JP2011043129A - Exhaust gas purifying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce and purify nitrogen oxide (NOx) mixed into exhaust gas by quickly solving the crystal of a precipitated reducing agent inside an injection nozzle in case of the initial stage of an engine started after the engine has been stopped for a long time period. <P>SOLUTION: An exhaust gas purifying device is positioned in an exhaust system of the engine and is provided with the injection nozzle 6 which injects and supplies liquid reducing agent to the upstream of the exhaust system of a reducing catalyst, and a tabular heat receiving fin 15 positioned at the injection nozzle 6 so that a flat section is placed along the flow of the exhaust gas to quickly heat the injection nozzle 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an engine exhaust gas purification device (hereinafter referred to as “exhaust gas purification device”) for reducing and purifying nitrogen oxide (NOx) in exhaust gas using a liquid reducing agent, and in particular, an injection nozzle for liquid reducing agent. The present invention relates to a technique for preventing clogging.

A technique has been put into practical use in which urea water is injected and supplied from an injection nozzle upstream of the exhaust system of a reduction catalyst with a reducing agent that reduces and purifies nitrogen oxides (NOx) contained in engine exhaust. The reducing agent is stored in a storage tank in a liquid state at room temperature, and a required amount is injected and supplied from the injection nozzle according to the operating state of the engine.
However, when the temperature of the injection nozzle rises due to the influence of exhaust heat and the temperature of the liquid reducing agent exceeds the boiling point of the solvent, only the solvent evaporates and the solute of the reducing agent precipitates in the injection nozzle, and the injection nozzle Clogging occurs, making it impossible to inject the reducing agent.
JP-A-2005-127318 (Patent Document 1) has been proposed as a corresponding technology.

JP 2005-127318 A

According to the prior art document, when the temperature of the liquid reducing agent is higher than the boiling point of the solvent and the solute is precipitated in the injection nozzle affected by the heat of the exhaust gas, when the temperature further rises and exceeds the melting point of the solute Since the solute melts, the clogging of the nozzle holes can be eliminated.
On the other hand, in a part that is not easily affected by the heat of the exhaust gas, for example, a pipe that supplies the liquid reducing agent to the injection nozzle, the temperature may rise above the boiling point of the solvent, but may not rise above the melting point of the solute. . In this case, since the solute remains deposited in the injection nozzle and its piping, the reducing agent is not supplied from the injection nozzle.

However, in the initial stage when the engine is started with the engine stopped for a long time, the temperature of the exhaust gas discharged from the exhaust port of the engine is lower than that at the completion of the warm-up operation of the engine. Manifolds, exhaust pipes, and the like are at a temperature close to normal temperature (outside temperature), and the temperature drops considerably as they flow to the injection nozzle that injects the reducing agent.
Even if the injection nozzle is exposed to the exhaust gas in the exhaust pipe in such a state, the injection nozzle absorbs the heat of the exhaust gas and cannot immediately dissolve the solute on which the reducing agent is deposited.
Therefore, in the initial stage when the engine is started with the engine stopped for a long time, nitrogen oxide (NOx) mixed in the exhaust gas until the crystal of the reducing agent deposited in the injection nozzle melts. There was a problem that it could not be reduced and purified.

  The present invention has been made to solve such a problem, and the object of the present invention is to increase the heat receiving temperature of the injection nozzle for injecting the reducing agent quickly and to increase the solute of the reducing agent thus precipitated. It is to provide an exhaust gas purifying device for an internal combustion engine that can quickly dissolve the gas and exhibit good nitrogen oxide (NOx) purifying performance.

  The present invention achieves such an object. The reduction catalyst is disposed in an exhaust system of an engine and reduces and purifies nitrogen oxides contained in the exhaust gas of the engine by a liquid reducing agent, and the exhaust of the reduction catalyst. An injection nozzle for injecting and supplying a liquid reducing agent is provided upstream of the system, and a flat plate-shaped heat receiving fin is arranged in the injection nozzle so that a flat portion follows the flow of the exhaust gas.

The heat of the exhaust gas is received by the heat receiving fin and heat conduction to the injection nozzle is promoted, whereby the urea crystals are melted and clogging of the injection nozzle nozzle is eliminated at an early stage.
In addition, since the heat receiving fins are flat and arranged along the flow of the exhaust gas, the amount of turbulence in the exhaust gas flow is suppressed, the heat conduction of the heat receiving fins from the exhaust gas is improved, and the exhaust gas is exhausted. Prevents pressure increase and engine output decrease.

  In the present invention, preferably, the planar portion of the heat receiving fin is parallel to an axis of an exhaust pipe through which the exhaust gas flows.

  Since the flat surface of the heat receiving fin is parallel to the axis of the exhaust pipe through which the exhaust gas flows, the exhaust gas flows without peeling from the flat surface of the heat receiving fin, so the heat of the exhaust gas efficiently flows into the flat heat receiving fin. Heat conduction is performed and the urea water injection nozzle is heated to promote the melting of the urea crystals.

  Preferably, in the invention of the present application, the injection nozzle has a vertical portion extending from an outer peripheral portion of the exhaust pipe toward the vicinity of the axis of the exhaust pipe, and a downstream portion of the exhaust system along the axis at a position near the axis. The heat receiving portion is formed in a substantially L shape with a lateral portion having an injection hole for injecting the reducing agent, and the outer peripheral portion is formed in a circular shape by fitting the central portion to the vertical portion. A fin may be provided.

  Since the outer shape of the heat receiving fin is circular, it is heated uniformly from the outer periphery of the nozzle cross section. Therefore, since the melting of the urea crystals starts evenly from the outer peripheral portion, the time until the melting is completed can be shortened.

  Preferably, in the present invention, the injection nozzle extends from the outer periphery of the exhaust pipe toward the vicinity of the axis, and extends toward the exhaust system downstream along the axis at a position near the axis. The heat receiving fin includes a flat portion of the heat receiving fin, an axis of the vertical portion, an axis of the horizontal portion, and a horizontal portion having an injection hole for injecting the reducing agent. Are located in the same plane, and are formed in an L-shape that is a flat plate that extends continuously over substantially the entire length of the vertical portion and the horizontal portion of the nozzle and the bent portion of the nozzle. And good.

  Since the heat receiving fins are provided in substantially the entire bent outer side of the injection nozzle located in the exhaust pipe, the time until the melting is completed can be shortened because the nozzles are heated simultaneously over the entire nozzle.

  In the present invention, preferably, the plate thickness of the exhaust system upstream end portion of the heat receiving fin is thin, and the plate thickness is smoothly increased toward the downstream side.

Since the plate thickness of the upstream end portion of the exhaust system upstream of the heat receiving fin is reduced, the disturbance of the flow of the exhaust gas can be minimized when the exhaust gas contacts the front end portion of the heat receiving fin.
Furthermore, the exhaust gas flowing through the flat surface of the heat receiving fin is prevented from being disturbed, and the exhaust gas flow has a cross-sectional shape that is difficult to separate from the surface of the heat receiving fin, so that the exhaust gas can efficiently conduct heat to the heat receiving fin. Nozzle heating can be promoted.

  According to the present invention, the heat receiving temperature received by the injection nozzle for injecting the reducing agent disposed in the exhaust pipe of the internal combustion engine is increased quickly and rapidly, so that the solute of the reducing agent that has precipitated is rapidly dissolved. An exhaust gas purification apparatus for an internal combustion engine that exhibits nitrogen oxide (NOx) purification performance can be provided.

1 shows a basic configuration diagram of an exhaust gas purification apparatus according to the present invention. FIG. (A) shows the appearance of the injection nozzle according to the first embodiment of the present invention, and (B) to (D) show the detailed shape of the heat receiving fin. (A) shows the external appearance of the injection nozzle concerning 2nd Embodiment of this invention, (B) shows XX cross-section detailed shape of (A).

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.
However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

(First embodiment)
FIG. 1 shows a basic configuration diagram of an exhaust gas purifying apparatus according to the present invention. Exhaust gas of an engine 1 is discharged from an exhaust manifold to a turbocharger 10 and is driven by an exhaust turbine of the turbocharger 10 to be dust and water droplets by an air cleaner 11. The intake air is compressed by an intake air compressor provided coaxially with the exhaust turbine. Since the pressurized intake air generates heat and expands, it is cooled by the intercooler 12 to increase the air density, and is sucked into the engine 1 and used for combustion of fuel in the engine. To drive.
The turbocharger 10 compresses the intake air in order to suppress the fuel consumption of the vehicle, cools the air generated by the compression by the intercooler 12, increases the air density, and increases the combustion pressure in the combustion chamber of the engine 1. To increase the output torque.

Therefore, as the combustion pressure in the combustion chamber of the engine 1 increases, the NOx concentration contained in the exhaust gas increases. Exhaust gas discharged from the turbocharger 10 is rendered harmless by HC (hydrocarbon) and CO (carbon monoxide) by the pre-stage oxidation catalyst 4. Next, urea water, which is a reducing agent, is injected into the exhaust gas from the injection nozzle 6 according to the present invention, and is reduced to water (H ₂ O) and nitrogen (N) by the NOx reduction catalyst and rendered harmless. Thereafter, it is further purified by the second oxidation catalyst 5 and released into the atmosphere.

However, urea has a crystal melting point of about 133 ° C. or higher and urea water has a boiling point of 100 ° C. in urea water (32.5%) for reducing NOx that is harmful. As described above, when the urea water solvent boils (evaporates), urea precipitates.
On the other hand, when the engine 1 is stopped, the reducing agent that has been sent to the injection nozzle 6 while the engine 1 is operating remains in the injection nozzle 6 as it is. Immediately after the engine 1 is stopped, the residual heat in the exhaust pipe 13 is often 100 ° C. or more, and the reducing agent remaining in the injection nozzle 6 is reduced by evaporation of the solvent before the inside of the exhaust pipe 13 and the surroundings are cooled. Crystals of the agent (urea) may be precipitated.
Therefore, in order to prevent clogging of the injection nozzle 6 so that the reducing agent can be appropriately injected from the injection nozzle 6, the temperature of the injection nozzle 6 is quickly raised after the engine 1 is started to reduce the reducing agent (urea). Must be dissolved.
FIG. 2A is a detailed view of the injection nozzle 6 disposed on the upstream side of the NOx reduction catalyst in the exhaust system.
In order to maintain the temperature of the injection nozzle 6 at about 133 ° C. or higher at an early stage by using the heat of the exhaust gas flowing in the exhaust system purification device 2, heat receiving fins 15 are provided.

The injection nozzle 6 includes a vertical portion 61 extending from the outer peripheral portion of the exhaust pipe 13 to the substantially central axis of the exhaust pipe 13 and a horizontal portion 62 bent from the end position of the vertical portion 61 toward the downstream side of the exhaust system. A plurality of nozzle holes 14 are arranged in the radial direction at the distal end portion of the lateral portion 62.
The injection hole 14 may be injected from the injection nozzle 6 so that the urea water diffuses toward the distal end portion of the lateral portion 62 toward the exhaust system downstream side.
The heat receiving fins 15 have a disk shape with the center part fitted on the vertical part 61 of the injection nozzle 6, and a plurality of the heat receiving fins 15 are arranged along the flow of the exhaust gas.
The heat receiving fins 15 are conditions for improving the heat reception from the exhaust gas, such that the size of the heat reception area, the exhaust gas flowing through the heat receiving surface is fast and smoothly flow through the heat receiving surface, and the exhaust gas flow does not separate from the heat receiving surface. It is desirable to make it.
In this embodiment, since the heat receiving fins 15 have a circular shape, the heat received by the heat receiving fins 15 is uniformly transferred from the entire outer periphery of the nozzle. Therefore, when urea is precipitated, the urea is rapidly melted. be able to.
Further, since the cross section of the tip of the heat receiving fin 15 particularly on the upstream side of the exhaust system is formed in an arc shape, when the exhaust gas collides with the tip, the heat receiving fin 15 is divided into upper and lower parts so as not to disturb the exhaust gas. Therefore, the heat transfer from the exhaust gas to the heat receiving fins 15 can be promoted smoothly without peeling off the flat surface.
It should be noted that the thinner the tip of the heat receiving fin 15, the more effective it can be divided up and down so that the exhaust gas is not disturbed.

(B) to (D) of FIG. 2 show detailed cross sections of the heat receiving fin, and the exhaust gas flowing on the heat receiving surface is fast and smoothly flows on the heat receiving surface, so that the exhaust gas flow does not separate from the heat receiving surface. The cross section of the heat receiving fin considered is illustrated. (B) has substantially the same plate thickness, and the circular outer peripheral edge has an arc-shaped cross section. (C) is a wedge shape in which the plate thickness on the upstream side of the exhaust system is thin, the downstream side of the exhaust system is thick, and the whole has a circular shape, and the outer peripheral edge has an arcuate cross section.
(D) is a streamline shape in which the plate thickness on the upstream side of the exhaust system is thin, and the downstream side of the exhaust system is thick. The whole has a disc shape, and the outer peripheral edge has an arc-shaped cross section.
Therefore, when the exhaust gas collides with the tip portion, the exhaust gas is smoothly divided into upper and lower parts and flows along the surface of the heat receiving fin so that the exhaust gas is not disturbed. Heat can be promoted.

(Second Embodiment)
As shown in FIG. 3A, the injection nozzle 6 includes a vertical portion 61 extending from the outer peripheral portion of the exhaust pipe 13 to a substantially central axis of the exhaust pipe 13, and an end position of the vertical portion 61 on the downstream side of the exhaust system. A plurality of injection holes 14 are arranged in the radial direction at the distal end of the horizontal portion 62.
The heat receiving fins 16 are located in the same plane including the vertical part 61 and the axis of the horizontal part 62 of the injection nozzle 6, and the outer vertical part 61 where the vertical part 61 and the horizontal part 62 are bent and substantially the entire area of the horizontal part 62. It is a continuous flat plate shape and is L-shaped. Further, as shown in FIG. 3B (cross section XX in FIG. 3A), the plate thickness of the upstream end portion of the exhaust system upstream of the heat receiving fin 16 is thin, and the outer peripheral surface mounting portion side of the injection nozzle 6 is thick. It is.
The heat receiving fin 16 has a cross-sectional shape that is flat as shown in FIGS. 2 (B) to 2 (D), or a thin tip end plate on the upstream side of the exhaust system. The same effect can be obtained even if the streamline shape or the triangular shape is increased on the jet nozzle outer peripheral surface mounting portion side on the downstream side of the system.

According to the present embodiment, since the heat receiving fins 16 can be provided continuously over substantially the entire vertical portion 61 and the horizontal portion 62 of the injection nozzle located in the exhaust pipe 13, the entire injection nozzle 6 is heated at the same time, so that it melts. Time to completion can be shortened.

  In particular, when urea water is deposited and the urea water injection nozzle is clogged, it is suitable for use in an exhaust gas purifying apparatus that needs to quickly eliminate clogging.

DESCRIPTION OF SYMBOLS 1 Engine 2 Purification apparatus 3 NOx reduction catalyst 4 Pre-stage oxidation catalyst 5 Post-stage oxidation catalyst 6 Injection nozzle 8 Reducing agent supply apparatus 9 Urea water tank 15, 16 Heat receiving fin 61 Vertical portion 62 Horizontal portion

Claims (5)

  A reduction catalyst that is disposed in the exhaust system of the engine and that reduces and purifies nitrogen oxides contained in the exhaust gas of the engine with a liquid reducing agent, and an injection that injects and supplies the liquid reducing agent upstream of the exhaust system of the reduction catalyst An exhaust gas purifying apparatus comprising a nozzle and provided with a flat plate-shaped heat receiving fin on the injection nozzle so that a flat portion thereof follows the flow of the exhaust gas.   The exhaust gas purification device according to claim 1, wherein the flat portion of the heat receiving fin is parallel to an axis of an exhaust pipe through which the exhaust gas flows.   The injection nozzle extends from the outer periphery of the exhaust pipe toward the vicinity of the axis, and extends toward the exhaust system downstream along the axis at a position near the axis, and injects the reducing agent. The heat-receiving fin, which is formed in a substantially L-shape having a lateral portion having an injection hole, has a central portion fitted on the vertical portion, and a circular outer peripheral portion is disposed. The exhaust gas purification apparatus according to 1 or 2.   The injection nozzle extends from the outer periphery of the exhaust pipe toward the vicinity of the axis, and extends toward the exhaust system downstream along the axis at a position near the axis, and injects the reducing agent. The heat receiving fin is formed in a substantially L shape including a horizontal portion having an injection hole, and the flat surface portion of the heat receiving fin, the axis of the vertical portion, and the axis of the horizontal portion are located in the same plane. The vertical portion of the injection nozzle and the horizontal portion of the injection nozzle are arranged in a flat plate shape that extends substantially over the entire length of the vertical portion and the horizontal portion, and is arranged in an L shape. Item 3. The exhaust gas purifying device according to Item 1 or 2.   5. The exhaust gas purifying apparatus according to claim 1, wherein a plate thickness of the upstream end portion of the exhaust system of the heat receiving fin is thin, and the plate thickness is smoothly increased toward the downstream side.

Images