Finite Element Stress Analysis of Two-Pole Turbogenerator Rotor

In the current paper the rotor (inductor) of two-pole turbogenerator is analyzed. This is the most loaded joint by mechanical and thermal loading. One of the urgent problems during design and manufacturing processes is the problem of rotor vibrations and balancing. Vibration of the two-pole rotor can be caused by several reasons. Special attention should be paid to the vibration with double rotational frequency that can be observed in general in rotors with significant l/D relation (relation of the rotor body length to its diameter). This vibration is caused by different rotor body stiffness in two main axes directions: axis of poles (axis of "big tooth") and neutral normal to the axis of poles. In order to compensate rotor body stiffness anisotropy in the current job the system of regular cross-slots in the zone of "big tooth" (Laffoon's slots or slits) is used. An integral characteristic is considered to evaluate rotor body stiffness dissymmetry: magnitude proportional to the difference of maximum static sags (located in the middle of rotor body) in the directions of principle moments of inertia. One of the most topical problems after application of such cross-slots is stress concentration at the bottom of slots. In the present paper the results of 3D multi-variant finite element (FE) structural analysis of stress concentration zones at the bottom of cross-slots under gravity and centrifugal loading are presented. Together with the results of finite element analysis analytical estimations after Neuber are quoted for stress concentration coefficients in U-like notches with arbitrary depth. Various statements of the contact problems for rotor under gravity and centrifugal loading were considered in order to analyze the effect of contact interaction consideration between various rotor parts on stressed state.

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