Research On The Influences Of Elastic-plastic Contact And Temperature Distribution On Tie-bolted Fastened Rotor Dynamics

Tie-bolted fastened rotor is widely adopted in heavy duty gas turbine for powerplant and aeroengines. In order to research the gas turbine technology independentlyin our country, the dynamics of tie-bolted fastened rotor with noncontinuousstructrue and under complicate temperature distribution is one of the key contents ofgas turbine technology. This paper aimed at the tie-bolted fastened rotor, studied theelastic-plastic contact of rough surfaces, investigated the method for the dynamicsmodeling and analysis of rotor with the consideration of temperature distribution.With the consideration of elastic-plastic contact between discs, the dynamicalcharactistics of tie-bolted fastened rotor were studied, the influence of axialtemperature distribution on the dynamics of tie-bolted rotor was analyzed, and thethermal bending of tie-bolted fastened rotor due to nonuniform circumferentialtemperature distribution was studied, the vibration charactistics of a tie-boltedfastened rotor with thermal bending during fast start up was investigated, whichcould provide a method and theory reference for the design and analysis oftie-bolted dynamical problems. The main content of this work include:For the contact problem between the discs of tie-bolted fastened rotor, theelastic-plastic contact behavior of a single asperity was studied based on finiteelement study and the single asperity elastic-plastic contact model which wassuitable for a wider range of interference was established. The elastic-plastic contactof rough surfaces was modeled based on the rough surface statistical model, and theelastic-plastic contact behaviors of rough surface were studied. The influences ofplasticity index on the elasitc-plastic contact behaviors of rough surfaces wereinvestigated. The surface roughness plasticity index and material propertiesplasticity index were defined to study the influences of surface roughness andmaterial properties on the contact behaviors of roughness seperately. The resultscould be a theory reference for the design and analysis of elastic-plastic contact ofrough surfces.In order to study the influence of axial temperature distribution on dynamics ofa rotor, a beam element with considering the variable axial parameters was proposedbased on the conventional beam element and the polynomial forms of the variationof axial parameters. A tapered rotor was modeled and studied, and the influences oftapered parameters on the dynamical characteristics of rotor were investigated.Based on the variation of Yang’s modulus with temperature, a rotor model with theconsideration of axial temperature was established, and the axial temperaturedistribution on the rotor dynamics were studied. The proposed element could provide a new method to consider the variable axial parameters in rotor finitemodeling.For the thermal bending of gas turbine rotor, the temperature distribution onrotor section was computated and studied based on finite difference method. Withthe principle of equivalent deformation, the equivalent thermal moment of thetemperature distribution on rotor section was proposed and the thermal deformaitonof a rotor under different axial distributions of the seciton temperature differencewas studied. The dynamical characteristics of a thermal bending rotor during faststart up was simulated, and the complicate vibration phenomenon under thecombination of thermal bending and unbalance was analyzed. The influence of thefading of thermal bending on the dynamics of a rotor was studied as well. Theresults could be a theory reference for the analysis and diagnosis of the vibraitonproblem during the fast start up of a gas turbine rotor.Based on the elasitc-plastic contact model of rough surfaces, the elastic-plasticcontact stiffness between discs of tie-bolted fastened rotor was studied and thedynamical model of a tie-bolted fastened rotor with the consideration ofelastic-plastic contact were established, The dynamics and its influences of atie-bolted fastened rotor were studied. A finite element model for the rotor axialtemperature was established, and the influence of thermal expansion and variation ofmaterial properties due to axial temperature distribution on the dynamics oftie-bolted fastened rotor was studied. The thermal bending of tie-bolted fastenedrotor was studied, and the dynamics of thermal bending tie-bolted fastened rotorduring fast start up was investigated.The test rig for the measurement of tighten force of rod was designed, and thetighten forces under different torques were measured, comparision with the resultsof analytical formulation was conducted. In order to reduce the difference of thetighten forces of rods, the vertical assemblage, symmetry crossing tightening andtighgen by steps were applied. The dynamical responses of tie-bolted fastened rotorwere measured under different torques, and the variations of the critical speeds withtighten forces were investigated. The experimental results were compared withtheory analysis, which validated the theory analysis.