流固耦合作用下可倾轴承瓦块颤振失稳研究

Research on the Flutter Instability Vibration of Tilting Pad Journal Bearing Considering Fluid-structure Interaction

以某试验台可倾轴承为对象,考虑瓦块与轴颈之间的运动耦合关系,建立可倾轴承油膜-瓦块流固耦合动力学模型。采用Newmark-β法求解可倾瓦块动态响应,得到升速过程中瓦块摆角及位移的波形、频谱。研究发现,在一定条件下,可倾轴承上瓦块会失去稳定位置,绕其支点作摆动及径向移动,导致瓦块颤振。随着转速升高,颤振幅度增大,一定转速后出现频率锁定现象,增加预载荷可以抑制瓦块颤振。计算和试验观测到的瓦块颤振特征相似。针对某台660 MW机组发生的不稳定振动故障进行了分析,发现颤振导致瓦背制动弹簧断裂,加剧了瓦块颤振,引发大幅振动,进而导致进油边乌金损坏、柱销及柱销孔磨损。通过增加预载荷及更换弹簧,解决了该机组不稳定振动问题。

Taking a tilting pad journal bearing of a test-bed as the research object,a dynamic model considering the coupling motion between pad and journal is established.The tilting pad response is solved by Newmark-βmethod.The waveform and frequency spectrum of pad swing angle and displacement during start up process are obtained.Results show that flutter caused by swing angle and displacement of pad will occur on certain conditions.The flutter amplitude increases as the rotation speed is increased.Frequency locking phenomenon occurs after a certain speed.The flutter instability can be controlled by increasing pad preload.The theoretical calculation results are consistent with the experiment results.Through the unstable vibration fault analysis of a 660 MW turbogenerator unit,it is found that flutter caused the breakage of the spring on the back of the pad.The broken spring aggravates the flutter of the pad and causes the large vibration.It results in the damage of babbit on oil inlet edge,eccentric abrasion of pins and pin holes.The problem can be solved by increasing pad preload and replacing the broken spring.