Fire protection nacelle system for an electric machine with cooling fins

Abstract

The invention relates to a nacelle system for an electric machine (2) provided with cooling fins (6), the nacelle system comprising a fairing (40) configured to conform to the outer shape of the electric machine provided with cooling fins, the fairing (40) comprising at least one firewall (44), the fairing (50) comprising a fairing wall (52) having an inner surface (52a) intended to be oriented facing the electric machine (2) and an opposite outer surface (52b) intended to be oriented away from the electric machine (2), the at least one firewall (54) being arranged between the inner surface (52a) and the outer surface (52b) of the fairing wall.

Description

Description Title of the invention: FIRE PROTECTION NACELLE SYSTEM FOR ELECTRIC MACHINE WITH COOLING FINS Technical Field

[0001] This disclosure relates to a nacelle system for an electric machine equipped with cooling fins. Prior art

[0002] Machines are known to be used in various fields (e.g., space, automotive, railway, marine, etc.) and whose operation requires cooling. To this end, these machines are, for example, equipped with cooling fins to evacuate all or part of the heat produced during their operation.

[0003] Such machines include, for example, electric motors, heat engines, generators, fans, heat exchangers, etc.

[0004] Although this type of machine is designed not to generate any electrical problems during operation, in certain situations or configurations of use of these machines, internal electrical faults can nevertheless occur.

[0005] In order to guarantee a satisfactory level of safety for the environment of these machines, and in particular for the systems which integrate these machines, it is important to contain such electrical faults internal to the machines to significantly limit the propagation of these faults, and the associated cascading effects, beyond the machines and in particular to the systems integrating them. Statement of the invention

[0006] This presentation aims to remedy at least part of these drawbacks.

[0007] To this end, the present disclosure relates to a nacelle system for an electric machine provided with cooling fins, the nacelle system comprising a fairing configured to match the external shape of the electric machine provided with cooling fins, the fairing comprising at least one fire-resistant wall, characterized in that the fairing comprises a fairing wall having an internal surface intended to be oriented facing the electric machine and an opposite external surface intended to be oriented away from the electric machine, said at least one fire-resistant wall being arranged between the internal surface and the external surface of the fairing wall.

[0008] The fairing surrounding the machine and its fins (for example, it may be an electric generator) makes it possible to optimize the cooling of this machine (by optimizing the fluid flows surrounding the machine in order to increase the quantity of heat exchanged between the cooling fins and the fluid flows to which the calories are evacuated) and said at least one fire wall integrated into the fairing makes it possible to contain, inside the envelope delimited by this fairing, any electrical faults internal to the machine and thus not to propagate them to the immediate environment of the nacelle system. Said at least one fire wall is made of one or more materials resistant to fire and in particular to very high temperatures.

[0009] According to other possible characteristics: -the fairing comprises a fairing wall having an internal surface intended to be oriented facing the electrical machine and an opposite external surface intended to be oriented away from the electrical machine, at least one fire-resistant wall also being arranged against the internal surface of the fairing wall; - said at least one fire wall is made in at least one of the following materials: Nomex (registered trademark), Diafirewall (registered trademark), mica, ceramic, Lexan (registered trademark); - said at least one fire-resistant wall comprises a multi-layer structure formed of an alternation of layers providing anti-electric arc protection and fire-resistant layers; -the nacelle system further comprises an adjustment device configured to hold the fairing and press it around the cooling fins of the electric machine, the fairing comprising at least one fairing portion, the adjustment device comprising at least one connecting means arranged between two ends of the fairing portion; -the fairing has a generally cylindrical shape.

[0010] The invention also relates to an electrical machine comprising a body, thermally conductive fins distributed around the body and a nacelle system as briefly set out above.

[0011] For example, the electric machine is an aircraft electric machine. Brief description of the drawings

[0012] Other characteristics and advantages of the subject of the present disclosure will emerge from the following description of embodiments, given as non-limiting examples, with reference to the appended figures.

[0013] [Fig. 1] Figure 1 is a schematic view of an electrical machine according to one embodiment of the invention.

[0014] [Fig. 2] Figure 2 is an enlarged schematic view of an area of ​​Figure 1 centered on the connecting means.

[0015] [Fig. 3] Figure 3 is a general schematic view of the nacelle system of Figure 1 without the electrical machine internal to the system.

[0016] [Fig. 4A] Figure 4A is a partial schematic cross-sectional view of a first possible configuration of a nacelle system fairing.

[0017] [Fig. 4B] Figure 4B is an enlarged schematic view of a portion of the fire wall 44 of Figure 4A according to a possible embodiment of this wall.

[0018] [Fig. 5A] Figure 5A is a partial schematic cross-sectional view of a second possible configuration of a nacelle system fairing.

[0019] [Fig. 5B] Figure 5B is an enlarged schematic view of a portion of the fairing configuration of Figure 5A.

[0020] [Fig. 5C] Figure 5C is an alternative embodiment of Figure 5B. Description of the embodiments

[0021] Figure 1 schematically illustrates an electrical machine 2 which is for example used in an aircraft. The machine 2 comprises a body 4 of cylindrical shape, thermally conductive fins 6 which are distributed around the body, at the external periphery thereof, and a nacelle system 8. The nacelle system 8 comprises a fairing 10 configured to match the shape of the electrical machine 2. The nacelle system also comprises in this embodiment an adjustment device 12 which is configured to hold the fairing 10 and to press it around the fins 6. In this embodiment, the nacelle system forms an assembly composed of the fairing 10 and the adjustment device 12.

[0022] The electrical machine 2 comprises, for example, an aircraft engine whose cooling fins are configured to carry out a heat exchange between these fins and the air in which the aircraft is moving. Here the cooling fluid is therefore air. In another application, the electrical machine can be cooled by means of a cooling fluid other than air.

[0023] The nacelle system 8 improves the cooling of the fins of the electric machine 2 (optimization of the heat exchange between the machine and the air passing through the fins).

[0024] The fairing 10 comprises a fairing portion 14, for example a thin metal sheet, for example 1 mm thick, formed for example from an aluminum alloy. In another embodiment, the fairing portion 14 is formed from another metallic, or polymer, or composite, or thermoplastic, or thermosetting material or from an aluminum alloy. It will be noted that the materials are selected according to the temperatures they must withstand and their thickness is adjusted accordingly. The fire-resistant material(s) used are generally flexible and are similar to a woven material, a foam, etc.

[0025] The fairing portion 14 is slightly flexible and is held in shape by the adjustment device 12 to best fit the cooling fins 6 of the electric machine 2.

[0026] In the embodiment shown in the figures, in particular figures 1 and 3, the shape is substantially cylindrical so that the fairing 10 takes the form of an annular ring of defined longitudinal or axial dimension, for example of the same dimension as a dimension of the electrical machine 2 along the longitudinal axis L, and of circular or elliptical cross-section, or substantially similar to the cross-section of the electrical machine 2.

[0027] The adjustment device 12 comprises at least one connecting means 16 (figure 1). The connecting means 16 comprises, for example, a tie rod 18 connecting two ends 20 of the fairing portion 14, so as to bring the two ends 20 together or to maintain these two ends at a constant distance from each other. Advantageously, the adjustment device 12 comprises at least one bracket 22 arranged on one end 20. Preferably, the adjustment device comprises two brackets 22, each being arranged on one of the two ends 20 of the fairing portion 14. The two brackets 22 are connected by the tie rod 18. The adjustment device 12 makes it possible, for example, to bring the two ends 20 of the fairing portion 14 into contact. The brackets 22 also make it possible to reinforce the fairing 10.

[0028] In the example illustrated in Figures 1 and 3, the fairing portion 14 of the nacelle system 8 is held by three assembly rods 18 which hold the fairing in a cylinder shape of constant circular section along the longitudinal axis L of the fairing 10 (it will be noted that a different number of rods can alternatively be envisaged). The adjustment device 12 also makes it possible to hold the fairing in a shape substantially similar to the cross section, relative to the longitudinal axis L, of the electric machine 2.

[0029] The assembly rods 18 can be removable so as to be able to separate the two ends 20 of the fairing portion 14 and thus to be able to remove the fairing 10 from the machine 2.

[0030] For example, a tie rod 18 is an adjustable mechanical part made with a screw system and / or lever closure and / or rocker closure. In particular, a tie rod 18 is configured to connect the brackets 22 while allowing the gap between these brackets to be adjusted. In the example of Figures 1 and 3, each of the three tie rods 18 connects two brackets 22 so as to keep them at a constant distance from each other.

[0031] The fairing 10 may comprise holes 24 (figs. 1 and 3) which are perforated in the material constituting the fairing or which are produced during the shaping of the fairing, for example, during a stamping process, and which are distributed along a periphery of the fairing, for example in a uniform manner. Alternatively, the holes may be distributed in a non-uniform manner on the fairing.

[0032] The adjustment device 12 may comprise fixing means 26 which are configured to be arranged in the holes 24 and to fix the fairing to the machine 2, preferably in contact with the fins of cooling 6, so as to optimize the flow of cooling fluid of the machine. The fixing means 26 may comprise, for example, screws and / or columns and / or washers. When the cooling fins 6 are in contact with the fairing, the latter also ensures the diffusion of heat.

[0033] Furthermore, the nacelle system may comprise an interface material 28 (visible in FIG. 1) in contact, on the one hand, with the fairing 10 and, on the other hand, with the fins 6, so as to protect the fins from contact with the fairing, in particular in the case of fragile fins. For example, the interface material 28 may be a thermosetting / thermoplastic material (PTFE or Teflon, epoxy, PEEK, organic coating) compatible with the material of the fins and which is selected appropriately, depending on the intended application and the configuration of the fairing,

[0034] Preferably, the interface material 28 comprises a thermally conductive material covering an inner surface of the fairing 10. It will be noted that the application of an organic coating on the fins can make it possible to improve the cooling by thermal convection due to the air flow which passes the fins.

[0035] The aforementioned adjustment device 12 makes it possible to place the fairing 10 in support on the cooling fins 6 so that the force exerted by the fairing on the fins is distributed substantially uniformly over the latter.

[0036] The fairing 10 is for example fixed to the machine 2 by the aforementioned removable fixing means 26 in order to be able to detach the fairing from the machine when this proves necessary. In addition, the fixing means 26 maintain the fairing 10 in a substantially cylindrical shape around the cooling fins.

[0037] When the machine 2 is housed in the shroud 10 which surrounds it, the shroud makes it possible to channel the air along a surface of the cooling fins so as to increase the quantity of heat exchanged between the fins and the air. In addition, an air flow is directed towards the fins and the cooling of the machine 2 is improved, in particular thanks to a reduction in pressure losses and / or a reduction in air leaks out of the fins. The air flow is thus concentrated exclusively at the fins. Furthermore, the heat exchange surface area of ​​the fins, when the machine 2 is surrounded by the shroud 10, is greater than the heat exchange surface area of ​​the fins when the machine 2 is not housed in the shroud. Channeling the air through the shroud thus makes it possible to improve the performance of the machine 2.For example, in the case of an aircraft engine, particularly an electric motor, this air channeling increases the engine's ability to provide power to propel the aircraft.

[0038] It will be noted that the adjustment device 12 is designed to allow the fairing 10 to perfectly match the shape of the machine 2 provided with cooling fins 6 so that all the available air can cool the fins.

[0039] As shown schematically in Figure 2, an enlarged area of ​​Figure 1 illustrates in detail a part of the adjustment device 12. The adjustment device 12 comprises, on the one hand, an assembly tie rod 18 connecting the two ends 20 of the fairing 10 and, on the other hand, a locking means 30 which makes it possible to lock the adjustment of the assembly tie rod 18 and, more generally, to lock the adjustment of the adjustment device 12. The locking means 30 makes it possible, for example, to avoid relative movements between the fairing 10 and the adjustment device 12 during vibrations of the fairing 10 and / or of the electric machine 2.

[0040] For example, the locking means 30 may comprise a nut provided with a device preventing the loosening of the nut without however preventing the disassembly of this nut. The locking means 30 may comprise a castellated nut and / or a nut with an incorporated ring and / or a locking nut and / or a self-locking nut.

[0041] The adjustment device 12 comprises a first bracket 22 arranged on a first end 20 which comprises a flanged edge 32 (figure 2). The flanged edge 32 makes it possible, for example, to reinforce the end 20, to protect a user when installing the nacelle system 8 and to facilitate the alignment of the two ends 20 of the fairing 10. The flanged edge 32 ensures a sealed junction of the two ends 20 of the fairing.

[0042] The bracket 22 has an access opening 34 arranged opposite the assembly tie rod 18 so as to facilitate access to the tie rod 18 and therefore to facilitate its installation.

[0043] Furthermore, the adjustment device 10 may comprise a fixing device 36 provided with a bracket 22 and which is arranged on the second end 20. The fixing device 36 thus makes it possible to reinforce the hold of the assembly tie rod 18 on the second end 20.

[0044] Figure 3 schematically represents only the nacelle system 8 of Figure 1, the electric machine 2 not being represented. It will be noted that the removable nature of the means for fixing the fairing to the machine and the configuration of the adjustment device 12, in particular the use of an assembly tie rod 18 as described previously, allows and facilitates the removal of the fairing 10.

[0045] Generally speaking, a fairing 10 (such as that described above but which is however not limited to this fairing and can take other embodiments), configured to match the external shape of an electrical machine 2 provided with cooling fins 6, comprises at least one fire-resistant wall (second skin) in the structure of the fairing in order to contain, at the level of the electrical machine-fairing pair, any internal electrical fault in the machine or its associated electronics. The firewall acts as a passive protective barrier against such electrical faults and makes it possible to contain fires of electrical origin, in particular electric arcs likely to occur at the level of the electrical machine 2. The use of the thermal optimization fairing (designed to channel the cooling air around the machine) to form a fire barrier within this fairing, makes it possible to maintain the compactness of the nacelle system without, however, weighing it down with an additional fairing. The fairing also ensures the protection of the fins and people during the handling of the electrical machine 2, in particular during its transport and its installation in situ, for example in the aircraft.In a particular embodiment where the fairing is assembled by means of a tie rod and screws, this makes it possible to press the fairing onto the fins in a tight manner, while applying a force distributed over the entire electrical machine 2.

[0046] Figure 4A illustrates a first possible embodiment of a fire-resistant wall (barrier) integrated into the fairing.

[0047] For this purpose, the fairing structure 40 which surrounds the cooling fins 6 arranged at the external periphery of the machine 2 comprises a fairing wall 42 having an internal surface 42a intended to be oriented facing the electric machine 2 and an opposite external surface 42b intended to be oriented away from the electric machine 2.

[0048] The fairing structure 40 comprises a fire wall 44 (here in the form of a cylindrical crown) which is disposed against the inner surface 42a of the fairing wall. The fire wall 44 is for example fixed against the inner surface 42a, for example by a conventional bonding technique, or by using an epoxy resin or neoprene or adhesive. For example, the fire wall 44 can be added by bonding on the internal surface of the fairing wall 42 before it is placed around the machine 2, either before the shaping (conformation) of the fairing wall 42 or after the shaping of the latter.

[0049] In this configuration, the fairing wall 42 is, for example, a metal wall but can also be made of polymer or composite. By arranging the fairing wall externally (and not internally) relative to the fire wall, this makes it possible to give the fairing thus obtained good mechanical strength of the assembly and to continue to ensure this mechanical strength even if the fire wall is used in the event of an electrical incident in the machine.

[0050] For example, the fire wall 44 is made of a material resistant to very high temperatures (in particular to flame temperatures of the order of 900 to 1000 °C and which are produced by the combustion of the materials of the electric arc) and, for example, in one of the following materials or in a mixture of some of these materials: Nomex (registered trademark), Diafirewall (registered trademark), mica, ceramic, Lexan (registered trademark). These materials provide very effective protection to contain the fire inside the envelope defined by the fire wall 44. Other materials with equivalent properties may also be suitable. The thickness of the wall 44 may be between 0.5 and 5.5 mm and for example equal to

[0051] Figure 4B illustrates a possible embodiment of the fire wall 44 in which this wall has a multi-layer structure, also called a sandwich structure. This structure thus comprises an alternation of successive layers (here the number is 4 layers but this number can of course vary according to the desired overall performance and the applications envisaged with, for example, 2 layers or more than 4 layers), with possibly air between each of them, starting from a lower layer 44a (the one in contact with the fins) which has an anti-electric arc function, which means that this layer can be in direct contact with an electric arc coming from the electrical machine 2 for a very short period of time (e.g. 200-300ms) and its material is therefore chosen to suit this use (e.g. thermoplastic, in particular PSU thermoplastic or arc-resistant charged polymer). This first layer protects the following upper layer(s). The structure comprises a second layer 44b providing a fire-resistant (barrier) function (e.g. Nomex (registered trademark)), then a third layer 44c providing an arc-resistant function (e.g. Lexan (registered trademark)) and a fourth layer 44d providing a fire-resistant function (e.g. Diafirewall (registered trademark)). For example, the arc-resistant layers may each have a thickness of 0.5 to 2mm and the fire-resistant layers a thickness of 2 to 5mm. The thickness of each layer in the wall structure 44 may vary.Generally speaking, the pattern formed by an arc-proof layer and a fire-proof layer can be repeated with possibly varying thickness from one pattern to another.

[0052] In Figure 4A, there is also shown (in dotted lines) above the structure 44 an optional section 45 of thermosetting material forming in some way a protective screen for the fairing wall located externally (above in Figure 4B but not shown) so that the latter retains its mechanical strength as much as possible.

[0053] Figure 5A illustrates a second possible embodiment of a fire-resistant wall (barrier) integrated into the fairing.

[0054] For this purpose, the fairing structure 50 which surrounds the cooling fins 6 arranged at the external periphery of the machine 2 comprises a fairing wall 52 having an internal surface 52a intended to be oriented facing the electric machine 2 and an opposite external surface 52b intended to be oriented away from the electric machine 2.

[0055] The fairing structure 50 comprises a fire wall 54 disposed between the inner surface 52a and the outer surface 52b of the fairing wall 52.

[0056] More particularly, Figure 5B is an enlarged partial view of the fairing wall 52 and shows a double wall structure P1, P2 framing the fire wall 54 externally and internally so as to form an overall sandwich structure: an outer fairing wall P1 is arranged against an outer surface 54a of the fire wall 54, while an inner fairing wall P2 is arranged against an inner surface 54b of the fire wall 54. The different walls have been shown spaced apart from each other in order to clearly identify them but this does not mean that they are separated from each other by an air gap. For example, the walls P1, 54 and P2 can be glued for their handling, conformation and installation around the machine.Then, the mechanical holding means (mechanical adjustment device of the fairing) such as the assembly tie rods ensure the structural mechanical holding of the sandwich assembly (multilayer). The sandwich structure can, for example, be produced by gluing the fire wall 54 to the external surface of the wall P2, then the external wall P1 is shaped and arranged around the fire wall 54. The mechanical holding of the assembled assembly is ensured as described above. Reverse assembly is also possible.

[0057] In this configuration, the inner fairing walls P2 and outer fairing walls P1 are, for example, metal walls but can also be made of polymer or composite which surround a layer of insulation 54 (monomaterial or not). This configuration guarantees the fairing structure 50 good mechanical strength and also makes it possible not to alter the air flow which runs along the fins 6, between the electrical machine 2 and the fairing structure.

[0058] For example, the fire wall 54 is made of a material resistant to very high temperatures and, for example, of one of the following materials or a mixture of some of these materials: Nomex (registered trademark), Diafirewall (registered trademark), mica, ceramic, Lexan (registered trademark). These materials provide very effective protection to contain the fire inside the envelope defined by the fire wall 54. Other materials with equivalent properties may also be suitable. The thickness of the wall 54 may be between 0.5 and 5.5 mm. The wall 54 may take the form of a sandwich structure as described above in relation to Figure 4B and everything mentioned may also apply here.

[0059] Figure 5C illustrates an alternative embodiment of the structure of Figure 5B in which an additional layer 56, for example made of thermosetting material, is arranged between the fins 6 and the structure 52 as a protective layer (analogous to the interface material 28 of Figure 1).

[0060] Whatever the form of embodiment of the fairing structure incorporating a fire wall, the structure thus produced ensures the channeling of the air flow onto the cooling fins of the electrical machine 2.

[0061] Generally speaking, it will be noted that the connecting means 16 described above can take other forms and, for example, take the form of a hinge or any other method of attaching the fairing portions 14 to each other, insofar as this connecting means remains adjustable in order to be able to adjust the fairing around the fins of the machine 2.

[0062] In an embodiment not shown, the adjustment device makes it possible to maintain the fairing in a shape corresponding to a machine whose shape is not cylindrical. In this embodiment, the fairing arranged around the cooling fins of the machine has a configuration comprising several fairing portions 14 and several connecting means 16, similar to those described above.

[0063] It will be noted that a fairing such as one of those described above can be adapted to an electric motor and / or a heat engine and / or a generator and / or a fan and / or a heat exchanger.

[0064] In particular, the electric machine 2 associated with the nacelle system and its fairing as defined above comprises, for example, an intelligent motor comprising an electric motor and its electronic control member which can be used in the aeronautical field.

[0065] In one embodiment, an aircraft engine comprising a nacelle system 8 as defined above forms a lightweight and compact aircraft engine module that is ready to be installed in an aircraft.

[0066] In particular, the structure of the aircraft engine module ensures efficient cooling of the engine, regardless of the aircraft in which the engine module is installed.

[0067] The installation of the engine module in an aircraft is facilitated, in particular thanks to the modular nature of the engine module, the efficient and autonomous cooling of the engine module, and the removable nature of the nacelle system 8.

[0068] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may 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 illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Claims

1. Nacelle system (8) for an electric machine (2) provided with cooling fins (6), the nacelle system (8) comprising a fairing (40; 50) configured to match the external shape of the electric machine provided with cooling fins, the fairing (40; 50) comprising at least one fire wall (44; 54), characterized in that the fairing (50) comprises a fairing wall (52) having an internal surface (52a) intended to be oriented facing the electric machine (2) and an opposite external surface (52b) intended to be oriented away from the electric machine (2), said at least one fire wall (54) being arranged between the internal surface (52a) and the external surface (52b) of the fairing wall.

2. A nacelle system according to claim 1, wherein the fairing (40) comprises a fairing wall (42) having an inner surface (42a) intended to be oriented facing the electric machine (2) and an opposite outer surface (42b) intended to be oriented away from the electric machine (2), at least one fire wall (44) also being disposed against the inner surface (42a) of the fairing wall.

3. Nacelle system according to claim 1 or 2, wherein said at least one fire wall (44; 54) is made of at least one of the following materials: Nomex (registered trademark), Diafirewall (registered trademark), mica, ceramic, Lexan (registered trademark).

4. Nacelle system according to any one of the preceding claims, wherein said at least one fire-resistant wall (44; 54) comprises a multi-layer structure formed of an alternation of a layer providing anti-electric arc protection and a fire-resistant layer.

5. Nacelle system according to any one of the preceding claims, further comprising an adjustment device (12) configured to hold the fairing (40; 50) and press it around the cooling fins (6) of the electric machine (2), the fairing (40; 50) comprising at least one fairing portion (14), the device adjustment (12) comprising at least one connecting means (16) arranged between two ends (20) of the fairing portion (14).

6. A nacelle system according to any preceding claim, wherein the fairing (40; 50) has a substantially cylindrical general shape.

7. Electrical machine (2) comprising a body (4), thermally conductive fins (6) distributed around the body (4) and a nacelle system (8) according to one of the preceding claims.

8. Electrical machine (2) according to the preceding claim, wherein the electrical machine (2) is an aircraft electrical machine.

Images