Numerical Investigations on the Aerodynamic Performance of Turbine Stage and Rotordynamic Characteristics of Stator Seal with Consideration of Supplementary Steam

摘要

The supplementary steam structure is used in the high pressure cylinder to increase the power output of steam turbine through increase the mass flow rate. In this work, the supplementary steam structure installed between the fifth and sixth stage of the high pressure cylinder of steam turbine is taken as the research object. The flow field and aerodynamic performance of the fifth and sixth stage was numerically investigated at different supplement steam rates using the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and k - turbulent model solutions. The inlet/outlet boundary flow conditions of the stator labyrinth seal of the sixth stage was determined based on the steady computations at three different supplementary steam rates. The unsteady flow field and rotordynamic coefficients of the stator labyrinth seal were calculated using the multi-frequency elliptical whirling orbit model and dynamic grid technique based on the unsteady RANS solutions. The numerical results show that the supplementary steam jet impacts on the hub regions of the stator blade of the sixth stage and results in the vortex flow. This flow behavior leads to the non-uniform inlet aerodynamic parameters at the entrance of the stator blade of the sixth stage. The aerodynamic performance decreases with the increase of the supplementary steam rates. The supplementary steam jet changes the inlet preswirl and boundary flow condition of the stator labyrinth seal of the sixth stage. The fluid excitation rotordynamic coefficients of the stator labyrinth seal would change due to the variation of the boundary flow condition. The detailed flow pattern of the turbine stage and variation of the rotordynamic coefficients of the stator labyrinth seal at different supplementary steam rates were also illustrated and discussed.