Design Optimization And Unbalance Response Analysis Of Dual Rotor Coupling System

For any rotor system, if the working speed is close to the critical speed, the vibrationwill significantly increase; Conversely, working speed is away from the critical speed, thevibration will be reduced a lot. Therefore, knowing the critical speeds of systems is veryimportant for the safe and stable operation of system. Referencing the structure of a certainaero-engine, this article proposes a dual-rotor experiment bench. The main features of theexperiment bench are: internal and external rotor were coupled together through anintermediary bearing, and separately driven by different motors; four wheel were used tosimulate the quality of low pressure compressor, high pressure compressor, high pressureturbine, low pressure turbine. This article used the Lumped Parameter Method to simplifythe model. According to structural features of dual-rotor, rotor dynamics analysis is carriedout using "direct transfer matrix method" proposed by Dr. Hu of Nanjing University ofAeronautics and Astronautics: the rotor critical speeds and vibration modes, unbalancedresponse analysis. The main work is as follows:Firstly, the calculation principles of two methods of rotor dynamics—transfer matrixmethod and finite element method are introduced.Secondly, we used Lumped Parameter Method to simplify the model, used transfermatrix method to calculate the critical speed of the rotors. The results is compared to theresults calculated by ANSYS. It is shown that the calculation results of transfer matrixmethod is accurate. Meanwhile, the affects of the supporting stiffness, speed ratio,gyroscopic moments, length-diameter ratio and other factors on the critical speed areanalysed. According to the analysis results, an optimization program of the structure of thedual-rotor system is proposed, the critical speed and vibration mode of the new structure arecalculated. The results show that the differences between the2-order and the3-order criticalspeeds are significantly increased, and the amplitudes when speed closed to2-order criticalspeed are significantly reduced.Thirdly, the transfer matrix method is used to solve the unbalance response of theoptimized system when each wheel has an unbalance value, unbalance responses changing with speeds of the four wheels and bearing Ⅳ are given.