DE102018204982A1 - Injection arrangement for introducing a reaction agent in an exhaust gas stream, exhaust pipe with such a Einbringanordnung, and internal combustion engine with such exhaust pipe - Google Patents

Abstract

The invention relates to an introduction arrangement (5) for introducing a reaction agent into an exhaust gas flow, comprising a reaction agent injector (9) and a wall section (11) encompassing at least a portion of an injector outlet (13) of the reaction agent injector (19). It is a heating device (15) which is adapted to at least partially to heat the wall portion (11) provided.

Description

The invention relates to a Einbringanordnung for introducing a reagent in an exhaust stream, an exhaust pipe with such a Einbringanordnung, and an internal combustion engine with such exhaust pipe.

Such an introduction arrangement has a reagent injector and a wall section which at least partially surrounds an injector outlet of the reagent injector.

This results in particular in compact exhaust systems, the problem of backflow of fine droplets of the reaction agent, which can not follow a flow of exhaust gas in an exhaust pipe to which the Einbringanordnung is arranged. This can be caused in particular by eddies in the exhaust gas flow. These deposits reduce the performance of the exhaust system significantly, so that it may exceed the specified exhaust emission limits.

So far, attempts are made to avoid such deposits by more space for the introduction of the reagent is made available, which is hardly possible in compact exhaust systems or their further reduction opposes. In principle, it is also possible to introduce the reactant only at sufficiently high exhaust gas temperatures, so that it is rapidly evaporated or reacted, which also helps to prevent deposits. However, this also means a waiver of introduction of the reagent at lower exhaust gas temperatures, which in turn results in increased emissions. The deposits can also be eliminated periodically by forced regeneration, but this leads to downtime and / or increased fuel consumption. This in turn has increased operating costs.

The invention has for its object to provide a Einbringanordnung for introducing a reagent in an exhaust stream, an exhaust pipe with such a Einbringanordnung and an internal combustion engine with such exhaust pipe, said disadvantages do not occur.

The object is achieved by providing the subject matters of the independent claims. Advantageous embodiments emerge from the dependent claims.

The object is achieved in particular by further developing a placement arrangement of the type mentioned above such that it has a heating device which is set up to heat the wall section at least in regions. In this way it can be avoided that the reagent droplets flowing back into the area around the injector outlet form deposits there by being vaporized and / or reacted. This is readily possible even with very compact exhaust systems, the heater even at low exhaust gas temperatures already provides a sufficient amount of heat to prevent the formation of deposits. Thus, the reactant can be introduced even at lower exhaust gas temperatures, so that increased emissions are avoided. Since the formation of deposits is already prevented, there is no need for measures to eliminate them, in particular no forced regeneration at periodic intervals.

The introduction arrangement serves in particular for introducing the reaction agent into the exhaust gas flow of an internal combustion engine, particularly preferably for reducing nitrogen oxide emissions.

The introduction arrangement is preferably set up for introducing a reducing agent into the exhaust gas flow. The term "reducing agent" is understood to mean both an agent which acts as a direct reducing agent and a reducing agent precursor product. In particular, the reducing agent may be ammonia or an ammonia precursor product. Most preferably, the reactant is an aqueous urea solution.

The wall section surrounds the injector outlet of the reagent injector, in particular along a circumferential line about a longitudinal axis of the reagent injector, at least in regions; preferably along a closed perimeter around the longitudinal axis of the reagent injector. In the latter case, the wall section completely surrounds the injector outlet.

The heating device is in particular designed to actively heat the wall section.

Specifically, the heater is not configured to heat an injector internal conduit within the injector for passage of the reagent; In particular, the heater is not configured to heat the reactant prior to its introduction into the exhaust stream. Rather, the heater is specifically configured to heat the wall portion which encompasses the injector outlet and thus prevent formation of deposits of backflowing reagent droplets.

As the wall portion engages around the injector outlet, the injector outlet itself does not become mitbeheizt. It is thus possible that backflowing droplets of reactants attach directly to the Injektorauslass so that deposits form there. However, this is harmless since the reactant is introduced, in particular injected, at high pressure into the exhaust gas flow, in particular at a pressure of at least 10 bar, so that deposits on the injector outlet are blown away by the reactant.

According to one embodiment of the invention, it is provided that the heating device is arranged directly on the wall section. The wall section is therefore not indirectly heated, for example, mediated by heat conduction, heat radiation, convection or the like by the heater. Rather, it is arranged directly in particular in physical, preferably in touching contact with the wall section at this and thus heated this directly. In this way, a very efficient and energetically economical heating of the wall section can be effected.

According to one embodiment of the invention, it is provided that the heating device is designed as an electric heater. Particularly preferably, the heating device has at least one resistive heating wire. The heating wire is preferably designed as a heating coil, in particular arranged, placed or guided. In this way, a simple, inexpensive and efficient heating device is provided.

According to one embodiment of the invention, it is provided that the at least one resistive heating wire is arranged in or on the wall section. In particular, it is possible for the resistive heating wire to be embedded in the wall section. In this way, he can heat the wall section particularly efficient. However, it can also be arranged on the wall section, in particular on a surface of the wall section. In this case, it is possible for the resistive heating wire to be arranged at an outer surface of the wall section which is intended to be remote from the exhaust gas flow, or at an inner surface of the wall section which intentionally faces the exhaust gas flow. The wall section itself preferably comprises a material with high thermal conductivity, in particular with a thermal conductivity that is at least as great as that of steel, wherein the thermal conductivity of the material particularly preferably at least 15 W / (mK), preferably more than 30 W / (mK) is. Particularly preferably, the wall section consists of such a material. The inner surface of the wall section facing the exhaust flow then becomes sufficiently warm even in a sufficiently short time when the resistive heating wire is arranged on the outer surface of the wall section facing away from the exhaust flow.

According to one embodiment of the invention, it is provided that the heating device is set up to heat the wall section to at least 300 ° C., preferably to more than 300 ° C. It has been found that deposits of the reaction agent on the wall section are prevented particularly efficiently at or above this temperature.

According to one embodiment of the invention, it is provided that the wall section protrudes in the direction of injection into the exhaust gas flow via the injector outlet of the reagent injector. In this way, the Injektorauslass can be partially shielded by the wall portion of the exhaust stream. In addition, it is possible for the wall section to at least co-determine a spray pattern of the injector.

The wall portion is preferably formed cone-shaped, wherein it protrudes cone-shaped over the Injektorauslass in the injection direction into the exhaust stream.

According to one embodiment of the invention it is provided that the wall portion is formed cone-shaped and seen in the injection direction - that is, in particular to the exhaust gas flow - opens. This allows a particularly efficient introduction of the reagent in the exhaust stream. The wall section can at least co-determine a spray pattern of the injector. In particular, a spray cone can be formed in this way.

According to one development of the invention, it is provided that the wall section is arranged on an injector holder for the reagent injector. The reagent injector itself is then preferably arranged on the injector holder, in particular fastened, wherein the injector holder can be fastened to an exhaust pipe, in particular welded into the exhaust pipe or welded thereto. Preferably, the injector holder is formed as a casting, which is welded in or on an exhaust pipe wall of an exhaust pipe.

Alternatively, it is possible that the wall portion is formed integrally with the reagent injector. In both embodiments, the already mentioned advantages are realized in a special way.

The object is also achieved by providing an exhaust pipe which has an introduction arrangement according to the invention or a placement arrangement according to one of the previously described embodiments. In connection with the exhaust pipe, in particular, the advantages already described arise.

Particularly preferably, the exhaust pipe to an exhaust pipe on which the Einbringanordnung is arranged. In particular, an injector holder is preferably welded to the exhaust pipe, in particular welded to the exhaust pipe or welded into the exhaust pipe, wherein the Reaktionsmittelinjektor arranged on the injector holder, in particular is fixed.

According to one embodiment of the invention it is provided that the exhaust pipe downstream of the introduction arrangement comprises an SCR catalyst which is adapted for the selective catalytic reduction of nitrogen oxides. At the SCR catalyst, the reactant is reacted with the nitrogen oxides comprised by the exhaust gas, thereby reducing the nitrogen oxides. In particular, in this case, the reactant is preferably formed as a reducing agent, in particular as an aqueous urea solution.

Finally, the object is also achieved by providing an internal combustion engine having an exhaust pipe according to the invention or an exhaust pipe according to one of the embodiments described above. In connection with the internal combustion engine, in particular, the advantages that have already been explained in connection with the introduction arrangement and the exhaust pipe result.

The internal combustion engine is preferably designed as a reciprocating engine. It is possible that the internal combustion engine is arranged to drive a passenger car, a truck or a commercial vehicle. In a preferred embodiment, the internal combustion engine is used to drive in particular heavy land or water vehicles, such as mine vehicles, trains, the internal combustion engine is used in a locomotive or a railcar, or ships. It is also possible to use the internal combustion engine to drive a defense vehicle, for example a tank. An exemplary embodiment of the internal combustion engine is preferably also stationary, for example, used for stationary power supply in emergency operation, continuous load operation or peak load operation, the internal combustion engine in this case preferably drives a generator. A stationary application of the internal combustion engine for driving auxiliary equipment, such as fire pumps on oil rigs, is possible. Furthermore, an application of the internal combustion engine in the field of promoting fossil raw materials and in particular fuels, for example oil and / or gas, possible. It is also possible to use the internal combustion engine in the industrial sector or in the field of construction, for example in a construction or construction machine, for example in a crane or an excavator. The internal combustion engine is preferably designed as a diesel engine, as a gasoline engine, as a gas engine for operation with natural gas, biogas, special gas or another suitable gas. In particular, when the internal combustion engine is designed as a gas engine, it is suitable for use in a cogeneration plant for stationary power generation.

• 1 eine schematische Darstellung eines Ausführungsbeispiels einer Brennkraftmaschine mit einem Ausführungsbeispiel einer Abgasleitung sowie einem Ausführungsbeispiel einer Einbringanordnung zum Einbringen eines Reaktionsmittels in einen Abgasstrom, und
• 2 eine Detail-Schnittansicht der Einbringanordnung gemäß 1.

The invention will be explained in more detail below with reference to the drawing. Showing:

• 1 a schematic representation of an embodiment of an internal combustion engine with an embodiment of an exhaust pipe and an embodiment of a Einbringanordnung for introducing a reagent in an exhaust stream, and
• 2 a detail sectional view of the Einbringanordnung according to 1 ,

1 shows a schematic representation of an embodiment of an internal combustion engine 1 with an exhaust pipe 3 , being on the exhaust pipe 3 an insertion assembly 5 for introducing a reaction agent into one in the exhaust pipe 3 is arranged flowing exhaust stream.

The introduction arrangement 5 is in particular adapted for introducing, preferably injecting, a reducing agent or reducing agent precursor product, in particular an aqueous urea solution. Downstream of the introduction assembly 5 is in the exhaust pipe 3 an SCR catalyst 7 arranged, which is adapted for the selective catalytic reduction of nitrogen oxides by reacting the reagent.

The introduction arrangement 5 has a reagent injector 9 on, as well as a wall section 11 , the one injector outlet 13 who is only in 2 can be seen, at least partially, completely encompassing here.

It is provided that the introduction arrangement 5 a heater 15 which is arranged to the wall portion 11 to heat at least in certain areas. In particular, the wall section becomes 11 through the heater 15 actively heated.

The heater 15 is in particular directly on the wall section 11 arranged.

By means of the heater 15 and the thus heated wall section 11 can deposits of backflowing reagent droplets on the wall section 11 effectively avoided.

The heater 15 is here as an electric heater 17 formed here in particular a resistive heating wire 19 , in particular in the form of a heating coil.

The resistive heating wire 19 can be in or on the wall section 11 be arranged. In the embodiment shown here, it is at a the exhaust gas stream intended remote from the outer surface 21 of the wall section 11 arranged.

The heater 15 is especially adapted to the wall section 11 to at least 300 ° C, preferably to more than 300 ° C to heat.

The wall section 11 is here cone-shaped and is above the Injektorauslass 13 seen in the direction of injection.

2 shows a detail sectional view of the embodiment of the insertion assembly 5 according to claim 1. The same and functionally identical elements are provided with the same reference numerals, so that reference is made to the preceding description. It becomes clear that the cone-shaped wall section 11 seen here in the direction of injection - in the exhaust gas flow into or to the exhaust gas flow - opens.

The wall section 11 is in the embodiment shown here on an injector holder 23 arranged, in particular integrally with the injector holder 23 is trained. The injector holder 23 is preferred in or on the exhaust pipe 3 welded. The injector holder is preferred 23 designed as a casting.

Alternatively, it is also possible that the wall section 11 in one piece with the reagent injector 9 is trained.

With the introduction arrangement proposed here 5 , the exhaust pipe 3 and the internal combustion engine 1 is at least in the vicinity of an injector outlet 13 deposition-free introduction of a reagent in an exhaust stream even with compact exhaust systems possible.

Claims (11)

Insertion arrangement (5) for introducing a reaction agent into an exhaust gas flow, comprising a reaction agent injector (9) and a wall section (11) encompassing at least a portion of an injector outlet (13) of the reagent injector (19), characterized by a heating device (15) arranged to heat the wall portion (11) at least partially. Insertion arrangement (5) according to Claim 1 , characterized in that the heating device (15) is arranged directly on the wall section (11). Insertion arrangement (5) according to one of the preceding claims, characterized in that the heating device (15) is designed as an electrical heating device (17), in particular with at least one resistive heating wire (19). Insertion arrangement (5) according to one of the preceding claims, characterized in that the at least one resistive heating wire (19) is arranged in or on the wall section (11). Insertion arrangement (5) according to one of the preceding claims, characterized in that the heating device (15) is arranged to heat the wall section (11) to at least 300 ° C, preferably to more than 300 ° C. Insertion arrangement (5) according to one of the preceding claims, characterized in that the wall section (11) - preferably cone-shaped - projecting beyond the Injektorauslass (13) of the reagent injector (9) in the injection direction. Insertion arrangement (5) according to one of the preceding claims, characterized in that the wall section (11) is conical in shape and opens as viewed in the direction of injection. Insertion arrangement (5) according to one of the preceding claims, characterized in that the wall section (11) a) arranged on an injector holder (23) for the Reagenzmittelinjektor (9), or b) is formed integrally with the Reaktionsmittelinjektor (9). Exhaust pipe (3), with a Einbringanordnung (5) according to one of Claims 1 to 8th , Exhaust pipe (3) after Claim 9 , characterized in that the exhaust pipe (3) downstream of the introduction assembly (5) comprises an SCR catalyst (7). Internal combustion engine (1), with an exhaust pipe (3) according to one of Claims 9 or 10 ,

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