| Vibration is the key problem of restricting the development of aero engines in China.According to statistics,more than 70%aircraft engine fault due to vibration,and more than 75%of the vibration are directly or indirectly caused by rotor imbalance,so the research on the characteristics of the unbalanced rotor system has become a focus of research content needs to be considered in the development of aero engine.However,the problem of unbalanced vibration of aero engine rotor systems is difficult to be solved by theoretical analysis and numerical simulation due to the fluid structure coupling conditions and complex nonlinear characteristics,a large number of experimental studies have to be carried out.A large number of tests mean higher costs and longer cycles,which seriously restrict the development of aero engines.Based on the dynamic similitude theory,this paper studies the dynamic similitude design method of the unbalanced characteristics of the rotor system and its supporting structure.By using the similar model to reconstruct the imbalance characteristics of the prototype,we use the model to study the imbalance characteristics of the rotor system and its dynamic balancing method,so as to save cost and shorten the development cycle.The main contents of this paper include the following parts:According to the differential equation of vibration of the rotor systems,using equation analysis method to deduce the similitude relationship of unbalance,unbalanced vibration response,inherent characteristics,structure parameters and material parameters between prototype and model of rotor system.The imbalance response,the axis orbit,the time domain response and the frequency domain response of the rotor system are used respectively to verify the correctness of the similitude relationship through numerical simulation and test.The feasibility of studying the unbalanced vibration characteristics of rotor systems by the similar model is proved,and a similar design method for the unbalance characteristic of the rotor system is proposed.In order to perfect the similar design method of the imbalance characteristic of aero engine rotor systems,a similar design research is carried out for squirrel cage elastic support of rotor systems.The sensitivity analysis theory is used to sort the key parameters of the squired cage elastic support.Then the similitude relationship of stiffness,bending stress,structural parameters and material parameters between prototype and model is derived through the expressions of stiffness and maximum bending stress of squirrel cage elastic support.Combined with sensitivity analysis,the similitude relationship between parameters with high sensitivity is used as a key parameter to express the similitude relationship of other parameters,so as to avoid rounding errors of similar parameters with high sensitivity and ensure the design accuracy of similar models.A similar design method for the squirrel cage elastic support is proposed,and the similar design method is verified by simulation.In order to eliminate the unbalanced vibration of rotor systems,aiming at the shortage of current dynamic balancing method in engineering application,a dynamic balancing method based on dynamic similitude model for rotor system is proposed.First of all,based on the dynamic similitude theory,the similitude relationship of influence coefficient for rotor system is established through the combination of equation analysis and dimensional analysis.The correctness of similitude relationship is verified by simulation and experiment.Based on the similitude relationship of influence coefficient,the influence coefficient of prototype system is predicted by similitude model,and is used to balance prototype rotor system.The balancing effect is proved well through numerical simulation. |
