Dynamic analysis of integrally shrouded group blades with rubbing and impact

Abstract

Forced vibration responses of integrally shrouded group blades are investigated in this paper. A lumped mass model of integrally shrouded group blades considering centrifugal stiffening of the blade and rubbing and impact between adjacent shrouds is established. In the proposed model, collision force is approximated by linear springs, and friction force is approximated by an exponential-type velocity-dependent model. Stick-slip-separation transition boundaries are determined. Runge–Kutta algorithm is used to compute vibration responses and study the effects of stiffness ratio, rotating speed and aerodynamic excitation amplitude on the vibration responses of integrally shrouded group blades. Vibration reduction effect of the shroud on the reference blade at the first dynamic resonance speed is illustrated. Numerical results indicate that stiffness ratio, initial gap and contact angle have a great effect on the normalised energy density (the value of which can represent vibration reduction effect of the shroud), and the reference blade can experience periodic, quasi-periodic and chaotic vibration due to nonsmooth behaviour at the shroud contact interfaces.