JP4407843B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine having a structure for injecting fuel required for reaction of a catalyst.

To purify exhaust gas from diesel engine vehicles (vehicles), in order to prevent NOx (nitrogen oxides) and PM (particulate matter) contained in the exhaust gas of diesel engines from being released into the atmosphere, An exhaust gas purifier combined with a selective reduction type 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 injection valve (which adds a reducing agent) for injecting fuel required for the reaction of the catalyst is provided on the upstream side, 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 injection valve is provided in an exhaust pipe portion, for example, a bent portion, just upstream of the catalyst as in Patent Document 1. For this reason, it is difficult to earn a distance for mixing the fuel and the exhaust gas between the fuel injection valve and the catalyst.

The reason why it is difficult to increase the distance for mixing the fuel and the exhaust gas due to the installation of the fuel injection valve and the catalyst is not limited to the case where there is a bend, but is also found in the exhaust gas purification apparatus having no bend.
As a countermeasure, an exhaust gas purifying apparatus having a structure in which a fuel injection valve is arranged at a point away from the exhaust pipe part 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

However, as in the above, there are circumstances in which it is difficult to earn a distance for mixing the fuel and the exhaust gas due to restrictions on the installation of the fuel injection valve and the catalyst.
Therefore, it is difficult for the exhaust gas purification device to sufficiently mix the injected fuel and the exhaust gas. For this reason, it is difficult to supply uniformly atomized fuel to the catalyst, and there is a problem that the catalyst cannot sufficiently perform its function.

  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 according to claim 1 adds an additive to the exhaust pipe portion immediately upstream of the catalyst so as to inject the downstream from the direction intersecting the exhaust gas flow flowing in the exhaust pipe portion. A cross section of the exhaust pipe portion is provided in the upstream exhaust pipe portion intersecting the injection flow of the additive injected from the additive injection valve, and the injection flow intersects the exhaust gas flow. An exhaust gas guiding portion having a shape equivalent to the side view seen from above was formed.

  According to the same configuration, the exhaust gas guide portion causes the exhaust gas flow path to have the same shape as the side view of the injected flow of the injected additive, so the exhaust gas is distributed all over the side surface of the injected fuel additive. As a result, an opportunity for sufficient contact between the exhaust gas and the additive is provided. As a result, the exhaust gas and the additive are sufficiently mixed, and the additive uniformly mixed with the exhaust gas is supplied to the catalyst even if the necessary distance between the additive injection valve and the catalyst is not ensured. The

According to the second aspect of the present invention, the exhaust gas guiding portion is configured to inject the injection gas in order to distribute the exhaust gas flow velocity in accordance with the flow velocity distribution of the additive injection flow so as to promote uniform mixing of the additive and the exhaust gas. In accordance with the shape that expands toward the tip of the flow, it was formed with a channel cross-sectional shape in which the upstream side of the jet flow was thin and the downstream side of the jet flow was thick.
In the invention according to claim 3, the exhaust pipe portion upstream from the catalyst is provided with an injection flow of the additive so that the additive and the exhaust gas can be sufficiently mixed while injecting the additive into a predetermined position. The exhaust gas guiding part is formed from the exhaust pipe part on the upstream side that intersects the injection flow of the additive in the exhaust pipe part. This configuration provides an opportunity for sufficient contact between the additive and the exhaust gas while suppressing the deflection of the jet flow caused by the exhaust gas flow and injecting the additive to a predetermined position.

  In the invention according to claim 4, the exhaust pipe portion upstream from the catalyst is provided with an additive so that the additive and the exhaust gas can be sufficiently mixed while injecting the additive into a predetermined position by another method. The exhaust gas guiding portion was formed from an upstream exhaust pipe portion intersecting with the additive injection flow in the exhaust pipe portion. The same configuration provides the opportunity for the additive and the exhaust gas to contact sufficiently while deflecting the jet flow with the exhaust gas flow and injecting the additive to a predetermined position.

According to a fifth aspect of the present invention, in order to prevent the deflected jet flow from affecting the exhaust pipe portion, the exhaust pipe portion on the downstream side that intersects with the additive jet flow has no exhaust gas. An escape portion was provided to avoid contact with the jet flow deflected by the collision.
The invention described in claim 6 employs a structure in which a predetermined flow passage area is kept constant from the upstream side of the exhaust pipe portion in the exhaust gas guiding portion so that the output of the engine does not further decrease.

According to the first aspect of the present invention, since the exhaust gas flow is distributed over the injection flow of the additive by the exhaust gas guiding portion, the exhaust gas of the exhaust gas flow and the additive of the injection flow are sufficiently brought into contact with each other. Can give an opportunity.
Therefore, the exhaust gas and the additive can be sufficiently mixed, and the additive uniformly mixed with the exhaust gas is supplied to the catalyst even if the distance necessary for mixing is not ensured between the additive injection valve and the catalyst. be able to. As a result, the function of the catalyst can be sufficiently exerted.

  According to the invention of claim 2, the flow rate of the additive and the exhaust gas after the collision is such that the upstream side where the penetration force is strong in the jet flow collides with the high flow rate exhaust gas whose flow rate is increased at the narrow flow path cross-section. The downstream side where the penetration force is weak collides with the low flow rate exhaust gas whose flow rate is reduced at the cross section of the thick channel, thereby promoting the uniform mixing of the additive and the exhaust gas. It can be fed to the catalyst.

According to the invention of claim 3, the exhaust gas and the additive can be sufficiently mixed while following the method of injecting the additive to a predetermined position while suppressing the deflection of the injection flow.
According to the invention of claim 4, the exhaust gas and the additive can be sufficiently mixed while following the method of deflecting the injection flow with the exhaust gas flow and injecting the additive into a predetermined position. it can.

According to the invention of claim 5, even if the jet flow is deflected by the exhaust gas flow, the escape portion does not allow the additive of the deflected jet flow to touch the wall surface of the exhaust pipe portion, so that good mixing is promised. Is done.
According to the invention of claim 6, since the exhaust pipe portion has a constant passage area from upstream to the exhaust gas guiding portion, the passage resistance does not increase and the engine output does not decrease.

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, 1 is an engine body of a diesel engine, 1a is an exhaust manifold (only part of which is shown), and 2 is a turbocharger connected to the outlet of the exhaust manifold 1a, for example, a turbocharger. Show.

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 (additive injection) for supplying fuel for catalytic reaction as an additive to the oxidation catalyst 5 described later. Valve) 23 is used in combination. 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 cylindrical housing 17 that houses the oxidation catalyst 5 of the catalytic converter 6 has an inlet portion 17a that is bent at the upper side and connected to the upper turbocharger 2 as shown in FIG. ing. Note that the outlet portion 17b communicating with the lower catalytic converter 9 is disposed downward. The housing 17 forms a bent part 15a in the exhaust pipe part 15 at a point immediately after the exhaust side of the diesel engine. A catalyst installation space is secured in a portion immediately below the bent portion 15a. The oxidation catalyst 5 is installed at 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, a wall portion on the outer peripheral side downstream of the bent portion 15 a or the bent portion 15 a in order to inject fuel required for the catalytic reaction to the oxidation catalyst 5. It has been. The fuel addition valve 23 has a fuel injection part for injecting fuel at the tip part. The fuel addition valve 23 is installed at the end of the cylindrical portion 24 that branches off from the outer peripheral portion downstream of the bent portion 15a and extends outward using the mounting flange 24a and the pedestal 25. Thereby, the fuel injection part at the tip of the fuel addition valve 23 faces the fuel injection path 24 b formed in the internal space of the cylindrical part 24. The fuel injection path 24b is inclined and extends in the direction opposite to the bending direction of the bent portion 15a, and the outlet end is directed from the center of the inlet end surface of the oxidation catalyst 5 toward the end (the inlet portion 17 side). Thereby, the fuel for the reaction of the oxidation catalyst 5 is injected from the point away from the exhaust gas flow into the oxidation catalyst 5 from the direction intersecting with the exhaust gas flow passing through the bent portion 15a. Specifically, as shown in FIG. 1, the fuel is formed in the downstream direction, that is, in front of the inlet end surface of the oxidation catalyst 5 from the direction of the angle θ1 that intersects the exhaust gas flow direction a at an acute angle. It is made to inject toward the mixing chamber 19 currently made. Thus, the downstream portion where the penetration force of the injection flow α is weakened collides with the exhaust gas at a point immediately upstream from the oxidation catalyst 5. Reference numeral 25 a denotes a cooling water channel formed inside the pedestal 25.

  On the other hand, in the exhaust pipe portion upstream from the oxidation catalyst 5, there is a point intersecting the fuel injection flow α injected from the fuel addition valve 23, for example, the exhaust pipe portion S in the region from the bent portion 15 a to the mixing chamber 19. An exhaust gas guiding unit 28 is provided. As shown in the cross-sectional view shown in FIG. 2 and the perspective view of FIG. 3, the exhaust gas guiding section 28 has a cross-sectional shape of the exhaust pipe portion S that intersects the jet flow α and a horizontal cross-section that intersects the exhaust gas flow. It becomes a shape equivalent to the injection area | region of the side view of the injection flow (alpha) seen from the direction. Specifically, the cross-sectional shape of the flow path of the exhaust pipe portion S is formed in substantially the same fan shape as the downstream shape obtained by projecting the jet flow α from the lateral direction. Thus, the exhaust gas guiding portion 28 has a flow passage cross-sectional shape in which the upstream portion of the injection flow α is narrow and the opposite downstream portion is thick, following the shape of the injection flow α that expands toward the tip. Have. Reference numeral 28a in FIG. 2 indicates a thin channel cross-sectional portion, and 28b indicates a thick channel cross-sectional portion. The exhaust gas guiding section 28 distributes the exhaust gas flow of the exhaust gas guiding section all over the injection flow of the additive to give an opportunity to make sufficient contact with the exhaust gas.

The flow passage area in the section from the inlet portion 17a that is the upstream end of the exhaust pipe portion 15 to the fuel mixing portion 28 is kept constant at a predetermined flow passage area. Of course, up to the exhaust gas guiding section 28, the cross-sectional shape is gradually changed to be the same as the jet flow α, so that unnecessary passage resistance is not generated.
The exhaust pipe portion downstream from the exhaust gas guiding portion 28 is shaped so as to expand in the radial direction. By the expanding portion 29 that expands, the fuel and exhaust gas that have finished the collision are supplied to the inlet end face of the oxidation catalyst 5 while being expanded in the radial direction. As the shape of the enlarged portion 29, a trumpet shape (bell mouth shape) in addition to the conical shape is effective for supplying the oxidation catalyst 5 with a uniform distribution.

  The fuel injected from the fuel addition valve 23 generates a reducing agent by the reaction of the oxidation catalyst 5, and the reducing agent removes NOx and SOx stored in the NOx trap catalyst 8. This is used to burn and remove the PM collected by the particulate filter 11 by the heat obtained by the above reaction. Therefore, the fuel addition valve 23 is used when a catalytic reaction such as NOx and SOx reduction removal and 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.

Next, the operation of the exhaust gas purification device 3 configured as described above will be described.
During operation of the diesel engine, exhaust gas exhausted from the diesel engine is, as shown in FIG. 1, exhaust manifold 1a, turbocharger 2, bent portion 15a, exhaust gas guiding portion 28, oxidation catalyst 5, NOx trap catalyst 8 and It is exhausted to the outside air through the particulate filter 11.

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.
Assume that it is time to remove the stored NOx and SOx and the 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 passes through the fuel injection path 24b as shown in FIGS. It is injected into the exhaust gas stream flowing in S. Thus, the fuel of the injection flow α and the exhaust gas of the exhaust gas flow collide with each other.

At this time, the exhaust pipe portion S that intersects from the upstream side that intersects with the downstream portion where the penetration force of the injection flow α weakens has an exhaust having a flow path cross section substantially the same shape as the injection region viewed from the lateral direction of the injection flow α. The gas guide 28 is formed. Therefore, the exhaust gas that has passed through the exhaust gas guiding portion 28 passes through the additive injection flow α while being distributed throughout.
This provides an opportunity for the exhaust gas of the exhaust gas stream and the fuel of the injection stream α to be in full contact. Thus, the exhaust gas and the fuel are in contact with each other, and the exhaust gas and the fuel are sufficiently mixed.

  At this time, the flow rate of the fuel and the exhaust gas is such that the fuel in the upstream injection flow α having a strong penetrating force close to the fuel addition valve 23 collides with the high flow rate exhaust gas whose flow rate is increased in the narrow flow path cross-sectional portion 28a, Since the fuel of the downstream injection flow α having a weak penetration force far from the fuel addition valve 23 collides with the low flow rate exhaust gas whose flow rate is reduced in the thick channel cross-sectional portion 28b, uniform mixing of the additive and the exhaust gas is performed. Is further obtained. The uniformly mixed fuel and exhaust gas travel toward the oxidation catalyst 5 while expanding in the radial direction by the expanding portion 29.

Here, since the exhaust gas flow and the injection flow α intersect at an acute angle to suppress the deflection of the injection flow α caused by the exhaust gas flow, the mixed fuel and the exhaust gas are predetermined in the oxidation catalyst 5. It is supplied to a position, for example, approximately the center of the inlet end face.
Therefore, the formation of the exhaust gas guiding portion 28 enables the fuel uniformly mixed with the exhaust gas to be supplied to the catalyst even if the distance necessary for mixing between the fuel addition valve 23 and the oxidation catalyst 5 is not ensured.

  Therefore, the function of the oxidation catalyst 5 can be sufficiently exhibited using the exhaust gas guiding portion 28. Of course, when the enlarged portion 29 is used in combination, the fuel can be supplied to the oxidation catalyst 5 with a more uniform distribution. In addition, the exhaust gas guiding portion 28 is formed so as to keep a predetermined flow passage area constant from the upstream side of the exhaust pipe portion 15, so that the flow passage resistance of the exhaust pipe portion 15 does not increase and the engine output decreases. Is suppressed.

In particular, when the exhaust gas guiding portion 28 is employed in an injection structure that makes the injection flow α intersect the exhaust gas flow at an acute angle, the exhaust flow can be sufficiently exhausted while following the method of injecting fuel to a predetermined position while suppressing the deflection of the injection flow α. Gas and fuel can be mixed.
4 and 5 show a second embodiment of the present invention.
The present embodiment is not an exhaust gas purification device having a structure in which the exhaust gas flow intersects the injection flow α at an acute angle as in the first embodiment, but the exhaust gas flow intersects the injection flow α substantially perpendicularly. The present invention is applied to an exhaust gas purification apparatus having a structure as described above.

  Specifically, the exhaust gas purification apparatus of this embodiment determines the injection direction of the fuel addition valve 23 at a point away from the oxidation catalyst 5, as in the first embodiment. In the exhaust pipe portion upstream from the oxidation catalyst 5, a path toward the oxidation catalyst 5 is formed so as to intersect the fuel injection flow α injected from the fuel addition valve 23 in a substantially vertical direction. Thus, contrary to the first embodiment, the injection flow α is pushed by the exhaust gas flow, the injection flow α is deflected from the initially deviated position to a desired point, and the fuel is injected to a predetermined position. . In the exhaust pipe portion upstream from the oxidation catalyst 5, the exhaust pipe portion S that intersects from the upstream immediately intersecting the injection flow α from the fuel addition valve 23 is similar to that in the first embodiment, as shown in FIG. An exhaust gas guiding portion 28 is provided in which the cross section of the flow path of the exhaust pipe portion as shown in the cross-sectional view is substantially the same as the injection region in a side view of the injection flow α.

Accordingly, in the exhaust gas purifying apparatus that deflects the injection flow α by the exhaust gas flow and injects the fuel to a predetermined position contrary to the first embodiment, the exhaust gas guiding unit 28 is used while following the same method. Thus, the exhaust gas and the fuel can be sufficiently mixed.
In particular, in the second embodiment, in order to prevent the deflected jet flow α from affecting the exhaust pipe portion 15, the wall surface of the exhaust pipe portion T on the downstream side intersecting the jet flow α is used as a relief portion, for example, a bay. A shaped recess 30 is formed. By this recess 30, it is possible to prevent the deflected jet flow α from coming into contact with the wall surface of the exhaust pipe portion T and to promise good mixing of exhaust gas and fuel. Moreover, the wall surface of the recess 30 rebounds the exhaust gas colliding with the recess 30 as shown by the arrow b in the direction of the injection flow α and collides with the fuel of the injection flow α again. The promotion of mixing can be expected.

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, in the above-described embodiment, the exhaust gas flow intersects the injection flow at an acute angle or intersects vertically. However, the present invention is not limited to this, and the exhaust gas flow intersects the injection flow. As long as the structure is such that it can be applied to any exhaust gas purifying device. Further, for example, in the embodiment described above, 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 the 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 using a NOx trap catalyst as a catalyst immediately downstream of the bent portion, providing a particulate filter downstream thereof, and providing 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, provided with a NOx trap catalyst, an oxidation catalyst, and a particulate filter downstream thereof, and provided with an addition valve upstream of the NOx trap catalyst Or an exhaust gas purification device with an addition valve upstream of the selective reduction catalyst or particulate filter. It may be applied to the Ming.

  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.

  Moreover, in embodiment mentioned above, although demonstrated using cone shape as the injection shape of the fuel addition valve 23, the additive injection valve which expands in flat and fan shape, or the additive injection valve from which an additive is injected from several injection holes But you can. When there are a plurality of injection holes, the outline of the plurality of injection flows is an injection region.

1 is a partially sectional side view showing a structure of an exhaust gas purification apparatus according to a first embodiment of the present invention. Sectional drawing in the exhaust-gas induction | guidance | derivation part which follows the AA line in FIG. The perspective view which shows the exhaust-gas induction | guidance part roughly. The sectional side view which shows the principal part of the exhaust-gas purification apparatus which concerns on the 2nd Embodiment of this invention. Sectional drawing which follows the BB line in FIG.

Explanation of symbols

1 Engine body 3 Exhaust gas purification device 5 Oxidation catalyst (catalyst)
15 Exhaust pipe portion 23 Fuel addition valve 28 Exhaust gas guide portion 30 Recessed portion (relief portion)
α jet flow

Claims (6)

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 immediately upstream of the catalyst and injects an additive supplied to the catalyst downstream from a direction intersecting with an exhaust gas flow flowing in the exhaust pipe portion;
Of the exhaust pipe portion upstream from the catalyst, the exhaust pipe portion is formed in an exhaust pipe portion that intersects the injection flow of the additive injected from the additive injection valve. An exhaust gas purifying device for an internal combustion engine, comprising: an exhaust gas guiding portion having a shape equivalent to an injection region in a side view as viewed from a direction intersecting with a gas flow.   The exhaust gas guiding portion has a flow path cross-sectional shape in which the upstream side of the jet flow is narrowed and the downstream side of the jet flow is thick, following a shape expanding toward the tip of the jet flow. Item 6. An exhaust gas purifying device for an internal combustion engine according to Item 1. The exhaust pipe portion upstream from the catalyst is configured to intersect the injection flow of the additive at an acute angle toward the catalyst,
3. The internal combustion engine according to claim 1, wherein the exhaust gas guiding portion is formed from an exhaust pipe portion on an upstream side intersecting an injection flow of the additive in the exhaust pipe portion. Exhaust gas purification device. An exhaust pipe section upstream from the catalyst is configured to intersect the injection flow of the additive in a direction substantially perpendicular to the catalyst,
3. The internal combustion engine according to claim 1, wherein the exhaust gas guiding portion is formed from an exhaust pipe portion on an upstream side intersecting an injection flow of the additive in the exhaust pipe portion. Exhaust gas purification device.   Of the exhaust pipe portion, a downstream exhaust pipe portion intersecting with the injection flow of the additive is provided with a relief portion that avoids contact with the jet flow deflected by collision with the exhaust gas. The exhaust gas purification device for an internal combustion engine according to claim 4.   The internal combustion engine according to any one of claims 1 to 5, wherein the exhaust gas guiding portion is formed so as to keep a predetermined flow path area constant from an upstream side of the exhaust pipe portion. Engine exhaust gas purification device.

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