Study Of Effects Of Support Stiffness On Rotor System Critical Speeds

The critical speed of aero-engine rotor system is one of the most important dynamic characteristics,in the design stage of aero-engine,the critical speed of the rotor system is one of the important design parameters.The proper allocation of critical speeds can make no critical speed is in the range of aero-engine operating speed,it has great significance in engineering.This paper focuses on the analysis of the influence of support stiffness on the critical speed of the rotor system,makes reasonable prediction for the adjustment of the critical speed of rotor system.Through calculating the vibration mode of rotor system,this paper gets the shaft deflections at rotor support positions,the influence of support stiffness on the critical speed obtained through analyzing the relative deflection can provide the reference for adjusting the critical speed of rotor system.This paper analyzes the influence of the casing support dynamic stiffness coupling on the critical speed of rotor system,and considers the coupling dynamic stiffness witch comes from the same casing support location and the same direction.The results show that using coupling support dynamic stiffness can reduce the calculation error compared with separate calculation of the casing and rotor system,residual error comes from dynamic stiffness coupling among the casing supports.This paper uses the ANSYS optimization module,applies the method of zero order optimization and first order optimization to optimize the support stiffness of rotor system.According to the critical speed requirement,the support stiffness of rotor system is optimized using optimization method.It can be proved that the above optimization is reasonable by calculating,but the optimization program is only applicable to small scale model.