BURNER DEVICE FOR A FUEL CELL SYSTEM

Abstract

The present invention relates to a burner device (10) for a fuel cell system (100), having a burner housing (20) with a burner inlet (22) for admitting a fuel/air mixture (BL) and a burner outlet (24) for discharging a burner exhaust gas/air mixture (BAL), additionally having a catalyst body (30) within the burner housing (20) comprising a catalyst cavity (32) into which the burner inlet (22) opens, wherein the catalyst body (30) is gas-permeable and has a catalyst surface (34) with an at least partly catalytic coating (36), wherein a bypass volume (40) is formed between the catalyst surface (34) and the burner housing (20), said bypass volume opening into the burner outlet (24), wherein the catalyst body (30) additionally has a longitudinal axis (LA), and the catalyst surface (34) has a cross-sectional contour (QK) which deviates from a circular shape at least in some sections with respect to the longitudinal axis (LA).

Claims

1. The burner device for a fuel cell system, having a burner housing with a burner inlet for admitting a fuel/air mixture (BL) and a burner outlet for discharging a burner exhaust gas/air mixture (BAL), further comprising a catalyst body within the burner housing with a catalyst cavity into which the burner inlet opens, wherein the catalyst body is gas-permeable and has a catalyst surface with an at least partly catalytic coating, wherein a bypass volume is formed between the catalyst surface and the burner housing said bypass volume opening into the burner outlet, wherein the catalyst body further comprises a longitudinal axis (LA), and the catalyst surface has a cross-sectional contour (QK) which deviates from a circular shape at least in some sections with respect to this longitudinal axis (LA).

2. Burner device according to claim 1, wherein the burner housing has an air inlet, in particular separate from the burner inlet, for admitting air into the bypass volume.

3. Burner device according to claim 2, wherein the air inlet has a control valve for controlling the mass flow of air into the bypass volume.

4. Burner device according to claim 1, wherein an air supply for a controlled supply of air (L) into the burner exhaust gas/air mixture (BAL) is arranged in and/or after the burner outlet.

5. Burner device according to claim 1, wherein the burner inlet, a cavity inlet in the catalyst cavity and/or the catalyst cavity have a mixing section for mixing air (L) and fuel (B).

6. Burner device according to claim 1, wherein the catalyst body is designed for a radial outlet of fuel/air mixture (BL) in relation to the longitudinal axis (LA), in particular exclusively for a radial outlet of fuel/air mixture (BL) in relation to the longitudinal axis (LA).

7. Burner device according to claim 1, wherein the cross-sectional contour (QK) extends between an inner radius (IR) and an outer radius (AR), in particular in an unified form in radial direction and/or in circumferential direction.

8. Burner device according to claim 1, wherein the cross-sectional contour (QK) is symmetrical or substantially symmetrical to the longitudinal axis (LA).

9. Burner device according to claim 1, wherein the cross-sectional contour (QK) is, at least in some sections, constant or substantially constant along the longitudinal axis (LA).

10. Burner device according to claim 1, wherein the cross-sectional contour (QK) is, at least in some sections, star-shaped.

11. Burner device according to claim 1, wherein the catalyst body is, at least in the region of the catalyst surface, porous, in particular completely or substantially completely porous.

12. Burner device according to claim 11, wherein the catalyst body has a varying porosity along the longitudinal axis (LA).

13. Burner device according to claim 1, wherein the catalyst surface has, at least in some sections, a surface normal (FN) which intersects an adjacent surface normal (FN) of the catalyst surface outside of the catalyst body.

14. Burner device according to claim 1, wherein the catalyst surface has at least in some sections, a surface normal (FN) which intersects the catalyst surface in an adjacent section.

15. Burner device according to claim 1, wherein the catalyst surface has at least one guide section for guiding the air in the bypass volume which in particular extends along or substantially along the longitudinal axis (LA).

16. Fuel cell system for generating electrical energy from a fuel and/or for generating fuel from electrical energy, comprising at least one burner device with the features of claim 1.

Description

[0033] Further advantages, features and details of the invention are explained in the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. In each case schematically:

[0034] FIG. 1 shows an embodiment of a burner device according to the invention,

[0035] FIG. 2 shows a further embodiment of a burner device according to the invention,

[0036] FIG. 3 shows a further embodiment of a burner device according to the invention,

[0037] FIG. 4 shows a further embodiment of a burner device according to the invention,

[0038] FIG. 5 shows a further embodiment of a burner device according to the invention,

[0039] FIG. 6 shows a possible partial cross-section through a catalyst body,

[0040] FIG. 7 shows a possible partial cross-section through a further catalyst body,

[0041] FIG. 8a shows a schematic representation of a fuel cell system according to the invention and

[0042] FIG. 8b shows a further schematic representation of a fuel cell system according to the invention.

[0043] FIG. 1 shows schematically a burner device 10 in a lateral cross-section along the longitudinal axis LA. This has two main elements. On the one hand there is the burner housing 20, in which the second main component is arranged in the form of the catalyst body 30. In the embodiment shown in FIG. 1, a fuel/air mixture BL can be introduced into the catalyst cavity 32 via the burner inlet 22. In order to produce the fuel/air mixture BL, a mixing section 50 is provided upstream of the burner inlet 22 which is supplied with fuel B and air L. The fuel/air mixture BL thus penetrates via the burner inlet 22 into the burner housing 20 and in particular into the catalyst cavity 32.

[0044] In addition, it can be seen in FIG. 1 that air L is introduced into the bypass volume 40 via an air inlet 26. A mixture of burner exhaust gas and air L forms as a burner exhaust gas/air mixture BAL, which leaves the bypass volume 40 again via the burner outlet 24.

[0045] In terms of its operating principle, the burner device 10 can be described as a hybrid burner. The fuel/air mixture BL penetrates the gas-permeable porous catalyst body 30 and reaches the catalyst surface 34, which has a catalytic coating 36. Due to the catalytic coating, a reaction of the fuel B is possible, so that radicals are formed which in turn allow a flame combustion of the remaining fuel B with the air L in the bypass volume 40. The resulting waste heat is discharged from the burner device 10, via the burner exhaust gas/air mixture BAL, via the burner outlet 24 and supplied to the other components of the fuel cell system 100.

[0046] FIG. 2 shows a cross-sectional contour QC of the catalyst body 30 according to the invention in a schematic cross-section transverse to the longitudinal axis LA. Four indentations are shown here which cause the cross-sectional contour QC to deviate from the circular shape. The catalyst cavity 32 is similarly designed, so that the fuel/air mixture BL passes radially through the porous catalyst body 30 to the corresponding indentations and bulges of the catalyst surface 34 and thus to the catalytic coating 36 thereon. FIG. 2 also shows that the four bulges, as fin-like guide sections 35 extending along the longitudinal axis LA, serve to guide the air L in the bypass volume 40.

[0047] FIG. 3 shows the embodiment from FIG. 2, but in relation to an inner radius IR and an outer radius AR. While basically any cross-sectional contour QC is possible, also an asymmetrical one, as long as it deviates from the circular shape, a regular design as shown in FIGS. 2 and 3 is advantageous. As can be seen here, the regular cross-sectional contour QC in this embodiment is oriented on a maximum outer radius AR and a minimum inner radius IR, so that the corresponding hybrid combustion functionalities in the circumferential direction and radial direction are comparable.

[0048] FIG. 4 shows a further embodiment of such a burner device 10. It differs from the variant of FIG. 1 in that the air supply into the bypass volume 40 can be regulated or controlled by means of a control valve 28. This makes it possible to adjust the stoichiometric ratio in the bypass volume 40 precisely and thus to control the combustion functionalities of the flame combustion even more precisely. It can also be seen in FIG. 4 that the mixing section 50 is integrated into a cavity inlet 33 of the burner inlet 22. Thus, the fuel/air mixture BL is formed directly at the inlet into the catalyst cavity 32, so that the overall system of the burner device 10 can be made even more compact in design. Furthermore, it can be seen in FIG. 4, by way of example, how the right-hand end face of the catalyst body 30 is designed to be gas-tight. This makes it possible to limit the catalytic effect to the circumferential surface of the catalyst body 30, which leads to an equalisation of the combustion functions.

[0049] FIG. 5 shows another embodiment of the burner device 10. Here, a mixing section 50 is integrated into the burner inlet 22 and protrudes into the catalyst cavity 32. This maximises the compact design of the burner device 10. In this embodiment too, an additional air supply 29 into the burner outlet 24 can be seen which allows air L to be added to the burner exhaust-air mixture via a control valve. This makes it possible on the one hand to influence the outlet temperature of the burner exhaust gas/air mixture BAL, but also to influence its stoichiometric ratio subsequently outside of the burner device 10.

[0050] FIG. 6 shows a further possibility of shaping the catalyst body 30. Here, the surface normal FN is shown at two positions of the catalyst surface 34. The two surface normals FN shown intersect outside of the catalyst body 30, so that a flame zone is formed between these two elevations in the indentation of the catalyst body 30. In this flame zone, flame-combusted fuel causes heat transmitted by radiation to reach an increased absorption area of the catalyst body 30 compared to the circular shape. The corresponding amount of heat reflected by thermal radiation is thus increased compared to a circular catalyst body 30.

[0051] FIG. 7 shows a further intensification of the above effect as a result of a further adapted cross-sectional contour QC. Here, the surface normal FN is aligned through the pronounced indentation of the catalyst body 30 in such a way that it directly intersects an adjacent section of the catalyst body 30. This maximises the reflection by thermal radiation explained in the preceding paragraph with reference to FIG. 6.

[0052] FIGS. 8a and 8b schematically show a fuel cell system 100, wherein here the fuel cell stack schematically comprises an anode section 110 and a cathode section 120. The supply to the cathode section 120 in FIG. 8b and the discharge from the cathode section 120 and from the anode section 110 in FIG. 8a are equipped with a burner device 10 which brings the advantages according to the invention. In FIG. 8a, a heat exchanger HEX is arranged in the supply of air L to the cathode section 120, which gives off waste heat from the cathode exhaust gas to the supplied air L before the exhaust gas is released into the environment.

[0053] The preceding explanation describes the present invention exclusively with reference to examples.

LIST OF REFERENCE SIGNS

[0054] 10 burner device [0055] 20 burner housing [0056] 22 burner inlet [0057] 24 burner outlet [0058] 26 air inlet [0059] 28 control valve [0060] 29 air supply [0061] 30 catalyst body [0062] 32 catalyst cavity [0063] 33 cavity inlet [0064] 34 catalyst surface [0065] 35 guide section [0066] 36 catalytic coating [0067] 40 bypass volume [0068] 50 mixing section [0069] 100 fuel cell system [0070] 110 anode section [0071] 120 cathode section [0072] HEX heat exchanger [0073] L air [0074] B fuel [0075] BL fuel/air mixture [0076] BAL burner exhaust gas/air mixture [0077] LA longitudinal axis [0078] QK cross-sectional contour [0079] IR inner radius [0080] AR outer radius [0081] FN surface normal