Torsional vibration analysis of a propulsive shafting system using enhanced Holzer method

• Main Authors: Wu, Hui-Tsai, 吳輝在
• Other Authors: Wu, Jia-Jang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/48848363594035719623

碩士 === 國立高雄海洋科技大學 === 輪機工程研究所 === 94 === In the existing literature, the conventional Holzer method was usually used for calculating the natural frequencies and mode shapes of a shaft-rotor system with mass moment of inertia of the shaft neglected. In fact, the shaft possesses mass moment of inertia, therefore, the numerical results obtained from the conventional Holzer method will agree with the torsional vibration characteristics of the practical shaft-rotor system only if the mass moment of inertia of the shaft is negligible. To improve the last drawback, this paper presents the enhanced Holzer method such that the mass moment of inertia of the shaft can be considered in the torsional vibration analysis. Firstly, the entire shaft is divided into multiple shaft elements and then the last element is replaced by an equivalent shaft-rotor element with mass moment of inertia of the shaft neglected. Where the torsional spring constant of the shaft element and that of the equivalent shaft-rotor element is exactly the same and the mass moment of inertia of the shaft element is replaced by that of the rotor of the equivalent shaft-rotor element. Assembly of the torsional spring constant and mass moment of inertia of each equivalent shaft-rotor element and the mass moment of inertia of each rotor yields the mathematical model of the entire shaft-rotor system. Finally, the natural frequencies and mode shapes of the shaft-rotor system can be determined by using the procedures similar with those of the conventional Holzer method. For validation, all the numerical results obtained from the enhanced Holzer method are compared with those obtained from the finite element method and good agreement is achieved. Because the expressions for the presented enhanced Holzer method are much easier than those of the finite element method, the presented technique will be meaningful from this point of view.