Research On The Dynamic Characteristics Of Rotor Blade Considering Dovetail Attachment

Gas turbine is a typical complex rotating machinery, a multi-technology high-tech product. Blade-disc rotor system which is connected by dovetail, as the core component of gas turbine, directly affects the safety and stability of the gas turbine operation. As the rotating blade runs repeatedly in extremely harsh environment for a long time, blade-disc is one of failure-prone components. In order to improve gas turbine performance, durability, reliability and life,it is necessary to study the dynamic characteristic of blade-disc system.In this paper, a further research is conducted into the dynamic characteristics of the blade-disc systerm on the basis of the study on the contact characteristics of the dovetail attachment.Firstly, a geometry model and a finite element model of the blade-disc system connected by dovetail are established. And the variations of contact characteristics resulting from different geometric parameters (dovetail root chamfer, contact area, rotating speed), different contact variables (contact stiffness, friction coefficient), different material parameters and different forms of constraint are analysed. Based on the analysis, draw some conclusions which can support our further study on the vibration response of the rotor blade.Secondly, taking into account the influence of centrifugal stress stiffening, spin softening and Coriolis force, when the aerodynamic load is applied, adopting the method of harmonic response analysis, amplitude-frequency response and dynamic stress response changing with vibration frequency are analyzed. The disc is simplified as a spring element, natural frequency and vibration response analysis is conducted. The simulation results is compared with the results of the blade-disc system model considering dovetail attachment, and prove the feasibility and scope of the simplified spring element model in considering the case of aerodynamic loads.Finally, under the load of rub-impact force, adopting the method of transient analysis, the influence of LS-DYNA rub-impact force and simplified half-sine pulse force on blade vibration stress are analysed. Half-sine pulse force model is modified. Modified model is exerted to spring simplified spring model and its vibration response is analysed. The simulation result is compared with the results of blade-disc model and proved the feasibility and scope of the simplified spring element model in considering the case of rub-impact force.