Numerical and experimental investigation on the vibro-impact responses analysis of shrouded blade

Abstract

A finite element model of shrouded blades is established to analyze the vibration responses due to the impact between adjacent blades. In the finite element model, the blade and the shroud are simulated using beam element and lumped mass, respectively. On the basis of the finite element model, a beam–beam impact model is developed to study the vibro-impact responses of shrouded blades. By comparing the natural frequencies and vibration responses, the finite element model is verified by an analytical model. In addition, a test rig is also set up to compare the results obtained from simulation and experiment, and the influences of different parameters such as shroud gap, excitation amplitude, and excitation frequency on the vibro-impact response are analyzed by finite element model and experiment. The results obtained from finite element model and experimental model indicate that the impacts between adjacent shrouded blades weaken with the increase of the shroud gaps and excitation frequency, and the vibro-impact responses between shrouded blades become strong with the increasing excitation amplitude. The results also show that the second-order flexural vibration of blade is easier to be excited and the super-harmonic resonance phenomenon closed to the second-order flexural natural frequency is more significant than that at other flexural natural frequencies. The reason is that the position of the external force applied on shrouded blade accords with its second-order flexural vibration mode.