Configuration of the last moving blade row of a multi-stage turbine

Abstract

A multi-stage axial-flow turbine structure where in order to reduce the energy content of the gaseous working medium leaving the last moving blade row in comparison to the available heat drop, the flow discharge cross-section area from the last moving row, compared to the flow discharge cross-section area of the penultimate moving row, is made larger by some 10 to 40 % than would correspond to the ratio of the increase in volume of the working medium from the penultimate to the last moving blade now. This is accomplished, for example, by increasing the ratio of the passage width to blade pitch and/or by increasing the annular flow area, this ratio being varied over the length of the blades of the last row in order to obtain a uniform velocity profile in the axial and tangential directions. The desired result can also be obtained by making the flow discharge cross-section area of all moving blade rows preceding the last row smaller by an amount corresponding to the reduction in heat drop of the last moving blade row brought about by enlarging its cross-section area such as by decreasing the ratio of passage width to blade pitch and/or by reducing the annular flow area.

Dependencies are inferred from the claim text.