Research On The Dynamic Characteristics Of Shrouded Blades With Impact-friction

Rotating shrouded blade is one of the critical components of rotating machinery, which work capability directly affects the stability and safety of the rotating machinery. The blade failure is common in engine vibration fault, according to literature, about 70% of engine fault is blade failure. The dry friction damping of shroud structure is commonly used to reduce the blade vibration, so it is important to study the impact-friction characteristics of shrouded blades. In this paper the shrouded blade as the research object, whose nonlinear dynamic characteristics with impact-friction are investigated by numerical simulation and model ex-periment. In this paper, the main research works are performed as follows:(1) The influence of shroud on blade natural frequency and the feasibility of the quality points simulating the shroud are studied based on ANSYS. Analytical model of rotating shrouded blade with centrifugal stiffening and spin softening is established based on energy method. The influences of different shroud lengths and different turning radius on the blade natural frequency and vibration response of the blade are studied by two models.(2) The impact dynamic model of rotating shrouded blade is established based on colli-sion theory, in which bending dynamic stiffness as the impact stiffness of the shroud. The in-fluence of aerodynamic force frequency on blade vibration response is studied based on the model. The effects of shroud gaps, the asymmetric gaps, the rotational speeds and the ampli-tude of aerodynamic forces on the dynamical responses of blades are disscussed.(3) The impact-friction dynamics model of rotating shrouded blade is established based on friction theory, in which the friction model adopts LuGre friction model and coulomb fric-tion model, the validity of the model is verified by literature, the friction effect on shrouds is analyzed based on the two models. The influences of different shroud angles and friction co-efficients on blade vibration response are studied based on the model.(4) The vibration responses without impact are studied under different accelerations. Then, the shrouded blade impact response with lifting speed is discussed, and the influences of shroud impact response with different parameters, such as shroud gaps, the asymmetric gaps and the amplitude of aerodynamic forces, are analyzed. Finially, the influences of shroud impact and friction response with different parameters, such as different shroud angles and different shroud gaps, are analyzed.(5) Through setting up the experimental platform, the influences of the shroud on the natural frequency are analyzed, and the validity of the analytical method is verified by finite element model and experiment. The acceleration vibration responses of the shrouded blade are measured, and the influences of the excitation amplitudes, excitation frequencies and the shroud gaps on the vibration responses of the blade are evaluated.