Hollow spar for manufacturing a composite blade with resin injection

Abstract

The invention relates to a spar (82) for a turbine engine blade, which spar comprises a body (85) having an elongate shape along a main axis (Z) along which it comprises a first portion (86) configured to be inside an airfoil of the blade (58) and a second portion (67) configured to be outside the airfoil (62) and to form a root (66) of the blade (58), characterised in that the body (85) comprises a cavity (98) that communicates with an outer surface (100) of the first portion (86) via an opening (102) and a plug (104) received in the cavity (98) that closes the opening (102) that defines a first duct (106) of an internal cooling circuit (96) that comprises at least one second duct (108) that passes through at least the second portion (67) and that communicates with the outside of the second portion (67).

Description

[0001] DESCRIPTION

[0002] TITLE: HOLLOW SPAR FOR MANUFACTURING A COMPOSITE BLADE WITH RESIN INJECTION

[0003] Technical field of the invention

[0004] The invention relates to a spar used in the manufacture of an aircraft turbomachine blade and a method of manufacturing such a spar.

[0005] Technical background

[0006] The state of the art includes documents WO-2010 / 061139-A2 and FR- 3.109.115-A1 , US-2012 / 082563-A1 , GB-680-014-A, US-4-156-582-A, DE- 566-638-C.

[0007] New generations of engines require blades with compact roots because their blades are designed to pivot around their radial axes in order to adapt their incidence to different flight regimes. This is the case, for example, in the case of a ducted turbomachine with a double-flow, for the outlet guide vanes or OGVs which are located downstream of the fan blades. This is also the case for the propeller blades of unducted turbomachines of the "open rotor" type.

[0008] This feature adds to the need to attach the blade to the disc or hub that carries it as deeply as possible, i.e. as close as possible to the axis of the disc or hub. It is therefore necessary to significantly reduce the size of the blade root.

[0009] However, the blade in operation is subject to numerous constraints. Indeed, the blade root is mainly subjected to bending and tensile stresses, in particular due to centrifugal forces on the blade and due to possible impacts with birds. In addition, the roots of the blades of "open rotor" type turbomachines can be subjected to alternating bending stresses caused by the intense bending vibrations exerted on the blades due to the absence of a nacelle conditioning the air flow, as is usually the case on ducted engines. In order to be able to oppose these alternating bending moments, the roots are prestressed in the hub and are therefore subjected to an additional circumferential mechanical load.

[0010] The blades used in this type of application generally comprise blades made of a composite material in order to improve their thermomechanical resistance capacity and reduce their mass. The composite material can be made from a preform obtained by three-dimensional (or 3D weaving) or two-dimensional (2D weaving) weaving of fibers. This weaving is intended to form a fiber reinforcement and is embedded in a matrix formed by injecting a resin during an RTM (resin transfer molding) or VARTM (vacuum assisted resin transfer molding) injection process.

[0011] Three-dimensional weaving is generally preferred in this type of application because it offers better resistance to delamination. The term "three-dimensional weaving" or "3D weaving" refers to a weaving method in which warp yarns are bonded to weft yarns in several layers. Preferably, but not limited to, the 3D weaving has an interlock structure (or reinforcement). Interlock weaving has improved impact resistance, particularly compared to 2D weaving. Similarly, the preform is woven in a single piece.

[0012] The composite material can be monolithic or include a core, for example foam, to form a composite sandwich material. The latter provides rigidity and lightness to the final part. Indeed, the interposition of a cellular core such as a honeycomb or foam between two monolithic skins or layers of fibrous reinforcement (densified by a resin or not impregnated by a resin) makes it possible, on the one hand, to considerably increase the bending stiffness of the final part and, on the other hand, to control the mass in parallel by introducing a low-density material at the core (for the core), where the mechanical loading is low.

[0013] Finally, the blade has a cavity intended to receive a first part of a metal spar, a second part of which, external to the blade, forms the root of the blade. During its manufacture, the first part of the spar is coated with glue then inserted into the blade preform then the assembly is placed in a two-part mold which is closed. The mold is then heated to a so-called injection temperature which allows good diffusion of the resin, generally an organic resin, in the fibers. In the case of a VARTM process, the vacuum is created in the mold, then the resin is injected. Then follows a consolidation step during which the mold is maintained at a baking temperature, generally higher than the injection temperature, to ensure the crosslinking of the resin.

[0014] This conventional design carries a risk of creep of the adhesive film. Indeed, the vacuum created in the mold cavity of -1 bar (= -1.105 Pa) and the concomitant drop in viscosity of the adhesive film exposed to the rise in temperature of the preform before consolidation tend to cause the adhesive to flow deep into the fiber strands of the preform by capillarity. This dispersion of the adhesive or creep in the preform, reduces the thickness of the adhesive joint and compromises the assembly of the spar to the preform.

[0015] Such dispersion should therefore be avoided in the context of structural bonding.

[0016] Summary of the invention

[0017] To overcome this drawback, it is proposed to cool the spar after it has been placed in the mold and throughout the resin injection period. Cooling the spar advantageously allows the spar to be kept at a temperature lower than the injection temperature, which prevents the adhesive from creeping and dispersing into the composite material of the preform. To achieve this, the invention proposes a hollow spar capable of being easily cooled.

[0018] For this purpose, the invention proposes a spar for a turbomachine blade, in particular an aircraft blade, said spar comprising a body having an elongated shape along a main axis and comprising along said main axis a first part configured to be inside a blade of the blade, and a second part configured to be outside the blade of the blade and to form a root of the blade, characterized in that the body comprises a cavity which opens into an external surface of said first part by forming an opening, and in that the spar further comprises:

[0019] - a plug which is fixed to the body, this plug being engaged in the cavity and closing the opening, and

[0020] - an internal cooling circuit comprising at least a first conduit which is delimited between the plug and walls of said cavity and at least a second conduit which communicates with said at least first conduit, which passes through at least the second part and which opens outside the second part.

[0021] According to other characteristics of the spar:

[0022] - said at least one second conduit is arranged near a median axis of the second part,

[0023] - the spar comprises at least two second conduits which each communicate with opposite ends of said at least one first conduit,

[0024] - said at least two second conduits open through orifices in the same internal face of the cavity,

[0025] - the stopper comprises a cover which closes the opening of the cavity, a pad which extends into the cavity from said cover, and a rib which extends from said pad in contact with the internal face of the cavity between said orifices, sealingly delimiting two chambers in the cavity,

[0026] - at least one passage passing through said buffer places said chambers in fluid communication,

[0027] - the internal face is opposite the opening,

[0028] - the external surface of the first part is arranged substantially transversely relative to the axis of the body, at one end of said body which is opposite its second part,

[0029] - according to a first embodiment of the invention, the pad comprises: • two lateral edges arranged in a sealed manner in contact with lateral surfaces of the cavity,

[0030] • the rib, joining the two lateral edges,

[0031] • a light passing through said buffer and forming the passage,

[0032] - the stamp is plate-shaped,

[0033] - according to second and third embodiments of the invention, the pad is of a shape complementary to the cavity and it comprises at least one helical groove which is hollowed out in the periphery of the pad along an entire length of said pad, this helical groove comprising a first end opening opposite the cover on a first side of the rib in a first of the two chambers, and a second end located close to the cover,

[0034] - the passage extends through the buffer and has a first end which communicates with the second end of the helical channel and a second end which communicates with a second of the two chambers,

[0035] - more particularly, in the second embodiment of the invention, the passage passes through the tampon along the entire length of the tampon and its second end opens opposite the cover on a second side of the rib in the second of the two chambers,

[0036] - in the third embodiment of the invention, the tampon comprises two helical channels which are hollowed out in its periphery, which are of the same pitch and which are arranged in a double helix arrangement along the entire length of the tampon, and which comprise first ends which open opposite the cover each on one side of the rib respectively in the first and second chambers and second ends situated close to the cover,

[0037] - the passage crosses the buffer transversely and opens at its first and second ends into the second ends of the gutters,

[0038] - the cover is formed in a lid which extends over the external surface of the first part, closing the opening, said lid being glued to said external surface,

[0039] - the external surface of the first part is flat and machined, - the cap is made of thermoplastic material, preferably by injection by additive manufacturing,

[0040] - the stopper is made by molding and machining a foam, in particular polymethacrylimide, having a density between 0.15 and 0.5 kg / m3,

[0041] - the first part of the body and the cavity have respective sections elongated transversely with respect to the main axis,

[0042] - the sections of the first part of the body and of the cavity have edges which are substantially homothetic to the intrados and extrados edges of the blade of the vane,

[0043] - in the three embodiments of the invention, preferably, the at least one first conduit extends only in the first part, the at least one second conduit extends only in the second part, and the at least one first conduit and the at least one second conduit are connected at the junction of the first and second parts.

[0044] The present invention also relates to a blade for an aircraft turbomachine, comprising a blade and a root, this blade comprising a spar as described above, a first part of which is inside the blade and a second part of which is outside the blade to form said root.

[0045] The invention also relates to a method of manufacturing a spar for a turbomachine blade of the type described above, characterized in that it comprises the steps of:

[0046] A) providing a plug, and providing a spar blank having a body of elongated shape along a main axis and comprising along said axis a first part configured to form the first part of the body of the spar and a second part configured to form the second part of the body of the spar, said first part comprising a cavity which opens into an external surface of said first part by forming an opening,

[0047] B) machining the at least one second conduit until it opens into said cavity,

[0048] C) inserting the plug into the cavity, D) fixing the plug to the body.

[0049] Brief description of the figures

[0050] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0051] [Fig. 1] Figure 1 is a schematic axial sectional view of an example of a turbomachine to which the invention applies;

[0052] [Fig. 2] Figure 2 is a side view of a turbomachine blade according to the invention;

[0053] [Fig. 3] Figure 3 is a detail view of the foot of the blade of Figure 2;

[0054] [Fig. 4] Figure 4 is a perspective view cut through a transverse plane of the blade of Figure 2;

[0055] [Fig. 5] Figure 5 is a schematic view of a molding installation for molding a turbomachine blade using a spar according to the invention;

[0056] [Fig. 6] Figure 6 is a sectional view of the body of a spar according to the invention;

[0057] [Fig. 7] Figure 7 is a side view of the cap of a first embodiment of a spar according to the invention;

[0058] [Fig. 8] Figure 8 is a sectional view of the first embodiment of a spar according to the invention;

[0059] [Fig. 9] Figure 9 is a sectional view of a second embodiment of a spar according to the invention;

[0060] [Fig. 10] Figure 10 is a sectional view of a third embodiment of a spar according to the invention;

[0061] [Fig. 11] Figure 11 is a schematic view of the helical channels and the passage of the plug of the third embodiment of the spar according to the invention;

[0062] [Fig. 12] Figure 12 is a block diagram illustrating the manufacturing steps of a method for manufacturing a spar according to the invention; [Fig. 13] Figure 13 is a block diagram of a method for manufacturing a turbomachine blade comprising a spar according to the invention.

[0063] Detailed description of the invention

[0064] The invention which will now be described here applies here to a spar for a turbomachine blade but it will be understood that it can apply to any spar used in the manufacture of any type of part which can be made from composite materials, without limitation of the invention.

[0065] The partial axial sectional view of Figure 1 shows a turbomachine 10 with a longitudinal axis X which comprises various components which can be made of composite materials, such as blades.

[0066] The turbomachine 10 of Figure 1 is, in a non-limiting manner of the invention, a turbomachine 10 with a double body and a pair of counter-rotating propellers 12, 14 of the “open rotor” type intended to be mounted on an aircraft. The invention applies here for example to the blades of these propellers but it could just as well be applied to other types of blades, such as for example outlet guide vanes OGV (acronym for Outlet Guide Vanes) used in a secondary flow channel of a shrouded double-flow turbomachine, without fundamentally changing the nature of the invention.

[0067] The turbomachine 10 shown here mainly comprises, along a central longitudinal axis X and the air flow F circulating in the turbomachine turboshaft engine from upstream to downstream, a gas generator assembly 16, a propulsion assembly 18 comprising the pair of counter-rotating propellers 12, 14 constituting the unducted fan ("open rotor") and, between the gas generator 16 and the propulsion assembly 18, a transmission assembly 20 of the power delivered by the gas generator 16 in the direction of the propellers 12, 14, at the output of which are driven, respectively, in rotation opposite to each other, two concentric external output shafts 46 and internal 48 secured to respective rotating casings 50, 52 of the upstream 12 and downstream 14 propellers of the propulsion assembly 18.For each propeller 12, 14, a respective device 54, 56 is provided for changing the pitch of the blades of each propeller to independently vary the pitch of the latter according to the different operating phases of the turboshaft engine, in order to optimize the aerodynamic performance thereof.

[0068] As illustrated in Figure 2, the propellers 12, 14 each comprise blades 58, 60 each with a blade 62, 64 oriented substantially along a radial axis Z and a root 66, 68 which is rotatably mounted in a pivot (not shown) of axis Z of the associated casing 50, 52. This root 66, 68 is moved by the respective device 54, 56 for changing the pitch of the blades 58, 60 of each propeller.

[0069] In this embodiment, the blades 58, 60 of the propellers 12, 14 are made of a composite material with a fibrous blade preform embedded in a resin.

[0070] As can be seen in Figure 4 which more specifically represents a blade 58, each blade 58 comprises an aerodynamic blade 62 which extends along an axis which is parallel here to the radial axis Z. The blade 62 comprises a lower surface 70 and an upper surface 72 which are opposite along a transverse axis Y (perpendicular to the longitudinal axis X) and which are connected upstream by a leading edge 74 and downstream by a trailing edge 76.

[0071] The blade 62 comprises a casing 78 made of composite material made from a preform of the blade 62 stiffened by injecting a resin into said preform of the blade 62. The external walls of the casing 78 form the intrados surface 70 and the extrados surface 72. The casing 78 comprises a central cavity 80 receiving a spar 82, preferably metallic.

[0072] Optionally, the cavity 80 can also receive a foam core 84, interposed between the spar 82 and the casing 78, as shown here in FIG. 4, but this configuration is not limiting of the invention, the spar 82 being able to occupy the entire cavity 80 of the casing, the blade 62 then being devoid of foam. The spar 82 comprises a body 85 which comprises a first part 86 which occupies the cavity 80 of the casing 78 and a second part arranged outside the casing 78 which forms the root 66 of the blade 58.

[0073] The composite material of the preform is obtained from a three-dimensional (or 3D weaving) or two-dimensional (2D weaving) weaving of threads. In the present invention, we understand by the expression "three-dimensional weaving" or "3D weaving" a weaving method in which warp threads are linked to weft threads on several layers. Preferably, the weaving of the composite material of the preform is three-dimensional because it offers better resistance to delamination. Preferably, but not limited to, the 3D weaving has an interlock structure (or reinforcement). The interlock weaving has improved impact resistance, in particular compared to a 2D weaving. Similarly, the preform is woven in a single piece.

[0074] The weaving of the preform is carried out by means of a weaving installation (not shown) comprising a loom which is configured for three-dimensional and / or two-dimensional weaving. The composite material comprises a plurality of warp threads and a plurality of weft threads which are respectively oriented in directions which are perpendicular (in the plane or even in the thickness for 3D weaving). The weaving is advantageously carried out flat in a general longitudinal direction.

[0075] The yarns or strands used to make the weaving include, for example, carbon, glass, ceramic, silica, silicon carbide, Kevlar, polyamide, alumina fibers or a mixture of these fibers.

[0076] As illustrated in Figures 5 and 13, to obtain such a turbomachine blade 58, a method for manufacturing an aircraft turbomachine blade 58 comprising a blade 62 made of composite material and a metal root 66, comprises at least the following steps:

[0077] - a step a) of providing a blade preform 88 by weaving fibers, and of providing a metal spar 82 whose body 85 comprises a first part 86 configured to be inserted into a cavity 80 of said preform and a second part 67 configured to remain outside the preform and to form the root 66 of the blade 58,

[0078] - a step b) of applying glue to the first part 86 of the spar 82,

[0079] - a step c) of introducing the first part 86 of the body 85 of the spar 82 covered with glue into the cavity 80 of the preform 88,

[0080] - a step d) of depositing the spar 82 and the preform 88 in a mold 90 in two parts 90A, 90B and closing the mold 90,

[0081] - a step e) heating the mold 90 to a first predetermined temperature using a means 91 for heating the mold 90,

[0082] - a step f) of injecting a resin into the mold 90 using an injector cylinder 92 in order to impregnate the preform 88,

[0083] - a step g) of consolidation of the resin during which the mold 90 is maintained at a second cooking temperature, generally higher than the first temperature, for a determined duration to ensure crosslinking of the resin.

[0084] This configuration corresponds to the basic configuration of an RTM (Resin Transfer Molding) process. Preferably, the process is a VARTM (Vacuum Assisted Resin Transfer Molding) process which generally also comprises an additional step I) of vacuuming the mold 90 which begins after step d) and before step f) during which a vacuum pump 94 performs a vacuum in the mold 90 prior to injecting the matrix into it.

[0085] A problem arises due to the difference between the operating temperature of the glue used to glue the spar 82 and the first temperature at which the resin is injected. Indeed, the injection temperature of the resin to which the mold 90 is subjected is a determined temperature which is quite high (of the order of 160°C for an epoxy resin) and which tends to fluidify the glue with which the spar 82 has been previously coated before the consolidation of the matrix occurs. As a result, the glue tends to flow from the spar 82 and to penetrate the fibers of the composite material of the preform 88, thus weakening the assembly of the spar 82 with the preform 88. However, as shown in FIG. 3, a blade 58 is subjected in operation, at the junction of its blade 62 with the spar 82, to significant tensile stresses T and bending stresses F. Any weakening of the bonded connection between the spar 82 and the preform 88 must be prohibited.

[0086] The invention therefore proposes a spar 82 making it possible to remedy this drawback by preventing such creep of the glue during heating of the mold 90.

[0087] In this context, the spar 86 makes it possible to implement in the method a step i) of cooling the spar 82.

[0088] As illustrated in Figure 13, the method according to the invention comprises a step i) of cooling or maintaining the spar 82 at a third temperature which is lower than the first temperature. This step i) begins before step e) and ends after step f). Then follows the consolidation step g) during which the mold 90 is maintained at the second curing temperature for a determined duration, for example 2 hours, to ensure crosslinking of the resin.

[0089] It will be understood that this step can begin at any time before step e). However, for practical reasons, as illustrated in Figure 13, this step i) preferably occurs after step d), i.e. after the introduction of the preform 88 and the spar 82 into the mold 90.

[0090] In practice, the temperature of the spar 82 must be well below the first injection temperature. For a determined injection temperature of the order of 160°C degrees, during step i) the spar 82 is maintained at a third temperature which corresponds to ambient temperature, i.e. at a temperature of substantially 20°C.

[0091] As illustrated in Figure 5 which relates to a molding installation 104 and in Figures 8 to 10 relating to a spar 82 according to the invention, a spar 82 is used which is crossed by at least one internal cooling circuit 96, in which a cooling fluid is circulated.

[0092] More particularly, as illustrated in FIGS. 8 to 10, the body 85 of the spar 82 has an elongated shape along the main axis Z and it comprises successively along this axis Z the first part 86 which is configured to be inside the blade of the vane, and the second part 67 configured to be outside the blade of the vane and to form the root 66 of the vane.

[0093] According to the invention, as illustrated in Figures 6 to 10, the body 85 comprises a cavity 98 which opens into an external surface 100 of the first part 86, forming an opening 102, and the spar 82 further comprises a plug 104 which is fixed to the body 85. This plug 104 is engaged in the cavity 98 and closes the opening 102.

[0094] According to the invention, as illustrated in Figures 8 to 10, the internal cooling circuit 96 comprises at least one first conduit 106, which is delimited between the plug 104 and walls 110 of the cavity 98, and at least one second conduit 108 which communicates with said at least first conduit 106, which passes through at least the second part 67 and which opens outside this second part.

[0095] Preferably and in a non-limiting manner of the invention, the at least one first conduit 106 passes through the first part 86 and the at least one second conduit 108 passes through the second part 67. More particularly, the at least one first conduit 106 extends only in the first part 86, the at least one second conduit 108 extends only in the second part 67 and the at least one first conduit 106 and the at least one second conduit 108 are connected at the junction of the first and second parts 86, 67.

[0096] This configuration is not limiting of the invention and it could for example be envisaged that the first conduit extends into the second part 67, the cavity 98 extending into the second part 67. Similarly, the at least one second conduit 108 could extend into the first part 98, for example by extending into the body thickness 85 and opening laterally into the cavity 98.

[0097] The spar 85 could comprise only one second conduit 108 communicating with the first conduit 106, these conduits being filled with a cooling fluid. However, in this configuration, the fluid could only evacuate the calories received by the spar 82 by conduction since it could not circulate. Also, preferably, the spar 82 comprises at least two second conduits 108 which each communicate with opposite ends of an associated first conduit 106.

[0098] In Figures 8 to 10, three embodiments of a spar 82 having only two second conduits 108 communicating with the ends of a first conduit 106 are shown, but it will be understood that without changing the nature of the invention, the spar 82 could have a greater number of pairs of second conduits 108 each associated with a first conduit. For example, the spar 82 could have two cavities 98, two plugs 104 delimiting two first conduits 106 and four second conduits 108 associated in pairs with the ends of a first conduit 106.

[0099] Also preferably, each second duct 108 is arranged close to the median axis Z of the second part 67. Indeed, as has been seen, the blade 58 being subjected in operation, at the junction of its blade with the spar 82, to significant tensile stresses T and bending stresses F, and the most critical zones for the mechanics being close to the external surface of the root 66, it is desirable that the second ducts 108 be as far away as possible from the external surfaces of the second part 67.

[0100] We will now describe with reference to Figures 7 to 10 first to third embodiments of the invention.

[0101] Generally speaking, the second conduits 108 open through orifices 112 in the same internal face 114 of one of the walls 110 of the cavity. Preferably, and in a non-limiting manner of the invention, the external surface 100 of the first part 85 is arranged substantially transversely relative to the axis Z of the body 85, at one end of said body which is opposite its second part 67. The internal face 114 into which the ducts 108 open is opposite this external surface 100 and also extends substantially transversely relative to the axis Z of the body 85. In the examples which have been shown here, the first part 86 of the body 85 and the cavity 98 have respective sections elongated transversely relative to the main axis Z. The sections of the first part 86 of the body 85 of the cavity 98 have edges which are substantially homothetic to the intrados 70 and extrados 72 surfaces of the blade of the vane previously described.

[0102] Generally, the plug 104 comprises a cover 116 which closes the opening 102 of the cavity 98, a pad 118 which extends into the cavity 98 from said cover 116 and a rib 120 which extends from the pad 118 in contact with the internal face 114 of the cavity between the orifices 112 of the second conduits 108 by sealingly delimiting two chambers 98a, 98b in the cavity 98. The pad 118 further comprises at least one passage 124 passing through the pad 118 which places said chambers 98a, 98b in fluid communication. In this way, the two chambers 98a and 98b define the first conduit 106 whose ends are connected to the second conduits 108.

[0103] In the first embodiment of the plug 104 which has been shown in FIG. 7, the plug 118 comprises two lateral edges 122 arranged in a sealed manner in contact with lateral surfaces of the walls 110 of the cavity 98, and the rib 120, which joins the two lateral edges 122. The plug 118 further comprises a light 123 forming the passage 124.

[0104] Without limiting the invention, the buffer 118 may be made in the form of a plate. The lumen 123 is in this case formed in the plate.

[0105] According to second and third embodiments of the invention which have been shown in figures 9 and 10 the plug 118 is of complementary shape to the cavity 98 and it comprises at least one helical groove 126, 126a, 126b which is hollowed out in the periphery of the plug 118 along an entire length of the plug 118. This helical groove 126 comprises a first end 128 opening opposite the cover 116 on a first side of the rib 120 in a first 98a of the two chambers 98a or 98b, and a second end 130 located close to the cover 116.

[0106] The passage 124 extends through the plug 118 and it has a first end 132 which communicates with the second end 130 of the helical channel 126 and a second end 134 which communicates with the second of the two chambers 98b. More particularly, according to a second embodiment of the invention which has been shown in FIG. 9, the plug 118 is of complementary shape to the cavity 98 and it has a single helical channel 126, which is hollowed out in the periphery of the plug 118 along an entire length of the plug. This helical channel 126 has a first end 128 opening opposite the cover 116 on a first side of the rib 120 in a first 98a of the two chambers 98a, 98b, and a second end 130 located near the cover 116.The passage 124 extends for the most part along the Z axis through the buffer 118 and it has a first end 132 which communicates with the second end 130 of the helical channel 126 and a second end 134 which opens directly into the second of the two chambers 98b.

[0107] In this case, the helical channel 126 and the passage 124 form the first conduit 106.

[0108] More particularly, according to a third embodiment of the invention which has been shown in Figure 10, the plug 118 is also of complementary shape to the cavity 98 but it comprises two helical channels 126a, 126b which are hollowed out in its periphery, which are of the same pitch and which are arranged in a double helix arrangement along the entire length of the plug 118, and which comprise first ends 128a, 128b which open opposite the cover each on one side of the rib 120 respectively in the first and second chambers 98a, 98b and, second ends 130a, 130b located near the cover 116.

[0109] In this embodiment, the passage 124 passes transversely through the buffer 118 and it opens at its first and second ends 132, 134 into the second ends 130a, 130b of the channels 126a, 126b.

[0110] In this case, the two helical channels 126a, 126b and the passage 124 which connects them form the first conduit 106, as shown schematically in Figure 11.

[0111] In the three embodiments that have been described here, the function of the cover 116 is to close the opening 102. For this purpose, it could fit exactly into the opening 102. However, in a preferred manner of the invention, the cover 116 is formed in a cover 136, and preferably in a single piece with this cover, this cover 136 extending over the external surface 100 of the first part by closing the opening 102. This cover 136 is glued to the external surface 100.

[0112] With regard to the material of the plug 104, this can be made of a thermoplastic material, preferably by injection, or by additive manufacturing, for all embodiments of the invention.

[0113] With regard more specifically to the second and third embodiments of the plug 104, the latter may alternatively be produced by molding and machining a foam, in particular polymethacrylimide, having a density of between 0.15 and 0.5 kg / m3. In particular, the production of the helical channels 126, 126a, 126b is carried out by machining. An example of a material used satisfying these characteristics is ROHACELL HERO foam (registered trademark).

[0114] As illustrated in Figure 12, the spar 82 can thus be obtained by a method which firstly comprises a step A) of providing a plug 104, and providing a spar blank having a body of elongated shape similar to that of the body 85 of the spar along a main axis Z and comprising along said axis a first part configured to form the first part 86 of the body 85 of the spar 82 and a second part configured to form the second part 67 of the body 85 of the spar 82. This first part comprising the cavity 98 which opens into an external surface of said first part by forming an opening. This opening will form the opening 102 of the body 85.

[0115] Then the method comprises a step B), of machining the at least one second conduit 108 until it opens into said cavity 98. Depending on the way in which the spar blank was obtained, the external surface 100 will also be dressed.

[0116] Then the method comprises steps C) of inserting the plug 104 into the cavity 98 and D) of fixing the plug 104 to the body 85. Generally the fixing will be carried out in a very simple manner by applying glue to the external surface 100 or under the cover 136. The invention therefore makes it possible to obtain in a very simple manner a spar 82 comprising an integrated cooling circuit.

Claims

CLAIMS 1. Spar (82) for a turbine engine blade (58), in particular an aircraft blade, said spar (82) comprising a body (85) having an elongated shape along a main axis (Z) and comprising along said main axis (Z) a first part (86) configured to be inside a blade (62) of the blade (58), and a second part (67) configured to be outside the blade (62) of the blade (58) and to form a root (66) of the blade (58), the body (85) comprising a cavity (98) which opens into an external surface (100) of said first part (86) by forming an opening (102), and in that the spar (82) further comprises: - a plug (104) which is fixed to the body (85), this plug (104) being engaged in the cavity (98) and closing the opening (102), and - an internal cooling circuit (96) comprising at least one first conduit (106) which is delimited between the plug (104) and walls (110) of said cavity (98) and at least two second conduits (108) which each communicate with opposite ends of said at least first conduit (106), which pass through at least the second part (67) and which open outside the second part (67), characterized in that: - said at least two second conduits (108) open through orifices (112) into the same internal face (114) of the cavity (98), - the plug (104) comprises a cover (116) which closes the opening (102) of the cavity (98), a pad (118) which extends into the cavity (98) from said cover (116), and a rib (120) which extends from said pad (118) in contact with the internal face (114) of the cavity (98) between said orifices (112) by sealingly delimiting two chambers (98a, 98b) in the cavity (98), - at least one passage (124) passing through said buffer (118) places said chambers (98a, 98b) in fluid communication.

2. Longeron (82) according to the preceding claim, characterized in that the internal face (114) is opposite the opening (102).

3. Longeron (82) according to one of the preceding claims, characterized in that the external surface (100) of the first part (86) is arranged substantially transversely relative to the axis (Z) of the body (85), at one end of said body (85) which is opposite its second part (67).

4. Longeron (82) according to one of claims 1 to 3, characterized in that the buffer (118) comprises: - two lateral edges (122) arranged in a sealed manner in contact with lateral surfaces of the cavity (98), - the rib (120), joining the two lateral edges (122), - a light (123) passing through said buffer and forming the passage (124).

5. Longeron (82) according to one of claims 1 to 3, characterized in that: - the pad (118) is of complementary shape to the cavity (98) and it comprises at least one helical groove (126, 126a, 126b) which is hollowed out in the periphery of the pad (118) along an entire length of said pad (118), this helical groove (126, 126a, 126b) comprising a first end (128, 128a, 128b) opening opposite the cover (116) on a first side of the rib (120) in a first (98a) of the two chambers (98a, 98b), and a second end (130, 130a, 130b) located near the cover (116), - the passage (124) extends through the buffer (118) and has a first end (132) which communicates with the second end (130, 130a, 130b) of the helical channel (126, 126a, 126b) and a second end (134) which communicates with a second (98b) of the two chambers (98a, 98b).

6. Longeron (82) according to the preceding claim, characterized in that the passage (124) passes through the buffer along the entire length of the buffer (118) and in that its second end (134) opens opposite the cover (116) on a second side of the rib (120) in the second (98b) of the two chambers (98a, 98b).

7. Side member (82) according to claim 5, characterized in that: - the pad (118) comprises two helical channels (126a, 126b) which are hollowed out in its periphery, which are of the same pitch and which are arranged in a double helix arrangement along the entire length of the pad (118), and which comprise first ends (128a, 128b) which open opposite the cover (116) each on one side of the rib (120) respectively in the first and second chambers (98a, 98b) and second ends (130a, 130b) located close to the cover, - the passage (124) crosses transversely the buffer (118) and opens at its first and second ends (132, 134) into the second ends (130a, 130b) of the channels (126a, 126b).

8. Longeron (82) according to one of claims 1 to 7, characterized in that the cover (116) is formed in a cover (136) which extends over the external surface (100) of the first part (86) by closing the opening (102), said cover (136) being glued to said external surface (100).

9. Longeron (82) according to one of the preceding claims, characterized in that the plug (104) is made: - made of thermoplastic material, preferably by injection, or by additive manufacturing, or by molding and machining a foam, in particular polymethacrylimide, having a density of between 0.15 and 0.5 kg / m3.

10. Longeron (82) according to one of the preceding claims, characterized in that the first part (86) of the body (85) and the cavity (98) have respective sections elongated transversely with respect to the main axis (Z).

11. Longeron (82) according to one of the preceding claims, characterized in that: - the at least one first conduit (106) extends only in the first part (86), - the at least one second conduit (108) extends only in the second part (67), and - the at least one first conduit (106) and the at least one second conduit (108) are connected at the junction of the first and second parts (86, 67).

12. Blade (58) for an aircraft turbomachine, comprising a blade (62) and a root (66), this blade (58) comprising a spar according to one of the preceding claims, a first part (67) of which is inside the blade (62) and a second part is outside the blade (62) to form said root (66).

13. Method for manufacturing a spar (82) according to one of claims 1 to 11, characterized in that it comprises the steps of: A) providing a plug (104), and providing a spar blank having a body (85) of elongated shape along a main axis (Z) and comprising along said axis a first part configured to form the first part (86) of the body (85) of the spar (82) and a second part configured to form the second part (67) of the body (85) of the spar (82), said first part comprising a cavity (98) which opens into an external surface (100) of said first part by forming an opening (102), B) machining the at least one second conduit (108) until it opens into said cavity (98), C) inserting the plug (104) into the cavity (108, D) fixing the cap (104) to the body (85).

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