JP2009156075A - 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 that sufficiently mixes additive and exhaust gas together even when a distance required for mixing is not secured between an additive injection valve and a catalyst. <P>SOLUTION: The exhaust emission control device for the internal combustion engine comprises a swirl flow generating part 30 provided in an exhaust pipe portion 15c on the upstream side of the catalyst 5 for generating the swirl flow of exhaust gas moving toward the catalyst. In this construction, the swirl flow of the exhaust gas generated by the swirl flow generating part 30 brings a residing time for the exhaust gas to give sufficient contact to the exhaust gas and the additive before being introduced into the catalyst 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine having a structure for injecting an additive supplied to a catalyst.

For purification of exhaust gas from diesel engine vehicles (vehicles), NOx trap catalyst or selection is used to prevent NOx (nitrogen oxide) and PM (particulate matter) contained in the exhaust gas of diesel engine from being released into the atmosphere. An exhaust gas purification device combined with a reduced NOx catalyst, a diesel particulate filter, or the like is used.
In such an exhaust gas purification device, a catalyst such as an oxidation catalyst, a NOx trap catalyst or a selective reduction type NOx catalyst, called a pre-stage catalyst, is provided in an exhaust pipe portion for exhausting exhaust gas exhausted from the engine to the outside. A structure in which a fuel addition valve (injecting a reducing agent) for injecting fuel required for the reaction of the catalyst is provided upstream, for example, upstream of the oxidation catalyst.

In such an exhaust gas purifying apparatus, in order for the front catalyst to react efficiently, it is important to sufficiently mix the injected fuel and the exhaust gas before the fuel flows into the front catalyst.
For this purpose, it is required to secure a sufficient fuel flight distance in the section from the fuel addition valve to the catalyst.

However, in order to increase the purification efficiency when the engine is cold as recently, for example, as disclosed in Patent Document 1, it is required to secure a catalyst installation location near the exhaust side of the engine. , It is difficult to ensure the flight distance of fuel.
That is, in order to make use of the installation of this catalyst, a fuel addition valve must be installed in the exhaust pipe portion immediately upstream of the catalyst as in Patent Document 1, and fuel and exhaust gas are mixed in the vicinity of the engine. It is difficult to earn distance.

As a countermeasure, there is an exhaust gas purifying device having a structure in which a fuel addition valve is disposed at a point away from the exhaust pipe portion and fuel is injected from a point away from the exhaust gas flow as disclosed in Patent Document 2. Proposed.
JP 2005-127260 A JP 2004-44483 A

In this exhaust gas purification device, in order to sufficiently mix the injected fuel and the exhaust gas before the fuel flows into the catalyst, a fuel injection path that branches from the exhaust pipe portion and extends considerably far is necessary. It is. However, it is difficult to secure such a fuel injection path near the engine.
For this reason, it has been difficult to sufficiently mix the injected fuel and the exhaust gas near an engine with many restrictions, and it has been difficult to supply uniform fuel to the catalyst.

  Accordingly, an object of the present invention is to provide an exhaust gas purification device for an internal combustion engine that can sufficiently mix the additive and the exhaust gas even if the distance necessary for mixing is not ensured between the additive injection valve and the catalyst. Is to provide.

In order to achieve the above object, the invention described in claim 1 is provided with a swirling flow generating portion for generating a swirling flow in the exhaust gas toward the catalyst in the exhaust pipe portion upstream of the catalyst.
According to this configuration, the swirl flow of the exhaust gas generated by the swirl flow generation unit provides a time for the exhaust gas to stay and provides an opportunity for sufficient contact between the exhaust gas and the additive.
In the invention according to claim 2, the swirl flow generator is configured so that the injection flow of the additive injected from the additive injection valve is the exhaust gas and the exhaust gas so that the exhaust gas and the additive are most effectively brought into contact with each other. It was provided in the mixed exhaust pipe part.

The invention according to claim 3 adopts a configuration in which a twisted portion for changing the flow of the exhaust gas into a spiral flow is provided in the exhaust pipe portion in the swirl flow generating portion so as to generate a swirl flow with a simpler structure. did.
In the invention according to claim 4, the exhaust gas is led from the upstream to the tangential direction of the inner peripheral surface of the exhaust pipe portion so that the swirl flow is generated in a simple structure by another method. A configuration using a tangential flow passage that induces a spiral flow is adopted.

According to the first aspect of the present invention, the exhaust gas stays in the swirling flow of the exhaust gas upstream of the catalyst, so that the exhaust gas and the additive are sufficiently brought into contact with each other before being introduced into the catalyst. Can give an opportunity.
Therefore, even if the distance necessary for mixing is not ensured between the additive injection valve and the catalyst, the exhaust gas and the additive can be sufficiently mixed. In addition, since the additive and the exhaust gas are directed to the catalyst while being diffused to the surroundings by the swirling flow, the mixed exhaust gas and the additive can be uniformly supplied to the catalyst. As a result, the function of the catalyst can be sufficiently exerted.

According to the second aspect of the present invention, it is possible to provide an opportunity for the exhaust gas and the additive to contact each other effectively.
According to the third and fourth aspects of the present invention, it is possible to generate a swirling flow with a simple structure.

The present invention will be described below based on the first embodiment shown in FIGS.
FIG. 1 shows an exhaust system of an internal combustion engine, for example, a diesel engine. In the figure, reference numeral 1 denotes an engine body of a diesel engine, 1a denotes an exhaust manifold (only part of which is shown), and 2 denotes a turbocharger connected to an outlet of the exhaust manifold 1a.

An exhaust gas purification device 3 is provided at the exhaust outlet of the turbocharger 2. In this exhaust gas purification device 3, for example, NOx (nitrogen oxide) in exhaust gas is occluded, and NOx removal system 3a for reducing and removing NOx occluded regularly and PM (particulate matter) are collected. The apparatus which combined PM collection system 3b to be used is used.
For example, the NOx removal system 3a includes a catalytic converter 6 in which an oxidation catalyst 5 (corresponding to the catalyst of the present application), which is connected in a downward direction from an exhaust outlet of the turbocharger 1a, is incorporated. A catalytic converter 9 having a built-in NOX trap catalyst 8 connected laterally after the catalytic converter 6 and a fuel addition valve for supplying fuel (additive) for catalytic reaction to the oxidation catalyst 5 described later (addition of the present application) The composition which is equivalent to the agent injection valve) 23 is used. The collection system 3b employs a configuration in which a catalytic converter 12 having a particulate filter 11 incorporated therein is connected to the catalytic converter 9. An exhaust pipe portion 15 that guides the exhaust gas exhausted from the diesel engine (engine body 1) to the outside is constituted by the catalytic converters 6, 9, 12 and the connection portion 13 connecting the converters.

  Among these, the vertical cylindrical housing 17 that houses the oxidation catalyst 5 of the catalytic converter 6 is formed, for example, in an approximately L shape on the upper side, and the inlet portion 17a connected to the upper turbocharger 2 is disposed sideways. I am letting. Note that the outlet portion 17b communicating with the lower catalytic converter 9 is disposed downward. The housing 17 forms a bent portion 15a bent in an L shape at a point immediately after the exhaust side of the diesel engine in the exhaust pipe portion 15. The oxidation catalyst 5 is housed at a point immediately below the bent portion 15a (a point close to the exhaust side of the diesel engine).

  The fuel addition valve 23 is provided at a point immediately above the oxidation catalyst 5, for example, on the outer peripheral side of the bent portion 15a, in order to perform fuel injection required for the catalytic reaction to the oxidation catalyst 5. The fuel addition valve 23 has a fuel injection part for injecting fuel at the tip part. From the outlet side of the bent portion 15a, as shown in FIG. 3, a cylindrical portion 24 extending in a direction away from the bent portion 15a, that is, outward is branched. The fuel addition valve 23 is installed at the distal end portion of the cylindrical portion 24 using an attachment flange 24 a and a pedestal 25. Thus, the fuel injection portion at the tip of the fuel addition valve 23 faces the fuel injection path 24 b formed in the internal space of the cylindrical portion 24. The fuel injection path 24b is inclined to the side opposite to the bending direction of the bent portion 15a, and the entire fuel injection path is directed to the mixing chamber 17c formed by the downstream extension portion and the inlet end face of the oxidation catalyst 5. Thus, the fuel addition valve 23 is installed so as not to be directly exposed to the high-temperature exhaust gas. In addition, a cooling water passage is formed in the base 25 to protect the fuel addition valve 23 from heat (water cooling).

  The fuel injected from the fuel addition valve 23 generates a reducing agent by the reaction of the oxidation catalyst 5, and the NOx occluded in the NOX trap catalyst 8 is reduced by this reducing agent, or obtained by the reaction of the oxidation catalyst 5. It is used to burn and remove PM collected by the particulate filter 11 by the heat generated. Therefore, the fuel addition valve 23 is used when a catalytic reaction such as NOx or SOx reduction or PM combustion removal is required during operation of the diesel engine by a control unit that controls the diesel engine, for example, an ECU (not shown). Fuel is injected.

  On the other hand, the swirl flow generating portion 30 is provided in the exhaust pipe portion upstream of the oxidation catalyst 5, for example, the exhaust pipe portion 15c on the outlet side of the bent portion 15a. The exhaust pipe portion 15 c is a portion where the fuel of the injection flow α injected from the fuel addition valve 23 collides with and mixes with the exhaust gas of the exhaust gas flow flowing in the exhaust pipe portion 15. As shown in FIGS. 2 and 3, the swirling flow generating unit 30 is configured by forming a twisted portion 31 in the exhaust pipe portion 15 c. Specifically, for example, the twisted portion 31 twists the tube portion from the lower end portion of the cylindrical portion 24 to the mixing chamber 17c in a spiral shape around the axis of the injection flow α injected from the fuel addition valve 23. A spiral passage structure is used. Due to the spiral passage formed by the twisted portion 31, the exhaust gas flow changes into a swirl flow while passing through the twisted portion 31. That is, the exhaust gas is diffused through the mixing chamber 17 c while generating a horizontal vortex from the upstream side, and then guided to the inlet end face of the oxidation catalyst 5.

By this swirl flow, the residence time of the exhaust gas is earned at a point where it is mixed with the injected fuel, and an opportunity to sufficiently contact the injected fuel is given.
That is, the operation of the exhaust gas purification device 3 configured as described above will be described. It is assumed that the diesel engine is now in operation.
The exhaust gas exhausted from the diesel engine at this time is exhausted to the outside air through the exhaust manifold 1a, the turbocharger 2, the bent portion 15a, the twisted portion 31, the oxidation catalyst 5, the NOX trap catalyst 8, and the particulate filter 11.

During this passage, NOx and SOx contained in the exhaust gas are occluded in the NOX trap catalyst 8, and PM is also collected by the particulate filter 11.
At this time, in the exhaust gas flow toward the mixing chamber 17c, a swirl flow is generated by the passage of the torsion part 31 as indicated by an arrow a in FIGS. The exhaust gas is introduced into the oxidation catalyst 5 through the mixing chamber 17c while maintaining its swirling flow and diffusing around.

Here, it is assumed that it is time to remove the stored NOx, SOx, and collected PM, and the fuel addition valve 23 is activated.
Then, the fuel for removing NOx, SOx, and PM from the fuel injection portion of the fuel addition valve 23 swirls in the exhaust pipe portion 15c through the fuel injection path 24b as shown in FIGS. Is injected into the exhaust gas stream. Thus, the injected fuel collides with the exhaust gas of the swirling exhaust gas flow, and the fuel of the injection flow α is mixed with the exhaust gas of the exhaust flow.

Here, since the exhaust gas stays in the exhaust pipe portion 15c due to swirling, the chance of coming into contact with the fuel is greatly increased.
Thereby, even if the distance from which the fuel and the exhaust gas are sufficiently mixed in the section from the fuel addition valve 23 to the oxidation catalyst 5 is not ensured, the opportunity of contact between the fuel and the exhaust gas caused by the swirling flow is increased. Thus, the fuel and the exhaust gas are sufficiently mixed before being introduced into the oxidation catalyst 5.

The mixed fuel and exhaust gas are supplied to the inlet end face of the oxidation catalyst 5 uniformly through the downstream mixing chamber 17 c while maintaining a swirling flow and spreading (diffusing) in the radial direction (periphery).
Therefore, the formation of the swirl flow generation unit 30 can uniformly supply the mixed fuel and the exhaust gas to the catalyst even if the necessary distance for mixing between the fuel addition valve 23 and the oxidation catalyst 5 is not ensured. As a result, the function of the oxidation catalyst 5 can be exhibited sufficiently.

In particular, the twisted portion 31 is provided in the exhaust pipe portion 17c where the injected fuel and the exhaust gas are mixed, so that the moment of contact with the fuel can be increased by making the most of the momentum of the swirling flow, and most effectively. Mixing of fuel and exhaust gas can be promoted.
In addition, for the generation of the swirling flow, a structure in which the twisted portion 30 is formed in the exhaust pipe portion on the upstream side of the oxidation catalyst 5 is adopted. In particular, if there is a bent portion 15a, the direction of the bent portion 15a can be diverted and the direction can be easily changed by the twisted portion 31, so that a swirl flow is likely to occur.

4 and 5 show a second embodiment of the present invention.
In this embodiment, the twisted portion 30 as in the first embodiment is not used to generate the swirl flow, but another method, that is, the exhaust gas is led out in the tangential direction to generate the swirl flow. The direction distribution part 40 is adopted.
Specifically, the tangential flow portion 40 has a cylindrical exhaust pipe portion 15c on the outlet side of the bent portion 15a as shown in FIGS. 4 and 5, for example. And the structure which made the base end part of the mouth part 42 which forms the inlet part 17a opened with respect to the point of the tangential direction on the internal peripheral surface of the cylindrical part 41 is used. As a result, the exhaust gas introduced into the cylindrical portion 41 swirls along the inner peripheral surface of the cylindrical portion 41 as shown by the arrow b in FIGS. Is induced.

Even with such a structure that generates a swirling flow, the residence time of the exhaust gas in the exhaust pipe portion 15c can be increased, and thus the same effect as that of the first embodiment can be obtained.
However, in FIGS. 4 and 5, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In addition, this invention is not limited to any embodiment mentioned above, You may implement in various changes within the range which does not deviate from the main point of this invention. For example, although the embodiment mentioned above gave the structure which generates a swirl flow using a twist part and a tangential circulation part, it may not be restricted to this but a swirl flow may be generated using other structures. In the above-described embodiment, the swirl flow generator is provided in the exhaust pipe portion where the exhaust gas flow and the injection flow are mixed. However, the swirl flow generator is not limited to this, and the swirl flow generator is provided at a point upstream from the fuel injection position. It may be provided.

  In addition, in the above-described embodiment, the exhaust gas purification device using the exhaust pipe portion having the bent portion has been described. However, the present invention is not limited thereto, and the present invention may be applied to an exhaust gas purification device having no bent portion. . Of course, in the above-described embodiment, an example is given in which the present invention is applied to an exhaust gas purification apparatus in which an oxidation catalyst is used as a catalyst immediately downstream of a bent portion, and a NOX trap catalyst and a particulate filter are provided downstream thereof. The exhaust gas purifying apparatus of other purification methods, for example, an exhaust gas that uses a NOX trap catalyst as a catalyst immediately downstream of the bent portion, has a particulate filter downstream thereof, and has an addition valve upstream of the NOX trap catalyst. Also in the gas purification device, an exhaust gas purification device using a NOX trap catalyst as a catalyst immediately downstream of the bent portion, a NOX trap catalyst, an oxidation catalyst, and a particulate filter provided downstream thereof, and an addition valve provided upstream of the NOX trap catalyst And an exhaust gas purification device equipped with a selective reduction catalyst or particulate filter directly downstream of the additive injection valve. It may be applied.

  Further, in the above-described embodiment, the fuel is used as the additive. However, any material may be used as long as it is supplied to the catalyst. For example, light oil, gasoline, ethanol, dimethyl ether, natural gas, propane gas, urea as a reducing agent. , Ammonia, hydrogen, carbon monoxide, etc. Further, a substance other than the reducing agent may be used. For example, air for cooling the catalyst, nitrogen, carbon dioxide, etc., air or ceria for promoting combustion removal of soot collected in the particulate filter, and the like may be used.

The perspective view which shows the exhaust-gas purification apparatus which concerns on the 1st Embodiment of this invention. FIG. 2 is a plan sectional view taken along line AA in FIG. 1. Sectional drawing which shows the structure of a rotational flow generation | occurrence | production part. The side view which carried out the partial cross section which shows the principal part of the exhaust-gas purification apparatus which concerns on the 2nd Embodiment of this invention. FIG. 5 is a plan sectional view taken along line BB in FIG. 4.

Explanation of symbols

1 Engine body 3 Exhaust gas purification device 5 Oxidation catalyst (catalyst)
15c Exhaust pipe part 23 Fuel addition valve (additive injection valve)
30 Rotating flow generating section 31 Torsion section 40 Tangential flow section

Claims (4)

An exhaust pipe that guides exhaust gas exhausted from the engine to the outside;
A catalyst housed in the exhaust pipe section;
An additive injection valve that is provided in an exhaust pipe portion upstream of the catalyst and supplies the additive to the catalyst;
An exhaust gas purifying apparatus for an internal combustion engine, comprising: a swirl flow generating portion that is provided in an exhaust pipe portion upstream of the catalyst and generates a swirl flow in the exhaust gas toward the catalyst.   2. The exhaust gas of the internal combustion engine according to claim 1, wherein the swirl flow generating portion is provided in an exhaust pipe portion where an additive injection flow injected from the additive injection valve is mixed with exhaust gas. Gas purification device.   3. The exhaust gas of an internal combustion engine according to claim 1, wherein the swirl flow generating portion has a twist portion that changes a flow of exhaust gas into a spiral flow in the exhaust pipe portion. 4. Gas purification device.   The swirl flow generating portion has a tangential flow portion in the exhaust pipe portion that induces a spiral flow by deriving exhaust gas from upstream in a tangential direction of the inner peripheral surface of the exhaust pipe portion. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2, wherein the exhaust gas purification apparatus is an internal combustion engine.

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