Propeller comprising a pivot equipped with means for introducing and / or ejecting an airflow

Abstract

The main object of the invention is a propeller (32) for a turbomachine (1) comprising a plurality of blades (48) and a blade support ring (47) provided with housings (50) each receiving a pivot (52) carrying the foot (58) of one of said blades (48), characterized in that at least one of the pivots (52) has means for introducing and / or ejecting (97a, 97b, 98a, 98b, 98c) an airflow intended to ventilate the blade foot (58).

Description

TECHNICAL FIELD The present invention relates to the field of turbomachinery, particularly to that of unfaired turbomachine propellers, and more specifically to the cooling of the components of these propellers, in particular the blade roots. It thus concerns a turbomachine propeller, and also the turbomachine incorporating such a propeller. The invention applies to all types of land-based or aeronautical turbomachinery, and in particular to aircraft turbomachinery such as turbojets and turboprops. More specifically, the invention finds a privileged application in the field of aircraft turbomachinery whose receiver comprises a pair of unfaired, counter-rotating propellers; this type of turbomachine is also known as an "open rotor" or "propfan" turbomachine. Such a turbomachine may, for example, have a fan mounted directly on the power turbine and outside the nacelle, or driven by a geared power turbine. PREVIOUS STATE OF THE ART Figure 1 schematically represents a turbomachine 1 with a doublet of unfaired contra-rotating propellers, known as an "open rotor", according to a classic embodiment of the prior art, as known from patent application FR 2 941 494. In Figure 1, direction A corresponds to the longitudinal or axial direction, parallel to the longitudinal axis 2 of the turbomachine 1. Direction B corresponds to the radial direction of the turbomachine 1. Furthermore, arrow 4 schematically represents the main direction of gas flow through the turbomachine 1. The terms "upstream" and "downstream" used in the following description should be considered in relation to this gas flow direction 4. In the front part, the turbomachine 1 has an air inlet 6 which continues towards the rear by a nacelle 8, the latter comprising overall an outer skin 10 and an inner skin 12, both centered on the axis 2 and radially offset from each other. The inner skin 12 forms an external radial casing for a gas generator 14, comprising, conventionally from front to rear, a low-pressure compressor 16, a high-pressure compressor 18, a combustion chamber 20, a high-pressure turbine 22, and an intermediate-pressure turbine 24. The compressor 16 and the turbine 24 are mechanically connected by a shaft 26, forming Thus, a low-pressure body, while the compressor 18 and the turbine 22 are mechanically connected by a shaft 28, forming a higher-pressure body. Consequently, the gas generator 14 preferably has a conventional, so-called twin-body design. Downstream of the intermediate pressure turbine 24 is a receiver 30 with a doublet of unshod, counter-rotating propellers, driven in this example by free-running power turbines. Alternatively, a geared power turbine can be used. More specifically, this receiver 30 is located downstream of a fixed housing 42, itself arranged in the rear extension of the external radial housing 12 of the gas generator 14. Moreover, the housings 12 and 42 can be made in one piece. The fixed housing 42 then extends rearward, narrowing in the radial direction, to form a fixed shaft 57 centered on the axis 2, forming the fixed housing of the receiver 30. The receiver 30 first comprises a first rotating assembly 32a equipped with a first propeller 32, a first free power turbine 34 driving this propeller, and a first rotating structural device 33 located in the axial extension of the free turbine 34 towards the front, interposed between the first stage of this turbine and the fixed housing 42. The rotating structural device 33 generally takes the form of a plurality of arms spaced circumferentially from each other and extending radially. These arms are connected to the The first propeller 32 carries the outer turbine housing 49, which is itself connected to the propeller 32 by means of a flange or a plurality of clips 44, allowing the propeller 32 to be radially offset outwards. The clips 44 have an internal radial end integral with the outer housing 49, and an external radial end integral with a polygonal ring (not shown in Figure 1) supporting the blades 48. These blades 48 project radially outwards from an outer propeller housing or cowling 46, one of the features of which is that it is located in the aerodynamic aft continuity of the outer skin 10 of the nacelle. Similarly, the receiver 30 comprises a second rotating assembly 36a equipped with a second propeller 36, a second free-running power turbine 38 driving this propeller, and a second rotating structural device 37 located in the axial extension of the free-running turbine 38 towards the rear, situated behind the last stage of this turbine 38. The rotating structural device 37, which extends essentially radially, supports the second propeller 36 by being connected to it, in particular, by a flange or a plurality of clips 51 allowing the propeller 36 to be radially offset outwards. Here too, the clips 51 have an internal radial end integral with the rotating structural housing 37, and an external radial end integral with a polygonal ring (not shown in Figure 1) supporting the blades 55. These blades 55 project radially outwards from a outer casing or hood 54, which is in the rear aerodynamic continuity of the outer hood 46 of the first propeller 32. Furthermore, the first and second free turbines 34, 38 are nested within each other to form a counter-rotating turbine pair. The stages of the first turbine 34 are thus arranged alternately with the stages of the second turbine 38, in direction A. This pair can therefore also be considered a turbine with two counter-rotating rotors. For illustrative purposes, the free turbines 34, 38 have no direct mechanical connection with the rotating components of the gas generator 14; that is, they neither drive nor are driven by elements 16, 18, 22, 24. Only the gases from the primary stream escaping from the intermediate pressure turbine 24 therefore ensure the rotation of these free turbines 34, 38 forming the counter-rotating turbine pair. With reference now more specifically to figures 2 to 4, the design of the first propeller 32 is shown in more detail, it being understood that the second propeller 36 has an identical or similar design, and will therefore not be described further. As mentioned previously, the propeller 32 has a polygonal ring 47 that supports the blades 48, this ring 47 forming a hub of the propeller. It has a plurality of housings 50 spaced circumferentially from each other, these housings 50 being called radial housings. Each of them receives a pivot 52, a bearing 80 being interposed between this pivot 52 and its associated housing 50 forming a bore, as shown in figure 3. Each pivot 52 has a lower portion 52a located inside its associated housing. This lower portion 52a is substantially cylindrical and hollow, presenting a cross-section generally shaped like a U open radially inwards. Furthermore, the pivot 52 extends radially outwards with an upper portion 52b situated above the ring 47. This upper portion 52b has a groove 56, schematically shown in Figure 4, whose function is to retain the root 58 of the associated blade 48. Thus, the pivot 52 supports the blade 48 and allows its angle of attack to be adjusted by controlling the rotation of this same pivot 52 within its housing 50 in the polygonal ring 47. The propeller 32 also includes the outer cowling 46, shown only in Figures 1 and 3. The outer surface of this cowling is open to the outside air. In this regard, it is noted that each blade 48 is equipped with a platform 59 from which its aerodynamic portion 60 projects radially outwards. Each circular platform 59 is positioned within an opening provided through the cowling 46, so as to obtain substantially flush aerodynamic junctions. As is most clearly visible in Figure 3, a blade cavity 64 is provided, associated with the blade 48. This cavity is intended to isolate the blade root from the rest of the turbomachine 1, by particular of the primary vein passing radially inwards. The cavity 64 has been schematically identified on figure 3 by the dashed line referenced 64. It is indeed closed radially outwards by the platform 59 and the outer cover 46 forming aerodynamic fairing, but also closed upstream by one or more covers 66, closed downstream by one or more covers 68, and closed radially outwards by one or more covers 70, here a single cover 70 fixed to the flange or the aforementioned clips 44. It is noted that a blade root cavity can be provided for each blade, as schematically shown in Figure 5, with an internal cover 70 provided for each blade, making the cavities independent of each other. Alternatively, a single blade root cavity can be shared by all 48 blades of the propeller 32, the single internal cover 70 then taking the form of a crown. As a ventilation option, each cavity 64 can, for example, be supplied with outside air by a scoop 72 or similar (e.g., a simple orifice), located on the outer cover 46. This scoop can, in particular, be placed downstream, and the air passing through cavity 64 can then, for example, be extracted by an outlet (not shown) located further upstream. As it passes through cavity 64, the fresh outside air surrounds and cools, by means of ventilation, the elements located within this cavity 64. in particular foot 58 of the blade as has been schematically represented by arrow 53. Ventilation and cooling of the propeller components 32, and in particular the blade roots 58, are difficult to achieve, especially due to the pressure conditions at low Mach number. However, such ventilation and cooling are particularly important when the blades 48 are made of composite materials, which have reduced resistance to high temperatures compared to metallic materials. In the configuration shown in Figure 1, known as the "pusher" configuration, in which the unfaired propellers are located at the rear, downstream of the combustion chamber, these propellers are positioned directly above the primary flow where the hot gases can reach 500°C. It is therefore essential to provide specific ventilation to prevent overheating of the blade roots of these unfaired propellers. However, the proposed solution described above relies solely on the pressure difference between the downstream dynamic air intake formed by scoop 72 and the upstream static air outlet. It is therefore highly dependent on aircraft speed, which proves detrimental during certain phases such as idle and takeoff, where the airflow at the blade root may be insufficient for adequate cooling. Furthermore, this solution, known from prior art, has the disadvantage of not achieving The cooling and ventilation of the blade roots 58 is achieved only through external means via the pivots 52. In other words, the blade roots 58 are not cooled by direct contact with the ventilation airflow, but solely through conduction and / or convection mechanisms due to contact with components that are themselves cooled by the ventilation flow. Consequently, the cooling of the blade roots 58 is not optimal. DESCRIPTION OF THE INVENTION The invention is thus intended to remedy at least partially the needs mentioned above and the drawbacks relating to the achievements of the prior art. The invention aims in particular to provide a solution to enable efficient ventilation and cooling of blade roots, especially those made of composite materials. The invention thus relates, according to one of its aspects, to a propeller for a turbomachine comprising a plurality of blades and a blade support ring provided with housings each receiving a pivot carrying the foot of one of said blades, characterized in that at least one of the pivots comprises means for introducing and / or ejecting an airflow intended to ventilate the blade foot. The propeller can in particular be an unfaired propeller. The airflow is in particular an outside airflow, specifically a cold outside airflow to allow for ventilation. The means of introducing and / or ejecting the airflow can constitute means of channeling the airflow. The means for introducing and / or expelling the airflow can be used to cool the blade root supported by the pivot. They can also be used to cool any other component requiring specific ventilation. Similarly, they can be used to expel a flow of hot air outside the area to be ventilated. In particular, they can be used to remove heat generated by the ventilation of the blade roots and / or originating from below the nacelle; cooling fins can, for example, be added to the hot air ejection means. Thanks to the invention, it is possible to ventilate and cool the blade roots by directing the ventilation airflow directly to the blade roots. The means for introducing and / or expelling the airflow can capture and direct the airflow in a guided manner to the precise location where ventilation is required, namely at the blade roots. The invention can also capture the airflow outside the boundary layer, i.e., above the nacelle, without impacting the mechanical strength and aerodynamics of the blades and the nacelle. Furthermore, the solution of the invention can create a thermal barrier between the leading and trailing faces of the blade root and the hot sources of the nacelle. The propeller according to the invention may further comprise one or more of the following characteristics taken individually or in any possible technical combinations. The means for introducing and / or ejecting the airflow can, at least in part, be integrated into the profile of the corresponding blade of said at least one of the pivots, in particular at the level of the leading edge and / or the trailing edge. The means for introducing and / or ejecting the airflow may include an orifice or, preferably, a dynamic scoop for introducing and / or ejecting the airflow. The pivot may be provided with at least one aerodynamically shaped post designed to engage in a corresponding slot in the blade, said at least one aerodynamically shaped post having means for introducing and / or ejecting the airflow. In particular, the blade slot may correspond to an opening made in the blade, and the aerodynamically shaped post of the pivot may have an aerodynamic shape that substantially follows the contour of the blade opening, notably having a shape substantially similar to that of the portion of the blade removed when making the opening. Thus, providing one or more aerodynamically shaped posts for the pivot can prevent any adverse impact on the blade's aerodynamics. Said at least one amount of aerodynamic shape can be formed in the pivot and / or reported onto the pivot. At least one aerodynamically shaped element and its corresponding blade housing can be formed at the leading edge of the blade, i.e., at the front of the blade. In this way, the aerodynamically shaped element can follow the blade's orientation and always face into the wind to capture the maximum amount of fresh air for ventilating the blade roots. Airflow inlet and / or outlet means may be formed within the thickness of at least one pivot. These means may be formed on the lateral surface of at least one pivot, particularly at the leading edge of the blade. Said at least one pivot may be provided with a first aerodynamically shaped post at the leading edge of the blade, capable of engaging in a first corresponding housing of the blade, and a second aerodynamically shaped post at the opposite edge of the blade, capable of engaging in a second corresponding housing of the blade, the first and second housings respectively comprising means for introducing and means for ejecting the airflow. The means for inserting and / or ejecting the pivot may allow the passage of cables for the operation of the turbomachine, including de-icing power supply cables and / or blade instrumentation cables. In particular, they may allow such cables to be routed on either side of the blade roots. The blades, in particular the blade roots, and / or said at least one pivot may be made of composite material. The pivot and / or the means of introducing and / or ejecting the airflow, in particular in the form of one or more dynamic scoops, can be made in different ways, for example using composite materials, metallic materials, by rapid prototyping or by molding. The pivot may include a lower part, in particular substantially cylindrical and hollow so as to present a cross-section in the general shape of a U open radially inwards, and an upper part situated above the blade support ring, this upper part having in particular a groove to retain the blade root. Furthermore, the pivot may include one or more platforms. The platform, particularly if circular in shape, may be positioned within an opening provided through the outer cowling of the propeller, so as to obtain substantially flush aerodynamic junctions. The blade may include an aerodynamic portion projecting radially outwards from the platform. Throughout this description, the stated characteristics relating to the pivot may apply to at least one of the lower part, the upper part, and the pivot platform. In particular, the lower part and / or the upper part and / or the pivot platform may include said introduction means and / or ejection of an airflow and / or said amount of aerodynamic shape. The invention also relates, according to another of its aspects, to a turbomachine characterized in that it comprises a propeller as defined above. The propeller can, for example, be located upstream or downstream of a combustion chamber of the turbomachine. The turbomachine can preferably be of the "open rotor" type. In particular, the turbomachine can comprise a pair of unfaired, counter-rotating propellers, each of the two propellers being a propeller as defined previously. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood upon reading the detailed description that follows, the non-limiting examples of its implementation, and upon examination of the schematic and partial figures in the attached drawing, on which: Figure 1 represents a schematic longitudinal half-sectional view of an aircraft turbomachine comprising a receiver with a doublet of contra-rotating propellers, according to a classical design of the prior art, - Figure 2 shows a partial perspective view of one of the counter-rotating propellers of the turbomachine shown in Figure 1, - Figure 3 shows a partial cross-sectional view showing the ring of in more detail propeller blade support, and surrounding components, - Figure 4 shows an exploded perspective view of a blade and its associated pivot, Figure 5 shows a perspective view of a prior art propeller, equipped with several blade root cavities, - Figure 6 illustrates, in perspective, an example of the realization of a propeller according to the invention, - Figure 7 illustrates a front view of the example implementation of Figure 6, and - Figure 8 illustrates, in cross-section, another example of an embodiment according to the invention. Throughout these figures, identical references may designate identical or analogous elements. Furthermore, the different parts represented in the figures are not necessarily shown on a uniform scale, in order to make the figures more legible. DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION Examples of embodiments of the invention relating to an aircraft turbomachine with a doublet of unfaired contra-rotating propellers will be described below with reference to Figures 6, 7 and 8, although these examples are not limiting. Figures 6, 7 and 8 are schematic and partial, and reference should be made to Figures 1 to 5 described above for the visualization of elements not shown in Figures 6, 7 and 8. With reference to figures 6 and 7, a first example of the realization of a propeller according to the invention has been illustrated. The pivot 52 includes a portion whose contour P rests on the outer propeller cowling 46, so that this portion is located above the nacelle, in contact with the air. It is said to be located above the nacelle line. The blade root 58, shown in dotted lines in Figure 6, is located under the outer propeller cowling 46, in other words under the nacelle line, as can be seen in particular in Figure 7. According to the invention, the pivot 52, and in particular the platform 59 of the pivot 52, includes means for introducing and / or ejecting an airflow intended to ventilate the blade root 58. In particular, the pivot 52, and especially the platform 59 of the pivot 52, includes a first aerodynamically shaped post 52e located on the front of the pivot 52, at the level of the leading edge of the blade 48, and a second aerodynamically shaped post 52f, located at the rear of the blade 48. The first 52nd and second 52f aerodynamically shaped uprights are suitable for engaging in first 48a and second 48b housings of blade 48. The first aerodynamically shaped upright 52e may include a means for introducing airflow, in particular a dynamic scoop 97a, and the second aerodynamically shaped upright 52f may include a means for ejecting airflow, in particular a dynamic scoop 97b. Scoops 97a and 97b can respectively capture and expel the ventilation airflow. Furthermore, the pivot 52, in particular the platform 59, includes in the thickness of its lateral surface 521 other means of introducing the airflow, namely scoops 98a, 98b and 98c, arranged on the front of the pivot 52 at the level of the leading edge of the blade 48. These scoops 98a to 98c can for example be uncovered when the pivot 52 rotates with the blade 48 and the step between the nacelle and the pivot 52 appears. As can be seen in Figures 6 and 7, the aerodynamically shaped uprights 52e and 52f, which include the inlet and / or outlet means 97a and 97b in the form of dynamic scoops, and the inlet means 98a to 98c also in the form of dynamic scoops, are located beyond the nacelle line so that they allow the inlet and / or outlet of a ventilation airflow outside the nacelle. Providing scoop 97a in a profiled part of the pivot 52, at the level of the leading edge of the blade 48, can allow a scoop always oriented in the same way as the blade 48, in other words with a low angle of incidence relative to the flow of the airflow, thus allowing a good capacity to capture air. Figure 7 illustrates more precisely, in front view, the flow of the airflow in the scoops 97a and 98a to 98c made in the pivot 52. More specifically, the airflow comes from the front of the blade 48 and is then directed towards the blade root 58, below the nacelle line, in the form, for example, of two flow channels Fi and F2 passing on each side of the blade root 58. More specifically, as illustrated, the first flow channel Fi can essentially include, for example, the airflows passing through scoops 97a, 98b and 98a, and the flow channel F2 can essentially include the airflows passing through scoops 97a, 98c and 98a. The flow channels Fi and F2, after passing on either side of the blade foot 58, can be joined and directed towards the edge of the blade 48 and / or the surface of the pivot 52 to be evacuated, in particular by means of the scoop 97b located at the rear of the blade 48. Figure 8 illustrates another example of the realization of a propeller conforming to the invention. In this example, scoops 97a and 97b can be provided in the pivot 52 in a manner similar to that described with reference to figures 6 and 7, to allow the passage of flow channels Fi and F2. Figure 8 illustrates more specifically that the inlet and / or outlet means, particularly in the form of scoops 97a and 97b, can also allow the passage of cables used for the operation of the turbomachine 1, for example, electrical power supply cables for de-icing. blade 48 and / or instrumentation cables for blade 48. In this particular example, a de-icing device 100 can be provided on the front of the blade 48 to which are connected electrical power cables 99 suitable for being placed in the means for introducing and / or ejecting the airflow provided in the pivot 52 up to under the base of the blade 58. By providing means for introducing and / or ejecting the airflow, particularly in the form of dynamic scoops, on the pivot 52 provided in particular with aerodynamically shaped uprights 97a, 97b, the invention can thus allow the blade roots 58 to be ventilated, and in particular to be cooled, by channeling the airflow directly to their contact allowing optimal ventilation. In all the examples described above, the blades 48 and / or the pivots 52 can be made of composite material. Of course, the invention is not limited to the examples of implementation that have just been described. Various modifications can be made to it by a person skilled in the art. The expression "containing one" should be understood as synonymous with "containing at least one", unless otherwise specified.

Claims

DEMANDS 1. Propeller (32) for turbomachine (1) comprising a plurality of blades (48) and a blade support ring (47) provided with housings (50) each receiving a pivot (52) carrying the foot (58) of one of said blades (48), said pivot (52) allowing the angle of incidence adjustment of the blade (48) which it carries by controlling the rotation of said pivot (52) within its housing (50) of the blade support ring (47), at least one of the pivots (52) comprising means for introduction and / or ejection (97a, 97b, 98a, 98b, 98c) of an airflow intended to ventilate the blade root (58), these means of introduction and / or ejection (97a, 97b, 98a, 98b, 98c) of the airflow being, at least in part, integrated into the profile of the blade (48) and comprising a dynamic scoop.

2. Propeller according to claim 1, characterized in that the means for introducing and / or ejecting the airflow (97a, 97b, 98a, 98b, 98c) are, at least in part, integrated at the level of the leading edge and / or trailing edge of the blade (48).

3. Propeller according to claim 1 or 2, characterized in that said at least one pivot (52) is provided with at least one aerodynamically shaped post (52e, 52f) adapted to engage in a corresponding housing (48a, 48b) of the blade (48), said at least one aerodynamically shaped post (52e, 52f) comprising means of introduction and / or ejection (97a, 97b) of the airflow.

4. Propeller 5. Previous, characterized by the corresponding aerodynamic shape of the blade's leading edge. according to the claim in that at least one amount (52e) and -the housing (48a) (48) are formed at the level of (48). 10.

5. Propeller according to any one of the previous claims, characterized in that means for introducing and / or ejecting (98a, 98b, 98c) the airflow are formed in the thickness of said at least one pivot (52), on the lateral surface (521) 15 of said at least one pivot (52), in particular at the level of the leading edge of the blade (48).

6. Propeller according to any one of the preceding claims, characterized in that 20 said at least one pivot (52) is provided with a first aerodynamically shaped post (52e) at the leading edge of the blade (48), capable of engaging in a corresponding first housing (48a) of the blade (48), and a second aerodynamically shaped post (52f) 25 at the opposite edge of the blade (48), capable of engaging in a corresponding second housing (48b) of the blade (48), the first (48a) and second (48b) housings having respectively means for introducing (97a) and means for ejecting (97b) the 30 airflow.

7. Propeller according to any one of the preceding claims, characterized in that the means for introducing and / or ejecting (97a, 97b) said at least one pivot (52) allow the passage of cables (99) for the operation of the turbomachine, in particular de-icing power supply cables and / or blade instrumentation cables (48).

8. Propeller according to any one of the preceding claims, characterized in that the blades (48) and / or said at least one pivot (52) are made of composite material.

9. Turbomachine (1) characterized in that it comprises a propeller (32) according to any one of the preceding claims.

10. Turbomachine according to claim 9, characterized in that said propeller (32) is located downstream of a combustion chamber (20) of said turbomachine, said turbomachine preferably comprising a pair of unfaired counter-rotating propellers, each of the two propellers (32, 36) being a propeller according to any one of claims 1 to 8.