US2972182A

US2972182A - Turbine and compressor blades

Info

Publication number: US2972182A
Application number: US714654A
Authority: US
Inventors: Kent Nelson Hector
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1957-02-22
Filing date: 1958-02-11
Publication date: 1961-02-21
Anticipated expiration: 1978-02-21

Description

Feb. 21, 1961 N. H. KENT TURBINE! AND COMPRESSOR BLADES Filed Feb. 11, 1958 2 Sheets-Sheet 1 FIG.2.

PIC-3.38.

F' I (5.3A.

INVE NTOR ATTORNEYS Feb. 21, 1961 N. H. KENT 2,972,182

TURBINE AND COMPRESSOR BLADES Filed Feb. 11, 1958 2 Sheets-Sheet 2 Neesorz, lNVENTO R ATTORN EYS 2,972,182 Patented Feb. 21, 1951 &5

2,972,182 TURBINE AND COMPRESSOR BLADES Nelson Hector Kent, Allestree, Derby, England, assignor to Roll's-Royce Limited, Derby, England, a British company Filed Feb. 11, 1958, Ser. No. 714,654

Claimspriority, application Great Britain Feb. 22, 1957 I 6 Claims. (CI. 291'56.8)

invention relates to the manufacture of blades and particularly turbine and compressor blades for internal combustion turbine engines for example from metals which are resistant to high temperature such as nickelchrome alloys.

Such blades may have passageways running axially of the blade for the flow of cooling or heating fluid such as air.

It has hitherto been proposed to form a blade of said type by a process including the following steps:

I (a) producing a billet,

(b) drilling a plurality of holes axially of the billet, the cross section of such holes being circular, and i (c) extruding the billet in a die with lubrication thereby to produce a blade section of approximate aerodynamic form, said holes being thereby deformed to be of substantially oval, elliptical or lenticular form, the major axes of which lie on or approximately parallel to the camber line of the blade.

According to the present invention the process of forming a blade in the manner described above is modified by drilling the holes to be of oval, elliptical or lenticular cross-section by an electrical drilling process, the extrusion of the billet being such as to extend the major axes of said holes and to decrease the minor axes thereof.

The adoption of the present invention enables blades to be produced having cooling passages with very high axis ratio.

In using the term axially we include holes which will eventually run through the blade spanwise and which may be inclined to the true axis of the blade and therefore initially of the billet. Thus for example in certain blade designs it may be desirable for the holes at the leading and trailing edges to be slightly so inclined to accommodate the narrowing of the blade toward the tip.

Electrical drilling processes used for the manufacture of blades in accordance with the present invention may include processes involving the removal of metal by electric spark action, by electric anodic action or by electric arc erosion or disintegration, such methods permitting the drilling of holes of oval, elliptical or lenticular form.

The billet may be initially of substantially rectangular cross-section, in which case deformation during the extrusion will take place substantially wholly between the two opposite faces of the rectangular section.

Preferably the holes are blind holes so that in the final extrusion these holes terminate adjacent the portion of the extrusion which is machined to form the root-fixing portion of the blade. Suitable holes may then be drilled in the root-fixing portion to connect with the holes in the profile portion of the blade which lead out through the tip shroud or platform.

The holes may be filled with a filler material prior to being extruded.

Preferably a split die is used for the extrusion which will facilitate the extrusion by pressure in a single sense. Filler material used in the manufacture of blades according to the present invention may be of low carbon steel and the filler material may be removed by dilute nitric acid to which a wetting agent has been added. A particularly suitable lubrication for the billet during extrusion may be obtained by nickel-plating the billet and applying a colloidal graphite to the extrusion die surface, as described in co-pending US. application Serial No. 702, 519 filed December 13, 1957, now Patent No. 2,947,076.

Platform portions may be formed at the tip and root portions of the blade either from material which is subsequently welded to or from metal left on the blade portion after extrusion or partly by one method and partly by the other. For this purpose the billet may be only partially extruded-that is to say a part of it will not be deformed in the extrusion process.

An example of this invention will be described by reference to the accompanying drawings.

Figure l is an elevation of a blade which may be manufactured by the process of the present invention.

Figure 1A is a view of the same blade in the direction at right angles to that of Figure 1.

Figure 2 is a vertical section through the billet from which the blade is to be extruded after the blind holes have been drilled.

Figure 2A is a section on the line IIA-IIA of Figure 2.

Figure 3 is an end view of one-half of the extrusion die.

Figure 3A shows the same one-half of the die in plan.

Figure 3B is a section through the two halves of the die on a plane at right angles to the two die faces.

Figure 4 is an elevation of the billet after extrusion.

Figure 4A is a section on the line IVA-IVA of Figure 4.

Figure 5 is a section on the line VV of Figure 4 after the blade profile portion has been twisted.

Figures 6 and 6A are diagrams showing the eifect on the drilled holes of the method of extrusion according to this invention.

Figure 7 shows a method of drilling the holes.

The billet 10 is formed from a cut bar by forging. Oval or elliptical blind holes 11 are then drilled in it by the electric arc drilling process described in co-pending US. application Serial No. 697,456 filed November 19, 1957 and illustrated in Figure 7. Rods of low carbon steel, e.g. of mild steel having a carbon content of less than 0.25% are inserted in the holes and are located by welding at the ends of the holes. The billet is then nickelplated to provide lubrication during extrusion and then heated and extruded in a split die, the two halves of which are shown at 12 and 13. In order to improve the lubrication during extrusion it has been found desirable to apply graphite to the surfaces of the extrusion die. During extrusion the reduction of cross-sectional area takes place substantially Wholly at right angles to the plane of the die split.

On removal from the die the billet has the shape shown in Figures 4 and 4A. The effect of the extrusion is to deform oval holes 11 into the shape shown in Figure 6A as a result of the extrusion pressure exerted in the direction of the arrow shown in Figure 6.

It will be appreciated that by initially drilling the holes to be elliptical and subsequently extruding the billet according to the method of this invention it is possible to produce blades with cooling passageways having a very high axis ratio.

The billet on removal from the die has a blade portion 14 and a non-extruded portion 15 from which an integral tip shroud will be machined.

The next step is to twist the blade portion 14 whereby a section as at VV of Figure 4 occupies the position shown in Figure 5 relative to the non-extruded portion of the billet 15.

Referring to Figures 1 and 1A it will be observed that the root-fixing portion of the blade comprises fir-tree fixing 20, a stem portion 21 and rudimentary platform portions 22. These parts are provided by the material at the tip 14a of the extruded section shown in Figure 4. Holes 24 are drilled through the 'fir-tree root 2'0 and stem portion 21 to connect with the flattened holes 1} in the blade profile portion.

From the unextruded portion 15 at the blade tip a tip platform 19 may be machined by means of a suitable cam profiling machining in known manner.

The filler material may be removed from the holes 11 at any time after extrusion and dilute nitric acid with a wetting agent added may be used for this purpose. 7

The initial drilling of the holes may be as described in co-pending U.S.application Serial No. 697,456 and illustrated in Figure 7.

The billet 18 is mounted in a carrier 22 which is caused gradually to travel downwards by a shaft 23 to which the carrier is bolted and which has a rack engaged by a pinion 25 carried by a shaft 26 supported in bearings from fixed structure 27 by a casing 28. Shaft 26 carries on one end a pinion 29 which is driven by a pinion 30 from an electric motor 31, the speed of which is controlled by a speed control 32. On the other end of shaft 26 is a pulley 33 carrying a weight 34 which helps to hold the billet steady. The electric motor drive causes the billet to descend at the rate of 0.02 to 0.08 inch per minute. An extension upward of shaft 23 slides through a bearing 35 supported from the fixed structure 27 and guides the shaft 23 vertically. V

A hollow tubular drill 35 is carried by a shaft 37 in a bearing 38 from the fixed structure. The drill is further supported by a series of X-shaped rods 39 from an upright cylinder 40 to which they are located by nuts 41. The rods at their point of intersection carry ring bearings 40a which support slidably the drill. The rods can be removed in turn as the drill passes further into the hole which it is forming in the billet. A sodium silicate solution of say one part of silicate to three parts of water or other suitable electrolyte solution is fed by compressed air from a tank 42 through pipe 43 to the hollow interior of shaft 37 whence it passes up through the hol low drill washing away the disintegrated debris and cooling the drill and billet at the point of disintegration. Thereafter it flows down between the drill and the walls of the hole to insulate the drill from the billet, the liquid passes from the cylinder 40 through escape pipe 45. The insulation of the side faces of the drill from the billet material is further increased by the formation of an anodic film which is not broken down by the reciprocation of the drill. At the bottom of shaft 37 an eccentric or crank 46 driven from a motor 47 through belt 48 causes the shaft 37 to be reciprocated or vibrated at a frequency from 3000 to 4000 cycles per minute.

A direct current or an alternating current superposed on a direct current is passed from lead 49 and drill 36 across the arc gap between drill and billet through the billet holder 22 and lead 50. Satisfactory drilling has V 4 been obtained using a voltage of between 6 and 24 giving rise to a maximum current of the order of amps.

I claim:

1. The method of forming from a metal which is resistant to high temperatures and for an internal combustion turbine engine a blade of the type which has cooling passages running axially thereof, including the following steps:

(a) producing a billet of said metal of roughly rectangular cross section having a major axis of the order of the finished width of the blade and a minor axis substantially greater than the finished thickness of the blade at its thickest point;

(b) drilling axially of the billet by an electric drill ing process a plurality of holes of generally elliptical cross section, having their major axes oriented generally the same as the major axis of the billet;

(c) filling each drilled hole with a close fitting filler of malleable metal capable of selectivedissolution for removal; 7' H (d) extruding the billet axially of the holes in .a die with lubrication to produce a blade section of approximately aerodynamic form by exerting extruding pressure in a direction to increase the major axes and decrease the minor axes of said drilled holes so that they become lenticular and a root section; Y

(e) machining the blade profile and then removing said filler.

2. The method claimed in claim 1 in which extrusion is carried out in a split die.

3. The method claimed in claim 1 in which the drilled holes are blind and in which registering holes are drilled through the rootportion of the billet after extrusion.

4. The method claimed in claim 3 in which part only of the billet is extruded including the blind portion and an integral tip shroud is machined from the non-extruded portion. 7

5. The method claimed in claim 4 in which the nonextruded portion of the billet terminates in an. inclined surface at its end adjacent the extruded portion.

6. The method claimed in claim 4 in which a root fixing portion is formed from the tip of the extruded portion of the billet.

References Cited in the file of this patent UNITED STATES PATENTS 2,013,622 1 Bedford et a1. Sept. 3, 1935 2,047,555 Gardner July 14, 1936 2,628,417 Peyches Feb. 17, 1953 2,751,988 Lemont et al. June 26, 1956 ,830,357 Tunstall et al Apr. 15, 1958 2,836,884 Graham Iune 3 i958 FOREIGN PATENTS 745,655 Great Britain Feb. 29, 1956 755,610 Great Britain Aug. 22, 1956 763,141 Great Britain a; Dec. 5,1956