> currently available<br />

mathematical s<strong>of</strong>tware. Direct numerical integration <strong>of</strong> the nonlinear<br />

equations <strong>of</strong> motion is presently the most widely used technique for<br />

simulating the behavior <strong>of</strong> nonlinear rotor systems.<br />

The present literature on the subject <strong>of</strong> rotordynamics consists <strong>of</strong><br />

several books and a wealth <strong>of</strong> technical manuscripts in mechanics,<br />

mechanical engineering, and aerospace engineering technical transactions.<br />

Several <strong>of</strong> these works are included in the References. A list <strong>of</strong><br />

rotordynamics books is contained in the bibliography <strong>of</strong> the vibrations<br />

text by Dimaragonas [4].<br />

Steady-State Rotor Motion<br />

The motion <strong>of</strong> a rotor system is most conveniently described in a fixed<br />

(inertial) Cartesian ðx, y, zÞ-coordinate system as illustrated in Fig. 2. One <strong>of</strong><br />

the coordinate axes, say the z-axis, is selected along the axis <strong>of</strong> the shaft and<br />

the x- and y-axes form a plane perpendicular to the shaft. The origin <strong>of</strong> the<br />

Copyright © 2003 Marcel Dekker, Inc.

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