FUEL CELL SYSTEM

Abstract

A fuel cell system is provided having a fuel cell and a jet pump control valve unit connected to an anode chamber with an intake connection and a pressure connection. A fuel gas control valve connecting a fuel gas source and the jet pump has a valve seat with a first sealing surface and at least two through-flow channels, and a moveable valve body with a second sealing surface. The valve body can be moved into a blocking position and a through-flow position using a valve body actuator. The sealing surfaces rest on one another in a common sealing plane and form a seal in the blocking position. A stroke gap is formed between the sealing surfaces in the through-flow position. The first or second sealing surface is arranged on a raised sealing level. A volume flow of a drive jet can be controlled by the valve body actuator.

Claims

1. A fuel-cell system (1), comprising a fuel cell (3) having an anode chamber (7) and a cathode chamber (9) as well as, connected with a suction port (17) and with a pressure port (19) on the anode chamber (7), and serving for recirculation of an anode gas and metered charging of the anode chamber (7) with fuel gas, a jet-pump control-valve unit (5) having a jet pump (13) and a fuel-gas control valve (15), wherein the fuel-gas control valve (15) is connected fluidically between a fuel-gas source (25) and the jet pump (13), with the following features: the fuel-gas control valve (15) comprises a valve seat (69) having a first sealing face (79) with at least two passage ducts (85) and a movable valve body (71) having a second sealing face (71); the valve body (71) can be moved into a blocking position and a passing position by means of a valve-body actuator (73), wherein the first sealing face (79) and the second sealing face (82) bear on one another in a common sealing plane (E) and form a seal with one another, while a stroke gap is formed between the first sealing face (79) and the second sealing face (82) in the passing position; the first sealing face (79) and/or the second sealing face (82) is disposed on a raised sealing plateau (81); a valve-seat surface in the region of the first sealing face (79) and/or a valve body surface (82) in the region of the second sealing face has/have an average peak-to-valley height of at most 1 μm; the volume flow of a propulsion jet that can be generated by means of a propulsion nozzle (67) of the jet-pump control-valve unit (5) can be controlled by pulse-width-modulated urging of the valve-body actuator (73).

2. The fuel-cell system (1) of claim 1, wherein the first sealing face (79) is disposed on the raised sealing plateau (81) and is formed by at least one annular face (84B), in which at least two passage ducts (85B) discharge respectively into a passage-duct outlet (87B).

3. The fuel-cell system (1) of claim 2, wherein the passage-duct outlets (87) are of circular, oval, triangular or trapezoidal shape.

4. The fuel-cell system (1) of claim 2, wherein a reference circumference or a sum of reference circumferences of the at least one annular face (84B) is at least 60 times, preferably at least 80 times, particularly preferably at least 100 times larger than the stroke gap in passing position.

5. The fuel-cell system (1) of claim 1, wherein the first sealing face (79) is disposed on the raised sealing plateau (81) and is formed by at least two face portions (83), in which respectively one passage duct (85) discharges into a passage-duct outlet (87).

6. The fuel-cell system (1) of claim 5, wherein the at least two face portions (83) are of respectively circular, oval, triangular or trapezoidal shape.

7. The fuel-cell system (1) of claim 5, wherein a sum of the circumferences of the at least two face portions (83) is at least 150 times, preferably at least 250 times, particularly preferably at least 350 times larger than the stroke gap in passing position.

8. The fuel-cell system (1) of claim 1, wherein the valve-body actuator (73) comprises a flux concentrator (97) and an armature (99) coupled with the valve body (71), wherein, in the passing position, an air gap is formed between the armature (99) and the flux concentrator (97).

9. The fuel-cell system (1) of claim 1, wherein the valve body (71) or an armature (99) that may be provided on the valve-body actuator (73) is stopped in the passing position against at least one stop element (74), which is designed to be particularly elastic and/or noise-reducing.

10. The fuel-cell system (1) of claim 1, wherein the valve body (71) is able to move along a movement axis (A) into the blocking position and passing position, wherein the fuel gas can flow into the fuel-gas control valve (15) in a manner transverse to the movement axis and can flow out of the fuel-gas control valve (15) along the movement axis (A).

11. The fuel-cell system (1) of claim 2, wherein the propulsion nozzle (67) has a propulsion-nozzle outlet (67′), wherein the distance between the propulsion-nozzle outlet (67′) and the first sealing face (79) is at most 160 times, preferably at most 130 times, larger than the stroke gap when the fuel-gas control valve is open.

12. The fuel-cell system (1) of claim 1, wherein the valve body (71) is able to move along a movement axis (A) into the blocking position and the passing position, wherein the valve body (71) has, on its end face (91) turned toward the valve seat (69), at least one recess (95), constructed in particular as a blind hole (93) or annular groove, which is in fluidic communication with at least one inflow duct (96) extending transversely relative to the movement axis (A) as far as the periphery of the valve body (71).

13. The fuel-cell system (1) of claim 1, wherein the fuel-gas control valve (15) comprises a sleeve-like valve housing (59), which receives the valve seat (69), the valve body (71) and the valve-body actuator (73).

14. The fuel-cell system (1) of claim 13, wherein the valve body (71) is guided movably by the valve housing (59) along a movement axis (A) into the blocking position and the passing position and in the process is in contact with the valve housing (59) inside an annular contact region (K) of the valve housing (59), wherein at least one inflow opening (109) extending transversely relative to the movement axis (A) is formed in a portion of the valve housing (59) starting from the contact region (K) and turned toward the valve seat (69), and wherein at least one compensating opening (111) extending transversely relative to the movement axis (A) is formed in a portion of the valve housing (59) starting from the contact region (K) and turned away from the valve seat (69).

15. The fuel-cell system of claim 1, wherein the axial elevation of the sealing plateau (81) relative to the end-face parts, adjoining the sealing face (79, 82) in question, of the valve body (71) or valve seat (69), and therefore the axial height of a pressure chamber (D) formed between the mutually facing end faces (90, 91) of valve seat (69) and valve body (71) amounts to at least 1.5 times, preferably at least 3 times the valve-body stroke.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0043] In the following, several exemplary embodiments of the invention will be explained in more detail on the basis of the drawing, wherein

[0044] FIG. 1 shows a schematic diagram of an inventive fuel-cell system,

[0045] FIG. 2 shows an axial section of a jet-pump control-valve unit of an inventive fuel-cell system,

[0046] FIG. 3 shows an enlarged axial section of the fuel-gas control valve of the jet-pump control-valve unit according to FIG. 2,

[0047] FIGS. 4a and 4b show the valve body of the fuel-gas control valve according to FIG. 3 in a side view (FIG. 4a) as well as a radial section (FIG. 4b),

[0048] FIGS. 5a to 6b show two different embodiments of a valve seat of an inventive fuel-cell system in respectively a plan view (FIGS. 5a, 6a) as well as an axial section (FIGS. 5b, 6b) and

[0049] FIG. 7 shows sections of plan views of four further different valve seats of inventive fuel-cell systems.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] FIG. 1 schematically shows an inventive fuel-cell system 1, which comprises a fuel cell 3 and a jet-pump control-valve unit 5. Fuel cell 3 has, in conventional manner, an anode chamber 7, a cathode chamber 9 and an electrolyte membrane 11 separating anode chamber 7 and cathode chamber 9 from one another.

[0051] Jet-pump control-valve unit 5 comprises a jet pump 13 and a fuel-gas control valve 15, is connected via a suction port 17 and a pressure port 19 to anode chamber 7 and serves for recirculation of an anode gas as well as for metered charging of anode chamber 7 with fuel gas.

[0052] For this purpose, the fuel gas present under high pressure in fuel source 25 first passes an opened shutoff valve 27, before its pressure is reduced in a pressure regulator 29 and the fuel gas flows into fuel-gas control valve 15. Under control of the fuel-gas control valve, the fuel gas then flows into jet pump 13, where—in known manner—it entrains anode gas, which is sucked through suction port 17 and mixed with the (fresh) fuel gas to produce mixed gas. The mixed gas exits jet pump 13 through pressure port 19 and flows past safety valve 35 and through an (optional) first condensate separator 37, before it flows into anode chamber 7 of fuel cell 3 through an anode-chamber inlet 39. In the region of anode-chamber inlet 39, state parameters of the mixed gas (e.g. temperature, pressure, mixing ratio) relevant to control and operation are recorded by means of a sensor 41. The anode gas sucked out of anode chamber 7 through an anode-chamber exit 43 passes a (second) condensate separator 45 used for separation of condensation water and flows past a flush valve 47, which permits removal of foreign gases (e.g. nitrogen) accumulated in the anode chamber. Condensation water collected in the first condensate separator 43 or second condensate separator 45 if such are provided can be drained via a condensate drain valve 49. To the foregoing extent, the exemplary embodiment illustrated in the drawing is based on prior art sufficiently known to the person skilled in the art, and so further explanations are not needed.

[0053] FIG. 2—which is partly not to scale for reasons of illustration of details—represents, in axial section, a jet-pump control-valve unit 5 of an inventive fuel-cell system 1 comprising a fuel-gas control valve 15 as well as a jet pump 13. Jet pump 13 has a jet-pump housing 51, in which a suction port 17, a pressure port 19 as well as a propulsion-jet port 53 are provided and which forms a mixing chamber 55 as well as a diffusor region 57. Since the jet-pump control-valve unit is based to this extent on prior art sufficiently known to the person skilled in the art, further explanations are unnecessary.

[0054] Fuel-gas control valve 15 comprises a sleeve-like valve housing 59, a valve seat 69, a valve body 71 and a valve-body actuator 73, and is inserted into a valve receptacle 61 receiving fuel-gas control valve 15 and directly adjoining jet-pump housing 51. Valve housing 59 is sealed relative to valve receptacle 61 by means of two O-rings 62. Valve receptacle 61 and jet-pump housing 51 could also be constructed in one piece, although they are not shown in such a manner in the drawing.

[0055] A fuel-gas port 63, via which fuel-gas source 25 is in fluidic communication with an annular fuel chamber 65 formed between valve receptacle 61 and valve housing 59, is provided in valve receptable 61. (In practice, the fuel-gas port 63 illustrated in the section plane for reasons of clarity is oriented not in this way but instead perpendicular to the section plane—and to suction port 17.)

[0056] A propulsion nozzle 67 projecting through propulsion-jet port 53 into mixing chamber 55 of jet pump 13 adjoins valve housing 59 on the jet-pump side. This propulsion nozzle 67 has a propulsion-nozzle outlet 67′. Fuel gas, which flows through fuel-gas port 63 into annular fuel chamber 65 and passes this when fuel-gas control valve 15 is open, then flows through propulsion nozzle 67 generating a propulsion jet into mixing chamber 55 of jet pump 13. There, the propulsion jet entrains anode gas sucked through suction port 17 and together with this enters diffusor region 57. The volume flow of the propulsion jet that can be generated by means of propulsion nozzle 67 of jet-pump control-valve unit 5 can be controlled by pulse-width-modulated urging of valve-body actuator 73. Alternatively to the embodiment illustrated in the drawing, propulsion nozzle 67 could also be constructed in one piece with valve housing 59 or jet-pump housing 51.

[0057] FIG. 3—which again is partly not to scale for reasons of illustration of details—represents fuel-gas control valve 15 of jet-pump control-valve unit 5 according to FIG. 2 (together with propulsion nozzle 67 screwed into valve housing 59) in an enlarged axial section. Valve seat 69, valve body 71, valve-body actuator 73, a stop element 74 and a valve cover 75 are received in sleeve-like valve housing 59.

[0058] Valve seat 69, sealed by means of an O-ring 77 relative to valve housing 59 and made from highly-filled PEEK, has a first sealing face 79 on its end face 90 turned toward valve body 71. This first sealing face 79 is disposed on a raised sealing plateau 81 projecting relative to the adjoining regions of end face 90 and is formed by eight circularly constructed face portions 83 (of which only two are visible in FIG. 3). In each face portion 83, respectively one passage duct 85 discharges into a passage-duct outlet 87. In the region of first sealing face 79, the valve-seat surface has an average peak-to-valley height Rz of approximately 2.5 μm (as measured originally, i.e. before initial operation of the fuel-gas control valve).

[0059] Valve body 71, made of steel, comprises a sliding ring 89 and on its end face 91 turned toward valve seat 69 has a second sealing face 82 as well as a recess 95 constructed as a blind hole 93, which is in fluidic communication with six inflow ducts 96 extending as far as the periphery of valve body 71 (see also FIGS. 4a and 4b). In the region of second sealing face 82, the valve-body surface has an average peak-to-valley height of approximately 0.25 μm.

[0060] Valve-body actuator 73 comprises an electromagnet M, a flux concentrator 97 and an armature 99 coupled with valve body 71. Flux concentrator 97 is sealed relative to valve housing 59 by means of an O-ring 101. Electromagnet M is joined via two contact points 103 with a cable 105, which is guided outward through a bushing 107 penetrating valve cover 75.

[0061] By means of valve-body actuator 73 as well as spring 108—braced on one side against valve body 71 and on the other side against stop element 74—the unit comprising armature 99 and valve body 71 can be moved along a movement axis A into a blocking position as well as a passing position, wherein, in the blocking position (as illustrated in FIG. 3), first sealing face 79 and second sealing face 82 bear on one another in a common sealing plane E and are sealed relative to one another, whereas, in the passing position (not illustrated), valve body 71—raised from valve seat 69—is stopped against stop element 74 and a stroke gap is formed between first sealing face 79 and second sealing face 81. For this purpose, valve body 71 is guided by means of sliding ring 89 through valve housing 59 and inside an annular contact region K of valve housing 59 is in contact with valve housing 59.

[0062] Valve housing 59 has eight inflow openings 109, eight compensating openings 111 and one outflow opening 113, wherein respectively only two inflow openings 109 and two compensating openings 111 are visible in FIG. 3. These inflow openings 109 are formed in a portion of valve housing 59 starting from contact region K and extending transversely relative to movement axis A in a manner turned toward valve seat 69; in contrast compensating openings 111 are formed in a portion of valve housing 59 starting from contact region K and extending transversely relative to movement axis A in a manner turned away from valve seat 69.

[0063] If fuel-gas control valve 15 is closed, valve body 71 is therefore in blocking position, and so fuel gas is able to accumulate in a pressure chamber D, which extends, clamped by raised sealing plateau 81, between the mutually facing end faces 90, 91 of valve seat 69 and valve body 71. Thus pressure chamber D can be supplied with fuel gas on the one hand by inflow ducts 96 as well as recess 95 formed as blind hole 93 and on the other hand with lateral flow around valve body 71. Thus, in blocking position of valve body 71, fuel gas under pressure and thus correspondingly compressed is directly present at the shortest possible distance from cooperating sealing faces 79, 82 and, when fuel-gas control valve 15 is opened, is able to expand into passage ducts 85, in order then to flow through outflow opening 113 out of fuel-gas control valve 15 along movement axis A.

[0064] FIGS. 5a, 5b and FIGS. 6a, 6b respectively show a valve seat 69A, 69B of two further embodiments of inventive fuel-cell system 1 in a plan view as well as an axial section.

[0065] Valve seat 69A according to FIGS. 5a and 5b—again made from highly filled PEEK—has a first sealing face 79A, which is disposed on a raised sealing plateau 81A projecting relative to adjoining end-face regions 90A. This sealing face 79A is formed by 24 circularly constructed face portions 83A, which are disposed along two concentric circles K1, K2. In each face portion 83A, respectively one passage duct 85A discharges into a passage-duct outlet 87A. In the region of first sealing face 79A, valve-seat surface 79′A has an original average peak-to-valley height of 2.5 μm.

[0066] In contrast, valve seat 69B according to FIGS. 6a and 6b—again made from highly filled PEEK—has a first sealing face 79B, which is disposed on a raised sealing plateau 81B projecting relative to adjoining end-face regions 90B and is formed by an annular face 84B. In annular face 84B, ten passage ducts 85B discharge into ten circularly constructed passage-duct outlets 87B (disposed along an imaginary circle K3). In the region of first sealing face 79B, valve-seat surface 79′B has an original average peak-to-valley height of 2.5 μm.

[0067] FIG. 7 shows axial sections of plan views of four different valve seats 69C, 69D, 69E and 69F of further embodiments of inventive fuel-cell system 1. Valve seats 69C to 69F respectively have a first sealing face 79C to 79F, which is disposed on a raised sealing plateau 81C to 81F. Sealing faces 79C to 79F are formed respectively by several face portions 83C to 83F, wherein these are constructed as elongated face portions 83C, oval face portions 83D, triangular face portions 83E and trapezoidal face portions 83F. In each face portion 83C to 83F, respectively one passage duct discharges into a passage-duct outlet 87C to 87F.