Method for operating a burner arranged in an exhaust system for an internal combustion engine of a motor vehicle, and motor vehicle

Abstract

The invention relates to a method for operating a burner (48) arranged in an exhaust system (10) for an internal combustion engine (12) of a motor vehicle and supplied with air and fuel, comprising an air duct (58) through which air flows, and an air pump (56) arranged in the air duct (58), by means of which the air can be conveyed through the air duct (58) and conveyed to the burner (48) in order to supply the burner (48) with air. A recirculating air duct (68) is provided, which is fluidically connected to the air duct (58) at a first connection point (V2) arranged downstream of the air pump (56) and at a second connection point (V3) arranged upstream of the air pump (56).

Description

[0001] The invention relates to a method for operating a burner arranged in an exhaust system for an internal combustion engine of a motor vehicle according to the preamble of claim 1. Furthermore, the invention relates to a motor vehicle, in particular a motor car.

[0002] DE 10 2019 008 965 A1 discloses an exhaust system for an internal combustion engine, comprising a nitrogen oxide storage catalyst through which exhaust gas from the internal combustion engine flows, and a burner supplied with air and fuel, by means of which a fuel-air mixture containing the fuel and air is to be combusted. Furthermore, DE 10 2021 001 580 A1 discloses a burner for an exhaust tract through which exhaust gas from an internal combustion engine of a motor vehicle flows.

[0003] The object of the present invention is to create an exhaust system for an internal combustion engine of a motor vehicle and a motor vehicle with such an exhaust system, so that a burner of the exhaust system can be operated particularly advantageously.

[0004] This problem is solved by an exhaust system with the features of claim 1 and by a motor vehicle with the features of claim 7. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0005] A first aspect of the invention relates to a method for operating a burner arranged in the exhaust system of an internal combustion engine of a motor vehicle and supplied with air and fuel. The motor vehicle, also referred to simply as a vehicle and preferably designed as a motor car, in particular as a passenger car or commercial vehicle, in its fully manufactured state comprises the internal combustion engine, also designed as a motor, internal combustion engine, or combustion power unit, and is capable of being driven by means of the internal combustion engine. Most preferably, the internal combustion engine is designed as a reciprocating engine. In the fully manufactured state of the motor vehicle, the internal combustion engine comprises the exhaust system. The exhaust system is permeable to exhaust gas from the internal combustion engine.During operation of the internal combustion engine, combustion processes take place within the engine, particularly in at least one or more combustion chambers, resulting in the exhaust gas, also known as engine exhaust. The engine exhaust can flow out of the respective combustion chamber and into the exhaust system, also referred to as the exhaust tract, and flow through it. The exhaust system includes the burner, which is supplied with fuel (especially liquid fuel) and with the aforementioned air, also known as burner air. Unless otherwise specified, any reference to air refers to burner air. For example, the exhaust system includes at least one additional component besides the burner, such as an exhaust aftertreatment element for treating the exhaust gas.The exhaust aftertreatment element is or includes, for example, a catalyst, in particular an SCR catalyst, wherein, for example, selective catalytic reduction (SCR) can be catalytically supported and / or effected by means of the SCR catalyst, such that, for example, the SCR catalyst is catalytically active for the SCR process. In selective catalytic reduction, any nitrogen oxides contained in the engine exhaust are at least partially removed from the exhaust gas by reacting the nitrogen oxides with ammonia to form nitrogen and water. The ammonia is provided, for example, by a reducing agent, particularly a liquid one, which could be, for example, an aqueous urea solution. Furthermore, it is conceivable that the exhaust aftertreatment element is or includes a particulate filter. In particular, the particulate filter is a diesel particulate filter (DPF).The particulate filter can be used to filter out any particles, especially soot particles, that may be contained in the exhaust gas.

[0006] A burner is used to combust a mixture, also known as a burner mixture, which comprises the burner air and the fuel. For this purpose, the burner has a combustion chamber, also called the main combustion chamber, in which the burner mixture can be combusted, in particular ignited and burned. The combustion chamber is specifically bounded by a chamber element, particularly a solid body, and in particular by an inner circumferential surface of the chamber element. The combustion of the burner mixture in the combustion chamber produces exhaust gas, also known as burner exhaust.The burner exhaust gas can, for example, flow out of the burner, particularly from the combustion chamber, and into an exhaust duct of the exhaust system through which the engine exhaust gas flows, especially at an inlet point located upstream of the aforementioned component in the direction of flow of the engine exhaust gas through the exhaust system, i.e., the exhaust duct. Thus, the component is permeable to the burner exhaust gas. For example, the burner exhaust gas mixes with the engine exhaust gas. Consequently, the burner exhaust gas, especially the burner exhaust gas mixed with the engine exhaust gas, can flow through the component, thereby heating it up.In particular, it is conceivable that the burner exhaust gas can flow out of the combustion chamber and into the exhaust manifold, thereby mixing with the engine exhaust gas and / or a gas flowing through the exhaust manifold, thus heating the engine exhaust gas or the gas. In other words, this can result in a particularly high temperature of the engine exhaust gas or the gas, also known as the exhaust gas temperature. The gas could, for example, be air flowing through the exhaust manifold, especially while the internal combustion engine is being towed, i.e., when the engine is not firing and therefore not producing exhaust gas. In this case, the gas, especially the air, is then pumped through the engine, particularly by means of a pump.The high exhaust gas temperature allows the component to be heated and / or kept warm, as the burner exhaust, engine exhaust, and gas flow through it. Thus, for example, the burner exhaust from the combustion chamber is introduced into the exhaust duct at the aforementioned inlet point, and consequently into the engine exhaust or gas flowing through the exhaust duct.

[0007] The exhaust system includes a supply line through which the combustion air flows to supply the burner. This supply line is also referred to as an air line. The exhaust system also includes an air pump, typically located in addition to the burner and the internal combustion engine. This pump forces the combustion air through the supply line to the burner, thus supplying it with combustion air. For example, the air pump may be an electric pump, which is electrically operated to supply the burner with combustion air, specifically to force the combustion air through the supply line to the burner.

[0008] The burner has at least one channel through which at least a portion of the burner air flows, arranged upstream of the combustion chamber in the direction of flow of the burner air through the channel. The combustion chamber can be supplied with the burner air flowing through the channel via this channel. The channel has, in particular, an outlet opening through which the combustion chamber can be supplied with the air flowing through the channel (burner air). For example, a swirl flow of the burner air flowing through the channel can be created by means of the channel, so that the burner air exhibits a swirl flow, at least within the combustion chamber. This allows the burner air to be mixed particularly effectively with the fuel, resulting in a particularly advantageous formation of the burner mixture, also referred to as mixture formation or mixture preparation.The burner air can be drawn out of the duct via the outlet opening and, in particular, introduced directly into the combustion chamber.

[0009] The burner, for example, has a closing element, designed as a flap, which is movable, particularly relative to the outlet opening and the chamber element, between a closed position and at least one open position, and is in particular pivotable. In the closed position, the outlet opening and thus the channel are fluidically separated from the combustion chamber by means of the closing element. In the open position, the closing element releases the outlet opening and the channel, so that in the open position the outlet opening and the channel, i.e., the channel via the outlet opening, are fluidically connected to the combustion chamber.In the closed position, the sealing element prevents engine exhaust from flowing from the exhaust duct through the combustion chamber into the outlet opening and the duct, for example, when the burner is deactivated and therefore not producing any burner exhaust gas, and the sealing element is in the closed position. This prevents components contained in the engine exhaust gas, such as carbon deposits and / or particles, from accumulating or settling in unwanted areas of the burner and thus excessively clogging the outlet opening or the duct.

[0010] To achieve particularly advantageous burner operation, the invention provides that the exhaust system includes a recirculating air line, in particular in addition to the supply line, which is fluidically connected to the supply line at a first connection point and at a second connection point. In the direction of flow of the burner air flowing through the supply line, which flows through the supply line during operation of the air pump and, in particular, also of the burner, the first connection point is arranged downstream of the air pump and preferably upstream of the burner.In the direction of flow of the burner air through the supply line, the second connection point is located upstream of the air pump and thus upstream of the burner, so that the second connection point is located upstream of the first connection point in the direction of flow of the burner air through the supply line. Thus, the connection points are spaced apart from each other in the direction of flow of the burner air through the supply line. Furthermore, in the direction of flow of the burner air through the supply line, the air pump is located between the connection points, that is, upstream of the first connection point and downstream of the second connection point. For example, the air pump is designed to pump the burner air through the supply line and compress it in the process, so that the air pump is also referred to as a compressor or is designed as a compressor.

[0011] Via the recirculation line, at least a portion of the air flowing through the supply line can be returned from the first connection point to the second connection point, bypassing the air pump. Specifically, at the first connection point, at least a portion of the burner air flowing through the supply line can be diverted from the supply line and introduced into the recirculation line. The portion of burner air diverted from the supply line at the first connection point and introduced into the recirculation line can then flow through the recirculation line and be routed from the first connection point to the second connection point, bypassing the air pump. At the second connection point, the diverted air flowing through the recirculation line can, in particular, flow back into the supply line, bypassing the air pump.

[0012] The characteristic that the air flowing through the recirculation line can be returned to the second connection point without passing through the air pump, and can then be introduced into the supply line at the second connection point without passing through the air pump, means that the recirculation line and the air flowing through it bypass the air pump. This means that the air flowing through the recirculation line does not pass through the air pump on its way from the first connection point to the second connection point and into the supply line. At the second connection point, the air flowing through the recirculation line can exit the recirculation line and (re)enter the supply line, and then, for example, pass through the air pump again. Because the air flowing through the recirculation line bypasses the air pump, the recirculation line is also referred to as a bypass line.

[0013] Furthermore, according to the invention, a valve element is provided by means of which the quantity, i.e., in particular a volume and / or mass flow rate, of the air (burner air) flowing through the recirculation line and thus bypassing the air pump can be adjusted. This means, in particular, that the quantity of air flowing through the recirculation line can be set to several different values ​​by means of the valve element, wherein, for example, at least or exactly one of the values ​​is 0, so that the recirculation line is fluidically blocked or can be blocked by means of the valve element. At least or exactly one second value is a value other than zero (0) whose absolute value is greater than 0. Most preferably, several second values ​​are values ​​other than 0, each with an absolute value greater than 0, wherein, in particular, the several second values ​​differ from each other in pairs.This allows the amount of air flowing through the recirculation line to be adjusted, and in particular regulated, to meet specific requirements by means of the valve element, so that a particularly advantageous supply of air to the burner and consequently a particularly advantageous operation of the burner can be achieved.

[0014] The invention is based in particular on the following findings and considerations: To operate the burner, for example, a control system can be provided, which is implemented, for example, by means of an electronic computing device, also referred to as a control unit, in order to regulate the burner and thus operate it in a controlled manner. Typically, the burner control system is divided into a so-called fuel path and a so-called air path. The fuel path receives quantity information from a lambda signal, which is generated, for example, from an air mass. The quantity information is, or characterizes, for example, the quantity of fuel with which the burner is or has been supplied.The air mass is or characterizes the mass of the burner air with which the burner is or was supplied, whereby the air mass is measured, for example, by means of an air mass meter, in particular a hot-film air mass meter (HFM). The lambda signal is or characterizes, for example, an oxygen content, in particular residual oxygen content, in the burner exhaust gas, whereby the oxygen content is measured, for example, by means of a lambda probe, which can, for example, provide the lambda signal. From the quantity information, an injection rate can then be derived, which is, for example, a quantity of fuel that is used to form the burner mixture or, for example, is introduced into the combustion chamber.In the air path, a requirement, particularly regarding the quantity of burner air, is derived from numerous measured variables, such as pressure and temperature, especially of the burner air, measured by sensors. From these parameters, the quantity of burner air, expressed as a volume or mass flow rate, with which the burner is supplied or to be supplied is determined, or in particular calculated. The quantity of burner air with which the burner is supplied or to be supplied is used, for example, as a control variable for the air pump, i.e., for operating the air pump and, in particular, its electrical power, speed, and control. Thus, the determined quantity of burner air with which the burner is to be supplied is used, for example, to operate the air pump, in particular to regulate or control it.

[0015] The aforementioned fuel is introduced into the combustion chamber, for example, via an injection valve, to form the burner mixture. The fuel path is highly dynamic and can be operated dynamically. For instance, a control frequency at which the injection valve can be actuated to introduce the fuel into the combustion chamber, and an opening duration of the injection valve, which remains open continuously during this time, allow for advantageous adjustment or setting—that is, variation of the fuel quantity—even under extreme fluctuations and ramps. This can be ensured, for example, by means of a learning function, even over a long service life and operating time of the burner. However, the air path typically behaves differently.The amount of burner air supplied to the burner, also referred to as or designed as air mass flow, is highly dependent on the back pressure in the exhaust duct, which is characterized by high momentum dynamics and steep ramps. Furthermore, the characteristic curve of the air pump, such as that of a compressor wheel used to compress the burner air, exhibits extreme nonlinearity when external conditions create an unfavorable relationship between mass flow and back pressure. This forces the efficiency of the air pump to decrease, particularly at the corners of its characteristic curve, making it difficult to operate, and especially to control, the air pump effectively.If the mass flow rate no longer matches the air pump's rotational speed due to backpressure dynamics, the air pump's operating point shifts to the left of its characteristic curve, and the air mass flow rate abruptly drops to zero. This extreme control challenge can severely limit the reliable operation of the air pump and thus the burner, especially with significant backpressure in the exhaust duct, high dynamic vehicle operation, or operation at high, higher, and extremely high temperatures, where air density and absolute pressure decrease.

[0016] The aforementioned problems and disadvantages can now be avoided by the invention. Compared to conventional solutions, the invention provides a recirculation line and a valve element, also referred to as a recirculation valve or designed as a recirculation valve. The recirculation line is or comprises a recirculation channel through which air flows, whereby the air flowing through the recirculation channel bypasses the air pump and thus does not flow through it. The recirculation line enables particularly advantageous operation, especially particularly advantageous control, of the air pump and thus of the burner. Flow separation in the air pump, also referred to as stalling or, for example, compressor stall, and especially at the impeller of the air pump, as well as the probability of the air pump falling outside its operating range, can be avoided or significantly minimized.Excessive sensitivity of the air pump or burner operation to altitude and temperature can be avoided, as can excessive sensitivity of the air pump or burner operation to back pressure in the exhaust duct. By using the recirculation line and the valve element, a similarly rapid control dynamic can be achieved for the air path as for the fuel path.The recirculating air line can ensure a stable supply of burner air to the burner with the available volume or mass flow of air and a pressure level on the air pump outlet side, whereby a particularly robust supply of burner air to the burner can be achieved in particular through a storage effect of flow energy in the recirculating air duct or in the air flowing through the recirculating air line, especially with regard to and also in the case of pressure peaks and disturbances in or from the overall system.

[0017] By means of the valve element, also referred to as or designed as a recirculation valve, the quantity of air flowing through the recirculation line, as well as the pressure, particularly of the air, at an outlet side of the air pump, can be advantageously set, particularly in combination with the rotational speed of the air pump, i.e., the impeller of the air pump. This is defined, for example, as a volume and / or mass flow rate, and can be controlled, particularly independently of the actual quantity of burner air currently required by the burner, defined, for example, as a volume and / or mass flow rate. Thus, burner output control does not require a change in efficiency or the rotational speed of the air pump, but can be set, particularly solely, by a corresponding switching state or position of the valve element.

[0018] The air pump is a turbomachine, which is typically a very sluggish system. Experience has shown that this sluggishness either leads to drastic operating limits and restrictions in dynamics and power spreads, or the turbomachine must be intelligently augmented with additional components to enable safe operation, particularly control, and an extension of the operating map. The invention makes the latter possible, thus enabling particularly robust and therefore safe operation of the burner.

[0019] When the burner is started, that is, when it is switched from its deactivated state to its activated state, the locking element is opened, thus moving from the closed position to the open position.

[0020] To achieve particularly advantageous operation of the burner, the invention also provides that the burner is operated, at least temporarily, in a cleaning mode. In this cleaning mode, air is pumped through the supply line and the recirculation line by means of the air pump while the valve element is open. During this cleaning mode, particularly while air continues to be pumped, the valve element is closed, especially abruptly, in order to flush and thereby clean the channel with the air pumped by the air pump.

[0021] An operation in which air is pumped through the supply line and the recirculation line while the valve element is open is also referred to as recirculation operation, which is thus carried out during or within the cleaning operation. The cleaning operation utilizes the energy stored in the air pumped during or within the recirculation operation. This energy is then used to flush and clean the duct by abruptly and rapidly closing the valve element, resulting in high mass flow rates and pressure gradients of the air pumped by the pump. Since the duct is designed, for example, to create the aforementioned swirling airflow, it is also referred to as a swirl generator. The cleaning operation allows for particularly efficient cleaning of the swirl generator.In particular, the flow energy stored during or within the recirculation mode can be used to effectively and efficiently clean the duct of dirt and deposits, thus preventing excessive clogging of the duct. This also ensures advantageous burner operation over a long service life, as, for example, a high mass flow rate and a high pressure gradient of the burner air can be maintained throughout this extended period.

[0022] In an advantageous embodiment of the invention, the valve element is electrically controlled to close it. This allows the valve element to be closed abruptly and as needed, thus making advantageous use of the flow energy stored in the air pumped during recirculation operation, without flushing and therefore cleaning the duct.

[0023] Therefore, it is preferably intended that the valve element in the recirculating air duct be electrically controllable in order to adjust the amount of air flowing through the recirculating air duct. This allows the amount of burner air flowing through the recirculating air duct to be adjusted particularly precisely and according to demand, thus enabling particularly efficient burner operation.

[0024] Another embodiment is characterized by an electronic computing device, also referred to as a control unit or designed as such, by means of which the valve element is electrically controlled or can be controlled. The electronic computing device is specifically designed to provide an electrical signal by means of which the valve element can be electrically controlled or is controlled. The valve element can, for example, receive the electrical signal, thereby enabling or allowing the valve element to be electrically controlled. This allows the valve element to be operated, and in particular regulated, as required, so that, for example, the amount of burner air flowing through the recirculating air duct can be adjusted, and in particular regulated, as required.In particular, this allows the valve element to be closed particularly advantageously in order to effectively and efficiently utilize the flow energy stored in the burner air during or in the recirculation mode in order to flush and thus clean the channel.

[0025] In a further, particularly advantageous embodiment of the invention, the valve element is switched from an open state, releasing the recirculation line, to a closed state, fluidically blocking the recirculation line. This allows a high impulse and a high pressure build-up or pressure gradient of the air delivered by the air pump to be generated or used to flush the duct effectively and efficiently.

[0026] Thus, the valve element is preferably switchable between a closed state, which fluidically blocks the recirculation duct, and an open state, which releases the recirculation duct. This means that in the closed state, the recirculation duct is fluidically blocked by the valve element, so that no air can flow through it. In this state, the amount of burner air flowing through the recirculation duct is zero. In the open state, air can flow through the recirculation duct, so that in this state, the amount of air flowing through the recirculation duct, or its value, is different from zero, and in particular greater than zero (0).

[0027] In a further, particularly advantageous embodiment of the invention, the valve element is switched between the closed state and several open states that release the recirculating air duct. These open states are the first open state and several further open states, each differing from the others with respect to a specific quantity. This allows for particularly advantageous operation, and especially advantageous control, of the burner. In other words, the valve element is switchable between the closed state and the several open states that release the recirculating air duct. This means that the valve element releases the recirculating air duct in the open states, but it is provided that the valve element releases the recirculating air duct to varying degrees or to different extents in the open states, considering the recirculating air duct in pairs.This allows the amount of burner air flowing through the recirculating air duct to be adjusted and, in particular, regulated with particular precision and according to demand, so that a particularly advantageous operation of the burner can be achieved.

[0028] In order to be able to adjust the amount of burner air flowing through the recirculation line, and thus the amount of burner air flowing through the recirculation line, particularly advantageously, in one embodiment of the invention it is provided that the valve element is arranged in the recirculation line.

[0029] A second aspect of the invention relates to a motor vehicle, also referred to simply as a vehicle, preferably designed as a motor car, in particular as a passenger car or as a commercial vehicle, which has an internal combustion engine by means of which the motor vehicle can be propelled. Furthermore, the motor vehicle, in particular the internal combustion engine, has an exhaust system through which exhaust gas from the internal combustion engine flows, 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.

[0030] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures 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.

[0031] The drawing shows in: Fig. 1 a schematic representation of an exhaust system for an internal combustion engine of a motor vehicle; Fig. 2. A further schematic representation of the exhaust system (in part); and Fig. 3 A schematic sectional view of a burner in the exhaust system.

[0032] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0033] Fig. Figure 1 shows a schematic representation of an exhaust system 10 for an internal combustion engine 12, also referred to as a motor, internal combustion engine, or combustion power unit, of a motor vehicle, preferably a car, which is also referred to as a vehicle. This means that the motor vehicle, in its fully manufactured state, has the internal combustion engine 12 and can be driven by means of the internal combustion engine 12. For example, the internal combustion engine 12 is designed as a diesel engine. A tank 14, also referred to as a fuel tank, is associated with the internal combustion engine, in which a fuel, in particular a liquid fuel, is stored or held for operating the internal combustion engine 12 during its combustion operation. The fuel is, for example, diesel fuel, which is also simply referred to as diesel.A low-pressure pump 16 transfers fuel from tank 14 to a high-pressure pump 18. The high-pressure pump 18 pressurizes the fuel and delivers it to injectors 20. Specifically, the high-pressure pump 18 delivers the fuel to a common fuel distribution element, also known as a rail, which is shared by the injectors 20. The high-pressure fuel can be temporarily stored in the fuel distribution element. The high-pressure fuel stored in the fuel distribution element is then distributed to the injectors 20, allowing the fuel to be injected directly into the respective combustion chambers and thus into the respective cylinders 22 of the internal combustion engine 12.Each cylinder 22 partially limits the respective combustion chamber of the internal combustion engine 12.

[0034] The internal combustion engine 12 has an intake tract 24, also referred to as the intake tract, through which air flows. The air flowing through the intake tract 24 is also called fresh air or combustion air. The fresh air flowing through the intake tract 24 is directed to and into the combustion chambers and thus to the cylinders 22. A fuel-air mixture is thus formed from the fuel and the fresh air, which is ignited in the respective combustion chamber and thus in the respective cylinder 22, in particular by auto-ignition, and subsequently burned. This results in exhaust gas from the internal combustion engine 12, also referred to as engine exhaust. The internal combustion engine 12 has an exhaust tract 26 through which the engine exhaust gas from the combustion chambers flows, which is, for example, a component of the exhaust system 10.The exhaust system 10 is permeable to the engine exhaust gas from the combustion chambers. The respective fuel-air mixture comprises fresh air and fuel. The internal combustion engine 12 also includes a charging device 28, which has at least one exhaust gas turbocharger 30. The exhaust gas turbocharger 30 comprises a compressor 32 arranged in the intake tract 24, by means of which the fresh air flowing through the intake tract 24 can be compressed. The exhaust gas turbocharger 30 also comprises a turbine 34 arranged in the exhaust tract 26 and driven by the engine exhaust gas, by means of which the compressor 32 can be driven, in particular via a shaft of the exhaust gas turbocharger 30. The exhaust system 10 has an exhaust aftertreatment device 36, which may, for example, comprise a nitrogen oxide storage catalyst 38, a particulate filter 40, and an SCR catalyst 42.The nitrogen oxide storage catalyst 38, also referred to as a storage catalyst, storage catalytic converter, or NOx storage catalyst, is designed to capture, retain, and, in particular, store any nitrogen oxides (NOx) contained in the engine exhaust gas. The nitrogen oxide storage catalyst 38, the particulate filter 40, and the SCR catalyst 42 are components of the exhaust system 10. These components are arranged sequentially in the direction of flow of the engine exhaust gas through the exhaust system 10, i.e., in series with one another. The engine exhaust gas can flow through the components. In this context, the components are exhaust aftertreatment elements by means of which the engine exhaust gas is or can be treated. The storage catalyst is arranged upstream of the particulate filter 40 in the direction of flow of the engine exhaust gas through the exhaust system 10, which in turn is arranged upstream of the SCR catalyst 42.The particulate filter 40 is designed, for example, to filter out any particles contained in the exhaust gas, especially soot particles, from the engine exhaust. In particular, if the internal combustion engine 12 is a diesel engine, the particulate filter 40 is designed, for example, as a diesel particulate filter.

[0035] Furthermore, a metering device 44 is provided, by means of which a reducing agent, in particular a liquid, such as an aqueous urea solution, can be introduced or is introduced into the exhaust gas flowing through the exhaust system 10 at a point S1, also referred to as the injection point. The exhaust system 10 has at least one exhaust channel through which the engine exhaust gas flows, and the reducing agent can be introduced, in particular injected, into the exhaust channel and thus into the engine exhaust gas flowing through the exhaust channel, particularly at point S1, for example, by means of the metering device 44. In the present case, the exhaust system 10 has a mixing chamber 46, which is arranged downstream of point S1 and upstream of the SCR catalyst 42.In the mixing chamber 46, for example, the reducing agent introduced into the exhaust channel and thus into the engine exhaust can mix with the exhaust gas (engine exhaust) flowing through the exhaust system 10 or the exhaust channel.

[0036] The exhaust system 10 also includes a burner 48. The burner 48 can be supplied with a fuel, particularly a liquid fuel, and with air, which is also referred to as burner air. For example, the fuel mentioned above is referred to as the fuel. By means of the burner 48, a mixture, also referred to as a burner mixture, can be formed from the burner air, with which the burner 48 can be supplied, is supplied, or was supplied, and from the fuel, with which the burner 48 can be supplied, was supplied, or is supplied. By means of the burner 48, the burner mixture can be combusted, in particular by forming a flame 50. This results, for example, in exhaust gas from the burner 48, which is also referred to as burner exhaust. It can be seen that the burner mixture comprises the burner air and the fuel with which the burner 48 can be supplied, is supplied, or was supplied.In particular, the burner exhaust gas can flow out of the burner 48 and into the exhaust duct, subsequently flowing through the exhaust duct, i.e., the exhaust system 10. It is evident that the burner exhaust gas can flow through the respective component, so that, for example, at least one of the components can be heated and / or kept warm by means of the burner exhaust gas. It is evident that the burner 48, in particular an inlet point where the burner exhaust gas and, for example, the flame 50 can be introduced into the exhaust duct and thus into the engine exhaust flowing through the exhaust duct, is located upstream of the nitrogen oxide storage catalyst 38 and / or upstream of the particulate filter 40 and / or upstream of the SCR catalyst 42. This allows, for example, the nitrogen oxide storage catalyst 38 and / or the particulate filter 40 and / or the SCR catalyst 42 to be heated and / or kept warm.

[0037] To supply the burner 48 with fuel, a fuel line 52 is provided. The fuel line 52 is fluidically connected at a first connection point V1 to a supply line 54, through which the fuel can be conveyed from the tank 14 to the injectors 20 or to the fuel distribution element. The connection point V1 is arranged downstream of the low-pressure pump 16 and upstream of the high-pressure pump 18 in the direction of fuel flow through the supply line 54. At least a portion of the fuel flowing through the supply line 54 can be diverted from the supply line 54 and introduced into the fuel line 52.The fuel diverted from supply line 54 via fuel line 52 can flow through fuel line 52 and is conveyed as fuel via fuel line 52 to burner 48, thus supplying burner 48 with the fuel flowing through fuel line 52. In this way, burner 48 is supplied with fuel from tank 14, with the fuel being used as the fuel source.

[0038] Furthermore, the burner 48 is equipped with its own electrically operated air pump 56, which is provided in addition to the internal combustion engine 12 and thus in addition to the charging device 28. An air line 58, designated as the supply line, is also provided, in which the air pump is located. The air pump 56 allows the burner 48 to be supplied with air, i.e., burner air, independently of the internal combustion engine 12 and thus independently of the charging device 28. In other words, air can flow through the air line 58, so that the burner 48 can be supplied with the air flowing through the air line 58, i.e., burner air. The air pump 56 can pump the air flowing through the air line 58.Thus, by means of the air pump 56, the burner air can be conveyed through the air line 58 and conveyed to the burner 48 in order to supply the burner 48 with the burner air.

[0039] A valve element 60 is arranged in the fuel line 52, by means of which the quantity of fuel with which the burner 48 can be supplied or is supplied is adjustable, in particular controllable. A valve element 62 is arranged in the air line 58, in particular downstream of the air pump 56, by means of which the quantity of air with which the burner 48 can be supplied or is supplied is adjustable, in particular controllable.

[0040] For example, an electronic computing device, also referred to as a control unit 64, is provided, specifically assigned to the burner 48. The control unit 64 is designed, for example, to actuate, in particular to control or regulate, the valve element 60. This allows, for example, the amount of fuel supplied to the burner 48 to be adjusted, in particular to be regulated or controlled, by the control unit 64 through actuation of the valve element 60. Alternatively or additionally, the control unit 64 can actuate, in particular to control or regulate, the valve element 62. Thus, the control unit 64 can, for example, adjust, in particular to control or regulate, the amount of air flowing through the air line 58 to supply the burner 48 by actuation, in particular to control or regulate, the valve element 62.In particular, this allows the ratio of burner air to fuel, also known as the combustion air ratio, to be adjusted to meet specific requirements.

[0041] In order to achieve particularly advantageous operation of the burner 48, the exhaust system 10 has a recirculation line 68, which is provided in addition to the air line 58 and is at least partially separated from it. The recirculation line 68 is or comprises a recirculation duct, which will be explained in more detail below. The recirculation line 68 is fluidically connected to the air line 58 at both a connection point V2 and a connection point V3. Fig. Figure 1 shows that, in the direction of flow of the air flowing through the air duct 58, also referred to as burner air, the connection point V2 is located downstream of the air pump 56 and upstream of the burner 48, in particular upstream of the valve element 62. In the direction of flow of the air flowing through the air duct 58, the connection point V3 is located upstream of the air pump 56 and thus upstream of the connection point V2. At connection point V2, at least a portion of the air flowing through the air duct 58 and supplied by the air pump 56, particularly during its operation, can be diverted from the air duct 58 and introduced into the recirculating air duct 68.The air branched off from air duct 58 and introduced into recirculation duct 68 can flow through recirculation duct 68 and is or is guided by means of recirculation duct 68 from connection point V2, bypassing air pump 56, to connection point V3, in particular, is or is returned. At connection point V3, the air flowing through recirculation duct 68 and thus bypassing air pump 56 can or is discharged from recirculation duct 68, bypassing air pump 56, and can or is (re)introduced into air duct 58. It is evident that air pump 56 is or is bypassed by the air flowing through recirculation duct 68. This means that the air flowing through the recirculating air line 68 bypasses the air pump 56 on its way from the connection point V2 to the connection point V3 and into the air line 58, and therefore does not flow through the air pump 56.

[0042] The exhaust system 10 also has a valve element 70 by means of which the quantity of air flowing through the recirculation line 68 and thus bypassing the air pump 56, for example as a volume flow and / or mass flow, can be adjusted, in particular regulated. In the case of the Fig. In the embodiment shown in Figure 1, the valve element 70 is located in the recirculating air line 68 and is arranged downstream of the connection point V3 and upstream of the connection point V2.

[0043] The valve element 70 is preferably electrically controllable in order to adjust the amount of air flowing through the recirculation line 68. For this purpose, the exhaust system 10 includes, for example, the control unit 64 by means of which the valve element 70 can be controlled.

[0044] The valve element 70 is preferably switchable between, in particular, a closed state that fluidly blocks the recirculation duct 68 and several open states that each release the recirculation duct 68. By switching the valve element 70 to the respective open state, a different value than zero can be set for the quantity of air flowing through the recirculation duct 68, wherein the values ​​greater than zero differ from each other, in particular in pairs. Since the recirculation duct 68 is fluidly blocked by the valve element 70 in the closed state, the value of the quantity of air flowing through the recirculation duct 68 is, so to speak, zero.

[0045] Out of Fig. 2 It is evident that the valve element 70, for example, has a valve part 74 which is movable between at least one closed position effecting the closed state and a respective open position effecting the respective open state, in particular translationally and / or rotationally, especially relative to the recirculated air line 68 and / or relative to the air line 58. Fig. Figure 2 illustrates the airflow towards the burner 48, particularly downstream of connection point V2 and downstream of air pump 56, as shown by arrow 76. Furthermore, it is shown that... Fig. 2. It is evident, for example, that an air filter 72 is arranged in the air duct 58 for filtering the air flowing through the air duct 58. In the case of the Fig. In the embodiment shown in Figure 2, the air filter 72 is arranged upstream of the air pump 56 and upstream of the connection point V3.

[0046] Finally, it shows Fig. 3 in a schematic longitudinal section view the burner 48. As seen from Fig. As can be seen in Figure 3, the burner 48 has a combustion chamber 78 in which the burner mixture, comprising the combustion air supplied to the burner 48 and the fuel supplied to the burner 48 (preferably liquid), is to be ignited and thereby combusted, i.e., ignited and thereby combusted during operation of the burner 48. The combustion chamber 78 is delimited, in particular directly, by a chamber element 80, which in this case is designed as a solid body, and in particular by an inner circumferential surface 82 of the chamber element 80. The burner 48 has an ignition device 84, which is designed in particular as a spark plug, glow plug, or glow pin, and is in particular electrically operated, by means of which the burner mixture, in particular in the combustion chamber 78, can be ignited.By means of the ignition device 84, in particular by using electrical energy by which the ignition device 84 can be supplied or is supplied, at least one ignition spark can be generated at at least or exactly one ignition point Z, by means of which the burner mixture in the combustion chamber 78 can be ignited and subsequently combusted, in particular by providing the burner exhaust gas and / or by providing the flame 50. It is evident that the ignition point Z is arranged in the combustion chamber 78. The chamber element 80 has at least one or, in this case, several flow openings 86 through which the burner exhaust gas from the combustion chamber 78 can flow. Thus, the burner exhaust gas can be discharged from the combustion chamber 78 via the flow openings 86 and introduced into the exhaust duct.

[0047] At the in Fig. In the embodiment shown in Figure 3, the burner 48 has a first channel 88 with a first swirl chamber 90, which is also referred to as the inner swirl chamber. A first portion of the burner air can flow through the first channel 88 and thus the first swirl chamber 90. A first swirl flow of the first portion of the burner air can be effected by means of the first swirl chamber 90. When air is mentioned below, unless otherwise specified, this refers to the burner air. The feature that the first swirl flow of the first portion of the air can be effected by means of the first swirl chamber 90 means, in particular, that the first portion of the air flows in a swirl pattern through at least a first sub-region of the swirl chamber 90 and / or flows out of the swirl chamber 90 in a swirl pattern and / or flows in a swirl pattern into and thus into the combustion chamber 78.The first channel 88 and, in this case, the first swirl chamber 90, each have, in particular, a first outlet opening 92, through which the first portion of air can flow in a first direction of passage of the outlet opening 92 and thus in a first direction of flow that coincides with the first direction of passage, or through which the first portion of air flows during operation of the burner 48. The burner 48 also has an injection element 94 by means of which the fuel can be introduced, at least indirectly, and in particular directly, into the channel 88 and thus, in this case, into the swirl chamber 90, and in particular injected. The injection element 94 is also referred to as an injection valve.The channel 88, and thus the swirl chamber 90, is therefore permeable to both the first portion of air and the fuel injected from the injection element 94, so that the outlet opening 92 is permeable to both the first portion of air and the fuel from the injection element 94. The first portion of air, and thus the fuel, can flow through the channel 88, and thus the swirl chamber 90 and the outlet opening 92, in the first flow direction, which is illustrated by arrow 96. The injection element 94 has, for example, at least or exactly one outlet opening, also referred to as an injection opening, or at least or exactly three outlet openings, also referred to as injection openings, wherein the respective outlet opening is permeable to the fuel supplied to the injection element 94.The injection element 94 can eject the fuel from its respective outlet opening and, in particular, introduce it at least indirectly, and especially directly, into the channel 88 and thus into the swirl chamber 90, forming a steel structure created by the fuel. In particular, the injection element 94 can introduce the fuel into the channel 88, bypassing the combustion chamber 78.

[0048] At the in Fig. In the embodiment shown in Figure 3, the burner 48 further comprises a second channel 98 with a second swirl chamber 100. The second swirl chamber 100 is an outer swirl chamber which surrounds at least a length of the first channel 88 and thus the first swirl chamber 90, and in particular completely, the first outlet opening 92, in a circumferential direction around the first flow direction. The first flow direction, through which the first portion of air and, in this case, also the fuel can flow, runs in the axial direction of the swirl chamber 90 or coincides with the axial direction of the swirl chamber 90. The circumferential direction of the inner swirl chamber (swirl chamber 90) runs around the axial direction of the inner swirl chamber (swirl chamber 90).The second channel 98, and thus the outer, second swirl chamber 100, whose axial direction coincides with that of the first swirl chamber 90, is designed to allow a second portion of the burner air to flow through it in a second direction and is configured to generate a second swirl flow of this second portion of air. The second flow direction and the first flow direction point in the same direction, so the second flow direction is also illustrated by arrow 96. The feature that the outer, second swirl chamber 100 is configured to generate the second swirl flow means that the second portion of air flows through the swirl chamber 100 in a swirl pattern and / or flows out of the swirl chamber 100 in a swirl pattern and / or flows into and thus into the combustion chamber 78 in a swirl pattern.In particular, it is provided that the second part of the burner air flows in a swirling motion through at least a second sub-area of ​​the swirl chamber 100 and / or flows out of the swirl chamber 100 in a swirling motion and / or flows in a swirling motion into and thus into the combustion chamber 78.

[0049] The second channel 98, and thus the outer, second swirl chamber 100, whose radial direction is perpendicular to the axial direction of the swirl chamber 100, has, in particular, a second outlet opening 102 through which the second portion of air flowing through the channel 98, and thus the swirl chamber 100, can flow in the second flow direction, and whose second direction of passage coincides with the second flow direction. The outlet opening 102 can be passed through in the second direction of passage, and thus in the second flow direction, by the second portion of air flowing through the channel 98, and thus the swirl chamber 100. The second flow direction, and thus the second direction of passage, coincides with the axial direction of the swirl chamber 100, and thus with the axial direction of the swirl chamber 90, whose radial direction is perpendicular to the axial direction of the swirl chamber 90 and, in this case, coincides with the radial direction of the swirl chamber 100.It can be seen that the outlet opening 102 is arranged downstream of the outlet opening 92 in the direction of airflow of the respective portion of the air and thus also in the direction of fuel flow, so that the outlet opening 102 can be permeated by the second portion of the air, the first portion of the air, and, in this case, also by the fuel. In the direction of airflow through channels 88 and 98 and thus through swirl chambers 90 and 100, the second outlet opening 102 is arranged downstream of the first outlet opening 92 and is connected in series with the first outlet opening 92, so that the second outlet opening 102 can be permeated by the second portion of the air, the first portion of the air, and, in this case, also by the fuel from channel 88 or swirl chamber 100.

[0050] The channel 88 is, for example, directly bounded by a solid component 104 of the burner 48. In this case, the channel 88 is directly bounded by an inner circumferential surface 106 of the component 104. In particular, the inner circumferential surface 106 directly forms or bounds a flow cross-section of the channel 88, the flow cross-section of which, in the first flow direction (arrow 96), is permeable to the first portion of the air and, in this case, also to the fuel. In this case, the channel 88 is designed as a nozzle, at least in a length L of the channel 88, such that the flow cross-section tapers in the first flow direction. The channel 88 has an end E facing the combustion chamber 78, at which the channel 88 terminates in the first flow direction.The outlet opening 92 is located at end E, so that, viewed in the first flow direction, the channel 88 and, in this case, also the swirl chamber 90 terminate at end E and thus at the outlet opening 92. Therefore, the first part of the air, and in this case also the fuel, can flow out of the channel 88 at and via end E and subsequently be fed into the combustion chamber 78.

[0051] The burner 48 has a sealing element 108 which, in particular relative to the chamber element 80, is located between at least one in Fig.The valve element 108 is movable, in particular pivotable, between the locking position shown in Figure 3 and at least one release position not shown. In the locking position, the outlet opening 92 is closed by the valve element 108 and thus fluidically separated from the combustion chamber 78. In the release position, the valve element 108 releases the outlet opening 92, so that the outlet opening 92 and, via the outlet opening 92, the channel 88 are fluidically connected to the combustion chamber 78.

[0052] In a method for operating the burner 48, the burner 48 is operated in a cleaning mode in which air is conveyed through the air line 58 and the recirculation line 68 by means of the air pump 56, while the valve element 70 is open, i.e., in its closed state. During the cleaning mode, particularly while air continues to be conveyed by the air pump 56, the valve element 70 is closed abruptly or suddenly in order to flush and thereby clean the channel 88 and thus the swirl chamber 90 with the air conveyed by the air pump 56 during the cleaning mode.By first pumping air through the air line 58 and the open recirculation line 68 using the air pump 56 while the valve element 70 is open, i.e., in its open state, a recirculation operation is carried out, through which a advantageously high flow energy can be stored in the air pumped by the air pump 56. If the valve element 70 is then abruptly opened during the cleaning operation, the high flow energy can be used to flush and clean the channel 88 and, in this case, the swirl chamber 90, that is, to remove any deposits. Reference symbol list 10 Exhaust system 12 Internal combustion engine 14 Tank 16 Low-pressure pump 18 High-pressure pump 20 injectors 22 cylinders 24 Intake tract 26 Exhaust system 28 Charging device 30 exhaust gas turbochargers 32 compressors 34 Turbine 36 Exhaust aftertreatment system 38 Nitrogen oxide storage catalyst 40 particulate filters 42 SCR catalyst 44 Dosing unit 46 Mixing chamber 48 burners 50 flames 52 Fuel line 54 Supply line 56 Air pump 58 Air duct 60 Valve element 62 Valve element 64 Control unit 68 Recirculation duct 70 Valve element 72 air filters 74 Valve part 76 Arrow 78 Combustion chamber 80 chamber element 82 inner circumferential surface 84 Ignition device 86 Flow opening 88 first channel 90 first swirl chamber 92 first outlet 94 Insertion element 96 Arrow 98 second channel 100 second swirl chamber 102 second outlet 104 Component 106 inner circumferential surface E End L Length range S1 position V1 liaison point V2 liaison point V3 junction Z Ignition point QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 008 965 A1

[0002] DE 10 2021 001 580 A1

[0002]

Claims

[1] Method for operating a burner (48) arranged in an exhaust system (10) for an internal combustion engine (12) of a motor vehicle and supplied with air and fuel, wherein: - the exhaust system (10) has: a supply line (58) through which air can flow, via which the burner (48) can be supplied with the air flowing through the supply line (58); and o an air pump (56) arranged in the supply line (58), by means of which the air can be conveyed through the supply line (58) and conveyed to the burner (48) in order to supply the burner (48) with air; and - the burner (48) has: a combustion chamber (78) in which a mixture comprising air and fuel is to be burned; and o at least one channel (88) through which air can flow, which has an outlet opening (92) through which the combustion chamber (78) can be supplied with the air flowing through the channel (88); and characterized by , that: - a recirculating air line (68) is provided which is fluidically connected to the supply line (58) at a first connection point (V2) arranged downstream of the air pump (56) and at a second connection point (V3) arranged upstream of the air pump (56), via which at least a part of the air flowing through the supply line (58) can be returned from the first connection point (V2) to the second connection point (V3) bypassing the air pump; - a valve element (70) is provided by means of which the quantity of air flowing through the recirculation line (68) and thereby bypassing the air pump (56) can be adjusted; - the burner (48) is operated in a cleaning operation in which: o air is pumped through the supply line (58) and the recirculation line (68) by means of the air pump (56) while the valve element (70) is open; and o the valve element (70) is closed in order to flush and thereby clean the channel (88) by means of the air supplied by the air pump (56). [2] Method according to claim 1, characterized by , that the valve element (70) is electrically controlled in order to close the valve element (70). [3] Method according to claim 1 or 2, characterized by an electronic computing device (64) by means of which the valve element (70) is electrically controlled. [4] Method according to any one of the preceding claims, characterized by , that the valve element (70) is switched from an open state releasing the recirculation line (68) to a closed state fluidically blocking the recirculation line (68). [5] Method according to claim 4, characterized by, that the valve element (70) is switched between the closed state and several open states releasing the recirculation line (68), namely the open state as the first open state and several further open states, the open states differing from each other with respect to a respective value of the quantity. [6] Method according to any one of the preceding claims, characterized by , that the valve element (70) is arranged in the recirculation line (68). [7] Motor vehicle, comprising an internal combustion engine (12) by means of which the motor vehicle can be driven, and an exhaust system (10) through which exhaust gas of the internal combustion engine (12) flows, which is designed to carry out a method according to one of the preceding claims.

Images