Exhaust gas burner and exhaust gas aftertreatment system

Abstract

The invention relates to an exhaust gas burner (10) for an exhaust gas aftertreatment system (1) of an internal combustion engine (2), with a combustion chamber (11), in which a mixture of an oxygen-containing gas and fuel can be burned in order to form a heating gas, wherein at least one injection valve (12) for injecting the fuel into the combustion chamber (11) is arranged on the combustion chamber (11), and wherein the combustion chamber (11) has a gas inlet for the gas and a heating gas outlet (27) for the heating gas, and with a mixing device (28) which has an inlet (32) for exhaust gas of the internal combustion engine (2), the heating gas outlet, means for mixing the exhaust gas with the heating gas, and an outlet (33) for the mixed gas. It is provided that at least the mixing device (28) is designed as a tubular module (29) which can be integrated into the exhaust gas aftertreatment system (1).

Description

[0001] Description

[0002] title

[0003] Exhaust gas burner and exhaust gas aftertreatment system

[0004] The invention relates to an exhaust gas burner for an exhaust gas aftertreatment system of an internal combustion engine, comprising a combustion chamber in which a mixture of an oxygen-containing gas and fuel can be combusted to form a heating gas, wherein at least one injection valve for injecting the fuel into the combustion chamber is arranged on the combustion chamber, and wherein the combustion chamber has a gas inlet for the gas and a heating gas outlet for the heating gas, and comprising a mixing device which has an inlet for exhaust gas of the internal combustion engine, the heating gas outlet, means for mixing the exhaust gas with the heating gas and an outlet for the mixed gas.

[0005] Furthermore, the invention relates to an exhaust gas aftertreatment system with the above-mentioned exhaust gas burner, which is fluidically connected upstream of an exhaust gas aftertreatment device.

[0006] State of the art

[0007] Exhaust gas burners of the type mentioned above are already known from the prior art. For example, published patent application DE 19 504208 A1 discloses an exhaust gas burner that is fluidically arranged upstream of a catalyst of an exhaust gas aftertreatment system. The exhaust gas burner has a combustion chamber to which air and fuel are supplied and combusted in the combustion chamber with the aid of an ignition device, and then added or mixed into the exhaust gas flow upstream of the catalyst. This ensures that the catalyst is heated particularly quickly to a favorable operating temperature. A similar solution is also proposed in published patent application DE 102009 053 379 A1. It is also provided that the fuel and the oxygen-containing gas are introduced coaxially into the combustion chamber.For this purpose, a guide device is assigned to the combustion chamber, which surrounds the injection valve at its end facing the combustion chamber along an axial section of the injection valve and thereby forms an air flow channel coaxial with the injection valve, the annular opening of which opens into the combustion chamber coaxial with the injection opening of the injection valve.

[0008] The known solutions from the state of the art have the disadvantage that optimal mixing of the exhaust gas with the heating gas either does not occur or has to be set up or adapted at great expense for each application because, for example, the exhaust gas aftertreatment systems of different motor vehicles and / or different internal combustion engines have different spatial conditions, have different courses and must meet different conditions.

[0009] Disclosure of the invention

[0010] The exhaust gas burner according to the invention with the features of claim 1 has the advantage over the prior art that it can be easily integrated into and adapted to an existing exhaust gas aftertreatment system. The solution according to the invention enables the integration of the exhaust gas burner according to the invention into an existing exhaust gas aftertreatment system without great effort, because the exhaust gas burner according to the invention already carries and advantageously integrates the means necessary for mixing the fuel gas and exhaust gas. According to the invention, this is achieved by designing at least the mixing device as a tubular module that can be integrated into the exhaust gas aftertreatment system.The mixing device, which forms part of the exhaust gas burner, is tubular, allowing it to be integrated into the exhaust gas aftertreatment system, for example, as an extension of an internal combustion engine exhaust pipe, without the need for any special additional precautions. Apart from the appropriate diameters of the tubular module and the exhaust pipe, as well as the downstream exhaust pipe / exhaust gas aftertreatment device, no additional considerations are required. Due to its tubular design, the exhaust gas burner with the mixing device can be advantageously integrated into the exhaust tract and connected to other tubular elements of the exhaust tract in a conventional manner, thus allowing the use of well-known and widely used fastening and connection options.The tubular design of at least the mixing device ensures that it can be integrated into the exhaust aftertreatment system in a space-optimized manner. All that's required is to create a longitudinal section for the mixing device in the exhaust tract, or remove it and replace it with the mixing device module. Because the mixing device itself already incorporates the provisions for mixing fuel gas and exhaust gas, no further modifications to the exhaust aftertreatment system are necessary.

[0011] The module preferably has an inlet flange that can be connected to an exhaust pipe and an outlet flange that can be connected to the exhaust pipe. The module is thus inserted into the exhaust pipe by means of the inlet flange and outlet flange and is connected to it on the inlet and outlet sides. This ensures simple and compact integration of at least the mixing device into the exhaust gas aftertreatment system. The exhaust pipe can be, for example, the outlet pipe of the internal combustion engine or the inlet pipe or the inlet of an exhaust gas aftertreatment device.

[0012] Preferably, the inlet flange and outlet flange are aligned and arranged flush with each other. This ensures that, to the greatest extent possible, undesirable flow losses occur when the exhaust gas from the internal combustion engine flows through the mixing device.

[0013] Furthermore, it is preferably provided that the inlet flange forms the inlet and the outlet flange forms the outlet. This means that the exhaust gas flows through the inlet into the exhaust gas burner or into the mixing device of the exhaust gas burner, and exhaust gas and heating gas flow out through the outlet as a mixed gas into the catalyst located downstream of it, so that the catalyst can be heated particularly quickly to its operating temperature by means of the exhaust gas burner. Furthermore, it is preferably provided that the combustion chamber is arranged outside the tube module. Thus, the combustion chamber itself is not located in the module through which the exhaust gas is also conducted, whereby the combustion chamber can be easily adapted to specific boundary conditions, such as its performance.For example, combustion chambers of different sizes or capacities can be connected to the same mixing device, allowing the exhaust gas burner to be adapted to different internal combustion engines and aftertreatment requirements with minimal effort. Furthermore, the combustion chamber can be repaired independently of the mixing device and replaced if necessary.

[0014] According to a preferred embodiment of the invention, the mixing device comprises a first pipe element through which the exhaust gas can be guided, and a second pipe element which is arranged in particular coaxially to the first pipe element, wherein the first pipe element has at least one heating gas inlet opening in its casing wall through which the heating gas can flow radially into the pipe element, and wherein the second pipe element has the heating gas outlet in its casing wall. The heating gas thus passes through the casing wall of the second or outer pipe element into an intermediate space between the first and the second pipe element. This allows the heating gas to flow around the first pipe element in order to be advantageously mixed with the exhaust gas of the internal combustion engine. The heating gas flows through the at least one heating gas inlet opening in the casing wall of the first pipe element into the first pipe element and is advantageously mixed there with the exhaust gas.The advantageous design ensures that the heating gas is fed radially into the exhaust gas, resulting in advantageous mixing of heating gas and exhaust gas within the first pipe element. Thus, the mixture from the exhaust gas burner outlet advantageously enters the exhaust gas aftertreatment system and, in particular, the downstream catalyst, preferably a three-way catalyst, in such a way that the latter is evenly exposed to the hot exhaust gas stream. Particularly preferably, the first pipe element has a plurality of heating gas inlet openings evenly distributed over its circumference, thus achieving a uniform introduction of the heating gas into the exhaust gas.

[0015] Particularly preferably, at least one, in particular several or all of the heating gas inlet openings are assigned at least one flow guide element, through which the heating gas is guided or passed through the respective heating gas inlet opening into the first pipe element. The flow guide element ensures that the heating gas flowing into the intermediate space is advantageously guided into the first pipe element. For this purpose, the respective flow guide element projects, for example, radially from the first pipe element into the intermediate space and is inclined or tangentially aligned in order to ensure advantageous introduction of the heating gas into the exhaust gas. Alternatively and / or additionally, a flow guide element is also assigned to the respective heating gas inlet opening on the inside of the first pipe element, through which flow guide element an advantageous introduction or introduction of the heating gas into the exhaust gas flow is ensured.

[0016] Preferably, the heating gas outlet is oriented tangentially to the first pipe element and / or the second pipe element, such that the heating gas is guided in the circumferential direction between the first pipe element and the second pipe element, creating a swirl chamber. This ensures that the heating gas flows around the first pipe element before entering the first pipe element, effectively executing a swirling motion or rotating around the first pipe element. As a result, the heating gas advantageously flows tangentially through the respective heating gas inlet opening into the first pipe element, where it mixes with the exhaust gas flowing through, allowing the downstream catalyst to reach its operating temperature particularly quickly.

[0017] According to a preferred embodiment of the invention, the mixing device and the combustion chamber are arranged together in the module. The mixing device and the combustion chamber are thus jointly enclosed in a tubular housing, so that the combustion chamber is also located in the module housing and can thus be integrated into the exhaust gas aftertreatment system in a particularly compact manner.

[0018] Furthermore, it is preferably provided that a sensor, in particular a lambda probe, is arranged between the combustion chamber and the heating gas outlet, by means of which the combustion process of the combustion chamber can be monitored.

[0019] The exhaust gas aftertreatment system according to the invention with the features of claim 12 is characterized by the inventive design of the exhaust gas burner. This results in the advantages already mentioned above.

[0020] Further advantages and preferred features and combinations of features emerge in particular from the above description and from the claims. The invention will be explained in more detail below with reference to the drawings.

[0021] Figure 1 shows an advantageous exhaust gas aftertreatment system in a schematic representation,

[0022] Figure 2 shows an advantageous exhaust gas burner of the

[0023] Exhaust aftertreatment system in a simplified representation,

[0024] Figures 3A to D show an advantageous mixing device of the exhaust gas burner according to different embodiments, and

[0025] Figure 4 shows another embodiment of the exhaust gas burner in a simplified sectional view.

[0026] Figure 1 shows a simplified representation of an advantageous exhaust gas aftertreatment system 1 for an internal combustion engine 2 of a motor vehicle, which in this case is designed as a reciprocating piston engine. The internal combustion engine 2 is assigned a fresh air tract 3 and an exhaust tract 4. From the exhaust valves of the internal combustion engine 2, an exhaust pipe 5 of the exhaust tract 4 leads to several exhaust gas aftertreatment devices 6, 7 and 8 of the exhaust gas aftertreatment system 1, wherein, viewed in the direction of flow, the first exhaust gas aftertreatment device 6 is a three-way catalytic converter, the second exhaust gas aftertreatment device 7 is a second three-way catalytic converter, and the third exhaust gas aftertreatment device 8 is a particulate filter. The exhaust gas from the internal combustion engine flows through the exhaust gas aftertreatment devices 6, 7, 8 one after the other and serves to reduce pollutant emissions and particles in the exhaust gas.

[0027] To ensure that the exhaust gas aftertreatment devices 6, 7, 8 reach their optimal operating temperature as quickly as possible, particularly after a cold start of the internal combustion engine 2, a heating device 9 with an exhaust gas burner 10 of the exhaust gas aftertreatment system 1 is also assigned to the exhaust tract 4. The exhaust gas burner 10 has a combustion chamber 11 to which fuel can be supplied through an injection valve 12 and oxygen-containing gas, in particular air, through a guide device 13 in order to be ignited and combusted in the combustion chamber with the aid of an ignition device 14. The combusted fuel / air mixture is supplied through an outlet opening 15 of the exhaust gas burner 10 to the exhaust tract 4 upstream of the first catalytic converter 6, such that the heated gas mixture increases the operating temperature of the exhaust gas aftertreatment devices 6, 7, 8 even before the internal combustion engine 2 provides the exhaust gas enthalpy required for heating the peripheral exhaust system.

[0028] A controllable valve device 16 is connected upstream of the exhaust gas burner 10, by means of which the supplied air flow can be adjusted. An air pump or air conveying device 17 is advantageously arranged upstream of the valve device 16, by means of which fresh air can be drawn in and conveyed toward the valve device 16. An air mass meter 18 and an air filter 19 are also connected upstream of the air conveying device 17.

[0029] A control unit 20 of the heating system controls or operates the air mass meter 18, the air pump 17, the valve device 16, and the exhaust gas burner 10 to generate the desired amount of heating gas, i.e., a combusted air-fuel mixture, which is fed to the exhaust tract 4 to heat the exhaust gas aftertreatment devices 6, 7, 8. The control unit 20 is in particular in communication with a control unit 21 of the internal combustion engine.

[0030] Figure 2 shows a simplified plan view of the exhaust gas burner 10 in a state integrated into the exhaust gas aftertreatment system 1. An exhaust pipe 22 coming from the internal combustion engine ends with a connecting flange 23. The inlet 24 of the first exhaust gas aftertreatment device 6, with a connecting flange 25, is located as an extension of the exhaust pipe 22. According to the present embodiment, the exhaust pipe 22 and the inlet 24 are arranged and aligned flush with one another. The exhaust gas burner 10 is arranged between the connecting flanges 23 and 25.

[0031] The exhaust gas burner 10 has the aforementioned combustion chamber 11, which contains the ignition device 14, the injection valve 12, and the guide device 13, which has the gas inlet for the oxygen-containing gas. Downstream of the combustion chamber 11, the exhaust gas burner 10 optionally has a lambda probe 26, by means of which the fuel / oxygen mixture can be monitored after combustion. The heating gas generated by the combustion in the combustion chamber 11 thus flows past the lambda probe 26 to a heating gas outlet 27, which opens into a mixing device 28. The mixing device 28 is designed to advantageously mix the heating gas with the exhaust gas coming from the exhaust pipe 22, so that the temperature of the mixture of exhaust gas and heating gas is so high that the downstream three-way catalytic converter is quickly and efficiently heated to its operating temperature.For this purpose, the mixing device 28 is designed to connect both the heating gas outlet 27 of the exhaust gas burner 10 and the exhaust gas pipe 22 to the adapter piece 35 or to the inlet funnel of the three-way catalytic converter 6.

[0032] For this purpose, the mixing device 28 is designed as a module 29 that can be integrated or is integrated into the gap between the exhaust pipe 22 and the inlet 24 or between the flanges 30 and 31. For this purpose, the mixing device 28 has an inlet flange 30 and an outlet flange 31, wherein the inlet flange has or forms an inlet 32 ​​for the exhaust gas and the outlet flange 31 has or forms an outlet 33 for the mixture of heating gas and gas. Optionally, the inlet flange 30 and the outlet flange 31 can be connected directly to the connecting flange 23 or 25, respectively. Alternatively, and as shown in the above embodiment, optional adapter pieces 34 and 35 are provided, which in particular implement an adaptation of a flow cross-section. In this case, the connecting piece 34 leads as an outlet funnel from the connecting flange 23 to the inlet flange 30 and is firmly connected to the latter.In particular, conventional methods such as screwing, welding, or gluing are used for the connection, or even detachable connections such as quick-release clamp connections. In particular, a non-destructively detachable connection technique, such as screwing, is used to enable easy disassembly for maintenance purposes or the like. The adapter piece 34 here reduces the flow cross-section of the exhaust pipe 22 to the smaller flow cross-section of the inlet flange 30 or the gas inlet 32. The adapter piece 35, in the present case as an inlet funnel of the exhaust gas aftertreatment device 6, is firmly connected to the outlet flange 31 on the one hand and to the connecting flange 25 on the other hand, in particular also by means of the above-mentioned methods, in particular by screwing. The adapter piece 35 thereby increases the flow cross-section from the outlet 33 to the inlet 24, viewed in the direction of flow.Optionally, at least one of the diameter changes or a change in the flow cross-section is omitted; in this case, the adapter pieces 34, 35 are tubular or cylindrical. The respective diameter change is selected in particular depending on boundary conditions, such as the performance of the internal combustion engine and / or the exhaust gas aftertreatment devices 6, 7, 8 and the exhaust gas burner 10. Optionally, the mixing device 28 can be connected or connected directly to the connecting flange 23 by means of the inlet flange 30 and directly to the connecting flange 25 by means of the outlet flange 31. In this case, for example, the adapter pieces 34, 35 are connected integrally to the mixing device 28, as also shown in the exemplary embodiments of Figure 3. Alternatively, the adapter pieces 34, 35 can be connected or connected detachably to the mixing device 28.Optionally, the adapter pieces 34, 35 are connected in one piece to the exhaust pipe 22 or to the inlet 24. In any case, the exhaust burner 10 is preferably inserted between the flanges 30 and 31 by means of the mixing device 28.

[0033] Figures 3A to D show different embodiments of the mixing device 28, each in a simplified partial sectional view.

[0034] Figure 3A shows the mixing device 28 according to a first exemplary embodiment. The mixing device 28 has a first tubular element 36, which has the inlet flange 30 at one end and the outlet flange 31 at the other end. The tubular element 36 is partially surrounded by a second tubular element 37, into which the heating gas outlet 27 opens. The further tubular element 37 is arranged, in particular, coaxially to the first tubular element 36. An inner diameter of the second tubular element 37 is, at least in some regions, larger than the outer diameter of the first tubular element, so that a space extending over the circumference of the first tubular element 36 is formed, which space, in particular, forms a swirl chamber. The second tubular element 37 is tightly connected to the first tubular element 36 at its axial end sides, so that the space 38 is sealed to the outside and heating gas flowing into the space 38 through the heating gas outlet 27 cannot escape to the outside.

[0035] In the region of the space 38, the first tubular element 36 has a plurality of heating gas inlet openings 39 arranged evenly distributed over the circumference of the first tubular element 36, of which only a few are provided with reference numerals here for reasons of clarity. According to the present exemplary embodiment, the heating gas inlet openings 39 are each designed in the manner of an elongated hole, with the respective elongated hole extending into the axially extending tubular element 36. Alternatively, the heating gas inlet openings 39 are each designed as a circular hole, oval, polygonal, or slot-shaped.

[0036] The heating gas flowing into the chamber 38 through the heating gas outlet 27 passes through the heating gas inlet openings 39 of the tubular element 36 into the interior of the raw element 36, through which the exhaust gas of the internal combustion engine 2 is also conducted. As a result, the heating gas advantageously mixes with the exhaust gas, with the mixing occurring so uniformly that a favorable reaction or rapid heating of the three-way catalyst in the downstream three-way catalyst as well as a uniform loading of the three-way catalyst is ensured.

[0037] The heating gas outlet 27 is arranged either radially to the first pipe element and the second pipe element 36, 37 or inclined to a radial orientation, in particular tangentially. In the first case, the heating gas flows radially onto the first pipe element 36 and is then distributed through the space 38. In the second case, the heating gas is introduced into the space 38 at an angle, so that it advantageously flows around the pipe element 36 in a type of swirling or rotating movement, which preferably ensures that the heating gas reaches all heating gas inlet openings 39 and thus particularly advantageously enters the exhaust gas flowing through the first pipe element 36. According to the present exemplary embodiment, the heating gas outlet 27 is arranged at least substantially downstream of the heating gas inlet openings 39, viewed in the axial extent.This also ensures that the heating gas is essentially distributed first in the space 38 before flowing into the heating gas inlet openings 39. As also shown in Figure 3A, the second tube element 37 optionally has a convex bulge 40 extending in particular over the entire circumference and projecting radially outwards, by means of which the space 38 is enlarged and the flow behavior of the heating gas into the space 38 is optimized.

[0038] According to the embodiment of Figure 3B, each of the heating gas inlet openings 39 is further assigned a flow guide element 41. According to the present embodiment, the flow guide elements 41 are formed as tongues punched out of the first tubular element 36 and bent radially inward.

[0039] The embodiment in Figure 30 differs from the previous embodiment in that the flow guide elements 41 are not bent inwards but radially outwards in order to guide the heating gas into the pipe element 36.

[0040] The embodiment of Figure 3D differs from the embodiment of Figure 3B in that the flow guide elements 41 are only bent radially inward. In the embodiment of Figure 3B, the flow guide elements 41 are also oriented obliquely, so that a favorable swirl is generated in the exhaust gas flow. For this purpose, the bent edge of the tongues or flow guide elements 41 in the embodiment of Figure 3B is oriented at an angle to an axial extension of the first tubular element 36. In the embodiments of Figures 3C and 3D, however, the bent edges are oriented parallel to the axial extension of the tubular element 36.

[0041] Figure 4 shows a further embodiment of the exhaust gas burner 10, which differs from the previous embodiments in that the combustion chamber 11 is completely arranged and optionally also the lambda probe 26, the injection valve 12 and guide device 13 are at least partially arranged within a common housing 42, wherein the pipe element 36 that carries the exhaust gas is also passed through the housing 42, and wherein the mixing device 28 is also arranged within the housing 42. This offers a particularly compact embodiment of the module 29, in which at least the combustion chamber 11 is also part of the module 29. This results in a particularly space-saving and compact embodiment that enables easy replacement and easy integration into the exhaust gas aftertreatment system 1.

[0042] Preferably, the exhaust gas burner 10 is arranged as close as possible to the first exhaust gas aftertreatment device 6 following in the flow direction in order to avoid heat losses along the transport route.

[0043] According to a further embodiment, the tubular element 36 is removed in the region of the tubular element 37, so that individual heating gas inlet openings can be omitted. Furthermore, the section of the tubular element 36 having the heating gas inlet openings 39 is preferably formed integrally with the remaining tubular element 36 or formed as a separate insert part, so that by replacing the insert part, the type of inlet openings 39, for example, with or without flow guide elements 41, can be easily adapted to different boundary conditions.

Claims

Claims 1. An exhaust gas burner (10) for an exhaust gas aftertreatment system (1) of an internal combustion engine (2), comprising a combustion chamber (11) in which a mixture of an oxygen-containing gas and fuel can be combusted to form a heating gas, wherein at least one injection valve (12) for injecting the fuel into the combustion chamber (11) is arranged on the combustion chamber (11), and wherein the combustion chamber (11) has a gas inlet for the gas and a heating gas outlet (27) for the heating gas, and comprising a mixing device (28) which has an inlet (32) for exhaust gas from the internal combustion engine (2), the heating gas outlet, means for mixing the exhaust gas with the heating gas, and an outlet (33) for the mixed gas, characterized in that at least the mixing device (28) is designed as a tubular module (29) which can be integrated into the exhaust gas aftertreatment system (1).

2. Exhaust gas burner according to claim 1, characterized in that the module (29) has an inlet flange (30) connectable or connected to an exhaust gas pipe (5) of the exhaust gas aftertreatment system (1) and an outlet flange (31) connectable or connected to the exhaust gas pipe (5).

3. Exhaust gas burner according to one of the preceding claims, characterized in that the inlet flange (30) and outlet flange (31) are aligned and arranged flush with one another.

4. Exhaust gas burner according to one of the preceding claims, characterized in that the inlet flange (30) forms the inlet (32) and the outlet flange (31) forms the outlet (33).

5. Exhaust gas burner according to one of the preceding claims, characterized in that the combustion chamber (11) is arranged outside the module (29).

6. Exhaust gas burner according to one of the preceding claims, characterized in that the mixing device (28) comprises a first pipe element (36) through which the exhaust gas can be guided, a second pipe element (37) which is arranged in particular coaxially to the first pipe element (36), wherein the first pipe element (36) has in its jacket wall at least one heating gas inlet opening (39) through which the heating gas can flow radially into the first pipe element (36), and wherein the second pipe element (37) has in its jacket wall the heating gas outlet (27).

7. Exhaust gas burner according to one of the preceding claims, characterized in that the first tubular element (36) has a plurality of heating gas inlet openings (39) arranged uniformly distributed over its circumference.

8. Exhaust gas burner according to one of the preceding claims, characterized in that at least one, in particular several or all of the heating gas inlet openings (39) are assigned at least one flow guide element (41), through which the heating gas is guided through the respective heating gas inlet opening (39) into the first pipe element (36).

9. Exhaust gas burner according to one of the preceding claims, characterized in that the heating gas outlet (27) is aligned tangentially to the first pipe element (26) and / or the second pipe element (37), so that the heating gas is directed between the first pipe element (36) and the second pipe element (37) is guided in the circumferential direction.

10. Exhaust gas burner according to one of the preceding claims, characterized in that the mixing device (28) and the combustion chamber (11) are arranged together in the module (29).

11. Exhaust gas burner according to one of the preceding claims, characterized in that a sensor, in particular a lambda probe (26), is arranged between the combustion chamber (11) and the heating gas outlet (27).

12. Exhaust gas aftertreatment system (1) for an internal combustion engine of a motor vehicle, with at least one exhaust gas aftertreatment device (6, 7, 8), in particular a catalyst or three-way catalyst, and with at least one exhaust gas burner (10) which is connected to the at least one exhaust gas aftertreatment device (7,8,9) is fluidically connected upstream, characterized by the design of the exhaust gas burner (11) according to one of claims 1 to 11.

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