Exhaust aftertreatment system for an internal combustion engine

Abstract

Exhaust gas aftertreatment system for an internal combustion engine, in particular for a marine diesel engine powered by heavy fuel oil, with an SCR catalyst which uses ammonia as a reducing agent, with a device for introducing a liquid, in particular an aqueous urea solution, into an exhaust gas stream upstream of the SCR catalyst, wherein the device for introducing the liquid into an exhaust gas stream is designed with at least one atomizing nozzle (10) designed as a two-component nozzle, via which the liquid can be introduced into the exhaust gas stream with the aid of compressed air in such a way that the liquid is miscible with the compressed air outside the respective atomizing nozzle (10) only immediately upon or after exiting the same, characterized in that the or each atomizing nozzle (10) comprises a nozzle base body (12), a nozzle air cap (13), and a nozzle insert (14), which are designed as turned parts,wherein the respective atomizing nozzle (10) can be connected to a nozzle lance (11) via the nozzle base body (12), and wherein the nozzle air cap (13) and the nozzle insert (14) are received and held in the nozzle base body (12), wherein the nozzle base body (12) of the atomizing nozzle (10) has, in addition to a first section (15), via which the nozzle base body (12) can be connected to the nozzle lance (11), a second section (21) which serves to receive the nozzle air cap (13) and the nozzle insert (14), wherein a recess (22) is formed on this second section (21) of the nozzle base body (12), into which both the nozzle air cap (13) and the nozzle insert (14) can be inserted in sections in order to fasten them to the nozzle base body (12).

Description

[0001] The invention relates to an exhaust gas aftertreatment system for an internal combustion engine according to the preamble of claim 1.

[0002] The unique feature of heavy fuel oil-powered internal combustion engines is that the fuel used, i.e., heavy fuel oil, has a high sulfur content. Sulfur oxides can react with other components of the exhaust gas and lead to deposits that impair the effectiveness of the exhaust gas purification system.

[0003] DE 10 2004 027 593 A1 discloses an internal combustion engine with exhaust gas turbocharging and exhaust gas purification. The exhaust gas turbocharging is implemented either as a single-stage or two-stage exhaust gas turbocharging system. The exhaust gas purification system comprises an SCR catalyst, which, in single-stage exhaust gas turbocharging, is positioned either downstream of the turbine of the exhaust gas turbocharger or upstream of the turbine of the exhaust gas turbocharger. In two-stage exhaust gas turbocharging, the SCR catalyst is positioned between a high-pressure turbine of a high-pressure exhaust gas turbocharger and a low-pressure turbine of a low-pressure exhaust gas turbocharger.

[0004] An SCR catalyst uses ammonia as a reducing agent. In prior art exhaust aftertreatment systems, an aqueous urea solution is introduced into the exhaust gas upstream of the SCR catalyst, where the aqueous urea solution is decomposed or evaporated into water vapor, carbon dioxide, and ammonia in the exhaust stream.

[0005] The urea solution is preferably introduced into the exhaust stream using an atomizing nozzle, which can be designed as a single-component or a dual-component nozzle. DE 10 2009 005 528 A1 discloses a dual-component nozzle used to introduce a liquid into the exhaust stream of an exhaust aftertreatment system with the aid of compressed air. The liquid to be atomized in the exhaust stream and the compressed air are only mixed immediately upon exiting the dual-component nozzle; within the dual-component nozzle, the liquid to be atomized and the compressed air are guided separately.

[0006] Similar atomizing nozzles are known from JP 2007- 40 118 A, JP 2007- 181 802 A or JP 2002- 224 592 A. Further prior art is known from DE 10 2004 026 725 A1, DE 89 03 842 U1 and DE 601 23 382 T2.

[0007] Proceeding from this, the invention is based on the object of creating an exhaust gas aftertreatment system with a novel device for introducing a liquid into an exhaust gas stream. This object is achieved by a device according to claim 1. According to the invention, the or each atomizing nozzle comprises a nozzle base body, a nozzle air cap and a nozzle insert, which are designed as turned parts, wherein the respective atomizing nozzle can be connected to a nozzle lance via the nozzle base body, and wherein the nozzle air cap and the nozzle insert are received and held in the nozzle base body. The or each atomizing nozzle of the device has a simple structure. The or each atomizing nozzle requires only three turned parts, namely the nozzle base body, the nozzle air cap and the nozzle insert, whereby the manufacturing costs for the or each atomizing nozzle and thus the device can be kept low.The nozzle body of each atomizing nozzle connects the respective atomizing nozzle to the nozzle lance, with the nozzle lance serving to separately supply the liquid to be atomized and the compressed air toward the respective atomizing nozzle. The nozzle air cap and the nozzle insert are housed or held in the nozzle body, guiding the liquid to be atomized and the compressed air separately, so that the liquid to be atomized can only be mixed with the compressed air immediately upon or after exiting the respective atomizing nozzle.

[0008] The nozzle base body of the atomizing nozzle has, in addition to a first section, via which the nozzle base body can be connected to the nozzle lance, a second section which serves to receive the nozzle air cap and the nozzle insert, wherein a recess is formed on this second section of the nozzle base body, into which both the nozzle air cap and the nozzle insert can be inserted in sections in order to fasten them to the nozzle base body.

[0009] Preferably, the nozzle base body of the respective atomizing nozzle has a first section for connecting the nozzle lance, wherein a central feed bore for the liquid and several, namely a first number, lateral feed bores for compressed air are formed on this first section of the nozzle base body, which communicate with corresponding lines in the nozzle lance.Furthermore, the nozzle base body of the respective atomizing nozzle has a second section for accommodating the nozzle air cap and the nozzle insert. This second section of the nozzle base body is formed with a central discharge bore for the liquid communicating with the central supply bore for the liquid and a plurality of lateral discharge bores for compressed air communicating with the lateral supply bores for compressed air. The second number of lateral discharge bores for compressed air is greater than the first number of lateral supply bores for compressed air. This design of the or each atomizing nozzle ensures effective cooling of the respective atomizing nozzle via the compressed air, thus preventing overheating of the respective atomizing nozzle.

[0010] Preferably, the nozzle insert defines a fluid flow structure that communicates with the central fluid discharge bore of the nozzle body, with the nozzle air cap concentrically surrounding the nozzle insert in sections, forming a compressed air flow structure that communicates with the lateral compressed air discharge bores of the nozzle body. This allows for a particularly simple connection of the nozzle air cap and the nozzle insert to the nozzle body.

[0011] According to an advantageous development, the nozzle insert protrudes at an outlet end relative to the nozzle air cap such that an outlet opening for the compressed air is located upstream of a liquid outlet opening, as seen in the direction of fluid flow. The nozzle insert preferably has a plurality of swirl slots inclined in the circumferential direction thereof, through which the compressed air can be guided and subjected to torsional acceleration.

[0012] These two features, namely the protrusion of the nozzle insert relative to the nozzle air cap and the swirl slots in the nozzle insert, are preferably used in combination, ensuring fine atomization of the liquid to be atomized in the exhaust stream with lower compressed air requirements. The reduced compressed air requirement can reduce operating costs.

[0013] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 shows a cross section through a device for introducing a liquid into an exhaust gas stream in the region of an atomizing nozzle of the device; Fig. 2a to 2b different views of a nozzle body of an atomizing nozzle; Fig. 3a to 3b show different views of a nozzle air cap of an atomizing nozzle; and Fig. 4a to 4c different views of a nozzle insert of an atomizing nozzle.

[0014] The invention relates to an exhaust aftertreatment system for an internal combustion engine.

[0015] The urea solution atomized into the exhaust stream by the device is decomposed into water vapor, carbon dioxide, and ammonia vapor in the exhaust stream, with the ammonia being used as a reducing agent in an SCR catalyst of the exhaust aftertreatment system. The device therefore introduces the urea solution into the exhaust stream upstream of the SCR catalyst, as seen in the direction of exhaust flow.

[0016] Fig. 1 shows a section of a device for introducing, namely atomizing, a liquid, namely an aqueous urea solution, into an exhaust gas stream in the region of an atomizing nozzle 10 designed as a two-component nozzle, which is connected to a nozzle lance 11.

[0017] In the atomizing nozzle 10, designed as a dual-fluid nozzle, the liquid to be atomized and the compressed air used to atomize the liquid in the exhaust stream are guided separately and mixed only immediately upon or after exiting the dual-fluid nozzle. The mixing of compressed air and the liquid to be atomized therefore takes place outside the atomizing nozzle 10.

[0018] It should already be pointed out at this point that several atomizing nozzles 10 can be connected to the nozzle lance 11, whereby liquid can then be introduced into the exhaust gas flow via each atomizing nozzle 10.

[0019] The Fig. The atomizing nozzle 10 shown in Figure 1 comprises three turned parts, namely a nozzle base body 12, a nozzle air cap 13, and a nozzle insert 14. The nozzle base body 12 serves, on the one hand, to connect the atomizing nozzle 10 to the nozzle lance 11 and, on the other hand, to accommodate the nozzle air cap 13 and the nozzle insert 14.

[0020] The nozzle body 12 of the atomizing nozzle 10, the Fig. 2a and Fig. 2b in different views, has a first section 15 for connecting the nozzle base body 12 to the nozzle lance 11, wherein on this first section 15 of the nozzle base body 12 a central feed bore 16 for the liquid to be atomized and several, namely a first number N1, lateral feed bores 17 for compressed air are formed.

[0021] In the example shown, the Fig. 2a, Fig. 2b, two lateral supply bores 17 for compressed air are formed on the first section 15 of the base body 12, which are diametrically opposite to the single, central supply bore 16 for the liquid.

[0022] In the area of ​​the first section 15, a circumferential shoulder 18 is formed on the outside, via which the nozzle base body 12 of the atomizing nozzle 10 can be attached to the nozzle lance 11. When the nozzle base body 12 of the atomizing nozzle 10 is connected to the nozzle lance 11, a flow channel 19 of the nozzle lance 11 for the liquid communicates with the central supply bore 16 of the nozzle base body 12 for the liquid. Furthermore, in this state, a flow channel 20 of the nozzle lance 11 for the compressed air communicates with the lateral supply bores 17 of the nozzle base body 12 for the compressed air.

[0023] The nozzle base body 12 of the atomizing nozzle 10 has, in addition to the first section 15, via which the nozzle base body 12 can be connected to the nozzle lance 11, a second section 21 which serves to receive the nozzle air cap 13 and the nozzle insert 14, wherein a recess 22 is formed on this second section 21 of the nozzle base body 12, into which both the nozzle air cap 13 and the nozzle insert 14 can be inserted in sections in order to fasten or hold them on the nozzle base body 12.

[0024] In the area of ​​this recess 22, a central discharge bore 23 for the liquid to be atomized is formed, via which the liquid to be atomized can be discharged from the nozzle base body 12 and fed to the nozzle insert 14, wherein this central discharge bore 23 for the liquid communicates with the central feed bore 16 for the liquid, namely in the embodiment shown via an obliquely running connecting bore 24.

[0025] In the area of ​​the recess 22 for the nozzle air cap 13 and the nozzle insert 14 (see Fig. 2a) a plurality of, namely a first number N2, lateral discharge bores 25 for compressed air are formed, which are arranged in the circumferential direction around the central discharge bore 23 for the liquid to be atomized, wherein the lateral discharge bores 25 for the compressed air communicate with the lateral supply bores 17 for the compressed air, so that the compressed air supplied to the nozzle base body 12 via the lateral supply bores 17 can be discharged from the nozzle base body 12 via the lateral discharge bores 25 and directed in the direction of the nozzle air cap 13 and the nozzle insert 14.

[0026] The second number N2 of lateral discharge bores 25 for compressed air is preferably greater than the first number N1 of lateral supply bores 17 for the compressed air, wherein in the illustrated embodiment, the second number N2 of lateral discharge bores 25 for the compressed air corresponds to twice the first number N1 of lateral supply bores 17 for the compressed air. In the illustrated embodiment, four lateral discharge bores 25 for compressed air and two lateral supply bores 17 for compressed air are formed on the nozzle base body 12. Each lateral supply bore 17 for compressed air communicates with two discharge bores 25 for compressed air.

[0027] The above design of the holes 17 and 25 in the nozzle body 12 carrying the compressed air allows effective cooling of the atomizing nozzle 20 with the aid of the compressed air, so that overheating of the atomizing nozzle 10 can be avoided.

[0028] As already explained, the nozzle insert 14 and the nozzle air cap 13 are received and held in the recess 22 on the second section 21 of the nozzle body 12, whereby, as best Fig. 1 can be removed, the nozzle insert 14 defines a liquid flow structure 26 for the liquid to be atomized, which communicates with the central discharge bore 23 for the liquid of the nozzle base body 12.

[0029] In the assembled state of the atomizing nozzle 10, the nozzle air cap 13 concentrically surrounds the nozzle insert 14 in sections, namely, forming a compressed air flow structure 27 between the nozzle insert 14 and the nozzle air cap 13. The nozzle insert 14 delimits the compressed air flow structure 27 radially inward and the nozzle air cap 13 delimits the compressed air flow structure 27 radially outward. The compressed air flow structure 27 communicates with the lateral discharge bores 25 for compressed air of the nozzle base body 12.

[0030] In the region of an outlet-side end 28 of the atomizing nozzle 10, the nozzle air cap 13 and the nozzle insert 14 define an annular gap as an outlet opening 29 for the compressed air, which concentrically surrounds an outlet opening 30 for the liquid to be atomized, which is formed by the nozzle insert 14.

[0031] The outlet opening 29 for the compressed air is located upstream of the outlet opening 30 for the liquid to be atomized, as seen in the flow direction of the liquid to be atomized. The nozzle insert 14 thus protrudes at the outlet end 28 of the atomizing nozzle 10 with its outlet opening 30 for the liquid to be atomized, opposite the nozzle air cap 13 and thus the outlet opening 29 for the compressed air. This allows for particularly fine atomization of the liquid to be atomized in the exhaust gas stream.

[0032] The nozzle insert 14 has a base body 31, which defines the liquid flow structure 26 with the outlet opening 30 for the liquid to be atomized. A circumferential projection 32 is formed on this base body 31. Several circumferentially inclined swirl slots 33 are formed on this projection 32 to guide the compressed air. The swirl slots can be subjected to torsional acceleration via these slots. This further improves the atomization of the liquid to be atomized in the exhaust gas stream.

[0033] As already explained, in the assembled state, the nozzle air cap 13 concentrically surrounds the nozzle insert 14 in sections. For this purpose, the nozzle air cap 13 has a central recess 34 into which the nozzle insert 14 protrudes. At the outlet end 28, the nozzle insert 14 protrudes from this recess 34, forming the outlet opening 29 for the compressed air, which is designed as an annular gap.

[0034] An inner contour 35 of the recess 34 of the nozzle air cap 13 is cylindrical in a first section 36 and truncated cone-shaped in a second section 37, wherein in the assembled state the projection 32 of the nozzle insert 14 which has the swirl slots 33 adjoins the cylindrically contoured section 36 of the inner contour 35 of the recess 34 of the nozzle air cap 13.

[0035] The nozzle insert 14 has an external thread 38 on a section opposite the outlet opening 30, via which the nozzle insert 14 can be screwed to the nozzle base body 12.

[0036] Likewise, the nozzle air cap 13 has an external thread 39 on a section opposite the outlet-side end 28, via which the nozzle air cap 13 can be screwed to the nozzle base body 12.

[0037] Then, when the nozzle insert 14 and the nozzle air cap 13 are both screwed with their external threads 38 and 39 to corresponding internal threads of the nozzle base body 12, a lock nut 40, which also interacts with the external thread 39 of the nozzle air cap 13, can be used to further secure the assemblies screwed to the nozzle base body 12, namely to secure the nozzle air cap 13 and the nozzle insert 14 to the nozzle base body 12. The lock nut 40 can also be omitted.

[0038] The atomizing nozzle 10 has a compact design and consists of only three turned parts. Its construction is simple and requires little assembly effort. As already mentioned, the atomizing nozzle 10 is easily mounted on the nozzle lance 11 via the nozzle base body 12.

[0039] The device for atomizing the liquid in an exhaust gas stream can have multiple atomizing nozzles 10 that engage the nozzle lance 11. The number of atomizing nozzles 10 used depends on the amount of liquid, i.e., the quantity of urea solution, to be atomized in the exhaust gas stream. If multiple atomizing nozzles 10 engage a nozzle lance 11, the last atomizing nozzle 10, viewed in the flow direction of the compressed air and the liquid to be atomized, is designed as shown in the figures.The or each of these atomizing nozzles 10 upstream of the last atomizing nozzle 10 in the direction of flow additionally has bores communicating with the central discharge bore 23 and the lateral discharge openings 25 in order to branch off part of the compressed air and part of the liquid to be atomized and to guide them via the channels 19, 20 of the nozzle lance 11 communicating with these bores in the direction of the or each of the atomizing nozzles 10 downstream thereof. List of reference symbols 10 atomizing nozzle 11 Nozzle lance 12 nozzle bodies 13 Nozzle air cap 14 Nozzle insert 15 first section 16 middle feed hole 17 side feed hole 18 paragraph 19 Liquid flow channel 20 Compressed air flow channel 21 second section 22 Recess 23 middle discharge hole 24 bore 25 side drain hole 26 Fluid flow structure 27 Compressed air flow structure 28 outlet end 29 Exit opening 30 Exit opening 31 basic bodies 32 lead 33 swirl slot 34 recess 35 inner surface Section 36 Section 37 38 external thread 39 external thread 40 Lock nut

Claims

[1] Exhaust gas aftertreatment system for an internal combustion engine, in particular for a marine diesel engine powered by heavy fuel oil, with an SCR catalyst which uses ammonia as a reducing agent, with a device for introducing a liquid, in particular an aqueous urea solution, into an exhaust gas stream upstream of the SCR catalyst, wherein the device for introducing the liquid into an exhaust gas stream is designed with at least one atomising nozzle (10) designed as a two-component nozzle, via which the liquid can be introduced into the exhaust gas stream with the aid of compressed air in such a way that the liquid is miscible with the compressed air outside the respective atomising nozzle (10) only immediately upon or after exiting the latter, characterized bythat the or each atomizing nozzle (10) comprises a nozzle base body (12), a nozzle air cap (13) and a nozzle insert (14), which are designed as turned parts, wherein the respective atomizing nozzle (10) can be connected to a nozzle lance (11) via the nozzle base body (12), and wherein the nozzle air cap (13) and the nozzle insert (14) are received and held in the nozzle base body (12), wherein the nozzle base body (12) of the atomizing nozzle (10) has, in addition to a first section (15), via which the nozzle base body (12) can be connected to the nozzle lance (11), a second section (21) which serves to receive the nozzle air cap (13) and the nozzle insert (14), wherein a recess (22) is formed on this second section (21) of the nozzle base body (12), into which both the nozzle air cap (13) and the nozzle insert (14) can be inserted section by section in order to fasten them to the nozzle base body (12). [2] Exhaust aftertreatment system according to claim 1, characterized bythat the nozzle base body (12) of the respective atomizing nozzle (10) has a first section (15) for connecting the nozzle lance (11), wherein on this first section (15) of the nozzle base body (12) a central feed bore (16) for the liquid and several, namely a first number, lateral feed bores (17) for compressed air are formed, which communicate with corresponding lines (19, 20) in the nozzle lance (11), and that the nozzle base body (12) of the respective atomizing nozzle (10) has a second section (21) for receiving the nozzle air cap (13) and the nozzle insert (14), wherein on this second section (21) of the nozzle base body (12) a central discharge bore (23) for the liquid communicating with the central feed bore (16) for the liquid and several, namely a second number, with the lateral feed bores (17) lateral discharge holes (25) communicating with each other for compressed air are designed for compressed air,wherein the second number of lateral discharge holes (25) for compressed air is greater than the first number of lateral supply holes (17) for compressed air., [3] Exhaust aftertreatment system according to claim 2, characterized by that the second number of lateral discharge bores (25) for compressed air of the nozzle base body (12) corresponds to twice the first number of lateral supply bores (17) for compressed air of the nozzle base body (12), wherein each lateral supply bore (17) for compressed air communicates with two lateral discharge bores (25) for compressed air. [4] Exhaust aftertreatment system according to claim 2 or 3, characterized bythat the nozzle insert (14) defines a liquid flow structure (26) communicating with the central discharge bore (23) for liquid of the nozzle base body (12), and that the nozzle air cap (13) concentrically surrounds the nozzle insert (14) in sections, forming a compressed air flow structure (27) communicating with the lateral discharge bores (25) for compressed air of the nozzle base body (12). [5] Exhaust gas aftertreatment system according to one of claims 1 to 4, characterized by that the nozzle insert (14) has on a circumferential projection (32) a plurality of swirl slots (33) inclined in the circumferential direction thereof, through which the compressed air can be guided and subjected to a torsional acceleration. [6] Exhaust gas aftertreatment system according to one of claims 1 to 5, characterized bythat the nozzle insert (14) protrudes at an outlet-side end (28) opposite the nozzle air cap (13) in such a way that an outlet opening (29) of the compressed air is located upstream of an outlet opening (30) of the liquid, seen in the flow direction of the liquid. [7] Exhaust gas aftertreatment system according to one of claims 1 to 6, characterized by that several atomizing nozzles (10) act on the nozzle lance (11).

Images