An experimental assessment of incidence losses in a radial inflow turbine rotor

Abstract

The non-optimum angle of incidence at the rotor inlet is the primary cause of reduced efficiency at off-design operating conditions in a radial turbine. Prediction of the complete performance characteristic, rather than just the design point, is desirable when considering the radial turbine as part of a dynamic system, such as a gas turbine engine, air cycle refrigeration plant or a turbocharger. The existing, rather unsatisfactory, incidence loss models are summarized and any published experimental information about the effect of incidence angle is reviewed. Through the analysis of data obtained from experiments conducted by the authors and reported elsewhere, correlations are drawn between the magnitude of the rotor loss and the gas incidence angle at the rotor inlet. As a consequence of the analysis, a negative value for the optimum incidence angle is confirmed and consistent trends are presented for the effects of varying incidence angle at different rotor speeds.