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针对某在建核电厂6 000 k W级大型柴油发电机组风冷器的轴流风机振动超标缺陷,研究并治理风机振动故障。通过振动测量与频谱分析,发现子风机体的主要振动频谱成分为12.5 Hz,对应风机的旋转频率12.33 Hz。对风机-支承系统进行模态测量与模态分析可知,12.5 Hz的振动分量接近风机-支承系统的第二阶固有频率13.6 Hz。研究认为导致风机振动超标的主要原因是支承刚度偏低,且风机旋转频率附近存在结构性共振。风机运行过程中振动剧烈并出现周期性振动波动现象,当风机由单机运行工况切换至风机组整体运行工况后,振动频谱中12.5 Hz分量的幅值显著增大。采取简单加固措施提高支承刚度后,风机的振动水平降至标准限值内。
Aiming at the excessive vibration of the axial fan of the air cooler of a 6 000 kW class diesel generator unit under construction in a nuclear power plant, the fan vibration fault is studied and treated. Through the vibration measurement and spectrum analysis, it is found that the main vibration frequency spectrum of the sub-fan body is 12.5 Hz, corresponding to the fan rotation frequency of 12.33 Hz. The modal measurement and modal analysis of the fan-support system show that the vibration component at 12.5 Hz is close to the second natural frequency of the fan-support system of 13.6 Hz. It is considered that the main cause of excessive fan vibration is the low bearing stiffness and the structural resonance near the fan rotating frequency. During the operation of the fan, the vibration was violent and periodic vibration was fluctuating. When the fan was switched from stand-alone operation to the overall operation condition of the fan unit, the amplitude of the 12.5 Hz component in the vibration spectrum increased significantly. After the simple reinforcement measures to increase the support stiffness, the vibration level of the fan drops to the standard limit.