Vibration analysis of cantilever shaft-disk system for transient response to impact jet

Abstract

Engineering systems such as water turbines, different types of compressors and similar rotodynamic applications are instances of shaft and disk assembly. Representation of such systems with shaft-disk assembly can be convenient to understand their dynamic response. Startup transient is considered as a critical operation in hydraulic turbines. In this work, vibration response is analyzed for transient loadings on a cantilever shaft-disk assembly to understand behavior exhibited by applications such as an overhung Pelton turbine. Mathematical model is obtained for the cantilever shaft and disk assembly. Water jet force due to impact during the starting and shutting down of a turbine unit is used as the transient excitation force. The response representing the vibration due to the impact force is derived from the governing equations of motion obtained using the mathematical model, solved and plotted using MATLAB for the first three vibration modes. The results thus obtained are validated with the results from simulation in ANSYS.