Development and validation of algorithms for vibration monitoring of aeronautical engines

Main concern of the aeronautical industry has been to increase engine efficiency in the last decades. This parameter is strictly related to the dynamic properties of blades and disk constituting modern multi-stage turbofan. As a consequence,the design of blades and disks is focused on weight reduction, giving room for the enhancing of mechanical vibrations. In such a context robust computational techniques and innovative measurement systems have become necessary tools to guarantee structural integrity of the engine. Furthermore, new testing methods have been introduced, as the one described in the main part of the thesis, in which a magnetic forcing in vacuum is applied to the reference test article. The topics developed in this thesis work concern the study of experimental data of Ge Avio's multi-stage bladed disks, starting from the development of algorithms to clean data and the creation of a GUI (Graphic User Interface) following a benchmarking activity. These tools were than applied to the aforementioned testing activity, both to traditional acquisition methods for vibration measurements, Strain Gauges (SGs), and to a more innovative method the blade tip timing (BTT). As a matter of fact, the influence of magnetic field on SGs measurements is not negligible, causing the rise of a disturbance proportional with rotational speed of the test article. Therefore, if on the one hand, algorithms to eliminate this linear offset were applied in order to correctly estimate Q factor and vibration amplitude of certain blades starting from SGs data, on the other hand, a laser based method was introduced (BTT), since it is not subject to magnetic disturbance by definition, and a comparison between the two methods is suggested. The same approach is conducted both at vary magnetic forcing and considering different rotor's configurations: Tuned and Intentionally mistuned one. A brief introduction to the theme of the intentional mistuning as a procedure to significantly decrease vibration amplification is given, and the results are showed in terms of comparison between the two blades families, and the consequent energy distribution besides the influence on the effective blade-to-blade coupling.