Low pressure steam turbine construction

Abstract

A low pressure multi-stage axial flow steam turbine comprises an outer housing and an inner housing structure constituting a carrier for the rows of guide blading of the various stages. A steam inflow housing located within the inner housing structure forms the boundary of a crescent-shaped intake duct which surrounds and admits steam to the first stage guide blading which flows through the duct in the same direction as that in which the turbine rotor rotates, and the cross sectional area of the intake duct decreases progressively in the direction of steam flow therethrough such that the tangential components of the steam velocity conform to a predetermined function. The curvature of the intake duct at the inner periphery thereof increases progressively in the direction of steam flow therethrough such that the radial components of the steam velocity conform to a second predetermined function. The two functions can be correlated such that the tangential and radial components of the steam velocity are at least approximately equal to each other for the same cross sectional locations along the duct. One crescent-shaped intake duct which supplies steam to the entire periphery of the first stage guide blading may be utilized, or two such ducts may be utilized, each supplying steam to one-half the periphery of the guide blading.