Burner for an exhaust tract through which exhaust gas from an internal combustion engine flows, internal combustion engine and process

Abstract

The invention relates to a burner (10) for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows, with an ignition device (16) and with a combustion chamber (12) in which a mixture comprising air and fuel is to be ignited and thereby combusted by means of the ignition device (16), wherein at least one cover element (50) is movable between at least a first position (52), in which the ignition device (16) is at least partially covered by the cover element (50), and at least a second position, in which the ignition device (16) is released by the cover element (50).

Description

The invention relates to a burner for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows, according to the preamble of claim 1. Furthermore, the invention relates to an internal combustion engine with such a burner and a method for operating such a burner. DE 10 2021 001 580 A1, DE 10 2023 005 071 B3 and DE 10 2023 000 389 B3 each disclose, considered separately, a burner for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows, with a combustion chamber in which a mixture comprising air and a liquid fuel is to be ignited and thereby burned. The object of the present invention is to provide a burner for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows, an internal combustion engine with such a burner and a method for operating such a burner, so that a mixture comprising air and a liquid fuel can be ignited particularly well. This problem is solved according to the invention by a burner for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows, comprising the features of claim 1, by an internal combustion engine for a motor vehicle comprising the features of claim 9, and by a method for operating a burner for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows, comprising the features of claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims. A first aspect of the invention relates to a burner for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows or through which exhaust gas flows. The motor vehicle is, for example, a car, in particular a passenger car or commercial vehicle. Preferably, the internal combustion engine, particularly in its fully manufactured state, includes the burner. Preferably, the burner can be arranged or is arranged in the exhaust tract of the internal combustion engine. The internal combustion engine preferably has at least one combustion chamber in which combustion processes take place, during which a fuel-air mixture is to be burned or is burned. The combustion chamber is, for example, designed as a cylinder. The combustion chamber is separate from the burner. In particular, the combustion chamber and the burner are spaced apart from each other. The internal combustion engine preferably has at least one intake manifold through which air can flow into the combustion chamber. This means that the air flowing through the intake manifold can be introduced into, or is introduced into, the combustion chamber of the internal combustion engine. The exhaust gas produced from the combustion of the fuel-air mixture in the combustion chamber can be discharged from the combustion chamber via the exhaust manifold. Thus, the exhaust gas can be discharged from the combustion chamber and introduced into the exhaust system. The burner has at least one ignition device and at least one combustion chamber in which a mixture comprising air and fuel is ignited by the ignition device and thereby combusted. In other words, combustion processes take place in the combustion chamber in which the mixture comprising air and fuel is to be burned, or is burned. These combustion processes can be initiated, or are initiated, by means of the ignition device, for example, by at least one spark provided by the ignition device. "Initiation" can be understood in particular as the initiation of the combustion processes, that is, the combustion in the combustion chamber.However, the combustion processes taking place in the burner's combustion chamber and those taking place in the combustion chamber of the internal combustion engine are distinct processes, occurring in different locations. For example, the fuel used is a liquid. The ignition system, for instance, is located at least partially within the combustion chamber. The burner preferably has at least one housing element, which can be referred to in particular as a combustion chamber housing or burner housing. The housing element delimits the combustion chamber at least partially, in particular predominantly or completely, for example in the radial direction of the combustion chamber and / or in the axial direction of the combustion chamber. Preferably, the burner has at least one outlet element, which in particular at least partially delimits the combustion chamber, for example in the axial direction of the combustion chamber. This outlet element has at least one burner outlet opening through which burner exhaust gas generated by the combustion of the mixture can be discharged from the combustion chamber to heat the exhaust tract of the internal combustion engine, in particular to heat at least one component arranged in the exhaust tract of the internal combustion engine, and in particular can be introduced into the exhaust tract or at least a longitudinal section of the exhaust tract. In particular, the outlet element is arranged on an outlet side of the combustion chamber, wherein the outlet side is, for example, an axial end face of the combustion chamber or the housing element. The outlet side can in particular be referred to as the gas outlet side. The component, which is arranged particularly in the exhaust system of the internal combustion engine, is preferably at least one catalyst. The catalyst can therefore be heated by means of the burner, in particular by means of the burner exhaust gas generated in the combustion chamber of the burner. In order to ignite the mixture particularly well by means of the ignition device, that is, to significantly improve the ignition capability of the burner or the ignition device, the invention provides at least one cover element, in particular arranged in the combustion chamber, which is movable between at least a first position and at least one second position, in particular a position different from the first position. This means that the cover element can be moved, or is moved, from the first position to the second position and / or from the second position to the first position. In other words, the cover element is displaceable at least between the first and second positions. In the first position, the ignition device is at least partially, in particular predominantly or completely, covered by the cover element.This means that in the first position, the ignition device can be shielded, or is shielded, at least partially, particularly from airflow and / or soot acting upon it. In other words, in the first position, the ignition device is protected from deposits, such as soot, by the cover element, causing these deposits to accumulate on the cover element instead of on the ignition device itself, and in particular, instead of on a surface of the ignition device. In the second position, the ignition device is at least partially, and in particular predominantly or completely, exposed to the cover element. In other words, in the second position, the cover element no longer protects the ignition device.This means that in the second position, the ignition device is not, in particular, completely covered by the cover element. Thus, in the second position, it is specifically intended that the mixture, particularly for ignition, can be guided to the ignition device, i.e., transported, and that this guiding or transporting to the ignition device can occur via the released cover element. Moving the cover element between positions can be understood, in particular, as moving the cover element between positions relative to the housing element. Preferably, the cover element is held, at least indirectly, and in particular directly, on the housing element by means of at least one holding device, in particular so that it is movable between the positions. In other words, the cover element is mounted, in particular movably, on the housing element by means of the holding device. The invention is based in particular on the following findings and considerations: Cold starts and cold start emissions of the internal combustion engine can be particularly important for the engine's emission behavior. To keep pollutant emissions from the internal combustion engine as low as possible, and, for example, to reliably achieve certification values ​​such as the EU7 standard, a focus regarding emission development can therefore be placed on cold starts and cold start emissions. Particularly in diesel engines in vehicles, a burner can be used for this purpose, which can condition the exhaust system (also referred to as the exhaust tract) within a temperature range, which can be described as the operating temperature range, and in particular without causing significant pollutant emissions of its own. In particular, the burner can be used to condition the component or...The catalyst in the exhaust system is heated so that it can at least reach its activation temperature, allowing it to perform its function even if the exhaust gas from the internal combustion engine is below this temperature. However, investigations have shown that deposits in the form of soot can accumulate on the ignition device, such as the spark plug, resulting in a high or even particularly high soot load on the ignition device.This can occur particularly during so-called passive burner operation, meaning when the burner is in a deactivated state and the internal combustion engine transports high or exceptionally high loads and high or exceptionally high soot mass flows into the exhaust gas, i.e., with the exhaust gas into the exhaust tract, and the exhaust gas enters the burner's combustion chamber via the burner outlet openings, which can lead to soot buildup without any additional measures on the ignition system. Specifically, ignition and combustion of the mixture do not occur in the deactivated state. In other words, no combustion processes take place in the combustion chamber when the burner is deactivated.In particular, because load collectives, which can also simply be referred to as collectives in which the motor vehicle is usually moved or can be moved, are so different, it cannot be ruled out that particularly high full load proportions with corresponding soot loading will occur. In contrast, the burner according to the invention allows the aforementioned disadvantages to be avoided particularly reliably. The cover element of the internal combustion engine according to the invention provides a protective concept for the spark plug, particularly against deposits. The ignition device can be protected from excessive soot buildup by means of the cover element, especially in the first position. In particular, the cover element is arranged at least in the vicinity, and especially in the immediate vicinity, of the ignition device, thus making the cover element an integrated solution for protecting the ignition device. Moving the cover element from the second position to the first position therefore provides an active measure to protect the ignition device, particularly permanently, from excessive soot buildup and, in particular, to maintain its ignitability.Overall, it is evident that the burner according to the invention, particularly the cover element, provides soot protection for the ignition device. This means that deposits, especially soot, on the ignition device can be kept to a minimum, thus keeping the ignition device free of deposits. This soot protection significantly improves the ignition capability of the ignition device and / or the burner, enabling the exhaust system, and especially the component located within it, to be heated particularly reliably, i.e., safely, by the burner and / or the burner exhaust gas, thereby keeping pollutant emissions from the internal combustion engine to a minimum.In particular, the fact that the ignition device, unlike a soot filter, does not have a combustion option makes the burner according to the invention especially advantageous, as the deposition of soot can be prevented. In a further embodiment, it is provided that, particularly with regard to the first and second positions, at least one electrode of the ignition device is at least partially, and in particular predominantly or completely, covered by the cover element in the first position. This means that in the first position, the electrode is shielded by the cover element, particularly from the airflow and / or soot contained in the airflow. In other words, the electrode is protected in the first position by the cover element, particularly from soot or other deposits. This reliably prevents the deposition of deposits, especially soot, on the electrode, thereby significantly improving ignition capability.Preferably, it is provided that at least one ignition spark for igniting the mixture can be provided or is provided by means of the electrode, that is, can be generated or is generated. In a further embodiment, the cover element is designed to be pivotable or pivoted about at least one pivot axis for movement between positions. This means that the cover element can be pivoted or is pivoted about the pivot axis between the first and second positions, for example, relative to the housing element. In other words, the cover element is designed as a cover flap, which can be described in particular as a closing flap for the ignition device. This allows the cover element to be moved between positions with minimal effort and / or with particular reliability. Covering or protecting the ignition device can thus be achieved with particular reliability, thereby ensuring reliable ignition capability. In a further embodiment, it is provided that the ignition device, in particular the electrode, extends at least partially, and in particular predominantly or completely, within a receiving space that is at least partially, and in particular predominantly or completely, bounded or formed by the housing element of the burner. In other words, the ignition device, and in particular the electrode, is arranged at least partially within the receiving space. The receiving space opens into the combustion chamber, and in particular into a main area of ​​the combustion chamber, via at least one through-opening, and in particular directly. In other words, the mixture located in the combustion chamber can be introduced into the receiving space via the through-opening and thereby guided to the ignition device, and in particular to the electrode, in order to ignite and thus combust the mixture.A flame resulting from ignition or combustion can thus spread through the through-opening into the combustion chamber, particularly into the main area of ​​the combustion chamber. In other words, the receiving chamber and the combustion chamber, especially the main area, are fluidically connected via the through-opening. Preferably, the through-opening is provided that in the first position, the through-opening is completely closed by the cover element, and in the second position, it is at least partially, and in particular predominantly or completely, uncovered by the cover element. In other words, in the first position, the through-opening is completely covered by the cover element, and in the second position, the through-opening is not closed or covered by the cover element. This means that in the second position, the through-opening is not covered or closed by the cover element. Thus, it is particularly intended that, with respect to the first and second positions, the transport of the mixture via the through-opening to the ignition device, in particular to the electrode, is only possible in the second position.It is therefore evident that in the first position, the passage of soot through the through-opening to the ignition device, in particular the electrode, can be prevented, which allows the soot loading or the deposits of the ignition device to be kept particularly low. In a further embodiment, it is provided that the cover element, particularly with regard to the first and second positions, rests in the first position against a wall of the housing element that at least partially, and in particular predominantly or completely, defines or forms the passage opening, and especially directly. In other words, the cover element directly contacts the wall in the first position. This allows the passage opening to be sealed particularly tightly in the first position, especially gas-tight, for example, airtight, thereby providing particularly good protection for the ignition device against soot buildup. In a further embodiment, it is provided that the cover element, specifically with regard to the first and second positions, is spaced away from the wall in the second position. This means that in the second position, at least a gap is provided between the cover element and the wall. In other words, the cover element does not touch the wall in the second position. The passage opening can thus be opened in a particularly simple manner, thereby ensuring, in a particularly simple manner, that the mixture reaches the ignition device, thus enabling particularly reliable ignition of the mixture. In a further embodiment, the burner has at least one swirl chamber through which the air, in particular the air forming the mixture, flows or is flowing, and which in particular is capable of causing or effecting a swirl flow of the air. This swirl chamber is thus preferably arranged upstream of the combustion chamber in the direction of air flow. The fact that the swirl chamber causes or can cause the swirl flow means, in particular, that the air flows through the swirl chamber in a swirl pattern at least in certain regions, and thus flows through at least a longitudinal region of the swirl chamber in a swirl pattern, and / or flows through at least a flow region arranged downstream of the swirl chamber, which is, for example, located in the combustion chamber, in a swirl pattern.In particular, it is conceivable that the air from the combustion chamber flows into the combustion chamber in a swirling pattern, so that it is preferably provided that the air has a swirling flow at least in the combustion chamber. Preferably, the burner has at least one feed element, which can also be referred to as a fuel feed element, arranged, for example, at least partially within the swirl chamber. The feed element is, for example, designed as an injection element. It is provided that the fuel can be introduced, particularly directly, into the swirl chamber by means of the feed element, or is introduced, particularly injected. In other words, the fuel enters the swirl chamber via the feed element, from which it can then enter the combustion chamber. For example, the feed element has at least one opening through which the fuel, particularly liquid fuel, can flow, and through which the fuel can be introduced, particularly injected, into the swirl chamber.The opening is preferably arranged in the swirl chamber, whereby the injection element, in particular a channel of the injection element through which the fuel can flow, opens into the swirl chamber via the opening. Preferably, the swirl chamber is designed to open into the combustion chamber via an outlet opening, particularly directly. In other words, the air flowing through the swirl chamber and / or the fuel introduced into the swirl chamber can be introduced, or is introduced, into the combustion chamber via the outlet opening. This means that the combustion chamber and the swirl chamber are fluidically connected to each other via the outlet opening, particularly directly. In a further embodiment, the burner has at least one closure element that is movable between at least one open position and one closed position. This means that the closure element is movable between the open position and the closed position, in particular from the open position to the closed position and / or from the closed position to the open position. "Movement" here can be understood to mean, in particular, movement relative to the housing element. In other words, the closure element is displaceable between the open position and the closed position. In the closed position, the outlet opening is, in particular, completely closed by the closure element. In other words, in the closed position, the outlet opening is, in particular, completely covered by the closure element.In the closed position, this prevents air and / or fuel from entering the swirl chamber through the outlet opening, which is closed. In the open position, the outlet opening is at least partially, and in particular predominantly or completely, uncovered by the closing element. This means that in the open position, the closing element does not cover the outlet opening. Therefore, in the open position, air and / or fuel can enter the combustion chamber from the swirl chamber through the open outlet opening. Thus, the closing element, particularly in the closed position, provides soot protection for the swirl chamber and / or directs airflow to the burner.In the closed position, this prevents a soot-laden flow from the combustion chamber back into the swirl chamber via the outlet opening, thus reliably preventing deposits, such as soot, in the swirl chamber and / or on the feed element. This flow could be the burner exhaust or the exhaust gas from the internal combustion engine, whereby the exhaust gas from the internal combustion engine may, for example, have flowed undesirably from the exhaust system into the combustion chamber. By preventing these deposits, the proper functioning of the swirl chamber, especially the air guide, and the feed element can be ensured. In a further embodiment, the swirl chamber is provided for, or at least partially defined by, at least one wetting element. In other words, the wetting element is provided for, or arranged in, or on the swirl chamber. It is provided that when the fuel is introduced, particularly into the swirl chamber, the wetting element is wettable by the fuel, particularly directly, forming at least one fuel film. In other words, the fuel, particularly the fuel exiting the introduction element through the opening, is applied to the wetting element as a fuel film.It is provided that the fuel film, which is formed or applied, in particular to the wetting element, can be exposed to, or is exposed to, the air flowing through the swirl chamber, in particular in a swirling motion, whereby at least a portion of the fuel can be atomized, i.e., in droplet form, or is detached from the fuel film in order to introduce the atomized fuel, in particular directly, into the combustion chamber via the outlet opening and, in particular, to the ignition device. In other words, the mixture is formed by the fuel applied, in particular sprayed, to the wetting element being detached in droplet form by an airflow flowing through the swirl chamber.This allows for particularly good atomization and thus excellent mixing of the mixture, especially without requiring particularly high injection pressure. The wetting element can therefore be understood to be, in particular, a film layer, and can also be referred to as a pre-filmer. This embodiment is based in particular on the following findings and considerations: Investigations have shown that, especially during passive burner operation—that is, when the burner is essentially off and the combustion engine is transporting particularly high loads and particularly high soot mass flows into the exhaust gas—the injector element and, for example, a delicate air guide in the prefilmer can become clogged very quickly, for example with soot, which can lead to reductions in the quantities of air and fuel. To prevent this, a sealing element, designed, for example, as a flap, can be used. This keeps the prefilmer free of deposits, especially soot, thus ensuring particularly good mixture formation. Overall, it is evident that a mechanism can be created which can act on a flap in the form of the cover element or on two flaps in the form of the cover element and the closure element, with the aim of protecting both the air guide as well as the insertion element and the ignition device from soot. A second aspect of the invention relates to an internal combustion engine for a motor vehicle, wherein the internal combustion engine comprises a burner, in particular arranged in an exhaust tract of the internal combustion engine, according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention and vice versa. A third aspect of the invention relates to a method for operating a burner for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows. The burner is preferably a burner according to the first aspect of the invention. The internal combustion engine is preferably an internal combustion engine according to the second aspect of the invention. Advantages and advantageous embodiments of the first and second aspects of the invention are to be regarded as advantages and advantageous embodiments of the third aspect of the invention, and vice versa. The burner has an ignition device and a combustion chamber in which a mixture comprising air and fuel is to be ignited by means of the ignition device and thereby burned, or is ignited and thereby burned. To ensure particularly good ignition of the mixture, i.e., to significantly improve the ignition capability of the burner or ignition device, the invention provides that at least one covering element, particularly one located in the combustion chamber, is moved between at least a first position, in which the ignition device is at least partially covered by the covering element, and at least a second position, in which the ignition device is exposed to the covering element. For example, at least one actuator is provided by means of which the covering element can be moved from the first position to the second position and / or from the second position to the first position. The actuator is, for example, designed as an electric machine.For example, at least one electronic computing device is provided by means of which the actuator can be controlled or is controlled to move the cover element between the positions. Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawing. The features and combinations of features mentioned above in the figure description and / or shown in the single figure alone can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. The drawing shows in the single figure a schematic partial sectional view of a burner according to the invention. The single figure shows, in a schematic partial sectional view, a burner 10 for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows or through which exhaust gas flows. Preferably, the motor vehicle is driven by means of the internal combustion engine. The term "exhaust system" can refer specifically to the exhaust system of an internal combustion engine. In certain operating conditions or situations of the internal combustion engine, a high exhaust gas temperature may be desirable, for example, to quickly heat and / or maintain the temperature of an exhaust aftertreatment device located within the exhaust system. However, in these operating conditions or situations, the exhaust gas temperature may be insufficiently high. The exhaust system, and in particular the exhaust aftertreatment device, can be heated and / or maintained by means of the burner 10. This means that, in addition to heating and / or maintaining the temperature using the exhaust gas, the exhaust system, and especially the exhaust aftertreatment device, can also be heated and / or maintained by means of the burner.This exhaust gas can be understood in particular as exhaust gas generated in a combustion chamber of the internal combustion engine from a fuel-air mixture. The combustion chamber, which is designed, for example, as a cylinder, is separate from the burner 10. The internal combustion engine is, for example, a diesel engine. The exhaust aftertreatment system includes, for example, at least one catalyst or is designed as a catalyst. The exhaust aftertreatment system or the catalyst is, for example, an oxidation catalyst, in particular a diesel oxidation catalyst, a nitrogen oxide storage catalyst, an SCR catalyst, or a particulate filter, in particular a diesel particulate filter. The exhaust gas from the internal combustion engine can be cleaned by means of the exhaust aftertreatment system. The burner 10 has at least one combustion chamber 12 in which a mixture comprising air and a fuel, in particular a liquid fuel, is to be ignited and thereby combusted. This means that the burner 10 can ignite and combust the mixture in the combustion chamber 12, in particular by forming a flame and in particular by providing burner exhaust gas. For example, the fuel is the fuel that is burned in the combustion chamber, which is designed as a cylinder, for instance, of the internal combustion engine. Therefore, the fuel can be used to refer to the combustion chamber. However, the exhaust gas from the burner is not the exhaust gas produced in the combustion chamber of the internal combustion engine. In the exemplary embodiment, the burner 10 has at least one injection element 14 by means of which, or via which, the fuel, in particular for forming the mixture, can be introduced into the combustion chamber 12, in particular directly. The injection element 14 is, for example, designed as an injection valve. For example, the burner 10 has at least one ignition device 16, in particular arranged in the combustion chamber 12, by means of which the mixture comprising air and fuel in the combustion chamber 12 is ignited and thereby combusted. The ignition device 16 is, for example, designed as a spark plug, glow plug, or glow pin. In the present case, the ignition device 16 has two electrodes 16a, 16b by means of which the mixture is ignited, in particular by providing at least one ignition spark. The burner 10 in this embodiment has at least one housing element 18, which can be referred to in particular as a combustion chamber housing. The housing element 18 at least partially, and in particular predominantly or completely, delimits the combustion chamber 12. In this embodiment, the combustion chamber 12, or the housing element 18, is at least substantially cylindrical. Furthermore, in this embodiment, the housing element 18 has at least one side wall 20, which at least partially, and in particular predominantly or completely, delimits the combustion chamber 12 in its radial direction 22. The housing element 18 also has, for example, at least one bottom element 24, which at least partially delimits the combustion chamber 12 in its axial direction 26, in particular at one end. The bottom element 24 and the side wall 20 can be formed integrally or separately.The base element 24 can in particular be referred to as a base wall. In the exemplary embodiment, the side wall 20 and the base element 24 are part of a lower housing part 28 of the housing element 18, wherein at least one upper housing part 29 of the housing element 18 adjoins the lower housing part 28, for example in axial direction 26 in the direction away from the base element 24. In the exemplary embodiment, the burner 10 has at least one outlet element 30, which in particular at one end of the combustion chamber 12, preferably in the axial direction 26, at least partially limits the combustion chamber 12 and which has at least one burner outlet opening 32, in particular through which the burner exhaust gas can flow, and through which the burner exhaust gas produced by the combustion of the mixture can be discharged from the combustion chamber 12 for heating the exhaust tract of the internal combustion engine, in particular the exhaust aftertreatment device, and in particular can be introduced into the exhaust tract, for example for supplying the exhaust aftertreatment device.The burner exhaust gas or flame can therefore be discharged from the combustion chamber 12, in particular from the burner 10, via the burner outlet opening 32, and especially introduced into the exhaust tract, for example into at least one duct element of the exhaust tract. The exhaust gas or flame can heat and / or keep the exhaust tract, and in particular the exhaust aftertreatment system, warm. In this embodiment, the outlet element 30 has a plurality of burner outlet openings 32, which are preferably designed as through-openings. The burner exhaust gas or flame can be discharged from the combustion chamber 12, particularly from the burner 10, via the burner outlet openings 32 to heat the exhaust tract of the internal combustion engine, especially the exhaust aftertreatment system, and can be introduced, for example, into the exhaust tract or the ducting element. This allows the exhaust tract, especially the exhaust aftertreatment system, to be heated or kept warm particularly effectively. The burner outlet openings 32 are permeable to the burner exhaust gas. In this embodiment, the outlet element 30 is plate-shaped, i.e., designed as a plate, which can be referred to as an outlet plate.In the exemplary embodiment, the outlet element 30 is designed as a perforated plate, in particular as a perforated disc. The outlet element 30 is, for example, at least partially formed by the base element 24. In particular, the outlet element 30 can be the base element 24, whereby the base element 24 can have the burner outlet openings 32. In the exemplary embodiment, the burner 10 has at least one swirl system, which in this case has at least one swirl chamber 34 through which air can flow or is flowing. The swirl chamber 34 can have one swirl region or several, in particular different, swirl regions, which can be understood as different sub-regions of the swirl system, in particular of the swirl chamber 34. The individual swirl regions can also be considered as individual swirl chambers, whereby the swirl system can also have several swirl chambers. Furthermore, the burner 10 in this case has at least one air supply section 36 through which air can flow or is flowing, and through which the air can be introduced or is introduced into the swirl chamber system, in particular into the swirl chamber 34.In the present case, the fuel can be introduced, in particular injected, into the swirl chamber 34 by means of the introduction element 14, which leads, in particular directly, into the combustion chamber 12 via an outlet opening 38, through which air and / or fuel can flow. In this embodiment, the swirl chamber 34 is at least partially bounded by at least one wetting element 40, which is designed, for example, as a film layer, which can in particular be referred to as a pre-filmer. When the fuel is introduced, the wetting element 40 can be wetted by the fuel, forming a fuel film. The wetting element 40 is, for example, a surface, particularly an inner surface, of a component that at least partially bounds or forms the swirl chamber 34. The fuel film can be acted upon by the air flowing through the swirl chamber, which is introduced into the swirl chamber 34, in particular via the air supply section 36. This causes at least a portion of the fuel to be atomized and released from the fuel film, allowing the atomized fuel to be introduced into the combustion chamber 12 via the outlet opening 38.The concept regarding mixture formation in the burner 10 thus includes an injection of the fuel onto the wetting element 40, from which the fuel is then detached in droplet form by airflow and transported, in particular by means of the outlet opening 38, to the ignition device 16, in particular to the electrodes 16a, 16b. In the exemplary embodiment, the burner 10 has at least one closure element 44 movable between at least one open position and one closed position 42, which is, for example, movably held or mounted on the housing element 18, particularly between the open position and the closed position 42. Thus, for example, a holding device 46 is provided, which can be referred to in particular as the first holding device 46, by means of which the closure element 44 is held, in particular at least indirectly or directly, on the housing element 18, in particular on the upper housing part 29. This closure element 44 prevents soot-containing gas from flowing back from the combustion chamber 12 into the swirl chamber 34 via the outlet opening 38, thereby preventing soot deposits in the swirl chamber 34 and / or on the insertion element 14, and in particular on the wetting element 40. In the present embodiment, the locking element 44 is designed to pivot about a pivot axis 48, which can be referred to as the first pivot axis 48, for movement between the open position and the closed position 42. The locking element 44 is thus preferably designed as a locking flap. As shown in the single figure, in this embodiment, the locking element 44, in the closed position 42, bears directly against the housing element 18, particularly against a wall that at least partially delimits the combustion chamber 12 and / or the swirl chamber 34. In the open position, the locking element 44 is preferably spaced apart from the housing element 18, so that in the open position, the locking element 44 preferably does not bear against the housing element 18 or against the wall. In order to ignite the mixture particularly well, at least one covering element 50 is provided, in particular designed separately from the sealing element 44, which is movable between at least a first position 52, in which the ignition device 16, in particular at least one of the electrodes 16a, 16b, preferably both electrodes 16a, 16b, is at least partially, in particular predominantly or completely, covered by the covering element 50, and at least a second position, in particular different from the first position 52, in which the ignition device 16, in particular at least one of the electrodes 16a, 16b, preferably both electrodes 16a, 16b, is released.In this case, a holding device 56 is provided, which can in particular be referred to as a second holding device 56, by means of which the cover element 50, in particular movable between the positions, is held or mounted on the housing element 18, for example on the upper housing part 29, at least indirectly or directly. This prevents soot-containing gas from reaching the ignition device 16, in particular the electrodes 16a, 16b, in the first position 52, thereby reliably preventing soot deposits on the ignition device 16, in particular on the electrodes 16a, 16b. The second position can thus be understood, for example, as a normal operating position of the cover element 50, wherein the cover element 50 preferably assumes this normal operating position when the burner 10 is fired, i.e., in an activated state in which the mixture is ignited by means of the ignition device 16 and thus combustion processes take place in the combustion chamber 12. The cover element 50 assumes the first position 52, for example, when the burner 10 is deactivated, in which the combustion processes, and thus in particular the ignition of the mixture, do not occur. However, in this deactivated state, exhaust gas from the internal combustion engine can still enter the combustion chamber 12 from the exhaust tract, for example, via the respective burner outlet opening 32, and in particular flow back into it.Since this exhaust gas can contain soot, the deposition of soot on the ignition device 16 can be reliably prevented by means of the cover element 50, even when the burner 10 is deactivated. In this design, the cover element 50 is pivotable about a pivot axis 58 to move between positions; this pivot axis 58 can be referred to as a second pivot axis 58. In the embodiment shown in the single figure, the ignition device 16, in particular the electrodes 16a, 16b, extends at least partially into a receiving space 60, which is at least partially bounded by the housing element 18, in particular by the upper housing part 29. This receiving space opens into the combustion chamber 12, or into a main area of ​​the combustion chamber 12, via a through-opening 62, in particular directly. In the first position 52, the through-opening 62 is, in particular, completely closed by the cover element 50, and in the second position, the through-opening 62 is at least partially uncovered by the cover element 50. As shown in the single figure, it is preferably provided that in the first position 52, the cover element 50 abuts a wall 64 of the housing element 18, in particular of the upper housing part 29, which at least partially bounds the through-opening 62. In the embodiment shown in the single figure, the cover element 50 is coupled to the second holding device 56, in particular to a base body or a bearing body of the second holding device 56, via at least one lever element 66. The lever element 66 is, for example, at least partially arc-shaped. Numerals, such as "first", "second", "third", etc., are intended solely for differentiation and do not, in particular, indicate an order. This means that the corresponding numerals can be interchanged arbitrarily. Reference symbol list 10 Burner 12 Combustion chamber 14 Insertion element 16 Ignition device 16a First electrode 16b Second electrode 18 Housing element 20 Side wall 22 Radial direction 24 Base element 26 Axial direction 28 Lower housing part 29 Upper housing part 30 Outlet element 32 Burner outlet opening 34 Swirl chamber 36 Air supply section 38 Outlet opening 40 Wetting element 42 Closed position 44 Closing element 46 First holding device 48 First pivot axis 50 Cover element 52 First position 56 Second holding device 58 Second pivot axis 60 Receiving space 62 Through opening 64 Wall 66 Lever element

Claims

Burner (10) for an exhaust tract through which exhaust gas of an internal combustion engine of a motor vehicle flows, with an ignition device (16) and with a combustion chamber (12) in which a mixture comprising air and a fuel is to be ignited by means of the ignition device (16) and thereby combusted, characterized by at least one cover element (50) which is movable between at least a first position (52) in which the ignition device (16) is at least partially covered by the cover element (50) and at least a second position in which the ignition device (16) is released by the cover element (50). Burner (10) according to claim 1, characterized in that in the first position (52) at least one electrode (16a, 16b) of the ignition device (16) is at least partially covered by the cover element (50). Burner (10) according to claim 1 or 2, characterized in that the cover element (50) is pivotable about a pivot axis (58) for movement between the positions (52). Burner (10) according to one of the preceding claims, characterized in that the ignition device (16) extends at least partially into a receiving space (60) which is at least partially limited by a housing element (18) of the burner (10) and which opens into the combustion chamber (12) via a through-opening (62), wherein the through-opening (62) is closed by the cover element (50) in the first position (52) and is at least partially released by the cover element (50) in the second position. Burner (10) according to claim 4, characterized in that the cover element (50) in the first position (52) rests against a wall (64) of the housing element (18) which at least partially limits the passage opening (62). Burner (10) according to claim 5, characterized in that the cover element (50) is spaced away from the wall (64) in the second position. Burner (10) according to one of the preceding claims, characterized by: • at least one swirl chamber (34) through which air can flow and at least one introduction element (14) by means of which the fuel can be introduced into the swirl chamber (34), which opens into the combustion chamber (12) via an outlet opening (38), and • at least one closure element (44) movable between at least one open position and one closed position (42), wherein in the closed position (42) the outlet opening (38) is closed by the closure element (44) and in the open position the outlet opening (38) is at least partially released by the closure element (44). Burner (10) according to claim 7, characterized in that the swirl chamber (34) is at least partially limited by at least one wetting element (40) which, when the fuel is introduced, can be wetted by the fuel forming a fuel film, wherein the fuel film can be acted upon by the air flowing through the swirl chamber (34), whereby at least a part of the fuel can be atomized and detached from the fuel film in order to introduce the atomized fuel into the combustion chamber (12) via the outlet opening (38). Internal combustion engine for a motor vehicle, with a burner (10) according to one of the preceding claims. Method for operating a burner (10) for an exhaust tract through which exhaust gas of an internal combustion engine of a motor vehicle flows, in which the burner (10) has an ignition device (16) and a combustion chamber (12) in which a mixture comprising air and a fuel is to be ignited and thereby combusted by means of the ignition device (16), characterized in that at least one cover element (50) is moved between at least a first position (52), in which the ignition device (16) is at least partially covered by the cover element (50), and at least a second position, in which the ignition device (16) is released by the cover element (50).

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