Research On Rotor Dynamic Characteristics And Vibration Reduction Under Large Maneuvering Condition

In the background of maneuvering turn and spiraling,taking the two-supporter double-disk cantilever rotor as the research model,some depth study has been done from these aspects: modeling the rotor system under large maneuvering conditions,researching the dynamic characteristics of the rotor with nonlinear bearing,studying the applicability of squeeze film damper(SFD)in the conditions of maneuvering,and so on.The research work aims to provide a method and reference for the study of rotor dynamics characteristics under the maneuvering environment,and supply a theoretical basis for the design of tester with large maneuvering overload.The main research contents and achievements are as follows:(1)Based on the Lagrange energy method,a method for modeling the rotor system with finite element beam was derived.According to the fixed interface modal synthesis method,the number of model degrees of freedom was reduced.These researches lay a theoretical foundation for the rotor finite element modeling and the improvement of response solving efficiency under the condition of maneuvering.(2)Based on the linear rotor system with squirrel-cage support,the influence of maneuvering turn and spiraling forward on the rotor response was studied.The variation of rotor response with each maneuvering parameter was analyzed.The results show that for the linear rotor system,the maneuvering turning load will make the rotor orbit have a static eccentricity.The spiraling forward load will not only bring the rotor response static eccentricity,but also make it appear “quasi-periodic” characteristics.For maneuvering turning,overload is the main parameter that affects the rotor response.For spiraling forward,overload and helix angle are the main maneuvering parameters that affect the rotor response.(3)The response of the nonlinear rotor systems with bearing was analyzed under maneuvering turning and spiraling conditions.The results show that the maneuvering load could increase the bearing stiffness,which called additional stiffness effect,and would make the bearing stiffness asymmetrical in the orthogonal direction.Therefore,the orbit of rotor would appear orthogonal asymmetry in maneuvering conditions.In addition,the response of rotor with bearing would behave quasi-periodic characteristics in some speeds and contain bearing-related frequencies.As the maneuvering load increases,some frequency components would be reduced or even disappear.In the spiraling forward condition,with helix angle increase,the envelope of rotor response would be closer to the ellipse.(4)Large maneuvering condition includes two enviroments of maneuvering and leveling flight.Taking into account these two environments,the influence of each damper's parameter on eccentricity was analyzed.Taking dual-disk cantilever rotor as the research object,the question whether SFD is available under large maneuvering conditions was answered.The results show that maneuvering overload causes static eccentricity to SFD,and excessive static eccentricity would cause SFD to work at an eccentricity of 0.4 or more for a long time.Appropriately increasing the stiffness of squirrel cage,oil film width and oil film clearance can reduce the eccentricity in maneuvering conditions,but the excessive stiffness of squirrel cage and oil film gap would cause the eccentricity to jump under the condition of level flight.By reducing the unbalance of rotor,the occurrence of the eccentricity jump can be effectively suppressed.According to the above analysis,the dynamic characteristics of SFD under the maneuvering and leveling flight are both analyzed,whose results show that for the rotor system in this paper,the SFD is hard to be available.(5)A design of a tester which can simulate large maneuvering load was proposed.The parameters of some main components were analyzed.The design provides a theoretical basis for the establishment of follow-up tester form the structural point.In summary,this paper mainly did these researches: developing a finite element modeling method of the rotor system under maneuvering conditions,analyzing the response of linear rotor system and nonlinear rotor system with bearing under large maneuvering conditions,exploring the applicability of SFD in the maneuvering environment with large overload,designing a tester structure which can simulate the maneuvering load.The research results have great theoretical significance for the design of rotor system under maneuvering conditions with large overload,the research of dynamic characteristics of complex rotor systems and the test aiming to simulate large maneuvering load.