DE102018129884A1 - Device for mixing fuel with the exhaust gas of an internal combustion engine and exhaust gas treatment system containing such a device - Google Patents

Abstract

The invention relates to a device for mixing fuel (2) with an exhaust gas flow of an internal combustion engine which is guided in an exhaust pipe (6), comprising a feed line for fuel (2) and a space for mixing fuel (2) and exhaust gas (3).
According to the invention, the space for mixing fuel (2) and exhaust gas (3) is designed as at least one mixing chamber (5) which is arranged outside the exhaust pipe (6) carrying the exhaust gas (3) and with which the exhaust gas ( 3) leading exhaust pipe (6) is integrally or non-positively or positively connected, the fuel (2) can be introduced from the feed line (4) into the mixing chamber (5) and by at least one electrically heated heating element (8) in the mixing chamber (5 ) is evaporable.

Description

The invention relates to a device for mixing fuel with an exhaust gas flow of an internal combustion engine guided in an exhaust pipe, comprising a feed line for fuel and a space for mixing fuel and exhaust gas.

State of the art:

• - Ungenügende Vermischung des Kraftstoffs mit dem Abgas
• - Ablagerungen von Kraftstoff oder Verbrennungsprodukten an den Wänden der abgasführenden Rohrleitungen
• - Erhöhter Abgasgegendruck, wenn Bauteile zur Verbesserung der Vermischung in das Abgasrohr eingebaut sind.

Devices for mixing fuel with exhaust gas for internal combustion engines are known, for example from the document DE 102011001596 A1 . They are used to regenerate particle filters and / or to change the composition of the exhaust gas.
Some known designs have the following disadvantages depending on the exhaust gas temperature:

• - Inadequate mixing of the fuel with the exhaust gas
• - Deposits of fuel or combustion products on the walls of the exhaust pipes
• - Increased exhaust gas back pressure if components are installed in the exhaust pipe to improve mixing.

It is an object of the present invention to enable a safe and rapid mixing of the additionally introduced fuel with the exhaust gas, which is largely independent of the temperature of the exhaust gas, and thereby to cause evaporation of the fuel and a mixing with the exhaust gas outside the exhaust pipe.

This object is achieved by the features of the first claim.

The invention includes the technical teaching that the space for mixing fuel and exhaust gas is designed as at least one mixing chamber which is arranged outside the exhaust pipe carrying the exhaust gas and is connected to the exhaust pipe carrying the exhaust gas in a cohesive, non-positive or positive manner, the Fuel can preferably be introduced into the at least one mixing chamber through at least one nozzle and can be vaporized into the at least one mixing chamber through at least one electrically heatable heating element.
The mixing chamber is mechanically and fluidically connected to the exhaust pipe, but is separated so far that the mixing takes place outside the exhaust pipe. This causes a reduction in diesel deposits and / or coking in the manifold or exhaust system. The heating element effects a reliable evaporation of the additionally introduced fuel regardless of the exhaust gas temperature. If the mixing chamber is to be positively connected to the exhaust pipe, a threaded connection or a connection with a non-releasable snap connection is recommended. In a preferred embodiment, the fuel is injected through at least one nozzle, but versions are also possible in which no nozzle is required.

The dependent claims 2 to 7 contain advantageous developments of the invention, the dependent claims 8 to 10 describe exhaust gas treatment systems which contain an inventive device for mixing.

According to an advantageous development of the invention, the at least one mixing chamber is at least partially spherical. This gives an advantageous relation of the volume to the inner surface. A conical design of the mixing chamber also offers advantages, namely an inexpensive manufacture of the mixing chamber and a good adaptation of the shape of the mixing chamber to the shape of the fuel jet emerging from the nozzle.

The mixing chamber and the exhaust pipe are preferably made of the same material. If they consist of two materials, the two materials should have two coefficients of linear expansion that differ by less than 5%. So there is no risk of temperature-related cracks.

In a first advantageous embodiment, the heating element is designed as a heating wire which is attached to the wall of the mixing chamber with its ends electrically insulated from the mixing chamber, the heating wire protruding into the mixing chamber. This version is very effective and is easy to manufacture.

In a second embodiment, the heating element is designed as a thick-film heater which is attached to the wall of the mixing chamber in an electrically insulated manner from the mixing chamber. This version is characterized by its robustness and strong effect, it also enables deposits in the mixing chamber to be easily burned free.

In a third embodiment, the heating element is designed as an incandescent rod which is attached to the wall of the mixing chamber in an electrically insulated manner from the mixing chamber and projects into the mixing chamber. This version offers the advantages of high robustness and simple manufacture. Heating elements designed as glow rods are known and available on the market.

The device advantageously has a plurality of mixing chambers which are connected to the exhaust pipe in such a way that the exhaust gas flow from the internal combustion engine acts on them one after the other. With this arrangement, the effect of the mixing chambers can be better controlled, and the device takes up less space if several smaller mixing chambers take the place of a large mixing chamber.

The device according to the invention is advantageously part of an exhaust gas treatment system of the internal combustion engine, in which the at least one mixing chamber is connected to a section assigned to the exhaust pipe, which is arranged between a first turbine of a first turbocharger and a second turbine of a second turbocharger. The turbochargers are assigned to the same internal combustion engine as the exhaust gas treatment system. The arrangement of the device between the two turbochargers results in a particularly good distribution of the mixing chamber products in the exhaust gas flow and a lower exhaust gas back pressure compared to an arrangement of the device in front of the first exhaust gas turbocharger.

Further advantageously, the fuel that can be mixed with the exhaust gas can be taken from at least one metering pump from a fuel tank or from a fuel return line of a fuel injection system of the internal combustion engine and can be injected into the at least one mixing chamber. When using a plurality of mixing chambers, a plurality of metering pumps assigned to the mixing chambers are preferably used.

If an electromagnetically driven reciprocating pump is used as the metering pump, the injection quantity can be controlled well by adapting the stroke frequency to the required quantity of fuel.

As an alternative to using at least one metering pump, the fuel that can be mixed with the exhaust gas can be taken from a fuel return line of a fuel injection system of the internal combustion engine. The fuel can then be supplied from at least one electrically switchable valve to the at least one mixing chamber, wherein if a plurality of mixing chambers are used, a plurality of valves assigned to the mixing chambers are preferably also used. This version does not require a metering pump if the return line is sufficiently high.

Further details, features and advantages of the invention will become apparent from the following description with reference to the drawing.

• 1 eine vereinfachte Schnittdarstellung der Ausführung mit einem Heizdraht,
• 2 eine vereinfachte Schnittdarstellung der Ausführung mit einer Dickschichtheizung
• 3 eine weitere Schnittdarstellung der Ausführung mit zwei Mischkammern
• 4 eine schematische Darstellung des Abgasbehandlungssystems mit einer Dosierpumpe und einer Mischkammer zwischen zwei Turboladern
• 5 eine schematische Darstellung des Abgasbehandlungssystems mit einem Ventil und einer Mischkammer zwischen zwei Turboladern

It shows:

• 1 a simplified sectional view of the design with a heating wire,
• 2nd a simplified sectional view of the version with a thick-film heater
• 3rd another sectional view of the version with two mixing chambers
• 4th is a schematic representation of the exhaust gas treatment system with a metering pump and a mixing chamber between two turbochargers
• 5 is a schematic representation of the exhaust gas treatment system with a valve and a mixing chamber between two turbochargers

1 shows a device according to the invention ( 1 ) for mixing fuel ( 2nd ) with a in an exhaust pipe ( 6 ) guided exhaust gas flow of an internal combustion engine. The device ( 1 ) has a supply line ( 4th ) for fuel ( 2nd ) and a fuel mixing room ( 2nd ) and exhaust gas ( 3rd ) on.
The space for mixing fuel ( 2nd ) and exhaust gas ( 3rd ) is a mixing chamber ( 5 ) trained outside of the exhaust gas ( 3rd ) leading exhaust pipe ( 6 ) is arranged and with which the exhaust gas ( 3rd ) leading exhaust pipe ( 6 ) cohesively or non-positively or positively connected.
The fuel ( 2nd ) from the supply line ( 4th ) through at least one nozzle ( 7 ) into the mixing chamber ( 5 ) injectable and by at least one electrically heated heating element ( 8th ) in the mixing chamber ( 5 ) evaporable.

The mixing chamber ( 5 ) is partially spherical.

The mixing chamber ( 5 ) and the exhaust pipe ( 6 ) consist of the same material.

The heating element ( 8th ) is as a heating wire ( 11 ) executed against the mixing chamber ( 5 ) electrically insulated with its ends on the mixing chamber ( 5 ) is arranged, the heating wire ( 11 ) into the mixing chamber ( 5 ) protrudes.

In another version according to 2nd is the heating element ( 8th ) as a thick film heater ( 12 ) executed against the mixing chamber ( 5 ) electrically insulated on the inside of the mixing chamber ( 5 ) is attached.

In a further embodiment, not shown, the heating element ( 8th ) as glow stick ( 13 ) executed against the mixing chamber ( 5 ) electrically insulated on the mixing chamber ( 5 ) is attached and into the mixing chamber ( 5 ) protrudes. The use and design of glow rods are known from diesel engines for preheating.

In a version according to 3rd the device ( 1 ) a plurality of mixing chambers ( 5 , 5 ' ) with the exhaust pipe ( 6 ) are connected in such a way that they are successively acted upon by the exhaust gas flow of the internal combustion engine.

4th shows an exhaust gas treatment system of the internal combustion engine with a device according to the invention ( 1 ), the mixing chamber ( 5 ) with the exhaust pipe ( 6 ) assigned section ( 15 ) connected between a first turbine of a first turbocharger ( 16 ) and a second turbine of a second turbocharger ( 17th ) is arranged, the turbocharger ( 16 , 17th ) are assigned to the same internal combustion engine as the exhaust gas treatment system.

The one with the exhaust gas ( 3rd ) mixable fuel ( 2nd ) is from a dosing pump ( 18th ) from a fuel tank ( 19th ) or from a fuel return line ( 21st ) of a fuel injection system of the internal combustion engine and into the at least one mixing chamber ( 5 ) injectable.

The dosing pump ( 18th ) is preferably designed as an electromagnetically driven reciprocating pump. When using a plurality of mixing chambers ( 5 ) preferably a plurality comes from the mixing chambers ( 5 ) assigned metering pumps ( 18th ) for use.

picture 5 shows an exhaust gas treatment system of the internal combustion engine with a device according to the invention ( 1 ), the one with the exhaust gas ( 3rd ) mixable fuel ( 2nd ) from a fuel return line ( 21st ) a fuel injection system of the internal combustion engine can be removed and an electrically switchable valve ( 22 ) the mixing chamber ( 5 ) can be supplied, with the use of a plurality of mixing chambers ( 5 ) preferably a plurality of valves ( 22 ) is used, which the mixing chambers ( 5 ) are assigned to each.

The foregoing description in accordance with the present invention is for illustrative purposes only and is not intended to limit the invention. Various changes and modifications are possible within the scope of the invention without leaving the scope of the invention and its equivalents.

Reference symbol list

1

Mixing device

2nd

fuel

3rd

Exhaust gas

4th

Supply

5

Mixing chamber

6

Exhaust pipe

7

jet

8th

Heating element

11

Heating wire

12

Thick film heating

13

Glow stick

15

Exhaust pipe section

16

turbocharger

17th

turbocharger

18th

Dosing pump

19th

Fuel tank

21st

Fuel return line

22

Valve

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102011001596 A1 [0002]

Claims (11)

Device (1) for mixing fuel (2) with an exhaust gas flow of an internal combustion engine guided in an exhaust pipe (6), comprising a feed line (4) for fuel (2) and a space for mixing fuel (2) and exhaust gas (3) , characterized in that the space for mixing fuel (2) and exhaust gas (3) is designed as at least one mixing chamber (5) which is arranged outside the exhaust pipe (6) carrying the exhaust gas (3) and with which the exhaust gas ( 3) leading exhaust pipe (6) is integrally or non-positively or positively connected, the fuel (2) can be introduced from the feed line (4) into the mixing chamber (5) and by at least one electrically heated heating element (8) in the mixing chamber (5 ) is evaporable. Device (1) after Claim 1 , characterized in that the fuel (2) can be injected into the mixing chamber (5) through at least one nozzle (7). Device (1) according to one of the preceding claims, characterized in that the mixing chamber (5) is at least partially spherical. Device (1) according to one of the preceding claims, characterized in that the mixing chamber (5) and the exhaust pipe (6) consist of the same material or of two materials, the two materials then having two coefficients of linear expansion which are less than 5 % differentiate. Device (1) according to one of the preceding claims, characterized in that the heating element (8) is designed as a heating wire (11) which is arranged with its ends on the mixing chamber (5) in an electrically insulated manner from the mixing chamber (5), the Heating wire (11) protrudes into the mixing chamber (5). Device (1) according to one of the Claims 1 to 4th , characterized in that the heating element (8) is designed as a thick-film heater (12) which is attached to the inside of the mixing chamber (5) in an electrically insulated manner from the mixing chamber (5). Device (1) according to one of the Claims 1 to 4th , characterized in that the heating element (8) is designed as an incandescent rod (13) which is attached to the mixing chamber (5) in an electrically insulated manner from the mixing chamber (5) and projects into the mixing chamber (5). Device (1) according to one of the preceding claims, characterized in that the device (1) has a plurality of mixing chambers (5) which are connected to the exhaust pipe (6) in such a way that they are successively acted upon by the exhaust gas flow of the internal combustion engine. Exhaust gas treatment system of the internal combustion engine with a device (1) according to one of the preceding claims, characterized in that the at least one mixing chamber (5) is connected to a section (15) associated with the exhaust pipe (6), which is connected between a first turbine of a first turbocharger ( 16) and a second turbine of a second turbocharger (17), the turbochargers (16, 17) being assigned to the same internal combustion engine as the exhaust gas treatment system. Exhaust gas treatment system of the internal combustion engine with a device (1) according to one of the Claims 1 to 8th characterized in that the fuel (2) which can be mixed with the exhaust gas (3) can be taken from at least one metering pump (18) from a fuel tank (19) or from a fuel return line (21) of a fuel injection system of the internal combustion engine and into the at least one mixing chamber ( 5) can be injected, the metering pump (18) preferably being designed as an electromagnetically driven reciprocating piston pump, and if a plurality of mixing chambers (5) are used, a plurality of metering pumps (18) assigned to the mixing chambers (5) are preferably used. Exhaust gas treatment system of the internal combustion engine with a device (1) according to one of the Claims 1 to 8th characterized in that the fuel (2) which can be mixed with the exhaust gas (3) can be taken from a fuel return line (21) of a fuel injection system of the internal combustion engine and can be supplied to the at least one mixing chamber (5) from at least one electrically switchable valve (22), wherein If a plurality of mixing chambers (5) are used, a plurality of valves (22) are preferably used, which are each assigned to the mixing chambers (5).

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