Rub-Impact Dynamics of Shrouded Blades under Bending-Torsion Coupling Vibration

Abstract

Shroud devices which are typical cyclic symmetric structures are widely used to reduce the vibration of turbine blades in aero engines. Asymmetric rub-impact of adjacent shrouds or aerodynamic excitation forces can excite the bending-torsion coupling vibration of shrouded blades, which will lead to complex contact motions. The aim of this paper is to study the rub-impact dynamic characteristics of bending-torsion coupling vibration of shrouded blades using a numerical method. The contact-separation transition mechanism under complex motions is studied, the corresponding boundary conditions are set up, and the influence of moments of contact forces and aerodynamic excitation forces on the motion of the blade is considered. A three-degree-of-freedom mass-spring model including two mass blocks with the same size and shape is established to simulate the bending-torsion coupling vibration, and the dynamic equations of shrouded blades under different contact conditions are derived. An algorithm based on the fourth-order Runge–Kutta method is presented for simulations. Variation laws of the forced response characteristics of shrouded blades under different parameters are studied, on the basis of which the method to evaluate the vibration reduction characteristics of the shrouded blade system when the motion of the blade is chaotic is discussed. Then, the vibration reduction law of shrouded blades under bending-torsion coupling vibration is obtained.

Comparative Analysis of Rub-Impact Dynamics of Shrouded Blades Based on the Bilinear Hysteresis Model and the Coulomb Friction Model

“…It is clear that fractional harmonics or chaos may appear in the system response under some parameters. In [31], a method to evaluate the vibration reduction characteristics of the blade when chaos or fractional harmonics occurs is proposed, P d is the percentage of the average steady-state power reduction of the system. Referring to reference [31], the vibration reduction formula can be written as Equations ( 12) and (13).…”

“…In [31], a method to evaluate the vibration reduction characteristics of the blade when chaos or fractional harmonics occurs is proposed, P d is the percentage of the average steady-state power reduction of the system. Referring to reference [31], the vibration reduction formula can be written as Equations ( 12) and (13). When no impact occurs between these two mass blocks during the whole process of motion, the displacements of the arbitrary point on the mass block are x 1 and y 1 .…”

“…Yang et al [29] investigated the influence of the parametric uncertainties on the dynamic characteristics of a rotor-blade system. He et al [30,31] studied the influence of the convective inertial force and Coriolis inertial force on the vibration reduction of dry friction damped blades considering the rotation of the bladed disc.…”

Effect of asymmetric shroud gap and shroud friction coefficient on vibration response of shrouded blades

“…The effect of normal contact stiffness, blade root support stiffness and shroud position on the vibration response of the system was analyzed. He et al 17 studied the dynamic characteristics of the shrouded blade bending-torsional coupling vibration by numerical method. A three-degree-of-freedom mass-spring model was established to simulate the bending-torsional coupling vibration of the shrouded blade under different contact conditions.…”

“…Many scholars have also studied the vibration behavior of shrouded blades under impact and friction conditions. 8–17 Sinha 8 studied the transient dynamic response of a rotating beam with and without pre-torsion when it is repeatedly rubbed with the shell. Chu et al 9 studied the mechanism of collision between shrouded blades with asymmetric gap and discussed the effect of the shroud gap on the dynamic response of shrouded blades.…”