Research On Fault Diagnosis Technology Of Intershaft Bearings In Aeroengine

Nowdays aeroengine usually uses a support structure with a intershaft bearing: such as PW's F119, Russian's AL-31 F and GE's CFM56 series. Intershaft bearing is prone to be damaged because of its special support position and poor operating conditions. When intershaft bearing is broken,sometimes it may cause excessive metal in the oil and need to be repaired, sometimes it may lead to serious accidents due to rupture of rotor. Therefore, it is necessary to the fault diagnosis of intershaft bearing.Aiming at intershaft bearing faults and their characteristics of signal transmission, the transmission paths of acoustic emission signals were studied, and fault feather acquisition methods based on acoustic emission signals of casing were determined. Based on a bearing fault simulation test bench, the acoustic emission signals of outer ring fault, inner ring fault,roller element fault and no fault of roller bearing were obtained and analyzed. This paper also collected fault signals of intershaft bearings in aeroengines, and preliminary diagnosis were given.In this paper a new signal analysis method was proposed which combined multi-scale morphological filtering and spatial correlation, and was used for the feature extraction of intershaft bearing acoustic emission signals. The simulation signals and rolling bearing outer ring acoustic emission experimental signals were used to validate the proposed method. It can be shown that this method can effectively extract the fault features of intershaft bearing acoustic emission signals. The method is simple and rapid, and it can extract minutiae of signal and preserve its main information at the same.A new method based on five-dimensional information entropy distance and SVM was proposed in this paper. Firstly, the five-dimensional information entropy distance of each fault was calculated, and then diagnosis was accomplished according to the methods proposed in the paper. It's shown that the method proposed in the paper can efficiently identify four faults,it's more suitale for inner and outer ring faults. The method was also verified with aeroengineacoustic emission data, and a satisfactory effect for intershaft bearing fault identification was obtained.