Analysis Of Dynamic Characteristics Of Shrouded Blade Damper Based On Bending-torsion Coupling

With the development of China’s aviation industry,more and more attention has been paid to the research of aero engine.Aero engine turbine blade vibration reduction is one of the important research directions.The high dynamic stress caused by blade vibration is the main cause of high cycle fatigue.The experiment and research show that the blade vibration can be effectively reduced by adding dry friction damper.Shroud damping structure is a typical dry friction damping structure,which has been widely used in turbine blade vibration reduction.At present,a lot of researches have been carried out on the rub impact dynamics of the blade damper,and remarkable progress has been made,mainly focusing on the dynamic model,dry friction contact model and the method of solving the nonlinear system response.However,due to the complex nonlinear characteristics of blade damper,which involves dynamics,tribology and other aspects,there are still some problems that need to be further studied,especially the dynamic modeling and vibration characteristics considering the bending torsional coupling vibration,and the dynamic characteristics considering the elastic deformation of blade crown.It is still of great theoretical and engineering value to study the dynamic modeling and vibration reduction characteristics of the dry friction damper.In this paper,based on the related research,the vibration and vibration reduction characteristics of turbine blade shroud damper are deeply studied.The specific research contents are as follows:(1)Considering the two-dimensional vibration model of the blade Crown Based on the positive collision,a two-dimensional mass model with two degrees of freedom is established.The friction force between the two crown is simulated by introducing a perfect bilinear hysteresis model,and the impact force between the adjacent crown is simulated by linear spring.The influence of blade vibration on the transition between viscous sliding and friction interface separation is considered.In this chapter,the dynamic equations of blades under different contact conditions are derived.The influence of stiffness ratio,initial clearance and exciting force amplitude on the nonlinear dynamic response of crown blades is studied.The work of this chapter lays a solid foundation for the follow-up research.(2)On the basis of the previous research,the dynamic characteristics of the blade in the case of bending torsional coupling vibration are studied.Based on the condition of blade bending torsional coupling vibration,a three degree of freedom lumped mass model was established by considering the influence of blade normal pressure and friction on the contact kinematics of blade centroid contact torque.The blade was simplified as a mass block with size and shape.The conditions of contact separation transformation under complex contact motion were analyzed,and the dynamic equations of blade under different rub impact contact were established.In the numerical simulation,the dichotomy method is introduced to capture the contact separation transformation and the stick slip transformation,and the fourth-order Runge-Kutta program is compiled for the accurate calculation of the system response.Firstly,the variation of response characteristics of shrouded blade with key parameters was studied.Finally,the vibration reduction law of blade is obtained,which provides a more scientific reference for the design of this kind of damper in engineering.(3)Based on the previous research,the influence of elastic deformation of two adjacent shrouds on the dynamics of the blade damper system was considered in this part.The analysis method was closer to engineering.In this part,a more accurate micro sliding friction model was introduced to model the dry friction contact,and the complex normal pressure and friction caused by the elastic deformation of the blade crown was analyzed.The simulation results in this part reveal the influence mechanism of the elastic deformation of the shroud on the system response,and obtain a more scientific vibration reduction law of the shrouded blade.