BURNER FOR AN EXHAUST-GAS AFTERTREATMENT SYSTEM, EXHAUST-GAS AFTERTREATMENT SYSTEM FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A burner for an exhaust-gas aftertreatment system. The burner includes a housing forming a combustion chamber. The housing has an outlet which is or can be connected to an exhaust-gas line of the exhaust-gas aftertreatment system. The burner further includes a fuel feed device for feeding fuel into the combustion chamber; a fresh-air feed device for feeding fresh air into the combustion chamber; and an ignition element for igniting a fresh-air/fuel mixture located in the combustion chamber. It is provided that the housing is designed such that the combustion chamber has a cylindrical main portion and a bulge protruding radially outward from the main portion, and that the ignition element is arranged in the bulge.

Claims

15. (canceled)

16. A burner for an exhaust-gas aftertreatment system, comprising: a housing forming a combustion chamber, the housing having an outlet which is or can be connected to an exhaust-gas line of the exhaust-gas aftertreatment system; a fuel feed device configured to feed fuel into the combustion chamber; a fresh-air feed device configured to feed fresh air into the combustion chamber; and an ignition element configured to ignite a fresh-air/fuel mixture located in the combustion chamber; wherein the housing is configured such that the combustion chamber has a cylindrical main portion and a bulge protruding radially outward from the main portion, and the ignition element is arranged in the bulge.

17. The burner according to claim 16, wherein the housing has a first housing part forming the main portion and a second housing part forming the bulge, wherein the first and the second housing part are manufactured separately from each other, and wherein the second housing part is arranged in an aperture in a casing wall of the first housing part.

18. The burner according to claim 17, wherein the first housing part has a circular cross-section.

19. The burner according to claim 17, wherein the second housing part has a cross-section with a C-shaped profile.

20. The burner according to claim 16, wherein the bulge extends in a circumferential direction of the main portion over a circumferential angle of 10 to 50.

21. The burner according to claim 16, wherein an axial extension of the bulge is smaller than an axial extension of the main portion.

22. The burner according to claim 16, wherein a ratio of a volume of the main portion to the volume of the bulge is 200:1 to 50:1.

23. The burner according to claim 16, wherein a yaw angle of the ignition element is in an angular range that begins with 0 and ends with 45, wherein the yaw angle describes a rotation of a longitudinal center axis of the ignition element relative to a longitudinal center axis of the main portion about a vertical axis, which is aligned perpendicularly to the longitudinal center axis of the main portion and runs through the longitudinal center axis of the main portion and through the ignition element.

24. The burner according to claim 16, wherein a pitch angle of the ignition element is in an angular range that begins with 0 and ends with 70, wherein the pitch angle describes a rotation of a longitudinal center axis of the ignition element relative to a longitudinal center axis of the main portion about a transverse axis which is aligned perpendicularly to the longitudinal center axis of the main portion and the vertical axis and runs through the ignition element.

25. The burner according to claim 16, wherein the ignition element is arranged such that a longitudinal center axis of the ignition element is aligned in parallel with a longitudinal center axis of the main portion.

26. The burner according to claim 16, wherein the housing has a rounding at least one transition from the main portion to the bulge.

27. The burner according to claim 16, wherein the ignition element is a ceramic glow plug.

28. The burner according to claim 17, wherein the fresh-air feed device has a sleeve-shaped fresh-air feed chamber, wherein the fresh-air feed chamber radially encloses the first housing part, and wherein the second housing part projects radially through the fresh-air feed chamber.

29. The burner according to claim 16, wherein the fuel feed device and the fresh-air feed device together form a two-fluid nozzle.

30. An exhaust-gas aftertreatment system for an internal combustion engine, comprising: a burner, including: a housing forming a combustion chamber, the housing having an outlet which is or can be connected to an exhaust-gas line of the exhaust-gas aftertreatment system, a fuel feed device configured to feed fuel into the combustion chamber, a fresh-air feed device configured to feed fresh air into the combustion chamber, and an ignition element configured to ignite a fresh-air/fuel mixture located in the combustion chamber, wherein the housing is configured such that the combustion chamber has a cylindrical main portion and a bulge protruding radially outward from the main portion, and the ignition element is arranged in the bulge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 shows an exhaust-gas aftertreatment system in a schematic representation, according to an example embodiment of the present invention.

[0023] FIG. 2 is a sectional view of a burner of the exhaust-gas aftertreatment system, according to an example embodiment of the present invention.

[0024] FIG. 3 is a further sectional view of the burner, according to an example embodiment of the present invention.

[0025] FIG. 4 is a further sectional view of the burner, according to an example embodiment of the present invention.

[0026] FIG. 5 is a further sectional view of the burner, according to an example embodiment of the present invention.

[0027] FIG. 6 is a sectional view of the burner according to a further exemplary embodiment of the present invention.

[0028] FIG. 7 is a sectional view of the burner according to a further exemplary embodiment of the present invention

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0029] FIG. 1 shows an exhaust-gas aftertreatment system 1 in a schematic representation. The exhaust-gas aftertreatment system 1 has an exhaust-gas line 2 having a catalyst 3. The exhaust-gas aftertreatment system 1 is assigned to an internal combustion engine 4 of a motor vehicle not shown in detail. An outlet of the internal combustion engine 4 is fluidically connected to the exhaust-gas line 2, so that exhaust gas arising during operation of the internal combustion engine 4 is fed to the exhaust-gas line 2. The exhaust gas of the internal combustion engine 4 flows through the catalyst 3 of the exhaust-gas line 2, wherein the catalyst 3 converts gaseous pollutants in the exhaust gas, such as NOx, HC or CO, into harmless products. The efficiency of the catalyst 3 corresponds to the temperature of the catalyst 3. In particular, at catalyst temperatures below a so-called light-off temperature, the aforementioned pollutants may not be completely converted by the catalyst 3. This may, for example, occur during a cold start of the internal combustion engine 4.

[0030] In order to accelerate the heating of the catalyst 3, in particular during a cold start of the internal combustion engine 4, the exhaust-gas aftertreatment system 1 has a burner 5. In the exhaust-gas aftertreatment system 1 shown schematically in FIG. 1, only one catalyst 3 is present and the burner 5 is fluidically connected to the exhaust-gas line 2 upstream of the catalyst 3. Preferably, the exhaust-gas aftertreatment system 1 has two catalysts 3 connected in series, wherein the burner 5 is in this case fluidically connected to the exhaust-gas line 2 upstream of the catalysts 3 or between the catalysts 3. The design of the burner 5 is explained in more detail below with reference to FIGS. 2, 3, 4, and 5. For this purpose, FIG. 2 is a longitudinal section of the burner 5. FIG. 3 is a cross-section of the burner 5 along the cross-sectional plane A-A shown in FIG. 2. FIG. 4 is a further cross-section of the burner 5 along the cross-sectional plane A-A shown in FIG. 2. FIG. 5 is a further sectional view of the burner 5, namely along the section plane B-B shown in FIG. 2.

[0031] The burner 5 has a housing 6 forming a combustion chamber 7. An outlet 8 of the housing 6 is fluidically connected to the exhaust-gas line 2. A fresh air-fuel mixture burned in the combustion chamber 7 can thus be fed into the exhaust-gas line 2 in order to heat the catalyst 3 thereby. The housing 6 is designed or shaped such that the combustion chamber 7 has a cylindrical main portion 9 and a bulge 10 protruding radially outward from the main portion 9 in relation to a longitudinal center axis 14 of the main portion 9. The housing 6 has a first housing part 11 forming the main portion 9. In the present case, the first housing part 11 has the outlet 8. The first housing part 11 is also cylindrical, wherein the first housing part 11 tapers in the region of the outlet 8. The housing 6 also has a second housing part 12 forming the bulge 10. The second housing part 12 is manufactured separately from the first housing part 11 and is arranged in an aperture 13 in a housing wall 16 of the first housing part 11. In the present case, the second housing part 12 is pot-shaped. The second housing part 12 is formed by a bottom 40 and four side walls 41, 42, 43, and 44. A first side wall 41 is opposite a second side wall 42. A third side wall 43 is opposite a fourth side wall 44, wherein the side walls 43 and 44 are not visible in FIG. 1 since they are outside the section plane. As can be seen in the figures, an inner surface 51 forming the bulge 10 of the second housing part 12 has a curved profile, so that the side walls 41, 42, 43, and 44 merge continuously into the bottom 40. There are therefore roundings at the transitions from the side walls 41, 42, 43, and 44 to the bottom 40. Alternatively, the transitions can also be designed without a rounding. In this case, the side walls 41, 42, 43, and 44 abruptly merge into the bottom 40. A maximum axial extension of the cylindrical main portion 9 is greater than a maximum axial extension of the bulge 10. The bulge 10 is thus limited to an axial portion of the main portion 9.

[0032] The housing 6 has multiple roundings, each of which is located at a transition from the main portion 9 to the bulge 10. As can be seen in FIG. 1, a rounding 48 and 49 is formed in the side walls 41 and 42, respectively. As can be seen in FIG. 2, for example, a rounding 50 is also formed in the third side wall 43. In the present case, the fourth side wall 44 is without a rounding, so that an edge is present at a transition from the main portion 9 to the bulge 10.

[0033] As can be seen in FIGS. 3 and 4, the first housing part 11 has a circular cross-section in the present case. Accordingly, the main portion 9 also has a circular cross-section. The second housing part 12 has a cross-section with a C-shaped profile, wherein an opening of the C-shaped profile faces the main portion 9. The bulge 10 extends in the circumferential direction of the main portion 9 only in portions along the main portion 9. In the present case, the bulge 10 extends in the circumferential direction over a circumferential angle of approximately 25 along the main portion 9. The ratio of the volume of the main portion 9 to the volume of the recess 10 is preferably 200:1 to 50:1, preferably 175:1 to 100:1, particularly preferably 150:1. This volume ratio is not exactly shown in the figures, which is due to the only schematic representation of the burner 5.

[0034] The burner 5 also has a fuel feed device 17, which is designed as a fuel injector 17 in the present case. The fuel feed device 17 is designed to feed fuel 18 to the combustion chamber 7. In the present case, the fuel feed device 17 is designed to meter the fuel 18 directly into the combustion chamber 7. For this purpose, the fuel feed device 17 has a fuel line 19, which is directly connected to the combustion chamber 7 through a fuel inlet 20. The burner 5 also has a fresh-air feed device 21, which is designed to feed fresh air 22 to the combustion chamber 7. For this purpose, the fresh-air feed device 21 has a fresh-air line 23, which is connected to the combustion chamber 7 through a fresh-air inlet 24. The fuel inlet 20 and the fresh-air inlet 24 are axially opposite the outlet 8. The fresh-air line 23 has a sleeve-shaped fresh-air feed chamber 25, which radially encloses the first housing part 11. The second housing part 12 projects radially through the fresh-air feed chamber 25. In the present case, the fuel feed device 17 and the fresh-air feed device 21 together form a two-fluid nozzle 26. If fuel 18 and fresh air 22 are fed to the combustion chamber 7 through the two-fluid nozzle 26, the fuel 18 is broken up into fine droplets by the fresh air 22, so that a fresh-air/fuel mixture 27 is obtained, in which the fuel 18 is finely distributed.

[0035] The burner 5 also has an ignition element 28 for igniting the fresh-air/fuel mixture 27 located in the combustion chamber 7. The ignition unit 28 has an ignition element 29 arranged in the bulge 10. The ignition element 29 projects through an aperture in the second housing part 12 into the bulge 10. The ignition element is aligned in parallel with the third side wall 43 and the fourth side wall 44. The ignition element 29 is arranged only in the bulge 10 of the combustion chamber 7, so that the ignition element 29 does not project into the cylindrical main portion 9. Rather, a free end 46 of the ignition element 29 has a retracted installation position relative to the main portion 9. There is thus a radial distance 31 between the ignition element 29 and the cylindrical main portion 9. In the present case, the ignition element 29 is a glow plug 29, particularly preferably a ceramic glow plug 29. However, the ignition element 29 can also be a different type of ignition element 29. According to a further exemplary embodiment, the ignition element 29 is designed as a spark plug.

[0036] According to the exemplary embodiment shown in FIG. 2, the ignition element 29 is arranged such that a longitudinal center axis 32 of the elongated ignition element 29 is aligned obliquely to the longitudinal center axis 14 of the main portion 9.

[0037] The alignment of the ignition element 29 relative to the longitudinal center axis 14 of the main portion 9 is described by a pitch angle of the ignition element 29 and a yaw angle of the ignition element 29. The yaw angle describes a rotation of the longitudinal center axis 32 of the ignition element 29 relative to the longitudinal center axis 14 of the main portion 9 about a vertical axis H, which is aligned perpendicularly to the longitudinal center axis 14 of the main portion 9 and runs through the longitudinal center axis 14 of the main portion and through the ignition element 29. The pitch angle describes a rotation of the longitudinal center axis 32 of the ignition element 29 relative to the longitudinal center axis 14 of the main portion 9 about a transverse axis Q, which is aligned perpendicularly to the longitudinal center axis 14 of the main portion 9 and the vertical axis H and runs through the ignition element 29.

[0038] According to the exemplary embodiment shown in FIG. 1, the pitch angle is approximately 20. However, a different pitch angle can also be provided. Preferably, the pitch angle is in an angular range that begins with 0 and ends with 70, particularly preferably in an angular range that begins with 20 and ends with 30.

[0039] The yaw angle of the ignition element 29 can be seen in FIG. 5. In the present case, the yaw angle is approximately 30. Preferably, the yaw angle is in an angular range that begins with 0 and ends with 45, particularly preferably in an angular range that begins with 10 and ends with 30. If the yaw angle is not equal to 0, the third side wall 43 and the fourth side wall 44 are aligned obliquely according to the yaw angle .

[0040] The functionality of the burner 5 is explained in more detail below with reference to FIG. 4. FIG. 4 shows the flow direction of the fresh-air/fuel mixture 27 in the combustion chamber 7. As can be seen in FIG. 4, the fresh-air/fuel mixture 27 flows in the sense of a swirl flow 33 through the cylindrical main portion 9 of the combustion chamber 7. The swirl flow 33 is generated by a swirl grid 47, which is arranged in the fresh-air line 23 upstream of the fresh-air inlet 24. At an opening area 15 of the bulge 10 that faces the main portion 9, a momentum exchange takes place between the swirl flow 33 in the main portion 9 and the gas volume of the bulge 10. The momentum exchange is facilitated by the rounding 50 in the third side wall 43. Due to the advantageous yaw angle , the flow direction of the fresh-air/fuel mixture 27 is perpendicular to the longitudinal center axis 32 of the ignition element 29, as can be seen in FIG. 5. The momentum exchange generates, in the bulge 10, a recirculation flow 35, which rotates in the opposite direction in relation to the swirl flow 33, in the bulge 10. The recirculation flow 35 has a reduced flow velocity in comparison to the swirl flow 33. Due to the lower flow velocity in the bulge 10, the convective heat transfer from the ignition element 29 is reduced in comparison to an arrangement of the ignition element 29 in the main portion 9. As a result, effective heating of the fresh-air/fuel mixture 27 can be achieved by means of the ignition element 29. This causes the fuel 18 of the fresh-air/fuel mixture 27 to evaporate quickly in the region of the bulge 10, which ultimately leads to quick ignition of the fresh-air/fuel mixture 27 at the same glow plug 29.

[0041] FIG. 6 is a longitudinal section through the burner 5 according to a further exemplary embodiment. In the burner 5 shown in FIG. 6, the pitch angle is 0. This results in the advantage that the radial extension of the combustion chamber 5 can be reduced.

[0042] FIG. 7 is a sectional view of the burner 5 according to a further exemplary embodiment. In the burner 5 shown in FIG. 7, the yaw angle is 0. This embodiment of the burner 5 is structurally particularly simple to realize.