Study On Vibration Transfer Characteristics Of Aeroengine

In the past few years,the industrialization in China develops rapidly and effectively.As a consequence,the rotating machinery,which is an important part of high-speed turbine machinery,is widely used in aerospace,power generation,automobile,ship propulsion,gas turbine machinery and other related equipments.As a typical representative of gas turbine machinery,the aero-engine has been widely developed in recent years with the strong support of the state,from the initial piston engine to the helicopter turboshaft engine,large passenger aircraft turbofan,turboprop engine and other forms of diversification,and then to the complexity of rotor structure to meet the needs of different industrialization.Rotor imbalance,as a common fault in rotating machinery,has a very severe impact on the healthy and stable operation of the rotor system.The effective reduction of it is the key factor to ensure the long-term safe and stable operation of the system.In order to pursue the characteristics of high thrust-weight ratio and wide comfort,the structure of the rotor becomes more and more flexible,and the problems of high load and high vibration follow.We add squeeze film dampers to the high and low pressure rotors to provide damping,support and reduce vibration.In the actual high pressure rotor,because of its narrow space and high operating temperature,it is impossible to install the corresponding sensors to measure the vibration parameters.If the transfer function relationship between the bearing and the casing can be determined and the corresponding vibration transfer characteristics can be studied,the vibration caused by the unbalance of the rotor can be accurately identified on the casing.Considering the above situation,the main work of the paper related to unbalance and vibration transfer characteristics of aero-engine is as follows:(1)Have a study on a squeeze film damper structure with central spring support,and analyse the influence of squeeze film damper on the dynamic characteristics of single rotor structure under different working conditions and characteristic parameters,especially the unbalance response.and stability analysis.In the analysis,the nonlinear law of the influence of the damper on the rotor vibration is found.(2)Establish finite element models of high and low pressure rotor of an aero-engine with squeeze film dampers respectively.By changing working conditions and characteristic parameters of the damper,the analysis results of the three-disk rotors are further verified.(3)Develop an analysing program of the rotor dynamics with SFD.The accuracy of the calculation is verified by comparing with analysis results in Dyrobes.On the basis of the relevant calculation by this program,the rotor dynamic balancing program under double-sides and double-speed based on the influence coefficient method is further developed.Among these,the balance speeds are selected in the speed range where the unbalance response changes approximately linearly.Through the vibration changes at the nodes of two bearings before and after balancing,it is shown that the dynamic balancing program can effectively reduce the vibration of the rotor,and the effectiveness of the program for rotor dynamic balancing is verified.(4)A dual-rotor finite element model with SFD is established.Then,SFD is added to each bearing node respectively to determine the optimal position which can make the rotor system have the best damping effect under the action of internal and external excitation alone.The harmonic response analysis of the whole engine model is carried out by using Ansys,and the transfer functions between the support nodes and the corresponding measuring points of the casing are determined.On the basis above,by applying unbalance excitation on the inner rotor with SFD,the corresponding unbalance response is identified at the casing measuring point with the vibration transfer.By comparing the vibration responses of each bearing node and each measuring point of the casing with or without the damper,we decide the damping performance of the damper.