Diaphragm for turbomachines and method of manufacture
AssigneeALSTOM Technology Ltd
InventorsBryan Roy Palmer, David Littlewood, David Paul Blatchford, Peter Frank Critchley, Adrian Lord
Life of this patent
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Abstract
A turbine diaphragm includes an annulus of static blades and an outer diaphragm ring surrounding the annulus of static blades and welded to the outer platforms. Each static blade has an inner platform, an aerofoil, and an outer platform. The inner platforms serve the function of an inner diaphragm ring, thereby reducing material and manufacturing costs. Furthermore, confronting edges of the inner platforms have an interference fit with each other and the aerofoils are in a state of torsional stress between the inner and outer platforms. The latter two features improve the dynamic characteristics of the diaphragm.
Claims15
A turbine diaphragm comprising:
- an annulus of static blades, each static blade comprising an inner platform, an aerofoil, and an outer platform;
- and
- an outer diaphragm ring surrounding the annulus of static blades and welded to the outer platforms;
- wherein the inner platforms together form an inner diaphragm ring, confronting edges of the inner platforms have an interference fit with each other, and the aerofoils are in a state of torsional stress between the inner and outer platforms;
- wherein mutually confronting edges of neighbouring inner and outer platforms comprise an interlocking cranked shape when seen in plan view;
- wherein confronting edges of the outer platforms comprise an interlocking double cranked shape when seen in plan view;
- and
- wherein each outer platform includes a leading edge and a trailing edge, wherein the mutually confronting edges of neighbouring outer platforms comprise, in sequence from the trailing edge to the leading edge of each outer platform:
- (a) a first axially aligned edge portion,
- (b) a first edge portion inclined to the axial direction,
- (c) a second axially aligned edge portion,
- (d) a second edge portion inclined to the axial direction, and (e) a third axially aligned edge portion, wherein the first, second, and third axially aligned edge portions are circumferentially offset from each other to form first, second, and third axially extending crank shaped arms, the first inclined edge portion connecting the first and second axially aligned edge portions and the second inclined edge portion connecting the second and third axially aligned edge portions, the first and second inclined edge portions thereby forming first and second inclined crank shaped arms.
A method of manufacturing a turbine diaphragm, the turbine diaphragm including an outer diaphragm ring and an annulus of aerofoil blades having radially inner and outer platforms formed integrally with aerofoils, neighbouring inner and outer platforms having mutually confronting edges that form interlocking cranked shapes when seen in plan view, the method comprising:
- initially assembling the annulus of blades so that selected confronting edge portions of neighbouring inner platforms are in contact with each other, while all confronting edge portions of neighbouring outer platforms have clearances between them;
- and
- radially compressing the annulus of blades with the outer diaphragm ring to a predetermined final diameter by forcible contact between an internal surface of the diaphragm ring and external surfaces of the outer platforms, so that clearances between selected confronting edge portions of the neighbouring outer platforms are closed up, the contact between the selected confronting edge portions of the neighbouring inner platforms becomes an interference fit, and an elastic torsional stress is formed in the aerofoils.
Dependencies are inferred from the claim text.