OPTIMIZED HEAT EXCHANGER WITH EJECTOR FOR TURBOMACHINE

Description

BE2025 / 5056 2 on a single set of injectors, this can lead to an uneven distribution of said secondary flow, which limits the overall cooling efficiency. Summary of the invention Technical problem The invention aims to provide a heat exchanger that minimizes aerodynamic losses while optimizing heat exchange between air and oil, in order to guarantee effective cooling even when the airflow entering the exchanger is insufficient, and this in a compact form without compromising the efficiency of the aircraft. Technical solution The invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft.For this purpose, the present invention relates to a heat exchanger for an air stream of a turbomachine, comprising a heat exchange zone provided with oil passages 15 and a heat exchange passage for a first airflow, remarkably in that the heat exchanger further comprises a jet-type ejector, configured to project a second airflow joining the first airflow, said ejector being directly formed with the heat exchange zone 20. According to an advantageous embodiment of the invention, the ejector extends across the heat exchange zone parallel to a direction of circulation of the first airflow. According to an advantageous embodiment of the invention, the ejector comprises a proximal part extending transversely to the first airflow and a distal part 25 extending parallel to said first airflow. According to an advantageous embodiment of the invention, the ejector comprises an elbow linking the proximal part and the distal part, said elbow being disposed at the level of a substantially central portion of the heat exchange zone.2025 / 5056 BE2025 / 5056 3 According to an advantageous embodiment of the invention, the distal part extends to the center of the heat exchange zone. According to an advantageous embodiment of the invention, the distal part comprises a first external face extending straight along the first airflow, and a second external face extending inclined with respect to said first airflow. According to an advantageous embodiment of the invention, the second airflow passes through the heat exchange zone exclusively at the ejector. According to an advantageous embodiment of the invention, the ejector comprises a distal end forming an outlet for the second airflow, disposed outside the heat exchange zone. According to an advantageous embodiment of the invention, the distal part has a longitudinal profile converging between the elbow and the distal end. According to an advantageous embodiment of the invention, the distal end is distant from the heat exchange zone by no more than one quarter of a total longitudinal extent 15 of the said heat exchange zone along the first airflow.According to an advantageous embodiment of the invention, the ejector extends continuously without change of direction in the heat exchange zone between approximately half of a longitudinal extent of the heat exchange zone and an outlet of the first airflow from said heat exchange zone. According to an advantageous embodiment of the invention, the ejector extends longitudinally along the first airflow in a convergent section of the heat exchange zone. According to an advantageous embodiment of the invention, the heat exchange zone comprises a divergent section along the first airflow upstream of the ejector. According to an advantageous embodiment of the invention, the heat exchange zone comprises heat exchange surfaces forming the heat exchange passage for the first airflow, the ejector being directly formed with said heat exchange surfaces.30 2025 / 5056 BE2025 / 5056 4 The invention also relates to an aircraft turbomachine, notably in that it comprises a heat exchanger according to the invention.It is understood that each detail of one of the above embodiments can be combined with each other detail of the other embodiments. Advantages provided 5 The integration of the jet-type ejector directly into the heat exchanger optimizes space and reduces the mass of the assembly while improving cooling efficiency. By projecting a second airflow which joins the first, the ejector creates a shearing effect generating effective suction within the heat exchange zone, thus ensuring improved ventilation 10 even when the incoming airflow is insufficient. Furthermore, the injection of the second airflow downstream of the outlet of the first airflow, from the heat exchange zone and up to a quarter of the longitudinal extent of the exchanger, ensures a homogeneous airflow in this zone, improving cooling performance while consolidating the compactness of the system.15 Moreover, the aerodynamic design of the static part of the ejector reduces pressure losses, thus contributing to increased thermal efficiency.Brief description of the drawings Figure 1 illustrates a schematic cross-sectional view of an aircraft turbomachine comprising a heat exchanger according to the present invention; Figure 2 shows a schematic longitudinal cross-sectional view of the heat exchanger of Figure 1, incorporating a jet-type ejector directly formed with said exchanger. Detailed description of embodiments The dimensions of the figures are not to scale and in particular the thicknesses or dimensions are adjusted to facilitate reading the figures. In this description, the term "longitudinal" designates the direction of airflow through the object in question. In other words, it refers to the orientation parallel to the path of the airflow, allowing the description of the arrangement (BE2025 / 5056 5) or the characteristics of the elements according to their alignment with this direction of flow. Figure 1 illustrates a schematic cross-sectional view of a turbomachine installed under the wing of an aircraft.In the upstream part of the aircraft 2, there is a propeller 14 driven in rotation by a turbine 16, via a speed reducer 18. The rotation of the propeller 14 generates a secondary airflow F2 which provides propulsion for the aircraft. The turbine 16 receives the combustion gases from a combustion chamber which is supplied with air by an internal airflow F1, corresponding to a primary airflow F1 which enters through an intake duct 22 which is placed immediately downstream of the propeller 14 at the beginning of a cowling 24 of the aircraft 2, and which then circulates through a primary airflow channel 20. The reducer 18 is supplied with lubricant by a lubricant circuit 26 which essentially comprises pipes 28, a pump 30 and a heat exchanger 15 4 intended to cool the lubricant, preferably oil circulating in the speed reducer 18. The cooling air for the exchanger 4 is preferably taken downstream of the inlet duct 22.For this purpose, an air inlet slot 34 can be used, for example, by being placed at the level of the vein 20 of the turbomachine 2, downstream of the inlet duct 22, to supply a supply duct 36 which provides a first flow of air to the heat exchanger 4 housed in an internal compartment 37 of the turbomachine 2, comprising an air vein 38 preferably forming a scoop 38 enlarged to receive said heat exchanger 4. The heat exchanger 4 can be disposed in the scoop 38, or can alternatively be disposed in an annular vein in which said heat exchanger 4 can extend continuously over 360° or in an interrupted manner forming a plurality of angular sectors. The turbomachine 2 includes a discharge duct 39, placed downstream of the heat exchanger 4 in order to prolong the air circulation in the latter.2025 / 5056 BE2025 / 5056 6 In this configuration, at high speed, during a long-duration flight, or in very cold conditions, the air entering the air intake slot 34, being conveyed by the supply duct 36 through the heat exchanger 4 and expelled by the exhaust duct 39, generally cools the heat exchanger 4 and the lubricant passing through it sufficiently. 5 On the other hand, at low speed, or in conditions where the airflow naturally reaching the air supply duct 36 is insufficient, for example during a standstill, idle on the ground, or taxiing in strong heat, it proves useful to accelerate the airflow in the heat exchanger 4.10 Aceteffet, la présent invention propose d’integrer un ejecteur 40 de type trompe à jette directe dans le exchangeur 4, et qui est configurable pour ejection un seconde flux d’airS à rejoin le premier flux d’airP.Le design de l’exchangeur 4ser rademente la long de la figure 2 dans la présent de description.The ejector 40 includes upstream (along the second airflow S), a sampling duct 15 42 connected to an injector 44 corresponding preferably to a compressor 44 of the turbomachine 2. Preferably, the second airflow S inside the sampling duct 42 can be allowed or stopped by a valve 46. In this configuration, the injection of the second airflow allows the first airflow to be accelerated and consequently, when necessary, the flow rate through the exchanger 4 to be increased, resulting in better cooling. An advantage of this is that integrating the ejector 40 directly within the exchanger 4 further compacts the assembly while improving oil cooling. Figure 2 shows a schematic longitudinal cross-sectional view of the heat exchanger 4 of Figure 1. The exchanger 4 includes a heat exchange zone 6 with oil passages (visible in Figure 1) and preferably heat exchange surfaces (not shown) forming a heat exchange passage for the first airflow 30.2025 / 5056 BE2025 / 5056 7 Advantageously, the ejector 40 is directly formed with the heat exchange zone 6, and more preferably formed with the heat exchange surfaces. Preferably, the exchanger 4 is obtained by additive manufacturing, and more preferably by selective powder bed fusion. 5 It can be seen that the ejector 40 comprises a proximal part 40.1 extending transversely to the first airflow P and a distal part 40.2 extending parallel to said first airflow. Preferably, the ejector 40 includes an elbow 40.3 connecting the proximal part 40.1 and the distal part 40.2. The elbow 40.3 is preferably disposed at the level of a substantially central portion 6.1 of the heat exchange zone 6. In this configuration, the ejector 40 can extend continuously without change of direction in the heat exchange zone 6 between about half of a longitudinal extent L of this zone 6 up to an outlet 6.2 of the first airflow P from the said heat exchange zone 6.This advantageously ensures a laminar flow of the second projected airflow S, without disturbing the first airflow P within the heat exchange zone 6. The heat exchange zone 6 preferably comprises a divergent section 20 6.3 along the first airflow P upstream of the ejector 40, and a convergent section 6.4 downstream of the bend 40.3 in which the distal part 40.2 extends parallel to the first airflow P. The convergent section 6.4 is fully traversed by the distal part 40.2 of the ejector 40, and so on, up to a distal end 40.4 of the said ejector 4025 forming an outlet 40.4 for the second airflow S. As illustrated, outlet 40.4 can be disposed outside the heat exchange zone 6. To this end, the ejector 40 opens downstream of said zone 6, along the first airflow P. In an alternative not shown, outlet 40.4 can be disposed within the heat exchange zone 6, upstream of outlet 6.230 of the first airflow P. 2025 / 5056 BE2025 / 5056 8 Preferably, the distal end 40.4 is distant from the heat exchange zone 6, and more precisely distant from the outlet 6.2, by at most one quarter of a total longitudinal extent L of said zone 6 along the first airflow P. In this configuration, the distal end 40.4 can be positioned downstream of the zone 6, at the same level as the outlet 6.2, and up to one quarter of the total longitudinal length 5 L. Advantageously, the ejector 40 creates a shearing effect between the second airflow S from the injector and the first airflow P exiting the exchanger 4, thus generating an air suction phenomenon across the heat exchange zone 6. This forces ventilation of 10 through the exchanger 4 under conditions where oil cooling is necessary, or when the inlet pressure is not sufficiently high relative to the outlet pressure to guarantee optimal flow. Furthermore, injecting the second airflow S directly downstream of outlet 6.2 and at most one-quarter of the longitudinal extent L ensures a uniform flow rate 15, thus improving cooling performance. See i.

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