Axial turbine for a gas turbine with limited play between blades and housing

Abstract

An axial turbine for a gas turbine including a rotor blade cascade is provided. The rotor blade cascade is formed from rotor blades each including, a front edge, a blade tip, and an annular space wall that surrounds the rotor blade cascade and includes an annular space inner side, enabling the annular space wall to be arranged directly adjacent to the blade tip forming a radial gap between the covering of the blade tip and the annual space inner side. When the turbine is in operation, the area of the blade tip with the highest pressure load is disposed in the region of the front edges, and the rotor blades in the region of their front edges include a radial projection and the annular space wall includes on the annular space inner side, a peripheral radial recess that interacts with the radial projections such that a minimum is established in the direction of the main through-flow of the turbine.

1 .- 8 . (canceled) 
     
     
         9 . An axial turbine for a gas turbine including a rotor blade cascade, comprising:
 a plurality of rotor blades each including a leading edge, a trailing edge, and a radially outwardly disposed, free-standing blade tip; and   a divergent annulus wall, encasing the rotor blade cascade, with an annulus inner side by which the annulus wall is arranged directly adjacently to the blade tips, forming a radial gap between the contours of the blade tips and the annulus inner side,   wherein the plurality of rotor blades at the plurality of blade tips each include a region with a highest pressure load of the plurality of blade tips between the leading edge and the trailing edge, and   wherein the plurality of rotor blades in the region of the highest pressure load include in each case a radial projection,   wherein the annulus wall on the annulus inner side includes an encompassing radial recess which, lying opposite the radial projections, is formed in such a way that a progression of the radial gap, as seen in the principal throughflow direction of the axial turbine, extends essentially with constant width in a wave-like, edge-free and step-free manner,   wherein the progression of the radial recess, as seen in the principal throughflow direction of the axial turbine, on the annulus inner side includes a first curvature section, a second curvature section adjoining the first, and a third curvature section adjoining the second, and   wherein the first curvature section is delimited from the second curvature section by a first inflection point and the second curvature section is delimited from the third curvature section by a second inflection point so that the curvatures of the first curvature section and the third curvature section include the same sign which is different from the sign of the curvature of the second curvature section.   
     
     
         10 . The axial turbine as claimed in  claim 11 , wherein the region of the highest pressure load of the rotor blade is arranged in a region of the leading edge. 
     
     
         11 . The axial turbine as claimed in  claim 12 , wherein the region of the highest pressure load of the rotor blade, amounts at most to 20% of a first height of the rotor blade and a remaining region of a second height of the rotor blade includes a further highest pressure load which is arranged in a region of the trailing edge. 
     
     
         12 . The axial turbine as claimed in  claim 12 , wherein the radial recess is arranged in the front third of the radial gap, as seen in the principal throughflow direction of the axial turbine. 
     
     
         13 . The axial turbine as claimed in  claim 12 , wherein a curvature of the first curvature section is greater than that of the third curvature section. 
     
     
         14 . The axial turbine as claimed in  claim 12 , wherein the progression of the radial projections, as seen in the principal throughflow direction of the axial turbine, on the plurality of sides of the radial projections facing the radial gap, is adapted to the progression of the radial recess. 
     
     
         15 . The axial turbine as claimed in  claim 11 , wherein the first inflection point is located in the region of the leading edge. 
     
     
         16 . The axial turbine as claimed in claim, wherein a plurality of sections of the radial gap, as seen in the principal throughflow direction of the axial turbine, which are upstream and downstream of and adjacent to the radial recess, are conical.