Study on vibration characteristics of three-stage brush seal rubbing fault of a counter-rotating aerojet engine

In order to solve the rotor-three-stage brush seal rubbing fault problem during the test run of a counter-rotating aerojet engine, based on the Fast Fourier Transform (FFT), the three-dimensional waterfall diagrams and color maps of different vibration measuring points on the casing, the frequency spectrum diagrams of the time-domain signal step section, and the amplitude maximum section are analyzed, respectively. The results show that the time-domain signal step section is the beginning of the engine fault, the amplitude maximum section is the serious fault section, and the amplitude of low and high-pressure fundamental frequency and abnormal high frequency of the serious fault section of each measuring point are higher than those of the beginning of the fault; in the low-frequency section, the fault causes a large number of components such as doubling frequencies k 1 f 1 , k 2 f 2 , and the combined frequency k 1 f 1 + k 2 f 2 of the low and high-pressure rotors to appear in the spectrum diagram. To investigate the cause of the fault, based on the results of the disassembly inspection and comparing the engine fault data with the normal vibration data, it is determined that the fault is caused by the increase in rotor vibration due to the rise in high-pressure rotational speed, which lead to the local rubbing between the rotor and the three-stage brush seal. Finally, the high-frequency 3 f 1 +6 f 2 feature in the vibration spectrum is explained in terms of the fault mechanism, and a universal identification method for rotor-three-stage brush seal rubbing fault is established.