Research On Dynamic Similarity Design Method And Experimental Verification For An Aero-engine Rotor System

Due to the complexity of the rotor system of an aero-engine,it is very difficult to obtain its dynamic characteristics accurately.On the one hand,there are some limitations in the accuracy of the theoretical model and simulation model,which leads to a large difference between the analytical results and the test data.On the other hand,since the large volume and high speed of the engine rotor,it is still very difficult to perform experimental research of the dynamics for the engine rotor because of the influence of the factors such as manufacturing cost,test conditions,test cycle,data analysis and so on.For this reason,similitude theory is usually used in engineering to design and manufacture models that are physically similar to the prototype,and the physical nature and laws of the prototype can be revealed on model test.At present,the research on the dynamic similarity of the rotor system,however,is not comprehensive,especially for the dynamic similarity design of the complex rotor system of an engine,there is still a lack of effective and practical solutions.Therefore,in this paper,the research on the dynamic similarity design method for the engine rotor system is carried out.A dynamic similarity design method suitable for the engine rotor system is presented first.Then the rotor test rig used to simulate the dynamic characteristics of the dual-rotor system of the engine is designed and built.Finally the effectiveness of the design method is validated by the model test.The main research contents and achievements are as follows:First of all,aiming at the modeling of the simplified model of the engine rotor system,the dynamic equivalent modeling method of the engine rotor system is studied.Based on the finite element parametric model and the dynamic optimization method,the equivalent modeling method of the rotor system is proposed,which realizes the one-dimensional and three-dimensional equivalent modeling of the engine rotor system.Compared with the traditional equivalent modeling method based on empirical formula conversion,this method has high accuracy and efficiency in modeling,and by this method the dynamic equivalent model can be quickly obtained with the dynamic characteristics similar to that of the engine rotor system.The effectiveness of the method is validated by simulation.Secondly,the dynamic similarity design method for the reduced scale model of the engine rotor system is studied.The dynamic similarity design method of the distortion similarity model of the engine rotor system is proposed.The dynamic similarity relationship of the distortion similarity model of the engine rotor system is established by this method,and then the reduced scale model of the engine rotor system is obtained by the similarity relationship.The method has high design accuracy and efficiency,and the rationality of the method is validated by the simulation results.The manufacturing cost and experimental difficulty for the dynamic similarity model of the engine rotor system can be effectively reduced by this method.Thirdly,in order to improve the accuracy of the dynamic similarity model of the engine rotor system,the research on model updating and validation for the dynamic similarity model of the rotor system is performed.Based on the test data,the model updating and validation method for the dynamic similarity model of the engine rotor system is proposed.The method synthesizes the techniques of modal test optimization,correlation analysis,error location,model updating and model validation.By this method,the dynamic similarity model with the dynamic characteristics consistent with that of the engine rotor system is obtained.This method can effectively improve the prediction accuracy of the dynamic similarity model,and has a good guiding effect on the accurate modeling of the engine rotor system.Fourth,the dynamic similarity design method for the engine rotor test rig is studied.For the problem for the dynamic similarity design of engine rotor system,a three-step method for the dynamic similarity design of the engine rotor system is proposed.This method is consist of the dynamic equivalent modeling,the distortion similarity model design,and the model updating and validation.By this design method,the dynamic similarity model of the dual-rotor system of the engine is designed,and the dynamic similarity model with high prediction accuracy is obtained.The design method is universally suitable for the dynamic similarity design of the rotor system,and it can provide an effective design method for the dynamic similarity design of an aero-engine rotor system.Finally,in order to validate the effectiveness of the dynamic similarity design method of the engine rotor system,a dual rotor test rig is built based on the dynamic similarity model of the dual-rotor system of the engine.The experimental verification research is carried out and the verification method is proposed.There are two steps to validate the dynamic similarity design method.In the first step,the similarity of the frequency and mode shapes of the dynamic similarity model is validated by modal test.In the second step,the critical speed and mode shape of the full-scale prototype is predicted by the dynamic similarity model obtained by the model updating,so as to further validate the effectiveness of the design method.This paper provides an effective and practical design method for the dynamic similarity design of the engine rotor system.This method has significant practical engineering application value,and can provide a reference for the dynamic similarity design of the whole engine.