叶顶汽封径向和轴向间隙对汽轮机泄漏量及主轴位移的影响

Influence of Radial and Axial Clearances of Blade Top Steam Seal on Steam Turbine Leakage and Main Shaft Displacement

通过对某化工厂汽轮机的叶顶汽封和主轴轴位移故障的分析,发现当漏气量增加到一定程度后会加快推力轴承的磨损,从而引起汽轮机轴位移逐渐增加,这表明汽封的损坏不仅引起泄漏增加还会导致主轴位移增加。采用FLUENT软件对叶顶汽封的流场进行数值模拟,研究汽轮机叶顶汽封的径向间隙和轴向间隙对汽轮机泄漏量及汽轮机主轴位移的影响,提出合理的工作间隙。研究发现:汽轮机叶顶汽封径向间隙是影响泄漏的重要因素,径向间隙增大将导致蒸汽泄漏量增大,汽轮机轴向推力增加,从而导致主轴位移增加;在总长度一定时,轴向间隙值对蒸汽泄漏量没有明显影响,但增加轴向间隙可以使进入汽封的蒸汽压力更加稳定。考虑到叶顶汽封的装配和热膨胀问题,对所研究的叶顶汽封提出了径向间隙为0.65 mm,轴向间隙为3.5 mm的修复方案,通过实践证明该方案现场修复是成功的。

Through the analysis of the displacement faults of the top seal and the spindle of a steam turbine in a chemical plant,it is found that the wear of thrust bearings will be accelerated when the air leakage increases to a certain extent and the shaft displacement of the steam turbine will gradually increase,which indicates that the damage of the seal not only causes the increase of leakage,but also causes the increase of the spindle displacement.The flow field of the top seal was simulated by using the FLUENT software,the influence of radial and axial clearance of the top seal on the leakage and the displacement of the main shaft of the turbine was studied,and the reasonable working clearance was put forward.The results show that the radial clearance of the steam seal on the top of the blade is an important factor affecting the leakage,and the increase of the radial clearance will lead to the increase of the steam leakage and the increase of the axial thrust of the steam turbine,which will lead to the increase of the spindle displacement.When the total length is fixed,the axial clearance has no obvious effect on the steam leakage,however the increase of the axial clearance can make the steam pressure to the seal more stable.Considering the assembly and thermal expansion of the blade top steam seal,a repair scheme with radial clearance of 0.65 mm and axial clearance of 3.5 mm was put forward for the studied blade top steam seal.Practice proves that the repair scheme is successful in site repair.