| ABSTRACT:Combined rotor is the key part of gas turbine, it is important to assess the performance degradation degree and analysis degradation characteristics for making maintenance during operation. In this dissertation, performance degradation problems of mistuning combined rotor considering rod relaxation are systematically investigated, in which interface rough was considered. The main research contents and results read as follows:Firstly, the finite element model of combined rotor was established, in which interface rough preload was effectively concluded. The interface contact stiffness was equivalent for modulus of elasticity of the virtual material layer, and mistuning preload was expressed by additional preload, so as to establish dynamics modeling including preload negative mistuning and positive mistuning.Secondly, the degradation characteristics of combined rotor were studied under the condition of preload tuned. Dynamic features of combined rotor was analyzed which considering rod relaxation and interface contact effect, the relations that natural frequency change with time was obtained. Then, by defining degradation degree of combined rotor, degradation path was described through dealing with degradation data; degradation assessment for combined rotor was completed as well. In the end, unbalance response analysis of combined rotor was conducted according to different degradation degree; degradation characteristics of combined rotor were obtained. Bending vibration natural frequency was tested through adjusting the preload of rod, and compared with theoretical analysis result, confirmed correctness of the theoretical model and reasonability of degradation degree parameter.Finally, the degradation characteristics of combined rotor ware analyzed under the condition of preload mistuned. The effect of velocity, rod number and disk stage on dynamic characteristics of the combined rotor was studied based on the preload mistuned dynamic model. Performance degradation characteristics of combined rotor that preload mistuning were analyzed as well; degradation path of mistuned combined rotor was described through dealing with degradation data, unbalance response analysis of mistuned combined rotor was conduct, the results showed that:negative mistuning has great effect on unbalance response amplitude of combined rotor with the increase of time.The outcomes of this dissertation improve the fundamental theories of the performance degradation of combine rotor in gas turbine; they also can be a support for studying and designing new high performance gas turbine and assessing the performance reliability for making maintenance during operation. |
