Investigation On The Nonlinear Dynamics Characteristics Of The Bladed-rotor/Casing Rubbing

The static clearance between the blade and casing is required to be smaller as the higher demand of efficiency of the rotating machinery, and so the possibility of rotor/stator rubbing rises up. On the one hand, as a common failure of the rotating machinery, rubbing could lead to various coupled fault and even fail the whole engine; on the other hand, as a kind of highly nonlinear phenomenon, rubbing is a kind of very complicated procedure which depends on many different parameters. Therefore, it is very necessary to propose a comprehensive parameterized model which can be applied into the research about the dynamics characteristics of the rubbing bladed-rotor.In this thesis, rubbing between bladed-rotor and casing has been investigated. Objects of investigation include mid-span bladed-rotor/casing system, mid-span no-blade rotor/casing system and asymmetric bladed-rotor/casing system. In this paper these systems has been modeled and corresponding numeric simulation has been conducted. Analysis and comparisons have been conducted on the spectrum domain and time domain. The main work of this thesis can be categorized as follow:(1) A new model of the blade/casing contact force, with the consideration of the effect the rotating blade as well as the local Hertz deformation of the casing, has been proposed. Contact forces have been obtained with various parameters applied into this model and analysis has been conducted for the influence of the geometric parameters of the blade as well as the casing material. Influence of these parameters to the dynamics characteristics of the rubbing bladed-rotor is also analyzed.(2) The proposed model is applied into the differential equations of the rubbing bladed-rotor. Numeric integrations and frequency analysis have been conducted with various parameters and different typical rubbing responses have been obtained. Emphasis is given on some special peaks on the spectrum and their physical meanings. Based on the comparisons between bladed-rotor/casing rubbing and no-blade rotor/casing rubbing, the characteristics of the bladed-rotor are discussed.(3) Equations of the asymmetric bladed-rotor system, which consist of the angular displacement of the rotor, are developed based on Lagrange equations and finite element method. Numeric simulations of the rubbing rotor are given with different angular speed and different typical responses are illustrated. The numeric results are used for verification for those obtained with the mid-span rotor model.