The development process for a new steam turbine low pressure (LP) section involves many contributors and requires many steps in order to meet a long list of requirements for mechanical integrity, aerodynamic performance, manufacturability, layout, and costs.At the end of the development process, because of all the uncertainties and difficulties of the design, Original Equipment Manufacturers are forced into an expensive validation step to assess the aeromechanical behavior and the performance level of the LP section.Testing a sub-component or testing a scaled model of the LP section are the approaches currently used in order to reduce this financial effort. In any case, testing campaigns are run at a limited number of operating conditions.&nbsp;Traditionally, a system of correlations has been used to build a performance model of the LP module. In this way it is possible to expand the usage of a limited set of experimental data to cover the application range encountered in the steam turbine market.&nbsp;Another approach, which has become feasible during the last decade, is the usage of CFD calculations.These two approaches include a certain amount of uncertainty in the performance of the LP section, mainly related to the losses caused by the moisture content in the flow.In the present paper, the results of the analysis of a cutting-edge low pressure section for small steam turbines are presented. The results are obtained by using a CFD commercial code with a set of user defined subroutines to model the effects of droplets nucleation and growth.Different operating conditions are considered, with different wetness at the exit and different pressure ratios, in order to show clearly the loss trend for different level of exit moisture.The numerical results are compared to the experimental data, showing a significant improvement in the performance predictability for the considered case and demonstrating the benefit of using a CFD approach instead of using existing correlations.

Two Phase Flow Cfd Modeling of a Steam Turbine Low Pressure Section: Comparison With Data and Correlations

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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