Analysis Of Dynamic Characteristics Of Circular Tie Rod Rotor-Bearing-Sealing System

Due to its high heat-power conversion efficiency,heavy-duty gas turbines are widely used in the fields of ships and power generation,and have a pivotal strategic position.After decades of research and development,the structure of heavy-duty gas turbines has become more and more abundant.The internal rotor has been developed from the original integral rotor to' the tie rod combined rotor that is now widely' used.The wheel discs of the tie rod rotor are independent,and they are connected together by tie rods.Due to the different arrangement of tie rods,tie rod rotors are divided into central tie rod rotors and circumferential tie rod rotors.The tie rod rotor has the advantages of high stiffness,high strength,easy disassembly and maintenance,but its structure is also more complicated than the overall rotor.This complex structural feature brings certain difficulties to the dynamic modeling of tie rod rotors.In this paper,the model rotor of the circumferential tie rod rotor is taken as the research object.According to the complex structure of the tie rod rotor,the microscopic rough surface contact is considered,and the overall dynamic model with the bearing and the sealing system is established for the circumferential tie rod rotor,and its dynamic characteristics are researched.First,starting with the micro-contact of the rough surface,using MATLAB to generate Gaussian random surface point coordinates of different roughness through the autocorrelation function method.Use ANSYS APDL command flow to achieve the creation of points and the connection between points,and then use the skin command to generate a rough surface 3D solid model.The rough surface solid models with different roughness were used to simulate contact with a rigid plane,and the orthogonal experimental polynomial fitting method was used to obtain the relationship function between contact stiffness and preload and roughness.Then,based on the Timoshenko beam element model,the dynamics of the circumferential tie rod rotor is modeled,and the dynamic characteristics of the circumferential tie rod rotor are solved using the finite element method to obtain the first four-order critical speed and the unbalanced response.By changing the total preload force of the tie rod and the roughness of the contact surface between the discs,the effects of the two changes on the dynamic characteristics of the circumferential tie rod rotor are explored respectively.The results show that increasing the pretension of the tie rod or reducing the roughness of the contact surface can increase the critical speed and vibration amplitude at critical speed.Finally,the dynamic model of tilting pad-rod rotor was established to investigate the effect of tilting pad bearing parameters on the stability of the circumferential rod rotor.The dynamic model of the seal-rod rotor is established to explore the influence of the seal parameters on the stability of the system.Then,the overall dynamic model of the circumferential tie rod rotor-tilt pad bearing-seal system is established,and its dynamic characteristics are analyzed.