| The Variable Stator Vane adjustment mechanism can adjust the angle of the vane according to the working state of the aero-engine to delay the stall of the compressor caused by the unstable air flow and expand the stability margin.The VSV adjustment mechanism is a spatial multi-stage linkage mechanism with multiple moving parts and multiple types of joints.The stuck failure often occurs in engineering practice and has not been effectively resolved.The stuck has a significant impact on the smoothness of the adjustment mechanism and the force of joints,reducing the control accuracy of the vanes,inducing clearance in the joints,and increasing wear.Therefore,it is urgent to carry out relevant research on the causes and solutions of stuck failure.However,most domestic and foreign scholars focus on the parametric analysis and kinematic optimization design of the VSV adjustment mechanism.And no scholars have explored the influence of joints characteristics,body flexibility,and driving modes on the stuck based on the overall analytical dynamic model of the VSV adjustment mechanism.For this reason,this paper carried out the research on the rigid-flexible coupling dynamics of the VSV adjusting mechanism considering the characteristics of the joints.Firstly,in order to solve the problem that the mass matrix of the link rotating in space changes with time,a detailed derivation formula is given.On this basis,the analytical dynamic model of the VSV adjusting mechanism is established by using Lagrange multiplier method,and the coordinate partitioning method is used to solve the dynamic equation.The correctness of the analytical model is verified by comparing with the Adams simulation results.Secondly,based on the coefficient of restitution method and Lu Gre model,the contact force model and friction model of joints are established.The force at the clearance is transformed by Euler transformation matrix and Rodriguez rotation formula,and decomposed into a three-dimensional vector force applied to generalized coordinates.Taking the sub-structure of the adjusting mechanism as the object,combined with the phenomenon in the reference and the Adams simulation results,the accuracy of the dynamic model with the clearance joint is verified.Then,the influence of the position,stiffness,value,and friction of the clearance joint on the dynamic characteristics of the VSV adjustment mechanism is studied.The order of the influence of each joint on the blocking force under the same clearance value is found.The experiment shows that the mechanism oscillates at a large amplitude of low frequency when the clearance is large,and oscillates at a small amplitude of high frequency when the clearance is small.After comparing the influence of different friction coefficients on eccentricity and blocking force,it is found that although friction will cause wear,the function of friction to restrain the vibration of mechanism can not be ignored.By comparing the results of uniform drive,harmonic drive and trapezoidal drive,it is shown that harmonic drive can reduce the blocking force during the movement,improve the dynamic stability of the mechanism,and suppress stuck.Finally,the neutral file of flexible body is generated by modal synthesis method in ANSYS,and imported into Adams to simulate and analyze considering the characteristics of joints.The rigid-flexible coupling relationship of the flexible piston,link and blade in the motion process is explored.The results show that the blocking force oscillates at high frequency near the baseline,and the oscillation frequency is negatively related to the stiffness of the flexible body.The blocking force is most affected by the flexibility of the link.Compared with the piston and blade,the stress of the link is the largest.The stress of the mechanism is the largest at the beginning of the movement,and the maximum stress point is near the joints. |
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