Design of a low pressure turbine stage with control stage characteristics for investigations of partial admission effects
Résumé
Partial admission is commonly used to control the power, especially of small scale steam turbines. However, asymmetric flow field results at the inlet of a turbine stage with part load control when one or more nozzles are closed. In this case a highly transient flow field with specific partial admission effects occurs. Especially the control stage of the turbine is high loaded in case of partial admission and therefore, additional losses result in the flow field. Those effects are investigated insufficiently, especially experimental data are rare. In this paper the reconstruction of an existing low pressure test facility to a control stage will be presented at first. According to the new stage design three dimensional CFD calculations are carried out with focus on the estimation of unsteady fluctuations and field of influence due to partial admission. Also the positions, where the important effects are noticeable are determined. After the numerical based design process and the numerical investigation to partial admission the test facility was modified and the measurement positions in the test facility are established.
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