Flowpath assembly for a turbine diaphragm and methods of manufacture

A method of manufacturing a turbine steam path assembly comprising the steps of:

• providing arcuate inner and outer bands of different diameters;
• providing a plurality of stator blades each having root and tip portions, an airfoil portion between said root and tip portions, and a footprint in a radial direction within which all surface areas of said airfoil portion projected in that direction onto a tangential plane normal to said generally radial direction lie either within or coincident with peripheral confines of said footprint;
• forming a plurality of circumferentially spaced openings through said inner band between inner and outer surfaces thereof for receiving the root portions of said blades;
• forming a plurality of circumferentially spaced openings through said outer band between inner and outer surfaces thereof of a cross-section larger than the openings through said inner band and at least as large as said footprint such that the blades are receivable through said outer openings;
• forming said tip portions of said blades with cross-sectional configurations at least as large as said footprint and generally complementary in cross-sectional shape thereto;
• arranging the inner and outer bands generally concentrically relative to one another;
• inserting said blades in a radially inward direction through the openings in said outer band to locate said root portions in the openings in said inner band and said tip portions in the openings in said outer band;
• providing stops at transitions between said root portions and said airfoil portions;
• engaging said stops against said inner band to preclude further radially inward inserting movement;
• and
• welding said blades to said inner and outer bands.

A flowpath assembly for the diaphragm of a turbine, comprising:

• circumferentially extending inner and outer bands spaced radially from one another, each of said bands having a plurality of circumferentially spaced openings extending through the bands between inner and outer surfaces thereof;
• a plurality of stator blades extending generally radially between said bands, each blade having root and tip portions for reception in the openings of the inner and outer bands, respectively, and a twisted and bowed airfoil portion extending between the root and tip portions;
• each said blade having a generally airfoil-shaped footprint in the generally radial direction within which all surface areas of said airfoil portion projected in that direction onto a tangential plane normal to said generally radial direction lie either within or coincident with peripheral confines of said footprint;
• said openings in said outer band having a generally airfoil-shaped cross-section at least as large as said footprint and generally complementary in shape relative to said footprint such that the blades are receivable through said outer openings with clearance, at least said tip portions of said blades having cross-sectional configurations at least as large as said footprint and substantially corresponding in cross-section to the cross-section of the openings though said outer band;
• said blades and inner and outer bands being welded to one another;
• the openings through said outer band being defined by walls extending generally parallel to one another between inner and outer surfaces of said outer band;
• said root portions of said blades having walls extending generally parallel to one another, the openings through said inner band being defined by walls extending generally parallel to one another and generally complementary in shape to the walls of said root portions;
• the walls of said openings in said inner and outer bands being generally parallel to one another;
• and
• said inner band being inclined in a radially outer direction from one edge to its opposite edge.

A flowpath assembly for the diaphragm of a turbine, comprising:

• circumferentially extending inner and outer bands spaced radially from one another, each of said bands having a plurality of circumferentially spaced openings extending through the bands between inner and outer surfaces thereof;
• a plurality of stator blades extending generally radially between said bands, each blade having root and tip portions for reception in the openings of the inner and outer bands, respectively, and a twisted and bowed airfoil portion extending between the root and tip portions;
• each said blade having a generally airfoil-shaped footprint in the generally radial direction within which all surface areas of said airfoil portion projected in that direction onto a tangential plane normal to said generally radial direction lie either within or coincident with peripheral confines of said footprint;
• said openings in said outer band having a generally airfoil-shaped cross-section at least as large as said footprint and generally complementary in shape relative to said footprint such that the blades are receivable through said outer openings with clearance, at least said tip portions of said blades having cross-sectional configurations at least as large as said footprint and substantially corresponding in cross-section to the cross-section of the openings though said outer band;
• said blades and inner and outer bands being welded to one another;
• and
• a transition on each said blade at the juncture of said root portion and said airfoil portion forming a stop engaging said inner band and projecting laterally beyond confines of said inner band opening receiving said root portion.