This article is the first of a set and describes the results of surface pressure measurements and flow visualizations in a cascade of improved steam turbine nozzle blade profiles. In the course of expansion of steam in turbines, the state path crosses the saturation line and the fluid nucleates to become a two-phase mixture. Formation and subsequent behaviour of the liquid lowers the performance of turbine wet stages. Turbine two-phase flow conditions can be reproduced satisfactorily under blow-down conditions for systematic study. Following earlier studies of some typical profiles the performance of a new design of blades is presented. A substantially improved aerodynamic performance has been achieved by the new profile.
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