AIRCRAFT PROPULSION ASSEMBLY COMPRISING A PROPELLER

Abstract

Aircraft propulsion system with axis (X), comprising: - an electric motor (14), - a propeller (12) positioned upstream or downstream of the motor configured to drive the propeller in rotation around the axis (X), - an internal cone (20) positioned upstream of the motor (14), - an external fairing (22) mounted around the internal cone (20) and forming an annular passage (P) with it, the external fairing (22) defining, at an upstream end (22a) of the passage, an inlet for outside air (E) flowing from upstream to downstream in the passage. Several mechanical support elements (24, 26) are arranged in the passage (P) between the external fairing (22) and the internal cone (20). The passage (P) and the mechanical support elements (24, 26) are configured to generate, at a downstream end (22b) of the passage, an upstream-downstream cooling airflow (F2) with sufficient flow to cool the electric motor. Figure for the abstract: Fig. 3.

Description

Title of the invention: AIRCRAFT PROPULSION ASSEMBLY COMPRISING A PROPELLER technical field

[0001] The present description relates to an aircraft propulsion assembly comprising a propeller. Previous technique

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft and to those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the impactful factors in all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion and, as essential complements to technological progress, aviation biofuels.

[0006] A propulsion system for an aircraft is known from document WO 2023 / 006473 A1, comprising an electric motor associated with an unfaired propeller located upstream of the motor. The electric motor drives the propeller, which, by rotating, provides propulsion for the aircraft equipped with this propulsion system.

[0007] In this document, the propulsion assembly comprises, in its upstream portion, a propeller cone on which propeller blades are angularly distributed. A fairing is positioned externally to the propeller cone and coaxially with it so as to create an annular internal space between them. This external fairing has a generally truncated shape at its upstream end to provide an outside air inlet. Outside air entering through this inlet flows from upstream to downstream within the annular internal space, which forms a guide duct. Furthermore, the propulsion assembly includes compressor blades attached to the propeller cone and positioned within the guide duct to create, from the incoming outside air, an accelerated airflow that serves to cool the electric motor located downstream.

[0008] This solution applies to the entire flight envelope, and in particular when the aircraft is at very low speed. Description of the invention

[0009] When the aircraft is in the climb phase, the electric motor is under considerable stress and therefore heats up significantly, thus requiring particularly efficient cooling. However, the inventors have observed that, during a climb phase, the flow of cooling air reaching the electric motor after passing through the guidance duct is not necessarily sufficient to ensure effective cooling of the electric motor.

[0010] There is therefore a need to improve the aforementioned propulsion system in order to be able to efficiently cool the electric machine when the aircraft is in the climb phase and thereby contribute to reducing the environmental impact of aircraft.

[0011] To this end, the present description relates to an aircraft propulsion system extending longitudinally along an X-axis, comprising: -an electric motor, -a propeller positioned upstream or downstream of the electric motor according to an upstream-downstream airflow direction in the propeller, the electric motor being configured to drive the propeller in rotation around the X axis, -an internal cone positioned upstream of the electric motor, -an external fairing in the general shape of a truncated external cone mounted around the internal cone and forming with the latter an annular passage P, the truncated external cone defining, at an upstream end of the annular passage, an air inlet E to allow outside air Fl to enter the annular passage and flow from upstream to downstream inside the annular passage, characterized in that several distinct mechanical support elements are arranged in the annular passage P between the truncated external cone and the internal cone in order to mechanically maintain the truncated outer cone on the inner cone while limiting the pressure loss on the airflow in the annular passage, the annular passage P and the mechanical support elements arranged in this annular passage being configured to generate, at a downstream end of the annular passage, an upstream-downstream cooling airflow F2 intended to pass through the electric motor and having a flow rate sufficient to cool the electric motor, particularly when the aircraft incorporating the propulsion assembly is in the climb flight phase.

[0012] Since the annular passage consists solely of mechanical support elements between the truncated outer cone and the inner cone, the airflow propagating through the annular passage is not, or only very slightly, impeded by these distinct elements, which are spaced far apart and do not serve to deflect the flow as it progresses through the passage between the upstream end (air inlet) and the downstream end (air outlet). The local mechanical support elements are simply shaped to avoid inducing a significant pressure drop in the portion of the flow that encounters them. Thus, the airflow passing through the annular passage exits it having been channeled only, without a significant change in direction and therefore without a substantial pressure drop, even when the aircraft incorporating the propulsion system reaches high speeds.This makes the airflow particularly effective at cooling the electric motor, even during the aircraft's climb phase. The propulsion system thus configured improves the flight behavior of an aircraft incorporating such a system. This propulsion system is therefore improved compared to that described in the prior art document, as explained above.

[0013] According to other possible characteristics: - the annular passage is devoid of vanes; - the truncated external cone has, at the upstream air inlet, a lip which is aerodynamically profiled, for example following a NACA type profile; -the electric motor is equipped on its external periphery with thermally conductive fins which are positioned on the path of the cooling airflow coming from the annular passage of the propeller; - the electric motor is equipped with a nacelle; - the aircraft propulsion system is possibly equipped with an air exhaust configured to collect the cooling airflow after it has passed through the electric motor; -the propeller can be positioned upstream of the electric motor and has several blades extending radially relative to the longitudinal axis X from a shaft of the motor, through the internal cone and the truncated external cone and away from the latter; -the propeller can be positioned downstream of the electric motor.

[0014] The invention also relates to an aircraft comprising an aircraft propulsion assembly as briefly described above. Brief description of the drawings

[0015] Other features and advantages of the subject matter of this presentation will become apparent from the following description of embodiments, given by way of non-limiting examples, with reference to the attached figures.

[0016] [Fig-1] Fig. 1 is a schematic view of an aircraft according to an embodiment of the invention.

[0017] [Fig.2] The [Fig.2] is a schematic view of a propulsion assembly integrated into the aircraft of the [Fig.1] and comprising a tractor propeller according to an embodiment of the invention.

[0018] [Fig.3] The [Fig.3] is a general schematic longitudinal cross-sectional view of part of the propulsion assembly of the [Fig.2].

[0019] [Fig.4] The [Fig.4] is a general schematic longitudinal cross-sectional view showing an exhaust downstream of the propulsion assembly of the [Fig.3].

[0020] [Fig.5] The [Fig.5] is a general schematic longitudinal sectional view showing another possible embodiment of a propulsion assembly integrated into the aircraft of the [Fig.1] comprising a propulsion propeller downstream of the engine. Description of the implementation methods

[0021] Figure 1 schematically illustrates an aircraft A comprising a wing structure formed by two wings W, on each of which several aircraft propulsion units 10 according to an embodiment of the invention can be mounted. The number of propulsion units can vary according to requirements. Other types of aircraft can, of course, be suitable for the integration of such propulsion units.

[0022] Aircraft A may also include at the forward tip of the fuselage a central propulsion assembly 50 known per se.

[0023] The propulsion assembly 10, schematically represented in [Fig. 2], extends longitudinally along an axis X, the arrow of which indicates a downstream-upstream orientation. The airflow external to the propulsion assembly 10, which enters it as will be seen later, is indicated by the arrow Fl directed from upstream to downstream. The propulsion assembly 10 generally comprises a propeller 12 positioned in the upstream part of the assembly 10 and an electric motor 14 positioned in the downstream part of this assembly and configured to drive the propeller 12 in rotation about the axis X.

[0024] The electric motor 14 is, for example, enclosed inside an external casing or nacelle 16. The electric motor 14 comprises, in a known manner, a part forming a stator and a rotor part which includes a rotor shaft connected to the propeller 12. The electric motor 14 includes components which require cooling, for example, electrical components, power components, magnetic windings and others.

[0025] The propeller 12 comprises, for its part, a plurality of propeller blades 18 which extend radially, relative to the longitudinal axis X, away from the propulsion assembly 10.

[0026] As shown in Figures 2 and 3, the propeller 12 comprises an internal cone, referred to in this mode as the propeller cone 20 (the upstream end of which can be seen in [Fig. 2]). The propeller blades 18 are mounted on the drive shaft (not visible in [Fig. 2]) and pass through this cone to extend radially from this cone, away from it.

[0027] The blades 18 are distributed angularly around the propeller cone 20 in a regular manner and are, for example, three in number, although this number may differ depending on the configurations.

[0028] The electric motor 14 is for example mechanically connected to the propeller 12 for its rotational drive by means of the motor's rotor shaft which extends axially inside the propeller cone and cooperates mechanically with the latter in a known manner.

[0029] As shown in [Fig. 3], the electric motor 14 is provided, on its radially external surface, with thermally conductive fins 15 which are projecting from its external surface. The fins 15 are configured to dissipate, by thermal conduction, the heat produced by the electric motor, particularly by its functional components, to the outside of the motor's outer casing. These fins may, for example, be in contact with the housing 16, to further improve heat exchange, as described in patent FR2208181.

[0030] The propeller 12 includes an external fairing 22 in the general shape of an external cone which is truncated at an upstream end 22a. The truncated external cone 22 is mounted around the helix cone 20 (internal), coaxially with the latter and provides, with it, an annular passage P which extends from the upstream end 22a to the downstream end 22b of the truncated external cone 22.

[0031] The truncated external cone 22 defines, at its upstream end 22a, an air inlet E which is configured to allow outside air (symbolized by the arrows Fl directed from upstream to downstream following the direction of the incoming airflow) to enter the annular passage P and flow from upstream to downstream inside the annular passage to the downstream end 22b through which the annular airflow, denoted F2, is discharged in the direction of the electric motor 14. As shown in [Fig. 3], the annular passage has a radial dimension that decreases from upstream to downstream, between the two upstream ends 22a and downstream ends 22b in order to accelerate the incoming airflow Fl. As an alternative, the passage section for the air stream can be of constant cross-section.

[0032] Furthermore, the truncated external cone 22 has, at the upstream air inlet E, an upstream lip 22a 1 which is aerodynamically profiled to allow optimal air intake into the annular passage for different angles of attack of the incoming airflow Fl and for different operating points of the propulsion system. The profile of the upstream lip is of the NACA type. Since the angles of attack and operating points are likely to vary from one aircraft to another, the shape of the profile is also likely to vary.

[0033] It will be noted that the blades 18 of the propeller 12 pass through through orifices which are made in the wall of the truncated external cone 22. According to an unrepresented variant, the blades 18 are directly mounted on the external cone 22. The elements called arms 24 and 26, which will be defined later, are then mechanically dimensioned to support the forces due to the work of the blades 18.

[0034] Furthermore, the propeller 12 comprises, for its mechanical stability, several mechanical support elements 24, 26 forming distinct radial structural arms arranged in the annular passage P at a distance from one another. These mechanical support elements 24, 26 extend radially between the truncated outer cone 22 and the propeller cone 20 in order to mechanically maintain the truncated outer cone 22 in a fixed position relative to the propeller cone 20. These elements 24, 26 are, for example, arranged along the annular passage at a distance from one another, as illustrated in [Fig. 3]. In addition, several elements 24, 26 can be positioned in the same transverse plane relative to the longitudinal axis X. They are then distributed along the same circumference of the inner cone 20, like the blades 18 mounted on the inner cone 20.It should be noted that the elements 24, which are positioned in the annular passage upstream of the elements 26, are generally positioned to minimize pressure losses. To this end, they are preferably aligned with each other (same angular position between elements 24 and 26). According to an alternative design (not shown), the elements 24 are angularly offset relative to the downstream elements 26. This creates a turbulent flow that improves heat exchange at the engine.

[0035] These elements 24, 26, called arms, primarily serve a mechanical function of transmitting forces between the two cones 20 and 22 and are designed to limit the pressure loss on the airflow propagating in the annular duct P and encountering these elements. Thus, these elements are aerodynamically profiled and, for example, along the longitudinal axis, have a streamlined shape from upstream to downstream. (like an aircraft wing profile) with a leading edge and a trailing edge joined by two lateral surfaces, for example convex. The arms 26 and 24 are regularly spaced angularly around the helix cone 20 and are, for example, three in number, although this number may differ depending on the configuration.

[0036] The airflow which passes through the annular passage P can flow freely inside the latter (with the exception of the elements 24,26 placed at points along the path of the airflow but which represent a relatively small surface compared to the free passage section offered to the flow) without encountering major obstacles (blades or any other aerodynamically profiled element with the aim of strongly deviating the angular orientation of the flow from an axial orientation) and without the direction of this airflow being strongly deviated as was the case in the prior art document WO 2023 / 006473 discussed above with compressor blades. It follows that the airflow is not slowed down, as was previously the case, when the aircraft is in the climb phase and reaches high speeds (these speeds are very dependent on the type of aircraft and its mission), but only channeled through the annular passage P.This allows for an airflow at the outlet of the annular passage P (downstream end 22b) with sufficient flow to cool the electric motor 14 located downstream, particularly when the aircraft is in its climb phase and the motor is generating considerable thermal power. For example, the airflow rate can be between 0.5 and 2 kg / s. It should also be noted that the airflow circulating in the annular passage P is preferentially accelerated due to the reduction in cross-sectional area from upstream to downstream.

[0037] The cooling airflow F2 flows annularily from the downstream end 22b of the propeller and enters axially into the engine block nacelle formed by the external cowling 16 surrounding the electric motor 14, more specifically into the annular space surrounding the motor, which is occupied by the fins 15 arranged radially in this space and extending axially so as to be angularly separated from each other. The airflow F2 is distributed in the areas located between two consecutive fins positioned in the path of the cooling airflow and flows along these fins, exchanging heat with them in order to cool them.

[0038] It should also be noted that the engine block nacelle includes, for example, in its downstream section, an exhaust 30 shown in [Fig. 4] which collects the cooling airflow F2 that has passed through the electric motor and expels it outside the propulsion assembly. This exhaust helps to limit pressure losses due to sudden changes in the cross-section of the air passage. This exhaust is shown here as a downstream fairing 30 positioned behind the engine 14, fitted with its external cowling 16, and aligned with the latter. The fairing 30 collects the flow F2 exiting the annular duct in which the cooling fins 15 are arranged and ejects it downstream through an exhaust nozzle 32 in the form of a flow F3. Other exhaust configurations are of course possible.

[0039] The configuration of Figures 3 and 4 shows that the engine is positioned immediately behind the propeller (downstream), without the need for a flow straightening device between the two. This is because the flow of the F2 stream is not significantly deflected by its channeling in the passage P with an exit gyration angle that would necessitate straightening, as is the case in document WO 2023 / 006473. Thus, the resulting propulsion assembly 10 can be axially shortened and have a reduced weight.

[0040] Figure 5 illustrates another embodiment in which the propeller blades 18' and their spinner 28 are positioned downstream of the electric motor 14. The upstream part of the propulsion assembly shown in Figures 3 and 4 remains identical, except that the blades of the traction propeller 18 in those figures are omitted. This upstream part 22' becomes static and connected to the motor and its nacelle. The propeller then becomes a propulsion propeller, and the propeller blades 18' are mounted through the downstream external spinner 28, which is aligned axially with the motor 14, and connected to the motor shaft at the rear, as were the blades of the propeller 18 in Figures 3 and 4.

[0041] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

Claims

Demands

1. An aircraft propulsion assembly extending longitudinally along an axis (X), comprising: - an electric motor (14), - a propeller (12) positioned upstream or downstream of the electric motor (14) in an upstream-downstream airflow direction within the propeller, the electric motor being configured to drive the propeller in rotation about the axis (X), - an internal cone (20) positioned upstream of the electric motor (14), - an external fairing (22) generally in the form of a truncated external cone mounted around the internal cone (20) and forming with the latter an annular passage (P), the truncated external cone (22) defining, at an upstream end (22a) of the annular passage, an air inlet (E) to allow outside air (Fl) to enter the annular passage and flow from upstream to downstream within the annular passage, characterized in that several mechanical support elements (24,26) separate elements are arranged in the annular passage (P) between the truncated outer cone (22) and the inner cone (20) in order to mechanically maintain the truncated outer cone on the inner cone while limiting the pressure loss on the airflow in the annular passage, the annular passage (P) and the mechanical support elements (24, 26) arranged in this annular passage being configured to generate, at a downstream end (22b) of the annular passage, an upstream-downstream cooling airflow (F2) intended to pass through the electric motor (14) and having a flow rate sufficient to cool the electric motor, particularly when the aircraft incorporating the propulsion system is in the climb phase.

2. Aircraft propulsion assembly according to the preceding claim, in which the annular passage (P) is devoid of blades.

3. Aircraft propulsion assembly according to claim 1 or 2, wherein the truncated external cone (22) has, at the upstream air inlet (E), a lip (22al) which is aerodynamically profiled, for example following a NACA type profile.

4. Aircraft propulsion assembly according to any one of the preceding claims, wherein the electric motor is provided on its outer periphery with thermally conductive fins (15) which are positioned on the path of the cooling airflow (F2) coming from the annular passage (P).

5. Aircraft propulsion assembly according to any one of the preceding claims, wherein the electric motor (14) is equipped with a nacelle (16).

6. Aircraft propulsion assembly according to any one of the preceding claims, comprising an air exhaust configured to collect the cooling airflow after passing through the electric motor (14).

7. Aircraft propulsion assembly according to any one of the preceding claims, wherein the propeller (12) is positioned upstream of the electric motor (14) and comprises several blades (18) extending radially relative to the longitudinal axis (X) from a shaft of the motor (14), through the inner cone (20) and the truncated outer cone (22) and away from the latter.

8. Aircraft propulsion assembly according to any one of claims 1 to 5, wherein the propeller (18') is positioned downstream of the electric motor (14).

9. Aircraft (A) comprising an aircraft propulsion assembly according to any one of the preceding claims.

Images