Exhaust gas burner and exhaust gas aftertreatment system

Abstract

The invention relates to an exhaust gas burner (10) for an exhaust gas aftertreatment system (1) of an internal combustion engine (2), comprising a housing (22), in which a combustion chamber (11) is formed, in which a mixture of an oxygen-containing gas and fuel can be burned to form a heating gas, wherein at least one injection valve (12) for injecting the fuel into the combustion chamber (11) and an ignition device (14) for igniting the injected fuel are arranged on the combustion chamber (11), and wherein the combustion chamber (11) comprises a gas inlet (13) for the gas and a heating gas outlet (15) for the heating gas, wherein the heating gas outlet (15) is formed by a tubular heating gas guide (26) which projects with the heating gas outlet (15) from the housing, and comprising a fastening flange (14), assigned to the heating gas outlet (15), for connecting the exhaust gas burner (10) to an inlet pipe (25) of the exhaust gas aftertreatment system (1). According to the invention, the heating gas guide (26) has a constant cross section along the entire longitudinal extension thereof or a cross section that only widens or only tapers in the direction of the heating gas outlet (15).

Description

[0001] Description

[0002] title

[0003] Exhaust gas burner and exhaust gas aftertreatment system

[0004] The present invention relates to an exhaust gas burner for an exhaust gas aftertreatment system of an internal combustion engine, comprising a housing in which a combustion chamber is formed in which a mixture of an oxygen-containing gas and fuel can be combusted to form a heating gas, wherein at least one injection valve for injecting the fuel into the combustion chamber and an ignition device for igniting the injected fuel are arranged on the combustion chamber, and wherein the combustion chamber has a gas inlet for the gas and a heating gas outlet for the heating gas, wherein the heating gas outlet is formed by a tubular heating gas guide which projects from the housing with the heating gas outlet, and with a mounting flange associated with the heating gas outlet for connecting the exhaust gas burner to an inlet pipe of the exhaust gas aftertreatment system.

[0005] Furthermore, the invention relates to an exhaust aftertreatment system for an internal combustion engine of a motor vehicle, comprising at least one exhaust aftertreatment device, in particular a catalyst or filter, and an exhaust burner flow-technically positioned upstream of the exhaust aftertreatment device.

[0006] Disclosure of the invention

[0007] The exhaust gas burner according to the invention, with the features of claim 1, offers the advantage of cost-effective and simplified manufacturing. In particular, machining steps for semi-finished products are eliminated. This results, among other things, in a quality guarantee necessary for mass production. The invention makes the exhaust gas burner component that is subjected to the highest thermal stress during operation particularly robust and, at the same time, simple. According to the invention, the flue gas guide has a constant cross-section along its entire longitudinal extent or a cross-section that widens or narrows only in the direction of the flue gas outlet. The flue gas guide is thus either designed as a cylindrical body with a cross-section that does not change over its entire longitudinal extent, or a cross-section that has at least overlaps and widens or narrows only in one direction.This simplifies both the manufacturing and assembly of the flue gas routing in the exhaust gas burner and ensures a particularly robust component.

[0008] Preferably, the flue gas guide has at least one spacer on its section located inside the housing, which rests against an inner surface of the housing. The spacer ensures the position of the flue gas guide within the housing and, in particular, allows it to be adjusted to maintain a radial distance between the flue gas outlet, the housing, and any other mounting flange.

[0009] Preferably, the at least one spacer is attached to the flue gas duct, particularly by a material bond, as a support element projecting radially outwards from the flue gas duct. Thus, the spacer projects radially from the flue gas duct, and in particular, the spacer lies in a plane perpendicular to the longitudinal extent of the flue gas duct.

[0010] Furthermore, it is preferably provided that the aforementioned section within the housing has several spacers arranged around the circumference of the flue gas guide, particularly evenly distributed. These spacers are designed like the spacer described above and are attached to the flue gas guide. By providing several spacers distributed around the circumference, it is ensured that the flue gas guide remains securely held in the desired position within the housing, even under unexpected external force. According to an alternative embodiment, the at least one spacer preferably extends in a ring shape around the entire circumference of the flue gas guide. This ensures that the spacer rests against the inside of the housing, particularly around its entire circumference, and guarantees a secure and robust mounting of the flue gas guide within the exhaust gas burner.Furthermore, the continuous design of the spacer extending across the circumference, which in this respect forms a spacer ring, ensures that the combustion chamber spacer is limited and the flow of heating gas can only leave the combustion chamber through the heating gas guide.

[0011] The flue gas path is preferably straight. This ensures that the flue gas path is aligned parallel to the longitudinal axis of the exhaust gas burner and guarantees a constant radial distance to the combustion chamber housing, particularly across the entire circumference. This design offers the advantage of simple and cost-effective manufacturing, as the flue gas path can be, and preferably is, designed as a flue gas pipe with a constant cross-section.

[0012] According to a further embodiment of the invention, the heating gas passage extends parallel to the housing. This results in the advantage already mentioned above.

[0013] According to an alternative embodiment of the invention, the flue gas guide preferably extends at an angle to the housing. This inclined design directs the flue gas flow in a desired direction. The flue gas guide itself remains straight, thus preserving the advantages in terms of manufacturing and assembly.

[0014] According to a further embodiment, the flue gas guide preferably has at least one curvature in its longitudinal path or a curved longitudinal path. This directs the flue gas in the desired direction, with the curvature ensuring that the flue gas flow can be deflected in any direction. Preferably, the at least one spacer extends in a plane perpendicular to the longitudinal path of the flue gas guide.

[0015] According to an alternative embodiment of the invention, the at least one spacer extends radially in a straight line. This provides a simple and robust spacer.

[0016] According to a further embodiment, at least one spacer is inclined to a plane extending perpendicular to the longitudinal extent of the flue gas passage. This can result in advantages in terms of assembly technology and, for example, provide a connection to the housing that advantageously takes into account temperature-related deformation.

[0017] According to a further embodiment of the invention, the spacer has at least one curvature. For example, the spacer is convex or concave in longitudinal section, which allows, for example, temperature-related changes in length to be advantageously compensated by the spacer.

[0018] The exhaust gas aftertreatment system according to the invention, comprising the features of claim 14, is characterized by the design of the exhaust gas burner according to the invention. The advantages already mentioned above result.

[0019] Further advantages and preferred features and combinations of features will become apparent in particular from the above description and from the claims. The invention will now be explained in more detail with reference to the drawing.

[0020] This shows

[0021] Figure 1 shows an advantageous exhaust aftertreatment system in a simplified representation.

[0022] Figure 2 shows an enlarged view of an exhaust gas burner of the exhaust gas aftertreatment system, Figures 3A to D show different embodiments of the

[0023] Exhaust gas burner from Figure 2,

[0024] Figures 4A to H show further embodiments of the exhaust gas burner,

[0025] Figure 5 shows another embodiment of the exhaust gas burner,

[0026] Figures 6A to D show further embodiments of the exhaust gas burner,

[0027] Figure 7 shows an embodiment of a heating gas routing system of the

[0028] exhaust burner

[0029] Figure 8 shows a schematic representation of the heating gas flow.

[0030] Figure 9 shows another embodiment of the exhaust gas burner with a lambda probe.

[0031] Figures 10A to D show further embodiments of a flue gas routing system for the exhaust gas burner.

[0032] Figure 1 shows a simplified representation of an advantageous exhaust aftertreatment system 1 for an internal combustion engine 2 of a motor vehicle, which in this case is designed as a reciprocating piston engine. The internal combustion engine 2 is associated with a fresh air intake tract 3 and an exhaust exhaust tract 4. From the exhaust valves of the internal combustion engine 2, an exhaust pipe 5 of the exhaust exhaust tract 4 leads to several exhaust aftertreatment devices 6, 7, and 8 of the exhaust aftertreatment system 1. In this case, viewed in the direction of flow, the first exhaust aftertreatment device 6 is a three-way catalytic converter, the second exhaust aftertreatment device 7 is a second three-way catalytic converter, and the third exhaust aftertreatment device 8 is a particulate filter. The exhaust aftertreatment devices 6, 7, and 8 are sequentially supplied with exhaust gas from the internal combustion engine and serve to reduce pollutant emissions and particulate matter in the exhaust gas.To ensure that the exhaust aftertreatment devices 6, 7, 8 reach their optimal operating temperature as quickly as possible, particularly after a cold start of the internal combustion engine 2, a heating device 9 with an exhaust gas burner 10 of the exhaust aftertreatment system 1 is also assigned to the exhaust tract 4. The exhaust gas burner 10 has a combustion chamber 11 to which fuel can be supplied via an injection valve 12 and oxygen-containing gas, in this case air, via a gas inlet 13, for example by means of a gas guide device, in order to be ignited and burned in the combustion chamber by means of an ignition device 14. The combusted fuel / air mixture is fed into the exhaust tract 4 upstream of the first catalyst 6 via an outlet opening 15 of the exhaust gas burner 10, so that the heated gas mixture already increases the operating temperature of the exhaust aftertreatment devices 6, 7, 8 before the internal combustion engine 2 itself has reached its required operating temperature.

[0033] An adjustable valve assembly 16 is connected upstream of the exhaust gas burner 10, by means of which the supplied airflow can be adjusted. An air pump or air supply device 17 is advantageously arranged upstream of the valve assembly 16, by means of which fresh air is drawn in and conveyed towards the valve assembly 16. An air mass meter 18 and an air filter 19 are also connected upstream of the air supply device 17.

[0034] A control unit 20 of the heating system controls and operates the air mass meter 18, the air pump 17, the valve assembly 16, and the exhaust gas burner 10 to generate the desired amount of hot gas resulting from the combustion of the air-fuel mixture. This hot gas is supplied to the exhaust tract 4 to heat the exhaust aftertreatment devices 6, 7, and 8. The control unit 20 communicates with a control unit 21 of the internal combustion engine. Figure 2 shows a simplified longitudinal section of the exhaust gas burner 10. The exhaust gas burner 10 has a housing 22 in which the combustion chamber 11 is formed. The aforementioned gas guide, which in this embodiment surrounds and preferably supports the injection valve 12, is not shown for clarity, nor is the ignition device 14. The housing 22 is essentially cylindrical, in particular circular cylindrical.At its end associated with the flue gas outlet 15, the housing 22 has a taper 23 in its longitudinal dimension. A mounting flange 24 is arranged or formed on the housing 22 at this tapered free end, serving to connect the housing 22, and thus the exhaust gas burner 10, to an inlet pipe 25 of the exhaust gas aftertreatment system 4. Preferably, the mounting flange is formed integrally with the housing 22 of the exhaust gas burner 10. The inlet pipe 25 is, for example, the exhaust gas pipe 5 or an inlet pipe branching off from the exhaust gas pipe 5.

[0035] The flue gas outlet 15 itself is formed by a flue gas guide 26, which is essentially tubular and lies partially within the housing 22. According to the present embodiment, the flue gas guide 26 has an orifice 27 at its end located in the housing 22 or the combustion chamber 11, which radially limits the combustion chamber 11 in certain areas. The orifice 27 extends in an annular shape over the entire circumference of the flue gas guide 26 and rests against an inner surface 28 of the housing 22 on its outer side. In longitudinal section, the orifice 27 has a V-shaped longitudinal section that widens towards the flue gas outlet 15. Thus, the orifice 27 has an opening 38 from which the diameter of the orifice 27 initially widens until it reaches the inner surface 28 of the housing 22.Longitudinally spaced from the orifice 27, a funnel section 29 is formed in the flue gas duct 26, in which the diameter of the flue gas duct 26 decreases again towards the flue gas outlet 15, in this case back to the dimension of the opening 38. The diameter of the flue gas outlet 15 is thus also smaller than the diameter of the inlet pipe 25 and the housing 22 in the area of ​​the mounting flange 24. This creates a kind of chamber between the orifice 27 and the funnel section 29. Because the diameter of the orifice 27 widens to such an extent that the flue gas duct 26 reaches the inner surface 28 of the housing 22, the tubular flue gas duct 26, together with the funnel section 29 and the orifice 27, forms a spacer 30 extending over the entire circumference of the flue gas duct 26.The spacer 30 ensures that the flue gas outlet 15, located in the tapered section downstream of the funnel section 29, is spaced apart from the mounting flange 24. This radial distance x ensures thermal decoupling between the flue gas outlet and the mounting flange 24.

[0036] The mounting flange 24, which connects the exhaust gas burner 10 to the exhaust gas aftertreatment system 4 and is welded to a counter-mounting flange 31 of the inlet pipe 25, is thus advantageously protected from the hot exhaust gases of the exhaust gas burner 11, which exit the flue gas outlet 15 downstream of the mounting flange. The mounting flange 24 is arranged axially offset from the flue gas outlet 15, in particular by means of the spacer 30, and is radially spaced from it. This ensures that the weld between the mounting flange 24 and the mounting flange 31 is reliably protected from material fatigue caused by heat.

[0037] Figures 3A to D show different embodiments of the exhaust gas burner 10, each in a simplified longitudinal section view. Elements known from the previously described embodiment are identified here and in the subsequent figures with the same reference numerals, so reference is made to the description above. The following discussion will focus primarily on the differences.

[0038] The embodiment shown in Figure 3A corresponds to the embodiment shown in Figure 2, except that the inlet pipe 25 is not shown. The orifice 27 forms a so-called flame wall 32, which, among other things, prevents liquid fuel located on the inside 28 of the housing 22 from entering the downstream exhaust aftertreatment tract through the hot gas outlet 15. Furthermore, the flame wall 32, or the orifice 27, prevents a flame generated by combustion in the combustion chamber 11 from traveling along the housing wall of the housing 22 to the mounting flange 24 and causing undesirable heating there.

[0039] In contrast, the embodiment shown in Figure 3B depicts a flue gas guide 26 that has a cross-section, in particular diameter, that is constant along its entire length. In this case, the flue gas guide 26 is circular.

[0040] To ensure the radial distance between the flue gas outlet 15 and the housing or the mounting flange 24, the flue gas guide 26 has one or more spacers 30 on its section located inside the housing 22. These spacers are formed by radially projecting support elements 33. The support elements 33 are attached at one end to the flue gas guide 26 and at the other end rest against the inner surface 28 of the housing 22, and are preferably permanently connected to it, for example by welding. In this embodiment as well, the spacers 30 advantageously ensure the radial distance x between the flue gas outlet 15 and the mounting flange 24.While in the previous embodiment the heating gas outlet 15 is located downstream of the mounting flange 24, according to the present embodiment of Figure 3B the heating gas outlet 15 is arranged or designed at the level of or only slightly upstream of the mounting flange 24.

[0041] The initial example in Figure 3C is characterized by a larger diameter for the flue gas channel 26 than in the embodiment shown in Figure 3B. In the embodiment shown in Figure 3D, the diameter of the flue gas channel 26 is even larger than in the preceding embodiments. This results in a gradual reduction of the radial distance between the flue gas outlet and the mounting flange 24 from the embodiments shown in Figure 3B to Figure 3D. However, a sufficient radial distance x is always maintained for thermal coupling. Optionally, in these and the following embodiments, only one spacer 30 is provided, extending over the entire circumference of the circular flue gas channel 26.

[0042] Figures 4A to H show further embodiments of the exhaust gas burner 10, each in a longitudinal section view. These are variants of the exhaust gas burner 10 according to the embodiment shown in Figure 3C. The embodiment shown in Figure 4A differs from the previous embodiment in that the spacer(s) 30 shown in the embodiment of Figure 3C, which extend radially in a plane perpendicular to the longitudinal extent of the flue gas channel 26, are now inclined to this plane. In the example shown in Figure 4A, the spacers 30 form an angle of less than 90° with the flue gas channel 26, with the angle being upstream of the spacers 30.

[0043] According to the embodiment shown in Figure 4B, the spacer(s) 30 are inclined in opposite directions. In the embodiments shown in Figures 3B to D and 4A and B, the spacers are arranged at intervals from the inner end of the flue gas channel 26 in the housing 22. In contrast, the embodiment shown in Figure 4C shows the spacer(s) 30 being arranged directly at the end of the flue gas channel 26 of the housing 22 and inclined in one direction or the other, or aligned in the plane perpendicular to its longitudinal extent. Figure 4C shows the embodiment in which the spacer(s) 30 are aligned as in the embodiment shown in Figure 4B.

[0044] The embodiment shown in Figure 4D differs from the previous embodiment in that the hot gas guide 26 does not extend parallel to the longitudinal axis of the combustion chamber 11 and thus parallel to the flow direction of the exhaust gas burner 10, but is inclined at an angle to it.

[0045] The embodiment shown in Figure 4E differs from the embodiment shown in Figure 3C, in particular, in that the flue gas guide 26 projects axially from the housing 22 of the exhaust gas burner 10, ensuring an axial distance y from the flue gas outlet 15 to the mounting flange 24, as already explained for the embodiments shown in Figures 2 and 3A. According to the embodiment shown in Figure 4F, the flue gas guide 26 has a curvature 37 at its downstream end section, which directs the flue gas in a desired direction.

[0046] The embodiments shown in Figures 4G and 4H differ from the embodiment shown in Figure 3C in particular in that the spacer(s) 30 each have a curvature radially outwards in their course, whereby the respective spacer 30 is concave or convex in longitudinal section.

[0047] Figure 5 shows a further embodiment that differs from the previous ones in that the flue gas guide 26 extends significantly further out of the housing 22 in order to maximize the distance y between the flue gas outlet 15 and the mounting flange 24. This also provides air gap insulation between the flue gas guide 26 and the inlet pipe 25 of the exhaust gas aftertreatment system 1.

[0048] Figures 6A to 6D show further embodiments of the exhaust gas burner 10, which differ in the design of the flue gas guide 26. These embodiments have in common that the cross-section or diameter of the flue gas guide 26 either increases only (Figures 6A to C) or decreases only (Figure 6D) in the direction of the flue gas outlet. According to Figure 6A, the flue gas guide 26 is conical with a cross-section that widens in the direction of flow. According to the embodiment shown in Figure 6B, the flue gas guide 26 is diffuser-shaped with a widening cross-section, the cross-section widening due to a curvature along its length. In this embodiment, the outer wall of the flue gas guide 26 is curved outwards.According to the embodiment shown in Figure 6C, the flue gas guide 26 is also designed in a diffuser-like manner, whereby in this case the curvature of the outer wall in the longitudinal direction of the flue gas guide 26 is convexly curved towards the flue gas outlet, so that the diameter widening in the longitudinal direction decreases. The embodiment shown in Figure 6D is characterized in that the cross-section or diameter of the flue gas guide 26 decreases towards the flue gas outlet 15, and here the flue gas guide 26 is also conically shaped.

[0049] Figure 7 shows an optional embodiment of the flue gas guide 26, in which several rings are drawn, each showing the cross-sectional shape of the flue gas guide 26 at different points along its longitudinal extent. The rearmost ring shows the contour or cross-sectional shape of the flue gas outlet 15, and the foremost ring shows the cross-sectional shape of the inlet opening 38 of the flue gas guide 26. This embodiment is characterized by the fact that the cross-section changes along the longitudinal extent of the flue gas guide 26 from the opening 38 to the flue gas outlet 25. Thus, according to the present embodiment shown in Figure 7, the cross-section at the inlet or opening 38 is circular, and the cross-section at the flue gas outlet 15 is oval. The cross-sectional shape is continuously changed or adapted from the opening 38 to the flue gas outlet 15.

[0050] Optionally, the cross-sectional area at the flue gas outlet 15 is at least as large, preferably larger, than the cross-sectional area of ​​the opening 38. According to another initial example, the cross-sectional areas at the inlet and outlet are always the same size, regardless of their shape or contour.

[0051] Figure 8 shows another longitudinal section of the exhaust gas burner 10 in the area of ​​the flue gas outlet 15, where the flow behavior of the flue gas is simplified. In addition to the previously described thermomechanical improvement resulting from the functional separation between the mounting flange 24 and the flue gas guide 26, ensured by the radial distance x between the flue gas guide 26 and the mounting flange 24, a geometric diameter change also occurs at the flue gas outlet 15. This results in the simplified flow behavior shown in Figure 8. This, in turn, offers improved possibilities for the standardized integration of a lambda probe at the burner outlet.A key feature of the preferred lambda probe arrangement is that it is not located in the main mass flow of the flue gas, but rather in a peripheral region of the main flow where increased turbulence occurs, as shown in Figure 8. This significantly reduces the temperature input from the flue gas to the lambda probe compared to standard or previously known solutions. Therefore, despite the high flue gas temperatures, a lambda probe can be safely positioned at the burner outlet or flue gas outlet 15.

[0052] Figure 9 shows an embodiment in which a lambda probe 34 is arranged on the inlet pipe 25 close to the mounting flange 31, particularly in the area so close to the flue gas outlet 15 that it is not in the main flue gas flow, as described above. Optionally, the inlet pipe 25 is also an adapter pipe that can be inserted between the exhaust gas aftertreatment system 4 and the exhaust gas burner 10, and can be adapted to different boundary conditions, for example, to allow for an advantageous flue gas routing and / or arrangement of a lambda probe 34.

[0053] To enable improved integration of the lambda probe 34 into the heating gas flow without unintentionally increasing the temperature load on the lambda probe significantly, the heating gas guide 26 preferably has a bypass opening 35 in the funnel section 29, which leads into the space between the heating gas outlet 15 and the mounting flange 24, so that a partial heating gas flow is supplied to the lambda probe 34 through the bypass opening 35. The arrangement of the bypass opening 35 is selected such that the heating gas flow advantageously affects the lambda probe 34.

[0054] Figures 10A to D show different embodiments for the realization of the bypass opening 35, in which the end section of the hot gas guide 26 is shown with the hot gas guide 25.

[0055] According to the embodiment shown in Figure 10A, the bypass opening 35 is arranged as a simple bore or recess with a closed outer edge in the funnel section 29 or in the end section, spaced apart from the heating gas outlet 15. 212263 POT

[0056] - 14 -

[0057] According to the embodiment shown in Figure 10B, the bypass opening 35 is designed as a V-shaped indentation or recess on its end face, such that the bypass opening 35 is open towards the flue gas outlet 15. According to the embodiment shown in Figure 10C, an air guide element 36 is associated with the bypass opening 35. In this embodiment, the air guide element 36 is bent inwards and is arranged at the downstream end of the bypass opening 35 in the direction of flue gas flow, as indicated by the arrows in Figures 10A to D. Thus, the air guide element 36 lies within the flue gas flow inside the flue gas guide 26 and directs a portion of the flue gas flow from the flue gas guide 26 through the bypass opening 35. In particular, the air guide element 36 is designed as a stamped and bent part, such that it is cut out of the outer wall of the flue gas guide 26 and bent into the flue gas guide 26.

[0058] The embodiment shown in Figure 10D differs from the previous embodiment in that the air guide element 36 is not bent inwards, into the hot gas guide 26, but outwards.

Claims

Claims 1. Exhaust gas burner (10) for an exhaust gas aftertreatment system (1) of an internal combustion engine (2), comprising a housing (22) in which a combustion chamber (11) is formed, in which a mixture of an oxygen-containing gas and fuel can be combusted to form a heating gas, wherein at least one injection valve (12) for injecting the fuel into the combustion chamber (11) and an ignition device (14) for igniting the injected fuel are arranged on the combustion chamber (11), and wherein the combustion chamber (11) has a gas inlet (13) for the gas and a heating gas outlet (15) for the heating gas, wherein the heating gas outlet (15) is formed by a tubular heating gas guide (26) which projects from the housing (22) along with the heating gas outlet (15), and with a mounting flange (14) associated with the heating gas outlet (15) for connecting the exhaust gas burner (10) to an inlet pipe (25) of the exhaust aftertreatment system (1), characterized in thatthat the flue gas duct (26) has a constant cross-section along its entire longitudinal extent or a cross-section that only widens or only narrows in the direction of the flue gas outlet (15).

2. Exhaust gas burner according to claim 1, characterized in that the flue gas guide (26) has at least one spacer (30) on its section lying inside the housing (22), which rests against an inner side (28) of the housing (22).

3. Exhaust gas burner according to one of the preceding claims, characterized in that the at least one spacer (30) is attached to the flue gas guide (26) in a support element (33) projecting radially from the flue gas guide (26), in particular by a material bond.

4. Exhaust gas burner according to one of the preceding claims, characterized in that the section has several sections extending over the circumference of the The flue gas guide (26) has, in particular, uniformly distributed spacers (30).

5. Exhaust gas burner according to one of the preceding claims, characterized in that the at least one spacer (30) extends in a ring shape over the entire circumference of the flue gas guide (26).

6. Exhaust gas burner according to one of the preceding claims, characterized in that the heating gas flow (26) is straight.

7. Exhaust gas burner according to claim 6, characterized in that the heating gas guide (26) extends parallel to the housing (22).

8. Exhaust gas burner according to claim 6, characterized in that the heating gas guide (26) extends inclined to the housing (22).

9. Exhaust gas burner according to one of the preceding claims, characterized in that the flue gas guide (26) has at least one curvature (37) in its longitudinal path.

10. Exhaust gas burner according to one of the preceding claims, characterized in that the at least one spacer (30) extends in a plane perpendicular to the longitudinal extent of the flue gas guide (26).

11. Exhaust gas burner according to one of the preceding claims, characterized in that the at least one spacer (30) extends in a straight line.

12. Exhaust gas burner according to one of the preceding claims, characterized in that the at least one spacer (30) extends inclined to a plane perpendicular to the longitudinal extent of the flue gas path.

13. Exhaust gas burner according to one of the preceding claims, characterized in that the at least one spacer (30) has at least one curvature. - 17 - 14. Exhaust aftertreatment system (1) for an internal combustion engine (2) of a motor vehicle, comprising at least one exhaust aftertreatment device (6, 7, 8), in particular a catalyst or filter, and comprising one of the Exhaust gas aftertreatment device (6,7,8) flow-technically upstream exhaust gas burner (10), characterized in that the exhaust gas burner (10) is designed according to one of claims 1 to 13.

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