MODEL-BASED IDENTIFICATION OF THE SHAFT LOCAL BOWS CAUSED BY ROTOR-TO-STATOR CONTACTS IN A STEAM TURBINE

摘要

The dynamic behavior of rotating machines due to faults can be simulated with model-based methods in which the faults are modeled with suitable sets of equivalent excitations. The friction forces due to rotor-to-stator rubs can cause time-varying thermal bows of the shafts. The equivalent bending moments that cause the shaft bows can be estimated with model-based identification methods developed in the frequency domain: these techniques minimize the error between the machine experimental vibrations induced by the rubs and the system response provided by the simulating model. In this paper, the results of the analysis of the experimental response of a large turbine-generator unit that was subjected to partial arc rubs are shown and discussed along with the diagnostic strategy used to identify the fault severity and the location of the shaft cross-sections where the heaviest rubs occurred. Comparisons between experimental data and simulated vibrations caused by the identified fault are shown.