An Investigation of the End-Wall Boundary Layer of a Turbine-Nozzle Cascade

Abstract

Abstract As a part of a research program aimed at an explanation of the low efficiencies measured near the casings of turbines, an experimental investigation of the flow through a rectilinear cascade of turbine nozzles was conducted to study the effects of the end-wall boundary layer on the flow pattern through the nozzles. Secondary flows in the boundary-layer fluid produce an accumulation of low-energy fluid in the cascade exit plane that is considerably different from the flow field of the two-dimensional wakes. To describe the effects of the secondary flows, detailed data are included showing blade-pressure-distribution variations through the end-wall boundary layer, flow directions, and total and static pressure at cascade discharge, both with and without an inlet boundary layer on the end wall. From these data, qualitative conclusions have been drawn concerning the nature and origin of these low-energy accumulations. The most significant of these conclusions are (a) that the end-wall boundary-layer behavior inside the nozzle passage is essentially independent of the boundary layer entering the cascade; (b) the low-energy fluid which appears in the suction-surface end-wall corner at cascade discharge has its origin only in the end-wall and suction-surface boundary layers.