Impact of mistuning in flutter stability analyses

Today, more than ever, the aerospace industry is moving towards reducing its environmental impact and improve the sustainability. For this reasons, a great emphasis is placed on producing lighter and more efficient engines and those objectives are reflected on it’s components among which we can find the Low Pressure Turbines (LPT). In fact, the development path, moved towards lighter and higher aspect ratios leading to blades more susceptible to vibrations. For this reasons the flutter, which is a vibration phenomenon, has increased its importance in aircraft jet engines since its first documented case reported in compressor blade in 1945. One of the most important features of flutter relates to its nature: a self-excited and self sustained phenomenon leading, based on the condition, to limit-cycle oscillations which consequently lowers the blade life due to high cycle fatigue, or even worse, an abrupt failure in few cycles since, as mentioned before, is self sustained, hence it increases its amplitude constantly due to the energy fed into the blade from the surrounding air. This thesis work, developed in collaboration with Avio Aero, has the aim to analyze the flutter stability of the bladed disk used in the European project ARiAS, by means of a 3D flutter solver and is the continuation of a previous thesis work by S. Raimondo. In particular, the tests carried out in this work evaluates the mistuning effect, for a total of four configurations, two tuned and two mistuned respectively, with different 3D flutter solver methodologies, three rotational speeds and two mode shapes.