Exhaust gas burner for an exhaust gas aftertreatment system, method for operation

Abstract

The invention relates to an exhaust gas burner (10) for an exhaust gas aftertreatment system (1) of an internal combustion engine (2), with a combustion chamber (11) in which a mixture of an oxygen-containing gas and fuel can be combusted to form a heating gas, wherein the combustion chamber (11) is assigned at least one injection valve (12) for injecting the fuel into the combustion chamber (11) and an ignition device (14) for igniting the mixture, wherein the combustion chamber (11) is assigned a gas inlet (25) for the gas and a heating gas outlet (15) for the heating gas, and wherein the gas inlet (25) is assigned an air guide device (13) which has an air guide channel (22) at one end of which a particularly rigid swirl device (24) is arranged, through which the gas enters the combustion chamber (11).It is provided that the air guidance device (13) upstream of the swirl device (24) has at least one air guidance element (29) in the air guidance channel (22) which is adjustable at least in such a way that, depending on the position of the air guidance element (22), the oxygen-containing gas hits the swirl device (24) in a uniformly or unevenly distributed manner.

Description

The present invention relates to an exhaust gas burner for an exhaust gas aftertreatment system of an internal combustion engine, having a combustion chamber in which a mixture of an oxygen-containing gas and fuel to form a heating gas can be burned, wherein at least one injection valve for injecting the fuel into the combustion chamber is assigned to the combustion chamber, wherein a gas inlet for the gas and a heating gas outlet for the heating gas are assigned to the combustion chamber, and wherein an air guide device is assigned to the gas inlet, said air guide device having an air guide duct, at one end of which a swirl device is arranged, through which the gas reaches the combustion chamber.Furthermore, the invention relates to a method for operating an exhaust gas burner and an exhaust gas aftertreatment system as described above.Prior ArtExhaust gas burners of the type mentioned at the beginning are already known from the prior art. For example, German Offenlegungsschrift DE 19 504 208 A1 discloses an exhaust gas burner which is fluidically connected upstream of a catalytic converter of an exhaust gas aftertreatment system for an internal combustion engine. The exhaust gas burner has a combustion chamber to which air and fuel are supplied and are burned in the combustion chamber with the aid of an ignition device in order subsequently to be added or mixed with the exhaust gas stream upstream of the catalytic converter as heating gas. This ensures that the catalytic converter is heated up to an advantageous operating temperature particularly quickly. A similar solution is also proposed in the laid-open specification DE 10 2009 053 379 A1. In this case, a guide device is also assigned to the combustion chamber, by means of which the oxygen-containing gas is introduced into the combustion chamber.In order to ensure advantageous mixing of the gas with the fuel, the guide device frequently has a swirl device with a so-called swirl grid, by means of which the inflowing gas is guided into a swirling movement within the combustion chamber. The gas thus rotates through the combustion chamber and thereby mixes particularly advantageously with the fuel, so that homogeneous combustion is ensured. For this purpose, the swirl grille has swirl elements or air guiding elements which lead to a fixedly set swirl factor, in particular swirl number.Disclosure of the InventionThe present invention has the advantage that, despite the use of a swirl device with a rigid swirl grid, advantageous operation of the exhaust gas burner can be optimally set at different operating points, in particular for starting operation and for continuous operation. The exhaust gas burner according to the invention offers the advantage of a cost-effective system with an in particular rigid swirl device and variable swirl cones. According to the invention, it is provided for this purpose that the air guiding device has, upstream of the swirl device, at least one air guiding element in the air guiding duct, which air guiding element is adjustable at least in such a way that, depending on the position of the air guiding element, the oxygen-containing gas impinges on the swirl device in a uniformly or non-uniformly distributed manner. The air guiding element located upstream of the swirl device thus ensures that the oxygen-containing gas flows against the swirl device differently during operation depending on the position of the air guiding element. Thus, the air guiding element can be adjusted in particular such that the gas impinges uniformly on the swirl device, resulting in a uniform swirl cone which leads in particular to advantageous uniform combustion of the gas-fuel mixture in the combustion chamber, and in particular can be adjusted such that the gas impinges on the swirl device in an unevenly distributed manner and thus forms an equally uneven swirl cone. In the present case, the uniform and non-uniform impingement on the swirl device is understood in particular in such a way that the swirl device has an inflow surface which lies at least substantially perpendicular to the flow axis or direction of the air guide duct. By adjusting the air guiding element, this inflow surface is evenly or non-uniformly distributedly impinged by the gas, resulting in a corresponding swirl cone downstream of the swirl device. The uneven impingement of the swirl device with the gas ensures that, for example, a region of the swirl device is recessed by the gas stream, so that no swirl flow is formed in this region either. This region is preferably situated in the vicinity of or in the region of an ignition device of the combustion chamber. This ensures that in this region there is a less strong swirl or no swirl in the gas flow, so that fuel which is injected by the injection valve into the combustion chamber in the direction of the ignition device is also not carried away from the glow plug by the low or non-present swirl in this region. A fuel jet is thus produced which is focused on the ignition device and ensures the ignition of the gas-fuel mixture in the combustion chamber. If, on the other hand, the air guiding element is adjusted in such a way that the gas strikes the inflow surface of the swirl device uniformly, a uniform or homogeneous jet is also produced in the combustion chamber, which leads to advantageous mixing of fuel and gas, so that overall a homogeneous gas-fuel distribution is produced in the combustion chamber, which leads to advantageous combustion during ongoing operation.According to a preferred development of the invention, an actuatable actuator is assigned to the air guiding element, by means of which actuator the air guiding element can be fixed in a plurality of positions in the air guiding channel for directing the gas flow. The air guiding element can thus be fixed in a plurality of positions by the actuator in order to influence the air flow for a selectable period of time in the respective position. This ensures that the desired operation of the exhaust gas burner is maintained for the necessary or desired period of time.Particularly preferably, the air guiding element is designed as a flap which is mounted pivotably in the air guiding channel. The design as a flap results in an advantageous air flow function of the air guiding element depending on its pivoted position. In particular, the air guiding element is designed in the manner of a throttle valve and in particular designed in such a way that, if required, the air guiding duct can also be completely closed.Particularly preferably, a pivot axis of the flap or of the air guiding element is at least substantially eccentric in the air guiding channel. The off-center position results in different sized flow cross sections being released in the air guiding channel above and below the axis of rotation when the air guiding element is pivoted. This has the effect, in particular, that the gas flow through the air guiding element is directed, depending on its pivoted position, at or against a selected inner side, in particular upper side or lower side of the air guiding channel and as a result strikes the inflow surface of the swirl device asymmetrically or non-uniformly.Furthermore, it is preferably provided that the air guiding element and the air guiding channel are formed in such a way that the air guiding element completely closes the air guiding channel in a first position. The air guiding element thus acts simultaneously as a shut-off valve of the exhaust gas burner, which prevents a return flow of heating gas if necessary.Furthermore, it is preferably provided that the air guiding element and the air guiding channel are designed such that the air guiding element in a second position frees the air guiding channel in regions and is oriented inclined to the flow direction of the air guiding channel, in particular at least in the region of the air guiding element. Due to the inclined alignment, the air flow is advantageously directed against one side of the air guide duct in order to advantageously ensure the unevenly distributed inflow to the swirl device.Furthermore, it is preferably provided that the air guiding element and the air guiding channel are designed in such a way that the air guiding element, in a third position, exposes the air guiding channel in regions and is oriented parallel to the flow direction of the air guiding channel, in particular at least in the region of the air guiding element. In this position, the maximum flow cross section of the air guide duct is released. Because the air guiding element itself lies in the air guiding channel, the entire flow cross section of the air guiding channel cannot be exposed. However, in the third position, the air guiding duct minimally influences the flow of the gas and in particular does not direct the gas flow at or against one side of the air guiding duct, rather a flow around the air guiding element takes place in such a way that downstream of the air guiding element an in particular homogeneous air flow distribution results in the air guiding duct and a uniformly distributed flow on the swirl device or its inflow surface. The third position of the air guiding element is preferably provided for the stationary burner operation of the exhaust gas burner, while the second position is provided in particular for a starting operation of the exhaust gas burner, in which a focused flow of the ignition device through the fuel is achieved by the non-uniform flow onto the swirl grid.Furthermore, it is preferably provided that at least one non-adjustable air guiding element is assigned to the adjustable air guiding element in the air guiding channel. The non-adjustable air guiding element, for example, achieves the effect that a flow cross section of the air guiding duct below the pivot axis of the air guiding element or on one side of the pivot axis of the air guiding element remains closed or at least substantially closed, even if the air guiding element is pivoted in the direction of the third position.Optionally, a non-adjustable air guiding element is preferably arranged downstream of the air guiding element, which leads to a separation of the partial flow or partial flows of the gas released by the air guiding element, which partial flow is also maintained downstream of the air guiding element. This results in an improved and focused incident flow to the swirl device. In particular, the air guiding element is designed as an air guiding plate which extends at least substantially downstream of the air guiding element in the flow direction. Optionally, the non-adjustable air guiding element extends from the pivotable air guiding element as far as the swirl device or almost to the swirl device.The method according to the invention for operating the exhaust gas burner is distinguished in that the adjustable air guiding element is adjusted as a function of a current operating state of the exhaust gas burner. This results in the advantages already mentioned above. In particular, the air guiding element is adjusted for a starting operation in such a way that it directs the gas flow non-uniformly onto the swirl device, in particular non-uniformly onto the inflow surface of the swirl grid, and for a burning operation or stationary operation in such a way that it directs the gas flow uniformly onto the swirl device, in particular uniformly onto the inflow surface of the swirl grid. The above-mentioned advantages result.Further advantages and preferred features and combinations of features emerge in particular from the description above and from the claims. The invention will be explained in more detail below with reference to the drawings. This is shown by FIG. 1 shows an advantageous exhaust gas aftertreatment system in a simplified illustration, FIG. 2 shows an advantageous exhaust gas burner of the exhaust gas aftertreatment system in a perspective illustration, FIGS. 3A to C show the exhaust gas burner in different operating states, in each case in a simplified illustration, FIGS. 4A and B show different operating states of the exhaust gas burner in a simplified cross-sectional illustration, respectively, FIG. 5 is a diagram for explaining an advantageous method for operating the exhaust gas burner, FIGS. 6A and B show different developments of the advantageous exhaust gas burner, each in a longitudinal sectional illustration, and FIG. 7 shows an enlarged detail view of the exhaust gas burner according to a further exemplary embodiment.FIG. 1 shows a simplified illustration of an advantageous exhaust gas aftertreatment system 1 for an internal combustion engine 2 of a motor vehicle, which is designed in the present case as a reciprocating piston engine. The internal combustion engine 2 is assigned a fresh air tract 3 and an exhaust tract 4. An exhaust pipe 5 of the exhaust tract 4 leads from the exhaust valves of the internal combustion engine 2 to a plurality of exhaust gas aftertreatment devices 6, 7 and 8 of the exhaust gas aftertreatment system 1, wherein in the present case, as seen in the direction of flow, the first exhaust gas aftertreatment device 6 is a three-way catalytic converter, the second exhaust gas aftertreatment device 7 is a second three-way catalytic converter and the third exhaust gas aftertreatment device 8 is a particle filter. The exhaust gas of the internal combustion engine flows through the exhaust gas after-treatment devices 6, 7, 8 in succession and serve to reduce pollutant emissions and particles of the exhaust gas.In order that the exhaust gas aftertreatment devices 6, 7, 8 reach their optimum operating temperature as quickly as possible, in particular after a cold start of the internal combustion engine 2, a heating device 9 with an exhaust gas burner 10 of the exhaust gas aftertreatment system 1 is furthermore assigned to the exhaust tract 4. The exhaust gas burner 10 has a combustion chamber 11 to which fuel and oxygen-containing gas, in particular air, can be supplied through an injection valve 12 and through a guide device 13 in order to be ignited and burnt in the combustion chamber with the aid of an ignition device 14. The burned fuel-air mixture is supplied through an outlet opening 15 of the exhaust gas burner 10 to the exhaust tract 4 upstream of the first catalytic converter 6, so that the heated gas mixture already increases the operating temperature of the exhaust gas aftertreatment devices 6, 7, 8 before the internal combustion engine 2 provides the exhaust gas enthalpy necessary for heating up the peripheral exhaust system.The exhaust gas burner 10 is preceded by an actuatable valve device 16, by means of which the supplied air flow can be adjusted. Upstream of the valve device 16, an air pump or air conveying device 17 is advantageously arranged, by means of which fresh air is sucked in and can be conveyed in the direction of the valve device 16. The air conveying device 17 is further preceded by an air mass flow meter 18 and an air filter 19.The air mass meter 18, the air pump 17, the valve device 16 and the exhaust gas burner 10 are controlled or operated by a control device 20 of the heating device in order to generate heating gas, i.e. a burnt air-fuel mixture, to the desired extent, which is supplied to the exhaust gas tract 4 for heating the exhaust gas aftertreatment devices 6, 7, 8. The control unit 20 is in particular in communication connection with a control unit 21 of the internal combustion engine.The valve device 16 forms a component of the air guiding device 13 in the present case, as will be discussed in more detail below.FIG. 2 shows the advantageous air guiding device 13 in a perspective illustration. The exhaust gas burner 10 is connected on the inlet side to the valve device 16 by an air guide duct 22. The valve device 16 has an actuatable actuator 23, which can be actuated in particular by the control unit 21 and / or 20. The actuator 23 is mechanically connected to an air guiding element 24, which is located in the air guiding duct 22 upstream of the exhaust gas burner 10. The air guide duct 22 opens into a swirl device 24, which forms a gas inlet 25 for the combustion chamber 11. The swirl device 24 has a rigid swirl grid 26 which is designed to set the inflowing gas into a swirling movement within the combustion chamber 11. For this purpose, the swirl grid 26 in the present case has a multiplicity of air guiding elements 27 which are arranged uniformly over the circumference of the gas inlet 25 and are aligned in such a way that the gas stream flowing through the swirl device 24 is set into the desired swirling movement, as is indicated by an arrow 28 in FIG. 2 by way of example. The air guiding elements 27 are located in a common plane perpendicular to the flow direction of the air guiding channel directly in front of the swirl device and thus form a common inflow surface which is oriented accordingly.FIGS. 3A to 3C show different operating states of the air guiding device 13, which can be achieved by the actuation of the actuator 23. The exhaust gas burner 10 together with the air guiding device 13 is shown in a longitudinal sectional illustration. As already mentioned above, the valve device 16 has a displaceable or adjustable valve element 29 in the form of a valve flap 30. In particular, the flap 30 is designed in the manner of a throttle flap. The flap 30 is mounted pivotably about a pivot axis 31 which extends transversely through the air guide channel 22. The pivot axis 31 preferably extends transversely or perpendicularly to the flow direction and is located in particular eccentrically in the air guide channel 22, i.e. does not pass through a center of the air guide channel 22, as seen in the cross section of the air guide channel.FIG. 3A shows an operating state in which the air guiding element 30 is pivoted by the actuator 23 into a position in which the air guiding element 30 or the flap extends parallel to the flow direction of the air guiding duct 22 in the region of the air guiding element 29 in order thus to free the maximum flow cross section of the air guiding duct 22.The air guide duct 22 is designed to supply the flow of the oxygen-containing gas to the swirl device 24 in this position of the air guide element 29, which is a release position or maximum position of the air guide element, in such a way that the gas flow uniformly acts on an inflow surface of the swirl grille, as viewed circumferentially. As a result, a uniform swirl of the gas flow occurs in the combustion chamber 11, which leads to advantageous mixing with the fuel likewise injected into the combustion chamber 11.In a second position, in particular a blocking position, the air guiding element 30 is pivoted by the actuator 23, as shown in FIG. 3A by a dashed line of the air guiding element 30, in such a way that it completely blocks the air guiding duct 22 and in particular prevents a return flow of hot gas from the combustion chamber 11.FIGS. 3B and 3C show intermediate positions or positions of the air guiding element 30, which are suitable for influencing the gas flow in such a way that an asymmetric swirl is produced in the exhaust gas burner 10, as is discussed in more detail below:According to the exemplary embodiment of FIG. 3B, the air guiding element 30 is pivoted in the paper plane counter-clockwise by more than 45° and by less than 90° from the position of FIG. 3A and into an inclined orientation in such a way that a flow cross section, even if only a small one, remains between the air guiding element 30 and the casing wall of the air guiding channel 22, through which the gas can flow into the downstream part of the air guiding channel 22 and reach the swirl device 24. Due to the reduced flow cross section, which is limited in particular to a region in the plane of the paper above the pivot axis 31, a gas flow through the air guide channel 22 results, which non-uniformly impinges on the inflow surface of the swirl grille 26, in particular in such a way that the swirl then arising in the combustion chamber 11 itself is incomplete or non-uniform.FIGS. 4A and 4B show, in comparison, the sequences of the different positions of the air guiding element 29 according to FIGS. 3A and 3B, in each case in a simplified cross-sectional illustration of the exhaust gas burner 10 in the region of the ignition device 14. The advantageous air guidance of the air guide duct 22 and the arrangement and position of the air guide element 30 result in the inflow surface of the swirl grille being acted upon non-uniformly by the gas in such a way that a strong swirling motion is produced in the combustion chamber, in particular only in regions which are situated at a distance from the ignition device 14, so that a region is produced in the region of the ignition device 14 in the combustion chamber 11, in which the swirling motion is formed in a reduced manner, as is indicated in FIG. 3B by flow surfaces of different sizes, which are drawn by arrows 28 which indicate the flow direction.The injection valve 12 is in particular an injection valve having a plurality of outlet openings, that is to say a so-called multi-hole valve. For example, the injection valve 12 has three outlet openings or injection openings, which each release a partial injection jet upon actuation of the injection valve 12. The injection valve 12 is arranged on the exhaust gas burner 10 in such a way that one of these partial injection jets is aligned with the ignition device 14 in the assembled state. Because in this region the swirl flow is reduced when the air guiding element 29 is inclined according to FIG. 3B, it follows that this one partial injection jet is less strongly influenced by the swirl than the other partial injection jets of the injection valve 12, which ensures that this partial injection jet is supplied to the ignition device 14 in a focused manner, and thus ensures particularly reliable and rapid ignition of the fuel. The further partial injection jets of the injection valve 12, which interact with the remaining part of the swirl cone of the inflowing gas, are, on the other hand, advantageously mixed with the oxygen-containing gas, so that overall an advantageous ignition of the air-fuel mixture in the combustion chamber 11 takes place.The adjustment of the air guiding element 30 thus results in the gas flow being adjustable at least in such a way that it is converted into a homogeneous swirl cone of the combustion chamber 11 or into an inhomogeneous swirl cone which is interrupted or reduced in particular in the region of the ignition device 14 in such a way that the fuel partial jet reaches the ignition device 14 in a focused manner.FIG. 3C shows a further exemplary embodiment which leads to the same or similar result, wherein the air guiding element 30 is pivoted not in the clockwise direction but in the counter-clockwise direction. This is achieved, for example, by a reverse installation of the valve device 16 or of the housing 34.The advantageous design results in the flow surfaces exposed in the plane of the drawing below and above the pivot axis 31 being of different sizes at a small opening angle. This has the result that the flow preferably flows past the top side and as a result asymmetrically acts on the swirl grid 26. The reduced enabled flow cross section is subject to pressure loss and is therefore disadvantageous for stationary combustion operation. For this, the air guiding element 30 is therefore preferably pivoted into the release position shown in FIG. 3A. For the starting process of the exhaust gas burner 1, however, the reduced flow cross section according to FIGS. 3B and 3C is advantageous in order to ensure the impaired swirl cone with focused fuel injection onto the ignition device 14 as explained above.The two designs according to FIGS. 3B and 3C are to be understood in particular as alternative designs; the air guiding element 30 is then pivotable in each case only in one direction into the position reducing the flow cross section. According to an optional exemplary embodiment, the valve device 16 is designed in such a way that the air guiding element 30 can be pivoted in both directions.The injection valve 12 is preferably designed and arranged in such a way that the fuel droplets of the fuel jet are deflected from the original direction during the injection hole outlet by the swirl of the gas, depending on their size and the associated flow followability. In a preferred design, at the level of the ignition location of the ignition device 14, a closed circular surface is achieved on the inner side of the jacket wall of the exhaust gas burner 11 in the combustion chamber 10 by combining the multiple jets of the injection valve 12.FIG. 5 shows, in a simplified diagram, the relationships between the air mass flow m L, the position of the throttle valve S between fully closed S 0 and fully or maximally opened S 1, and the gas pressure p at the valve device 16 over time t. The starting process of the exhaust gas burner 10 is characterized in that the injection process of the fuel preferably begins between t 0 and t 1 that is to say likewise at the time in which the air guiding element 29 is moved into a first open position. The combustion process preferably starts after approximately 100 μs after the injection begins, particularly preferably already with the very first injection. The time duration t 0 to t 1 is preferably a maximum of 2 seconds. The course of the throttle valve position, as shown in FIG. 5, is to be understood purely as an example.In addition, further structural changes can be made which optimize the starting process and the stationary burner operation.FIGS. 6A and 6B show for this purpose further exemplary embodiments of the exhaust gas burner 10 with the air guiding device 13, which are used for the purpose of improved focusing of the incident flow of the swirl device 24.According to the exemplary embodiment of FIG. 6A, a non-adjustable air guiding element 32 is arranged downstream of the air guiding element 30, in the present case in the form of an air guiding plate, which extends at least substantially parallel to the gas flow or the flow direction of the air guiding duct 22 downstream of the pivotable air guiding element 29.According to the exemplary embodiment of FIG. 6B, the non-adjustable air guiding element 32 extends from the adjustable air guiding element 30 as far as an air distribution chamber 33 upstream of the swirl device 24. The duct separation achieved by the air guiding element 32 has the result that up to a specific opening angle of the air guiding element 30, only one of the duct halves is flowed through primarily by the gas and, in the case of a complete opening of the air guiding element 30, as shown for example in FIG. 3, both partial ducts are flowed through, in particular in an equally distributed manner.In order to realize this separation even for larger opening angles of the air guiding element 30, for example in order to avoid pressure losses, it is provided according to a further exemplary embodiment, as shown in FIG. 7, that a further non-displaceable air guiding element 33 is arranged upstream of the air guiding element 30, which in this case serves as a closing element and is designed in such a way that it prevents the gas from flowing through or flowing past below the air guiding element 30, as viewed in the paper plane, for a predefined pivot angle of the air guiding element 30 from the release position according to FIG. 3A in the direction of the open position according to one of FIGS. 3B or C. This ensures that the partial air flow below the air guiding element 29 is only released or enabled at a later point in time.The exhaust gas burner 10 with the air guiding device 13 is also distinguished by a preferred alignment of the air guiding device 13 with respect to the combustion chamber 11, which is selected in particular depending on the arrangement of the ignition device 14 on the combustion chamber 11, in order to optimally utilize the advantages of the uneven or asymmetrical swirl in the exhaust gas chamber 11.Optionally, and as shown by way of example in FIGS. 6B and 2, the valve device 16 has a housing 34, which further forms the air-guiding duct 22 or is integrated therein in such a way that the air-guiding duct 22 is guided through the housing 34.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 19 504 208 A1

[0003] DE 10 2009 053 379 A1

[0003]

Claims

Exhaust gas burner (10) for an exhaust gas aftertreatment system (1) of an internal combustion engine (2), having a combustion chamber (11) in which a mixture of an oxygen-containing gas and fuel to form a heating gas can be burnt, wherein the combustion chamber (11) is assigned at least one injection valve (12) for injecting the fuel into the combustion chamber (11) and an ignition device (14) for igniting the mixture, wherein the combustion chamber (11) is assigned a gas inlet (25) for the gas and a heating gas outlet (15) for the heating gas, and wherein the gas inlet (25) is assigned an air guide device (13) which has an air guide duct (22), at one end of which an in particular rigid swirl device (24) is arranged, through which the gas reaches the combustion chamber (11), characterized in that, the air guiding device (13) has, upstream of the swirl device (24), at least one air guiding element (29) in the air guiding duct (22), which is adjustable at least in such a way that, depending on the position of the air guiding element (22), the oxygen-containing gas impinges on the swirl device (24) in a uniformly or non-uniformly distributed manner.Exhaust gas burner according to Claim 1, characterized in that the air-guiding device (13) is designed in such a way that, depending on the position of the air-guiding element (29), the gas is introduced homogeneously into the combustion chamber (11) by the swirl device (24) or focused on the ignition device (14).Exhaust gas burner according to one of the preceding claims, characterized in that the air guiding element (29) is assigned an actuatable actuator (23), by means of which the air guiding element (29) can be fixed in a plurality of positions in the air guiding duct (22) for directing the gas flow.Exhaust gas burner according to one of the preceding claims, characterized in that the air-guiding element (29) is designed as a flap (30) which is mounted pivotably in the air-guiding duct (22).Exhaust gas burner according to one of the preceding claims, characterized in that a pivot axis (31) of the air guiding element (29) is at least substantially eccentric in the air guiding duct (22).Exhaust gas burner according to one of the preceding claims, characterized in that the air-guiding element (29) and the air-guiding duct (22) are designed in such a way that the air-guiding element (29) completely closes the air-guiding duct (22) in a first position.Exhaust gas burner according to one of the preceding claims, characterized in that the air-guiding element (29) and the air-guiding duct (22) are designed in such a way that, in a second position, the air-guiding element (29) opens up the air-guiding duct (22) in regions and is oriented upstream of the air-guiding element (29) at an inclination to the flow direction of the air-guiding duct (22).Exhaust gas burner according to one of the preceding claims, characterized in that the air-guiding element (29) and the air-guiding duct (22) are designed in such a way that, in a third position, the air-guiding element (29) opens up the air-guiding duct (22) in regions and is oriented parallel to the flow direction of the air-guiding duct (22) upstream of the air-guiding element (29).Exhaust gas burner according to one of the preceding claims, characterized in that the adjustable air-guiding element (29) is assigned at least one non-adjustable air-guiding element (32) in the air-guiding duct (22).Exhaust gas burner according to one of the preceding claims, characterized in that the non-adjustable air-guiding element (32) is arranged upstream and / or downstream of the adjustable air-guiding element (29).Exhaust gas burner according to one of the preceding claims, characterized in that the non-adjustable air guiding element (32) extends downstream of the adjustable air guiding element (29) at least substantially in the flow direction of the air guiding duct (22).Method for operating an exhaust gas burner (11) according to one of Claims 1 to 11, characterized in that the air-guiding element (29) is adjusted as a function of an operating state of the exhaust gas burner (11).

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