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

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 hollow cylindrical 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 (23) for the gas and a heating gas outlet (15) for the heating gas. According to the invention, at least one temperature-control-medium channel (28), through which a liquid and / or gaseous temperature-control medium can be conveyed, is arranged at least on a lateral wall (22) of the combustion chamber (11).

Description

[0001] R.409926

[0002] - 1 -

[0003] Description

[0004] title

[0005] Exhaust burner for an exhaust aftertreatment system, exhaust aftertreatment system and process

[0006] The present invention relates to an exhaust gas burner for an exhaust gas aftertreatment system of an internal combustion engine, comprising a hollow cylindrical 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.

[0007] Furthermore, the invention relates to an exhaust aftertreatment system for an internal combustion engine of a motor vehicle, comprising at least one exhaust aftertreatment device and at least one exhaust burner, which is fluidically connected upstream of the at least one exhaust aftertreatment device.

[0008] Furthermore, the invention relates to a method for operating the exhaust gas burner or the exhaust gas aftertreatment system as described above.

[0009] State of the art

[0010] Exhaust gas burners of the type mentioned above are already known from the prior art. For example, the patent application discloses

[0011] DE 19504208 A1 an exhaust gas burner which 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. R.409926

[0012] - 2 -

[0013] and are burned in the combustion chamber using an ignition device, and subsequently added or mixed into the exhaust gas stream upstream of the catalyst. This ensures that the catalyst is heated to an advantageous operating temperature particularly quickly. A similar solution is also proposed in German patent application DE 102009053379 A1.

[0014] Disclosure of the invention

[0015] The exhaust gas burner according to the invention, with the features of claim 1, has the advantage that the combustion chamber and optionally other parts of the exhaust gas burner are advantageously temperature-controlled, thus preventing, in particular, the formation of condensate in the combustion chamber. During phases in which the exhaust gas burner cools down because no fuel gas is being generated, and in which exhaust gas from the internal combustion engine may flow back into the combustion chamber, water from the exhaust gas can condense if the dew point is undershot. As a result, when the exhaust gas burner is restarted, this condensate is present in the combustion chamber in liquid form or, depending on the operating temperature, also in the form of ice. If the exhaust gas burner is then restarted, the condensate can be stirred up and thus become a hazard for the downstream exhaust gas aftertreatment devices, which can suffer a so-called thermal shock if the condensate hits them.The same applies to the ignition device as well as to an optional lambda probe associated with the exhaust gas burner, which can be sensitive to such a thermal shock. Because, according to the invention, at least the outer wall of the combustion chamber is temperature-controlled, the formation of condensate in the so-called passive phases of the exhaust gas burner, when no heating gas is generated, can be reliably prevented. At the same time, the invention ensures that, in active phases when heating gas is generated by the exhaust gas burner, overheating of the exhaust gas burner is prevented or at least further delayed by temperature control. For this purpose, the invention provides that at least one temperature control channel is arranged on at least one outer wall of the combustion chamber, through which a liquid and / or gaseous temperature control agent can be conveyed to temperature-control the outer wall of the combustion chamber. If necessary, temperature control agent R.409926.

[0016] - 3 -

[0017] The temperature control fluid is conveyed through the channel, thereby tempering, or cooling, the combustion chamber wall. In particular, during passive phases of the exhaust gas burner, the fluid is conveyed to transfer heat to the combustion chamber wall, thus preventing condensation from forming on the inner wall. Furthermore, during active phases of the exhaust gas burner, the fluid is preferably conveyed through the channel to extract heat from the burner, thereby preventing it from overheating.

[0018] Preferably, the temperature control fluid channel extends at least substantially over the circumference of the burner casing. This allows the temperature control fluid to be distributed over the entire circumference of the exhaust gas burner, ensuring uniform heat input and output. Particularly preferably, the temperature control fluid channel covers at least 50% of the exhaust gas burner, especially the burner casing. The temperature control fluid channel is particularly associated with an area or section of the exhaust gas burner that cools down first during passive operation.

[0019] Furthermore, it is preferably provided that the temperature control fluid channel runs at least partially in the direction of flow along the longitudinal extent of the combustion chamber. This ensures that the temperature control fluid flows parallel to the longitudinal extent of the exhaust gas burner during operation. Preferably, the temperature control fluid channel is designed such that the temperature control fluid flows at least substantially in the direction of flow through the exhaust gas burner, or alternatively, against the flow direction.

[0020] It is further preferably provided that the temperature control fluid channel runs at least partially in a helical fashion along the jacket wall in the direction of flow, thereby increasing the duration of contact of the temperature control fluid with the jacket wall of the exhaust gas burner. Preferably, the jacket wall or the temperature control fluid channel has several cooling fins extending longitudinally or in a helical fashion on its outer surface, which ensure improved heat dissipation from the temperature control fluid to the jacket wall or vice versa. R.409926

[0021] -4 -

[0022] Preferably, the temperature control fluid channel has a channel inlet and a channel outlet, with the channel inlet being located close to the gas inlet and the channel outlet close to the flue gas outlet. This ensures that the temperature control fluid flows through the channel, particularly in the direction from the gas inlet to the channel outlet, so that the exhaust gas burner is either heated first, especially in the area close to the gas inlet, to prevent condensation, or cooled.

[0023] Preferably, a swirl device is associated with the gas inlet, wherein the temperature control channel surrounds the swirl device at least partially. This ensures that the swirl device itself is also temperature-controlled and advantageously prevents condensation there as well.

[0024] Preferably, a gas guide is also installed upstream of the gas inlet, in which the swirl device is arranged, with the temperature control channel surrounding the guide at least partially. The guide is specifically designed to advantageously introduce fresh air into the swirl device to ensure a uniform distribution of the gas in the combustion chamber. Because the exhaust gas can also flow back to this point during passive operation, it is advantageous that condensation is also prevented here by means of the temperature control channel.

[0025] According to a preferred embodiment of the invention, a lambda probe is associated with the exhaust gas burner, which is located, in particular, downstream of the hot gas outlet of the combustion chamber, with the temperature control channel extending up to the lambda probe. This ensures that the lambda probe is also temperature-controlled and protected from condensation.

[0026] Preferably, the channel inlet and / or outlet have a connection to the engine cooling circuit. This allows the temperature control channel to be connected to the engine cooling circuit of the internal combustion engine to which the exhaust gas burner is assigned. If the engine coolant is routed or pumped through the temperature control channel during operation, this results in the following: R.409926

[0027] - 5 -

[0028] The exhaust gas burner is heated to the operating temperature of the coolant, for example, 80 to 90 degrees Celsius, thus reliably preventing condensation. During active operation of the exhaust gas burner, i.e., when combustion in the combustion chamber generates hot gas, the coolant from the internal combustion engine cools the exhaust gas burner, thereby extending its heating periods. Optionally, a coolant pump is available that circulates coolant through the temperature control channel independently of the internal combustion engine's operation, enabling cooling, heating, or temperature control of the exhaust gas burner even when the engine is off.

[0029] The exhaust gas aftertreatment system according to the invention, comprising the features of claim 9, is characterized by the design of the exhaust gas burner according to the invention. This results in the advantages already mentioned above.

[0030] The internal combustion engine according to the invention, with the features of claim 10, is characterized by the exhaust aftertreatment system according to the invention. This results in the advantages mentioned above. In particular, a cooling circuit of the internal combustion engine is fluidically connected to the temperature control channel of the exhaust gas burner. Optionally, a pumping device is also provided, by which the coolant can be pumped through the temperature control channel independently of the operation of the internal combustion engine. This results in the advantages already mentioned above:

[0031] Further advantages and preferred features and combinations of features will become apparent in particular from the foregoing and from the claims. The invention will now be explained in more detail with reference to the drawings. To this end, we show...

[0032] Figure 1 shows an advantageous exhaust aftertreatment system in a schematic representation, R.409926

[0033] - 6 -

[0034] Figure 2 shows an advantageous exhaust gas burner of the exhaust gas aftertreatment system in a simplified longitudinal section view according to a first embodiment.

[0035] Figure 3 shows the exhaust gas burner in a simplified longitudinal section view according to a second embodiment, and

[0036] Figure 4 shows the exhaust gas burner in a simplified longitudinal section view according to a third embodiment.

[0037] Figure 1 shows a simplified representation of an advantageous exhaust 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 associated with a fresh air intake tract 3 and an exhaust exhaust tract 4. From the exhaust valves of the internal combustion engine 2, an exhaust pipe 5 of the exhaust exhaust tract 4 leads to several exhaust aftertreatment devices 6, 7, and 8 of the exhaust aftertreatment system 1. In this case, viewed in the direction of flow, the first exhaust aftertreatment device 6 is a three-way catalytic converter, the second exhaust aftertreatment device 7 is a second three-way catalytic converter, and the third exhaust aftertreatment device 8 is a particulate filter. The exhaust aftertreatment devices 6, 7, and 8 are sequentially supplied with exhaust gas from the internal combustion engine and serve to reduce pollutant emissions and particulate matter in the exhaust gas.

[0038] To ensure that the exhaust aftertreatment devices 6, 7, 8 reach their optimal operating temperature as quickly as possible, especially after a cold start of the internal combustion engine 2, a heating device 9 with an exhaust gas burner 10 of the exhaust 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 via an injection valve 12 and oxygen-containing gas, in particular air, via a guide device 13, in order to be ignited and burned in the combustion chamber by means of an ignition device 14. The burned fuel / air mixture is fed to the exhaust tract 4 upstream of the first catalyst 6 via a heating gas outlet 15 of the exhaust gas burner 10, so that the heated gas mixture

[0039] - 7 -

[0040] The operating temperature of the exhaust aftertreatment devices 6,7,8 is already increased before the internal combustion engine 2 provides the necessary exhaust enthalpy to heat the peripheral exhaust system.

[0041] An adjustable valve assembly 16 is connected upstream of the exhaust gas burner 10, by means of which the supplied airflow can be adjusted. An air pump or air supply device 17 is advantageously arranged upstream of the valve assembly 16, by means of which fresh air is drawn in and conveyed towards the valve assembly 16. An air mass meter 18 and an air filter 19 are also connected upstream of the air supply device 17.

[0042] A control unit 20 of the heating system controls and operates the air mass meter 18, the air supply unit 17, the valve assembly 16, and the exhaust gas burner 10 to generate the desired amount of heating gas, i.e., a combusted air-fuel mixture, which is supplied to the exhaust tract 4 to heat the exhaust aftertreatment devices 6, 7, and 8. The control unit 20 is in communication with a control unit 21 of the internal combustion engine.

[0043] Figure 2 shows a simplified longitudinal section of the exhaust gas burner 10 according to a first embodiment. The combustion chamber 11 is hollow and cylindrical and has a shell wall 22, which at one end face adjoins a guide element 24 forming a gas inlet 23, and at the other end face of which the flue gas outlet 15 is located. The guide element 24 has a connection port that is connected or connectable to the valve assembly 16. Furthermore, the guide element 24 has an air guide such that the supplied airflow advantageously strikes a swirl device 25, in particular a swirl grid, associated with the gas inlet 23, in order to then flow in a swirl motion through the combustion chamber 11.

[0044] The flue gas outlet 15 is formed on a tubular insert 26, which has a baffle 27 with an R.409926 at its end lying in the combustion chamber 11.

[0045] - 8 -

[0046] has an inner diameter that is smaller than the inner diameter of the combustion chamber 11.

[0047] Furthermore, a temperature control channel 28 is arranged on the casing wall 22. According to the present embodiment, the temperature control channel 28 extends over the entire length of the combustion chamber 11 or the casing wall 22 and over the entire circumference of the casing wall 22, except for the area in which the ignition device 14 passes through the casing wall 22. The temperature control channel 28 has a temperature control inlet 29, which is arranged close to the guide element 24 or the gas inlet 23, and a temperature control outlet 30, which is arranged close to the hot gas outlet 15. The temperature control channel 28 is designed in the manner of a water jacket or a casing of the combustion chamber 11, in particular the casing wall 22, so that the temperature control medium flowing through the temperature control channel 28 can transfer heat, in particular to the casing wall 22, or carry it away from it.Particularly preferably, the outer wall 22 itself forms the inner wall of the temperature control medium channel 28. According to an alternative embodiment, the inner wall of the temperature control medium channel 28 rests on the outer surface of the outer wall 22.

[0048] The temperature control medium inlet 29 preferably has an engine cooling circuit connection 29' through which it is connected to a coolant circuit of the internal combustion engine 2, and the temperature control medium outlet 30 preferably also has an engine cooling circuit connection 30*, so that the temperature control medium channel 28 is integrated or can be integrated into the cooling circuit of the internal combustion engine 2 and is permeated or can be permeated by the coolant of the internal combustion engine 2. In this respect, the coolant of the internal combustion engine 2 constitutes the temperature control medium for the temperature control medium channel 28.

[0049] According to one embodiment, the temperature control medium channel 28 is permanently connected to the cooling circuit of the internal combustion engine 2 and is thus continuously supplied with coolant from the internal combustion engine 2 during operation. Optionally, a controllable pumping device, in particular a coolant pump, is assigned to the cooling circuit, which, if necessary, also supplies the coolant.

[0050] - 9 -

[0051] The pump then activates when the internal combustion engine 2 is switched off. This enables, in particular, demand-based temperature control of the exhaust gas burner 10, preferably depending on an exhaust gas temperature model and / or a temperature sensor assigned to the exhaust gas burner 10. For example, if heat is to be removed from the exhaust gas burner 10 before the internal combustion engine 2 has started, the pump is preferably activated to initiate the coolant circulation.

[0052] During phases in which the exhaust gas burner 10 is activated and the mixture of fresh air flowing in through the gas inlet 23 and fuel injected or sprayed through the injection valve 12 is ignited and combusted by means of the ignition device 14, temperatures are generated in the exhaust gas burner 10 that are generally higher than the temperature of the coolant of the internal combustion engine 2, thus providing advantageous cooling of the exhaust gas burner by the coolant or temperature control medium. During phases in which the exhaust gas burner 10 is deactivated, in so-called passive phases, the exhaust gas burner 10 cools down, with the coolant coming from the internal combustion engine 2 preventing the exhaust gas burner 10 from cooling to temperatures below the dew point of water traps, so that during passive operation, exhaust gas flowing back from the internal combustion engine 2 into the exhaust gas burner 10 does not condense.This prevents condensate from forming in the exhaust gas burner 10, especially on the inside of the combustion chamber 11, the swirl device 25 or in the connection nozzle to the valve device 16, and from causing a thermal shock, for example at the ignition device 14, when the exhaust gas burner 10 is restarted.

[0053] In particular, with the help of the optional pumping device, the coolant can be pumped in such a way that the exhaust gas burner 10 is always optimally heated, both to prevent the formation of condensate and, during active operation of the exhaust gas burner 10 (i.e., during a heating phase), to protect it from excessively high temperatures and thus extend its burn time. During passive operation, the combustion chamber 11 is thus surrounded by the cooling water of the internal combustion engine 2 and maintained at a temperature of 80 to 90 degrees Celsius, thereby preventing the formation of condensate or at least minimizing its formation on the inside of the casing wall 22R.409926.

[0054] - 10 -

[0055] The heat output is reduced. During the heating phase, the coolant allows heat to be dissipated from the exhaust gas burner 10, thereby keeping the ignition device 14 and the injection device 12 at a temperature below a limit of 140 degrees Celsius, thus enabling longer combustion times of the exhaust gas burner 10. This, for example, allows for the advantageous regeneration of a downstream particulate filter. Reheating at a lower power level is also possible. Heat that may affect the exhaust gas burner from adjacent components, such as a nearby turbocharger, can also be dissipated through the water jacket or the coolant in the temperature control channel 28.

[0056] Furthermore, the temperature control jacket or the temperature control channel 28 results in the combustion chamber 11 being advantageously acoustically insulated.

[0057] Figure 3 shows a second embodiment of the exhaust gas burner 10 in a further longitudinal section view, wherein elements already known from Figure 2 are provided with the same reference numerals, and reference is made to the description above in this respect. In the following, only the differences between the embodiments will be discussed.

[0058] According to the embodiment shown in Figure 3, the temperature control medium channel 28 has one or more flow guide elements 33 extending through the temperature control medium channel 28 and preferably being integrally connected, in particular in one piece, to the outer wall 22 of the combustion chamber 11. The flow guide elements 33 serve in particular to increase the flow path of the temperature control medium through the temperature control medium channel, thereby enabling increased heat input or output.

[0059] In addition, the flow guide elements 33 provide further surfaces that interact with the temperature control medium and thus lead to increased heat transfer of the temperature control medium channel 28.

[0060] According to the present embodiment of Figure 3, a flow guide element 33 is provided which extends helically through the R.409926

[0061] - 11 -

[0062] The temperature control fluid channel 28 extends so that the temperature control fluid also flows through the channel 28 in a helical fashion and flows around the outer wall 22 of the combustion chamber 11. In particular, the pitch of the helical flow guide element 33 is selected such that it corresponds at least substantially to the swirl motion of the gas in the combustion chamber 11. While, according to the present embodiment, the temperature control fluid channel 28 is traversed in the direction of flow in the combustion chamber 11, according to a further embodiment, the temperature control fluid channel 28 is traversed in the opposite direction, so that the temperature control fluid inlet 29 and outlet 30 are reversed.

[0063] Figure 4 shows a further embodiment of the exhaust gas burner 10, which differs from the embodiment of Figure 2 in that a sensor section 31 is connected downstream of the combustion chamber 11, which includes a lambda probe 32. The sensor section 31 is formed integrally with the combustion chamber 11 or the exhaust gas burner 10, or, as indicated by a dashed dividing line, as a separate component that is rigidly connected to the exhaust gas burner 10. The lambda probe 32 serves, in particular, downstream of the pipe element 26, which forms the flue gas outlet 15. Specifically, the lambda probe 32 is formed in an extension of the combustion chamber 11. Preferably, the outer wall 22 extends integrally into the extension, or the extension is formed as a separate element and attached to the end face of the outer wall 22.In any case, the temperature control medium channel 28 preferably extends to the lambda probe 32, so that the probe is also temperature-controlled by the temperature control medium. Optionally, the temperature control medium channel 28 is designed as a single piece or in multiple pieces. Optionally, the temperature control medium channel 28 also has one or more flow guide elements 33, which advantageously determine the flow path of the temperature control medium through the temperature control medium channel 28.

[0064] Optionally, the temperature control fluid outlet 30 is connected to at least one of the exhaust aftertreatment devices 6,7,8, so that the temperature control fluid leaving the temperature control fluid channel 28 is subsequently used to temperature control other components, in particular the exhaust aftertreatment devices.

Claims

R.409926 - 13 - Claims 1. Exhaust gas burner (10) for an exhaust gas aftertreatment system (1) of an internal combustion engine (2), comprising a hollow cylindrical 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 (23) for the gas and a heating gas outlet (15) for the heating gas, characterized in that at least one temperature control medium channel (28) is arranged on at least one shell wall (22) of the combustion chamber (11), through which a liquid and / or gaseous temperature control medium can be conveyed.

2. Exhaust gas burner according to claim 1, characterized in that the tempering medium channel (28) extends at least substantially over the circumference of the shell wall (22).

3. Exhaust gas burner according to one of the preceding claims, characterized in that the tempering medium channel (28) extends at least sectionally in the direction of flow in the longitudinal extent of the combustion chamber (11).

4. Exhaust gas burner according to one of the preceding claims, characterized in that the tempering medium channel (28) runs at least partially in a threaded manner along the shell wall (22) in the direction of flow.

5. Exhaust gas burner according to one of the preceding claims, characterized in that the temperature control medium channel (28) has a temperature control medium inlet (29) and a temperature control medium outlet (30), R.409926 - 14 - wherein the temperature control medium inlet (29) is located near the gas inlet (23) and the temperature control medium outlet (30) is located near the heating gas outlet (15).

6. Exhaust gas burner according to one of the preceding claims, characterized in that a guide device (13) for the gas is connected upstream of the gas inlet (23), in which a swirl device (25) is arranged, wherein the tempering agent channel (28) surrounds the guide device (13) at least section by section.

7. Exhaust gas burner according to one of the preceding claims, characterized in that a lambda probe (32) is associated with the exhaust gas burner (10), which is located in particular downstream of the hot gas outlet (15) of the combustion chamber (11), and that the temperature control medium channel (28) extends to the lambda probe (32).

8. Exhaust gas burner according to one of the preceding claims, characterized in that the duct inlet (29) and / or the duct outlet (30) have a motor cooling circuit connection (29', 30').

9. Exhaust aftertreatment system (1 ) for an internal combustion engine (2) of a motor vehicle, comprising at least one exhaust aftertreatment device (6,7,8), in particular a catalyst or three-way catalyst, and comprising at least one exhaust burner (10) which is fluidically connected upstream of the at least one exhaust aftertreatment device (6,7,8), characterized by the design of the exhaust burner (10) according to one of claims 1 to 8.

10. Internal combustion engine (2) with an exhaust aftertreatment system (1) according to claim 9, characterized in that the temperature control medium channel (28) is integrated into a coolant circuit of the internal combustion engine (2).

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