Ejector for a fuel cell system and fuel cell system

Abstract

An ejector with a suction nozzle is disclosed, with a drive nozzle and with a mixing tube, to which is assigned an adjustment device for the at least region-wise adjustment of a flow cross-section of the mixing tube. Inside the drive nozzle, an axially movable needle which is designed to adjust a flow cross-section of the drive nozzle is arranged and a coupling mechanism is provided which connects the adjustment device to the needle or to an actuator actuating the needle in such a way that the adjustment device adjusts or changes the flow cross-section of the mixing tube as a function of an axial needle movement. A fuel cell system with such an ejector is also disclosed.

Claims

1. An ejector, comprising: a suction nozzle; a drive nozzle; a mixing tube including an adjustment device for the at least region-wise adjustment of a flow cross-section of the mixing tube; an axially movable needle inside the drive nozzle that is designed to adjust a flow cross-section of the drive nozzle; and a coupling mechanism that connects the adjustment device to the needle or to an actuator actuating the needle such that the adjustment device adjusts or alters the flow cross-section of the mixing tube as a function of axial movement of the needle.

2. The ejector according to claim 1, wherein an inner wall of the mixing tube includes an elastic membrane that can be moved between a first position forming a reduced flow cross-section of the mixing tube and a second position forming an enlarged flow cross-section of the mixing tube.

3. The ejector according to claim 2, wherein a restoring force acts when the membrane is in the first position or when the membrane is moved from the second position into the first position.

4. The ejector according to claim 2, further comprising a dimensionally stable stiffening element coupled to or embedded within the membrane.

5. The ejector according to claim 2, wherein the adjustment device includes an annular or helical or belt-shaped element that at least indirectly abuts an outer shell of the membrane, that is configured to move the membrane between the first position and the second position, and that is connected by the coupling mechanism such that movement of the membrane takes place as a function of the axial movement of the needle within the drive nozzle.

6. The ejector according to claim 2, wherein the adjustment device includes a pressure chamber designed to move the membrane between the first and the second positions when a piston coupled to the coupling mechanism is at least partially pushed into or withdrawn from the pressure chamber.

7. The ejector according to claim 2, wherein the coupling mechanism includes a traction element or an actuating rod.

8. The ejector according to claim 2, wherein the coupling mechanism includes a shaft that is connected to the adjustment device in a rotationally fixed manner and that is designed to be rotationally driven by the axial movement of the needle.

9. The ejector according to claim 2, wherein the coupling mechanism includes a transmission gear adapted to transfer the axial movement of the needle with a predetermined gear ratio to the movement of the membrane.

10. A fuel cell system having a fuel cell stack which is integrated into an anode circuit, into which an ejector is fluidically coupled, the injector comprising: a suction nozzle; a drive nozzle; a mixing tube including an adjustment device for the at least region-wise adjustment of a flow cross-section of the mixing tube; an axially movable needle inside the drive nozzle that is designed to adjust a flow cross-section of the drive nozzle; and a coupling mechanism that connects the adjustment device to the needle or to an actuator actuating the needle such that the adjustment device adjusts or alters the flow cross-section of the mixing tube as a function of axial movement of the needle.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Additional advantages, features and details arise from the claims, the following description of embodiments of the invention and on the basis of the drawings. The following is shown:

(2) FIG. 1 a sectional view of a schematically represented ejector,

(3) FIG. 2 section I-I from FIG. 1,

(4) FIG. 3 a sectional view of an additional schematically represented ejector,

(5) FIG. 4 a sectional view of an additional schematically represented ejector,

(6) FIG. 5 a sectional view of an additional schematically represented ejector,

(7) FIG. 6 a sectional view of an additional schematically represented ejector,

(8) FIG. 7 a sectional view of an additional schematically represented ejector,

(9) FIG. 8 a sectional view of an additional schematically represented ejector,

(10) FIG. 9 a sectional view of an additional schematically represented ejector,

(11) FIG. 10 a sectional view of an additional schematically represented ejector,

(12) FIG. 11 a sectional view of an additional schematically represented ejector,

(13) FIG. 12 a sectional view of an additional schematically represented ejector,

(14) FIG. 13 a sectional view of an additional schematically represented ejector,

(15) FIG. 14 a sectional view of an additional schematically represented ejector,

(16) FIG. 15 a sectional view of an additional schematically represented ejector,

(17) FIG. 16 a schematically represented coupling part of the coupling mechanism of the ejector according to FIG. 15,

(18) FIG. 17 a sectional view through an additional coupling part,

(19) FIG. 18 a sectional view through an additional coupling part, and

(20) FIG. 19 a sectional view of a further additional coupling part.

DETAILED DESCRIPTION

(21) Various ejectors are described in the figures, wherein the same components are provided with the same reference signs. All ejectors have a suction nozzle 100, a drive nozzle 102 and a mixing tube 104. The ejectors shown also have a diffuser 114 connected to the mixing tube 106. The drive nozzle 102 can be fluidically connected via a port 116 to a fuel storage (not shown in detail) so that through the port 116, fresh fuel can be fed into the mixing tube 104 via the drive nozzle 102. The suction nozzle 100, on the other hand, has a port 118, through which the recirculated fuel that was not consumed in a fuel cell stack (not shown in detail) is introduced or sucked in.

(22) A needle 108 having a needle tip 122 tapering conically in the direction of the nozzle opening 120 of the drive nozzle 102 is arranged inside the drive nozzle 102, in particular concentrically thereto. Moreover, the drive nozzle 102 itself is designed with a nozzle section 124 tapering in the direction of the nozzle opening 120. A flow cross-section 604 of the drive nozzle 102 can be varied by means of the needle 108. For this purpose, the needle 108 is axially movable so that upon a movement of the needle 108 in the direction of the nozzle opening 120, the flow cross-section 604 of the drive nozzle 102 is reduced. When the needle 108 is moved axially in a direction turned away from the nozzle opening 120, the flow cross-section 604 is increased and a larger proportion of fresh fuel can enter the mixing tube 104. For the movement of the needle 108, an actuator 112 is provided, which is formed, for example, as a linear drive. Moreover, the suction nozzle 100 is formed with a nozzle section 126 tapering in the direction of the mixing tube 104.

(23) A flow cross-section 602 of the mixing tube 104 can be varied by means of an adjustment device 106. This adjustment device 106 for adjusting a flow cross-section 602 of the mixing tube 104 is at least region-wise connected by means of a coupling mechanism 110 to the needle 108 or to the actuator 112 actuating the needle 108 in such a manner that the adjustment device 106 adjusts or changes the flow cross-section 602 of the mixing tube 104 as a function of an axial needle movement.

(24) If the fuel cell system is to be operated at a low load, the flow cross-sections 602, 604 are kept as small as possible. In this case, the needle 108 is moved in the direction of the nozzle opening 120, which reduces the flow cross-section 604 of the drive nozzle 102. Due to the coupling mechanism 110, the adjustment device 106 then also reduces the flow cross-section 602 of the mixing tube 104. In the opposite case, for example if the fuel cell system is to be operated with a large load, the needle 108 is retracted by means of the actuator 112 and the flow cross-section 604 of the drive nozzle 102 is again increased. More fresh fuel then flows through the drive nozzle 102, whereby the recirculated fuel is also “taken along” more strongly via the suction nozzle 100. At the same time, the flow cross-section 602 of the mixing tube 104 again expands.

(25) An inner wall 128 of the mixing tube 104 is formed entirely from an elastic membrane 130, which is movable between a first position forming a reduced flow cross-section 602 of the mixing tube 104 and a second position forming an enlarged flow cross-section 602 of the mixing tube 104. The membrane 130 is subject to a pre-loading so that a restoring force acts if the membrane 130 is located in the first position or if the membrane 130 is moved from the second position to the first position. This means that the membrane 130 has an impulse to maximize the flow cross-section 602. In order to adjust the flow cross-section 602, the adjustment device 106 has an annular or helical or ribbon-shaped element which at least indirectly abuts on an outer shell 134 of the membrane 130 and by means of which the membrane 130 can be moved between the first position and the second position, wherein the element is connected by means of the coupling mechanism 110 in such a manner that the movement of the membrane 130 takes place as a function of the axial movement of the needle 108 within the drive nozzle 102. Alternatively, the adjustment device 106 may comprise a pressure chamber 136 that is designed to move the membrane 130 between the first and second positions if a piston 138 assigned to the coupling mechanism 110 is at least partially pushed into or withdrawn from the pressure chamber 136 (FIG. 11 (see below)).

(26) In the ejector shown in FIG. 1, a thread 140, which is fixed at one end to the needle 108 or to the needle body 142 and at the other end to the ejector body 144, is wound around the membrane 130 in a ring shape, in particular in a helical shape. The thread 140 can also be a string, a wire, a cable or the like. It is preferably subjected to mechanical stress, wherein it is also preferably elastic. For movement, the ejector shown in FIG. 1 has several rotating but stationary deflection rollers 146 mounted opposite the ejector body 144, around which deflection rollers the thread 140 is guided. If the needle 108 is moved in the direction of the nozzle opening 120 of the drive nozzle 102, the thread 140 is tensioned and thus constricts the membrane 130 so that the flow cross-section 602 of the mixing tube 104 is reduced. If the needle 108 is retracted again, the flow cross-section 602 is increased again due to the elasticity of the membrane 130. In order to ensure that the membrane 130 is kept as straight as possible in the area of the mixing tube 104, thus with a constant diameter, at least one stiffening element 132 is arranged on the outer shell 134 of the membrane 130, which stiffening element is formed in particular as a fixed, dimensionally stable strut.

(27) In the sectional view according to FIG. 2, it can be seen that there are several stiffening elements 132 distributed over the circumference of the membrane 130, which stiffening elements are arranged in particular in a manner evenly distributed over the outer shell 134 of the membrane 130. The thread 140 is thus applied only indirectly to the outer shell 134, as it interacts with the membrane 130 through or via the stiffening elements 132.

(28) The ejector according to FIG. 3 differs from the ejector according to FIG. 1 in that several threads, namely two of the threads 140, are provided, which are coupled at one end to the needle 108 and at the other end to the ejector body 144. A different number, for example more than two threads 140, is also possible.

(29) FIG. 4 shows a variant of an ejector with which the thread 140, the cord, the wire, the cable or the like is not elastically formed, for which purpose it is mounted in a spring-loaded manner opposite the ejector body 144. For this purpose, a spring element 148 is arranged between the thread end and the fixing on the ejector body 144.

(30) For the design of the coupling mechanism 110, it may be necessary to provide a transmission of the needle movement and the movement of the membrane 130. For this reason, it is proposed in FIG. 5 that the coupling mechanism 110 comprises a transmission gear 150, which is designed to transfer the axial movement of the needle 108 at a predetermined gear ratio to the movement of the membrane 130. As in the ejectors described above, a thread 140 is also wound around the membrane 130 in this case, allowing the flow cross-section 602 of the mixing tube 104 to be adjusted. This thread 140 is connected at one end to the ejector body 144 and at the other end to a transmission wheel of the transmission gear 150. The transmission gear 150 comprises a transmission step which is formed with a smaller diameter and to which a second thread 152, cord, wire, cable or the like is fixed. This second thread 152 is then connected at the other end to the needle 108 so that the movement of the needle 108 is transferred to the movement of the membrane 130 with a gear ratio specified by the transmission gear 150.

(31) The ejector according to FIG. 6 shows the possibility of connecting a rod assembly 154, which is guided by a bearing 156 and to which the thread 140 is fixed, to the needle 108. This also offers the possibility of coupling the movement of the needle 108 and the movement of the membrane 130. The thread 140 by means of which the mixing tube 104 can be varied is attached to the end of the rod. A deflection roller 146, or several of them, can also be used here.

(32) FIG. 7 shows a rod assembly 154 that interacts with a transmission gear 150, which in turn is connected to the thread 140 with a transmission step. In this case, the transmission gear 150 can comprise a gear wheel 158 with which a gear rack 160 of the rod assembly 154 meshes.

(33) In order to keep the deflection of the membrane 130 straight in the area of the mixing tube 104, it may be necessary to provide a guide 162 for the stiffening elements 132, thus for the dimensionally stable struts, on the membrane 130, as can be seen in the ejector according to FIG. 8. The stiffening elements 132 thus have a bar that is guided outwards, in particular radially, in a groove.

(34) FIG. 9 shows an ejector in which the stiffening elements 132 are embedded in the membrane 130 so that the thread 140, the cord, the wire, the cable or the like abuts directly on the outer shell 134 of the membrane 130.

(35) With regard to the guide of the stiffening elements 132, it may also be sensible to provide guides 162 in the ejector body 144, which enable only radial evasion of the stiffening elements 132. The stiffening elements 132 can, for example, completely surround the outer shell 134 of the membrane 130. For example, these can be formed from an elastomer. The guides 162 are arranged in a manner radially spaced from the membrane 130 so that the movement of the membrane 130 for adjusting the desired flow cross-section 602 is not obstructed.

(36) FIG. 11 shows an ejector in which the adjustment device 106 comprises a pressure chamber 136 that is designed to move the membrane 130 between the first and second positions if a piston 138 assigned to the coupling mechanism 110 is at least partially pushed into or withdrawn from the pressure chamber 136. The piston 138 is fixed to a rod assembly 154, which in turn is coupled to the needle 108. If the needle 108 is moved in the direction of the nozzle opening 120, the piston 138 enters the pressure chamber 136, whereby the membrane 130 performs an evasive movement and the flow cross-section 602 is thus reduced. The flow cross-section 602 is increased again if the piston 138 is pulled out of the pressure chamber 136 due to a retraction of the needle 108. With the variant of an ejector with pressure chamber 136 shown in FIG. 12, a guide 162 is again provided as already explained in connection with the ejector from FIG. 8.

(37) In the ejector according to FIG. 13, a belt 164, which is attached to a shaft 166, is wound around the membrane 130. If this shaft 166 is rotated, the belt 164 is wound up, reducing the flow cross-section 602 of the mixing tube 104. In this case, the shaft 166 is both part of the coupling mechanism 110 and part of the adjustment device 106. The needle 108 is formed with a gear rack 160 that meshes along a gear wheel 158, as a result of which an intermediate shaft 168 is rotationally driven around its longitudinal axis. The intermediate shaft 168 is thus rotatably mounted in a stationary manner opposite the ejector body 144. The intermediate shaft 186 has a second toothing 170, which forms a coupling with a spur gear 172 of the shaft 166. If the needle 108 is moved axially, the gear wheel 158 is rotationally driven due to the movement of the gear rack 106, whereby the toothing 170 also drives the spur gear 172 of the shaft 166. This winds up or unwinds the belt 164. For a particularly reliable movement, it has proven to be sensible if the width of the belt 164 corresponds to the width of the mixing tube 104 itself or the width of the membrane 130.

(38) In the ejector according to FIG. 14, the actuator 112 is not designed as a linear drive but as a rotating drive that rotates the shaft 166. In this case, the shaft 166 has a threaded section or a gear rack that interacts with a counter-toothing. The counter-toothing is coupled to the needle 108 so that when the shaft 166 is rotated by means of the actuator 112, the result is an axial movement of the needle 108 on the one hand, and a winding-up or unwinding of the belt 164 takes place on the other hand.

(39) FIG. 15 shows an ejector in which the actuator 112 moves the needle axially and at the same time rotates it. This rotation can be transferred by means of a belt drive 174 to a first shaft part 176, which is connected in a rotationally fixed manner via a coupling 180 to a second shaft part 178, thus to the shaft 166 interacting with the belt 164. Although the coupling 180 is designed to be rotationally fixed, it enables an axial movement of the first shaft part 176 in relation to the second shaft part 178. This can be seen, for example, in FIG. 16, since the coupling 180 (for example, the second shaft part 178) has an area which the first shaft part 176 can enter in a manner axially movable but rotationally fixed.

(40) FIGS. 17, 18 and 19 show various sections showing a rotationally fixed but axially movable coupling of the first shaft part 176 and the second shaft part 178. In FIG. 17, the first shaft part 176 has a spring that engages in a fit of the second shaft part 178. FIG. 18, two spring parts are provided on the first shaft part 176. In FIG. 19, the second shaft part 176 has a rectangular, in particular square, cross-section, which is guided in a complementary section of the second shaft part 178.

(41) The ejectors described above are characterized by their flexible adaptability to different operating conditions of a fuel cell system. This can be achieved in particular on the basis of the coupled movement of the needle 108 and the associated adjustment of the flow cross-section 602 of the mixing tube 104.

(42) In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.