立式主泵水膜涡动故障诊断及机理分析

Aiming at the diagnosis of subsynchronous vibration problem which exists in multiple vertical reactor coolant pumps(RCPs for short)in a domestic nuclear power plant, the signal processing methods such as time-frequency analysis, 2D holospectrum are employed to analyze the vibration data of pump shaft. The time domain and frequency domain characteristics of vibration data during start-up and normal operation phase is summarized, according to which the basic reason of the subsynchronous vibration problem of RCPs is thought to be water film whirl failure occurring in the water-lubricated bearing. The mechanism of water-film whirl problem of vertical sliding bearing is further studied aiming at explaining the above phenomenon. Based on the fluid continuity theory and Newtonian fluid characteristics, the frequency characteristics of the water-film half-speed whirl is explained. According to the fact that the bearing water supply pressure is slightly higher than 15.4 MPa in the operating condition, the pressure distribution characteristics of the lubricating water inside the bearing are obtained, and the direction of the resultant force of the lubrication water pressure is further studied, which shows that the exciting force of self-excited vibration is provided by the water film whirl. A dynamic numerical model of water-film whirl failure is established to obtain the corresponding vibration characteristics. The above research has certain reference value for the fault diagnosis of water-film whirl and design improvement of vertical rotor.