JP6759823B2 - Exhaust pipe - Google Patents

Description

The present invention relates to an exhaust pipe, and more particularly to an exhaust pipe for circulating exhaust gas discharged from an engine.

Some exhaust pipes of this type are provided with an injector that supplies a reducing agent or unburned fuel to the exhaust aftertreatment device on the downstream side. The exhaust aftertreatment device includes a selective reduction catalyst (hereinafter, SCR) that purifies a nitrogen compound (hereinafter, NOx) contained in the exhaust gas, a NOx storage reduction catalyst (hereinafter, LNT), and an exhaust gas. Those provided with an oxidation catalyst (hereinafter, DOC) that oxidizes carbon monoxide (CO) and hydrocarbons (HC) are known (see, for example, Patent Documents 1 and 2).

The SCR selectively reduces and purifies NOx contained in the exhaust gas by using ammonia produced by hydrolyzing urea water injected into the exhaust pipe from the injector by the heat of the exhaust as a reducing agent. The LNT occludes NOx contained in the exhaust gas when the exhaust gas has a lean atmosphere, and reduces the stored NOx with HC when the exhaust gas becomes a rich atmosphere due to the HC injected from the injector. Purify.

Japanese Unexamined Patent Publication No. 2012-107634 Japanese Unexamined Patent Publication No. 2013-24075

By the way, in order to improve the purification efficiency of SCR, LNT, and DOC, the exhaust gas having a high flow velocity is directed to the vicinity of the injection port of the injector, and the reducing agent injected from the injector is effectively diffused into the exhaust gas. It is preferable to make the distribution of the reducing agent supplied to the catalyst uniform.

Further, the exhaust pipe is provided with various sensors for detecting the state amount of the exhaust gas. In order to improve the measurement accuracy of these sensors, it may be preferable to slow down the flow velocity of the exhaust gas flowing in the vicinity of the sensor unit.

An object of the present disclosure technique is to provide an exhaust pipe having a simple structure and capable of effectively adjusting the flow velocity of exhaust gas.

The technique of the present disclosure is an exhaust pipe for passing exhaust gas discharged from an internal combustion engine, which is provided in the exhaust pipe and has a pipe axial length of one side surface facing the inner wall of one pipe in the one pipe. It is formed longer than the axial length of the other side surface facing the inner wall of the pipe on the opposite side of the wall, and the flow velocity of the exhaust gas flowing along the one side surface is larger than the flow velocity of the exhaust gas flowing along the other side surface. It is characterized by being provided with a rectifying member for speeding up.

Further, an injector for injecting a liquid may be provided on the inner wall side of the one pipe on the downstream side of the rectifying member.

Further, the exhaust pipe may be arranged on the upstream side of an exhaust aftertreatment device provided with a selective reduction catalyst, and the injector may inject urea water.

Further, the exhaust pipe may be arranged on the upstream side of an exhaust aftertreatment device provided with a NOx storage reduction catalyst, and the injector may inject unburned fuel.

Further, the exhaust pipe may be arranged on the upstream side of an exhaust aftertreatment device provided with an oxidation catalyst, and the injector may inject unburned fuel.

Further, a sensor for acquiring the state amount of the exhaust gas may be provided on the inner wall side of the other pipe on the downstream side of the rectifying member.

Further, the rectifying member may be formed in the shape of an arc blade whose cross-sectional shape is convex in an arc shape toward the inner wall side of one of the pipes.

Further, an exhaust brake device including a shaft rotatably provided in the exhaust pipe on the upstream side of the injector and a valve fixed to the shaft and capable of opening and closing the exhaust flow path is further provided, and the shaft is the valve of the valve. When the liquid is injected from the injector while projecting from one side surface, one side surface of the valve may be directed toward the inner wall of the pipe on the injector side, and the shaft and the valve may function as the rectifying member. ..

According to the technique of the present disclosure, it is possible to provide an exhaust pipe capable of effectively adjusting the flow velocity of the exhaust gas with a simple configuration.

It is a schematic overall block diagram which shows the engine exhaust system to which the exhaust pipe which concerns on 1st Embodiment is applied. It is a schematic cross-sectional view which shows the exhaust pipe and the 1st rectifying member which concerns on 1st Embodiment. It is a schematic sectional drawing which shows the exhaust pipe and the 2nd rectifying member which concerns on 1st Embodiment. It is a schematic overall block diagram which shows the exhaust pipe and the exhaust brake device which concerns on 2nd Embodiment. It is a schematic cross-sectional view which shows the exhaust pipe and the rectifying member which concerns on 2nd Embodiment. It is a schematic whole block diagram which shows an example of the exhaust pipe and the sensor which concerns on other embodiment.

Hereinafter, the exhaust pipe according to the embodiment of the present invention will be described with reference to the accompanying drawings. The same parts are designated by the same reference numerals, and their names and functions are also the same. Therefore, detailed explanations about them will not be repeated.

[First Embodiment]
FIG. 1 is a schematic overall configuration diagram showing an engine exhaust system to which the exhaust pipe according to the first embodiment is applied. An upstream pipe 12 is connected to the exhaust manifold 11 of the diesel engine (hereinafter, simply referred to as an engine) 10. Further, the front casing 20A of the front-stage aftertreatment device 20 is connected to the downstream end of the upstream pipe 12, and the connection pipe 13 is connected to the downstream end of the front casing 20A. Further, the rear casing 40A of the post-stage aftertreatment device 40 is connected to the downstream end of the connection pipe 13, and the downstream pipe 14 is connected to the downstream end of the rear casing 40A.

The upstream pipe 12 is formed in a substantially cylindrical shape, and an exhaust pipe injector 15 for injecting unburned fuel (HC) diagonally with respect to the pipe axis direction is provided in the upstream pipe 12 in the pipe wall. There is. Further, inside the upstream pipe 12, a first rectifying member 60, which will be described in detail later, is provided.

The pre-stage post-treatment device 20 includes a first DOC 21 and a particulate filter (hereinafter, filter) 22 in order from the exhaust upstream side in a substantially cylindrical front-stage casing 20A whose diameter is larger than that of the upstream pipe 12. There is.

The first DOC 21 is formed by supporting a catalyst component or the like on the surface of a ceramic carrier such as a cordierite honeycomb structure. When unburned fuel is supplied by the exhaust pipe injector 15, the first DOC 21 oxidizes the unburned fuel to raise the exhaust temperature.

The filter 22 is formed, for example, by arranging a large number of cells partitioned by a porous partition wall along the flow direction of exhaust gas, and alternately sealing the upstream side and the downstream side of these cells. .. The filter 22 collects particulate matter (PM) in the exhaust gas in the pores and surface of the partition wall, and when the estimated amount of PM accumulation reaches a predetermined amount, the exhaust pipe injector 15 sends unburned fuel to the first DOC 21. Filter forced regeneration control is carried out to supply and raise the exhaust gas temperature to the PM combustion temperature.

The connecting pipe 13 is formed in a substantially straight cylindrical shape, and a urea water injector 17 for injecting urea water obliquely with respect to the pipe axis direction is provided in the connecting pipe 13. The urea water injected from the urea water injector 17 is hydrolyzed by the exhaust heat to produce ammonia, which is supplied to the downstream SCR41 as a reducing agent. Further, a second rectifying member 70, which will be described in detail later, is provided inside the connecting pipe 13.

The post-stage post-processing device 40 includes an SCR 41 and a second DOC 42 in order from the exhaust upstream side in a substantially cylindrical rear-stage casing 40A whose diameter is larger than that of the connecting pipe 13.

The SCR41 is formed by supporting zeolite or the like on a porous ceramic carrier, for example. The SCR 41 adsorbs ammonia supplied as a reducing agent from the urea water injector 17, and selectively reduces and purifies NOx from the exhaust gas passing by the adsorbed ammonia.

The second DOC 42 is formed by supporting a catalyst component or the like on the surface of a ceramic carrier such as a cordierite honeycomb structure, and has a function of oxidizing ammonia slipped downstream from the SCR 41.

Next, the details of the first rectifying member 60 will be described with reference to FIG. The first rectifying member 60 is provided in the upstream pipe 12 on the upstream side of the exhaust pipe injector 15. More specifically, the first rectifying member 60 has a pipe axial length of one side surface 60A facing the exhaust pipe inner wall 12A on the exhaust pipe injector 15 side facing the exhaust pipe inner wall 12B on the anti-exhaust pipe injector 15 side. The cross-sectional shape of the 60B is formed into a substantially arc blade shape that is convex in an arc shape toward the exhaust pipe injector 15 so as to be longer than the length in the pipe axial direction.

As described above, in the upstream pipe 12 on the upstream side of the exhaust pipe injector 15, the first rectifying member having a substantially arc blade shape in which the curvature (or change in curvature) on the exhaust pipe injector 15 side is larger than that on the anti-exhaust pipe injector 15 side. By arranging the 60, the flow velocity of the exhaust gas flowing along the one side surface 60A of the first rectifying member 60 becomes faster than the flow velocity of the exhaust gas flowing along the other side surface 60B.

As a result, the exhaust gas having a high flow velocity can be applied to the exhaust gas 15A of the exhaust pipe injector 15, and the unburned fuel injected from the exhaust pipe injector 15 can be effectively diffused into the exhaust gas. Further, by diffusing the unburned fuel into the exhaust gas, it is possible to make the distribution of the unburned fuel supplied to the first DOC21 (see FIG. 1) uniform.

The shape of the upstream pipe 12 may be either a linear shape shown in FIG. 2A or a curved shape shown in FIG. 2B. Further, the length of the first rectifying member 60 in the pipe axis direction, the thickness in the pipe diameter direction, the curvature, etc. are appropriately optimized according to the pipe diameter of the upstream pipe 12, the specifications of the engine 10, the injection angle of the exhaust pipe injector 15, and the like. You can set it to a value.

Next, the details of the second rectifying member 70 will be described with reference to FIG. The second rectifying member 70 is provided in the connecting pipe 13 on the upstream side of the urea water injector 17. More specifically, the second rectifying member 70 has a pipe axial length of one side surface 70A facing the exhaust pipe inner wall 13A on the urea water injector 17 side facing the exhaust pipe inner wall 13B on the anti-urea water injector 17 side. The cross-sectional shape of the 70B is formed into a substantially arc blade shape that is convex in an arc shape toward the urea water injector 17 so as to be longer than the length in the pipe axis direction.

In this way, in the connecting pipe 13 on the upstream side of the urea water injector 17, the curvature (or change of curvature) on the urea water injector 17 side is larger than that on the anti-urea water injector 17 side. By arranging the 70, the flow velocity of the exhaust gas flowing along the one side surface 70A of the second rectifying member 70 becomes faster than the flow velocity of the exhaust gas flowing along the other side surface 70B.

As a result, the exhaust gas having a high flow velocity is applied to the injection port 17A of the urea water injector 17, and the urea water injected from the urea water injector 17 can be effectively diffused into the exhaust gas. Further, by diffusing the urea water into the exhaust gas, the efficiency of ammonia production is effectively promoted, and the distribution of ammonia supplied to SCR41 (see FIG. 1) can be made uniform.

The shape of the connecting pipe 13 may be either a linear shape shown in FIG. 3A or a curved shape shown in FIG. 3B. Further, the length of the second rectifying member 70 in the pipe axis direction, the thickness in the pipe diameter direction, the curvature, etc. are appropriately optimized according to the pipe diameter of the connecting pipe 13, the specifications of the engine 10, the injection angle of the urea water injector 17, and the like. You can set it to a value.

[Second Embodiment]
Next, the details of the exhaust pipe according to the second embodiment will be described with reference to FIGS. 4 and 5. The exhaust pipe of the second embodiment is obtained by replacing the first rectifying member 60 (or the second rectifying member 70) of the first embodiment with the exhaust brake device 80. Other configurations are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 4, the exhaust brake device 80 has at least a disc shape that is fixed to the shaft 81 by a shaft 81 rotatably supported by the upstream pipe 12 and a bolt (not shown) to open and close the exhaust flow path. The shutter valve 82 is provided with an air cylinder 83 operated by compressed air supplied from an air tank (not shown), and a link mechanism 85 for connecting the shaft 81 and the rod 84 of the air cylinder 83.

When the exhaust brake is activated, compressed air is supplied to the air cylinder 83 to push out the rod 84, and the link mechanism 85 rotates the shaft 81 to close the shutter valve 82. On the other hand, when the exhaust brake is not operating, the supply of compressed air is stopped, and the rod 84 is pushed back into the air cylinder 83 by the urging force of a spring (not shown), so that the shutter valve 82 is opened.

Next, the details of the arrangement relationship between the exhaust brake device 80 and the exhaust pipe injector 15 of the present embodiment will be described with reference to FIG. The cross-sectional shape of the shaft 81 and the shutter valve 82 in the direction orthogonal to the rotation axis is such that the shaft 81 projects from substantially the center of one side surface 82A of the shutter valve 82. In the present embodiment, in the exhaust brake device 80, when the exhaust brake is not operating (when the shutter valve 82 is opened), one side surface 82A of the shutter valve 82 faces the exhaust pipe inner wall 12A on the exhaust pipe injector 15 side. It is attached to the upstream pipe 12.

That is, when the exhaust brake is not activated when the shutter valve 82 is opened, one side surface 82A of the shutter valve 82 on which the shaft 81 protrudes faces the exhaust pipe inner wall 12A on the exhaust pipe injector 15 side, so that the shutter valve 82 The flow velocity of the exhaust gas flowing along the outer periphery of the one side surface 82A and the shaft 81 is faster than the flow velocity of the exhaust gas flowing along the other side surface 82B. By applying such an open state of the shutter valve 82 to the injection port 15A of the exhaust pipe injector 15 at the time of forced regeneration of the filter in which unburned fuel is injected from the exhaust pipe injector 15, the temperature rise of the catalyst, and the SOx purge process. Exhaust gas with a high flow velocity can be applied, and unburned fuel can be effectively diffused into the exhaust gas.

[Other]
The present invention is not limited to each of the above-described embodiments, and can be appropriately modified and implemented without departing from the spirit of the present invention.

For example, the NOx catalyst is not limited to SCR41 and may be LNT. Even when the NOx catalyst is LNT, the unburned fuel injected from the exhaust pipe injector 15 during the NOx purge process or the SOx purge process can be effectively diffused into the exhaust gas.

Further, as shown in FIG. 6, the rectifying member 60 (70) may be arranged on the upstream side of the sensor 90 (for example, NOx / lambda sensor) whose measurement accuracy improves as the exhaust gas flow velocity becomes slower. In this case, the rectifying member 60 (70) may be arranged in the exhaust pipe 12 (13, 14) so as to be convex in an arc shape on the side opposite to the sensor 90.

Further, the engine 10 is not limited to a diesel engine, and can be widely applied to other engines such as a gasoline engine.

10 Engine 11 Exhaust manifold 12 Upstream piping 13 Connection piping 14 Downstream piping 15 Exhaust pipe injector 17 Urea water injector 20 Pre-stage aftertreatment device 21 1st DOC
22 Filter 40 Post-stage post-processing device 41 SCR
42 2nd DOC
60 1st rectifying member 70 2nd rectifying member

Claims (7)

An exhaust pipe that circulates exhaust gas discharged from an internal combustion engine.
It is provided in the exhaust pipe, and the axial length of one side surface facing the inner wall of one pipe is formed longer than the axial length of the other side surface facing the inner wall of the pipe opposite to the inner wall of one pipe. A rectifying member that makes the flow velocity of the exhaust gas flowing along the one side surface faster than the flow velocity of the exhaust gas flowing along the other side surface .
An exhaust pipe comprising a sensor for acquiring a state amount of exhaust gas on the inner wall side of the other pipe on the downstream side of the rectifying member . The exhaust pipe according to claim 1, wherein an injector for injecting a liquid is provided on the inner wall side of the one pipe on the downstream side of the rectifying member. The exhaust pipe according to claim 2, wherein the exhaust pipe is arranged on the upstream side of an exhaust aftertreatment device including a selective reduction catalyst, and the injector injects urea water. The exhaust pipe according to claim 2, wherein the exhaust pipe is arranged on the upstream side of an exhaust aftertreatment device including a NOx storage reduction catalyst, and the injector injects unburned fuel. The exhaust pipe according to claim 2, wherein the exhaust pipe is arranged on the upstream side of an exhaust aftertreatment device including an oxidation catalyst, and the injector injects unburned fuel. The rectifying member is formed in the shape of an arc blade whose cross-sectional shape is convex in an arc shape toward the inner wall side of one of the pipes.
The exhaust pipe according to any one of claims 1 to 5 . An exhaust pipe that circulates exhaust gas discharged from an internal combustion engine.
An injector that injects liquid onto the inner wall side of one of the exhaust pipes,
It is provided with a shaft rotatably provided in an exhaust pipe on the upstream side of the injector, and an exhaust brake device including a valve fixed to the shaft and capable of opening and closing the exhaust flow path.
The shaft projects from one side surface of the valve, and when a liquid is injected from the injector, one side surface of the valve is directed toward the inner wall of the pipe on the injector side, and one side surface of the valve and the shaft. The flow velocity of the exhaust gas flowing along the outer circumference is made faster than the flow velocity of the exhaust gas flowing along the other side surface of the valve facing the inner wall of the pipe opposite to the inner wall of the pipe on the injector side.
The exhaust pipe is characterized by that .

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