Exhaust purification system

Abstract

To provide an exhaust emission control system for promoting atomization and vaporization of liquid droplets of an additive to disperse the liquid droplets uniformly in the radial direction of an exhaust introduction passage before exhaust gas including the injected liquid additive passes through the exhaust introduction passage and then reaches an exhaust emission control device on the downstream side.SOLUTION: A collision plate having an injection surface is disposed in an exhaust introduction passage. The injection surface includes: a collision region with which an additive injected from an addition valve collides; and a downstream region located downstream of the collision region. The downstream region includes a liquid droplet collision wall with which liquid droplets of the additive moved to the downstream side by exhaust gas collides. The liquid droplet collision wall is formed by a surface of either of a projection part and a recessed part.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an exhaust gas purification system, for example, to an exhaust gas purification system applied to an internal combustion engine mounted on a vehicle. [Background technology]

[0002] There is known an internal combustion engine that is installed in a vehicle and has an oxidation catalyst and DPF (Diesel Particulate Filter) in the exhaust passage. The oxidation catalyst oxidizes and purifies carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust (combustion gas, exhaust gas) of the internal combustion engine. The DPF captures particulate matter (PM) contained in the exhaust.

[0003] When the amount of particulate matter deposited in the DPF (specifically, its estimated value) exceeds a threshold value, a "DPF regeneration process" is executed in which high-temperature exhaust gas is introduced into the DPF to burn the particulate matter. In order to increase the temperature inside the oxidation catalyst during the DPF regeneration process and thereby increase the temperature of the exhaust gas flowing out of the oxidation catalyst and into the DPF, a fuel addition valve (fuel injection valve) may be disposed upstream of the oxidation catalyst in the exhaust flow passage.

[0004] In this configuration, in order to prevent a portion of the oxidation catalyst from becoming locally extremely hot, it is desirable that the added (injected) fuel is uniformly dispersed in the radial direction of the exhaust flow path when it flows into the oxidation catalyst. Therefore, for example, Patent Document 1 proposes an embodiment in which a collision plate is provided at a position in the exhaust pipe where the fuel injected from the fuel addition valve collides. In this embodiment, the fuel flowing over the collision plate is encouraged to scatter in the form of mist around the surroundings. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-168907 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in recent years, when there is a demand for smaller internal combustion engines, it may be difficult to ensure a sufficient distance in the exhaust passage from the fuel addition valve to the oxidation catalyst. In this case, even if the above-mentioned embodiment is adopted, there is a risk that the fuel will not be sufficiently diffused between when it is injected by the fuel addition valve and when it flows into the oxidation catalyst.

[0007] The present invention has been devised in view of the above circumstances, and has an object to provide an exhaust gas purification system that can quickly diffuse fuel injected from a fuel addition valve. [Means for solving the problem]

[0008] The exhaust purification system according to the present disclosure includes an exhaust purification device, an exhaust introduction passage, an additive valve, and an impact plate. The exhaust purification device purifies exhaust from an internal combustion engine. The exhaust introduction passage introduces exhaust to the exhaust purification device. The additive valve injects a liquid additive into exhaust flowing through the exhaust introduction passage. The impact plate is disposed inside the exhaust introduction passage and has an injection surface including a collision area where the additive injected from the additive valve impacts. The impingement plate may be configured to divide the flow path of the exhaust between a side of the ejection surface and a side opposite the ejection surface.

[0009] The exhaust purification system further includes one or more droplet collision walls on which droplets of the additive moved downstream by the exhaust collide. The droplet collision walls are provided by any one of a protrusion and a recess that protrude toward the exhaust gas and are formed in a downstream region of the injection surface downstream of the collision region. The droplet collision walls may be provided by the surfaces of the multiple protrusions. In this case, the protrusions may include those constituting an upstream protrusion row arranged in a direction substantially perpendicular to the exhaust gas flow direction. In addition, the protrusions may include downstream protrusions arranged so as to appear between "protrusions constituting the upstream protrusion row and adjacent to each other" when viewed from the upstream side along the exhaust gas flow direction.

[0010] The additive (e.g., fuel) injected from the additive valve diffuses in the exhaust gas inlet passage and flows into the exhaust gas purification device (e.g., oxidation catalyst). The injected additive (especially droplets with large particle size and high penetration power) collides with the collision area of ​​the collision plate, causing scattering and adhesion.

[0011] Some of the droplets scattered in the collision area collide with a droplet collision wall in the downstream area (i.e., an area downstream of the collision area on the collision plate (injection surface) with respect to the exhaust flow in the exhaust inlet passage), causing scattering and adhesion again. If multiple droplet collision walls are formed in the downstream area, a certain droplet may collide with the droplet collision wall multiple times, and each time the droplet may split into multiple droplets with smaller diameters. Alternatively, the droplets that have adhered to the downstream area may be prevented from moving downstream due to exhaust gas by the droplet collision wall, causing them to vaporize there.

[0012] In other words, the formation of a droplet collision wall in the downstream region on the collision plate promotes atomization (change to droplets with smaller particle size, atomization) and vaporization of the additive, which in turn promotes the diffusion of the additive injected from the additive valve in the exhaust inlet passage. Therefore, at the downstream end of the exhaust inlet passage (i.e., the exhaust inlet portion in the exhaust purification device), the additive is more likely to be uniformly dispersed in the radial direction of the exhaust inlet passage.

[0013] According to another feature of the present disclosure, the collision plate is disposed such that the distance between a back surface of the collision plate relative to the ejection front surface and an inner wall surface of the exhaust introduction passage opposed to the back surface becomes smaller toward the downstream side.

[0014] According to this configuration, the amount of exhaust gas impinging on the rear surface of the impingement plate is increased, so that even if the temperature of the impingement plate is reduced due to the additive adhering to the injection surface of the impingement plate, the transfer of thermal energy from the exhaust gas to the impingement plate is promoted, and as a result, the amount of temperature reduction of the impingement plate is reduced, and therefore the vaporization of the fuel adhering to the injection surface is promoted.

[0015] In addition, with this configuration, the rear surface of the collision plate functions as a throttle of the exhaust flow path, and a difference occurs between the exhaust flow velocity on the rear surface side of the collision plate and the exhaust flow velocity on the injection surface side of the collision plate, which generates turbulence in the section downstream of the collision plate in the exhaust introduction path, further promoting the diffusion of the additive.

[0016] According to another feature of the present disclosure, the droplet collision wall is provided by a surface of either a protrusion or a recess that protrudes toward the exhaust gas and is formed on an inner wall surface of the exhaust gas introduction passage downstream of the collision plate. The droplet collision wall may be provided by a surface of an annular recess formed continuously on the inner wall surface of the exhaust introduction passage downstream of the collision plate. The annular recess may be disposed in a curved portion of the exhaust introduction passage.

[0017] In some cases, droplets of the additive adhering to the inner wall of the exhaust inlet passage downstream of the collision plate in the exhaust flow may move downstream due to the exhaust gas. The droplets moving downstream may collide with a droplet collision wall formed on the inner wall of the exhaust inlet passage, or the droplets may be prevented from moving further downstream by the droplet collision wall, which further promotes atomization and vaporization of the droplets.

[0018] According to another feature of the present disclosure, the impingement plate is disposed at a curved portion of the exhaust inlet passage. In this case, the multiple protrusions may include a downstream protrusion that constitutes a downstream protrusion row, which is a protrusion that includes a downstream protrusion and is arranged in a direction approximately perpendicular to the flow direction, and the arrangement direction of the downstream protrusion row may be inclined relative to the arrangement direction of the upstream protrusion row in accordance with the curved portion.

[0019] Turbulence of the exhaust gas occurs at the curved portion of the exhaust gas introduction passage (i.e., the portion where the exhaust gas introduction passage is a curved pipe), and the additive is injected from the addition valve into the turbulent flow. In addition, the turbulence of the exhaust gas becomes even more intense at the position where the turbulent exhaust gas flow on the injection surface side of the collision plate and the turbulent exhaust gas flow on the back side of the collision plate join together. This further promotes atomization and vaporization of the droplets. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic configuration diagram of an engine system to which an exhaust purification system is applied. [Diagram 2] FIG. 2 is an enlarged view of the exhaust purification system. [Diagram 3] FIG. 3 is an end view taken along line III-III of FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. [Diagram 5] 3 is an enlarged view of an impact plate included in the exhaust purification system. FIG. [Figure 6] FIG. 11 is a cross-sectional view of a collision plate according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] A first embodiment will be described with reference to Figs. 1 to 5. The same reference numbers in the description refer to the same elements having the same functions without duplicate description. An exhaust purification system according to the present invention is applied to an exhaust flow path of an engine system 1 shown in Fig. 1. The engine system 1 includes an internal combustion engine 2, an intake system 3, an exhaust system 4, a turbocharger 6, and an ECU 7. The internal combustion engine 2 in this embodiment is a four-cylinder diesel engine mounted on a vehicle (not shown) as a driving force source.

[0022] The internal combustion engine 2 includes a fuel injection valve 21 and a crank angle sensor 22. The fuel injection valve 21 injects high-pressure fuel supplied from an accumulator chamber (not shown) of a common rail device into a cylinder in response to an instruction from the ECU 7. The crank angle sensor 22 outputs a pulse signal to the ECU 7 every time a crankshaft (not shown) of the internal combustion engine 2 rotates by a predetermined angle.

[0023] The intake system 3 includes an intake pipe 31 and an intake manifold 32. A downstream end of the intake pipe 31 is connected to the intake manifold 32. The intake manifold 32 introduces air (fresh air) into each cylinder of the internal combustion engine 2.

[0024] The exhaust system 4 includes an exhaust manifold 41, an exhaust pipe 42, a fuel addition valve 43, a first oxidation catalyst 44, a DPF (Diesel Particulate Filter) 45, a urea water addition valve 46, an SCR (Selective Catalytic Reduction) 47, a second oxidation catalyst 48, NOx sensors 51a-51b, temperature sensors 52a-52d, and a differential pressure sensor 53.

[0025] A downstream end of the exhaust manifold 41 is connected to an exhaust pipe 42. The exhaust manifold 41 introduces exhaust (combustion gas) discharged from each cylinder of the internal combustion engine 2 into the exhaust pipe 42. A fuel addition valve 43, a first oxidation catalyst 44, a DPF 45, a urea water addition valve 46, an SCR 47, and a second oxidation catalyst 48 are respectively provided in the exhaust pipe 42 in this order.

[0026] The fuel addition valve 43 injects fuel into the exhaust pipe 42 in response to an instruction from the ECU 7. The first oxidation catalyst 44 is a diesel oxidation catalyst (DOC) that oxidizes and purifies carbon monoxide (CO), hydrocarbons (HC), and the like contained in the exhaust gas. The DPF 45 collects particulate matter (PM) contained in the exhaust gas.

[0027] The urea water addition valve 46 injects urea water into the exhaust pipe 42 in response to a command from the ECU 7. The SCR 47 reduces and purifies nitrogen oxides (NOx) contained in the exhaust gas using ammonia gas produced by hydrolysis of the urea water injected from the urea water addition valve 46. The second oxidation catalyst 48 oxidizes and purifies the residual ammonia gas discharged from the SCR 47.

[0028] The NOx sensors 51a and 51b detect the NOx concentration, which is the concentration of nitrogen oxides contained in the exhaust gas, and output a signal indicative of the NOx concentration to the ECU 7. The NOx sensor 51a is disposed in the exhaust pipe 42 at a position between the DPF 45 and the urea water addition valve 46. The NOx sensor 51b is disposed in the exhaust pipe 42 at a position between the SCR 47 and the second oxidation catalyst 48.

[0029] The temperature sensors 52a, 52b, 52c, and 52d detect the exhaust temperature and output a signal indicating the temperature to the ECU 7. The temperature sensor 52a is disposed in a position between the fuel addition valve 43 and the first oxidation catalyst 44 in the exhaust pipe 42. The temperature sensor 52b is disposed in a position between the first oxidation catalyst 44 and the DPF 45 in the exhaust pipe 42. The temperature sensor 52c is disposed in a position between the DPF 45 and the urea water addition valve 46 in the exhaust pipe 42. The temperature sensor 52d is disposed in a position between the SCR 47 and the second oxidation catalyst 48 in the exhaust pipe 42.

[0030] The differential pressure sensor 53 detects a pressure difference Pd, which is the difference between the pressure of the exhaust gas flowing into the DPF 45 and the pressure of the exhaust gas flowing out from the DPF 45, and outputs a signal indicative of the pressure difference Pd to the ECU .

[0031] The turbocharger 6 includes a compressor 61 and a turbine 62 that are linked to each other. The compressor 61 is disposed in the intake pipe 31. The turbine 62 is disposed in the exhaust pipe 42 at a position upstream of the fuel addition valve 43. The turbocharger 6 uses exhaust pressure to drive (rotate) the turbine 62, thereby driving (rotating) the compressor 61, and pressurizes the air to be taken into each cylinder of the internal combustion engine 2.

[0032] The ECU 7 is an electronic control unit including a CPU, a ROM, a RAM, and an EEPROM. The CPU sequentially executes a predetermined program to read data, perform numerical calculations, and output the results of the calculations. The ROM stores the programs executed by the CPU and maps (look-up tables), etc. The RAM temporarily stores data referenced by the CPU. The EEPROM retains the stored data even when the ECU 7 stops operating.

[0033] The ECU 7 is connected to an accelerator opening sensor 71 and a vehicle speed sensor 72. The accelerator opening sensor 71 detects an accelerator pedal opening Ap, which is the opening of an accelerator pedal (not shown) operated by a driver of a vehicle equipped with the internal combustion engine 2 to accelerate the vehicle, and outputs a signal representing the accelerator pedal opening Ap to the ECU 7. The vehicle speed sensor 72 detects a vehicle speed Vs, which is the traveling speed of the vehicle equipped with the internal combustion engine 2, and outputs a signal representing the vehicle speed Vs to the ECU 7.

[0034] The ECU 7 acquires the engine speed NE of the internal combustion engine 2 based on the pulse signal input from the crank angle sensor 22. The ECU 7 acquires the crank angle CA of a specific cylinder included in the internal combustion engine 2 based on the pulse signal input from the crank angle sensor 22 and a pulse input from a cam position sensor (not shown).

[0035] The ECU 7 acquires a required load Lr for the internal combustion engine 2 based on the accelerator pedal opening Ap, the vehicle speed Vs, etc. The ECU 7 determines a fuel injection pattern including (a plurality of) combinations of fuel injection timing represented by the crank angle CA and the fuel injection amount at that timing based on the required load Lr, the engine rotation speed NE, etc. The ECU 7 causes the fuel injection valve 21 of each cylinder to inject fuel in accordance with the fuel injection pattern.

[0036] Furthermore, the ECU 7 executes an "exhaust gas purification process" for controlling the fuel addition valve 43, the urea water addition valve 46, etc., based on the detection values ​​of the NOx sensors 51a-51b, the temperature sensors 52a-52d, and the differential pressure sensor 53, etc. The exhaust gas purification process includes a "DPF regeneration process."

[0037] The DPF regeneration process is a process for burning and removing the accumulated particulate matter when an estimated amount of particulate matter trapped and accumulated in the DPF 45 exceeds a predetermined threshold. The DPF regeneration process is performed by injecting (discharging) fuel through the fuel addition valve 43 and causing the exhaust gas, the temperature of which has increased as a result of the injected fuel being oxidized in the first oxidation catalyst 44, to flow into the DPF 45. The ECU 7 estimates the amount of particulate matter accumulated in the DPF 45 based on the pressure difference Pd detected by the differential pressure sensor 53. The ECU 7 determines the amount of fuel injected from the fuel addition valve 43, the injection timing, and the like, based on the exhaust gas temperature detected by the temperature sensors 52a, 52b, and 52c.

[0038] As shown in Figures 1 and 2, the fuel addition valve 43 is disposed in the curved portion 42a located between the turbine 62 and the temperature sensor 52a in the exhaust pipe 42. Fuel (i.e., liquid additive) is supplied to the fuel addition valve 43 through a fuel supply pipe (not shown). In Figure 2, only the mounting position of the temperature sensor 52a is shown. The axis Lc represents the longitudinal center of the exhaust pipe 42. An impact plate 81 is disposed within the curved portion 42a.

[0039] The section of the exhaust pipe 42 from the turbine 62 to the first oxidation catalyst 44, including the curved portion 42a, is also referred to as the "exhaust introduction passage" for convenience. The exhaust introduction passage, the fuel addition valve 43, the first oxidation catalyst 44, and the collision plate 81 are also collectively referred to as the "exhaust purification system" for convenience. In this case, the first oxidation catalyst 44 is also referred to as the "exhaust purification device" for convenience.

[0040] As shown in FIG. 3, the exhaust flow passage in the exhaust pipe 42 at the curved portion 42a is divided into a first flow passage 42a1 and a second flow passage 42a2 by an impact plate 81. The surface of the impact plate 81 that defines the first flow passage 42a1 is also referred to as an injection surface 81a. The fuel addition valve 43 is disposed in the exhaust pipe 42 so as to inject fuel into the exhaust in the first flow passage 42a1. As shown in FIGS. 2 to 4, a plurality of protrusions 82 are formed on the surface of the impact plate 81 (specifically, the injection surface 81a). The dashed lines drawn between the plurality of protrusions 82 and the inner wall surface of the exhaust pipe 42 in FIG. 2 indicate the boundaries between the flat portion of the impact plate 81 and the curved portions at both ends (see FIG. 3). The temperature sensor 52a is omitted in FIG. 4 (and FIG. 6 described later).

[0041] The fuel addition valve 43 is disposed on the curved portion 42a so as to inject fuel toward region R1 shown in Fig. 5. A protrusion 82a, which is one of the protrusions 82, is disposed in region R1 on the injection surface 81a. Of the fuel injected from the fuel addition valve 43, droplets having a relatively strong penetrating force collide with the injection surface 81a including the surface of the protrusion 82. The region on the injection surface 81a with which the fuel injected from the fuel addition valve 43 (directly) collides is also referred to as the "impingement region" for convenience, and is generally represented by region R2 in Fig. 5. The region downstream of the collision region on the injection surface 81a is also referred to as the "downstream region" for convenience, and is generally represented by region R3.

[0042] Each of the protrusions 82 in the downstream region is also referred to as a "protrusion" for convenience. A protrusion is a convex portion, a step, or the like (surface) that protrudes toward the exhaust gas in the downstream region or the inner wall of the exhaust introduction passage and is formed so that the cross-sectional area of ​​the exhaust gas flow passage is reduced at that location. The surfaces of the protrusions and recesses described below are also referred to as a "droplet collision wall" for convenience.

[0043] Some of the droplets that collide with the ejection surface 81a are reflected (scattered, dispersed) by the ejection surface 81a and become droplets with smaller particle diameters. Other parts of the droplets that collide with the ejection surface 81a adhere (remain) on the ejection surface 81a. Some of the droplets that are scattered by the ejection surface 81a move downstream and collide with the surface (side surface or upper surface) of the protrusion 81a that is downstream of the position where they were scattered. Some of the droplets that adhere to the ejection surface 81a are peeled off from the ejection surface 81a by the exhaust gas flowing through the first flow path 42a1 (i.e., are separated from the ejection surface 81a) and move downstream to collide with the surface of the protrusion 82. When the droplets collide with the protrusion 82 repeatedly, atomization (atomization) of the droplets is promoted.

[0044] Other parts of the droplets adhering to the ejection surface 81a move downstream on the ejection surface 81a. At this time, the surface (side surface) of the protrusion 82 may block the droplets from moving downstream. When the protrusion 82 blocks the droplets from moving downstream, the droplets remain on the ejection surface 81a for a long time. This increases the possibility that the droplets will evaporate on the ejection surface 81a.

[0045] The droplet Df shown in FIG. 5 is an example of a droplet attached to the ejection surface 81a. In this example, the droplet Df is peeled off from the ejection surface 81a by the exhaust gas flowing through the first flow path 42a1, moves downstream along the arrow A1, collides with the protrusion 82b, and is scattered, and splits into a plurality of droplets with smaller particle sizes. One of the split droplets moves along the arrow A2 in the exhaust gas and collides with another one of the protrusions 82. Meanwhile, the other one of the split droplets moves along the arrow A3 on the ejection surface 81a and is blocked by the other one of the protrusions 82. Next, the droplet moves along the arrow A4 on the ejection surface 81a by the exhaust gas, is blocked by the other one of the protrusions 82, and is vaporized there.

[0046] 4, the cross-sectional area of ​​the second flow passage 42a2 becomes smaller toward the downstream. In other words, the distance Dp between the surface of the collision plate 81 (i.e., the back surface 81b of the ejection surface 81a) that forms the second flow passage 42a2 in the collision plate 81 and the inner wall surface of the exhaust pipe 42 facing the back surface 81b becomes smaller toward the downstream of the exhaust pipe 42.

[0047] The flow passage distance Dp is expressed, for example, as the distance between the back surface 81b and the exhaust pipe 42 on the back surface 81b side in a cross-sectional view (i.e., FIG. 4) obtained by cutting the exhaust pipe 42 along a plane that includes the axis Lc and is perpendicular to the back surface 81b. As shown in FIG. 4, the flow passage distance Dp at the upstream end of the collision plate 81 is distance D1. The flow passage distance Dp at the downstream end of the collision plate 81 is distance D2. The distance D2 is smaller than the distance D1 (i.e., D1>D2), and therefore the flow passage cross-sectional area of ​​the second flow passage 42a2 decreases downstream.

[0048] Since the in-flow path distance Dp becomes smaller toward the downstream side, the amount of exhaust gas colliding with the back surface 81b increases. Therefore, even if the temperature of the collision plate 81 decreases due to the collision of the fuel injected from the fuel addition valve 43, the back surface 81b is heated by the exhaust gas. As a result, the amount of decrease in temperature of the collision plate 81 decreases, and the vaporization of the fuel droplets adhering to the injection surface 81a (for example, the droplets that move on the injection surface 81a along the above-mentioned arrows A3 and A4) is promoted.

[0049] In addition, since the flow passage cross-sectional area of ​​the second flow passage 42a2 becomes smaller toward the downstream, the flow velocity of the exhaust gas in the second flow passage 42a2 increases. On the other hand, since the flow passage cross-sectional area of ​​the first flow passage 42a1 becomes larger toward the downstream, the flow velocity of the exhaust gas in the first flow passage 42a1 decreases. Therefore, turbulence occurs at the point where the first flow passage 42a1 and the second flow passage 42a2 join near the downstream end of the collision plate 81, and the diffusion of the fuel injected from the fuel addition valve 43 is promoted.

[0050] Recesses 91a and 91b are formed in the section of the exhaust pipe 42 between the curved portion 42a (specifically, the collision plate 81) and the first oxidation catalyst 44. Each of the recesses 91a and 91b is an annular recess provided on the inner wall surface of the exhaust pipe 42. In other words, the inner diameter of the exhaust pipe 42 in the section where the recess 91a is formed (i.e., the distance from the axis Lc to the inner wall surface) is larger than the upstream and downstream sections adjacent to the recess 91a. Similarly, the inner diameter of the exhaust pipe 42 in the section where the recess 91b is formed is larger than the upstream and downstream sections adjacent to the recess 91b.

[0051] When the droplets of fuel injected from the fuel addition valve 43 adhere to the inner wall of the exhaust pipe 42, move downstream with the exhaust gas, and enter the recess 91a (i.e., collide with the inner wall surface of the exhaust pipe 42 that forms the bottom and side surfaces of the recess 91a), the droplets are scattered and atomized. Alternatively, when the droplets enter the recess 91a and are prevented from moving downstream, the droplets are vaporized there. Similarly, when the droplets of fuel adhering to the inner wall of the section between the recesses 91a and 91b in the exhaust pipe 42 enter the recess 91b, the atomization and vaporization of the droplets is promoted.

[0052] Each of the recesses 91a, 91b in the inner wall of the exhaust introduction passage is also simply referred to as a "recess." The recess is a continuous groove (e.g., annular recess) and a localized depression (on the surface) formed in the downstream region or in the inner wall of the exhaust introduction passage so that the exhaust flow cross-sectional area is increased at that location.

[0053] Next, the exhaust purification process performed using the urea water addition valve 46 will be described. As shown in Fig. 1, the urea water addition valve 46 is disposed in a curved portion 42b located between the DPF 45 and the SCR 47 in the exhaust pipe 42. Urea water (i.e., liquid additive) is supplied to the urea water addition valve 46 from a urea water tank (not shown). When a predetermined condition is met, the ECU 7 causes the urea water addition valve 46 to inject urea water. A collision plate 83 having a shape similar to that of the collision plate 81 is disposed in the curved portion 42b.

[0054] More specifically, the urea water addition valve 46 is disposed so as to inject (discharge) urea water into an injection area on the injection surface, which is the surface of the collision plate 83 facing the urea water addition valve 46. A plurality of protrusions having a shape similar to that of the protrusion 82 are provided in the injection area on the injection surface of the collision plate 83 and in a downstream area on the injection surface downstream of the injection area. Therefore, when urea water is injected from the urea water addition valve 46 onto the collision plate 83, atomization and vaporization of the injected urea water is promoted, similar to the case where fuel is injected from the fuel addition valve 43 onto the collision plate 81.

[0055] In addition, two annular recesses similar to the recesses 91a, 91b are formed in the section of the exhaust pipe 42 between the collision plate 83 and the SCR 47. These annular recesses promote atomization and evaporation of the urea water attached to the inner wall surface of the exhaust pipe 42. Note that the collision plate 83 and the annular recess provided downstream of the collision plate 83 have similar shapes and functions to the collision plate 81 and the recesses 91a, 91b, so further specific illustrations and explanations will be omitted.

[0056] The section of the exhaust pipe 42 from the DPF 45 to the SCR 47, including the curved portion 42b, is also referred to as the "exhaust introduction passage" for convenience. The exhaust introduction passage, the urea water addition valve 46, the SCR 47, and the collision plate 83 are also collectively referred to as the "exhaust purification system" for convenience. In this case, the SCR 47 is also referred to as the "exhaust purification device" for convenience.

[0057] As described above, the fuel injected into the exhaust pipe 42 by the fuel addition valve 43 is atomized and vaporized by the projections 82 (particularly the projections 82 provided in the downstream region of the injection surface 81a) provided on the collision plate 81 and the recesses 91a and 91b. In addition, since the collision plate 81 is provided on the curved portion 42a and the back surface 81b of the collision plate 81 approaches the inner wall surface of the opposing exhaust pipe 42 toward the downstream of the exhaust pipe 42, turbulence occurs at the junction of the first flow path 42a1 and the second flow path 42a2. Therefore, when the injected fuel flows into the first oxidation catalyst 44, it is uniformly dispersed in the radial direction of the exhaust pipe 42, and as a result, it is possible to prevent a part of the first oxidation catalyst 44 from becoming locally hot when the DPF regeneration process is performed.

[0058] Similarly, atomization and vaporization of the urea water injected from the urea water addition valve 46 is promoted by the protrusions formed in the downstream region of the collision plate 83 disposed in the curved portion 42b and the annular recessed portion formed downstream of the collision plate 83. As a result, the concentration of urea flowing into the SCR 47 is uniformly distributed in the radial direction of the SCR 47.

[0059] <Second embodiment> Next, a second embodiment will be described. In the first embodiment, the curved portion 42a is provided with a collision plate 81. In contrast, in the second embodiment, the curved portion 42a is provided with a collision plate 84. The difference will be described below.

[0060] Similar to the cross section of the collision plate 81 shown in Fig. 4, a cross section of the collision plate 84 is shown in Fig. 6. The fuel addition valve 43 injects fuel toward an injection surface 84a of the collision plate 84. A plurality of steps are formed on the injection surface 84a.

[0061] More specifically, a surface 84a2, which is adjacent to the surface 84a1 including the collision area of ​​the ejection surface 84a and is in the downstream area, is approximately perpendicular to the surface 84a1, and therefore one of the steps is formed. Since the exhaust flow path formed by the surface 84a1 of the collision plate 84 (and other inner wall surfaces of the exhaust pipe 42) is (locally) reduced by the surface 84a2, the step formed by the surface 84a2 corresponds to a protrusion protruding into the exhaust. That is, a plurality of protrusions (steps in this embodiment) are formed in the downstream area of ​​the collision plate 84.

[0062] The fuel droplets injected from the fuel addition valve 43 and colliding with or adhering to the surface 84a1 of the injection surface 84a are likely to move downstream and collide with or come into contact with one or more protrusions. In other words, the atomization and vaporization of the fuel is promoted by the collision plate 84, and thus the fuel is more likely to be uniformly dispersed in the radial direction of the exhaust pipe 42 when it flows into the first oxidation catalyst 44.

[0063] Although the embodiment of the present invention has been described with reference to the above structure, it will be apparent to those skilled in the art that many modifications, improvements, and variations are possible without departing from the scope of the present invention. Accordingly, the present invention includes all modifications, improvements, and variations that do not depart from the spirit and scope of the appended claims. The present invention is not limited to the specific structure described above, and can be modified, for example, as follows:

[0064] The collision plate 81 was disposed in the exhaust pipe 42 so as to divide the exhaust flow into the first flow path 42a1 and the second flow path 42a2. In other words, the length of each of the first flow path 42a1 and the second flow path 42a2 in the direction of the axis Lc was approximately equal to the length of the collision plate 81 in the direction of the axis Lc. Alternatively, the collision plate 81 may be fixed in the exhaust pipe 42 by a stay (for example, a rod-shaped metal member), a wire, or the like.

[0065] The collision plate 81 and the collision plate 83 are respectively disposed at the curved portion 42a and the curved portion 42b of the exhaust pipe 42. Alternatively, one or both of the collision plate 81 and the collision plate 83 may be disposed in a straight portion (section) of the exhaust pipe 42.

[0066] The protruding portion formed in the downstream region of the collision plate 81 was a plurality of protrusions 82. Alternatively, the protruding portion formed in the downstream region may be configured by two columnar members protruding from the downstream region of the collision plate 81 and a rod-shaped member (beam member) connecting the columnar members at a position spaced apart from the collision plate 81. Alternatively, the downstream region of the collision plate 81 may be provided with a recess formed by a depression, a groove, or the like. Furthermore, both the protruding portion and the recessed portion may be provided in the downstream region of the collision plate 81.

[0067] The recesses 91a, 91b are formed in the section of the exhaust pipe 42 between the collision plate 81 and the first oxidation catalyst 44. Alternatively, the inner wall of the exhaust pipe 42 may be provided with a protrusion formed by a projection, a step, or the like. Alternatively, the recesses 91a, 91b may be omitted. Furthermore, the recesses 91a, 91b are annular recesses (i.e., grooves continuously provided along the inner wall of the exhaust pipe 42), but may be a plurality of depressions arranged in an annular shape.

[0068] The engine system 1 includes the turbocharger 6 (i.e., one turbocharger). Alternatively, the engine system 1 may include two turbochargers (the turbocharger 6 and the additional turbocharger). For example, the engine system 1 may be configured so that the exhaust gas that has passed through the turbine of the additional turbocharger without passing through the turbine 62 flows into a section of the exhaust pipe 42 between the collision plate 81 and the first oxidation catalyst 44. [Explanation of symbols]

[0069] 1. Engine system 2. Internal combustion engine 3…Intake system 4…Exhaust system 6…Turbocharger 7…ECU 21...Fuel injector 22...Crank angle sensor 31…Intake pipe 32…Intake manifold 41...Exhaust manifold 42…Exhaust pipe 42a…Bend 42a1...First flow path 42a2...Second flow path 42b…Bend 43…Fuel addition valve 44...First oxidation catalyst 45…DPF 46...Urea solution addition valve 47…SCR 48...Second oxidation catalyst 51a, 51b...NOx sensor 52a, 52b, 52c, 52d...Temperature sensors 53...Differential pressure sensor 61…Compressor 62…Turbine 71...Accelerator opening sensor 72...Vehicle speed sensor 81...Collision plate 81a…Injection surface 81b…Back 82, 82a, 82b...protrusion 83, 84...Collision plate 84a…Injection surface 84a1, 84a2…Surface 91a, 91b...recess A1, A2, A3, A4...Arrows D1, D2…distance Df…Droplet Lc…Axis line R1, R2, R3…area

Claims

1. An exhaust purification device that purifies exhaust gas from an internal combustion engine; an exhaust gas introduction passage for introducing the exhaust gas into the exhaust gas purification device; an additive valve that injects a liquid additive into the exhaust gas flowing through the exhaust gas introduction passage; an impingement plate disposed inside the exhaust introduction passage, the impingement plate having an injection surface including a collision area with which the additive injected from the additive valve impinges, and dividing the exhaust flow path into an injection surface side and an opposite side to the injection surface; An exhaust purification system comprising: a plurality of droplet collision walls on which droplets of the additive moving downstream by the exhaust collide; The droplet collision walls include a surface of a plurality of protrusions formed in a downstream region of the injection surface downstream of the impingement region and protruding toward the exhaust gas; The protrusions include those constituting an upstream protrusion row arranged in a direction substantially perpendicular to the exhaust gas flow direction, and The protrusions include downstream protrusions that constitute the upstream protrusion row and are arranged so as to appear between the protrusions adjacent to each other when viewed from the upstream side along the flow direction. Exhaust purification system.

2. 2. The exhaust gas purification system according to claim 1, The collision plate is The exhaust gas introduction passage is provided at a curved portion of the exhaust gas introduction passage. The protrusions include a downstream protrusion row that includes the downstream protrusion and is arranged in a direction substantially perpendicular to the flow direction, and The arrangement direction of the downstream protrusion row is inclined with respect to the arrangement direction of the upstream protrusion row according to the curved portion. Exhaust purification system.

3. An exhaust purification device for purifying exhaust gas from an internal combustion engine; an exhaust gas introduction passage for introducing the exhaust gas into the exhaust gas purification device; an additive valve that injects a liquid additive into the exhaust gas flowing through the exhaust gas introduction passage; an impingement plate disposed inside the exhaust introduction passage and having an injection surface including a collision area on which the additive injected from the additive valve impinges; An exhaust purification system comprising: one or more droplet collision walls on which droplets of the additive moved downstream by the exhaust collide; The droplet collision wall is The nozzle is provided by a surface of either a protrusion or a recess formed in a downstream region of the ejection surface downstream of the collision region and protruding toward the exhaust gas, and further The droplet collision wall is The exhaust gas inlet passage is provided by a surface of an annular recess formed continuously on an inner wall surface of the exhaust gas inlet passage downstream of the collision plate. Exhaust purification system.

4. In the exhaust purification system according to claim 3, The annular recess is The exhaust gas inlet passage is provided at a curved portion of the exhaust gas inlet passage. Exhaust purification system.

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