JP5093066B2 - Engine exhaust system structure - Google Patents

Description

  The present invention relates to an exhaust system structure of an engine.

Conventionally, by removing harmful substances contained in exhaust gas from diesel engines such as nitrogen oxide (NOx), carbon monoxide (CO), and particulate matter (hereinafter simply referred to as PM), exhaust gas is reduced. Various technologies for purification have been developed.
As an example, in Patent Document 1 below, as shown in FIG. 2 of the same document, there is a technique of injecting fuel (FE) from the fuel addition valve (20) into the exhaust pipe (2).
JP 2006-77691 A

However, in the technique of Patent Document 1, there is a possibility that the exhaust gas (EG) and the fuel (FE) cannot be sufficiently stirred.
Further, as in the technique of Patent Document 1, when the fuel addition valve (20) protrudes into the exhaust pipe (2), the fuel addition valve (20) is directly exposed to the heated exhaust gas (EG). It will be. For this reason, there exists a possibility that deterioration of a fuel addition valve (20) may accelerate | stimulate.

On the other hand, FIG. 6 shows a structure (trial structure) created in the process of creating the exhaust system structure of the engine of the present invention. The structure shown in FIG. 6 is hereinafter referred to as a prototype structure 100.
In this prototype structure 100, an exhaust connection pipe 101 formed in a substantially Y shape is provided.
An exhaust outlet (not shown) of a turbocharger (not shown) provided in an engine (not shown) is connected to one inlet 102 in the exhaust connection pipe 101.

An injector 104 that injects fuel into the exhaust connection pipe 101 is provided at the other inlet 103 of the exhaust connection pipe 101.
An exhaust passage 106 is connected to an outlet 105 in the exhaust connection pipe 101.
An oxidation catalyst 107 is provided in the exhaust passage 106, and a NOx trap catalyst 108 is disposed below the oxidation catalyst 107.

  Then, by injecting fuel from the injector 104 into the exhaust connection pipe 106, exhaust gas containing a relatively large amount of fuel components can be flowed into the oxidation catalyst 107 and the NOx trap catalyst 108. . Thus, the oxidation in the oxidation catalyst 107 is promoted, and the NOx component occluded in the NOx trap catalyst 108 is released from the oxidation catalyst 107 and the NOx trap catalyst 108 (so-called NOx purge is executed). It can be done.

Here, it is preferable that the fuel injected from the injector 104 does not adhere to the wall surface of the exhaust connection pipe 101. For this reason, the injector 104 is set to a penetrating force that does not adhere to the wall surface in the process in which the spray of injected fuel is diffused.
However, if the straightness of the injected fuel is ensured, the fuel and exhaust gas injected from the injector 104 are not sufficiently agitated in the exhaust connection pipe 106 and directly flow into the oxidation catalyst 107 and a part of the NOx trap catalyst 108. A situation will occur.

In other words, the fuel injected from the injector 104 is not sufficiently diffused and cannot pass through the oxidation catalyst 107 and the entire NOx trap catalyst 108 in a balanced manner. For this reason, the exhaust catalyst cannot be efficiently purified as a whole of the oxidation catalyst 107 and the NOx trap catalyst 108.
Further, the fuel that has flowed directly into a part of the oxidation catalyst 107 is vaporized in the oxidation catalyst 107 thereafter. At this time, the temperature of the oxidation catalyst 107 is partially lowered due to the heat of vaporization of the fuel, and the purification efficiency of the exhaust gas further decreases.

  On the other hand, an exhaust gas containing a high-concentration fuel component, that is, a region where exhaust gas in an extremely rich atmosphere flows (see symbol Fa in FIG. 6), or a fuel that has not been vaporized, is part of the oxidation catalyst 107 and the NOx trap catalyst 108. In a region where the liquid flows as it is (refer to reference numeral Fa in FIG. 6), a severe chemical reaction partially occurs, and the temperature distribution of the oxidation catalyst 107 and the NOx trap catalyst 108 is uneven.

This point will be described again with reference to FIGS. 7 and 8A to 8C.
Here, FIG. 7 shows a case where the horizontal cross section of the oxidation catalyst 107 or the NOx trap catalyst 108 (see symbols CS1, CS2, and CS3 in FIG. 6) is viewed from above. In FIG. 7, it is assumed that, in the portions indicated by P1 to P5, in the portions P1 and P2, exhaust gas in an extremely rich atmosphere flows or the fuel that has not been vaporized flows in a liquid state.

8A shows the temperature at the first horizontal cross section CS1 of the oxidation catalyst 107 shown in FIG. 6, and FIG. 8B shows the temperature at the second horizontal cross section CS2 of the oxidation catalyst 107 shown in FIG. 8C shows the temperature at the third horizontal section CS3 of the NOx trap catalyst 108 shown in FIG.
As shown in FIG. 8A, the portion P1 (see the alternate long and short dash line) and the portion P2 (see the alternate long and two short dashes line) in the first horizontal section CS1 of the oxidation catalyst 107 are caused by the heat of vaporization of the fuel adhering to the oxidation catalyst 107. It can be seen that it is locally cooled.

On the other hand, as shown in FIGS. 8B and 8C, in the second horizontal cross section CS2 of the oxidation catalyst 107 and the third horizontal cross section CS3 of the NOx trap catalyst 108, the portion P1 (see the alternate long and short dash line) ) And the portion P2 (refer to the two-dot chain line) are locally heated by heat (reaction heat) generated by oxidation of the fuel component.
As described above, the uneven temperature distribution in the oxidation catalyst 107 and the NOx trap catalyst 108 is caused by the fact that the exhaust gas in the rich atmosphere is not supplied in a well-balanced manner to the entire oxidation catalyst 107 and the NOx trap catalyst 108. For this reason, the exhaust gas purification efficiency by the oxidation catalyst 107 and the NOx trap catalyst 108 is lowered, and it becomes difficult to improve the exhaust gas performance.

  The present invention has been devised in view of such problems, and an object of the present invention is to provide an engine exhaust system structure that can further improve exhaust gas performance and contribute to environmental protection.

To achieve the above object, the fuel exhaust system structure for an engine according to the present invention, an exhaust system structure for an engine, which injects an exhaust passage connected to an exhaust port of the engine, the fuel in the exhaust passage A fuel colliding member that collides with the fuel injected from the fuel injection means and diffuses the fuel, and the exhaust passage is formed in a curved shape so that the exhaust gas discharged from the engine flows. the main passage and has a sub passage which fuel injected from the connected to the outer peripheral wall side of the curved portion of the main passage fuel injection means flows, the fuel struck member, the main passage and said to together and provided to the outer peripheral wall of the main passage at a connection portion near to the auxiliary passage, the fuel projected shape of the struck member is approximated a projection shape has been fuel injected by the fuel injection means this formed to have a shape that It is characterized in.

The exhaust system structure for an engine of the present invention, the fuel struck member is preferably extending perpendicular to the injection direction of the fuel by the fuel injection means.
The exhaust system structure for an engine of the present invention, both ends of the fuel the struck member is preferably supported each on the inner wall of the auxiliary passage.

The exhaust system structure for an engine of the present invention, the fuel struck member are preferably molded into a cylindrical or cylindrical shape.

The exhaust system structure for an engine of the present invention, the fuel struck member are preferably molded into a semi-cylindrical or semi-cylindrical shape.
The exhaust system structure for an engine of the present invention, the fuel struck member are preferably molded into a flat plate shape.

According to the exhaust system structure of the engine of the present invention, it is possible to promote the agitation of the fuel and the exhaust gas by diffusing the fuel in the exhaust passage, and contribute to environmental protection by further improving the exhaust gas performance. I can do it .
The projected shape of the fuel-impacted member is shaped to approximate the projected shape of the injected fuel.
Therefore, it is possible to efficiently make the fuel collide with the fuel collision member.
The fuel struck member is lever is shaped so as to extend perpendicular to the injection direction of the fuel efficiently fuel can be diffused.
Also, lever opposite ends of the fuel the struck member being respectively supported on the inner wall of the auxiliary passage, or bent fuel collision member, it is possible to prevent a situation in which or broken.
In addition, by forming the fuel-impacted member into a columnar or cylindrical shape, it is possible to prevent the increase in cost while improving the mountability of the fuel-impacted member in the exhaust passage and to appropriately diffuse the fuel in the exhaust passage. It can be made .
In addition, by forming the fuel-impacted member into a semi-column or semi-cylindrical shape, it is possible to prevent the flow of the exhaust gas from being obstructed while preventing an increase in cost, and to appropriately diffuse the fuel in the exhaust passage. I can do it .
In addition, by molding the fuel collision member into a flat plate shape, it is possible to prevent the flow of the exhaust gas from being obstructed while preventing an increase in cost, and to appropriately diffuse the fuel in the exhaust passage .

Hereinafter, an engine exhaust system structure according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating the overall configuration, and FIG. 2 is a schematic cross-sectional view taken along the line II-II in FIG. It is sectional drawing.
FIG. 3A is a graph schematically showing the air-fuel ratio when the fuel-impacted member (impactor) is disposed “outside” of the main passage (exhaust gas passage), and FIG. It is a graph which shows typically an air fuel ratio at the time of arranging a collision member "inside" a main passage.

As shown in FIGS. 1 and 2, a diesel engine (engine) 11 mounted on a vehicle 10 is provided with a turbocharger 12.
In addition, an inlet 15 of a first exhaust pipe (exhaust pipe) 14 is connected to the outlet 13 of the turbocharger 12. Hereinafter, expressions such as “upstream” or “downstream” are used, but these are based on the flow of exhaust gas discharged from the diesel diesel engine 11.

The turbocharger 12 has a turbine-compressor (not shown). By rotating the turbine-compressor with exhaust gas discharged from the diesel diesel engine 11, the turbocharger 12 can perform intake air supercharging of the diesel diesel engine 11. ing.
The first exhaust pipe 14 is a component formed in a substantially Y-shape having a main passage 31 and a sub-passage 32.

  Among these, the main passage 31 is a substantially L-shaped passage through which the exhaust gas discharged from the diesel diesel engine 11 flows. The main passage 31 has an inlet 15 connected to an exhaust port (not shown) of the diesel engine 11 via the turbocharger 12, and an outlet 16 connected to the inlet 18 of the second exhaust pipe 17. A portion of the main passage 31 formed in a curved shape is referred to as a curved portion 31c.

The sub passage 32 is a straight passage connected to the curved portion 31 c of the main passage 31. In addition, an injector (fuel injection means) 26 is provided on the protruding portion 32 b of the sub passage 32. The sub-passage 32 is configured such that the fuel F injected from the injector 26 flows through the sub-passage 32.
The second exhaust pipe 17 is provided with an oxidation catalyst (exhaust catalyst) 21, and a NOx trap catalyst (exhaust catalyst) 22 is provided downstream of the oxidation catalyst 21 and below the oxidation catalyst 21. .

Among these, the oxidation catalyst 21 is provided in the vicinity of the diesel diesel engine 11 so that the exhaust gas discharged from the diesel diesel engine 11 can flow into the oxidation catalyst 21 with a relatively high temperature. Yes. Further, the oxidation catalyst 21 contains noble metals such as platinum (Pt) and rhodium (Rh), and these noble metals oxidize carbon oxide (CO) and hydrocarbons (HC) contained in the exhaust gas to produce carbon dioxide. by chemically changing to carbon and (CO2) and water (H 2 _O), so that the exhaust gas can be purified.

Incidentally, the injection direction C ₂₆ of the fuel by the injector 26 is set to substantially match the center of the oxidation catalyst 21.
The NOx trap catalyst 22 contains an alkali metal (for example, barium (Ba)) as a NOx occlusion material, so that NOx in the exhaust gas can be occluded. Further, the NOx occlusion material can occlude NOx components in the exhaust gas when the exhaust gas is in a lean atmosphere, and can release the stored NOx into the exhaust gas when the exhaust gas is in a rich atmosphere. ing.

  In addition, the NOx occlusion material of the NOx trap catalyst 22 may occlude sulfur oxide (SOx), which is a reaction product of the sulfur component contained in the fuel and oxygen, instead of NOx. In order to release the SOx occluded in the NOx trap catalyst 22 from the NOx trap catalyst 22, the exhaust gas may be made rich as in the case of NOx.

The control for releasing NOx stored in the NOx trap catalyst 22 from the NOx trap catalyst 22 is referred to as NOx purge, and the control for releasing SOx stored in the NOx trap catalyst 22 from the NOx trap catalyst 22 is referred to as S purge.
An impactor (fuel covering) is disposed in the main passage 31, in the vicinity of the portion (connection portion) where the main passage 31 and the sub-passage 32 are connected, and in the vicinity of the outer peripheral wall 31 a of the curved portion 31 c. (Impact member) 30 is provided.

The impactor 30 is a component that causes the fuel F injected from the injector 26 to collide and diffuse the fuel F in the main passage 31.
Further, the impactor 30 is orthogonal direction to the injection direction C ₂₆ of the fuel F by the injector 26 (i.e., the paper depth direction of FIG. 1, the vertical direction in FIG. 2) is molded into a cylindrical shape extending in . As shown in FIG. 2, both ends 30 a and 30 b of the impactor 30 are fixed to the inner wall 32 a of the sub passage 32.

Further, as shown in FIG. 2, when viewed this impactor 30 from the injection direction C ₂₆ of the fuel F by the injector 26, (projected shape of the plane perpendicular to the injection direction C ₂₆₎ projected shape of the impactor 30 is rectangular It is. Further, if the injection direction C ₂₆ of the fuel F viewed injector 26, projected shape (see in FIG. 2 reference numerals Fp (F)) of the fuel F injected from the injector 26 is also rectangular.
That is, the outer shape of the impactor 30 is shaped so as to approximate the projected shape Fp of the fuel F injected from the injector 26.

Since the exhaust system structure of an engine according to an embodiment of the present invention is configured as described above, the following operations and effects are achieved.
As shown in FIG. 1, an impactor 30 is provided in the vicinity of the connecting portion between the main passage 31 and the sub-passage 32, in the main passage 31, and close to the outer peripheral wall 31a of the curved portion 31c. ing.

Thus, as indicated by an arrow A in FIG. 1 and as indicated by a symbol Fd (F) in FIG. 2, the fuel F injected from the injector 26 collides with the impactor 30, so that the fuel is generated inside the main passage 31. It becomes possible to diffuse F and promote stirring with the exhaust gas.
Moreover, since the flow velocity of the exhaust gas flowing through the main passage 31 is faster in the vicinity of the outer peripheral wall 31a than in the vicinity of the inner peripheral wall 31b, the fuel F diffused by the impactor 30 and the exhaust gas can be mixed quickly.

Thereafter, the exhaust gas that is well stirred with the fuel F flows into the entire oxidation catalyst 21 and the NOx trap catalyst 22.
Here, the difference in the stirring effect between the fuel F and the exhaust gas between the case where the impactor 30 is provided “outside” the main passage 31 and the case where the impactor 30 is provided “inside” the main passage 31. The results of the experiment examining the above will be described using the graphs shown in FIGS. 3 (A) and 3 (B).

FIG. 3A shows the air-fuel ratio (thin solid line) in the vicinity of the upstream end of the NOx trap catalyst 22 and the NOx trap catalyst when the impactor 30 is provided not in the main passage 31 but in the sub passage 32. 22 is a graph showing the air-fuel ratio (bold solid line) in the vicinity of the downstream end of 22.
On the other hand, FIG. 3B shows an empty space near the upstream end of the NOx trap catalyst 22 when the impactor 30 is provided inside the main passage 31 as in the present invention in the present embodiment described above with reference to FIG. 3 is a graph showing the fuel ratio (thin solid line) and the air-fuel ratio (thick solid line) in the vicinity of the downstream end of the NOx trap catalyst 22;

In these experiments, the fuel F was injected from the injector 26 over the period indicated by the symbol Tf in FIGS. 3 (A) and 3 (B).
When the impactor 30 is provided not in the main passage 31 but in the sub-passage 32, as shown in FIG. 3 (A), 2.5 seconds after the injection of the fuel F is started by the injector 26. It can be seen that the exhaust gas atmosphere on both the upstream side (thin solid line) and the downstream side (thick solid line) of the NOx trap catalyst 22 becomes rich after a certain amount of time has passed.

On the other hand, when the impactor 30 is provided inside the main passage 31, as shown in FIG. 3B, immediately after the injection of the fuel F by the injector 26 is started, the NOx trap catalyst 22 is provided. It can be seen that both the exhaust gas atmosphere on the upstream side (thin solid line) and the downstream side (thick solid line) become rich.
That is, the impactor 30 is disposed in the main passage 31 and in the vicinity of the portion (connection portion) where the main passage 31 and the sub-passage 32 are connected, as in the present invention in the present embodiment described above with reference to FIG. In addition, the fuel F injected from the injector 26 and the exhaust gas discharged from the diesel engine 11 are provided at a position close to the outer peripheral wall 31a of the curved portion 31c, rather than being provided “outside” of the main passage 31. However, FIG. 3 (A) and FIG. 3 (B) show that the mixture is well stirred and the vaporization of the fuel F is promoted.

Therefore, according to this invention in this embodiment mentioned above, it becomes possible to accelerate | stimulate stirring with the fuel F injected from the injector 26, and waste gas, and it can aim at the further improvement of waste gas performance and can contribute to environmental protection. It is.
In addition, the amount of fuel F injected can be suppressed by agitation of fuel F and exhaust gas. That is, in order to enrich the exhaust gas atmosphere in a state where the fuel F and the exhaust gas are not sufficiently stirred, the injection amount of the fuel F must be increased. However, such measures lead to deterioration of fuel consumption, and further, the exhaust gas enriched only into a part of the oxidation catalyst 21 and the NOx trap catalyst 22 is caused to flow.

  On the other hand, according to the present invention in the present embodiment described above, the fuel F, the exhaust gas, and the agitation are promoted to keep the air-fuel ratio balance while suppressing the injection amount of the fuel F to the necessary minimum. The enriched exhaust gas can be caused to flow into the whole of the oxidation catalyst 21 and the NOx trap catalyst 22. Therefore, when NOx purge or S purge is executed, NOx or SOx can be efficiently purged from the NOx trap catalyst 22.

Further, the impactor 30, because it is shaped to extend perpendicular to the injection direction C ₂₆ of the fuel F by the injector 26, it is possible to collide efficiently fuel F to the impactor 30. Therefore, the fuel F can be diffused efficiently in the exhaust passage 30.
Moreover, as shown in FIG. 2, since both ends 30a and 30b of the impactor 30 are supported by the inner wall 32a of the sub-passage 32, the impactor 30 can be prevented from being bent or broken.

Further, since the projected shape of the impactor 30 is shaped so as to approximate the projected shape Fp of the fuel F injected by the injector 26, the fuel F can collide with the impactor 30 efficiently. Therefore, the fuel F can be diffused efficiently in the exhaust passage 30.
In addition, by forming the impactor 30 into a cylindrical shape, the fuel F is appropriately diffused in the main passage 31 while improving the mountability of the impactor 30 in the main passage 31 and suppressing the molding cost of the impactor 30. I can do it.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the spirit of the present invention.
In the above-described embodiment, the case where the first exhaust pipe 14 is connected to the exhaust port of the diesel engine 11 via the turbocharger 12 has been described as an example, but the present invention is not limited to this. For example, the first exhaust pipe 14 may be directly connected to an exhaust port of an engine that does not have the turbocharger 12.

Moreover, in the above-mentioned embodiment, although the diesel engine 11 was demonstrated as an example, it is not limited to this. For example, a gasoline engine may be used instead of the diesel engine 11.
In the above-described embodiment, the case where the oxidation catalyst 21 and the NOx trap catalyst 22 are used as the exhaust catalyst has been described. However, the present invention is not limited to this. For example, not only the oxidation catalyst 21 and the NOx trap catalyst 22, but also an SCR (Selective Catalytic Reduction) catalyst, an HC trap catalyst, or the like may be used in combination with various variations.

  Moreover, in the above-mentioned embodiment, although the case where the impactor 30 was shape | molded by the column shape was demonstrated as an example, it is not limited to this. For example, a semi-cylindrical impactor 40 as shown in FIG. 4 may be used as a first modification of one embodiment of the present invention, and a flat plate shape as shown in FIG. 5 as a second modification thereof. The impactor 50 may be used.

  Alternatively, a cylindrical impactor (not shown) having a hollow cross section may be used instead of the cylindrical impactor 30, or a semi-cylindrical impactor (not shown) having a hollow cross section may be used instead of the semi-columnar impactor 40. ) May be used.

It is a mimetic diagram showing the whole exhaust system structure of an engine concerning one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a main part configuration of an exhaust system structure of an engine according to an embodiment of the present invention, and schematically shows a cross-section taken along line II-II in FIG. 1. (A) is a graph schematically showing an exhaust gas air-fuel ratio when a fuel-impacted member (impactor) is disposed “outside” of the main passage (exhaust gas passage), and (B) is a fuel-impacted member (impactor) Is a graph schematically showing an exhaust gas air-fuel ratio in the case of being disposed “inside” the main passage (exhaust gas passage). It is a schematic diagram which shows the whole structure of the exhaust system structure of the engine which concerns on the 1st modification of one Embodiment of this invention. It is a schematic diagram which shows the whole structure of the exhaust system structure of the engine which concerns on the 2nd modification of one Embodiment of this invention. It is a mimetic diagram showing the structure (trial structure) created in the process of creating the engine exhaust system structure concerning one embodiment of the present invention. (A) is a schematic horizontal cross-sectional view corresponding to the location indicated by reference character CS1 in FIG. 6, and (B) is a schematic horizontal cross-sectional view corresponding to the location indicated by reference character CS2 in FIG. ) Is a schematic horizontal sectional view corresponding to a portion indicated by reference numeral CS3 in FIG. (A) is a graph schematically showing the temperature at the location indicated by reference character CS1 in FIG. 6, (B) is a graph schematically showing the temperature at the location indicated by reference character CS2 in FIG. 6, (C) is It is a graph which shows typically the temperature in the location shown by code | symbol CS3 in FIG.

Explanation of symbols

11 Diesel engine (engine)
14 First exhaust pipe (exhaust passage)
26 Injector (fuel injection means)
30, 40, 50 Impactor (fuel collision member)
30a One end of impactor 30b Other end of impactor 31 Main passage 31a Outer peripheral wall of main passage 32 Sub passage 32a Inner wall of sub passage C ₂₆ Fuel injection direction Fp Projected shape of injected fuel

Claims (6)

Engine exhaust system structure,
An exhaust passage connected to the exhaust port of the engine;
Fuel injection means for injecting fuel into the exhaust passage;
A fuel collision member that collides with the fuel injected from the fuel injection means and diffuses the fuel;
The exhaust passage is
A main passage formed in a curved shape through which the exhaust gas discharged from the engine flows;
A sub-passage connected to the outer peripheral wall side of the curved portion of the main passage and through which the fuel injected from the fuel injection means flows,
The fuel collision member is
Together and provided to the outer peripheral wall of the main passage at a connection portion near the main passage and the sub passage, the fuel projected shape of the impacted members, fuel injected by the fuel injection means An exhaust system structure for an engine, which is formed so as to have a shape that approximates the projected shape of the engine. The fuel collision member is
The engine exhaust system structure according to claim 1, wherein the engine exhaust system structure extends perpendicularly to an injection direction of the fuel by the fuel injection means. Both ends of the fuel collision member are
3. The engine exhaust system structure according to claim 1, wherein the exhaust system structure is supported on an inner wall of the sub passage . The fuel collision member is
The engine exhaust system structure according to any one of claims 1 to 3 , wherein the engine exhaust system structure is formed into a columnar or cylindrical shape. The fuel collision member is
The engine exhaust system structure according to any one of claims 1 to 3 , wherein the engine exhaust system structure is formed into a semi-column or a semi-cylindrical shape. The fuel collision member is
The engine exhaust system structure according to any one of claims 1 to 3 , wherein the engine exhaust system structure is molded into a flat plate shape.

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