Vibration Analysis of Vertical Turbine Pump

Abstract

Turbo machines consists of many rotating parts constitutes complex dynamic system. While Designing rotors of such turbo machineries, it is very important to consider vibration characteristics into account. Rotating systems running at speeds close to the natural frequency of the system results in excessive deformation and large stresses can occur which leads to catastrophic failure of the system. This dissertation work focuses on performing vibration analysis to identify critical operating speeds for three stage vertical turbine pump.

The vibration characteristic for the above said pump is to be studied with the help of CAE tools by converting the physical model of the vertical turbine pump into a simplified lumped parameter system. The same is to be verified by analytical approach. Modification in the pump design is required in case of operating speed falling in the range of critical speed in order to make the system performance more robust and reliable.

In the present work, the bench mark study of single rotor system is performed to identify the methodology for carrying out vibration analysis (torsional and lateral) for the rotating system. The result of the bench mark study is used to produce Campbell diagram which is an essential tool to predict vibration characteristics of rotating system. As the physical system is complex, the lumped mass model considering various connections, power transmitting elements and inertias of rotating parts have been developed. The concept developed through bench mark study is applied to lumped parameter VTP model and critical speeds are evaluated. The analytical computation for determining system’s natural frequencies using Holzer method shows close confirmation with FEA results.