Methods for Generating Rotordynamic Models in Retrofits of Large Steam Turbines From On-Site Measurements Available to Purchase

In turbine modernization projects accurate knowledge about the existing configuration and the prediction of the retrofitted configuration is vital for the success of the retrofit. Great progress has been made in recent years with laser-scanning techniques to capture the geometry of the existing configuration and convert it into CAD models for further design work. Equally important are proper structural dynamics models which are vital for reliably predicting the behavior of the new configuration at an early project stage. This paper discusses the application of on-site experimental modal analysis and vibration measurements during turbine operation from which the rotordynamic model of the turbine-generator including its supports and residual unbalance can be derived. Frequency response data and identification techniques are applied in combination with finite-element modeling to update the rotordynamic model based on measurements. The capabilities and limitations of the presented methods for predicting the vibration behavior by means of the established model are shown for the example of a large steam turbine unit retrofit.