Research On Crack Position Sensitivity Of Combined Rotor Degradation

Gas turbine property will keep decreasing over time from starting operation to malfunction, namely the gas turbine degradation which is mainly due to degradation of the combined rotor that is the major part in gas turbine. Therefore, it is very necessary to make a study on the degradation law of combined rotors itself. Aiming at practical problems in project, a dynamic model for torsional vibration for combined rotor with m rods and n disks was established by utilizing the bond graph. Then, the position sensitivity of combined rotor degradation due to the microcrack on disks and rods was studied.Firstly, with regard to the non-continuous feature of combined rotors and the contact effect between disks, in this paper, relevant mechanical assumptions for combined rotors were made and base on the bond graph, a dynamic model for torsional vibration of combined rotors with m rods and n disks was established. It can be not only used to study the combined rotors degradation, but also used to analyzing the general dynamic characteristics of combined rotors.Secondly, in order to verify the validity of the model, the vibration characteristics of an experimental combined rotor was calculated and tested and then the comparison was drawn between theoretical calculation result, test result and theoretical calculation result for a continuous integral rotor. The result shows that the model established by this paper is valid, and there is a large difference between the combined rotor and the continuous integral rotor.Finally, the position sensitivity of combined rotor degradation due to the microcrack on disks and rods was studied. The result shows that the most sensitive position of combined rotor degradation due to the disk microcrack is on the centre disk and the most sensitive position of combined rotor degradation due to the rod microcrack is on each end of the rod. The outcomes of this dissertation develop the method for analyzing and establishing the combined rotor model. And they can be a theoretical support for structure optimize design, research on property degradation mechanism, law and trend prediction of combined rotors.