On the stability of rotating blade arrays

A mathematical model consisting of an array of rotating pendulums was built to study the stability of an array of rotating blades and the dynamic interaction between the blades and the rotor. This model can be solved in closed form, yielding some general results regarding the stability of the system, particularly for the effects of the blade–rotor interaction and of blade damping. The closed form solution so obtained is then checked against a more realistic finite element method (FEM) model in which the blades are modelled as beams. As a result, the possibility that the disc–blades interaction gives way to instability even in the case of undamped systems, which has been known for many years, is confirmed for the case of in-plane oscillations of ‘long’ blades. The damping associated to bladed arrays, although rotating, is shown not to have an unstabilizing effect but, on the contrary, to help in counteracting the above-mentioned instability.