US2225769A - Turbine blade - Google Patents

Description

Dec. 24, 1940.

J. D. CONRAD 2,225,769

TURBINE BLADE- Filed March 17, 1939 2 q nl m In a,

&' h m '1 U a 2 m *2; i M \q \I" 1 mag A WITNESSES: I INVENTOR JOSEPH D. Connno.

I BY alarm ATTORNEY Patented Dec. 24, 1940 UNITED STATES TURBINE BLADE Joseph D. Conrad, Springfield, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 17,

9 Claims.

This invention relates to elastic fluid turbines,

and it has for an object the provision of improved blading for apparatus of this character.

A further object of the invention is the pro- 5 vision of a plurality of caulking strips for the root portion of a double, T-root blade and 50 associated therewith as to provide improved anchorage thereof to the blade-carrying member to enable the blade to withstand high, intermittent axial and tangential forces present in partial peripheral admission blading of this character.

Yet another object of the invention is provision of a double, T-root blade having an outer root head portion whose dimension axially of the blade-carrying member is greater than the corresponding dimension of the projecting blade portion, whereby tilting of the blade under axial loading is resisted.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing forming a part of this application, in which:

The single figure is a fragmentary, longitudinal sectional View of an axial-flow turbine showing an application of the present invention to the first impulse stage blading thereof.

In the drawing there is shown a turbine rotor I and a stator II, the latter being provided with a passage I2 for flow of motive fluid to the nozzles [3.

These nozzles are of the partial peripheral admission type, and are comprised by a nozzle group bolted or otherwise secured to the stator ll. Inasmuch as the motive fluid is supplied to the blades throughout only a portion of the circumference of the blade row, the blades pass into and out of the nozzle zone during each revolution of the rotor. Furthermore, as turbines of this type frequently operate under pressures of 750 lbs. and above, it will be apparent that the blades are subject to intermittent forces or blows corresponding to the pressure. This intermittent force has effective components in both axial and tangential directions. At the same time, the blades are subject to a constant radial or centrifugal force, assuming, of course, that the speed of the turbine is constant.

As shown, there is a pair of moving blades l5 and an intervening row of stationary reversing blades M. The blades l5 have their root portions l6 mounted in slots l1 extending circumferentially of the rotor Ill and having cross-sections approximating the blade root outlines.

Each blade root I6 is comprised by a spacing portion l8 having radial faces 19, and outer and inner pairs of lateral lugs 20 and 2|, respectively, provided with outwardly-facing abutment faces 22 and 23, respectively. An outer neck portion 1939, Serial No. 262,473

24 connects the spacing portion l8 and the outer J pair of lateral lugs 20 and an inner neck portion 25 connects the outer and inner pairs of lateral lugs 20 and 2|.

The outer lugs 20 have inner inclined faces 21. The corresponding inclined faces of the slot sides are provided with caulking seats 28 in which are disposed caulking pieces 29 compressively engaging the inclined lug faces 21 near their outer ends.

The bottoms of the slots I! are provided with caulking seats 3|, receiving caulking pieces 32 compressively engaging the inner faces 33 of the blades.

Due to the special construction of the nozzle block, and the bolting arrangement therefor, the space available for the section BB of the rotor, between said nozzle block and the first row of blades, is necessarily limited and would normally provide a weak point in the construction.

In order to relieve stresses on the section BB insofar as possible, the blade i5 is provided with the inner lateral lugs 20 taking a material portion of the centrifugal forces acting upon the blade. With a material portion of these centrifugal forces carried by the inner lugs 20, it is possible to reduce the size of the section BB, making it possible to increase the section AA, at the outer neck portion 24 of the blade root. Increase of this dimension at AA gives more strength in this section and further provides for corresponding increase in the dimension of the outer lugs 20, this, in turn, resulting in wider spacing of the same and consequent increase in the resistance of the blade to tilting under axial loading.

The use of the two sets of caulking pieces, 29 and 32, insures of firm frictional contact of all four faces on the lugs with their corresponding slot surfaces, thereby providing for maximum resistance to tilting of the blade under both axial and tangential loading.

With the caulking pieces 29 positioned adjacent the free or outer ends of the lugs 20, the radial components of the forces applied thereto will be as widely spaced as possible, thereby increasing the steadying effect thereof.

It is to be noted that these caulking pieces 29 engage faces of the lugs 20 which are disposed at material angles to the longitudinal axis of the rotor In. This insures that the components of the forces provided by the caulking pieces in planes normal to the planes of the surface engaged thereby, will be at a maximum to resist tilting of the blade under axial loading.

Throughout the specification and claims all terms and expressions relating to location or direction refer to such location or direction with respect to the axis of rotation of the blade-carrying member or rotor 10.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In a turbine, a rotor having a blade root slot and a row of blades having roots in the slot; said roots being of the T-type to provide lateral lugs having outwardly facing abutment faces,

said slot conforming approximately in cross-section to the root outline to provide circumferential abutment faces engaging the root abutment faces; said lugs having inner inclined faces converging toward the inner root ends; caulking seats provided at the slot sides adjacent to the outer ends of the lugs; and caulking in said seats and en gaging compressively said inclined faces of the lugs.

2. In a turbine, a rotor having a blade root slot and a row of blades having roots in the slot; said roots being of the T-type to provide lateral lugs having outwardly facing abutment faces, said slot conforming approximately in cross-section to the root outline to provide circumferential abutment faces engaging the root abutment faces; said lugs having inner inclined faces converging toward the inner root ends; caulking seats provided at the slot sides adjacent to the inclined faces of the lugs and caulkingin said seats and engaging compressively said inclined faces of the lugs.

3. In a turbine, a rotor having a blade root slot and a row of blades having roots in the slot; said roots being of the double T-type to provide inner and outer pairs of lateral lugs having outwardlyfacing abutment faces; said slot conforming approximately in cross-section to the root outline to provide inner and outer pairs of opposed circumferential abutment faces; the lugs of said outer pairs having inner inclined faces converging toward the inner root ends; caulking seats provided at the slot sides adjacent to the outer ends of the lugs of the outer pairs; and caulking in said seats and engaging compressively said inclined faces of the lugs of the outer pairs.

4. In a turbine, a rotor having a blade root slot and a row of blades having roots in the slot; said roots being of the double T-type to provide inner and outer pairs of lateral lugs having outwardlyfacing abutment faces; said slot conforming approximately in cross-section to the root outline to provide inner and outer pairs of opposed circumferential abutment faces; the lugs of said outer pairs having inner inclined faces converging toward the inner root ends; caulking seats provided at the slot sides adjacent to the inclined faces of the lugs of the outer pairs; and caulking in said seats and engaging compressively said inclined faces of the lugs of the outer pairs.

5. In a turbine, a rotor having a root slot and a row of blades having roots in the slot; said roots being of the double T-type having inner and outer pairs of lateral lugs providing inner and outer pairs of outwardly-facing abutment faces, having outer spacing portions provided with parallel side faces, and having neck portions between the outer spacing portions and the outer pairs of lugs and between the outer and the in ner pairs of lugs; said outer neck portion being substantially wider than the inner neck portion; said slot conforming approximately in cross-section to the root outline to provide inner and outer pairs of opposed circumferential abutment faces engaging the root abutment faces and to provide a pair of parallel faces engaging the side faces of the spacing portions; said outer lugs having inner inclined faces converging toward the inner root ends; caulking seats provided at the slot sides adjacent to the outer ends of the outer pairs of lugs and at the bottom of the slot; and caulking in said seats and engaging compressively the inclined faces of the outer pairs of lugs and the inner ends of the roots.

6. In a turbine, a rotor having a blade root slot and a row of blades having roots in the slot; said roots being of the T-type to provide lateral lugs having outwardly facing abutment faces, said slot conforming approximately in cross-section to the root outline to provide circumferential abutment faces engaging the root abutment faces; said lugs having inner inclined faces converging toward the inner root ends; caulking seats provided at the slot sides adjacent to the outer ends of the lugs and at the bottom of the slot; and caulking in said seats and engaging compressively said inclined faces of the lugs and the inner ends of the roots.

7. In a turbine, a rotor having a blade root slot and a row of blades having roots in the slot; said roots being of the T-type to provide lateral lugs having outwardly facing abutment faces, said slot conforming approximately in cross-section to the root outline to provide circumferential abutment faces engaging the root abutment faces; said lugs having inner inclined faces converging toward the inner root ends; caulking seats provided at the slot sides adjacent to the inclined faces of the lugs and at the bottom of the slot; and caulking in said seats and engaging compressively said inclined faces of the lugs and the inner ends of the roots.

8. In a turbine, a rotor having a blade root slot and a row of blades having roots in the slot; said roots being of the double T-type to provide inner and outer pairs of lateral lugs having outwardly facing abutment faces; said slot conforming approximately in cross-section to the root outline to provide inner and outer pairs of opposed circumferential abutment faces engaging the root abutment faces; said outer pairs of lugs having inner inclined faces converging toward the inner root ends; caulking seats provided at the slot sides adjacent to the outer ends of the outer pairs of lugs and at the bottom of the slot; and caulking in said seats and engaging compressively said inclined faces of the outer pair of lugs and the inner end faces of the roots.

9. In a turbine, a rotor having a blade root slot and a row of blades having roots in the slot; said roots being of the double T-type to provide inner and outer pairs of lateral lugs having outwardly facing abutment faces; said slot conforming approximately in cross-section to the root outline to provide inner and outer pairs of opposed circumferential abutment faces engaging the root abutment faces; said outer pairs of lugs having inner inclined faces converging toward the inner root ends; caulking seats provided at the slot sides adjacent to the inclined faces of the outer pairs of lugs and at the bottom of the slot; and caulking in said seats and engaging compressively said inclined faces of the outer pair of lugs and the inner end faces of the roots.

JOSEPH D. CONRAD.

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