Lateral and torsional vibration analysis of gas turbine rotor system

Abstract

The current study is designed to determine the torque and resonant shear stresses present in the shafts of the system rotor based on the torsional critical frequencies, mode shapes, and torque predictions. The lateral analysis is an indication of the unit's response sensitivity to the anticipated level of unbalance is measured based on the frequency location. This study includes the lateral analysis of a 15.75KVA gas turbine (GT) generator. The rotor is considered a continuous system with flexible bearing supports. The total rotor length is divided into 50 sections with -three bearings supports. According to this study, modes and natural frequencies were calculated using the DYROBES software, based on the mass and stiffness distributions of the beam elements. The transfer matrix method presents the torsional natural frequencies using modes, modes shapes, and Campbell diagrams. TORTAS program is also used to calculate the shear stresses caused by transient response for defective conditions. Campbell diagram presents that there is no interference between calculated torsional natural frequencies in the range of ±10% operating speed of the rotor. The maximum torsional stress for the events that were studied for the weakest section of the shaft was 39.65 ksi is within the accepted level.