TORSIONAL VIBRATION ANALYSIS FOR ROTODYNAMIC MACHINES : A COMPREHENSIVE APPROACH

Abstract

Torsional vibration poses significant risks for users of turbomachinery, as it can lead to severe damage to shafts, gear teeth, or couplings. Early detection of these failures is challenging, highlighting the importance of a thorough torsional vibration analysis in turbomachinery design. This paper reviews practical design approaches to ensure systems can effectively address torsional vibration issues. While identifying natural frequencies is usually feasible, accurately predicting torsional vibration problems based on this information is challenging. This paper focuses on post-natural frequency analysis steps, briefly discussing methods like Holzer's method for determining natural frequencies and mode shapes, with detailed treatments available in existing literature. The paper then explores the creation of interference or Campbell diagrams, emphasizing the need to understand excitation frequencies from sources like gears, vaned impellers, and electric motors. Unique challenges related to synchronous motor-driven systems are also addressed. Once interference points are identified, users have two options: modify designs to eliminate interferences or subject the points to further analysis. The paper recommends analyzing all interference points before considering costly design changes. It suggests methods, such as examining mode shapes or torque vs. speed curves, to eliminate non-critical interference points. For remaining points, a damped forced vibration analysis is recommended, with guidelines provided for various machinery classes. Practical solutions are proposed for identified problem areas. Finally, key analysis procedures applicable to most turbomachinery systems are discussed, highlighting their practical applications.