US2559131A - Hollow blade for gas turbines and the like - Google Patents

Description

y 3, 1951 H. OESTRICH EI'AL 2,559,131

HOLLOW BLADE FOR GAS TURBINES AND THE LIKE Filed April 11. 1949 s sheets-sheet 1 y-1 Fig.3

IIIIII/IIIIIIIIIIIIIIIIIIIIII!Ir r; u- 4 July 3', 1951 H. OESTRICH EIAL HOLLOW BLADE FOR GAS TURBINES AND THE LIKE Filed April 11. 1949 3 Sheets-Sheet 2 s Sheets-Sheet 3 HOLLOW BLADE FOR GAS TURBINES AND THE LIKE July 3, 1951 Filed April 11, 1949 Patented July 3, 1951 HOLLOW nuns Foa GAS 'rnnamss AND run-mm Hermann Oestrich, Hans Rosskopf, Alfred Renner, and Jakob ValteaDecize, France; said Rosskopf, said Renner, and said Valter assignors to said Oestrich Application April 11, 1949, Serial No. 86,703

In France April 22, 1948 Our invention has for its object a hollow blade cooled from the inside and preferably executed by means of a blank of sheet metal that is intended for gas turbines and the like machines operating with a flow of fluid.

In all blades of this type known to this day. the securing of a blade to a blade carrier, such as a turbine wheel is executed by means of wedging pins or keys or again through the engagement in zig-zag grooves of'wedging members or of suitable shaped parts.

The cooling fluid is introduced either laterally through ports provided in the vicinity of the root of the blade on the leading edge and the trailing edge of the latter or again through a recess provided between the root of the blade and the blade carrier, said recess being provided in one side of theroot assuming the shape of a case, which I side extends beyond the blade carrier. In both cases, the channels feeding the blades communicate with a chamber formed by a covering metal sheet and the blade carrier and into which is introduced the cooling fluid.

The drawbacks of known blades of this type consist in that they hardly satisfy the conditions of mechanical resistance and of secure fixation that are necessary for turbine blades, that the root of the blade and corresponding recess in the blade carrier are of a comparatively dimcult execution, that the securing inside the blade of the diaphragm intended for instance for the guiding of the cooling medium is a difficult matter, that the blades are interchangeable with some difllculty and the introduction of the cooling fluid into the blade leads to considerable losses by reason of the marked bands of the circuit and unavoidable losses.

The object of the invention is to provide a hollow blade that allows removing the above drawbacksand also the execution of a blade root, starting from a single blank of sheet metal. This is obtained by forming the blade in the following manner:

The metal sheet forming the wall of the blade is bent at one end so as to form the root, the cross-section of which assumes preferably the shape of a segment of a circle. The connection between the root and the body of the blade is performed at the ends of said segment along both sides of the bent blade through a plane 13 Claims. (01. 60-41) surface that provides together with the root for the fitting and guiding of the blade over the turbine wheel. The root is reinforced by an inserted pin and shows at its lower end one or more openings intended for the axial passage of the cooling fluid from the turbine wheel.

The hollow blade forming the object of the invention includes therefore a Laval type or similar root, that is well known per se and has proved satisfactory for solid blades.

The following description and accompanying drawings given by way of example and by no means in a binding sense will allow understanding how the invention may be executed, the features appearing in the drawings and in the specification forming obviously part of said invention. In said drawings:

Fig. 1 is a lateral elevational view of a hollow blade according to the invention.

Fig. 2 is 'a cross-section on a larger scale through line AA of Fig. 1.

Fig. 3 is a cross-section through line BB of Fig. 2.

Fig. 4 illustrates a modified shape that may be given to the trailing edge of the blade.

Figs. 5, 6 and 7 illustrate respectively in elevational view, in cross-sectional view and in longi- 'tudinal section a flat blank of sheet metal used for executing the blade.

Figs. 8 and 9 illustrate a manner of mounting the blade according to the invention on a turbine rotor. Fig. 8 is a partial elevational view of the rotor seen from the side corresponding to the leading edge while Fig. 9 is a crosssection through line 12-13 of Fig. 8.

The blade shown in Figs. 1 to 3 is obtained through the folding inside dies, by means of shaped tools, of a flat blank of sheet metal as illustrated in Figs. 5, 6 and 7. One end of the the joining surface at the lower end of the root between the lugs 1a and lb forming said root and that are welded together along said joining surface 6. The pin 4 is welded to the sheet metal forming the blade at both ends of said spindle and along the joining surface 6. In the example illustrated, the welding seam 8 provided on the side corresponding to the leading edge of the blade extends throughout the periphery of the pin 4 while the welding for the side corresponding to the trailing edge of the blade extends only over the lower half of the root for reasons of mechanical resistance. For similar reasons, the welding seam closing the body I of the blade extends over the trailing edge 10 only up to a point ll (Fig. 1) From this standpoint, it should be remarked that it is also possible to weld the pin 4 to the sheet metal forming the blade I and also to weld the latter along the joint 6 and further to weld the trailing edge It] in a manner such that the blade may be hermetically sealed throughout its surface except for the opening 5 provided in the root for the introduction of the cooling fluid and also for the opening provided for the output of said cooling fluid that is preferably provided at the tip of said blade.

In register with the opening 5, the pin 4 assumes a lesser cross-section so that the cooling fluid may pass into the inside of the blade to either side of the reduced pin portion 40. along the direction illustrated by the arrows. The crosssection of the reduced part of the pin may be given any desired shape. Instead of reducing the diameter of the pin, it is also possible to provide a gap in it or to perforate it in register with the opening 5. Preferably, the pin may be constituted by two separate members that are fitted into the root through the opposed ends thereof.

When the blade includes as in the embodiment illustrated a diaphragm l2 that serves for guiding the cooling air or for damping the vibrations or again simultaneously for both purposes said diaphragm' 12 engages the slot I3 of the pin 4 and extends into the lower end of the root where it is welded to the pin 4.

The root illustrated that has a transversal cross-section in the shape of a circular sector may be replaced by a-root of any desired crosssection that may be for instance square, rectanguerated through points or along a continuous line.

The starting material used for producing the blade through a folding of a flat sheet of metal is constituted according to the invention by a blank l5 cut to the desired shape as illustrated in Figs. 5, 6 and '7. When flat, said blank appears substantially as a rectangular member provided at one end with four rectangular lugs, l6-l1--l8-l9 adapted to'form the root of the blade. The size and spacing of the lugs are defined by the size of the openings to be provided in the root and by the diameter of the latter. It is preferable to make use of a metal sheet the thickness of which gradually decreases from the root towards the tip of the blade as illustrated in Fig. 7, that is a cross-section through line D-D of Fig. 5. The two edges Illa and lb of the blank that are to bear against one another after folding so as to form the trailing edge ll) of the blade are bevelled on their inner side in the manner illustrated in Fig. 6, that is a cross-section through line C-C of Fig. 5.

Preferably the depth of the bevel diminishes gradually from the root towards the tip of the blade as shown in dotted lines at 20a. and 20b in Fig. 5.

In order to provide for the shaping of the blank with a. decreasing thickness and possibly also with a bevelled edge, it is of advantage to use for instance rolling mill rolls inside which the desired .section is machined.

In order to produce the blade assuming the shape according to the invention, it is possible to use inplace of the flat sheet metal blank as disclosed a socket or. tube-shaped member that is stamped or drawn to the desired shape.

In the manner of mounting the blade according to the invention on a turbine wheel as illustrated in Figs. 8 and 9, said blade is fitted in corresponding grooves 2| or the rim 22. The reference number 23 designates the disc of the wheel carrying the blades while .24 designates a locking ring engaging the grooves [4 of the different blades, 25 a balancing member and 26 one of the channels provided through the rim 22 and through which the cooling fluid is fed to the blade or to the openings 5 provided in the root of the blades and progressing in the direction of the arrows. Fig. 8 shows in interrupted lines three such channels 26 that receive the cooling fluid from the chamber 21 formed by the disc 23, the rim 22 and the cover 28. This cooling fluid is fed to said chamber through suitable ducts that are not illustrated.

As illustrated in Fig. 9, the cooling fluid is admitted into the blade and flows through same without any sharp turns and the channelling system shows no leaking point.

Obviously various modifications may be brought to the hollow blade that has just been described in particular through substitution of equivalent technical means for those referred to without unduly widening thereby the scope of the invention as defined in accompanying claims.

What we claim is: l

1. In an inwardly cooled blade for gas turbines or the like machines having a hollow sheet metal body through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body atthe root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a tubular root assembly; and a pin fitted in said assembly, said assembly and said pin having corresponding apertures therethrough to provide a cooling fluid inlet passage to saidhollow body.

2. An inwardly cooled blade for gas turbines or the like machines comprising in combination a hollow sheet metal body through which a cooling fluid is adapted to pass constituted by a blank folded longitudinally through the major part of its length, corresponding lugs projecting from said body at the root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a tubular root assembly; and a pin fitted in said assembly, said assembly and said pin having corresponding apertures therethrough to provide a cooling fluid inlet passage to said hollow body 3. an inwardly cooled blade for gas turbines or the like machines having a hollow sheet metal body through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body at the root end of the front or the like machines having a hollow sheet metal body through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body at the root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a tubular root assembly, flat portions being provided between said body and the bent part of said lugs, said flat portions being parallel with one another and spaced by a distance less than the maximal width of said tubular assembly; and a pin fitted in said assembly, said assembly and said pin having corresponding apertures therethrough to provide a cooling fluid inlet passage to said hollow body.

5. An inwardly cooled blade for gas turbines or the like machines comprising in combination a hollow sheet metal body through which a cooling fluid is adapted to pass constituted by a blank folded longitudinally through the major part of its length, corresponding lugs projecting from said body at the root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a cylindrical tubular root assembly; and a pin fitted in said assembly, said assembly and said pin having corresponding apertures therethrough to provide a cooling fluid inlet passage to said hollow body.

6. In an inwardly cooled blade for gas turbines or the like machines having a hollow sheet metal body through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body at the root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a tubular root assembly, a welded seam being provided between the abutted ends of said lugs at the lower part of said root assembly; and a pin fitted in said assembly, said assembly and said pin having corresponding apertures therethrough to provide a cooling fluid inlet passage to said hollow body.

7. In an inwardly cooled blade for gas turbines or the like machines having a hollow sheet metal body through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body at the root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a tubular root assembly, a welded seam being provided between the abutted ends of said lugs at the lower part of said root assembly; and a pin fltted in said assembly, said assembly and said pin having corresponding apertures therethrough to provide a cooling fluid inlet passage to said hollow body, said pin being welded to said lugs along said welded seam and at its ends.

8. In an inwardly cooled blade for gas turbines or the, like machines having a hollow sheet m'etalbody through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body at the root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a tubular root assembly; and a pin fltted in said assembly, said assembly having an aperture therethrough and said pin having a reduced cross-section in register with said aperture to provide a cooling fluid inlet passage to said hollow body.

9. In an inwardly cooled blade for gas turbines or the like machines having a hollow sheet metal body through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body at the root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a tubular root assembly; and a pin fitted in said assembly, said assembly having an aperture therethrough and said pin including two parts separated by a gap registering with said aperture to provide a cooling fluid inlet passage to said hollow body.

10. In an inwardly cooled blade for gas turbines or the like machines having a hollow sheet metal body through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body at the root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a tubular root assembly; a pin provided with a diametrical slot fitted in said assembly and a metal sheet diaphragm located longitudinally inside the blade and including an extension engaging said slot in said pin and welded to said pin, said assembly and said pin having corresponding apertures therethrough to provide a cooling fluid inlet passage to said hollow body.

. 11. In an inwardly cooled blade for gas turbines or the like machines having a hollow sheet metal body through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body at the root end of the front and rear end thereof,-said lugs being bent with their outer ends in abutting relationship so as to form a cylindrical tubular root assembly; and a pin fitted in said assembly, said assembly and said pin having corresponding apertures therethrough to provide a cooling fluid inlet passage to said hollow body.

12. In an inwardly cooled blade for gas turbines or the like machines having a hollow sheet metal body through which a cooling fluid is adapted to pass, the provision of corresponding lugs projecting from said body at the root end of the front and rear end thereof, said lugs being bent with their outer ends in abutting relationship so as to form a polygonal tubular root assembly; and a pin fitted in said assembly, said assembly and said pin having corresponding apertures therethrough to provide a cooling fluid inlet passage to said hollow body.

13. An inwardly cooled blade for gas turbines or the like machines comprising in combination a hollow sheet metal body through which a cooling fluid is adapted to pass constituted by a blank folded longitudinally through the major part of its length; two pairs of spaced lugs projecting from said hollow body at the root end of the front and rear part thereof respectively, said lugs being bent with their outer ends in abutting relationship so as to form a tubular root assembly 7 provided with a central aperture therethrouth; UNITED STATES PATENTS and a pin fitted in said assembly, said pin havina Number Name m apertm thelfithrou h corresponding to 33m B65373 Budd Jan 15 1901 central aperture to provide a cooling fluid inlet 752,340 Hohwarth Feb. 16 1904 P 8 to said W i 1,200,775 swinger June 4, 191a 1,530,249 Eveleth Mar. 1'7. 1925 HERMAN OESTRICH- 1,001,402 Lorenzen Sept. 2a, 1920 ms ROSSKOPF- 2,220,420 Meyer Nov. 5, 1940 ALFRED RENNER- 2,251,920 Erb m Aug. 12, 1941 JAKQB 'F l0 2,297,440 Zellbeck Sept. 29, 1942 2:93:: 22: 12:: 2; o y REFERENCES CITED 2,459,429 Jacobi Jan. 18, 1949 The following references are of record in the 2,482,990 Olson Sept. 2'7, 1949 Nuinber Country Date 359,349 Great Britain Oct. 22, 1931

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