关键词: 汽轮发电机, 振动, 摩擦, 热变形, 故障诊断

Abstract: To investigate the periodic synchronous vibration fluctuations in turbine generator unis, the thermal shock effect caused by rub between carbon brushes and slip ring was considered. A coupled dynamic equation of bending and thermal deformation was established in the rotating coordinate system. The mechanism of periodic vibration and its influencing factors were analyzed based on the eigenvalue properties of the coupled dynamic equation. The research indicates that under synchronous forward precession, the contact point be-tween the carbon brush and the shaft of the turbine generator is fixed. The heat generated by rub is transferred to the shaft, creating a temperature difference across the section, which excites the vibrational fluctuations. The damping force model is used to establish the rub force equation between the carbon brush and the slip ring. The vibration rotation direction obtained from this is the same as the rotation direction when the rotating speed is below the critical speed, and opposite to the rotation direction when the rotating speed is above the critical speed. This model can explain this type of rub induced vibration phenomenon quite well. When operating within the resonance region, increasing damping can effectively reduce vibration fluctuations. When operating outside the resonance zone, the effect of increasing damping is limited. It is necessary to strengthen the ventilation and cooling of the slip ring, appropriately reduce the contact pressure between the carbon and the slip ring, and reduce the friction coefficient between the carbon brush and the slip ring, as well as between the carbon brush holder.

Key words: turbine generator, vibration, rub, thermal bend, fault diagnosis