Exhaust gas turbine and method for operating the same

Abstract

Exhaust gas turbine (31) for expanding exhaust gas, with a turbine housing (33) which has an inflow housing section (35) for exhaust gas to be expanded and an outflow housing section (36) for expanded exhaust gas, with a turbine rotor (34) received by the turbine housing (33), wherein the turbine rotor (34) is rotatable about a rotation axis R, with a metering device (42) for a reducing agent or a precursor substance of a reducing agent, wherein the reducing agent or the precursor substance can be introduced into the expanded exhaust gas via the metering device (42), with a swirl atomizer (43) for the reducing agent or the precursor substance rotating together with the turbine rotor (34), wherein the reducing agent or the precursor substance can be atomized in the expanded exhaust gas via the swirl atomizer (43), wherein the swirl atomizer (43) acts on the turbine rotor (34) at a downstream, hub-side section of the turbine rotor (34), characterized in that downstream of the turbine rotor (34) in extension of the rotational axis of the turbine rotor (34) an impact body (44) for the reducing agent or precursor substance introduced into the exhaust gas and atomized is arranged at a defined distance from the swirl atomizer (43), wherein the impact body (44) is a separate assembly mounted on the turbine housing (33), the defined distance of the impact body (44) from the swirl atomizer (43) corresponds to a maximum of 7 times the diameter of the turbine rotor (34).

Description

The invention relates to an exhaust gas turbine. The invention further relates to a method for operating an exhaust gas turbine.The basic structure of an exhaust gas turbocharger is known from DE 10 2016 125 189 A1. An exhaust gas turbocharger has an exhaust gas turbine for expanding exhaust gas of an internal combustion engine, wherein energy is obtained during the expansion of the exhaust gas. The exhaust gas turbocharger further comprises a compressor for compressing charge air to be supplied by the internal combustion engine, specifically by utilizing the energy obtained during the expansion of the exhaust gas. The exhaust turbine includes a turbine housing and a turbine rotor. The compressor has a compressor housing and a compressor rotor. The turbine rotor and compressor rotor are coupled via a shaft that is supported in a bearing housing.WO 2018 / 080 371 A1 discloses an exhaust gas turbine of an exhaust gas turbocharger which has a metering device for reducing agent or a precursor substance of a reducing agent. By means of this metering device, the reducing agent or the precursor substance can be introduced into the exhaust gas expanded in the exhaust gas turbine, wherein the metering device directs the reducing agent or the precursor substance onto a swirl atomizer, which acts on the turbine rotor at a hub-side section of the turbine rotor and rotates together with the turbine rotor. The reducing agent or the precursor substance of the reducing agent can be atomized in the expanded exhaust gas via the swirl atomizer. The reducing agent serves for the reduction of nitrogen oxides in the exhaust gas, in particular in the region of an SCR catalyst which is arranged downstream of the exhaust gas turbine and to which the expanded exhaust gas can be fed together with the reducing agent atomized in the exhaust gas.WO 2020 / 014 564 A1 discloses further prior art.There is the problem that deposits of solid constituents of the reducing agent or of the precursor substance of the reducing agent form on assemblies of the exhaust gas turbine, for example on the swirl atomizer, the metering device or else on the turbine housing, such as deposits of urea decomposition products such as cyanuric acid or melamine, for example. This is disadvantageous.There is therefore a need for an exhaust gas turbine in which the risk of deposits formed from solid constituents of the reducing agent or the precursor substance of the reducing agent on components thereof is reduced. Proceeding from this, the object of the invention is to create a novel exhaust gas turbine and a method for operating the same.According to a first aspect, this object is achieved by an exhaust gas turbine according to claim 1. According to this, the exhaust gas turbine has, downstream of the turbine rotor, in prolongation of the axis of rotation of the turbine rotor, an impact body for the reducing agent introduced into the exhaust gas and atomized or the precursor substance, which is arranged at a defined distance from the swirl atomizer, wherein the impact body is a separate assembly mounted on the turbine housing, wherein the defined distance of the impact body from the swirl atomizer corresponds at most to 7 times a diameter of the turbine rotor.By providing the baffle body downstream of the turbine rotor in extension of the axis of rotation of the turbine rotor with a defined distance between the baffle body and the swirl atomizer in the direction of the axis of rotation, an effective atomization of the reducing agent or the precursor substance of the reducing agent in the expanded exhaust gas can be ensured, whereby the risk of deposits of solid constituents of the reducing agent or the precursor substance forming on the swirl atomizer, the metering device and the turbine housing is reduced.According to an advantageous development of the first aspect, the distance of the baffle body from the swirl atomizer, as seen in the direction of the axis of rotation of the turbine rotor, corresponds to at most 6 times, preferably at most 5 times, particularly preferably at most 4 times, the diameter of the turbine rotor. This distance between the impact body and the swirl atomizer is particularly advantageous.According to an advantageous development of the first aspect, the baffle body is thermally decoupled from the turbine housing. Preferably, the impact body has the reducing agent or the precursor substance atomized in the expanded exhaust gas on a first side of exhaust gas expanded in the exhaust gas turbine and has the exhaust gas not expanded in the exhaust gas turbine on an opposite second side. The thermal decoupling of the baffle body and turbine housing reduces the risk that deposits from solid constituents of the reducing agent or the precursor substance form on the baffle body. When the impact body has on the second side impinged with non-expanded and thus relatively hot exhaust gas, such deposits possibly forming on the first side of the impact body can be effectively thermally decomposed.According to a second aspect, this object is achieved by an exhaust gas turbine according to claim 10. According to this, the swirl atomizer has a cavity and, on a wall delimiting the cavity, which wall extends parallel to the axis of rotation of the turbine rotor or at an acute angle of at most 40° to the axis of rotation of the turbine rotor, openings via which the reducing agent or the precursor substance enters the expanded exhaust gas from the cavity, wherein at least one opening has a longitudinal central axis deviating from other openings. This configuration of the swirl atomizer can likewise reduce the risk that deposits of solid constituents of the reducing agent or of the precursor substance of the reducing agent form on assemblies of the exhaust gas turbine. This configuration is furthermore particularly preferred for effective atomization of the reducing agent or the precursor substance thereof.According to an advantageous development of the second aspect, the openings are arranged in at least two planes which are offset as viewed in the direction of the axis of rotation of the turbine rotor, separating walls which project inwardly into the swirl sprayer preferably being arranged between the offset planes. This development permits particularly effective atomization of the precursor substance of the reducing agent or of the reducing agent in the expanded exhaust gas.Preferably, both aspects are used in combination with one another on an exhaust gas turbine.Methods of operating an exhaust turbine according to the invention are defined in claims 15 to 18.Preferred developments of the invention are evident from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being restricted thereto. The following shows: FIG. 1 shows a perspective view of an exhaust gas turbocharger having an exhaust gas turbine according to the invention, FIG. 2 is a perspective view of another exhaust turbine according to the invention, FIG. 3 shows a further development of FIG. 1, FIG. 4 shows a further refinement of FIG. 1, FIG. 5 shows a cross section through a swirl atomizer of an exhaust gas turbine according to the invention, FIG. 6 shows a cross section through a further swirl atomizer of an exhaust gas turbine according to the invention, FIG. 7 shows a cross section through a further swirl atomizer of an exhaust gas turbine according to the invention, FIG. 8 shows a cross section through a further swirl atomizer of an exhaust gas turbine according to the invention, FIG. 9 shows a cross section through a further swirl atomizer of an exhaust gas turbine according to the invention, FIG. 10 shows a cross section through a further swirl atomizer of an exhaust gas turbine according to the invention, FIG. 11 is a cross-section through a further swirl atomizer of an exhaust gas turbine according to the invention, FIG. 12 shows a cross section through a further swirl atomizer of an exhaust gas turbine according to the invention, FIG. 13 is a cross-section through a further swirl atomizer of an exhaust gas turbine according to the invention, FIG. 14 is a cross-section through a further swirl atomizer of an exhaust gas turbine according to the invention, FIG. 15 shows assemblies of a further exhaust gas turbocharger having an exhaust gas turbine according to the invention, FIG. 16 shows a further development of FIG. 15, FIG. 17 shows assemblies of a further exhaust gas turbine according to the invention, FIG. 18 shows assemblies of a further exhaust gas turbine according to the invention.The invention relates to an exhaust gas turbine which is in particular a component of an exhaust gas turbocharger of an internal combustion engine, in particular an internal combustion engine operated with diesel fuel or heavy oil.FIG. 1 shows an exhaust gas turbocharger 30 having an exhaust gas turbine 31 according to the invention, which serves for expanding exhaust gas of an internal combustion engine. The exhaust gas turbocharger 30 further comprises a compressor 32 for compressing charge air to be supplied by the internal combustion engine, wherein the energy obtained in the exhaust gas turbine 31 during the expansion of the exhaust gas is used in this case.The exhaust turbine 31 includes a turbine casing 33 and a turbine rotor 34. The turbine housing 33 has an inflow housing section 35 and an outflow housing section 36, wherein exhaust gas to be expanded by the inflow housing section 35 can be supplied to the turbine rotor 34, and wherein exhaust gas expanded by the turbine rotor 34 can be discharged by the outflow housing section 36. The exhaust gas turbine 31 shown in FIG. 1 is a radial turbine in which the exhaust gas to be expanded flows against the turbine rotor 34 in the radial direction via the inflow housing section 35. The expanded exhaust gas is discharged from the turbine rotor 34 in the axial direction.The compressor 32 has a compressor housing 37 and a compressor rotor 38, and the compressor rotor 38 is coupled to the turbine rotor 34 via a shaft 39 which is mounted in a bearing housing 40 of the exhaust gas turbocharger 30. The rotation axis R of the turbine rotor 34 corresponds to a rotation axis R of the compressor rotor 38 and the rotation axis of the shaft 39.The bearing housing 40 is connected to both the compressor housing 37 and the turbine housing 33, namely the inflow housing section 35 thereof. Furthermore, FIG. 1 shows a silencer 41 which is connected to the compressor housing 37, wherein the charge air is conducted via the silencer 41.The exhaust gas expanded in the exhaust gas turbine 31 is guided after leaving the exhaust gas turbocharger 30 in the direction of a catalytic converter (not shown), in particular in the direction of an SCR catalytic converter, in order to reduce the proportion of nitrogen oxide in the exhaust gas.The reducing agent or a precursor substance of the reducing agent required for the selective catalytic reduction in the SCR catalyst can be introduced into the expanded exhaust gas in the region of the exhaust turbine 31 downstream of the turbine rotor 34 via a metering device 42 of the exhaust turbine 31, wherein in FIG. 1 the metering device 42 introduces the reducing agent or the precursor substance of the reducing agent into the exhaust gas in the direction of the axis of rotation R of the turbine rotor 34 in the opposite direction to the flow direction of the expanded exhaust gas.The exhaust gas turbine 31 according to the invention furthermore has a swirl atomizer 43 for the reducing agent or the precursor substance of the reducing agent introduced into the expanded exhaust gas via the metering device 42, wherein the swirl atomizer 43 acts on the turbine rotor 34 at a hub-side section of the turbine rotor 34, which section is downstream, as seen in the direction of flow of the exhaust gas, and rotates together with the turbine rotor 34. The reducing agent or the precursor substance of the reducing agent, which is directed onto the swirl atomizer 43 via the metering device 42, can be atomized in the expanded exhaust gas via the swirl atomizer 43.According to a first aspect of the invention, the exhaust gas turbine 31 has, downstream of the turbine rotor 34, as seen in the flow direction of the exhaust gas, an impact body 44 for the reducing agent or the precursor substance of the reducing agent as an extension of the rotational axis R of the turbine rotor 34, wherein, as seen in the direction of the rotational axis R of the turbine rotor 34, a distance X in the direction of the rotational axis R (see FIGS. 1, 2 ) between the impact body 44 and the swirl atomizer 43 corresponds to at most 7 times a diameter of the turbine rotor 34.In particular, the distance X of the impact body 44 from the swirl atomizer 43 when viewed in the direction of the axis of rotation R of the turbine rotor 34 corresponds at most to 6 times the diameter of the turbine rotor 34, preferably at most to 5 times the diameter of the turbine rotor 34, particularly preferably at most to 4 times the diameter of the turbine rotor 34.The impact body 44 is designed in the form of a plate in the exemplary embodiment of FIG. 1.The baffle 44 is an assembly which is separate from the turbine housing 33 and mounted on the turbine housing 33, and is preferably thermally decoupled from the turbine housing 33. It can thus be seen from FIG. 1 that a gap 46 is formed between the baffle body 44 and a closure body 45 of the outflow housing section 36 of the turbine housing 33, which gap serves for the thermal decoupling of the baffle body 44 from the turbine housing 33.The baffle body 44 is positioned in a deflection region 47 of the outflow housing section 36 of the turbine housing 33, wherein in this deflection region 47 the expanded exhaust gas, which flows axially away from the turbine rotor 34, is deflected, namely by at least 70°, preferably by at least 80°, particularly preferably by at least 89°, with respect to the axis of rotation R.The baffle body 44, which is preferably thermally decoupled from the turbine housing 33, can prevent reducing agent or the precursor substance of the reducing agent from reaching the turbine housing 33 and from depositing or depositing solid constituents of the reducing agent or the precursor substance of the reducing agent on the turbine housing 33, in particular solid urea decomposition products such as cyanuric acid or melamine.The baffle body 44, which is preferably thermally decoupled from the turbine housing 33, has a higher temperature than the turbine housing 33, so that droplets of the reducing agent or of the precursor substance, which reach the baffle body 44, can be effectively decomposed. The defined distance x of the baffle body 44 from the swirl atomizer 43 is of particular advantage in order to counteract the formation of such deposits.FIG. 2 shows a development of the exemplary embodiment of FIG. 1, in which the baffle body 44, in contrast to FIG. 1, is not contoured in the manner of a plate or flat, but rather is curved in the manner of a trough or concave, as seen in the flow direction of the exhaust gas downstream of the turbine rotor 34. The impact body 44 can be designed as a hollow ball segment.FIG. 3 shows a further development of the exemplary embodiment of FIG. 1, in which exhaust gas is introduced into the gap 46 between the impact body 44 and the closure body 45 of the turbine housing 33 via a feed device 48, namely relatively hot exhaust gas which has not been expanded in the exhaust gas turbine 31. In this case, the baffle body 44 has then, on a first side facing the turbine rotor 34, impinged by the exhaust gas expanded in the exhaust gas turbine 31 with the reducing agent atomized in the expanded exhaust gas or the atomized precursor substance of the reducing agent, whereas the baffle body has, on an opposite second side facing away from the turbine rotor 34, impinged by non-expanded exhaust gas which is hotter than the expanded exhaust gas.The further development of FIG. 3 allows a particularly advantageous thermal decoupling of the baffle body 44 from the turbine housing 33 and a particularly effective decomposition of droplets of the reducing agent or of the precursor substance of the reducing agent which reach the first side of the baffle body 44.While the thermal decoupling of the baffle body 44 and turbine housing 33 is thus effected via an air gap insulation in the embodiment of FIG. 1, it is additionally provided in the embodiment of FIG. 3 to flow hot exhaust gas to the baffle body 44 on the side facing away from the turbine rotor 34 and thus to heat the same from behind. The exhaust gas that can be supplied to the baffle 44 via the supply device 48 can be branched off from the supply casing portion 35 of the turbine casing 33, for example, upstream of the turbine rotor 34. It is particularly advantageous to remove the exhaust gas supplied via the supply device 48 upstream of the exhaust gas rotor 34, since there is a higher pressure level than downstream of the exhaust gas rotor or in the region of the baffle body 44.A further advantageous development of the exhaust gas turbine 31 of FIG. 1 is shown in FIG. 4. in the development of FIG. 4 it is shown that the metering device 42 extends through the impact body 44 and accordingly extends in the region of the turbine housing 33 exclusively in the axial direction of the axis of rotation R of the turbine rotor 34. In this case, the metering device 42 also extends through the closure body 45 of the turbine housing 33.With the above features of the exhaust gas turbine 31 according to the invention, it is possible to prevent deposits from solid decomposition products of the reducing agent or the precursor substance of the reducing agent, such as cyanuric acid or melamine, in particular from depositing on the baffle body 44 and the turbine housing 33 and on the metering device 42 preferably also on the swirl atomizer 43.The effectiveness of atomizing the reducing agent or the precursor substance of the reducing agent in the exhaust gas can be increased if the swirl atomizer 43 is constructed as shown in Figs. 5 to 14. FIGS. 5 to 14 show preferred embodiment variants for the swirl atomizer 43 together with the metering device 42, wherein arrows 49 in FIGS. 5 to 14 visualize the flow of the expanded exhaust gas in the region of the swirl atomizer 43 and arrows 50 visualize the supply of the reducing agent or the precursor substance of the reducing agent to the swirl atomizer 43.The swirl atomizers 43 of FIGS. 5 and 6 each have a cavity 51, wherein the reducing agent 50 is introduced into this cavity 51 via the metering device 42 in order to then be atomized via the swirl atomizer 43 and moved in the direction of the impact body 44. In FIG. 5, the swirl atomizer 43 is of bell-shaped or cup-shaped design, walls 52, 53 of the swirl atomizer 43 delimiting the cavity 51 thereof. Thus, the swirl atomizer 43 of FIG. 5 has a bottom wall 52, which is completely closed in FIG. 5 and which extends perpendicularly to the axis of rotation R of the turbine rotor 34 and thus to the axis of rotation of the swirl atomizer 43. Starting from this bottom wall 52, a tube-like wall 53 extends parallel or at an acute angle β to the axis of rotation R of the turbine rotor 34 or swirl atomizer 43, wherein this acute angle β is a maximum of 40°, preferably a maximum of 30°, preferably a maximum of 20°, particularly preferably a maximum of 10°. This wall 53 extends from the bottom wall 52 in the direction of the baffle body 44. In order to ensure particularly effective atomization of the reducing agent 50 or the precursor substance of the reducing agent via the swirl atomizer 43, it is provided in the exemplary embodiment of FIG. 5 that free ends of the wall 53 facing the swirl body 44 enclose an acute angle α between a radially outer region and a radially inner region of the wall 53, which is at most 60°, preferably at most 45°, particularly preferably at most 35°. In FIG. 5, the swirl body 43 is open at the end opposite the bottom wall 52, and is accordingly designed in the form of an open cup or an open bell.FIG. 7 shows a further development of the swirl atomizer 43 of FIG. 5, wherein in the exemplary embodiment of FIG. 7 it is provided according to a second aspect of the invention that the wall 53 of the swirl atomizer 43, which extends parallel to the axis of rotation or at the acute angle β obliquely to the axis of rotation R of the turbine rotor 34 or swirl atomizer 43, has openings 54 via which the reducing agent or the precursor substance of the reducing agent enters the expanded exhaust gas from the cavity 51. This can ensure particularly advantageous atomization of the reducing agent or of the precursor substance of the reducing agent, as a result of which the risk of deposits of decomposition products of the reducing agent or of the precursor substance of the reducing agent forming on the baffle body 44 or on the turbine housing 36 or on the swirl atomizer 43 can be reduced.It should be pointed out at this point that this second aspect of the invention is preferably used in combination with the first aspect of the invention on an exhaust gas turbine 31. However, the two aspects according to the invention can also be used independently of one another.FIG. 9 shows a modification of the swirl atomizer 43 of FIG. 7, according to which the openings 54 shown in FIG. 9 have mutually different orientations or longitudinal central axes in the region of the wall 53. This can further improve the atomization of the reducing agent 50 or of the precursor substance of the reducing agent 50. In FIGS. 7 and 9, the dashed arrows show the direction in which the atomized reducing agent 50 exits from the cavity 51 of the respective swirl atomizer 43 and enters the exhaust gas 49. In FIGS. 7 and 9, the exhaust gas can emerge from the cavity 51 of the swirl atomizer 43 on the one hand at the open end of the swirl body 43 and on the other hand via the openings 54 in two planes offset as viewed in the direction of the axis of rotation R of the turbine rotor 34 or swirl atomizer 43.FIG. 11 shows a further development of the swirl atomizer 43 of FIG. 9, in which separating walls 55 are formed between the outlet planes offset as viewed in the direction of the axis of rotation of the turbine rotor 34 or swirl atomizer 43, which separating walls are directed inwards into the cavity 51 starting from the wall 53.In the case of a relatively small amount of reducing agent 50 introduced into the swirl sprayer 43, these separating walls 55 ensure that all reducing agent 50 initially exits from the cavity 51 via the openings 54 and enters the exhaust gas 59.With a larger amount of reducing agent and / or with low rotational speeds of the swirl sprayer 43, the level of reducing agent to be sprayed in the cavity 51 can increase to such an extent that the reducing agent to be sprayed then overcomes the separating walls 55 and flows to the right in FIG. 11 in order then also to exit the cavity 51 of the swirl sprayer 43 via the open end thereof and enter the exhaust gas 49. For this purpose, it is important that the outlet opening of the metering device 42 is positioned in the cavity 51 of the swirl atomizer 43 in such a way that it lies between the bottom wall 52 and the separating walls 55.FIGS. 5, 7, 9 and 11 all show swirl atomizers 43 which are designed open at their end opposite the bottom wall 52, which are thus contoured in the form of an open cup or an open bell. In contrast, FIGS. 6, 8, 10 and 12 show modifications of swirl atomizers 43 which are closed at their end opposite the bottom wall 52 by a further wall 56, wherein in FIGS. 6, 8, 10 and 12 the metering device 42 extends through this closed wall 56 opposite the bottom wall 52. Here, the metering device 43 is accordingly contoured in the form of a closed cup or a closed bell.In the exemplary embodiments of FIGS. 6, 8, 10 and 12, the tubular wall 53, which extends between the closed walls 52 and 56, extends parallel to the axis of rotation R of the turbine rotor 34 or swirl atomizer 43, wherein the openings 54 are introduced into this tubular wall 53, via which the reducing agent 50 or the precursor substance of the reducing agent 50 exits from the cavity 51 of the respective swirl atomizer 43 and enters the exhaust gas 49. The tubular wall 53 extends parallel or at an acute angle β to the axis of rotation R of the turbine rotor 34 or swirl atomizer 43, wherein this acute angle β is a maximum of 40°, preferably a maximum of 30°, preferably a maximum of 20°, particularly preferably a maximum of 10°.In FIGS. 8, 10 and 12, these openings 54 are positioned in different planes, namely in at least two planes offset as seen in the direction of the axis of rotation R of the turbine rotor 34 or swirl atomizer 43. In FIG. 12, between these planes, in accordance with FIG. 11, the separating walls 55 are again formed, which extend inward from the wall 53 into the cavity 51 of the swirl atomizer 43.With all the swirl atomizers 43 shown, it is possible to atomize the reducing agent 50 or the precursor substance thereof in a particularly advantageous manner and introduce it into the expanded exhaust gas 49, namely, while avoiding a hollow spray cone of atomized reducing agent 50 or of atomized precursor substance of the reducing agent. If such a hollow spray cone is avoided, it is ensured that no circular deposit line of reducing agent or precursor substance of the reducing agent forms on the baffle body 44, which is preferably used in combination with the swirl body 43. The openings 54 in the wall 53 of the respective swirl atomizer 43 counteract the formation of a hollow spray cone made of atomized reducing agent or atomized precursor substance in a particularly effective manner, wherein these openings 54 can have different orientations, that is to say can run with different orientations with respect to the axis of rotation R of the swirl atomizer 43. Longitudinal central axes of the openings 54 can extend perpendicular or inclined to the flow direction of the expanded exhaust gas 49.Whereas in FIGS. 5 to 12 the swirl atomizers 43 shown are all designed rotationally symmetrically except for the orientation of the openings 54, FIGS. 13 and 14 show modifications of the swirl atomizer 43 of FIG. 5 which are not designed rotationally symmetrically in the region of the open end and thus of a break-off edge of the swirl atomizer 43. This also advantageously prevents the formation of a hollow spray cone of atomized reducing agent. In FIG. 13, the wall 53 is formed with different lengths as viewed in the axial direction thereof. In FIG. 14, different angles α are provided in the region of the tear-off edge or the free end of the wall 53 between the radially outer and the radially inner region of the wall 53.It can be provided that on the wall 53, namely a radially inner surface 58 of the wall 53, adjacent to the cavity 51 of the respective swirl atomizer 54, guide grooves or guide grooves are formed for the reducing agent or the precursor substance of the reducing agent, wherein these guide grooves or guide grooves extend straight or helically in the direction of the axis of rotation R of the respective swirl atomizer 43 and guide the reducing agent 50 or the precursor substance of the reducing agent 50, which is introduced into the cavity 51 of the respective swirl atomizer 43 via the metering device 42, in the direction of the open end or the openings of the swirl atomizer 43. Such guide grooves or guide grooves can be used in all the swirl atomizers 43 of FIGS. 5 to 14.In the exemplary embodiments of FIGS. 1 to 14, the metering device 42 feeds the reducing agent or the precursor substance to the swirl atomizer 43 in the opposite direction to the flow direction of the expanded exhaust gas and in the direction of the axis of rotation R of the turbine rotor 43. In contrast, FIGS. 15 and 16 show exemplary embodiments in which the respective metering device 42 feeds the reducing agent or the precursor substance to the respective swirl atomizer 43 in the flow direction of the expanded exhaust gas and in the direction of the axis of rotation R of the turbine rotor 34 and thus swirl atomizer 43.In FIGS. 15, 16, the reducing agent or the precursor substance is supplied through the shaft 39 mounted in the bearing housing 40 and through the hub of the turbine rotor 34. There is then no risk of deposits of decomposition products of the reducing agent or the precursor substance of the reducing agent being deposited on the metering device 42, which deposits can lead to a clogging of the metering device 42.FIG. 16 shows a further development of the embodiment of FIG. 15, in which the swirl atomizer 43 is surrounded radially on the outside at least in sections by a guide device 57. By means of such a guide device 57, the atomized reducing agent or the atomized precursor substance of the reducing agent can be concentrated in a narrower region within the expanded exhaust gas. Further, the reducing agent 50 is prevented from being applied to the outflow housing portion 36 of the turbine housing 33. This embodiment is not limited to the supply of the reducing agent via the shaft 39, but can also be applied in the embodiments shown in Figs. 1-14 of the supply of the reducing agent discharged in the direction of flow.The guide device 57 is preferably designed such that the flow velocity of the exhaust gas in the region of the deflection thereof, i.e. in the deflection region 47 of the outflow housing section 36, is higher than the mean flow velocity of the exhaust gas in order to improve the deflection of the reducing agent 50 or of the precursor substance of the reducing agent 50 in the deflection region 47. In the exemplary embodiment shown, the guide device 57 narrows at an end facing the impact body 44.The guide device 57 is preferably firmly connected to the turbine wheel 34 and rotates together with the turbine wheel 34 and together with the swirl atomizer 43.Although the connection of the guide device 57 to the turbine wheel 34 is preferred, it is also possible for the guide device 57 to be fastened to the turbine housing 33, i.e. to be of fixed design.FIGS. 17 and 18 show embodiments of an exhaust gas turbine 31 according to the invention, in which the metering device 42 feeds the reducing agent 50 or the precursor substance of the reducing agent 50 to the swirl atomizer 43 perpendicularly to the flow direction of the expanded exhaust gas or in the flow direction of the exhaust gas to be expanded and perpendicularly to the direction of the axis of rotation R of the turbine rotor 34 and thus of the swirl atomizer 43. The swirl atomizers 43 of FIGS. 17 and 18 do not require a hollow space, but rather the reducing agent 50 or the precursor substance thereof is guided on an outer surface 58 of the swirl atomizer 43, which is frustoconical in FIG. 17 and conically contoured in FIG. 18. In FIG. 17, the diameter of the frustoconically contoured swirl atomizer 43 widens as viewed in the flow direction of the expanded exhaust gas, but in FIG. 18, the diameter of the frustoconically contoured swirl atomizer 43 narrows as viewed in the flow direction of the expanded exhaust gas.On the outer surface 58 of the swirl body 43 guiding the reducing agent 50 or the precursor substance of the reducing agent 50, guide grooves or guide grooves can again be formed, which extend in the longitudinal direction or in the flow direction of the expanded exhaust gas and serve for guiding the reducing agent 50 to be atomized or the precursor substance to be atomized.In the exemplary embodiments of FIGS. 15, 16, 17 and 18, the details of the impact body 44 described with reference to FIGS. 1 to 4 are preferably used.In all the embodiments of the invention described above, it is possible for the swirl atomizer 43 and / or the metering device 42 and / or the baffle 44 to be coated at least in sections with a hydrophobic coating and / or a catalytically active coating.A hydrophobic coating can be a coating of nanoparticles which consist of TiO 2, Al 2 O 3 and / or SiO 2. Such a hydrophobic coating may simultaneously have catalytically active properties and then comprise, for example, SiO 2- stabilized TiO 2 or WO 3.The metering device 42 and / or the swirl atomizer 43 and / or the baffle body 44 are preferably manufactured at least in sections from a stainless steel, in particular an austenitic stainless steel. This can prevent corrosion of these assemblies.It is possible to produce these assemblies from stainless steel, preferably from austenitic stainless steel, only in the region of their surfaces and to produce the same internally from a less valuable material, for example from a cast steel or black steel. Manufacturing costs can thereby be reduced.All the above-described structural details of the gas turbines 31 according to the invention serve the purpose of counteracting the formation of deposits of the reducing agent or of the precursor substance of the reducing agent on assemblies of the exhaust gas turbine 31, in particular on the swirl atomizer 43 and / or the metering device 42 and / or the baffle body 44.This risk can be further reduced if the exhaust turbine is operated as described below.In a first embodiment of a method according to the invention for operating the gas turbines 31 described above, it is provided that a viscosity of an aqueous reducing agent solution or an aqueous solution of the precursor substance of the reducing agent and water is adjusted to at least 1.33 mPas, preferably to at least 1.35 mPas, particularly preferably to at least 1.38 mPas. This is preferably done by setting a proportion of the reducing agent in the aqueous reducing agent solution or the precursor substance in the solution of the precursor substance to at least 35%, preferably to at least 37%, particularly preferably to at least 39%.According to a further method aspect according to the invention, which can be used in combination or else alone, it is provided to determine the amount of reducing agent 50 introduced into the expanded exhaust gas via the metering device 42 or the amount of introduced precursor substance of the reducing agent as a function of the rotational speed of the exhaust gas turbine 31 or as a function of a rotational speed of an internal combustion engine interacting with the same and / or as a function of a power of the exhaust gas turbine 31 or a power of the internal combustion engine interacting with the same and / or as a function of a temperature of the exhaust gas. In this case, it can be provided that, if the rotational speed of the exhaust gas turbine or of the internal combustion engine and / or the power of the exhaust gas turbine or of the internal combustion engine and / or the exhaust gas temperature falls below a respective limit value, the introduction of the reducing agent or of the precursor substance of the reducing agent into the exhaust gas is stopped. Above the respective limit value, the quantity of reducing agent or precursor substance introduced can be increased with increasing rotational speed and / or power and / or exhaust gas temperature, in particular linearly or stepwise. After stopping the introduction of reducing agent or precursor substance of the reducing agent, the metering device is preferably blown and / or blown free with compressed air or exhaust gas in order to remove reducing agent or precursor substance of the reducing agent from the same.List of reference characters30 Exhaust gas turbocharger 31 Exhaust gas turbine 32 Compressor 33 Turbine housing 34 Turbine rotor 35 Inflow housing section 36 Outflow housing section 37 Compressor housing 38 Compressor rotor 39 Shaft 40 Bearing housing 41 Muffler 42 Metering device 43 Swirl atomizer 44 Baffle body 45 Closure body 46 Gap 47 Deflection region 48 Feed device 49 Exhaust gas 50 Reducing agent 51 Cavity 52 Wall 53 Wall 54 Opening 55 Partition wall 56 Wall 57 Guide device 58 Surface

Claims

Exhaust gas turbine (31) for expanding exhaust gas, having a turbine housing (33) which has an inflow housing section (35) for exhaust gas to be expanded and an outflow housing section (36) for expanded exhaust gas, having a turbine rotor (34) which is accommodated by the turbine housing (33), the turbine rotor (34) being rotatable about an axis of rotation R, having a metering device (42) for a reducing agent or a precursor substance of a reducing agent, the reducing agent or the precursor substance being introducible into the expanded exhaust gas via the metering device (42), having a swirl atomizer (43), which rotates together with the turbine rotor (34), for the reducing agent or the precursor substance, the reducing agent or the precursor substance being capable of being atomized in the expanded exhaust gas via the swirl atomizer (43), the swirl atomizer (43) being capable of being atomized at a downstream, downstream, downstream, downstream, relatively high-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, Hub-side section of the turbine rotor (34) acts on the turbine rotor (34), characterized in that downstream of the turbine rotor (34), as an extension of the axis of rotation of the turbine rotor (34), an impact body (44) for the reducing agent introduced into the exhaust gas and atomized or the precursor substance is arranged at a defined distance from the swirl atomizer (43), wherein the impact body (44) is a separate assembly mounted on the turbine housing (33), the defined distance of the impact body (44) from the swirl atomizer (43) corresponds at most to 7 times a diameter of the turbine rotor (34).Exhaust gas turbine (31) according to Claim 1, characterized in that the distance of the baffle body (44) from the swirl sprayer (43) corresponds to at most 6 times, preferably at most 5 times, particularly preferably at most 4 times, the diameter of the turbine rotor (34).Exhaust gas turbine (31) according to Claim 1 or 2, characterized in that the baffle body (44) is arranged in a deflection region (47) of the turbine housing (33) into the outflow housing section (36) thereof, wherein the expanded exhaust gas can be deflected in the deflection region (47) by at least 70°, preferably by at least 80°, particularly preferably by at least 89°, with respect to the axis of rotation of the turbine rotor (34).Exhaust gas turbine (31) according to one of Claims 1 to 3, characterized in that the baffle body (44) is contoured in the manner of a plate or in the manner of a flat, or the baffle body (44) is contoured in the manner of a trough or in the manner of a concave curve.Exhaust gas turbine (31) according to one of Claims 1 to 4, characterized in that the baffle body (44) is thermally decoupled from the turbine housing (33).Exhaust gas turbine (31) according to one of Claims 1 to 5, characterized in that the baffle body (44) has, on a first side, impinged by the exhaust gas expanded in the exhaust gas turbine (31), the reducing agent atomized in the expanded exhaust gas or the precursor substance, and in that the baffle body (44) has, on an opposite second side, impinged by exhaust gas not expanded in the exhaust gas turbine (31).Exhaust gas turbine (31) according to one of Claims 1 to 6, characterized in that the metering device (42) feeds the reducing agent or the precursor substance to the swirl sprayer (43) opposite to the flow direction of the expanded exhaust gas and in the direction of the axis of rotation of the turbine rotor (34), namely through the baffle body (44), or the metering device (42) feeds the reducing agent or the precursor substance to the swirl sprayer (43) in the flow direction of the expanded exhaust gas and in the direction of the axis of rotation of the turbine rotor (34), namely through the hub of the turbine rotor (34), or the metering device (42) feeds the reducing agent or the precursor substance to the swirl sprayer (43) in the flow direction of the exhaust gas to be expanded and perpendicularly to the direction of the axis of rotation of the turbine rotor (34).Exhaust gas turbine (31) according to one of Claims 1 to 7, characterized in that the swirl sprayer (43) has guide grooves and / or guide grooves for the reducing agent or the precursor substance on a surface (58) which guides the reducing agent or the precursor substance.Exhaust gas turbine (31) according to one of Claims 1 to 8, characterized in that the metering device (42) and / or the swirl sprayer (43) and / or the baffle body (44) is coated at least in sections with a hydrophobic coating and / or catalytically active coating, and / or the metering device (42) and / or the swirl sprayer (43) and / or the baffle body (44) consists at least in sections of a stainless steel, preferably of an austenitic stainless steel.Exhaust gas turbine (31) for expanding exhaust gas, having a turbine housing (33) which has an inflow housing section (35) for exhaust gas to be expanded and an outflow housing section (36) for expanded exhaust gas, having a turbine rotor (34) which is accommodated by the turbine housing (33), the turbine rotor (34) being rotatable about an axis of rotation R, having a metering device (42) for a reducing agent or a precursor substance of a reducing agent, the reducing agent or the precursor substance being introducible into the expanded exhaust gas via the metering device (42), having a swirl atomizer (43), which rotates together with the turbine rotor (34), for the reducing agent or the precursor substance, the reducing agent or the precursor substance being capable of being atomized in the expanded exhaust gas via the swirl atomizer (43), the swirl atomizer (43) being capable of being atomized at a downstream, downstream, downstream, downstream, relatively high-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, low-speed, Hub-side section of the turbine rotor (34) engages on the turbine rotor (34), characterized in that the swirl sprayer (43) has a cavity (51), the swirl sprayer (43) has openings (54) on a wall (53) delimiting the cavity (51), which extends parallel to the axis of rotation of the turbine rotor (34) or at an acute angle of at most 40° to the axis of rotation of the turbine rotor (34), via which openings the reducing agent or the precursor substance enters the expanded exhaust gas from the cavity (51), wherein at least one opening (54) has a longitudinal central axis deviating from other openings (54).Exhaust gas turbine (31) according to Claim 10, characterized in that the respective wall (53) with the openings (54) extend at an acute angle of not more than 30°, preferably of not more than 20°, particularly preferably of not more than 10°, with respect to the axis of rotation of the turbine rotor (34).Exhaust gas turbine (31) according to Claim 10 or 11, characterized in that the reducing agent or the precursor substance of the reducing agent passes out of the cavity (51) of the swirl sprayer (43) and into the expanded exhaust gas in at least two planes offset as viewed in the direction of the axis of rotation of the turbine rotor (34), separating walls (55) which project inwardly into the swirl sprayer (43) preferably being arranged between these offset planes.Exhaust gas turbine (31) according to one of Claims 1 to 12, characterized in that the swirl sprayer (43) is surrounded at least in sections radially on the outside by a guide device (57).An exhaust turbine (31) according to any one of claims 1 to 9 and any one of claims 10 to 13.Method for operating an exhaust gas turbine (31) according to one of Claims 1 to 14, characterized in that a viscosity of a preferably aqueous reducing agent solution or of a solution of the precursor substance of the reducing agent and preferably water is adjusted to at least 1.33 mPas, preferably to at least 1.35 mPas, particularly preferably to at least 1.38 mPas.Method according to claim 15, characterised in that a proportion of the reducing agent in the reducing agent solution or the precursor substance in the solution of the precursor substance is adjusted to at least 35%, preferably to at least 37%, particularly preferably to at least 39%.Method for operating an exhaust gas turbine (31) according to one of Claims 1 to 14, in particular method according to Claim 15 or 16, characterized in that a quantity of the reducing agent introduced into the expanded exhaust gas via the metering device (42) or of the precursor substance of the reducing agent is determined as a function of the turbine rotational speed of the exhaust gas turbine (31) or a rotational speed of an internal combustion engine interacting therewith and / or as a function of a power of the exhaust gas turbine (31) or a power of an internal combustion engine interacting therewith and / or as a function of a temperature of the exhaust gas.Method according to claim 17, characterised in that when a limit value of the turbine rotational speed of the exhaust turbine (31) or the rotational speed of the internal combustion engine interacting therewith is undershot and / or when a limit value of the power of the exhaust turbine (31) or the power of the internal combustion engine interacting therewith is undershot and / or when a limit value of the temperature of the exhaust gas is undershot, the introduction of the reducing agent or the precursor substance into the exhaust gas is stopped.

Images