DE102011076467A1 - Apparatus used for metering e.g. fuel into exhaust gas stream of internal combustion engine mounted in vehicle, has recessed grooves that are connected with inner wall of lance casing channels incorporated in swirl channels - Google Patents

Abstract

The metering apparatus comprises a spray tube (50) having an exhaust-gas end that is provided with cylindrical lateral recessed grooves. The cylindrical lateral recessed grooves are connected together with an inner wall of the lance casing channels. The lateral channels are incorporated in the exhaust-side end face of the spray tube swirl channels that are opened into a cylindrical swirl chamber provided with a running injection hole. An independent claim is included for method for metering fuel and/or adjuvant.

Description

State of the art

The increasingly stringent exhaust gas legislation makes after-treatment of the exhaust gas necessary in internal combustion engines, in particular in self-igniting internal combustion engines, in order to reduce the proportion of nitrogen oxides in the exhaust gas. An established method for reducing nitrogen oxides in exhaust gases is Selective Catalytic Reduction (SCR). In the SCR process, the nitrogen oxides are reduced to nitrogen and water by means of a fuel and / or auxiliary supplied to the exhaust gas stream. As a fuel and / or excipient often comes under the brand name AdBlue available eutectic urea-water solution used. The fuel and / or excipient is stored in a reservoir and conveyed via a supply system to a dosing and injected into the exhaust stream of the internal combustion engine.

A device for conveying, dosing and injecting a fuel and / or excipient is for example from the German patent application DE 10 2011 004 365.9 known. The dosing system disclosed in this patent application has a two-part dosing line, the first part having a small cross-section and provided with a liquid-repellent coating and the second part of the dosing line has a large cross-section and is made of a refractory material which wets from the liquid can be. About compressed air, the reducing agent is driven through the delivery line. Due to the liquid-repellent coating of the first line section, drops are formed which are moved with the compressed air. Due to the comparatively small surface of the droplets, only a small evaporation of water occurs. A low evaporation rate is crucial, since with a larger loss of water a crystallization of the urea takes place and thereby could clog the dosing. The second conduit section is in contact with the exhaust system and has temperatures that are too high for urea to crystallize out.

At the atomization of the fuel and / or auxiliary high demands are made. In order to avoid deposits in the exhaust system, for example, the aqueous urea solution must be atomized into small droplets with an average diameter (SMD = Sauter Mean Diameter) of preferably <30 μm. There must be no bimodal aerosol with many very small and a few large drops. The generation of small drops can be achieved by a high exit velocity of the fuel and / or excipient from a spray hole, while the formation of large drops must be avoided. For this purpose, however, large amounts of compressed air are required, otherwise there would be a risk that due to the coincidence of a larger amount of fuel and / or excipient with a small amount of compressed air large drops.

Disclosure of the invention

The inventive device for dosing a fuel and / or auxiliary, in particular a reducing agent in an exhaust stream of an internal combustion engine comprises a spray pipe, wherein the spray pipe at the exhaust side end has a cylinder with laterally recessed grooves, which form together with the inner wall of the spray tube sheath ducts. The jacket channels pass into swirl channels, which open into a swirl chamber with at least one spray hole.

For the spray tube, a tube with a round cross-section is preferably used and the cylinder is preferably designed as a circular cylinder whose outer diameter corresponds to the inner diameter of the spray tube. In one embodiment, the swirl channels and / or the swirl chamber are incorporated in the exhaust side end face of the cylinder.

The grooves in the cylinder are preferably formed spirally, wherein each two of the spiral grooves have an opposite direction of rotation. The pitch of the spiral grooves is chosen so that the sheath channels formed by the grooves and the inner wall of the spray tube cross at least once.

In a further embodiment of the invention, the grooves on the lateral surface of the cylinder are arranged so that they extend from the upper end face to the lower end face wavy, wherein two adjacent grooves cross at least once. The waveform may be, for example, round, so that the grooves run serpentine on the lateral surface. In the case of an angular waveform, a jagged course of the grooves results over the lateral surface.

The fuel and / or excipient, before it is passed into the spray tube, mixed with a conveyor, in particular compressed air or exhaust gas of the internal combustion engine. The mixed fluid stream enters the jacket channels. Small pressure differences in the fluid flow in the sheath channels are balanced at the intersections between the sheath channels. After passing through the jacket channels, the fluid is homogenized. Subsequently, the fluid enters the swirl channels.

The jacket channels are preferably eccentric in the swirl channels. In a further embodiment, the transition is configured centrically and / or funnel-shaped.

From the swirl channels, the fluid continues to flow into the swirl chamber. The swirl chamber is preferably cylindrical with a round base. In a further embodiment, the swirl chamber is designed as a truncated cone, wherein embodiments with round top surfaces are also preferred.

The transitions from the sheath channels into the swirl channels as well as the transitions from the swirl channels into the swirl chamber are each preferably eccentric, so that the fluid is mixed with a high degree of swirl. In a further embodiment, the transitions between the swirl channels and the swirl chamber are funnel-shaped.

In order to preserve the twist, the injection hole is located directly under the swirl chamber. The injection hole is preferably arranged centrally under the swirl chamber. The fluid exits evenly with a high swirl from the spray hole and is uniformly finely atomized. The homogenization of the fluid made sure that always sufficient amounts of compressed air for atomizing the fuel and / or excipient are available and no large drops can occur.

In a preferred embodiment of the device according to the invention the diameter of the swirl chamber is limited to twice the diameter of the injection hole to maintain the twist in the spray hole.

In a further preferred embodiment, the length to diameter ratio of the injection hole is chosen to be less than 1 in order to maintain the twist.

Advantages of the invention

The inventive device for dosing a fuel and / or auxiliary, in particular a reducing agent, in an exhaust stream of an internal combustion engine, the fuel and / or excipient is reliably and uniformly atomized, without causing larger drops occur. This is achieved by the crossing jacket channels of the spray tube. Pressure fluctuations that lead to an unfavorable ratio of fuel and / or excipient to the fluid and thus the formation of large drops at the injection hole are compensated at the intersections of the sheath channels. Furthermore, the arrangement of the swirl channels and swirl chamber causes the fluid to become highly swirled, which reduces the size of the droplets produced at the spray hole. Together, both measures allow the device according to the invention to reduce the amount of fluid used without creating a bimodal aerosol with small and large drops. Possible deposits from the fuel and / or excipient in the exhaust system due to large drops are effectively prevented while saving medium.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

1 shows an embodiment of the device designed as a compressed air-assisted dosing system in a schematic representation,

2 shows an embodiment of the dosing module of the device according to the invention,

3 shows the spray tube of the dosing module from the front.

4 shows a further embodiment of the spray tube from the front.

5 shows a view of the spray pipe with cylinder from above,

6 represents a first section through the spray pipe with cylinder and

7 represents a second section through the spray tube with cylinder.

8th shows a section through a further embodiment of the spray tube with central transitions between the sheath channels and the swirl channels.

9 represents a section through another embodiment of the spray tube with cylinder with funnel-shaped swirl channels.

Embodiments of the invention

1 shows a schematic representation of the device according to the invention for dosing a fuel and / or excipient in an exhaust stream of an internal combustion engine.

The fuel and / or the excipient 12 gets out of a tank 10 with a conveyor module 14 through a fuel and / or auxiliary line 16 in the dosing module 40 promoted. For the fuel and / or excipient 12 is it to Carrying out the selective catalytic reduction, in particular by a eutectic urea-water solution available under the brand name AdBlue. In the dosing module 40 becomes the fuel and / or auxiliary 12 with a pumped medium 22 mixed, wherein it is in the pumped medium 22 in particular compressed air or exhaust gas of the internal combustion engine is. The compressed air 22 is from the compressed air supply 20 of the vehicle via a compressed air line 24 the dosing module 40 fed. The compressed air 22 drives the urea-water solution through the spray tube 50 , From there, the urea-water solution enters the exhaust system 70 injected, where an aerosol 62 arises. The aerosol 62 comes in contact with the exhaust stream 72 , The urea-water solution produces the actual reducing agent, gaseous ammonia NH ₃ . By the ammonia are in the exhaust stream 72 containing nitrogen oxides reduced to water and nitrogen. A control unit 30 controls the conveyor module 14 and the dosing module 40 to inject exactly the amount of reducing agent required for nitrogen oxide reduction.

2 shows a schematic representation of the dosing of the device for dosing a fuel and / or excipient.

The dosing module 40 is the fuel and / or excipient on the line 16 and the pumped medium 22 over the line 24 fed. The fuel and / or excipient 12 passes through the metering valve 42 and the pumped medium 22 directly over the line 24 into the mixing chamber 44 , The mixture is passed over the spray tube 50 in the exhaust stream 72 the exhaust system 70 introduced where an aerosol 62 arises. The required amount of the fuel and / or the excipient 12 is from the controller 30 via the dosing valve 42 set.

3 shows a section through the spray pipe with the cylinder from the front.

In the spray tube 50 is a cylinder at the exhaust end 52 admitted. In the lateral surface of the cylinder 52 are lateral grooves 53 let in, which together with the inner wall 51 the spray tube 50 the jacket channels 54 form. The grooves 53 in the cylinder 52 are preferably formed spirally, wherein in each case two of the spiral grooves 53 have an opposite sense of rotation. Are for example on the lateral surface of the cylinder 52 eight grooves 53 distributed, run four grooves 53 clockwise and four grooves 53 counterclockwise. The slope of the spiral grooves 53 is chosen so that the sheath channels 54 at least one crossing point 55 in which two or more of the sheath channels 54 to meet. At the exhaust side facing end face of the cylinder 52 are swirl channels 56 incorporated, which the sheath channels 54 with a swirl chamber 57 connect in the center of the face. The swirl chamber 57 can be cylindrical and, for example, is located centrally above a spray hole 58 , which is in the end face of the spray tube 50 located and with the exhaust system 70 in contact.

4 shows a further embodiment of the spray tube from the front.

In the spray tube 50 is at the exhaust side of the cylinder 52 admitted. The grooves 53 on the lateral surface of the cylinder 52 run in the illustrated embodiment in the form of wavy lines from the upper end face of the cylinder 52 to the lower end face of the cylinder 52 and form with the inner wall 51 the spray tube 50 the jacket channels 54 , The waveform is chosen so that each two adjacent grooves intersect at least once. Instead of in 4 shown round waveform are also angular shapes possible. At the exhaust side, lower end face of the cylinder 52 are swirl channels 56 incorporated, which the sheath channels 54 with the swirl chamber arranged in the center of the end face 57 connect. In this embodiment, the swirl chamber is 57 as to the exhaust side tapered truncated cone 59 executed and flows into the spray hole 58 , which is in the end face of the spray tube 50 located and with the exhaust system 70 in contact.

5 represents the spray tube with the cylinder from above.

5 shows the cylinder 52 with four grooves 53 which together with the inner wall 51 the spray tube 50 the wall channels 54 form. That in the mixing chamber 44 produced mixture of fuel and / or excipient 12 with pumped medium 22 flows into the wall channels at this point 54 one.

6 shows a section through the spray pipe with the cylinder.

In the sectional view in 6 is the spray tube 50 with the cylinder 52 shown. The cut runs near a crossing point 55 so that the distance between two sheath channels 54 here is smaller than in the representation according to 4 ,

7 represents a further section through the spray tube with the cylinder.

In the in 7 illustrated section through the spray pipe 50 with the cylinder 52 are the transitions through the grooves 53 and the inner surface 51 the spray tube 50 formed jacket channels 54 in the swirl channels 56 shown. Furthermore, in the 6 the swirl chamber 57 represented, in which the swirl channels 56 lead. To the fluid, whose Streamlines with the reference numeral 60 are shown to put under a twist, are the swirl channels 56 arranged so that the sheath channels 54 in this eccentric transition and the swirl channels 56 eccentric in the swirl chamber 57 lead. The transition from the sheath channels 54 in the swirl channels 56 However, for example, it can also be executed concentric or funnel-shaped tapered. The fluid exits the swirl chamber 57 over the spray hole 58 and generates an aerosol 62 , which deals with the exhaust gas flow 72 mixed. The injection hole 58 is preferably immediately below the swirl chamber 57 arranged. Further, it is preferable that the injection hole 58 centric under the swirl chamber 57 is arranged. In order to maintain the swirl of the fluid, it is further preferred that the diameter of the swirl chamber 57 to twice the diameter of the spray hole 58 limited. Also advantageous for obtaining the twist is a length to diameter ratio of the spray hole 58 , which is not greater than 1.

8th shows a section through a further embodiment of the spray tube with central transitions between the sheath channels, the swirl channels and the swirl chamber.

In 8th is a section through another embodiment of the spray tube 50 shown. Of the 8th it can be seen that the sheath channels 54 centric in the swirl channels 56 go over and that the swirl channels 56 slightly eccentric in the swirl chamber 57 lead. The one in the swirl chamber 57 required twist can be due to the exact arrangement of the swirl channels 56 and their transitions into the swirl chamber 57 be set. The fluid flows as with the reference numerals 60 provided lines indicated by the sheath channels 54 in the swirl channels 56 and flows into the swirl chamber 57 further. From there it passes over the spray hole 58 in the exhaust system 70 one.

9 shows a section through another embodiment of the spray tube with funnel-shaped swirl channels.

The in 9 shown section through the spray tube 50 shows a further embodiment of the swirl channels 56 , The swirl channels 56 run funnel-shaped onto the swirl chamber 57 to. The width of the swirl channels 56 is at the transition to the sheath channels 54 largest and at the transition to the swirl chamber 57 the smallest. The initial size of the swirl channels 56 is at the transition between the sheath channels 54 and the swirl channels 56 chosen in the illustrated embodiment, that between the jacket channels 54 and the swirl channels 56 no bottleneck arises. However, other embodiments are possible. The fluid flows as with the reference numerals 60 provided lines indicated by the sheath channels 54 in the swirl channels 56 and flows into the swirl chamber 57 further. From there it passes over the spray hole 58 in the exhaust system 70 one.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely 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.

Cited patent literature

• DE 102011004365 [0002]

Claims (11)

Device for metering in a fuel and / or adjuvant ( 12 ), in particular a reducing agent, into an exhaust gas stream ( 72 ) of an internal combustion engine, comprising a spray pipe ( 50 ), characterized in that the spray tube ( 50 ) at the exhaust-side end of a cylinder ( 52 ) with laterally embedded grooves ( 53 ), which together with the inner wall ( 51 ) of the spray tube sheath channels ( 54 ), wherein the jacket channels ( 54 ) in swirl channels ( 56 ), which enter a swirl chamber ( 57 ) with at least one spray hole ( 58 ). Device according to claim 1, characterized in that the grooves ( 53 ) in the cylinder ( 52 ) are spirally formed, wherein each two of the spiral grooves ( 53 ) have an opposite direction of rotation. Device according to one of the preceding claims, characterized in that the jacket channels ( 54 ) at least one intersection ( 55 ) exhibit. Device according to one of the preceding claims, characterized in that the jacket channels ( 54 ) eccentrically or centrically and / or funnel-shaped into the swirl channels ( 56 ) pass over. Device according to one of the preceding claims, characterized in that the swirl channels ( 56 ) eccentrically and / or funnel-shaped into the swirl chamber ( 57 ). Device according to one of the preceding claims, characterized in that the swirl chamber ( 57 ) cylindrical or in the form of a truncated cone ( 59 ) is executed. Device according to one of the preceding claims, characterized in that the swirl chamber ( 57 ) immediately above the spray hole ( 58 ) is arranged. Device according to one of the preceding claims, characterized in that the swirl chamber ( 57 ) centrically above the injection hole ( 58 ) is arranged. Device according to one of the preceding claims, characterized in that the diameter of the swirl chamber ( 57 ) smaller than or equal to the diameter of the injection hole ( 58 ). Device according to one of the preceding claims, characterized in that the ratio of length to diameter of the injection hole ( 58 ) is less than or equal to 1.0. Method for metering in a fuel and / or adjuvant ( 12 ), in particular a reducing agent, into an exhaust gas stream ( 72 ) of an internal combustion engine with a metering module ( 40 ), comprising a mixing chamber ( 44 ), in which the fuel and / or excipient ( 12 ) with a pumped medium ( 22 ), in particular compressed air or exhaust gas of an internal combustion engine, is mixed and a spray tube ( 50 ), characterized in that the mixture before dosing into the exhaust gas stream ( 72 ) in the spray tube ( 50 ) is homogenized.

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