High pressure turbine bucket including a cavity beneath a recessed tip

Abstract

The invention relates to a method for manufacturing a wheel blade (11) of a turbine engine, the wheel blade comprising a pressure face wall (14) and a suction face wall (15) spaced apart from each other, the wheel blade (11) comprising a tip end (S) having: - a bottom wall (18) extending from the pressure face wall (14) to the suction face wall (15), each of the pressure face wall and the suction face wall comprising a free edge (19, 21) extending beyond the bottom wall (18) to delimit, with the bottom wall (18), a groove shape (B); - a partition wall (22) extending from the pressure face wall (14) to the suction face wall (15) and spaced apart from the bottom wall (18) to delimit, with the bottom wall (18), a cavity (C) under the groove-shaped tip end; the method comprising: - a molding step to form at least the pressure face wall (14), the suction face wall (15) and the partition wall (22); - a step of forming the bottom wall (18) by additive manufacturing using the addition of a metal material.

Description

Technical Field

[0001] This invention relates to the manufacture of turbine blades (such as blades of turbojet engines, turboprop engines, helicopter gas turbines or auxiliary power units (APUs)) or blades of industrial gas turbines. Background Technology

[0002] exist Figure 1 In the turbojet engine shown in Figure 1, air enters the intake duct 2 and passes through a fan comprising a series of rotating blades 3, and is then split into a central main stream and secondary streams surrounding the main stream.

[0003] The main stream is compressed by compressor stages 4 and 6 before reaching combustion chamber 7. Afterward, the main stream expands through turbine 8 and is then expelled, generating thrust. The secondary stream is directly driven by the fan to generate the main thrust.

[0004] Each turbine 8 includes a series of radially oriented blades that are evenly spaced around a rotating shaft AX, which is rotatably mounted in an outer housing 9 surrounding the assembly.

[0005] The blades are cooled by air flowing through them, such as from a compressor or secondary flow, which enters at the root of the blade and exits through holes formed in the walls of the blades.

[0006] This impeller includes a tub-shaped tip, referred to as a grooved tip, which may include a cavity below the tub-shaped tip, in which air circulates to improve cooling of the tip.

[0007] Therefore, the complex internal and external shapes of these blades make manufacturing them by casting difficult: each hollow section must be defined by a core that must be rigidly held in the mold during the casting process. In fact, the complexity of the blade's shape, including the cavity beneath the recessed apex, makes manufacturing it by casting particularly difficult and therefore costly.

[0008] In this context, the object of the present invention is to provide a solution for simplifying the manufacturing of a blade that includes a cavity below a recessed tip, which improves cooling at the tip of the blade. Summary of the Invention

[0009] Therefore, the present invention relates to a method for manufacturing a turbine blade, the blade comprising pressure facets and suction facets spaced apart from each other, the blade comprising a tip having:

[0010] - Bottom wall, which extends from the pressure side wall to the suction side wall, the pressure side wall and the suction side wall each including a free edge that extends beyond the bottom wall to define a groove shape at the tip of the impeller together with the bottom wall;

[0011] - A partition wall that extends from the pressure side wall to the suction side wall and is spaced apart from the bottom wall, so as to define, together with the bottom wall, the cavity below the recessed top;

[0012] The methods include:

[0013] - Molding step to form at least pressure wall, suction wall and partition wall;

[0014] - The step of forming the bottom wall by adding metal material using additive manufacturing methods.

[0015] This solution allows the cavity to be formed below the grooved top without requiring a complex core arrangement to form the blank, which significantly simplifies the molding process and reduces the scrap rate during production.

[0016] The present invention also relates to a method defined in which the additive manufacturing method is a laser melting metal powder deposition method.

[0017] The present invention also relates to a method defined such that it includes forming dust holes in a bottom wall.

[0018] The invention also relates to a method in which dust holes in the bottom wall are oriented obliquely toward the edges of the pressure side wall and / or the suction side wall.

[0019] The present invention also relates to a method defined in which dust holes are formed in a partition wall that are offset from dust holes in a bottom wall.

[0020] The present invention also relates to a method in which the distance between each dust hole in the partition wall and the periphery of the impeller formed by the pressure side wall and the suction side wall is shorter than the distance between the corresponding dust hole in the bottom wall and the periphery of the impeller.

[0021] The present invention also relates to a method defined such that it includes forming dust holes through a bottom wall, each dust hole in the bottom wall being positioned facing a dust hole in a partition wall.

[0022] The present invention also relates to a method in which the number of dust holes formed through the bottom wall is the same as the number of dust holes formed through the partition wall.

[0023] The present invention also relates to a method defined in such a way as forming an air supply conduit in the impeller leading to a cavity below a recessed top.

[0024] The present invention also relates to a turbine blade for a turbine engine, which is obtained using a method defined in this invention.

[0025] The present invention also relates to a turbine engine comprising blades defined in such a way as to the present invention. Attached Figure Description

[0026] Figure 1 It is a longitudinal cross-sectional view of a known turbojet engine;

[0027] Figure 2 This is a full perspective view of the blade according to the present invention;

[0028] Figure 3 It is a cross-sectional view along a plane perpendicular to the axis of rotation of the blade according to the first embodiment of the present invention;

[0029] Figure 4 This is a perspective view of the top end of the blade according to a first embodiment of the present invention;

[0030] Figure 5 It is a cross-sectional view along a plane perpendicular to the axis of rotation of the blade according to the second embodiment of the present invention;

[0031] Figure 6 It is a cross-sectional view along a plane perpendicular to the axis of rotation of the blade according to the third embodiment of the present invention. Detailed Implementation

[0032] exist Figure 2 In the figure, according to the invention, the impeller denoted by reference numeral 11 includes a root P and a blade 12, through which the impeller is fixed to a rotor element (not shown), the blade being supported by the root P, and the root and blade being separated by a platform 13.

[0033] The blade 12 has a twisted shape about a so-called spanwise axis EV, which is perpendicular to the axis AX. The blade includes a base through which the blade is connected to the platform 13, and the base extends radially to a tip S, which constitutes the free end of the blade 12.

[0034] The two main walls of the blade 12 (i.e., the pressure side wall 14 and the suction side wall 15 of the blade) are spaced apart from each other in the central portion of the blade 11 and join at the leading edge 16 and the trailing edge 17 of the blade 11.

[0035] The tip S of the impeller 11 includes a bottom wall 18 that is generally perpendicular to the direction EV, extending from the pressure side wall to the suction side wall. This bottom wall (see...) Figure 3The end ends of the free edges 19 and 21 of the pressure wall 14 and the suction wall 15 are positioned toward the axis AX. The bottom wall 18, together with these edges 19 and 21, defines a hollow portion that opens in the direction opposite to that toward the axis AX, referred to as a grooved apex and denoted as B, located at the apex S.

[0036] like Figure 3 As shown, the impeller includes a cavity C below the recessed top end, the cavity being defined along the direction EV by a bottom wall 18 and a partition wall 22 extending from the pressure side wall 14 to the suction side wall 15, while the partition wall is spaced apart from and substantially parallel to the wall 18.

[0037] The impeller 11 includes cooling ducts located between the pressure wall 14 and the suction wall 15, extending substantially in the spanwise direction EV between the root P and the partition wall 22. These ducts are supplied with cold air collected at the root P to cool the various regions of the impeller.

[0038] Air flowing through these ducts (reference numeral 20 in the accompanying drawings) is discharged through dust holes 23 formed through the partition wall 22, and then through complementary dust holes 24 formed through the bottom wall 18. Thus, air from the cooling ducts enters the cavity C below the recessed top via holes 23 and exits to the recessed top B via holes 24. Therefore, this dust-removing air cools the bottom wall 18 and the cavity C below the recessed top (i.e., the impeller tip) without increasing the flow rate of air directed to the impeller for cooling.

[0039] Dust holes (such as holes 23 and 24) have a larger cross-section than other blade cooling holes to ensure that dust or impurities present in the cooling air collected at the root of the blade and originating from the external environment are removed to the outside of the blade.

[0040] To ensure effective dust removal from the impeller, each dust hole 24 in the bottom wall 18 is positioned along the direction EV toward a corresponding dust hole 23 in the partition wall 22, and the number of dust holes in the bottom wall is the same as the number of dust holes in the partition wall. More generally, the total cross-section of the holes in the bottom wall is equal to the total cross-section of the holes in the partition wall to ensure effective dust removal.

[0041] Alternatively, such as Figure 3 and Figure 4 As shown, dust holes 23 and 24 are offset from each other, causing air entering the cavity C below the recessed top from hole 23 to form a jet directed toward the bottom wall 18, thereby providing impingement cooling to the bottom wall 18. Impingement cooling provides an increased heat exchange coefficient, thus ensuring effective cooling.

[0042] More specifically, such as Figure 4 As shown, each hole 24 formed in the bottom wall 18 is offset from the corresponding hole 23 formed in the partition wall, that is, the projection of the hole 23 along the spanning direction EV on the bottom wall 18 is a certain distance away from the corresponding hole 24 formed in the bottom wall 18.

[0043] exist Figure 3 and Figure 4 In the example shown, the dust holes formed in walls 18 and 22 extend in the spanwise direction EV. However, it is advantageous that the holes 24 formed in the bottom wall 18 extend obliquely relative to the spanwise direction to provide air jets oriented toward edges 19 and 21, thereby cooling the edges.

[0044] To enhance cooling of edges 19 and 21, each hole 23 formed in the partition wall is advantageously positioned longitudinally toward a corresponding hole 24 formed in the bottom wall 18. Thus, the jet of air generated by the hole 23 is directed directly toward the corresponding hole 24 to pass almost directly through it, thereby ensuring effective cooling of the portion of edge 19 or 21 ventilated through the inclined hole 24. Therefore, advantageously, each hole in the partition wall at least partially opens to the corresponding hole in the bottom wall, which also allows for impact cooling before dust removal. The orientation of the holes 24 toward edges 19 and 21 ensures impact cooling of these edges.

[0045] In this case, the cooling air originating from the hole 23 will not impact the bottom wall 18: therefore, the cooling of the edge is more advantageous than the cooling of the cavity C below the grooved top.

[0046] like Figure 6 As shown, a greater flow of cooling air can be supplied to the cavity C below the recessed top by setting a pipe 26 to increase the flow of dust holes 24 oriented toward the edges 19 and 21, thereby further increasing the cooling of the edges 19 and 21.

[0047] To increase the thermal resistance of the impeller, the outer surface of the bottom wall 18 can be covered with a thermal barrier coating.

[0048] According to the present invention, the blade is obtained by first manufacturing a blank from a casting process, the blank forming the body of the blade including its root P, pressure face wall 14 and suction face wall 15 and at least partition wall 22, and then forming a bottom wall 18 on the blank by additive manufacturing to define the cavity C below the grooved top and the grooved top B.

[0049] A blank is obtained by casting using a mold and a set of cores, the set of cores comprising at least two elements spaced apart from each other along the spanning direction EV by a distance corresponding to the thickness of the partition wall. These core elements are mounted in the mold such that they are away from the inner surfaces of the mold, so as to define, together with these inner surfaces, the pressure wall 14 and the suction wall 15.

[0050] Before positioning the deposition apparatus near the partition wall 22, a bottom wall 18 is formed by positioning a blank in a clamping tool. The deposition apparatus mainly includes a metal powder deposition nozzle and a laser beam for melting the deposited powder.

[0051] This equipment is capable of performing additive manufacturing operations using a method known as Laser Metal Deposition (LMD). Other equipment may be provided for forming the partition wall 22 by additive manufacturing according to the LMD method or other similar methods.

[0052] Therefore, continuous metal layers are deposited and fused together to form the bottom wall 18 in a uniform manner. The apparatus is movable to cover the entire span of the bottom wall 18 to be formed via a sweeping motion. Alternatively, the blades can be positioned such that the spanwise axis EV of the blades extends horizontally, or is substantially inclined during the addition of metal material, such that the wall is formed in a near-vertical direction by additive manufacturing to minimize the draft angle during processing.

[0053] After the bottom wall is formed by adding metallic material, the bottom wall 18 may optionally be modified by machining (e.g., by electrical discharge machining or chemical treatment) to reduce the roughness of the outer surface of the bottom wall, thereby reducing the external heat exchange coefficient and thus reducing surface heating.

[0054] Advantageously, the bottom wall 18 is formed by adding a metallic material to have a non-constant thickness, defining a recess at each dust hole, for example, on the inner surface of the bottom wall (i.e., the surface closest to the root P). Thus, each recess forms an enlarged opening of the corresponding dust hole to facilitate the intake of air originating from the cavity C below the recessed top. Therefore, these recesses allow for a reduction in the number of holes 24 formed in the bottom wall 18, and / or a reduction in the cross-section of these holes, to increase the air velocity within the cavity below the recessed top, thereby improving cooling of the top.

Claims

1. A method for manufacturing a turbine blade (11), the blade comprising pressure facets (14) and suction facets (15) spaced apart from each other, the blade (11) comprising a tip (S) having: - Bottom wall (18) extending from the pressure surface wall (14) to the suction surface wall (15), the pressure surface wall (14) and the suction surface wall (15) each including free edges (19, 21) extending beyond the bottom wall (18) to define a groove shape (B) together with the bottom wall (18) at the tip (S) of the impeller (11); - A partition wall (22) extends from the pressure surface wall (14) to the suction surface wall (15) and is spaced apart from the bottom wall (18) to define, together with the bottom wall (18), a cavity (C) below the recessed top; The method includes: - A molding step to form at least the pressure wall (14), the suction wall (15), and the partition wall (22); - The step of forming the bottom wall (18) by adding metal material using an additive manufacturing method.

2. The method according to claim 1, wherein, The additive manufacturing method is a laser melting metal powder deposition (LMD) method.

3. The method according to claim 1, wherein the method includes forming dust holes in the bottom wall (18).

4. The method according to claim 3, wherein, The dust holes in the bottom wall (18) are oriented at an angle toward the free edges (19, 21) of the pressure wall (14) and / or the suction wall (15).

5. The method according to claim 3, the method comprising forming dust holes in the partition wall (22) that are offset from the dust holes in the bottom wall (18).

6. The method according to claim 5, wherein, The distance between each dust hole in the partition wall (22) and the periphery of the blade formed by the pressure wall (14) and the suction wall (15) is shorter than the distance between the corresponding dust hole in the bottom wall (18) and the periphery of the blade.

7. The method according to claim 5, wherein, Each dust hole in the bottom wall (18) is positioned at least partially facing the dust hole in the partition wall (22).

8. The method according to claim 5, wherein, The number of dust holes formed through the bottom wall (18) is the same as the number of dust holes formed through the partition wall (22).

9. The method of claim 1, wherein the method comprises forming an air supply duct (26) in the impeller leading to the cavity (C) below the grooved top end.

10. A turbine blade for a turbofan engine, said blade being obtained using the method according to claim 1.

11. A turbine engine, the turbine engine comprising the blades according to claim 10.

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