Fuel cell ejector

Abstract

An ejector (10) for a fuel cell (1), comprising: a housing (16), comprising a converging pipe (15), a suction chamber (14) and a diverging pipe (8) which are arranged sequentially and communicate from one side to the other in an axial direction (A) of the housing (16), the housing (16) further comprising a first inlet (6) communicating with the interior of the housing (16) and a second inlet (7) communicating with the interior of the housing (16); a nozzle (12) which is located inside the housing (16) and is fixed to the housing (16), the nozzle (12) comprising a deformable end portion (21) extending into the converging pipe (15), and a first fluid passage (p1) being formed in the nozzle (12);andan adjusting device (17) which is at least partially located inside the housing (16), the adjusting device (17) comprising an adjusting element (18) extending at least partially around the nozzle (12), the adjusting element (18) being movable along the axial direction (A) and being configured to interact with the end portion (21) such that a cross-sectional area (S) of at least a portion (13) of the first fluid passage (p1) varies depending on the axial position of the adjusting element (18) Figure 3;

Description

Title of the invention: Ejector for fuel cell

[0001] The invention relates to the gas supply of a fuel cell.

[0002] A fuel cell allows the production of electricity thanks to two coupled chemical reactions: the oxidation of a reducing fuel on a first electrode or anode and the reduction of an oxidant on a second electrode or cathode. The electricity produced circulates in a circuit powered by the two electrodes. To date, hydrogen is commonly used as fuel and oxygen contained in the air as oxidant.

[0003] The fuel cell finds particular utility in the field of transport which to date essentially uses fossil energy derived mainly from oil. The use of this energy produces a significant quantity of carbon dioxide contributing to the increase in the greenhouse effect at the global level. Other pollutants such as particles or nitrogen oxides are also produced by the use of fuels derived from oil.

[0004] The main advantage of using a fuel cell using hydrogen and oxygen as feed gas is that the only product of the chemical oxidation and reduction reactions is water, causing no pollution or contribution to the greenhouse effect.

[0005] Concretely, in a membrane fuel cell, hydrogen is introduced in gaseous form at the anode. In the presence of a catalyst, such as platinum contained in the anode, the hydrogen releases electrons in the anode according to the following reaction:

[0006] H2 -> 2H+ + 2e .

[0007] The electrons e released at the anode will reach the cathode through an electrical circuit using the energy produced by the fuel cell and the protons H+, released during this first reaction, will migrate towards the cathode by crossing a membrane. At the cathode, the protons H+ will combine with the oxygen O2 and the electrons e still in the presence of a catalyst according to a second reaction:

[0008] 2H+ + 2e + 1 / 2 O2 -> H2O.

[0009] Both chemical reactions are exothermic.

[0010] The supply of hydrogen H2 can be done either intermittently or continuously. In the latter case, during the chemical reaction at the anode, not all of the hydrogen H2 circulating in gaseous form is used and the excess hydrogen H2 is returned upstream of the anode by means of a recirculation aid, called an ejector.

[0011] The ejector generally comprises a nozzle intended to increase the speed of the gas supply at its entry into the suction chamber. For this purpose, the nozzle has a convergent end portion which opens into a suction chamber of the ejector and which allows the supply of a high-pressure hydrogen flow. Upstream of the suction chamber, the ejector also has a convergent pipe arranged around the nozzle in which the excess hydrogen circulates. The acceleration of the hydrogen flow in the nozzle generates a depression in the suction chamber allowing the suction of the excess hydrogen.

[0012] In certain architectures, the fuel cell is powered by a pump and a variable flow ejector. The pump ensures the recirculation of the hydrogen coming from the cell when this cell delivers a low power then the variable flow ejector gradually takes over, when the power of the cell increases, for the supply of hydrogen to the cell until it ensures the entire flow rate of the hydrogen flow required by the cell and the management of the recirculation of the hydrogen by Venturi effect.

[0013] The variable flow rate ejector must be able to control the flow rate of the hydrogen flow at the nozzle outlet in order to adapt the flow rate of the hydrogen flow entering the fuel cell to the operating requirements of said fuel cell. For this purpose, the ejectors of the prior art generally propose reducing the outlet section of the nozzle by means of a tip arranged inside the nozzle and movable along the axis of the nozzle, the tip being configured to partially close an outlet opening through which the hydrogen flow circulates before entering the suction chamber. Depending on the axial position of the tip, the outlet opening is more or less wide and the flow rate of the hydrogen flow at the nozzle outlet is more or less high.

[0014] This known solution, however, has the disadvantage of being relatively complex to implement. Furthermore, the presence of a tip inside the nozzle can generate disturbances in the flow of hydrogen circulating inside the nozzle, which can negatively impact the control of the flow rate of the hydrogen flow at the outlet.

[0015] The invention therefore aims to propose an ejector for a fuel cell which allows control of the flow rate of the hydrogen stream at the outlet of the nozzle and which does not have the aforementioned drawbacks.

[0016] According to a general definition, the invention relates to an ejector for a fuel cell, comprising:

[0017] - a housing, comprising a converging pipe, a suction chamber and a diverging pipeline which are arranged sequentially and communicate from one side to the other in an axial direction of the housing, the housing further comprising a first inlet communicating with the interior of the housing and a second inlet com- communicating with the inside of the case;

[0018] - a nozzle which is located inside the housing and is attached to the housing, the nozzle comprising a deformable end portion extending into the converging pipe, the end portion and the converging pipe being fitted and spaced apart from each other in a radial direction of the housing, and a first fluid passage being formed in the nozzle, a second fluid passage being formed between the nozzle and the converging pipe, wherein the first inlet is in communication with the suction chamber via the first fluid passage, and the second inlet is in communication with the suction chamber via the second (fluid) passage; and

[0019] - an adjustment device which is at least partially located inside the housing, the adjustment device comprising an adjustment element extending at least partially around the nozzle, the adjustment element being movable along the axial direction and being configured to interact with the end portion such that a cross-sectional area of ​​at least a portion of the first fluid passage varies depending on the axial position of the adjustment element.

[0020] Thus configured, the ejector of the invention makes it possible to control the flow rate of the hydrogen stream at the outlet of the nozzle by means of an adjustment element which extends around the nozzle. This adjustment element therefore does not generate disturbances in the flow of hydrogen circulating inside the nozzle.

[0021] The ejector of the invention may also include one or more of the following characteristics:

[0022] - the nozzle comprises a base fixed to the housing, said base having a hollow cylindrical extension extending along a central axis and being defined by a central cavity forming an upstream portion of the first fluid passage, and an end ring fixed to the base, said end ring being formed of a first substantially cylindrical segment at least partially covering the hollow cylindrical extension of the base and a plurality of second petal-shaped segments articulated on the first segment and arranged circumferentially around the central axis, all of said second segments at least partially defining the terminal portion of the nozzle.

[0023] - each of the second segments of the end ring is made of a material elastically deformable and is configured to elastically move away from the central axis when not under any stress from the adjustment element.

[0024] - the first segment of the end ring is provided with at least one groove along of its external peripheral wall, said at least one groove being configured to cooperate with at least one projecting shape protruding radially from an internal wall of the adjustment element so as to ensure a threaded connection between said element of adjustment and said end ring.

[0025] - an external cylindrical wall of the adjustment element is provided with teeth intended to cooperate with the corresponding teeth of a toothed wheel rotated by a motor so as to ensure rotation of the adjustment element around the central axis, said adjustment element moving simultaneously in translation along the central axis due to the threaded connection between the adjustment element and the end ring.

[0026] - the adjustment element is provided with an internal surface which is configured to enter in contact with an upper edge of each of the second segments of the end ring during translational movement of the adjustment element along the central axis, said internal surface tending to radially bring said upper edge closer to the central axis when the adjustment element moves axially towards the converging pipe.

[0027] - the internal surface is formed from a succession of several contiguous sections, conical shape, centered on the central axis, each of the conical sections being defined by a generatrix forming an angle with the central axis.

[0028] - the internal surface comprises a first conical section whose ge generator forms an angle of the order of 15° with the central axis and a second conical section whose generator forms an angle of the order of 8° with the central axis.

[0029] - each of the second segments of the end ring is separated from a second segment directly adjacent by a slot extending radially from an axial opening of the end ring, the cross-sectional area of ​​said axial opening varying according to the inclination of said second segments relative to the central axis.

[0030] - the base comprises a plurality of petal-shaped legs articulated on the cylindrical extension and configured to come to bear elastically against the end ring at the level of the slots separating each of the second segments, thus preventing the passage of a fluid through said slots.

[0031] Other characteristics and advantages of the present invention will emerge clearly from the detailed description below of an embodiment of the invention given by way of non-limiting example, with reference to the appended drawings in which:

[0032] [Fig-1] is a schematic representation of a hydrogen supply unit of a fuel cell.

[0033] [Fig.2] is a schematic representation of an ejector.

[0034] [Fig.3] is a perspective and cutaway view of an ejector according to a method of rea lization of the invention.

[0035] [Fig.4] is a sectional view of the nozzle equipping the ejector of [Fig.3].

[0036] [Fig.5a] is a partial, sectional view of the ejector of [Fig.3], in the case where the ejector outlet opening is maximum.

[0037] [Fig.5b] is a partial, sectional view of the ejector of [Fig.3], in the case where the ejector outlet opening is minimal.

[0038] [Fig.6] is an axial view of the ejector nozzle of [Fig.3].

[0039] [Fig.7] is a view of the nozzle of [Fig.6], without its end ring.

[0040] [Fig.8] is an enlarged view of detail D shown in [Fig.4].

[0041] The invention is described in relation to a membrane-type fuel cell, using hydrogen as a reducing gas and atmospheric oxygen as an oxidizing gas. It is understood that the invention is not limited to this type of fuel cell. The invention can be implemented in any type of fuel cell using at least one gas for which a recirculation of an excess of at least one of the gases is implemented during a chemical reaction internal to the fuel cell.

[0042] With reference to [Fig.l], a hydrogen supply unit for a fuel cell 1 is shown schematically. The fuel cell 1 may in particular comprise an anode and a cathode separated by a membrane. A pressurized tank 2 makes it possible to supply the fuel cell with hydrogen. The pressurized hydrogen at the outlet of the tank 2 first flows through a shut-off valve 3, a pressure reducer 4, which lowers the pressure of the hydrogen, and a hydrogen ejection valve 5, before being delivered to a first inlet 6 of an ejector 10. The pressure at the outlet of the pressure reducer 4 remains sufficient to be converted into kinetic energy generating a depression at a second inlet 7 of the ejector 10. The ejector 10 comprises a diverging pipe 8 forming an outlet of the ejector 10. The diverging pipe 8 supplies hydrogen, via a supply pipe 9, to the fuel cell 1.The hydrogen circulates inside the fuel cell 1 and a portion of the excess hydrogen exits the fuel cell 1 through an extraction channel 11 leading this excess towards the second inlet 7 of the ejector 10 to be sucked in by the hydrogen coming from the first inlet 6.

[0043] [Fig.2] schematically represents an ejector 10 allowing the recirculation culation of hydrogen. This figure shows the two inlets 6 and 7 as well as the diverging pipe 8 forming the outlet of the ejector 10. The inlet 6 extends into the ejector 10 by a nozzle 12 making it possible to accelerate the hydrogen coming from the tank 2. For this purpose, a first fluid passage pl is formed in the nozzle 12, said first passage pl communicating the first inlet 6 with a suction chamber 14 of the ejector 10. The nozzle 12 comprises in particular a convergent end portion 21 opening into the suction chamber 14 at an outlet opening 13. In the case of the ejector of the invention, and as described below, the outlet opening 13 has a cross-sectional surface S which can be modified by so as to vary the flow rate of the hydrogen stream at the inlet of the suction chamber 14. Upstream of the suction chamber 14, the ejector 10 comprises a converging pipe 15 arranged around the nozzle 12 into which the extraction channel 11 opens. A second fluid passage p2 is thus formed between the nozzle 12 and the converging pipe 15, said second passage p2 communicating the second inlet 7 with the suction chamber 14. The acceleration of the hydrogen in the nozzle 12 generates a depression in the suction chamber 14 allowing the suction of the hydrogen present in the extraction channel 11. Downstream of the suction chamber 14, the mixture of hydrogen coming from the tank 2 and the extraction channel 11 is slowed down in the diverging pipe 8.

[0044] [Fig. 3] shows, in cutaway, an ejector 10 according to the invention. The ejector 10 comprises a housing 16 in which a converging pipe 15, a suction chamber 14, a diverging pipe 8 and an extraction pipe 11 are made. The housing 16 contains and supports a nozzle 12. The nozzle 12, when placed in the housing 16, the converging pipe 15, the suction chamber 14 and the diverging pipe 8 are of revolution and extend along the same axis A. The extraction pipe 11 is tubular and extends along an axis A' perpendicular to the axis A.

[0045] [Fig. 4] represents the nozzle 12 of the ejector 10. The nozzle 12 is notably formed of a base 19, which is fixed to the housing 16, and of an end ring 20, which is fixed on the base 19.

[0046] The base 19 comprises a hollow cylindrical extension 191 extending along the central axis A. The cylindrical extension 191 has a central cavity 192, which is in fluid communication with the first inlet 6 of the ejector 10 at a first end 193 of the cylindrical extension 191. The base 19 further comprises a plurality of triangular petal-shaped legs 195, hinged to the cylindrical extension 191 at a second end 194 of the cylindrical extension 191 and arranged circumferentially around the central axis A. The legs 195 will advantageously be formed of an elastic material such that each leg 195 will tend to move away from the central axis A at its free end 197. As shown in [Fig.7], each of the legs 195 of the base 19 is separated from a directly adjacent leg 195 by a slot 196 extending radially from an axial opening 13' of the base 19 which opens into the suction chamber 14. The internal space of the base 19 thus forms an upstream part of the first fluid passage pl, as defined previously.

[0047] As shown in Figures 4 and 6, the end ring 20 of the nozzle 12 is formed of a first substantially cylindrical segment 201 partially covering the cylindrical extension 191 of the base 19 and a plurality of second segments 202 in the shape of a triangular petal, articulated on the first segment 201 and arranged circumferentially around the central axis A, the assembly of said second segments 202 defining an end portion 21 of the nozzle 12. The segments 202 will advantageously be formed of an elastic material such that each segment 202 will tend to move away from the central axis A at its free end 207. Each of the segments 202 is separated from a directly adjacent segment 202 by a slot 206 extending radially from an axial opening 13 of the end ring 20 which opens into the suction chamber 14. Each of the segments 202 further comprises a central edge 208 which extends radially from the free end 207.

[0048] As shown in Figures 3 and 4, the ejector 10 further comprises an adjustment device 17, comprising in particular an adjustment element 18 and means for moving said adjustment element 18. The adjustment element 18 extends at least partially around the nozzle 12. This adjustment element 18 has a cylindrical shape which is slightly flared at an end portion which is axially aligned with the terminal portion 21 of the nozzle 12. Another end portion of the adjustment element 18, which is aligned with the first segment 201 of the end ring 20, is provided with teeth 184 projecting from the external cylindrical wall 183 of the adjustment element 18, said teeth 184 forming a toothed crown with which the corresponding teeth 222 of a toothed wheel 22 rotated by a motor mesh. 23. It is thus possible to generate a rotary movement of the adjustment element 18 around the central axis A by means of the motor 23.

[0049] Furthermore, the adjustment element 18 is provided with one or more projecting shapes 182 protruding radially from its inner wall 181. This or these projecting shapes 182 cooperate(s) with one or more grooves 204 formed along the outer peripheral wall 203 of the first segment 201 of the end ring 20 such that a threaded connection is established between the adjustment element 18 and the end ring 20. Thus, when the adjustment element 18 rotates around the axis A, it simultaneously moves in translation along the axis A due to this threaded connection. During this axial movement, the adjustment element 18 is configured to interact with the end portion 21 of the nozzle 12 in such a way that the cross-sectional surface S of the axial opening 13 of the end ring 20 varies according to the axial position of the adjustment element 18.

[0050] In particular, the adjustment element 18 is provided with an end portion 186 which is oriented towards the converging pipe 15 and which has a conical shape which flares outwards. The end portion 186 comprises an internal surface 185 which is configured to come into contact with an upper edge 205 of each of the second segments 202 of the end ring 20 during translational movement of the adjustment element 18 along the central axis A, said upper edge 205 partly delimiting the central edge 208. The internal surface 185 is in particular configured to generate a radial displacement of the upper edge 205 of each of the second segments 202 in the direction of the central axis A when the adjustment element 18 moves axially in the direction of the converging pipe 15, thereby reducing the cross-sectional area S of the axial opening 13 of the end ring 20, and, conversely, to generate a radial displacement of the upper edge 205 of each of the second segments 202 away from the central axis A when the adjustment element 18 moves axially away from the converging pipe 15, thereby increasing the cross-sectional area S of the axial opening 13 of the end ring 20.8], the internal surface 185 of the end portion 186 is formed from a succession of several contiguous sections, of conical shape, centered on the central axis A, each of the conical shape sections being defined by a generatrix forming an angle with the central axis A. In particular, the internal surface 185 comprises a first section 185a of conical shape whose generatrix forms an angle a1 of the order of 15° with the central axis A and a second section 185b of conical shape whose generatrix forms an angle a2 of the order of 8° with the central axis A.

[0052] Thus, in the position shown in [Fig.5a], the adjustment element 18 is positioned relative to the base 19, such that the axial distance between a radial rim 198 of the base 19 and an end edge 188 of the adjustment element 18, which faces said radial rim 198, is equal to dl. In this position, the second segments 202 come to bear against the first section 185a of the internal surface 185 of the adjustment element 18, thus generating a distance in the radial direction between the second segments 202 and the central axis A which is maximum for the ejector 10. This position will therefore make it possible to maximize the cross-sectional surface S of the axial opening 13 of the end ring 20, and, consequently, to maximize the gas flow rate downstream of the nozzle 12. In an advantageous example of the invention, this surface S may be substantially circular and have a diameter of 4 mm.

[0053] In the position shown in [Fig.5b], the adjustment element 18 is positioned relative to the base 19, such that the axial distance between a radial rim 198 of the base 19 and an end edge 188 of the adjustment element 18, which faces said radial rim 198, is equal to d2. In this position, the second segments 202 bear against the first section 185b of the internal surface 185 of the adjustment element 18, thus generating a distance in the radial direction between the second segments 202 and the central axis A which is minimal for the ejector 10. This position will therefore make it possible to minimize the cross-sectional area S of the axial opening 13 of the end ring 20, and, consequently, to minimize the gas flow rate downstream of the nozzle 12. In an advantageous example of the invention, this surface S may be substantially circular and have a diameter of 2 mm.

[0054] The invention is obviously not limited to the embodiment described below. In particular, in other embodiments of the invention, the internal surface 185 of the adjustment element 18 may comprise a number of contiguous conical sections greater than two. In particular, all the components of the ejector or some of them may be made entirely or partially from a plastic material.

Claims

1. Claims Ejector (10) for a fuel cell (1), comprising: - a housing (16), comprising a converging duct (15), a suction chamber (14) and a diverging duct (8) which are arranged sequentially and communicate from one side to the other in an axial direction (A) of the housing (16), the housing (16) further comprising a first inlet (6) communicating with the interior of the housing (16) and a second inlet (7) communicating with the interior of the housing (16); - a nozzle (12) which is located inside the housing (16) and is fixed to the housing (16), the nozzle (12) comprising a deformable end portion (21) extending into the converging pipe (15), the end portion (21) and the converging pipe (15) being fitted and spaced apart from each other in a radial direction (R) of the housing (16), and a first fluid passage (pl) being formed in the nozzle (12), a second fluid passage (p2) being formed between the nozzle (12) and the converging pipe (15), wherein the first inlet (6) is in communication with the suction chamber (14) via the first fluid passage (pl), and the second inlet (7) is in communication with the suction chamber (14) via the second fluid passage (p2); and - an adjustment device (17) which is at least partially located inside the housing (16), the adjustment device (17) comprising an adjustment element (18) extending at least partially around the nozzle (12), the adjustment element (18) being movable along the axial direction (A) and being configured to interact with the end portion (21) such that a cross-sectional area (S) of at least a portion (13) of the first fluid passage (pl) varies depending on the axial position of the adjustment element (18), characterized in that the nozzle (12) comprises a base (19) fixed to the housing (16), said base (19) having a hollow cylindrical extension (191) extending along a central axis (A) and being defined by a central cavity (192) forming an upstream part of the first passage (pl) of fluid, and an end ring (20) fixed on the base (19), said end ring (20) being formed of a first substantially cylindrical segment (201) at least partially covering the hollow cylindrical extension (191) of the base (19) and of a plurality of second petal-shaped segments (202) articulated on the first segment (201) and arranged circumferentially around the central axis (A), all of said second segments (202) at least partially defining the terminal portion (21) of the nozzle (12), and in that each of the second segments (202) of the end ring (20) is made of an elastically deformable material and is configured to move elastically away from the central axis (A) when it is not subjected to any stress from the adjustment element (18).

2. Ejector (10) according to claim 1, characterized in that the first segment (201) of the end ring (20) is provided with at least one groove (204) along its external peripheral wall (203), said at least one groove (204) being configured to cooperate with at least one projecting shape (182) protruding radially from an internal wall (181) of the adjustment element (18) so as to ensure a threaded connection between said adjustment element (18) and said end ring (20).

3. Ejector (10) according to claim 2, characterized in that an external cylindrical wall (183) of the adjustment element (18) is provided with teeth (184) intended to cooperate with the corresponding teeth (222) of a toothed wheel (22) rotated by a motor (23) so as to ensure rotation of the adjustment element (18) around the central axis (A), said adjustment element (18) moving simultaneously in translation along the central axis (A) due to the threaded connection between the adjustment element (18) and the end ring (20).

4. Ejector (10) according to one of claims 1 to 3, characterized in that the adjustment element (18) is provided with an internal surface (185) which is configured to come into contact with an upper edge (205) of each of the second segments (202) of the end ring (20) during translational movement of the adjustment element (18) along the central axis (A), said internal surface (185) tending to radially bring said upper edge (205) closer to the central axis (A) when the adjustment element (18) moves axially towards the converging pipe (15).

5. Ejector (10) according to claim 4, characterized in that the surface internal (185) is formed from a succession of several contiguous sections (185a, 185b), of conical shape, centered on the central axis (A), each of the sections (185a, 185b) of conical shape being defined by a generatrix forming an angle (al, a2) with the central axis (A).

6. Ejector (10) according to claim 5, characterized in that the internal surface (185) comprises a first section (185a) of conical shape whose generator forms an angle (al) of the order of 15° with the central axis (A) and a second section (185b) of conical shape whose generator forms an angle (a2) of the order of 8° with the central axis (A).

7. Ejector (10) according to one of claims 1 to 6, characterized in that each of the second segments (202) of the end ring (20) is separated from a second segment (202) directly adjacent by a slot (206) extending radially from an axial opening (13) of the end ring (20), the cross-sectional surface (S) of said axial opening (13) varying as a function of the inclination of said second segments (202) relative to the central axis (A).

8. Ejector (10) according to claim 7, characterized in that the base (19) comprises a plurality of petal-shaped tabs (195) articulated on the cylindrical extension (191) and configured to come to bear elastically against the end ring (20) at the level of the slots (206) separating each of the second segments (202), thus preventing the passage of a fluid through said slots (206).

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