水轮发电机组上机架共振分析及补气减振

Research on upper bracket resonance and air admission damping of hydroelectric unit

对Himmelti电站水轮发电机组进行了稳定性试验研究,发现机组上机架在特定负荷时振动严重超标.根据实测的试验数据分析了发电机上机架振动信号与蜗壳进口、顶盖和尾水管压力脉动信号的关系,并对上机架和定子机座整体进行了动力特性分析,提取了该整体结构的固有频率,发现由于水轮机压力脉动在该负荷时的频率与上机架结构的固有频率接近,从而引起了上机架结构的共振.为寻求减振方案,还对机组进行了补气试验,即从水轮机顶盖向转轮内补入高压空气.实测补气后机组的压力脉动信号和振动信号,对蜗壳进口、顶盖和尾水管压力脉动信号进行频谱分析,发现引起机组上机架结构共振的频率成分消失,机组的整体振动幅值也大大减小.根据电站的实际情况提出了可操作的补气减振方案,即采用在原有自然补气阀下侧接入压力补气管的处理方案,方案实施后电站运行记录显示,机组在该负荷区域运行时,无共振现象发生.

The stability test research for turbine generator set of Himmetli power station showed that the vibration amplitude of upper bracket was out of limits in specific load zone.Based on the measured experimental data,the relationship between vibration signals of upper bracket and pressure pulsation signals of spiral case inlet,head cover and draft tube is analyzed.The dynamic characteristics of upper bracket and stator bracket are analyzed and the natural frequency is obtained.The results show that the frequency of turbine pressure pulsation in the load zone is close to the natural frequency of upper bracket,which leads to the resonance of structure of the upper bracket.The test of air admission for vibration reduction,adding high pressure air from head cover into runner,has also been done.The results show that,through the spectrum analysis of the pressure pulsation signals of spiral case inlet,head cover and draft tube after air admission,the frequency which causes resonance has disappeared and the vibration amplitude has been reduced greatly.Based on the actual situation of power plant,some practicable measures of air admission,that is,inserting the pressure air compensating pipe under the original natural air compensating valve side,are proposed.After putting these measures into practice,no resonance phenomenon occurs when the unit operates in that specific load zone.