DE102022212014A1 - Burner unit in the exhaust tract of an internal combustion engine - Google Patents

Abstract

The invention relates to a burner unit (10) in the exhaust tract of an internal combustion engine, with a multi-way catalyst arranged in the exhaust tract and/or an SCR system (Selective Catalytic Reduction) for treating the exhaust gases. This is tempered by means of a gas flow (32) emerging from a combustion chamber (20) of the burner unit (10). The burner unit (10) has a swirl unit (16) adjacent to the combustion chamber (20), at least one swirl channel (50) of which opens into the combustion chamber (20) with a projection (56, 56', 56") parallel or orthogonal to the main axis (12) of the burner unit (10).
Furthermore, the invention relates to the use of the burner unit (10) in the exhaust tract of a self-igniting or spark-ignited internal combustion engine for tempering a multi-way catalyst.

Description

Technical area

The invention relates to a burner unit in the exhaust tract of an internal combustion engine, with a multi-way catalyst arranged in the exhaust tract for treating the exhaust gases, which is tempered by means of a gas flow emerging from a combustion chamber of the burner unit. The invention also relates to the use of the burner unit in the exhaust tract of a self-igniting or externally ignited internal combustion engine for tempering a multi-way catalyst.

State of the art

DE 41 32 814 A1 relates to a method and a device for detoxifying exhaust gases from an internal combustion engine. In the first few minutes after starting a cold internal combustion engine, approximately 70% to 80% of the total emissions of HC and CO are emitted, since the catalyst is not yet at operating temperature. It is therefore proposed that the catalyst be heated to operating temperature by a burner system that responds to control signals from a control unit. This significantly reduces emissions of HC and CO.

DE 195 04 208 A1 refers to an exhaust gas converter with a catalyst and a burner upstream of it. The catalyst only carries out a catalytic conversion of undesirable exhaust gas components after it has been heated to its operating temperature. For this purpose, a burner with a burner tube leading into the exhaust line and supplied with fuel and air is installed upstream of the converter to accelerate the heating of the catalyst and to generate a further conversion of undesirable exhaust gas components in the exhaust line upstream of the catalyst. Areas of the burner that extend into the exhaust line are covered with catalytically active material on their surface exposed to the exhaust gas flow.

The introduction of the so-called RDE (Real Driving Emissions) boundary conditions has resulted in ambitious boundary conditions for the heating of catalysts. The now possible spontaneous cold urban departure with high loads without idling phase pushes previously planned internal engine catalyst heating to its limits, especially if further reduced emission values, such as those expected with EU7, have to be complied with at the same time. In this context, an exhaust gas burner to accelerate the TWC light-off (Three Way Catalyst, light off = start of conversion) and/or SCR systems (Selective Catalytic Reduction) has proven to be an extremely effective measure. For the use of exhaust gas burners in self-igniting internal combustion engines (the burner unit is also operated with diesel fuel), it has been shown that a significantly higher swirl level is required in this application than is the case for gasoline operation. This means that the flow is deflected more towards the outside of the combustion chamber when it enters the combustion chamber of the exhaust gas burner at a comparatively higher swirl level, thereby promoting backflow inside the injector chamber in the center of the combustion chamber through a wide flow field towards the injector. This results in a higher heat release in the immediate vicinity of the injector. Although this is advantageous for complete combustion within the combustion chamber, it does result in the component temperatures in this local area rising significantly. The focus here is particularly on the fuel injector and its injector tip temperature. The temperatures at the injector tip should be below 140 °C if possible. Due to the fact that, depending on the specification, diesel fuel only evaporates at significantly higher temperatures than gasoline, wetting of the injector tip with fuel caused by the injection can lead to non-premixed, rich combustion due to the proximity of the flame in the combustion chamber, which is diffusion-controlled. This results in an increased number of particles being produced in this area of the flame and deposits forming on the injector tip. Such deposits generally have sponge-like properties, meaning that more and more fuel is deposited there and, as a result, soot formation is increased, so that this effect is self-reinforcing. Furthermore, the deposits formed on the injector tip can lead to the injector's spray holes becoming blocked or to a certain injection pattern (spray targeting) undergoing a geometric change. In both cases, this can significantly affect the functionality of the exhaust gas burner, starting with a deterioration in emissions and ending with restrictions in starting robustness.

Description of the invention

According to the invention, a burner unit is proposed which is arranged in the exhaust tract of an internal combustion engine, with a multi-way catalyst arranged in the exhaust tract and/or an SCR system (Selective Catalytic Reduction) for treating the exhaust gases, which is tempered by means of a gas flow emerging from a combustion chamber of the burner unit, wherein the burner unit has a swirl unit adjacent to the combustion chamber, at least one swirl channel of which projects into the combustion chamber with a projection parallel or orthogonal to a main axis of the burner unit.

This advantageously ensures that the supply air, which is provided with a swirl in the circumferential direction in the combustion chamber, is deflected or swirled by the boundary walls of the combustion chamber in such a way that a flame that forms in the combustion chamber does not spread in the direction of the injector tip of the fuel injector and the heat input is therefore reduced because the flame runs out in a lean mixture in this area due to the supply air (quenching). Because the flame no longer reaches the fuel injector, this reduces the maximum temperature of the injector and fundamentally prevents it from coking.

In an advantageous development of the burner unit proposed according to the invention, the swirl unit imparts a rotational movement in the circumferential direction to the supply air flowing into the combustion chamber, relative to the main axis of the combustion chamber. In this way, the flame in the combustion chamber can be stabilized and made uniform.

In an advantageous development of the burner unit proposed according to the invention, the swirl unit comprises an injector shaft for accommodating a fuel injector such that its injector tip opens into the swirl channel. This arrangement ensures that the injector tip remains at a safe distance from the flame front spreading in the combustion chamber and maximum temperatures in the area of the injector tip can be effectively avoided.

In an advantageous development of the burner unit proposed according to the invention, a swirl cone of the air flow exiting the swirl channel is selected such that the supply air flowing into the combustion chamber keeps a flame generated in the combustion chamber away from the swirl channel.

In an advantageous development of the burner unit proposed according to the invention, the projection by which the swirl channel projects into the combustion chamber is between 2 mm and 10 mm, preferably between 3 mm and 7 mm, relative to the injector tip of the fuel injector.

In an advantageous development of the burner unit proposed according to the invention, the swirl channel is designed to be conical. This is particularly easy to implement in terms of manufacturing technology.

In a further advantageous embodiment of the burner unit proposed according to the invention, the swirl channel has a continuous cross-sectional reduction up to a nozzle part. This makes it possible to accelerate the supply air fed into the combustion chamber and provided with a swirl in the circumferential direction, which has a positive effect on the combustion within the combustion chamber.

In an advantageous embodiment, the swirl channel can alternatively be formed by spherical shells that are either arranged parallel to one another with identical curvature, forming a constant flow cross-section, or arranged converging to one another, forming a decreasing flow cross-section. These two design variants also promote the generation of swirl within the combustion chamber.

In an advantageous embodiment, the burner unit is designed such that the swirl channel is formed by rotary shell shapes that are arranged either in parallel arrangement with identical curvature, forming a constant flow cross-section, or in a converging arrangement, forming a decreasing flow cross-section. The advantages outlined above can also be achieved with this alternative embodiment.

In the burner unit proposed according to the invention, it is possible to form the swirl channel in the swirl unit by means of a flat conical surface and a spherical shell. Other modifications are also possible.

In an advantageous development of the burner unit proposed according to the invention, the swirl channel of the combustion chamber can also supply the incoming supply air in an orthogonal direction, relative to the main axis of the combustion chamber. The air inflow, which is perpendicular to the main axis of the combustion chamber, can promote the swirl that acts in the direction of rotation. The design variant also makes it possible to keep the flame, which spreads within the combustion chamber in the direction of the injector tip, favoring the backflow effect, away from it in order to limit the maximum temperatures there.

Alternatively, in the burner unit proposed according to the invention, it is also possible to design the swirl channel in a mirrored arrangement with respect to a vertical axis, for example to a swirl channel with a conical shape. In this embodiment, the swirl channel The walls bounding the chamber are inclined in opposite directions, i.e. facing the combustion chamber.

Furthermore, the invention relates to the use of the burner unit in the exhaust tract of a self-igniting or spark-ignited internal combustion engine for tempering a multi-way catalyst and/or an SCR system (Selective Catalytic Reduction).

Advantages of the invention

The burner unit proposed according to the invention can be used, particularly in the case of self-igniting internal combustion engines, to ensure that the flame spreading in the combustion chamber causes excessive heat input to the injector tip of the fuel injector due to backflow effects. The extension of the swirl channel in the axial direction or the air supply in the orthogonal direction prevents the flame front from reaching the injector tip of the fuel injector. This is due on the one hand to the strongly opposing flow during flame propagation and to the fact that the flame generated in the combustion chamber is "quenched" by the air in the area immediately in front of the mouth of the swirl channel, i.e. the flame runs out in a lean mixture. Since the flame no longer reaches the fuel injector, in particular its injector tip, in the burner unit proposed according to the invention, this reduces the maximum temperature of the injector and fundamentally prevents coking on the injector tip of the fuel injector.

In the solution proposed according to the invention, the projection by which the swirl channel projects into the combustion chamber, starting from the injector tip of the fuel injector, is between 3 mm and 7 mm.

The burner unit proposed according to the invention makes it possible to significantly reduce the maximum temperature at the injector tip of the fuel injector. A maximum temperature of over 300 °C with a burner running time of 25 s with, for example, 25 kW can be reduced to a level of less than 25 °C by the solution proposed according to the invention.

Furthermore, the solution proposed according to the invention can prevent a self-reinforcing effect, in particular coking of the injector tip, by avoiding sponge-like deposits. This allows the service life of the fuel injector used to be significantly increased, and the starting robustness of a burner unit proposed according to the invention is also significantly improved by the solution proposed according to the invention.

Furthermore, it should be emphasized that the significant reduction in the maximum temperature at the injector tip of the fuel injector is accompanied by the great advantage that no additional coolant circuit, such as cooling mass from the engine circuit of the internal combustion engine, has to be diverted to the fuel injector in order to control the temperature of the fuel injector. This is a unique selling point, since the proposed combustion control within the combustion chamber can achieve a significant reduction in costs.

The design of the swirl channel in the burner unit proposed according to the invention, in particular in its swirl unit, can be done in a variety of ways. For example, conical surfaces can be mentioned, which can be arranged parallel to one another to form a constant flow cross-section, or which have a flow cross-section that decreases in the flow direction of the incoming supply air up to a nozzle part. In addition to flat surfaces, as can be used in the conical design of the swirl channel, spherical shells can also be used in the solution proposed according to the invention, which can be arranged parallel to one another with identical curvature or can also be placed in a converging arrangement. In addition, it is also possible to use gyroscopic shell shapes, which can also be installed in such a way that they represent a constant flow cross-section for the incoming supply air or can be placed converging.

Mixed forms of flat surfaces and spherical, i.e. curved, elements for the design of the swirl channel are also possible.

Furthermore, in an alternative embodiment of the burner unit proposed according to the invention, an orthogonal inflow of the incoming air can be realized, in which the incoming air is supplied perpendicular to the main axis of the combustion chamber. This has an advantageous effect on the swirl point that is established. The greater the swirl generated in the combustion chamber, the better the atomization of the fuel used, especially diesel in self-igniting internal combustion engines, can be achieved, which is extremely beneficial for complete combustion. In addition to an orthogonal introduction of the supplied air into the combustion chamber, it is also possible to arrange the swirl in a mirrored manner to the vertical axis. channel, which, for example, realizes an arrangement tilted about a vertical axis towards the combustion chamber.

Short description of the drawings

Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

• 1 eine Brennereinheit gemäß dem Stand der Technik mit auf den Krafstoffinjektor unmittelbar auftreffender Flammenfront,
• 2 eine erste Ausführungsvariante der erfindungsgemäß vorgeschlagenen Brennereinheit mit einem Drallkanal, der in einer Konizität ausgebildet ist,
• 3 eine Gegenüberstellung der Temperaturniveaus an der Injektorkuppe des Kraftstoffinjektors in der Variante gemäß dem Stand der Technik nach 1 und bei der erfindungsgemäß vorgeschlagenen ersten Ausführungsvariante gemäß 2,
• 4 eine zweite Ausführungsvariante der Brennereinheit mit einem Drallkanal, der einen sich in Strömungsrichtung der einströmenden Zuluft abnehmenden Strömungsquerschnitt aufweist,
• 5 eine dritte Ausführungsvariante der Brennereinheit mit einem Drallkanal, der aus parallel zueinander angeordneten Kugelschalen gebildet ist,
• 6 eine vierte Ausführungsvariante der Brennereinheit mit einem Drallkanal, der aus aufeinander zulaufenden Kugelschalen mit einem abnehmenden Strömungsquerschnitt ausgeführt ist,
• 7 eine fünfte Ausführungsvariante der Brennereinheit mit einem Drallkanal, der durch Kreiselschalenformen begrenzt wird, wobei hier ein konstanter Strömungsquerschnitt für die einströmende Zuluft verwirklicht ist,
• 8 eine sechste Ausführungsvariante der Brennereinheit mit einem Drallkanal mit Kreiselschalenformen, die zueinander so angeordnet sind, dass sich in Strömungsrichtung der einströmenden Zuluft ein abnehmender Strömungsquerschnitt einstellt,
• 9 eine Mischform, bei der der Drallkanal der erfindungsgemäß vorgeschlagenen Brennereinheit durch eine ebene konische Fläche einerseits und durch eine Kreiselschalenform andererseits begrenzt ist,
• 10 eine orthogonale Einströmung der einströmenden Zuluft in die Brennkammer und
• 11 eine Anordnung der Brennereinheit, bei der der Drallkanal an der vertikalen Achse gespiegelt ist, im Vergleich zur Variante gemäß 2.

Show it:

• 1 a burner unit according to the state of the art with a flame front directly impinging on the fuel injector,
• 2 a first embodiment of the burner unit proposed according to the invention with a swirl channel which is formed in a conicity,
• 3 a comparison of the temperature levels at the injector tip of the fuel injector in the variant according to the state of the art according to 1 and in the first embodiment proposed according to the invention according to 2 ,
• 4 a second design variant of the burner unit with a swirl channel which has a flow cross-section that decreases in the flow direction of the incoming supply air,
• 5 a third variant of the burner unit with a swirl channel formed from spherical shells arranged parallel to each other,
• 6 a fourth design variant of the burner unit with a swirl channel made up of converging spherical shells with a decreasing flow cross-section,
• 7 a fifth design variant of the burner unit with a swirl channel which is limited by rotary shell shapes, whereby a constant flow cross-section for the incoming supply air is realized,
• 8th a sixth design variant of the burner unit with a swirl channel with rotary shell shapes, which are arranged in such a way that a decreasing flow cross-section is established in the flow direction of the incoming supply air,
• 9 a mixed form in which the swirl channel of the burner unit proposed according to the invention is limited by a flat conical surface on the one hand and by a gyroscopic shell shape on the other hand,
• 10 an orthogonal inflow of the incoming supply air into the combustion chamber and
• 11 an arrangement of the burner unit in which the swirl channel is mirrored on the vertical axis, compared to the variant according to 2 .

1 shows a burner unit 10 according to the prior art. In 1 a burner unit 10 is shown which is designed essentially symmetrically to its main axis 12. The burner unit 10 comprises a fuel injector 14 which is inserted into an injector shaft 40 of a swirl unit 16. The swirl unit 16 has a swirl grid 18, via which a swirl is imposed on the incoming supply air 22 which flows via an air supply 28 over the circumference of the combustion chamber 20. This causes the incoming supply air 22 to swirl within the combustion chamber 20.

The combustion chamber 20 is assigned an ignition chamber 24, into which a glow plug 26 extends. The ignition chamber 24 ignites an ignitable mixture of fuel entering the combustion chamber 20 via the fuel injector 14 and supply air 22 flowing into the combustion chamber 20 with a swirl. Downstream of a front side 44 of the combustion chamber 20 there is an outlet 30, via which an escaping gas flow 32 leaves the combustion chamber 20 of the burner unit 10, for example in the direction of a multi-way catalyst or an SCR system (Selective Catalytic Reduction). As can be seen from 1 As can be seen, the incoming supply air 22 leaves the swirl unit 16 with a swirl cone 34, which here is oriented, for example, against the lateral boundary wall of the combustion chamber 20. A flame 46 that forms in the combustion chamber 20 generates, on the one hand, a gas flow 32 that exits in accordance with an air flow direction 36 in the direction of the outlet 30 and, on the other hand, a backflow 38 of the flame 46 towards the front side 44 of the combustion chamber 20, ie in particular onto an injector tip 42 of the fuel injector 14 embedded in the injector shaft 40 of the swirl unit 16. In the case of self-igniting internal combustion engines, it has been found that a significantly higher swirl level is necessary compared to other designs. This means that the incoming supply air 22 is deflected more strongly outwards when it enters the combustion chamber 20 at a comparatively higher swirl level, and the return flow 38 to the fuel injector 14, in particular the injector tip 42 in the center of the combustion chamber 20, is promoted by a wider flow field. This means that more heat is released at the fuel injector 14. As a result, the component temperatures in this area, ie in particular in the area of the injector tip 42, increase significantly locally. Due to the fact that diesel fuel, depending on the specification, only evaporates at significantly higher temperatures, wetting of the injector tip 42 of the fuel injector 14 with fuel caused by the injection due to the proximity of the flame 46 can lead to non-premixed, rich combustion that takes place in a diffusion-controlled manner. This means that more particles are produced in this area of the flame 46 and deposits form on the injector tip 42. These deposits generally have sponge-like properties, so that more and more fuel can accumulate and, as a result, soot formation increases. This effect is therefore self-reinforcing. The deposits that form on the injector tip 42 can, among other things, lead to the spray holes of the fuel injector 14 becoming blocked or the injection pattern of the fuel injector 14 changing. In both cases, this can significantly affect the functionality of the burner unit 10, for example leading to a deterioration in emissions or even restrictions in starting robustness.

Embodiments of the invention

In the following description of the embodiments of the invention, identical or similar elements are designated by identical reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only represent the subject matter of the invention schematically.

2 shows a first embodiment of the burner unit 10 proposed according to the invention.

As shown in the illustration 2 As can be seen, in the first embodiment of the burner unit 10 proposed according to the invention there is a swirl channel 50 which extends from the front side 44 of the combustion chamber 20 by an extension 52, here in the axial direction 54, into the combustion chamber 20 of the burner unit 10. A projection 56 into the combustion chamber 20 resulting from the extension 52 of the swirl channel 50 lies in the burner unit 10 proposed according to the invention according to the first embodiment according to 2 in the order of magnitude between 3 mm and 7 mm, relative to the injector tip 42 of the fuel injector 14. The projection 56 can also have larger values, such as the 1 The projection 56, 56`, 56" is defined depending on the mouth of the fuel injector 14, ie the outer edge of the swirl channel 50 such that the projection 56, 56`, 56" ends where a virtual line runs between the injector tip 42 and the ignition location, ie the glow plug 26, as in 2 In the event that the swirl channel 50 opens further out (cf. projections 56` and 56"), the projection 56 can also assume larger values as shown in 2 indicated by the projections 56` and 56". The imaginary line between the glow plug 26, ie the ignition location, and the tip of the injector tip 42 essentially characterizes the spray angle of the fuel injector 14. As a rule, it has proven advantageous that there is the geometric possibility of injecting the fuel without transporting air to the ignition location, in this case in the direction of the glow plug 26. In this way, enrichment during the start-up phase is ensured and thus also a robust start of the burner unit 10 in the millisecond range.

Alternatively, it is possible to form the inner edge of the swirl channel 50 opening into the combustion chamber 20 in a projection 56, as an alternative to 2 and in the further 3 to 11 illustrated embodiment, in which an outer side of the swirl channel 50 projects by the projection 56, 56` and if necessary 56" beyond the injector tip 42 into the combustion chamber 20.

Through the 2 The extension 52 of the swirl channel 50 shown in the axial direction 54 prevents the flame 46 from spreading to the fuel injector 14 or its injector tip 42 or even into the swirl channel 50. This is due both to the opposite flow of the flame propagation and to the fact that the flame 46 runs out in a lean mixture due to the air in this area, ie is "quenched". As a result, the flame 46 no longer reaches the fuel injector 14, so that in this way both the maximum temperature at the injector tip 42 is reduced and the coking of the fuel injector 14 at its injector tip 42 can be fundamentally prevented.

The extension 52 of the swirl channel 50 into the combustion chamber 20 results in the peak temperature at the injector tip 42 of the fuel injector 14 being able to be reduced. This is in 3 shown.

3 shows that in 1 In the embodiment shown in accordance with the state of the art, a temperature profile 58 occurs at the injector tip 42, which is characterized by a peak temperature level 60. The peak temperature (burning time = 25 s) which is present over an exposure time 64 of up to 25 s is in the order of about 300 °C for a cold start process, starting from -10 °C. In contrast, 3 that in the burner unit 10 proposed according to the invention, as for example in a first version in 2 is shown, there is a gradual temperature increase 66, plotted over the exposure time 64. Here, due to the distance between the flame front of the flame 46 at the injector tip 42, a gradually increasing temperature gradient, plotted over time, gradually occurs. The maximum temperature increase at the injector tip 42 as shown in 3 is only in the order of < 30 °C.

From the representation according to 4 a second embodiment of the burner unit 10 proposed according to the invention emerges, in which the swirl channel 50, which here also extends by the extension 52 in relation to the front side 44 of the combustion chamber 20, projects into the latter and is designed in a conicity 68. In the case of the 4 The conicity 68 shown is one in which the swirl channel 50, which has a cross-sectional reduction 70 in the flow direction of the incoming supply air 22, reduces in terms of its flow cross-section in the direction of a nozzle part 72 with an outlet nozzle. This can accelerate the flow of the incoming supply air 22 into the combustion chamber 20 of the burner unit 10. 4 shows that according to this second embodiment of the burner unit 10 proposed according to the invention, the swirl cone 34 is set, starting from the nozzle opening of the nozzle part 72, so that the flame 46 is kept further away from the front side 44, which delimits the combustion chamber 20 in the area of the swirl unit 16, and the backflow 38 that occurs in the flame front of the flame 46 can be kept away from the injector tip 42 of the fuel injector 14 mounted in the injector shaft 40. This creates the situation in 3 shown favorable temperature profile according to a gradual temperature increase 66 with a low temperature gradient at the injector tip 42 of the fuel injector 14.

As can be seen from the illustration according to 4 As can also be seen, the swirl channel 50 or its conicity 68 is represented by flat surfaces of the swirl channel 50. The swirl unit 16 comprises said swirl grille 18, through which a swirl cone 34 is impressed on the inflowing supply air 22, which flows to the swirl unit 16 via the air supply 28. Depending on the speed of the inflowing supply air 22 and the flow configuration of the swirl channel 50, the corresponding swirl cone 34 is positioned at the opening of the swirl channel 50 in the combustion chamber 20, at a distance of the projection 56 from the front side 44.

Also in the version according to 4 the fuel injector 14 is arranged concentrically to the main axis 12 of the combustion chamber 20 of the burner unit 10. The flame 46 that forms in the combustion chamber 20 does not reach the injector tip 42 of the fuel injector 14, so that no unacceptably high temperature increase or coking can occur and the fuel injector can therefore be kept essentially free of deposits. The outflowing gas flow 32 exits the combustion chamber 20 via the outlet 30 and heats in particular a 4 a multi-way catalyst (not shown), an SCR system (Selective Catalytic Reduction) or another component in the exhaust tract of an internal combustion engine that is to be heated to operating temperature for a short time at low outside temperatures.

Above the combustion chamber 20 of the burner unit 10 there is said ignition chamber 24 which accommodates a glow plug 26 which ignites the mixture of incoming supply air 22, which flows into the combustion chamber 20 under the swirl cone 34, and the fuel flowing into the combustion chamber 20 via the fuel injector 14, i.e. this fuel/air mixture.

The significant reduction in the maximum temperature at the injector tip 42 of the fuel injector 14 of the burner unit 10 proposed according to the invention achieved according to the invention advantageously means that no additional coolant circuit, for example represented by cooling water from the circuit of the internal combustion engine, has to be created in order to cool the fuel injector 14. This can be saved due to the relatively low heat input into the injector tip 42 by the solution proposed according to the invention.

According to the illustration 5 A further, third embodiment variant of the burner unit 10 proposed according to the invention can be seen.

5 shows that the swirl channel 50 of the swirl unit 16 in this third embodiment is formed by spherical shells 74, which are arranged in a parallel arrangement 76 at a distance from one another, forming a flow channel for the incoming supply air 22. In the parallel arrangement 76 of the spherical shells 74, forming the swirl channel 50, in the third embodiment of the burner unit 10 the extension 52 protrudes into the combustion chamber 20 at the top, relative to the front side 44 of the combustion chamber 20. At the exit point of the incoming supply air 22, which is impressed with the swirl cone 34 after passing through the swirl channel 50 with the swirl grille 18, the incoming supply air 22 exits the spherical shells 74 and enters the combustion chamber 20 with the swirl cone 34. The 5 shown configuration of the flame 46 within the combustion chamber 20. The backflow 38 associated with the formation of the flame front of the flame 46 is effectively kept away from the opening of the swirl channel 50 in the combustion chamber 20 and in particular from the injector tip 42 of the fuel injector 14, accommodated in the injector shaft 40 of the swirl unit 16. Consequently, the injector tip 42 of the fuel injector 14 is formed according to the third embodiment of the burner unit 10 according to 5 the gradual temperature increase 66 with a relatively small temperature gradient according to 3 a.

The supply air 22 flowing in via the air supply 28 passes through the ignition chamber 24, in which it causes the ignition required to ignite the fuel/air mixture formed in the combustion chamber 20.

The escaping gas flow 32 flows in the flow direction 36 through the outlet 30 into a multi-way catalyst (not shown), an SCR system (Selective Catalytic Reduction) or another component of the exhaust tract of an internal combustion engine.

6 shows a further, fourth embodiment of the burner unit 10 proposed according to the invention. In this embodiment, the swirl channel 50 is also formed by spherical shells 74 which are spaced apart from one another. In contrast to a 5 The swirl channel 50 according to the embodiment in FIG. 1 has a parallel arrangement 76 of the spherical shells 74 6 a tapered arrangement 78, so that in the swirl channel 50 a cross-sectional reduction 70 similar to that in 4 illustrated embodiment variant. Due to the tapered arrangement 78 of the spherical shells 74, forming a cross-sectional reduction 70 in the flow direction of the supply air 22, the inflowing supply air 22 is accelerated in the direction of the outlet 30 of the swirl channel 50, spaced by the projection 56 from the front side 44 of the combustion chamber 20 into the latter. In this embodiment variant of the burner unit 10 proposed according to the invention, the backflow 38 which occurs in the flame front of the flame 46 is also guided into an area of the combustion chamber 20 in which a lean air/fuel mixture is present, so that the flame 46 runs out there and no heat can be introduced into the swirl channel 50 or into the injector tip 42 of the fuel injector 14.

7 is a further embodiment of the burner unit 10 proposed according to the invention, the swirl channel 50 of which is represented in this embodiment by gyroscope-shaped shells 80. The gyroscope-shaped shells 80 delimiting the swirl channel 50 are in the embodiment of the burner unit 10 according to 7 arranged so that a constant flow cross-section 82 is established in the swirl channel 50. Also in the 7 In the embodiment variant of the burner unit 10 shown, the swirl channel 50, formed by the gyroscopic shells 80 with a constant flow cross-section 82, opens into the combustion chamber 20 in the projection 56 at a distance in the axial direction 54 from the front side 44 of the combustion chamber 20. The swirl unit 16 assigned to the front side 44 of the combustion chamber 20 is provided with the swirl grille 18, through which the inflowing supply air 22 passing through the swirl grille 18 reaches the combustion chamber 20 in the swirl cone 34 and accordingly promotes the formation of a homogeneous fuel-air mixture.

The fuel/air mixture formed in the combustion chamber 20 from atomized fuel injected by the fuel injector 14 and supply air 22 flowing in the swirl cone 34 is ignited by the glow plug 26 of the ignition chamber 24.

In this embodiment variant, the flame 46 also generates the escaping gas flow 32, which flows via the outlet 30 in the direction of a multi-way catalyst (not shown here) or an SCR system (Selective Catalytic Reduction) in the exhaust tract of an internal combustion engine in order to bring the components mentioned here as examples to operating temperature.

The design variant according to 8th is a modification of the burner unit 10 according to the invention according to 7 can be found in the 8th In the embodiment of the burner unit 10 shown, the swirl channel 50 has a constant cross-sectional reduction 70 in the direction of the mouth of the swirl channel 50 into the combustion chamber 20. The swirl channel 50 is in the embodiment of the burner unit 10 according to 8th also formed by gyroform shells 80, which, however, represent a decreasing cross-section 84, ie a cross-section reduction 70 of the swirl channel 50. In this embodiment, the swirl channel 50 also protrudes beyond the projection 56 as an extension 52 over the front side 44 of the combustion chamber 20 of the burner unit 10, so that the swirl channel 50 encases the injector tip 42 of the fuel injector 14 to a certain extent. The backflow 38 that occurs within the flame 46 in the combustion chamber 20 and the associated heat input is kept away from the mouth of the swirl channel 50 in the combustion chamber 20, so that in particular the injector tip 42 of the fuel injector 14 is protected from excessive heat input. In the 8th The variant of the swirl channel 50 shown in FIG. 1 by means of gyroscopic shells 80 is also used in connection with 3 mentioned gradual temperature increase 66 is achieved at the injector tip 42 of the fuel injector 14. The resulting escaping gas flow 32 flows via the outlet 30 into a 8th a multi-way catalyst (not shown), an SCR system (Selective Catalytic Reduction) or another component in the exhaust tract of the internal combustion engine.

9 shows a variant of the burner unit 10, in which the swirl channel 50 is delimited by a flat conical surface 86 in the swirl unit 16 on the one hand and a gyro shell 88 assigned to it here. This results in a swirl channel 50 which is formed from combined components of the variants of the swirl channels 50 already described above. Here too, it is ensured that the swirl channel 50, starting from the front side 44 of the combustion chamber 20, has an extension 52 into it, so that, viewed in the axial direction 54, the projection 56 of the swirl channel 50 results. The air flow of incoming supply air 22 exiting from the mouth of the swirl channel 50 into the combustion chamber 20 exits from this in the swirl cone 34, so that the flame 46 is established in the combustion chamber 20. Its return flow 38, which is directed towards the mouth of the swirl channel 50, is kept away from the injector tip 42, so that the heat input into the injector tip 42 of the fuel injector 14 remains manageable. The flame 46 generates the outflowing gas flow 32 in the combustion chamber 20, which leaves the combustion chamber 20 via the outlet 30.

10 shows a variant of the burner unit 10 proposed according to the invention, in which the swirl channel 50 enables an orthogonal inflow 90 of the incoming supply air 22 into the combustion chamber 20. In this variant, the swirl grille 18 is not accommodated in the swirl unit 16, but is located in the flow cross-section of the swirl channel 50, which in this variant is characterized by a constant flow cross-section 82 and is oriented essentially perpendicular to the main axis 12 of the combustion chamber 20. This arrangement of the swirl channel 50 results in a strong flow deflection of the incoming supply air 22 and the 10 shown swirl cone 34, into which the supply air 22 flowing into the combustion chamber 20 exits. In this embodiment variant too, the heat input by the backflow 38 from the flame 46 can be kept away from the injector tip 42 of the fuel injector 14, so that the heat input into the fuel injector 14 remains within narrow limits, which on the one hand increases the service life of the fuel injector 14 and on the other hand excludes the risk of coking during frequent cold start operation.

11 Finally, another embodiment of the burner unit 10 proposed according to the invention is shown in FIG. In this embodiment, the swirl channel 50 is designed in such a way that it is a mirrored variant 94 of the swirl channel 50, as shown in 2 Compared to the variant according to 2 the swirl channel 50 is as shown in 11 , inclined with respect to a vertical axis 96, towards the combustion chamber 20. Here too, the swirl grille 18 is integrated in the swirl channel 50, which has a cross-sectional reduction 70 or a constant cross-section 82. The incoming supply air 22 passes the swirl grille 18 coming from the air supply 28 and enters the interior of the combustion chamber 20 of the burner unit 10 according to the swirl cone 34. The flame 46, which is generated within the combustion chamber 20, creates the escaping gas flow 32, which exits at the end of the burner unit 10 after passing through the outlet 30 and brings, for example, a multi-way catalyst, an SCR system (Selective Catalytic Reduction) or other components present in the exhaust tract of an internal combustion engine to operating temperature.

In all cases, based on the 2 to 11 In the embodiments described of the burner unit 10 proposed according to the invention, the swirl channel 50, having an extension 52 in the form of a projection 56 in relation to the front side 44, projects into the combustion chamber 20. In this way, in all embodiments of the burner unit 10 proposed according to the invention, it can be ensured that excessive heat input, in particular into the injector tip 42 of the fuel injector 14 of the burner unit 10 accommodated in the injector shaft 40, is avoided. By means of the solution proposed according to the invention, the flame 46 or its flame front is pushed back into the combustion chamber 20 in such a way that a sufficient distance is established in relation to the injector tip 42 of the fuel injector 40 or to the mouth of the swirl channel 50 in the combustion chamber 20. The return flow 38 of the flame 46 is relocated to a region of the combustion chamber 20 where the flame 46 runs out, ie is “quenched”.

In all versions according to the 2 to 11 an outlet cross-section of the combustion chamber 20 is designated with reference number 98. The burner unit 10 proposed according to the invention can be used for both self-igniting and externally ignited internal combustion engines. The burner unit 10 can be operated with the fuels intended for the internal combustion engine, ie petrol or diesel, just as it is possible to operate a burner unit 10 that is used on a self-igniting internal combustion engine with petrol instead of diesel.

The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, a large number of modifications are possible within the scope specified by the claims, which are within the scope of expert action.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 4132814 A1 [0002]
• DE 19504208 A1 [0003]

Claims (13)

Burner unit (10) in the exhaust tract of a self-igniting internal combustion engine with a multi-way catalyst arranged in the exhaust tract or an SCR system (Selective Catalytic Reduction) for treating the exhaust gases, which is tempered by means of a gas flow (32) emerging from a combustion chamber (20) of the burner unit (10), characterized in that the burner unit (10) has a swirl unit (16) adjacent to the combustion chamber (20), at least one swirl channel (50) of which projects parallel or orthogonal to a main axis (12) of the burner unit (10) with a projection (56, 56`, 56") into the combustion chamber (20). Burner unit (10) according to Claim 1 , characterized in that the swirl unit (16) imparts a rotational movement in the circumferential direction, relative to the main axis (12) of the combustion chamber (20), to the supply air (22) flowing into the combustion chamber (20). Burner unit (10) according to Claims 1 and 2 , characterized in that the swirl unit (16) has an injector shaft (40) for receiving a fuel injector (14), the injector tip (22) of which opens into the swirl channel (50). Burner unit (10) according to Claims 1 until 3 , characterized in that a swirl cone (34) of the air flow emerging from the swirl channel (50) is selected such that the supply air (22) flowing into the combustion chamber (20) keeps a flame (46) generated in the combustion chamber (20) away from the swirl channel (50). Burner unit (10) according to Claims 1 until 4 , characterized in that the projection (56, 56`, 56") with which the swirl channel (50) projects into the combustion chamber (20) is between 2 mm and 10 mm, preferably between 3 mm and 7 mm. Burner unit (10) according to Claims 1 until 5 , characterized in that the swirl channel (50) is designed in a conicity (68). Burner unit (10) according to Claims 1 until 6 , characterized in that the swirl channel (50) has a continuous cross-sectional reduction (70) up to a nozzle part (72). Burner unit (10) according to Claims 1 until 7 , characterized in that the swirl channel (50) is formed by spherical shells (74) which are arranged - either in parallel arrangement (76) to one another with identical curvature forming a constant flow cross-section (82) or - in a converging arrangement (78) forming a decreasing flow cross-section (84). Burner unit (10) according to Claims 1 until 8th , characterized in that the swirl channel (50) is formed by gyroscopic shells (80) which are arranged - either in parallel arrangement (76) to one another with identical curvature, forming a constant curvature cross-section (82), or - in a converging arrangement (78) forming a decreasing flow cross-section (84). Burner unit (10) according to Claims 1 until 9 , characterized in that the swirl channel (50) in the swirl unit (16) is formed by a flat conical surface (86) and by a spherical shell (88). Burner unit (10) according to Claims 1 until 5 , characterized in that the swirl channel (50) of the combustion chamber (20) supplies the incoming supply air (22) in an orthogonal inflow (90) relative to the main axis (12) of the combustion chamber (20). Burner unit (10) according to Claims 1 until 6 , characterized in that the swirl channel (50) is designed in relation to a vertical axis (96) in a mirrored arrangement (94) of the swirl channel (50) formed in a conicity (68). Use of the burner unit (10) according to one of the Claims 1 until 12 in the exhaust tract of a self-igniting or spark-ignited internal combustion engine to control the temperature of a multi-way catalyst.

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