Multi-objective optimization of an axial flow hydraulic turbine with a collection device to be installed in an open channel

In this study, a multi-objective optimization design method was developed by combining, among other methods, single-phase flow analysis and the optimization method to simultaneously optimize the runner and collection device of an axial-flow hydraulic turbine with a collection device, using the power coefficient and axial thrust coefficient as objective functions. To verify the effectiveness of this design method, the characteristics of the optimized turbine were investigated through verification experiments and multiphase flow analysis, and were compared with the results of single-phase flow analysis. The results of single-phase flow analysis showed that the axial thrust coefficient of the optimized turbine was equivalent to that of the original turbine, while the power coefficient improved dramatically. However, the results of the multiphase flow analysis showed that although the axial thrust coefficient of the optimized turbine was increased compared to that of the original turbine, the power coefficient was significantly higher than that of the results in the single-phase flow analysis, due to a significant increase in the efficiency of the turbine, as well as an increase in the loading coefficient and the inlet velocity ratio, unlike the single-phase flow analysis. This indicates that this design method is effective in terms of output improvement.