燃气轮机组压气机失速引发的不稳定振动分析

Analysis on Unstable Vibration Caused by Stall of Gas Turbine Compressor

针对某台大型燃气轮机组上发生的不稳定振动,通过对多次启停机和带负荷过程的振动测试,总结了燃气轮机不稳定振动特征。测试结果表明:在压气机进口侧轴承上振动较为明显,在其他轴承上也有反映;不稳定振动发生时的主频率为18~21Hz,该频率非实时转动频率的整数倍;故障发生后,振动幅值大幅度波动;故障具有一定的随机性和突发性,在启动升速和定速带负荷过程中都有可能发生。通过分析和比较气流激振和油膜失稳两类相似故障特征之间的差异,判断出不稳定振动是由燃气轮机组压气机失速引发的。该燃气轮机组没有配套水洗功能,长时间运行后因进口导叶(inlet guide vane,IGV)角度偏差和叶片积垢而发生失速故障。通过调整IGV开度,可解决燃气轮机组上发生的不稳定振动故障。

Aiming at the problem of unstable vibration of a large gas turbine, this paper summarizes characteristics of unstable vibration based on vibration tests for multiple start-up and shut-down processes and on-load operation. The test result indicates that vibration on the inlet side bearing of the compressor is more evident and also on other bearings. The main frequency when unstable vibration occurring is 18~21 Hz, which is not an integral multiple of real-time rotatory frequency. Vibration amplitude greatly fluctuates after the failure and the failure has a certain randomness and suddenness which is likely to occur in the process of start-up and on-load operation. By analyzing and comparing differences between two kinds of similar fault characteristics including stall and oil film instability, it figures out that unstable vibration is caused by stall of the gas turbine compressor. This gas turbine was not equipped with washing function and would break down with stall failure after long time operation due to angle deviation of the inlet guide vane (IGV) and fouling on the blade. By adjusting IGV opening, the fault of unstable vibration on the gas turbine is to be solved.