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), having 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) and an ignition device (14) for igniting the injected fuel are arranged on the combustion chamber (11), and wherein a guide device (13) having a gas inlet (30), a gas outlet (32) associated with the combustion chamber (11) and in particular annular in shape, and a flow chamber (27) arranged coaxially to the injection valve (12) and extending axially as far as the gas outlet (32) is assigned to the combustion chamber (11).It is provided that the gas inlet (30) opens into the flow chamber (27) in particular radially, as seen in the circumferential direction of the flow chamber (27), and that the flow chamber (17) has a recess (37) for a connecting cable or a connecting plug of the injection valve (12) on the side diametrically opposite the gas inlet (30).

Description

[0001] The invention relates to an exhaust gas burner for an exhaust gas aftertreatment system of an internal combustion engine, having a combustion chamber in which a mixture of an oxygen-containing gas and fuel can be combusted to form a heating gas, wherein at least one injection valve for injecting the fuel into the combustion chamber and an ignition device for igniting the injected fuel in the combustion chamber are arranged on the combustion chamber, and wherein a guide device with a gas inlet, with a gas outlet assigned to the combustion chamber and in particular annular, and with a flow chamber arranged coaxially to the injection valve and extending axially to the gas outlet is assigned to the combustion chamber.

[0002] Furthermore, the invention relates to an exhaust gas aftertreatment system for an internal combustion engine of the motor vehicle, with at least one exhaust gas aftertreatment device, which is designed, for example, as a catalytic converter, three-way catalytic converter or particulate filter, and with at least one exhaust gas burner which is fluidically connected upstream of the at least one exhaust gas aftertreatment device. State of the art

[0003] Exhaust gas burners of the type mentioned above are already known from the prior art. For example, published patent application DE 19 504 208 A1 discloses an exhaust gas burner that is fluidically connected 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, before being subsequently 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 10 2009 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.

[0004] The flow chamber is designed, for example, as in DE 10 2009 053 379 A1, as a swirl chamber into which the gas is introduced tangentially, so that the gas in the flow chamber experiences a swirling or rotational movement around the longitudinal center axis of the exhaust gas burner and thus enters the combustion chamber rotating or with swirl, which advantageously supports mixing with the fuel that is also injected into the combustion chamber. In order to be able to make electrical contact with the injection valve for its control, it usually has a connection plug or a connection cable, each of which protrudes laterally from the injection valve. Because in conventional solutions this connection plug or the connection cable can come into geometric conflict with the flow chamber, the injection valve is only arranged partially within the flow chamber or is only axially surrounded by the flow chamber in certain areas.This allows the cable connection or connector of the injector to remain accessible, but results in an overall axial length increase in the exhaust burner. The flow chamber must remain large enough to ensure even gas distribution upstream of the gas outlet, ensuring that it is evenly introduced into the combustion chamber. The protrusion of the injector from the flow chamber also makes it susceptible to contamination, water ingress, stone chipping, or heat ingress from the surrounding exhaust system. Furthermore, the freestanding position of the injector also has a negative impact on noise levels, as noise emissions from the injector can propagate unhindered.

[0005] The present invention is based on the object of providing an improved integration of the injection valve into the flow chamber. Disclosure of the invention

[0006] The exhaust gas burner according to the invention with the features of claim 1 has the advantage that, despite maintaining a compact embodiment of the exhaust gas burner, a more in-depth integration of the injection valve into the region of the flow chamber is possible, wherein a different type of air guide nevertheless ensures a uniform air feed into the combustion chamber. According to the invention, it is provided for this purpose that the gas inlet opens into the flow chamber, in particular radially, as viewed in the circumferential direction of the flow chamber, and that a recess is formed on the side of the flow chamber diametrically opposite the gas inlet to form a cable passage for a connection cable of the injection valve or for a connection plug of the injection valve. In contrast to the usual solution of a tangential inflow, the present invention thus provides for a radial inflow into the flow chamber, at least as viewed in the circumferential direction.This directs the gas flow centrally or radially into the flow chamber. Because the flow chamber is arranged coaxially to the injection valve, it has an outer and an inner casing and is therefore designed like a ring sleeve. Due to the radial introduction of the gas, it hits the inside of the inner casing and is guided in equal parts past the inner casing in the circumferential direction on both sides into the flow chamber. On the diametrically opposite side of the flow chamber, the two partial gas flows meet again. The rotationally symmetrical design of the flow chamber creates a stagnation point when the gas flows meet because the momentum of the two flows cancels each other out. This means that there is no flow velocity in the circumferential direction at this point.According to the invention, this circumstance is exploited to form the recess in the flow chamber at this point in order to pass through the connecting cable or the connecting plug of the injection valve. A recess in the flow chamber is not understood to be an opening in the flow chamber, but rather an interruption in the flow chamber that prevents the gas from flowing further, in favor of the cable or plug feedthrough. The solution according to the invention allows the injection valve to be further integrated into the flow chamber, with the cable connection or the connecting cable being passed through in the area in which no or only slight flow occurs anyway, so that the influence of the cable feedthrough on the flow behavior of the gas is negligible.If the gas inlet orientation deviates from a radial orientation, or if the inlet flow has a tangential flow component in addition to a purely radial component, the stagnation point shifts to the opposite side. Preferably, the recess is shifted accordingly to the stagnation point, even if it is then no longer exactly diametrically opposite the gas inlet.

[0007] According to a preferred development of the invention, the flow chamber has a first end face assigned to the combustion chamber and a second end face facing away from the combustion chamber, wherein the second end face is oriented at least in sections at an angle to the first end face to form the recess. The fact that the second end face is oriented at least in sections at an angle to the first side results in an asymmetrical design of the flow chamber seen in longitudinal section, wherein the flow chamber is thereby maximally long - viewed in axial extension - in particular on the side of the gas inlet and maximally short on the side of the cable feedthrough. The inclined end face interrupts the flow chamber in favor of the cable or plug feedthrough of the plug-in valve.Because the flow in the circumferential direction of the flow chamber is only slightly impaired by the inclination of the front side, this has the advantage of a sufficiently good inflow of the gas into the combustion chamber in order to realize a safe and clean combustion of the fuel in the gas.

[0008] Furthermore, it is preferably provided that the flow chamber has an outer shell and an inner shell, as already mentioned above, wherein at least the inner shell has a curvature to form the recess. The curvature is provided in addition to or as an alternative to the inclined orientation of the second end face. The curvature ensures a passage adapted to the connector plug or the connecting cable, which enables a particularly space-saving design.

[0009] Furthermore, it is preferably provided that the injection valve has a lateral connection plug and is mounted such that the connection plug is arranged on the side of the injection valve facing away from the gas inlet. This results in the advantage already mentioned above that the injection valve is arranged in a space-saving manner thanks to the advantageous design of the flow chamber. In addition, the advantageous integration of the injection valve in the flow chamber ensures that it is better protected against external influences. An additional cover optionally completely encloses the injection valve between the cover and the flow chamber, so that it is optimally protected against external influences such as stone chips, moisture or the like. As an alternative to the connection plug, the injection valve has a connection cable which is arranged accordingly on the side of the injection valve.

[0010] Preferably, the gas inlet opens into the flow chamber at an angle of less than 90° to a longitudinal center axis of the flow chamber. This allows the gas to be introduced into the flow chamber in a preferred direction, particularly toward the combustion chamber, to ensure optimal penetration of the combustion chamber.

[0011] Particularly preferably, the gas inlet has an inlet channel that can be connected to a valve device. At least the end section of the inlet channel leading to the gas inlet is oriented radially to the flow chamber in the circumferential direction and, viewed in the longitudinal direction of the flow chamber, at the aforementioned angle of less than 90 degrees to ensure optimal introduction of the gas flow.

[0012] The exhaust gas aftertreatment system according to the invention with the features of claim 7 is characterized by the inventive design of the exhaust gas burner. This results in the advantages already mentioned above.

[0013] 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. Fig. 1 an advantageous exhaust aftertreatment system in a simplified representation, Fig. 2A and B show an advantageous embodiment of an exhaust gas burner of the exhaust gas aftertreatment system in different representations and Fig. 3 an advantageous embodiment of the exhaust gas burner in a longitudinal section.

[0014] Fig. 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. In this case, 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, and 8 one after the other and serves to reduce pollutant emissions and particles in the exhaust gas.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 this case 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, so 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 itself has reached its necessary operating temperature.

[0015] 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. Advantageously, an air pump or air conveying device 17 is 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.

[0016] 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 heated gas, 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. Optionally, the burner control unit 20 can be integrated into the control unit 21 of the internal combustion engine.

[0017] Fig. Figure 2A shows the exhaust gas burner in a simplified longitudinal section according to an advantageous embodiment. The combustion chamber 11 has a circumferential casing wall 22 and a first end 23, in which the heating gas outlet 15 is formed, as well as a second end 24 facing away from the first end 23, to which the guide device 13 is assigned. The ignition device 14 has a glow pin or glow plug, the free end of which terminates in a recess 25 in the casing wall 22.

[0018] The guide device 13 has an inlet channel 26, which is or can be connected at one end to the valve device 16. Furthermore, the guide device 13 has a flow chamber 27, which is sleeve-shaped with an annular cross-section. The flow chamber 27 thus has an outer shell 28 and an inner shell 29, which are arranged coaxially to one another and form the flow chamber 27 between them. The outer shell 28 has a recess in the gas inlet 30, into which the inlet channel 26 opens. Furthermore, the flow chamber 27 has a swirl grille 31 facing the end face 24, which is followed fluidically by an annular outflow opening 23, which opens into the combustion chamber 11.The inner casing 29 of the flow chamber 27 partially surrounds the injection valve 12, which is arranged coaxially therewith, the valve opening of which is arranged at the level of the outlet opening 32 and coaxial therewith, so that fuel and gas can be introduced coaxially to one another into the combustion chamber 11. The swirl grid 31 imparts a swirling motion to the inflowing gas, so that the gas rotates within the combustion chamber 11 and leads to improved mixing of gas and fuel.

[0019] The injection valve 12 has a laterally projecting connector plug 33, which is diametrically opposite the inlet channel 26. The inlet channel 26 is aligned parallel to the longitudinal extension or to the axial longitudinal center axis of the exhaust gas burner 10 and is arranged and configured such that, viewed in the circumferential direction, it opens radially into the flow chamber 27 through the gas inlet 30.

[0020] Fig. 2B shows a simplified sectional view - in different sectional planes in the longitudinal extension of the exhaust gas burner 10 according to Fig. 2A - the inlet channel 26 and the flow chamber 27. The annular sleeve-shaped design of the flow chamber 27 results in an annular cavity or flow space into which the gas flows from the gas inlet 30. Because the gas inlet 30 and the end section of the inlet channel 26 are aligned radially in the circumferential direction, the gas is introduced radially into the flow chamber, as indicated by an arrow 34 in Fig. 2B. There, the gas first encounters the inner shell 29 and, due to the radial introduction, is evenly divided into two jet halves or flow parts, which then flow into the flow chamber 27 on both sides, as shown by arrows 35.

[0021] On the side facing away from the inlet channel 26, in particular exactly diametrically opposite the gas inlet 30, the two partial flows meet again. Due to the uniform introduction into the flow chamber 7 from two sides, a stagnation point 36 is created in the flow chamber 27 diametrically opposite the inlet 30, at which the impulses of the partial flows cancel each other out. As a result, there is no flow velocity of the gas in the circumferential direction of the burner axis at this point. Instead, the gas is forced towards the swirl grille at this point. Since the flow around the flow chamber 27 is interrupted at this point anyway, this is exploited to form a recess 37 in the flow chamber 27 at this point, through which the connector plug 33 of the injection valve 12 can be guided or is guided to the outside, as shown in Fig. 2A. The flow chamber 27 has an end face 38 facing the end face 24 of the combustion chamber 11, in which the outflow opening 32 is also formed, and a second end face 39 facing away from the end face 38. To form the recess 37, the end face 39 is aligned at an angle to the end face 38, so that the axial extent of the flow chamber 27 is shorter in the region of the stagnation point 36 than in the region of the gas inlet 30. This inclined alignment creates the free space or the recess 37, through which the connecting plug 33 of the valve 12 is advantageously guided.

[0022] According to a further embodiment, the end face 39 is only partially inclined to the end face 38 in order, for example, to maximize the flow volume of the flow chamber.

[0023] According to a further embodiment, the end faces 38, 39 are aligned parallel to one another, wherein in the region of the flow chamber opposite the gas inlet 30 a concave curvature is formed in the inner shell 29 and optionally also in the outer shell 28, so that in particular an axial curvature is created, by means of which the recess 37 is created.

[0024] Fig. Figure 3 shows a perspective, partially sectional view of the exhaust gas burner 10 according to the previous embodiment. A connecting cable 40 is plugged into the connector 33, which is connected, for example, to the control unit 20 to control the operation of the injection valve 12.

[0025] To protect the injection valve 12 from external influences, a cover 41 is optionally provided, which, together with the guide device 13, forms a valve chamber in which the injection valve 12 is completely enclosed. This advantageously protects the injection valve 12 from external influences, in particular from stone chips, contamination, moisture, and heat input. List of reference symbols 1 exhaust aftertreatment system 2 internal combustion engine 3 Fresh air wing 4 Exhaust system 5 Exhaust pipe 6 Exhaust aftertreatment system 7 Exhaust aftertreatment system 8 Exhaust aftertreatment system 9 Heating device 10 exhaust gas burners 11 Combustion chamber 12 Injector 13 Guidance device 14 Ignition device 15 Outlet opening 16 Valve device 17 Air conveyor 18 air mass meter 19 Air filter 20 Control unit 21 Control unit 22 Shell wall 23 front end 24 front ends 25 recess 26 Inlet channel 27 Flow chamber 28 Outer jacket 29 inner jacket 30 Gas inlet 31 swirl grille 32 Outlet opening 33 connector plugs 34 Arrow 35 Arrow 36 stagnation point 37 recess 38 front side 39 front side 40 connection cables 41 lids

Claims

[1] 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) and an ignition device (14) for igniting the injected fuel are arranged on the combustion chamber (11), and wherein a guide device (13) with a gas inlet (30), with a gas outlet (32) associated with the combustion chamber (11) and in particular annular, and with a flow chamber (27) arranged coaxially to the injection valve (12) and extending axially to the gas outlet (32) is associated with the combustion chamber (11), characterized bythat the gas inlet (30) opens radially into the flow chamber (27) as seen in the circumferential direction of the flow chamber (27) and that on the side diametrically opposite the gas inlet (30) the flow chamber (27) has a recess (37) for a connecting cable or a connecting plug (33) of the injection valve (12). [2] Exhaust gas burner (10) according to claim 1, characterized by that the flow chamber (27) has a first end face (38) associated with the combustion chamber (11) and a second end face (39) facing away from the combustion chamber (11), wherein the second end face (39) is oriented at an incline to the first end face (38) to form the recess (37). [3] Exhaust gas burner (10) according to one of the preceding claims, characterized by that the flow chamber (27) has an outer shell (28) and an inner shell (29), wherein at least the inner shell (29) has a radial and / or axial curvature for forming the recess (37). [4] Exhaust gas burner (10) according to one of the preceding claims, characterized by that the injection valve (12) has a lateral connection plug (33) and is mounted such that the connection plug (33) is arranged on the side of the injection valve (12) facing away from the gas inlet (30). [5] Exhaust gas burner (10) according to one of the preceding claims, characterized by that the gas inlet (30) opens into the flow chamber (27) at an angle of less than 90° to a longitudinal center axis of the flow chamber (27). [6] Exhaust gas burner (10) according to one of the preceding claims, characterized by that the gas inlet (30) has an inlet channel (26) which can be connected to a valve device (16) of the exhaust gas aftertreatment system (1). [7] Exhaust gas aftertreatment system (1) for an internal combustion engine (2) of a motor vehicle, comprising at least one exhaust gas aftertreatment device (6, 7, 8), in particular a catalytic converter, three-way catalytic converter or particulate filter, and comprising at least one exhaust gas burner (10) which is fluidically connected upstream of the at least one exhaust gas aftertreatment device (7, 8, 9), characterized by the design of the exhaust gas burner (10) according to one of claims 1 to 6.

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