JP2018053751A - Exhaust inner fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a heated quantity of a tip of a fuel injection nozzle.SOLUTION: An exhaust inner injection device comprises a main passage 1 in which a main flow F1 of exhaust gas discharged from an internal combustion engine flows, a concave part 2 opened and communicated on and with the main passage, a mounting hole 13 opened and communicated on and with the concave part, and a fuel injection nozzle 15 inserted and mounted in and to the mounting hole. The concave part is defined at least by a cylindrical wall 21 formed on a main passage side, and a throttle wall 22 formed between the cylindrical wall and the mounting hole. The exhaust inner injection device is constituted to generate a swirl flow F3 inside the cylindrical wall based on an exfoliation flow F2 exfoliated from the main flow at a an opening end of the concave part and at a position of a main flow upstream end, and restrain the swirl flow toward the mounting hole by the throttle wall.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an in-exhaust injection device, and more particularly to an in-exhaust injection device for injecting fuel into exhaust gas discharged from an internal combustion engine.

  There is known an in-exhaust injection device for injecting fuel into exhaust gas discharged from an internal combustion engine. This apparatus mainly injects fuel to regenerate an aftertreatment device such as a particulate filter or a NOx storage reduction catalyst downstream from the device. The apparatus includes a fuel injection nozzle installed facing the exhaust passage.

JP 2009-115057 A

  There is a problem that the tip of the fuel injection nozzle facing the exhaust passage is heated by the heat from the exhaust gas. If the tip of the nozzle falls into an excessively high temperature state, the carbonized fuel (deposit) may be clogged in the injection hole and fuel injection may be hindered. Therefore, it is desirable to suppress the temperature rise at the nozzle tip as much as possible.

  For this reason, generally, a recess is provided in the exhaust passage, and the nozzle tip is disposed so as to face the recess. If it carries out like this, it can suppress that the exhaust gas in an exhaust passage directly hits a nozzle front-end | tip part, and can reduce the heat quantity which the nozzle front-end | tip part receives, ie, the amount of heat.

  However, the separation flow separated from the exhaust gas main flow at the position of the opening end of the recess and the upstream end in the main flow direction may enter the recess and directly hit the nozzle tip. If this happens, the amount of heat at the nozzle tip increases, and the above-mentioned nozzle hole clogging may occur.

  Accordingly, the present invention has been made in view of such circumstances, and an object thereof is to provide an in-exhaust injection device capable of suppressing the amount of heat at the tip of the fuel injection nozzle.

According to one aspect of the invention,
A main passage through which a main flow of exhaust gas discharged from the internal combustion engine flows;
A recess opened and communicated with the main passage;
A mounting hole opened and communicated with the recess;
A fuel injection nozzle inserted into the mounting hole and attached;
With
The recess is defined by at least a cylindrical wall formed on the main passage side, and a throttle wall formed between the cylindrical wall and the mounting hole,
Based on the separation flow separated from the main flow at the position of the opening end of the recess and the main flow upstream end, a swirl flow is generated inside the cylindrical wall, and the swirl flow is directed toward the mounting hole. An in-exhaust injection device is provided that is configured to be suppressed by the above.

  Preferably, the throttle wall is formed so that a cross-sectional area of the recess defined by the cylindrical wall is reduced as it goes toward the mounting hole.

  Preferably, the throttle wall is formed in a crane neck shape having a diameter reduced toward the mounting hole.

  Preferably, the in-exhaust injection device further includes a convex portion that is disposed adjacent to the concave portion on the upstream side of the main flow and protrudes toward the main passage.

  Preferably, the concave portion is also defined by a round surface wall formed on the main passage side of the cylindrical wall.

  Preferably, the main passage has a curved passage, and the concave portion is disposed at an outer corner portion of the curved passage.

  Preferably, the main passage, the recess, and the mounting hole are formed in an exhaust adapter that is a cast product.

  According to the present invention, an excellent effect that the amount of heat at the tip of the fuel injection nozzle can be suppressed is exhibited.

It is sectional drawing which shows the whole in-exhaust injection apparatus which concerns on this embodiment. It is sectional drawing which expands and shows the principal part of the in-exhaust injection device which concerns on this embodiment. It is sectional drawing for demonstrating the effect | action of this embodiment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  An in-exhaust injection device according to an embodiment of the present invention is applied to a compression ignition internal combustion engine, that is, a diesel engine as a vehicle power source mounted on a vehicle. The vehicle is a large vehicle such as a truck, but the type, type, application, etc. of the vehicle is not particularly limited, and may be a small vehicle such as a passenger car. Also, the type of internal combustion engine can be changed as necessary. For example, the engine may be a gasoline engine. The in-exhaust injection device is a device for injecting fuel into the exhaust gas discharged from the engine.

  FIG. 1 shows the entire exhaust gas injection apparatus according to the present embodiment. FIG. 2 is an enlarged view of a main part of the in-exhaust injection device. In the following description, the directions such as up, down, left, and right are referred to only with respect to the illustrated arrangement of the illustrated embodiment for convenience. It should be noted that the illustrated arrangement is changed depending on the vehicle-mounted layout or the like, and the actual directions may be different from the illustrated directions.

  The in-exhaust injection device of the present embodiment includes a main passage 1 through which a main flow F1 of exhaust gas discharged from an engine (not shown) flows, a recess 2 that is open to and communicated with the main passage 1, and a recess 2 A mounting hole 3 that is open and communicated, and an injector or a fuel injection nozzle 4 that is inserted into and attached to the mounting hole 3 are provided.

  In the present embodiment, the main passage 1, the recess 2 and the mounting hole 3 are formed in the exhaust adapter 5. The exhaust adapter 5 is a cast product cast from a metal material such as iron. Since the main passage 1 and the like are formed in the exhaust adapter 5, the degree of freedom of these shapes can be increased. Further, since the mounting hole 3 is formed in the exhaust adapter 5, the heat of the fuel injection nozzle 4 is released to the exhaust adapter 5 having a large heat capacity, and the temperature rise of the fuel injection nozzle 4 can be suppressed.

  The exhaust adapter 5 is provided in the exhaust system of the engine. In the present embodiment, an exhaust brake valve 6 is connected to the upstream side of the exhaust adapter 5, and an exhaust pipe 7 is connected to the downstream side of the exhaust adapter 5. A turbocharger (not shown) turbine is provided upstream of the exhaust brake valve 6. A plurality of aftertreatment devices (not shown) for purifying exhaust gas are provided on the downstream side of the exhaust pipe 7. Each of the plurality of aftertreatment devices includes an oxidation catalyst, a particulate filter (referred to as DPF), a selective reduction type NOx catalyst (referred to as SCR), and an ammonia oxidation catalyst, which are sequentially arranged from the upstream side.

  Thus, the fuel injection nozzle 4 of this embodiment is installed in the downstream of a turbine, and the upstream of an aftertreatment apparatus. However, the installation position can be changed as necessary.

The oxidation catalyst oxidizes and purifies unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust gas, heats the exhaust gas with the reaction heat at this time, raises the temperature of the exhaust gas, and converts NO in the exhaust to NO Oxidizes to ₂ . The DPF is a so-called continuous regeneration type DPF with a catalyst, which collects particulate matter (PM) such as soot contained in the exhaust gas and continuously burns and removes the collected PM. The SCR reduces NOx in the exhaust gas using ammonia resulting from the urea water added on the upstream side as a reducing agent. The ammonia oxidation catalyst oxidizes and purifies excess ammonia discharged from the SCR.

  As is well known, when the amount of accumulated PM in the DPF exceeds a predetermined amount, filter regeneration is performed in which the accumulated PM is forcibly burned and removed to recover the PM trapping ability. During the regeneration of the filter, fuel is injected from the fuel injection nozzle 4. Then, this fuel is burned by the oxidation catalyst, and high-temperature and rich exhaust gas is discharged from the oxidation catalyst. This high-temperature rich exhaust gas is supplied to the DPF, and the deposited PM in the DPF is burned and removed.

  In addition, when a NOx storage reduction catalyst (referred to as LNT) is provided in place of the SCR, LNT regeneration that periodically removes NOx and sulfur components stored in the LNT is performed. Fuel is also injected from the fuel injection nozzle 4 during the LNT regeneration.

  An upstream end flange 8 is integrally provided at the upstream end portion of the exhaust adapter 5, and the downstream end portion of the exhaust brake valve 6 is fixed thereto by a fastener such as a bolt. A downstream end flange 9 is integrally provided at the downstream end of the exhaust adapter 5. An exhaust pipe flange 10 is integrally fixed to the upstream end of the exhaust pipe 7 by welding. The exhaust pipe flange 10 is fixed to the downstream end flange 9 by a fastener such as a bolt. A cylindrical portion 11 that defines the downstream end portion of the main passage 1 is formed at the downstream end portion of the exhaust adapter 5, and the cylindrical portion 11 is fitted and inserted into the exhaust pipe 7.

  The main passage 1 extends from the upper side to the lower side and is curved so as to bend gently to the left as it goes downward. More specifically, the main passage 1 has an upstream straight section L1 extending from the upper end or the upstream end to a predetermined distance below or downstream, a bending section L2 that bends to the left from the end of the upstream straight section L1, and a bending. A section is divided into a downstream straight section L3 that extends diagonally to the left from the end of the section L2 to the lower end or downstream end of the main passage 1. A straight path is formed in the upstream straight section L1 and the downstream straight section L3, and a curved path is formed in the curved section L2. The main passage 1 extends along the central axis C, and the cross-sectional shape perpendicular to the central axis C is basically circular. The main passage 1 is defined by a main passage inner wall 12.

  The recessed part 2 is arrange | positioned at the side part of the main channel | path 1, more specifically, the outer corner part, ie, right side part of the curved channel | path formed in the curved area L2. The mounting hole 3 is opened at the closed end of the recess 2 on the side opposite to the main passage (the side away from the main passage 1, the right side in the figure). The fuel injection nozzle 4 is constructed and arranged so as to inject fuel in a conical shape around the spray axis S and along the recess axis 2 and thus into the main passage 1 along a predetermined spray angle θ. . The spray axis S, the spray angle θ, and the spray penetration force are set so that the injected fuel spray B does not directly contact the main passage 1 and the inner wall of the recess 2. This is because when the direct contact occurs, the fuel is carbonized at the contact point, causing problems such as reducing the passage area. The spray axis S and the main passage center axis C intersect with each other with a predetermined acute angle α.

  In the case of this embodiment, the recess 2, the mounting hole 3, and the fuel injection nozzle 4 are arranged coaxially with the spray axis S. However, the mounting hole 3 and the fuel injection nozzle 4 are not necessarily coaxial with the spray axis S, and may be inclined with respect to the spray axis S. The recess 2 may also be slightly inclined with respect to the spray axis S within a range where direct contact of the fuel spray B does not occur. The mounting hole 3 has a stepped shape, and has a stepped hole formed on the side of the main passage (closest to the main passage 1, the left side in the drawing) and on the side opposite to the main passage 1. And a radial hole 14.

  The tip hole 13 has a constant inner diameter and a predetermined length. A front end portion (referred to as a nozzle front end portion) 15 of the fuel injection nozzle 4 is fitted and inserted into the front end hole 13 so that heat from the nozzle front end portion 15 is directly released to the exhaust adapter 5. The nozzle tip 15 also has a constant outer diameter and a predetermined length. Inside the exhaust adapter 5, a cooling hole 16 in which refrigerant is stored is formed so as to surround the outer peripheral side of the tip hole 13. The refrigerant of this embodiment is engine cooling water. The cooling hole 16 is provided with an inlet and an outlet (not shown) so that the cooling water in the cooling hole 16 is constantly exchanged. Thus, the nozzle tip portion 15 is cooled by the cooling water.

  The base end portion of the fuel injection nozzle 4 is fixed in close contact with the step-shaped enlarged hole 14. By this tightly fixed portion and the tightly fitted portion of the tip hole 13 and the nozzle tip portion 15, the exhaust gas leakage from the main passage 1 is reliably prevented.

  The exhaust injection device of the present embodiment further includes a convex portion 17. The convex portion 17 is disposed adjacent to the concave portion 2 on the upstream side in the main flow direction (referred to as the main flow upstream side), and protrudes into the main passage 1. For reference, a virtual line E shows a cross-sectional shape of the main passage 1 when it is assumed that there is no convex portion 17.

  The convex part 17 is also arrange | positioned in the outer corner part of the bending area L2. The convex portion 17 has a cross-sectional shape or an inclined surface shape that linearly extends from the starting point of the bending section L2 into the main passage 1, and a cross-sectional shape that defines a substantially triangular cross-section together with the virtual line E Have The concave portion 2 starts from the top portion of the convex portion 17 located on the innermost side of the main passage 1 and on the downstream side in the main flow direction (referred to as the main flow downstream side).

  FIG. 2 shows details in the vicinity of the recess 2. As shown in the figure, a well-known sack portion 19 is formed to protrude from the tip surface 18 of the nozzle tip portion 15. A nozzle hole (not shown), which is a fuel injection port, is formed at the tip of the sack portion 19. In the present embodiment, the fuel injection nozzle 4 is a single hole type having one injection hole, but may be a multihole type having a plurality of injection holes. The tip position of the sack portion 19, that is, the outlet position of the nozzle hole is aligned with the tip position 13 </ b> A of the tip hole 13.

  The recess 2 is defined by at least a cylindrical wall 21 formed on the main passage side and a throttle wall 22 formed between the cylindrical wall 21 and the mounting hole 3 (specifically, the tip hole 13). In the case of the present embodiment, the recess 2 includes the rounded surface wall 23 arranged closest to the main passage side, the cylindrical wall 21 arranged adjacent to the anti-main passage side of the rounded surface wall 23, and the anti-main passage of the cylindrical wall 21. And a diaphragm wall 22 arranged adjacent to the side. A tip hole 13 is disposed adjacent to the throttle wall 22 on the side opposite to the main passage. The rounded wall 23 is represented by a section from position a to position b, the cylindrical wall 21 is represented by a section from position b to position c, and the diaphragm wall 22 is represented by a section from position c to position d. There is a tip position 13A of the tip hole 13 at the position d.

  The cylindrical wall 21 has a cylindrical shape or a substantially cylindrical shape with the spray axis S as the center. In the present embodiment, the lower end edge 21A of the cylindrical wall 21 is parallel to the spray axis S, while the upper end edge 21B of the cylindrical wall 21 is slightly inclined so that the radius becomes smaller toward the opposite main passage side. Yes. However, the upper end edge 21B of the cylindrical wall 21 may also be parallel to the spray axis S.

  The throttle wall 22 is formed so as to reduce the cross-sectional area of the recess 2 defined by the cylindrical wall 21 (the area of the cross section perpendicular to the spray axis S) toward the tip hole 13. In the case of the present embodiment, the throttle wall 22 is formed in a crane neck shape that decreases in diameter toward the tip hole 13. That is, the restricting wall 22 has a first rounded surface portion 24 that bends in a diameter-reducing direction abruptly as it goes from the position c to the opposite main passage side, and a sudden and rounded shape as it goes from the position d toward the main passage side. It has the 2nd round surface part 25 which curves in a radial direction, and the conical surface part 26 which connects these 1st round surface parts 24 and the 2nd round surface part 25 linearly. The opposite main passage side end of the second round surface portion 25 is connected to the tip hole 13 in a tangential manner.

  The rounded surface wall 23 forms an opening end of the recess 2 that opens into the main passage 1. The upper end portion of the concave portion 2 is an end portion on the upstream side in the main flow direction (referred to as main flow upstream end portion), and the lower end portion of the concave portion 2 is an end portion on the downstream side in the main flow direction (referred to as main flow downstream end portion). The mainstream upstream end portion 23 </ b> A of the rounded surface wall 23 smoothly connects the top portion of the convex portion 17 and the cylindrical wall 21. The mainstream downstream end 23B of the rounded surface wall 23 also smoothly connects the main passage inner wall 12 and the cylindrical wall 21 below. The mainstream upstream end 23A of the rounded wall 23 has a smaller radius of curvature than the mainstream downstream end 23B and a length in the spray axis S direction.

  Next, the operation of this embodiment will be described.

  As shown in FIG. 1, the main flow F1 of the exhaust gas flows from the upper side to the lower side in the main passage 1 substantially along the direction of the central axis C as indicated by an arrow. On the other hand, in the outer corner portion of the bending section L2, the main flow F1 is positively guided by the convex portion 17 to the main passage side (left side) or the central axis C side. As a result, the main flow F1 is guided away from the recess 2, and the main flow F1 can be prevented from entering the recess 2 and further reaching the nozzle tip 15.

  On the other hand, as shown in FIG. 3, the flow of the main flow F <b> 1 along the wall surface of the convex portion 17 is separated from the convex portion 17 when it reaches the rounded surface wall 23, and the separation flow F <b> 2 heading toward the concave portion 2. Generate. The separated flow F2 collides with at least one of the round surface wall 23 and the cylindrical wall 21, is reflected, and generates a swirling flow F3 that swirls around the spray axis S inside the cylindrical wall 21. In this way, the swirl flow F3 is generated based on the separated flow F2.

  However, on the side opposite to the main passage (right side) of the cylindrical wall 21, there is a throttle wall 22 that reduces the cross-sectional area of the recess 2 relatively rapidly. The throttle wall 22 suppresses the swirling flow F <b> 3 from moving toward the tip hole 13, and hence the nozzle tip 15. As a result, the swirl flow F3 does not substantially occur inside the throttle wall 22 or is small even if it occurs. Even if the swirl flow F <b> 3 is generated, the flow velocity is very low as compared with the swirl flow F <b> 3 in the cylindrical wall 21.

  Therefore, even if the hot swirling flow F3 does not directly hit or hits the nozzle tip 15, more specifically, the sack 19 of the nozzle tip face 18 that faces the recess 2 and has the injection hole, Is greatly limited. It is considered that the heat received from the exhaust gas at the nozzle tip 15 is dominated by radiation rather than by direct transmission. Accordingly, the amount of heat that the nozzle tip 15 receives from the high-temperature exhaust gas per unit time, that is, the amount of heat, can be suppressed. And it is possible to suppress the temperature rise of the nozzle front-end | tip part 15, and to suppress the injection hole clogging by carbonized fuel.

  As described above, the in-exhaust injection device of the present embodiment is configured to suppress the swirling flow F <b> 3 generated inside the cylindrical wall 21 from being directed toward the mounting hole 3 by the throttle wall 22. For this reason, the amount of heat of the nozzle tip 15 can be effectively suppressed.

  If the temperature of the nozzle tip portion 15 is excessively increased, the hardness of the seat portion inside the sack portion 19 and the needle valve that can be separated and seated on the seat portion decreases, and there is a possibility that these wears occur. However, according to this embodiment, since the temperature rise of the nozzle tip 15 can be suppressed, such wear can also be suppressed.

  Further, the fuel injected from the fuel injection nozzle 4 may adhere to the inner wall of the recess in the vicinity of the nozzle tip 15 and carbonize and accumulate, which may cause injection failure and injection hole clogging.

  However, according to the present embodiment, the gas flow velocity in the inner region of the throttle wall 22 located immediately after the nozzle hole outlet is slow, so that it is not easily affected by the gas flow, and fuel is injected through the inner region smoothly. can do. Therefore, it is possible to suppress fuel adhesion and carbonization in the vicinity of the nozzle tip 15 and injection failure and injection hole clogging associated therewith.

  Also, if the exhaust gas mainstream is easy to reach the nozzle tip as in the conventional structure, soot contained in the mainstream tends to adhere to and accumulate on the nozzle tip and its vicinity, causing clogging of the nozzle holes. Become. However, in the case of the present embodiment, the swirl flow F3 derived from the main flow F1 is difficult to reach the inner region of the nozzle tip 15 and the throttle wall 22 in the vicinity thereof, so that such deposition and deposition of soot can be suppressed.

  Note that the amount of heat at the nozzle tip 15 can also be suppressed by changing the position of the fuel injection nozzle 4 to the position on the side opposite to the main passage. However, in this case, the fuel spray collides with the inner wall of the recess 2 and an appropriate fuel is obtained. There is a possibility that the injection cannot be performed. In the present embodiment, since the amount of heat at the nozzle tip 15 can be suppressed while the position of the fuel injection nozzle 4 is as close to the recess 2 as possible, it is possible to simultaneously solve the fuel spray collision and the suppression of the amount of heat.

  As mentioned above, although embodiment of this invention was described in detail, the following other embodiments are also possible for this invention.

  (1) The shape of the diaphragm wall is not limited to a crane neck shape, and may be another shape that produces the same effect as described above. For example, the diaphragm wall may have a ring-shaped projecting wall that projects all around the center of the recess, or may have a stepped or stepped diameter.

  (2) The main passage, the concave portion, and the mounting hole are not necessarily formed in the exhaust adapter. For example, the main passage may be formed of an exhaust pipe, the recess and the mounting hole may be formed in separate cast parts, and the exhaust pipe and the cast parts may be fixed to each other by welding or bolting. All of the main passage, the concave portion and the mounting hole may be formed of a pipe material, and all of them may be integrated by welding or the like.

  (3) If possible, the convex portion may be omitted. Moreover, you may form the main channel | path which a recessed part opens with a linear channel | path instead of a curved channel | path.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Main channel | path 2 Concave 3 Mounting hole 4 Fuel injection nozzle 5 Exhaust adapter 17 Convex part 21 Cylindrical wall 22 Restriction wall 23 Round surface wall F1 Main flow F2 Separation flow F3 Swirl

Claims (7)

A main passage through which a main flow of exhaust gas discharged from the internal combustion engine flows;
A recess opened and communicated with the main passage;
A mounting hole opened and communicated with the recess;
A fuel injection nozzle inserted into the mounting hole and attached;
With
The recess is defined by at least a cylindrical wall formed on the main passage side, and a throttle wall formed between the cylindrical wall and the mounting hole,
Based on the separation flow separated from the main flow at the position of the opening end of the recess and the main flow upstream end, a swirl flow is generated inside the cylindrical wall, and the swirl flow is directed toward the mounting hole. An exhaust-injection apparatus characterized by being configured to suppress by the above. 2. The in-exhaust injection device according to claim 1, wherein the throttle wall is formed so that a cross-sectional area of the concave portion defined by the cylindrical wall is reduced toward the attachment hole. The in-exhaust injection device according to claim 1 or 2, wherein the throttle wall is formed in a crane neck shape having a diameter reduced toward the mounting hole. The in-exhaust injection device according to any one of claims 1 to 3, further comprising a convex portion that is disposed adjacent to the concave portion on the upstream side of the main flow and protrudes into the main passage. . The in-exhaust injection device according to any one of claims 1 to 4, wherein the concave portion is also defined by a round surface wall formed on the main passage side of the cylindrical wall. The exhaust injection apparatus according to any one of claims 1 to 5, wherein the main passage has a curved passage, and the concave portion is disposed at an outer corner portion of the curved passage. The exhaust injection apparatus according to any one of claims 1 to 6, wherein the main passage, the recess, and the mounting hole are formed in an exhaust adapter that is a cast product.

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