JP2018071399A - Piping unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piping unit which can improve a damming property of a reductant while suppressing an increase of a pressure loss.SOLUTION: This disclosed embodiment comprises piping for guiding an exhaust gas which forms a swirl flow and a reductant toward an exhaust emission purification catalyst, and a plate protruding toward a center side of the piping from a portion shifted to a lower part of a vertical direction at an internal peripheral face of the piping. In a piping unit of this embodiment, when setting an end part located at a swirl direction side of the swirl flow at the plate as a first end part, and an end part located at a reverse direction side of a swirl direction at the plate as a second end part, a position of the first end part in the vertical direction is higher than a position of the second end part in the vertical direction.SELECTED DRAWING: Figure 2A

Description

  The present disclosure relates to a piping unit that guides exhaust gas and a reducing agent to an exhaust purification catalyst.

  Conventionally, an exhaust gas purification device purifies nitrogen oxides in exhaust gas by selective catalytic reduction by supplying a reducing agent into the exhaust gas upstream of the carrier holding the catalyst.

  Further, by providing a plate erected toward the exhaust passage central side on the inner wall of the piping unit on the exhaust upstream side of the alumina mat holding the carrier, the liquid reducing agent flowing along the inner wall of the piping unit Damping is performed before the mat (see, for example, Patent Document 1).

JP 2013-127208 A

  The plate of the piping unit is required to have improved performance for blocking the reducing agent. However, the plate also causes an increase in pressure loss in the piping unit.

  Therefore, an object of the present disclosure is to provide a piping unit capable of improving a reducing agent damming ability while suppressing an increase in pressure loss.

One form of the present disclosure is:
Piping that guides the exhaust gas and the reducing agent that make a swirling flow toward the exhaust purification catalyst;
A plate projecting toward the center side of the pipe from a portion near the vertical downward direction on the inner peripheral surface of the pipe,
When the end on the swirl direction side of the swirl flow in the plate is a first end, and the end on the opposite side of the swirl direction is the second end of the plate, the end of the first end The vertical position is higher than the vertical position of the second end,
Directed to the piping unit.

  According to the present disclosure, it is possible to provide a piping unit capable of improving the reducing agent blocking ability while suppressing an increase in pressure loss.

The figure which shows the whole structure of the exhaust system which employ | adopted the piping unit which concerns on 1st embodiment of this indication. It is a figure which shows the detailed structure of the piping unit of FIG. 1, Comprising: Sectional drawing when the cross section which follows the line A-A 'of FIG. 2 is a cross-sectional view of the cross section taken along line C-C ′ of FIG. The figure which shows the modification of the damming plate of FIG. The figure which shows the whole structure of the exhaust system which employ | adopted the piping unit which concerns on 2nd embodiment of this indication. FIG. 5 is a diagram showing a detailed configuration of the piping unit of FIG. 4, and is a cross-sectional view when a cross section taken along line E-E ′ of FIG.

  Hereinafter, the piping unit according to the present disclosure will be described in detail with reference to the drawings.

<0. Definition>
Table 1 below shows the meanings of acronyms and abbreviations used in the present embodiment.

<1-1. Configuration of First Embodiment>
As shown in FIG. 1, a vehicle V is mounted with an exhaust system 1 </ b> A that employs a piping unit 17 </ b> A (see FIG. 2A) according to the first embodiment, and an internal combustion engine 3 connected thereto.

  First, the internal combustion engine 3 will be described. The internal combustion engine 3 is a diesel engine, for example. In the internal combustion engine 3, fuel is burned in the combustion chamber to generate exhaust gas. This exhaust gas is sent to the exhaust system 1A.

Next, the basic configuration of the exhaust system 1A will be described.
The exhaust system 1A has an exhaust passage 11 that guides exhaust gas from the internal combustion engine 3 to the atmosphere (outside the vehicle). Several post-processing devices 13 are arranged in the exhaust flow path 11. In the present disclosure, as the post-processing device 13, a DPF 13A and an SCR 13B are exemplified.

  The DPF 13A is a diesel particulate diffuser, and collects particulate matter (hereinafter referred to as PM) in exhaust gas flowing into the DPF 13A. Further, if the temperature of the exhaust gas is equal to or higher than the self-regeneration temperature, the DPF 13A burns and removes the collected PM (so-called self-regeneration).

  The SCR 13B is an example of an exhaust purification catalyst, and is disposed on the downstream side of the DPF 13A in the exhaust passage 11. Further, an injector 15 for injecting urea water as a reducing agent is provided between the DPF 13A and the SCR 13B in the exhaust passage 11. Thereby, not only the exhaust gas but also ammonia generated by spraying urea water on the exhaust gas is introduced into the SCR 13B as a reducing agent.

  When the temperature of the exhaust gas passing through the SCR 13B exceeds a predetermined temperature, the supplied ammonia and the nitrogen oxide (hereinafter referred to as NOx) contained in the supplied exhaust gas are reduced to detoxify the NOx. To do. Therefore, the injector 15 preferably injects urea water into the exhaust passage 11 when the temperature of the exhaust gas into which the SCR 13B flows is equal to or higher than a predetermined temperature. Note that the predetermined temperature is appropriately determined appropriately in consideration of the reaction temperature between ammonia and NOx by experiments and simulations in the design and development stage of the exhaust system 1A.

  Water, nitrogen, and carbon dioxide generated by treating exhaust gas with each of the post-treatment devices 13 are discharged into the atmosphere through a muffler (not shown).

<1-2. Detailed configuration of piping unit>
In the first embodiment, the exhaust flow path 11 meanders in a portion between the DPF 13A and the SCR 13B, so that the exhaust gas to be guided is swirled without having a mixer as in the second embodiment. It is configured to make. In addition, since it describes in the Unexamined-Japanese-Patent No. 2011-247128 about the exhaust flow path which can produce | generate a swirl flow, the detailed description is refrained.

  Further, in the exhaust passage 11, a piping unit 17A as shown in FIGS. 2A and 2B is provided immediately upstream of the SCR 13B in the exhaust gas flow direction. The piping unit 17A includes a U-shaped piping 171A and a damming plate 173.

  A case 19 containing the SCR 13B is connected to the downstream end DE of the U-shaped pipe 171A so that fluid communication is possible. Here, as described in Patent Document 1, the SCR 13B is press-fitted into the case 19 with its peripheral surface covered with a fibrous mat 101 such as an alumina mat.

  On the other hand, the upstream end UE of the U-shaped pipe 171A is connected to the DPF 13A so as to be in fluid communication via another pipe (not shown).

Here, in the present disclosure, the opening of the upstream end UE has a circular shape, and the opening of the downstream end DE has a circular shape when the damming plate 173 is removed. Further, the center of the opening of the upstream end UE and O _U, when the center of the opening of the downstream end DE and O _D, the position in the vertical direction z of the center O _D is lower than the position in the vertical direction z of the center O _U It has become. Thus, the U-shaped pipe 171A does not make a U-turn on the exhaust gas flow path parallel to the horizontal plane xy, but the exhaust gas flow path is relatively lower on the U-shaped pipe 171A on the downstream side than on the upstream side. It has become. The exhaust gas and the reducing agent flow into such a U-shaped pipe 171A in a state of a clockwise swirling flow as indicated by an arrow A at the downstream end DE. The swirl flow is generated by the mixer chamber 110 provided on the upstream side of the U-shaped pipe 171A. By such a swirling flow, the reducing agent is uniformly diffused in the exhaust gas, whereby the exhaust gas can be efficiently purified in the SCR 13B. The direction of arrow A indicates the swirling direction of the swirling flow.

  The damming plate 173 is a plate-like member that protrudes toward a central side of the U-shaped pipe 171A from a part of the downstream end DE or a part of the inner peripheral surface in the vicinity thereof in the vertical downward direction. It is made with.

  Hereinafter, the outer shape of the damming plate 173 will be described in detail when viewed in plan from the traveling direction y of the swirling flow at the downstream end DE. For this purpose, first, the following is defined. Hereinafter, “plan view from the traveling direction y of the swirling flow at the downstream end DE” is simply referred to as “plan view from the traveling direction y”.

Of the two intersections between the straight line O _U O _D and the inner peripheral surface, the intersection on the line segment O _U O _{D is} defined as P _U and the other intersection is defined as P _D.

The damming plate 173 has a first end FE in the turning direction A and a second end SE in the direction opposite to the turning direction A. When viewed in a plan view in the traveling direction y, first end FE, compared terms P ₁ on the inner peripheral surface toward the center O _D, the a line segment extending by a length d _1, a second end SE is from the point P ₂ on the inner peripheral surface toward the center O _D, the line segment extending by a length d _2. Here, the angle formed by the line segment P ₁ O _D and the line segment O _D P _U is θ _1, and the angle formed by the line segment P ₂ O _D and the line segment O _D P _D is θ ₂ . For convenience, illustration of d ₁ and d ₂ is omitted.

In the present disclosure, the points P ₁ , P ₂ , the lengths d ₁ , d _2, and the lengths of the first end FE in the vertical direction z are higher than the position of the second end SE in the vertical direction z. The values of the angles θ ₁ and θ ₂ are determined. In the configuration example of FIG. 2A, the position in the vertical direction z of the point P ₁ is higher than the position in the vertical direction z of the point P _2, the length d ₁ is shorter than the length d _2, angle theta ₁ is angle theta Designed to be smaller than ₂ .

In the configuration example of FIG. 2A, the damming plate 173 has an intermediate portion I existing between the first end portion FE and the second end portion SE. When viewed in a plan view in the traveling direction y, the intermediate portion I is a line segment extending in the horizontal direction x, one end of the intermediate portion I is directly the tip of the center O _D side of the second end SE is connected to, the other end, and the distal end of the center O _D side in the end FE, the center is connected via an arc O _D.

<1-3. Action and effect of piping unit>
The piping unit 17A of the present disclosure includes a damming plate 173 having an outer shape as described above when viewed in plan from the traveling direction y, at the downstream end DE of the U-shaped piping 171A and in the vicinity thereof.

  In the piping unit 17A, not only the exhaust gas and the reducing agent flow toward the SCR 13B while turning in the turning direction A inside the U-shaped piping 171A, but also the bottom of the U-shaped piping 171A with a part of the reducing agent in a liquid state. May flow toward the SCR 13B. However, by providing the blocking plate 173, it is possible to prevent the liquid reducing agent from entering the case 19, thereby preventing the reducing agent from penetrating into the fibrous mat 101 surrounding the peripheral surface of the SCR 13B.

  More specifically, the exhaust gas and the reducing agent come toward the dam plate 173 while turning in the turning direction A. Under the influence of the swirling flow, in the liquid reducing agent collected immediately before the damming plate 173, the downstream portion in the swirling direction A may rise more than the upstream portion. However, since the dam plate 173 has a higher vertical position of the first end portion FE in the turning direction A, the liquid reducing agent that may rise up enters the case 19 in the first end portion FE. This can prevent penetration of the reducing agent into the fibrous mat 101 surrounding the peripheral surface of the SCR 13B.

  Conversely, the dam plate 173 has a lower position in the vertical direction z of the second end SE in the direction opposite to the swivel direction A. However, the liquid reduction that accumulates immediately before the dam plate 173 due to the swirl flow. In the agent, a portion near the direction opposite to the turning direction A falls and becomes depressed. Therefore, the liquid reducing agent can be prevented from entering the case 19 beyond the second end portion SE.

  Further, as described above, since the vertical position of the second end portion SE is lower than that of the first end portion FE, an increase in pressure loss when the swirling flow passes through the piping unit 17A can be suppressed.

<1-4. Other configuration examples>
The dam plate 173 may employ the five configurations shown in FIG. 3 in addition to the configuration example of FIG. 3, the damming plate 173 has a U-shaped pipe 171 </ b> A from at least a part of the inner peripheral surface of the U-shaped pipe 171 </ b> A on the vertically lower side when viewed in plan from the traveling direction y of the swirling flow. The first end FE in the swirling direction A of the swirling flow and the second end SE in the direction opposite to the swirling direction A, and the first end The vertical position of the FE is higher than the vertical position of the second end SE. Even with these configurations, <1-3. The effects described in <Action and Effect of Piping Unit> are exhibited.

<1-5. Addendum>
The piping unit 17A may be provided to the user while attached to the vehicle V. However, the piping unit 17A alone may be provided to the user as a maintenance part or the like.

<2-1. Configuration of Second Embodiment>
As shown in FIG. 4, the second embodiment is different from the first embodiment in that an exhaust system 1B is connected to the internal combustion engine 3 instead of the air system 1A. Other than that, there is no difference between the two embodiments.

Further, the exhaust system 1B is different from the exhaust system 1A in the following two points.
(1) The exhaust flow path 11 does not necessarily meander between the DPF 13A and the SCR 13B, and may be linear (2) The pipe unit 17B is provided instead of the pipe unit 17A

  Other than the above, there is no difference between the two embodiments. Therefore, in FIG. 4, the same reference numerals are assigned to the components corresponding to the configuration of FIG.

  The piping unit 17B is provided in the exhaust passage 11 immediately upstream of the SCR 13B in the flow direction of the exhaust gas. As shown in FIG. I have.

  A damming plate 173 is provided at or near the downstream end DE of the straight pipe 171B, as in the first embodiment.

  Further, in the straight pipe 171B, the upstream side in the traveling direction y of the swirling flow with respect to the dam plate 173 and the downstream side of the injector 15 (more specifically, the injection position of the reducing agent) A mixer 175 is provided. In this mixer 175, the exhaust gas containing the reducing agent is swirled.

  Also in the piping unit 17B as described above, <1-3. The effects described in <Action and Effect of Piping Unit> are exhibited.

<2-2. Addendum>
In the second embodiment, the mixer 175 is provided in the piping unit 17B. However, the present invention is not limited to this, and the mixer 175 is provided anywhere in the exhaust passage 11 as long as it is upstream of the dam plate 173 in the traveling direction y of the swirl flow and downstream of the injector 15. It does not matter.

  In the second embodiment, as in the first embodiment, the SCR 13B is press-fitted into a case 19 different from the piping unit 17B. However, the present invention is not limited to this, and the damming plate 173 may be provided on the case 19 side in the same manner as described above. In this case, as shown on the right side of FIG. 2B, the piping unit includes a case 19 as a piping, a damming plate 173, and an SCR 13B.

  Moreover, <1-4. Other Configuration Examples> and <1-5. The contents described in <Appendix> also apply to the second embodiment.

  The piping unit of the present disclosure can improve the reducing agent damming ability while suppressing an increase in pressure loss, and is suitable for a passenger car or a commercial vehicle equipped with a diesel engine or the like.

17A, 17B Piping unit 171A U-shaped piping 171B Straight piping 173 Damping plate FE First end SE Second end 13B SCR (Exhaust gas purification catalyst)

Claims (3)

Piping that guides the exhaust gas and the reducing agent that make a swirling flow toward the exhaust purification catalyst;
A plate projecting toward the center side of the pipe from a portion near the vertical downward direction on the inner peripheral surface of the pipe,
When the end on the swirl direction side of the swirl flow in the plate is a first end, and the end on the opposite side of the swirl direction is the second end of the plate, the end of the first end The vertical position is higher than the vertical position of the second end,
Piping unit. The pipe includes a chamber that generates a swirl flow of exhaust gas and a reducing agent on the upstream side of the plate in the traveling direction of the swirl flow.
The piping unit according to claim 1. A mixer provided on the upstream side in the direction of travel of the swirl flow in the pipe rather than the plate,
The piping unit according to claim 1 further provided.

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