Effect of the Contact Surfaces Orientation in the Shrouded Flanges and Level of Vibration Excitation in the Rotor Blades on their Vibration Stress State

The authors present the results of the numerical experiments on the determination of the effect of shrouding coupling parameters in the rotor blades on their forced vibrations using an assembly of two blades as an example. The task is solved in the variation of the inclination angle of the shrouded flanges as the parameter of their contact interaction and amplitude of the kinematic excitation of vibrations caused by the harmonic displacement of the root section of the assembly. The displacement amplitude in the plane of the assembly vibrations and stress intensity in the blade airfoil is accepted as the characteristic of the forced blade vibrations. The finite element models of the blade assembly, which are based on the linear 8- and 4-nodal contact finite elements, are used to perform the investigation. The authors have obtained the dependencies of the selected characteristics of forced vibrations within the blade airfoil on the inclination angle of the contact surfaces of their shrouded flanges to the plane of rotation of the rotor wheel and level of kinematic excitation of the assembly vibrations. It is implied that the variation in the angle has a considerable effect on the stress state in the blades under investigation and it results in the occurrence of the local minimum of their forced vibration characteristics. Here the increase in the amplitude of the kinematic displacement of the root section in the assembly causes the increase of rigidity of the shrouded blade coupling and reduction in the triggered energy scatter.