The influences of tip-clearance on the performance of nozzle blades of radial turbines

The effective turning angle of a nozzle becomes smaller and the pressure loss becomes larger as the tip-clearance of a turbine nozzle becomes larger. The mean flow angle at the nozzle exit was measured in four independent ways, and the results agreed well with each other. In order to predict the influence of the tip clearance on the nozzle characteristics, a simple flow model was proposed based on the measured pressure distribution on the nozzle blades, and the predicted exit mean flow angle and the pressure loss or the flow coefficient were compared with the experimental data with which good agreement was demonstrated.