Burner for an exhaust system of an internal combustion engine

Abstract

Burner for use in an exhaust system of an internal combustion engine with a housing (1) that delimits a combustion chamber (2) and forms a hot gas outlet (8) of the combustion chamber (2) and a fresh gas inlet (6), and with a fuel injector (5) for introducing fuel into the combustion chamber (2), wherein a fresh gas guide (4) connects the fresh gas inlet (6) to the combustion chamber (2) and wherein the fresh gas guide (4) at least partially surrounds the combustion chamber (2) in at least one section, characterized by a design of the fresh gas guide (4) such that a main flow direction of the fresh gas in at least one subsection of the section of the fresh gas guide (4) surrounding the combustion chamber (2) is directed opposite to a main flow direction of gas in the adjacent section of the combustion chamber (2).

Description

[0001] The invention relates to a burner for use in an exhaust system of an internal combustion engine. The invention further relates to an internal combustion engine with such a burner.

[0002] The emission limits applicable to internal combustion engines are becoming increasingly stricter. This applies particularly to internal combustion engines designed to power motor vehicles. In order to comply with these emission limits, the conversion capability of exhaust aftertreatment devices integrated into the exhaust systems of these internal combustion engines must be present as soon as possible after a cold start. This requires that the exhaust aftertreatment devices reach their light-off temperatures (also known as "light-off temperatures") as quickly as possible after a cold start, at which point sufficient effectiveness for exhaust aftertreatment can be assumed.

[0003] It is known to temporarily and specifically heat exhaust aftertreatment devices. This can be achieved both through engine-related measures aimed at causing an internal combustion engine to emit exhaust gas at a relatively high exhaust temperature, as well as through active heating measures, for example, using electric heaters or burners. Such a burner can, in particular, use the same fuel as the one intended for operating the internal combustion engine.

[0004] DE 101 16 535 A1 and DE 10 2010 022 933 A1 each disclose a bypass jet engine for propelling an aircraft.

[0005] DE 10 2015 209 148 A1 also describes a turbojet engine for an aircraft.

[0006] DE 10 2015 204 983 A1 discloses a heat exchanger for a waste heat utilization device of a motor vehicle.

[0007] The invention is based on the object of improving a burner which is intended for use in an exhaust system of an internal combustion engine.

[0008] This problem is solved by the subject matter of the patent claims.

[0009] A burner according to the invention, which is intended for use in an exhaust system of an internal combustion engine, comprises at least one housing which delimits a combustion chamber and forms a hot gas outlet of the combustion chamber and a fresh gas inlet. Fresh gas, which can in particular be air, is to be supplied to the burner and specifically to the combustion chamber via the fresh gas inlet. This fresh gas is then provided for combustion with fuel that is also introduced into the combustion chamber. For this purpose, the burner comprises a fuel injector. A fresh gas duct connects the fresh gas inlet to the combustion chamber, wherein the fresh gas duct surrounds the combustion chamber in at least one section at least partially, preferably completely or as completely as possible.The fresh gas guide can preferably directly surround the combustion chamber, so that the combustion chamber is separated from the fresh gas guide by only one wall, in particular a single-layer wall. It is preferably provided that the fresh gas guide at least partially surrounds the combustion chamber over at least 2 / 3 or, preferably, at least 4 / 5, or, particularly preferably, over the entire longitudinal extent, which leads from an inlet end, in which a fuel outlet of the fuel injector and / or an opening of the fresh gas guide is arranged, to the hot gas outlet. This configuration of the fresh gas guide makes it possible to realize an advantageous cooling effect with respect to the outside of the burner housing, whereby advantageous integration into an internal combustion engine or into a motor vehicle comprising such an internal combustion engine can be achieved.Furthermore, this design of the fresh gas guide allows preheating of the fresh gas before it enters the combustion chamber, which can have an advantageous effect on the combustion of fuel with the fresh gas within the combustion chamber.

[0010] According to the invention, the fresh gas duct is further configured such that a main flow direction of the fresh gas in at least one subsection of the section of the fresh gas duct surrounding the combustion chamber is directed opposite to a main flow direction of gas in the adjacent or neighboring section of the combustion chamber. This allows for a particularly good transfer of thermal energy from the combustion chamber to the fresh gas, thus achieving a correspondingly good cooling effect and correspondingly good preheating of the fresh gas.

[0011] The “main flow direction” is understood to mean a direction of gas flow in the fresh gas guide and the combustion chamber, which results from the structural design of the fresh gas guide and the combustion chamber as flow-guiding cavities as the most direct possible path for the flow of the respective gas from an inlet (fresh gas inlet in the case of the fresh gas guide; opening of the fresh gas guide into the combustion chamber in the case of the combustion chamber) to an outlet (opening of the fresh gas guide into the combustion chamber in the case of the fresh gas guide; hot gas outlet in the case of the combustion chamber).

[0012] According to a preferred embodiment of a burner according to the invention, the fresh gas inlet can be arranged behind an opening of the fresh gas guide into the combustion chamber with respect to a direction of travel of the combustion chamber. The "direction of travel" is understood to mean the direction of travel of the combustion chamber along its longitudinal extent and thus in the direction of the hot gas outlet. This allows the at least partially opposing orientation of the main flow directions of the fresh gas and the gas within the combustion chamber to be achieved through a relatively simple design.

[0013] According to a further preferred embodiment of a burner according to the invention, the fresh gas guide can be designed such that the main flow direction of the fresh gas in a first fresh gas guide section is not opposite to the main flow direction of gas in the adjacent section of the combustion chamber and is preferably parallel to it, whereas in a second fresh gas guide section it has the opposite orientation. This allows for a particularly pronounced heat transfer to the fresh gas in the second fresh gas guide section, while this is less pronounced in the first fresh gas guide section. This makes it possible to avoid excessive cooling of the hot gas exiting the burner. This prevents any restriction of the functional use of the hot gas.

[0014] An advantageous heat transfer to the fresh gas flowing through the fresh gas guide can further be achieved by ensuring that the ratios of the sizes of the opening cross sections of the fresh gas guide to the adjacent opening cross sections of the combustion chamber are between 1:1 and 1:3.

[0015] A structurally advantageous embodiment of the burner according to the invention can be achieved by having the combustion chamber extend in a straight line in a first combustion chamber section and in a second combustion chamber section, with the lines in the first section and the second section being aligned at an angle to one another. This allows for advantageous integration into the exhaust system of the internal combustion engine, particularly with regard to the required installation space.

[0016] According to an advantageous development of such a burner according to the invention, it can be provided that the first fresh gas guide section, in which the main flow directions of the gases are not opposite and in particular are co-current, adjoins the second combustion chamber section.

[0017] According to a preferred embodiment of a burner according to the invention, an opening of the fresh gas guide into the combustion chamber can be annular, in particular a closed annular, and at least partially surrounds a fuel outlet of the fuel injector. This allows for an advantageous mixing of fuel that has exited from the fuel outlet of the fuel injector with fresh gas that has entered the combustion chamber via the opening.

[0018] The same purpose can be served if, as is preferably provided, a (first) swirl element for generating a swirl flow of the fresh gas is integrated into the mouth of the fresh gas guide into the combustion chamber. “Integration” is understood to mean an arrangement of the swirl element in which it influences the fresh gas entering or having entered the combustion chamber to generate the swirl flow. For this purpose, the swirl element can preferably be integrated into the mouth opening or form the mouth opening itself. However, it can also be positioned in front of or behind the mouth opening. Such a swirl flow leads to advantageous mixing of the fresh gas with the fuel. This mixing can then be further improved by having a second swirl element upstream of the first swirl element (with respect to the direction of the fresh gas flow).Such a second swirl element can also achieve the most even distribution of the fresh gas over the circumference of the orifice with the first swirl element integrated therein, which can also have an advantageous effect with regard to mixing the fresh gas with the fuel.

[0019] According to a preferred embodiment of a burner according to the invention, a wall element can be provided which partially blocks an opening cross-section of the combustion chamber and thereby divides the combustion chamber into a primary chamber and a secondary chamber, wherein the fuel outlet of the fuel injector and the opening of the fresh gas guide into the combustion chamber are located in the primary chamber, and the hot gas outlet is located in the secondary chamber. Such a wall element can stabilize a flame resulting from the combustion of a mixture of the fuel and the fresh gas within the primary chamber. It can also be provided that combustion of such a mixture takes place exclusively or primarily in the primary chamber, while the secondary chamber can serve merely to guide the hot gas resulting from such combustion.However, combustion, particularly post-combustion of fuel, can also occur in the secondary chamber.

[0020] The invention also relates to an internal combustion engine comprising an internal combustion engine forming at least one combustion chamber and an exhaust system for discharging exhaust gas originating from the at least one combustion chamber. A burner according to the invention is integrated into the exhaust system. The burner can, in particular, be associated with at least one exhaust gas aftertreatment device, so that its operation is intended to heat the exhaust gas aftertreatment device in a targeted and as-needed manner. For this purpose, the burner can, in particular, be arranged directly upstream (with respect to the flow direction of exhaust gas in the exhaust system) of the exhaust gas aftertreatment device.Such heating can be provided in particular before or immediately after a cold start of the internal combustion engine when the exhaust gas aftertreatment device has a temperature that is below its light-off temperature, above which sufficient effectiveness for the intended exhaust gas aftertreatment can be assumed. However, such heating can also be provided to achieve a temporarily particularly high temperature of the exhaust gas aftertreatment device with the aim of regenerating the exhaust gas aftertreatment device. Furthermore, it can preferably be provided that the fuel injector is integrated into a fuel supply system of the internal combustion engine in order to supply it with fuel that is also provided for operating the internal combustion engine. Likewise preferably, it can be provided that the fresh gas inlet of the burner is fluidly connected to a fresh gas line of the internal combustion engine.Such a fresh gas line serves to supply fresh gas, which essentially consists of (ambient) air, to the internal combustion engine for combustion with fuel in at least one combustion chamber. A connecting line connecting the fresh gas line of the internal combustion engine to the fresh gas inlet of the burner can branch off, in particular, downstream of an air filter integrated into the fresh gas line, allowing purified fresh gas or purified air to be supplied to the burner.

[0021] The invention also relates to a motor vehicle, in particular a land vehicle, particularly preferably a wheel-based and non-rail-bound motor vehicle (preferably a car or a truck), with an internal combustion engine according to the invention. The internal combustion engine of the internal combustion engine can be provided, in particular, for the (direct or indirect) provision of the traction drive power for the motor vehicle.

[0022] The invention is explained in more detail below with reference to an exemplary embodiment illustrated in the drawing. The drawing shows, in a partially simplified representation: Fig. 1: a burner according to the invention.

[0023] The one in the Fig. The burner shown in Figure 1 comprises a housing 1 that defines a combustion chamber 2. The combustion chamber 2 extends from an inlet end to an outlet end. Perpendicular to this extension, the combustion chamber 2 has essentially circular opening cross-sections. The inlet end of the combustion chamber 2 is defined by an inlet element 3 designed in the form of an insert, which, as part of the housing 1, forms the opening of a fresh gas guide 4 and accommodates an end section of a fuel injector 5.

[0024] The fresh gas guide 4 is delimited by the housing 1, which is designed with at least a double wall for this purpose. This fresh gas guide 4 connects a fresh gas inlet 6 to the combustion chamber 2 and serves to introduce fresh gas, which was supplied to the burner via the fresh gas inlet 6, into the combustion chamber 2, where the fresh gas mixes with fuel, which was introduced via the fuel injector 5. This fuel-fresh gas mixture can then be ignited in the combustion chamber 2, and specifically in a primary chamber 2a of this combustion chamber 2, by means of an ignition device 7, which in the present embodiment is electrically embodied.The fuel-fresh gas mixture thus burned leads to a generation of hot gas (exhaust gas from the combustion), which can be discharged via a hot gas outlet 8 formed by the housing 1 at the outlet end of the combustion chamber 2 and introduced into an exhaust system (not shown) of an internal combustion engine into which the burner is integrated.

[0025] The division of the combustion chamber 2 into the primary chamber 2a and a secondary chamber 2b is achieved by means of a wall element 9 arranged centrally within an opening cross-section of the combustion chamber 2 and oriented perpendicularly with respect to the main gas flow direction therein. This wall element 9 only partially blocks the opening cross-section of the combustion chamber 2 (in a central section), whereby a flame from the combustion of the fuel-fresh gas mixture can be stabilized in a central region of the primary chamber 2a. The hot gas generated in the primary chamber 2a by combustion flows around the wall element 9 and thereby flows into the secondary chamber 2b, in which this hot gas flow is deflected by an angle of, for example, between 45° and 75° and then discharged via the hot gas outlet 8 arranged at the rear end of the secondary chamber 2b.The deflection of the hot gas flow results from an angular alignment of a first combustion chamber section 2c and a second combustion chamber section 2d, which each run in a straight line.

[0026] The fresh gas inlet 6 formed by the housing 1 is arranged in the region of the transition between the first combustion chamber section 2c and the second combustion chamber section 2d, wherein the direction of extension of the fresh gas inlet 6 and thus the direction of flow of the fresh gas entering the fresh gas guide 4 is perpendicular or radial with respect to the main flow direction of gas in the first combustion chamber section 2c. Starting from the fresh gas inlet 6, the fresh gas guide 4 is designed such that a main flow direction of the fresh gas in a first fresh gas guide section 4a of the fresh gas guide 4 is at least partially parallel to the main flow direction of gas (hot gas) within the second combustion chamber section 2d.A half-shell-shaped deflection element 10, which is part of the housing 1, deflects the fresh gas entering the fresh gas guide 4 via the fresh gas inlet 6 in the direction of the outlet end of the combustion chamber 2. Shortly before the hot gas outlet 8 of the combustion chamber 2, the fresh gas is deflected in the fresh gas guide 4 in the direction of the inlet end of the combustion chamber 2 and the fresh gas thereby flows in a second fresh gas guide section 4b in the opposite direction to the main flow direction of the gas (exhaust gas or fuel-fresh gas mixture) in the first combustion chamber section 2c. At the inlet end of the combustion chamber 2, the flow of the fresh gas is deflected by almost 180° as a result of a corresponding design of the fresh gas guide 4 and then enters an annular pre-chamber 13 via an annular (second) swirl element 12, which is delimited by the inlet element 3.This second swirl element 12 comprises a plurality of annularly arranged guide elements 14, oriented obliquely with respect to the main flow direction in the first combustion chamber section 2c. Passage openings are formed between the guide elements 14 through which the fresh gas can flow, creating a swirling flow of the fresh gas. This swirling flow within the prechamber 13 ensures the most even distribution of the fresh gas possible over the circumference of the fuel injector 5, which the prechamber 13 surrounds in an annular manner.This uniform distribution can compensate for an uneven distribution of the fresh gas on the inlet side of the second swirl element 12, which can result from the fresh gas being supplied unevenly to the second swirl element 12 as a result of the deflection by the deflection element 10 and a partial blockage of the flow guide in the fresh gas guide 4 by the ignition device 7 and a temperature sensor 15, which are accommodated in the housing 1 and extend into the combustion chamber 2, specifically into the primary chamber 2a. The fresh gas is introduced from the pre-chamber 13 into the combustion chamber 2 via a further (first) swirl element 11, which corresponds to the second swirl element 12 except for a different diameter. The first swirl element 11 therefore forms the opening of the fresh gas guide 4 into the combustion chamber 2.

[0027] The fresh gas duct 4 surrounds the combustion chamber 2 as completely as possible, thereby achieving a good transfer of thermal energy from the combustion chamber 2 to the fresh gas flowing through the fresh gas duct 4. This largely complete enclosure of the combustion chamber 2 is interrupted essentially only in those areas where the ignition device 7 and the temperature sensor 15 protrude through the housing 1 into the combustion chamber 2.

[0028] The housing 1 can preferably be designed in multiple parts. An inner housing can be provided which delimits the combustion chamber 2 on the inside. An outer housing surrounds the inner housing and thus delimits the fresh gas guide 4 on the inside and, in combination with the outside of the inner housing, forms the walls that delimit the secondary chamber 2b. This first housing component 1a also comprises the wall element 9, which divides the combustion chamber 2 into the primary chamber 2a and the secondary chamber 2b. A second housing component 1b delimits the primary chamber 2a of the combustion chamber 2 on the circumference. This second housing component 1b can be designed as a simple, straight tube which, in addition to the end openings, has two circumferential openings for receiving the ignition device 7 and the temperature sensor 15.The second housing component 1b can surround the first housing component 1a in one section and be connected to it in a gas-tight manner, for example by welding. A third housing component 1c forms the outer housing wherever the fresh gas guide 4 surrounds the inner housing. In an outlet section in the region of the outlet end of the combustion chamber 2, the combustion chamber 2 is not surrounded by the fresh gas guide 4 and thus also not by the third housing component 1c. In the region of this outlet section, an annular connecting flange 16 is provided, which serves to securely connect the burner to an exhaust pipe of the exhaust system of the internal combustion engine. This connecting flange 16 can be connected, for example welded, to the inner housing or the first housing component 1a and / or to the third housing component 1c, which forms a large part of the outer housing.The third housing component 1c forms a receiving opening within which a holder 17 can be fixedly positioned, each forming a receiving opening for the ignition device 7 and the temperature sensor 15. The open end of the tubular, second housing component 1b is closed at the inlet end of the combustion chamber 2 by means of the inlet element 3. The inlet element 3 can be designed as a continuous unit with a cover component 18 that closes the third housing component, which forms the majority of the outer housing, in the region of the inlet end of the combustion chamber 2 and that forms a receptacle for the fuel injector 5. The unit comprising the inlet element 3 and the cover component 18 can be regarded as the fourth housing component 1d. The various housing components 1a, 1b, 1c, 1d can each be designed as one-piece or multi-piece.

[0029] The burner further comprises a cooling system for the targeted cooling of the fuel injector 5, the ignition device 7, and the temperature sensor 15 using a preferably liquid coolant. For this purpose, the cooling system comprises two coolant nozzles 19 for supplying and discharging the coolant, as well as cooling channels 20 that fluidly connect the coolant nozzles 19. The cooling channels 20 are formed in particular in the holder and in the inlet element 3. LIST OF REFERENCE SYMBOLS 1 housing 1a first housing component 1b second housing component 1c third housing component 1d fourth housing component 2 combustion chamber 2a Primary chamber of the combustion chamber 2b Secondary chamber of the combustion chamber 2c first combustion chamber section 2d second combustion chamber section 3 Inlet element 4 Fresh gas supply 4a first fresh gas supply section 4b second fresh gas supply section 5 Fuel injector 6 Fresh gas inlet 7 Ignition device 8 Hot gas outlet 9 Wall element 10 Deflection element 11 first swirl element 12 second swirl element 13 Pre-chamber of the inlet element 14 Guide element of a swirl element 15 Temperature sensor 16 Connection flange 17 Bracket 18 Cover component 19 Coolant nozzle 20 cooling channel QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 101 16 535 A1

[0004] DE 10 2010 022 933 A1

[0004] DE 10 2015 209 148 A1

[0005] DE 10 2015 204 983 A1

[0006]

Claims

[1] Burner for use in an exhaust system of an internal combustion engine, comprising a housing (1) which delimits a combustion chamber (2) and forms a hot gas outlet (8) of the combustion chamber (2) and a fresh gas inlet (6), and comprising a fuel injector (5) for introducing fuel into the combustion chamber (2), wherein a fresh gas guide (4) connects the fresh gas inlet (6) to the combustion chamber (2) and wherein the fresh gas guide (4) at least partially surrounds the combustion chamber (2) in at least one section, characterized by a design of the fresh gas guide (4) such that a main flow direction of the fresh gas in at least one subsection of the section of the fresh gas guide (4) surrounding the combustion chamber (2) is directed opposite to a main flow direction of gas in the adjacent section of the combustion chamber (2). [2] Burner according to claim 1, characterized bythat the fresh gas inlet (6) is arranged behind an opening of the fresh gas guide (4) into the combustion chamber (2) with respect to a direction of travel of the combustion chamber (2). [3] Burner according to claim 1 or 2, characterized by a design of the fresh gas guide (4) such that the main flow direction of the fresh gas in a first fresh gas guide section (4a) is not opposite to the main flow direction of gas in the adjacent section of the combustion chamber (2) and is opposite in a second fresh gas guide section (4b). [4] Burner according to one of the preceding claims, characterized by that the ratios of the sizes of the opening cross-sections of the fresh gas guide (4) to the adjacent opening cross-sections of the combustion chamber (2) are between 1:1 and 1:

3. [5] Burner according to one of the preceding claims, characterized bythat the combustion chamber (2) runs in a straight line in a first combustion chamber section (2c) and in a second combustion chamber section (2d), wherein the courses in the first combustion chamber section (2c) and the second combustion chamber section (2d) are aligned at an angle to one another. [6] Burner according to claim 4 and claim 5, characterized by that the first fresh gas guide section adjoins the second combustion chamber section (2d). [7] Burner according to one of the preceding claims, characterized by that a / the opening of the fresh gas guide (4) into the combustion chamber (2) is ring-shaped and surrounds a fuel outlet of the fuel injector (5). [8] Burner according to one of the preceding claims, characterized by that a (first) swirl element (11) for generating a swirl flow of the fresh gas is integrated into a / the opening of the fresh gas guide (4) into the combustion chamber (2). [9] Burner according to claim 8 characterized bya second swirl element (12) arranged upstream of the first swirl element (11). [10] Burner according to one of the preceding claims, characterized by a wall element (9) which partially blocks an opening cross-section of the combustion chamber (2) and thereby divides the combustion chamber (2) into a primary chamber (2a) and a secondary chamber (2b), wherein a / the fuel outlet of the fuel injector (5) and a / the mouth of the fresh gas guide (4) into the combustion chamber (2) are located in the primary chamber (2a) and the hot gas outlet (8) is located in the secondary chamber (2b).

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