On model updating of turbo-generator sets

Models can be used for simulating the dynamical behaviours of rotating machinery or specific faulty conditions. Efficient model updating techniques could be very useful for increasing the accuracy of the models. Model updating of rotor systems is significantly different with respect to the well known model updating techniques and related modal analyses performed in the field of vibrating structures. This paper investigates both the difficulties and the conditions of rotor vibrations measuring tests as well as the approximations introduced in the rotor model. Some experimental cases of turbo-generator machines show the difficulties and problems in the identification of eigen-frequencies and damping modal parameter. In the second part of the paper uncertainties and non linearity of the model are investigated. An example of updating of some shaft and bearing parameters, by means of an evolutionary algorithm, for fitting the natural frequencies of a shaft line, is presented and discussed. Model updating techniques of bearing coefficients are also discussed and a procedure is proposed to avoid misleading results of usually employed model updating approaches.