Profile loss and turbulence modelling in radial outflow turbine cascades

Abstract

Radial outflow turbines (ROTs) offer an alternative to single-stage high-work axial turbines, for example, in steam and organic Rankine cycle applications. Previous studies have shown that axial turbine loss correlations tend to over-predict losses in comparison with numerical data. However, only part of the most used loss correlations has so far been subjected to analysis while, additionally, the effect of turbulence modelling has not been widely covered in the open literature exploring ROTs. This study, therefore, examines the accuracy of a particular loss model known as Traupel's model on ROT profile loss prediction by comparing it with validated numerical simulations. In addition, the effects of different turbulence models on the flow fields are studied in detail. In doing so, this research shows that Traupel's model tends to over-predict loss. Crucially, the turbulence modelling approach is found to affect results significantly, which mainly originate from differences in the boundary layer and turbulence predictions.