Identification of the Modal Parameters of a Flexibly Supported Rigid Casing

Abstract

Satisfactory means for evaluating the vibration behavior of gas turbine installations where it is impractical to obtain a satisfactory model of the support structure and where it has natural frequencies in the operating range are not yet available. This paper investigates the feasibility of identifying the modal parameters of a flexibly supported rigid casing to predict the unbalance response of the contained rotor. Assumed known are the location of the principal axes of inertia of the casing. Numerical experiments demonstrate that the identification procedure works well even with a measurement accuracy of only two significant digits. Thus, the procedure is expected to be practically feasible, though no sensitivity studies have yet been carried out to determine the limitations imposed by the assumed location of the principal axes.