JP2008128111A - Additive evaporation acceleration structure for exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make liquid additive evaporate and mix in exhaust gas with a small structure without generating exhaust gas pressure loss. <P>SOLUTION: The additive evaporation acceleration structure for an exhaust emission control device is provided with a casing 4 in a middle of an exhaust pipe 2 guiding exhaust gas of a diesel engine 1 and with a catalyst 5 in the casing 4, has the liquid additive 7 added in exhaust gas G in the upstream of the catalyst 5 and mixed with the exhaust gas G by evaporation, and executes exhaust emission control by guiding the exhaust gas G having additive mixed therein to the catalyst 5. An evaporation plate 17 having a plurality of ventilation holes 16, of which sum total of the section area is equivalent to or greater than the section area inside the exhaust pipe 2 is installed in a gas passage 15 connecting the exhaust pipe 2 and the casing 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for purifying exhaust gas by adding a liquid additive to the exhaust gas from a diesel engine and evaporating it, and introducing the exhaust gas mixed with the evaporated gas to a catalyst provided in an exhaust pipe. In particular, the present invention relates to an additive evaporation promotion structure for an exhaust emission control device that can evaporate and mix a liquid additive into exhaust gas with a small structure and that does not cause exhaust pressure loss.

  2. Description of the Related Art An exhaust gas purifying apparatus having a catalyst for reducing nitrogen oxides (NOx) contained in exhaust gas in an exhaust pipe that guides exhaust gas from a diesel engine has been known, and an example is shown in FIG. As shown, exhaust gas G from the diesel engine 1 is led to a casing 4 having a diameter larger than that of the exhaust pipe 2 through the exhaust pipe 2 and the enlarged diameter portion 3, and a catalyst 5 is provided in the casing 4. In the exhaust purification device 6, an additive supply means 8 for supplying the liquid additive 7 to the exhaust pipe 2 upstream from the catalyst 5 is provided, and the liquid additive 7 is added to and mixed with the exhaust gas G by the additive supply means 8. After that, the catalyst is guided to the catalyst 5 for NOx purification.

  As such an exhaust purification device 6, a NOx purification catalyst 5 a is installed in the casing 4, and a liquid additive comprising a hydrocarbon (HC) -based reducing agent such as diesel oil of diesel engine fuel is provided by an upstream additive supply means 8. The additive 7a is added to and mixed with the exhaust gas G, or the selective reduction catalyst 5b is installed in the casing 4, and the liquid additive 7b made of urea water or the like is supplied to the exhaust gas G by the additive supply means 8. There are some which are added and mixed.

  The liquid additive 7 such as light oil or urea water supplied to the exhaust gas G by the additive supply means 8 needs to be mixed with the exhaust gas G in the state of evaporated gas and led to the catalyst 5. Therefore, downstream of the additive supply means 8, as shown in FIGS. 4 and 5, the exhaust gas G and the liquid additive 7 are dispersed in the exhaust pipe 2 and the liquid additive 7 is added. An evaporating plate 10 having a plurality of vent holes 9 arranged to promote evaporation by colliding with droplets is arranged.

Patent Documents 1 and 2 show general techniques of the exhaust purification apparatus as described above. Patent Document 3 discloses a plate having vent holes for dispersing and equalizing the flow of exhaust gas on the downstream side of the reducing agent supply means for supplying the reducing agent to the exhaust gas and on the upstream side of the catalyst. Has been.
Japanese Patent Application No. 11-166410 JP 2006-70771 A JP-A-2005-214186

  However, in the conventional exhaust purification apparatus, as shown in FIG. 4, the droplets of the liquid additive 7 collide with each other to promote evaporation, and the evaporated gaseous additive is uniformly mixed with the exhaust gas. Since the evaporating plate 10 is installed in the exhaust pipe 2, the evaporating plate 10 narrows the flow path cross section of the exhaust pipe 2, which increases exhaust pressure loss and lowers the fuel consumption of the diesel engine 1. Etc. had occurred. That is, the sum of the cross-sectional areas of the vent holes 9 of the evaporation plate 10 provided in the exhaust pipe 2 is smaller than the cross-sectional area in the exhaust pipe 2, so that exhaust pressure loss occurs.

  On the other hand, in order to suppress the exhaust pressure loss, when the vent holes 9 of the evaporation plate 10 are formed so that the total cross-sectional area of the vent holes 9 is maximized, Since the portion is reduced, it is difficult for the droplets of the liquid additive 7 to collide, and there is a problem that the droplets of the liquid additive 7 cannot be vaporized well.

  As a method for solving the problem of exhaust pressure loss, the configuration shown in FIG. 6 is conceivable. That is, a gentle taper passage 11 having a gradually increasing diameter is provided between the rear portion of the additive supply means 8 in the exhaust pipe 2 and the casing 4, and the addition is performed without installing the evaporation plate 10 as shown in FIG. The liquid additive 7 supplied by the agent supply means 8 is evaporated in the gentle taper passage 11 and mixed with the exhaust gas G.

  However, in the case of the configuration shown in FIG. 6, there is a problem that the shape of the exhaust purification device 6 becomes longer due to the provision of the gentle taper passage 11, and thus it becomes difficult to mount the exhaust purification device 6 on the vehicle. There is a problem.

  The present invention has been made in view of the above circumstances, and by adding a liquid additive to the exhaust gas from a diesel engine and evaporating it, the exhaust gas mixed with the evaporated gas is led to a catalyst provided in an exhaust pipe and exhausted. Provided is an additive evaporation promotion structure for an exhaust purification apparatus that can evaporate and mix a liquid additive into exhaust gas with a small structure and prevents exhaust pressure loss in an exhaust purification apparatus that performs purification. It is something to try.

  The additive evaporation promotion structure of the exhaust purification apparatus of the present invention is provided with a casing in the middle of an exhaust pipe for guiding exhaust gas of a diesel engine, and a catalyst is provided in the casing, and a liquid additive is added to the exhaust gas upstream of the catalyst. The exhaust gas is mixed with exhaust gas by evaporation, and the exhaust gas mixed with the additive is guided to the catalyst to perform exhaust gas purification. The additive evaporation promoting structure of the exhaust gas purification apparatus includes the exhaust pipe and the casing. In the gas passage to be connected, an evaporation plate having a plurality of vent holes and having a total cross-sectional area of each vent hole equal to or greater than the cross-sectional area in the exhaust pipe is provided.

  In the additive evaporation promotion structure of the exhaust gas purification apparatus, a gas passage connecting the exhaust pipe and the casing has a first taper portion whose diameter is expanded from the exhaust pipe, and is connected to the first taper portion and has a diameter larger than that of the exhaust pipe. It is preferable to have a cylindrical portion having a small diameter and a second tapered portion that expands from the cylindrical portion toward the casing, and to provide an evaporation plate in the cylindrical portion.

  Further, in the additive evaporation promotion structure of the exhaust gas purification apparatus, a gas passage connecting the exhaust pipe and the casing has a diameter equal to that of the casing and is formed in a gas inlet portion of the casing, and an exhaust gas It is preferable that a taper part which expands from a pipe | tube toward a large diameter cylinder part is provided, and an evaporation plate is provided in the said large diameter cylinder part.

  Thus, in the additive evaporation promotion structure of the exhaust purification apparatus of the present invention, the gas passage connecting the exhaust pipe and the casing has a plurality of vent holes, and the total area of the vent holes is within the exhaust pipe. Since the evaporation plate that is equal to or larger than the cross-sectional area is installed, the problem of exhaust pressure loss due to the installation of the evaporation plate can be solved, and the shape structure of the exhaust emission control device can be downsized.

  According to the additive evaporation promotion structure of the exhaust purification apparatus of the present invention, it is possible to eliminate the problem of exhaust pressure loss even if an evaporation plate is installed, and to further reduce the size structure of the exhaust purification apparatus. Can be played.

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

  FIG. 1 shows an example of an additive evaporation promotion structure of an exhaust emission control device embodying the present invention. In FIG. 1, the same components as those in FIGS. Only the features of the present invention will be described in detail.

  As shown in FIG. 1, a first taper portion 12 that expands from the exhaust pipe 2 between the rear position and the casing 4 provided with the catalyst 5 from the position where the additive supply means 8 in the exhaust pipe 2 is installed. A gas passage having a cylindrical portion 13 connected to the first tapered portion 12 and having a diameter larger than that of the exhaust pipe 2 and smaller than that of the casing 4, and a second tapered portion 14 whose diameter increases from the cylindrical portion 13 toward the casing 4. 15 is provided. Then, an evaporation plate 17 having a plurality of air holes 16 is installed inside the cylindrical portion 13 as shown in FIGS.

  The ventilation holes 16 provided in the evaporation plate 17 are formed so that the total area of the ventilation holes 16 is equal to or larger than the cross-sectional area inside the exhaust pipe 2. At this time, as shown in FIG. 2, the cylindrical portion 13 has a larger cross-sectional area than the exhaust pipe 2, and thus the planar shape of the evaporation plate 17 provided in the cylindrical portion 13 can be increased. It is easy to form the air holes 16 so that the size is larger than the cross-sectional area inside the exhaust pipe 2.

  Next, the operation of the above embodiment will be described.

  As shown in FIG. 1, a first taper portion 12 that expands from the exhaust pipe 2 between the rear position and the casing 4 from the position where the additive supply means 8 in the exhaust pipe 2 is installed, and a first taper portion. 12 is provided with a gas passage 15 having a cylindrical portion 13 having a diameter larger than that of the exhaust pipe 2 and being smaller than that of the casing 4 and a second tapered portion 14 having a diameter increasing from the cylindrical portion 13 toward the casing 4. An evaporation plate 17 having a plurality of ventilation holes 16 is installed inside the cylindrical portion 13, and the total area of the ventilation holes 16 of the evaporation plate 17 is equal to or greater than the cross-sectional area inside the exhaust pipe 2. Since the vent hole 16 is formed so as to be, the problem of exhaust pressure loss caused by installing the evaporation plate 17 can be reliably solved. Therefore, problems such as a decrease in fuel consumption of the diesel engine due to exhaust pressure loss can be reduced.

  Further, since the planar shape of the evaporation plate 17 provided in the cylindrical portion 13 can be increased, the vent holes 16 are formed so that the total area of the vent holes 16 is larger than the cross-sectional area inside the exhaust pipe 2. However, since the area of the meat portion where the air holes 16 do not exist can be increased, the liquid additive 7 droplets collide well with the evaporation plate 17 to evaporate and mix the liquid additive 7 droplets. Can be performed satisfactorily.

  Further, by shortening the length of the gas passage 15, the shape structure of the exhaust gas purification device 6 can be reduced in size, so that it becomes easy to mount the exhaust gas purification device 6 on the vehicle.

  FIG. 3 shows another example of the embodiment of the present invention. The casing 4 is located between the rear position of the exhaust pipe 2 and the casing 4 provided with the catalyst 5 from the position where the additive supply means 8 is installed. A gas passage 20 having a large diameter cylindrical portion 18 formed in the gas inlet portion of the casing 4 and a tapered portion 19 having a diameter that increases from the exhaust pipe 2 toward the large diameter cylindrical portion 18. Provided. An evaporation plate 22 having a plurality of ventilation holes 21 is installed inside the large-diameter cylindrical portion 18. At this time, the vent holes 21 provided in the evaporation plate 22 are formed so that the total sum of the areas of the vent holes 21 is equal to or larger than the cross-sectional area inside the exhaust pipe 2.

  Accordingly, the large-diameter cylindrical portion 18 shown in FIG. 3 has a diameter larger than that of the cylindrical portion 13 in FIG. 1 with respect to the exhaust pipe 2, and thus the plane of the evaporation plate 22 provided in the large-diameter cylindrical portion 18. The shape is also larger than that of the evaporation plate 17 in FIG. Therefore, even if the diameter of each vent hole 21 of the evaporation plate 22 is set smaller than the diameter of the vent hole 16 in FIG. 1, the total area of each vent hole 21 can be made larger than the cross-sectional area inside the exhaust pipe 2. Increasing the meat part of the evaporation plate 22 increases the chance that the droplet of the liquid additive 7 collides with the evaporation plate 22, and the evaporation / mixing of the droplet of the liquid additive 7 can be further improved. .

  Note that the additive evaporation promotion structure of the exhaust purification apparatus of the present invention is not limited to the above-described embodiment. Exhaust purification provided with various catalysts that need to be evaporated by adding a liquid additive to the exhaust gas. Of course, various changes can be made without departing from the scope of the present invention as well as being applicable to the apparatus.

It is a general | schematic cutting side view which shows an example of the additive evaporation promotion structure of the exhaust gas purification apparatus which implements this invention. It is a front view of the evaporation plate with which FIG. 1 was equipped. It is a general | schematic cut side view which shows the other example of the additive evaporation promotion structure of the exhaust gas purification apparatus which implements this invention. It is a general | schematic cut side view which shows an example of the additive evaporation promotion structure of the conventional exhaust gas purification apparatus. It is a front view of the evaporation plate with which the structure of FIG. 4 was equipped. It is a general | schematic cut side view which shows the other example of the additive evaporation promotion structure of the conventional exhaust gas purification apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Exhaust pipe 4 Casing 5 Catalyst 6 Exhaust purification device 7 Liquid additive 8 Additive supply means 12 1st taper part 13 Cylinder part 14 2nd taper part 15 Gas passage 16 Ventilation hole 17 Evaporating plate 18 Large diameter cylinder part 19 Taper 20 Gas passage 21 Vent 22 Evaporating plate G Exhaust gas

Claims (3)

  A casing is provided in the middle of an exhaust pipe for guiding exhaust gas of a diesel engine, and a catalyst is provided in the casing. A liquid additive is added to the exhaust gas upstream of the catalyst and mixed with the exhaust gas by evaporation, and the additive is mixed. An additive evaporation promoting structure of an exhaust purification device that conducts exhaust purification by introducing exhaust gas to the catalyst, the gas passage connecting the exhaust pipe and the casing has a plurality of vent holes, and An additive evaporation accelerating structure for an exhaust gas purification apparatus, wherein an evaporation plate having a total cross-sectional area of each vent hole equal to or greater than a cross-sectional area in the exhaust pipe is provided.   A gas passage connecting the exhaust pipe and the casing has a first taper portion whose diameter is expanded from the exhaust pipe, a cylinder portion connected to the first taper portion and having a diameter larger than that of the exhaust pipe and smaller than that of the casing, and from the cylinder portion to the casing. The additive evaporation promotion structure for an exhaust gas purification apparatus according to claim 1, further comprising a second taper portion that increases in diameter toward the center, and an evaporation plate is provided in the cylinder portion.   A gas passage connecting the exhaust pipe and the casing has a diameter equal to that of the casing and is formed at the gas inlet of the casing, and a tapered portion that expands from the exhaust pipe toward the large diameter cylinder section The additive evaporation promotion structure for an exhaust emission control device according to claim 1, wherein an evaporation plate is provided in the large-diameter cylindrical portion.

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