Study On The Dynamic Characteristics Of The Rod Rotor In The State Of Detuning

Gas turbine and its combined cycle are the integration of core technologies of many disciplines.The power generation technology of modern gas turbine has entered the stage of rapid development.The pull rod rotor is the core structure of the whole gas turbine system,so it is of great significance to study the mechanical characteristics of the rotor under the condition of detuning for the safe operation of the gas turbine.From the structural analysis,the pull rod rotor is a nonlinear structure with a large number of joints,which makes the subsequent dynamic analysis more complex.In this paper,the theoretical analysis and experimental research methods are used to study the dynamic characteristics of the rod rotor in the state of tension detuning.Generally speaking,the size of the preload and the properties of the interface are the main factors that affect the contact stiffness of the interface.Based on the fractal contact theory,this paper considers the change of the stiffness of the interface when the preload changes.The virtual material method is used to equivalent the contact stiffness of the interface,and the contact stiffness between the interfaces is simulated by changing the elastic modulus,Poisson's ratio,density and other parameters of the virtual material.Taking the rotor as the research object,the model of the mistuned rotor is established considering the contact stiffness of the joint surface.The influence of the detuning factors,such as the detuning of the pre tightening force,the number of detuning rods and the position of detuning rods,on the overall natural frequency of the rotor is analyzed by using the finite element software.At the same time,the corresponding test platform is designed and built,and the change rule of the natural frequency of the pull rod rotor is measured,which verifies the validity of the model.The results show that the first-order natural frequency of the pull rod rotor is always smaller than that of the whole pull rod rotor;the more the pull rod is out of tune,the smaller the first-order natural frequency of the pull rod rotor is;when the pull rod rotor loses the circumferential symmetry structure due to the out of tune factor,the higher the natural frequency of the horizontal and vertical bending vibration of the pull rod rotor is Small inequality.At last,the harmonic response of the rotor is analyzed by using the finite element method.It is found that the resonance peak appears at the first natural frequency of the rotor.