JP5869888B2 - Exhaust purification equipment - Google Patents

Description

  The present invention relates to an exhaust emission control device.

  Conventionally, as an exhaust purification device for purifying exhaust gas flowing through an exhaust passage of an engine, for example, one described in Patent Document 1 is known. An exhaust purification device described in Patent Document 1 includes a first casing in which a DOC (Diesel Oxidation Catalyst) and a DPF (Diesel Particulate Filter) are accommodated, and an injection nozzle that injects urea water (reducing agent) into exhaust gas. A pipe to which the (injection device) is attached, and a second casing in which SCR (Selective Catalytic Reduction) is accommodated. Moreover, the exhaust emission control device described in Patent Document 1 forms a hole in the entire pipe by inserting the upstream side of the pipe into the first casing so as to extend in a direction substantially perpendicular to the axial direction of the first casing. The downstream side of the pipe is connected to the second casing. And NOx of exhaust gas is reduced and purified using ammonia generated by the injection of urea water.

JP 2011-099390 A

  By the way, since the particle diameter of a reducing agent will become large if the injection angle of a reducing agent is narrowed, it is preferable to enlarge the injection angle of a reducing agent as much as possible. However, in the exhaust emission control device described in Patent Document 1, since the hole connecting the first casing and the pipe is formed in the entire pipe, when the injection angle of the reducing agent is widened, the reducing agent is first introduced through the hole. It leaks into one casing.

  Further, when a hole is formed in the entire pipe as in the exhaust gas purification device described in Patent Document 1, exhaust gas flows only from the downstream side of the pipe, so that the reducing agent immediately after injection does not diffuse sufficiently. A good reduction reaction cannot be obtained.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the exhaust gas purification apparatus which can fully perform spreading | diffusion of a reducing agent, suppressing a leakage of a reducing agent from a pipe. .

  An exhaust purification device according to the present invention is an exhaust purification device for purifying exhaust gas flowing in an exhaust passage of an engine, and is disposed on a downstream side of a cylindrical casing and the casing with respect to the axial direction of the casing. A pipe inserted in the casing so as to extend in a substantially vertical direction, and an injection device for injecting a reducing agent into the pipe from the upstream end of the pipe, and the pipe inserted in the casing A through hole forming part in which a through hole communicating with the casing is formed and a through hole non-forming part that is arranged downstream of the through hole forming part and does not form a through hole are formed in the insertion part. It is characterized by.

  According to the exhaust emission control device of the present invention, the exhaust gas flows into the pipe by forming the through hole forming portion on the upstream side of the insertion portion and forming the non-through hole forming portion on the downstream side of the insertion portion. In addition, the leakage of the reducing agent from the pipe can be suppressed even if the injection angle of the reducing agent is widened. Furthermore, by forming the through-hole forming portion on the upstream side of the through-hole non-forming portion, exhaust gas can flow into the pipe from the upstream side, so that the reducing agent can be diffused immediately after injection. This makes it possible to sufficiently diffuse the reducing agent. And since the through-hole non-formation part is covered with the high temperature exhaust gas which flows through the inside of a casing, even if a reducing agent adheres to a through-hole non-formation part, the vaporization of this reducing agent can be accelerated | stimulated.

  In this case, it is preferable that the through hole forming portion is formed on the upstream side of the position where the injection region of the reducing agent injected from the injection device and the inner wall surface of the pipe meet. If comprised in this way, it can suppress further that a reducing agent leaks from a pipe.

  According to the present invention, it is possible to sufficiently diffuse the reducing agent while suppressing leakage of the reducing agent from the pipe.

It is a figure showing the schematic structure of the exhaust-air-purification device concerning one embodiment of the present invention. It is an enlarged view which shows the principal part of the exhaust gas purification apparatus of FIG. It is the schematic for demonstrating the exhaust gas purification apparatus of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

  FIG. 1 is a diagram illustrating a schematic configuration of an exhaust emission control apparatus according to an embodiment. As shown in FIG. 1, an exhaust emission control device 10 of this embodiment purifies exhaust gas (hereinafter simply referred to as “exhaust gas”) exhausted from an engine such as a diesel engine in a vehicle such as a truck. . This exhaust purification device 10 is mounted on an exhaust passage 1 through which exhaust gas flows, and includes a DOC 11, a DPF 12, an injection device 13, and an SCR 14.

  The exhaust passage 1 is at least defined by a first casing 2, a pipe (wall portion) 3 and a second casing 4, and these are arranged in this order from the upstream side to the downstream side. The first casing 2 and the second casing 4 are formed in a cylindrical shape, and are juxtaposed so that the flow of exhaust gas is substantially parallel to each other. The pipe 3 connects the downstream side of the first casing 2 and the upstream side of the second casing 4. The pipe 3 extends straightly in a direction substantially orthogonal to the longitudinal direction of the first casing 2, and then extends to bend toward the upstream side of the second casing 4.

  The DOC 11 is for oxidizing the unburned fuel in the exhaust gas, and is disposed on the upstream side in the first casing 2. The DPF 12 collects particulates (particulate matter) in the exhaust gas that has passed through the DOC 11, and is disposed in the first casing 2 on the downstream side of the DOC 11.

The injection device 13 injects and adds a reducing agent to the exhaust gas immediately after passing through the DPF 12. The injection device 13 here generates ammonia by injecting urea water as a reducing agent to cause a thermal decomposition reaction and a hydrolysis reaction shown in the following formula (1).
(NH ₂ ) ₂ CO → NH ₃ + HNCO (thermal decomposition reaction)
HNCO + H ₂ O → NH ₃ + CO ₂ (hydrolysis) (1)

The SCR 14 purifies the exhaust gas by selectively reducing NOx in the exhaust gas using the added reducing agent. The SCR 14 is disposed in the second casing 4. The SCR 14 here causes the reduction reaction shown in the following formula (2) using the generated ammonia to selectively reduce and purify NOx. Note that an ammonia reduction catalyst (not shown) that oxidizes excess ammonia is provided at the rear stage of the second casing 4.
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (Standard)
6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O (Slow) (2)
NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O (Fast)

  Next, the main part of the exhaust emission control device 10 described above will be described in detail with reference to FIGS. FIG. 2 is an enlarged view showing a main part of the exhaust gas purification apparatus of FIG. FIG. 3 is a schematic view for explaining the exhaust purification device of FIG.

  As shown in FIG. 2 and FIG. 3, the upstream side of the pipe 3 is inserted downstream of the DPF 12 in the first casing 2. The insertion portion 3 a of the pipe 3 inserted in the first casing 2 is a direction substantially perpendicular to the axial direction of the first casing 2 so that the flow of exhaust gas is substantially orthogonal to the first casing 2. It extends to. Further, the upstream open end of the pipe 3 is closed by the wall surface of the first casing 2.

  The injection device 13 is attached to the upstream end portion of the pipe 3 so that the reducing agent is injected from the upstream end portion of the pipe 3 along the extending direction of the pipe 3. The injection device 13 injects a reducing agent into the pipe 3. In other words, the pipe 3 contains the injection area A of the reducing agent injected from the injection device 13. The injection device 13 here has a nozzle 13 a located inside the pipe 3, and injects the reducing agent toward the downstream side of the pipe 3.

  The insertion portion 3a of the pipe 3 is disposed on the upstream side and has a through-hole forming portion 16 formed with a through-hole 15 through which exhaust gas flows into the inside, and is disposed on the downstream side of the through-hole forming portion 16 and passes therethrough. A through hole non-forming portion 17 in which the hole 15 is not formed is formed. The through-holes 15 are small openings penetrating the inside and outside of the pipe 3, and are formed at regular intervals on the entire circumference of the pipe 3 in the through-hole forming portion 16 in order to allow the exhaust port to flow from the entire circumference of the pipe 3. Yes. The through hole 15 can be formed, for example, by punching the through hole forming portion 16 of the pipe 3. In this case, from the viewpoint of ease of manufacture, the through holes 15 preferably have the same shape. . However, the shape and number of the through holes 15 formed in the through hole forming portion 16 are not particularly limited.

  As shown in FIG. 3, the through hole forming portion 16 is formed on the upstream side from the position where the injection region A of the reducing agent injected from the injection device 13 and the inner wall surface 3 b of the pipe 3 are combined. The injection region A is a silhouette having a substantially conical shape with the injection device 13 as a vertex. The injection region A can be obtained geometrically based on, for example, the injection angle of the reducing agent injected from the injection device 13. In this case, the through hole forming part 16 is preferably formed with the through hole 15 from the upstream end of the insertion part 3a.

  In the exhaust purification apparatus 10 configured as described above, as shown in FIG. 1, first, exhaust gas from the engine is oxidized by the DOC 11 in the first casing 2, and then the particulates in the exhaust gas are changed. It is collected by DPF12. As shown in FIGS. 2 and 3, immediately after passing through the DPF 12, the exhaust gas flows into the pipe 3 through the through-hole 15 formed in the through-hole forming portion 16, and is substantially perpendicular to the pipe 3. Flows like a bend.

  Then, the reducing agent is injected from the injection device 13 and added to the exhaust gas flowing from the through hole 15, and ammonia is generated by the thermal decomposition reaction and the hydrolysis reaction.

  At this time, as described above, the through hole forming portion 16 in which the through hole 15 is formed is upstream from the position where the injection region A of the reducing agent injected from the injection device 13 and the inner wall surface 3b of the pipe 3 are combined. Therefore, the reducing agent injected from the injection device 13 is diffused into the pipe 3 without leaking from the through hole 15 and mixed with the exhaust gas flowing from the through hole 15 immediately after injection. Is done.

  Further, since the through-hole non-forming part 17 is covered and heated by the high-temperature exhaust gas flowing in the casing, even if the reducing agent adheres to the through-hole non-forming part 17 without vaporizing, the through-hole non-forming part 17 Vaporization of the reducing agent attached by the heat of the forming portion 17 is promoted.

  Thereafter, as shown in FIG. 1, the exhaust gas containing ammonia flows into the second casing 4, and NOx in the exhaust gas is selectively reduced and purified by the SCR 14. And it supplies to the ammonia reduction catalyst of a back | latter stage.

  As described above, according to the present embodiment, the through-hole forming portion 16 is formed on the upstream side of the insertion portion 3a, and the through-hole non-forming portion 17 is formed on the downstream side of the insertion portion 3a. 3 and the leakage of the reducing agent from the pipe 3 can be suppressed even if the injection angle of the reducing agent is widened.

  Furthermore, by forming the through-hole forming portion 16 upstream of the through-hole non-forming portion 17, exhaust gas can flow into the pipe 3 from the upstream side, so that the reducing agent is diffused immediately after injection. Can do. This makes it possible to sufficiently diffuse the reducing agent.

  Moreover, since the through-hole non-forming portion 17 is covered with the high-temperature exhaust gas flowing through the first casing 2, the reducing agent does not vaporize while passing through the through-hole forming portion 16, and the through-hole non-forming portion 17. Even if the reducing agent in the droplets adheres to this, vaporization of the reducing agent can be promoted.

  In the present embodiment, the through hole forming portion 16 is formed on the upstream side from the position where the injection region A of the reducing agent and the inner wall surface 3b of the pipe 3 are combined, so that the reducing agent leaks from the pipe 3. Can be further suppressed.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention can be modified without departing from the scope described in the claims or applied to other embodiments. May be.

  For example, in the above-described embodiment, the through holes 15 are described as being formed at equal intervals around the entire circumference of the pipe 3 in the through hole forming portion 16, but the formation positions and formation intervals of the through holes 15 can be changed as appropriate. it can. For example, a large-diameter through hole 15 is formed on the opposite side of the DPF 12, a small-diameter through hole 15 is formed on the DPF 12 side, or a large number of through holes 15 are formed on the opposite side of the DPF 12. Can form a small number of through-holes 15. By forming the through hole 15 in this way, the exhaust gas inflow resistance in the through hole 15 disposed on the downstream side is increased, and the exhaust gas inflow resistance in the through hole 15 disposed on the upstream side is decreased. Therefore, the flow rate of the exhaust gas flowing into the pipe 3 can be made uniform in the circumferential direction of the pipe 3.

  Moreover, in the said embodiment, the through-hole formation part 16 was demonstrated as what is formed in the upstream rather than the position where the injection area A of the reducing agent injected from the injection device 13 and the inner wall surface 3b of the pipe 3 are combined. However, it may be formed up to a position where the injection region A of the reducing agent injected from the injection device 13 and the inner wall surface 3b of the pipe 3 are combined, or may be formed downstream from this position.

  Moreover, in the said embodiment, although the truck was illustrated as a vehicle, a bus | bath, a tractor, or another vehicle may be sufficient, for example. In the above description, the term “abbreviated” allows manufacturing and design errors.

  In the above embodiment, the exhaust purification device that reduces and purifies the exhaust gas NOx using ammonia generated by the injection of urea water has been exemplified. However, for example, the exhaust purification using other reducing agents such as light oil It is good also as an apparatus.

  DESCRIPTION OF SYMBOLS 1 ... Exhaust flow path, 2 ... 1st casing (casing), 3 ... Pipe, 3a ... Insertion part, 3b ... Inner wall surface, 4 ... Second casing, 10 ... Exhaust gas purification device, 13 ... Injection device, 13a ... Nozzle , 15 through-holes, 16 through-hole forming portions, 17 through-hole non-forming portions, A.

Claims (1)

An exhaust purification device for purifying exhaust gas flowing through an exhaust passage of an engine,
A cylindrical casing;
A pipe disposed on the downstream side of the casing and inserted in the casing so as to extend in a direction substantially perpendicular to the axial direction of the casing;
An injection device for injecting a reducing agent into the pipe from an upstream end of the pipe,
A through hole forming portion in which a through hole communicating with the casing is formed in an insertion portion of the pipe inserted in the casing, and the through hole is not formed by being disposed on the downstream side of the through hole forming portion. A through hole non-forming portion is formed ,
The exhaust purification device, wherein the through hole forming portion is formed upstream of a position where an injection region of the reducing agent injected from the injection device and an inner wall surface of the pipe are combined .

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