关键词: 汽轮机, 汽封改造, 振动, 膨胀不畅, 动静碰摩

Abstract: Steam seal modification can improve the thermal efficiency of steam turbines. Unfortunately it also may induce vibration problems in some units, among which some of them are quite stubborn and tough to be resolved. In this paper, the cause analysis is conducted on the vibrations observed after the honeycomb seal retrofit in the steam turbine shaft seal. The analysis concludes that the reason of the vibrations lies in the mismatch between the seal technical characteristics and the HIP shaft sealing process design, which causes the deformation of the steam seal and to some extents impedes the expansion of the HIP cylinder, thus consequentially gives rise to persistent frictional vibration at the steam seal. Based on the analysis, the paper also suggests that since significant temperature discrepancies exist between the seal steam and the casing temperatures in the HIP cylinder of many steam turbines under low load conditions, the honeycomb seal should be chosen with caution in order to avoid the frictional vibration problem.

Key words: steam turbine unit, steam seal modification, vibration, expansion impediment, rubbing