DK201970656A1

DK201970656A1 - Injector for injecting a gaseous reducing agent into the exhaust gas stream of an internal combustion engine

Info

Publication number: DK201970656A1
Application number: DKPA201970656A
Authority: DK
Inventors: Jeannerot Thibaut; Hansen Jorn; Guldner Morgane; Geant Ludovic
Original assignee: Faurecia Systemes D'echappement
Priority date: 2018-10-26
Filing date: 2019-10-21
Publication date: 2020-06-02
Also published as: FR3087835B1; DK180870B1; FR3087835A1

Abstract

This injector comprises at least one injection nozzle (34), a dosing system for providing a dosed flow of the gaseous reducing agent to the or each injection nozzle (34), and an injection line (38) connecting the dosing system to the or each injection nozzle (34). The injection line (38) comprises at least one buffer chamber (50), an upstream pipe (52) connecting the buffer chamber (50) to the dosing system (36), and a downstream pipe (54) connecting the buffer chamber (50) to a respective injection nozzle (34). The buffer chamber (50) has an enlarged flow section relatively to the upstream pipe (52).

Description

Injector for injecting a gaseous reducing agent into the exhaust gas stream of an internal combustion engine

The present invention concerns an injector for injecting a gaseous reducing agent into the exhaust gas stream of an internal combustion engine, the injector being of the type comprising at least one injection nozzle, a dosing system for providing a dosed flow of the gaseous reducing agent to the or each injection nozzle, and an injection line connecting the dosing system to the or each injection nozzle.

The invention further concerns an exhaust line for an internal combustion engine comprising such an injector, and an automotive vehicle comprising such an exhaust line.

The gaseous reducing agent comprises for example ammonia, a mix of air and ammonia, or a mix of ammonia and neutral gas such as helium.

The internal combustion engines of automotive vehicles are known for producing nitrogen oxides also referred to as “NOx”. These can be a can be a significant source of air pollution as they contribute to the formation of smog and acid rain, and affect tropospheric ozone. Thus, it is desirable to eliminate NOx contained in the exhaust gas of these engines.

To that end, it has been developed a method known as “Selective Reduction Catalyst” (SCR), wherein ammonia is used for reducing NOx into harmless nitrogen. The most common manner of implementing this method consists in injecting into the exhaust line a liquid urea agent that will be mixed with the exhaust gas and subjected to thermalhydrolysis to transform into ammonia, before the mix of exhaust gas and ammonia goes through a SCR catalyst wherein the ammonia reduces the NOx into nitrogen.

This method however is not very effective.

It has been found out that it is much more effective to inject directly ammonia into the exhaust line, upstream of the SCR catalyst, rather than the above-mentioned liquid urea agent. This way, the first step mentioned above is eliminated.

This observation has led to the development of injectors of the above-mentioned type, which are known for instance from FR 2 994 455. These injectors are commonly used in replacement of the injectors of liquid urea agent.

However, these known injectors are not entirely satisfactory. Indeed, it has been found out that, when the ambient temperature is low, after the shut off of the engine, the injection nozzles of these injectors are usually clogged by ammonia salts formed by a chemical reaction between water, carbonic dioxide, and the reducing agent. It is then impossible to inject ammonia cannot into the mixer, and the NOx treatment is ineffective.

DK 2019 70656 A1

When the injection nozzle is partially clogged, several hours are needed before the injection nozzle to be unclogged and the injector can work. In the meantime, the exhaust gas cannot be depolluted.

An aim of the invention is therefore to prevent or at least reduce clogging of the injection nozzle by salts formed by the reaction between the reducing agent, water and carbonic dioxide, in order to allow to the injector of the type mentioned above to be operational when required after starting of the engine.

To that end, the invention deals with an injector of the type mentioned above, wherein the injection line comprises at least one buffer chamber, an upstream pipe connecting the buffer chamber to the dosing system, and a downstream pipe connecting the buffer chamber to a respective injection nozzle, the buffer chamber having an enlarged flow section relatively to the upstream pipe.

According to specific embodiments of the invention, the injector further presents one or several of the features mentioned below, considered independently or along any technically possible combination:

- the downstream pipe has a length inferior to 15 cm ;

- the buffer chamber is fluidically interposed between the upstream and downstream pipes ;

- the buffer chamber is configured for cooling down faster than the upstream and downstream pipes at stopping of the internal combustion engine ;

- the buffer chamber has an enlarged flow section relatively to the downstream pipe ;

- the injector comprises cooling means configured for increasing the heat exchange surface between the buffer chamber and an ambient fluid ;

- the cooling means comprises cooling fins extending outwardly from the body of an housing of the buffer chamber ;

- the buffer chamber is defined within a housing, said housing consisting of a corrugated tube ;

- the injector comprises a thermal bridge for conducting heat between the upstream and downstream pipes while thermally bypassing the buffer chamber ;

- both upstream and downstream pipes extend through a bottom of the buffer chamber and open into the buffer chamber through an opening that is at a distance from said bottom ;

- the injector comprises heating means for accelerated heating of the buffer chamber at starting of the internal combustion engine ;

DK 2019 70656 A1

- the heating means comprises a feeding line opening into the buffer chamber for collecting exhaust gas and providing the collected exhaust gas to the buffer chamber, and a controlled valve mounted on said feeding line for selectively opening and closing the feeding line ;

- the injector comprises a single buffer chamber, the volume of which being comprised between 10 cm³ and 100 cm³, for example 50 cm³, or the injector comprises a plurality of buffer chambers, the total volume of which being comprised between 10 cm³and 100 cm³, for example 50 cm³.

The invention also deals with an exhaust line for an internal combustion engine comprising a mixer configured to be crossed by exhaust gas produced by the internal combustion engine and an injector as defined above for injecting the gaseous reducing agent into said mixer.

The invention further deals with an automotive vehicle comprising an exhaust line as defined above.

Other features and advantages of the invention will become apparent from a detailed description which is given thereof below, as an indication and by no means as a limitation, with reference to the appended figures, wherein:

- Figure 1 is a general scheme of an exhaust line according to the invention,

- Figure 2 is a cross-section view of a section of the exhaust line of Figure 1, according to a first embodiment of the invention,

- Figure 3 is a cross-section view of a section of the exhaust line of Figure 1, according to a second embodiment of the invention,

- Figure 4 is a cross-section view of a section of the exhaust line of Figure 1, according to a third embodiment of the invention,

- Figure 5 is a cross-section view of a section of the exhaust line of Figure 1, according to a fourth embodiment of the invention,

- Figure 6 is a cross-section view of a section of the exhaust line of Figure 1, according to a fifth embodiment of the invention, and

- Figure 7 is a cross-section view of a section of the exhaust line of Figure 1, according to a sixth embodiment of the invention.

The exhaust line 10 shown in Figure 1 is part of an automotive vehicle (not shown).

This exhaust line 10 conducts an exhaust gas stream generated by an engine 12 of the automotive vehicle through various upstream exhaust components 14 to reduce emission and control noise as known. The various upstream exhaust components 14 can include one or more of the following: pipes, filters, valves, catalysts, mufflers etc.

DK 2019 70656 A1

In the example configuration, the exhaust line 10 comprises a diesel oxidation catalyst (DOC) 16 having an inlet 18 and an outlet 20 positioned downstream of the upstream exhaust components 14, so that these upstream exhaust components 14 direct engine exhaust gases into the DOC 16.

In the shown example, the exhaust line 10 further comprises a diesel particulate filter (DPF) 21 positioned downstream of the DOC 16. This DPF is able to remove contaminants from the exhaust gas as known.

The exhaust line 10 also comprises a selective catalytic reduction (SCR) catalyst 22 having an inlet 24 and an outlet 26, and downstream exhaust components 28 positioned downstream of the SCR catalyst 22. This SCR catalyst 22 is here positioned downstream of the DOC 16 and of the optional DPF 21.

Optionally, the SCR catalyst 22 can comprise a catalyst that is configured to perform a selective catalytic reduction function and a particulate filter function.

The various downstream exhaust components 28 include for instance one or more of the following: pipes, filters, valves, catalysts, mufflers etc.

The upstream 14 and downstream 28 components can be mounted in various different configurations and combinations dependent upon vehicle application and available packaging space.

The exhaust line 10 further comprises, upstream of the inlet 24 of the SCR catalyst 22, a mixer 30 configured to be crossed by the exhaust gas stream before it enters the SCR catalyst 22. This mixer 30 is here positioned downstream from the outlet 20 of the DOC 16 and of the optional DPF 21.

The mixer 30 is preferably configured to generate a swirling or rotary motion of the exhaust gas stream. Alternatively, the mixer 30 consists of a simple pipe.

The exhaust line 10 also comprises an injector 32 to inject a gaseous reducing agent into the exhaust gas stream into the mixer 30 so that the mixer 30 can mix the reducing agent and exhaust gas thoroughly together.

The gaseous reducing agent here comprises ammonia. .

In variant, the reducing agent comprises a mix of ammonia with air, or a mix of ammonia with neutral gas such as helium.

The injector 32 includes an injection nozzle 34 positioned within the mixer 30 to direct injected reducing agent into the mixer 30 to mix with the engine exhaust gas, a dosing system 36 for providing a dosed flow of reducing agent to the injection nozzle 34, and an injection line 38 connecting the dosing system 34 to the injection nozzle 32.

The dosing system 36 comprises a source of reducing agent 40, a dosing valve 42 for dosing the quantity of reducing agent provided to the injection nozzle 34, and a

DK 2019 70656 A1 controller 44 for controlling the dosing valve 32 so as to control dosing of the reducing agent as known.

The source of reducing agent 40 here consists of an ammonia source. This source typically comprises a tank (not shown) in which gaseous ammonia is stored under pressure. In variant, the source comprises urea or strontium chloride (SrCL) salts intended to be heated to generate ammonia.

With reference to Figures 2 to 7, the injection line 38 comprises a buffer chamber 50, an upstream pipe 52 connecting the buffer chamber 50 to the dosing system 36, and a downstream pipe 54 connecting the buffer chamber 50 to the injection nozzle 34.

Preferably, the downstream pipe 54 has substantially the same flow-section as the nozzle 34.

The buffer chamber 50 is outside the mixer 30.

The buffer chamber 50 is defined within a housing 56.

The buffer chamber 50 has an enlarged flow section relatively to the upstream pipe 52. In other words, the flow section of the buffer chamber 50 is larger than the flow section of the upstream pipe 52.

In the examples, the upstream pipe 52 and the buffer chamber 50 have a tubular shape with a circular section. The buffer chamber 50 then has an enlarged diameter relatively to the upstream pipe 52. In other words, the diameter of the buffer chamber 50 is larger than the diameter of the upstream pipe 52.

The ratio between the flow section of the buffer chamber 50 and the flow section of the upstream pipe 52 is preferably comprised between 2 and 200, more preferably between 10 and 150, for example 100.

Thanks to this change of flow section between the buffer chamber 50 and the upstream pipe 52, it has been surprisingly found out that, when stopping of the internal combustion engine 12, the buffer chamber 50 cools down faster than the upstream pipe 52. Therefore, the buffer chamber 50 is a preferential area to stock the potential crystallized salts, thus preventing clogging the injector 32.

The buffer chamber 50 is fluidically interposed between the upstream and downstream pipes 52, 54. In other words, the buffer chamber 50 and the upstream and downstream pipes 52, 54 are connected in such a manner that flow coming from one of the pipes 52, 54 has to flow though the buffer chamber 50 before reaching the other pipe 52, 54.

In the shown examples, the buffer chamber 50 is spaced apart from the mixer 30. The downstream pipe 54 then comprises an outer portion 57 extending outside the mixer 30, said outer portion 57 having preferably a length inferior to 15 cm.

DK 2019 70656 A1

In alternatives (not shown), the buffer chamber 50 is placed alongside the mixer 30. The downstream pipe 54 then extends uniquely in the mixer 30; in other words, the outer portion 57 of the downstream pipe 54 has a length equal to zero.

In the embodiment of Figure 2, the buffer chamber 50 has a flow section that is substantially equal to the flow section of the downstream pipe 54.

In this embodiment, the downstream pipe 54 and the buffer chamber 50 have a tubular shape with a circular section. The buffer chamber 50 then has a diameter substantially equal to that of the downstream pipe 54.

In the embodiments of Figures 3 to 7, the buffer chamber 50 is configured for cooling down faster than both the upstream and downstream pipes 52, 54 at stopping of the internal combustion engine 12. It has been found out that this feature allowed the buffer chamber 50 to be a preferential area for the salts to crystallize, preventing clogging of the downstream pipe 54.

To that end, the buffer chamber 50 has, in these embodiments, an enlarged flow section relatively to the downstream pipe 54. In other words, the flow section of the buffer chamber 50 is larger than the flow section of the downstream pipe 54.

In these examples, the downstream pipe 54 and the buffer chamber 50 have a tubular shape with a circular section. The buffer chamber 50 then has an enlarged diameter relatively to the downstream pipe 54. In other words, the diameter of the buffer chamber 50 is larger than the diameter of the downstream pipe 54.

The ratio between the flow section of the buffer chamber 50 and the flow section of the downstream pipe 54 is preferably comprised between 2 and 200, more preferably between 10 and 150, for example 100. For example, the ratio between the flow section of the buffer chamber 50 and the flow section of the downstream pipe 54 is similar to the ratio between the flow section of the buffer chamber 50 and the flow section of the upstream pipe 52.

In the embodiment of Figure 3, the injection line 38 comprises two buffer chambers 50, and an intermediate pipe 58 connecting these buffer chambers 50. In this embodiment 50, the flow section of both buffer chambers 50 is also larger than the flow section of the intermediate pipe 58.

The flow section of the buffer chambers 50 is therefore larger than the flow section of the upstream pipe 52 and/or the downstream pipe 54 and/or the intermediate pipe 58.

Preferably, the upstream pipe 52, the downstream pipe 54 and the intermediate pipe 58 have the same flow section.

DK 2019 70656 A1

The ratio between the flow section of each buffer chamber 50 and the flow section of the upstream pipe 52 and/or of the downstream pipe 54 and/or of the intermediate pipe 58 is comprised between 20 and 80, for example 50.

In other alternatives (not shown), the injection line 38 may comprise more than two buffer chambers 50, these chambers then being connected to each other by intermediate pipes similar to the intermediate pipe 58.

Preferably, the volume of each buffer chamber 50 depends on the number of buffer chambers 50 of the injector 32.

Therefore, a plurality of buffer chambers 50 with reduced volume allows having the same technical advantage compared to only one buffer chamber 50 with a large volume.

The volume of the buffer chamber 50 when the injector 32 comprises only one buffer chamber 50, or the total volume of the buffer chambers 50, when the injector 32 comprises a plurality of buffer chambers 52, is preferably comprised between 10 cm³ and 100 cm³, for example 50 cm³.

The use of several buffer chambers 52 with reduced volume compared to only one large buffer chamber 52 allows having a compact injector 32 with the same efficiency

In the embodiments of Figures 4 to 7, the injection line 38 comprises a single buffer chamber 50.

In the embodiments of Figures 4 to 6, the buffer chamber 50 is configured for having an accelerated cooling at stopping of the internal combustion engine 12, comparatively to the cooling of the upstream and downstream pipes 52, 54. It has been found out that such an accelerated cooling further contributed to obtain preferentially the crystallization of the salts in the buffer chamber 50.

To that end, the housing 56 comprises, in the embodiment of Figure 4, cooling means 60 configured for increasing the heat exchange surface between the buffer chamber 50 and an ambient fluid, this ambient fluid typically being ambient air.

Here, this cooling means 60 comprises cooling fins 62 extending outwardly from a cylindrical body 64 of the housing 56 within which the buffer chamber 50 is defined. These cooling fins 62 are, in the shown example, disc-shaped and extend around the buffer chamber 50. Alternatively (not shown), the cooling fins 62 consists of ridges extending parallel to a main axis of the buffer chamber 50.

The cooling fins 62 are preferably made in one piece with the housing 56. Alternatively, the cooling fins 62 are added on the housing 56 and/or made out of material different from the material of the housing 56.

In the embodiment of Figure 5, accelerated cooling of the buffer chamber 50 is obtained by having the housing 56 consisting of a corrugated tube.

DK 2019 70656 A1

More particularly, the corrugated tube comprises a succession of parallel outward ridges and inward furrows. The ridges forms internal cavity wherein the potential salts formed with the reducing agent may crystalize and be stocked. Moreover, the ridges comprise an optimal heat exchange surface with the ambient air.

In the embodiment of Figure 6, accelerated cooling of the buffer chamber 50 is obtained by having the injector 32 comprising a thermal bridge 66 for conducting heat between the upstream and downstream pipes 52, 54 while thermally bypassing the buffer chamber 50.

In the shown example, the thermal bridge 66 consists of a metallic piece welded between the upstream pipe 52 and the downstream pipe 54. In variant (not shown), the thermal bridge 66 is formed by the welded contact between the upstream pipe 52 and the downstream pipe 54.

Preferably, the thermal conductivity of the thermal bridge 66 is higher than 20 W.m^-1.K^-1.

Another feature of the embodiment of Figure 6 is that both upstream and downstream pipes 52, 54 extend through a lower bottom 68 of the buffer chamber 50 and open into the buffer chamber 50 through an opening 70 that is at a distance from said lower bottom 68.

In this way, the potential formed salts can be stocked on both sides of upstream and downstream pipes 52, 54 without clogging said upstream and downstream pipes 52, 54.

In another variant, the upstream pipe 52 and the downstream pipe 54 are concentric. The upstream pipe 52 surrounds the downstream pipe 54. In other words, the downstream pipe 54 is internal.

In the embodiment of Figure 7, the injector 32 comprises heating means 72 for accelerated heating of the buffer chamber 50 at starting of the internal combustion engine 12. It has been found out that such an accelerated heating further contributed to decompose the potential formed salts in the injection line 38 and help eliminating them rapidly.

Here, the heating means 72 comprises a feeding line 74 opening into the buffer chamber 50 for collecting exhaust gas upstream of the mixer 30 and providing the collected exhaust gas to the buffer chamber 50, a controlled valve 76 mounted on said feeding line 74 for selectively opening and closing the feeding line 74, and a controller 78.

The controller 78 is configured for controlling the controlled valve 76 so that the controlled valve 76 opens at starting of the engine 12 and closes before first provision of reducing agent by the dosing system 36.

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In the shown example of this embodiment, the injection line 38 also comprises a check valve 80 mounted on the upstream pipe 52, said check valve 80 being configured so as to allow circulation of fluid from the dosing system 36 to the buffer chamber 50, and prevent fluid from flowing from the buffer chamber 50 toward the dosing system 36. This check valve 80 is preferably close to the buffer chamber 50, that is to say, at a distance from the buffer chamber 50 of less than 10 cm.

Thanks to the invention mentioned above, clogging of the injection nozzle 34 is prevented or at least significantly reduced. Also, in case partial clogging does occur, the injector 32 can be unclogged quickly at startup and, thus, is quickly efficient.

As a result thereof, unavailability time of the injector 32 at starting of the gaseous reducing agent dosing phase is reduced.

Although features of the invention have been disclosed in several embodiments, it is to be understood that these embodiments may be combined to each other, and that the invention also extends to these combinations. For instance, the buffer chamber 50 may have a flow section that is substantially equal to the flow section of the downstream pipe 54, while being configured for having an accelerated cooling at stopping of the internal combustion engine 12 comparatively to the cooling of the upstream and downstream pipes 52, 54. Thus, the buffer chamber 50 may be configured for cooling down faster than both the upstream and downstream pipes 52, 54 even without the buffer chamber 50 having an enlarged flow section relatively to the downstream pipe 54.

Also, even though the injector 32 described here comprises a single injection nozzle 34, the invention is not limited to this single embodiment. In alternatives (not shown) of the invention, the injector 32 comprises several injection nozzles 34, each nozzle 34 then being connected to the anti-backflow device 56 by a respective downstream pipe 54.

Claims

10 CLAIMS

1. - An injector (32) for injecting a gaseous reducing agent into the exhaust gas stream of an internal combustion engine (12), the injector (32) comprising at least one injection nozzle (34), a dosing system (36) for providing a dosed flow of the gaseous reducing agent to the or each injection nozzle (34), and an injection line (38) connecting the dosing system (36) to the or each injection nozzle (34), characterized in that the injection line (38) comprises at least one buffer chamber (50), an upstream pipe (52) connecting the buffer chamber (50) to the dosing system (36), and a downstream pipe (54) connecting the buffer chamber (50) to a respective injection nozzle (34), the buffer chamber (50) having an enlarged flow section relatively to the upstream pipe (52).

2. - The injector (32) of claim 1, wherein the downstream pipe (54) has a length inferior to 15 cm.

3. - The injector (32) of claim 1 or 2, wherein the buffer chamber (50) is fluidically interposed between the upstream and downstream pipes (52, 54).

4. - The injector (32) of any one of the previous claims, wherein the buffer chamber (50) is configured for cooling down faster than the upstream and downstream pipes (52, 54) at stopping of the internal combustion engine (12).

5. - The injector (32) of claim 4, wherein the buffer chamber (50) has an enlarged flow section relatively to the downstream pipe (54)

6. - The injector (32) of claim 4 or 5, comprising cooling means (60) configured for increasing the heat exchange surface between the buffer chamber (50) and an ambient fluid.

7. - The injector (32) of claim 6, wherein the cooling means (60) comprises cooling fins (62) extending outwardly from the body (64) of an housing (56) of the buffer chamber (50).

8. - The injector (32) of anyone of claims 4 to 7, wherein the buffer chamber (50) is defined within a housing (56), said housing (56) consisting of a corrugated tube.

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9. - The injector (32) of anyone of claims 4 to 8, comprising a thermal bridge (66) for conducting heat between the upstream and downstream pipes (52, 54) while thermally bypassing the buffer chamber (50).

10. - The injector (32) of anyone of the previous claims, wherein both upstream and downstream pipes (52, 54) extend through a bottom (68) of the buffer chamber (50) and open into the buffer chamber (50) through an opening (70) that is at a distance from said bottom (68).

11. - The injector (32) of anyone of the previous claims, comprising heating means (72) for accelerated heating of the buffer chamber (50) at starting of the internal combustion engine (12).

12. - The injector (32) of claim 11, wherein the heating means (72) comprises a feeding line (74) opening into the buffer chamber (50) for collecting exhaust gas and providing the collected exhaust gas to the buffer chamber (50), and a controlled valve (76) mounted on said feeding line (74) for selectively opening and closing the feeding line (74).

13. - The injector (32) of anyone of the previous claims, comprising a single buffer chamber (50), the volume of which being comprised between 10 cm³ and 100 cm³, for example 50 cm³, or the injector (32) comprises a plurality of buffer chambers (52), the total volume of which being comprised between 10 cm³ and 100 cm³, for example 50 cm³.

14. - An exhaust line (10) for an internal combustion engine (12) comprising a mixer (30) configured to be crossed by an exhaust gas stream produced by the internal combustion engine (12) and the injector (32) of anyone of the previous claims for injecting the gaseous reducing agent into said exhaust gas stream.

15.- An automotive vehicle comprising the exhaust line (10) of claim 14.