DE102016112336A1 - Exhaust after treatment system and internal combustion engine - Google Patents

Abstract

Exhaust gas aftertreatment system (3) for an internal combustion engine (1), having at least one SCR catalytic converter (9) arranged in a reactor chamber (10) with an exhaust gas feed line (8) leading to the reactor chamber (10), with an exhaust gas outlet leading away from the reactor chamber (10) (11) with a feed line (12) for introducing a reducing agent into the exhaust gas, and with a downstream of the respective introduction device (12) arranged mixing section (14) for mixing the exhaust gas with the reducing agent upstream of the reactor space ( 10), wherein in the exhaust gas inlet (8) in the region of the mixing section (14), a compensation element (21) for compensating thermal expansion and for vibration isolation is integrated.

Description

The invention relates to an exhaust aftertreatment system of an internal combustion engine and an internal combustion engine with such an exhaust aftertreatment system.

In combustion processes in stationary internal combustion engines, which are used for example in power plants, as well as combustion processes in non-stationary internal combustion engines, which are used for example on ships, resulting in nitrogen oxides, these nitrogen oxides typically in the combustion of sulfur-containing fossil fuels, such as coal, hard coal , Brown coal, petroleum, heavy fuel oil or diesel fuels. Therefore, such internal combustion engines are assigned exhaust aftertreatment systems that serve the cleaning, in particular the denitrification, of the exhaust gas leaving the internal combustion engine.

To reduce nitrogen oxides in the exhaust gas, so-called SCR catalysts are used in practice in exhaust gas aftertreatment systems known from practice. In a SCR catalyst, a selective catalytic reduction of nitrogen oxides, wherein for the reduction of nitrogen oxides as a reducing agent ammonia (NH ₃ ) is required. The ammonia (NH ₃ ) or an ammonia precursor substance, such as urea, for this purpose, is introduced into the exhaust gas in liquid form upstream of the SCR catalyst, wherein the ammonia or the ammonia precursor substance upstream of the SCR catalyst with the exhaust gas is mixed. For this purpose, mixing paths between the introduction of the ammonia or of the ammonia precursor substance and the SCR catalyst are provided according to the practice.

Although exhaust gas aftertreatment, in particular nitrogen oxide reduction, can already be successfully carried out using exhaust gas aftertreatment systems which comprise an SCR catalytic converter known from practice, there is a need to further improve the exhaust aftertreatment systems. In particular, there is a need to enable effective exhaust gas aftertreatment in a compact design.

Proceeding from this, the present invention has the object to provide a novel exhaust aftertreatment system and an internal combustion engine with an exhaust aftertreatment system, which enable effective exhaust aftertreatment in a compact design.

This object is achieved by an exhaust aftertreatment system according to claim 1. According to the invention, a compensating element for compensating for thermal expansions and vibration decoupling is integrated into the exhaust gas feed line in the region of the mixing section. This allows for a compact design of the exhaust aftertreatment system effective exhaust aftertreatment.

Preferably, the compensation element is designed as a bellows compensator. A bellows-type compensator enables a particularly compact design of the exhaust aftertreatment system.

According to an advantageous development, a distance of the compensating element from the introduction device of the reducing agent corresponds at most to 7 times, preferably at most 5 times, particularly preferably at most 3 times, the diameter of the exhaust gas supply line in the region of the introduction device. Also, this development allows for a compact design of the exhaust aftertreatment system effective exhaust aftertreatment.

According to a further advantageous embodiment, a protective element shields the compensation element from the flow side. Preferably, for this purpose, the compensation element is integrated into the exhaust gas feed line in the mixing section such that an upstream end of the compensation element is at a downstream end of a compensation element leading portion of the exhaust gas supply line and a downstream end of the compensation element to an upstream end of the compensating element leading away portion of the Exhaust gas supply line connects, wherein at the downstream end of the compensating element leading portion of the exhaust gas supply line, the protective element engages. Also, this development allows for a compact design of the exhaust aftertreatment system effective exhaust aftertreatment. In particular, it is prevented that in the region of the compensating element urea decomposition products, such. Deposit melamine or cyanuric acid, which affect the function of the compensation element.

The internal combustion engine according to the invention is defined in claim 8.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

1 a schematic perspective view of an internal combustion engine with an exhaust aftertreatment system according to the invention;

2 a detail of the exhaust aftertreatment system of 1 ,

The invention relates to an exhaust aftertreatment system of an internal combustion engine, such. As a stationary internal combustion engine in a power plant or on a ship used, non-stationary internal combustion engine.

In particular, the invention relates to an exhaust aftertreatment system of a heavy fuel marine diesel engine, which is preferably designed as a 2-stroke marine diesel engine.

1 shows an arrangement of an internal combustion engine 1 with an exhaust gas turbocharging system 2 and an exhaust aftertreatment system 3 , In the internal combustion engine 1 it may be unsteady or stationary internal combustion engine, in particular a transiently operated marine engine. Exhaust gas, which cylinder 4 the internal combustion engine 1 leaves is in the exhaust charging system 2 used to extract from the thermal energy of the exhaust gas mechanical energy for compression of the internal combustion engine 1 to gain supplied charge air.

So shows 1 an internal combustion engine 1 with an exhaust gas turbocharging system 2 , which has at least one exhaust gas turbocharger 5 includes. Exhaust gas, which is the cylinder 4 the internal combustion engine 1 leaves, flows over a turbine 6 the exhaust gas turbocharger 5 and is relaxed in the same, wherein thereby obtained energy in a compressor (not shown) of the exhaust gas turbocharger 5 is used to compress charge air. Preferably, the internal combustion engine comprises 1 a two-stage turbocharging system 2 with a high-pressure turbocharger and a low-pressure turbocharger.

In addition to the exhaust charging system 2 includes the internal combustion engine 1 the exhaust aftertreatment system 3 , which is an SCR exhaust aftertreatment system. The SCR exhaust aftertreatment system 3 is preferably between the cylinders 4 the internal combustion engine 1 and the exhaust charging system 2 switched, so therefore exhaust, which is the cylinder 4 the internal combustion engine 1 leaves, first via the SCR exhaust aftertreatment system 3 and only then via the exhaust gas charging system 2 to be led.

1 shows an exhaust gas supply line 8th , about the exhaust, starting from the cylinders 4 the internal combustion engine 1 towards an SCR catalyst 9 can be performed in a reactor room 10 is arranged. Further shows 1 an exhaust gas discharge 11 , the discharge of the exhaust gas from the SCR catalyst 9 towards the turbine 6 the exhaust gas turbocharger 5 serves.

The internal combustion engine 1 of the 1 has one for all cylinders 4 common exhaust collector 7 on. Exhaust gas, which is the cylinders 4 the internal combustion engine 1 leaves, is starting from the exhaust collector 7 via the exhaust gas supply line 8th towards the exhaust aftertreatment system 3 namely, the respective reactor space 10 and the respective SCR catalyst 9 , and downstream of the exhaust aftertreatment system 3 over the exhaust gas turbocharger 5 the exhaust charging system 2 feasible.

The to the reactor room 10 and thus to the reactor room 10 positioned SCR catalyst 9 leading exhaust gas supply 8th as well as from the reactor room 10 and thus from the SCR catalyst 9 leading exhaust gas discharge 11 or the exhaust collector 4 and the exhaust gas discharge 11 are preferably coupled via a bypass (not shown), in which a shut-off device is integrated. When the shut-off device is closed, the bypass is closed so that no exhaust gas can flow through the bypass. Then, however, when the obturator is opened, exhaust gas can flow through the bypass, directly from the exhaust gas supply line 8th in the exhaust gas discharge 11 bypassing the reactor space 10 and the SCR catalyst positioned in the reactor space 9 ,

The exhaust gas supply line 8th the exhaust aftertreatment system 3 is a loading device 12 assigned, can be introduced via the in the exhaust stream, a reducing agent, in particular ammonia or an ammonia precursor substance, which is needed to in the range of the SCR catalyst 9 Defined to implement nitrogen oxides of the exhaust gas.

In this introduction device 12 the exhaust aftertreatment system 3 it is preferably an injection nozzle, via which the ammonia or the ammonia precursor substance, such as urea or a urea water solution, in the exhaust gas flow within the Abgaszuführleitung 8th is injected. 2 illustrated with a cone 13 the injection of the reducing agent into the exhaust gas flow in the region of the exhaust gas supply line 8th ,

The route of the exhaust aftertreatment system 3 , seen in the flow direction of the exhaust gas downstream of the introduction device 12 and upstream of the SCR catalyst 9 lies, is called a mixed route 14 designated. In particular, the exhaust gas supply line 8th downstream of the introduction device 12 the mixing section 14 in which the exhaust gas with the reducing agent upstream of the SCR catalyst 9 can be mixed.

The exhaust collector 7 and the mixing section 14 the internal combustion engine 1 are preferably together with the exhaust gas supply line 8th combined into a common assembly. In this case, according to the preferred embodiment, the exhaust lead 8th which the mixing section 14 at least partially formed, seen in the flow direction of the exhaust gas coaxially behind the exhaust manifold 7 positioned.

According to 1 is the respective assembly of the internal combustion engine 1 which the exhaust collector 7 , the mixed route 14 and the exhaust gas supply line 8th designed, designed such that the exhaust gas, starting from the respective exhaust manifold 7 the respective mixing section 14 can be fed without deflection. In 1 Accordingly, the exhaust gas experiences only when entering the exhaust manifold 7 in the area of cylinder-side exhaust gas discharge points 16 and entering the reactor room 10 in the region of a downstream end 15 the exhaust gas supply line 8th upstream of the SCR catalyst 9 a diversion. This is advantageous in order to ensure effective exhaust aftertreatment in a compact design.

1 . 2 clarify with arrows 17 the flow of exhaust gas. 1 can be taken that the exhaust 7 in the area of the cylinder-side exhaust gas discharge points 16 is deflected in about 90 ° or approximately 90 ° and in the exhaust manifold 7 flows. Starting from the exhaust collector 7 the exhaust gas flows without deflection through the exhaust gas supply line 8th to the downstream end 15 the exhaust gas supply line 8th located in the area of the reactor room 10 empties. In the area of this end 15 the exhaust gas supply line 8th experiences a flow deflection by about 180 ° or approximately 180 °, the exhaust after this flow deflection via the SCR catalyst 9 to be led.

The exhaust gas supply line 8th flows with the downstream end 15 in the reactor room 10 , According to a preferred embodiment, the exhaust gas supply line 8th in the region of its downstream end 15 under formation of a diffuser 18 widened funnel-shaped. As a result, the flow cross section of the exhaust gas supply line increases 8th in the area of the downstream end 15 , wherein it can be provided that seen in the flow direction of the exhaust gas upstream of the diffuser 18 the downstream end 15 the exhaust gas supply line 8th the flow cross section of the same initially reduced.

The exhaust gas supply line 8th and the exhaust gas discharge 11 grab a common first page 19 of the reactor space 10 at. In this case, the exhaust gas supply line extends 8th starting from this first page 19 such in the reactor room 10 into that, the downstream end 15 the exhaust gas supply line 8th adjacent to one of the first page 19 of the reactor space 10 opposite second side 20 of the reactor space 10 is positioned. The exhaust gas discharge 11 leads to the first page 19 in the reactor room 10 , About the exhaust gas supply line 8th supplied exhaust gas is in the range of the second side 20 of the reactor space 10 that is the downstream end 15 the exhaust gas supply line 8th is opposite, then diverted, then flows over the SCR catalyst 9 and then on the first page 19 in the field of exhaust gas discharge 11 , The exhaust gas discharge 11 surrounds the exhaust gas supply line 8th adjacent to the first page 19 of the reactor space 10 partially outside, preferably concentric.

In the exhaust gas supply line 8th is in the area of the mixing section 14 , ie downstream of the introduction device 12 for the reducing agent and upstream of the reactor space 10 and thus upstream of the SCR catalyst 9 , a compensation element 21 integrated, which serves the compensation of thermal expansion and vibration isolation.

Thermal expansions in the area of the exhaust gas supply line 8th as well as vibrations in the area of the exhaust gas supply line 8th that arise when operating the exhaust aftertreatment system 3 with the internal combustion engine running 1 as well as running exhaust charging system 2 the internal combustion engine 1 can be compensated.

About the integration of such a compensation element 21 into the exhaust gas supply line 8th in the area of the mixing section 14 can be ensured in a compact design of the exhaust aftertreatment system and thus ultimately the internal combustion engine, an effective exhaust aftertreatment.

In the compensation element 21 it is preferably a bellows compensator.

The compensation element 21 is so in the exhaust gas supply line 8th in the area of the mixing section 14 integrated that an upstream end 21a of the compensation element 21 at a downstream end 22a one to the compensation element 21 leading section 8a the exhaust gas supply line 8th attacks, whereas a downstream end 21b of the compensation element 21 at an upstream end 23 one of the compensation element 21 leading section 8b the exhaust gas supply line 8th attacks.

A distance of the compensating element 21 from the introduction device 12 for the reducing agent corresponds to a maximum of 7 times, preferably at most 5 times, more preferably at most 3 times, the diameter of the exhaust gas supply line 8th in the area of the introduction device 12 , So the diameter of the compensation element 21 leading section 8a the exhaust gas supply line 8th in the area of the introduction device 12 for the reducing agent. This is for optimum compensation of thermal expansion and for optimal vibration isolation in a compact design below Ensuring effective exhaust aftertreatment particularly preferred.

It should be noted at this point that the compensation element 21 especially if the reactor space 10 and thus the SCR catalyst 9 as shown in the embodiment, upstream of an exhaust gas turbocharger 5 is arranged, additionally compensated for shear forces, in particular to compensate for gas pressure occurring due to an increased pressure.

After a development is provided that in the exhaust gas inlet 8th integrated compensation element 21 from the exhaust gas flow through a protective element 24 is covered. The protective element 24 engages on the compensation element 21 leading section 8a the exhaust gas supply line 8th and extends from this section 8a the exhaust gas supply line 8th namely, from the downstream end 22 of the section 8a the exhaust gas supply line 8th , seen in the direction of flow in the direction of the compensation element 21 away-leading section 8b the exhaust gas supply line 8th , and covers the compensation element 21 from the exhaust flow. On the upstream side of the compensating element 21 is the same from the protective element closed there 24 completely covered. At the downstream side of the compensating element 21 is the same thing about the protective element open there 24 accessible. Through the protective element 24 can be an unrestricted function of the compensation element 21 be ensured to compensate for thermal expansion and for vibration isolation, on the other hand prevents reducing agent decomposition products on the compensating element 21 deposit and impair its function.

As already stated, can by the compensation element 21 In a particularly compact design an effective exhaust aftertreatment of the cylinder 4 the internal combustion engine 1 leaving exhaust gas are guaranteed.

In the embodiment of 1 is the common assembly, which is the exhaust collector 7 , the mixed route 14 , the exhaust gas supply line 8th and also in the exhaust gas supply line 8th integrated compensation element 21 provides, carried out such that the exhaust gas from the exhaust manifold 7 the respective mixing section 14 can be fed without deflection. This is, as already stated above, preferred. In contrast, embodiments are possible in which the exhaust gas in its flow starting from the exhaust manifold 7 in the area of the mixing section 14 and thus in the area of the exhaust gas supply line 8th undergoes a simple deflection, that is, once deflected, and preferably by a maximum of 90 °, namely the passage from the exhaust manifold 7 into the exhaust gas supply line 8th and therefore in the area of the mixing section 14 , If a multiple deflection of the exhaust gas is required for reasons of space on the internal combustion engine, it is provided in the sense of the invention that the assembly, which the exhaust manifold 7 , the exhaust gas supply line 8th , the mixed route 14 and the compensation element 21 is prepared, is formed such that the exhaust gas from the exhaust manifold 7 the mixing section 14 with a maximum of 3-fold deflection or a diversion of the exhaust gas between the exhaust manifold 7 and mixed route 14 of a maximum of 270 °, preferably with a maximum of 2-fold deflection or a deflection of the exhaust gas between the exhaust manifold 7 and mixed route 14 of a maximum of 180 °, the mixing section 14 is supplied. A deflection of the exhaust gas between the exhaust manifold 7 and mixed route 14 a maximum of 90 ° is preferred, most preferred is the deflection-free supply of the exhaust gas, starting from the exhaust manifold 7 towards the mixing section 14 , These details also allow effective exhaust aftertreatment in a compact design.

The common assembly, which is the exhaust collector 7 , the mixed route 14 , the compensation element 21 and the exhaust gas supply line 8th formed, is preferably formed such that a distance between one of the SCR catalyst 9 or reactor space 10 most distant cylinder-side exhaust port 16 in the respective exhaust collector 7 and the SCR catalyst 9 or reactor space 10 a maximum of 6 times, preferably a maximum of 4 times, more preferably a maximum of 2 times, the distance between the SCR catalyst 9 or reactor space 10 most distant cylinder-side exhaust port 16 in the exhaust collector 7 and one from the SCR catalyst 9 or reactor space 10 closest cylinder-side exhaust port 16 in the exhaust collector 7 equivalent. This is also advantageous in order to ensure effective operation of the internal combustion engine with a compact design and effective exhaust aftertreatment and to minimize the length of the compensating element.

In the illustrated embodiment, the reactor space 10 and thus the SCR catalyst 9 exhaust gas flow side upstream of an exhaust gas turbocharger 5 arranged. It is also possible that the reactor room 10 and thus the SCR catalyst 9 Abströmströmungsseitig downstream of an exhaust gas turbocharger are arranged. Furthermore, it is possible that the reactor space 10 and thus the SCR catalyst 9 exhaust gas flow side are connected between a high-pressure exhaust gas turbocharger and a low-pressure exhaust gas turbocharger.

The above details are particularly suitable for use in 2-stroke internal combustion engines, which are operated with residual oil or with heavy oil or natural gas. However, the invention can also be used in 4-stroke internal combustion engines.

LIST OF REFERENCE NUMBERS

1

Internal combustion engine

2

Turbocharging System

3

aftertreatment system

4

cylinder

5

turbocharger

6

turbine

7

collector

8th

exhaust lead

8a

section

8b

section

9

SCR catalyst

10

reactor chamber

11

Flue gas discharge

12

introducing device

13

Injection cone

14

mixing section

15

The End

16

Exhaust opening point

17

flow

18

diffuser

19

page

20

page

21

compensation element

21a

The End

21b

The End

22

The End

23

The End

24

protection element

Claims (12)

Exhaust aftertreatment system ( 3 ) for an internal combustion engine ( 1 ), with at least one in a reactor space ( 10 ) arranged SCR catalyst ( 9 ), with one to the reactor space ( 10 ) leading exhaust gas supply ( 8th ), with one from the reactor space ( 10 ) leading off exhaust gas discharge ( 11 ), with one of the exhaust gas supply line ( 8th ) associated delivery device ( 12 ) for introducing a reducing agent into the exhaust gas, and with a downstream of the respective introduction device ( 12 ) arranged mixing section ( 14 ) for mixing the exhaust gas with the reducing agent upstream of the reactor space ( 10 ), characterized in that in the exhaust gas supply line ( 8th ) in the area of the mixing section ( 14 ) a compensation element ( 21 ) is integrated to compensate for thermal expansion and vibration isolation. Exhaust after-treatment system according to claim 1, characterized in that the compensating element ( 21 ) is designed as a bellows compensator. Exhaust after-treatment system according to claim 1 or 2, characterized in that a distance of the compensating element ( 21 ) from the introduction device ( 12 ) a maximum of 7 times the diameter of the exhaust gas supply line ( 8th ) in the region of the introduction device ( 12 ) corresponds. Exhaust after-treatment system according to claim 3, characterized in that the distance of the compensating element ( 21 ) from the introduction device ( 12 ) a maximum of 5 times the diameter of the exhaust gas supply line ( 8th ) in the region of the introduction device ( 12 ) corresponds. Exhaust after-treatment system according to claim 4, characterized in that the distance of the compensating element ( 21 ) from the introduction device ( 12 ) at most 3 times the diameter of the exhaust gas supply line ( 8th ) in the region of the introduction device ( 12 ) corresponds. Exhaust gas after-treatment system according to one of claims 1 to 5, characterized in that a protective element ( 24 ) the compensation element ( 21 ) shields the flow side. Exhaust after-treatment system according to one of claims 1 to 6, characterized in that the compensating element ( 21 ) in the exhaust gas supply line ( 8th ) in the area of the mixing section ( 14 ) is integrated such that an upstream end ( 21a ) of the compensating element ( 21 ) to a downstream end ( 22 ) one to the compensation element ( 21 ) section ( 8a ) of the exhaust gas supply line ( 8th ) and a downstream end ( 21b ) of the compensating element ( 21 ) to an upstream end ( 23 ) one of the compensation element ( 21 ) leading section ( 8b ) of the exhaust gas supply line ( 8th ), wherein at the downstream end ( 22 ) of the compensation element ( 21 ) section ( 8a ) of the exhaust gas supply line ( 8th ) the protective element ( 24 ), which the compensation element ( 21 ) shields the flow side. Internal combustion engine ( 1 ), with several cylinders ( 4 ), with at least one for a group of cylinders ( 4 ) common exhaust collector ( 7 ), and with an exhaust aftertreatment system ( 3 ) according to one of claims 1 to 7, wherein the exhaust gas from the respective exhaust gas collector ( 7 ) via the exhaust aftertreatment system ( 3 ) and downstream of the exhaust aftertreatment system ( 3 ) via at least one exhaust gas turbocharger ( 5 ) of an exhaust gas charging system ( 2 ) of the internal combustion engine ( 1 ) is feasible. Internal combustion engine according to claim 8, characterized in that the respective exhaust gas collector ( 7 ), the respective mixing section ( 14 ) and the respective Compensation element ( 21 ) are combined to form a common assembly. Internal combustion engine according to claim 9, characterized in that the respective common assembly is designed such that a distance between one of the respective SCR catalyst ( 9 ) or respective reactor space ( 10 ) farthest cylinder-side exhaust gas discharge point ( 16 ) in the respective exhaust collector ( 7 ) and the respective SCR catalyst ( 9 ) or respective reactor space ( 10 ) a maximum of 6 times, preferably a maximum of 4 times, more preferably a maximum of 2 times, the distance between the respective SCR catalyst ( 9 ) or respective reactor space ( 10 ) farthest cylinder-side exhaust gas discharge point ( 16 ) in the respective exhaust collector ( 7 ) and one of the respective SCR catalyst ( 9 ) or respective reactor space ( 10 ) closest to the cylinder exhaust port ( 16 ) in the respective exhaust collector ( 4 ) corresponds. Internal combustion engine according to one of claims 8 to 10, characterized in that the exhaust gas, starting from the respective exhaust manifold ( 7 ) of the respective mixing section ( 14 ) with a maximum of 3-fold deflection, preferably with a maximum of 2-fold deflection, more preferably with a maximum of 1-fold deflection, can be fed. Internal combustion engine according to one of claims 8 to 11, characterized in that the exhaust gas, starting from the respective exhaust gas collector ( 7 ) of the respective mixing section ( 17 ) with a deflection of a maximum of 270 °, preferably with a deflection of a maximum of 180 °, particularly preferably with a deflection of a maximum of 90 °, can be fed.

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