Ejector for a fuel cell

Abstract

The invention relates to an ejector (10) for a fuel cell (1), comprising: - a housing (16), comprising a converging pipeline (15), a mixing chamber (14) and a diverging pipeline (8), which are sequentially arranged and communicate from side to side in an axial direction (A) of the housing (16), wherein the housing (16) further comprises a first inlet (6) communicating with the inside of the housing (16) and a second inlet (7) communicating with the inside of the housing (16); - a nozzle (12) which is located inside the housing (16); - a needle (19) which is housed at least partially inside the mixing chamber (14) and movable in the axial direction (A) inside the nozzle (12); 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 around the mixing chamber (14); wherein the adjustment element (18) and the needle (19) are connected to each other.

Description

[0001] FUEL CELL EJECTOR

[0002] The invention relates to the gas supply of a fuel cell.

[0003] A fuel cell produces electricity through 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. Currently, hydrogen is commonly used as the fuel and oxygen from the air as the oxidant.

[0004] Fuel cells are particularly useful in the transportation sector, which currently relies primarily on fossil fuels, primarily oil. The use of this fossil fuel produces a significant amount of carbon dioxide, contributing to the increase in the global greenhouse effect. Other pollutants, such as particulate matter and nitrogen oxides, are also produced by the use of petroleum-based fuels.

[0005] The main advantage of using a fuel cell with 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.

[0006] 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:

[0007] H2-> 2H + + 2nd-,

[0008] 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 H protons + will combine with oxygen O2 and electrons e- still in the presence of a catalyst according to a second reaction:

[0009] 2H + + 2e- + 1 / 2 O2 -> H2O.

[0010] Both chemical reactions are exothermic.

[0011] The hydrogen H2 supply can be either intermittent or continuous. 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.

[0012] The ejector generally comprises a nozzle intended to increase the speed of the feed gas as it enters the mixing chamber. For this purpose, the nozzle comprises a convergent end portion which opens onto a mixing chamber of the ejector and which allows the supply of a high-pressure hydrogen flow. Upstream of the mixing chamber, the ejector further comprises a convergent pipe arranged around the nozzle in which the excess hydrogen circulates. The acceleration of the hydrogen flow in the nozzle generates a vacuum upstream of the mixing chamber allowing the suction of the excess hydrogen.

[0013] In some architectures, the fuel cell is powered by a pump and a variable flow ejector. The pump ensures the recirculation of excess hydrogen from the cell when the cell is delivering low power, then the variable flow ejector gradually takes over, as the cell power increases, for the supply of hydrogen to the cell until it ensures the full flow rate of the hydrogen flow required by the cell and the management of the hydrogen recirculation by Venturi effect. In other architectures, the fuel cell uses two parallel ejectors for the gas supply.

[0014] The aim of the invention is to propose a fuel cell architecture which does not require the use of a pump or two ejectors in parallel.

[0015] The variable flow rate ejector must be able to control the flow rate of the hydrogen stream at the nozzle outlet in order to adapt the flow rate of the hydrogen stream 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 stream circulates before entering the mixing chamber. Depending on the axial position of the tip, the outlet opening is more or less wide and the flow rate of the hydrogen stream at the nozzle outlet is more or less high.

[0016] In such ejectors, the mixing chamber is usually a straight tube in which the hydrogen flow at the nozzle outlet and the excess hydrogen flow mix before entering the diffusion chamber. The diameter of the mixing chamber influences the maximum hydrogen flow rate that can pass and the maximum suction pressure that can be achieved with the ejector. This diameter is often optimized to ensure the best performance of the ejector under certain specific operating conditions. In particular, the mixing chamber of a low hydrogen flow rate ejector usually has a smaller diameter than a mixing chamber of a high hydrogen flow rate ejector. It is therefore useful to be able to also modify the diameter of the mixing chamber to increase the performance of the ejector over a wide range of hydrogen flow rates.The performance of an ejector is often evaluated by observing an index called entrainment rate, which corresponds to the ratio between the mass flow rate of the excess hydrogen flow and the mass flow rate of the hydrogen flow at the nozzle outlet. However, it has been analyzed that, among the parameters influencing the entrainment rate, those having the greatest impact are the diameter of the nozzle outlet opening and the diameter of the mixing chamber.

[0017] It is therefore useful to be able to vary these two parameters in a coordinated manner within an ejector.

[0018] However, the solutions currently available have the disadvantage of being relatively complex to implement and do not allow the ejector's performance to be optimized over a wide range of hydrogen flow rates.

[0019] The invention therefore aims to propose an ejector for a fuel cell which makes it possible to increase the drive rate and which does not have the aforementioned drawbacks.

[0020] According to a general definition, the invention relates to an ejector for a fuel cell, comprising:

[0021] - a housing, comprising a converging pipeline, a mixing 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 communicating with the interior of the housing;

[0022] - a nozzle which is located inside the housing, the nozzle comprising an 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 mixing chamber via the first fluid passage, and the second inlet is in communication with the mixing chamber via the second fluid passage;

[0023] - a needle housed at least partially inside the mixing chamber and movable in the axial direction inside the nozzle, the needle being configured to adjust a cross-sectional area of ​​at least a portion of the first passage; and

[0024] - an adjustment device which is at least partially located inside the housing, the adjustment device comprising an adjustment element extending around the mixing chamber, said adjustment element being movable along the axial direction and being configured to adjust a cross-sectional area of ​​the mixing chamber; wherein the adjustment element and the needle are connected to each other such that the cross-sectional area of ​​said at least a part of the first passage varies depending on the axial position of the adjustment element in the housing.

[0025] Thus configured, the ejector of the invention will allow the diameter of the nozzle outlet opening and the diameter of the mixing chamber to be varied due to the coordinated action of the needle and the adjustment element. An increase in the drive rate will thus be achieved. The solution of the invention also has the advantage of being relatively simple to implement, while allowing the performance of the ejector to be optimized over a wide range of hydrogen flow rates.

[0026] The ejector of the invention may also include one or more of the following features:

[0027] - the adjustment element is configured to vary the cross-sectional area of ​​the mixing chamber in a manner opposite to the variation of the cross-sectional area of ​​said at least a portion of the first passage.

[0028] - the adjustment element is formed of an at least partially conical structure centered around an axis and formed of four sub-parts, said sub-parts being distributed regularly around the circumference of said structure, each of the sub-parts being provided with an internal surface of semi-cylindrical shape, the mixing chamber being delimited at least partially by the internal surfaces of said sub-parts and having a cross-section of circular shape, wherein the sub-parts are concomitantly movable relative to the axis of the adjustment element so as to move away from, respectively towards, said axis under the action of displacement means, thus increasing, respectively decreasing, the surface of the cross-section of the mixing chamber, and wherein the needle is slidably connected to each of the sub-parts so that, when the sub-parts are moved,the needle moves along an axial direction towards, respectively away from, the nozzle, thereby decreasing, respectively increasing, the cross-sectional area of ​​said at least one part of the first passage.,

[0029] - the adjustment element is configured to vary the cross-sectional area of ​​the mixing chamber in a similar manner to the variation of the cross-sectional area of ​​said at least a portion of the first passage.

[0030] - the adjustment element is formed of an at least partially conical structure centered around an axis and formed of four sub-parts, said sub-parts being distributed regularly around the circumference of said structure, each of the sub-parts being provided with an internal surface of semi-cylindrical shape, the mixing chamber being delimited at least partially by the internal surfaces of said sub-parts and having a cross-section of circular shape, wherein the sub-parts are concomitantly movable relative to the axis of the adjustment element so as to move towards, respectively away from, said axis under the action of displacement means, thus decreasing, respectively increasing, the surface of the cross-section of the mixing chamber, and wherein the needle is slidably connected to each of the sub-parts so that, when moving the sub-parts,the needle moves along an axial direction towards, respectively away from, the nozzle, thereby decreasing, respectively increasing, the cross-sectional area of ​​said at least one part of the first passage.,

[0031] - each sub-part of the adjustment element is connected to an adjacent sub-part by means of an assembly tab, said assembly tab extending along one of the end edges of the sub-part and being slidably received inside a corresponding groove of the adjacent sub-part, each of the sub-parts being slidably connected to the housing so as to be able to move along a direction of movement oriented obliquely relative to the axis of the adjustment element, wherein one of the sub-parts is movable along said direction of movement under the action of an actuator, the movement of said sub-part generating a concomitant movement of the other sub-parts due to the sliding connection of the sub-parts to each other.

[0032] - the actuator comprises an electric or pneumatic motor capable of moving an actuating bar along an axial direction, said actuating bar being configured to concomitantly move one of the sub-parts of the adjustment element.

[0033] - the actuating bar is provided with a cylindrical segment, which is housed in a central cavity of a forked structure protruding radially from the outer periphery of said sub-part, and a pair of stop elements surrounding said cylindrical segment, each stop element being configured to come into contact with the forked structure when moving the actuating bar along the axial direction and in a given direction of movement.

[0034] - one of the sub-parts of the adjustment element is provided with a wing projecting radially from its external periphery, said wing being formed at least partially from a magnetic material and being arranged between a pair of electromagnetic coils positioned around the axis of the adjustment element, said electromagnetic coils being capable, in reaction to an excitation, of causing a displacement of the wing in an axial direction and in a given direction of displacement.

[0035] - the needle comprises a cylindrical body having a conically shaped end disposed within the nozzle at the first passage, the needle further comprising four connecting tabs extending radially from the cylindrical body, two contiguous connecting tabs being disposed at right angles to each other, wherein each connecting tab is slidably received in a corresponding groove of the adjustment element, said groove extending between two radially oriented inner walls of said adjustment element, said inner walls being configured to contact said connecting tab upon movement of the adjustment element along the axial direction, thereby causing the needle to move concomitantly along the axial direction.

[0036] 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:

[0037] [Fig. 1] is a schematic representation of a hydrogen supply unit of a fuel cell.

[0038] [Fig. 2] is a schematic representation of an ejector.

[0039] [Fig. 3] is a perspective and cutaway view of an ejector according to a first embodiment of the invention.

[0040] [Fig. 4] is a longitudinal sectional view of the ejector of Figure 3.

[0041] [Fig. 5] is a sectional view of the ejector adjustment element of Figure 4 along section plane P.

[0042] [Fig. 6a] is a side view of the ejector adjusting device of Figure 3, in a first position of the adjusting element.

[0043] [Fig. 6b] is a view similar to Fig. 6a, in a second position of the adjustment element.

[0044] [Fig. 7a] is a sectional view along the section plane P1 of the adjustment device of Figure 6a.

[0045] [Fig. 7b] is a sectional view along the section plane P2 of the adjustment device of Figure 6b.

[0046] [Fig. 8] is a cross-sectional view of an ejector according to a second embodiment of the invention.

[0047] [Fig. 9] is a perspective and cutaway view of an ejector according to a third embodiment of the invention.

[0048] [Fig. 10] is a cross-sectional view of the ejector of Figure 9.

[0049] [Fig. 1 1a] is a side view of the ejector adjusting device of Fig. 9, in a first position of the adjusting element.

[0050] [Fig. 11 b] is a view similar to Fig. 11a, in a second position of the adjustment element.

[0051] [Fig. 12a] is a sectional view along the section plane P3 of the adjustment device of Figure 1 1a. [Fig. 12b] is a sectional view along the section plane P4 of the adjustment device of Figure 1 1b.

[0052] The invention is described in relation to a membrane-type fuel cell, using hydrogen as the reducing gas and atmospheric oxygen as the 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.

[0053] With reference to Figure 1, a hydrogen supply unit for a fuel cell 1 is schematically represented. 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 gas towards the second inlet 7 of the ejector 10 to be sucked in by the hydrogen coming from the first inlet 6.

[0054] Figure 2 schematically represents an ejector 10 allowing the recirculation 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 pf1 is formed in the nozzle 12, said first passage pf1 connecting the first inlet 6 with a mixing chamber 14 of the ejector 10. The nozzle 12 comprises in particular a convergent end portion 21 opening onto the mixing 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 area S1 which can be modified by means of a needle (not shown in FIG. 2) so as to vary the flow rate of the hydrogen stream at the inlet of the mixing chamber 14 and the mixing chamber 14 has a cross-sectional area S2 which can be modified so as to vary the flow rate of the hydrogen stream inside the mixing chamber 14. The mixing chamber 14 has, in the embodiments described below, a cross-section of circular or substantially circular shape. Upstream of the mixing 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 pf2 is thus formed between the nozzle 12 and the converging pipe 15, said second passage pf2 communicating the second inlet 7 with the mixing chamber 14. The acceleration of the hydrogen in the nozzle 12 generates a depression upstream of the mixing chamber 14 allowing the suction of the excess hydrogen present in the extraction channel 11. Downstream of the mixing chamber 14, the mixing of the hydrogen coming from the reservoir 2 and the extraction channel 11 is slowed down in the diverging pipe 8.

[0055] With reference to Figures 3 and 4, an ejector 10 is shown according to a first embodiment of the invention. The ejector 10 comprises a housing 16 in which a converging pipe 15, a mixing chamber 14, a diverging pipe 8 and an extraction pipe 11 are formed. The housing 16 is provided with a first fluid inlet opening 6 at a front wall 161, said first opening 6 extending into the housing 16 in a nozzle 12. The nozzle 12 comprises in particular a converging end portion 21 opening onto the mixing chamber 14 at an outlet opening 13. This end portion 21 defines a first fluid passage pf1. It is surrounded by the converging pipe 15, the space formed between the terminal part 21 of the nozzle 12 and the converging pipe 15 forming a second fluid passage pf2 which communicates a second fluid inlet opening 7 with the mixing chamber 14.The nozzle 12, the converging pipe 15, the mixing 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.

[0056] The ejector further comprises an adjustment device 17, comprising in particular an adjustment element 18 and means 22, 23 for moving said adjustment element 18. The adjustment element 18 extends around the mixing chamber 14. This adjustment element 18 has a substantially conical external shape centered around an axis A and comprises four sub-parts 181, 182, 183 and 184 distributed regularly around the circumference of the substantially conical structure, as shown in FIGS. 4 and 5. Each of the sub-parts 181-184 is provided with an external surface, respectively 181j, 182j, 183j and 184j, of at least partially conical shape and an internal surface, respectively 181i, 182i, 183i and 184i, of semi-cylindrical shape.Thus configured, the internal surfaces 181 i- 184i of the sub-parts 181-184 delimit a substantially cylindrical internal volume having a circular cross-section, said internal volume forming the mixing chamber 14 of the ejector 10. As shown in FIG. 5, each sub-part 181-184 of the adjustment element 18 is provided along one end edge 187a with an assembly tab 188a and along another end edge 187b with a groove 188b having a shape complementary to that of the assembly tab 188a. The assembly tabs 188a and the grooves 188b are in particular configured to allow a sliding connection of each sub-part to an adjacent sub-part. In particular, the assembly tabs 188a and the grooves 188b will advantageously have an orthoradial orientation, being distributed regularly around the axis A.Thus, for example, the sub-part 181 is slidably connected to the two sub-parts 182 and 184 which are directly adjacent to it, on the one hand, by the insertion of its assembly tab 188a inside the groove 188b of the sub-part 182 and, on the other hand, by the insertion of the assembly tab 188a of the sub-part 184 inside its groove 188b. This connection by mutual interlocking of the sub-parts 181-184 has the advantage of making the sub-parts 181-184 integral during their displacement in the radial and axial direction. This displacement in the radial and axial direction of the sub-parts 181-184 is ensured, on the one hand, by the sliding connection of each sub-part 181-184 to the housing 16 and, on the other hand, by the action exerted by an actuator 23, shown in Figures 3 and 4, on the sub-part 181.

[0057] In the configuration of Figures 3 to 5, each sub-part 181-184 has a rib 189 projecting from its external surface 181j-184j, said rib 189 having a transverse T-shaped profile which is complementary to the T-shaped profile of a guide groove 162 formed in the housing 16. The ribs 189 and the associated guide grooves 162 have an oblique orientation relative to the axis A of the adjustment element 18, so that the sliding of the ribs 189 along the guide grooves 162 generates a displacement of each sub-part 181-184 along a direction of displacement oriented obliquely relative to the axis A. Thus, as shown in Figure 4, the sub-part 181 will be able to move along a direction D1 which makes an angle +a with the axis A in the section plane of Figure 4, and subsection 183 will be able to move along a direction D3 which makes an angle -a with the axis A in the section plane of figure 4.Similarly, the sub-parts 182 and 184 will be able to move along a direction oblique to the axis A, the angle formed by said oblique direction and the axis A being respectively equal to +a and -a in a plane orthogonal to the section plane of Figure 4. Thus configured, the sub-parts 181-184 will tend to move away from the axis A, when they move axially in the direction of the nozzle 12, which, consequently, will increase the distance between the internal surfaces 181 i-184i, thus increasing the surface area S2 of the cross-section of the mixing chamber 14. Conversely, they will tend to move closer to the axis A, when they move axially in the direction of the diverging pipe 8, which, consequently, will decrease the distance between the internal surfaces 181 i-184i, thus reducing the surface area S2 of the cross section of the mixing chamber 14.As explained further on, in connection with figures 6a, 6b and 7a, 7b, this displacement of the sub-parts 181-184 will thus make it possible to adapt the diameter of the mixing chamber 14 to the flow rate of the fluid at the outlet of the nozzle 12, with the aim of improving the performance of the ejector, and, in particular, of increasing the entrainment rate.

[0058] In the configuration shown in Figures 3 and 4, the actuator 23 used to generate a movement of the sub-part 181 is an electric or pneumatic motor which acts on an actuating bar 22 so as to move it along an axial direction A1. The actuating bar 22 is provided with a cylindrical segment 222, which is housed in a central cavity 185 of a forked structure 186 projecting radially from the rib 189 of the sub-part 181. The actuating bar 22 further comprises a pair of stop elements 221, 223 surrounding the cylindrical segment 222. Each stop element 221, 223 is dimensioned so as to project radially from the cylindrical segment 222 so that it is capable of coming into contact with the forked structure 186 when the actuating bar 22 is moved along the axial direction A1 and in a given direction of movement.The stop elements 221, 223 will thus make it possible to transmit a translational movement along the axis A1 to the forked structure 186, and, consequently, to the sub-part 181. As explained previously, this axial displacement of the sub-part 181 will generate a radial displacement of the sub-part 181 in the direction of the axis A or, on the contrary, in a direction causing it to move away from the axis A, and, concomitantly, a radial and axial displacement of the other sub-parts 182-184 of the adjustment element 18.

[0059] The alternative embodiment of the invention shown in Figure 8 is distinguished from that described previously by the fact that the actuator used to generate a movement of the sub-part 181 comprises a pair of electromagnetic coils 24, 25 positioned around the axis A of the adjustment element 18. The coils 24, 25 are arranged on either side of a wing 190 which protrudes radially from the rib 189 of the sub-part 181. This wing 190 is formed at least partially of a magnetic material so that the coils 24, 25 are capable, in reaction to an excitation, of causing a movement of the wing 190, and, consequently, of the sub-part 181, in an axial direction A1 and in a given direction of movement.

[0060] As shown in Figures 4 and 5, the ejector 10 is also equipped with a needle 19 which makes it possible to vary the cross-sectional area S1 of the outlet opening 13 of the nozzle 12. This surface S1 having a direct impact on the flow rate of the fluid at the outlet of the nozzle 12, it will thus be possible to vary the flow rate of the hydrogen flow at the inlet of the mixing chamber 14. Advantageously, this needle 19 has a cylindrical body 191 housed at least partially inside the mixing chamber 14 and a pointed end 192 of conical shape arranged inside the nozzle 12 at the outlet opening 13. The needle 19 further comprises four substantially flat connecting tabs 193, extending radially from the cylindrical body 191, the connecting tabs 193 being arranged at right angles to each other.Each connecting tab 193 is slidably received in a corresponding radial groove 180 formed in the sub-portion 181-184 of the adjustment element 18 which faces it. The radial grooves 180 are therefore also arranged at right angles to each other, regardless of the position of the adjustment element 18 along the axis A. Each of the grooves 180 extends between a first pair of internal walls 180a, 180b oriented radially and axially spaced from the corresponding sub-portion 181-184, and between a second pair of internal walls (not shown) oriented radially and perpendicular to the internal walls 180a, 180b of said sub-portion 181-184.When moving said sub-part 181-184 along its direction of movement, the inner walls 180a, 180b will come into contact with one of the connecting tabs 193 of the needle 19, thereby causing the needle 19 to move concomitantly along the axial direction A. The second pair of inner walls further prevents the connecting tab 193 from moving perpendicular to the inner walls 180a, 180b. As a result, the needle 19 is kept constantly aligned with the axis A regardless of the position of the needle 19 in the housing 16.

[0061] Thus, due to this connection between the adjustment element 18 and the needle 19 via the connecting tabs 193, it is possible to simultaneously vary the cross-sectional area S1 of the nozzle 12 at the outlet opening 13, and, consequently, the flow rate of the hydrogen stream at the outlet of the nozzle 12, and the axial position of the adjustment element 18 in the housing 16, and, consequently, the flow rate of the hydrogen stream in the mixing chamber 14, by means of a single actuator 23.

[0062] The ejector 10 according to the embodiment of Figures 3 and 4 is characterized in that the adjustment element 18 is configured to vary the cross-sectional area S2 of the mixing chamber 14 in a manner opposite to the variation of the cross-sectional area S1 of the nozzle 12 at the outlet opening 13.

[0063] With reference to figures 6a and 7a, a first operating configuration of the ejector 10 is shown according to the embodiment described previously.

[0064] In this configuration, the motor 23 has acted on the actuating bar 22 so that the forked structure 186 is at a distance d1 from a reference position defined by the motor 23. This position of the forked structure 186 has generated a specific axial position of the adjustment element 18 along the axis A. In this axial position, the adjustment element 18 has a relatively open configuration, in which the sub-parts 181-184 are spaced from each other, which gives the mixing chamber 14 a relatively large diameter DU. The tip of the needle 19 (shown in dotted lines in Figure 6a) is, in turn, at an axial distance d+d1 from the aforementioned reference position, d being the axial distance between the tip of the needle 19 and the forked structure 186.In this position, the tip of the needle 19 relatively significantly reduces the cross-sectional area S1 of the outlet opening 13 of the nozzle 12.

[0065] With reference to figures 6b and 7b, a second operating configuration of the ejector 10 is shown according to the embodiment described previously.

[0066] In this configuration, the motor 23 has acted on the actuating bar 22 so that the forked structure 186 is at a distance d2 from the reference position defined by the motor 23, d2 being less than d1. This position of the forked structure 186 has generated a specific axial position of the adjustment element 18 along the axis A. In this axial position, the adjustment element 18 has a closed configuration, in which the sub-parts 181-184 are in contact with each other, which gives the mixing chamber 14 a diameter DI2 less than DI1. The tip of the needle 19 (shown in dotted lines in Figure 6b) is, for its part, at an axial distance d+d2 from the aforementioned reference position, the axial distance d between the tip of the needle 19 and the forked structure 186 being in principle constant.It is therefore further away from the nozzle 12 and slightly reduces the cross-sectional area S1 of the outlet opening 13 of the nozzle 12.

[0067] The ejector 10 according to the embodiment of Figures 9 and 10 is distinguished from that of Figures 3 and 4 by the use of an adjustment element 18 modified so as to vary the cross-sectional area S2 of the mixing chamber 14 in a similar manner to the variation of the cross-sectional area S1 of the nozzle 12 at the outlet opening 13.

[0068] For this purpose, the ribs 189 and the associated guide grooves 162 allowing the sliding connection of the sub-parts 181-184 of the adjustment element 18 to the housing 16 have an oblique orientation relative to the axis A which is opposite to those of the ribs 189 and the guide grooves 162 of the adjustment element 18 of Figures 3 and 4. Thus, as shown in Figure 10, the sub-part 181 will be able to move along a direction D1 which makes an angle -a with the axis A in the section plane of Figure 10, and the sub-part 183 will be able to move along a direction D3 which makes an angle +a with the axis A in the section plane of Figure 10. Similarly, the sub-parts 182 and 184 will be able to move along a direction oblique to the axis A, the angle formed by said oblique direction and the axis A being respectively equal to -a and +a in a plane orthogonal to the section plane of figure 10.Thus configured, the sub-parts 181-184 will tend to move closer to the axis A, when they move axially towards the nozzle 12, which, consequently, will decrease the distance between their internal surfaces, thus reducing the surface area S2 of the cross-section of the mixing chamber 14. Conversely, they will tend to move away from the axis A, when they move axially towards the diverging pipe 8, which, consequently, will increase the distance between their internal surfaces, thus increasing the surface area S2 of the cross-section of the mixing chamber 14.

[0069] During axial movement of the guide element 18, internal walls 180a, 180b of this guide element 18 will come into contact with one of the connecting tabs 193 of the needle 19, thus causing the needle 19 to move concomitantly along the axial direction A. Thus, when the guide element 18 approaches axially the nozzle 12, it causes the needle 19 to approach the nozzle 12, thus reducing the cross-sectional area S1 of the nozzle 12 at the outlet opening 13. Conversely, when the guide element 18 approaches axially the diverging pipe 8, it causes the needle 19 to move away from the nozzle 12, thus increasing the cross-sectional area S1 of the nozzle 12 at the outlet opening 13.

[0070] With reference to figures 11a and 12a, a first operating configuration of the ejector 10 is shown according to the embodiment described previously.

[0071] In this configuration, the motor 23 has acted on the actuating bar 22 so that the forked structure 186 is at a distance dT from a reference position defined by the motor 23. This position of the forked structure 186 has generated a specific axial position of the adjustment element 18 along the axis A. In this axial position, the adjustment element 18 has a closed configuration, in which the sub-parts 181-184 are in contact with each other, which gives the mixing chamber 14 a relatively small diameter DI1'. The tip of the needle 19 is, for its part, at an axial distance d'+d1' from the aforementioned reference position, d' being the axial distance between the tip of the needle 19 and the forked structure 186. In this position, the tip of the needle 19 reduces relatively significantly the cross-sectional area S1 of the outlet opening 13 of the nozzle 12.

[0072] With reference to figures 11 b and 12 b, a second operating configuration of the ejector 10 is shown according to the embodiment described previously.

[0073] In this configuration, the motor 23 has acted on the actuating bar 22 so that the forked structure 186 is at a distance d2' from the reference position defined by the motor 23, d2' being less than dT. This position of the forked structure 186 has generated a specific axial position of the adjustment element 18 along the axis A. In this axial position, the adjustment element 18 has a relatively open configuration, in which the sub-parts 181-184 are spaced from each other, which gives the mixing chamber 14 a diameter DI2' greater than DIT. The tip of the needle 19 is, in turn, at an axial distance d'+d2' from the aforementioned reference position, the axial distance d' between the tip of the needle 19 and the forked structure 186 being in principle constant. It is therefore further away from the nozzle 12 and slightly reduces the cross-sectional area S1 of the outlet opening 13 of the nozzle 12.

[0074] The invention is obviously not limited to the embodiments described below. In particular, in other embodiments of the invention, it will be possible to modify the shape and structure of the constituent elements of the ejector, while remaining within the scope of protection defined by the appended claims.

Claims

CLAIMS 1. Ejector (10) for a fuel cell (1), comprising: - a housing (16), comprising a converging pipe (15), a mixing chamber (14) and a diverging pipeline (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), the nozzle (12) comprising an 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 (pf1) being formed in the nozzle (12), a second fluid passage (pf2) being formed between the nozzle (12) and the converging pipe (15), wherein the first inlet (6) is in communication with the mixing chamber (14) via the first fluid passage (pf1), and the second inlet (7) is in communication with the mixing chamber (14) via the second fluid passage (pf2); - a needle (19) housed at least partially inside the mixing chamber (14) and movable in the axial direction (A) inside the nozzle (12), the needle (19) being configured to adjust a cross-sectional surface (S1) of at least a portion (13) of the first passage (pf1); and an adjustment device (17) which is at least partially located inside the housing (16), the adjusting device (17) comprising an adjusting element (18) extending around the mixing chamber (14), said adjusting element (18) being movable along the axial direction (A) and being configured to adjust a cross-sectional area (S2) of the mixing chamber (14); wherein the adjusting element (18) and the needle (19) are connected to each other such that the cross-sectional area (S1) of said at least one portion (13) of the first passage (pf1) varies depending on the axial position of the adjusting element (18) in the housing (16).

2. Ejector (10) according to claim 1, characterized in that the adjustment element (18) is configured to vary the cross-sectional area (S2) of the chamber of mixing (14) in a manner opposite to the variation of the cross-sectional area (S1) of said at least one part (13) of the first passage (pf1).

3. Ejector (10) according to claim 2, characterized in that the adjustment element (18) is formed of an at least partially conical structure centered around an axis (A) and formed of four sub-parts (181-184), said sub-parts (181-184) being distributed regularly around the circumference of said structure, each of the sub-parts (181-184) being provided with an internal surface (181 i-184i) of semi-cylindrical shape, the mixing chamber (14) being delimited at least partially by the internal surfaces (181 i-184i) of said sub-parts (181-184) and having a cross-section of circular shape, in which the sub-parts (181-184) are movable concomitantly with respect to the axis (A) of the adjustment element (18) so as to move away from, respectively approach, said axis (A) under the action of displacement means (22, 23), thus increasing, respectively decreasing,the cross-sectional area (S2) of the mixing chamber (14), and wherein the needle (14) is slidably connected to each of the sub-parts (181-184) such that, upon movement of the sub-parts (181-184), the needle (19) moves along an axial direction (A) towards, respectively away from, the nozzle (12), thereby decreasing, respectively increasing, the cross-sectional area (S1) of said at least one part (13) of the first passage (pf1)., 4. Ejector (10) according to claim 1, characterized in that the adjustment element (18) is configured to vary the cross-sectional area (S2) of the mixing chamber (14) in a similar manner to the variation of the cross-sectional area (S1) of said at least one part (13) of the first passage (pf1).

5. Ejector (10) according to claim 4, characterized in that the adjustment element (18) is formed of an at least partially conical structure centered around an axis (A) and formed of four sub-parts (181-184), said sub-parts (181-184) being distributed regularly around the circumference of said structure, each of the sub-parts (181-184) being provided with an internal surface (181 i-184i) of semi-cylindrical shape, the mixing chamber (14) being delimited at least partially by the internal surfaces (181 i-184i) of said sub-parts (181-184) and having a cross-section of circular shape, in which the sub-parts (181-184) are movable concomitantly with respect to the axis (A) of the adjustment element (18) so as to moving closer to, respectively moving away from, said axis (A) under the action of displacement means (22, 23), thus decreasing, respectively increasing,the surface (S2) of the cross-section of the mixing chamber (14), and wherein the needle (19) is slidably connected to each of the sub-parts (181-, 184) so that, upon moving the sub-portions (181-184), the needle (19) moves along an axial direction (A) towards, respectively away from, the nozzle (12), thereby decreasing, respectively increasing, the cross-sectional area (S1) of said at least one portion (13) of the first passage (pf1).

6. Ejector (10) according to claim 3 or 5, characterized in that each sub-part (181-184) of the adjustment element (18) is connected to an adjacent sub-part by means of an assembly tab (188a), said assembly tab (188a) extending along one of the end edges (187a) of the sub-part (181-184) and being slidably received inside a corresponding groove (188b) of the adjacent sub-part, each of the sub-parts (181-184) being slidably connected to the housing (16) so as to be able to move along a direction of movement (D1, D3) oriented obliquely with respect to the axis (A) of the adjustment element (18), wherein one (181) of the sub-parts (181-184) is movable along said direction of movement (D1) under the action of an actuator (23),the movement of said sub-part (181) generating a concomitant movement of the other sub-parts (182-184) due to the sliding connection of the sub-parts between them., 7. Ejector (10) according to claim 6, characterized in that the actuator (23) comprises an electric or pneumatic motor capable of moving an actuating bar (22) along an axial direction (A1), said actuating bar (22) being configured to concomitantly move one of the sub-parts (181) of the adjustment element (18).

8. Ejector (10) according to claim 7, characterized in that the actuating bar (22) is provided with a cylindrical segment (222), which is housed in a central cavity (185) of a forked structure (186) protruding radially from the external periphery (181j) of said sub-part (181), and a pair of stop elements (221, 223) surrounding said cylindrical segment (222), each stop element (221, 223) being configured to come into contact with the forked structure (186) during movement of the actuating bar (22) along the axial direction (A1) and in a given direction of movement.

9. Ejector (10) according to claim 6, characterized in that one of the sub-parts (181) of the adjustment element (18) is provided with a wing (190) projecting radially from its external periphery (181j), said wing (190) being formed at least partially of a magnetic material and being arranged between a pair of electromagnetic coils (24, 25) positioned around the axis (A) of the adjustment element (18), said electromagnetic coils (24, 25) being capable, in reaction to an excitation, of causing a displacement of the wing (190) in an axial direction (A1) and in a given direction of movement.

10. Ejector (10) according to one of the preceding claims, characterized in that the needle (19) comprises a cylindrical body (191) having a conical end (192) disposed inside the nozzle (12) at the first passage (pf1), the needle (19) further comprising four connecting tabs (193) extending radially from the cylindrical body (191), two contiguous connecting tabs (193) being disposed at right angles to each other, wherein each connecting tab (193) is slidably received in a corresponding groove (180) of the adjustment element (18), said groove (180) extending between two radially oriented internal walls (180a, 180b) of said adjustment element (18), said internal walls (180a, 180b) being configured to come into contact with each other. contact with said connecting tab (193) when moving the adjustment element (18) along the axial direction (A),thereby causing the needle (19) to move concomitantly along the axial direction (A).,

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