Method for manufacturing a turbine engine part and the thereby produced part

Abstract

A method for manufacturing a turbine engine part in which a first rough casting element includes a first face and a second face opposite to each other is assembled by the second face on an orifice which has a second element of the part. The method includes machining a through-cavity in the first element which opens at the first face and from the second face of the first element and machining the first face of the first element so as to form an area suitable for ensuring the attachment of a conduit on the first element. The machining of the cavity and of the first face is achieved by using a machining reference frame based on the second element.

Claims

1. A method for manufacturing a turbine engine part, the method comprising: providing a rough casted, solid attachment plate and an outer shroud, the solid attachment plate comprising a first face and a second face opposite to the first face, the first face configured for attachment of a conduit thereto, and the outer shroud having an orifice formed therein; after the providing of the rough casted, solid attachment plate and the outer shroud, welding the second face of the solid attachment plate on the outer shroud such that the orifice of the outer shroud is covered by the second face of the solid attachment plate, and such that a radially outer surface of the outer shroud is in contact with the second face of the solid attachment plate; after the assembling of the solid attachment plate to the outer shroud, machining a cavity in the solid attachment plate such that the cavity is centered with the orifice of the outer shroud, the cavity being a through-cavity extending from the first face to the second face of the solid attachment plate; and after the machining the cavity, machining the first face of the solid attachment plate to form an attachment area for attaching the conduit to the solid attachment plate such that the attachment area is centered with the orifice of the outer shroud.

2. The manufacturing method according to claim 1, wherein the turbine engine part is a turbine rear frame, the conduit is an outlet tube of a transient exhaust valve, and wherein an air flow leaving the transient exhaust valve crosses the solid attachment plate by passing through the cavity.

3. The manufacturing method according to claim 1, wherein the machining the first face forms attachments lugs for attaching the solid attachment plate to the conduit through pin bushings.

4. The manufacturing method according to claim 3, wherein the attachment lugs comprise six attachment lugs.

5. The manufacturing method according to claim 1, wherein attachment lugs are made on the first face of the solid attachment plate, the attachment lugs being portions of the first face which comprise a circular portion, and which protrude from a remainder of the first face, the attachment lugs each including a planar surface.

6. The manufacturing method according to claim 1, wherein the outer shroud comprises an attachment clamp.

7. The manufacturing method according to claim 1, wherein the rough casted, solid attachment plate comprises four side faces perpendicular to the first face and the second face, the first face of the solid attachment plate and the second face of the solid attachment plate being parallel to each other.

8. The manufacturing method according to claim 7, wherein the machining the first face of the solid attachment plate to form the attachment area comprises milling of the first face so as to form six lugs, and is configured to remove material from the solid attachment plate so that any point of the six lugs is separated by a strictly positive safely distance from any point of the four side faces.

9. The manufacturing method according to claim 1, wherein the machining the first face of the solid attachment plate to form the attachment area comprises milling of the first face of the solid attachment plate so as to form six lugs.

10. The manufacturing method according to claim 9, wherein the milling of the first face of the solid attachment plate so as to form six lugs is configured to remove material from the solid attachment plate during a first pass so as to form a second planar surface parallel to the first face of the solid attachment plate, the second planar surface being positioned, in a direction orthogonal to the first face of the solid attachment plate, between the first face of the solid attachment plate and the second face of the solid attachment plate.

11. The manufacturing method according to claim 10, wherein the milling of the first face of the solid attachment plate so as to form six lugs is further configured to remove material from the solid attachment plate during a second pass so as to form a third planar surface, the third planar surface being positioned between the second planar surface and the second face of the solid attachment plate.

12. The manufacturing method according to claim 9, wherein the machining the first face of the solid attachment plate to form the attachment area further comprises making of six pierced holes, each pierced hole being positioned at a center of a lug of the six lugs, respectively.

13. The manufacturing method according to claim 12, wherein four of the six pierced holes virtually define four corners of a rectangle in a plane parallel to the first face of the solid attachment plate, the two other pierced holes of the six pierced holes being positioned on sides of the rectangle.

14. The manufacturing method according to claim 1, wherein the machining the first face of the solid attachment plate to form the attachment area comprises surfacing of the first face of the solid attachment plate so as to correct flatness defects of the first face of the solid attachment plate.

15. The manufacturing method according to claim 1, wherein the outer shroud is a cylindrical axisymmetrical part relative to a central axis, wherein after the welding of the second face of the solid attachment plate on the outer shroud, the solid attachment plate protrudes from the outer shroud by radially extending outwards from the outer shroud.

Description

DESCRIPTION OF THE FIGURES

(1) Other features, objects and advantages of the present invention will become apparent upon reading the detailed description which follows, and with reference to the appended drawings, given as non-limiting examples and wherein:

(2) FIG. 1 illustrates a turbine rear frame for a turbine engine according to the state of the art;

(3) FIG. 2 illustrates a detailed view of the attachment of an outlet tube of a transient exhaust valve to the mouth of the turbine rear frame illustrated in FIG. 1;

(4) FIG. 3 illustrates a detailed view of a mouth of the turbine rear frame of FIGS. 1 and 2;

(5) FIG. 4 represents a flow chart of the steps of a first embodiment of the manufacturing method;

(6) FIG. 5 illustrates a possible embodiment wherein the part to be manufactured is a turbine rear frame of a turbine engine, the first element is a mouth for attaching an outlet tube of a transient exhaust valve, and the second element is an outer shroud of said turbine rear frame;

(7) FIG. 6 illustrates a top view of FIG. 5;

(8) FIG. 7 illustrates the embodiment illustrated in FIGS. 5 and 6 wherein the mouth is attached to an outlet tube of a transient exhaust valve.

DESCRIPTION OF ONE OR SEVERAL EXEMPLARY EMBODIMENTS

(9) In FIG. 4, a first embodiment is illustrated of a method for manufacturing a part for a turbine engine, notably an aircraft turbine engine.

(10) The method for manufacturing the part comprises a first step 100 consisting of assembling a first element and a second element together. The assembling of the first element on the second element must notably give the possibility of attaching a conduit to the part by attaching said conduit to the first element. The assembling may for example be carried out by welding the first element on the second element. The assembling is carried out with a first rough casting assembly. By rough casting, is meant that no step modifying the first element was carried out after manufacturing by casting said first element. The first and the second element may be of diverse shapes. The method is particularly suitable for giving the possibility of assembling an element forming a mouth or an inlet on which will be attached a conduit on a more bulkier element, so as to allow the fluid circulating in the conduit to penetrate into said more bulkier element by passing through said mouth or inlet. Thus, preferentially, the first element is a mouth or an inlet adapted so as to be attached to a conduit, and the second element is a hollow element for which the size is greater than that of the first element.

(11) In order that the attachment of the conduit to the mouth be leak-proof, it is necessary that the machining of said mouth be accurate.

(12) The first element comprises a first face on which the conduit is attached to said first element, a second face which is attached to the second element, and an edge which connects the first face to the second face. The first face and the second face are opposite to each other and parallel. The fact that the walls are parallel facilitates the machining of the first face of the first element when said first element is attached on the second element.

(13) The first element is assembled to the second element through its second face on the edges of an orifice which said second element has. The assembling may be carried out by welding the second face of the first element to the edges of the orifice of the second element.

(14) The method comprises a second step 200 consisting of machining the first element in order to form a cavity inside of said first element, the walls of which are machined. The thereby made cavity entirely crosses the first element. The machining carried out during the second step 200 is carried out by using a machining reference frame which is based on the second element. In other words, the path of the machining tool on the first element in order to machine it is located in the space relatively to the second element. According to a first possible alternative, the first rough casting element may comprise before the second step 200 a preformed cavity in its centre obtained during the foundry operation. In this first alternative, the second step 200 consists in machining the walls of the preformed cavity, so as to form a cavity at the centre of the first element, the walls of which are machined. According to a second possible alternative, the first element is a solid, i.e. not comprising any preformed cavity. Thus, in this second alternative, the second machining step 200 consists of digging a cavity at the centre of the first element, the thereby dug cavity therefore comprising machined walls.

(15) The manufacturing method comprises a third step 300 consisting of machining a first face of the first element in order to form attachment means, so as to form an area suitable for ensuring the attachment of the conduit on the first element. The machining of the first face of the first element during the third step 300 is carried out by using the same machining reference frame as during the second step 200, i.e. the machining reference frame which is based on the second element. According to a possible alternative, the machining during the third step 300 is carried out by achieving surfacing of the first face of the first element, by producing several pierced holes on said first face, and by tapping said pierced holes made on said first face. According to another possible alternative, the machining carried out during the third step 300 comprises the producing of lugs on the first face of the first element by digging into said first face of the first element, and that the pierced holes which are made on said first face during the third step 300 are located at the center of said lugs. The lugs are portions of the first face of the first element which protrude from the remainder of said first face and which have at least partly a rounded or globally rounded shape. The lugs allow attachment of the first element to a conduit by screwing a threaded element into the tapped pierced holes located at the centre of said lugs, for example a pin bushing. The third step 300 may also only consist in the production of pierced holes on the first face of the first element.

(16) Preferentially, the machining of the first face of the first element during the third step 300 is carried out by leaving a safety distance between the lugs and the outer edge of the first element, so that even if the first element deforms during the assembling with the second element, the lugs may be entirely formed in the first face of the first element without being trimmed. This alternative is notably preferred when the assembling of the first element to the second element is achieved by welding since welding deforms the second element and the first element.

(17) By using the second element as a machining reference frame for the second step 200 and third step 300 gives the possibility of simplifying the manufacturing method by keeping a single reference frame for the machining of said first element. By using the second element as a machining reference frame for the third step 300 also gives the possibility of increasing the accuracy of the machining of the attachment means as compared with the state of the art. Indeed, the machining reference frame is not based on a rough casting surface. Moreover, by machining the walls of the cavity during the second step 200 before forming attachment means during the third step 300, gives the possibility of compensating for the deformations generated during the assembling of the first and of the second element, thereby ensuring proper alignment of the cavity with the attachment means formed during the third step 300.

(18) According to a possible alternative, the second element comprises a connecting device, for example an attachment clamp, giving the possibility of attaching said second element to the remainder of the turbine engine. Preferentially, the machining reference frame for the second step 200 and the third step 300 is based on the connecting device of the second element. By the fact that the machining reference frame for the second step 200 and the third step 300 is based on the means for attachment of the second element gives the possibility of ensuring better accuracy in the positioning of the cavity formed during the second step 200 and of the attachment means formed during the third step 300 relatively to the remainder of the turbine engine, and thus better accuracy in the positioning relatively to the conduit. Indeed, the positioning of the second element relatively to the remainder of the turbine engine is determined by the positioning of the connecting device connecting said second element to the remainder of the turbine engine.

(19) In FIGS. 5 to 7, an example is illustrated, wherein the manufacturing method is used for manufacturing a turbine rear frame 7 of a turbine engine for an aircraft by assembling a mouth 8 for attaching an outlet tube 10 of a transient exhaust valve to an outer shroud 9 of said turbine rear frame 7. FIGS. 5 to 7 illustrate the turbine rear frame 7 once the manufacturing method has finished.

(20) In the example illustrated in FIGS. 5 to 7, the part described earlier corresponds to the turbine rear frame 7, the first assembly corresponds to the mouth 8, the second assembly corresponds to the outer shroud 9, and the conduit which is attached to said first element corresponds to the outlet tube 10 of the transient exhaust valve. In the example illustrated in FIGS. 5 to 7, the outer shroud 9 is identical with the outer shroud 3 of the turbine rear frame 1 of the state of the art.

(21) In the alternative shown in FIGS. 5 to 7, the mouth 8 is a hollow hexahedron with a rectangular section which comprises a first face 81, a second face parallel to the first face 81 (not visible in FIGS. 5 to 7), as well as four side faces 82 which are perpendicular to the first face 81 and the second face. The mouth 8 also comprises a cavity 83 in its centre which opens onto the first face 81 and onto the second face of said mouth 8. According to a possible alternative, the cavity 83 is of a rectangular shape.

(22) In this example illustrated in FIGS. 5 to 7, the mouth 8 is attached to the outer shroud 9 by welding during the first step 100 of the manufacturing method. During step 100, when the mouth 8 is welded onto the outer shroud 9, the mouth 8 is still raw x-foundry. The rough casting mouth 8 is for example a hexahedron, six faces of which are planar. The rough casting mouth 8 comprises a preformed cavity resulting from the manufacturing of said mouth 8 by foundry, this preformed cavity opens onto the first face 81 and onto the second face of said mouth 8. However, according to a possible alternative, the rough casting mouth 8 may be solid (without any preformed cavity resulting from the manufacturing of said mouth 8 by foundry). For the assembling of the mouth 8 on the outer shroud 9, the mouth 8 is placed facing an orifice which is made in the outer shroud 9. The orifice formed in the outer shroud 9 has a length and a width substantially identical with the length and with the width of the second face of the mouth 8. The perimeter of the second face of the mouth 8 is then welded to the edges of the formed orifice in the outer shroud 9. Once assembled to the outer shroud 9, the mouth 8 protrudes from the outer shroud 9 by radially extending outwards from said outer shroud 9.

(23) Once the mouth 8 is assembled to the outer shroud 9, said mouth 8 is machined during the second step 200. To do this, the mouth 8 is machined so as to form the cavity 83, the walls 84 of which are machined during the second step 200. In the case when the rough casting mouth 8 comprises a preformed cavity, the walls of the preformed cavity are machined by milling in order to remove material in order to enlarge said preformed cavity and obtain the cavity 83 visible in FIGS. 5 to 7. This material removal step during the second step 200 gives the possibility of compensating for the deformations produced during the first step 100. The machining operation achieved during the second step 200 uses a machining reference frame based on the outer shroud 9. In other words, the path covered by said machining tool during the milling of the mouth 8 is located in the space relatively to the outer shroud 9. Preferentially, the machining reference frame of this machining operation is based on an attachment clamp 91 of the outer shroud 9 through which the turbine rear frame 7 is attached downstream from the low pressure turbine of the turbine engine. If the mouth 8 does not comprise any preformed cavity, the cavity 83 is entirely dug into said mouth 8.

(24) Following the second step 200 wherein the walls 84 of the cavity 83 are machined, the first face 81 is machined so as to form an area suitable for ensuring the attachment of the mouth 8 with the outlet tube 10 of the transient exhaust valve. This machining is carried out by using the machining reference frame based on the outer shroud 9 which was used beforehand during step 200. In other words, the path covered by the machining tool during the machining operation of the third step 300 is located in the space relatively to the outer shroud 9. Preferentially, the machining reference frame of this machining operation is based on an attachment clamp 91 of the outer shroud 9 by which the turbine rear frame 7 is attached downstream from the low pressure turbine of the turbine engine. In the alternative shown in FIGS. 5 to 7, the machining carried out during the third step 300 comprises milling of the first face 81 so as to form lugs 85 (six lugs 85 in FIGS. 5 to 7) and the making of a pierced hole 86 at the centre of said lugs 85. Surfacing of the first face 81 may also be achieved during the third step 300 in order to correct the flatness defects of said first face 81, thereby improving the seal of the attachment with the outlet tube 10.

(25) The lugs 85 are portions of the first face 81 which comprise at least one circular or globally circular portion, and which protrude from the remainder of said first face 81. The lugs 85 are planar surfaces forming an attachment clamp on which a complementary attachment clamp of the outlet tube 10 of the transient exhaust valve is configured so as to be attached. The complementary attachment clamp of the outlet tube 10 comprises lugs which are located facing the lugs 85 when the outlet tube 10 is attached to the mouth 8. The lugs made in the outlet tube 10 comprise pierced holes which are located facing the pierced holes 86 when the outlet tube 10 is attached to the mouth 8.

(26) The milling of the first face 81 of the third step 300 in the alternative illustrated in FIGS. 5 to 7 is carried out in the following way: A first pass is carried out by removing the material from the first face 81 so as to form the lugs 85, thereby forming a first planar surface 87 comprising the lugs 85 and a second surface 88 also planar which is shifted relatively to the first surface 87 while being recessed in the thickness of the mouth 8. The first surface 87 comprises six portions protruding from the remainder of said first surface 87 which form the lugs 85. A second pass is carried out by again removing material from the first face 81 by following the contour of the lugs 85 formed during the first pass, thereby forming a third planar surface 89 which is shifted relatively to the second surface 88 while being recessed in the thickness of the mouth 8. The second pass tends to suppress the second surface 88 by digging in it in order to form the third surface 89 and thereby gain mass. As visible in FIGS. 5 to 7, it is possible that a portion of the second surface 88 remains at the end of the third machining operation 300 since the second pass cannot be carried out on the entirety of the contour of the first surface 87.

(27) The pierced holes 86 may be tapped in order to allow attachment of the outlet tube 10 to the mouth 8 through pin bushings or with simple bolts. A pin bushing is an attachment member comprising a threaded body which is screwed into a tapped hole and which comprises at least one key which may be driven into a groove dug in the thread of the body of the key so as to block the rotation of said threaded body inside said tapped hole in order to prevent said body from unscrewing. In FIG. 7, only screws 11 are visible, these screws 11 each cooperating with a pin bushing located inside a pierced hole 86 of the mouth 8.

(28) The mouths 8 illustrated in FIGS. 5 to 7 are less bulky than the mouths 2 of the state of the art illustrated in FIGS. 1 to 3, thereby giving the possibility of lightening the turbine rear frame 7 made with the mouths 8.

(29) Moreover, in order to take into account the deformations of the outer shroud 9 and of the mouth 8 due to the welding operation, the machining of the first face 81 during the third step 300 is carried out by providing safety distances for the machining during the design of the mouth 8. For example, a minimum safety distance A is provided between the contour of the lugs 85 and the outer edge of the mouth 8 formed with the side faces 82. This safety distance A may ensure that even if the mouth 8 deforms subsequently to the welding, the lugs 85 may nevertheless be entirely formed in the first face 81 without being trimmed.

(30) The mouth 8 according to the alternative illustrated in FIGS. 5 to 7 comprises six lugs 85 and six pierced holes 86, while the mouth 2 according to the state of the art illustrated in FIGS. 1 to 3 only comprises four lugs and four pierced holes, since the fact that the first face 81 and the second face of the mouth 8 are parallel makes the surface of the first face 81 of the mouth 8 greater than the surface of the first face 21 of the mouth 2 of the state of the art (by having the same surface area for the second faces of the mouth 8 and of the mouth 2 of the state of the art). By increasing the number of lugs 85 and of pierced holes 86, and therefore of pin bushings 11 or bolts, it is possible to maintain the same seal level for a greater surface.

(31) Moreover, the fact that the machining reference frame for the second step 200 and the third step 300 is based on the attachment clamp 91 gives the possibility of ensuring more accurate positioning of the cavity 83 machined during the second step 200 and of the attachment means generated during the third step 300 relatively to the outlet tube 10 of the transient exhaust valve.