CH714920A2 - Fuel cell comprising a fluid compressor. - Google Patents

Abstract

The invention relates to a fuel cell (100) comprising a two-stage fluid compressor (1) comprising a housing (2) having a fluid inlet and a compressed fluid outlet and enclosing a shaft (7) mounted rotation about a longitudinal axis, a first compression wheel and a second compression wheel mounted back to back on said shaft (7), said first compression wheel constituting a first compression stage and said second compression wheel constituting a second compression stage, and a motor positioned between the first compression wheel and the second compression wheel and arranged to rotate the shaft (7). The casing (2) comprises an inner housing (50) traversing extending coaxially with the longitudinal axis and in which is disposed at least the motor, said inner housing (50) having an inner wall (52) arranged to form, with the motor, channels (54) between at least said inner wall (52) and the motor, said channels (54) extending between the first compression stage and the second compression stage, allowing the motor to be cooled at the contact of the fluid to be compressed circulating in the channels (54). In addition, the housing (2) comprises on its surface at least one cavity (60a, 60b) forming at least one integrated housing arranged to receive at least one electronic component (4a, 4b) of the compressor, said integrated housing extending into direction of the inner wall (52) to allow said electronic component (4a, 4b) to be cooled by the fluid to be compressed circulating in the channels (54) through the inner wall (52).

Description

Description

FIELD OF THE INVENTION The present invention relates to a fuel cell comprising a two-stage high speed fluid compressor comprising a casing having a fluid inlet and a compressed fluid outlet and containing a shaft mounted in rotation around a longitudinal axis, a first compression wheel and a second compression wheel mounted back to back on said shaft, said first compression wheel constituting a first compression stage and said second compression wheel constituting a second compression stage, and a motor, preferably a synchronous electric motor, positioned between the first compression wheel and the second compression wheel and arranged to rotate the shaft.

Background of the invention [0002] Such fluid compressors are generally called turbochargers or centrifugal compressors. They are equipped with a stator and a rotor forming a synchronous permanent magnet motor (brushless motor). Compressors of this type can reach very high speeds, for example from 100,000 to 500,000 rpm. The motor drives the compression wheels at high speed, the compression wheels compressing the fluid. The fluid used here is air. The use of two compression wheels makes it possible to compress the fluid twice as much.

These compressors generally include a first circuit for the circulation of the fluid to be compressed and a second circuit for the circulation of a coolant used to cool the compressor, and more particularly the motor and the bearings supporting the motor shaft. on the one hand and electronic components on the other. In fact, the rotation at high speed of the motor causes very significant heating, so that the elements of the compressor must be cooled so as not to be damaged. These circuits are generally provided outside the compressor as such, at least as far as the cooling circuit is concerned.

As a result, these compressors are very bulky and cannot be integrated in a restricted environment.

In addition, the heat recovered by the coolant is lost, which constitutes a significant loss of energy.

Claims (15)

Summary of the invention [0006] The aim of the invention is in particular to overcome the various drawbacks of fuel cells comprising a known high-speed compressor. More specifically, an objective of the invention is to provide a fuel cell comprising a very compact two-stage high-speed fluid compressor. Another object of the invention is to provide a fuel cell comprising a two-stage high-speed fluid compressor having a high rotational speed, a large compression ratio and optimum energy efficiency, while occupying a volume restricted. To this end, the present invention relates to a fuel cell comprising a two-stage fluid compressor comprising a casing having a fluid inlet and a compressed fluid outlet and containing a shaft mounted in rotation about a longitudinal axis , a first compression wheel and a second compression wheel mounted back to back on said shaft, said first compression wheel constituting a first compression stage and said second compression wheel constituting a second compression stage, and a motor positioned between the first compression wheel and the second compression wheel and arranged to rotate the shaft. According to the invention, the housing comprises a through internal housing extending coxially to the longitudinal axis and in which is disposed at least the motor, said internal housing having an internal wall arranged to form, with the motor, channels between at least said interior wall and the motor, said channels extending between the first compression stage and the second compression stage, allowing the motor to be cooled in contact with the fluid to be compressed flowing in the channels. In addition, the casing comprises on its surface at least one cavity forming at least one integrated housing arranged to receive at least one electronic component of the compressor, said integrated housing extending in the direction of the interior wall to allow said electronic component to be cooled by the fluid to be compressed circulating in the channels through the interior wall. Thus, the fuel cell according to the invention comprises a compressor which uses one and the same fluid to carry out the compression and for the cooling of the compressor. The arrangement of the channels used both for the circulation of the fluid to be compressed and for the cooling of the various elements of the compressor makes it possible to obtain a very compact compressor and therefore a very compact fuel cell. In addition, the fuel cell according to the invention comprises a compressor which makes it possible to recover all the heat losses from the engine, the bearings supporting the engine shaft and the electronics, to transform them into useful work. Thus, the fuel cell according to the invention comprises a compressor which has a high rotational speed, a large compression ratio and an optimum energy efficiency, while occupying a limited volume. CH 714 920 A2 BRIEF DESCRIPTION OF THE DRAWINGS The aims, advantages and characteristics of the present invention will appear more clearly in the following detailed description of an embodiment of the invention given solely by way of nonlimiting example and illustrated by the attached drawings. on which ones: fig. 1 shows a schematic view of a fuel cell according to the invention comprising a high speed compressor seen in perspective, FIG. 2 shows an exploded view of the compressor of FIG. 1 along the longitudinal axis, fig. 3 shows a partially exploded perspective view of the compressor of FIG. 1 seen from above, fig. 4 is a view in longitudinal section of the compressor of FIG. 1, fig. 5 is a sectional view along line C-C of FIG. 4, fig. 6 is a perspective view of the shaft carrying the compression wheels and the rotor, FIG. 7 is an enlarged sectional view of the compressor at the bearings, and FIG. 8 is a perspective view of the plate carrying the electronic components. Detailed description of the invention With reference to FIG. 1, there is shown schematically a fuel cell 100 according to the invention comprising a two-stage high speed fluid compressor 1, of the turbocharger or centrifugal compressor type. In the following description, the term "fluid" means air. With the exception of the compressor described below, the elements making up the fuel cell are known per se and do not require a specific description here. The compressor 1 comprises a casing 2, made of aluminum, the upper face 2a of which is closed by an upper cover 3a and the front faces 2b and rear 2c are closed respectively by a front cover 3b and by a rear cover 3c. The side faces 2d of the casing are joined at their base to form a bottom 2e having, in cross section, a U-shape. The upper cover 3a is positioned on the side of the electronic components 4 of the compressor, as will be seen below. Thus, access to the electronic components 4 integrated in the compressor as will be seen below, is easy, access being made by the upper cover 3a. The front and rear covers 3b, 3c are used to reach the interior of the compressor (motor, rotor, bearings, etc.). A seal 20 is interposed between the upper face 2a of the casing 2 and the upper cover 3a. This seal 20 protects the electronic components 4 against dust and moisture. The casing 2 has a fluid inlet to be compressed 5 provided on the front cover 3b and a tangential outlet of compressed fluid 6 provided on one of the side faces 2d of the casing 2. Referring to FIG. 4, the cover 2 contains a ceramic shaft 7, mounted in rotation about a longitudinal axis AA passing through the front 2b and rear faces 2c, a first centrifugal compression wheel 8 and a second centrifugal compression wheel 10 mounted back to back at each end of the shaft 7, said first compression wheel 8 constituting a first compression stage and said second compression wheel 10 constituting a second compression stage. More particularly, the shaft 7 is hollow and contains a threaded rod 11, at each end of which is screwed one of the compression wheels 8,10, which allows easy mounting and dismounting of the compression wheels. Thus, the two compression wheels 8 and 10 are driven on the same shaft 7, which allows better energy efficiency and the avoidance of a reduction gear. The rear of the compression wheels 8 and 10 have a labyrinth seal in order to control the pressures in the compressor and balance the axial forces. The casing 2 also contains a synchronous electric motor 12 positioned between the first compression wheel 8 and the second compression wheel 10 and arranged to rotate the shaft 7. The motor 12 comprises a stator 14 and a rotor which interact to form a synchronous permanent magnet electric motor (brushless motor). More particularly, the stator 14 is formed by a coil 14a and two ferrite elements 14b, mounted fixed relative to the casing 2. The rotor comprises a magnet 16a made integral with the shaft 7, for example by gluing, and is covered with '' a carbon fiber liner 16b. Titanium flanges 16c are fixed (for example by gluing) to the lateral ends and make it possible to ensure the resistance of the rotor to centrifugal forces at high speeds. The shaft 7 is rotatably mounted on the casing 2 around its longitudinal axis AA by means of at least one front radial bearing 18, a rear radial bearing 22 and an axial bearing 24. The compressor comprises a support for front radial bearing 26 for carrying the front radial bearing 18, a rear radial bearing support 28 for carrying the rear radial bearing 22, arranged to be positioned around the shaft 7, respectively at the front and at the rear of the engine 16. At the rear, a volute 29 is also provided between the rear radial bearing support 28 and the rear cover 3c. The volute 29 includes the orifice leading to the tangential outlet 6 of fluid, after compression. An axial bearing support 30 is also provided for CH 714 920 A2 carry the axial bearing 24 arranged to be positioned around the shaft 7, between the first compression wheel 8 and the front radial bearing support 26. It is obvious that the axial bearing could be provided for rear of the engine. The bearings are non-contact, of aerodynamic type, in order to generate little friction. They do not require lubrication and require very little maintenance. More particularly, with reference to FIG. 6, the axial bearing 24 is an aerodynamic bearing and is constituted by a disc comprising on at least one of its faces first grooves 24a3, preferably spiral, arranged to create an air film. The front radial bearings 18 and rear 22 are aerodynamic bearings, and the shaft 7 has opposite the radial bearings front 18 and rear 22 of the second grooves 32 arranged to create an air film. Referring to FIG. 7, the front radial bearing support 26 comprises at least a first groove 34 positioned opposite a second groove 36 provided on the front radial bearing 18, said first groove 34 and said second groove 36 being arranged to receive an O-ring of front bearing 38. In fig. 7, two sets of grooves 34, 36 are provided. Likewise, the rear radial bearing support 28 comprises at least a third groove positioned opposite a fourth groove provided on the rear radial bearing 22, said third groove and said fourth groove being arranged to receive an O-ring for the rear bearing. The grooves provided on the front radial bearing 18 and on the rear radial bearing 22 have the rounded bottom. The axial and radial maintenance of the radial bearings 18, 22 is carried out only respectively by said O-rings. These make it possible to ensure the centering of the radial bearings 18, 22, to compensate for the radial clearances, to dampen the vibrations and to maintain their axial position. In addition, this assembly saves space, making it possible to further increase the compactness of the compressor. The radial retention and the centering of the threaded rod 11 carrying the two compression wheels 8 and 10 at the center of the shaft 7 are produced by means of a seal 39 (cf. fig. 4) mounted in a groove provided on the threaded rod 11. In addition, the front radial bearing support 26 includes a fifth groove 40 provided for the passage of air. Similarly, the rear radial bearing support 28 includes a sixth groove provided for the passage of air. These fifth and sixth grooves, as well as holes communicating between each important point of the bearings, allow the pressure to be balanced throughout the compressor, and in particular between the seals. This is to avoid dislodging the seals. Referring to Figs. 2, 4 and 5, the casing 2 comprises an interior through-housing 50 extending coxially to the longitudinal axis AA between the front face 2b and the rear face 2c of the casing 2 and receiving the front radial bearing support 26 and the bearing radial front 18, the motor 12 and its shaft 7, the rear radial bearing support 28 and the rear radial bearing 22, the second compression wheel 10 and the volute 29. On the side of the front face 2b, the internal housing 50 is closed by the front cover 3b which integrates the first compression wheel 8, the axial bearing support 30 and the axial bearing 24. On the side of the rear face 2c, the interior housing 50 is closed by the rear cover 3c. The interior housing 50 has an interior wall 52 arranged to form, with the motor 12, channels 54 between at least said inner wall 52 and the motor 12, said channels 54 extending between the first compression stage and the second compression stage, allowing the motor 12 to be cooled in contact with the fluid to be compressed flowing in the channels 54. More specifically, in the variant shown here, the internal wall 52 of the internal housing 50 has a circular cross section and the two ferrite elements 14b of the stator 14 of the motor 12 have, on their external faces, longitudinal recesses 55 (cf. Fig. 5), extending along the longitudinal axis AA, giving the motor a substantially polygonal cross section (here dodecagonal), so that the recesses 55 or the faces of the ferrite elements 14b of the motor 12 which are not in contact with the interior wall 52 form with said interior wall 52 said channels 54 for the circulation of the fluid to be compressed. More generally, all the parts of the compressor located along the longitudinal axis between the first compression stage and the second compression stage are dimensioned and arranged to form said channels 54 for circulation of the fluid to be compressed extending between the first compression stage and the second compression stage. Thus, channels 54 are formed between the front cover 3b and the axial bearing support 303 between the front radial bearing support 26 and the inner wall 52 (for this purpose, the shoulder 56 of the front radial bearing support 26 bears. on the inlet of the housing 50 has slots 58 provided in correspondence with the channels 54 for the circulation of the fluid to be compressed), between the ferrite elements 14b of the motor 12 and the interior wall 52 as described above, between the support of rear radial bearing 28 and the inner wall 52, between the volute 29 and the inner wall 52 and between the rear cover 3c and the volute 29. These channels 54 are designed to avoid turbulence in the compressor. In addition, there is advantageously provided at least one orifice (for example the point referenced 57a in Fig. 4) arranged to allow the fluid to be compressed flowing in the channels 54 to enter the motor 12 and to flow between the stator 14 and the rotor 16 and at least one orifice (for example the points referenced 57b in FIG. 4) arranged to allow the fluid to be compressed to leave the motor 12 and join said channels 54 after having cooled the motor 12. Similarly, it is advantageously provided at least one orifice (for example the points referenced 59a in Fig. 4) arranged to allow the fluid to be compressed flowing in the channels 54 to flow near the axial bearings 24, radial before 18 and rear radial 22, and at least one orifice (corresponding for example to the same points referenced 57b in FIG. 4) arranged to allow the fluid to be compressed to join said channels 54 after having cooled said axial bearings 24, front radial 18 and rear radial 22. CH 714 920 A2 Thus, after entering the first compression stage through the inlet 5, the fluid to be compressed passes through the channels 54 through the parts of the compressor situated along the longitudinal axis between the first compression stage and the second compression stage to join the second compression stage. Therefore, the fluid to be compressed, when it passes between the inner wall 52 and the ferrite elements 14b of the engine, cools the latter and recovers the calories lost from the engine in order to increase its efficiency before entering the second compression stage. In addition, the orifices 57a, 57b, 59a make it possible to produce a slight deflection of the flow so that the fluid to be compressed also circulates between the stator 14 and the rotor 16 and in the bearings to cool these elements and recover the heat losses at the level of the motor and the heat losses due to friction in the bearings. In addition, with reference to Figs. 3 and 5, the casing 2 comprises on its surface at least one cavity 60a, 60b forming at least one integrated housing arranged to receive at least one electronic component of the compressor, said integrated housing extending in the direction of the interior wall 52, at closer to the channels 54, to allow said electronic component to be cooled by the fluid to be compressed circulating in the channels 54 via the interior wall 52, itself being in contact with the fluid to be compressed circulating in the channels 54 . Advantageously, the casing 2 comprises, on the same surface defining its upper inner face 62, several cavities 60a, 60b each forming an integrated housing arranged to receive an electronic component of the compressor, said cavities 60a, 60b being provided at least above and at least on one side, and preferably on each side, of the inner wall 52 of the inner housing 50 of the casing 2. Thus, the integrated housings and therefore the electronic components placed in these integrated housings are disposed as close as possible to the fluid to be compressed which circulates in the channels 54 in contact with the interior wall 52, so that said fluid to be compressed can recover the heat emitted by said electronic components via said interior wall 52. Preferably, at least one of the cavities 60a, 60b extends longitudinally at least partially along the circulation channels 54 of the fluid to be compressed to form an integrated housing extending longitudinally over at least part of the upper inner face 62 of the casing 2. Thus, the integrated housings follow the channels 54 so as to obtain a maximum heat exchange zone between the electronic components arranged in the integrated housings and the fluid to be compressed, by means of said inner wall 52. Advantageously, and with reference to FIG. 8, the compressor comprises at least one plate 64 arranged to receive the electronic components 4 of the compressor, said plate 64 carrying on its underside at least electronic components 4a, 4b extending longitudinally, along the longitudinal axis AA, said plate 64 being positioned above the upper internal face 62 of the casing 2 so that said electronic components 4a, 4b extending longitudinally on the lower face of the plate 64 are housed respectively in their integrated housings extending longitudinally at at least partially along the circulation channels 54 of the fluid to be compressed. On the upper face of the plate 64 are provided other electronic components 4c arranged so as to be housed in the upper cover 3a. For example, the electronic components 4a are transistors which are arranged longitudinally on each side of the plate, and vertically to the plate 64 in order to have as much contact area as possible with the casing and to be the most as close as possible to the fluid to be compressed via the interior wall 52 on each side of the motor 12. It is obvious that, if there is enough room for this, the transistors can all be arranged in one and same side of the engine. In addition, the integrated housings, and in particular the integrated housings which extend longitudinally at least partially along the channels 54 for circulation of the fluid to be compressed, may comprise a leaf spring 66, preferably arranged longitudinally, and arranged for maintain the electronic component 4a disposed in said integrated housing in abutment against the wall of the integrated housing in the direction of the internal wall 52. The electronic components 4b are for example capacitors in the form of a tube of circular cross section and are arranged longitudinally on the underside of the plate 64 so as to be housed in cavities 60b with the corresponding rounded bottom provided above of the motor 12 in order to have as much contact surface as possible with the casing and to be as close as possible to the fluid to be compressed via the interior wall 52 above the motor 12. It is possible to provide at the bottom of the cavity 60b of the thermal paste allowing better contact between the capacitor and the casing 2. Thus, the fluid to be compressed which circulates in the channels 54 also recovers the heat losses from the electronic components of the compressor, these being arranged as close as possible to said fluid to be compressed. In addition, the interior of the compressor is optimized, and in particular the upper surface of the casing is cut so as to accommodate the electronic components of the compressor in a small volume making it possible to produce a very compact compressor. Advantageously, the upper inner face 62 of the casing 2 has a hole 68 arranged to allow the passage of cables between the motor 12 and the electronic components 4, said hole 68 being sealed so as to have no leakage of fluid to be compressed. To this end, resin is poured into the hole 68 by introducing cable elements into the resin during casting. The other cable elements linked respectively to the motor 12 and to the electronic components 4 are then welded to the cable elements cast in the resin in the hole 68. Other passages CH 714 920 A2 of waterproof cables 70 and 72 are provided on the rear face 2c of the casing 2 for example for the output of the control cable and for the output of the power cable, which allows a connection in complete safety. Preferably, the compressor comprises a pressure and temperature sensor 74 between the two compression stages, allowing self-regulation of the compressor. The fluid compressor used in the invention achieves very high rotational speeds, between 100,000 rpm and 500,000 rpm. It allows the fluid compressed in the first compression stage to pass substantially throughout the system to recover all the heat lost, and in particular the heat lost at the engine, bearings and electronic components, in order to increase its efficiency before d '' enter the second compression stage (the temperature of the fluid to be compressed increases, its pressure also increases). In addition, the use of the only fluid to be compressed to cool the compressor, without the aid of an additional cooling circuit, as well as the arrangement of the electronic components in the compressor to have electronics integrated in the casing, make it possible to get a very compact compressor. The fuel cell according to the invention comprising the compressor described above therefore has a high rotational speed and a large compression ratio while occupying a small volume. For example, a compressor used in the invention has a compression ratio greater than 3, and a power of the order of 4 kW for dimensions L χ I xh in cm of the order of 14 x 8 x 11 for a weight of only 1.5 kg. claims 1. Fuel cell (100) comprising a two-stage fluid compressor (1) comprising a casing (2) having a fluid inlet (5) and an outlet (6) of compressed fluid and containing a mounted shaft (7) rotating about a longitudinal axis (AA), a first compression wheel (8) and a second compression wheel (10) mounted back to back on said shaft (7), said first compression wheel (8) constituting a first compression stage and said second compression wheel (10) constituting a second compression stage, and a motor (12) positioned between the first compression wheel (8) and the second compression wheel (10) and arranged to set in motion rotation of the shaft (7), characterized in that the casing (2) comprises an internal housing (50) passing through, extending coxially to the longitudinal axis (AA) and in which at least the motor (12) is disposed, said interior housing (50) having an interior wall (52) arranged for ur forming, with the motor (12), channels (54) between at least said interior wall (52) and the motor (12), said channels (54) extending between the first compression stage and the second compression stage compression, allowing the motor (12) to be cooled in contact with the fluid to be compressed flowing in the channels (54), and in that the casing (2) comprises on its surface at least one cavity (60a, 60b) forming at at least one integrated housing arranged to receive at least one electronic component (4) of the compressor, said integrated housing extending in the direction of the interior wall (52) to allow said electronic component (4) to be cooled by the fluid to be compressed circulating in the channels (54) via the interior wall (52). 2. Fuel cell according to claim 1, characterized in that the internal wall (52) of the internal housing (50) of the casing (2) has a circular cross section and in that the engine (12) has on its external face hollows (55), said hollows (55) forming with said interior wall (52) said channels (54) for the circulation of the fluid to be compressed. 3. Fuel cell according to one of the preceding claims, characterized in that the casing (2) comprises, on the same surface defining its upper internal face (62), several cavities (60a, 60b) each forming an integrated housing arranged to receive an electronic component (4a, 4b) of the compressor, said cavities (60a, 60b) being provided at least above and at least on one side of the inner wall (52) of the casing (2). 4. Fuel cell according to one of the preceding claims, characterized in that the cavity (60a, 60b) extends longitudinally at least partially along the channels (54) for circulation of the fluid to be compressed to form an integrated housing s 'extending longitudinally. 5. Fuel cell according to the preceding claim, characterized in that the fluid compressor (1) comprises at least one plate (64) arranged to receive the electronic components (4) of the compressor, said plate (64) bearing on its face lower at least of the electronic components (4a, 4b) extending longitudinally, said plate (64) being positioned above the upper inner face (62) of the casing (2) so that said electronic components (4a, 4b) extending longitudinally on the underside of the plate (64) are housed respectively in their integrated housings extending longitudinally at least partially along the channels (54) for circulation of the fluid to be compressed. 6. Fuel cell according to one of the preceding claims, characterized in that the integrated housing comprises a leaf spring (66) arranged to hold the electronic component (4a) disposed in said integrated housing in abutment against the wall of the integrated housing in direction of the internal wall (52). 7. Fuel cell according to one of the preceding claims, characterized in that the fluid compressor (1) comprises an upper cover (3a) for closing the upper face (2a) of the casing (2), said upper cover (3a) being positioned on the side of the electronic components (4). CH 714 920 A2 8. Fuel cell according to one of the preceding claims, characterized in that the motor (12) comprises a stator (14) and a rotor (16) and in that at least one orifice (57a) is provided to allow the fluid to be compressed flowing in the channels (54) to enter the motor (12) and to flow between the stator (14) and the rotor (16) and at least one orifice (57b) arranged to allow the fluid to compress out of the engine (12) and join said channels (54) after cooling the engine (12). 9. Fuel cell according to one of the preceding claims, characterized in that the shaft (7) is rotatably mounted on the casing (2) by means of at least one front radial bearing (18), a radial bearing rear (22) and an axial bearing (24). 10. Fuel cell according to claim 9, characterized in that there is provided at least one orifice (59a) arranged to allow the fluid to be compressed flowing in the channels (54) to circulate in the vicinity respectively of the front radial bearing (18 ), the rear radial bearing (22) and the axial bearing (24), and at least one orifice (57b) arranged to allow the fluid to be compressed to join said channels (54) after having cooled said front radial bearing (18), rear radial bearing (22) and axial bearing (24). 11. Fuel cell according to one of claims 9 and 10, characterized in that the axial bearing (24) is an aerodynamic bearing and in that it has on at least one of its faces first grooves (24a ) arranged to create an air film. 12. 12. Fuel cell according to one of claims 9 and 10, characterized in that the front radial bearing (18) and the rear radial bearing (22) are aerodynamic bearings and in that the shaft (7) has opposite the front radial bearing (18) and the rear radial bearing (22) second grooves (32) arranged to create an air film. 13. 13. Fuel cell according to one of claims 9 to 12, characterized in that the fluid compressor (1) comprises a front radial bearing support (26) and a rear radial bearing support (28), arranged for positioning around the shaft (7), respectively at the front and at the rear of the motor (12), in that said front radial bearing support (26) comprises at least one first groove (34) positioned opposite a second groove (36) provided on the front radial bearing (18), said first groove (34) and said second groove (36) being arranged to receive a front bearing seal (38), and in that said rear radial bearing support (28) comprises at least a third groove positioned opposite a fourth groove provided on the rear radial bearing (22), said third groove and said fourth groove being arranged to receive a rear bearing seal. 14. 14. Fuel cell according to claim 13, characterized in that the front radial bearing support (26) comprises a fifth groove (40) provided for the passage of air and in that the rear radial bearing support (28 ) includes a sixth groove provided for the passage of air. 15. 15. Fuel cell according to one of the preceding claims, characterized in that the casing (2) has a hole (68) arranged to allow the passage of cables between the engine (12) and the electronic components (4) , said bore (68) being sealed. CH 714 920 A2