JP2009030561A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine with improved reducing efficiency of nitrogen oxide, by distributing and flowing reducing agent into a reducing agent, according to a flow rate distribution of exhaust gas flowing in an inlet surface of a reducing catalyst. <P>SOLUTION: The exhaust emission control device for an internal combustion engine is arranged in an exhaust passage of the internal combustion engine. The exhaust emission control device has the reducing catalyst, and an injector injecting the reducing agent into the exhaust passage at the upstream of the reducing catalyst. The injector has a fan spray nozzle injecting to spread the reducing agent like a fan, and an impinging plate disposed at a position opposed to the inlet surface of the reducing catalyst, changing a travelling direction of the reducing agent by impinging the reducing agent injected from the injector, and guiding the reducing agent to the inlet surface of the reducing catalyst. The impinging plate has a plurality of impinging surfaces. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for reducing and purifying nitrogen oxides in exhaust gas discharged from an internal combustion engine. In particular, the present invention relates to an exhaust emission control device in which the flow direction of exhaust gas is bent immediately before the reduction catalyst.

Conventionally, the nitrogen oxides contained in the exhaust gas discharged from an internal combustion engine (hereinafter, referred to as NO _X.) To remove the exhaust gas purification device provided with a selective reduction catalyst and the injection device of the liquid reducing agent Are known. Such an exhaust purification device sprays a liquid reducing agent, such as an aqueous urea solution, into the exhaust gas upstream of the reduction catalyst, mixes it, flows it into the reduction catalyst, and hydrolyzes the liquid reducing agent in the reduction catalyst. Nitrogen oxide is purified by a reduction reaction between ammonia and nitrogen oxide.

  As a device for supplying the reducing agent into the exhaust passage, the compressed air is mixed with the liquid reducing agent in the mixing chamber and atomized and then supplied from a nozzle in the exhaust pipe, or a so-called air assist type device or an exhaust pipe. There is an injection type apparatus that sprays a reducing agent from an injection hole into an exhaust passage by pumping a liquid reducing agent to an attached injector and opening and closing a passage that leads to the injection hole of the injector. Among these, in the type in which the reducing agent is sprayed using an injector, the particles of the reducing agent are not easily diffused, and the spray distribution flowing into the inlet surface of the reduction catalyst is easily biased.

  When the sprayed reducing agent flowed in a biased distribution toward the inlet of the reduction catalyst, it was not used for the reduction reaction of nitrogen oxides in the ammonia produced in the region where the amount of reducing agent inflow was large. In a region where ammonia is released into the atmosphere as it is and the amount of reducing agent inflow is small, there is a risk that the nitrogen oxides in the exhaust gas will not be sufficiently reduced and will be released into the atmosphere as they are. Therefore, a mixer and a collision plate are arranged in the exhaust passage so that the distribution of the liquid reducing agent reaching the reduction catalyst is uniform (see, for example, Patent Documents 1 and 2).

Japanese Patent Laying-Open No. 2003-232218 (FIG. 2) JP 2007-32472 A (FIG. 1)

  However, there are various forms of the exhaust passage on the upstream side of the reduction catalyst, and the flow rate distribution of the exhaust gas flowing into the inlet face of the reduction catalyst varies depending on the form of each exhaust purification device. In particular, when the exhaust gas flow direction is bent immediately before the reduction catalyst, the flow rate and flow rate of the exhaust gas flowing into the inlet surface of the reduction catalyst tend to vary from region to region. Therefore, as in Patent Documents 1 and 2, even when a mixer or a collision plate is arranged in the exhaust passage to facilitate the dispersion of the reducing agent in the exhaust gas, the reducing agent on the inlet surface of the reduction catalyst If the distribution does not match the exhaust gas flow rate distribution, the same problem as described above may occur as a result.

Therefore, the inventors of the present invention have made diligent efforts to use an injector provided with a fan spray nozzle as an injector of an exhaust purification device, and reduce the injected fan-shaped reducing agent by colliding with a plurality of collision surfaces of the collision plate. The inventors have found that such a problem can be solved by changing the traveling direction to the catalyst side, and have completed the present invention.
That is, the present invention relates to an exhaust emission control device capable of improving the reduction efficiency of nitrogen oxides by distributing a reducing agent in accordance with the flow rate distribution of exhaust gas flowing into the inlet surface of the reduction catalyst and flowing it into the reduction catalyst. The purpose is to provide.

  According to the present invention, an exhaust gas of an internal combustion engine that is disposed and used in an exhaust passage of an internal combustion engine and includes a reduction catalyst and an injector for injecting a reducing agent into the exhaust passage on the upstream side of the reduction catalyst. The purifying device is an injector having a fan spray nozzle in which the reducing agent to be injected has a fan shape, and the reducing agent injected from the injector is caused to collide with a position facing the inlet surface of the reduction catalyst. An exhaust purification device for an internal combustion engine is provided, characterized in that it includes a collision plate that changes the traveling direction of the reducing agent and guides the reducing agent to the inlet surface of the reduction catalyst, and the collision plate includes a plurality of collision surfaces. Such a problem can be solved.

  Further, in configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, the exhaust passage has a bent portion immediately before the reduction catalyst, and the exhaust gas flows into the reduction catalyst with the flow direction changed immediately before the reduction catalyst. Thus, the collision plate is preferably arranged at a position facing the inlet surface of the reduction catalyst at the bent portion.

  Further, in configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, the collision plate is disposed so as to extend along a fan-shaped plane injected from the injector, and the plurality of collision surfaces are in the injection direction of the reducing agent. It is preferable to arrange along.

  In configuring the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the angles of the plurality of collision surfaces of the collision plate are preferably set according to the flow rate distribution of the exhaust gas flowing into the inlet surface of the reduction catalyst.

According to the exhaust gas purification apparatus for an internal combustion engine of the present invention, the spray of the reducing agent is less affected by the flow of the exhaust gas, and the distribution of the reducing agent reaching the inlet surface of the reduction catalyst can be adjusted. In other words, an injector equipped with a fan spray nozzle has features such as high atomization and high penetration force. Therefore, the reduction led to the inlet surface of the reduction catalyst by adjusting the arrangement and angle of multiple collision surfaces. The distribution of the agent can be made steady. Therefore, it is possible to prevent the reduction catalyst from flowing out to the downstream side due to partial excess of either ammonia or NO _{x in} the reduction catalyst, and to improve the reduction efficiency of NO _{x in} the exhaust gas.
Also, with such a configuration, the injector and the collision plate can be arranged close to the reduction catalyst, so that the length of the exhaust passage can be shortened, the exhaust purification device can be miniaturized, and the heat release is reduced. It is also possible to reduce the active temperature range of the reduction catalyst.

  Further, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the exhaust passage immediately before the reduction catalyst is provided by providing a bent portion of the exhaust passage immediately before the reduction catalyst and disposing a collision plate at a position facing the inlet surface of the reduction catalyst. Even when the straight portion of the passage is short, the reducing agent can be guided to the inlet surface of the reduction catalyst in accordance with the flow rate distribution of the exhaust gas flowing into the reduction catalyst.

  Further, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, the reducing agent injected in a fan shape by arranging the collision plate and the collision surface along a predetermined direction corresponding to the shape of the spray of the reducing agent from the injector. Can be caused to partially collide with the collision surface and be led to the reduction catalyst side, so that the distribution of the reducing agent guided to the inlet surface of the reduction catalyst can be easily adjusted.

Further, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, the angle of the plurality of collision surfaces is set according to the flow rate distribution of the exhaust gas flowing into the inlet surface of the reduction catalyst, so that the amount of NO _x flowing into the reduction catalyst is reduced. commensurate distribution in could be made to flow the reducing agent can reduce the amount of ammonia or NO _X is passes through the reduction catalyst.

DESCRIPTION OF EMBODIMENTS Embodiments relating to an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be specifically described below with reference to the drawings. However, this embodiment shows one aspect of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.
In the drawings, the same members are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  FIG. 1 and FIG. 2 are diagrams showing the configuration of an exhaust gas purification apparatus (hereinafter simply referred to as “exhaust gas purification apparatus”) 10 for an internal combustion engine according to an embodiment of the present invention. FIG. 1A shows a side view of the exhaust purification device 10 viewed from a direction orthogonal to the axial direction, and FIG. 1B shows the exhaust purification device 10 of FIG. The rear side view seen from the side is shown. FIG. 2 is a view of the XX cross section of FIG. 1B as seen in the direction of the arrow, and shows a cross-sectional view of the exhaust purification device 10 cut along the axial direction.

As shown in FIGS. 1 and 2, the exhaust purification apparatus 10 according to the present embodiment includes a casing 11 as a casing, a reduction catalyst 13 accommodated in the casing 11, and an injector 35 fixed to the casing 11. The collision plate 15 disposed in the injection direction of the injector 35 is a main element. Further, an oxidation catalyst 17 is disposed on the downstream side of the reduction catalyst 13 in the casing 11.
The exhaust gas purification device 10 is mainly used in an exhaust passage of a diesel engine.

A casing 11 that is a casing of the exhaust gas purification apparatus 10 is a cylindrical member made of a material such as stainless steel, and a reduction catalyst 13 that selectively reduces NO _x in the exhaust gas is disposed therein. An oxidation catalyst 17 is disposed on the downstream side. These reduction catalyst 13 and oxidation catalyst 17 are accommodated in cylindrical housings 21a and 21b, respectively.

The reduction catalyst 13 used in the exhaust purification apparatus 10 of this embodiment is a selective reduction type reduction catalyst that selectively reduces and purifies NO _x contained in exhaust gas. The reduction catalyst 13 is a known catalyst, for example, a porous carrier, strontium or barium as an active component, an alkaline earth metal such as magnesium, a rare earth metal such as cerium and lanthanum, or a noble metal such as platinum and rhodium. Etc. can be used.

Further, the oxidation catalyst 17 provided downstream of the reduction catalyst 13, if, among the aqueous urea solution as a reducing agent is generated hydrolyzed ammonia amount that has not been used for the reduction of the NO _X is directly passed Even in such a case, the oxidation catalyst 17 is used to oxidize and release NO ₂ with relatively low toxicity. The oxidation catalyst 17 may be a known catalyst, for example, a catalyst in which platinum is supported on alumina and a predetermined amount of a rare earth element such as cerium is added.

  Further, an exhaust introduction chamber 23 is provided further upstream of the reduction catalyst 13, and an exhaust introduction pipe 25 to which the exhaust pipe of the internal combustion engine is connected so as to face the exhaust introduction chamber 23. A storage chamber 29 is provided further downstream of the oxidation catalyst 17, and an exhaust lead-out pipe 27 having a plurality of holes 27 a through which exhaust gas passes is connected to the storage chamber 29. An exhaust pipe is connected to the exhaust lead-out pipe 27.

  An injector 35 is attached to the outer periphery of the casing 11 at a portion corresponding to the exhaust introduction chamber 23 so that the tip of the nozzle of the injector 35 faces the exhaust introduction chamber 23. The injector 35 is, for example, an ON-OFF valve that performs electromagnetic control to open and close the passage leading to the injection hole. The injector 35 is pumped by a pump or the like so that the liquid reducing agent is always maintained at a predetermined pressure value. It is sprayed when opened.

Further, the injection hole formed in the nozzle of the injector 35 is formed in a rectangular slit shape so that the spray of the reducing agent to be injected is formed in a flat fan shape, and injection with a strong penetrating force is performed. It has become. Further, the rectangular slit-shaped injection holes are formed in the axial direction of the casing 11 so that the spray of the flat fan-shaped reducing agent injected from the injector 35 is formed along a cross section orthogonal to the central axis of the casing 11. It arrange | positions so that it may orthogonally cross.
Moreover, in the example of this embodiment, in order to avoid the damage of the injector 35 by the heat | fever of exhaust gas, the injector 35 provided with the radiation fin 35a is used.

The amount of reducing agent injected by the injector 35, for example, engine speed and the load state of the internal combustion engine is determined in accordance with the discharge amount of NO _X is estimated based on the fuel injection quantity, etc., in accordance with the injection quantity injector 35 DUTY control is performed.
As the reducing agent used, an aqueous urea solution is typical. For example, when this urea aqueous solution is used, urea (NH ₃ ) is generated by hydrolysis of urea injected into the exhaust passage by heat in the exhaust gas, and this NH ₃ and NO in the exhaust gas are generated. _{When X} (NO or NO ₂ ) reacts in the reduction catalyst, NO _X is reduced, decomposed into nitrogen (N ₂ ) and water (H ₂ O), and discharged. In addition to this, a material capable of reducing NO _x such as unburned fuel (HC) can be used as the liquid reducing agent.

  Further, a collision plate 15 is provided in the traveling direction of the reducing agent spray injected from the injector 35 so that the reducing agent spray can collide. The collision plate 15 is made of a heat-resistant material such as stainless steel, and includes a plurality of collision surfaces 15a. The flat fan-shaped reducing agent spray partially collides, so that the traveling direction is changed and reduced. It is guided toward the inlet surface of the catalyst 13.

  Next, with reference to FIG. 3 and FIG. 4, the structure of the injector 35 and the collision board 15 with which the exhaust gas purification apparatus 10 of this embodiment was equipped is demonstrated in detail. 3 shows a perspective view of the injector 35 and the collision plate 15, FIG. 4 (a) shows a view of the injector 35 and the collision plate 15 from the downstream side in the axial direction of the casing, and FIG. The figure which looked at the injector 35 and the collision board 15 from the side is shown.

  As shown in FIGS. 3 and 4, a collision plate 15 is disposed on the traveling direction side of the reducing agent spray injected from the injector 35, so that the fan-shaped spray injected from the injector 35 can collide. ing. The collision plate 15 in the present embodiment is provided with a plurality of collision portions 15c having collision surfaces 15a inclined with respect to the surface of the substrate 15b on the surface of the plate-like substrate 15b, and among the peripheral edges of the substrate 15b. A U-shaped wall portion 15d is provided along the edge opposite to the injector 35 side.

The collision plate 15 is fixed by welding to the cover plate 11 a on the end surface of the casing, and is disposed so as to face the inlet surface of the reduction catalyst 13. That is, the portion of the base plate 15 b of the collision plate 15 faces the flat fan-shaped spray plane of the reducing agent injected from the injector 35.
However, the collision plate 15 is not necessarily fixed to the cover plate 11a of the casing, and may be fixed to the body of the injector or the casing itself.

  Further, the plurality of collision portions 15c provided in the collision plate 15 are arranged along the traveling direction of the spray of the reducing agent injected from the injector 35 (in the example of FIGS. 3 and 4 arranged in five rows). , Except for the collision portions 15ce in the row farthest from the injector 35, they are separated at the central portion, and a space is formed therebetween. As the distance from the injector 35 increases, the distance between the two separated collision portions 15c decreases. Accordingly, the spray located on the outer side of the sprayed flat fan-shaped reducing agent spray collides with the collision portion 15ca closer to the injector 35, and the spray located at the center collides with the most distant collision portion 15ce. It has become.

These collision parts 15c are for directing the traveling direction of the spray of the reducing agent injected from the injector 35 to the inlet surface of the reduction catalyst 13, and the position of the collision part 15c and the inclination angle of the collision surface 15a. Accordingly, the position reaching the inlet surface of the reduction catalyst 13 can be adjusted.
In addition, since the collision plate 15 is disposed on the front surface of the reduction catalyst 13, the exhaust gas turbulence factor is increased, and the flow rate distribution itself of the exhaust gas on the front surface of the reduction catalyst 13 can be improved.

  There are no particular restrictions on the number, location, size, and angle of inclination of the collision surface 15a, and various modes are conceivable. In the exhaust emission control device of this embodiment, the injector 35 having a fan spray nozzle is used as the injector 35, and injection with strong penetrating power is possible. Therefore, the injected reducing agent has an influence of the flow of exhaust gas. It is difficult to receive, and the reducing agent can be guided toward the targeted position on the inlet surface of the reduction catalyst 13 according to the form of the collision portion 15c. Accordingly, since the flow rate distribution of the reducing agent that reaches the inlet surface of the reduction catalyst 13 can be made steady, the reducing agent is distributed in accordance with the flow rate distribution of the exhaust gas according to the configuration of the exhaust passage and flows into the reduction catalyst 13. To be able to.

For example, the collision portions 15ca to 15ce of the collision plate 15 shown in FIGS. 3 and 4 are arranged at the same interval, and are all formed as collision surfaces 15a having the same inclination angle. Therefore, as shown in FIG. 5, the spray of the reducing agent that has collided with each of the collision surfaces 15 a and changed the traveling direction so that a relatively large amount of the reducing agent reaches the region closer to the injector 35. It has become.
However, in order to approximate the flow rate distribution of the exhaust gas reaching the inlet surface of the reduction catalyst 13 and the flow rate distribution of the reducing agent in accordance with the form of the exhaust passage, each of the flow rates is calculated using CFD (fluid numerical calculation). The shape of the collision plate 15 can be optimized by designing the flow rate distributions to coincide.

Further, the U-shaped wall portion 15d arranged along the edge of the collision plate 15 functions as a tray when the reducing agent drips. When the injector 35 is closed, etc., the penetration force of the sprayed reducing agent is weakened, so that it adheres to the collision portion 15c and liquefies to cause dripping. Therefore, this liquid dripping is collected by the wall 15d, the reducing agent is evaporated by the heat of the wall 15d heated by the exhaust gas, and flows into the reduction catalyst 13 on the flow of the exhaust gas. .
However, the U-shaped wall portion 15d may be omitted.

  As explained so far, in the exhaust gas purification apparatus configured to bend the flow direction of the exhaust gas upstream of the reduction catalyst, it is provided with a fan spray nozzle that is formed in a flat fan shape and that has a strong penetration force. By using the injector and the collision plate for changing the traveling direction of the spray of the fan-like reducing agent, the reducing agent flowing into the inlet surface of the reduction catalyst can be distributed and stabilized in a desired state. Therefore, the reducing agent can be guided to the reduction catalyst according to the flow rate distribution of the exhaust gas reaching the inlet surface of the reduction catalyst, and the flow rate distribution of the exhaust gas reaching the reduction catalyst is uneven. However, the reducing agent can be supplied in accordance with the distribution.

In addition, it is not necessary to ensure a long distance between the mixing and diffusing member and the reducing catalyst for the purpose of allowing the reducing agent and exhaust gas to mix and diffuse and uniformly flow into the reducing catalyst. It becomes possible to make it close to the catalyst. Therefore, the exhaust pipe can be shortened, the exhaust purification device can be reduced in size, heat release on the upstream side of the reduction catalyst can be suppressed, and the temperature of the reduction catalyst can be easily maintained at the activation temperature. As a result, NO _x in the exhaust gas can be efficiently reduced.

It is a figure for demonstrating the structure of the exhaust gas purification apparatus concerning embodiment of this invention. It is sectional drawing for demonstrating the structure of the exhaust gas purification apparatus concerning embodiment of this invention. It is a perspective view for demonstrating the structure of a collision board. It is the front view and side view for demonstrating the structure of a collision board. It is a figure which shows a mode that the reducing agent which collided with the collision board is guide | induced.

Explanation of symbols

10: Exhaust purification device, 11: casing, 11a: cover plate, 13: reduction catalyst, 15: collision plate, 15a: collision surface, 15b: base, 15c: collision portion, 15d: wall portion, 17: oxidation catalyst, 21a 21b: housing, 23: exhaust introduction chamber, 25: exhaust introduction pipe, 27: exhaust outlet pipe, 27a: hole, 29: storage chamber, 35: injector, 35a: radiating fin

Claims (4)

In an exhaust gas purification apparatus for an internal combustion engine, which is disposed and used in an exhaust passage of an internal combustion engine, and includes a reduction catalyst and an injector for injecting a reducing agent into the exhaust passage on the upstream side of the reduction catalyst.
The injector is an injector provided with a fan spray nozzle in which the reducing agent to be injected becomes a fan shape,
A collision plate for guiding the reducing agent to the inlet surface of the reduction catalyst by causing the reducing agent injected from the injector to collide to change the traveling direction of the reducing agent at a position facing the inlet surface of the reduction catalyst; An exhaust gas purification apparatus for an internal combustion engine, wherein the collision plate has a plurality of collision surfaces. The exhaust passage has a bent portion immediately before the reduction catalyst, and the exhaust gas is changed in flow direction immediately before the reduction catalyst and flows into the reduction catalyst,
2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the collision plate is disposed at a position facing the inlet surface of the reduction catalyst in the bent portion.   The collision plate is disposed so as to extend along a fan-shaped plane injected from the injector, and the plurality of collision surfaces are arranged along the injection direction of the reducing agent. Item 3. An exhaust emission control device for an internal combustion engine according to Item 1 or 2.   4. The angle of the plurality of collision surfaces of the collision plate is set according to a flow rate distribution of exhaust gas flowing into an inlet surface of the reduction catalyst. 5. Exhaust gas purification device for internal combustion engine.

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