Numerical Modeling of the Axial Turbine Workflow to Improve Its Efficiency

The paper describes the results of the multi-criteria optimization of three-stage low-pressure. The aim of the optimization is to improve turbine workflow by three criteria: turbine outlet flow angle, value of residual swirl at the turbine outlet, and turbine efficiency. Full reprofiling of all blade rows is carried out while solving the optimization problem. Reprofiling includes a change in both shape of flat blade sections (profiles) and three-dimensional shape of the blades. Five numerical models of LPT with different density of computational mesh were created. All these models allow predicting the trend of the LPT characteristics, but they give a quantitative difference in the calculated parameters. The model with the fewest elements with turbulence model Spalart-Allmaras provides the shortest calculation time of one point of LPT characteristics. In addition, it allows predicting the LPT characteristics and can be used for optimization studies. The model with the most elements was used for the final check of the results obtained as the most accurate mesh. During the optimization, new LPT variants were found. They provide a decrease in the average value of the outlet angle by 12.9 degrees, as well as a decrease in the residual flow swirl at the turbine outlet by 9.8 degrees. These changes are possible due to some drop of efficiency (0.12%).