Analysis of the influence of extraction chamber non-uniformity flow in a steam turbine on the post-extraction stage

The paper presents a numerical investigation of the influence of regenerative steam extraction on the formation of circumferential flow non-uniformity and its impact on the post-extraction stage of a steam turbine. In contrast to most existing studies, the simulation was performed considering the full geometry of the extraction chamber and outlet pipe, with full-annulus modeling of the post-extraction stage and without circumferential averaging of flow parameters. Numerical simulations were carried out using a CFD solver implemented in the NUMECA software package. It is shown that when the extraction chamber and nozzle guide vane are coupled through direct parameter transfer (connect), a pronounced quasi-steady circumferential non-uniformity is formed, which cannot be captured using periodic approaches. The influence of this non-uniformity on the integral stage characteristics, including the relative internal efficiency, has been established. The obtained results confirm the necessity of accounting for the real extraction pipe geometry when analyzing steam turbine flow paths.
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