Numerical investigation of partial admission losses in radial inflow turbines

Radial inflow turbines are taken as potential power conversion units for many power cycles where full admission is employed. The partial admission turbine is usually selected for small-scale power output due to the reduced mass flow rate and machining constraints, resulting in substantial low efficiency. The flow characteristics in different partial admission ratios are still unknown. The suitability of existing correlations for partial admission losses is also questionable since the partial admission loss model is usually established upon experimental results of axial turbines. In this paper, the three-dimensional computational fluid dynamics method is utilized to investigate flow characteristics within partial admission radial inflow turbines. The partial admission ratio varies from 0.05 to 0.9. The numerical loss break-down is then performed and compared against existing empirical correlations in literature, where the partial admission ratio from 0.158 to 0.526 is of interest. The suitable partial admission loss model (Stuter & Traupel windage loss model and Stenning expansion loss model) is finally selected and successfully employed to design partial admission radial inflow turbines preliminarily. The relative error of 3% is attained by comparing mean-line and numerical results. This paper provides insight into the partial admission loss mechanism within radial inflow turbines.