Gas Turbine Bolt Connection Structure Thermal Creep And Dynamics Research

Bolt tightening structure has been widely adopted during the design process of gas turbine, on the one hand, due to gas turbine structure is very complex, bolt tightening structure can help to reduce difficulties during assembly process, on the other hand, it allows designers to do the machining work according to requirements of the different parts. But there are some inevitable disadvantages for this connection method, it weakens the strength and stiffness of the structure compared to the continuous structure, in the meantime, the thermal and mechanical transfer laws among bolted flange joints have been changed, so it leads to the contact behavior between contact pairs becomes extremely complex, contact interface slippage may occur, which impacts dynamics of gas turbine in return. However, for the bolt tightening structure, the phenomenon of contact interface slip will affect engine assembly accuracy and the body vibration, and, if the slippage between drum and disk has been accumulated for several cycles, the thermal creep will influence rotor vibration of turbine, So it is very meaningful to study on dynamic problems of gas turbine caused by thermal creep among joints.First, the finite element simulation analysis model of contact thermal creep between typical bolt tightening joints has been established in this paper, the mechanism of contact interface thermal creep is analyzed, and the influence factors are qualitatively studied, then the corresponding conclusions are obtained.Then, with a certain type of actual aircraft engine as the research object. First with the aid of computational fluid dynamics simulation method, the thermal boundary conditions of combustion casing and high pressure rotor of turbine in a running cycle are obtained, second establishing the finite element models respectively, the high-cycle contact interfaces thermal creep simulation research are developed for both models, finally the rule of both combustion casing assembly concentricity and the eccentricity of the rotor consideri ng centrifugal force along with the change of running cycles are obtained, it will provide the basis for subsequent rotor dynamics analysis.Eventually, the rotor dynamics analysis model of gas turbine is established based on finite element method. Due to the thermal creep will impact the rotor disk unbalance response, therefore, combined with the disk eccentricity result obtained before, the rotor critical speed and unbalance response are obtained. Finally complete the analysis of the thermal creep phenomenon on rotor dynamic characteristics. At the same time, author design and set up gas turbine test bed of distributed rod fastening rotor static thermal creep, conducting the experimental verification about phenomenon of bolt tightening structure thermal cr eep and get the conclusion finally.