Reduced order model of gas turbine bladed discs.

From the last century until today, the electricity demand has been constantly increasing and gas turbines have played a progressively key role in the energy sector due to the large amount of energy they can produce, their limited size and the great reliability over their service life since they have fewer moving parts than reciprocating engines. However, since climate change and sustainability are no longer negligible issues, environmental attention is growing stronger. Gas turbine technologies also need to meet environmental requirements, so much so that their structural characteristics take extreme advantage of the properties of the materials with which they are made. The optimization of the design of each component is important to reduce fuel consumption, which results in lower costs and reduced environmental impact. In the designing process of a component, its dynamic behavior is pivotal, but it is also important to consider its computational costs which can prevent cost effectiveness and time efficiency. Therefore, it is necessary to search for methods that allow a lower computational cost for the dynamic analysis of complex structures. In this thesis, the proposal is to use Component Mode Synthesis techniques to fill this need for detailed dynamic analysis tools. These techniques are based on the idea of dividing complex structures into smaller and simpler substructures which dynamic behavior determination is less onerous. The method which will be implemented in this thesis is the Craig-Bampton one. It is used to calculate the reduced mass and stiffness matrices of a sector of a bladed disc. The dynamic behavior of the entire bladed disc is then evaluated by applying the cyclic symmetry property of the sector of the bladed disc. The procedure has been applied to a simplified bladed disc model with two different blade configurations (free standing and shrouded) and to an industrial bladed disc model, provided by Ansaldo Energia S.p.a. . The results show an interesting potential, enough to justify the introduction of this procedure in the design process of industrial bladed discs.