JP5365795B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine capable of mixing a reducer with exhaust gas while sufficiently securing an opportunity of the contact of the reducer and the exhaust gas utilizing a casing having a wide space. <P>SOLUTION: An airflow generating chamber 25 for changing an exhaust gas flow from one end into a doughnut-shaped vortex flow &beta; in which small vortex flows are arranged continuously along the body inner surface of the casing is formed in the casing 6. A spray nozzle 20 for spraying the reducer in a wide angle from the center toward the doughnut-shaped vortex flow &beta; generated on the body inner surface is provided at the other end side wall surface of the airflow generating chamber. Since the reducer is sprayed into the doughnut-shaped vortex flow of the exhaust gas swirling on the body section inner surface of the casing from the center of the vortex flow toward the vortex flow, the reducer and the exhaust gas can be sufficiently mixed. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that purifies exhaust gas discharged from the internal combustion engine.

  BACKGROUND ART An exhaust emission control device for a diesel engine (internal combustion engine) has a structure in which a reducing agent is injected into an exhaust gas exhausted from the internal combustion engine for purification. In many cases, a passage is provided between a front-stage casing containing a diesel particulate filter (hereinafter referred to as DPF) and a rear-stage casing containing a selective reduction NOx catalyst (hereinafter referred to as SCR catalyst) serving as a purification catalyst. Therefore, a structure is used in which an aqueous urea solution as a reducing agent is sprayed into the exhaust gas with a spray nozzle from the upstream side of the SCR catalyst.

By the way, the urea aqueous solution sprayed from the spray nozzle uses the exhaust heat of the exhaust gas and ammonia that is hydrolyzed by the water vapor in the exhaust gas to obtain a NOx reduction action with the SCR catalyst, thereby reducing NOx in the exhaust gas. Therefore, it is required that the urea aqueous solution as the reducing agent is sufficiently mixed with the exhaust gas to supply ammonia evenly to the SCR catalyst.
Therefore, in the exhaust purification device, the urea aqueous solution can be mixed into the exhaust gas using a structure in which the urea aqueous solution is sprayed along the flow direction of the exhaust gas from the passage arranged upstream of the selective reduction type NOx catalyst. (See, for example, Patent Document 1).

JP 2008-274878 A

  However, since the spray nozzle having the same structure injects the urea aqueous solution along the passage direction, the urea aqueous solution is forced to be sprayed into the exhaust gas with a narrow-angle spray shape that fits in the passage. For this reason, the opportunity for contact between the exhaust gas and the urea aqueous solution is limited, and the urea aqueous solution may not be sufficiently mixed with the exhaust gas. In particular, since the length of the passage tends to be suppressed by downsizing the exhaust gas purification device, the urea aqueous solution is mixed with the exhaust gas even if a means for causing an air flow change in the passage is taken as seen in Patent Document 1. There were limits.

  Accordingly, an object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can mix a reducing agent and exhaust gas while sufficiently ensuring an opportunity for the reducing agent and exhaust gas to contact each other by utilizing a casing having a wide space. It is to provide.

In order to achieve the above object, the invention of claim 1 converts an exhaust gas flow from one end into a donut-shaped swirl flow in which small swirl flows continue along the circumferential direction of the inner surface of the body of the casing. the product chamber is provided, the other end of the wall surface of the air flow generating chamber, toward the center side to the toroidal vortex generated in the barrel inner surface, provided with a spray nozzle for spraying a reducing agent wide manner, air flow generating chamber A partition wall having a converging through hole is provided in the center at a point away from the other end wall of the casing, and the exhaust gas flow converged by passing through the converging through hole is caused to collide with the other end wall. By diffusing, a donut-shaped spiral flow is generated in the space between the partition wall and the other end wall along the circumferential direction of the inner surface of the trunk, and the spray nozzle is connected to the other end side of the air flow generation chamber. Placing a spraying part in the center of the wall, reducing agent from the spraying part It is sprayed toward the donut-shaped swirl generated around the spraying part in a hollow cone-shaped spray shape, and the outlet part of the casing is the exhaust gas while maintaining the swirl of the peripheral wall of the airflow generation chamber It is in the point where the
According to this configuration, the reducing agent and the exhaust gas are mixed by spraying the reducing agent toward the spiral flow from the center side of the doughnut-shaped spiral flow of the exhaust gas swirling on the inner surface of the body portion of the casing. As a result, the reducing agent is sufficiently diffused in the swirling exhaust gas flow in the wide casing, and the opportunity for the reducing agent and the exhaust gas to contact each other is greatly ensured, so that the reducing agent and the exhaust gas are sufficiently mixed.

According to the first aspect of the present invention, the reducing agent is sufficiently diffused into the exhaust gas flow swirling in a donut shape in a wide casing, and the chance of contacting the exhaust gas with the reducing agent is greatly increased.
Therefore, the reducing agent is well mixed with the exhaust gas. In particular, the donut-shaped swirl flow is a swirl flow that is generated to the maximum by making the most of the space in the casing body of the casing, so that the opportunity for sufficient contact between the reducing agent and the exhaust gas is given, and sufficient mixing results are achieved. I can expect.

In addition , a donut-shaped spiral flow can be generated in the casing with a simple structure in which a partition wall having a converging through hole in the center is provided in the casing.
In addition , since the reducing agent is sprayed into a donut-shaped spiral flow in a hollow cone-like spray shape, it is possible to secure many opportunities for the sprayed reducing agent and exhaust gas to contact each other, further reducing the exhaust gas and reducing agent. Can be mixed effectively.

In addition, since the exhaust gas flows out from the outlet of the casing and continues to the purification catalyst while maintaining the swirl flow, mixing of the exhaust gas and the reducing agent continues even in the path to the purification catalyst, making it even more effective. The exhaust gas and the reducing agent can be mixed.

1 is a partially cutaway perspective view showing an exhaust gas purification apparatus according to a first embodiment of the present invention. Sectional drawing which follows the AA line in FIG. Sectional drawing which follows the BB line in FIG. The perspective view for demonstrating spray of the reducing agent with respect to a donut-shaped spiral flow. Sectional drawing which shows the principal part of the 2nd Embodiment of this invention.

Hereinafter, the present invention will be described based on a first embodiment shown in FIGS.
In FIG. 1, reference numeral 1 denotes a diesel engine as an internal combustion engine. The exhaust pipe 1 a of the diesel engine 1 is provided with an exhaust purification device 2 that purifies exhaust gas discharged from the engine 1. For example, a structure in which the front-stage purification unit 3 and the rear-stage purification unit 10 are connected by a connection pipe 17 that is a passage is used for the exhaust purification device 2.

  Among these, the purification | cleaning part 3 has the inlet_port | entrance part 4 in the edge part of an upstream (equivalent to the one end side of this application), and has the cylindrical casing 6 which has the outlet part 5 in the downstream edge part. The inlet 4 is connected to the exhaust pipe 1 a of the diesel engine 1. In the casing 6, a diesel particulate filter 7 (hereinafter referred to as DPF 7) that collects particulate matter (hereinafter referred to as PM) in the exhaust gas, a pre-stage oxidation catalyst 8 (pre-stage catalyst) that continuously regenerates the DPF 7. It is stored with. That is, the structure is such that PM can be removed from the exhaust gas while the DPF 7 is regenerated.

  Similarly, the purification unit 10 has a cylindrical casing 13 having an inlet 11 at an upstream end and an outlet 12 at a downstream end. Of these, the inlet 11 is connected to the outlet 5 of the casing 6 via the connecting pipe 17. Moreover, the exit part 12 becomes an air release side. In the casing 13, an ammonia selective reduction type NOx catalyst 14 (hereinafter referred to as SCR catalyst 14) corresponding to the purification catalyst of the present application is housed together with a rear-stage oxidation catalyst 15 (rear-stage catalyst) that suppresses the ammonia flowing out from the SCR catalyst 14. It has been.

  Further, on the upstream side of the SCR catalyst 14, a liquid-only urea water injection nozzle 20 (which corresponds to the spray nozzle of the present application, hereinafter simply spraying a reducing agent required for the operation of the SCR catalyst 14, for example, an aqueous urea solution, into the exhaust gas. A spray nozzle 20). That is, the sprayed urea aqueous solution (reducing agent) is hydrolyzed by the exhaust heat of the exhaust gas and the water vapor in the exhaust gas, so that ammonia that produces the NOx reduction action of the SCR catalyst 14 is generated. Thereby, NOx in the exhaust gas discharged from the diesel engine 1 is purified by the NOx reduction action of the SCR catalyst 14.

  Here, the urea aqueous solution used for NOx purification (by NOx reduction action) is required to be sufficiently mixed with the exhaust gas. Therefore, in this embodiment, the mixer unit 21 utilizing the space in the casing 6 is employed. Specifically, the exhaust gas receiving chamber 23 formed at the outlet end of the DPF 7 is used here, and the exhaust gas flow from the DPF 7 is supplied to a part of the receiving chamber 23 to the inner periphery of the trunk portion 6 of the casing 6. A mixer structure is employed in which an air flow generation chamber 25 that is changed into a donut-shaped spiral flow in which small spiral flows are formed along the surface and an aqueous urea solution is sprayed from the center side of the spiral flow by the injection nozzle 20 is adopted. 2 and 3 show cross sections of the mixer unit 21 (a cross-sectional view taken along the line AA in FIG. 1 and a cross-sectional view taken along the line BB).

Specifically, as shown in FIGS. 1 to 3, the air flow generation chamber 25 is a converging through hole for converging the exhaust gas flow at a downstream side of the exhaust receiving chamber 23 that is a predetermined distance away from the outlet end of the DPF 7. For example, a partition wall 27 having a circular through hole 26 in the center is provided to partition the exhaust receiving chamber 23, and an annular flat chamber is formed on the downstream side (exit side). That is, as shown in FIG. 2, the flat airflow generation chamber 25 converges through the through-hole 26 while the exhaust gas flow flowing out from the outlet end of the DPF 7 reaches the outlet portion 5 , and the exhaust gas flow that has converged is the end wall. The structure is such that the exhaust gas diffuses to the surroundings by the collision with the central portion of the No. 27, the behavior of the diffused exhaust gas flow swirls, and a small swirl flow α (swirl flow) swirling along the flow direction of the exhaust gas is generated. . The small spiral flow α group swirling around the through hole 26 becomes a spiral flow having a shape continuous along the inner peripheral surface of the body portion 6a, that is, a donut-shaped spiral flow β.

  As shown in FIG. 2, the injection nozzle 20 is provided on the wall surface opposite to the through hole 26 with the airflow generation chamber 25 interposed therebetween, here in the center of the end wall 27. Although not shown, the injection nozzle 20 is connected to a urea water supply unit configured by a urea aqueous solution tank or a urea aqueous solution pump for supplying a urea aqueous solution. The tip of the injection nozzle 20 has a spray portion 20a that sprays a urea aqueous solution in a hollow cone-like spray shape a at a wide angle. The spray part 20a protrudes from the center of the wall surface of the end wall 27 into the airflow generation chamber 25, which corresponds to the center part of the generated spiral flow β. Thus, the urea aqueous solution is sprayed from the spray unit 20a toward the donut-shaped spiral flow β generated around the spray unit 20a.

The urea aqueous solution has a combination of a donut-shaped swirl flow β formed on the inner peripheral surface of the barrel portion 6a and a structure in which the urea aqueous solution is sprayed at a wide angle to each part of the donut-shaped swirl flow β from the center side. A wide space of the casing 6 is used to allow mixing in the exhaust gas.
In addition, the outlet portion 5 communicating with the connection pipe 17 keeps the swirl flow α of the exhaust gas generated in the airflow generation chamber 25 while maintaining the center of the airflow generation chamber 25 in the outflow point, for example, the peripheral wall of the airflow generation chamber 25. It is formed at a passing point. As a result, the exhaust gas can be guided to the SCR 14 through the connecting pipe 17 while maintaining the small spiral flow α (swirl flow).

According to such a mixer structure, the urea aqueous solution is sufficiently mixed with the exhaust gas by the diffusion effect brought about by the donut-shaped spiral flow β generated in a wide area in the casing 6.
That is, the doughnut-shaped spiral flow β is generated by the exhaust gas flow converged by passing through the through hole 26 colliding with the center of the end wall 27 as shown in FIGS. The diffused exhaust gas flow is generated by receiving the exhaust gas flow passing through the through hole 26 and swirling in the exhaust gas circulation direction. Specifically, the donut-shaped spiral flow β is formed by a small spiral flow α group generated on the circumferential side of the air flow generation chamber 25 at this time.

On the other hand, as shown in FIGS. 1 to 3, the urea aqueous solution forms the same swirl flow β from the center of the doughnut-shaped swirl flow β from the spray portion 20 a in a hollow cone-shaped spray shape a. Sprayed toward the small swirl flow α.
Then, the urea aqueous solution is sufficiently diffused in the exhaust gas swirling in the wide space inside the trunk portion 6a. Thereby, urea aqueous solution is mixed with waste gas, ensuring the opportunity to contact waste gas sufficiently. Thus, the urea aqueous solution is hydrolyzed by the exhaust heat of the exhaust gas and the water vapor in the exhaust gas to become ammonia. Subsequently, as shown in FIG. 3, the exhaust gas is guided from the outlet 5 to the SCR 14 while maintaining the spiral flow α, and the hydrolysis of the urea aqueous solution further proceeds.

  Accordingly, when the doughnut-shaped spiral flow β and the wide-angle spray are combined, the chance of contact between the urea aqueous solution and the exhaust gas can be greatly increased, so that the urea aqueous solution serving as the reducing agent and the exhaust gas can be sufficiently mixed. Thereby, ammonia is sufficiently generated and the SCR 14 can function sufficiently. In particular, the donut-shaped spiral flow β is a spiral flow that is generated by maximally utilizing the space in the body portion 6a of the casing 6, so that the opportunity of sufficient contact between the aqueous urea solution and the exhaust gas is ensured and sufficient mixing is achieved. We can expect results.

  Moreover, since the urea aqueous solution is sprayed from the spraying portion 20a to the doughnut-shaped spiral flow β in a hollow cone-like spray shape a, it is possible to secure many opportunities for contact between the urea aqueous solution and the exhaust gas. Can be mixed effectively. In addition, since the outlet portion 5 is provided at a point where the exhaust gas flows out while maintaining the swirl flow α, the mixing of the urea aqueous solution and the exhaust gas can be continued using the path from the casing 6 to the SCR 14, which is further effective. In particular, the urea aqueous solution and the exhaust gas can be mixed.

In particular, the air flow generation chamber 25 that brings about such an effect is only required to install the partition wall 27 having the through holes 26 in the casing 6 and has a simple structure.
FIG. 5 shows a second embodiment of the present invention.
In the present embodiment, the outlet 12 of the casing 13 is not simply formed on the peripheral wall of the airflow generation chamber 25 as in the first embodiment, but the tangential direction of the airflow generation chamber 25 among the peripheral walls of the airflow generation chamber 25. It is formed at the point.

Even if it does in this way, exhaust gas can be made to flow out, maintaining spiral flow (alpha), and there exists an effect similar to 1st Embodiment.
However, in the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
Note that the present invention is not limited to any of the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention. For example, in any of the above-described embodiments, the air flow generation chamber 25 has a structure in which the partition wall 27 is provided so as to partition the inside of the casing 6, but in order to easily generate a donut-shaped spiral flow, for example, in FIG. As shown by the two-dot chain line, an arcuate guide surface portion 30 may be provided on the outer peripheral wall surface of the airflow generation chamber 25 (annular flat chamber). Moreover, although embodiment mentioned above mentioned what applied this invention to the exhaust gas purification apparatus using DPF7, the front | former stage oxidation catalyst 8, SCR14, and the back | latter stage oxidation catalyst 15, it does not restrict to this but comprises using another catalyst. The present invention may be applied to an exhaust gas purification apparatus, and in short, any exhaust gas purification apparatus having a structure in which a reducing agent is sprayed into exhaust gas may be used.

2 Exhaust purification device 4 Inlet part 5 Outlet part 6 Casing 6a Body part 14 Ammonia selective reduction type NOx catalyst (purification catalyst)
17 Connection pipe (passage)
20 Urea water injection nozzle (spray nozzle)
23 Exhaust receiving chamber 23a End wall (other end wall)
25 Airflow generation chamber 26 Through hole (converging through hole)
27 Bulkhead α Small spiral flow β Donut-shaped spiral flow

Claims (1)

Exhaust gas from an internal combustion engine having a casing that circulates exhaust gas of the internal combustion engine from one end side to the other end side through the body portion and leads from the outlet portion to the purification catalyst, and in which the reducing agent is sprayed into the exhaust gas from the upstream side of the purification catalyst A purification device,
In the casing, there is provided an air flow generation chamber that changes the exhaust gas flow from one end side into a donut-shaped spiral flow in which a small spiral flows along the circumferential direction of the inner surface of the body portion of the casing,
On the wall surface on the other end side of the air flow generation chamber, there is a spray nozzle for spraying a reducing agent required for the operation of the purification catalyst in a wide angle toward the donut-shaped spiral flow generated on the inner surface of the body portion from the center side. provided it is,
The air flow generation chamber is configured by providing a partition wall having a converging through hole in the center at a point away from the other end wall of the casing, and the exhaust gas flow converged by passing through the converging through hole is the other end wall. Diffusing to the surroundings by collision with the partition wall, and in the space between the partition wall and the other end wall, a small spiral flow generates a donut-shaped spiral flow that continues along the circumferential direction of the inner surface of the body part,
The spray nozzle has a spray portion disposed in the center of the wall surface on the other end side of the air flow generation chamber, and the reducing agent is generated from the spray portion in a hollow cone-shaped spray shape and is generated around the spray portion. Shall spray toward the spiral flow of
An exhaust gas purification apparatus for an internal combustion engine , wherein the outlet portion of the casing is provided at a point on the peripheral wall of the airflow generation chamber where exhaust gas flows out while maintaining a spiral flow .

Images