Efficiency predictions for axial-flow turbines

Abstract In order to compare the relative merits of various turbine geometries, computer programmes have been written for two loss-correlations and these have been used to predict both total-to-total and total-to-static turbine efficiencies over a wide range of geometries. The two correlations give good agreement when both stator and rotor blades are “nozzle” blades (i.e. blades with zero inlet angle), but show significant differences when either blade is an equiangular “impulse” blade, due solely to differences in the predicted secondary losses. Both correlations indicate that stage exit swirl or contraswirl is often desirable for optimum performance even when the total-to-static efficiency is the criterion.