New approach to calculations of turbine stages and regeneration extraction points

The article presents 200MW LP turbine stage calculations taking into account leakage flows over rotor blades in the regeneration extraction point area. A methodology is described which allows the user to shorten the time-consuming CFD calculations solving the Navier-Stokes equation system in the examined area. A two-stage procedure was applied in which two types of calculations were coupled together. The first type is a one-to-one passage calculation of a steam flow through the turbine stages in the vicinity of the extraction point. This type of calculations preserves the circumferential periodicity condition. The second type is a circumferentially non-symmetrical calculation of the flow through an inter-stage diffuser with an extraction chamber. The calculations were preformed using 3D CFD codes, FlowER and FLUENT, in the two above mentioned areas, respectively. The solution was found using an iterative procedure for these areas coupled by boundary conditions, until convergence of calculations was reached.