Research On Nonlinear Output Frequency Response Function Characteristic Of Rotor System With Rub-Impact Fault

The paper makes a deep research on rubbing fault diagnosis. Based on the deficiencies of the traditional spectrum characteristic analysis method on rubbing fault diagnosis, a fault diagnosis method of rub-impact based on nonlinear output frequency response function (NOFRF) is proposed and some useful innovation results are obtained. The research contents in this paper are mainly as follows1. The topic and research significance of this subject are introduced, the methods of nonlinear system identification, the domestic and foreign research situation of nonlinear output frequency response function and the development result of rub impact fault are discussed, the main content and innovation of this paper is given based on this.2. The dynamic model of rub impact rotor was established, and the change of NOFRF value in different rotor and stator clearance condition was discussed and analyzed. When the rub fault is slight, as if using the traditional spectrum analysis method for fault diagnosis, will not be able to more accurately identify the rub fault, and each order NOFRF value of system was analysisd by the method of nonlinear output frequency response function can accurately identify system of rub fault, effectively overcome the disadvantages of traditional methods. When the rotor system does not have a rub impact fault, the system has only the G1(jωF) value is not zero, the other all the order NOFRF value is equal to zero, which can be a good response to the state of the normal operation of the rotor system.3. The change of the NOFRF value of the rotor system with misalignment-rubbing coupled fault of the rotor system under different misalignment and different misalignment was discussed and analyzed. With the increase of the misalignment, G2(j2ωF) and G4(j2coF) value increase amplitude was bigger. With the increase of the misalignment angle, G2(j2ωF) and G4(j2coF) value was increase, and the G3(jωF) decreases. Therefore, it is able to identify the misalignment of the rotor system by the change of G2(j2ωF), G4(j2coF)and G3(jωF) value.4. The change of the NOFRF value of the rotor system with loose-rubbing coupled fault of the rotor system in different loose stiffness and different impact stiffness coefficient was discussed and analyzed. At the touch of impact stiffness coefficient unchanged, the values of G2(j2ωF) and G4(j2ωF) of the rotor system are increasing with the decrease of the loosening stiffness, and the increase of G2(j2ωF) is more than that of the rotor system, therefore, the system can be identified by the change of G2(j2ωF) and G4(j2coF). When the loose stiffness unchanged, the values of G3(jωF) and G3(j3coF) of the rotor system are increasing with the aggravation of the rub-impact, and the increase of G3(jωF) is more than that of the rotor system, therefore, the system can be identified by the change of G3 (jωF).5. The change of the NOFRF value of the rotor system with rubbing-crack coupled fault of the rotor system in different crack depth and different rotor and stator clearance was discussed and analyzed. At the same crack depth, with rubbing aggravated gradually, G2(j2coF) and G4(j2coF) value were increasing, and from the spectrum basically did not see second harmonic amplitude changes, so the NOFRF method can reflect rubbing coupling fault of crack case, touch small amplitude variation degree of friction. When 8=1×10-5m, with the deepening of the crack, the NOFRF value of the rotor system were increaced, especially G2(j2ωF) and G4(j2ωF) value increase amplitude is bigger, and from the corresponding frequency spectrum, the amplitude change is not obvious, therefore, the system of crack fault can be identified by the change of G2(j2ωF)and G4(j2ωF).6. A comprehensive summary about this paper is made and the research work which is necessary to focus on furtherly are summarized and prospected.