JP4327445B2 - Exhaust purification equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control device.
[0002]
[Prior art]
Conventionally, exhaust purification has been performed with an exhaust purification catalyst installed in the middle of an exhaust pipe. As this type of exhaust purification catalyst, when the exhaust air-fuel ratio is lean, NOx in the exhaust gas is oxidized and temporarily stored in the form of nitrate, and when the oxygen concentration in the exhaust gas decreases, unburned HC or There is known an NOx occlusion reduction catalyst having the property of decomposing and releasing NOx through CO or the like for reduction and purification.
[0003]
In this NOx occlusion reduction catalyst, when the occlusion amount of NOx increases and reaches the saturation amount, no more NOx can be occluded. Therefore, the oxygen concentration of the exhaust gas that periodically flows into the NOx occlusion reduction catalyst is reduced. It is necessary to reduce and release NOx by decomposition. For example, when used in a gasoline engine, the operating air-fuel ratio of the engine is reduced (the engine is operated at a rich air-fuel ratio), thereby reducing the oxygen concentration in the exhaust gas and unburned HC in the exhaust gas. Reduction components such as CO can be increased to promote decomposition and release of NOx.
[0004]
However, when the NOx storage reduction catalyst is used as an exhaust gas purification device for a diesel engine, it is difficult to operate the engine at a rich air-fuel ratio. For this reason, by adding fuel to the exhaust gas upstream of the NOx storage reduction catalyst, the added fuel is thermally decomposed in high-temperature exhaust gas to produce a large amount of hydrocarbon, and this hydrocarbon is reduced. It is necessary to reduce the oxygen concentration in the exhaust gas by reacting with oxygen on the NOx storage reduction catalyst as an agent.
[0005]
On the other hand, as a measure to reduce particulate matter (particulate matter) discharged from diesel engines, an exhaust purification catalyst such as an oxidation catalyst supported on a particulate filter or a flow-through oxidation catalyst is placed in the middle of the exhaust pipe. Has already been equipped. By using such an oxidation catalyst, it is possible to promote the oxidation reaction of the particulates collected in the particulate filter and the particulates in the exhaust gas, and to reduce the particulates by combustion removal.
[0006]
However, such an oxidation catalyst has an active temperature region, and if the operation state continues at an exhaust temperature that falls below the lower limit temperature of activation, the oxidation catalyst will not be activated and the particulates will not be burned and removed well. The malfunction that can happen. If necessary, fuel is added to the exhaust gas on the upstream side, and the added fuel is pyrolyzed in high-temperature exhaust gas to produce a large amount of hydrocarbons, which are then oxidized on the oxidation catalyst. It has been proposed to increase the catalyst bed temperature positively by the heat of reaction.
[0007]
As described above with some examples, the fuel is added to the upstream side of the exhaust purification catalyst (NOx storage reduction catalyst, oxidation catalyst, or particulate filter carrying these) installed in the middle of the exhaust pipe. The idea itself has been proposed in the past.
[0008]
For example, a fuel addition injector is installed in an exhaust port of a cylinder head, fuel is added to exhaust gas by exhaust port injection by the injector, and the added fuel is stirred by a turbine and supplied to an exhaust purification catalyst. A means for adding fuel to exhaust gas by such exhaust port injection has already been developed for practical use in some passenger cars and the like (for example, Patent Document 1). reference).
[0009]
However, in large vehicles equipped with diesel engines, it is possible to add fuel by installing an injector on the inlet side of the exhaust purification catalyst in the middle of the exhaust pipe from the viewpoint of ensuring the reliability of the EGR device and turbocharger. A means for adding fuel with an injector in the middle of an exhaust pipe has been proposed (see, for example, Patent Document 2).
[0010]
[Patent Document 1]
JP 2001-280125 A [Patent Document 2]
Japanese Patent Laid-Open No. 2000-240429
[Problems to be solved by the invention]
However, when an injector is provided in the middle of the exhaust pipe in this way, it is possible to reliably avoid burning caused by exposure of the injector to high-temperature exhaust gas and seizure in the flow path of the added fuel. Therefore, it is considered necessary to take some thermal countermeasures for the injector, but the equipment itself in the middle of the exhaust pipe of the injector is still under development, and there are still practical means for the thermal countermeasures for the injector. The fact is not proposed.
[0012]
The present invention has been made in view of the above circumstances, and is highly practical exhaust gas purification capable of reliably avoiding burnout of an injector installed in the middle of an exhaust pipe and seizure in the flow path of an added fuel. The object is to provide a device.
[0013]
[Means for Solving the Problems]
The present invention is equipped with an exhaust purification catalyst in the middle of an exhaust pipe, and fuel is added along the exhaust pipe upstream of the bent portion upstream of the bent portion upstream of the exhaust purification catalyst of the exhaust pipe. And an injection space is formed in the direction along the exhaust pipe downstream of the bent portion from the tip of the nozzle of the injector, and fuel is supplied to the flow path in the exhaust pipe downstream of the bent portion via the injection space. Exhaust gas characterized in that it is configured to be able to inject, and the spray center of the nozzle of the injector has a required inclination angle toward the upstream side of the bent portion with respect to the center line of the exhaust pipe downstream of the bent portion This relates to a purification device.
[0014]
Thus, since the fuel is added from the tip of the injector nozzle to the flow path in the exhaust pipe through the injection space, the tip of the injector nozzle is converted into high-temperature exhaust gas. It is not exposed and burnout of the nozzle of the injector and seizure in the flow path of the added fuel are reliably avoided.
[0015]
Moreover, even if the injection space is interposed between the tip of the nozzle of the injector and the flow path in the exhaust pipe in this way, the injector itself is attached along the exhaust pipe upstream of the bent portion. Therefore, it is possible to arrange the injector as a compact accessory that does not overhang.
Further, since the spray center of the nozzle of the injector is configured to have a required inclination angle toward the upstream side of the bent portion with respect to the center line of the exhaust pipe downstream of the bent portion, the flow of exhaust gas from the upstream of the bent portion The added fuel is more miscible with the exhaust pipe, and the problem that the added fuel is difficult to be mixed inside the bent portion in the bent direction due to the influence of the main flow of exhaust gas that tends to be displaced outward in the bent direction of the exhaust pipe is eliminated. become.
[0016]
In the present invention, it is preferable that the injection space has a conical shape with the tip of the injector as a vertex, and the apex angle of the conical shape is set larger than the injection angle of the nozzle of the injector.
[0017]
In this way, all the fuel injected from the nozzle of the injector is injected into the flow passage in the exhaust pipe without adhering to the inner peripheral surface of the injection space, and is well added to the exhaust gas flowing through the flow passage. Therefore, effective fuel addition is realized with an appropriate control amount as intended by electronically controlling the opening period of the electromagnetic valve in the injector.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
1 to 3 show an example of an embodiment for carrying out the present invention. Reference numeral 1 in FIG. 1 denotes a diesel engine equipped with a turbocharger 2, and an intake 4 led from an air cleaner 3 is connected to an intake pipe. 5 is introduced to the compressor 2a of the turbocharger 2 and pressurized, and the pressurized intake air 4 is distributed and introduced to each cylinder of the diesel engine 1 via the intercooler 6.
[0021]
Further, exhaust gas 8 discharged from each cylinder of the diesel engine 1 through the exhaust manifold 7 is sent to the turbine 2b of the turbocharger 2 through the exhaust pipe 9, and the exhaust gas 8 driving the turbine 2b is of a catalyst regeneration type. Particulates are collected through the particulate filter 10 (exhaust gas purification catalyst) and then discharged outside the vehicle.
[0022]
Furthermore, an injector 11 for fuel addition is provided along the exhaust pipe 9 upstream of the bent portion 9a on the outer side in the bending direction of the bent portion 9a that is bent in a substantially L shape upstream of the particulate filter 10 in the exhaust pipe 9. A part of the fuel guided from a fuel tank (not shown) or the like to the base end portion of the injector 11 is bent from the tip end portion of the injector 11. 9a is injected into the flow path in the exhaust pipe 9 through the injection space 12 formed in the direction along the exhaust pipe 9 downstream.
[0023]
As shown in FIG. 2, the injection space 12 has a conical shape with the tip of the nozzle 11a of the injector 11 as the apex, and the apex angle α of the conical shape is set larger than the injection angle β of the nozzle 11a of the injector 11. It has been made.
[0024]
Further, the spray center of the nozzle 11a of the injector 11 is configured to have a required inclination angle θ toward the upstream side of the bent portion 9a with respect to the center line of the exhaust pipe 9 downstream of the bent portion 9a.
[0025]
In addition, a water jacket 14 having a cylindrical shape substantially concentric with the injector 11 is bored inside the boss portion 13 that holds the injector 11, and the front end side of the injector 11 in the water jacket 14 ( A water supply port 15 is provided on the lower end side and the side away from the exhaust pipe 9, and a drain port 16 is provided on the water jacket 14 on the base end side (upper end side) of the injector 11 and on the side close to the exhaust pipe 9. Is provided.
[0026]
A part of the cooling water of the diesel engine 1 is supplied to the water supply port 15 and the cooling water extracted from the drain port 16 is returned to a thermostat (temperature controller) (not shown).
[0027]
Thus, if the exhaust gas purification device is configured in this way, fuel is added to the flow path in the exhaust pipe 9 from the tip of the nozzle 11a of the injector 11 through the injection space 12, so that the nozzle 11a As a result, the nozzle 11a of the injector 11 is burned out and seizure in the flow path of the added fuel is reliably avoided.
[0028]
Moreover, even if the injection space 12 is interposed between the tip end of the nozzle 11a of the injector 11 and the flow path in the exhaust pipe 9, the injector 11 itself follows the exhaust pipe 9 upstream of the bent portion 9a. Since it is attached, the injector 11 can be arranged as a compact accessory that does not protrude greatly from the exhaust pipe 9.
[0029]
Here, the drawing amount x (see FIG. 2) of the nozzle 11a with respect to the flow path in the exhaust pipe 9 is appropriately determined by the temperature of the exhaust gas 8 flowing in the flow path in the exhaust pipe 9, and the nozzle of the injector 11 The pull-in amount x of the nozzle 11a necessary to maintain the tip temperature of the 11a at the heat resistance guarantee limit (for example, about 180 ° C.) needs to be increased as the exhaust temperature on the exhaust pipe 9 side becomes higher (see FIG. 3).
[0030]
However, the increasing / decreasing tendency of the pull-in amount x with respect to the exhaust temperature changes because various factors such as the diameter of the nozzle 11a of the injector 11 and the heat transfer area with the water jacket 14 are related in a complicated manner. It is preferable to appropriately set the pull-in amount x that does not hinder the temperature on an actually measured basis for each diesel engine 1.
[0031]
On the other hand, in the present embodiment, since the apex angle α of the conical shape of the injection space 12 is set larger than the injection angle β of the nozzle 11a of the injector 11, the fuel injected from the nozzle 11a of the injector 11 is injected into the injection space. All are injected into the flow path in the exhaust pipe 9 without adhering to the inner peripheral surface of the exhaust gas 12, and are well added to the exhaust gas 8 flowing through the flow path. As a result, effective fuel addition is realized with an appropriate control amount as intended by electronically controlling the valve opening period of the electromagnetic valve in the injector 11.
[0032]
Further, the spray center of the nozzle 11a of the injector 11 has a required inclination angle θ toward the upstream side of the bent portion 9a with respect to the center line of the exhaust pipe 9 downstream of the bent portion 9a. Due to the influence of the main flow of the exhaust gas 8 which tends to be displaced outwardly in the bending direction of the bent portion 9a of the exhaust pipe 9, the added fuel becomes inwardly bent in the bent portion 9a. The problem of being difficult to mix will be eliminated.
[0033]
The exhaust purification apparatus of the present invention is not limited to the above-described embodiment. For exhaust purification catalysts that require the addition of hydrocarbons, in addition to catalyst regeneration type particulate filters, NOx reduction catalysts (selection) Reduction type catalyst), NOx occlusion reduction catalyst, particulate filter combined with NOx occlusion reduction catalyst, oxidation catalyst etc. may be adopted, and fuel added by injector is a general diesel engine Of course, different fuels such as kerosene may be used in addition to the light oil used for the fuel, and various changes can be made without departing from the scope of the present invention.
[0034]
【The invention's effect】
According to the exhaust emission control device of the present invention described above, various excellent effects as described below can be obtained.
[0035]
(I) According to the invention described in claim 1 of the present invention, the injection space is interposed between the tip of the nozzle of the injector and the flow path in the exhaust pipe, so that the tip of the nozzle is exhausted at a high temperature. Since it can be protected from being exposed to gas, burnout of the nozzle of the injector and seizure in the flow path of the added fuel can be reliably avoided, and the injector is an incidental equipment that does not protrude greatly from the exhaust pipe. Furthermore, the mixing of the added fuel with respect to the flow of the exhaust gas from the upstream of the bent portion can be greatly improved, so that the bent portion of the bent portion of the exhaust pipe is offset to the outside in the bending direction. senna added fuel in the mainstream of the effect of exhaust gas Ru can eliminate the problem that difficult to be mixed in the bending inward of the bend.
[0036]
(II) According to the invention described in claim 2 of the present invention, the fuel from the nozzle of the injector is all injected into the flow path in the exhaust pipe without adhering to the inner peripheral surface of the injection space. Therefore, it is possible to achieve effective fuel addition with an appropriate control amount as intended by electronically controlling the valve opening period of the solenoid valve in the injector. .
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an embodiment for carrying out the present invention.
FIG. 2 is an enlarged cross-sectional view showing details of an installation location of the injector of FIG.
FIG. 3 is a graph showing the relationship between exhaust temperature and nozzle pull-in amount.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Diesel engine 8 Exhaust gas 9 Exhaust pipe 9a Bending part 10 Catalyst regeneration type particulate filter (exhaust purification catalyst)
11 Injector 11a Nozzle 12 Injection space α Conical apex angle β of injection space Injection angle θ of injector Inclination angle of spray center of injector with respect to exhaust pipe center line downstream of bent portion x Amount of nozzle drawn into flow path in exhaust pipe

Claims (2)

An exhaust purification catalyst is installed in the middle of the exhaust pipe, and a fuel addition injector is provided along the exhaust pipe upstream of the bent portion upstream of the bent portion upstream of the exhaust purification catalyst. In addition, an injection space is formed in the direction along the exhaust pipe downstream of the bent portion from the tip of the nozzle of the injector so that fuel can be injected into the flow path in the exhaust pipe downstream of the bent portion via the injection space. An exhaust emission control device characterized in that the spray center of the nozzle of the injector has a required inclination angle toward the upstream side of the bent portion with respect to the center line of the exhaust pipe downstream of the bent portion .   2. The exhaust according to claim 1, wherein the injection space has a conical shape with the tip of the nozzle of the injector as an apex, and the apex angle of the conical shape is set larger than the injection angle of the nozzle of the injector. Purification equipment.

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