Performance Evaluation of Low-Pressure Axial Turbine using CFD-based Throughflow Method

The CFD-based throughflow (TF) method was applied to assess the accuracy of predicting the performance of a low-pressure axial turbine. In comparison to commercial CFD analyses, the CFD-based TF accurately estimated the performance parameters such as the choking mass flow rate, expansion ratio and total-to-total efficiency for an initial axial turbine design within minutes. Evaluation against the performance test results for the final manufactured axial turbine revealed that the CFD-based TF yielded predictions of the mass flow rate, expansion ratio and efficiency with a maximum error of 1.61%. However, limitations of the CFD-based TF were identified in resolving the passage vortex and the tip clearance flow due to its characteristics using only a singe computational cell in the pitchwise direction, leading to a local numerical error increase near 20% and 80% spans particularly influenced by these two flow features. Despite these constraints, the demonstrated accuracy suggests potential for integrating the CFD-based TF into the axial turbine design process for predicting the performance quickly.