Closed circuit for cooling the engine of an aircraft propulsion plant

Abstract

An aircraft propulsion plant including an electric motor having a rotor and a stator mechanically linked to a base which can be mounted at the rear of an aircraft fuselage, a fan rotated by the rotor, a set of fixed blades located downstream of the fan, and a nacelle comprising an outer casing and a fan casing surrounding the fan and the set of fixed blades. The nacelle is mechanically linked to the base through the set of fixed blades. This configuration enables a cooling circuit to be formed for enabling the heat produced by the electric motor at the location of the stator to be evacuated towards the fixed blades and the nacelle where it is dissipated. Furthermore, this heat may be used for the de-icing of the nacelle lip.

Claims

1. An aircraft propulsion plant comprising: an electric motor having a rotor and a stator mechanically connected to a base which can be mounted on a rear part of an aircraft fuselage; a fan driven in rotation by the rotor; a set of fixed blades situated downstream of the fan, the fixed blades being mechanically connected to a fixed shaft that is fixed to the base; a nacelle having an outer casing and a fan casing surrounding the fan and the set of fixed blades, the nacelle being mechanically connected to the set of fixed blades; and a cooling circuit to transport thermal energy generated by the electric motor, the cooling circuit extending at least partly in the stator whence is taken thermal energy to be evacuated to the set of fixed blades where thermal energy is at least partly dissipated by convection in a flow of air accelerated by the fan and passing through the propulsion plant, the set of fixed blades being connected to the stator directly or via the fixed shaft.

2. The aircraft propulsion plant of claim 1, wherein the cooling circuit is extended beyond the set of fixed blades in the nacelle between the fan casing and the outer casing such that at least a portion of thermal energy transported by the cooling circuit is evacuated via the fan casing and/or the outer casing of the nacelle.

3. The aircraft propulsion plant of claim 2, wherein the outer casing and the fan casing join in a front part of the nacelle to form a lip and a part of the cooling circuit situated in the nacelle passes the lip so as to be able to de-ice it.

4. The aircraft propulsion plant of claim 1, wherein the cooling circuit includes circulation channels extending longitudinally in at least some of the fixed blades of the set of fixed blades in a form of cavities or of tubes.

5. The aircraft propulsion plant of claim 1, wherein the stator extends at least partly in the base upstream of the fan.

6. The aircraft propulsion plant of claim 1, wherein a dielectric fluid is used both as a heat-transfer fluid in the cooling circuit and as a lubricant in the electric motor.

7. An aircraft fuselage subassembly comprising a fuselage rear part and a propulsion plant of claim 1 mechanically connected by its base to the fuselage rear part.

8. An aircraft including an aircraft fuselage subassembly of claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the disclosure herein are disclosed by the following description of nonlimiting embodiments of the various aspects of the disclosure herein. The description refers to the appended figures which are also given by way of nonlimiting examples of embodiments of the disclosure herein:

(2) FIG. 1 represents a perspective view of an aircraft;

(3) FIG. 2 represents a side view in section of the propulsion plant;

(4) FIG. 3a represents a detail view in section and in perspective of a fixed blade with cavities;

(5) FIG. 3b represents a detail view in section and in perspective of a fixed blade with tubes;

(6) FIG. 4 represents a side view in section of a variant propulsion plant;

(7) FIG. 5 represents a side view in section of another variant propulsion plant.

DETAILED DESCRIPTION

(8) FIG. 1 has already been described in the preamble to the present description.

(9) FIG. 2 shows a BLI type propulsion plant 2 including a drive unit consisting of or comprising an electric motor 5 including a rotor 8 and a stator 9. The stator 9 is mechanically connected to a set of fixed blades 13. A fan 12 situated upstream of the set of fixed blades 13 is mechanically connected to the rotor 8 of the electric motor 5, which drives it in rotation.

(10) A nacelle 14 including an outer casing 15 and a fan casing 16 surrounds the fan 12 and the set of fixed blades 13. The nacelle 14 is mechanically connected to the base 10 via the set of fixed blades 13. All the mechanical loads to which the nacelle 14 is subjected are therefore transmitted to the set of fixed blades 13 which in turn transmit them to the base 10 via a fixed shaft 18.

(11) The rotor 8 of the electric motor 5 drives in rotation the fan 12, which accelerates a flow of air 17 aspirated at the entry of the nacelle 14 and straightened downstream of the fan 12 by the set of fixed blades 13 before being ejected out of the propulsion plant 2 via the rear end of the nacelle 14.

(12) When the BLI propulsion plant 2 is operating the electric motor 5 generates heat. This is evacuated by a cooling system including a cooling circuit 19. A first part of the cooling circuit 20 is situated in the stator 9 where it captures thermal energy generated by the electric motor 5. A second part of the cooling circuit 21 extends in the fixed blades of the set of fixed blades 13 whilst a third part 22 of the cooling circuit 19 extends in the nacelle 14 between the outer casing 15 and the fan casing 16. All the parts of the cooling circuit 19 together form a closed circuit in which a heat-transfer fluid circulates. The configuration of the cooling circuit indicated hereinabove is described by way of illustration only and could vary according to circumstances, in particular the configuration of the rotor, stator and fixed shaft assembly as shown in FIGS. 4 and 5. Likewise, it is not obligatory to extend the cooling circuit 19 to the nacelle 14.

(13) In a variant embodiment not represented in the figures the cooling circuit includes a heat pipe connecting together the stator 9 of the electric motor 5, the set of fixed blades 13 and the nacelle 14. The heat pipe is made of a heat-conducting material and is sized in order to be able to drain thermal energy generated by the electric motor and accumulated in the stator 9 to the set of fixed blades 13 and the nacelle 14, where it is dissipated by convection with the flows of air flowing along those elements.

(14) In the example from FIG. 2 the heat-transfer fluid circulating in the cooling circuit 19 enables an exchange of heat between the electric motor 5 encapsulated in the propulsion plant 2 and, on the one hand, the flow of air 17 passing through the set of fixed blades 13 and, on the other hand, the ambient air surrounding and/or passing through the nacelle 14. The arrows drawn on the cooling circuit 19 in FIG. 2 indicate the direction of circulation of the heat-transfer fluid in the closed circuit.

(15) Thermal energy produced by the electric motor 5 when operating therefore heats the heat-transfer fluid circulating in the first part of the cooling circuit 20 at the level of the stator 9.

(16) The hot heat-transfer fluid arrives in the second part of the cooling circuit 21 at the level of the set of fixed blades 13 where a first exchange of heat occurs by forced convection with the flow of cold air leaving the fan 12. Indeed, because the electric motor 5 does not generate hot combustion gas, the flow of air 17 passing through the propulsion plant 2 remains cold and may be used to effect at least a first stage of cooling at the level of the set of fixed blades 13 of the hot heat-transfer fluid leaving the stator 9. The partly cooled heat-transfer fluid coming from the set of fixed blades 13 then arrives in the third part of the cooling circuit 22 at the level of the nacelle 14. A second exchange of heat occurs in the nacelle 14. The residual heat conveyed by the heat-transfer fluid is dissipated there by convection across the inner surface of the fan casing 16 and across the outer surface of the outer casing 15.

(17) Finally, the completely cooled heat-transfer fluid returns via the cooling circuit 19 to the set of fixed blades 13 and then to the stator 9, thus forming a closed circuit. Thermal levels of the heat-transfer fluid vary in the various parts of the cooling circuit 19. The part of the cooling circuit situated in the stator 9 and in which the heat-transfer fluid flows toward the fixed blades 26 corresponds to the highest temperature of the heat-transfer fluid. That is to say its temperature where it collects heat at the level of the stator 9. The part of the cooling circuit situated in the fixed blades 26 and the nacelle 14 in which the heat-transfer fluid flows at the base of the fixed blades toward the lip 35 of the nacelle and the part of the cooling circuit situated in the stator in which the heat-transfer fluid flows at the base of the fixed blades toward the end of the stator 9 corresponds to an intermediate temperature of the heat-transfer fluid. That is to say its temperature where it begins to cool on passing through the set of fixed blades 13 and arriving in the nacelle 14 and where it begins to cool on returning into the stator 9. The part of the cooling circuit situated in the nacelle 14 and the fixed blades 26 in which the heat-transfer fluid flows from the lip 35 of the nacelle to the stator 9 corresponds to the lowest temperature level of the heat-transfer fluid. That is to say its temperature where it returns from the nacelle 14 to the stator 9 via the set of fixed blades 13.

(18) The second part of the cooling circuit 21 at the level of the set of fixed blades 13 is formed by longitudinal circulation channels in the fixed blades 26 of the set of fixed blades 13 as shown in FIGS. 3a and 3b. All or only some of the fixed blades 26 include heat-transfer fluid circulation channels. The number of fixed blades 26 including these circulation channels depends in particular on the quantity of heat to be dissipated at the level of the set of fixed blades 13 and on the geometrical characteristics of those circulation channels. Various options exist for producing these circulation channels in the fixed blades 26.

(19) For example, in FIG. 3a the circulation channels take the form of cavities 27 and 29 produced during production of the fixed blades 26 by machining, forging or casting. The fixed blades 26 include two cavities, a first cavity 27 in which circulates the hot heat-transfer fluid 28 coming from the stator 5 and a second cavity 29 in which circulates the cold heat-transfer fluid 30 coming from the stator 5.

(20) A second embodiment of the circulation channels in the fixed blades 26 is shown in FIG. 3b. In this other embodiment of the circulation channels longitudinal tubes are inserted into channels that may be bored in the body of the fixed blades 26. The hot heat-transfer fluid 32 coming from the stator 5 circulates in a first tube 31. Whereas the cold heat-transfer fluid 34 returning to the stator 5 circulates in a second tube 33.

(21) The cavities 27 and 29 have the advantage of optimizing the shape of the circulation channels to maximize the areas of heat exchange and the flow section of the heat-transfer fluid in the fixed blade. Nevertheless, it is more costly to produce hollow blades 26 including the cavities 27 and 29 than to drill them and to insert therein the tubes 31 and 33.

(22) As shown in FIG. 2, in the front part of the nacelle 14 is found an air intake opening into an inner duct consisting of or comprising the fan casing 16. This inner duct channels the air toward the fan 12. The air intake is provided with a lip 35 the inner edge of which is joined to the fan casing 16 and the outer edge of which is joined to the outer casing 15 of the nacelle 14. This lip 35 has an aerodynamic function and a function of protecting the drive system against, for example, the penetration of birds into the duct leading to the fan 12.

(23) During flight phases frost or ice may form at the level of the air intake of the fan 12. The accumulation of ice upstream of the fan may have an influence on the performance of the BLI propulsion plant 2 and in extreme cases lumps of ice may be detached and aspirated into the fan casing 16 to strike the blades of the fan 16. A de-icing system is generally installed in the lip 35 to prevent the formation of frost or ice.

(24) As indicated hereinabove and shown in FIG. 2, two exchanges of heat occur during the circulation of the heat-transfer fluid in the cooling circuit 19 in order to cool it. A first exchange of heat occurs at the level of the set of fixed plates 13 and a second exchange of heat occurs at the level of the nacelle 14. By causing the front portion of the third part of the cooling circuit 22 to pass along the lip 35 it is possible to use that part of the cooling circuit as a system for de-icing the nacelle 14 and thus for preventing the formation of frost or of ice at the level of the lip 35.

(25) The heat-transfer fluid used in the cooling circuits is generally a fluid selected for its specific heat, that is to say the quantity of energy to be added to raise by one degree Kelvin the temperature per unit mass of the fluid. In parallel with this, the electric motor 5 must also be lubricated when it is operating. It is therefore judicious to choose a dielectric heat-transfer fluid also having lubricating properties for lubricating the electric motor 5 as well as cooling it.

(26) FIG. 2 shows an example of an interior architecture of the propulsion plant 2 in which the stator 9 is fixed directly to the set of fixed blades 13 and extends substantially upstream of the latter. Likewise, the rotor 8 is mechanically connected to the fan 12 and extends substantially upstream of the latter. Thus, the electric motor is partly accommodated in the base 10.

(27) FIG. 4 shows a variant inner architecture of the propulsion plant 2 in which the stator 9 is no longer connected directly to the set of fixed blades 13 but to the base 10. In this situation the stator 9 is substantially integrated inside the base, which moves it away from the set of fixed blades 13 compared to the FIG. 2 configuration.

(28) Consequently, the cooling circuit is routed differently. Indeed, the part of the cooling circuit situated at the level of the set of fixed blades 13 no longer being in the immediate vicinity of the part of the cooling circuit extending in the stator 9, they must both be connected by circulation channels extending longitudinally in the fixed shaft 18 between the set of fixed blades 13 and the part of the base 10 to which the fixed shaft 18 is fixed.

(29) FIG. 5 shows another variant of the inner architecture of the propulsion plant 2 in which the electric motor 5 is positioned substantially downstream of the fan 12 and of the set of fixed blades 13. In this configuration the stator 9 is connected directly to the set of fixed blades 13 and extends substantially downstream of the latter, just like the rotor 8 extends downstream of the fan 12. The stator 9 being connected directly to the set of fixed blades 13, the first part of the cooling circuit 20 extending in the stator 9 can be connected directly to the second part of the cooling circuit 21 extending in the set of fixed blades 13. As in the architecture shown in FIG. 2, this configuration enables a more compact cooling circuit 19 to be obtained. These three embodiments of the concept of the disclosure herein that lies in the use of the nacelle 14 and of the set of fixed blades 13 to cool the electric motor 5 show that the disclosure herein can be adapted to other types of architecture of the propulsion plant 2 using an electric motor 5.

(30) As described hereinabove the heat exchangers forming part of the cooling circuit 19 are integrated into members already existing in the BLI propulsion plant 2. Thus, implementing the disclosure herein necessitates no or only few additional parts. In addition to the advantages described in the introductory part of the description, the integration of ancillary functions into members already present in the propulsion plant 2, such as cooling the electric motor 5 or de-icing the nacelle 14, enable the structure of the propulsion plant 2 to be lightened and simplified, which commensurately reduces the production and maintenance costs thereof whilst improving the overall energy efficiency of the aircraft. The same goes for the use of the heat-transfer fluid to lubricate the electric motor 5. Because of its large inner and outer convection areas, the nacelle 14 forms a high-performance heatsink for dissipating the heat produced by the electric motor 5.

(31) As indicated in the foregoing description, the various aspects of the disclosure herein, such as for example the inner architecture of the propulsion plant, the nacelle de-icing, cooling and motor lubrication functions, may be implemented separately or in any combination according to the context and in variant configurations different from those described hereinabove.

(32) While at least one example embodiment of the invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a”, “an” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.