Improving of the aerodynamic characteristics of turbine transonic nozzle vane cascades

Abstract

A detailed experimental investigation of two transonic turbine nozzle vane cascades aimed at improving their characteristics is carried out. The initial cascades had a convex suction side in the outlet area between the throat and trailing edge with skew angles equal to 11° and 15°. Only the shape of this suction side part was modernized. Different approaches to modernizing the cascades were used: in the first cascade with the flow outlet angle equal to around 17° and with the reduced flow outlet velocity λ1 = 1, a rectilinear segment with the skew angle decreased to 9° was formed on the suction side near the trailing edge, and in the second cascade with the flow outlet angle equal to around 23° and λ1 = 1.11, inverse concavity was formed in the same zone of cascade outline. A smaller flow over-expansion degree downstream of the throat was obtained in both cascades, the point of maximum velocity shifted toward the trailing edge, and lower flow velocity was obtained near the trailing edge. The study results confirmed that owing to the modernization, the profile loss coefficient at 0.9 = λ1 = 1.1 has decreased by 0.4–0.6%.